TG2 as a novel breast cancer prognostic marker promotes cell proliferation and glycolysis by activating the MEK/ERK/LDH pathway.

ABSTRACT

BACKGROUND: Breast cancer (BC) is the most common malignant tumor among women worldwide. Tissue transglutaminase 2 (TG2) has been reported as a major player across several types of cancer. However, the effects of TG2 in breast cancer are less known. METHODS: The expression of TG2 in patients with BC was detected by immunochemistry staining and RT-qPCR. The correlation of TG2 expression and clinicopathological factors or overall survival (OS) was analyzed by Chi-square test, Kaplan-Meier, and Cox-regression analysis. The effects of TG2 on cell proliferation and glycolysis were investigated in vivo and in vitro by gain- and loss-of-function experiments. RESULT: Both mRNA and protein levels of TG2 were overexpressed in BC tissues and cultured cells. Clinical stage (p = 0.011), molecular subtype (p<0.001) and survival status (p<0.001) were significantly correlated with TG2 expression. Specifically, TG2 expression was positively associated with the clinical stage (r = 0.193, p = 0.005) and OS (r = 0.230, p = 0.001), while negatively associated with molecular subtype (r = - 0.161, p = 0.020). Overexpressed TG2 was a prognostic factor of poor OS by Cox-regression analysis. Gain- and loss-of-function experiments indicated that cell proliferation and glycolysis were regulated by TG2 via the MEK/ERK/LDH pathway. TG2-induced activation of the MEK/ERK/LDH pathway and glycolysis were attenuated by MEK inhibitor U0126. CONCLUSION: TG2 is overexpressed in BC, which can serve as an independent prognostic factor for OS. TG2 promotes tumor cell proliferation and increases glycolysis associated with the activation of the MEK/ERK/LHD pathway.