Differential expression and function of SVIP in breast cancer cell lines and in silico analysis of its expression and prognostic potential in human breast cancer

The heterogeneity of cancer strongly suggests the need to explore additional pathways to target. As cancer cells have increased proteotoxic stress, targeting proteotoxic stress-related pathways such as endoplasmic reticulum stress is attracting attention as new anticancer treatments. One of the downstream responses to endoplasmic reticulum stress is endoplasmic reticulum-associated degradation (ERAD), a major degradation pathway that facilitates proteasome-dependent degradation of unfolded or misfolded proteins. Recently, SVIP, an endogenous ERAD inhibitor, has been implicated in cancer progression, especially in glioma, prostate, and head and neck cancers. Here, the data of several RNA-seq and gene array studies were combined to evaluate the SVIP gene expression analysis on a variety of cancers, with a particular focus on breast cancer. SVIP was found to be overexpressed in primary breast tumors compared to normal tissues correlated well with its promoter methylation status and genetic alterations. Similarly, immunoblotting analysis showed that SVIP was expressed significantly higher in breast cancer cell lines compared to non-tumorigenic epithelial cell line. On the other hand, the expression of the key proteins of gp78-mediated ERAD did not exhibit such a pattern. Interestingly, silencing of SVIP enhanced the proliferation of p53 wt MCF7 cells but not p53 mutant T47D cells, however increased migration ability of both cell lines. Interestingly, SVIP expression is high in primary breast tumors but low in breast metastatic tumors. This correlates well with a lower probability of survival of breast cancer patients with lower SVIP expression compared to the patients with overexpressed SVIP. Overall, our data revealing the differential expression and function of SVIP on breast cancer cell lines together with in silico data analysis suggest that SVIP may have complex functions in breast cancer progression and has the potential to be a therapeutic target for breast cancer.