MESP2 binds competitively to TCF4 to suppress gastric cancer progression by regulating the SKP2/p27 axis.

Gastric cancer (GC) is a major cause of human deaths worldwide, and is notorious for its high incidence and mortality rates. Mesoderm Posterior Basic Helix-loop-helix (bHLH) transcription factor 2 (MESP2) acts as a transcription factor with a conserved bHLH domain. However, whether MESP2 contributes to tumorigenesis and its potential molecular mechanisms, remain unexplored. Noticeably, MESP2 expression levels are decreased in GC tissues and cell lines compared to those in normal tissue. Further, in vitro and in vivo experiments have confirmed that MESP2 overexpression suppresses GC cell growth, migration, and invasion, whereas MESP2 knockdown results in the exact opposite. Here, we present the first report that MESP2 binds to transcription factor 7-like 2 (TCF7L2/TCF4) to inhibit the activation of the TCF4/beta-catenin transcriptional complex, decrease the occupancy of the complex on the S-phase kinase Associated Protein 2 (SKP2) promoter, and promote p27 accumulation. MESP2 knockdown facilitated tumorigenesis, which was partially suppressed by SKP2 knockdown. Taken together, we conclude that MESP2 binds competitively to TCF4 to suppress GC progression by regulating the SKP2/p27 axis, thus offering a potential therapeutic strategy for future treatment.

FOXO3a­SIRT6 axis suppresses aerobic glycolysis in melanoma.

Melanoma, the most aggressive human skin tumor, has a very short survival time, and there are currently no effective treatments. Alterations in cell metabolism, such as enhanced aerobic glycolysis, have been identified as hallmarks of cancer cells. In the present study, bioinformatics studies using online databases revealed that FOXO3a expression was lower in melanoma tissues compared with normal tissues and nevus. Additionally, Kaplan­Meier analysis showed that high expression of FOXO3a predicted an improved prognosis for patients with melanoma. Furthermore, Pearson correlation analysis indicated that the expression of FOXO3a was positively correlated with SIRT6 expression and negatively correlated with the expression levels of a number of glycolysis­associated genes. Chromatin immunoprecipitation and luciferase assays showed that FOXO3a was enriched in the SIRT6 promoter region and promoted its transcription. Then, SIRT6 was overexpressed in FOXO3a­knockdown MV3 cells and downregulated in FOXO3a­overexpressing MV3 cells by using lentivirus­mediated stable infection. The results showed that SIRT6 knockdown or overexpression rescued the effects of FOXO3a overexpression or knockdown, respectively, on glycolysis, as determined by glucose uptake, glucose consumption and lactate production assays, the expression of glycolytic genes and glucose stress flux tests. SIRT6 overexpression also suppressed FOXO3a knockdown­induced tumor growth in a mouse model. The present findings indicated that the FOXO3a­SIRT6 regulatory axis inhibited glucose metabolism and tumor cell proliferation in melanoma, and provided novel insight into potential therapeutic strategies to treat this disease.