Effect of 17β estradiol on proliferation of MM cell lines and MM patient cells. ARH 77, OCI My-5, RPMI 8226, S6B45, and U266 MM cell lines (A) as well as purified MM cells from 2 patients (B) were cultured with 0.5 (▪), 5.0 (▨), and 50 (▧) μmol/L of E2 for 48 hours. ³H-TdR uptake was compared with DNA synthesis of cells cultured in media alone. Mean CPM and SEM for cultures with media alone were as follows: ARH (3,501 ± 148), OCI-My-5 (8,618 ± 1,081), RPMI 8226 (329,241 ± 11,774), S6B45 (118,811 ± 16,543), U266 (35,304 ± 6,033), MM patient no. 1 (2,949 ± 981), and MM patient no. 2 (12,965 ± 3,799).