ENHANCEMENT OF ANTINEOPLASTIC EFFECT AND ATTENUATION OF SISTER-CHROMATID EXCHANGES BY PROSTAGLANDIN E(2) IN EHRLICH ASCITES TUMOR-CELLS TREATED WITH CYCLOPHOSPHAMIDE IN-VIVO

Reduced sister chromatid exchanges (SCE) frequency in response to cycl ophosphamide (CP) was observed when Ehrlich ascites tumour (EAT) cells were exposed in vivo to 2 mu g/g body weight of prostaglandin E(2) (P GE(2)). 1h before i.p. injection of 5-bromodeoxyuridine (BrdUrd) adsor bed to activated charcoal, EAT-bearing mice treated i.p. with CP appea red to have increased SCE rates and cell division delays. PGE(2) had n o effect on survival and in inhibiting tumour growth. CP had only a sl ight non-significant effect on survival and in inhibiting tumour growt h. In mice treated with the combined CP (5 mu g/g bd wt) plus PGE(2) ( 2 mu g/g bd wt) a significant enhancement (P < 0.01) of survival time was accompanied by inhibition of tumour growth (P < 0.01) in compariso n with the untreated controls. These data imply that SCEs might result from errors in a repair process which might involve a PGE(2) sensitiv e step.