Different effects of corticotropin-releasing factor and urocortin 2 on apoptosis of prostate cancer cells in vitro

Abstract

Urocortin (Ucn), a corticotropin-releasing factor (CRF)-related neuropeptide binding both CRF type 1 receptor (CRFR1) and CRFR2, has recently been found in prostate cancer. However, no report has yet been known to elucidate the roles of Ucn in prostate cancer via the two receptors. In this study, the expression of both CRFR1 and CRFR2 in the mouse prostate cancer cell line RM-1 were detected and cellular apoptosis was monitored in the presence of CRF or Ucn2, the CRFR1-and CRFR2-selective agonist respectively. CRF promoted apoptosis while Ucn2 exerted the opposite effect. CRF reduced Bcl-2 expression, induced Bax expression, and hyperpolarized the mitochondrial membrane potential to activate caspase-9. On the contrary, Ucn2 increased Bcl-2 expression and decreased Bax expression, in which phosphorylation of Akt and cyclic AMP response element-binding (CREB) was involved. Pretreatment with phosphatidylinositide 3-kinase/Akt inhibitor (LY-294002) prior to Ucn2 led to downregulation of CREB phosphorylation and hence reduced Bcl-2 expression. These effects of CRF and Ucn2 were abolished by antalarmin (Anta) and antisauvagine-30, the CRFR1-and CRFR2-selective antagonist respectively. In LNCaP cell line, similar effects on cell apoptosis by CRF and Ucn2 were observed. In summary, our results demonstrated CRFR1 and CRFR2 expression in prostate cancer and indicated the opposite apoptotic roles of the two different CRFRs. These data may contribute to uncovering the pathophysiological function of endogenous Ucn in prostate tumorigenesis and progression.

Corticotropin-releasing hormone receptors mediate apoptosis via cytosolic calcium-dependent phospholipase A2 and migration in prostate cancer cell RM-1

“…1b, lower) showed that siRNA3 transfection attenuated CRH-induced apoptosis (5.305 vs 9.7625%) and strengthened inhibition by Ucn2 of apoptosis induced by TG (4.5925 vs 8.18%), indicating that cPLA 2 was an apoptotic inducer in CRH/Ucn2 treatment. The presence of several cells showing apple-green fluorescence indicated that CRH family peptides affected apoptosis at an early time, consistent with our previous research (Jin et al 2011).…”

“…We previously found that CRH activated CRHR1 to induce apoptosis through reducing ratio of Bcl-2:Bax expression, lowering mitochondrial membrane potential, and activating caspase-9. In addition, CRHR2 activated by Ucn2 had the opposite effects to those of CRHR1 in mouse prostate cancer cell line RM-1 (Jin et al 2011). We found that CRH induced apoptosis through androgen receptor (Jin et al 2012) and inhibited transforming growth factor b-induced epithelialmesenchymal transition via CRHRs in breast cancer cells (our unpublished data).…”

“…Immunoblotting was carried out as previously described (Jin et al 2011). Briefly, total cell lysate was collected, and the amount of protein was determined by the Bradford method.…”

“…Annexin V-FITC/propidium iodide (PI) double staining was carried out according to a procedure described previously (Jin et al 2011). Briefly, RM-1 cells were transfected with siRNA against cPLA 2 and then treated with CRH/Ucn2 to detect apoptosis.…”

“…At present, there is no clear consensus as to the precise effect of cPLA 2 in apoptosis, as strong evidence both in favor and against apoptosis has been presented (Huber et al 2007, Lei et al 2008. Our previous data of distinct effects of active CRHRs in apoptosis of mouse RM-1 prostate cancer cells ( Jin et al 2011) prompted us to explore whether cPLA 2 is involved in CRHR-mediated apoptosis and its precise role in apoptosis in RM-1 cell.…”