Pyrrolidine dithiocarbamate exerts anti-proliferative and pro-apoptotic effects in renal cell carcinoma cell lines

Abstract

Background: The activation of nuclear factor-kappaB (NF-kappaB) has been implicated in the development, progression and metastasis of renal cell carcinoma (RCC). This study investigates the effect of pyrrolidine dithiocarbamate (PDTC), a NF-kappaB inhibitor, on two metastatic human RCC cell lines, ACHN and SN12K1.

Methods: RCC cell lines and normal cells were exposed to 25 or 50 microM of PDTC. Apoptosis was measured by flow cytometry and TdT-mediated nick end labelling methods. Cell viability and proliferation were measured by MTT and BrdU assays, respectively. Expression of NF-kappaB subunits, IkappaBs, IkappaB Kinase (IKK) complex and apoptotic regulatory proteins were analysed by western blotting and/or immunofluorescence. DNA-binding activity of NF-kappaB subunits were measured by ELISA.

Results: RCC cell lines had a higher basal level expression of all the five subunits of NF-kappaB than normal primary cultures of human proximal tubular epithelial cells or HK-2 cells. PDTC decreased the viability and proliferation of RCC, but not normal cells. Of the two RCC cell lines, ACHN had a higher basal level expression of all the five NF-kappaB subunits than SN12K1 and was more resistant to PDTC. While PDTC induced an overall decrease in expression of all the five NF-kappaB subunits in both RCC cell lines, unexpectedly, it increased the nuclear expression of NF-kappaB in ACHN, but not in SN12K1. PDTC reduced the DNA-binding activity of all the NF-kappaB subunits and the expression of the IKK complex (IKK-alpha, IKK-beta and IKK-gamma) and the inhibitory units IkappaB-alpha and IkappaB-beta. PDTC induced a significant increase in apoptosis in both RCC cell lines. This was associated with a decrease in expression of the anti-apoptotic proteins, Bcl-2 and Bcl-(XL), without marked changes in the pro-apoptotic protein Bax.

Conclusion: These data suggest that PDTC has the potential to be an anticancer agent in some forms of RCC.