To study biochemical units related to growth and regression of experimental hormonally dependent mammary carcinomas which mimic human cancers. To investigate the mechanism of microsomal G6PD activity disappearance in DBcAMP induced regressing tumors which will elucidate the role of the cyclic AMP system in tumor regression. To study the correlations between tumor regressions induced by hormonal deprivation with that induced by DBcAMP treatment. Also to study the changes in G6PD activity and enzyme pattern during tumor regression and regrowth with estrogen injection and to correlate these findings with binding activity of estrogen and cAMP in the tumor cytosol and nucleus.