Abstract
Breast cancer is the most common cancer type in woman worldwide. Recurrence of breast cancer is connected to poor prognosis, therefore novel treatments to prevent the recurrence are required. PDH generates acetyl-CoA from pyruvate and drives TCA cycle. PDH complex is composed of five subunits. In our previous study, knockdown of PDH-E1β subunit in breast cancer MDA-MB-231 cells reduced tumor formation in mice. In the present study, we used spheroid as an in vitro model to clarify the mechanism behind the tumor suppression in PDH-E1β KD cells. Wild type (WT) cells formed spheroid in three days, whereas PDH-E1β KD cells required seven days to form one. To investigate the effects of PDH-E1β on extracellular matrix (ECM) degradation, we examined the expression of MMPs, which are the main enzymes to degrade ECM. Expression of MMP19 and MMP28 were increased in PDH-E1β KD cells. Further, spheroid formation was rescued and formed in three days by the addition of MMP inhibitor. We have previously shown that CREB, a transcription factor, induces MMP1. Thus, we hypothesized that CREB is activated and induces MMP19 and MMP28 in PDH-E1β KD cells. Phosphorylation of CREB was increased in PDH-E1β KD cells, and PDH-E1β KD cells transfected with CREB siRNA also formed spheroid in three days. Knockdown of CREB decreased MMP19 but not MMP28 in PDH-E1β KD cells. Altogether, it is indicated that CREB induces the transcription of MMP19, and inhibit spheroid formation.
