Reversal of multidrug resistance by B859-35, a metabolite of B859-35, niguldipine, verapamil and nitrendipine

Abstract

It has been shown previously that verapamil and other calcium antagonists and calmodulin inhibitors can reverse multidrug resistance. We compared the potency of the dihydropyridine derivatives (4R)-3-[3-(4,4-diphenyl-1-piperadinyl)-propyl]-5-methyl-1,4-dihydr o-2,6- dimethyl-4-(3-nitrophenyl)-pyridine-3,5-dicarboxylate-hydrochloride (B859-35), a metabolite of B859-35, niguldipine and (R)-nitrendipine to that of (RS)-verapamil in reversing multidrug resistance. The accumulation of the fluorescent dye rhodamine 123, which is transported by the P-glycoprotein, was determined by a flow cytometer. Multidrug-resistant human HeLa KB-8-5 and Walker rat carcinoma cells were incubated in the presence and in absence of the drugs indicated above. We found that 0.1 microM B859-35 increases the accumulation of rhodamine 123 in multidrug-resistant KB-8-5 and Walker cells more effectively than 1 microM (RS)-verapamil. In sensitive KB-3-1 cells addition of the drugs had no significant influence on the accumulation of rhodamine 123. IN KB-8-5 cells, 10 nM Adriamycin caused a reduction of cell growth to 85% compared to untreated controls (= 100%). If 1 microM B859-35, B859-35 metabolite, niguldipine, verapamil or (R)-nitrendipine was added to 10 nM Adriamycin, growth reduction compared with untreated controls increased to 12%, 11%, 23%, 63%, and 82% respectively. The effect of 0.1 microM B859-35 was a reduction in proliferation to 38%, that of 0.1 microM verapamil to 72%. These data illustrate that B859-35, a compound with antitumor activity in several tumors, is at least ten times more potent than racemic verapamil in reversing multidrug resistance.

Resistance to the new anti-cancer phospholipid ilmofosine (BM 41 440)

“…Ilmofosine was obtained from Boehringer Mannheim, Mannheim, Germany, dissolved in 20 mm Tris-HCl, pH 7.4, and stored at +40C. Dexniguldipine-HCl (B859-35;Hofmann et al, 1992) was obtained from Byk-Gulden, Konstanz, Germany, and dissolved in dimethylsulphoxide in glassware. The final concentration of the solvent in treated cultures and controls did not exceed 0.1%, and this was non-toxic.…”

“…After addition of 60 gl (5 jg ml') of rhodamine 123 per ml of cell suspension, fluorescence (excitation at 488 nm) was detected by a flow cytometer Figure 3. Emission was observed with a 530/30-nm filter and fluorescence intensity was expressed as the mean of 5000 cells gated by forward-and side-scattered light to measure only viable and single cells (Hofmann et al, 1992).…”

“…As shown in Table 1 (Hofmann et al, 1992). The mean of two independent determinations is indicated cell line.…”

“…It has been shown previously that dexniguldipine-HCl (B8509-035) is approximately ten times more potent in reversing multidrug resistance than verapamil. To reverse multidrug resistance completely, 0.1 tM of the compound is sufficient (Hofmann et al, 1992). In order to investigate whether inhibition of P-glycoprotein by dexniguldipine-HCl increases the antiproliferative activity of ilmofosine, we treated CCRF/VCR1000 cells with both drugs concomitantly.…”

“…The fluorescent dye rhodamine 123 has been shown to act as an excellent substrate for the P-glycoprotein (Hofmann et al, 1992). Figure 9 Detection of the MDR1 and MDR2 mRNA levels by polymerase chain reaction.…”