TSPAN31 Activates Fatty Acid Metabolism and PI3K/AKT Pathway to Promote Tumor Progression in Breast Cancer.

Breast cancer (BC) is one of the most common human malignancies, but the mechanisms of BC have not been fully elucidated. Recently, tetraspanin 31 (TSPAN31) is reported to be linked to cancer progression. However, the function of TSPAN31 remains unclear in BC. Investigation of the function and potential mechanism of TSPAN31 in BC was the purpose of this study. Immunohistochemistry, western blot, and quantitative real-time polymerase chain reaction were applied to measure TSPAN31 expression. Loss and gain functional experiments were utilized to survey the influences of TSPAN31 on BC biological process, including cell growth, invasion, migration, and fatty acid metabolism. Mechanistically, Kyoto Encyclopedia of Genes and Genomes analysis based on DepMap database and Gene Set Enrichment Analysis based on The Cancer Genome Atlas database were executed to find TSPAN31-related pathway. Western blot was carried out to assess the changes of fatty acid synthase (FASN), sterol regulatory element binding protein 1 (SREBP1), acyl-CoA synthetase long-chain family member 1 (ACSL1), phosphatidylinositol 3-kinase (PI3K), phosphorylated (p)-PI3K, protein kinase B (AKT), and p-AKT. In human non-triple negative breast cancer tissues and cells, TSPAN31 expression was upregulated. TSPAN31 knockdown induced BC cell apoptosis, inhibited cell proliferation, invasion, migration, and fatty acid metabolism, and reduced the protein levels of FASN, SREBP1, ACSL1, p-PI3K/PI3K, and p-AKT/AKT. In contrast, TSPAN31 overexpression led to the opposite results. Additionally, the activator of PI3K (740 Y-P) attenuated the inhibition of TSPAN31 knockdown on fatty acid metabolism, proliferation, and invasion in BC cells. Through activation of fatty acid metabolism and PI3K/AKT pathway, TSPAN31 played a carcinogenic role in BC. For the mechanism of BC tumorigenesis, our study provides an interesting insight.