Malignant Mesothelioma Tumors Research Articles

Regional delivery of mesothelin-targeted chimeric antigen receptor T-cell effectively and safely targets colorectal cancer liver metastases in mice.

Liver metastasis is the major cause of colorectal cancer related death. Mesothelin (MSLN)-targeted chimeric antigen receptor (CAR) T-cell therapy has been illustrated effective and safe through regional delivery of breast cancer, ovarian cancer and malignant mesothelioma tumors. Herein, we investigated the safety, efficacy, and immune microenvironment of regional delivery of MSLN (CAR) T-cell in the treatment of colorectal carcinoma liver metastases (CRLM). Second-generation MSLN CAR T-cells were administered by portal vein (PV) or caudal vein (CV, systemic administration) delivery in an orthotopic MSLN+ CRLM nonobese diabetic (NOD)/severe combined immunodeficient (SCID)/γc-/- (NSG) mouse model. A total of 20 mice were randomly divided into control group, non-transduced T cell (NT)-CV group, NT-PV group, MSLN CAR T-cell CV (MSLN-CV) group, and MSLN CAR T-cell PV (MSLN-PV) group, with each group containing four mice to examine the safety and efficacy. The bioluminescence intensity (BLI) of tumor burden, tumor tissue macroscopic and microscopic observation were used to evaluate treatment efficacy. The safety was examined by body weight, survival time, and vital organ damage of mice. CAR T-cell infiltration and cytokine concentration were analyzed by flow cytometry, and immunostaining. The change of immune microenvironment between regional delivery and systemic delivery was investigated on an immune reconstructed CRLM patient-derived xenograft (PDX) model. Additionally, T cell subsets and immunosuppressive markers were examined. PV administration of 1×107/100 μL MSLN CAR T-cells in 20 NSG mice was well tolerated, and no overt toxicity was observed. The tumor burden in the PV group was obviously alleviated. The BLI was (0.73±0.52)×109 in PV group and (1.97±0.11)×109 in CV group (P<0.05), CD8+ granzyme B (GB)+ T cell percentage (MSLN-CV 4.42%±0.47% vs. MSLN-PV 13.5%±4.67%, P<0.01) and cytokine concentration were obviously increased in the MSLN-PV group. In the immune reconstituted CRLM PDX model, intratumor (IT) delivery of MSLN CAR T-cells exhibited much more infiltration of CD4+ and CD8+ T cells accompanied with elevated expression levels of PD-1, LAG-3, and TIM-3. Regional delivery of MSLN-targeted CAR T-cell therapy has encouraging results in the orthotopic CRLM NSG mouse model and PDX model, and converts the tumor microenvironment from cold to hot. This study may provide a new therapeutic approach for CRLM. Further clinical study is needed.

A pan-cancer analysis of TTC9A expression level and its correlation with prognosis and immune microenvironment

To investigate the expression level of tetratricopeptide repeat protein 9A in tumors and its association with the patients' prognosis and immune infiltration. TTC9A expression in different tumor tissues and its association with prognosis, DNA methylation, tumor mutation burden (TMB), and microsatellite instability (MSI) were analyzed based on data from TCGA and GTEx. TIMER and xCell were used to analyze the relationship between TTC9A expression and immune infiltration. Western blotting and RT-qPCR were used to detect the expression of TTC9A in 4 types of cancer cell lines. TTC9A expressions were significantly increased in many tumors and down-regulated in a few cancer types (P < 0.05). Western blotting and RT-qPCR showed that TTC9A expressions were elevated in lung, colon and liver cancer cells but decreased in bladder cancer cells. In head and neck squamous cell carcinoma, renal clear cell carcinoma, renal papillary cell carcinoma, low-grade glioma, malignant mesothelioma, and endometrial carcinoma tumors, a high expression of TTC9A was strongly correlated with better overall survival (OS), disease-specific survival (DSS), and progression-free interval (PFI) (P < 0.05), but was correlated with worse OS, DSS, and PFI in lung adenocarcinoma, pancreatic adenocarcinoma, adrenal carcinoma, and rectal adenocarcinoma (P < 0.05). TTC9A hypermethylation was associated with a more favorable prognosis of glioblastoma multiforme, low- grade glioma, uveal melanoma, and ovarian plasmacytoid cystadenocarcinoma (P < 0.05) but with poor prognosis of squamous cell carcinoma of the uterine cervix and intracervical adenocarcinoma, squamous cell carcinoma of head and neck, squamous cell carcinoma of the lungs, adrenal carcinoma, and endometrial carcinoma (P < 0.05). In most of the cancer types, TTC9A was significantly correlated with the level of immune cell infiltration (P < 0.05). TTC9A can be used as a prognostic marker for a variety of cancers and is strongly associated with TBM, MSI and immune cell infiltration.

Interdisciplinary diagnostics and therapy of malignant mesothelioma

The asbestos-related malignant mesothelioma (MM) is one of the common occupational cancers in Germany with approximately 1000 new cases per year. Provided that the appropriate diagnostic criteria are fulfilled, MM can be diagnosed with high specificity from both histological and cytological specimens. However, many MM are detected cyto-/histologically only at advanced stages. Clinical/radiological aspects complement each other and enable interdisciplinary assessment of tumor stage and individualized decisions on the best possible therapeutic options. Diagnostically, video-assisted thoracoscopy (VATS) has the highest priority. Therapy planning is based on the MM subtype, tumor spread and stage, and the patient's clinical condition. MM has generally a very unfavorable prognosis. Accordingly, the standard therapy aims at a macroscopic radical tumor resection in terms of cytoreduction within the framework of a suitable multimodal therapy concept (chemotherapy, radiotherapy, psychooncology). The aim of palliative measures should be primarily symptom control. Overall, interdisciplinary diagnosis and therapy of MM is crucial for the best possible care of MM patients.

Population Pharmacokinetics and Exposure-Response Analysis for the CTLA-4 Inhibitor Tremelimumab in Metastatic NSCLC Patients in the Phase III POSEIDON Study.

Blockade of CTLA-4 by tremelimumab combined with anti-PD-L1 durvalumab and chemotherapy provided increased antitumor activity and long-term survival benefits in first-line metastatic non-small cell lung cancer (mNSCLC) in the phase III POSEIDON study. We performed population pharmacokinetic modeling for tremelimumab using data from 1,605 patients across 6 studies (including POSEIDON) in multiple tumors (lung cancer, bladder cancer, malignant mesothelioma, and other solid tumors), and identified a 2-compartment model with linear and time-varying clearance for tremelimumab. Cox proportional hazard regression models were applied to 326 patients with mNSCLC from POSEIDON to evaluate the association between exposure metrics and efficacy end points, adjusting for baseline prognostic covariates. Improved progression-free survival (PFS) and overall survival (OS) in the tremelimumab arm (in combination with durvalumab and chemotherapy) was associated with higher tremelimumab exposure (e.g., minimum concentration at 5th dose (Cmin,dose5 ) and area under the curve at 5th dose (AUCdose5 )). However, further case-matching analyses yielded hazard ratios for the comparison of tremelimumab-treated patients in the Cmin,dose5 quartile 1 (Q1) subgroup with matched chemotherapy-treated patients of 1.04 (95% confidence interval (CI): 0.76-1.44) for OS and 0.99 (95% CI: 0.72-1.36) for PFS, suggesting that the observed apparent exposure-response relationship might be confounded. No relationship between tremelimumab exposure and safety (grade ≥3 treatment-emergent adverse events [AEs], AEs of special interest, or discontinuation due to AEs) was identified. These results support the consistent benefit observed with tremelimumab 75 mg every 3 weeks for up to 5 doses in combination with durvalumab and chemotherapy in POSEIDON as first-line therapy for mNSCLC.

Malignant mesothelioma tumours: molecular pathogenesis, diagnosis, and therapies accompanying clinical studies.

The pathetic malignant mesothelioma (MM) is a extremely uncommon and confrontational tumor that evolves in the mesothelium layer of the pleural cavities (inner lining- visceral pleura and outer lining- parietal pleura), peritoneum, pericardium, and tunica vaginalis and is highly resistant to standard treatments. In mesothelioma, the predominant pattern of lesions is a loss of genes that limit tumour growth. Despite the worldwide ban on the manufacture and supply of asbestos, the prevalence of mesothelioma continues to increase. Mesothelioma presents and behaves in a variety of ways, making diagnosis challenging. Most treatments available today for MM are ineffective, and the median life expectancy is between 10 and 12 months. However, in recent years, considerable progress has already been made in understanding the genetics and molecular pathophysiology of mesothelioma by addressing hippo signaling pathway. The development and progression of MM are related to many important genetic alterations. This is related to NF2 and/or LATS2 mutations that activate the transcriptional coactivator YAP. The X-rays, CT scans, MRIs, and PET scans are used to diagnose the MM. The MM are treated with surgery, chemotherapy, first-line combination chemotherapy, second-line treatment, radiation therapy, adoptive T-cell treatment, targeted therapy, and cancer vaccines. Recent clinical trials investigating the function of surgery have led to the development of innovative approaches to the treatment of associated pleural effusions as well as the introduction of targeted medications. An interdisciplinary collaborative approach is needed for the effective care of persons who have mesothelioma because of the rising intricacy of mesothelioma treatment. This article highlights the key findings in the molecular pathogenesis of mesothelioma, diagnosis with special emphasis on the management of mesothelioma.

The amino-acid stress sensing eIF2α kinase GCN2 is a survival biomarker for malignant mesothelioma

BackgroundMalignant mesothelioma is a tumour that is strongly associated with a history of asbestos exposure, and which derives from mesothelial cells that line the serous cavities of the body. The tumour most commonly arises in the pleural cavity, but can also arise in the pericardium, peritoneum, and tunica vaginalis. At present the lesion has a very poor prognosis and is an incurable form of cancer with median survival times of up to 19 months being quoted for some histological subtypes. A large proportion of mesotheliomas have been shown to be arginine auxotrophic, leading to new research for therapeutics which might exploit this potential vulnerability.MethodsWe measured the levels of General Control Non-derepressible 2 (GCN2) protein in malignant mesothelioma tumour samples and determined whether these levels correlate with clinical outcomes.ResultsWe observed that the expression levels of GCN2 correlated with patient survival and was an independent prognostic variable in pairwise comparisons with all available clinical data.ConclusionThese findings suggest that GCN2 levels provides prognostic information and may allow for stratification of care pathways. It may suggest that targeting GCN2 is a viable strategy for mesothelioma therapy development.

Long-Chain Acyl Coenzyme A Dehydrogenase, a Key Player in Metabolic Rewiring/Invasiveness in Experimental Tumors and Human Mesothelioma Cell Lines.

Cross-species investigations of cancer invasiveness are a new approach that has already identified new biomarkers which are potentially useful for improving tumor diagnosis and prognosis in clinical medicine and veterinary science. In this study, we combined proteomic analysis of four experimental rat malignant mesothelioma (MM) tumors with analysis of ten patient-derived cell lines to identify common features associated with mitochondrial proteome rewiring. A comparison of significant abundance changes between invasive and non-invasive rat tumors gave a list of 433 proteins, including 26 proteins reported to be exclusively located in mitochondria. Next, we analyzed the differential expression of genes encoding the mitochondrial proteins of interest in five primary epithelioid and five primary sarcomatoid human MM cell lines; the most impressive increase was observed in the expression of the long-chain acyl coenzyme A dehydrogenase (ACADL). To evaluate the role of this enzyme in migration/invasiveness, two epithelioid and two sarcomatoid human MM cell lines derived from patients with the highest and lowest overall survival were studied. Interestingly, sarcomatoid vs. epithelioid cell lines were characterized by higher migration and fatty oxidation rates, in agreement with ACADL findings. These results suggest that evaluating mitochondrial proteins in MM specimens might identify tumors with higher invasiveness.

Abstract CT006: First-in-class, first-in-human phase 1 trial of VT3989, an inhibitor of yes-associated protein (YAP)/transcriptional enhancer activator domain (TEAD), in patients (pts) with advanced solid tumors enriched for malignant mesothelioma and other tumors with neurofibromatosis 2 (NF2) mutations

Abstract Background: Inactivation of the Hippo pathway is a common finding in MM and other cancers, leading to constitutive YAP activation, but has thus far been undruggable. NF2 encodes Merlin that activates Hippo kinase resulting in inactivation of YAP, which is the major effector of Hippo signaling. NF2-deficient tumors, often due to inactivating NF2 mutations (NF2m), are dependent on YAP for growth. VT3989 is an oral, highly potent and selective inhibitor of TEAD palmitoylation, which blocks YAP function and has shown promising preclinical activity. Materials and Methods: This FIH trial used a 3 + 3 dose escalation design and evaluated VT3989 from 25 to 200 mg QD continuously and 50 to 200 mg intermittently. Pts with refractory solid tumors, ECOG PS 0-1, serum albumin &amp;gt; 2.5, urinary protein creatinine ratio ≤ 0.5 mg/mg and albumin creatinine ratio ≤ 100 mg/g were enrolled. Objectives were to determine the safety, tolerability and recommended Phase 2 dose (RP2D) of VT3989; to evaluate antitumor activity, pharmacokinetics (PK) and correlate NF2m and other alterations in tumor and ctDNA with response. Results: 67 pts have been enrolled. Median age 63.5y (21-83y), ECOG PS 0:1 13:54 pts. Median prior therapies 3 (range 0-8). Tumor types: 42 MM (29 pleural and 13 non-pleural) and 25 solid tumors including 9 meningioma and 4 sarcoma pts. 34 pts had NF2m (29 somatic and 5 germline). All MM pts had progressed on prior platinum/pemetrexed; all but 2 had prior immune checkpoint inhibitors. VT3989 is safe and well tolerated with no dose limiting toxicities. No MTD was defined up to 200 mg QD. The most common AEs are proteinuria, albuminuria and peripheral edema, mainly observed with the continuous schedule. There were 7 possibly related G3 AEs (fatigue, ALT, AST, dehydration, dyspnea, hypotension and peripheral edema) and 1 G4 cardiomyopathy. No pt developed decreased renal function or nephrotic syndrome. VT3989 has a 12-15 day half-life, dose proportional PK and reaches steady state within 2 weeks. Seven pts (6 refractory MM and 1 NF2m sarcoma) achieved RECIST v1.1 partial responses (PRs) with 4 confirmed, 3 unconfirmed (1 pending). 3 PRs in MM pts are ongoing up to 18+ months. The clinical benefit response rate (PR + SD &amp;gt; 8 weeks, per protocol) in MM pts is 57%. Of the 6 MM pts (1 pericardial, 1 pleural/peritoneal and 4 peritoneal) with PR, 2 have NF2m, 3 are wildtype, and 1 is unknown. Conclusions: VT3989 is safe and well tolerated with durable RECIST v1.1 antitumor responses in pts with advanced MM and NF2m cancers, providing the first early clinical proof-of-concept for effectively drugging the Hippo-YAP-TEAD pathway. RP2D optimization including further schedule evaluation and expansion are ongoing in pts with MM and NF2m tumors. Citation Format: Timothy A. Yap, David J. Kwiatkowski, Jayesh Desai, Ibiayi Dagogo-Jack, Michael Millward, Hedy L. Kindler, Anthony W. Tolcher, Sophia Frentzas, Archie W. Thurston, Len Post, F Andrew Dorr. First-in-class, first-in-human phase 1 trial of VT3989, an inhibitor of yes-associated protein (YAP)/transcriptional enhancer activator domain (TEAD), in patients (pts) with advanced solid tumors enriched for malignant mesothelioma and other tumors with neurofibromatosis 2 (NF2) mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT006.

YAP1 is essential for malignant mesothelioma tumor maintenance

Malignant pleural mesothelioma, a tumor arising from the membrane covering the lungs and the inner side of the ribs, is a cancer in which genetic alterations of genes encoding proteins that act on or are part of the Hippo-YAP1 signaling pathway are frequent. Dysfunctional Hippo signaling may result in aberrant activation of the transcriptional coactivator protein YAP1, which binds to and activates transcription factors of the TEAD family. Recent studies have associated elevated YAP1 protein activity with a poor prognosis of malignant mesothelioma and its resistance to current therapies, but its role in tumor maintenance is unclear. In this study, we investigate the dependence of malignant mesothelioma on YAP1 signaling to maintain fully established tumors in vivo. We show that downregulation of YAP1 in a dysfunctional Hippo genetic background results in the inhibition of YAP1/TEAD-dependent gene expression, the induction of apoptosis, and the inhibition of tumor cell growth in vitro. The conditional downregulation of YAP1 in established tumor xenografts leads to the inhibition of YAP1-dependent gene transcription and eventually tumor regression. This effect is only seen in the YAP1-activated MSTO-211H mesothelioma xenograft model, but not in the Hippo-independent HCT116 colon cancer xenograft model. Our data demonstrate that, in the context of a Hippo pathway mutated background, YAP1 activity alone is enough to maintain the growth of established tumors in vivo, thus validating the concept of inhibiting the activated YAP1-TEAD complex for the treatment of malignant pleural mesothelioma patients.

Reactive oxygen species in the progression and treatment of malignant mesothelioma

Malignant mesothelioma (MM) is an aggressive cancer that affects the pleural and peritoneal mesothelial lining of the lungs and abdomen. Survival rates for patients with MM remain extremely low and effective treatments are limited. MM tumors harbor both genotypic and phenotypic features that indicate MM tumor cells are under increased oxidative stress, similar to other aggressive cancers. This increased oxidative stress in MM cells supports aggressive growth while providing a therapeutic vulnerability exploitable by redox-modulating compounds. MM tumor cells also exhibit altered mitochondrial structure and function that contribute to the disease through perturbations in metabolism and reactive oxygen species (ROS) production and metabolism. Targeting the altered redox status in cancer through increasing cellular ROS levels directly or inhibiting cellular antioxidant pathways and disrupting ROS scavenging mechanisms has become an exciting area for therapeutic intervention. This review discusses ROS sources and signaling, mitochondrial structure and function and targeting mitochondria ROS as a therapeutic approach for the treatment of MM.

Management of Patients with Malignant Peritoneal Mesothelioma: The Evolving Role of Surgery and Immunotherapy

Malignant peritoneal mesothelioma, a neoplastic process that arises from the peritoneal membranes and presents as a diffuse malignant process, has an incidence of approximately 400-600 new cases annually in the United States. Systemic chemotherapy regimens, like the combination of cisplatin and pemetrexed, have response rates of approximately 25% in peritoneal mesothelioma. Due to chemotherapy’s poor response rates, the first line approach to treating malignant peritoneal mesothelioma over the last 30 years has been surgical resection with regional intra-peritoneal chemotherapy in appropriately selected patients. Hyperthermic intraoperative intraperitoneal perfusion with chemotherapy with cisplatin or mitomycin c for 90 to 120 minutes is the most commonly reported type of regional chemotherapy that is administered during surgical cytoreduction. Favorable prognostic factors for patient outcomes after cytoreduction and hyperthermic intraperitoneal perfusion with chemotherapy tend to be favorable operative characteristics (lower peritoneal cancer index, better complete cytoreduction score), less aggressive tumor characteristics (epithelioid histology, low Ki-67, well-differentiated), and other patient characteristics (young, female, fewer comorbidities). Recently, there has been considerable interest in the utility of immune checkpoint inhibitors either alone or in combination with chemotherapy for patients with mesothelioma. Data demonstrate that programmed death-ligand 1 may be highly expressed in a large proportion of malignant peritoneal mesothelioma tumors and therefore the evaluation of checkpoint blockade in this patient population is a high clinical priority.

Oxytocin receptor is a promising therapeutic target of malignant mesothelioma.

Malignant mesothelioma (MM) is one of the most aggressive tumors. We conducted bioinformatics analysis using Cancer Cell Line Encyclopedia (CCLE) datasets to identify new molecular markers in MM. Overexpression of oxytocin receptor (OXTR), which is a G‐protein–coupled receptor for the hormone and neurotransmitter oxytocin, mRNA was distinctively identified in MM cell lines. Therefore, we assessed the role of OXTR and its clinical relevance in MM. Kaplan‐Meier and Cox regression analyses were applied to assess the association between overall survival and OXTR mRNA expression using The Cancer Genome Atlas (TCGA) datasets. The function of OXTR and the efficacy of its antagonists were investigated in vitro and in vivo using MM cell lines. Consistent with the findings from CCLE datasets analysis, OXTR mRNA expression was highly increased in MM tissues compared with other cancer types in the TCGA datasets, and MM cases with high OXTR expression showed poor overall survival. Moreover, OXTR knockdown dramatically decreased MM cell proliferation in cells with high OXTR expression via tumor cell cycle disturbance, whereas oxytocin treatment significantly increased MM cell growth. OXTR antagonists, which have high selectivity for OXTR, inhibited the growth of MM cell lines with high OXTR expression, and oral administration of the OXTR antagonist, cligosiban, significantly suppressed MM tumor progression in a xenograft model. Our findings suggest that OXTR plays a crucial role in MM cell proliferation and is a promising therapeutic target that may broaden potential therapeutic options and could be a prognostic biomarker of MM.

Somatic Epigenetic Silencing of RIPK3 Inactivates Necroptosis and Contributes to Chemoresistance in Malignant Mesothelioma.

Receptor-interacting protein kinase 3 (RIPK3) phosphorylates effector molecule MLKL to trigger necroptosis. Although RIPK3 loss is seen in several human cancers, its role in malignant mesothelioma is unknown. This study aimed to determine whether RIPK3 functions as a potential tumor suppressor to limit development of malignant mesothelioma. RIPK3 expression was examined in 66 malignant mesothelioma tumors and cell lines. Promoter methylation and DNMT1 siRNA studies were performed to assess the mode of RIPK3 silencing in RIPK3-deficient malignant mesothelioma cells. Restoration of RIPK3 expression in RIPK3-negative malignant mesothelioma cells, either by treatment with 5-aza-2'-deoxycytidine or lentiviral expression of cDNA, was performed to assess effects on cell viability, necrosis, and chemosensitization. Loss of RIPK3 expression was observed in 42/66 (63%) primary malignant mesotheliomas and malignant mesothelioma cell lines, and RT-PCR analysis demonstrated that downregulation occurs at the transcriptional level, consistent with epigenetic silencing. RIPK3-negative malignant mesothelioma cells treated with 5-aza-2'-deoxycytidine resulted in reexpression of RIPK3 and chemosensitization. Ectopic expression of RIPK3 also resulted in chemosensitization and led to necroptosis, the latter demonstrated by phosphorylation of downstream target MLKL and confirmed by rescue experiments. Mining of RIPK3 expression and survival outcomes among patients with malignant mesothelioma available from The Cancer Genome Atlas repository revealed that promoter methylation of RIPK3 is associated with reduced RIPK3 expression and poor prognosis. These data suggest that RIPK3 acts as a tumor suppressor in malignant mesothelioma by triggering necroptosis and that epigenetic silencing of RIPK3 by DNA methylation impairs necroptosis and contributes to chemoresistance and poor survival in this incurable disease.

Targeting and Efficacy of Novel mAb806-Antibody-Drug Conjugates in Malignant Mesothelioma.

Epidermal growth factor receptor (EGFR) is highly overexpressed in malignant mesothelioma (MM). MAb806 is a novel anti-EGFR antibody that selectively targets a tumor-selective epitope. MAb806-derived antibody drug conjugates (ADCs), ABT-414, ABBV-221 and ABBV-322, may represent a novel therapeutic strategy in MM. EGFR and mAb806 epitope expressions in mesothelioma cell lines were evaluated using an array of binding assays, and the in vitro cell effects of ABT-414 and ABBV-322 were determined. In vivo therapy studies were conducted in mesothelioma xenograft and patient-derived xenograft (PDX) tumor models. We also performed biodistribution and imaging studies to allow the quantitative targeting of MM by mAb806 using a 89Zr-labeled immunoconjugate—ch806. A high EGFR expression was present in all mesothelioma cell lines evaluated and mAb806 binding present in all cell lines, except NCIH-2452. ABT-414 and ABBV-322 resulted in significant tumor growth inhibition in MM models with high EGFR and mAb806 epitope expressions. In contrast, in an EGFR-expressing PDX model that was negative for the mAb806 epitope, no growth inhibition was observed. We demonstrated the specific targeting of the mAb806 epitope expressing MM tumors using 89Zr-based PET imaging. Our data suggest that targeting EGFR in MM using specific ADCs is a valid therapeutic strategy and supports further investigation of the mAb806 epitope expression as a predictive biomarker.

Targeting Multiple EGFR-expressing Tumors with a Highly Potent Tumor-selective Antibody-Drug Conjugate.

ABBV-321 (serclutamab talirine), a next-generation EGFR-targeted antibody-drug conjugate (ADC) incorporates a potent pyrrolobenzodiazepine (PBD) dimer toxin conjugated to the EGFR-targeting ABT-806 affinity-matured AM1 antibody. ABBV-321 follows the development of related EGFR-targeted ADCs including depatuxizumab mafodotin (depatux-m, ABT-414), ABT-806 conjugated to monomethyl auristatin F (MMAF), and ABBV-221 (losatuxizumab vedotin), AM1 antibody conjugated to monomethyl auristatin E (MMAE). The distinct tumor selectivity of ABBV-321 differentiates it from many previous highly active antibody PBD conjugates that lack a therapeutic window. Potency of the PBD dimer, combined with increased binding of AM1 to EGFR-positive tumor cells, opens the possibility to target a wide array of tumors beyond those with high levels of EGFR overexpression or amplification, including those insensitive to auristatin-based ADCs. ABBV-321 exhibits potent antitumor activity in cellular and in vivo studies including xenograft cell line and patient-derived xenograft glioblastoma, colorectal, lung, head and neck, and malignant mesothelioma tumor models that are less sensitive to depatux-m or ABBV-221. Combination studies with ABBV-321 and depatux-m suggest a promising treatment option permitting suboptimal, and potentially better tolerated, doses of both ADCs while providing improved potency. Collectively, these data suggest that ABBV-321 may offer an extended breadth of efficacy relative to other EGFR ADCs while extending utility to multiple EGFR-expressing tumor indications. Despite its highly potent PBD dimer payload, the tumor selectivity of ABBV-321, coupled with its pharmacology, toxicology, and pharmacokinetic profiles, support continuation of ongoing phase I clinical trials in patients with advanced EGFR-expressing malignancies.

Cytogenomic characterization of three murine malignant mesothelioma tumor cell lines

BackgroundMalignant mesothelioma (MM) is a rare aggressive cancer primary located in pleura and lung. MMs can be divided into biphasic, epithelioid and sarcomatoid subtypes. In majority of cases MMs are induced by asbestos fiber exposure. As latency period after asbestos exposure ranges between ~ 10 and 60 years MMs are mainly observed in elder people. Human MM, being a rare tumor type, lacks detailed cytogenetic data, while molecular genetic studies have been undertaken more frequently. However, murine MM cell lines are also regularly applied to get more insight into MM biology and to test new therapy strategies.ResultsHere the murine MM cell lines AB1, AB22 and AC29 were studied by molecular cytogenetics and molecular karyotyping. Interestingly, yet there were no genetic or genomic studies undertaken for these already in 1992 established cell lines. The obtained data on genomic imbalances in these murine cell lines was translated into the human genome as previously reported based on human and murine genomic browsers.ConclusionsIt turned out that all three cell lines showed high similarities in copy number variants as observed typically in human MM. Also, all three cell lines were most similar to human epithelioid MMs, and should be used as models therefore.

Cross-Species Proteomics Identifies CAPG and SBP1 as Crucial Invasiveness Biomarkers in Rat and Human Malignant Mesothelioma.

Malignant mesothelioma (MM) still represents a devastating disease that is often detected too late, while the current effect of therapies on patient outcomes remains unsatisfactory. Invasiveness biomarkers may contribute to improving early diagnosis, prognosis, and treatment for patients, a task that could benefit from the development of high-throughput proteomics. To limit potential sources of bias when identifying such biomarkers, we conducted cross-species proteomic analyzes on three different MM sources. Data were collected firstly from two human MM cell lines, secondly from rat MM tumors of increasing invasiveness grown in immunocompetent rats and human MM tumors grown in immunodeficient mice, and thirdly from paraffin-embedded sections of patient MM tumors of the epithelioid and sarcomatoid subtypes. Our investigations identified three major invasiveness biomarkers common to the three tumor sources, CAPG, FABP4, and LAMB2, and an additional set of 25 candidate biomarkers shared by rat and patient tumors. Comparing the data to proteomic analyzes of preneoplastic and neoplastic rat mesothelial cell lines revealed the additional role of SBP1 in the carcinogenic process. These observations could provide new opportunities to identify highly vulnerable MM patients with poor survival outcomes, thereby improving the success of current and future therapeutic strategies.

Abstract 4858: Oncogenic HIPPO-YAP1: in vivo target validation of YAP1 in malignant mesothelioma

Abstract Yes associated protein YAP1 (YAP1) is a cofactor of gene transcription and exerts its action through association with transcription factors from the TEAD family. Activity of YAP1-TEAD is tightly regulated by the HIPPO pathway and upon activation the expression of pro-survival and anti-apoptotic genes is induced. The HIPPO pathway consists of a series of Ser/Thr kinases, which lead to the phosphorylation of YAP1, and hence to its inactivation by either sequestration in the cytoplasm, or degradation. HIPPO pathway deletions and YAP1 activation are particularly prevalent (&amp;gt; 60 %) in patients with malignant pleural mesothelioma. We use a malignant mesothelioma tumor cell line with a HIPPO deleted genetic background (MSTO-211H, LATS1 loss) to demonstrate, that downregulation of YAP1 leads to the inhibition of YAP1-dependent gene expression, the induction of apoptosis and the inhibition of cell growth in vitro. When these cell lines are grown as an in vivo subcutaneous xenograft in mice, downregulation of YAP1 leads to the inhibition of YAP1-dependent gene expression and eventually results in the regression of established tumors. This effect is specific to YAP1 activated mesothelioma models and is not observed in the HIPPO pathway independent HCT116 colon cancer model. We show here, that YAP1 activity alone is required for tumor maintenance in vivo in the context of HIPPO pathway genetic alterations, and thus confirm the relevance of this target for a drug discovery approach. Citation Format: Loreley Calvet, Odette Dos Santos, Véronique Jean-Baptiste, Emmanuel Spanakis, Yvette Ruffin, Isabelle Sanchez, Jessica Mestadier, Stéphane Soubigou, Sylvie Feteanu, Pascale Picard, Chagri Boumaya, Jack Pollard, Colette Dib, Sukhvinder Sidhu, Laurent Debussche, Iris Valtingojer. Oncogenic HIPPO-YAP1: in vivo target validation of YAP1 in malignant mesothelioma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4858.

S100A4 is a Biomarker of Tumorigenesis, EMT, Invasion, and Colonization of Host Organs in Experimental Malignant Mesothelioma.

Recent findings suggest that S100A4, a protein involved in communication between stromal cells and cancer cells, could be more involved than previously expected in cancer invasiveness. To investigate its cumulative value in the multistep process of the pathogenesis of malignant mesothelioma (MM), SWATH-MS (sequential window acquisition of all theoretical fragmentation spectra), an advanced and robust technique of quantitative proteomics, was used to analyze a collection of 26 preneoplastic and neoplastic rat mesothelial cell lines and models of MM with increasing invasiveness. Secondly, proteomic and histological analyses were conducted on formalin-fixed paraffin-embedded sections of liver metastases vs. primary tumor, and spleen from tumor-bearing rats vs. controls in the most invasive MM model. We found that S100A4, along with 12 other biomarkers, differentiated neoplastic from preneoplastic mesothelial cell lines, and invasive vs. non-invasive tumor cells in vitro, and MM tumors in vivo. Additionally, S100A4 was the only protein differentiating preneoplastic mesothelial cell lines with sarcomatoid vs. epithelioid morphology in relation to EMT (epithelial-to-mesenchymal transition). Finally, S100A4 was the most significantly increased biomarker in liver metastases vs. primary tumor, and in the spleen colonized by MM cells. Overall, we showed that S100A4 was the only protein that showed increased abundance in all situations, highlighting its crucial role in all stages of MM pathogenesis.

The Biology of Malignant Mesothelioma and the Relevance of Preclinical Models.

Malignant mesothelioma (MM), especially its more frequent form, malignant pleural mesothelioma (MPM), is a devastating thoracic cancer with limited therapeutic options. Recently, clinical trials that used immunotherapy strategies have yielded promising results, but the benefits are restricted to a limited number of patients. To develop new therapeutic strategies and define predictors of treatment response to existing therapy, better knowledge of the cellular and molecular mechanisms of MM tumors and sound preclinical models are needed. This review aims to provide an overview of our present knowledge and issues on both subjects. MM shows a complex pattern of molecular changes, including genetic, chromosomic, and epigenetic alterations. MM is also a heterogeneous cancer. The recently described molecular classifications for MPM could better consider inter-tumor heterogeneity, while histo-molecular gradients are an interesting way to consider both intra- and inter-tumor heterogeneities. Classical preclinical models are based on use of MM cell lines in culture or implanted in rodents, i.e., xenografts in immunosuppressed mice or isografts in syngeneic rodents to assess the anti-tumor immune response. Recent developments are tumoroids, patient-derived xenografts (PDX), xenografts in humanized mice, and genetically modified mice (GEM) that carry mutations identified in human MM tumor cells. Multicellular tumor spheroids are an interesting in vitro model to reduce animal experimentation; they are more accessible than tumoroids. They could be relevant, especially if they are co-cultured with stromal and immune cells to partially reproduce the human microenvironment. Even if preclinical models have allowed for major advances, they show several limitations: (i) the anatomical and biological tumor microenvironments are incompletely reproduced; (ii) the intra-tumor heterogeneity and immunological contexts are not fully reconstructed; and (iii) the inter-tumor heterogeneity is insufficiently considered. Given that these limitations vary according to the models, preclinical models must be carefully selected depending on the objectives of the experiments. New approaches, such as organ-on-a-chip technologies or in silico biological systems, should be explored in MM research. More pertinent cell models, based on our knowledge on mesothelial carcinogenesis and considering MM heterogeneity, need to be developed. These endeavors are mandatory to implement efficient precision medicine for MM.