Prostaglandin E augments the effect of chemotherapy on B-16 melanoma in vivo☆

Abstract The effectiveness of six chemotherapeutic agents (adriamycin, dopamine, 5-FU, nitrogen mustard, thioTEPA, and vincristine) on B-16 melanoma growth in vivo was compared with the effects of 16,16-dimethyl-PGE 2 -methyl ester, a long-acting synthetic analog of PGE 2 (di-M-PGE 2 ) and of chemotherapy plus di-M-PGE 2 . Although all the drugs were effective in slowing growth (adriamycin, dopamine, and 5-FU) or decreasing tumor size from baseline values (nitrogen mustard, thioTEPA, and vincristine), the addition of di-M-PGE 2 augmented the growth inhibitory effects of each. Changes in tumor diameters were associated with similar changes in tumor cell numbers. In addition, the combinations of di-M-PGE 2 plus nitrogen mustard and vincristine decreased the plating efficiency in a clonogenic assay to a greater extent than did either di-M-PGE 2 or the cytotoxic drugs alone. Finally, this augmentation was not associated with systemic toxicity or changes in leukocyte count.