Tyrosine Kinase Inhibitor Resistant Cells Research Articles

PARP1 promotes EGFR-TKI drug-resistance via PI3K/AKT pathway in non-small-cell lung cancer.

Tyrosine kinase inhibitor (TKI) resistance is the main type of drug resistance in lung cancer patients with epidermal growth factor receptor (EGFR) mutations, but its underlying mechanism remains unclear. The purpose of this work was to investigate the mechanism by which PARP1 regulates EGFR-TKI resistance to identify potential targets for combating drug resistance. The GEO databases, TCGA databases, western blot and qPCR studies were used to investigate the expression of PARP1 in lung cancer cells and tissues and its correlation with the prognosis of lung cancer. The expression of PARP1 in lung cancer TKI resistant cell PC9-ER and TKI sensitive cell PC9 was analyzed by qPCR and western blot. After knocking down of PARP1, CCK-8 assays, colony formation, flow cytometry were used to investigate its impact on erlotinib sensitivity, cell survival, cell cycle, and apoptosis. RNA-seq was used to investigate the mechanism by which PARP1 participates in EGFR-TKI resistance, and the results were validated in vitro and in vivo studies. PARP1 was highly expressed in both lung cancer tissues and cells. Subsequently, increased PARP1 expression was observed in PC9-ER compared with its parental cell line. Knockdown of PARP1 increased erlotinib sensitivity, promoted cell apoptosis, and suppressed cell growth. RNA-seq and previous studies have shown that the PI3K/AKT/mTOR/P70S6K pathway is involved in PARP1-mediated TKI resistance, and these results were confirmed by Western blot in vitro and in vivo. PARP1 may serve as a potential therapeutic target for reversing EGFR-TKI resistance in NSCLC via the PI3K/AKT/mTOR/P70S6K pathway.

Abstract 1829: Brusatol overcomes tyrosine kinase inhibitors resistance in myeloid leukemia cells by inhibiting translation of fast turnover protein cyclin D1 and Mcl-1

Abstract Myeloid leukemia is characterized with fast proliferation and apoptosis evasion, which are controlled by mutant or activated tyrosine kinase signalings. Tyrosine kinase inhibitors (TKI) targeting BCR-ABL in chronic myeloid leukemia (CML) and FLT3-ITD in acute myeloid leukemia (AML) significantly improved the therapy, but not cure, due to the general resistance. Overactivated mTOR protein translation pathway is believed to be one of the mechanisms causing resistance and that targeting protein translation should be one effective approach to overcome resistance. Brusatol is a quassinoid extracted from the fruit of Brucea javanica and an inhibitor of protein translation. We tested its antiproliferation and apoptosis induction in a variety of AML and CML cell lines as well as in TKI resistant cell lines. Brusatol effectively inhibits the growth of seven leukemia cell lines with GI50 values less than 20 nM. Brusatol induces apoptosis in AML cell lines and induces G0/G1 phase arrest in CML cell lines. Brusatol decreases the levels of fast turnover protein cyclin D1 and Mcl-1. In FLT3-ITD inhibitor sorafenib resistant MOLM-13/Sor cell line brusatol exhibits similar growth inhibition and apoptosis induction with the parental MOLM-13 cells, associated with inhibition of Mcl-1 and FLT3-ITD proteins. In BCR-ABL inhibitor imatinib resistant K562/STI cell line brusatol is effective as in parental K562 cells, associated with inhibition of cyclin D1 and BCR-ABL proteins. Brusatol at 2 mg/kg effectively inhibit tumor growth of K562 xenografts without causing toxicity to normal organs. These data indicate that brusatol inhibits oncogenic protein translation and has potential to be used to treat TKI resistant leukemia. Citation Format: Huiming Hua, Ying Yang, Guangfuxin Lin, Jingyi Zhang, Samuel Waxman, Yongkui Jing. Brusatol overcomes tyrosine kinase inhibitors resistance in myeloid leukemia cells by inhibiting translation of fast turnover protein cyclin D1 and Mcl-1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1829.

Abstract 1958: EGFR and mTOR signaling facilitate RET-independent resistance to selective RET-TKIs

Abstract RET fusions are an oncogenic driver mutation occurring in 1-2% non-small cell lung cancer (NSCLC). Currently, RET-selective tyrosine kinase inhibitors (TKIs) selpercatinib and pralsetinib are approved for this patient population, demonstrating favorable antitumor activity and safety profiles in advanced RET fusion-positive NSCLC. However, tumors eventually become refractory to selective RET inhibitor monotherapy. We sought to identify signaling pathways which mediate RET-independent acquired resistance to RET inhibitors and effective therapeutic combinations to overcome resistance. Using LC-2/ad (CCDC6-RET) NSCLC cells, we assessed the expression and activation of critical signaling pathways at a proteomic level following RET knockdown using reverse-phase protein array. RET knockdown resulted in rapidly increased adaptive upregulation of EGFR, HER2, MET, mTOR and MEK pathway signaling; observations were confirmed by Western Blotting. To determine whether EGFR or MET signaling facilitate RET inhibitor resistance, LC-2/ad and NCCE-TH1101 (KIF5B-RET) NSCLC cells were treated with increasing concentrations of selpercatinib or pralsetinib with or without ligands for these receptors, EGF or HGF respectively, and after five days cell viability was measured by CellTiter Glo. EGFR and MET signaling promoted RET TKI resistance in both cell lines. Next, to evaluate whether blockade of EGFR or MET signaling could enhance the activity of RET inhibitors, we treated LC-2/ad and NCCE-TH1101 cells with RET TKIs alone or in combination with the EGFR TKI erlotinib or poziotinib, or the MET inhibitor SU11274. We observed an additive effect with EGFR but not MET inhibitors when combined with RET TKIs. Western blot analysis revealed that EGFR signaling could reactivate mTOR and MAPK signaling after RET TKI treatment. Therefore, we next tested whether inhibition of these downstream pathways might enhance RET TKI sensitivity. We observed that treatment of LC-2/ad and NCCE-TH1101 cells with an mTOR inhibitor (everolimus) or a MEK inhibitor (trametinib) in combination with RET TKIs increased the anti-tumor activity or RET inhibitors. Finally, we established cells with acquired resistance to selpercatinib and pralsetinib. RET TKI resistant cells did not harbor secondary RET fusion mutations but underwent epithelial to mesenchymal transition and exhibited pan-RET inhibitor resistance. Moreover, RET TKI resistant cells showed increased cell surface expression of EGFR and MET by flow cytometry. RET TKI resistant cells were sensitive to mTOR or MEK inhibitors in combination with RET TKIs. Collectively, our findings indicate that in RET-fusion positive NSCLC tumor cells, activation of bypass pathways including the EGFR, MAPK, mTOR pathways may facilitate RET inhibitor resistance and that blockade of bypass pathways may enhance the efficacy of selective RET inhibitors and overcome acquired RET TKI resistance. Citation Format: Tomohiro Takehara, Monique B. Nilsson, Ximeng Liu, Hibiki Udagawa, Naoto Morikawa, Alissa Poteete, Junqin He, Xiaoxing Yu, Thiru Arumugam, Koichi Goto, John V. Heymach. EGFR and mTOR signaling facilitate RET-independent resistance to selective RET-TKIs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1958.

SHP2 Inhibition Overcomes Adaptive and Acquired Resistance to FLT3 TKI to Improve Efficacy Against FLT3/ITD AML

FMS-like tyrosine kinase-3 (FLT3) is a receptor tyrosine kinase (RTK) that is frequently mutated in acute myeloid leukemia (AML), with the internal tandem mutation (FLT3/ITD) conferring a poor prognosis to AML patients. This makes FLT3/ITD AML a validated target for treatment with tyrosine kinase inhibitors (TKI), but their success has been hindered by mechanisms of resistance including rapid signal reprogramming known as adaptive resistance and acquired resistance gained through long-term treatment. Past work from our lab has shown that FLT3/ITD cells undergo adaptive resistance, through the rapid reactivation of ERK signaling within 24 hours of sustained FLT3 inhibition. To improve therapy of FLT3/ITD AML it is important to identify therapeutic targets that overcome this ERK reactivation. Since adaptive ERK reactivation is often due to the relief of negative feedback loops that result in the activation of other RTK, we performed an RTK phospho-array on the FLT3/ITD cell line MV4;11. 48-hour treatment with the FLT3 TKI sorafenib resulted in increased activation of IGF-R, HER3 and AXL. While recent work from our lab found that combining AXL and FLT3 inhibition abrogated the ERK reactivation and exerted greater antileukemic effects, the activation of multiple RTKs suggests that targeting a signaling hub that inhibits multiple RTKs at once will likely prove more efficacious in overcoming this adaptive response. Recent literature has implicated SH2-containing protein tyrosine phosphatase 2 (SHP2) as a therapeutic target in adaptive ERK reactivation in other cancers. SHP2 acts directly downstream of RTKs and is involved in the activation of the ERK pathway. Therefore, we explored whether the addition of an SHP2 inhibitorto FLT3 TKI can overcome the adaptive response and increase treatment efficacy. To explore this possibility, we first treated the FLT3/ITD cell lines Molm14 and MV4;11 as well as FLT3/ITD patient samples with FLT3 TKI alone or in combination with an SHP2 inhibitor for 24 hours. The addition of SHP099 to sorafenib decreased the expected ERK reactivation in a dose-dependent manner. Furthermore, combination treatment with synergized to decrease proliferation and increase apoptosis in the FLT3/ITD cell lines. Impressively, in a long-term assay, treatment with the combination for just 72 hours greatly reduced leukemic cell recovery. To determine whether this combination would improve efficacy in vivo, we engrafted NSG mice with Molm14 cells and treated them for 4 weeks via oral gavage. The combination of SHP099 with gilteritinib group resulted in a statistically significantly lower leukemia burden compared to either treatment alone and the vehicle control. The combination group also had prolonged survival compared to the other groups. In addition to rapid adaptive resistance, there are mechanisms of acquired resistance that render traditional FLT3 TKI treatments ineffective against FLT3/ITD AML cells. We next examined the effects of SHP2 inhibition on FLT3-TKI resistant cells models that were generated by growing and maintaining Molm14 and MV4;11 cells in the presence of FLT3 TKI. The combination of FLT3 TKI and SHP099 resensitized the cells to FLT3 TKI, resulting in decreased ERK phosphorylation, decreased proliferation and increased apoptosis of these FLT3 TKI resistant cells. We also explored the effects of treating the FLT3/ITD mutant cell lines with the combination of SHP099 and several of the cytotoxic chemotherapy agents typically used in the treatment of AML including cytarabine and daunorubicin. While daunorubicin or cytarabine alone had little effect on the level of phosphorylated ERK, the addition of SHP099 decreased ERK activation and the combination synergized to exert greater to decrease proliferation and increase apoptosis. These studies reveal that combining FLT3 TKI treatment with an allosteric SHP2 inhibitor decreases the adaptive ERK reactivation observed in FLT3/ITD cells. The finding that SHP099 synergized with both FLT3 TKI and chemotherapy agents in different FLT3-mutated AML models speaks to the versatile efficacy of SHP2 inhibition in multiple AML models. Taken together, the data suggests that SHP2 inhibition can help overcome both adaptive and acquired resistance in FLT3/ITD AML and is a candidate to try to improve patient outcomes.

PD17-07 COMBINATION THERAPY FOR TKI RESISTANT KIDNEY CANCER VIA BLOCKING ERΒ/CIRCRNA-DGKD/MIR-125-5P/VE-CADHERIN SIGNAL INDUCED VASCULOGENIC MIMICRY

You have accessJournal of UrologyCME1 Apr 2023PD17-07 COMBINATION THERAPY FOR TKI RESISTANT KIDNEY CANCER VIA BLOCKING ERΒ/CIRCRNA-DGKD/MIR-125-5P/VE-CADHERIN SIGNAL INDUCED VASCULOGENIC MIMICRY Jie Ding, Yixi Hu, Chawnshang Chang, Edward M. Messing, Jean Joseph, and Shuyuan Yeh Jie DingJie Ding More articles by this author , Yixi HuYixi Hu More articles by this author , Chawnshang ChangChawnshang Chang More articles by this author , Edward M. MessingEdward M. Messing More articles by this author , Jean JosephJean Joseph More articles by this author , and Shuyuan YehShuyuan Yeh More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003272.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Tyrosine kinase inhibitors (TKIs), pazopanib and sunitinib, are widely used in renal cell carcinoma (RCC) therapy by inhibiting tumor angiogenesis. However, most patients become insensitive or develop resistance toward TKI therapy eventually, and the underlying mechanisms have not yet been fully elucidated. Our goal is to reveal the molecular mechanisms of TKI resistant RCC to find a potential combination therapy for TKI-resistant RCC. METHODS: The human RCC cell lines: 786-O, A498, Caki-1, and SW-839 were used. Lentiviral plasmids were used to generate gene engineering tools. The qPCR and Western blot were used to evaluate the gene expressions at RNA and protein levels, respectively. Vasculogenic mimicry (VM) assays were performed to examine vascular-like structure formation ability of cancer cells. Protein-DNA binding complexes were detected by Chromatin immunoprecipitation (ChIP) assays. The human DGKD promoter region was cloned into pGL3 vector for Luciferase Assays. Preclinical mouse RCC model was used to evaluate the anti-cancer effect of pazopanib and circRNA-DGKD blockage in TKI resistant RCC. RESULTS: TKI resistant RCC cells showed increased ability of forming VM to counteract the TKI-suppression function both in vivo and in vitro. Mechanism dissection revealed that pazopanib (or sunitinib)-resistant RCC cells had an increased ERβ, consequently enhancing the circRNA-DGKD expression. In turn, circRNA-DGKD could increase VE-cadherin expression via sponging the miR-125-5p. Supportively, targeting circRNA-DGKD intercepted the RCC VM formation, reduced metastases and improved survival in an orthotopic RCC mouse model. Collectively, the findings may aid in the development of novel therapies for metastatic or TKI-resistant RCC. CONCLUSIONS: Our study reveals that the resistance to TKIs (pazopanib or sunitinib) occurs by increasing vasculogenic mimicry (VM) ability to counteract the TKI angiogenesis suppression function. Furthermore, we find a potential therapy to more effectively treat TKI resistant RCC by blocking ERβ/circRNA-DGKD/miR-125-5p/VE-cadherin pathway together with pazopanib administration. Source of Funding: This work was partially supported by URMC Urology Department Research fund and George H. Whipple Professorship Endowment © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e498 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Jie Ding More articles by this author Yixi Hu More articles by this author Chawnshang Chang More articles by this author Edward M. Messing More articles by this author Jean Joseph More articles by this author Shuyuan Yeh More articles by this author Expand All Advertisement PDF downloadLoading ...

A novel coumarin derivative DBH2 inhibits proliferation and induces apoptosis of chronic myeloid leukemia cells

With the development of tyrosine kinase inhibitor (TKI) resistance, finding the novel effective chemotherapeutic agent is of seminal importance for chronic myelogenous leukemia (CML) treatment. This study aims to find the effective anti-leukemic candidates and investigate the possible underlying mechanism. We synthesized the novel coumarin derivatives and evaluated their anti-leukemic activity. Cell viability assay revealed that compound DBH2 exhibited the potent inhibitory activity on the proliferation of CML K562 cells and TKI resistant K562 cells. Morphological observation and flow cytometry confirmed that DBH2 could selectively induce cell apoptosis and cell cycle arrest at G2/M phase of the K562 cells, which was further confirmed on the bone marrow cells from CML transgenic model mice and CD34+ bone marrow leukemic cells from CML patients. Treatments of DBH2 in combination with imatinib could prolong the survival rate of SCL-tTA-BCR/ABL transgenic model mice significantly. Quantitative RT-PCR revealed that DBH2 inhibited the expression of STAT3 and STAT5 in K562 cells, and caspase-3 knockout alleviated the DBH2 induced apoptosis. Furthermore, DBH2 could induce the expression of PARP1 and ROCK1 in K562 cells, which may play the important role in caspase-dependent apoptosis. Our results concluded that coumarin derivative DBH2 serves as a promising candidate for the CML treatment, especially in the combination with imatinib for the TKI resistant CML, and STAT/caspase-3 pathway was involved in the molecular mechanism of anti-leukemic activity of DBH2.

Genome‑wide expression and methylation analyses reveal aberrant cell adhesion signaling in tyrosine kinase inhibitor‑resistant CML cells

Although chronic myeloid leukemia (CML) can be effectively treated using BCR-ABL1 kinase inhibitors, resistance due to kinase alterations or to BCR-ABL1 independent mechanisms remain a therapeutic challenge. For the latter, the underlying mechanisms are widely discussed; for instance, gene expression changes, epigenetic factors and alternative signaling pathway activation. In the present study, in vitro-CML cell models of resistance against the tyrosine kinase inhibitors (TKIs) imatinib (0.5 and 2 µM) and nilotinib (0.1 µM) with biological replicates were generated to identify novel mechanisms of resistance. Subsequently, genome-wide mRNA expression and DNA methylation were analyzed. While mRNA expression patterns differed largely between biological replicates, there was an overlap of 71 genes differentially expressed between cells resistant against imatinib or nilotinib. Moreover, all TKI resistant cell lines demonstrated a slight hypermethylation compared with native cells. In a combined analysis of 151 genes differentially expressed in the biological replicates of imatinib resistance, cell adhesion signaling, in particular the cellular matrix protein fibronectin 1 (FN1), was significantly dysregulated. This gene was also downregulated in nilotinib resistance. Further analyses showed significant FN1-downregulation in imatinib resistance on mRNA (P<0.001) and protein level (P<0.001). SiRNA-mediated FN1-knockdown in native cells reduced cell adhesion (P=0.02), decreased imatinib susceptibility visible by higher Ki-67 expression (1.5-fold, P=0.04) and increased cell number (1.5-fold, P=0.03). Vice versa, recovery of FN1-expression in imatinib resistant cells was sufficient to partially restore the response to imatinib. Overall, these results suggested a role of cell adhesion signaling and fibronectin 1 in TKI resistant CML and a potential target for novel strategies in treatment of resistant CML.

Abstract 1827: CD70 is a novel therapeutic target for EGFR mutant NSCLC with acquired, EMT-associated EGFR TKI resistance

Abstract Approximately 15% of all patients with non-small cell lung cancer (NSCLC) and nearly 35% of Asian patients with NSCLC harbor activating mutations within the epidermal growth factor receptor (EGFR). Although these patients are initially highly sensitive to first or second generation EGFR tyrosine kinase inhibitors (TKIs) including erlotinib or third-generation inhibitors including osimertinib, EGFR TKI-refractory disease inevitably emerges. While therapeutic strategies to target resistant disease that emerges though secondary EGFR mutations or MET amplification have been developed, there remains a void of therapeutic options for patients where resistance occurs through EGFR-independent mechanism such as epithelial to mesenchymal transition (EMT) or transformation to small cell lung cancer (SCLC). To identify cell surface proteins that could be targeted by antibody-based or adoptive cell therapy approaches we interrogated RNAseq data from EGFR mutant NSCLC cell lines (HCC827 and HCC4006) and their associated EGFR TKI resistant variants previously shown to have developed resistance through EMT and filtered gene expression data to include only genes which transcribed proteins localized to the cell surface. We identified CD70 as a being highly upregulated in EGFR TKI resistant cells (p = 7.2e-42). Given that CD70 expression is highly restricted and only transiently expressed on immune cells, CD70 was selected as a top candidate cell surface protein for targeting studies. Western blotting and flow cytometry analysis confirmed CD70 protein levels to be highly upregulated in EGFR TKI resistant cells that had undergone EMT but not in cells harboring secondary EGFR mutations or MET amplifications. We also observed CD70 upregulation in osimertinib-treated drug tolerant persister cells, indicating that CD70 upregulation is an early event in the evolution of TKI resistance. Moreover, patient-derived models of acquired EGFR TKI resistance also exhibited CD70 positivity. Our data also indicated that in EGFR mutant NSCLC cells, CD70 could be upregulated through decreased CD70 promoter methylation as well as by the EMT regulators, transforming growth factor-β (TGF-β) and ZEB1, both of which were upregulated in TKI resistant cells. In EGFR TKI resistant cells, CD70 knockdown impaired cell viability and invasiveness, and stimulation of CD70 using the exogenous binding partner CD27 resulted in activation of AKT and MAPK, pathways known to be re-activated with acquired TKI resistance. CD70-targeting approaches including anti-CD70 antibody drug conjugates (ADCs) and CD70-targeting CAR T cell and CAR NK cells showed promising in vitro and in vivo activity against CD70 positive tumor cells and in osimertinib drug-tolerant persister cells. These results identify CD70 as a novel therapeutic target for EGFR mutant tumors with acquired EGFR TKI resistance that merits further investigation in the clinic. Citation Format: Monique B. Nilsson, Yan Yang, Sonia Patel, Simon Heeke, Xiuning Le, Thiru Aruguman, Jacqulyne Robichaux, Xiaoxing Yu, Alissa Poteete, Xiaoyang Ren, Lixia Diao, Li Shen, Qi Wang, Fahao Zhang, Leticia Campos Clemente, Luisa Solis Soto, Chunhua Shi, Hai Tran, Jason Bock, Jing Wang, Ignacio I. Wistuba, John D. Minna, John V. Heymach. CD70 is a novel therapeutic target for EGFR mutant NSCLC with acquired, EMT-associated EGFR TKI resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1827.

Abstract CT559: Capmatinib plus osimertinib vs platinum-pemetrexed doublet chemotherapy as second-line therapy in patients with stage IIIB/IIIC or IV EGFR-mutant, T790M-negative NSCLC harboring MET amplification

Abstract Background: MET amplification can arise as a bypass resistance mechanism to EGFR tyrosine kinase inhibitors (TKIs) and occurs in ~5-26% of EGFR TKI resistant EGFR-mutant non-small cell lung cancer (NSCLC). These patients (pts) have limited treatment options, particularly in the EGFR T790M negative (T790M−) setting. Capmatinib, a MET inhibitor, is approved in more than 10 countries for the treatment of metastatic MET exon 14 skipping NSCLC. In preliminary studies, capmatinib plus EGFR TKIs showed antitumor activity in the post-EGFR TKI, EGFR-mutant NSCLC setting. GEOMETRY-E (NCT04816214) is a randomized, controlled, open-label, multicenter, phase 3 study evaluating the efficacy and safety of capmatinib + osimertinib vs platinum-pemetrexed doublet chemotherapy as second line treatment in the advanced NSCLC setting. Methods: This ongoing study began enrollment in September 2021 and is recruiting adult pts with stage IIIB/IIIC or IV EGFR-mutant, T790M−, MET-amplified NSCLC who had progressed on either 1st/2nd generation EGFR TKIs, osimertinib or other 3rd generation EGFR TKIs. Pts with neurologically unstable, symptomatic CNS metastases or those requiring increasing doses of steroids ≤2 weeks prior to study entry to manage CNS symptoms are ineligible. This is a 2-part study where Part 1 (initial run-in, ~10 pts) will confirm the recommended dose for the randomized Part 2 and evaluate the safety and tolerability of capmatinib + osimertinib. In Part 1, pts will receive oral capmatinib 400 mg twice daily + osimertinib 80 mg once daily in 21-day cycles. Part 2 will evaluate the efficacy and safety of capmatinib + osimertinib vs platinum (cisplatin/carboplatin)-pemetrexed. Part 2 will enroll ~225 pts, in 2:1 randomization, stratified by the presence of brain metastases (yes/no) and prior treatment with 3rd generation EGFR TKIs (yes/no). In Part 1, the primary endpoint is the incidence of dose limiting toxicities during the first 21 days of treatment. Secondary endpoints include safety; tolerability; pharmacokinetics (PK); investigator-assessed overall response rate (ORR), duration of response (DOR), time to response (TTR), disease control rate (DCR) and progression-free survival (PFS) per the Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1). In Part 2, the primary endpoint is blinded independent review committee (BIRC)-assessed PFS per RECIST 1.1. The key secondary endpoints are ORR by BIRC per RECIST 1.1 and overall intracranial response rate (OiRR) by BIRC per Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM). Other secondary endpoints include DOR, TTR and DCR by BIRC; investigator-assessed PFS after next line of treatment; PK; safety; overall survival; patient-reported outcomes; intracranial DCR, duration of and time to intracranial response by BIRC per RANO-BM. Citation Format: Yi-Long Wu, Ji-Youn Han, Terufumi Kato, Fabrice Barlesi, Edward B. Garon, Federico Cappuzzo, Yuji Shibata, Nathalie Smith, Sadhvi Khanna, Riccardo Belli, Alejandro Yovine, Daniel Tan. Capmatinib plus osimertinib vs platinum-pemetrexed doublet chemotherapy as second-line therapy in patients with stage IIIB/IIIC or IV EGFR-mutant, T790M-negative NSCLC harboring MET amplification [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT559.

Abstract 548: EGFR CAR-NK cells demonstrate potent activity against EGFR TKI resistant NSCLC

Abstract The leading cause of cancer-related deaths in the US is non-small cell lung cancer (NSCLC), and about 10-15% of NSCLC cases harbor EGFR activating mutations. While these patients are initially responsive to EGFR tyrosine kinase inhibitors (TKIs), they eventually experience progression and develop acquired TKI resistance. Currently, there are no approved therapies for NSCLC patients with acquired resistance to the third-generation EGFR TKI osimertinib (OSI). Moreover, EGFR-TKI resistant NSCLCs are refractory to immune checkpoint inhibitors. Therefore, novel treatment strategies are urgently needed. Chimeric antigen receptors (CARs) have been used to enhance the anti-tumor activity of immune effector cells. Here, we developed CAR-based therapies targeting EGFR as a novel strategy to overcome immune suppression and target EGFR TKI-resistant NSCLC. We designed multi-generational EGFR CAR constructs and transduced them into T and natural killer (NK) cells to generate CAR-T and CAR-NK cells, respectively. We then evaluated their activity against NSCLC cell lines in vitro using firefly luciferase assays. EGFR CAR-T and CAR-NK cells showed potent cytotoxicity against NSCLC cells expressing EGFR including EGFR wild-type and mutant NSCLCs, as well as NSCLC cells with acquired resistance to OSI. However, EGFR CAR-T cells showed decreased killing activity against OSI-resistant NSCLC cells compared to their parental cells. In contrast, EGFR CAR-NK cells showed stronger cytotoxicity against NSCLC with acquired OSI resistance as compared to parental cells. Transcriptomic analysis revealed that NSCLC cells with acquired resistance to TKI had undergone epithelial-mesenchymal transition and had downregulated expression of genes related to antigen presentation and upregulated expression of B7-H6 (NCR3LG1), which have been reported to be associated with increased responsiveness to NK cells. Moreover, treatment of TKI resistant cells with OSI resulted in upregulation of cell surface EGFR and potentiated CAR-NK cells-mediated killing. TGF-β is a critical immune-suppressive cytokine. We found that EGFR-TKI resistant NSCLC cells elaborated expression of TGF-β as compared to parental cells. Blockade of the TGF-β pathway using galunisertib significantly enhanced the activity of EGFR CAR-NK cells against OSI-resistant NSCLC cells. Next, we engineered the dominant-negative TGF-β receptor II (DNTGFBRII) into our EGFR CAR constructs. The expression of DNTGFBRII inhibited the phosphorylation of SMAD2 and the downregulation of granzyme B and perforin induced by TGF-β. DNTGFBRII-CAR-NK cells showed higher killing activity against OSI-resistant NSCLC cells and were resistant to TGF-β-mediated immunosuppression. In conclusion, EGFR CAR-NK cells show significant anti-tumor activity to EGFR TKI-resistant NSCLC cells, and the cytotoxicity is enhanced in combination with OSI treatment and blockade of the TGF-β pathway. Citation Format: Yan Yang, Monique Nilsson, Sonia Patel, Jacqulyne Robichaux, Alissa Poteete, Xiaoxing Yu, Fahao Zhang, Simon Heeke, Yu Qian, Junqin He, John Heymach. EGFR CAR-NK cells demonstrate potent activity against EGFR TKI resistant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 548.

Capmatinib plus osimertinib versus platinum-pemetrexed doublet chemotherapy as second-line therapy in patients with stage IIIb/IIIc or IV EGFR-mutant, T790M-negative NSCLC harboring MET amplification.

TPS9153 Background: MET amplification can arise as a bypass resistance mechanism to EGFR tyrosine kinase inhibitors (TKIs) and occurs in ̃5-26% of EGFR TKI resistant EGFR-mutant non-small cell lung cancer (NSCLC). These patients (pts) have limited treatment options, particularly in the EGFR T790M negative (T790M−) setting. Capmatinib, a MET inhibitor, is approved in about ten countries for the treatment of metastatic MET exon 14 skipping NSCLC. In preliminary studies, capmatinib plus EGFR TKIs showed antitumor activity in the post-EGFR TKI, EGFR-mutant NSCLC setting. GEOMETRY-E (NCT04816214) is a randomized, controlled, open-label, multicenter, phase 3 study evaluating the efficacy and safety of capmatinib + osimertinib vs platinum-pemetrexed doublet chemotherapy as second line treatment for advanced NSCLC. Methods: This ongoing study began enrollment in September 2021 and is recruiting adult pts with stage IIIB/IIIC or IV EGFR-mutant, T790M−, MET-amplified NSCLC who had progressed on either 1st/2nd generation EGFR TKIs, osimertinib or other 3rd generation EGFR TKIs. Pts with neurologically unstable, symptomatic CNS metastases or those requiring increasing doses of steroids ≤2 weeks prior to study entry to manage CNS symptoms are ineligible. This is a 2-part study where Part 1 (initial run-in,̃10 pts) will confirm the recommended dose for the randomized Part 2 and evaluate the safety and tolerability of capmatinib + osimertinib. In Part 1, pts will receive oral capmatinib 400 mg twice daily + osimertinib 80 mg once daily in 21-day cycles. Part 2 will evaluate the efficacy and safety of capmatinib + osimertinib vs platinum (cisplatin/carboplatin)-pemetrexed. Part 2 will enroll ̃225 pts, in 2:1 randomization, stratified by the presence of brain metastases (yes/no) and prior treatment with 3rd generation EGFR TKIs (yes/no). In Part 1, the primary endpoint is the incidence of dose limiting toxicities during the first 21 days of treatment. Secondary endpoints include safety; tolerability; pharmacokinetics (PK); investigator-assessed overall response rate (ORR), duration of response (DOR), time to response (TTR), disease control rate (DCR) and progression-free survival (PFS) per the Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1). In Part 2, the primary endpoint is blinded independent review committee (BIRC)-assessed PFS per RECIST 1.1. The key secondary endpoints are ORR by BIRC per RECIST 1.1 and overall intracranial response rate (OiRR) by BIRC per Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM). Other secondary endpoints include DOR, TTR and DCR by BIRC; investigator-assessed PFS after next line of treatment; PK; safety; overall survival; patient-reported outcomes; intracranial DCR, duration of and time to intracranial response by BIRC per RANO-BM. Clinical trial information: NCT04816214.

74TiP Capmatinib plus osimertinib vs platinum-pemetrexed doublet chemotherapy as second-line therapy in patients with stage IIIB/IIIC/IV EGFR-mutant, T790M-negative, MET-amplified NSCLC

MET amplification can arise as a bypass mechanism of resistance to EGFR tyrosine kinase inhibitors (TKIs) occurring in ∼5–26% of patients (pts) with EGFR TKI resistant EGFR-mutant non-small cell lung cancer (NSCLC). Few treatment options exist for these pts, particularly in the EGFR T790M negative (T790M−) setting. Capmatinib, a MET inhibitor, is approved in more than 10 countries for the treatment of metastatic MET exon 14 skipping NSCLC. Preliminary studies have shown that capmatinib plus EGFR TKIs demonstrated antitumor activity in pts with EGFR TKI resistant EGFR-mutant NSCLC.

MiR-519d-3p enhances the sensitivity of non-small-cell lung cancer to tyrosine kinase inhibitors.

Non-small cell lung cancer (NSCLC) is the leading cause of cancer mortality worldwide. Tyrosine kinase inhibitors (TKIs) are currently the most effective chemotherapy for NSCLC. However, most cancer patients develop TKI resistance at tumor relapse stage. We firstly measured the expression change of miR-519d-3p in TKI resistance NSCLC cells. We then ectopically expressed miR-519-3p in TKI resistant cells to study its functional impact on cell proliferation, migration, invasion and cell sensitivity to gefitinib. The downstream target of miR-519-3p was identified by bioinformatics and validated in luciferase reporter assay and western blotting analysis. We also studied the reversing effect of the candidate target in NSCLC cells expressing miR-519d-3p. Lastly, we compared the miR-519d-3p level in NSCLC patients with good or poor response to gefitinib. miR-519d-3p level was downregulated in TKI resistant NSCLC cells. The restoration of miR-519d-3p in these NSCLC cells inhibited cell proliferation, invasion and migration; enhanced cell sensitivity to gefitinib. EPAS1 was identified and validated as downstream target of miR-519d-3p. Co-expressing EPAS1 antagonized the inhibitory effect of miR-519d-3p on NSCLC cells. MiR-519d-3p was downregulated in NSCLC patients with poor response to gefitinib. Targeting miR-519d-3p/EPAS1 axis may provide alternative treatment for TKI-resistant NSCLC.

Aurora A Kinase As a Promising Therapeutic Target in Philadelphia Chromosome Positive Leukemia Cells

Introduction: ABL tyrosine kinase inhibitor (TKI), imatinib and second-generation ABL TKIs, such as nilotinib and dasatinib have demonstrated the potency against chronic myeloid leukemia (CML) and Philadelphia chromosome (Ph) positive acute lymphoblastic leukemia (Ph+ALL) patients. However, resistance to ABL TKI can develop in CML patients due to BCR-ABL point mutations. Moreover, ABL TKIs do not eliminate the leukemia stem cells (LSCs). Residual CML cells are present in bone marrow microenvironment. These cells are contained within a niche in the bone marrow and are often impervious to current treatments. Aurora kinases are novel family of serine/threonine kinases that play a critical role in regulating many of the processes that are pivotal to mitosis. Aurora kinases comprises three members, designated aurora A, B, and C. Amplification of aurora kinase gene is oncogenic and has been observed in several cancers including hematologic malignancies. Therefore, new approach to the treatment for Ph-positive cells with aurora kinase inhibitors may improve the outcome of leukemia patients.Materials and methods: In this study, we investigated whether aurora kinase inhibitor could suppress Ph-positive leukemia cells including T315I mutation and primary samples.Results: One of aurora kinase A inhibitor, alisertib inhibits proliferation of leukemia cells. We found alisertib treatment inhibited the growth of Ph-positive leukemia cells in a dose dependent manner and phosphorylation of aurora kinase A was reduced. Alisertib inhibits proliferation in imatinib resistant cells including T315I mutation. In the cell cycle analysis, alisertib induces a G2/M phase arrest in Ph-positive cells. Intracellular ROS levels were also increased in a dose dependent manner. Combined treatment of Ph-positive cells with ABL tyrosine kinase inhibitors, imatinib or ponatinib and alisertib caused significantly more cytotoxicity than each drug alone. Apoptotic and Caspase 3/7 positive cells were also increased. Ph-positive cells were treated with alisertib and cellular senescence was determined by senescence- associated β-galactosidase (SA-β-gal) staining. Senescent cells were increased in a time and dose dependent manner. SA-β-gal positive cells were reduced by N-Acetyl-L-cysteine treatment. Small interfering RNA mediated knockdown of the Aurora A gene causes a proliferation defect and enhances ABL TKI activity in Ph-positive cells. We next examined tumor formation in mice model. We injected subcutaneously 1×107 T315I mutant cells in nude mice. A dose of 20 mg/kg/day p.o of ponatinib and 30 mg/kg/day p.o of alisertib inhibited tumor growth and reduced tumor volume compared with control mice. We also found that co-treatment with ponatinib and alisertib increased mouse survival. Co-treatment with ponatinib and alisertib showed reduced mouse spleen weight and size. The treatments were well tolerated with no animal health concerns observed.Conclusion: The results of our study indicate that the aurora kinase inhibitor may be a powerful strategy against ABL TKI resistant cells including T315I mutation and enhance cytotoxic effects of ABL TKI against those Ph-positive leukemia cells. DisclosuresTauchi:Otsuka pharmaceutical KK: Honoraria, Research Funding, Speakers Bureau; Bristol-Myers Squibb KK: Honoraria, Research Funding, Speakers Bureau; Novartis pharma KK: Honoraria, Research Funding, Speakers Bureau; Phizer KK: Honoraria, Research Funding, Speakers Bureau. Ohyashiki:Bristol-Myers Squibb KK: Honoraria, Research Funding, Speakers Bureau; Phizer KK: Honoraria, Research Funding, Speakers Bureau; Novartis pharma KK: Honoraria, Research Funding, Speakers Bureau; Celegen KK: Consultancy, Honoraria, Research Funding, Speakers Bureau; Kyowa Hakko Kirin KK: Honoraria; Otsuka pharmaceutical KK: Honoraria; Jansen pharmaceutical KK: Honoraria, Research Funding; Celegen KK: Consultancy, Honoraria, Research Funding, Speakers Bureau; Phizer KK: Honoraria, Research Funding, Speakers Bureau; Fujirebio KK: Honoraria; Dainippon Sumitomo KK: Honoraria, Research Funding, Speakers Bureau; Nippon Shinyaku: Honoraria, Research Funding, Speakers Bureau; Taiho pharmaceutical KK: Honoraria; Alexion: Honoraria; MSD KK: Honoraria; Novartis pharma KK: Honoraria, Research Funding, Speakers Bureau; Bristol-Myers Squibb KK: Honoraria, Research Funding, Speakers Bureau; Otsuka pharmaceutical KK: Honoraria; Jansen pharmaceutical KK: Honoraria, Research Funding; Fujirebio KK: Honoraria; Nippon Shinyaku: Honoraria, Research Funding, Speakers Bureau; Chugai pharmaceutical KK: Research Funding; Dainippon Sumitomo KK: Honoraria, Research Funding, Speakers Bureau; Taiho pharmaceutical KK: Honoraria; Alexion: Honoraria; MSD KK: Honoraria; Kyowa Hakko Kirin KK: Honoraria; Chugai pharmaceutical KK: Research Funding.

Effective degradation of EGFRL858R+T790M mutant proteins by CRBN-based PROTACs through both proteosome and autophagy/lysosome degradation systems.

Targeted therapy of treating patients with specific tyrosine kinase inhibitors (TKIs) is currently the standard care for epidermal growth factor receptor (EGFR) mutant non-small cell lung cancer. However, the inevitably developed drug resistance in patients to EGFR TKIs is the biggest obstacle for cancer targeted therapy. About 60% of drug resistance to the 1st generation of EGFR TKIs was resulted from an acquired T790M mutation in the kinase domain of EGFR protein. Proteolysis targeting chimera (PROTAC) is a lately-developed technology to target point of interest proteins for degradation. Because EGFR-mutant lung cancers are highly dependent on EGFR proteins, designing specific PROTAC molecules to degrade EGFR proteins from cancer cells provides a very promising strategy to treat such patients and eradicate drug resistance. Currently, there is no cereblon (CRBN)-based PROTAC reported able to degrade T790M-containing EGFR resistant proteins. In this study, we synthesized two novel CRBN-based EGFR PROTACs, SIAIS125 and SIAIS126, based on EGFR inhibitor canertinib and cereblon ligand pomalidomide. These two degraders displayed potent and selective antitumor activities in EGFR TKI resistant lung cancer cells. Firstly, they could selectively degrade EGFRL858R+T790M resistant proteins in H1975cells at the concentration of 30-50nM, and EGFREx19del proteins in PC9 cells. But they did not degrade EGFREx19del+T790M mutant proteins in PC9Brca1 cells or wild type EGFR in A549 lung cancer cells. They could also selectively inhibit the growth of EGFR mutant lung cancer cells but not that of normal cells or A549cells. Secondly, the degradation of EGFRL858R+T790M proteins was long lasting up to 72h. Thirdly, these degraders displayed better inhibition of EGFR phosphorylation in H1975cells and PC9Brca1 cells comparing to canertinib. Finally, these degraders could also induce significant apoptosis and cell cycles arrest in H1975cells. Pre-incubation with canertinib, pomalidomide or ubiquitination inhibitor MLN4924 totally blocked EGFR degradation by PROTACs. Mechanistic studies showed that PROTAC could induce autophagy in lung cancer cells. PROTAC-induced EGFR degradation acted through both ubiquitin/proteosome system and ubiquitin/autophagy/lysosome system. Elevating autophagy activities enhanced EGFR degradation and cell apoptosis induced by PROTACs. Our research not only offered a novel PROTAC tool to target EGFR TKI drug resistance in lung cancer, but also firstly demonstrated that the involvement of autophagy/lysosome system in PROTAC- mediated target protein degradation.

Saikosaponin D exhibits anti-leukemic activity by targeting FTO/m6A signaling.

Purpose: The implementation of targeted therapies for acute myeloid leukemia (AML) has been challenging. Fat mass and obesity associated protein (FTO), an mRNA N6-methyladenosine (m6A) demethylase, functions as an oncogene that promotes leukemic oncogene-mediated cell transformation and leukemogenesis. Here, we investigated the role of Saikosaponin-d (SsD) in broad anti-proliferation effects in AML and evaluated the m6A demethylation activity by targeting FTO of SsD.Methods: It was examined whether and how SsD regulates FTO/m6A signaling in AML. The pharmacologic activities and mechanisms of actions of SsD in vitro, in mice, primary patient cells, and tyrosine kinase inhibitors-resistant cells were determined.Results: SsD showed a broadly-suppressed AML cell proliferation and promoted apoptosis and cell-cycle arrest both in vitro and in vivo. Mechanistically, SsD directly targeted FTO, thereby increasing global m6A RNA methylation, which in turn decreased the stability of downstream gene transcripts, leading to the suppression of relevant pathways. Importantly, SsD also overcame FTO/m6A-mediated leukemia resistance to tyrosine kinase inhibitors.Conclusion: Our findings demonstrated that FTO-dependent m6A RNA methylation mediated the anti-leukemic actions of SsD, thereby opening a window to develop SsD as an epitranscriptome-base drug for leukemia therapy.

The Pivotal Role of Nicotinamide Phosphoribosyl Transferase in Chronic Myeloid Leukemia Cells Under Hypoxic Condition

Introduction: ABL tyrosine kinase inhibitors (TKIs) improved outcomes for patients with chronic myeloid leukemia (CML) and Philadelphia chromosome (Ph)-positive leukemia. However, ABL TKIs do not eliminate the leukemia stem cells (LSCs) in the bone marrow, which may represent the most important event in leukemia relapse after TKI discontinuation. Bone marrow is also considered a tissue with limited oxygen supply. Therefore, new approach against leukemia stem cells, which is presented in bone marrow under hypoxia, may improve the outcome of CML patients. Nicotinamide phosphoribosyl transferase (NAMPT) is the rate limiting enzyme of the primary pathway for maintaining cellular NAD+ and that regulates intracellular adenosine triphosphate (ATP) levels in mammalian cells. It has been reported that NAMPT expression is upregulated in several human cancers. Materials and methods: In this study, we established ABL TKI resistantin vitrocell line models (K562 imatinib-R, K562 nilotinib-R, K562 ponatinib-R and Ba/F3 T315I) and used Ph-positive leukemia cell lines. We also investigated whether NAMPT inhibitor could suppress Ph-positive leukemia cells including T315I mutation and ABL TKI resistant under hypoxic condition. Results: In chemical library screen of compounds, NAMPT inhibitor, CHS828 is selected the candidate drug for ABL TKI resistant cells under hypoxic condition. Drug repositioning and repurposing can be an important part of any drug discovery. Therefore, we examined NAMPT efficacy by using Ph-positive leukemia cell lines. We first investigated the NAMPT expression by microarray gene expression data from the online Gene Expression Omnibus (GEO). Gene expression of NAMPT is increased in CML patients compared to normal samples from the public microarray datasets of GSE13159. Protein expression of NAMPT is found in Ph-positive leukemia cell lines including ABL TKI resistant cells. In hypoxia, gene expression of NAMPT was increased in Ph-positive cells compare to normoxic condition. We next examined efficacy of NAMPT inhibitor, CHS828 in Ph-positive leukemia cell lines. We found that CHS828 treatment for 72 h decreased cell viability of Ph-positive cell lines in a dose dependent manner. We also found that CHS828 inhibited the proliferation of ABL TKI resistant cells (K562 imatinib-R, K562 nilotinib-R, K562 ponatinib-R) and T315I mutant Ba/F3 cells under hypoxic condition. The rate of cell cycle progression was delayed and cells were blocked in G2/M phase. Nuclear factor-kappaB (NF-kB) is also implicated in cancer development. CHS828 inhibited constitutive NF-kB activity in the time and dose dependent manner. Intracellular ATP, which is the most important source of energy for cellular reactions, was drastically decreased after CHS828 treatment. NAD+ plays a vital role in diverse cellular processes that govern human health and disease. Intracellular NAD+ was decreased after CHS828 treatment. The wound healing effect was evaluated at 0, 24, 48, and 72 h by using NIH3T3 cells. In wound healing results, CHS828 treatment inhibited cellular migration of NIH3T3 cells. We next investigated the efficacy of ABL TKI and CHS828 against Ph-positive leukemia cell lines. ABL TKI and CHS828 treatment induced cellular growth inhibition compared with each drug alone. Caspase 3/7 activity was also increased after ABL TKIs and CHS828 treatment. ABL TKI and CHS828 reduced the colony formation ability of Ph-positive cells under hypoxic condition. Thein vivoefficacies of one of ABL TKI, ponatinib and CHS828 were evaluated in a mouse xenograft model. Ponatinib and CHS828 inhibited the growth of T315I mutant Ba/F3 cellsin vivomore than the control vehicle. We also found that co-treatment with ponatinib and CHS828 increased mouse survival. Combination treatment with ponatinib and CHS828 was also well tolerated, with no animal deaths in the treated mice. Conclusion: The results of our study indicate that the ABL TKI and CHS828 may be a powerful strategy against Ph-positive cells including ABL TKI resistant cells and provide the promising clinical relevance as a candidate drug for treatment of CML stem cells of the bone marrow microenvironment under hypoxic condition. Disclosures No relevant conflicts of interest to declare.

Activating JAK-mutations confer resistance to FLT3 kinase inhibitors in FLT3-ITD positive AML in vitro and in vivo.

An important limitation of FLT3 tyrosine kinase inhibitors (TKIs) in FLT3-ITD positive AML is the development of resistance. To better understand resistance to FLT3 inhibition, we examined FLT3-ITD positive cell lines which had acquired resistance to midostaurin or sorafenib. In 6 out of 23 TKI resistant cell lines we were able to detect a JAK1 V658F mutation, a mutation that led to reactivation of the CSF2RB-STAT5 pathway. Knockdown of JAK1, or treatment with a JAK inhibitor, resensitized cells to FLT3 inhibition. Out of 136 patients with FLT3-ITD mutated AML and exposed to FLT3 inhibitor, we found seven different JAK family mutations in six of the cases (4.4%), including five bona fide, activating mutations. Except for one patient, the JAK mutations occurred de novo (n = 4) or displayed increasing variant allele frequency after exposure to FLT3 TKI (n = 1). In vitro each of the five activating variants were found to induce resistance to FLT3-ITD inhibition, which was then overcome by dual FLT3/JAK inhibition. In conclusion, our data characterize a novel mechanism of resistance to FLT3-ITD inhibition and may offer a potential therapy, using dual JAK and FLT3 inhibition.

Delineation of cell death mechanisms induced by synergistic effects of statins and erlotinib in non-small cell lung cancer cell (NSCLC) lines.

Hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) have been shown to overcome tyrosine kinase inhibitor (TKI) resistance in epithelial growth factor receptor (EGFR) mutated non-small cell lung cancer (NSCLC) cells in vivo and in vitro. However, little is known about the putative induction of non-apoptotic cell death pathways by statins. We investigated the effects of pitavastatin and fluvastatin alone or in combination with erlotinib in three NSCLC cell lines and examined the activation of different cell death pathways. We assessed apoptosis via fluorometric caspase assay and poly (ADP-ribose) polymerase 1 (PARP) cleavage. Furthermore, annexinV/propidium iodide (PI) flow cytometry was performed. Small molecule inhibitors benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD), necrostatin 1 (Nec1), ferrostatin 1 (Fer1), Ac-Lys-Lys-Norleucinal (Calp1) were used to characterise cell death pathway(s) putatively (co-)activated by pitavastatin/erlotinib co-treatment. Synergism was calculated by additivity and isobolographic analyses. Pitavastatin and fluvastatin induced cell death in EGFR TKI resistant NSCLC cells lines A549, Calu6 and H1993 as shown by caspase 3 activation and PARP cleavage. Co-treatment of cells with pitavastatin and the EGFR TKI erlotinib resulted in synergistically enhanced cytotoxicity compared to pitavastatin monotherapy. Flow cytometry indicated the induction of alternative regulated cell death pathways. However, only co-treatment with mevalonic acid (Mev) or the pan-caspase inhibitor zVAD could restore cell viability. The results show that cytotoxicity mediated by statin/erlotinib co-treatment is synergistic and can overcome erlotinib resistance in K-ras mutated NSCLC and relies only on apoptosis.

The Role of Hypoxia on ABL Tyrosine Kinase Inhibitor Resistant Chronic Myeloid Leukemia Cells

Introduction: ABL tyrosine kinase inhibitors (TKIs) improved outcomes for patients with chronic myeloid leukemia (CML) and Philadelphia chromosome (Ph)-positive leukemia, however, some patients are still resistance to ABL TKIs. One of the most common mechanisms involves point mutations in the kinase domain of BCR-ABL1, however, mechanisms of intrinsic resistance without point mutation of ABL kinase domain are not fully understood. Moreover, ABL TKIs cannot cure the Ph-positive leukemia patients because of leukemia stem cells in the bone marrow niche. Therefore, new approach against leukemia stem cells may improve the outcome of Ph-positive leukemia patients. Hypoxia is an important component of the bone marrow microenvironment. Because oxygen tension plays a key role in driving normal hematopoiesis, leukemia stem cells may be maintained in hypoxic areas of the bone marrow. Materials and methods: In this study, we established ABL TKI-resistant in vitro cell line models (K562 imatinib-R, K562 nilotinib-R, K562 dasatinib-R, K562 ponatinib-R and Ba/F3 T315I). We investigated gene expression profiles in cultured ABL TKI resistant cells and parental cell line, K562 in normoxia and hypoxia condition by DNA microarray. Results: We first investigated gene expression profiles in cultured K562 cells in hypoxia condition. We found gene expression of insulin-like growth factor 1 (IGF1) was increased K562 cells in hypoxia condition by DNA microarray. We next examined ABL TKI resistant cell lines (K562 imatinib-R, K562 nilotinib-R, K562 dasatinib-R, K562 ponatinib-R) in this study. We could not detect the BCR-ABL point mutation in ABL TKI resistant cells. We found gene expression of insulin-like growth factor 1 (IGF1) receptor (IGF1R) was increased ABL TKI resistant K562 cells. IGF1R gene amplification was confirmed by RT-PCR analysis. IGF is tightly regulated by six related IGF-binding proteins (IGFBPs). One of IGFBP, IGFBP5 is related to imatinib sensitivity and resistant in chronic myeloid leukemia (CML) patients (GSE12211). In hypoxia condition, several IGFBPs were also increased in ABL TKI resistant cells. IGF cause intracellular signaling that ultimately results in cellular growth and proliferation. Thus, we initially examined whether addition of IGF1R inhibition could enhance ABL TKIs sensitivity. One of IGF1R inhibitor, linsitinib was inhibited ABL TKI resistant cells and parental cell line, K562 in hypoxia condition. ABL TKI resistant cell lines were more sensitive against linsitinib. Combined treatment of ABL TKI resistant cells and K562 cells with ABL TKIs and linsitinib caused more cytotoxicity than each drug alone in hypoxia condition. Caspase 3/7 activity and cellular cytotoxicity was also increased after ABL TKIs and linsitnib treatment. In the colony formation method, the number of cell colonies were also reduced in hypoxia condition. Intracellular ATP levels have been implicated in vitro as a determinant of cell death by apoptosis. The concentrations of intracellular ATP were reduced after ABL TKIs and linsitinib. We next blocked IGF1R function by small interfering RNA (siRNA). SiRNA transfected cells were reduced cellular proliferation. We also found drug sensitivity of the cells to the imatinib was increased compared to mock-transfected cells. Apoptotic cells and caspase 3/7 activity were increased after imatinib treatment in siRNA transfected cells. Conclusion: The IGF1 pathway is involved in Ph-positive leukemia cells in hypoxia condition and ABL TKI resistant in CML cells. We also provide the promising clinical relevance as a candidate drug for treatment of residual leukemia cells in bone marrow niche which is in hypoxia condition. Disclosures No relevant conflicts of interest to declare.