Lactoferrin Inhibits the Development of T2D-Induced Colon Tumors by Regulating the NT5DC3/PI3K/AKT/mTOR Signaling Pathway

Although increasing evidence shows the association between type 2 diabetes (T2D) and colorectal cancer, the related mechanism remains unclear. This study examined the suppressive effect of lactoferrin (LF) on the development of T2D-induced colon cancer. First, a co-cultured cell model consisting of NCM460 and HT29 cells was constructed to mimic the progression of T2D into colon cancer. The migration ability of NCM460 cells increased significantly (p < 0.05) after cultivation in HT29 cell medium (high glucose), while LF suppressed the progression of T2D to colon cancer by regulating the 5′-nucleotidase domain-containing 3 (NT5DC3) protein and the PI3K/AKT/mTOR signaling pathway in diabetic BALB/c mice and in cell models. A mutation assay of the phosphorylation site in the NT5DC3 protein and a surface plasmon resonance (SPR) protein binding test were performed to further ascertain a mechanistic link between LF and the NT5DC3 protein. The results indicated that LF specifically bound to the NT5DC3 protein to activate its phosphorylation at the Thr6 and Ser11 sites. Next, metabolic-specific staining and localization experiments further confirmed that LF acted as a phosphate donor for NT5DC3 protein phosphorylation by regulating the downstream metabolic pathway in T2D-induced colon tumors, which was specifically accomplished by controlling Thr6/Ser11 phosphorylation in NT5DC3 and its downstream effectors. These data on LF and NT5DC3 protein may suggest a new therapeutic strategy for cancer prevention, especially in T2D patients susceptible to colon cancer.