Functions of p38 mitogen-activated protein kinase alpha and beta in human pancreatic cancer cells

Abstract

Objective To elucidate possible functions of p38α and p38β in human pancreatic cancer. Methods Expression of p38α, p38β, p38γ and p38δ were determined by immunoblot in 7 cultured human pancreatic cancer cell lines. To selectively inhibit p38α or p38β, cell clones were established in a stable manner expression either p38α short hairpin RNA (shRNA) or p38β shRNA. Proliferation, single cell movement, in vitro migration, colony forming ability as well as in vivo tumorigenicity were determined by methyl thiazol tetrazolium (MTT) assay, video-time laps microscopy, boyden-chamber, soft-agar assay, tumor formation and growth in nude mice respectively. Results All pancreatic cancer cells showed p38 isoforms protein expression at various levels. Selective inhibition of p38α or p38β in Mia Paca-2 and Panc-1 cells revealed that both kinases enhance cell proliferation and anchorage-independent growth. Single cell movement and cell invasion were markedly reduced in p38α shRNA expressing clones, but not altered in p38β shRNA expressing clones. Inhibition of p38α enhanced in vivo tumorigenicity profoundly in Mia Paca-2 and Panc-1 cells. In Mia Paca-2 cell, the in vivo tumor formation rate of two p38β shRNA expressing clones is 18.3% and 50.0% respectively, which decreased significantly comparing to the wild type cell and null vector transfection cell. The tumor volume decreased significantly either (P<0.05). In Panc-1 cell, the in vivo tumor formation rate of two p38β shRNA expressing clones is 25.0% and 12.5% respectively. Conclusion p38 mitogen activated protein kinases (p38MAPKs) are expressed in pancreatic cancer cells and the isoforms may exert different functions. Key words: p38 mitogen-activated protein kinase; Pancreatic cancer; p38α; p38β