Prostaglandin E production by Lewis lung carcinoma: mechanism for tumor establishment in vivo.

Prostaglandin E (PGE) concentrations in supernatants of in vitro cultured Lewis lung carcinoma (LLC) cells were measured by radioimmunoassay. Growth of cells correlated with an increase in PGE concentrations in the media. This elevation of PGE in the LLC supernatant could be prevented by the culturing of the cells with indomethacin, a prostaglandin synthesis inhibitor. Serum PGE levels of LLC-implanted mice were also measured. As the tumors developed in vivo, the systemic levels of PGE increased. For examination of the in vivo effect of PGE2 on tumor growth, LLC-implanted C57BL/6 mice were treated with exogenous PGE2, which resulted in an increase in the frequency of tumor establishment. In contrast, oral administration of indomethacin to LLC-implanted mice resulted in a reduced rate of tumor establishment, growth, and metastasis. A relationship between PGE2 production by tumor cells and their survival in a host was indicated.