Downregulation of CPT2 promotes proliferation and inhibits apoptosis through p53 pathway in colorectal cancer

Background: Downregulation of Carnitine palmitoyltransferase-2 (CPT2) has been shown to be highly associated with the progression of several cancers, but little known about its expression, biological functions and mechanisms in colorectal Cancer (CRC).

Methods: Bioinformatics analysis of The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) data sets was used to explore the expression of CPT2, the relationship between CPT2 expression and clinicopathologic features, as well as the overall survival of CRC. Cox's proportional hazards regression model was used to analyze independent prognostic factors of CRC. In vitro, CRC tissues were analyzed by RT-qPCR, IHC, IF and western blotting to verify CPT2 expression. Colony formation, CCK-8, cell cycle, Apoptosis, transwell and wound healing assays were performed to examine the functions of CPT2 in CRC. In vivo, nude mouse xenograft experiment was used to further examine the effect of CPT2 on tumorigenesis. Furthermore, gene set enrichment analysis (GSEA) was conducted to explore the downstream pathway of CPT2. The regulation of p53 pathway by CPT2 was verified by RT-qPCR and Western blotting.

Results: CPT2 expression was frequently downregulated in CRC and correlated with poor prognosis. Low CPT2 expression was significantly associated with age, lymph node metastasis, distant metastasis and TMN stage. Univariate and multivariate analysis indicated that low CPT2 expression was an independent prognostic factor for poorer overall survival. Functionally, overexpression of CPT2 in CRC cells induced growth suppression, cell cycle arrest at the G1 phase, enhanced Apoptosis and reduced cell migration and invasion. Conversely, knockdown of CPT2 contributed to cell proliferation, migration and invasion, increased the proportion of S phase cells, decreased the proportion of G1 phase cells and inhibited Apoptosis. Mechanistically, we found that CPT2 overexpression can increase p53 expression by activating p-p53, leading to p21, Bax, cleaved caspase-9, cleaved Caspase-3 and cleaved PARP activation and Bcl2, MDM2 deactivation, thereby inhibiting tumor proliferation and promoting Apoptosis. CPT2 knockdown yielded opposite results.

Conclusion: These findings suggest that CPT2 may be a novel prognostic marker of CRC and downregulation of CPT2 can promote proliferation and inhibit Apoptosis through p53 pathway in CRC. Strategies targeting CPT2 may be developed as therapies for CRC.

Apoptosis; CPT2; Colorectal cancer; Proliferation; p53 pathway.