SPAG4 enhances mitochondrial respiration and aerobic glycolysis in colorectal cancer cells by activating the PI3K/Akt signaling pathway.

Abstract

Aerobic glycolysis plays a pivotal role in the progression of tumors. Previously, a glycolysis-associated prognostic model in CRC was constructed and the glycolysis-related gene SPAG4 was discovered to be upregulated in CRC and was correlated with adverse prognosis. To date, however, no study has elucidated the specific role of SPAG4 in the development of CRC. In our study, CRC cells were transfected with si-SPAG4 or OE-SPAG4 to evaluate the influence of SPAG4 silencing or overexpression on CRC cell malignant behaviors. CRC cell proliferation and metastasis were detected via CCK-8, colony formation, and Transwell assays. The oxygen consumption rate and extracellular acidification rate of CRC cells were determined by using an XF24 extracellular flux analyzer. The expression of SPAG4, key mitochondrial markers (NDUFA1, SDHB, ATP5A, and PGC-1α), key enzymes involved in glycolysis (GLUT1, HK2, LDHA, PKM2, and PFK1), and PI3K/Akt pathway-molecules and downstream transcription factor HIF-1α was assessed by RT-qPCR and western blot analysis. SPAG4 expression in CRC and normal tissue samples was tested through immunohistochemical staining. Finally, SPAG4-overexpressed CRC cells were treated with LY294002 to validate the inhibition of PI3K/Akt pathway on CRC cell malignant phenotypes. Our results showed that SPAG4 was upregulated in CRC cells and tissues, and high expression SPAG4 predicted shorter overall survival time. SPAG4 knockdown inhibited while SPAG4 overexpression enhanced CRC cell proliferation, migration, invasion, mitochondrial respiration, and aerobic glycolysis. Overexpressing SPAG4 elevated p-PI3K, p-Akt, p-mTOR, and HIF-1α protein levels, which were restored after LY294002 treatment. Furthermore, LY294002 abolished the promotion of SPAG4 overexpression on CRC malignant phenotypes. Collectively, SPAG4 plays an oncogenic role in CRC by promoting mitochondrial respiration and aerobic glycolysis through activating the PI3K/Akt signaling. These findings suggest that inhibition of SPAG4-mediated glucose metabolism may represent a potential strategy for the clinical treatment of CRC.