Expression of mismatch repair gene PMS2 in nasopharyngeal carcinoma and regulation by glycogen synthase kinase-3β in vivo and in vitro

Detection of GSK-3β activation index in pediatric chronic tonsillitis is an indicator for chronic recurrent inflammation

PURPOSE

Chronic tonsillitis (TC) is among the most common bacterial diseases in pediatric otolaryngology. We aimed to evaluate the expression of glycogen synthase kinase 3β (GSK-3β) in a cohort of children with chronic tonsillitis (TC), and the correlation between GSK-3β activity index and inflammatory profiles of TC.

MATERIALS AND METHODS

The expression of GSK-3β was comparably evaluated between children with TC (n = 26) and tonsillar hypertrophy (TH, n = 26). GSK-3β expression was detected by immunohistochemistry, RT-qPCR, and Western blot. The inflammatory profiles between the TC and TH groups were also evaluated.

RESULTS

We found that while GSK-3β was highly expressed in both TC and TH groups, no significant difference were detected at mRNA and protein levels between groups. The protein level of p-GSK-3β was significantly lower in the TC group as compared to the TH group. Additionally, the inflammatory markers, including NF-κB, T-bet, and IFN-γ were higher in the TC group compared to TH group. The GSK-3β activation index was positively correlated with the levels of NF-κB, T-bet, and IFN-γ in the TC group.

CONCLUSIONS

Our findings suggested that GSK-3β activation index was demonstrated to be a clinically applicable indicator for chronic recurrent inflammation in pediatric TC.

Inhibition of GSK 3β activity is associated with excessive EZH2 expression and enhanced tumour invasion in nasopharyngeal carcinoma

Background

Enhancer of zeste homolog 2 (EZH2) has been shown to contribute to tumour development and/or progression. However, the signalling pathway underlying the regulation of EZH2 in nasopharyngeal carcinoma (NPC) remains unclear. Since EZH2 contains the putative Glycogen synthase kinase 3 beta (GSK3β) phosphorylation motif ADHWDSKNVSCKNC (591) and may act as a possible substrate of GSK-3β, it is possible that inactivation of GSK3β may lead to excessive EZH2 expression in NPC.

Method

We first examined the expression of EZH2 and phosphorylated GSK3β (p-GSK3β) by immunohistochemical staining in NPC samples. Then, we evaluated the interaction of GSK3β and EZH2 using immunoprecipitation and immune blot. Moreover, we determined the effect of inhibition of GSK3β activity on EZH2 expression and tumor invasiveness in NPC cell lines in vitro. Finally, we evaluated the invasive properties of NPC cells after knocking down EZH2 expression with EZH2 siRNA.

Results

We found that expression of EZH2 correlated with phosphorylated GSK3β (p-GSK3β) at Ser 9 (an inactivated form of GSK3β) in human nasopharyngeal carcinoma (NPC) samples. We also provided evidence that GSK3β is able to interact with EZH2 using immunoprecipitation and immune blot. Furthermore, we found that inhibition of GSK3β activity can lead to upregulation of EZH2 in NPC cell lines in vitro, with enhanced local invasiveness. By knocking down EZH2 expression with EZH2 siRNA, we found that these invasive properties were EZH2 dependent.

Conclusion

Our findings indicate that GSK3β inactivation may account for EZH2 overexpression and subsequent tumour progression, and this mechanism might be a potential target for NPC therapy.