Diacylglycerols Enhance the Anti‐tumor Effect of Glucocorticoid on L5178Y Lymphoblasts in vivo

1,2‐Dioleoyl‐rac‐glycerol, a potent activator of protein kinase C, was found to enhance the growth‐inhibitory effect of triamcinolone acetonide on L5178Y lymphoblasts in adrenalectomized, male DBA/2 mice. On the other hand, in mice without adrenalectomy, it markedly inhibited tumor growth without increasing the plasma level of corticosterone or adrenocorticotropic hormone or reducing the body weight. These results suggest that diacylglycerol enhances the action of endogenous glucocorticoid to a sufficient level to inhibit the growth of lymphoblasts. Of various diacylglycerols with different carbon chain lengths tested, 1,2‐dioleoyl‐rac‐glycerol was the most potent growth inhibitor and was maximally effective at a dose of above 30 μg/100 g body weight. This finding suggests that diacylglycerols may he useful for enhancing the antitumor effect of a low dose of glucocorticoid or endogenous glucocorticoid on lymphoblasts without any significant side effect.