Effects of protein kinase inhibitors 1(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) and N-[2-guanidinoethyl]-5-isoquinolinesulfonamide hydrochloride (HA1004) on calcitriol-induced differentiation of HL-60 cells

HL-60 promyelocytic leukemia cells were induced to differentiate by 1,25-dihydroxyvitamin D3 (calcitriol) into mature monocytes. Differentiation was assessed by nitro blue tetrazolium dye reduction, nonspecific esterase activity, and DNA synthesis. Terminal differentiation of cultures induced by calcitriol (10 nM) was inhibited by 80% when cells were treated simultaneously with protein kinase inhibitors 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) (32 [mu]M) and N-[2-guanidinoethyl]-5-isoquionlinesulfonamide hydrochloride (HA1004) (320 [mu]M). The 50 for inhibition of calcitriol-induced differentiation was approximately 15 [mu]M for H-7 and 170 [mu]M for HA1004. The IC50 values for H-7 and HA1004 antagonism of calcitriol-induced differentiation are quantitatively and relatively correlated to their known action to inhibit protein kinase C activity. Treatment of cells with concentrations of 0-32 [mu]M H-7 or 0-320 [mu]M HA1004 alone did not affect cell growth, differentiation, or trypan blue exclusion. However, higher concentrations of H7 (> 32 [mu]M) and HA1004 (> 320 [mu]M) were found to be cytotoxic. The data presented suggest that calcitriol-induced differentiation is antagonized by inhibitors of protein kinase and are consistent with the hypothesis that kinase C activity is required for HL-60 cell differentiation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27400/1/0000432.pd