Recurrent RhoGAP gene fusion CLDN18-ARHGAP26 promotes RHOA activation and focal adhesion kinase and YAP-TEAD signalling in diffuse gastric cancer.

OBJECTIVE: Genomic studies of gastric cancer have identified highly recurrent genomic alterations impacting RHO signalling, especially in the diffuse gastric cancer (DGC) histological subtype. Among these alterations are interchromosomal translations leading to the fusion of the adhesion protein CLDN18 and RHO regulator ARHGAP26. It remains unclear how these fusion constructs impact the activity of the RHO pathway and what is their broader impact on gastric cancer development. Herein, we developed a model to allow us to study the function of this fusion protein in the pathogenesis of DGC and to identify potential therapeutic targets for DGC tumours with these alterations. DESIGN: We built a transgenic mouse model with LSL-CLDN18-ARHGAP26 fusion engineered into the Col1A1 locus where its expression can be induced by Cre recombinase. Using organoids generated from this model, we evaluated its oncogenic activity and the biochemical effects of the fusion protein on the RHOA pathway and its downstream cell biological effects in the pathogenesis of DGC. RESULTS: We demonstrated that induction of CLDN18-ARHGAP26 expression in gastric organoids induced the formation of signet ring cells, characteristic features of DGC and was able to cooperatively transform gastric cells when combined with the loss of the tumour suppressor geneTrp53. CLDN18-ARHGAP26 promotes the activation of RHOA and downstream effector signalling. Molecularly, the fusion promotes activation of the focal adhesion kinase (FAK) and induction of the YAP pathway. A combination of FAK and YAP/TEAD inhibition can significantly block tumour growth. CONCLUSION: These results indicate that the CLDN18-ARHGAP26 fusion is a gain-of-function DGC oncogene that leads to activation of RHOA and activation of FAK and YAP signalling. These results argue for further evaluation of emerging FAK and YAP-TEAD inhibitors for these deadly cancers.

An Enhancer-Driven Stem Cell-Like Program Mediated by SOX9 Blocks Intestinal Differentiation in Colorectal Cancer.

BACKGROUND AND AIMS: Genomic alterations that encourage stem cell activity and hinder proper maturation are central to the development of colorectal cancer (CRC). Key molecular mediators that promote these malignant properties require further elucidation to galvanize translational advances. We therefore aimed to characterize a key factor that blocks intestinal differentiation, define its transcriptional and epigenetic program, and provide preclinical evidence for therapeutic targeting in CRC. METHODS: Intestinal tissue from transgenic mice and patients were analyzed by means of histopathology and immunostaining. Human CRC cells and neoplastic murine organoids were genetically manipulated for functional studies. Gene expression profiling was obtained through RNA sequencing. Histone modifications and transcription factor binding were determined with the use of chromatin immunoprecipitation sequencing. RESULTS: We demonstrate that SRY-box transcription factor 9 (SOX9) promotes CRC by activating a stem cell-like program that hinders intestinal differentiation. Intestinal adenomas and colorectal adenocarcinomas from mouse models and patients demonstrate ectopic and elevated expression of SOX9. Functional experiments indicate a requirement for SOX9 in human CRC cell lines and engineered neoplastic organoids. Disrupting SOX9 activity impairs primary CRC tumor growth by inducing intestinal differentiation. By binding to genome wide enhancers, SOX9 directly activates genes associated with Paneth and stem cell activity, including prominin 1 (PROM1). SOX9 up-regulates PROM1 via a Wnt-responsive intronic enhancer. A pentaspan transmembrane protein, PROM1 uses its first intracellular domain to support stem cell signaling, at least in part through SOX9, reinforcing a PROM1-SOX9 positive feedback loop. CONCLUSIONS: These studies establish SOX9 as a central regulator of an enhancer-driven stem cell-like program and carry important implications for developing therapeutics directed at overcoming differentiation defects in CRC.

GGA2 and RAB13 promote activity-dependent ß1-integrin recycling.

ß1-integrins mediate cell-matrix interactions and their trafficking is important in the dynamic regulation of cell adhesion, migration and malignant processes, including cancer cell invasion. Here, we employ an RNAi screen to characterize regulators of integrin traffic and identify the association of Golgi-localized gamma ear-containing Arf-binding protein 2 (GGA2) with ß1-integrin, and its role in recycling of active but not inactive ß1-integrin receptors. Silencing of GGA2 limits active ß1-integrin levels in focal adhesions and decreases cancer cell migration and invasion, which is in agreement with its ability to regulate the dynamics of active integrins. By using the proximity-dependent biotin identification (BioID) method, we identified two RAB family small GTPases, i.e. RAB13 and RAB10, as novel interactors of GGA2. Functionally, RAB13 silencing triggers the intracellular accumulation of active ß1-integrin, and reduces integrin activity in focal adhesions and cell migration similarly to GGA2 depletion, indicating that both facilitate active ß1-integrin recycling to the plasma membrane. Thus, GGA2 and RAB13 are important specificity determinants for integrin activity-dependent traffic.

Loss of ADAM9 expression impairs ß1 integrin endocytosis, focal adhesion formation and cancer cell migration.

The transmembrane protease ADAM9 is frequently upregulated in human cancers, and it promotes tumour progression in mice. In vitro, ADAM9 regulates cancer cell adhesion and migration by interacting with integrins. However, how ADAM9 modulates integrin functions is not known. We here show that ADAM9 knockdown increases ß1 integrin levels through mechanisms that are independent of its protease activity. In ADAM9-silenced cells, adhesion to collagen and fibronectin is reduced, suggesting an altered function of the accumulated integrins. Mechanistically, ADAM9 co-immunoprecipitates with ß1 integrin, and both internalization and subsequent degradation of ß1 integrin are significantly decreased in ADAM9-silenced cells, with no effect on ß1 integrin recycling. Accordingly, the formation of focal adhesions and actin stress fibres in ADAM9-silenced cells is altered, possibly explaining the reduction in cell adhesion and migration in these cells. Taken together, our data provide mechanistic insight into the ADAM9-integrin interaction, demonstrating that ADAM9 regulates ß1 integrin endocytosis. Moreover, our findings indicate that the reduced migration of ADAM9-silenced cells is, at least in part, caused by the accumulation and altered activity of ß1 integrin at the cell surface.

Regulation of Cell Migration and ß1 Integrin Trafficking by the Endosomal Adaptor GGA3.

The integrin family of cell adhesion receptors link extracellular matrices to intracellular signaling pathways and the actin cytoskeleton; and regulate cell migration, proliferation and survival in normal and diseased tissues. The subcellular location of integrin receptors is critical for their function and deregulated trafficking is implicated in various human diseases. Here we identify a role for Golgi-localized gamma-ear containing Arf-binding protein 3 (GGA3), in regulating trafficking of ß1 integrin. GGA3 knockdown reduces cell surface and total levels of α2, α5 and ß1 integrin subunits, inhibits cell spreading, reduces focal adhesion number, as well as cell migration. In the absence of GGA3, integrins are increasingly retained inside the cell, traffic toward the perinuclear lysosomal compartment and their degradation is enhanced. Integrin traffic and maintenance of integrin levels are dependent on the integrity of the Arf binding site of GGA3. Furthermore, sorting nexin 17 (SNX17), a critical regulator of integrin recycling, becomes mislocalized to enlarged late endosomes upon GGA3 depletion. These data support a model whereby GGA3, through its ability to regulate SNX17 endosomal localization and through interaction with Arf6 diverts integrins from the degradative pathway supporting cell migration.

Integrin traffic - the update.

Integrins are a family of transmembrane cell surface molecules that constitute the principal adhesion receptors for the extracellular matrix (ECM) and are indispensable for the existence of multicellular organisms. In vertebrates, 24 different integrin heterodimers exist with differing substrate specificity and tissue expression. Integrin-extracellular-ligand interaction provides a physical anchor for the cell and triggers a vast array of intracellular signalling events that determine cell fate. Dynamic remodelling of adhesions, through rapid endocytic and exocytic trafficking of integrin receptors, is an important mechanism employed by cells to regulate integrin-ECM interactions, and thus cellular signalling, during processes such as cell migration, invasion and cytokinesis. The initial concept of integrin traffic as a means to translocate adhesion receptors within the cell has now been expanded with the growing appreciation that traffic is intimately linked to the cell signalling apparatus. Furthermore, endosomal pathways are emerging as crucial regulators of integrin stability and expression in cells. Thus, integrin traffic is relevant in a number of pathological conditions, especially in cancer. Nearly a decade ago we wrote a Commentary in Journal of Cell Science entitled 'Integrin traffic'. With the advances in the field, we felt it would be appropriate to provide the growing number of researchers interested in integrin traffic with an update.

Mutational signature-based identification of DNA repair deficient gastroesophageal adenocarcinomas for therapeutic targeting.

Homologous recombination (HR) and nucleotide excision repair (NER) are the two most frequently disabled DNA repair pathways in cancer. HR-deficient breast, ovarian, pancreatic and prostate cancers respond well to platinum chemotherapy and PARP inhibitors. However, the frequency of HR deficiency in gastric and esophageal adenocarcinoma (GEA) still lacks diagnostic and functional validation. Using whole exome and genome sequencing data, we found that a significant subset of GEA, but very few colorectal adenocarcinomas, show evidence of HR deficiency by mutational signature analysis (HRD score). High HRD gastric cancer cell lines demonstrated functional HR deficiency by RAD51 foci assay and increased sensitivity to platinum chemotherapy and PARP inhibitors. Of clinical relevance, analysis of three different GEA patient cohorts demonstrated that platinum treated HR deficient cancers had better outcomes. A gastric cancer cell line with strong sensitivity to cisplatin showed HR proficiency but exhibited NER deficiency by two photoproduct repair assays. Single-cell RNA-sequencing revealed that, in addition to inducing apoptosis, cisplatin treatment triggered ferroptosis in a NER-deficient gastric cancer, validated by intracellular GSH assay. Overall, our study provides preclinical evidence that a subset of GEAs harbor genomic features of HR and NER deficiency and may therefore benefit from platinum chemotherapy and PARP inhibitors.

Increased frequency of CHD1 deletions in prostate cancers of African American men is associated with rapid disease progression without inducing homologous recombination deficiency.

We analyzed genomic data derived from the prostate cancer of African and European American men in order to identify differences that may contribute to racial disparity of outcome and that could also define novel therapeutic strategies. In addition to analyzing patient derived next generation sequencing data, we performed FISH based confirmatory studies of Chromodomain helicase DNA-binding protein 1 (CHD1) loss on prostate cancer tissue microarrays. We created CRISPR edited, CHD1 deficient prostate cancer cell lines for genomic, drug sensitivity and functional homologous recombination (HR) activity analysis. We found that subclonal deletion of CHD1 is nearly three times as frequent in prostate tumors of African American men than in men of European ancestry and it associates with rapid disease progression. We further showed that CHD1 deletion is not associated with homologous recombination deficiency associated mutational signatures in prostate cancer. In prostate cancer cell line models CHD1 deletion did not induce HR deficiency as detected by RAD51 foci formation assay or mutational signatures, which was consistent with the moderate increase of olaparib sensitivity. CHD1 deficient prostate cancer cells, however, showed higher sensitivity to talazoparib. CHD1 loss may contribute to worse outcome of prostate cancer in African American men. A deeper understanding of the interaction between CHD1 loss and PARP inhibitor sensitivity will be needed to determine the optimal use of targeted agents such as talazoparib in the context of castration resistant prostate cancer.

Epigenomic signatures of sarcomatoid differentiation to guide the treatment of renal cell carcinoma.

Renal cell carcinoma with sarcomatoid differentiation (sRCC) is associated with poor survival and a heightened response to immune checkpoint inhibitors (ICIs). Two major barriers to improving outcomes for sRCC are the limited understanding of its gene regulatory programs and the low diagnostic yield of tumor biopsies due to spatial heterogeneity. Herein, we characterized the epigenomic landscape of sRCC by profiling 107 epigenomic libraries from tissue and plasma samples from 50 patients with RCC and healthy volunteers. By profiling histone modifications and DNA methylation, we identified highly recurrent epigenomic reprogramming enriched in sRCC. Furthermore, CRISPRa experiments implicated the transcription factor FOSL1 in activating sRCC-associated gene regulatory programs, and FOSL1 expression was associated with the response to ICIs in RCC in two randomized clinical trials. Finally, we established a blood-based diagnostic approach using detectable sRCC epigenomic signatures in patient plasma, providing a framework for discovering epigenomic correlates of tumor histology via liquid biopsy.

RAS/RAF Comutation and ERBB2 Copy Number Modulates HER2 Heterogeneity and Responsiveness to HER2-directed Therapy in Colorectal Cancer.

PURPOSE: ERBB2-amplified colorectal cancer is a distinct molecular subtype with expanding treatments. Implications of concurrent oncogenic RAS/RAF alterations are not known. EXPERIMENTAL DESIGN: Dana-Farber and Foundation Medicine Inc. Colorectal cancer cohorts with genomic profiling were used to identify ERBB2-amplified cases [Dana-Farber, n = 47/2,729 (1.7%); FMI, n = 1857/49,839 (3.7%)]. Outcomes of patients receiving HER2-directed therapies are reported (Dana-Farber, n = 9; Flatiron Health-Foundation Medicine clinicogenomic database, FH-FMI CGDB, n = 38). Multisite HER2 IHC and genomic profiling were performed to understand HER2 intratumoral and interlesional heterogeneity. The impact of concurrent RAS comutations on the effectiveness of HER2-directed therapies were studied in isogenic colorectal cancer cell lines and xenografts. RESULTS: ERBB2 amplifications are enriched in left-sided colorectal cancer. Twenty percent of ERBB2-amplified colorectal cancers have co-occurring oncogenic RAS/RAF alterations. While RAS/RAF WT colorectal cancers typically have clonal ERBB2 amplification, colorectal cancers with co-occurring RAS/RAF alterations have lower level ERRB2 amplification, higher intratumoral heterogeneity, and interlesional ERBB2 discordance. These distinct genomic patterns lead to differential responsiveness and patterns of resistance to HER2-directed therapy. ERBB2-amplified colorectal cancer with RAS/RAF alterations are resistant to trastuzumab-based combinations, such as trastuzumab/tucatinib, but retain sensitivity to trastuzumab deruxtecan in in vitro and murine models. Trastuzumab deruxtecan shows clinical efficacy in cases with high-level ERBB2-amplified RAS/RAF coaltered colorectal cancer. CONCLUSIONS: Co-occurring RAS/RAF alterations define a unique subtype of ERBB2-amplified colorectal cancer that has increased intratumoral heterogeneity, interlesional discordance, and resistance to trastuzumab-based combinations. Further examination of trastuzumab deruxtecan in this previously understudied cohort of ERBB2-amplified colorectal cancer is warranted.

Development of Combination Strategies for Focal Adhesion Kinase Inhibition in Diffuse Gastric Cancer.

PURPOSE: Diffuse gastric cancer (DGC) is an aggressive and frequently lethal subtype of gastric cancer. Because DGC often lacks genomic aberrations that indicate clear candidate therapeutic targets, it has been challenging to develop targeted therapies for this gastric cancer subtype. Our previous study highlighted the contribution of focal adhesion kinase (FAK) in the tumorigenesis of DGC and the potential efficacy of small-molecule FAK inhibitors. However, drug resistance to monotherapy often hinders the efficacy of treatment. EXPERIMENTAL DESIGN: We generated a genome-scale library of open reading frames (ORF) in the DGC model of Cdh1-/-RHOAY42C/+ organoids to identify candidate mechanisms of resistance to FAK inhibition. Compensatory activated pathways were also detected following treatment with FAK inhibitors. Candidates were investigated by cotargeting in vitro and in vivo experiments using DGC. RESULTS: We found that cyclin-dependent kinase 6 (CDK6) promoted FAK inhibitor resistance in ORF screen. In addition, FAK inhibitor treatment in DGC models led to compensatory MAPK pathway activation. Small-molecule CDK4/6 inhibitors or MAPK inhibitors effectively enhanced FAK inhibitor efficacy in vitro and in vivo. CONCLUSIONS: Our data suggest that FAK inhibitors combined with MAPK inhibitors or CDK4/6 inhibitors warrant further testing in clinical trials for DGC.

Replicative stress in gastroesophageal adenocarcinoma is associated with chromosomal instability and sensitivity to DNA damage response inhibitors.

Gastroesophageal adenocarcinoma (GEA) is an aggressive, often lethal, malignancy that displays marked chromosomal instability (CIN). To understand adaptive responses that enable CIN, we analyzed paired normal, premalignant, and malignant gastric lesions from human specimens and a carcinogen-induced mouse model, observing activation of replication stress, DNA damage response (DDR), and cell cycle regulator p21 in neoplastic progression. In GEA cell lines, expression of DDR markers correlated with ploidy abnormalities, including high-level focal amplifications and whole-genome duplication (WGD). Moreover, high expression of DNA damage marker H2AX correlated with CIN, WGD, and inferior patient survival. By developing and implementing a composite diagnostic score that incorporates TP53 mutation status, ploidy abnormalities, and H2AX expression, among other genomic information, we can identify GEA cell lines with enhanced sensitivity to DDR pathway inhibitors targeting Chk1/2 and Wee1. Anti-tumor properties were further augmented in combination with irinotecan (SN38) but not gemcitabine chemotherapy. These results implicate specific DDR biomarkers and ploidy abnormalities as diagnostic proxy that may predict premalignant progression and response to DDR pathway inhibitors.

Replicative stress in gastroesophageal cancer is associated with chromosomal instability and sensitivity to DNA damage response inhibitors.

Gastroesophageal adenocarcinoma (GEA) is an aggressive malignancy with chromosomal instability (CIN). To understand adaptive responses enabling DNA damage response (DDR) and CIN, we analyzed matched normal, premalignant, and malignant gastric lesions from human specimens and a carcinogen-induced mouse model, observing activation of replication stress, DDR, and p21 in neoplastic progression. In GEA cell lines, expression of DDR markers correlated with ploidy abnormalities, such as number of high-level focal amplifications and whole-genome duplication (WGD). Integrating TP53 status, ploidy abnormalities, and DDR markers into a compositive score helped predict GEA cell lines with enhanced sensitivity to Chk1/2 and Wee1 inhibition, either alone or combined with irinotecan (SN38). We demonstrate that Chk1/2 or Wee1 inhibition combined with SN38/irinotecan shows greater anti-tumor activity in human gastric cancer organoids and an in vivo xenograft mouse model. These findings indicate that specific DDR biomarkers and ploidy abnormalities may predict premalignant progression and response to DDR pathway inhibitors.

Nucleotide excision repair deficiency is a targetable therapeutic vulnerability in clear cell renal cell carcinoma.

Purpose: Due to a demonstrated lack of DNA repair deficiencies, clear cell renal cell carcinoma (ccRCC) has not benefitted from targeted synthetic lethality-based therapies. We investigated whether nucleotide excision repair (NER) deficiency is present in an identifiable subset of ccRCC cases that would render those tumors sensitive to therapy targeting this specific DNA repair pathway aberration. Experimental Design: We used functional assays that detect UV-induced 6-4 pyrimidine-pyrimidone photoproducts to quantify NER deficiency in ccRCC cell lines. We also measured sensitivity to irofulven, an experimental cancer therapeutic agent that specifically targets cells with inactivated transcription-coupled nucleotide excision repair (TC-NER). In order to detect NER deficiency in clinical biopsies, we assessed whole exome sequencing data for the presence of an NER deficiency associated mutational signature previously identified in ERCC2 mutant bladder cancer. Results: Functional assays showed NER deficiency in ccRCC cells. Irofulven sensitivity increased in some cell lines. Prostaglandin reductase 1 (PTGR1), which activates irofulven, was also associated with this sensitivity. Next generation sequencing data of the cell lines showed NER deficiency-associated mutational signatures. A significant subset of ccRCC patients had the same signature and high PTGR1 expression. Conclusions: ccRCC cell line based analysis showed that NER deficiency is likely present in this cancer type. Approximately 10% of ccRCC patients in the TCGA cohort showed mutational signatures consistent with ERCC2 inactivation associated NER deficiency and also substantial levels of PTGR1 expression. These patients may be responsive to irofulven, a previously abandoned anticancer agent that has minimal activity in NER-proficient cells.

Nucleotide excision repair deficiency is a targetable therapeutic vulnerability in clear cell renal cell carcinoma.

Due to a demonstrated lack of DNA repair deficiencies, clear cell renal cell carcinoma (ccRCC) has not benefitted from targeted synthetic lethality-based therapies. We investigated whether nucleotide excision repair (NER) deficiency is present in an identifiable subset of ccRCC cases that would render those tumors sensitive to therapy targeting this specific DNA repair pathway aberration. We used functional assays that detect UV-induced 6-4 pyrimidine-pyrimidone photoproducts to quantify NER deficiency in ccRCC cell lines. We also measured sensitivity to irofulven, an experimental cancer therapeutic agent that specifically targets cells with inactivated transcription-coupled nucleotide excision repair (TC-NER). In order to detect NER deficiency in clinical biopsies, we assessed whole exome sequencing data for the presence of an NER deficiency associated mutational signature previously identified in ERCC2 mutant bladder cancer. Functional assays showed NER deficiency in ccRCC cells. Some cell lines showed irofulven sensitivity at a concentration that is well tolerated by patients. Prostaglandin reductase 1 (PTGR1), which activates irofulven, was also associated with this sensitivity. Next generation sequencing data of the cell lines showed NER deficiency-associated mutational signatures. A significant subset of ccRCC patients had the same signature and high PTGR1 expression. ccRCC cell line-based analysis showed that NER deficiency is likely present in this cancer type. Approximately 10% of ccRCC patients in the TCGA cohort showed mutational signatures consistent with ERCC2 inactivation associated NER deficiency and also substantial levels of PTGR1 expression. These patients may be responsive to irofulven, a previously abandoned anticancer agent that has minimal activity in NER-proficient cells.

Early TP53 Alterations Shape Gastric and Esophageal Cancer Development.

Gastric and esophageal (GE) adenocarcinomas are the third and sixth most common causes of cancer-related mortality worldwide, accounting for greater than 1.25 million annual deaths. Despite the advancements in the multi-disciplinary treatment approaches, the prognosis for patients with GE adenocarcinomas remains poor, with a 5-year survival of 32% and 19%, respectively, mainly due to the late-stage diagnosis and aggressive nature of these cancers. Premalignant lesions characterized by atypical glandular proliferation, with neoplastic cells confined to the basement membrane, often precede malignant disease. We now appreciate that premalignant lesions also carry cancer-associated mutations, enabling disease progression in the right environmental context. A better understanding of the premalignant-to-malignant transition can help us diagnose, prevent, and treat GE adenocarcinoma. Here, we discuss the evidence suggesting that alterations in TP53 occur early in GE adenocarcinoma evolution, are selected for under environmental stressors, are responsible for shaping the genomic mechanisms for pathway dysregulation in cancer progression, and lead to potential vulnerabilities that can be exploited by a specific class of targeted therapy.

SORLA regulates endosomal trafficking and oncogenic fitness of HER2.

The human epidermal growth factor receptor 2 (HER2) is an oncogene targeted by several kinase inhibitors and therapeutic antibodies. While the endosomal trafficking of many other receptor tyrosine kinases is known to regulate their oncogenic signalling, the prevailing view on HER2 is that this receptor is predominantly retained on the cell surface. Here, we find that sortilin-related receptor 1 (SORLA; SORL1) co-precipitates with HER2 in cancer cells and regulates HER2 subcellular distribution by promoting recycling of the endosomal receptor back to the plasma membrane. SORLA protein levels in cancer cell lines and bladder cancers correlates with HER2 levels. Depletion of SORLA triggers HER2 targeting to late endosomal/lysosomal compartments and impairs HER2-driven signalling and in vivo tumour growth. SORLA silencing also disrupts normal lysosome function and sensitizes anti-HER2 therapy sensitive and resistant cancer cells to lysosome-targeting cationic amphiphilic drugs. These findings reveal potentially important SORLA-dependent endosomal trafficking-linked vulnerabilities in HER2-driven cancers.

AMPK negatively regulates tensin-dependent integrin activity.

Tight regulation of integrin activity is paramount for dynamic cellular functions such as cell matrix adhesion and mechanotransduction. Integrin activation is achieved through intracellular interactions at the integrin cytoplasmic tails and through integrin-ligand binding. In this study, we identify the metabolic sensor AMP-activated protein kinase (AMPK) as a ß1-integrin inhibitor in fibroblasts. Loss of AMPK promotes ß1-integrin activity, the formation of centrally located active ß1-integrin- and tensin-rich mature fibrillar adhesions, and cell spreading. Moreover, in the absence of AMPK, cells generate more mechanical stress and increase fibronectin fibrillogenesis. Mechanistically, we show that AMPK negatively regulates the expression of the integrin-binding proteins tensin1 and tensin3. Transient expression of tensins increases ß1-integrin activity, whereas tensin silencing reduces integrin activity in fibroblasts lacking AMPK. Accordingly, tensin silencing in AMPK-depleted fibroblasts impedes enhanced cell spreading, traction stress, and fibronectin fiber formation. Collectively, we show that the loss of AMPK up-regulates tensins, which bind ß1-integrins, supporting their activity and promoting fibrillar adhesion formation and integrin-dependent processes.

Tensin-4-dependent MET stabilization is essential for survival and proliferation in carcinoma cells.

Inappropriate MET tyrosine kinase receptor signaling is detected in almost all types of human cancer and contributes to malignant growth and MET dependency via proliferative and antiapoptotic activities. Independently, Tensin-4 (TNS4) is emerging as a putative oncogene in many cancer types, but the mechanisms of TNS4 oncogenic activity are not well established. Here, we demonstrate that TNS4 directly interacts with phosphorylated MET via the TNS4 SH2-domain to positively regulate cell survival, proliferation, and migration, through increased MET protein stability. In addition, TNS4 interaction with ß1-integrin cytoplasmic tail positively regulates ß1-integrin stability. Loss of TNS4 or disruption of MET-TNS4 interaction triggers MET trafficking toward the lysosomal compartment that is associated with excessive degradation of MET and triggers MET-addicted carcinoma cell death in vitro and in vivo. Significant correlation between MET and TNS4 expression in human colon carcinoma and ovarian carcinoma suggests TNS4 plays a critical role in MET stability in cancer.