Protein phosphatase-2A modulates the serine and tyrosine phosphorylation of paxillin in Lewis lung carcinoma tumor variants

Cellular adhesion and motility, processes regulated by focal adhesion assembly and disassembly, can influence a tumor cell's ability to metastasize. Focal adhesion dynamics are, in turn, influenced by the serine and tyrosine phosphorylation state of paxillin. Using Lewis lung carcinoma (LLC) tumor variants, this study shows the importance of the serine/threonine protein phosphatase-2A (PP-2A) in maintaining adherence and restricting tumor cell motility, and modulating the serine and tyrosine phosphorylation of paxillin. Treating non-metastatic LLC-C8 tumor variants with okadaic acid to inhibit PP-2A activity resulted in cell rounding and increased motility. These effects on motility and adherence were accompanied by increased serine and decreased tyrosine phosphorylation of paxillin. These results suggest PP-2A regulation of paxillin phosphorylation may have a role in controlling tumor cell adherence and motility.