Effects of indomethacin on the growth of cultured mammary tumors.

We have studied the relative prostaglandin E (PGE) synthesizing abilities of a number of mammary tumor lines cultured in vitro. These lines differ in a number of biologic characteristics including tumorigenicity, immunogenicity and metastatic potential. They also synthesize different levels of PGE and these levels are in the same relative order as seen in situ. The metastatic tumor lines 4526 and 410.4 synthesize more PGE than does the non-metastatic tumor line 410. Synthetic activity of all lines decreases with time in culture. Relative synthetic capacity is not correlated with cell doubling time as the highest PGE levels are seen with the slowest growing (68H) and fastest growing (4526) cell lines. Indomethacin is able to inhibit the synthesis of PGE in vitro in a dose-dependent manner and the presence of indomethacin results in stimulation of cell division.