The orphan nuclear receptor Liver Receptor Homologue-1 (LRH-1) has roles in development, bile-acid homeostasis and steroidogenesis. It also promotes tumourigenesis in gastric, colon, pancreatic and breast cancer. In breast cancer, LRH-1 stimulates proliferation and increases intratumoural estrogen levels. Our previous expression profiling identified the heterogeneous ribonucleoproteins (hnRNPs) as potential LRH-1 target genes in MCF-7 cells. Here, we aimed to determine the effects of hnRNPs and LRH-1 in regulating breast cancer cell proliferation and metabolism.
LRH-1 expression was knocked down by siRNA in two breast cancer cell lines, MDA-231 and MCF-7. qPCR, western blot and immunocytochemistry were used to assess mRNA and protein levels of target genes. Cell proliferation and lactate production measured to assess the effect of LRH-1 and hnRNPs on cell metabolism.
Levels of hnRNPA1 and A2/B1 were reduced by 50% (p<0.01) in cells with LRH-1 levels knocked down compared with control cells. Cy-Quant Assay revealed a 50% and 25% (p<0.01) decreased proliferation rate in LRH-1 knockdown and hnRNPA1 knockdown cells. In addition, expression of pyruvate kinase M2 (PKM2) was reduced and PKM1 levels increased in LRH-1 and hnRNPA1 knockdown cells. Lactate production was decreased 20% (p<0.01) these cells.
The actions of LRH-1 in breast cancer development are poorly understood. Here we identified hnRNPA1 and hnRNPA2/B1 as regulated by LRH-1. Our results indicate that knocking down LRH-1 reduced hnRNPA1 and hnRNPA2/B1 expression, decreasing aerobic glycolysis as evidenced by a reduction in lactate production and decreased cell proliferation. Although the underlying mechanism for this regulation is not clear, this finding suggests a unique LRH-1 mediated link to tumour cell metabolism.