Expression and activation of lyn in macrophages treated in vitro with cisplatin: regulation by kinases, phosphatases and Ca2+/calmodulin

Cisplatin [cis-dichlorodiammine platinum (II)], a potent chemoimmunotherapeutic drug, activates macrophages to tumoricidal state which is inhibited by protein tyrosine kinase(s) inhibitor. Cisplatin induces protein tyrosine phosphorylation of a number of cellular proteins suggesting the involvement of protein tyrosine kinase(s) in the activation process of macrophages. Therefore, the effect of cisplatin treatment on the expression and activation of lyn, a protein tyrosine kinase of src family, in macrophages was investigated. The underlying mechanism of lyn expression and activation was also analyzed. Cisplatin treatment increased lyn expression and activation in macrophages within 5 min of treatment. The expression and activation of lyn were observed to be biphasic processes in cisplatin-treated macrophages with the first peak appearing at 15 min and the second peak at 2 h of treatment. The appearance of second phase of lyn activation and second phase of lyn expression were two unrelated processes. The second peak of lyn activation was produced by the autocrine action of some soluble product(s) of cisplatin-treated macrophages, whereas the second phase of lyn expression was due to some intracellular factor. It was further observed that cisplatin-induced lyn expression and activation involves serine/threonine phosphatases 1/2A, protein tyrosine phosphatases, protein tyrosine kinase and protein kinase C. It was also observed that Ca2+/calmodulin and calmodulin-dependent kinases are involved in the regulation of cisplatin-induced lyn expression and activation in macrophages.