Tumor Responsiveness to the Metastasis-Stimulatory Effects of Prostaglandin E2 is Restricted by Protein Phosphatases

Prostaglandin E2 (PGE2) is secreted by both tumor and host cells, and can enhance tumor dissemination (1,2). However, the amount of PGE2 that tumor cells secrete does not necessarily reflect their metastatic capacity (1). We have shown that cloned metastatic Lewis lung carcinoma cells (LLC-LN7) secrete less PGE2 than do cloned nonmetastatic LLC (LLC-C8) cells, but are more responsive to PGE2 in their in vitro motility and in vivo metastasis (1,3,4). Such differences in responsiveness to PGE2 have also been demonstrated for fibrosarcoma clones (1).