Constitutive activation of stimulatory guanine nucleotide binding protein (G(s)alpha QL)-mediated signaling increases invasiveness and tumorigenicityof PC-3M prostate cancer cells

An abnormal stimulation of cAMP signaling cascade has been implicated in va rious human carcinomas, Since the agents activating G(s)alpha-mediated sign aling pathways have been shown to increase in vitro proliferation of prosta te cancer cells, present studies examined the G(s)alpha-mediated signaling in tumorigenicity and invasiveness of PC-3M prostate cancer cells. PC-3M ce lls were stably transfected with plasmids containing either wild type (G(s) alpha-WT) or constitutively active (gsp mutant of G(s)alpha or G(s)alpha-QL ) CDNAs. The stable transfectants were then tested for: (1) colony formatio n in soft agar; (2) cell migration and penetration of basement matrix in an in vitro invasion assay; and (3) the ability to form tumors and metastases in nude mice. PC-3M cells expressing G(s)alpha-QL protein displayed 15-fol d increase in their ability to migrate and penetrate the basement membrane as compared to parental PC-3M cells or those expressing G(s)alpha-WT. G(s)a lpha-QL transfectants also displayed a dramatically greater rate of growth in soft agar, and greater tumorigenicity and metastasis forming ability whe n orthotopically implanted in nude mice. All mice receiving PC-3M cells pro duced primary tumors within 5 weeks after implantation. However, the cells expressing G(s)alpha-QL displayed a significantly faster tumor growth as as sessed by prostate weight (greater than 20-fold as compared to PC-3M cells) , and produced metastases in kidneys, 12 mph nodes, blood vessels, bon el m esentery and intestine. Interestingly, expression of G(s)alpha-WT reduced t he ability of PC-3M cells to form tumors in nude mice. These results sugges t that persistent activation of G(s)alpha-mediated signaling cascade can dr amatically accelerate tumorigenesis and metastasizing ability of prostate c ancer cells.