Durable Response to Vismodegib in PTCH1 F1147fs Mutant Relapsed Malignant Pleural Mesothelioma: Implications for Mesothelioma Drug Treatment

Unleashing precision: A review of targeted approaches in pleural mesothelioma

This review delves into the intricate landscape of pleural mesothelioma (PM), emphasizing the need for nuanced therapeutic strategies. While platinum-based chemotherapy remains a cornerstone, the advent of immune checkpoint inhibitors (ICIs), notably through the Checkmate 743 trial, has reshaped treatment paradigms. Challenges persist due to patient heterogeneity and a lack of specific biomarkers. Targeting genotypic and phenotypic alterations emerges as a promising avenue, demanding precision oncology in this rare disease. CDKN2A loss, prevalent in PM, may respond to CDK4/6 inhibitors. Defects in MMR and HR suggest tailored approaches with ICI or PARP inhibitors, respectively. Ongoing trials explore novel inhibitors and promising targets like mesothelin. Implementing these strategies requires overcoming challenges in patient selection, combination therapies, biomarker identification, and cost considerations. Collaboration is crucial for transforming these insights into impactful clinical interventions, heralding the era of personalized and precision medicine for PM.

Update on gene fusions and the emerging clinicopathological landscape of peritoneal and pleural mesotheliomas and other neoplasms

BACKGROUND

Mesothelioma is a rare and aggressive malignant neoplasm arising from mesothelial cells, which occasionally manifests recurrent fusions. EWSR1/FUS-CREB, YY1, MAP3K8, NR4A3, and ALK-rearranged proliferations have been reported in limited series with no clear histological or clinical correlations, limiting clinicians' ability to assess prognosis and integrate these new entities into therapeutic decisions. The aim of this study was to better characterize these rearranged proliferations histologically, molecularly, and clinically.

METHODS

Clinical, pathological, and comprehensive transcriptome and mutation data were collected for each case.

RESULTS

A total of 41 tumors were included, encompassing 7 ALK, 10 MAP3K8, 4 NR4A3, 8 ESWR1/FUS::ATF1, 8 EWSR1::YY1, and 4 SUFU-fused cases. We found a female predominance, except for cases harboring NR4A3 and SUFU; and most patients were around 60 years of age, but those harboring ALK or EWSR1/FUS::ATF1 gene fusions were younger. Each group exhibited distinct histological, immunohistochemical, molecular features, and oncological courses. Specifically, MAP3K8 and ALK presented PAX8+ papillary proliferations, ESWR1/FUS::ATF1 and EWSR1::YY1 displayed angiomatoid fibrous histiocytoma-like patterns, while SUFU showcased 'tissue culture'-like spindle cell proliferation. Poor prognosis factors were the pleural site, male sex, Ki67 ≥10%, and ESWR1/FUS::ATF1 or SUFU gene fusions.

CONCLUSIONS

This study significantly broadens the spectrum of mesothelial tumors associated with fusions, offering insight into novel epithelioid (mesothelial) proliferations with distinctive histological appearances, molecular profiles, and prognoses to guide adapted treatments for patients.

Clinical Next Generation Sequencing Application in Mesothelioma: Finding a Golden Needle in the Haystack

Mesothelioma comprises a group of rare cancers arising from the mesothelium of the pleura, peritoneum, tunica vaginalis testis and pericardium. Mesothelioma is generally associated with asbestos exposure and has a dismal prognosis, with few therapeutic options. Several next generation sequencing (NGS) experiments have been performed on mesothelioma arising at different sites. These studies highlight a genomic landscape mainly characterized by a high prevalence (>20%) of genomic aberrations leading to functional losses in oncosuppressor genes such as BAP1, CDKN2A, NF2, SETD2 and TP53. Nevertheless, to date, evidence of the effect of targeting these alterations with specific drugs is lacking. Conversely, 1-2% of mesothelioma might harbor activating mutations in oncogenes with specifically approved drugs. The goal of this review is to summarize NGS applications in mesothelioma and to provide insights into target therapy of mesothelioma guided by NGS.

Genomic landscape of pleural and peritoneal mesothelioma tumours

BACKGROUND

Malignant pleural and peritoneal mesotheliomas are rare malignancies with unacceptable poor prognoses and limited treatment options. The genomic landscape is mainly characterised by the loss of tumour suppressor genes and mutations in DNA repair genes. Currently, data from next-generation sequencing (NGS) of mesothelioma tumours is restricted to a limited number of cases; moreover, data comparing molecular features of mesothelioma from the pleural and peritoneal origin with NGS are lacking.

METHODS

We analysed 1113 pleural mesothelioma and 355 peritoneal mesothelioma samples. All tumours were sequenced with the FoundationOne® or FoundationOne®CDx assay for detection of substitutions, insertion-deletions, copy-number alterations and selected rearrangements in at least 324 cancer genes.

RESULTS

This analysis revealed alterations in 19 genes with an overall prevalence of at least 2%. Alterations in BAP1, CDKN2A, CDKN2B, NF2, MTAP, TP53 and SETD2 occurred with a prevalence of at least 10%. Peritoneal, compared to pleural mesothelioma, was characterised by a lower prevalence of alterations in CDKN2A, CDKN2B and MTAP. Moreover, we could define four distinct subgroups according to alterations in BAP1 and CDKN2A/B. Alterations in Hedgehog pathway-related genes (PTCH1/2 and SUFU) and Hippo pathway-related gene (NF2) as well as KRAS, EGFR, PDGFRA/B, ERBB2 and FGFR3 were detected in both cohorts.

CONCLUSION

Here, we report the molecular aberrations from the largest cohort of patients with mesothelioma. This analysis identified a proportion of patients with targetable alterations and suggests that molecular profiling can identify new treatment options for patients with mesothelioma.

Analysis of Primary Cilium Expression and Hedgehog Pathway Activation in Mesothelioma Throws Back Its Complex Biology

The primary cilium (PC) is a sensory organelle present on the cell surface, modulating the activity of many pathways. Dysfunctions in the PC lead to different pathologic conditions including cancer. Hedgehog signaling (Hh) is regulated by PC and the loss of its control has been observed in many cancers, including mesothelioma. Malignant pleural mesothelioma (MPM) is a fatal cancer of the pleural membranes with poor therapeutic options. Recently, overexpression of the Hh transcriptional activator GL1 has been demonstrated to be associated with poor overall survival (OS) in MPM. However, unlike other cancers, the response to G-protein-coupled receptor smoothened (SMO)/Hh inhibitors is poor, mainly attributable to the lack of markers for patient stratification. For all these reasons, and in particular for the role of PC in the regulation of Hh, we investigated for the first time the status of PC in MPM tissues, demonstrating intra- and inter-heterogeneity in its expression. We also correlated the presence of PC with the activation of the Hh pathway, providing uncovered evidence of a PC-independent regulation of the Hh signaling in MPM. Our study contributes to the understanding MPM heterogeneity, thus helping to identify patients who might benefit from Hh inhibitors.

Tumor Immune Microenvironment and Genetic Alterations in Mesothelioma

Malignant pleural mesothelioma (MPM) is a rare and fatal disease of the pleural lining. Up to 80% of the MPM cases are linked to asbestos exposure. Even though its use has been banned in the industrialized countries, the cases continue to increase. MPM is a lethal cancer, with very little survival improvements in the last years, mirroring very limited therapeutic advances. Platinum-based chemotherapy in combination with pemetrexed and surgery are the standard of care, but prognosis is still unacceptably poor with median overall survival of approximately 12 months. The genomic landscape of MPM has been widely characterized showing a low mutational burden and the impairment of tumor suppressor genes. Among them, BAP1 and BLM are present as a germline inactivation in a small subset of patients and increases predisposition to tumorigenesis. Other studies have demonstrated a high frequency of mutations in DNA repair genes. Many therapy approaches targeting these alterations have emerged and are under evaluation in the clinic. High-throughput technologies have allowed the detection of more complex molecular events, like chromotripsis and revealed different transcriptional programs for each histological subtype. Transcriptional analysis has also paved the way to the study of tumor-infiltrating cells, thus shedding lights on the crosstalk between tumor cells and the microenvironment. The tumor microenvironment of MPM is indeed crucial for the pathogenesis and outcome of this disease; it is characterized by an inflammatory response to asbestos exposure, involving a variety of chemokines and suppressive immune cells such as M2-like macrophages and regulatory T cells. Another important feature of MPM is the dysregulation of microRNA expression, being frequently linked to cancer development and drug resistance. This review will give a detailed overview of all the above mentioned features of MPM in order to improve the understanding of this disease and the development of new therapeutic strategies.

Precision Therapy for Mesothelioma: Feasibility and New Opportunities

Malignant pleural mesotheliomas (MPMs) are characterised by their wide variation in natural history, ranging from minimally to highly aggressive, associated with both interpatient and intra-tumour genomic heterogeneity. Recent insights into the nature of this genetic variation, the identification of drivers, and the emergence of novel strategies capable of targeting vulnerabilities that result from the inactivation of key tumour suppressors suggest that new approaches to molecularly strategy therapy for mesothelioma may be feasible.