Inhibition of B-16 melanoma growth in vivo by a synthetic analog of prostaglandin E2.

The effect of systemic administration of 16,16-dimethyl prostaglandin E2-methyl ester (di-M-PGE2) on the growth of B-16 melanoma tumors has been studied in C57BL/6J mice. Daily i.p. injection of 5 mu of di-M-PGE2 commencing on the day of tumor inoculation with 10(5) and 10(6) viable cells delayed appearance of tumors; for the smaller tumor inoculum, it also increased median survival among treated mice from 23 to 33 days. Di-M-PGE2 treatment of mice with established tumors caused significant inhibition of tumor growth, as measured by a number of parameters including tumor diameters and volumes. At the time of sacrifice, di-M-PGE2-treated mice had tumors that were an average of 32% smaller (by weight), contained 60% fewer melanoma cells, and had higher concentrations of cyclic adenosine 3':5'-monophosphate and cyclic guanosine 3':5'-monophosphate (+225% and +100%, respectively).