Sulindac sulfide inhibits growth of colorectal cancer cells through cyclin D1 attenuation in a Protein Kinase G dependent pathway

초록

Background: There is accumulating evidence that sulindac sulfide, active metabolite of the non-steroidal anti-inflammatory prodrug sulindac, inhibits the colorectal cancer growth [1; 2]. Although the role of sulindac sulfide in inhibiting growth of colorectal cancer has been established, the precise mechanism is still obscure. Objectives: Our goal was to study the effect of sulindac sulfide in SW480 human colon cancer cells to determine the underlying molecular mechanism of colorectal cancer regression. Methods: SW480 human cells grown in DMEM medium were assayed for cell proliferation and cGMP-PDE enzymatic activity. To elucidate the role of PKG in transcription control we constructed a series of expression vectors of wild type, constitutively active and dominant negative mutants of PKG. The transcriptional regulators of cyclin D1, such as, c-fos, c-jun, SRE and TRE were studied by using the luciferase reporter assay. Results: The present study indicates that sulindac sulfide inhibits the proliferation of SW480 human colon cancer cells. Our data also suggest that sulindac sulfide decreases the enzymatic activity of subcellular cGMP-phosphodiesterase (PDE), thereby increasing intracellular levels of cGMP and PKG. Increased PKG downregulate the transcription of cyclin D1 when transiently transfected in SW480 cells. Constitutively active mutants of PKG showed marked transcriptional downregulation of c-fos in SW480 cells. We also found that the constitutively active mutants of PKG negatively regulate the activation of SRE and TRE, suggesting their involvement in the regulation of cyclin D1.