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Breast cancer metastasis is the second leading cause of female mortality worldwide. Because of the heterogeneity within the group, metastatic biomarkers for triple-negative breast cancer (TNBC) providing predictive and prognosis values are urgently needed. Using RNA-Seq, we analyzed the transcriptome profiles of two groups of TNBCs tumors with or without distant metastasis. Whole transcriptome sequencing identified a set of genes implicated in TNBC metastasis with major roles in cell-cell adhesion, immune-modulation, and Wnt/β-catenin pathways. We further selected the SHISA3 gene and studied its biological significance through a series of in vitro and in vivo experiments. SHISA3 is a tumor suppressor gene, involved in several types of cancer. However, little is known concerning the role of SHISA3 in TNBC. Our in vitro and in vivo studies demonstrate that overexpression of SHISA3 inhibits TNBCs cell proliferation, metastasis and colony formation, and TNBC growth in xenografts. Mechanistically, SHISA3 inhibits TNBCs development and growth via downregulation of the epithelial-mesenchymal transition. Taken together, these results identified SHISA3 as a novel tumor suppressor gene in TNBC and suggest that SHISA3 could serve as a therapeutic target for TNBC patients., Competing Interests: None., (AJCR Copyright © 2021.)

ANXA1, first described in the context of inflammation, appears to be deregulated in many cancers and increased in melanomas compared with melanocytes. To date, few studies have investigated the role of ANXA1 in melanoma progression. Furthermore, this protein is expressed by various cell types, including immune and endothelial cells. We therefore analyzed the specific roles of ANXA1 using melanoma and stromal cells in two human cell lines (A375-MA2 and SK-MEL-28) in vitro and in Anxa1 null C57Bl6/J mice bearing B16Bl6 tumors. We report decreased proliferation in both ANXA1 siRNA A375-MA2 and SK-MEL-28, but cell-dependent effects of ANXA1 in migration in vitro . However, we also observed a significant decrease of B16Bl6 tumor growth associated with a reduction of Ki-67 positive cells in Anxa1 null mice compared with wild-type mice. Interestingly, we also found a significant reduction of spontaneous metastases, which can be attributed to decreased angiogenesis concomitantly with greater immune cell presence in the Anxa1 null stromal context. This study highlights the pejorative role of ANXA1 in both tumor and stromal cells in melanoma, due to its involvement in proliferation and angiogenesis., Competing Interests: None., (AJCR Copyright © 2021.)

Basal-like breast cancer is among the most aggressive cancers and there is still no effective targeted treatment. In order to identify new therapeutic targets, we performed mRNA-Seq on eight breast cancer cell lines. Among the genes overexpressed in basal-like tumors, we focused on the RhoA and RhoB genes, which encode small GTPases known to play a role in the actin cytoskeleton, allowing cells to migrate. qRT-PCR and Western blotting were used for expression studies. Migratory and invasive properties were analysed by wound healing and Boyden chambers assays. Stress fibers formation was evaluated by fluorescent actin labeling. Rho siRNA, small inhibitor Rhosin treatment and BRCA1 transfection were performed to study the role of Rho and BRCA1 proteins. We showed that strong expression of RhoA and low expression of RhoB was associated with the basal-like subtype of breast cancer. Decreasing RhoA expression reduced the migratory and invasive capacities of basal-like cell lines, while decreasing RhoB expression increased these capacities. Rhosin, an inhibitor of RhoA, could also reduce the migration of basal-like cell lines. Rho proteins are involved in the formation of stress fibers, a conformation of the actin cytoskeleton found in migrating cells: inhibition of RhoA expression decreased the formation of these fibers. BRCA1 , a gene frequently inactivated in basal-like tumors, appears to play a role in the differential expression of RhoA and RhoB in these tumors, as the restoration of BRCA1 expression in a BRCA1-mutated basal-like cell line decreased expression of RhoA and increased expression of RhoB, resulting in reduced migratory capacity. These results suggest Rho proteins as potential therapeutic targets for basal-like and BRCA1-mutated breast cancer, as migration and acquisition of mesenchymal properties are key functional pathways in these tumors with high metastatic potential., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

Basal-like breast cancers are among the most aggressive cancers and effective targeted therapies are still missing. In order to identify new therapeutic targets, we performed Methyl-Seq and RNA-Seq of 10 breast cancer cell lines with different phenotypes. We confirmed that breast cancer subtypes cluster the RNA-Seq data but not the Methyl-Seq data. Basal-like tumor hypermethylated phenotype was not confirmed in our study but RNA-Seq analysis allowed to identify 77 genes significantly overexpressed in basal-like breast cancer cell lines. Among them, 48 were overexpressed in triple negative breast cancers of TCGA data. Some molecular functions were overrepresented in this candidate gene list. Genes involved in antioxydation, such as SOD1, MGST3 and PRDX or cadherin-binding genes, such as PFN1, ITGB1 and ANXA1, could thus be considered as basal like breast cancer biomarkers. We then sought if these genes were linked to BRCA1, since this gene is often inactivated in basal-like breast cancers. Nine genes were identified overexpressed in both basal-like breast cancer cells and BRCA1 mutated cells. Amongst them, at least 3 genes code for proteins implicated in epithelial cell migration and epithelial to mesenchymal transition (VIM, ITGB1 and RhoA). Our study provided several potential therapeutic targets for triple negative and BRCA1 mutated breast cancers. It seems that migration and mesenchymal properties acquisition of basal-like breast cancer cells is a key functional pathway in these tumors with a high metastatic potential., Competing Interests: Competing Interests: The authors have declared that no competing interest exists.