Co-targeting of FAK and MDM2 triggers additive anti-proliferative effects in mesothelioma via a coordinated reactivation of p53

FAK inhibitors in cancer, a patent review - an update on progress

INTRODUCTION

Focal adhesion kinase (FAK) is a cytoplasmic non-receptor tyrosine kinase over-expressed in various malignancies which is related to various cellular functions such as adhesion, metastasis and proliferation.

AREAS COVERED

There is growing evidence that FAK is a promising therapeutic target for designing inhibitors by regulating the downstream pathways of FAK. Some potential FAK inhibitors have entered clinical phase research.

EXPERT OPINION

FAK could be an effective target in medicinal chemistry research and there were a variety of FAKIs have been patented recently. Here, we updated an overview of design, synthesis and structure-activity relationship of chemotherapeutic FAK inhibitors (FAKIs) from 2017 until now based on our previous work. We hope our efforts can broaden the understanding of FAKIs and provide new ideas and insights for future cancer treatment from medicinal chemistry point of view.

Targeting focal adhesion kinase (FAK) for cancer therapy: FAK inhibitors, FAK-based dual-target inhibitors and PROTAC degraders

Focal adhesion kinase (FAK), a non-receptor tyrosine kinase, plays an essential role in regulating cell proliferation, migration and invasion through both kinase-dependent enzymatic function and kinase-independent scaffolding function. The overexpression and activation of FAK is commonly observed in various cancers and some drug-resistant settings. Therefore, targeted disruption of FAK has been identified as an attractive strategy for cancer treatment. To date, numerous structurally diverse inhibitors targeting distinct domains of FAK have been developed, encompassing kinase domain inhibitors, FERM domain inhibitors, and FAT domain inhibitors, with several FAK inhibitors advanced to clinical trials. Moreover, given the critical role of FAK scaffolding function in signal transduction, FAK-targeted PROTACs have also been developed. Although no current FAK-targeted therapeutics have been approved for the market, the combination of FAK inhibitors with other anticancer drugs has shown considerable promise in the clinic. This review provides an overview of current drug discovery strategies targeting FAK, including the development of FAK inhibitors, FAK-based dual-target inhibitors and proteolysis-targeting chimeras (PROTACs) in both literature and patent applications. Accordingly, their design and optimization process, mechanisms of action and biological activities are discussed to offer insights into future directions of FAK-targeting drug discovery in cancer therapy.

SETDB1 tumour suppressor roles in near-haploid mesothelioma involve TP53

BACKGROUND

Mutational inactivation of the SETDB1 histone methyltransferase is found in a subset of mesothelioma, particularly in cases with near-haploidy and TP53 mutations. However, the tumourigenic consequences of SETDB1 inactivation are poorly understood.

METHODS

In this study, we investigated SETDB1 tumour suppressor functions in mesothelioma and explored biologic relationships between SETDB1 and TP53.

RESULTS

Immunoblotting of early passage cultures showed that SETDB1 was undetectable in 7 of 8 near-haploid mesotheliomas whereas SETDB1 expression was retained in each of 13 near-diploid mesotheliomas. TP53 aberrations were present in 5 of 8 near-haploid mesotheliomas compared to 2 of 13 near-diploid mesotheliomas, and BAP1 inactivation was demonstrated only in near-diploid mesotheliomas, indicating that near-haploid and near-diploid mesothelioma have distinct molecular and biologic profiles. Lentiviral SETDB1 restoration in near-haploid mesotheliomas (MESO257 and MESO542) reduced cell viability, colony formation, reactive oxygen species levels, proliferative marker cyclin A expression, and inhibited growth of MESO542 xenografts. The combination of SETDB1 restoration with pemetrexed and/or cisplatin treatment additively inhibited tumour growth in vitro and in vivo. Furthermore, SETDB1 restoration upregulated TP53 expression in MESO542 and MESO257, whereas SETDB1 knockdown inhibited mutant TP53 expression in JMN1B near-haploid mesothelioma cells. Likewise, TP53 knockdown inhibited SETDB1 expression. Similarly, immunoblotting evaluations of ten near-diploid mesothelioma biopsies and analysis of TCGA expression profiles showed that SETDB1 expression levels paralleled TP53 expression.

CONCLUSION

These findings demonstrate that SETDB1 inactivation in near-haploid mesothelioma is generally associated with complete loss of SETDB1 protein expression and dysregulates TP53 expression. Targeting SETDB1 pathways could be an effective therapeutic strategy in these often untreatable tumours.

FAK-mediated phosphorylation at Y464 regulates p85β nuclear translocation to promote tumorigenesis of ccRCC by repressing RB1 expression

PI3K regulatory subunit p85s normally stabilizes and regulates catalytic subunit p110s in the cytoplasm. Recent studies show that p110-free p85s in the nucleus plays important roles in biological processes. However, the mechanisms by which p85s translocate into the nucleus remain elusive. Here, we describe the mechanism by which p85β translocates into the nucleus to promote ccRCC tumorigenesis. Phosphorylation of p85β at the Y464 by FAK facilitates its nuclear translocation in the kidney through enhancing the binding of p85β to KPNA1. PIK3R2/p85β is highly expressed in ccRCC samples and associated with overall survival of ccRCC patients. Nuclear but not cytoplasmic p85β performs oncogenic functions by repressing RB1 expression and regulating the G1/S cell cycle transition. Nuclear p85β represses RB1 expression by stabilizing histone methyltransferase EZH1/EZH2 proteins. Last, the FAK inhibitor defactinib significantly suppresses the tumor growth of ccRCC with high p85β Y464 levels.

The Role of E-Cadherin and microRNA on FAK Inhibitor Response in Malignant Pleural Mesothelioma (MPM)

Malignant pleural mesothelioma (MPM) is an aggressive malignancy with limited effective treatment options. Focal adhesion kinase (FAK) inhibitors have been shown to efficiently suppress MPM cell growth initially, with limited utility in the current clinical setting. In this study, we utilised a large collection of MPM cell lines and MPM tissue samples to study the role of E-cadherin (CDH1) and microRNA on the efficacy of FAK inhibitors in MPM. The immunohistochemistry (IHC) results showed that the majority of MPM FFPE samples exhibited either the absence of, or very low, E-cadherin protein expression in MPM tissue. We showed that MPM cells with high CDH1 mRNA levels exhibited resistance to the FAK inhibitor PND-1186. In summary, MPM cells that did not express CDH1 mRNA were sensitive to PND-1186, and MPM cells that retained CDH1 mRNA were resistant. A cell cycle analysis showed that PND-1186 induced cell cycle disruption by inducing the G2/M arrest of MPM cells. A protein−protein interaction study showed that EGFR is linked to the FAK pathway, and a target scan of the microRNAs revealed that microRNAs (miR-17, miR221, miR-222, miR137, and miR148) interact with EGFR 3′UTR. Transfection of MPM cells with these microRNAs sensitised the CHD1-expressing FAK-inhibitor-resistant MPM cells to the FAK inhibitor.

Biomarker-guided targeted and immunotherapies in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a lethal thoracic malignancy whose incidence is still increasing worldwide. MPM is characterized by frequent inactivation of tumor-suppressor genes (TSGs), e.g., the homozygous deletion of CDKN2A/2B and various genetic alterations that inactivate BAP1, NF2, LATS1/2, and TP53. The leading cause for the poor prognosis of patients with MPM is the lack of effective treatment options, with conventional chemotherapy being the standard of care in the clinic, which has remained unchanged for almost 20 years. Precision oncology, a burgeoning effort to provide precise cancer treatment tailored to unique molecular changes in individual patients, has made tremendous progress in the last decade in several cancers, but not in MPM. Recent studies indicate a high degree of tumor heterogeneity in MPM and the importance to optimize histological and molecular classifications for improved treatment. In this review, we provide an up-to-date overview of recent advances in MPM by focusing on new stratifications of tumor subgroups, specific vulnerabilities associated with functional loss of TSGs and other biomarkers, and potential clinical implications. The molecularly based subdivisions not only deepen our understanding of MPM pathobiology, but more importantly, they may raise unprecedented new hopes for personalized treatment of MPM patients with biomarker-guided targeted and immunotherapies.

Progress in the Development of Small Molecular Inhibitors of Focal Adhesion Kinase (FAK)

Focal adhesion kinase (FAK) is a nonreceptor intracellular tyrosine kinase that plays an essential role in cancer cell adhesion, survival, proliferation, and migration through both its enzymatic activities and scaffolding functions. Overexpression of FAK has been found in many human cancer cells from different origins, which promotes tumor progression and influences clinical outcomes in different classes of human tumors. Therefore, FAK has been considered as a promising target for small molecule anticancer drug development. Many FAK inhibitors targeting different domains of FAK with various mechanisms of functions have been reported, including kinase domain inhibitors, FERM domain inhibitors, and FAT domain inhibitors. In addition, FAK-targeting PROTACs, which can induce the degradation of FAK, have also been developed. In this Perspective, we summarized the progress in the development of small molecular FAK inhibitors and proposed the perspectives for the future development of agents targeting FAK.

RNA editing in mesothelioma: a look forward

RNA editing is a post-transcriptional process increasing transcript diversity, thereby regulating different biological processes. We recently observed that mutations resulting from RNA editing due to hydrolytic deamination of adenosine increase during the development of mesothelioma, a rare cancer linked to chronic exposure to asbestos. This review gathers information from the published literature and public data mining to explore several aspects of RNA editing and their possible implications for cancer growth and therapy. We address possible links between RNA editing and particular types of mesothelioma genetic and epigenetic alterations and discuss the relevance of an edited substrate in the context of current chemotherapy or immunotherapy.

AXL Inactivation Inhibits Mesothelioma Growth and Migration via Regulation of p53 Expression

Malignant mesothelioma is a locally aggressive and highly lethal neoplasm. Dysregulation and activation of Gas6/AXL tyrosine kinase signaling are associated with mesothelioma progression, but the mechanisms of these AXL tumorigenic roles are poorly understood. p53 mutants in lung carcinoma upregulate AXL expression by binding and acetylating the AXL promoter. Although TP53 mutations are uncommon in mesothelioma, we hypothesized that these tumors might have alternative feedback mechanisms between AXL and p53. In the current report, we investigated AXL regulation of TP53 transcription, expression, and biological function in mesothelioma. AXL expression was stronger in mesothelioma than most of the other tumor types from the TCGA gene expression profile dataset. AXL knockdown by shRNA induced wild-type and mutant p53 expression in mesothelioma cell lines, suggesting that AXL pro-tumorigenic roles result in part from the suppression of p53 function. Likewise, induced AXL inhibited expression of wild type p53 in COS-7 cells and 293T cells. Immunofluorescence staining showed nuclear colocalization of AXL and p53; however, association of AXL and p53 was not demonstrated in immunoprecipitation complexes. The AXL effects on p53 expression resulted from the inhibition of TP53 transcription, as demonstrated by qRT-PCR after AXL silencing and TP53 promotor dual luciferase activity assays. Chromatin immunoprecipitation-qPCR and sequencing showed that AXL bound to the initial 600 bp sequence at the 5' end of the TP53 promoter. AXL inhibition (shRNA or R428) reduced mesothelioma cell viability, migration, and invasion, whereas TP53 shRNA knockdown attenuated antiproliferative, migration, and invasive effects of AXL silencing or AXL inactivation in these cells. These studies demonstrate a novel feedback regulation loop between AXL and p53, and provide a rationale for mesothelioma therapies targeting AXL/p53 signaling.

Oncolytic Adenovirus Expressing ST13 Increases Antitumor Effect of Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Against Pancreatic Ductal Adenocarcinoma

Oncolytic adenoviruses (OAds) are promising agents for cancer therapy, representing a novel therapeutic strategy for pancreatic ductal adenocarcinoma (PDAC). However, there are challenges associated with the successful use of an OAd alone, involving the security of the viral vector and screening of an effective antitumor gene. In the present study, a novel OAd CD55-ST13-tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) was constructed in which the dual therapeutic genes ST13 and TRAIL were inserted, featuring the carcinoembryonic antigen (CEA) as a promoter to control E1A and deletion of the 55 kDa E1B gene. ST13, known as a colorectal cancer suppressor gene, exhibited lower expression in PDAC than in tumor-adjacent tissues and was associated with poor prognosis in PDAC patients. In vitro studies demonstrated that CD55-ST13-TRAIL was effective in promoting the expression of ST13 and TRAIL in CEA-positive pancreatic cancer cells. Moreover, CD55-ST13-TRAIL exhibited a synergistic effect toward tumor cell death compared with CD55-ST13 alone or CD55-TRAIL alone, and inhibited tumor cell proliferation and induced cell apoptosis dependent on caspase pathways in PDAC cells. Furthermore, xenograft experiments in a mouse model indicated that CD55-ST13-TRAIL significantly inhibited tumor growth and improved the survival of animals with xenografts. The findings demonstrate that oncolytic virotherapy under the control of the promoter CEA enables safe and efficient treatment of PDAC, and suggest that it represents a promising candidate for the treatment of metastatic diseases.

MDM2 Inhibition in a Subset of Sarcoma Cell Lines Increases Susceptibility to Radiation Therapy by Inducing Senescence in the Polyploid Cells

Purpose

Inhibition of p53 by amplification of MDM2 is one of the key contributors in the oncogenesis of a subset of soft tissue sarcoma (STS) known as well-/dedifferentiated liposarcoma. A small molecule MDM2 antagonist, nutlin-3, induces the p53 pathway by disrupting the interaction between MDM2 and p53. Radiation therapy is an integral component for treating liposarcoma and induces p53. Based on wild-type TP53 status in liposarcoma, it was investigated whether MDM2 inhibition with irradiation led to enhanced reactivation of p53 and subsequent p53-mediated effects in liposarcoma.

Methods and Materials

Clonogenic assays, immunoblotting, flow cytometry/fluorescence-activated cell sorting, and senescence assays were employed in liposarcoma cell lines after co-treatment with nutlin-3 and radiation.

Results

Upon treatment with nutlin-3, 2 of the well-/dedifferentiated liposarcoma (MDM2^Amp/TP53^WT) cell lines displayed radiosensitivity with sensitization enhancement ratio values of >1. In contrast, the cell line with mutant TP53 showed sensitization enhancement ratio values of ∼1. Immunoblotting revealed induced reactivation of the p53-MDM2-p21 signaling axis in response to combination therapy in all cell lines with wild-type TP53. Removal of MDM2 inhibitor (with or without radiation therapy) led to the emergence of ploidy-based heterogeneous subpopulations (4N and >4N) in TP53 wild-type cells and not in TP53 mutant cells. Immunoblotting of cell cycle markers (G1, G2/M) revealed the generation of 4N G1 cells. Sorting and long-term fate analysis of different populations (2N, 4N, and >4N) by colony assay displayed attenuated colony-forming potential and augmented senescence of the 4N and >4N cells contributing to the radiosensitization effect.

Conclusions

Nutlin-3 increases the vulnerability of liposarcoma cell lines to radiation by augmented activation of p53. The cells underwent senescence. Presence and activation of p53 are required for exertion of the radiosensitizing effect by nutlin-3, but this is not the sole determinant of the effect. This study opens avenues for the clinical translation in a stratified group of patients with liposarcoma.

Modulation of Calretinin Expression in Human Mesothelioma Cells Reveals the Implication of the FAK and Wnt Signaling Pathways in Conferring Chemoresistance towards Cisplatin

Malignant mesothelioma (MM) is an aggressive asbestos-linked neoplasm, characterized by dysregulation of signaling pathways. Due to intrinsic or acquired chemoresistance, MM treatment options remain limited. Calretinin is a Ca²⁺-binding protein expressed during MM tumorigenesis that activates the FAK signaling pathway, promoting invasion and epithelial-to-mesenchymal transition. Constitutive calretinin downregulation decreases MM cells’ growth and survival, and impairs tumor formation in vivo. In order to evaluate early molecular events occurring during calretinin downregulation, we generated a tightly controlled IPTG-inducible expression system to modulate calretinin levels in vitro. Calretinin downregulation significantly reduced viability and proliferation of MM cells, attenuated FAK signaling and reduced the invasive phenotype of surviving cells. Importantly, surviving cells showed a higher resistance to cisplatin due to increased Wnt signaling. This resistance was abrogated by the Wnt signaling pathway inhibitor 3289-8625. In various MM cell lines and regardless of calretinin expression levels, blocking of FAK signaling activated the Wnt signaling pathway and vice versa. Thus, blocking both pathways had the strongest impact on MM cell proliferation and survival. Chemoresistance mechanisms in MM cells have resulted in a failure of single-agent therapies. Targeting of multiple components of key signaling pathways, including Wnt signaling, might be the future method-of-choice to treat MM.

The roles of nuclear focal adhesion kinase (FAK) on Cancer: a focused review

FAK is a tyrosine kinase overexpressed in cancer cells and plays an important role in the progression of tumors to a malignant phenotype. Except for its typical role as a cytoplasmic kinase downstream of integrin and growth factor receptor signaling, related studies have shown new aspects of the roles of FAK in the nucleus. FAK can promote p53 degradation through ubiquitination, leading to cancer cell growth and proliferation. FAK can also regulate GATA4 and IL-33 expression, resulting in reduced inflammatory responses and immune escape. These findings establish a new model of FAK from the cytoplasm to the nucleus. Activated FAK binds to transcription factors and regulates gene expression. Inactive FAK synergizes with different E3 ligases to promote the turnover of transcription factors by enhancing ubiquitination. In the tumor microenvironment, nuclear FAK can regulate the formation of new blood vessels, affecting the tumor blood supply. This article reviews the roles of nuclear FAK in regulating gene expression. In addition, the use of FAK inhibitors to target nuclear FAK functions will also be emphasized.

Emerging Medical Treatments for Meningioma in the Molecular Era

Meningiomas are the most common type of primary central nervous system tumors. Approximately, 80% of meningiomas are classified by the World Health Organization (WHO) as grade I, and 20% of these tumors are grade II and III, considered high-grade meningiomas (HGMs). Clinical control of HGMs, as well as meningiomas that relapse after surgery, and radiation therapy is difficult, and novel therapeutic approaches are necessary. However, traditional chemotherapies, interferons, hormonal therapies, and other targeted therapies have so far failed to provide clinical benefit. During the last several years, next generation sequencing has dissected the genetic heterogeneity of meningioma and enriched our knowledge about distinct oncogenic pathways driving different subtypes of meningiomas, opening up a door to new personalized targeted therapies. Molecular classification of meningioma allows a new design of clinical trials that assign patients to corresponding targeted agents based on the tumor genetic subtypes. In this review, we will shed light on emerging medical treatments of meningiomas with a particular focus on the new targets identified with genomic sequencing that have led to clinical trials testing novel compounds. Moreover, we present recent development of patient-derived preclinical models that provide platforms for assessing targeted therapies as well as strategies with novel mechanism of action such as oncolytic viruses.

Angiopoietin-like protein 3 blocks nuclear import of FAK and contributes to sorafenib response

Background

Poor drug response of sorafenib is a major challenge which reduces clinical benefit of renal cell carcinoma (RCC) patients. It is therefore of great clinical significance to elucidate the underlying mechanism to restore the therapeutic response to sorafenib.

Methods

Angiopoietin-like protein 3 (ANGPTL3) protein levels were measured by western blot and immunohistochemistry in two cohorts of RCC patients. Loss-of-function and gain-of-function experiments were performed to investigate the biological roles of ANGPTL3 in response to sorafenib treatment in RCC cells. Human proteome microarray and immunoprecipitation analysis were performed to explore the molecular mechanisms underlying the functions of ANGPTL3.

Results

ANGPTL3 was upregulated in sorafenib-responsive RCC, which correlated with clinically good sorafenib response. Knockdown of ANGPTL3 conferred sorafenib-tolerance traits to RCC cells, whereas overexpression of ANGPTL3 restored sorafenib sensitivity in RCC cells. Mechanistically, ANGPTL3 bound to Focal Adhesion Kinase(FAK) and restained sorafenib induced nuclear translocation of FAK, leading to attenuate the ubiquitination of p53, which contributed to cellular apoptosis and enhanced sorafenib response.

Conclusions

ANGPTL3 may be a novel predictor for the response of sorafenib therapy in RCC patients, and a potential target in improving its therapeutic effect.

Dynamics of p14ARF and Focal Adhesion Kinase-Mediated Autophagy in Cancer

It has been widely shown that the focal adhesion kinase (FAK) is involved in nearly every aspect of cancer, from invasion to metastasis to epithelial–mesenchymal transition and maintenance of cancer stem cells. FAK has been shown to interact with p14ARF (alternative reading frame)—a well-established tumor suppressor—and functions in the negative regulation of cancer through both p53-dependent and -independent pathways. Interestingly, both FAK and ARF (human and mouse counterpart) proteins, as well as p53, are involved in autophagy—a process of “self-digestion”—whose main function is the recycling of cellular components and quality control of proteins and organelles. In the last years, an unexpected role of p14ARF in the survival of cancer cells has been underlined in different cellular contexts, suggesting a novel pro-oncogenic function of this protein. In this review, the mechanisms whereby ARF and FAK control autophagy are presented, as well as the role of autophagy in cell migration and spreading. Integrated investigation of these cell functions is extremely important to understand the mechanism of the basis of cell transformation and migration and thus cancer development.

Good Guy or Bad Guy? The Duality of Wild-Type p53 in Hormone-Dependent Breast Cancer Origin, Treatment, and Recurrence

"Lactation is at one point perilously near becoming a cancerous process if it is at all arrested", Beatson, 1896. Most breast cancers arise from the milk-producing cells that are characterized by aberrant cellular, molecular, and epigenetic translation. By understanding the underlying molecular disruptions leading to the origin of cancer, we might be able to design novel strategies for more efficacious treatments or, ambitiously, divert the cancerous process. It is an established reality that full-term pregnancy in a young woman provides a lifetime reduction in breast cancer risk, whereas delay in full-term pregnancy increases short-term breast cancer risk and the probability of latent breast cancer development. Hormonal activation of the p53 protein (encode by the TP53 gene) in the mammary gland at a critical time in pregnancy has been identified as one of the most important determinants of whether the mammary gland develops latent breast cancer. This review discusses what is known about the protective influence of female hormones in young parous women, with a specific focus on the opportune role of wild-type p53 reprogramming in mammary cell differentiation. The importance of p53 as a protector or perpetrator in hormone-dependent breast cancer, resistance to treatment, and recurrence is also explored.

Heterogeneous Contributing Factors in MPM Disease Development and Progression: Biological Advances and Clinical Implications

Malignant pleural mesothelioma (MPM) tumors are remarkably aggressive and most patients only survive for 5–12 months; irrespective of stage; after primary symptoms appear. Compounding matters is that MPM remains unresponsive to conventional standards of care; including radiation and chemotherapy. Currently; instead of relying on molecular signatures and histological typing; MPM treatment options are guided by clinical stage and patient characteristics because the mechanism of carcinogenesis has not been fully elucidated; although about 80% of cases can be linked to asbestos exposure. Several molecular pathways have been implicated in the MPM tumor microenvironment; such as angiogenesis; apoptosis; cell-cycle regulation and several growth factor-related pathways predicted to be amenable to therapeutic intervention. Furthermore, the availability of genomic data has improved our understanding of the pathobiology of MPM. The MPM genomic landscape is dominated by inactivating mutations in several tumor suppressor genes; such as CDKN2A; BAP1 and NF2. Given the complex heterogeneity of the tumor microenvironment in MPM; a better understanding of the interplay between stromal; endothelial and immune cells at the molecular level is required; to chaperone the development of improved personalized therapeutics. Many recent advances at the molecular level have been reported and several exciting new treatment options are under investigation. Here; we review the challenges and the most up-to-date biological advances in MPM pertaining to the molecular pathways implicated; progress at the genomic level; immunological progression of this fatal disease; and its link with developmental cell pathways; with an emphasis on prognostic and therapeutic treatment strategies.

A link between the fibroblast growth factor axis and the miR-16 family reveals potential new treatment combinations in mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive malignancy with very limited therapeutic options. Fibroblast growth factor (FGF) signals play important roles in mesothelioma cell growth. Several FGFs and FGF receptors (FGFRs) are predicted targets of the miR‐15/16 family, which is downregulated in MPM. The aim of this study was to explore the link between the miR‐15/16 family and the FGF axis in MPM. Expression analyses via RT‐qPCR showed downregulation of the FGF axis after transfection with miR‐15/16 mimics. Direct interaction was confirmed by luciferase reporter assays. Restoration of miR‐15/16 led to dose‐dependent growth inhibition in MPM cell lines, which significantly correlated with their sensitivity to FGFR inhibition. Treatment with recombinant FGF2 prevented growth inhibition and further reduced the levels of FGF/R‐targeting microRNAs, indicating a vicious cycle between miR‐15/16 down‐ and FGF/FGFR signaling upregulation. Combined inhibition of two independent miR‐15/16 targets, the FGF axis and Bcl‐2, resulted in additive or synergistic activity. Our data indicate that post‐transcriptional repression of FGF‐mediated signals contributes to the tumor suppressor function of the microRNA‐15/16 family. Inhibiting hyperactivated FGF signals and Bcl‐2 might serve as a novel therapeutic combination strategy in MPM.