ANTITUMOR EFFECT OF ALPHA-ISOMER OF ANORDRIN IN-VITRO AND CELL-CYCLE ARREST AT G(1) PHASE

Alpha isomer of anordrin (2alpha, 17alpha-diethyl-A-norandrostane-2bet a, 17beta-diol dipropionate, alpha-Ano) inhibited mouse hepatoma (Hep A) and P388 cell growth in vitro. Alpha-Ano (20 mug.ml-1) inhibited th e incorporation of [H-3]uridine and [H-3]thymidine into RNA and DNA wi thin 3 h, but the inhibition of L-[H-3]lysine incoporating into protei n was not obvious. Alpha-Ano had no effect on the DNA-dependent RNA sy nthsis with purified nuclei of Hep A cells. It is suggested that the i nhibition of RNA and DNA syntheses is the major cause of the cytostati c effect. Alpha-Ano blocked the P388 cells at G1/G0 phase, and the del ay in G1/G0 to S phase transition plays an important role in the inhib ition of P388 cell growth.