Induction Of PUMA Research Articles

Abstract 3334: Combined treatment with PG3 and Nelfinavir induced synergistic apoptosis though sustained activation of integrated stress response

Abstract Integrated stress response (ISR) activation has been linked to many human diseases, including cancer and neurological diseases. The ISR controls protein synthesis and proteostasis. ISR main effector ATF4 transcriptional factor regulates the balance between survival and cell death. Under acute ISR, ATF4 promotes cell adaptation and survival. Sustained ISR leads to ATF4-mediated apoptosis. In many cancers, mutations or overexpression of oncogenes, results in enhanced cell proliferation and increased protein synthesis, which activate the ISR. Therefore, protein translation is reduced to maintain proteostasis. In other words, many cancers are primed by the ISR. Therefore, additional push by small molecule ISR-inducers will disrupt the balance and force cancer cells to enter apoptosis. Nelfinavir activates ATF4 through inhibition of eIF2α specific phosphatases CReP and GADD34. PG3 upregulates ATF4 through the HRI/eIF2α/ATF4 pathway. We hypothesize that combined treatment of PG3 and Nelfinavir will sustain upregulation of ATF4, and lead to ATF4-mediated cell apoptosis. Cell viability assays indicated that the combined treatment potently and synergistically inhibited cell viability in colorectal cancer cell lines HT29, SW480 and HCT116 p53−/−, osteosarcoma cell line U2OS and breast cancer cell lines MCF7 and T47D. The combined treatment sustained the induction of ATF4 and enhanced the expression of its proapoptotic target genes, CHOP and PUMA, and cell apoptosis. We confirmed that the enhanced induction of ATF4, CHOP and PUMA is through the ISR because ISRIB (ISR inhibitor) blocked the combined treatment-induced upregulation of ATF4, CHOP and PUMA. Citation Format: Xiaobing Tian, Wafik S. El-Deiry. Combined treatment with PG3 and Nelfinavir induced synergistic apoptosis though sustained activation of integrated stress response [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 3334.

Subtype-selective induction of apoptosis in translocation-related sarcoma cells induced by PUMA and BIM upon treatment with pan-PI3K inhibitors

Translocation-related sarcomas (TRSs) harbor an oncogenic fusion gene generated by chromosome translocation and account for approximately one-third of all sarcomas; however, effective targeted therapies have yet to be established. We previously reported that a pan-phosphatidylinositol 3-kinase (PI3K) inhibitor, ZSTK474, was effective for the treatment of sarcomas in a phase I clinical trial. We also demonstrated the efficacy of ZSTK474 in a preclinical model, particularly in cell lines from synovial sarcoma (SS), Ewing’s sarcoma (ES) and alveolar rhabdomyosarcoma (ARMS), all of which harbor chromosomal translocations. ZSTK474 selectively induced apoptosis in all these sarcoma cell lines, although the precise mechanism underlying the induction of apoptosis remained unclear. In the present study, we aimed to determine the antitumor effect of PI3K inhibitors, particularly with regards to the induction of apoptosis, against various TRS subtypes using cell lines and patient-derived cells (PDCs). All of the cell lines derived from SS (six), ES (two) and ARMS (one) underwent apoptosis accompanied by the cleavage of poly-(ADP-ribose) polymerase (PARP) and the loss of mitochondrial membrane potential. We also observed apoptotic progression in PDCs from SS, ES and clear cell sarcoma (CCS). Transcriptional analyses revealed that PI3K inhibitors triggered the induction of PUMA and BIM and the knockdown of these genes by RNA interference efficiently suppressed apoptosis, suggesting their functional involvement in the progression of apoptosis. In contrast, TRS-derived cell lines/PDCs from alveolar soft part sarcoma (ASPS), CIC-DUX4 sarcoma and dermatofibrosarcoma protuberans failed to undergo apoptosis nor induce PUMA and BIM expression, as well as cell lines derived from non-TRSs and carcinomas. Thus, we conclude that PI3K inhibitors induce apoptosis in selective TRSs such as ES and SS via the induction of PUMA and BIM and the subsequent loss of mitochondrial membrane potential. This represents proof of concept for PI3K-targeted therapy, particularly such TRS patients.

Synthetical lethality of Werner helicase and mismatch repair deficiency is mediated by p53 and PUMA in colon cancer

Synthetic lethality is a powerful approach for targeting oncogenic drivers in cancer. Recent studies revealed that cancer cells with microsatellite instability (MSI) require Werner (WRN) helicase for survival; however, the underlying mechanism remains unclear. In this study, we found that WRN depletion strongly induced p53 and its downstream apoptotic target PUMA in MSI colorectal cancer (CRC) cells. p53 or PUMA deletion abolished apoptosis induced by WRN depletion in MSI CRC cells. Importantly, correction of MSI abrogated the activation of p53/PUMA and cell killing, while induction of MSI led to sensitivity in isogenic CRC cells. Rare p53-mutant MSI CRC cells are resistant to WRN depletion due to lack of PUMA induction, which could be restored by wildtype (WT) p53 knock in or reconstitution. WRN depletion or treatment with the RecQ helicase inhibitor ML216 suppressed in vitro and in vivo growth of MSI CRCs in a p53/PUMA-dependent manner. ML216 treatment was efficacious in MSI CRC patient-derived xenografts. Interestingly, p53 gene remains WT in the majority of MSI CRCs. These results indicate a critical role of p53/PUMA-mediated apoptosis in the vulnerability of MSI CRCs to WRN loss, and support WRN as a promising therapeutic target in p53-WT MSI CRCs.

Eltanexor Effectively Reduces Viability of Glioblastoma and Glioblastoma Stem-Like Cells at Nano-Molar Concentrations and Sensitizes to Radiotherapy and Temozolomide.

Current standard adjuvant therapy of glioblastoma multiforme (GBM) using temozolomide (TMZ) frequently fails due to therapy resistance. Thus, novel therapeutic approaches are highly demanded. We tested the therapeutic efficacy of the second-generation XPO1 inhibitor Eltanexor using assays for cell viability and apoptosis in GBM cell lines and GBM stem-like cells. For most GBM-derived cells, IC50 concentrations for Eltanexor were below 100 nM. In correlation with reduced cell viability, apoptosis rates were significantly increased. GBM stem-like cells presented a combinatorial effect of Eltanexor with TMZ on cell viability. Furthermore, pretreatment of GBM cell lines with Eltanexor significantly enhanced radiosensitivity in vitro. To explore the mechanism of apoptosis induction by Eltanexor, TP53-dependent genes were analyzed at the mRNA and protein level. Eltanexor caused induction of TP53-related genes, TP53i3, PUMA, CDKN1A, and PML on both mRNA and protein level. Immunofluorescence of GBM cell lines treated with Eltanexor revealed a strong accumulation of CDKN1A, and, to a lesser extent, of p53 and Tp53i3 in cell nuclei as a plausible mechanism for Eltanexor-induced apoptosis. From these data, we conclude that monotherapy with Eltanexor effectively induces apoptosis in GBM cells and can be combined with current adjuvant therapies to provide a more effective therapy of GBM.

Xanthohumol inhibits non-small cell lung cancer by activating PUMA-mediated apoptosis

Deregulation of apoptosis signaling is an important feature of cancer cells and plays an essential role in tumorigenesis. Xanthohumol is an active ingredient in Traditional Chinese Medicines Hops (Humulus lupulus L.). Recently studies have shown the profound anti-tumor activities of Xanthohumol in multiple cancer models. However, its potency in non-small cell lung cancer (NSCLC) and the underlying mechanisms are still elusive. Here, we have investigated the potency of Xanthohumol against NSCLC cells in vitro and xenograft mouse models. Xanthohumol suppressed cell viability, colony formation and induced apoptosis in A549, H520, and H358 cells. Xanthohumol activated mitochondrial apoptosis through upregulation of (p53-upregulated modulator of apoptosis) PUMA expression. After Xanthohumol treatment, the Akt activity was inhibited, which resulted in dephosphorylation of FOXO3a and PUMA induction. Silent PUMA or FOXO3a impaired Xanthohumol-induced apoptosis in NSCLC cells. In nude mice, Xanthohumol administration suppressed NSCLC xenograft tumor growth and increased PUMA expression in tumor tissues. Briefly, our studies revealed a novel mechanism by which Xanthohumol exerted its anti-tumor activity in a PUMA-dependent manner in NSCLC cells.

Abstract P210: MDM2 gene amplification as a predictive biomarker for the MDM2 inhibitor milademetan

Abstract MDM2 is an E3 ubiquitin ligase that plays a critical role in the degradation of the tumor suppressor p53. Milademetan (RAIN-32) is an orally available, small molecule inhibitor of MDM2 that disrupts the MDM2-p53 protein complex thereby restoring p53 expression and activity. Milademetan has demonstrated anti-tumor activity in de-differentiated liposarcoma, a tumor type characterized by MDM2 gene amplification (amp) and WT TP53, in the phase I study of monotherapy milademetan (NCT01877382). Here we investigate the use of MDM2 gene amplification as a predictive biomarker for the selection of patients with advanced cancers who might benefit from milademetan. In this study we evaluated milademetan in MDM2 gene amp cancer models from a variety of tumor types using both in vitro assays, including 2D viability assays and organoid models, as well as in vivo patient-derived xenografts. We employed a mutual exclusivity analysis between MDM2 copy number (CN) and TP53 mutation status using publicly available next generation sequencing data to derive an optimal MDM2 CN threshold for patient selection and present clinical data from patients with MDM2 amp tumors treated with milademetan in the phase 1 study (NCT01877382). Three cell lines, CCFSTTG1 (astrocytoma), DKMG (glioblastoma), and SJSA1 (osteosarcoma), with MDM2 amp were identified and demonstrated inhibition of cell proliferation by milademetan with GI50 <100 nM. Evidence of MDM2 target engagement and activation of p53 was demonstrated through induction of p21 and PUMA, transcriptional targets of p53. Four patient-derived organoid models from diverse cancers (2 lung adenocarcinoma, 1 cholangiocarcinoma, and 1 renall cell carcinoma) were identified with MDM2 amp and WT TP53 and demonstrated differential selectivity compared to non-MDM2 amp models also with WT TP53 (head and neck scquamous cell carcinoma, endometrial carcinoma). Xenograft models from tumor types including gastric, lung adenocarcinoma and osteosarcoma with MDM2 amp showed dose-dependent anti-tumor activity to milademetan in vivo. Induction of MIC-1, a p53 target gene, was observed in vivo following milademetan dosing. An MDM2 CN threshold of ≥ 12 was derived using mutual exclusivity analysis using the AACR Genie dataset across solid tumor types. Using TCGA Pan-Cancer Atlas dataset, we identified 1.1% of cancers that met the criteria of MDM2 CN ≥ 12 and WT TP53. Finally, 3 patients (breast cancer, synovial sarcoma, and small cell lung cancer) with MDM2 CN ≥ 12 were previously enrolled on the U101 study of milademetan, Schedule D (3 days on 11 days off), which was determined to be the dose schedule for future clinical trials, and all 3 patients experienced tumor reduction with 2 patients demonstrating a partial response and 1 confirmed partial response. Milademetan shows evidence of preclinical and clinical anti-tumor activity in genetically selected tumors using MDM2 amp and WT TP53 as selection criteria. A basket study evaluating milademetan in solid tumors with MDM2 CN ≥ 12 and WT TP53 (MANTRA-2) is planned. Citation Format: Vijaya G. Tirunagaru, Mrinal M. Gounder, Prasanna R. Kumar, David S. Hong, Robert C. Doebele. MDM2 gene amplification as a predictive biomarker for the MDM2 inhibitor milademetan [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P210.

Aurora Kinase Inhibition Overcomes Primary Venetoclax Failure and Leads to Synthetic Lethality in BCL2-Positive Lymphomas Via Upregulation of P53/P21/BAX Axis

Aurora Kinase Inhibition Overcomes Primary Venetoclax Failure and Leads to Synthetic Lethality in BCL2-Positive Lymphomas Via Upregulation of P53/P21/BAX Axis

BRD9 inhibition promotes PUMA-dependent apoptosis and augments the effect of imatinib in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are primarily characterized by activating mutations of tyrosine kinase or platelet-derived growth factor receptor alpha. Although the revolutionary therapeutic outcomes of imatinib are well known, the long-term benefits of imatinib are still unclear. The effects of BRD9, a recently identified subunit of noncanonical BAF complex (ncBAF) chromatin remodeling complexes, in GISTs are not clear. In the current study, we evaluated the functional role of BRD9 in GIST progression. Our findings demonstrated that the expression of BRD9 was upregulated in GIST tissues. The downregulation or inhibition of BRD9 could significantly reduce cellular proliferation, and facilitates apoptosis in GISTs. BRD9 inhibition could promote PUMA-dependent apoptosis in GISTs and enhance imatinib activity in vitro and in vivo. BRD9 inhibition synergizes with imatinib in GISTs by inducing PUMA upregulation. Mechanism study revealed that BRD9 inhibition promotes PUMA induction via the TUFT1/AKT/GSK-3β/p65 axis. Furthermore, imatinib also upregulates PUMA by targeting AKT/GSK-3β/p65 axis. In conclusion, our results indicated that BRD9 plays a key role in the progression of GISTs. Inhibition of BRD9 is a novel therapeutic strategy in GISTs treated alone or in combination with imatinib.

Fluorizoline-induced apoptosis requires prohibitins in nematodes and human cells.

We previously showed that fluorizoline, a fluorinated thiazoline compound, binds to both subunits of the mitochondrial prohibitin (PHB) complex, PHB1 and PHB2, being the expression of these proteins required for fluorizoline-induced apoptosis in mouse embryonic fibroblasts. To investigate the conservation of this apoptotic mechanism, we studied the effect of PHB downregulation on fluorizoline activity on two human cell lines, HEK293T and U2OS. Then, we asked whether PHBs mediate the effect of fluorizoline in a multicellular organism. Interestingly, reduced levels of PHBs in the human cells impaired the induction of apoptosis by fluorizoline. We observed that fluorizoline has a detrimental dose-dependent effect on the development and survival of the nematode model Caenorhabditis elegans. Besides, such effects of fluorizoline treatment in living nematodes were absent in PHB mutants. Finally, we further explored the apoptotic pathway triggered by fluorizoline in human cell lines. We found that the BH3-only proteins NOXA, BIM and PUMA participate in fluorizoline-induced apoptosis and that the induction of NOXA and PUMA is dependent on PHB expression.

RETRACTED ARTICLE: Inhibition of EZH2 enhances the therapeutic effect of 5-FU via PUMA upregulation in colorectal cancer

Although the survival rate of patients with cancer have increased due to the use of current chemotherapeutic agents, adverse effects of cancer therapy remain a concern. The reversal of drug resistance, reduction in harmful side effects and accelerated increase in efficiency have often been addressed in the development of combination therapeutics. Tazemetostat (EPZ-6438), a histone methyltransferase EZH2 selective inhibitor, was approved by the FDA for the treatment of advanced epithelioid sarcoma. However, the effect of tazemetostat on colorectal cancer (CRC) and 5-FU sensitivity remains unclear. In this study, the enhancement of tazemetostat on 5-FU sensitivity was examined in CRC cells. Our findings demonstrated that tazemetostat combined with 5-FU exhibits synergistic antitumor function in vitro and in vivo in CRC cells. In addition, tazemetostat promotes PUMA induction through the ROS/ER stress/CHOP axis. PUMA depletion attenuates the antitumor effect of the combination therapy. Therefore, tazemetostat may be a novel treatment to improve the sensitivity of tumors to 5-FU in CRC therapy. In conclusion, the combination of 5-FU and tazemetostat shows high therapeutic possibility with reduced unfavorable effects.

TMOD-15. EFFICACY OF THE MDM2 INHIBITOR KRT-232 IN GLIOBLASTOMA PATIENT-DERIVED XENOGRAFT MODELS

Abstract Non-genotoxic reactivation of p53 by MDM2 inhibitors represents a promising therapeutic strategy for tumors with wild-type TP53, particularly tumors harboring MDM2 amplification. MDM2 controls p53 levels by targeting it for degradation, while disruption of the MDM2-p53 interaction causes rapid accumulation of p53 and activation of the p53 pathway. We examined the efficacy of the small molecule MDM2 inhibitor KRT-232, alone and in combination with radiation therapy (RT), in MDM2-amplified and/or p53 wildtype patient-derived xenograft (PDX) models of glioblastoma in vitro and in vivo. In vitro, glioblastoma PDX explant cultures showed sensitivity to KRT-232, both tumors with MDM2 amplification (GBM108 and G148) and non-amplified but TP53-wildtype lines (GBM10, GBM14, and GBM39), with IC50s ranging from 300-800 nM in FBS culture conditions. A TP53 p.F270C mutant PDX (GBM43) was inherently resistant, with IC50 >3000 nM. In the MDM2-amplified GBM108 line, KRT-232 led to a robust (5-6 fold) induction of p53-target genes p21, PUMA, and NOXA, with initiation of both apoptosis and senescence. Expression of p21 and PUMA was greater with KRT-232 in combination with RT (25-35 fold induction), while stable knock-down of p53 in GBM108 led to complete resistance to KRT-232. In contrast, GBM10 showed lower induction of p21 and PUMA (2-3 fold) and was more resistant to KRT-232. In an orthotopic GBM108 xenograft model, treatment with KRT-232 +/- RT for one week extended survival from 22 days (placebo) to 46 days (KRT-232 alone); combination KRT-232 + RT further extended survival (77 days) over RT alone (31 days). KRT-232 is an effective treatment in a subset of glioblastoma pre-clinical models alone and in combination with RT. Further studies are underway to understand the mechanisms conferring innate sensitivity or resistance to KRT-232.

Pitavastatin induces apoptosis in oral squamous cell carcinoma through activation of FOXO3a.

Statins are a class of lipid‐lowering drugs that have recently been used in drug repositioning in the treatment of human cancer. However, the underlying mechanism of statin‐induced cancer cell death has not been clearly defined. In the present study, we evaluated the anticancer effect of pitavastatin on oral squamous cell carcinoma (OSCC), SCC15 and SCC4 cells and found that FOXO3a might be a direct target in pitavastatin‐induced cancer cell death. Our data revealed that pitavastatin selectively suppressed cell viability and induced intrinsic apoptosis in a FOXO3a‐dependent manner in SCC15 cells while no effect was observed in SCC4 cells. Notably, treatment with pitavastatin in SCC15 cells induced the nuclear translocation of FOXO3a via dual regulation of two upstream kinases, AMPK and Akt, resulting in the up‐regulation of PUMA, a transcriptional target gene of FOXO3a. Furthermore, our data revealed that FOXO3a‐mediated PUMA induction plays a role in pitavastatin‐induced intrinsic apoptosis in SCC15 cells. Taken together, our findings suggest that pitavastatin activates the FOXO3a/PUMA apoptotic axis by regulation of nuclear translocation of FOXO3a via Akt/FOXO3a or AMPK/FOXO3a signalling. Therefore, these findings might help to elucidate the underlying mechanism of the anticancer effects of pitavastatin on OSCC.

Gilteritinib induces PUMA-dependent apoptotic cell death via AKT/GSK-3β/NF-κB pathway in colorectal cancer cells.

As a highly potent and highly selective oral inhibitor of FLT3/AXL, gilteritinib showed activity against FLT3D835 and FLT3‐ITD mutations in pre‐clinical testing, although its role on colorectal cancer (CRC) cells is not yet fully elucidated. We examined the activity of gilteritinib in suppressing growth of CRC and its enhancing effect on other drugs used in chemotherapy. In this study, we observed that, regardless of p53 status, treatment using gilteritinib induces PUMA in CRC cells via the NF‐κB pathway after inhibition of AKT and activation of glycogen synthase kinase 3β (GSK‐3β). PUMA was observed to be vital for apoptosis in CRC cells through treatment of gilteritinib. Moreover, enhancing induction of PUMA through different pathways could mediate chemosensitization by using gilteritinib. Furthermore, PUMA deficiency revoked the antitumour role of gilteritinib in vivo. Thus, our results indicate that PUMA mediates the antitumour activity of gilteritinib in CRC cells. These observations are critical for the therapeutic role of gilteritinib in CRC.

Peroxiredoxin 5 Silencing Sensitizes Dopaminergic Neuronal Cells to Rotenone via DNA Damage-Triggered ATM/p53/PUMA Signaling-Mediated Apoptosis.

Peroxiredoxins (Prxs) are a family of thioredoxin peroxidases. Accumulating evidence suggests that changes in the expression of Prxs may be involved in neurodegenerative diseases pathology. However, the expression and function of Prxs in Parkinson’s disease (PD) remains unclear. Here, we showed that Prx5 was the most downregulated of the six Prx subtypes in dopaminergic (DA) neurons in rotenone-induced cellular and rat models of PD, suggesting possible roles in regulating their survival. Depletion of Prx5 sensitized SH-SY5Y DA neuronal cells to rotenone-induced apoptosis. The extent of mitochondrial membrane potential collapse, cytochrome c release, and caspase activation was increased by Prx5 loss. Furthermore, Prx5 knockdown enhanced the induction of PUMA by rotenone through a p53-dependent mechanism. Using RNA interference approaches, we demonstrated that the p53/PUMA signaling was essential for Prx5 silencing-exacerbated mitochondria-driven apoptosis. Additionally, downregulation of Prx5 augmented rotenone-induced DNA damage manifested as induction of phosphorylated histone H2AX (γ-H2AX) and activation of ataxia telangiectasia mutated (ATM) kinase. The pharmacological inactivation of ATM revealed that ATM was integral to p53 activation by DNA damage. These findings provided a novel link between Prx5 and DNA damage-triggered ATM/p53/PUMA signaling in a rotenone-induced PD model. Thus, Prx5 might play an important role in protection against rotenone-induced DA neurodegeneration.

Screening of Cellular Stress Responses Induced by Ambient Aerosol Ultrafine Particle Fraction PM0.5 in A549 Cells.

Effects of airborne particles on the expression status of markers of cellular toxic stress and on the release of eicosanoids, linked with inflammation and oxidative damage, remain poorly characterized. Therefore, we proposed a set of various methodological approaches in order to address complexity of PM0.5-induced toxicity. For this purpose, we used a well-characterized model of A549 pulmonary epithelial cells exposed to a non-cytotoxic concentration of ambient aerosol particle fraction PM0.5 for 24 h. Electron microscopy confirmed accumulation of PM0.5 within A549 cells, yet, autophagy was not induced. Expression profiles of various cellular stress response genes that have been previously shown to be involved in early stress responses, namely unfolded protein response, DNA damage response, and in aryl hydrocarbon receptor (AhR) and p53 signaling, were analyzed. This analysis revealed induction of GREM1, EGR1, CYP1A1, CDK1A, PUMA, NOXA and GDF15 and suppression of SOX9 in response to PM0.5 exposure. Analysis of eicosanoids showed no oxidative damage and only a weak anti-inflammatory response. In conclusion, this study helps to identify novel gene markers, GREM1, EGR1, GDF15 and SOX9, that may represent a valuable tool for routine testing of PM0.5-induced in vitro toxicity in lung epithelial cells.

H1, a derivative of tetrandrine, enhances the efficacy of 5-FU in Bel7402/5-FU cells via suppressing STAT3/MCL-1 and inducing PUMA

Currently, 5-fluorouracil (5-FU) resistance became a major obstacle to its clinical use for patients with hepatocellular carcinoma (HCC). It’s urgent to develop a novel strategy for enhancing the therapeutic efficacy of 5-FU. Herein, we found that H1 (a derivative of Tetrandrine) exerted a potent anti-MDR effect on growth of 5-FU resistant HCC cells (Bel7402/5FU). The resistant fold (RF) of 5-FU is over 160-fold, while the RF of H1 is only 4.8-fold in Bel7402/5-FU cells. Further studies demonstrated that blockage of STAT3/MCL-1 signaling and induction of PUMA is responsible to anti-MDR activity of H1. Moreover, combination of H1 and 5-FU (Ratio = 1:2) could synergistically induce apoptosis of Bel7402/5-FU cells. Co-treatment of H1 enhances the suppression of p-STAT3 and MCL-1, and significantly increases PUMA expression. Finally, the combination of H1 and 5-FU results in an increase of cleaved PARP. Taken together, H1 effectively improve the cytotoxic effect of 5-FU against Bel7402/5-FU cells via blocking STAT3/MCL-1 pathway and inducing PUMA. Our findings suggested that combination 5-FU with anti-MDR agents might present a novel strategy to enhance the therapeutic efficacy of 5-FU in resistant HCC.

Abstract 698: Enhancing apoptosis to improve the therapy of EGFR-mutant lung cancer

Abstract EGFR-TKIs have shown clinical efficacy in EGFR-mutant lung cancer patients, but most of the cases eventually develop resistance to the drugs, including the third-generation EGFR-TKI. Here, we develop a cell death mechanism-based combination strategy to enhance the therapeutic effect of EGFR-TKIs as well as to overcome the acquired resistance to EGFT-TKI in EGFR-mutant lung cancer. Through high-throughput screening of a custom pathway inhibitor library (-1000 drugs), we discovered Aurora kinase inhibitors that synergized with a third-generation EGFR-TKI (AZD9291) to induce apoptosis in EGFR-mutant lung cancer cells. Aurora kinase inhibitors enhanced AZD9291-mediated induction of BIM and PUMA, two important sentinels interconnecting the EGFR signal transduction pathway and the mitochondrial apoptotic machinery BAX and BAK. Combined inhibition of Aurora kinases and EGFR prevented the emergence of EGFR-TKI resistant clones in clonogenic assays. Interestingly, AZD9291 resistant lung cancer cells exhibited greater sensitivity to Aurora kinase inhibitors compared with parental cells. In conclusion, we found that the combination of AZD9291 and Aurora kinase inhibitors synergistically induced BIM and PUMA-mediated apoptosis, which may render a promising strategy to improve the therapy of EGFR-mutant lung cancer. <!–EndFragment–> Citation Format: Kosuke Tanaka, Song Han, Yogesh T. Ganesan, James J. Hsieh, Emily H. Cheng. Enhancing apoptosis to improve the therapy of EGFR-mutant lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 698.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

BET inhibitor I-BET151 sensitizes GBM cells to temozolomide via PUMA induction.

A significant roadblock in treatment of GBM multiforme (GBM) is resistance to temozolomide (TMZ). In this study, we investigated whether I-BET151, a specific BET inhibitor, could sensitize GBM cells to TMZ. Our findings showed that the action of I-BET151 could augment the effect of TMZ on cancer cells U251 and U87 cells. In U251 cells, administration of I-BET151 increased the TMZ-induced apoptosis GBM cells. I-BET151 remarkably enhanced the activities of caspase-3. In addition, I-BET151 promoted TMZ-induced migration and invasion in GBM cells. Moreover, I-BET151 increased the amount of reactive oxygen species as well as superoxide anions with a decrease of activity of SOD and the anti-oxidative properties of GBM cells. I-BET151 also induced increased PUMA expression, which is required for the functions of I-BET151 and regulates the synergistic cytotoxic effects of i-BET151 and TMZ in GBM cells. I-BET151 with TMZ also showed synergistic cytotoxic effects in vivo. These point out to an approach to tackle GBM using TMZ along with BET inhibitors.

Ginseng metabolite protopanaxadiol interferes with lipid metabolism and induces endoplasmic reticulum stress and p53 activation to promote cancer cell death.

Protopanaxadiol (PPD), a ginseng metabolite generated by the gut bacteria, was shown to induce colorectal cancer cell death and enhance the anticancer effect of chemotherapeutic agent 5-FU. However, the mechanism by which PPD promotes cancer cell death is not clear. In this manuscript, we showed that PPD activated p53 and endoplasmic reticulum (ER) stress and induced expression of BH3-only proteins Puma and Noxa to promote cell death. Induction of Puma by PPD was p53-dependent, whereas induction of Noxa was p53-independent. On the other hand, PPD also induced prosurvival mechanisms including autophagy and expression of Bcl2 family apoptosis regulator Mcl-1. Inhibition of autophagy or knockdown of Mcl-1 significantly enhanced PPD-induced cell death. Interestingly, PPD inhibited expression of genes involved in fatty acid and cholesterol biosynthesis and induced synergistic cancer cell death with fatty acid synthase inhibitor cerulenin. As PPD-induced ER stress was not significantly affected by inhibition of new protein synthesis, we suggest PPD may induce ER stress directly through causing lipid disequilibrium.