The autophagy GABARAPL1 gene is epigenetically regulated in breast cancer models.

BACKGROUND: The GABARAP family members (GABARAP, GABARAPL1/GEC1 and GABARAPL2 /GATE-16) are involved in the intracellular transport of receptors and the autophagy pathway. We previously reported that GABARAPL1 expression was frequently downregulated in cancer cells while a high GABARAPL1 expression is a good prognosis marker for patients with lymph node-positive breast cancer. METHODS: In this study, we asked using qRT-PCR, western blotting and epigenetic quantification whether the expression of the GABARAP family was regulated in breast cancer by epigenetic modifications. RESULTS: Our data demonstrated that a specific decrease of GABARAPL1 expression in breast cancers was associated with both DNA methylation and histone deacetylation and that CREB-1 recruitment on GABARAPL1 promoter was required for GABARAPL1 expression. CONCLUSIONS: Our work strongly suggests that epigenetic inhibitors and CREB-1 modulators may be used in the future to regulate autophagy in breast cancer cells.

High expression of QSOX1 reduces tumorogenesis, and is associated with a better outcome for breast cancer patients.

INTRODUCTION: The gene quiescin/sulfhydryl oxidase 1, QSOX1, encodes an enzyme directed to the secretory pathway and excreted into the extracellular space. QSOX1 participates in the folding and stability of proteins and thus could regulate the biological activity of its substrates in the secretory pathway and/or outside the cell. The involvement of QSOX1 in oncogenesis has been studied primarily in terms of its differential expression in systemic studies. QSOX1 is overexpressed in prostate cancers and in pancreatic adenocarcinoma. In contrast, QSOX1 gene expression is repressed in endothelial tumors. In the present study, we investigated the role of QSOX1 in breast cancer. METHODS: We analyzed QSOX1 mRNA expression in a cohort of 217 invasive ductal carcinomas of the breast. Moreover, we investigated QSOX1's potential role in regulating tumor growth and metastasis using cellular models in which we overexpressed or extinguished QSOX1 and xenograft experiments. RESULTS: We showed that the QSOX1 expression level is inversely correlated to the aggressiveness of breast tumors. Our results show that QSOX1 leads to a decrease in cell proliferation, clonogenic capacities and promotes adhesion to the extracellular matrix. QSOX1 also reduces the invasive potential of cells by reducing cell migration and decreases the activity of the matrix metalloproteinase, MMP-2, involved in these mechanisms. Moreover, in vivo experiments show that QSOX1 drastically reduces the tumor development. CONCLUSIONS: Together, these results suggest that QSOX1 could be posited as a new biomarker of good prognosis in breast cancer and demonstrate that QSOX1 inhibits human breast cancer tumorogenesis.

The ATG8 Family Proteins GABARAP and GABARAPL1 Target Antigen to Dendritic Cells to Prime CD4+ and CD8+ T Cells.

Vaccine therapy is a promising method of research to promote T cell immune response and to develop novel antitumor immunotherapy protocols. Accumulating evidence has shown that autophagy is involved in antigen processing and presentation to T cells. In this work, we investigated the potential role of GABARAP and GABARAPL1, two members of the autophagic ATG8 family proteins, as surrogate tumor antigen delivery vectors to prime antitumor T cells. We showed that bone marrow-derived dendritic cells, expressing the antigen OVALBUMIN (OVA) fused with GABARAP or GABARAPL1, were able to prime OVA-specific CD4+ T cells in vitro. Interestingly, the fusion proteins were also degraded by the proteasome pathway and the resulting peptides were presented by the MHC class I system. We then asked if the aforementioned fusion proteins could improve tumor cell immunogenicity and T cell priming. The B16-F10 melanoma was chosen as the tumor cell line to express the fusion proteins. B16-F10 cells that expressed the OVA-ATG8 fused proteins stimulated OVA-specific CD8+ T cells, but demonstrated no CD4+ T cell response. In the future, these constructions may be used in vaccination trials as potential candidates to control tumor growth.

ATG9A Is Overexpressed in Triple Negative Breast Cancer and Its In Vitro Extinction Leads to the Inhibition of Pro-Cancer Phenotypes.

Early detection and targeted treatments have led to a significant decrease in mortality linked to breast cancer (BC), however, important issues need to be addressed in the future. One of them will be to find new triple negative breast cancer (TNBC) therapeutic strategies, since none are currently efficiently targeting this subtype of BC. Since numerous studies have reported the possibility of targeting the autophagy pathway to treat or limit cancer progression, we analyzed the expression of six autophagy genes (ATG9A, ATG9B, BECLIN1, LC3B, NIX and P62/SQSTM1) in breast cancer tissue, and compared their expression with healthy adjacent tissue. In our study, we observed an increase in ATG9A mRNA expression in TNBC samples from our breast cancer cohort. We also showed that this increase of the transcript was confirmed at the protein level on paraffin-embedded tissues. To corroborate these in vivo data, we designed shRNA- and CRISPR/Cas9-driven inhibition of ATG9A expression in the triple negative breast cancer cell line MDA-MB-436, in order to determine its role in the regulation of cancer phenotypes. We found that ATG9A inhibition led to an inhibition of in vitro cancer features, suggesting that ATG9A can be considered as a new marker of TNBC and might be considered in the future as a target to develop new specific TNBC therapies.

Olfactory epithelium destruction by ZnSO4 modified sulfhydryl oxidase expression in mice.

Experimental destruction of olfactory neurons stimulates proliferation and differentiation of local neural precursors and is used as a model to study in vivo mechanisms for degeneration and regeneration of the nervous system. Quiescin-sulfhydryl oxidases (QSOX) have a potential role in the control of the cell cycle or growth regulation and have recently been described in the central nervous system. In mice, we show an expression of QSOX in olfactory mucosa. Northern- and western-blot analysis show that the destruction of olfactory epithelium is associated with a reversible reduction in QSOX expression. Interestingly, QSOX is not localized in olfactory neurons (ON) but in cells of the lamina propria, suggesting that olfactory epithelium destruction may act as a signal of down-regulation of QSOX expression.

QSOX1 inhibits autophagic flux in breast cancer cells.

The QSOX1 protein (Quiescin Sulfhydryl oxidase 1) catalyzes the formation of disulfide bonds and is involved in the folding and stability of proteins. More recently, QSOX1 has been associated with tumorigenesis and protection against cellular stress. It has been demonstrated in our laboratory that QSOX1 reduces proliferation, migration and invasion of breast cancer cells in vitro and reduces tumor growth in vivo. In addition, QSOX1 expression has been shown to be induced by oxidative or ER stress and to prevent cell death linked to these stressors. Given the function of QSOX1 in these two processes, which have been previously linked to autophagy, we wondered whether QSOX1 might be regulated by autophagy inducers and play a role in this catabolic process. To answer this question, we used in vitro models of breast cancer cells in which QSOX1 was overexpressed (MCF-7) or extinguished (MDA-MB-231). We first showed that QSOX1 expression is induced following amino acid starvation and maintains cellular homeostasis. Our results also indicated that QSOX1 inhibits autophagy through the inhibition of autophagosome/lysosome fusion. Moreover, we demonstrated that inhibitors of autophagy mimic the effect of QSOX1 on cell invasion, suggesting that its role in this process is linked to the autophagy pathway. Previously published data demonstrated that extinction of QSOX1 promotes tumor growth in NOG mice. In this study, we further demonstrated that QSOX1 null tumors present lower levels of the p62 protein. Altogether, our results demonstrate for the first time a role of QSOX1 in autophagy in breast cancer cells and tumors.

Involvement of sulfhydryl oxidase QSOX1 in the protection of cells against oxidative stress-induced apoptosis.

The QSOX1 protein, belonging to a new class of FAD-linked Quiescin/Sulfhydryl oxidase, catalyzes disulfide bond formation. To give new insight into the biological function of QSOX1, we studied its involvement in oxidative stress-induced apoptosis and cell recovery of PC12 cells. By real time RT-PCR and flow cytometric analysis, we show that the QSOX1 mRNA and protein levels increased late after the beginning of oxidative treatment and were sustained for 72 h. These levels were still high when the PC12 cells were not dying but had resumed proliferation. The kinetics of QSOX1 expression suggest a more protective effect of QSOX1 rather than an involvement of this protein in apoptosis. Human breast cancer MCF-7 cell lines overexpressing the guinea pig QSOX1 protein submitted to the same treatments appeared less sensitive to cell death than the MCF-7 control cells. The protective effect is partly due to a preservation of the mitochondrial polarization generally lost after an oxidative stress. These results strengthen our hypothesis of a protective role of QSOX1 against apoptosis.

Onset of direct 17-beta estradiol effects on proliferation and c-fos expression during oncogenesis of endometrial glandular epithelial cells.

In normal endometrial glandular epithelial cells (GEC), 17beta-estradiol (E2) enhances proliferation and c-fos expression only in the presence of growth factors. On the contrary, growth factors are not required for the E2 effects in cancerous cells. Thus, a repression of E2 action could exist in normal cells and be turned off in cancerous cells, allowing a direct estrogen-dependent proliferation. To verify this hypothesis, we established immortalized and transformed cell models, then investigated alterations of E2 effects during oncogenesis. SV40 large T-antigen was used to generate immortalized GEC model (IGEC). After observation of telomerase reactivation, IGEC model was transfected by activated c-Ha-ras to obtain transformed cell lines (TGEC1 and TGEC2). The phenotypic, morphological, and genetic characteristics of these models were determined before studying the E2 effects. In IGEC, the E2 action on proliferation and c-fos expression required the presence of growth factors, as observed in GECs. In TGECs, this action arose in the absence of growth factors. After IGEC transformation, the activation of ras pathway would substitute the priming events required for the release of repression in GEC and IGEC and thus permit direct E2 effects. Our cell models are particularly suitable to investigate alterations of gene regulation by E2 during oncogenesis.