Mcl-1 Protein Research Articles

Combined Usage of Navitoclax and A-1210477 to Treat AcuteLymphoblastic Leukemia

Mcl-1 protein has been a key targeted therapeutic protein in treating acute lymphoblastic leukemia because of itsresistance to other previously known drugs. However, a newly synthesized chemical A-1210477 has proven to possessenough affinity to bind to the Mcl-1 protein and disrupt its normal function. As a result, scientists started to test thepotency of A-1210477 combined with other drugs to treat various cancers. This study will examine the effect ofA-1210477 and Bcl-2 inhibitor navitoclax combined to treat acute lymphoblastic leukemia Bal-KHc cell line both invitro by MTT and Annexin V/PI Facs as well as in vivo by measuring the tumor volume in xenograft.

Overexpression of MCL-1 provides OCI-Ly1 with resistance toVenetocalx

Overexpression of MCL-1 is an antiapoptotic member of the BCL-2 family and has been seen in various human tumors,correlating with the patient’s poor prognosis. This study tested whether cancers overexpress MCL-1 to gain resistance tovenetoclax. The expression of MCL-1 protein was measured by Western blot. Cell viability after venetoclax and MCL-1inhibitor AZD5991 was added was measured by MTT. FP-based binding assays measured Venetoclax’s binding affinityfor MCL-1. The result of the study would give insights into venetoclax resistance and the overexpression of MCL-1 inNHL OCI-Ly1. Future studies should focus on new drugs that can circumvent this resistance if the hypothesis is correct.

Novel multitarget small molecule inhibitor LCI133 and synthetic lethality in endometrial carcinoma via CDK9/PI3K axis.

e15118 Background: Despite advances in molecular characterization of endometrial carcinoma (EC), options for effective targeted therapy against EC remain limited. PI3K/PTEN/AKT/mTOR signaling is the most frequently mutated pathway in EC, but targeted inhibition often results in resistance via compensatory signaling. In response, the Molecular Targeted Therapeutics Laboratory has designed multidimensional small molecules in silico to (1) target compensatory molecular signaling pathways to induce synthetic lethality, (2) circumvent combination therapy-induced toxicity, complicated pharmacokinetics, and undesirable drug-drug interactions by placing each inhibitory domain in a single target inhibitor, and (3) prevent acquired resistance by inhibiting kinome adaptation. The objective of this study is to assess the synthetic lethality response generated in EC by combinations of PI3K, BRD4, CDK4/6, and CDK9 inhibition through multitargeted small molecule inhibitors LCI132, LCI133, and LCI136. Methods: Following primary screening in a cell-free assays for potency against target proteins, LCI132, LCI133, and LCI136 were screened against five EC cell lines for 48 hours; and cell viability assays were performed. Two EC cell lines (AN3 CA and RL95-2) were chosen for subsequent mechanistic studies and were treated with multitarget or single agent inhibitor for 24 hours; and cells were assessed by flow cytometry for cytostatic or cytotoxic response, and lysates were prepared accordingly for Western blot (WB) analysis. EC cells were also treated as indicated with multitarget or single target inhibitors for time-course assessment of MYC, HEXIM1, and MCL1 relative gene expression by qRT-PCR. Results: EC cell lines showed differential sensitivity to multitarget inhibitors with LCI133 proving most broadly potent, particularly against AN3 CA (IC50 248 nM) and RL95-2 (105 nM). LCI133 induced significant G2 phase cell cycle arrest in AN3 CA ( pFDR< 0.05) and the apoptotic response in AN3 CA ( pFDR< 0.05)and RL95-2 ( pFDR< 0.05). qRT-PCR revealed all LCI compounds decreased AN3 CA HEXIM1 and MCL1 gene expression in a time-dependent manner, with LCI133 inhibiting expression up to 24 hours post-treatment. In AN3 CA, LCI133 dose-dependently decreased phosphorylation of RNA polymerase II (S2) and Akt (S473) and decreased total MCL-1 protein levels as assessed by WB, suggesting on-target simultaneous inhibition. Further studies revealed that LCI133 induces apoptosis in a caspase-dependent manner, resulting in increased levels of cleaved PARP protein. Conclusions: Multitarget PI3K/CDK4/6/9 inhibitors LCI133 and LCI136 are nanomolar potent in AN3 CA and RL95-2 EC cell lines. LCI133 ablated expression of antiapoptotic protein MCL-1 and induced caspase-dependent apoptosis in AN3 CA, implicating PI3K and CDK9 inhibition as a synthetic lethality combination in PTEN/PI3K co-mutated EC.

Dynamic BH3 profiling identifies pro-apoptotic drug combinations for the treatment of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) has relatively ineffective first/second-line therapy for advanced disease and only 18% five-year survival for early disease. Drug-induced mitochondrial priming measured by dynamic BH3 profiling identifies efficacious drugs in multiple disease settings. We use high throughput dynamic BH3 profiling (HTDBP) to identify drug combinations that prime primary MPM cells derived from patient tumors, which also prime patient derived xenograft (PDX) models. A navitoclax (BCL-xL/BCL-2/BCL-w antagonist) and AZD8055 (mTORC1/2 inhibitor) combination demonstrates efficacy in vivo in an MPM PDX model, validating HTDBP as an approach to identify efficacious drug combinations. Mechanistic investigation reveals AZD8055 treatment decreases MCL-1 protein levels, increases BIM protein levels, and increases MPM mitochondrial dependence on BCL-xL, which is exploited by navitoclax. Navitoclax treatment increases dependency on MCL-1 and increases BIM protein levels. These findings demonstrate that HTDBP can be used as a functional precision medicine tool to rationally construct combination drug regimens in MPM and other cancers.

Protein Levels of Anti-Apoptotic Mcl-1 and the Deubiquitinase USP9x Are Cooperatively Upregulated during Prostate Cancer Progression and Limit Response of Prostate Cancer Cells to Radiotherapy.

Radiotherapy constitutes an important therapeutic option for prostate cancer. However, prostate cancer cells often acquire resistance during cancer progression, limiting the cytotoxic effects of radiotherapy. Among factors regulating sensitivity to radiotherapy are members of the Bcl-2 protein family, known to regulate apoptosis at the mitochondrial level. Here, we analyzed the role of anti-apoptotic Mcl-1 and USP9x, a deubiquitinase stabilizing Mcl-1 protein levels, in prostate cancer progression and response to radiotherapy. Changes in Mcl-1 and USP9x levels during prostate cancer progression were determined by immunohistochemistry. Neutralization of Mcl-1 and USP9x was achieved by siRNA-mediated knockdown. We analyzed Mcl-1 stability after translational inhibition by cycloheximide. Cell death was determined by flow cytometry using an exclusion assay of mitochondrial membrane potential-sensitive dye. Changes in the clonogenic potential were examined by colony formation assay. Protein levels of Mcl-1 and USP9x increased during prostate cancer progression, and high protein levels correlated with advanced prostate cancer stages. The stability of Mcl-1 reflected Mcl-1 protein levels in LNCaP and PC3 prostate cancer cells. Moreover, radiotherapy itself affected Mcl-1 protein turnover in prostate cancer cells. Particularly in LNCaP cells, the knockdown of USP9x expression reduced Mcl-1 protein levels and increased sensitivity to radiotherapy. Posttranslational regulation of protein stability was often responsible for high protein levels of Mcl-1. Moreover, we demonstrated that deubiquitinase USP9x as a factor regulating Mcl-1 levels in prostate cancer cells, thus limiting cytotoxic response to radiotherapy.

Synergistic Action of MCL-1 Inhibitor with BCL-2/BCL-XL or MAPK Pathway Inhibitors Enhances Acute Myeloid Leukemia Cell Apoptosis and Differentiation.

Acute myeloid leukemia (AML) is a hematological malignancy characterized by excessive proliferation of abnormal myeloid precursors accompanied by a differentiation block and inhibition of apoptosis. Increased expression of an anti-apoptotic MCL-1 protein was shown to be critical for the sustained survival and expansion of AML cells. Therefore, herein, we examined the pro-apoptotic and pro-differentiating effects of S63845, a specific inhibitor of MCL-1, in a single-agent treatment and in combination with BCL-2/BCL-XL inhibitor, ABT-737, in two AML cell lines: HL-60 and ML-1. Additionally, we determined whether inhibition of the MAPK pathway had an impact on the sensitivity of AML cells to S63845. To assess AML cells' apoptosis and differentiation, in vitro studies were performed using PrestoBlue assay, Coulter electrical impedance method, flow cytometry, light microscopy and Western blot techniques. S63845 caused a concentration-dependent decrease in the viability of HL-60 and ML-1 cells and increased the percentage of apoptotic cells. Combined treatment with S63845 and ABT-737 or MAPK pathway inhibitor enhanced apoptosis but also induced differentiation of tested cells, as well as altering the expression of the MCL-1 protein. Taken together, our data provide the rationale for further studies regarding the use of MCL-1 inhibitor in combination with other pro-survival protein inhibitors.

Anti-Apoptotic and Pro-Apoptotic Bcl-2 Family Proteins in Peri-Implant Diseases.

Intrinsic apoptosis, which is regulated by Bcl-2 family proteins, has an important role in chronic inflammatory diseases. The aim of the study was to identify the tissue levels and ratios of anti- and pro-apoptotic Bcl-2 family proteins in peri-implant diseases. Twenty-three individuals with peri-implant mucositis, 25 individuals with peri-implantitis, and 24 controls were included. The following clinical parameters were recorded: keratinized mucosa width, modified bleeding index, probing depth, modified plaque index, modified gingival index, and keratinized tissue thickness. Marginal alveolar bone assessments were performed by a software program. Granulation tissues were collected during treatments of peri-implant diseases. The control tissue samples were collected during the second stage of implant surgery. The tissue levels of Bcl-2 family pro-apoptotic (Bak, Bax, active caspase-3) and anti-apoptotic (Bcl-2, Bcl-xL, Mcl-1) proteins were determined by multiplex immunoassay method. The pro-apoptotic proteins; Bak, Bax and anti-apoptotic proteins Bcl-2, Bcl-xL, Mcl-1 were detected significantly higher in controls compared with patients with peri-implant mucositis and peri-implantitis (p < .001), respectively. The higher active caspase-3 levels were also detected in controls in comparison with peri-implant mucositis (p = .018) and peri-implantitis (p = .005). Anti-apoptotic: pro-apoptotic protein ratios (Bcl-2:Bax, p < .001; Bcl-2:Bak, p = .01; Bcl-xL: Bax, p = .006, Bcl-xL:Bak, p = .011; Mcl-1:Bak, p < .001) were significantly increased in diseased groups. A positive correlation was demonstrated between clinical variables and anti-apoptotic: pro-apoptotic ratios. Our findings indicate dysregulation of the Bcl-2 family proteins in peri-implant diseases. This unregulated response may disturb the homeostasis of peri-implant tissue.

Abstract 4978: Combination of a clinical stage-hedgehog inhibitor, GT1708, improves Venetoclax-induced apoptosis by down-regulating MCL-1 proteins in AML cells

Abstract Acute Myeloid Leukemia (AML) is the third hematological malignancies with the worst relative overall 5-year survival rate (11.7%) in hematological malignancies. AML is a heterogeneous disease with a broad spectrum of genomic changes and molecular mutations that lead to a poor prognosis and clinical outcome. Leukemic stem cells progress to myoblasts that continue to proliferate without differentiating, namely, immature blasts in AML. The hedgehog (HH)/glioma-associated oncogene homolog (GLI) signaling pathway is essential for embryonic and stem cell developments. This pathway has been one of the most promising targets for drug discovery and developments for AML. Although HH inhibitor Glasdegib in combo with low-dose cytarabine achieved FDA approval for AML, Venetoclax (BCL-2 inhibitor/ABT-199) plus a hypomethylating agent (HMA) have been dominating the regimens in AML recently. Here we reported GT1708, a HH inhibitor, improves ABT-199 (venetoclax)-induced apoptosis by down-regulating MCL-1 proteins in AML cells. GT1708 is a potent HH inhibitor (IC50=0.11 nM in HH pathway-driven cellular assay) and inhibited GLI expression with doses of 1, 3 and 10 mpk in a HH-dependent medulloblastoma animal models. In Molm-13 (AML) cells, GT1708 was shown to down-regulate the expression of MCL-1 proteins (anti-apoptotic proteins). In contrast, ABT-199 increased the expression of MCL-1. Furthermore, ABT+Aza (Azacidine/HMA drug) induced more MCL-1 expression than ABT-199. Importantly, GT1708 was shown to induce the expression of cleaved-PARP (c-PARP/apoptotic marker) and to increase c-PARP expression when combined with ABT-199. Due to ABT+Aza induced MCL-1 overexpression, the combination of both agents failed to induce c-PARP, suggesting MCL-1 overexpression conferring resistance to ABT+Aza therapy in Molm-13 cells. GT1708 was further evaluated in flow cytometry-based apoptotic assays. GT1708, ABT-199 and Aza were demonstrated to induce an early apoptosis by 9.98%, 47.5%, and 8.64%, respectively. In comparation, ABT+GT1708 were revealed to induce a 61% of apoptosis superior to 47% or 48.5% of apoptosis induced by either ABT or ABT+Aza in Molm-13 cells. These results confirm the role of MCL-1 overexpression in conferring resistance to ABT+Aza therapy, which can be overcome by ABT+GT1708 combo. GT1708/ABT combo were also shown a marginable superior antitumor activity than ABT along in Molm-13 animal models. GT1708 has been testing in a phase I study in AML patients with previous multiple lines of regimens. GT1708 has been shown to reduce blast counts in three of 13 AML patients treated with higher doses and demonstrated favorite PK and safety profiles. In brief, these results support the clinical development of GT1708 in combination with ABT-199 in AML patients. Citation Format: Liandong Ma, Qianxiang Zhou, Honghua Yan, Min Dong, Xiahe Han, Jiangwie Li, Jie Qu, Weidong Qian, Youzhi Tong. Combination of a clinical stage-hedgehog inhibitor, GT1708, improves Venetoclax-induced apoptosis by down-regulating MCL-1 proteins in AML cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4978.

Abstract 6155: Lurbinectedin exhibits combinatorial activity with BCL2/BCL2L1 inhibitors in vitro and in vivo by modulation of MCL1 expression

Abstract Lurbinectedin (Zepzelca) is a marine-derived anti-tumor agent currently approved for metastatic small cell lung cancer (SCLC). Lurbinectedin has been previously shown to exert its anti-tumor effect by binding to the minor groove of DNA and inhibition of nucleotide excision repair. In addition, lurbinectedin inhibits transcription by inducing degradation of RNA polymerase II. While these activities hint towards a general mechanism, specific molecular targets for lurbinectedin remain obscure. We demonstrate that in vitro, Lurbinectedin specifically induced downregulation of MCL1 protein, a member of the BCL2 family of pro-survival proteins, in a dose- (0-30 nM) and time-dependent manner (0-24 h) by Western analysis. Expression of other pro-survival proteins BCL2 and BCL2L1 were not affected. The downregulation of MCL1 was consistent in all nine tumor cell lines tested regardless of indication. Increased activity or expression of MCL1 is a known compensatory mechanism to offset loss of BCL2 or BCL2L1. We therefore hypothesized that lurbinectedin induced MCL1 loss, along with inhibition of the pro-survival proteins BCL2 and BCL2L1 would lead to an enhancement in cell killing. Consistent with the dominant pro-survival role of BCL2 in SCLC, the combination of lurbinectedin with a specific BCL2 inhibitor (venetoclax) in vitro induced synergistic cytotoxicity (measured by Bliss Sum analysis) in a panel of small cell lung cancer lines. In solid tumor lines other than SCLC, the combination of lurbinectedin with a specific BCL2L1 inhibitor (A-1331852) was also synergistic. Correspondingly in vivo, enhancement in the efficacy of lurbinectedin was observed in combination with venetoclax in SCLC models, while in solid tumor models other than SCLC the combination with a specific BCL2L1 inhibitor enhanced efficacy. Collectively, these data identify MCL1 as a specific lurbinectedin target and suggest that combinations that target other pro-survival proteins may represent a viable strategy to enhance the anti-tumor activity of lurbinectedin. Citation Format: Kedar S. Vaidya, Aparna Gupta, Robert Hauptschein, Robin C. Humphreys. Lurbinectedin exhibits combinatorial activity with BCL2/BCL2L1 inhibitors in vitro and in vivo by modulation of MCL1 expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6155.

Abstract 1574: Homoharringtonine is effective in treating acute lymphoblastic leukaemia via modulation of apoptotic pathway

Abstract Acute lymphoblastic leukaemia (ALL) is an aggressive and highly lethal malignancy caused by clonal mutations in lymphoid progenitor cells. The prognosis for adult ALL remains poor, with only 30-40% of adult patients achieving long-term remission. Therefore, novel therapies are needed. Homoharringtonine (HHT) is a natural-derived plant alkaloid from tree of Cephalotaxus. FDA approved the use of HHT in the treatment of chronic myeloid leukaemia (CML) in 2012. Limited pre-clinical or clinical studies were conducted for therapeutic efficacy and molecular mechanisms of HHT on ALL to the best of our knowledge. To fill this knowledge gap, here we investigated the antileukemic activity of HHT in T lymphoblastic leukaemia (T-ALL) and B lymphoblastic leukaemia (B-ALL). In this study, T-ALL cell lines namely JURKAT, MOLT-4, LOUCY, CCRF-CEM and B-ALL cell clines namely PALL-2, SUP-B15 were used. Cell viability was reduced upon treatment of HHT at time and dose-dependent manner. Percentage of apoptotic cells that determined by flow cytometric analysis of PI and Annexin V double staining was increased upon treatment of HHT. Moreover, HHT was able to induce apoptosis in both T-ALL and B-ALL cell lines. Western blot analysis showed that MCL-1 protein level was reduced upon treating with HHT for 24 hours. The above findings provide conclusive evidence for the therapeutic effect of HHT on various ALL cell lines by modulating the apoptotic pathway. Citation Format: Anan Jiao, Kei Ching Yuen, Rahman Ud DIN, On Yi Phoebe Wong, Sin Chun-Fung. Homoharringtonine is effective in treating acute lymphoblastic leukaemia via modulation of apoptotic pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1574.

Abstract 1631: Combination of olverembatinib (HQP1351) with BCL-2 inhibitor lisaftoclax (APG-2575) overcomes resistance in gastrointestinal stromal tumors (GISTs)

Abstract GISTs are common malignant mesenchymal tumors that occur in the GI tract, with an estimated incidence rate of 1% to 2%. About 75% to 80% of patients with GIST have mutations in the KIT gene, while 5% to 10% have mutations in the platelet-derived growth factor receptor α (PDGFRA) gene. Tyrosine kinase inhibitors (TKIs) offer patients an improved quality of life but increased pharmacological resistance to TKIs is often observed. BCL-2 is expressed in &amp;gt;80% of GISTs, and amplification of BCL-2 and BCL-xL are common features associated with disease progression. One approach to enhance GIST eradication is to concurrently inhibit oncogenic KIT signaling while actively engaging apoptotic pathways. Olverembatinib (HQP1351) is a new, third-generation TKI that targets BCR-ABL1, KIT and PDGFRA and is currently in development for relapsed or refractory chronic myeloid leukemia and GIST. Lisaftoclax (APG-2575) is a selective BCL-2 inhibitor under development for hematologic malignancies. The purpose of this study was to evaluate whether combining a BCL-2 inhibitor, lisaftoclax, with olverembatinib enhances treatment effect on imatinib-resistant GISTs. Compared to imatinib-sensitive GIST cell lines (GIST882 and GIST-T1), increased BCL-2 protein expression was observed in imatinib-resistant GIST cells, particularly in GIST430, GIST48, and GIST48B lines. Cell-based antiproliferation studies showed additive activity of olverembatinib and lisaftoclax in imatinib-resistant GIST cells. In vivo studies using imatinib-resistant GIST430 cell-derived xenograft models further revealed that coadministration of olverembatinib at 15 mg/kg (every other day for 3 weeks) with lisaftoclax at 50 mg/kg (daily for 3 weeks) resulted in enhanced antitumor effects compared to either agent alone. Tumor growth inhibition (TGI) rates for combined treatment with olverembatinib and lisaftoclax reached 76.8%, which was superior to the TGI rate of either agent alone: 57.6% and 31.2% for olverembatinib and lisaftoclax, respectively. Regarding putative mechanisms, olverembatinib treatment was shown to downregulate BCL-xL and MCL-1 protein expression, possibly via inhibition of KIT signal pathway and downstream signal transducer and activator of transcription 3 (STAT3). Lisaftoclax triggered apoptosis by disrupting the BCL-2:BIM complex. Therefore, selective inhibition of BCL-2, aided by TKI-mediated MCL-1 and BCL-XL inhibition, markedly augmented cleavage of caspase-3 and poly (ADP-ribose) polymerase 1 (PARP-1), thus triggering apoptosis and subsequently enhancing antitumor effects. Our results demonstrate that olverembatinib and BCL-2 inhibitor lisaftoclax have additive antitumor effects in imatinib-resistant GIST. This novel dual approach may have the potential for treating patients with GISTs whose disease has progressed after treatment with TKIs. Citation Format: Ping Min, Guangfeng Wang, Eric Liang, Bingxing Wu, Huidan Yu, Dajun Yang, Yifan Zhai. Combination of olverembatinib (HQP1351) with BCL-2 inhibitor lisaftoclax (APG-2575) overcomes resistance in gastrointestinal stromal tumors (GISTs) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1631.

Cytarabine-induced destabilization of MCL1 mRNA and protein triggers apoptosis in leukemia cells

Although cytarabine (Ara-C) is the mainstay of treatment for acute myeloid leukemia (AML), its cytotoxic mechanisms for inducing apoptosis are poorly understood. Therefore, we investigated the Ara-C-induced cell death pathway in human AML U937 cells. Ara-C-induced downregulation of MCL1 is associated with the induction of mitochondrial depolarization and apoptosis. Ara-C triggered NOX4-mediated ROS production, which in turn activated p38 MAPK but inactivated AKT. Ara-C-induced DNA damage modulates p38 MAPK activation without affecting AKT inactivation in U937 cells. Inactivated AKT promotes GSK3β-dependent CREB phosphorylation, which in turn increases NOXA transcription, thereby triggering the degradation of MCL1 protein. Activated p38 MAPK induces HuR downregulation, leading to accelerated MCL1 mRNA turnover. A similar pathway also explains the Ara-C-induced THP-1 cell death. Collectively, our data confirm that Ara-C-triggered apoptosis in the AML cell lines U937 and THP-1 is mediated through the destabilization of MCL1 mRNA and protein. Furthermore, Ara-C acts synergistically with the BCL2 inhibitor ABT-199 to induce cell death in ABT-199-resistant and parental U937 cells by inhibiting MCL1 expression.

The Role of BCL-2 and PD-1/PD-L1 Pathway in Pathogenesis of Myelodysplastic Syndromes.

Myelodysplastic syndromes (MDSs) belong to a group of clonal bone marrow malignancies. In light of the emergence of new molecules, a significant contribution to the understanding of the pathogenesis of the disease is the study of the B-cell CLL/lymphoma 2 (BCL-2) and the programmed cell death receptor 1 (PD-1) protein and its ligands. BCL-2-family proteins are involved in the regulation of the intrinsic apoptosis pathway. Disruptions in their interactions promote the progression and resistance of MDSs. They have become an important target for specific drugs. Bone marrow cytoarchitecture may prove to be a predictor of response to its use. The challenge is the observed resistance to venetoclax, for which the MCL-1 protein may be largely responsible. Molecules with the potential to break the associated resistance include S63845, S64315, chidamide and arsenic trioxide (ATO). Despite promising in vitro studies, the role of PD-1/PD-L1 pathway inhibitors has not yet been established. Knockdown of the PD-L1 gene in preclinical studies was associated with increased levels of BCL-2 and MCL-1 in lymphocytes T, which could increase their survival and promote tumor apoptosis. A trial (NCT03969446) is currently underway to combine inhibitors from both groups.

Protein biomarkers for response to XPO1 inhibition in haematologic malignancies.

XPO1 (Exportin-1) is the nuclear export protein responsible for the normal shuttling of several proteins and RNA species between the nucleocytoplasmic compartment of eukaryotic cells. XPO1 recognizes the nuclear export signal (NES) of its cargo proteins to facilitate its export. Alterations of nuclear export have been shown to play a role in oncogenesis in several types of solid tumour and haematologic cancers. Over more than a decade, there has been substantial progress in targeting nuclear export in cancer using selective XPO1 inhibitors. This has resulted in recent approval for the first-in-class drug selinexor for use in relapsed, refractory multiple myeloma and diffuse large B-cell lymphoma (DLBCL). Despite these successes, not all patients respond effectively to XPO1 inhibition and there has been lack of biomarkers for response to XPO1 inhibitors in the clinic. Using haematologic malignancy cell lines and samples from patients with myelodysplastic neoplasms treated with selinexor, we have identified XPO1, NF-κB(p65), MCL-1 and p53 protein levels as protein markers of response to XPO1 inhibitor therapy. These markers could lead to the identification of response upon XPO1 inhibition for more accurate decision-making in the personalized treatment of cancer patients undergoing treatment with selinexor.

Synergistic Antitumor Effect of Everolimus Combined with Gemcitabine on Diffuse Large B-Cell Lymphoma

To investigate the effects of mTOR inhibitors everolimus (EVE) and gemcitabine (GEM) on the proliferation, apoptosis and cell cycle of diffuse large B-cell lymphoma (DLBCL) cell line U2932, and further explore the molecular mechanisms, so as to provide new ideas and experimental basis for the clinical treatment of DLBCL. The effect of EVE and GEM on the proliferation of U2932 cells was detected by CCK-8 assay, the IC50 of the two drugs was calculated, and the combination index (CI=) of the two drugs was calculated by CompuSyn software. The effect of EVE and GEM on apoptosis of U2932 cells was detected by flow cytometry with AnnexinV-FITC/PI staining. Flow cytometry with propidium iodide (PI) staining was used to detect the effect of EVE and GEM on the cell cycle of U2932 cells. Western blot assay was used to detect the effects of EVE and GEM on the channel proteins p-mTOR and p-4EBP1, the anti-apoptotic proteins MCL-1 and Survivin, and the cell cycle protein Cyclin D1. Both EVE and GEM could significantly inhitbit the proliferation of U2932 cells in a time- and dose-dependent manner (r=0.465, 0.848; 0.555, 0.796). According to the calculation of CompuSyn software, EVE combined with GEM inhibited the proliferation of U2932 cells at 24, 48 and 72 h with CI=<1, which had a synergistic effect. After treated U2932 cells with 10 nmol/L EVE, 250 nmol/L GEM alone and in combination for 48 h, both EVE and GEM induced apoptosis, and the difference was statistically significant compared with the control group (P<0.05). The apoptosis rate was significantly enhanced after EVE in combination with GEM compared with single-agent (P<0.05). Both EVE and GEM alone and in combination significantly increased the proportion of cells in G1 phase compared with the control group (P<0.05). The proportion of cells in G1 phase was significantly increased when the two drugs were combined (P<0.05). The expression of p-mTOR and effector protein p-4EBP1 was significantly downregulated in the EVE combined with GEM group, the expression of anti-apoptotic proteins MCL-1, Survivin and cell cycle protein cyclin D1 was downregulated too (P<0.05). EVE combined with GEM can synergistically inhibit the proliferation of U2932 cells, and the mechanism may be that they can synergistically induce apoptosis by downregulating the expression of MCL-1 and Survivin proteins and block the cell cycle progression by downregulating the expression of Cyclin D1.

Targeted silencing of the MCL-1 gene using multi-layered dendrimer-based nanoconstructs achieves efficient tumor regression in xenografted mice models

The setback in the practical clinical use of RNA interference (RNAi)-based cancer treatment stems from the lack of targeted small interfering RNA (siRNA) delivery. Here, we show that luteinizing hormone-releasing hormone(LHRH) analog-tethered multi-layered polyamidoamine (PAMAM) nanoconstructs silence the anti-apoptotic MCL-1 gene in LHRH receptor overexpressing human breast (MCF-7) and prostate cancer (LNCaP) cells with 70.91 % and 74.10 % efficiency, respectively. These results were confirmed by RT-PCR. The Acridine orange/Ethidium bromide (AO/EB) dual staining revealed that the silencing of MCL-1 induced apoptosis in both the cell lines. In vivo tumor regression studies performed using MCF-7 and LNCaP xenografted severe combined immunodeficiency(SCID) mice demonstrated highly improved tumor regression in groups treated with targeted nanoconstructs complexed with MCL-1 siRNA (T + siMCL-1) compared to the other treatment groups. The quantitative RT-PCR results of tumor tissues demonstrated significant MCL-1 gene silencing, i.e., 73.76 % and 92.63 % in breast and prostate tumors, respectively, after T + siMCL-1 treatment. Reduction in MCL-1 protein expression as assessed by immunohistochemistry further confirmed these results. Furthermore, the caspase 3/7 assay demonstrated apoptosis in the MCL-1 silenced tissues. The study strongly suggests that targeted delivery of siRNAs using multi-layered dendrimer nanostructures could be an effective therapy for LHRH overexpressing cancers.

AL amyloidosis clonal plasma cells are regulated by microRNAs and dependent on anti-apoptotic BCL2 family members.

Noncoding RNAs such as microRNAs (miRNAs) have attracted attention as biological pathway regulators, which differ from chromosomal translocations and gene point mutations. Their involvement in the molecular mechanisms underlying light chain (AL) amyloidosis pathogenesis is yet to be elucidated. To decipher specific miRNA expression profile in AL-amyloidosis and to examine how miRNAs are involved in AL pathogenesis. The expression profile of miRNAs and mRNA from bone marrow (BM)-derived CD138+ cells were determined using the NanoString nCounter assay and RNA-Seq, respectively. The effect of aberrantly expressed miRNAs on potential molecular targets was analyzed by qRT-PCR, Western blot, Mito-potential assay, and Annexin-PI staining. Genes which were significantly differentially expressed between AL-amyloidosis and MM, were found to be involved in cell growth and apoptotic mechanisms. Specifically, BCL2L1, MCL1, and BCL2 were upregulated in AL-amyloidosis compared with MM and controls. The levels of miR-181a-5p and miR-9-5p, which regulate the above-mentioned genes, were lower in BM samples from AL-amyloidosis compared with controls, providing a mechanism for BCL2 family gene upregulation. When miR-9-5p and miR-181a-5p were overexpressed in ALMC1 cells, BCL2L1, MCL1, and BCL2 were downregulated and induced apoptosis. Treatment of ALMC-1 cells with venetoclax, (BCL-2 inhibitor), resulted in the upregulation of those miRNAs, the downregulation of BCL2, MCL1, and BCL2L1 mRNA and protein levels, and subsequent apoptosis. Our findings suggest that miR-9-5p and miR-181a-5p act as tumor-suppressors whose downregulation induces anti-apoptotic mechanisms underlying the pathogenesis of AL-amyloidosis. The study highlights the post-transcriptional regulation in AL-amyloidosis and provides pathogenetic evidence for the potential use of BCL-2 inhibitors in this disease.

Codelivery of BCL2 and MCL1 Inhibitors Enabled by Phenylboronic Acid-Functionalized Polypeptide Nanovehicles for Synergetic and Potent Therapy of Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is the most refractory hematologic malignancy characterized by acute onset, rapid progression, and high recurrence rate. Here, codelivery of BCL2 (ABT199) and MCL1 (TW37) inhibitors using phenylboronic acid-functionalized polypeptide nanovehicles to achieve synergetic and potent treatment of AML is adopted. Leveraging the dynamic boronic ester bonds, BN coordination, and π-π stacking, the nanovehicles reveal remarkably efficient and robust drug coencapsulation. ABT199 can induce a series of pro-apoptotic reactions by promoting the dissociation of the pro-apoptotic protein Bim from BCL2, while the released Bim is often captured by MCL1 protein overexpressed in AML. TW37 has a strong inhibitory ability to MCL1, thereby can restrain the depletion of Bim protein. Dual inhibitor-loaded nanoparticles (NPAT) reveal excellent stability, acid/enzyme/H2 O2 -triggered drug release, and significant cytotoxicity toward MOLM-13-Luc and MV-411 AML cells with low half maximal inhibitory concentrations of 1.15 and 7.45ng mL-1 , respectively. In mice bearing MOLM-13-Luc or MV-411 AML cancer, NPAT reveal significant inhibition of tumor cell infiltration in bone marrow and main organs, potent suppression of tumor growth, and remarkably elevated mouse survival. With facile construction, varying drug combination, superior safety, synergetic efficacy, the phenylboronic acid-functionalized smart nanodrugs hold remarkable potential for AML treatment.

E3 Ubiquitin Ligase TRIP12 Controls Exit from Mitosis via Positive Regulation of MCL-1 in Response to Taxol.

Chemotherapy resistance is a major hurdle in cancer treatment. Taxol-based chemotherapy is widely used in the treatment of cancers including breast, ovarian, and pancreatic cancer. Loss of function of the tumor suppressor F-box WD-40 domain containing 7 (FBW7) mutations leads to the accumulation of its substrate MCL-1 which is associated with Taxol resistance in human cancers. We recently showed that E3 ubiquitin ligase TRIP12 is a negative regulator of FBW7 protein. In this study, we find that Taxol-induced mitotic block in cancer cells is partly controlled by TRIP12 via its positive regulation of MCL-1 protein. Genetic inhibition of TRIP12 accelerates MCL-1 protein degradation in mitosis. Notably, introducing double-point mutations in lysines 404/412 of FBW7 to arginine which makes it resistant to proteasomal degradation, leads to the sharp reduction of MCL-1 protein levels and sensitizes cancer cells to Taxol-induced cell death. Finally, TRIP12 deletion leads to enhanced mitotic arrest and cell death in an FBW7 and MCL-1 dependent manner in multiple cell lines including colorectal and ovarian cancer but not in breast cancer. Thus, the TRIP12/FBW7/MCL-1 axis may provide a therapeutic target to overcome Taxol-associated chemotherapy resistance in cancer.

AT-101 Enhances the Antitumor Activity of Lenalidomide in Patients with Multiple Myeloma.

Bcl-2 and Mcl-1 proteins play a role in multiple myeloma (MM) cell survival, for which targeted inhibitors are being developed. AT-101 is an oral drug, which disrupts Bcl-2 and Mcl-1 function, impedes mitochondrial bioenergetic processes and induces apoptosis in MM cells. When combined with lenalidomide and dexamethasone (Rd), AT-101 significantly reduced tumor burden in an in vivo xenograft model of MM. These data provided rationale for a phase I/II study to establish the effective dose of AT-101 in combination with Rd (ARd regimen) in relapsed/refractory MM. A total of 10 patients were enrolled, most with high-risk cytogenetics (80%) and prior stem cell transplant (70%). Three patients were lenalidomide-refractory, 2 were bortezomib-refractory and 3 were daratumumab-refractory. The ARd combination was well tolerated with most common grade 3/4 adverse events being cytopenia's. The overall response rate was 40% and clinical benefit rate was 90%. The median progression free survival was 14.9 months (95% CI 7.1-NE). Patients responsive to ARd showed a decrease in Bcl-2:Bim or Mcl-1:Noxa protein complexes, increased CD8+ T and NK cells and depletion of T and B-regulatory cells. The ARd regimen demonstrated an acceptable safety profile and promising efficacy in patients with relapsed/refractory MM prompting further investigation in additional patients.