Regulation of a Family of Homeodomain Transcription Factor PAX mRNA Expression in PC‐3 Human Prostate Cancer Cells by Nutrient Limitation

Abstract

Purpose: To examine the role of nutrient availability in regulating gene expression in PC-3 cells, the expression patterns of transcription factors PAX under amino acid or glucose limitation were investigated. Materials and Methods: PC-3 cells were incubated in MEM, or MEM free of amino acids or glucose for 0, 2, 4, 8, 12, 16 and 24 hours. Real-time qRT-PCR and western blot analysis were used to detect mRNA and protein expression. Results: Pax1/6/9 mRNA expression was demonstrated in PC-3 whereas Pax2 was not detected in PC-3 by qRT-PCR. Deprivation of amino acids or glucose induced the expression of activating transcription factor ATF3 mRNA in PC-3 cells, whereas Pax1/6/9 mRNA expression was reduced by both conditions, among which Pax9 exhibited the most significant down-regulation. For Pax9, a 3 fold reduction of mRNA expression was observed from 0 to 8 hours, followed by an increased expression from 8 to 16 hours, indicating the temporal requirement of Pax9 expression in PC-3 cells under nutrient limitation. Western blot showed the phosphorylation levels of kinases, MEK1/2 and ERK1/2, in the mitogen activated protein kinases (MAPK) pathway, increased in PC-3 cells after amino acid deprivation for 2 to 8 hours, and then decreased after 8 hours, which correlated to the initial down-regulation and the later recovering of Pax9 gene expression. Conclusions: These results suggest regulation of Pax gene expression is linked to MAPK pathway activation and may play an important role in the response of PC-3 cells to the environmental changes.