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

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.