Functional analyses of C13orf19/P38IP in prostate cell lines.

Human C13orf19 was previously identified to be downregulated in prostate cancer (PCa) but its function is unknown to date. In the present study, C13orf19 mRNA expression was inhibited by siRNA transfection. Furthermore, a possible regulation by androgens and the previously postulated interaction with p38 MAP kinase (p38MAPK) was investigated. The siRNA-mediated downregulation of the C13orf19 mRNA expression in the prostate cell lines PC-3 and BPH-1 was examined by quantitative PCR. Cellular viability, apoptosis, cell cycle distribution and clonogenic survival were investigated. In addition, the effects of C13orf19 downregulation in combination with chemotherapy on overall cell survival were studied. The inhibition of C13orf19 mRNA expression to 12% (after 12 h) and 55% (after 96 h) in PC-3 cells attested to a strong and persistent molecular effect provoked by the siRNA-D5 construct. However, no obvious effects on doubling time and cellular morphology were observed. Cell cycle distribution, clonogenic survival, apoptosis and cell viability showed no alterations, even after combining siRNA transfection with chemotherapy. Therefore, it can be concluded that the reduced expression of C13orf19 in PCa is not involved in the malignant transformation of the cells. A possible androgen dependence of C13orf19 mRNA expression was investigated by treating LNCaP cells with the androgen R1881 and in combination with the antiandrogen, bicalutamide. C13orf19 is expressed independently of the androgen. To analyze the putative interaction between C13orf19 and p38MAPK, PC-3 and BPH-1 cells were treated with the p38MAPK inhibitor, SB203580, and C13orf19 mRNA expression was examined. Additionally, the expression and phosphorylation status of p38MAPK after the inhibition of C13orf19 was investigated by Western blotting. No interaction between C13orf19 and p38MAPK was identified. Therefore, the gene should forthwith be named C13orf19 or Fam48A and not P38IP.