Inhibition of Cyclin Dependent Kinase 4/6 Overcomes Primary Resistance to Programmed Cell Death 1 Blockade in Malignant Mesothelioma

A CDKN2B-Associated Immune Prognostic Model for Predicting Immune Cell Infiltration and Prognosis in Esophageal Carcinoma

Objective

Studies have indicated that cyclin dependent protein kinase inhibitor 2B (CDKN2B) deletion is one of the most common changes in esophageal cancer (EC) which affects its progression and prognosis. This study explored the association between CDKN2B deletion, immunophenotype, and the prognosis of EC.

Methods

We investigated CDKN2B status and RNA expression, identified differentially expressed immune-associated genes between wild-type CDKN2B (CDKN2BWT) and deleted CDKN2B (CDKN2Bdeletion) in Cancer Genome Atlas (TCGA) EC samples. We also a constructed an immune prognostic model (IPM) based on these genes. Thereafter, the effects of IPM on the immune microenvironment of EC were analyzed. Finally, we established a nomogram by integrating the IPM and other clinical factors.

Results

CDKN2B deletion leads to downregulation of the immune response in EC. A total of 136 immune-associated genes were identified based on the CDKN2B deletion status, and three genes with remarkable potential as individual targets were selected for model construction. An IPM was developed and validated, it showed good performance in differentiating patients with a low or high risk of poor prognosis, and its predictive ability was independent of traditional clinical features. High-risk patients with EC had increased T follicular helper cells (Tfh) and M0 macrophages, and lower infiltration levels of resting CD4 memory T cells resting, and naive B cells. The nomogram developed for clinical application showed good predictive performance.

Conclusions

Our results suggested that CDKN2B deletion was associated with the survival and immune microenvironment in EC. IPM is not only an effective indicator of the immune response and prognosis, but also suggest potential targets for immunotherapy in patients with EC.

Soluble mesothelin-related peptide as a prognosticator in pleural mesothelioma patients receiving checkpoint immunotherapy

BACKGROUND

Immune checkpoint therapy (ICT) has significantly impacted the treatment of malignant pleural mesothelioma (MPM). Despite some promising results from combination therapies, nearly half of MPM patients do not benefit, underscoring the urgent need for reliable predictive biomarkers. This study assesses the prognostic value of serum soluble mesothelin-related peptide (SMRP) and PD-L1 levels in MPM patients receiving ICT.

METHODS

We conducted a retrospective analysis of 125 MPM patients treated with ICT by measuring pre-ICT serum levels of SMRP and PD-L1. We also examined the correlation of these serum levels with tumor mRNA expressions of mesothelin and PD-L1. Both univariable and multivariable Cox regression analyses were used to determine independent prognosticators for overall survival (OS). A prospective ICT clinical trial and our historical cohort were included for validation.

RESULTS

Seventy-seven patients (62%) were treated with either anti-PD-(L)1 monotherapy, and the remaining 38% received combination ICT. Higher pre-ICT SMRP levels were observed in epithelioid MPM compared to nonepithelioid MPM. Serum PD-L1 levels did not differ significantly between the different histologic groups. Univariable analysis identified durable clinical benefit, development of immune-related adverse events, and SMRP levels as significantly associated with OS. Multivariable analysis confirmed SMRP as an independent prognostic factor, with lower levels (≤1.35 nmol/L) correlating with improved OS. The association of high SMRP with worse prognosis was validated in the prospective ICT clinical trial cohort and not in our historical cohort treated without ICT.

CONCLUSIONS

SMRP is a promising serum biomarker for predicting survival in MPM patients treated with ICT and warrants prospective investigation.

CDKN2A Low cancer cells outcompete macrophages for microenvironmental zinc to drive immunotherapy resistance

Approximately 50% of cancers exhibit decreased CDKN2A expression ( CDKN2A Low ), which is linked to immune checkpoint blockade (ICB) resistance. While CDKN2A is traditionally recognized as a tumor suppressor and cell cycle regulator, we have previously put forth a new paradigm demonstrating its role in intracellular metabolic reprogramming. Whether the metabolic derangement due to CDKN2A loss alters metabolites within the tumor microenvironment (TME) and how that affects the immune compartment and ICB response has never been investigated. Here we found that CDKN2A Low cancer cells reorganize zinc compartmentalization by upregulating the zinc importer SLC39A9 in the plasma membrane, leading to intracellular zinc accumulation in cancer cells and concurrent zinc depletion in the TME. This competition for zinc results in zinc-starved tumor-associated macrophages (TAMs), leading to reduced phagocytic activity. Increasing zinc in TAMs through multiple approaches, including a dietary intervention that increases availability of TME zinc, re-educates these TAMs to a pro-phagocytic phenotype. Remarkably, both knockdown of Slc39a9 in cancer cells or providing a high zinc diet sensitizes Cdkn2a Low tumors to ICB. TAMs, not T cells, are indispensable for ICB response. Clinically, TAMs from CDKN2A Low cancer patients have decreased zinc signatures, corresponding to reduced phagocytosis signatures. Moreover, patients with low circulating zinc levels have reduced time-to-event outcomes compared to those with higher zinc levels. Our work reveals a previously unrecognized mechanism through which CDKN2A Low cancer cells outcompete TAMs for zinc, directly disrupting their function and ICB efficacy.

LKB1 dictates sensitivity to immunotherapy through Skp2-mediated ubiquitination of PD-L1 protein in non-small cell lung cancer

BACKGROUND

Loss-of-function mutations of liver kinase B (LKB1, also termed as STK11 (serine/threonine kinase 11)) are frequently detected in patients with non-small cell lung cancer (NSCLC). The LKB1 mutant NSCLC was refractory to almost all the antitumor treatments, including programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) blockade therapy. Unfortunately, mechanisms underlying resistance to immunotherapy are not fully understood. In this study, we deciphered how LKB1 regulated sensitivity to anti-PD-1/PD-L1 immunotherapy.

METHODS

We investigated the mutational landscape of LKB1 mutant NSCLC in next generation sequencing (NGS) data sets. Expression of LKB1, PD-L1 and S-phase kinase-associated protein 2 (Skp2) in NSCLC samples were assessed by immunohistochemistry (IHC). The tumor microenvironment (TME) profiling of LKB1 wild type (WT) and mutant NSCLC was performed using fluorescent multiplex IHC. Mass spectrometry and enrichment analysis were used to identify LKB1 interacting proteins. Mechanistic pathways were explored by immunoblotting, ubiquitination assay, cycloheximide chase assay and immunoprecipitation assay.

RESULTS

By using NGS data sets and histological approaches, we demonstrated that LKB1 status was positively associated with PD-L1 protein expression and conferred a T cell-enriched "hot" TME in NSCLC. Patients with good responses to anti-PD-1/PD-L1 immunotherapy possessed a high level of LKB1 and PD-L1. Skp2 emerged as the molecular hub connecting LKB1 and PD-L1, by which Skp2 catalyzed K63-linked polyubiquitination on K136 and K280 residues to stabilize PD-L1 protein. Inhibition of Skp2 expression by short hairpin RNA or its E3 ligase activity by compound #25 abrogated intact expression of PD-L1 in vitro and generated a T cell-excluded "cold" TME in vivo. Thus, the LKB1-Skp2-PD-L1 regulatory loop was crucial for retaining PD-L1 protein expression and manipulation of this pathway would be a feasible approach for TME remodeling.

CONCLUSION

LKB1 and Skp2 are required for intact PD-L1 protein expression and TME remodeling in NSCLC. Inhibition of Skp2 resulted in a conversion from "hot" TME to "cold" TME and abrogated therapeutic outcomes of immunotherapy. Screening LKB1 and Skp2 status would be helpful to select recipients who may benefit from anti-PD-1/PD-L1 immunotherapy.

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.

Pharmacological inhibition of CDK4/6 impairs diffuse pleural mesothelioma 3D spheroid growth and reduces viability of cisplatin-resistant cells

Introduction

Diffuse pleural mesothelioma (DPM) of the pleura is a highly aggressive and treatment-resistant cancer linked to asbestos exposure. Despite multimodal treatment, the prognosis for DPM patients remains very poor, with an average survival of 2 years from diagnosis. Cisplatin, a platinum-based chemotherapy drug, is commonly used in the treatment of DPM. However, the development of resistance to cisplatin significantly limits its effectiveness, highlighting the urgent need for alternative therapeutic strategies. New selective inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6) have shown promise in various malignancies by inhibiting cell cycle progression and suppressing tumor growth. Recent studies have indicated the potential of abemaciclib for DPM therapy, and a phase II clinical trial has shown preliminary encouraging results.

Methods

Here, we tested abemaciclib, palbociclib, and ribociclib on a panel of DPM cell lines and non-tumor mesothelial(MET-5A) cells.

Results

Specifically, we focused on abemaciclib, which was the mosteffective cytotoxic agent on all the DPM cell lines tested. Abemaciclib reduced DPM cell viability, clonogenic potential, and ability to grow as three-dimensional (3D) spheroids. In addition, abemaciclib induced prolonged effects, thereby impairing second-generation sphere formation and inducing G0/G1 arrest and apoptosis/ necrosis. Interestingly, single silencing of RB family members did not impair cell response to abemaciclib, suggesting that they likely complement each other in triggering abemaciclib's cytostatic effect. Interestingly, abemaciclib reduced the phosphorylation of AKT, which is hyperactive in DPM and synergized with the pharmacological AKT inhibitor (AKTi VIII). Abemaciclib also synergized with cisplatin and reduced the viability of DPM cells with acquired resistance to cisplatin.

Discussion

Overall, our results suggest that CDK4/6 inhibitors alone or in combination with standard of care should be further explored for DPM therapy.

Preclinical evaluation of CDK4 phosphorylation predicts high sensitivity of pleural mesotheliomas to CDK4/6 inhibition

Malignant pleural mesothelioma (MPM) is an aggressive cancer with limited therapeutic options. We evaluated the impact of CDK4/6 inhibition by palbociclib in 28 MPM cell lines including 19 patient-derived ones, using various approaches including RNA-sequencing. Palbociclib strongly and durably inhibited the proliferation of 23 cell lines, indicating a unique sensitivity of MPM to CDK4/6 inhibition. When observed, insensitivity to palbociclib was mostly explained by the lack of active T172-phosphorylated CDK4. This was associated with high p16INK4A (CDKN2A) levels that accompany RB1 defects or inactivation, or (unexpectedly) CCNE1 overexpression in the presence of wild-type RB1. Prolonged palbociclib treatment irreversibly inhibited proliferation despite re-induction of cell cycle genes upon drug washout. A senescence-associated secretory phenotype including various potentially immunogenic components was irreversibly induced. Phosphorylated CDK4 was detected in 80% of 47 MPMs indicating their sensitivity to CDK4/6 inhibitors. Its absence in some highly proliferative MPMs was linked to very high p16 (CDKN2A) expression, which was also observed in public datasets in tumours from short-survival patients. Our study supports the evaluation of CDK4/6 inhibitors for MPM treatment, in monotherapy or combination therapy.

Biological mechanisms of resistance to immune checkpoint inhibitors and overcoming this resistance: Challenges in medical oncology

Immune checkpoint inhibitors have opened up new possibilities in clinical oncology. Monoclonal antibodies have shown their high clinical efficiency. They block CTLA-4, PD-1, and PD-L1 receptors and activate the immune response. Many patients have stable and even complete responses. However, some patients have primary or acquired resistance. Therefore, the treatment results in this category of patients are not predictable. Mechanisms of resistance to immune checkpoint inhibitors have not been definitively studied. Many theories try to explain the mechanisms of this phenomenon. Our study aimed to structure and combine the data into groups depending on the etiological factor that reduces the immune response. In addition, based on understanding the mechanisms of resistance and the results of recent clinical studies, we aimed to identify the main ways to overcome it. Therefore, mechanisms that lead to resistance may be associated with tumor properties, tumor microenvironment, or patient characteristics. Tumor properties that reduce the immune response include a) low tumor mutation burden and loss of tumor neoantigens, b) changes in the processing or presentation of neoantigens, and c) changes in signaling pathways of tumor development and epigenetic modifications in genes. The tumor microenvironment is represented by stromal and immune cells, extracellular matrix, cytokines, and blood vessels. Each structure can enhance or reduce the immune response and contribute to the acquired resistance to immune checkpoint inhibitors. The effectiveness of the treatment depends not only on the cells in the tumor microenvironment but also on the metabolic background. In addition, the basic characteristics of the patient ( gender, gut microbiota, HLA-I genotype) can modify the immune response. Based on knowledge about the mechanisms of resistance to immune checkpoint inhibitors, several therapeutic strategies aimed at activating antitumor activity have been evaluated. All of them are based on combining immune checkpoint inhibitors with other drugs. One of the most common options is a combination of PD-1/PD-L1 and CTLA-4 inhibitors. Alternative immune checkpoints are TIM-3, LAG-3, TIGIT and VISTA. Combining immunotherapy with chemotherapy, targeted therapy, neoangiogenesis inhibitors, epigenetic modifiers, PARP or TGF-β inhibitors enhances antitumor response by preventing depletion of effector T cells, enhancing T cell infiltration in the tumor, changes on the tumor microenvironment, and decreasing the accumulation of immunosuppressive cells. This review explores the biological mechanisms of resistance and potential ways of solving this problem.

Genomic Landscape of Pleural Mesothelioma and Therapeutic Aftermaths

PURPOSE OF REVIEW

In this article, we provide a comprehensive analysis of recent progress in the genetic characterisation of pleural mesothelioma, and the translation of these findings to clinical practice.

RECENT FINDINGS

Advancements in sequencing technology have allowed the identification of driver mutations and improved our understanding of how these mutations may shape the mesothelioma tumour microenvironment. However, the identification of frequently mutated regions including CDKN2A, BAP1 and NF2 have, to date, not yet yielded targeted therapy options that outperform standard chemo- and immunotherapies. Similarly, the association between mutational profile and the immune microenvironment or immunotherapy response is not well characterised. Further research into the link between tumour mutational profile and response to therapy is critical for identifying targetable vulnerabilities and stratifying patients for therapy.

Cancer cell-intrinsic PD-1: Its role in malignant progression and immunotherapy

Programmed cell death protein-1 (PD-1), also called CD279, is coded by the PDCD1 gene and is constitutively expressed on the surface of immune cells. As a receptor and immune checkpoint, PD-1 can bind to programmed death ligand-1/programmed death ligand-2 (PD-L1/PD-L2) in tumor cells, leading to tumor immune evasion. Anti-PD-1 and anti-PD-L1 are important components in tumor immune therapy. PD-1 is also expressed as an intrinsic variant (iPD-1) in cancer cells where it plays important roles in malignant progression as proposed by recent studies. However, iPD-1 has received much less attention compared to PD-1 expressed on immune cells although there is an unmet medical need for fully elucidating the mechanisms of actions to achieve the best response in tumor immunotherapy. iPD-1 suppresses tumorigenesis in non-small cell lung cancer (NSCLC) and colon cancer, whereas it promotes tumorigenesis in melanoma, hepatocellular carcinoma (HCC), pancreatic ductal adenocarcinoma (PDAC), thyroid cancer (TC), glioblastoma (GBM), and triple-negative breast cancer (TNBC). In this review, we focus on the role of iPD-1 in tumorigenesis and development and its molecular mechanisms. We also deeply discuss nivolumab-based combined therapy in common tumor therapy. iPD-1 may explain the different therapeutic effects of anti-PD-1 treatment and provide critical information for use in combined anti-tumor approaches.

The mechanism and clinical application of DNA damage repair inhibitors combined with immune checkpoint inhibitors in the treatment of urologic cancer

Urologic cancers such as kidney, bladder, prostate, and uroepithelial cancers have recently become a considerable global health burden, and the response to immunotherapy is limited due to immune escape and immune resistance. Therefore, it is crucial to find appropriate and effective combination therapies to improve the sensitivity of patients to immunotherapy. DNA damage repair inhibitors can enhance the immunogenicity of tumor cells by increasing tumor mutational burden and neoantigen expression, activating immune-related signaling pathways, regulating PD-L1 expression, and reversing the immunosuppressive tumor microenvironment to activate the immune system and enhance the efficacy of immunotherapy. Based on promising experimental results from preclinical studies, many clinical trials combining DNA damage repair inhibitors (e.g., PARP inhibitors and ATR inhibitors) with immune checkpoint inhibitors (e.g., PD-1/PD-L1 inhibitors) are underway in patients with urologic cancers. Results from several clinical trials have shown that the combination of DNA damage repair inhibitors with immune checkpoint inhibitors can improve objective rates, progression-free survival, and overall survival (OS) in patients with urologic tumors, especially in patients with defective DNA damage repair genes or a high mutational load. In this review, we present the results of preclinical and clinical trials of different DNA damage repair inhibitors in combination with immune checkpoint inhibitors in urologic cancers and summarize the potential mechanism of action of the combination therapy. Finally, we also discuss the challenges of dose toxicity, biomarker selection, drug tolerance, drug interactions in the treatment of urologic tumors with this combination therapy and look into the future direction of this combination therapy.

A Selective ALDH1A3 Inhibitor Impairs Mesothelioma 3-D Multicellular Spheroid Growth and Neutrophil Recruitment

Aldehyde dehydrogenase 1A3 (ALDH1A3), one of the three members of the aldehyde dehydrogenase 1A subfamily, has been associated with increased progression and drug resistance in various types of solid tumours. Recently, it has been reported that high ALDH1A3 expression is prognostic of poor survival in patients with malignant pleural mesothelioma (MPM), an asbestos-associated chemoresistant cancer. We treated MPM cells, cultured as multicellular spheroids, with NR6, a potent and highly selective ALDH1A3 inhibitor. Here we report that NR6 treatment caused the accumulation of toxic aldehydes, induced DNA damage, CDKN2A expression and cell growth arrest. We observed that, in CDKN2A proficient cells, NR6 treatment induced IL6 expression, but abolished CXCL8 expression and IL-8 release, preventing both neutrophil recruitment and generation of neutrophil extracellular traps (NETs). Furthermore, we demonstrate that in response to ALDH1A3 inhibition, CDKN2A loss skewed cell fate from senescence to apoptosis. Dissecting the role of ALDH1A3 isoform in MPM cells and tumour microenvironment can open new fronts in the treatment of this cancer.

Targeting the Molecular and Immunologic Features of Leiomyosarcoma

Leiomyosarcoma (LMS) is a rare, aggressive mesenchymal tumor with smooth muscle differentiation. LMS is one of the most common histologic subtypes of soft tissue sarcoma; it most frequently occurs in the extremities, retroperitoneum, or uterus. LMS often demonstrates aggressive tumor biology, with a higher risk of developing distant metastatic disease than most sarcoma histologic types. The prognosis is poor, particularly in patients with uterine disease, and there is a need for the development of more effective therapies. Genetically, LMS is karyotypically complex and characterized by a low tumor mutational burden, with frequent alterations in TP53, RB1, PTEN, and DNA damage response pathways that may contribute to resistance against immune-checkpoint blockade monotherapy. The LMS immune microenvironment is highly infiltrated with tumor-associated macrophages and tumor-infiltrating lymphocytes, which may represent promising biomarkers. This review provides an overview of the clinical and pathologic behavior of both soft tissue and uterine LMS and summarizes the genomic and immune characteristics of these tumors and how they may provide opportunities for the development of biomarker-based immune therapies.

Immune Checkpoint Therapy Combinations in Adult Advanced MiT Family Translocation Renal Cell Carcinomas

BACKGROUND

There remains a paucity of data regarding the efficacy of immune checkpoint therapy (ICT) combinations ± vascular endothelial growth factor (VEGF) targeted therapy (TT) in translocation renal cell carcinoma (tRCC).

METHODS

This is a retrospective study of patients with advanced tRCC treated with ICT combinations at 11 centers in the US, France, and Belgium. Only cases with confirmed fluorescence in situ hybridization (FISH) were included. Objective response rates (ORR) and progression-free survival (PFS) were assessed by RECIST, and overall survival (OS) was estimated by Kaplan-Meier methods.

RESULTS

There were 29 patients identified with median age of 38 (21-70) years, and F:M ratio 0.9:1. FISH revealed TFE3 and TFEB translocations in 22 and 7 patients, respectively. Dual ICT and ICT + VEGF TT were used in 18 and 11 patients, respectively. Seventeen (59%) patients received ICT combinations as first-line therapy. ORR was 1/18 (5.5%) for dual ICT and 4/11 (36%) for ICT + VEGF TT. At a median follow-up of 12.9 months, median PFS was 2.8 and 5.4 months in the dual ICT and ICT + VEGF TT groups, respectively. Median OS from metastatic disease was 17.8 and 30.7 months in the dual ICT and ICT + VEGF TT groups, respectively.

CONCLUSION

In this retrospective study of advanced tRCC, limited response and survival were seen after frontline dual ICT combination therapy, while ICT + VEGF TT therapy offered some efficacy. Due to the heterogeneity of tRCC, insights into the biological underpinnings are necessary to develop more effective therapies.

Applications and mechanisms of the cyclin-dependent kinase 4/6 inhibitor, PD-0332991, in solid tumors

Abnormal CDK4/6-Rb-E2F signal transduction is a common finding in tumors and is a driving factor for the excessive proliferation of various tumor cells. PD-0332991, a highly specific, small molecule inhibitor for CDK4 and 6, has been shown to inhibit tumor growth by abrogating the phosphorylating capacity of CDK4/6 and suppressing Rb phosphorylation. It has been promoted for the treatment of breast cancer and potentially for other tumor types such as liver cancers, lung cancers and sarcomas. Due to the risk of monotherapy resistance, PD-0332991 is commonly used in combination with other drugs. Such combination treatments have proved able to inhibit tumor proliferation more effectively, induce stronger senescence and apoptosis, and enhance the efficiency of immunotherapy. Therefore, tumor cells with senescence induced by PD-0332991 are now used as ideal screening tools of cytolytic drugs with more efficient and thorough anti-tumor properties. With more extensive understandings about the branching points between senescence and apoptosis, it is possible to refine the dosage of PD-0332991. Better characterization of resistant cells, of inhibitors and of adverse effects such as leukopenia are needed to overcome obstacles in the use of PD-0332991. In this review of PD-0332991 research, we hope to provide guidance of transitions from laboratory findings to clinical applications of PD-0332991 and to facilitate PD-0332991-based multi-inhibitor combination therapies for various tumors.

Isolated BAP1 Genomic Alteration in Malignant Pleural Mesothelioma Predicts Distinct Immunogenicity with Implications for Immunotherapeutic Response

Malignant pleural mesothelioma (MPM), an aggressive cancer of the mesothelial cells lining the pleural cavity, lacks effective treatments. Multiple somatic mutations and copy number losses in tumor suppressor genes (TSGs) BAP1, CDKN2A/B, and NF2 are frequently associated with MPM. The impact of single versus multiple genomic alterations of TSG on MPM biology, the immune tumor microenvironment, clinical outcomes, and treatment responses are unknown. Tumors with genomic alterations in BAP1 alone were associated with a longer overall patient survival rate compared to tumors with CDKN2A/B and/or NF2 alterations with or without BAP1 and formed a distinct immunogenic subtype with altered transcription factor and pathway activity patterns. CDKN2A/B genomic alterations consistently contributed to an adverse clinical outcome. Since the genomic alterations of only BAP1 was associated with the PD-1 therapy response signature and higher LAG3 and VISTA gene expression, it might be a candidate marker for immune checkpoint blockade therapy. Our results on the impact of TSG genotypes on MPM and the correlations between TSG alterations and molecular pathways provide a foundation for developing individualized MPM therapies.

The Rocky Road from Preclinical Findings to Successful Targeted Therapy in Pleural Mesothelioma

Pleural mesothelioma (PM) is a rare and aggressive disease that arises from the mesothelial cells lining the pleural cavity. Approximately 80% of PM patients have a history of asbestos exposure. The long latency period of 20-40 years from the time of asbestos exposure to diagnosis, suggests that multiple somatic genetic alterations are required for the tumorigenesis of PM. The genomic landscape of PM has been characterized by inter- and intratumor heterogeneity associated with the impairment of tumor suppressor genes such as CDKN2A, NF2, and BAP1. Current systemic therapies have shown only limited efficacy, and none is approved for patients with relapsed PM. Advances in understanding of the molecular landscape of PM has facilitated several biomarker-driven clinical trials but so far, no predictive biomarkers for targeted therapies are in clinical use. Recent advances in the PM genetics have provided optimism for successful molecular strategies in the future. Here, we summarize the molecular mechanism underlying PM pathogenesis and review potential therapeutic targets.

A Glimpse in the Future of Malignant Mesothelioma Treatment

Malignant mesothelioma (MMe) is a rare neoplasm with few therapeutic options available. The landscape of effective therapy for this disease remained unchanged in the last two decades. Recently, however, the introduction of Immune Checkpoint Inhibitors (ICIs) led to small, but nevertheless, promising improvements. However, many efforts are still needed to radically improve the prognosis of MMe. In this review, we analyze all those therapeutic strategies for MMe that are still in a preclinical or early clinical phase of development. In particular, we focus on novel antiangiogenic drugs and their possible combination with immunotherapy. Furthermore, we describe also more complex strategies such as microRNA-loaded vectors, oncolytic viruses, and engineered lymphocytes.