Comparison of staurosporine and four analogues: their effects on growth, rhodamine 123 retention and binding to P-glycoprotein in multidrug-resistant MCF-7/Adr cells

Abstract

Summary The potent kinase inhibitor staurosporine and its protein kinase C (PKC)-selective analogue CGP 41251 are known to sensitise cells with the multidrug resistance (MDR) phenotype mediated by Pglycoprotein (P-gp) to cytotoxic agents. Here four PKC-selective staurosporine cogeners, CGP 41251, UCN-01, RO 31 8220 and GF 109203X, were compared with staurosporine in terms of their MDR-reversing properties and their susceptibility towards P-gp-mediated drug efflux from MCF-7/Adr cells. Staurosporine was the most potent and the bisindolylmaleimides RO 31 8220 and GF 109203X the least potent cytostatic agents. When compared with MCF-7 wild-type cells, MCF-7/Adr cells were resistant towards the growth-arresting properties of RO 31 8220 and UCN-01, with resistance ratios of 12.6 and 7.0 respectively. This resistance could be substantially reduced by inclusion of the P-gp inhibitor reserpine. The ratios for GF 109203X, staurosporine and CGP 41251 were 1.2, 2.0 and 2.9 respectively, and they were hardly affected by reserpine. These results suggest that RO 31 8220 and UCN-01 are avidly transported by P-gp but that the other compounds are not. Staurosporine and CGP 41251 at 10 and 20 nm, respectively, decreased efflux of the P-gp probe rhodamine 123 (R123) from MCF-7/Adr cells, whereas RO 31 8220 and GF 109203X at 640 nm were inactive. CGP 41251 was the most effective and GF 109203X the least effective inhibitor of equilibrium binding of [3H]vinblastine to its specific binding sites, probably P-gp, in MCF-7/Adr cells. Overall, the results imply that for this class of compound the structural properties that determine susceptibility towards P-gp-mediated substrate transport are complex. Comparison with ability to inhibit PKC suggests that the kinase inhibitors affect P-gp directly and not via inhibition of PKC. Among these compounds CGP 41251 was a very potent MDR-reversing agent with high affinity for P-gp and least affected by P-gp-mediated resistance, rendering it an attractive drug candidate for clinical development.

Combined treatment with the checkpoint abrogator UCN-01 and MEK1/2 inhibitors potently induces apoptosis in drug-sensitive and -resistant myeloma cells through an IL-6–independent mechanism

“…27 Although enhanced expression of Pgp has been shown to reduce, albeit weakly, uptake of small molecule inhibitors such as flavopiridol, 47 it has been found to be somewhat more effective in diminishing the toxicity of UCN-01 in MCF-7 breast cancer cells. 48 However, the finding that Dox40 MM cells were fully sensitive to UCN-01/PD184352 toxicity argues that Pgp-related mechanisms do not play a major role in determining the response of MM cells to either of these agents. Resistance of MM.1R cells to dexamethasone has been attributed to a mutation in the steroid receptor.…”

Co-ordinate loss of protein kinase C and multidrug resistance gene expression in revertant MCF-7/Adr breast carcinoma cells

“…PKC activators also increased drug accumulation and decreased drug sensitivity in MCF-7/Adr (Fine et al, 1988) and KM12L4a cells (Dong et al, 1991), and induced MDRJ gene expression in normal human lymphocytes (Chaudhary and Roninson, 1992). Conversely, a variety of PKC inhibitors, such as staurosporine (Sato et al, 1990), the staurosporine analogues CGP 41251 (Utz et al, 1994; Budworth et al, 1996) and GF 109203X , calphostin C (Bates et al, 1993) and safingol (Sachs et al, 1995), reversed P-gp-mediated mdr. However, reversal of drug resistance caused by staurosporine analogues is probably associated with direct interaction with P-gp rather than with PKC inhibition (Smith and Zilfou, 1995;Gekeler et al, 1996;Goodfellow et al, 1996;Budworth et al, 1996).…”

“…Conversely, a variety of PKC inhibitors, such as staurosporine (Sato et al, 1990), the staurosporine analogues CGP 41251 (Utz et al, 1994; Budworth et al, 1996) and GF 109203X , calphostin C (Bates et al, 1993) and safingol (Sachs et al, 1995), reversed P-gp-mediated mdr. However, reversal of drug resistance caused by staurosporine analogues is probably associated with direct interaction with P-gp rather than with PKC inhibition (Smith and Zilfou, 1995;Gekeler et al, 1996;Goodfellow et al, 1996;Budworth et al, 1996). The aim of this study was to investigate the link between PKC and mdr by analysis of changes in expression of the PKC and MDR] genes in drug-selected mdr cells, cultured without the selective pressure of drug in the medium.…”

Substrate-specific effects of pirinixic acid derivatives on ABCB1-mediated drug transport

“…Our data shed further light on the complexity of substrate interactions with ABCB1 adding to previous reports that had suggested that the mode and/or strength of ABCB1 interaction may differ among ABCB1 substrates [25][26][27][28][29][30]. Notably, the composition of the cell membrane and ABCB1 polymorphisms/ mutations are also known to modulate ABCB1 function and substrate specificity [23;31].…”