3.4. Sost Is a Regulator of MALAT1 in Prostate Cancer Cells
Microarray revealed that MALAT1 was up-regulated in prostate cancer cells co-cultured with WT osteoblasts compared to PC3 alone, suggesting that factors secreted by osteoblasts up-regulate MALAT1. Subsequently, we co-cultured PC3 cells with UMR osteoblasts and, using qPCR, confirmed that the factors secreted by osteoblasts up-regulated MALAT1 expression in prostate cancer. The qPCR data showed a ~6-fold increase in MALAT1 expression in PC3 cells co-cultured with UMR osteoblasts compared to PC3 monocultures (Figure 4B). To test whether Sost is a regulator of MALAT1 in prostate cancer we cultured PC3 cells with recombinant human SOST for 48 h and quantified MALAT1 expression using qPCR. Treatment with recombinant SOST resulted in ~5.6-fold reduction in MALAT1 expression (Figure 4B), suggesting that Sost in the tumor microenvironment may have an inhibitory effect on MALAT1 and down-regulation of Sost in the bone microenvironment may enhance MALAT1 expression in prostate cancer.