Metastases account for 90% of cancer-related deaths; thus, it is vital to understand the biology of tumour dissemination. Here, we collected and monitored >50 patient specimens ex vivo to investigate the cell biology of colorectal cancer (CRC) metastatic spread to the peritoneum. This reveals an unpredicted mode of dissemination. Large clusters of cancer epithelial cells displaying a robust outward apical pole, which we termed tumour spheres with inverted polarity (TSIPs), were observed throughout the process of dissemination. TSIPs form and propagate through the collective apical budding of hypermethylated CRCs downstream of canonical and non-canonical transforming growth factor-β signalling. TSIPs maintain their apical-out topology and use actomyosin contractility to collectively invade three-dimensional extracellular matrices. TSIPs invade paired patient peritoneum explants, initiate metastases in mice xenograft models and correlate with adverse patient prognosis. Thus, despite their epithelial architecture and inverted topology TSIPs seem to drive the metastatic spread of hypermethylated CRCs.

BackgroundThe WW domain-containing oxidoreductase (WWOX) gene, frequently altered in breast cancer, encodes a tumor suppressor whose function is mediated through its interactions with cancer-related proteins, such as the pro-apoptotic protein p73α.ResultsTo better understand the involvement of WWOX in breast tumorigenesis, we performed a yeast two-hybrid screen and co-immunoprecipitation assays to identify novel partners of this protein. We characterized the vesicular overexpressed in cancer pro-survival protein 1 (VOPP1) as a new regulator of WWOX. In breast cancer cells, VOPP1 sequestrates WWOX in lysosomes, impairs its ability to associate with p73α, and inhibits WWOX-dependent apoptosis. Overexpressed VOPP1 potentiates cellular transformation and enhances the growth of transplanted tumors in vivo. VOPP1 is overexpressed in breast tumors, especially in tumors that retain WWOX. Moreover, increased expression of VOPP1 is associated with reduced survival of patients with WWOX-positive, but not with WWOX-negative, tumors.ConclusionsThese findings emphasize the importance of the sequestration of WWOX by VOPP1 in addition to WWOX loss in breast tumors and define VOPP1 as a novel oncogene promoting breast carcinogenesis by inhibiting the anti-tumoral effect of WWOX.Electronic supplementary materialThe online version of this article (10.1186/s12915-018-0576-6) contains supplementary material, which is available to authorized users.

BackgroundKindlin-1, − 2, and − 3 are the three members of the Kindlin family. They are best known as regulators of integrin functions, contributing to fundamental biological processes such as cell survival, adhesion and migration. Their deregulation leads to diverse pathologies including a broad range of cancers in which both, tumor-promoting and tumor-inhibiting functions have been described.MethodsTo better characterize Kindlins implication in breast cancer, in vitro experiments were performed in a series of cancer cell lines. We first assessed their expression profiles and subcellular distributions. Then, their involvement in breast cancer cell morphology, migration and invasion was verified by examining phenotypic changes induced by the depletion of either isoforms using RNA interference. An expression study was performed in a series of breast cancer patient derived xenografts (n = 58) to define the epithelial and stromal contribution of each Kindlin. Finally, we analyzed the expression levels of the three Kindlins in a large series of human breast tumors, at the RNA (n = 438) and protein (n = 129) levels and we evaluated their correlation with the clinical outcome.ResultsWe determined that Kindlin-1 and Kindlin-2, but not Kindlin-3, were expressed in breast tumor cells. We uncovered the compensatory roles of Kindlin-1 and -2 in focal adhesion dynamics and cell motility. Remarkably, Kindlin-2 had a predominant effect on cell spreading and Kindlin-1 on cell invasion. In line with these experimental observations, Kindlin-1 overexpression was associated with a worse patients’ outcome. Notably, Kindlin-3, expressed by tumor infiltrating leukocytes, also correlated with a poor prognosis of breast cancer patients.ConclusionThis study demonstrates that each one of the Kindlin family members has a different expression profile emphasizing their redundant and complementary roles in breast tumor cells. We highlight the specific link between Kindlin-1 and breast cancer progression. In addition, Kindlin-3 overexpression in the tumor microenvironment is associated with more aggressive breast tumors.These results suggest that Kindlins play distinctive roles in breast cancer. Kindlins may be useful in identifying breast cancer patients with a worst prognosis and may offer new avenues for therapeutic intervention against cancer progression.Electronic supplementary materialThe online version of this article (10.1186/s13046-018-0955-4) contains supplementary material, which is available to authorized users.

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Background: Triple-negative breast cancer (TNBC) accounts for ~15% of all invasive breast cancers. This heterogeneous group of tumors is the most aggressive and difficult-to-treat subtype of breast cancer. We previously demonstrated that Kindlin-1 is overexpressed in TNBC and patients with high Kindlin-1 have a worse prognosis. We determined that Kindlin-1 plays a major role in the epithelial to mesenchymal transition, tumor growth and breast cancer metastasis. TNBC have also been reported to express high levels of EGFR, in ~70% of the cases. Unfortunately, anti-EGFR therapy in TNBC fails to show a clinical benefit. In this study, we aimed to investigate a potential link between EGFR/RAS/MAPK pathway and Kindlin-1 in TNBC, and to propose new therapeutic strategies based on our findings. Methods: First, a gene set enrichment analysis was performed in 58 breast cancer cell lines (CCLE dataset) to detect the signaling pathways differentially enriched in cells expressing high levels of Kindlin-1. We next evaluated whether Kindlin-1 expression could be associated to an increased MAPK signaling by testing the mutational status and phosphorylation of key effectors of the pathway. To determine whether Kindlin-1 could be a predictive biomarker for the response to MEK inhibitors, we assessed its expression in sensitive versus resistant cell lines. Finally, we examined in vivo the anti-tumor efficacy of Selumetinib in a series of 27 triple negative breast cancer patient derived xenografts (PDX), highly representative of the originating tumor in terms of biology and therapeutic sensitivity. These PDX models have been characterized for Kindlin-1 expression (at RNA and protein levels). The sensitivity to MEKi of the TNBC PDX models was examined with regard to their Kindlin-1 expression. Results: Gene set enrichment analysis put in evidence that EGFR/RAS/MAPK pathway is upregulated in breast cancer cells with high Kindlin-1 expression. Although mutations are infrequent in breast cancer, an increased Kindlin-1 expression was observed in a subset of EGFR/RAS-activated cell lines (mutated or amplified). Moreover, TNBC expressing high levels of Kindlin-1 showed an increased phosphorylation of key effectors (ERK, MEK). We also demonstrated that Kindlin-1 mRNA expression was significantly increased in sensitive cell lines to different MEK inhibitors such as Trametinib (p=0.007) or Selumetinib (p=0.005) compared with resistant cells. In addition, in preclinical TNBC PDX models treated with Selumetinib there was a correlation between tumor growth inhibition and Kindlin-1 protein expression (r=0.57; p=0.017). Conclusion: Our findings indicate that Kindlin-1 expression may be a promising predictive biomarker of MEK inhibitors response in TNBC and may offer new therapeutic opportunities for patients with limited treatment options and refractory cancer types to current treatments. Citation Format: Paula Azorin, Florian Bonin, Zakia Tariq, Florence Coussy, Elisabetta Marangoni, Rosette Lidereau, Keltouma Driouch. Kindlin-1 expression is associated with EGFR/RAS/MAPK activation and response to MEK inhibitors in triple-negative breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3182.