RET-rearranged non-small-cell lung cancer and therapeutic implications.

First-line tyrosine kinase inhibitors are standard of care for non-small-cell lung cancers (NSCLC) harbouring an epidermal growth factor receptor mutation, anaplastic lymphoma kinase fusion or c-ros oncogene 1 rearrangement. Other targetable oncogenic drivers have been identified but testing for these is neither funded nor commonly performed in Australia. Using a case example, we discuss the importance of considering several other genomic aberrations in our population, such as rearrangements in the RET proto-oncogene, which occur in 1-2% of lung adenocarcinoma. New oncogenic drivers and corresponding targeted agents are constantly being discovered; these will continue to refine the treatment of non-small-cell lung cancer in the era of precision medicine.

Clinical correlates of severe thrombocytopenia from temozolomide in glioblastoma patients.

BACKGROUND/AIM: This study was conducted retrospectively to evaluate rates of thrombocytopenia and their clinical impact during chemo-radiotherapy for glioblastomas and to elucidate associated clinical factors. METHODS: A total of 64 patients who received temozolomide chemotherapy at our institution was included; 35 patients received full-dose chemo-radiotherapy as per the STUPP protocol (Group A), and 9 patients received abbreviated radiotherapy with concurrent chemotherapy (Group B). Twenty patients received temozolomide alone with an intended 12 cycles of therapy for first relapse at least 6 months after completion of adjuvant chemotherapy (Group C). RESULTS: In Group A, 27 of 35 (77%) patients completed the chemo-radiotherapy phase; 14% had grade 3-4 thrombocytopenia leading to discontinuation. Of 27 patients, 16 (59%) completed adjuvant chemotherapy. There were no grade 3-4 thrombocytopenias, but 4% discontinued due to grade 2 thrombocytopenias. In Group B, four of nine (45%) patients completed the chemo-radiotherapy phase; 11% had grade 3-4 thrombocytopenias and discontinued treatment. Three of four (75%) patients completed adjuvant chemotherapy. Of these, 75% had grade 3-4 thrombocytopenias, but none discontinued. Finally, in Group C, 8 of 20 (40%) patients completed, with 10% discontinuing due to thrombocytopenias and the rest due to disease progression. In exploratory analyses, being female increased the risk of myelosuppresion, and there was a trend noticed in patients having a higher body surface area. CONCLUSION: Our toxicity data were within range of the literature. We identified the group of patients that have increased thrombocytopenia risk. Larger pooled retrospective series and prospective studies are required.

Osimertinib in uncommon EGFR exon 21 L861R and EGFR exon 18 deletion-insertion mutant non-small cell lung cancer-case report.

Background: Tyrosine kinase inhibitors (TKIs) have changed the treatment landscape for patients with advanced non-small cell lung cancer (NSCLC) found to have oncogene-driven activating epidermal growth factor receptor (EGFR) mutations. Whilst there have been a handful of case reports of sensitivity to first-generation TKIs in EGFR L861R mutations, the efficacy of the third-generation TKI osimertinib in NSCLC patients with EGFR L861R and EGFR exon 18 deletion-insertion mutations is limited. Case Description: We report two patients from our institution with uncommon EGFR mutations treated with first-line osimertinib. Our first patient, a 72-year-old male with metastatic lung adenocarcinoma was identified to harbour a rare EGFR L861R mutation and was commenced on osimertinib. After a follow-up period of 18 months, the patient is continuing to experience treatment benefit with imaging showing a good partial response. The second patient, a 60-year-old male also with metastatic lung adenocarcinoma and an EGFR exon 18 deletion-insertion mutation achieved a partial response for 6.6 months. Upon progression, he was commenced on carboplatin and pemetrexed chemotherapy however died from subsequent pneumonia. He had an overall survival (OS) from time of diagnosis of 7.6 months. Conclusions: We demonstrate clinical efficacy of first-line osimertinib in the treatment of advanced NSCLC harbouring uncommon EGFR L861R and EGFR exon 18 deletion-insertion mutations. These results may be suggestive of the wider applicability of osimertinib in the treatment of uncommon EGFR mutant NSCLC.

Implementation of a nurse-led, multidisciplinary model of care for older adults with cancer: a process evaluation protocol.

INTRODUCTION: Cancer is predominantly a disease of older adults, with an increasing number of cancer diagnoses in individuals aged 65 or older. Multiple geriatric factors have been shown to impact patient outcomes in cancer treatment. However, oncology specialists are not well adapted to incorporate geriatric assessment into practice due to a lack of resources and knowledge of the specialty.The primary aim of this study is to implement and evaluate a nurse-led, multidisciplinary model of care for older adults with cancer at two public tertiary hospitals in Melbourne, Australia. METHODS AND ANALYSIS: This study will aim to assess 200 patients across 2 sites. Both sites will assess individuals with lung cancer; the second site will also include individuals with genitourinary, upper gastrointestinal and colorectal cancers.This process evaluation will use quantitative and qualitative methods to explore the reach, effectiveness, adoption, implementation, and maintenance (RE-AIM) of the nurse-led, multidisciplinary model of care. ETHICS AND DISSEMINATION: Ethical approval and local governance approvals have been obtained by Austin Health and Monash Health Human Research Ethics committees. Dissemination will occur via publications, conferences, social medical and local engagement with clinicians, consumers and managers.

Brief Report: Real-World Toxicity and Survival of Combination Immunotherapy in Pleural Mesothelioma-RIOMeso.

BACKGROUND: Australia has one of the highest rates of asbestos-associated diseases. Mesothelioma remains an area of unmet need with a 5-year overall survival of 10%. First-line immunotherapy with ipilimumab and nivolumab is now a standard of care for unresectable pleural mesothelioma following the CheckMate 743 trial, with supportive data from the later line single-arm MAPS2 trial. RIOMeso evaluates survival and toxicity of this regimen in real-world practice. METHODS: Demographic and clinicopathologic data of Australian patients treated with ipilimumab and nivolumab in first- and subsequent-line settings for pleural mesothelioma were collected retrospectively. Survival was reported using the Kaplan-Meier method and compared between subgroups with the log-rank test. Toxicity was investigator assessed using Common Terminology Criteria for Adverse Events version 5.0. RESULTS: A total of 119 patients were identified from 11 centers. The median age was 72 years, 83% were male, 92% had Eastern Cooperative Oncology Group less than or equal to 1, 50% were past or current smokers, and 78% had known asbestos exposure. In addition, 50% were epithelioid, 19% sarcomatoid, 14% biphasic, and 17% unavailable. Ipilimumab and nivolumab were used first line in 75% of patients. Median overall survival (mOS) was 14.5 months (95% confidence interval [CI]: 13.0-not reached [NR]) for the entire cohort. For patients treated first line, mOS was 14.5 months (95% CI: 12.5-NR) and in second- or later-line patients was 15.4 months (95% CI: 11.2-NR). There was no statistically significant difference in mOS for epithelioid patients compared with nonepithelioid (19.1 mo [95% CI: 15.4-NR] versus 13.0 mo [95% CI: 9.7-NR], respectively, p = 0.064). Furthermore, 24% of the patients had a Common Terminology Criteria for Adverse Events grade greater than or equal to 3 adverse events, including three treatment-related deaths. Colitis was the most frequent adverse event. CONCLUSIONS: Combination immunotherapy in real-world practice has poorer survival outcomes and seems more toxic compared with clinical trial data. This is the first detailed report of real-world survival and toxicity outcomes using ipilimumab and nivolumab treatment of pleural mesothelioma.

Pulmonary metastases: a rare manifestation of the most common cancer.

Basal cell carcinoma (BCC) is the most common human malignancy but rarely metastasises. We report on two patients with symptomatic lung metastases and a past history of recurrent BCC excisions. In our first patient, a heavy smoker with multiple lung lesions, histology of a resected nodule was first reported as non-small cell lung cancer but a repeat nodule biopsy a year later was recognised as a pulmonary metastasis from primary cutaneous BCC. Our second patient, a young never-smoker with two previous BCC, was confirmed as having a pulmonary metastasis from BCC on the lung resection specimen. Pulmonary metastasis from an unidentified primary site is a common clinical situation. These patients emphasise the importance of considering the most common cancer as a potential primary.

Real-World Analysis of Clinical Characteristics and Survival Outcomes in Patients With Extensive-Stage SCLC Treated With First-Line Chemoimmunotherapy.

Introduction: There are no clinically validated prognostic biomarkers in the management of extensive-stage SCLC (ES-SCLC). We explored the association between clinical characteristics and survival outcomes in patients with ES-SCLC treated with chemoimmunotherapy. Methods: In this retrospective cohort study, patients with ES-SCLC treated with first-line platinum-etoposide chemotherapy and atezolizumab were identified from medical records. Pretreatment clinical characteristics, biochemical parameters, and tumor and treatment characteristics were collected. Univariate and multivariate Cox regression were used to evaluate treatment effect on progression-free survival (PFS) and overall survival (OS). Results: We evaluated 75 patients in total. The median PFS and OS were 6.1 months and 9.2 months, respectively. Statistically significant associations were found with lower lactate dehydrogenase and improved OS (hazard ratio [HR] = 1.0, 95% confidence interval [CI]: 1.0-1.01, p = 0.006), whereas higher age (HR = 0.94, 95% CI: 0.90-0.98, p = 0.006) and lower neutrophil-to-lymphocyte ratio (HR = 1.08, 95% CI: 1.02-1.14, p = 0.005) were associated with improved PFS. The number of chemotherapy cycles received were associated with both an improved PFS (HR = 0.57, 95% CI: 0.37-0.89, p = 0.011) and OS (HR = 0.5, 95% CI: 0.30-0.84, p = 0.008). Conclusions: This study highlights the important effect of chemotherapy on survival. Furthermore, the association between lactate dehydrogenase and neutrophil-to-lymphocyte ratio on survival further suggests that baseline tumor burden and optimizing sarcopenia are important factors for clinicians to consider as we seek to develop personalized treatment for this disease.

Circulating Tumour DNA (ctDNA) as a Predictor of Clinical Outcome in Non-Small Cell Lung Cancer Undergoing Targeted Therapies: A Systematic Review and Meta-Analysis.

BACKGROUND: Liquid biopsy (LB) analysis using (ctDNA)/cell-free DNA (cfDNA) is an emerging alternative to tissue profiling in (NSCLC). LB is used to guide treatment decisions, detect resistance mechanisms, and predicts responses, and, therefore, outcomes. This systematic review and meta-analysis evaluated the impact of LB quantification on clinical outcomes in molecularly altered advanced NSCLC undergoing targeted therapies. METHODS: We searched Embase, MEDLINE, PubMed, and Cochrane Database, between 1 January 2020 and 31 August 2022. The primary outcome was progression-free survival (PFS). Secondary outcomes included overall survival (OS), objective response rate (ORR), sensitivity, and specificity. Age stratification was performed based on the mean age of the individual study population. The quality of studies was assessed using the Newcastle-Ottawa Scale (NOS). RESULTS: A total of 27 studies (3419 patients) were included in the analysis. Association of baseline ctDNA with PFS was reported in 11 studies (1359 patients), while that of dynamic changes with PFS was reported in 16 studies (1659 patients). Baseline ctDNA-negative patients had a trend towards improved PFS (pooled hazard ratio [pHR] = 1.35; 95%CI: 0.83-1.87; p < 0.001; I2 = 96%) than ctDNA-positive patients. Early reduction/clearance of ctDNA levels after treatment was related to improved PFS (pHR = 2.71; 95%CI: 1.85-3.65; I2 = 89.4%) compared to those with no reduction/persistence in ctDNA levels. The sensitivity analysis based on study quality (NOS) demonstrated improved PFS only for good [pHR = 1.95; 95%CI: 1.52-2.38] and fair [pHR = 1.99; 95%CI: 1.09-2.89] quality studies, but not for poor quality studies. There was, however, a high level of heterogeneity (I2 = 89.4%) along with significant publication bias in our analysis. CONCLUSIONS: This large systematic review, despite heterogeneity, found that baseline negative ctDNA levels and early reduction in ctDNA following treatment could be strong prognostic markers for PFS and OS in patients undergoing targeted therapies for advanced NSCLC. Future randomised clinical trials should incorporate serial ctDNA monitoring to further establish the clinical utility in advanced NSCLC management.

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.

The role of BCL-2 family proteins and therapeutic potential of BH3-mimetics in malignant pleural mesothelioma.

Introduction: With limited recent therapeutic changes, malignant pleural mesothelioma (MPM) is associated with poor survival and death within 12 months, making it one of the most lethal malignancies. Due to unregulated asbestos use in developing countries and home renovation exposures, cases of MPM are likely to present for decades. As MPM is largely driven by dysregulation of tumor suppressor genes, researchers have examined other mechanisms of subverting tumor proliferation and spread. Over-expression of pro-survival BCL-2 family proteins impairs cells from undergoing apoptosis, and BH3-mimetics  targeting them are a novel treatment option across various cancers, though have not been widely investigated in MPM.Areas covered: This review provides an overview of MPM and its current treatment landscape. It summarizes the role of BCL-2 family proteins in tumorigenesis and the therapeutic potential of BH3-mimetics . Finally, it discusses the role of BCL-2 proteins in MPM and the pre-clinical rationale for investigating BH3-mimetics as a therapeutic strategy.Expert opinion: As a disease without readily actionable oncogene driver mutations and with modest benefit from immune checkpoint inhibition, novel therapeutic options are urgently needed for MPM. Hence, BH3-mimetics provide a promising treatment option, with evidence supporting dependence on pro-survival BCL-2 proteins for MPM cell survival.

Lung squamous cell carcinoma with rare epidermal growth factor receptor mutation G719X: a case report and literature review.

Asians who develop non-small cell lung cancer (NSCLC) have a chance of approximately 50% of harboring the epidermal growth factor receptor (EGFR) mutation. The G719X mutation in EGFR has 3 subtypes (i.e., G719A, G719C, or G719S), all of them being classified as uncommon EGFR mutations. The EGFR mutation G719X is most often associated with lung adenocarcinoma. Conversely, its occurrence in lung squamous cell carcinoma is rare. Its response to tyrosine kinase inhibitor (TKI) treatment remains unknown. A 50-year-old Asian male with no smoking history was admitted to our hospital (Affiliated Hospital of Qingdao University) with an irritating dry cough and 1 month of progressive dyspnea. The patient was diagnosed with lung squamous cell carcinoma (cT4N3M0, stage IIIC). Lung biopsy revealed the presence of EFGR G719X mutation. The patient received a tracheobronchial stent, targeted therapy, chemotherapy, seed implantation and radiotherapy, and survived for 25.4 months following diagnosis. It is crucial that gene mutation analysis is performed in non-smoking male squamous cell carcinoma patients. Compared to lung adenocarcinoma patients with rare G719X mutation, this lung squamous cell carcinoma patient with G719X-mutant tumor had a higher sensitivity to 2nd-generation EGFR-TKI treatment, but similar progression-free survival. Importantly, the patient clearly benefited from the used comprehensive treatment plan. This article seeks to shed light on the treatment of lung squamous cell carcinoma patients with the uncommon EGFR G719X mutation.

A novel BH3-mimetic, AZD0466, targeting BCL-XL and BCL-2 is effective in pre-clinical models of malignant pleural mesothelioma.

Malignant pleural mesothelioma (MPM) is an aggressive cancer with treatment limited to Cisplatin and Pemetrexed chemotherapy. Recently, we showed that drugs targeting the BCL-2-regulated apoptosis pathway could kill MPM cell lines in vitro, and control tumor growth in vivo. These studies showed BCL-XL was the dominant pro-survival BCL-2 family member correlating with its high-level expression in cells and patient tumor samples. In this study we show another inhibitor, AZD4320 that targets BCL-XL (and BCL-2), can also potently kill MPM tumor cells in vitro (EC50 values in the 200 nM range) and this effect is enhanced by co-inhibition of MCL-1 using AZD5991. Moreover, we show that a novel nanoparticle, AZD0466, where AZD4320 is chemically conjugated to a PEGylated poly-lysine dendrimer, was as effective as standard-of-care chemotherapy, Cisplatin, at inhibiting tumor growth in mouse xenograft studies, and this effect was enhanced when both drugs were combined. Critically, the degree of thrombocytopenia, an on-target toxicity associated with BCL-XL inhibition, was significantly reduced throughout the treatment period compared to other BCL-XL-targeting BH3-mimetics. These pre-clinical findings provide a rationale for the future clinical evaluation for novel BH3-mimetic formulations in MPM, and indeed, other solid tumor types dependent on BCL-XL.

Nivolumab resulting in persistently elevated troponin levels despite clinical remission of myocarditis and myositis in a patient with malignant pleural mesothelioma: case report.

Malignant pleural mesothelioma (MPM) remains a deadly disease with limited therapeutic options beyond platinum/pemetrexed chemotherapy. Immune checkpoint inhibitors have demonstrated modest benefit in the second to later-line settings. An MPM patient from our institute developed myocarditis and myositis after 2 cycles of second-line nivolumab. Despite immunosuppression with corticosteroids and mycophenolate mofetil, there was ongoing rise in troponin levels which remained elevated for months. The patient developed an impressive but brief response following cessation of nivolumab. Myocarditis and myositis are rare complications of immune checkpoint inhibitors. Clinicians should be aware of these possible complications as myocarditis can result in mortality.

A First-in-Human Dose Finding Study of Camrelizumab in Patients with Advanced or Metastatic Cancer in Australia.

PURPOSE: Camrelizumab inhibits PD-1 in non-clinical models and showed typical non-clinical pharmacokinetic (PK) and safety profiles for an IgG4 monoclonal antibody. We report results from the First-in-Human Phase 1 trial of camrelizumab in Australian population. METHODS: Camrelizumab was administered to patients with advanced solid tumors who had failed standard therapies. In the dose-escalation phase (n=23), camrelizumab was administered intravenously at 1 mg/kg, 3 mg/kg, 6 mg/kg, and 10 mg/kg every 2 weeks. In dose expansion (n=26), camrelizumab was given at 200 mg or 600 mg every 4 weeks. RESULTS: Two dose-limiting toxicities were observed during dose escalation: transaminase elevation and diarrhea (both grade 3). Overall, treatment-related adverse events were consistent with the expected toxicity profile of immune checkpoint inhibition, with the striking exception of the dose-related development of angiomatous skin lesions characterized as reactive cutaneous capillary endothelial proliferation. The PK profile showed a dose-progressive increase in half-life from 3 days at 1 mg/kg to 7 days at 10 mg/kg. Moreover, receptor occupancy assays showed a PD-1 occupancy of >50% in most patients out to 28 days post-dose. The objective response rate was 15.2% (95% CI 6.3-28.9). CONCLUSION: Camrelizumab has manageable toxicity and encouraging preliminary antitumor activity in advanced solid tumors in Australia. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02492789.

BCL-XL is an actionable target for treatment of malignant pleural mesothelioma.

Despite having one of the lowest survival rates of all cancers, there have been no new approved treatments for malignant pleural mesothelioma (MPM) in over a decade. Standard-of-care treatment relies on Cisplatin plus Pemetrexed chemotherapy. Here, we tested a suite of BH3-mimetic drugs targeting BCL-2 pro-survival proteins of the intrinsic apoptotic pathway. We found BCL-XL is the dominant pro-survival protein in a panel of cell lines in vitro, though potent, synergistic cell killing occurred with MCL-1 co-targeting. This correlates with high-level expression of BCL-XL and MCL-1 in cell lines and a large cohort of patient tumour samples. BCL-XL inhibition combined with Cisplatin also enhanced cell killing. In vivo BCL-XL inhibition was as effective as Cisplatin, and the combination enhanced tumour growth control and survival. Genetic ablation of MCL-1 also enhanced the effects of BCL-XL inhibitors, in vivo. Combined, these data provide a compelling rationale for the clinical investigation of BH3-mimetics targeting BCL-XL in MPM.

A pilot study of intrahepatic yttrium-90 microsphere radioembolization in combination with intravenous cisplatin for uveal melanoma liver-only metastases.

BACKGROUND: Metastatic uveal melanoma is a highly aggressive disease with no standard of care treatment option. A large proportion of patients have liver-only metastatic disease which raises the question if liver-directed therapy can be efficacious in this subpopulation. AIMS: The study aims to evaluate the safety and efficacy of radiosensitizing chemotherapy in combination with yttrium-90 microspheres in patients with uveal melanoma with liver-only metastases. METHODS AND RESULTS: This single arm, open labeled, non-randomized study enrolled 10 patients with liver-only metastatic uveal melanoma between November 2012 and January 2018. Eligible patients received intrahepatic yttrium-90 microspheres followed by intravenous cisplatin (20 mg/m2) for 5 days. Ten patients were enrolled, but nine patients received treatment who were included in the final analysis with a median follow-up of 30 months (range 7 to 44). Five (50%) were female, five (50%) had an elevated lactate dehydrogenase (LDH), and one (10%) had prior anti-PD-1 therapy. The combination was well tolerated with no greater than or equal to grade 3 toxicity observed. The liver objective response rate (ORR) was 33% (3/9), the median progression-free survival (PFS) in the liver was 3 months (95% CI, 3-NA), and the extrahepatic PFS was 3 months (95% CI, 3-NA). Seventy-eight percent (7/9) received an immune checkpoint inhibitor on disease progression, with no responses seen. The median overall survival (OS) was 10 months (95% CI, 7-NA). CONCLUSION: The combination of cisplatin with yttrium-90 microspheres was well tolerated; however, it was associated with intrahepatic disease control of relatively short duration. No responses were seen in patients treated with immune checkpoint inhibitors post radioembolization.

Standard dose osimertinib for erlotinib refractory T790M-negative EGFR-mutant non-small cell lung cancer with leptomeningeal disease.

BACKGROUND: Leptomeningeal spread in non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutations who experience disease progression on TKIs portends a poor prognosis. Mutation profiling of tumour DNA in cerebrospinal fluid (CSF) samples can be used to determine the presence of the EGFR T790M resistance mutation, indicating that osimertinib, a CNS-penetrating 3rd generation TKI may be efficacious. METHODS: Eight patients on EGFR TKIs who progressed with cytology-proven leptomeningeal disease at our institution were studied. EGFR mutations were profiled in CSF using droplet digital PCR (ddPCR) and compared to matched plasma samples. Clinical characteristics and survival outcomes on subsequent therapies tailored to ddPCR analysis were reported. RESULTS: None of the four patients who developed leptomeningeal disease while receiving 1st generation EGFR TKIs developed the EGFR T790M mutation in CSF. One patient who did not have extra-cranial disease and was EGFR T790M-negative in both plasma and CSF was nevertheless treated with standard-dose osimertinib, and achieved a rapid and durable response lasting 9 months to date. Three patients developed leptomeningeal disease on osimertinib, with one patient developing the EGFR C797S mutation in a cis-allelic conformation with the EGFR T790M mutation in plasma. CONCLUSIONS: Standard-dose osimertinib resulted in a clinically meaningful response in a patient with EGFR T790M-negative 1st generation EGFR TKI refractory leptomeningeal disease. Next generation sequencing and ddPCR has a role at identifying the C797S mutation and its allelic conformation with the T790M mutation with clinical implications.

BCL-XL and MCL-1 are the key BCL-2 family proteins in melanoma cell survival.

Malignant melanoma is one of the most difficult cancers to treat due to its resistance to chemotherapy. Despite recent successes with BRAF inhibitors and immune checkpoint inhibitors, many patients do not respond or become resistant to these drugs. Hence, alternative treatments are still required. Due to the importance of the BCL-2-regulated apoptosis pathway in cancer development and drug resistance, it is of interest to establish which proteins are most important for melanoma cell survival, though the outcomes of previous studies have been conflicting. To conclusively address this question, we tested a panel of established and early passage patient-derived cell lines against several BH3-mimetic drugs designed to target individual or subsets of pro-survival BCL-2 proteins, alone and in combination, in both 2D and 3D cell cultures. None of the drugs demonstrated significant activity as single agents, though combinations targeting MCL-1 plus BCL-XL, and to a lesser extent BCL-2, showed considerable synergistic killing activity that was elicited via both BAX and BAK. Genetic deletion of BFL-1 in cell lines that express it at relatively high levels only had minor impact on BH3-mimetic drug sensitivity, suggesting it is not a critical pro-survival protein in melanoma. Combinations of MCL-1 inhibitors with BRAF inhibitors also caused only minimal additional melanoma cell killing over each drug alone, whilst combinations with the proteasome inhibitor bortezomib was more effective in multiple cell lines. Our data show for the first time that therapies targeting specific combinations of BCL-2 pro-survival proteins, namely MCL-1 plus BCL-XL and MCL-1 plus BCL-2, could have significant benefit for the treatment of melanoma.

Mismatch Repair Protein Defects and Microsatellite Instability in Malignant Pleural Mesothelioma.

INTRODUCTION: Malignant pleural mesothelioma is an aggressive malignancy with limited systemic therapy options. Promising results have been reported with use of anti-programmed cell death 1 therapy; however, its benefits appear to be confined to a subgroup of patients. Microsatellite instability (MSI) results from the inactivation of DNA mismatch repair genes and results in a high tumor mutational burden, a phenomenon that has not been seen with mesothelioma. MSI and protein absence have been shown to correlate in colorectal cancer, such that most centers have adopted immunohistochemistry (IHC) to screen for MSI-high colorectal cancers. We profiled a large cohort of patients with mesothelioma to determine the rate of negative IHC staining results the four common mismatch repair proteins. DESIGN: A tissue microarray comprising 335 patients with malignant pleural mesothelioma were used. IHC for the four common mismatch repair proteins (mutL homolog 1; PMS1 homolog 2, mismatch repair system component; mutS homolog 2; and mutS homolog 6) was performed. Programmed death ligand 1 IHC staining with the E1L3N clone was also performed. DNA was isolated from IHC equivocal samples and analyzed for microsatellite instability by using the Promega MSI Analysis System (version 1.2, Promega, Madison, WI). RESULTS: Of the patients profiled, 329 had intact mismatch repair proteins by IHC. Six samples with IHC testing results indicating absent mismatch repair protein were analyzed for MSI and confirmed to be negative. Of the six IHC-negative samples, five were negative for programmed death ligand 1 staining and one sample had more than 5% staining. CONCLUSION: In this large retrospective series, we were unable to identify any patients with malignant pleural mesothelioma with microsatellite instability. Response to anti-programmed cell death 1-based immunotherapy may be driven by other mechanisms.