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Upregulation of SHMT2 Promotes Tumor Growth and Poor Prognosis of Breast Cancer through Activating VEGF and MAPK Signaling Pathway


 Background: Serine hydroxymethyltransferase 2 (SHMT2) is a key enzyme in Serine/glycine metabolism. SHMT2 is very important for tumor cell growth and proliferation as well as metabolism. Here, we investigated the regulatory effects of SHMT2 on breast cancers growth and identified the underlying mechanisms of functions.Methods: We detected the expression of SHMT2 in breast cancer cells and tissues by immunohistochemistry and Western blotting.We investigated the functional and molecular mechanisms by which SHMT2 downregulation or overexpression regulates the growth and apoptosis of breast cancer cells in vivo and in vitro. Results: We found SHMT2 was highly expressed in BRCA cell lines and tumor tissues. Strong SHMT2 expression showed a positive correlation with the poor prognoses of patients with breast cancers. SHMT2 knockdown by shRNA significantly inhibited cell growth and induced apoptosis in vitro, and whereas SHMT2 overexpression promoted tumor growthin in subcutaneous xenograft model. RNA-seq revealed that high expression of SHMT2 not only promoted serine metabolism, nucleotide metabolism, oxidative phosphorylation and proteasome independent degradation pathways. It also activated the cell survival signaling pathway and antagonized the apoptosis pathway. The observed molecular regulation of cell growth was accompanied by the activited of the MAPK, VEGF pathways and suppressed of the mitochondrial mediated apoptosis pathway that was mediated by the SHMT2 up-regulation. Conclusions: These results indicate that SHMT2 plays a critical role in regulating breast cancers growth and could serve as a therapeutic target for breast cancer therapy.