PTEN regulates apoptotic cell death through PI3-K/Akt/GSK3β signaling pathway in DMH induced early colon carcinogenesis in rat

Phosphatidylinositol 3-kinase (PI3-K) and Akt (protein kinase B), are both essential signaling molecules that are up-regulated in various cancers. Here, we examined the molecular mechanisms by which PI3-K and Akt expression are regulated by glycogen synthase kinase-3 beta (GSK-3 beta) and the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) in the early stages of experimental colon carcinogenesis. 1,2-dimethylhydrazine (DMH) was utilized for the induction of colon cancer while piroxicam, a traditional non-steroidal anti-inflammatory drug and c-phycocyanin, a biliprotein from Spirulina platensis (cyanobacterium) as the chemopreventive agents. Western blotting and immunofluorescence results indicated that the expression of PI3-K and Akt was promoted in the DMH group while least apoptosis was detected in this group as analyzed by Hoechst 33342-propidium iodide co-staining. DMH group further detected lower GSK-3 beta and PTEN expression as compared to other groups. Piroxicam and c-phycocyanin treatment resulted significant apoptotic cell death while showing low PI3-K and Akt expressions. Mitochondrial membrane potential (Delta Psi(M)) alterations (examined by JC-1 and rhodamine 123 labeling of colonocytes) and fluorescence intensity measurement of ROS level, were also analyzed showing the raised Delta Psi(M) while reduced ROS levels in DMH group, however piroxicam and c-phycocyanin treatment resulted in falling of Delta Psi(M) although both stimulated the ROS production as analyzed by flow cytometry. The present study thus identified that piroxicam, a traditional NSAID and c-phycocyanin, a newly discovered COX-2 selective inhibitor, constitute remarkable chemopreventive targets in mediating apoptosis in the DMH induced early rat colon carcinogenesis via regulating PI3-K/Akt/GSK-3 beta/PTEN signaling pathways. Further, a combination of the two drugs provides a better therapeutic option, than the monotherapy regimen. (C) 2012 Elsevier Inc. All rights reserved.