BIM expression in treatment-naive cancers predicts responsiveness to kinase inhibitors

Abemaciclib-induced epithelial-mesenchymal transition mediated by cyclin-dependent kinase 4/6 independent of cell cycle arrest pathway

Abemaciclib (ABM), a cyclin-dependent kinase 4/6 inhibitor, shows pharmacological effects in cell cycle arrest. Epithelial-mesenchymal transition is an important cellular event associated with pathophysiological states such as organ fibrosis and cancer progression. In the present study, we evaluated the contribution of factors associated with cell cycle arrest to ABM-induced epithelial-mesenchymal transition. Treatment with 0.6 µM ABM induced both cell cycle arrest and epithelial-mesenchymal transition-related phenotypic changes. Interestingly, the knockdown of cyclin-dependent kinase 4/6, pharmacological targets of ABM or cyclin D1, which forms complexes with cyclin-dependent kinase 4/6, resulted in cell cycle arrest at the G1-phase and induction of epithelial-mesenchymal transition, indicating that downregulation of cyclin-dependent kinase 4/6-cyclin D1 complexes would mimic ABM. In contrast, knockdown of the Rb protein, which is phosphorylated by cyclin-dependent kinase 4/6, had no effect on the expression level of α-smooth muscle actin, an epithelial-mesenchymal transition marker. Furthermore, ABM-induced epithelial-mesenchymal transition was not affected by Rb knockdown, suggesting that Rb is not involved in the transition process. Our study is the first to suggest that cyclin-dependent kinase 4/6-cyclin D1 complexes, as pharmacological targets of ABM, may contribute to ABM-induced epithelial-mesenchymal transition, followed by clinical disorders such as organ fibrosis and cancer progression. This study suggests that blocking epithelial-mesenchymal transition might be a promising way to prevent negative side effects caused by a medication (ABM) without affecting its ability to treat the disease.

Directly targeting BAX for drug discovery: Therapeutic opportunities and challenges

For over two decades, the development of B-cell lymphoma-2 (Bcl-2) family therapeutics has primarily focused on anti-apoptotic proteins, resulting in the first-in-class drugs called BH3 mimetics, especially for Bcl-2 inhibitor Venetoclax. The pro-apoptotic protein Bcl-2-associated X protein (BAX) plays a crucial role as the executioner protein of the mitochondrial regulated cell death, contributing to organismal development, tissue homeostasis, and immunity. The dysregulation of BAX is closely associated with the onset and progression of diseases characterized by pathologic cell survival or death, such as cancer, neurodegeneration, and heart failure. In addition to conducting thorough investigations into the physiological modulation of BAX, research on the regulatory mechanisms of small molecules identified through biochemical screening approaches has prompted the identification of functional and potentially druggable binding sites on BAX, as well as diverse all-molecule BAX modulators. This review presents recent advancements in elucidating the physiological and pharmacological modulation of BAX and in identifying potentially druggable binding sites on BAX. Furthermore, it highlights the structural and mechanistic insights into small-molecule modulators targeting diverse binding surfaces or conformations of BAX, offering a promising avenue for developing next-generation apoptosis modulators to treat a wide range of diseases associated with dysregulated cell death by directly targeting BAX.

L858R emerges as a potential biomarker predicting response of lung cancer models to anti-EGFR antibodies: Comparison of osimertinib vs. cetuximab

EGFR-specific tyrosine kinase inhibitors (TKIs), especially osimertinib, have changed lung cancer therapy, but secondary mutations confer drug resistance. Because other EGFR mutations promote dimerization-independent active conformations but L858R strictly depends on receptor dimerization, we herein evaluate the therapeutic potential of dimerization-inhibitory monoclonal antibodies (mAbs), including cetuximab. This mAb reduces viability of cells expressing L858R-EGFR and blocks the FOXM1-aurora survival pathway, but other mutants show no responses. Unlike TKI-treated patient-derived xenografts, which relapse post osimertinib treatment, cetuximab completely prevents relapses of L858R+ tumors. We report that osimertinib's inferiority associates with induction of mutagenic reactive oxygen species, whereas cetuximab's superiority is due to downregulation of adaptive survival pathways (e.g., HER2) and avoidance of mutation-prone mechanisms that engage AXL, RAD18, and the proliferating cell nuclear antigen. These results identify L858R as a predictive biomarker, which may pave the way for relapse-free mAb monotherapy relevant to a large fraction of patients with lung cancer.

The Resistance to EGFR-TKIs in Non-Small Cell Lung Cancer: From Molecular Mechanisms to Clinical Application of New Therapeutic Strategies

Almost 17% of Western patients affected by non-small cell lung cancer (NSCLC) have an activating epidermal growth factor receptor (EGFR) gene mutation. Del19 and L858R are the most-common ones; they are positive predictive factors for EGFR tyrosine kinase inhibitors (TKIs). Currently, osimertinib, a third-generation TKI, is the standard first-line therapy for advanced NSCLC patients with common EGFR mutations. This drug is also administered as a second-line treatment for those patients with the T790M EGFR mutation and previously treated with first- (erlotinib, gefitinib) or second- (afatinib) generation TKIs. However, despite the high clinical efficacy, the prognosis remains severe due to intrinsic or acquired resistance to EGRF-TKIs. Various mechanisms of resistance have been reported including the activation of other signalling pathways, the development of secondary mutations, the alteration of the downstream pathways, and phenotypic transformation. However, further data are needed to achieve the goal of overcoming resistance to EGFR-TKIs, hence the necessity of discovering novel genetic targets and developing new-generation drugs. This review aimed to deepen the knowledge of intrinsic and acquired molecular mechanisms of resistance to EGFR-TKIs and the development of new therapeutic strategies to overcome TKIs' resistance.

Integrated CRISPR screening and drug profiling identifies combination opportunities for EGFR, ALK, and BRAF/MEK inhibitors

Anti-tumor efficacy of targeted therapies is variable across patients and cancer types. Even in patients with initial deep response, tumors are typically not eradicated and eventually relapse. To address these challenges, we present a systematic screen for targets that limit the anti-tumor efficacy of EGFR and ALK inhibitors in non-small cell lung cancer and BRAF/MEK inhibitors in colorectal cancer. Our approach includes genome-wide CRISPR screens with or without drugs targeting the oncogenic driver ("anchor therapy"), and large-scale pairwise combination screens of anchor therapies with 351 other drugs. Interestingly, targeting of a small number of genes, including MCL1, BCL2L1, and YAP1, sensitizes multiple cell lines to the respective anchor therapy. Data from drug combination screens with EGF816 and ceritinib indicate that dasatinib and agents disrupting microtubules act synergistically across many cell lines. Finally, we show that a higher-order-combination screen with 26 selected drugs in two resistant EGFR-mutant lung cancer cell lines identified active triplet combinations.

Effect of BIM expression on the prognostic value of PD-L1 in advanced non-small cell lung cancer patients treated with EGFR-TKIs

The role of Programmed Cell Death Ligand 1 (PD-L1) expression in predicting epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKIs) efficacy remains controversial. Recent studies have highlighted that tumor-intrinsic PD-L1 signaling can be modulated by STAT3, AKT, MET oncogenic pathway, epithelial-mesenchymal transition, or BIM expression. This study aimed to investigate whether these underlying mechanisms affect the prognostic role of PD-L1. We retrospectively enrolled patients with EGFR mutant advanced stage NSCLC who received first-line EGFR-TKI between January 2017 and June 2019, the treatment efficacy of EGFR-TKI was assessed. Kaplan-Meier analysis of progression-free survival (PFS) revealed that patients with high BIM expression had shorter PFS, regardless of PD-L1 expression. This result was also supported by the COX proportional hazard regression analysis. In vitro, we further proved that the knockdown of BIM, instead of PDL1, induced more cell apoptosis following gefitinib treatment. Our data suggest that among the pathways affecting tumor-intrinsic PD-L1 signaling, BIM is potentially the underlying mechanism that affects the role of PD-L1 expression in predicting response to EGFR TKI and mediates cell apoptosis under treatment with gefitinib in EGFR-mutant NSCLC. Further prospective studies are required to validate these results.

The Role of Proteomics and Phosphoproteomics in the Discovery of Therapeutic Targets and Biomarkers in Acquired EGFR-TKI-Resistant Non-Small Cell Lung Cancer

The discovery of potent EGFR-tyrosine kinase inhibitors (EGFR-TKIs) has revolutionized the treatment of EGFR-mutated lung cancer. Despite the fact that EGFR-TKIs have yielded several significant benefits for lung cancer patients, the emergence of resistance to EGFR-TKIs has been a substantial impediment to improving treatment outcomes. Understanding the molecular mechanisms underlying resistance is crucial for the development of new treatments and biomarkers for disease progression. Together with the advancement in proteome and phosphoproteome analysis, a diverse set of key signaling pathways have been successfully identified that provide insight for the discovery of possible therapeutically targeted proteins. In this review, we highlight the proteome and phosphoproteomic analyses of non-small cell lung cancer (NSCLC) as well as the proteome analysis of biofluid specimens that associate with acquired resistance in response to different generations of EGFR-TKI. Furthermore, we present an overview of the targeted proteins and potential drugs that have been tested in clinical studies and discuss the challenges of implementing this discovery in future NSCLC treatment.

Endogenous and imposed determinants of apoptotic vulnerabilities in cancer

The intrinsic apoptosis pathway is controlled by the BCL-2 family of proteins. Although the pro-survival members of this family can help cancer cells evade apoptosis, they may also produce apoptotic vulnerabilities that can potentially be exploited therapeutically. Apoptotic vulnerabilities can be driven by endogenous factors including altered genetics, signaling, metabolism, structure and lineage or differentiation state as well as imposed factors, the most prominent being exposure to anti-cancer agents. The recent development of BH3 mimetics that inhibit pro-survival BCL-2 family proteins has allowed these apoptotic vulnerabilities to be targeted with demonstrable clinical success. Here, we review the key concepts that are vital for understanding, uncovering, and exploiting apoptotic vulnerabilities in cancer for the potential improvement of patient outcomes.

BCL2L11 Induction Mediates Sensitivity to Src and MEK1/2 Inhibition in Thyroid Cancer

Patients with advanced thyroid cancer, including advanced papillary thyroid cancer and anaplastic thyroid cancer (ATC), have low survival rates because of the lack of efficient therapies available that can combat their aggressiveness. A total of 90% of thyroid cancers have identifiable driver mutations, which often are components of the MAPK pathway, including BRAF, RAS, and RET-fusions. In addition, Src is a non-receptor tyrosine kinase that is overexpressed and activated in thyroid cancer, which we and others have shown is a clinically relevant target. We have previously demonstrated that combined inhibition of Src with dasatinib and the MAPK pathway with trametinib synergistically inhibits growth and induces apoptosis in BRAF- and RAS-mutant thyroid cancer cells. Herein, we identified the pro-apoptotic protein BCL2L11 (BIM) as being a key mediator of sensitivity in response to combined dasatinib and trametinib treatment. Specifically, cells that are sensitive to combined dasatinib and trametinib treatment have inhibition of FAK/Src, MEK/ERK, and AKT, resulting in the dramatic upregulation of BIM, while cells that are resistant lack inhibition of AKT and have a dampened induction of BIM. Inhibition of AKT directly sensitizes resistant cells to combined dasatinib and trametinib but will not be clinically feasible. Importantly, targeting BCL-XL with the BH3-mimeitc ABT-263 is sufficient to overcome lack of BIM induction and sensitize resistant cells to combined dasatinib and trametinib treatment. This study provides evidence that combined Src and MEK1/2 inhibition is a promising therapeutic option for patients with advanced thyroid cancer and identifies BIM induction as a potential biomarker of response.

Bcl-xL Is a Key Mediator of Apoptosis Following KRASG12C Inhibition in KRASG12C-mutant Colorectal Cancer

Novel covalent inhibitors of KRASG12C have shown limited response rates in patients with KRASG12C-mutant (MT) colorectal cancer. Thus, novel KRASG12C inhibitor combination strategies that can achieve deep and durable responses are needed. Small-molecule KRASG12C inhibitors AZ'1569 and AZ'8037 were used. To identify novel candidate combination strategies for AZ'1569, we performed RNA sequencing, siRNA, and high-throughput drug screening. Top hits were validated in a panel of KRASG12CMT colorectal cancer cells and in vivo. AZ'1569-resistant colorectal cancer cells were generated and characterized. We found that response to AZ'1569 was heterogeneous across the KRASG12CMT models. AZ'1569 was ineffective at inducing apoptosis when used as a single agent or combined with chemotherapy or agents targeting the EGFR/KRAS/AKT axis. Using a systems biology approach, we identified the antiapoptotic BH3-family member BCL2L1/Bcl-xL as a top hit mediating resistance to AZ'1569. Further analyses identified acute increases in the proapoptotic protein BIM following AZ'1569 treatment. ABT-263 (navitoclax), a pharmacologic Bcl-2 family inhibitor that blocks the ability of Bcl-xL to bind and inhibit BIM, led to dramatic and universal apoptosis when combined with AZ'1569. Furthermore, this combination also resulted in dramatically attenuated tumor growth in KRASG12CMT xenografts. Finally, AZ'1569-resistant cells showed amplification of KRASG12C, EphA2/c-MET activation, increased proinflammatory chemokine profile and cross-resistance to several targeted agents. Importantly, KRAS amplification and AZ'1569 resistance were reversible upon drug withdrawal, arguing strongly for the use of drug holidays in the case of KRAS amplification. Taken together, combinatorial targeting of Bcl-xL and KRASG12C is highly effective, suggesting a novel therapeutic strategy for patients with KRASG12CMT colorectal cancer.

Mechanisms of EGFR-TKI-Induced Apoptosis and Strategies Targeting Apoptosis in EGFR-Mutated Non-Small Cell Lung Cancer

Homeostasis is achieved by balancing cell survival and death. In cancer cells, especially those carrying driver mutations, the processes and signals that promote apoptosis are inhibited, facilitating the survival and proliferation of these dysregulated cells. Apoptosis induction is an important mechanism underlying the therapeutic efficacy of epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) for EGFR-mutated non-small cell lung cancer (NSCLC). However, the mechanisms by which EGFR-TKIs induce apoptosis have not been fully elucidated. A deeper understanding of the apoptotic pathways induced by EGFR-TKIs is essential for the developing novel strategies to overcome resistance to EGFR-TKIs or to enhance the initial efficacy through therapeutic synergistic combinations. Recently, therapeutic strategies targeting apoptosis have been developed for cancer. Here, we review the state of knowledge on EGFR-TKI-induced apoptotic pathways and discuss the therapeutic strategies for enhancing EGFR-TKI efficiency. We highlight the great progress achieved with third-generation EGFR-TKIs. In particular, combination therapies of EGFR-TKIs with anti-vascular endothelial growth factor/receptor inhibitors or chemotherapy have emerged as promising therapeutic strategies for patients with EGFR-mutated NSCLC. Nevertheless, further breakthroughs are needed to yield an appropriate standard care for patients with EGFR-mutated NSCLC, which requires gaining a deeper understanding of cancer cell dynamics in response to EGFR-TKIs.

Non-small Cell Lung Cancer with EGFR or HER2 Exon 20 Insertion Mutations: Diagnosis and Treatment Options

Molecular testing is performed upon diagnosis of non-small cell lung cancer (NSCLC) because of the large success of targeted therapies for oncogenic mutations. Epidermal growth factor receptor (EGFR) mutations are the most commonly identified mutation in NSCLC, and EGFR exon 20 insertion mutations (exon20ins) are the third most common mutation in EGFR following EGFR exon 19 deletions and exon 21 L858R mutations. EGFR exon20ins have regularly demonstrated resistance to classical EGFR inhibition. Two treatments-mobocertinib and amivantamab-have recently been the first drugs to be approved by the US Food and Drug Administration (FDA) for treatment of lung cancers with these mutations following platinum-based therapy. Research surrounding these two drugs demonstrates strong efficacy, but with an intense array of side effects. Another targetable driver mutation is the human epidermal growth factor receptor 2 (HER2) exon20ins, representing approximately 2-3% of NSCLC patients. This mutation has been heavily studied in vitro as well as clinically, and trastuzumab deruxtecan was just recently granted accelerated FDA approval based on the high efficacy demonstrated in the Destiny-Lung01 study. However, similar to their EGFR counterparts, HER2 inhibitors also have evidence of toxicity in clinical studies. In this paper, we discuss the limited response of EGFR and HER2 exon20ins to a wide range of standard treatment regimens, such as platinum-based chemotherapy and classic EGFR tyrosine kinase inhibitors, as well as immunotherapy. We also review recently approved and upcoming targeted therapeutic options, considering what research is presently being done regarding efficacy and the reduction of side effects, as well as the agents' risks and benefits for incorporation into an approved treatment regimen.

Establishment of an acquired lorlatinib-resistant cell line of non-small cell lung cancer and its mediated resistance mechanism

PURPOSE

Although lorlatinib, the third generation of echinoderm microtubule protein 4-anaplastic lymphoma kinase (EML4-ALK) tyrosine kinase inhibitor (TKI), overcame the previous generation ALK-TKIs' drug resistance problems, but the mechanism of lorlatinib resistance remained unclear. Furthermore, optimal chemotherapy for lorlatinib-resistant non-small cell lung cancer (NSCLC) patients was still unknown.

METHODS

A lorlatinib-resistant NSCLC cell line SNU-2535LR was generated by gradually increasing dose of lorlatinib to crizotinib-resistant cell line SNU-2535 in vitro. To study the resistance mechanism of SNU-2535LR cells, we applied CCK-8 assay to detect the sensitivity of crizotinib and the reverse effect of APR-246, a p53 activator, on lorlatinib-induced resistance and different chemotherapy drugs to SNU-2535LR cells. We also detected the expressions of EML4-ALK-related proteins of SNU-2535LR cells via western blot.Please confirm that author names have been identified correctly and are presented in the right order.Dear Editor:     I have carefully confirmed that the author names have been identified correctly and are presented in right order.Thank you very much!                                                                     Your sincerely BoXie RESULTS: The sensitivity of SNU-2535LR cells to lorlatinib was decreased significantly than that of SNU-2535 cells. EML4-ALK fusion was decreased both at protein level and DNA level in SNU-2535LR cells. More interesting, the crizotinib-resistant mutation ALK p.G1269A disappeared, while new TP53 mutation emerged in SNU-2535LR cells. APR-246 can reverse the lorlatinib resistance in SNU-2535LR cells, with a reversal index of 4.768. Compared with SNU-2535 cells, the sensitivity of SNU-2535LR cells to gemcitabine, docetaxel and paclitaxel was significantly increased (P < 0.05), but decreased to cisplatin (P < 0.05).

CONCLUSION

This study demonstrated that the combination of p53 protein agonist and lorlatinib may provide a new therapeutic strategy for NSCLC patients with lorlatinib resistance and TP53 mutation. Furthermore, the results also provide guidance for selecting optimal chemo-regimens for NSCLC patients after ALK-TKIs failure.

Targeting apoptosis to manage acquired resistance to third generation EGFR inhibitors

A significant clinical challenge in lung cancer treatment is management of the inevitable acquired resistance to third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs), such as osimertinib, which have shown remarkable success in the treatment of advanced NSCLC with EGFR activating mutations, in order to achieve maximal response duration or treatment remission. Apoptosis is a major type of programmed cell death tightly associated with cancer development and treatment. Evasion of apoptosis is considered a key hallmark of cancer and acquisition of apoptosis resistance is accordingly a key mechanism of drug acquired resistance in cancer therapy. It has been clearly shown that effective induction of apoptosis is a key mechanism for third generation EGFR-TKIs, particularly osimertinib, to exert their therapeutic efficacies and the development of resistance to apoptosis is tightly associated with the emergence of acquired resistance. Hence, restoration of cell sensitivity to undergo apoptosis using various means promises an effective strategy for the management of acquired resistance to third generation EGFR-TKIs.

Minimal residual disease in EGFR-mutant non-small-cell lung cancer

Targeted therapy with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) is an effective treatment for EGFR-mutant non-small-cell lung cancer (NSCLC), however most patients invariably relapse after a period of minimal residual disease (MRD). This mini-review explores the mechanistic pathways leading to tumour dormancy, cellular senescence and epigenetic changes involving YAP/TEAD activation. We describe the various approaches of utilising TKIs in combination with agents to intensify initial depth of response, enhance apoptosis and target senescence-like dormancy. This mini-review will also highlight the potential novel therapies under development targeting MRD to improve outcomes for patients with EGFR-mutant NSCLC.

Pharmacologic Inhibition of SHP2 Blocks Both PI3K and MEK Signaling in Low-epiregulin HNSCC via GAB1

Preclinical and clinical studies have evidenced that effective targeted therapy treatment against receptor tyrosine kinases (RTKs) in different solid tumor paradigms is predicated on simultaneous inhibition of both the PI3K and MEK intracellular signaling pathways. Indeed, re-activation of either pathway results in resistance to these therapies. Recently, oncogenic phosphatase SHP2 inhibitors have been developed with some now reaching clinical trials. To expand on possible indications for SHP099, we screened over 800 cancer cell lines covering over 25 subsets of cancer. We found HNSCC was the most sensitive adult subtype of cancer to SHP099. We found that, in addition to the MEK pathway, SHP2 inhibition blocks the PI3K pathway in sensitive HNSCC, resulting in downregulation of mTORC signaling and anti-tumor effects across several HNSCC mouse models, including an HPV+ patient-derived xenograft (PDX). Importantly, we found low levels of the RTK ligand epiregulin identified HNSCCs that were sensitive to SHP2 inhibitor, and, adding exogenous epiregulin mitigated SHP099 efficacy. Mechanistically, epiregulin maintained SHP2-GAB1 complexes in the presence of SHP2 inhibition, preventing downregulation of the MEK and PI3K pathways. We demonstrate HNSCCs were highly dependent on GAB1 for their survival and knockdown of GAB1 is sufficient to block the ability of epiregulin to rescue MEK and PI3K signaling. These data connect the sensitivity of HNSCC to SHP2 inhibitors and to a broad reliance on GAB1-SHP2, revealing an important and druggable signaling axis. Overall, SHP2 inhibitors are being heavily developed and may have activity in HNSCCs, and in particular those with low levels of epiregulin.

Early Steps of Resistance to Targeted Therapies in Non-Small-Cell Lung Cancer

Simple Summary

Patients with lung cancer benefit from more effective treatments, such as targeted therapies, and the overall survival has increased in the past decade. However, the efficacy of targeted therapies is limited due to the emergence of resistance. Growing evidence suggests that resistances may arise from a small population of drug-tolerant persister (DTP) cells. Understanding the mechanisms underlying DTP survival is therefore crucial to develop therapeutic strategies to prevent the development of resistance. Herein, we propose an overview of the current scientific knowledge about the characterisation of DTP, and summarise the new therapeutic strategies that are tested to target these cells.

Abstract

Lung cancer is the leading cause of cancer-related deaths among men and women worldwide. Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are effective therapies for advanced non-small-cell lung cancer (NSCLC) patients harbouring EGFR-activating mutations, but are not curative due to the inevitable emergence of resistances. Recent in vitro studies suggest that resistance to EGFR-TKI may arise from a small population of drug-tolerant persister cells (DTP) through non-genetic reprogramming, by entering a reversible slow-to-non-proliferative state, before developing genetically derived resistances. Deciphering the molecular mechanisms governing the dynamics of the drug-tolerant state is therefore a priority to provide sustainable therapeutic solutions for patients. An increasing number of molecular mechanisms underlying DTP survival are being described, such as chromatin and epigenetic remodelling, the reactivation of anti-apoptotic/survival pathways, metabolic reprogramming, and interactions with their micro-environment. Here, we review and discuss the existing proposed mechanisms involved in the DTP state. We describe their biological features, molecular mechanisms of tolerance, and the therapeutic strategies that are tested to target the DTP.

Adapted to Survive: Targeting Cancer Cells with BH3 Mimetics

A hallmark of cancer is cell death evasion, underlying suboptimal responses to chemotherapy, targeted agents, and immunotherapies. The approval of the antiapoptotic BCL2 antagonist venetoclax has finally validated the potential of targeting apoptotic pathways in patients with cancer. Nevertheless, pharmacologic modulators of cell death have shown markedly varied responses in preclinical and clinical studies. Here, we review emerging concepts in the use of this class of therapies. Building on these observations, we propose that treatment-induced changes in apoptotic dependency, rather than pretreatment dependencies, will need to be recognized and targeted to realize the precise deployment of these new pharmacologic agents.

SIGNIFICANCE

Targeting antiapoptotic family members has proven efficacious and tolerable in some cancers, but responses are infrequent, particularly for patients with solid tumors. Biomarkers to aid patient selection have been lacking. Precision functional approaches that overcome adaptive resistance to these compounds could drive durable responses to chemotherapy, targeted therapy, and immunotherapies.

Preclinical Models for Acquired Resistance to Third-Generation EGFR Inhibitors in NSCLC: Functional Studies and Drug Combinations Used to Overcome Resistance

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) are currently recommended as first-line treatment for advanced non-small-cell lung cancer (NSCLC) with EGFR-activating mutations. Third-generation (3rd G) EGFR-TKIs, including osimertinib, offer an effective treatment option for patients with NSCLC resistant 1st and 2nd EGFR-TKIs. However, the efficacy of 3rd G EGFR-TKIs is limited by acquired resistance that has become a growing clinical challenge. Several clinical and preclinical studies are being carried out to better understand the mechanisms of resistance to 3rd G EGFR-TKIs and have revealed various genetic aberrations associated with molecular heterogeneity of cancer cells. Studies focusing on epigenetic events are limited despite several indications of their involvement in the development of resistance. Preclinical models, established in most cases in a similar manner, have shown different prevalence of resistance mechanisms from clinical samples. Clinically identified mechanisms include EGFR mutations that were not identified in preclinical models. Thus, NRAS genetic alterations were not observed in patients but have been described in cell lines resistant to 3rd G EGFR-TKI. Mainly, resistance to 3rd G EGFR-TKI in preclinical models is related to the activation of alternative signaling pathways through tyrosine kinase receptor (TKR) activation or to histological and phenotypic transformations. Yet, preclinical models have provided some insight into the complex network between dominant drivers and associated events that lead to the emergence of resistance and consequently have identified new therapeutic targets. This review provides an overview of preclinical studies developed to investigate the mechanisms of acquired resistance to 3rd G EGFR-TKIs, including osimertinib and rociletinib, across all lines of therapy. In fact, some of the models described were first generated to be resistant to first- and second-generation EGFR-TKIs and often carried the T790M mutation, while others had never been exposed to TKIs. The review further describes the therapeutic opportunities to overcome resistance, based on preclinical studies.

Resistance mechanisms to osimertinib and emerging therapeutic strategies in nonsmall cell lung cancer

PURPOSE OF REVIEW

This review aims to introduce the resistance mechanisms to osimertinib, discuss the therapeutic strategies, and make clinical updates in overcoming resistance to osimertinib.

RECENT FINDINGS

Osimertinib has shown favorable efficacy on second-line and first-line treatments in EGFR-mutant advanced nonsmall cell lung cancer (NSCLC). However, the presence of primary and acquired resistance to osimertinib restricts its clinical benefits. The primary resistance mainly consists of BIM deletion polymorphism and EGFR exon 20 insertions. Meanwhile, the heterogeneous mechanisms of acquired resistance include EGFR-dependent (on-target) and EGFR-independent (off-target) mechanisms. EGFR C797S mutation, MET amplification, HER2 amplification, and small cell lung cancer transformation were identified as frequent resistance mechanisms. Recently, more novel mechanisms, including rare EGFR point mutations and oncogenic fusions, were reported. With the results of completed and on-going clinical trials, the emerging therapeutic strategies of postosimertinib progression are summarized.

SUMMARY

The resistance mechanisms to osimertinib are heterogeneous and gradually perfected. The combination of osimertinib with bypass targeted therapy and other therapeutic approaches emerge as promising strategies.

Prognostic Value of BIM Deletion in EGFR-Mutant NSCLC Patients Treated with EGFR-TKIs: A Meta-Analysis

BACKGROUND

Resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) is inevitable in EGFR-mutant non-small-cell lung cancer (NSCLC) patients. A germline 2903 bp deletion polymorphism of Bcl-2-like protein 11 (BIM) causes reduced expression of proapoptotic BH3-only BIM protein and blocks TKI-induced apoptosis of tumor cells. Yet the association between the deletion polymorphism and response to EGFR-TKI treatment remains inconsistent among clinical observations. Thus, we performed the present meta-analysis.

METHODS

Eligible studies were identified by searching PubMed, Embase, and ClinicalTrials.gov databases prior to March 31, 2021. Hazard ratios (HRs) and 95% confidence intervals (CIs) of progression-free survival (PFS) and overall survival (OS) and odds ratios (ORs) and 95% CIs of objective response rate (ORR) and disease control rate (DCR) were calculated by using a random effects model. Sensitivity, metaregression, and publication bias analyses were also performed.

RESULTS

A total of 20 datasets (3003 EGFR-mutant NSCLC patients receiving EGFR-TKIs from 18 studies) were included. There were 475 (15.8%) patients having the 2903-bp intron deletion of BIM and 2528 (84.2%) wild-type patients. BIM deletion predicted significantly shorter PFS (HR = 1.35, 95% CI: 1.10-1.64, P = 0.003) and a tendency toward an unfavorable OS (HR = 1.22, 95% CI: 0.99-1.50, P = 0.068). Patients with deletion polymorphism had lower ORR (OR = 0.60, 95% CI: 0.42-0.85, P = 0.004) and DCR (OR = 0.59, 95% CI: 0.38-0.90, P = 0.014) compared with those without deletion.

CONCLUSION

BIM deletion polymorphism may confer resistance to EGFR-TKIs and can be used as a biomarker to predict treatment response to EGFR-TKIs in EGFR-mutant NSCLC patients from Asian populations.

IRS1 phosphorylation underlies the non-stochastic probability of cancer cells to persist during EGFR inhibition therapy

Stochastic transition of cancer cells between drug-sensitive and drug-tolerant persister phenotypes has been proposed to play a key role in non-genetic resistance to therapy. Yet, we show here that cancer cells actually possess a highly stable inherited chance to persist (CTP) during therapy. This CTP is non-stochastic, determined pre-treatment and has a unimodal distribution ranging from 0 to almost 100%. Notably, CTP is drug specific. We found that differential serine/threonine phosphorylation of the insulin receptor substrate 1 (IRS1) protein determines the CTP of lung and of head and neck cancer cells under epidermal growth factor receptor inhibition, both in vitro and in vivo. Indeed, the first-in-class IRS1 inhibitor NT219 was highly synergistic with anti-epidermal growth factor receptor therapy across multiple in vitro and in vivo models. Elucidation of drug-specific mechanisms that determine the degree and stability of cellular CTP may establish a framework for the elimination of cancer persisters, using new rationally designed drug combinations.

Molecular Mechanism of EGFR-TKI Resistance in EGFR-Mutated Non-Small Cell Lung Cancer: Application to Biological Diagnostic and Monitoring

Non-small cell lung cancer (NSCLC) is the most common cancer in the world. Activating epidermal growth factor receptor (EGFR) gene mutations are a positive predictive factor for EGFR tyrosine kinase inhibitors (TKIs). For common EGFR mutations (Del19, L858R), the standard first-line treatment is actually third-generation TKI, osimertinib. In the case of first-line treatment by first (erlotinib, gefitinib)- or second-generation (afatinib) TKIs, osimertinib is approved in second-line treatment for patients with T790M EGFR mutation. Despite the excellent disease control results with EGFR TKIs, acquired resistance inevitably occurs and remains a biological challenge. This leads to the discovery of novel biomarkers and possible drug targets, which vary among the generation/line of EGFR TKIs. Besides EGFR second/third mutations, alternative mechanisms could be involved, such as gene amplification or gene fusion, which could be detected by different molecular techniques on different types of biological samples. Histological transformation is another mechanism of resistance with some biological predictive factors that needs tumor biopsy. The place of liquid biopsy also depends on the generation/line of EGFR TKIs and should be a good candidate for molecular monitoring. This article is based on the literature and proposes actual and future directions in clinical and translational research.

Targeting Aurora B kinase prevents and overcomes resistance to EGFR inhibitors in lung cancer by enhancing BIM- and PUMA-mediated apoptosis

The clinical success of EGFR inhibitors in EGFR-mutant lung cancer is limited by the eventual development of acquired resistance. We hypothesize that enhancing apoptosis through combination therapies can eradicate cancer cells and reduce the emergence of drug-tolerant persisters. Through high-throughput screening of a custom library of ∼1,000 compounds, we discover Aurora B kinase inhibitors as potent enhancers of osimertinib-induced apoptosis. Mechanistically, Aurora B inhibition stabilizes BIM through reduced Ser87 phosphorylation, and transactivates PUMA through FOXO1/3. Importantly, osimertinib resistance caused by epithelial-mesenchymal transition (EMT) activates the ATR-CHK1-Aurora B signaling cascade and thereby engenders hypersensitivity to respective kinase inhibitors by activating BIM-mediated mitotic catastrophe. Combined inhibition of EGFR and Aurora B not only efficiently eliminates cancer cells but also overcomes resistance beyond EMT.

Cell-intrinsic mechanisms of drug tolerance to systemic therapies in cancer

In cancer patients with metastatic disease, the rate of complete tumor response to systemic therapies is low, and residual lesions persist in the majority of patients due to early molecular adaptation in cancer cells. A growing body of evidence suggests that a subpopulation of drug-tolerant « persister » cells - a reversible phenotype characterized by reduced drug sensitivity and decreased cell proliferation - maintains residual disease and may serve as a reservoir for resistant phenotypes. The survival of these residual tumor cells can be caused by reactivation of specific signaling pathways, phenotypic plasticity (i.e., transdifferentiation), epigenetic or metabolic reprogramming, downregulation of apoptosis as well as transcriptional remodeling. In this review, we discuss the molecular mechanisms that enable adaptive survival in drug-tolerant cells. We describe the main characteristics and dynamic nature of this persistent state, and highlight the current therapeutic strategies that may be used to interfere with the establishment of drug-tolerant cells, as an alternative to improve objective response to systemic therapies and delay the emergence of resistance to improve long-term survival.

ER+ Breast Cancer Strongly Depends on MCL-1 and BCL-xL Anti-Apoptotic Proteins

Breast cancer is the most frequent type of cancer and the major cause of mortality in women. The rapid development of various therapeutic options has led to the improvement of treatment outcomes; nevertheless, one-third of estrogen receptor (ER)-positive patients relapse due to cancer cell acquired resistance. Here, we use dynamic BH3 profiling (DBP), a functional predictive assay that measures net changes in apoptotic priming, to find new effective treatments for ER+ breast cancer. We observed anti-apoptotic adaptations upon treatment that pointed to metronomic therapeutic combinations to enhance cytotoxicity and avoid resistance. Indeed, we found that the anti-apoptotic proteins BCL-xL and MCL-1 are crucial for ER+ breast cancer cells resistance to therapy, as they exert a dual inhibition of the pro-apoptotic protein BIM and compensate for each other. In addition, we identified the AKT inhibitor ipatasertib and two BH3 mimetics targeting these anti-apoptotic proteins, S63845 and A-1331852, as new potential therapies for this type of cancer. Therefore, we postulate the sequential inhibition of both proteins using BH3 mimetics as a new treatment option for refractory and relapsed ER+ breast cancer tumors.

Dexmedetomidine alleviates cardiomyocyte apoptosis and cardiac dysfunction may be associated with inhibition of RhoA/ROCK pathway in mice with myocardial infarction

The global incidence of myocardial infarction has been consistently high, and it is one of the main causes of poor cardiovascular prognosis. Dexmedetomidine (DEX) is a highly selective α2 receptor agonist. Recent studies have found that DEX has a protective effect on myocardial infarction, but its specific mechanism is still unclear. In this experiment, we permanently ligated the anterior descending branch of mice to explore the protective mechanism of DEX against myocardial infarction. Our study found that intraperitoneal injection of DEX for 7 days after myocardial infarction in mice can increase the reduction of ejection fraction (EF) and fractional shortening (FS) caused by myocardial infarction and significantly reduce the release of serum markers. The results of myocardial HE and Sirius red staining suggest that the changes in the myocardial structure of mice after using DEX are reduced. Immunohistochemistry shows that DEX reduces the expression of ROCK1 protein after myocardial infarction. TUNEL staining and the protein expression levels of cleaved caspase-3 and cleaved caspase-9 were used to detect cell apoptosis and results make clear that DEX can reduce the apoptosis caused by myocardial infarction. Western blot experiments showed that DEX can reduce the expression levels of ROCK1 and ROCK2 (Rho-kinase). At the same time, it was observed that DEX improved the Bcl-2/Bax ratio. The above results indicate that DEX reduces cardiomyocyte apoptosis and improves cardiac function likely through inhibiting the RhoA/ROCK signaling pathway. This study may provide new insights into the protective effect of DEX after myocardial infarction in mice.

Multistage-responsive nanovehicle to improve tumor penetration for dual-modality imaging-guided photodynamic-immunotherapy

The exploration of an intelligent multifunctional imaging-guided therapeutic platform is of great significance because of its ideal delivery efficiency and controlled release. In this work, a tumor microenvironment (TME)-responsive nanocarrier (denoted as MB@MSP) is designed for on-demand, sequentially release of a short D-peptide antagonist of programmed cell death-ligand 1 (named as P^DPPA-1) and a photosensitizer methylene blue (MB). Fe₃O₄-Au located in the core of MB@MSP is used as a magnetic resonance imaging and micro-computed tomography imaging contrast agent for noninvasive diagnosis of solid tumors and simultaneous monitoring of drug delivery. The P^DPPA-1 coated on MB@MSP can be shed due to the cleavage of the peptide substrate by matrix metalloproteinase-2 (MMP-2) that is highly expressed in the tumor stroma, and disulfide bonding is further broken when it encounters high levels of glutathione (GSH) in TME, which finally leads to significant size reduction and charge-reversal. These transitions facilitate penetration and uptake of nanocarriers against tumors. Noticeably, the released P^DPPA-1 can block the immune checkpoint to create an environment that favors the activation of cytotoxic T lymphocytes and augment the antitumor immune response elicited by photodynamic therapy, thus significantly improving therapeutic outcomes. Studies of the underlying mechanisms suggest that the designed MMP-2 and GSH-sensitive delivery system not only induce apoptosis of tumor cells but also modulate the immunosuppressive tumor microenvironment to eventually augment the suppression tumor metastasis effect of CD8⁺ cytotoxic T cells. Overall, the visualization of the therapeutic processes with comprehensive information renders MB@MSP an intriguing platform to realize the combined treatment of metastatic tumors.

Epidermal Growth Factor Receptor Expression and Resistance Patterns to Targeted Therapy in Non-Small Cell Lung Cancer: A Review

Globally, lung cancer is the leading cause of cancer-related death. The majority of non-small cell lung cancer (NSCLC) tumours express epidermal growth factor receptor (EGFR), which allows for precise and targeted therapy in these patients. The dysregulation of EGFR in solid epithelial cancers has two distinct mechanisms: either a kinase-activating mutation in EGFR (EGFR-mutant) and/or an overexpression of wild-type EGFR (wt-EGFR). The underlying mechanism of EGFR dysregulation influences the efficacy of anti-EGFR therapy as well as the nature of resistance patterns and secondary mutations. This review will critically analyse the mechanisms of EGFR expression in NSCLC, its relevance to currently approved targeted treatment options, and the complex nature of secondary mutations and intrinsic and acquired resistance patterns in NSCLC.

Phase IB Study of Osimertinib in Combination with Navitoclax in EGFR-mutant NSCLC Following Resistance to Initial EGFR Therapy (ETCTN 9903)

PURPOSE

Osimertinib is an effective therapy in EGFR-mutant non-small cell lung cancer (NSCLC), but resistance invariably develops. Navitoclax is an oral inhibitor of BCL-2/BCL-xL that has exhibited synergy with osimertinib in preclinical models of EGFR-mutant NSCLC. In hematologic malignancies, BCL-2 family inhibitors in combination therapy effectively increase cellular apoptosis and decrease drug resistance.

PATIENTS AND METHODS

This single-arm phase Ib study evaluated safety, tolerability, and feasibility of osimertinib and navitoclax, including dose expansion in T790M-positive patients at the recommended phase II dose (RP2D). Eligible patients had advanced EGFR-mutant NSCLC with prior tyrosine kinase inhibitor exposure. Five dose levels were planned with osimertinib from 40 to 80 mg orally daily and navitoclax from 150 to 325 mg orally daily.

RESULTS

A total of 27 patients were enrolled (18 in the dose-escalation cohort and nine in the dose-expansion cohort): median age 65, 67% female, 48% exon 19 del, and 37% L858R, median one prior line of therapy. The most common adverse events were lymphopenia (37%), fatigue (22%), nausea (22%), and thrombocytopenia (37%). No dose-limiting toxicities were seen in dose-escalation cohort; osimertinib 80 mg, navitoclax 150 mg was chosen as the RP2D. Most patients (78%) received >95% of planned doses through three cycles. In expansion cohort, objective response rate was 100% and median progression-free survival was 16.8 months. A proapoptotic effect from navitoclax was demonstrated by early-onset thrombocytopenia.

CONCLUSIONS

Oral combination therapy with navitoclax and osimertinib was safe and feasible at RP2D with clinical efficacy. Early thrombocytopenia was common, supporting an target engagement by navitoclax. Further study of BCL-2/BCL-xL inhibition to enhance osimertinib activity is warranted.

Antitumour immunity regulated by aberrant ERBB family signalling

Aberrant signalling of ERBB family members plays an important role in tumorigenesis and in the escape from antitumour immunity in multiple malignancies. Molecular-targeted agents against these signalling pathways exhibit robust clinical efficacy, but patients inevitably experience acquired resistance to these molecular-targeted therapies. Although cancer immunotherapies, including immune checkpoint inhibitors (ICIs), have shown durable antitumour response in a subset of the treated patients in multiple cancer types, clinical efficacy is limited in cancers harbouring activating gene alterations of ERBB family members. In particular, ICI treatment of patients with non-small cell lung cancers with epidermal growth factor receptor (EGFR) alterations and breast cancers with HER2 alterations failed to show clinical benefits, suggesting that EGFR and HER2 signalling may have an essential role in inhibiting antitumour immune responses. Here, we discuss the mechanisms by which the signalling of ERBB family members affects not only autonomous cancer hallmarks, such as uncontrolled cell proliferation, but also antitumour immune responses in the tumour microenvironment and the potential application of immune-genome precision medicine into immunotherapy and molecular-targeted therapy focusing on the signalling of ERBB family members.

Targeting transcription of MCL-1 sensitizes HER2-amplified breast cancers to HER2 inhibitors

Human epidermal growth factor receptor 2 gene (HER2) is focally amplified in approximately 20% of breast cancers. HER2 inhibitors alone are not effective, and sensitizing agents will be necessary to move away from a reliance on heavily toxic chemotherapeutics. We recently demonstrated that the efficacy of HER2 inhibitors is mitigated by uniformly low levels of the myeloid cell leukemia 1 (MCL-1) endogenous inhibitor, NOXA. Emerging clinical data have demonstrated that clinically advanced cyclin-dependent kinase (CDK) inhibitors are effective MCL-1 inhibitors in patients, and, importantly, well tolerated. We, therefore, tested whether the CDK inhibitor, dinaciclib, could block MCL-1 in preclinical HER2-amplified breast cancer models and therefore sensitize these cancers to dual HER2/EGFR inhibitors neratinib and lapatinib, as well as to the novel selective HER2 inhibitor tucatinib. Indeed, we found dinaciclib suppresses MCL-1 RNA and is highly effective at sensitizing HER2 inhibitors both in vitro and in vivo. This combination was tolerable in vivo. Mechanistically, liberating the effector BCL-2 protein, BAK, from MCL-1 results in robust apoptosis. Thus, clinically advanced CDK inhibitors may effectively combine with HER2 inhibitors and present a chemotherapy-free therapeutic strategy in HER2-amplified breast cancer, which can be tested immediately in the clinic.

Erlotinib and Trametinib in Patients With EGFR-Mutant Lung Adenocarcinoma and Acquired Resistance to a Prior Tyrosine Kinase Inhibitor

Inhibition of the MEK/ERK pathway is critical for Bcl-2-like protein 11 (BIM)-mediated epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI)-induced apoptosis, and dysregulation of this pathway may be a mechanism of acquired resistance. Therefore, MEK inhibition with trametinib and an EGFR TKI may resensitize tumors with acquired resistance. Limited targeted therapies are available after progression on EGFR TKIs, and it is in this setting that we completed a phase I/II study of erlotinib and trametinib.

METHODS

Patients with metastatic EGFR-mutant lung adenocarcinoma and acquired resistance to an EGFR TKI received combination erlotinib 75 mg and trametinib 1.5 mg daily until progression or unacceptable side effects. The primary objective was objective response rate determined using RECIST version 1.1.

RESULTS

Twenty-three patients were accrued; patients had received a median of two lines of prior TKI therapy (61% prior osimertinib), and 48% had acquired EGFR T790M. We confirmed one partial response (1/23, 4%, 95% CI, 0 to 22). The median progression-free survival was 1.8 months, and the median overall survival was 21 months. Diarrhea (87%), acneiform rash (87%), and fatigue (52%) were the most common treatment-related adverse events. Two patients who had tumor shrinkage both harbored a BRAF fusion.

CONCLUSION

Addition of trametinib to erlotinib in the acquired resistance setting in an unselected population is not efficacious. Future studies should focus on targeted therapies in molecularly selected populations. Acquired BRAF fusions in patients with EGFR-sensitizing mutations may be a molecular subset where EGFR and MEK combination therapy could be studied further.

Precursor B-ALL Cell Lines Differentially Respond to SYK Inhibition by Entospletinib

BACKGROUND

Impaired B-cell receptor (BCR) function has been associated with the progress of several B-cell malignancies. The spleen tyrosine kinase (SYK) represents a potential therapeutic target in a subset of B-cell neoplasias. In precursor B-acute lymphoblastic leukemia (B-ALL), the pathogenic role and therapeutic potential of SYK is still controversially discussed. We evaluate the application of the SYK inhibitor entospletinib (Ento) in pre- and pro-B-ALL cell lines, characterizing the biologic and molecular effects.

METHODS

SYK expression was characterized in pre-B-ALL (NALM-6) and pro-B-ALL cell lines (SEM and RS4;11). The cell lines were exposed to different Ento concentrations and the cell biological response analyzed by proliferation, metabolic activity, apoptosis induction, cell-cycle distribution and morphology. BCR pathway gene expression and protein modulations were further characterized.

RESULTS

Ento significantly induced anti-proliferative and pro-apoptotic effects in NALM-6 and SEM, while barely affecting RS4;11. Targeted RNAseq revealed pronounced gene expression modulation only in NALM-6, while Western Blot analyses demonstrated that vital downstream effector proteins, such as pAKT, pERK, pGSK3β, p53 and BCL-6, were affected by Ento exposure in the inhibitor-sensitive cell lines.

CONCLUSION

Different acting modes of Ento, independent of pre-BCR dependency, were characterized, unexpected in SEM. Accordingly, SYK classifies as a potential target structure in a subset of pro-B-ALLs.

Clinical implications of germline BCL2L11 deletion polymorphism in pretreated advanced NSCLC patients with osimertinib therapy

INTRODUCTION

B-cell lymphoma 2-like 11 (BCL-2-like 11, BCL2L11, also known as BIM) deletion polymorphism (BIM-del) has been associated with resistance to first-generation epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), and is a poor prognostic factor for EGFR-mutant non-small-cell lung cancer (NSCLC) patients. Nevertheless, the impact of BIM-del in advanced NSCLC patients treated with the third-generation EGFR-TKI osimertinib remains undetermined. This study aims to evaluate the relationship between BIM-del and therapeutic efficacy of osimertinib in pretreated NSCLC patients.

METHODS

Patients subjected to EGFR T790 M detection and prior osimertinib treatment between December 2015 and December 2019 in our hospital were enrolled in this study. Peripheral blood samples from these patients were collected to detect BIM-del by polymerase chain reaction. Cox proportional hazards models were used to analyze the clinical outcomes of patients with and without BIM-del.

RESULTS

In total, 152 Chinese Han NSCLC patients-including 143 T790M-positive and nine T790M-negative patients-were enrolled. BIM-del was detected in only 17.5 % of T790M-positive patients (25/143). The majority of patients were aged <65 years (81.8 %, 117/143), were female (58.7 %, 84/143), were non-smokers (82.5 %, 118/143), had Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-1 (88.8 %, 129/143), and exhibited metastases in the central nervous system (CNS) (54.5 %, 78/143). There were no associations between the BIM-del and clinical characteristics (including age, sex, histology, smoking status, stage, ECOG PS score, and CNS metastases). Patients with BIM-del had a poorer objective response rate than those without (28.0 % versus 52.5 %, p = 0.026). Besides, BIM-del was associated with a significantly shorter progression-free survival (PFS) and a moderately shorter overall survival (OS) (8.3 versus 10.5 months, p = 0.031 and 15.9 versus 25.2 months, p = 0.1, respectively). Multivariate analysis indicated that BIM-del was an independent prognostic factor for PFS but not for OS in EGFR T790 M NSCLC patients.

CONCLUSIONS

BIM-del is associated with poor clinical responses and outcomes, and might be a negative predictive and prognostic biomarker in EGFR T790 M NSCLC patients with osimertinib treatment.

[Research Progress of New Generation EGFR-TKIs after Third-generation]

肺癌是全球死亡率最高的癌种。第一、二代表皮生长因子受体酪氨酸激酶抑制剂（epidermal growth factor receptor-tyrosine kinase inhibitors, EGFR-TKIs）的出现，在一定程度上极大地提高了非小细胞肺癌（non-small cell lung cancer, NSCLC）患者的生存期及生活质量，但大多数患者在经过一段时间的无进展生存期后会产生耐药性，其中以T790M突变为主要耐药机制。针对此耐药突变出现的是以奥希替尼为代表的第三代EGFR-TKIs，其效果显著，然而仍不可避免的出现耐药性，如：C797S突变、间质表皮转化（mesenchymal-epithelial transition, MET）、RAS突变、BRAF突变、小细胞肺癌（small cell lung cancer, SCLC）转化、上皮间质细胞转化（epithelial mesenchymal transition, EMT）等。但是目前第三代EGFR-TKIs耐药后并没有标准有效的治疗方案。故本文主要阐述三代后的新一代EGFR-TKIs的研究进展，为后续的研究及治疗提供一定的参考。

Resminostat, a histone deacetylase inhibitor, circumvents tolerance to EGFR inhibitors in EGFR-mutated lung cancer cells with BIM deletion polymorphism

Drug-tolerant cells are mediators of acquired resistance. BIM-intron2 deletion polymorphism (BIM-del) is one of the mechanisms underlying the resistance to epidermal growth factor tyrosine kinase inhibitor (EGFR-TKI)-mediated apoptosis that induces drug tolerance. Here, we investigated whether resminostat, a histone deacetylase inhibitor, circumvents BIM-del-associated apoptosis resistance. The human EGFR-mutated non-small cell lung cancer (NSCLC) cell line PC-9 and its homozygous BIM-del-positive variant (PC-9 BIMi2- / -), established by editing with zinc finger nuclease, were used. In comparison with PC-9 cells, PC-9 BIMi2- / - cells were less sensitive to apoptosis mediated by EGFR-TKIs such as gefitinib and osimertinib. The combined use of resminostat and an EGFR-TKI preferentially induced the expression of the pro-apoptotic BIM transcript containing exon 4 rather than that containing exon 3, increased the level of pro-apoptotic BIM protein (BIMEL), and stimulated apoptosis in vitro. In a subcutaneous tumor model derived from PC-9 BIMi2- / - cells, gefitinib monotherapy decreased tumor size but retained residual lesions, indicative of the presence of tolerant cells in tumors. The combined use of resminostat and gefitinib increased BIMEL protein level and induced apoptosis, subsequently leading to the remarkable shrinkage of tumor. These findings suggest the potential of resminostat to circumvent tolerance to EGFR-TKIs associated with BIM deletion polymorphism. J. Med. Invest. 67 : 343-350, August, 2020.

Histone Deacetylase Inhibition in Non-small Cell Lung Cancer: Hype or Hope?

Epigenetic modulation, including acetylation, methylation, phosphorylation, and ubiquitination, plays a pivotal role in regulation of gene expression. Histone acetylation-a balance between the activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs)-is one of the key epigenetic events. Our understanding of the role of HDACs in cancer is evolving. A number of HDAC isoenzymes are overexpressed in a variety of malignancies. Aberrant histone acetylation is associated with dysregulation of tumor suppressor genes leading to development of several solid tumors and hematologic malignancies. Pre-clinical studies have demonstrated that HDAC-1 gene expression is associated with lung cancer progression. Histone hypoacetylation is associated with more aggressive phenotype in adenocarcinoma of the lung. HDAC inhibitors (HDACi) have pleiotropic cellular effects and induce the expression of pro-apoptotic genes/proteins, cause cellular differentiation and/or cell cycle arrest, inhibit angiogenesis, and inhibit transition to a mesenchymal phenotype. Consequently, treatment with HDACi has shown anti-proliferative activity in non-small cell lung cancer (NSCLC) cell lines. Despite promising results in pre-clinical studies, HDACi have shown only modest single agent activity in lung cancer clinical trials. HDAC activation has been implicated as one of the mechanisms causing resistance to chemotherapy, molecularly targeted therapy, and immune checkpoint inhibition. Therefore, there is a growing interest in combining HDACi with these agents to enhance their efficacy or reverse resistance. In this paper, we review the available preclinical and clinical evidence for the use of HDACi in NSCLC. We also review the challenges precluding widespread clinical utility of HDACi as a cancer therapy and future directions.

Targeting HER3, a Catalytically Defective Receptor Tyrosine Kinase, Prevents Resistance of Lung Cancer to a Third-Generation EGFR Kinase Inhibitor

Although two growth factor receptors, EGFR and HER2, are amongst the best targets for cancer treatment, no agents targeting HER3, their kinase-defective family member, have so far been approved. Because emergence of resistance of lung tumors to EGFR kinase inhibitors (EGFRi) associates with compensatory up-regulation of HER3 and several secreted forms, we anticipated that blocking HER3 would prevent resistance. As demonstrated herein, a neutralizing anti-HER3 antibody we generated can clear HER3 from the cell surface, as well as reduce HER3 cleavage by ADAM10, a surface metalloproteinase. When combined with a kinase inhibitor and an anti-EGFR antibody, the antibody completely blocked patient-derived xenograft models that acquired resistance to EGFRi. We found that the underlying mechanism involves posttranslational downregulation of HER3, suppression of MET and AXL upregulation, as well as concomitant inhibition of AKT signaling and upregulation of BIM, which mediates apoptosis. Thus, although HER3 is nearly devoid of kinase activity, it can still serve as an effective drug target in the context of acquired resistance. Because this study simulated in animals the situation of patients who develop resistance to EGFRi and remain with no obvious treatment options, the observations presented herein may warrant clinical testing.

Inhibition of MEK1/2 Forestalls the Onset of Acquired Resistance to Entrectinib in Multiple Models of NTRK1-Driven Cancer

NTRK1 gene fusions are actionable drivers of numerous human malignancies. Here, we show that expression of the TPR-NTRK1 fusion kinase in immortalized mouse pancreatic ductal epithelial (IMPE) (pancreas) or mouse lung epithelial (MLE-12) cells is sufficient to promote rapidly growing tumors in mice. Both tumor models are exquisitely sensitive to targeted inhibition with entrectinib, a tropomyosin-related kinase A (TRKA) inhibitor. Initial regression of NTRK1-driven tumors is driven by induced expression of BIM, such that BIM silencing leads to a diminished response to entrectinib in vivo. However, the emergence of drug-resistant disease limits the long-term durability of responses. Based on the reactivation of RAF>MEK>ERK signaling observed in entrectinib-treated tumors, we show that the combination of entrectinib plus the MEK1/2 inhibitor cobimetinib dramatically forestalls the onset of drug resistance in vivo. Collectively, these data provide a mechanistic rationale for rapid clinical deployment of combined inhibition of TRKA plus MEK1/2 in NTRK1-driven cancers.

Phase I safety and pharmacokinetic study of YM155, a potent selective survivin inhibitor, in combination with erlotinib in patients with EGFR TKI refractory advanced non-small cell lung cancer

PURPOSE

This phase I study was conducted to evaluate the safety and pharmacokinetics of YM155, a potent, selective survivin inhibitor, in combination with erlotinib in patients with EGFR TKI refractory advanced non-small cell lung cancer (NSCLC).

METHODS

The pimary objectives were to evaluate the safety and tolerability of YM155 at escalating doses (3.6, 4.8, 6.0, and 8.0 mg/m²/days) administered every 3 weeks as continuous intravenous infusion over 168 h in combination with erlotinib at a fixed dose (150 mg, once a day). Secondary objectives were to assess the pharmacokinetics of YM155, antitumor activity, and the relationship between biomarkers and efficacy. The changes in survivin expression in biopsied tumor pre- and post-YM155 administration and serum cytokine levels were also analyzed.

RESULTS

Fifteen patients were treated. The most common YM155-related adverse event was the presence of urine microalbumin, whereas grades 3/4 toxicities were rare. One patient who received 4.8  mg/m²/days YM155 developed a dose-limiting grade 2 serum creatinine elevation. YM155 exposure in plasma showed dose proportionality across all dose ranges tested. No pharmacokinetic interaction occurred between YM155 and erlotinib. The serum cytokines IL-8, G-CSF, and MIP-1b showed decreasing trends in patients who achieved progression-free survival of ≥ 12 weeks. Durable stable disease for ≥ 24 weeks was observed in two patients.

CONCLUSION

Up to 8.0 mg/m²/days YM155 administered every 3 weeks in combination with erlotinib exhibited a favorable safety profile and moderate clinical efficacy. These results suggest that inhibiting survivin is a potential therapeutic strategy for select patients with EGFR TKI refractory NSCLC.

TRIAL REGISTRATION

UMIN000031912 at UMIN Clinical Trials Registry (UMIN-CTR).

Targeting apoptosis in cancer therapy

For over three decades, a mainstay and goal of clinical oncology has been the development of therapies promoting the effective elimination of cancer cells by apoptosis. This programmed cell death process is mediated by several signalling pathways (referred to as intrinsic and extrinsic) triggered by multiple factors, including cellular stress, DNA damage and immune surveillance. The interaction of apoptosis pathways with other signalling mechanisms can also affect cell death. The clinical translation of effective pro-apoptotic agents involves drug discovery studies (addressing the bioavailability, stability, tumour penetration, toxicity profile in non-malignant tissues, drug interactions and off-target effects) as well as an understanding of tumour biology (including heterogeneity and evolution of resistant clones). While tumour cell death can result in response to therapy, the selection, growth and dissemination of resistant cells can ultimately be fatal. In this Review, we present the main apoptosis pathways and other signalling pathways that interact with them, and discuss actionable molecular targets, therapeutic agents in clinical translation and known mechanisms of resistance to these agents.

PRKCQ inhibition enhances chemosensitivity of triple-negative breast cancer by regulating Bim

BACKGROUND

Protein kinase C theta, (PRKCQ/PKCθ) is a serine/threonine kinase that is highly expressed in a subset of triple-negative breast cancers (TNBC) and promotes their growth, anoikis resistance, epithelial-mesenchymal transition (EMT), and invasion. Here, we show that PRKCQ regulates the sensitivity of TNBC cells to apoptosis triggered by standard-of-care chemotherapy by regulating levels of pro-apoptotic Bim.

METHODS

To determine the effects of PRKCQ expression on chemotherapy-induced apoptosis, shRNA and cDNA vectors were used to modulate the PRKCQ expression in MCF-10A breast epithelial cells or triple-negative breast cancer cells (MDA-MB231Luc, HCC1806). A novel PRKCQ small-molecule inhibitor, 17k, was used to inhibit kinase activity. Viability and apoptosis of cells treated with PRKCQ cDNA/shRNA/inhibitor +/-chemotherapy were measured. Expression levels of Bcl2 family members were assessed.

RESULTS

Enhanced expression of PRKCQ is sufficient to suppress apoptosis triggered by paclitaxel or doxorubicin treatment. Downregulation of PRKCQ also enhanced the apoptosis of chemotherapy-treated TNBC cells. Regulation of chemotherapy sensitivity by PRKCQ mechanistically occurs via regulation of levels of Bim, a pro-apoptotic Bcl2 family member; suppression of Bim prevents the enhanced apoptosis observed with combined PRKCQ downregulation and chemotherapy treatment. Regulation of Bim and chemotherapy sensitivity is significantly dependent on PRKCQ kinase activity; overexpression of a catalytically inactive PRKCQ does not suppress Bim or chemotherapy-associated apoptosis. Furthermore, PRKCQ kinase inhibitor treatment suppressed growth, increased anoikis and Bim expression, and enhanced apoptosis of chemotherapy-treated TNBC cells, phenocopying the effects of PRKCQ downregulation.

CONCLUSIONS

These studies support PRKCQ inhibition as an attractive therapeutic strategy and complement to chemotherapy to inhibit the growth and survival of TNBC cells.

Functional miRNA Screening Identifies Wide-ranging Antitumor Properties of miR-3622b-5p and Reveals a New Therapeutic Combination Strategy in Ovarian Tumor Organoids

Novel therapeutic strategies are urgently required for the clinical management of chemoresistant ovarian carcinoma, which is the most lethal of the gynecologic malignancies. miRNAs hold promise because they play a critical role in determining the cell phenotype by regulating several hundreds of targets, which could constitute vulnerabilities of cancer cells. A combination of gain-of-function miRNA screening and real-time continuous cell monitoring allows the identification of miRNAs with robust cytotoxic effects in chemoresistant ovarian cancer cells. Focusing on miR-3622b-5p, we show that it induces apoptosis in several ovarian cancer cell lines by both directly targeting Bcl-xL and EGFR-mediating BIM upregulation. miR-3622b-5p also sensitizes cells to cisplatin by inhibiting Bcl-xL in ovarian cancer cell lines escaping BIM induction. miR-3622b-5p also exerts antimigratory capacities by targeting both LIMK1 and NOTCH1. These wide-ranging antitumor properties of miR-3622b-5p in ovarian cancer cells are mimicked by the associations of pharmacologic inhibitors targeting these proteins. The combination of an EGFR inhibitor together with a BH3-mimetic molecule induced a large decrease in cell viability in a panel of ovarian cancer cell lines and several ovarian patient-derived tumor organoids, suggesting the value of pursuing such a combination therapy in ovarian carcinoma. Altogether, our work highlights the potential of phenotype-based miRNA screening approaches to identify lethal interactions which might lead to new drug combinations and clinically applicable strategies.

Phase I study of vorinostat with gefitinib in BIM deletion polymorphism/epidermal growth factor receptor mutation double-positive lung cancer

Patients with epidermal growth factor receptor (EGFR)‐mutated non‐small cell lung cancer (NSCLC) harboring BIM deletion polymorphism (BIM deletion) have poor responses to EGFR TKI. Mechanistically, the BIM deletion induces preferential splicing of the non‐functional exon 3‐containing isoform over the functional exon 4‐containing isoform, impairing TKI‐induced, BIM‐dependent apoptosis. Histone deacetylase inhibitor, vorinostat, resensitizes BIM deletion‐containing NSCLC cells to EGFR‐TKI. In the present study, we determined the safety of vorinostat‐gefitinib combination and evaluated pharmacodynamic biomarkers of vorinostat activity. Patients with EGFR‐mutated NSCLC with the BIM deletion, pretreated with EGFR‐TKI and chemotherapy, were recruited. Vorinostat (200, 300, 400 mg) was given daily on days 1‐7, and gefitinib 250 mg was given daily on days 1‐14. Vorinostat doses were escalated based on a conventional 3 + 3 design. Pharmacodynamic markers were measured using PBMC collected at baseline and 4 hours after vorinostat dose on day 2 in cycle 1. No dose‐limiting toxicities (DLT) were observed in 12 patients. We determined 400 mg vorinostat as the recommended phase II dose (RP2D). Median progression‐free survival was 5.2 months (95% CI: 1.4‐15.7). Disease control rate at 6 weeks was 83.3% (10/12). Vorinostat preferentially induced BIM mRNA‐containing exon 4 over mRNA‐containing exon 3, acetylated histone H3 protein, and proapoptotic BIM_EL protein in 11/11, 10/11, and 5/11 patients, respectively. These data indicate that RP2D was 400 mg vorinostat combined with gefitinib in BIM deletion/EGFR mutation double‐positive NSCLC. BIM mRNA exon 3/exon 4 ratio in PBMC may be a useful pharmacodynamic marker for treatment.

Concomitant genetic alterations having greater impact on the clinical benefit of EGFR-TKIs in EGFR-mutant advanced NSCLC than BIM deletion polymorphism

BACKGROUND

In previous studies, the predictive role of BIM deletion polymorphism with respect to responses to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) has been controversial. The potential reasons for these inconsistent findings were unknown.

METHODS

Data from CTONG0901 clinical trial and medical records of Guangdong Lung Cancer Institute (GLCI) were retrospectively pooled. A total of 194 and 141 EGFR-mutant non-small cell lung cancer (NSCLC) patients treated with first- and second-generation EGFR-TKIs were examined in the CTONG0901 and GLCI cohorts, respectively. Sixty-eight patients were treated with third-generation EGFR-TKIs in the GLCI cohort. The BIM gene status was examined by next-generation sequencing.

RESULTS

The frequency of BIM deletion polymorphism was 11.3% and 17.0% in CTONG0901 and GLCI cohorts, respectively. For first- and second-generation EGFR-TKIs in CTONG0901 cohort, objective response (ORR) was 54.5% in BIM deletion group versus 56.4% in wild-type BIM group (P = .87); disease control rate (DCR) was 90.9% versus 88.4% (P = 1.00); progression-free survival (PFS) was 10.5 versus 11.2 months (P = .59); and overall survival (OS) was 20.5 versus 20.5 months (P = .73). In GLCI cohort, ORR was 54.2% versus 60.7% (P = .55); DCR was 91.7% versus 96.6% (P = .27); PFS was 10.1 versus 11.6 months (P = .63); and OS was 58.5 versus 45.0 months (P = .93). For third-generation EGFR-TKIs, ORR was 18.2% versus 63.2% (P = .02); DCR was 81.8% versus 96.5%, (P = .12); PFS was 5.8 versus 9.0 months (P = .13); and OS was 30.0 versus 24.8 months (P = .85). Cox regression analysis showed that concomitant genetic alterations could adversely affect the response to EGFR-TKIs, but not BIM deletion.

CONCLUSIONS

The presence of BIM deletion showed no relation to an impaired response to first-, second-, and third-generation EGFR-TKIs in NSCLC patients. The factors influencing the response of EGFR-TKIs were concomitant genetic alterations, but not BIM deletion.

Role of BIM Deletion Polymorphism and BIM Expression as Predictive Biomarkers to Maximize the Benefit of EGFR-TKI Treatment in EGFR-Positive NSCLC

Objective:

BIM is a modulator of apoptosis that is triggered by EGFR-TKIs. This study evaluated the role of BIM deletion and its expression as predictor of EGFR-TKI treatment outcome.

Methods:

The medical record of 185 EGFR-positive advanced non-small cell lung cancer (NSCLC) patients with/ without EGFR-TKI treatment between 9/2012 and 12/2014 were retrospectively reviewed. BIM deletion polymorphism and expression were tested by RT-PCR and immunohistochemistry, respectively. Survival outcomes in EGFR-TKI-treated patients were analyzed according to treatment sequence and EGFR mutation. The correlation between BIM deletion polymorphism, expression, response rate (as a function of EGFR-TKI treatment) and schedule was also explored.

Result:

EGFR-TKIs were administered to 139 (75.1%) of the 185 patients: as the first-line in 52 (37.4%) patients and as later-line treatment in 87 (62.6%) patients. Median overall survival (mOS) was significantly longer in EGFR-TKIs treated patients (28.9 vs. 7.4 months, P<0.001). Among L858R-mutated patients, median progression-free survival (mPFS) was significantly longer in first-line EGFR TKI treatment than a later-line (12.6 vs. 6.3 months, P=0.03). BIM deletion polymorphism and expression was detected in 20.2% and 52.7%, respectively. Patients without BIM deletion polymorphism had a significantly longer mOS when treated with a first-line than with a later-line EGFR-TKI (28.9 vs. 20.7 months, P= 0.04). Patients without BIM expression had a significantly longer mPFS (9.6 vs. 7.3 months, P=0.01) better mOS and response rate (RR).

Conclusion:

BIM deletion polymorphism and expression may predict an EGFR-TKI response in patients with EGFR-positive during therapy.

Destabilization of NOXA mRNA as a common resistance mechanism to targeted therapies

Most targeted cancer therapies fail to achieve complete tumor regressions or attain durable remissions. To understand why these treatments fail to induce robust cytotoxic responses despite appropriately targeting oncogenic drivers, here we systematically interrogated the dependence of cancer cells on the BCL-2 family of apoptotic proteins after drug treatment. We observe that multiple targeted therapies, including BRAF or EGFR inhibitors, rapidly deplete the pro-apoptotic factor NOXA, thus creating a dependence on the anti-apoptotic protein MCL-1. This adaptation requires a pathway leading to destabilization of the NOXA mRNA transcript. We find that interruption of this mechanism of anti-apoptotic adaptive resistance dramatically increases cytotoxic responses in cell lines and a murine melanoma model. These results identify NOXA mRNA destabilization/MCL-1 adaptation as a non-genomic mechanism that limits apoptotic responses, suggesting that sequencing of MCL-1 inhibitors with targeted therapies could overcome such widespread and clinically important resistance.

MAPK-targeted therapies fail to achieve complete remission. Here, the authors show that anti-apoptosis resistance is acquired in these targeted therapies through the mRNA destabilization of NOXA which leads to dependence on MCL-1, and that sequential combination of MCL-1 inhibition with targeted therapies overcomes this resistance.

BIM Deletion Polymorphism Confers Resistance to Osimertinib in EGFR T790M Lung Cancer: a Case Report and Literature Review

The third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) osimertinib (AZD9291) has shown significant clinical efficacy against the EGFR T790M mutation in non-small cell lung cancer (NSCLC) patients. However, resistance inevitably occurs, and the mechanisms leading to treatment failure need to be further investigated. The B-cell lymphoma 2 (BCL-2)-like 11 (BIM) deletion polymorphism, which occurs at a frequency of 21% in East Asians but is absent in African and European populations, has been associated with resistance to first-generation EGFR TKIs, such as gefitinib and erlotinib; and is a poor prognostic factor for NSCLC patients with EGFR mutations. Nevertheless, the significance of this BIM deletion polymorphism in the resistance to osimertinib has not been reported. Here, we show for the first time that a NSCLC patient harboring the EGFR L858R/T790M mutations, as well as the BIM deletion polymorphism, exhibited poor clinical outcomes with osimertinib treatment. This result suggests that the BIM deletion polymorphism might have prognostic value for determining NSCLC patient outcomes following osimertinib treatment.