Diverse resveratrol sensitization to apoptosis induced by anticancer drugs in sensitive and resistant leukemia cells

Naturally occurring dietary compound resveratrol (RES), possessing chemopreventive and cytostatic properties, has been shown as potent sensitizer for apoptosis induced by a variety of anticancer drugs. Cell cycle analysis in sensitive promyelocytic leukemia HL60 cell line and its multidrug-resistant variant HL60/VCR (P-gp positive) treated with RES resulted in cell cycle arrest in S-phase in both cell variants. Flow cytometry measurements showed diverse activities of RES in combination with anticancer drugs doxorubicin (DOX), cycloheximide (CHX), busulfan (BUS), gemcitabine (GEM) and paclitaxel (PTX), in some cases resulting in apoptosis induction, preferentially at the expense of S-phase. Thus, RES could become a candidate to enhance the efficacy of combination anticancer therapy in a variety of human cancer cells inclusive leukemias.

Flavonoid quercetin, but not apigenin or luteolin, induced apoptosis in human myeloid leukemia cells and their resistant variants

Flavonoids and their in vivo metabolites are neuroprotective, cardioprotective and chemopreventive agents acting as hydrogen-donating antioxidants or modulators functioning at protein kinase and lipid signaling pathways. In presented study treatments of human leukemia cells HL60 and their MDR-1 resistant subline HL60/VCR by flavonoids apigenin (API), luteolin (LUT), quercetin (QU) and anticancer drug doxorubicin (DOX) are reported. Of all flavonoids used only QU treatments led in both cell lines to DNA fragmentation, cleavage of poly (ADP- ribose) polymerase (PARP), up-regulation of proapoptotic Bax and posttranslational modification (phosphorylation) of antiapoptotic Bcl-2. Cytochrome c and p21WAF1/CIP1 levels remained unchanged in these cells. Furthermore, treatments of both cell lines by QU and in its combined application with DOX increased phosphorylation of ERK, while Akt-1 and phosphorylated Akt-1 levels were not changed. All these events resulted in effective induction of apoptosis associated with down-regulation of P-glycoprotein in resistant cells. Presented results suggest that in human leukemia cells QU is a potent regulator of the cell apoptotic program associated with the modulation of several signaling molecules.

PSC 833 induces apoptosis in drug-sensitive human leukemia cell line and modulates resistance to paclitaxel in its multidrug-resistant variant

BACKGROUND

The non-immunosuppressive cyclosporine analog PSC 833 has been shown to reverse multidrug-resistance of neoplastic cells including the MDR-1 gene coded P-glycoprotein (P-gp)-mediated cells resistant to paclitaxel.

MATERIALS AND METHODS

Apoptosis was demonstrated in drug-sensitive HL-60 and multidrug-resistant human promyelocytic leukemia HL-60/ADR (MRP) and HL-60/VCR (MDR-1) cells in vitro with the aid of flow cytometry, DNA analysis and western blotting.

RESULTS

The techniques used herein determined accumulation of paclitaxel/PSC 833 induced apoptotic cells with sub-G0 (hypodiploid) DNA content and blocked in the G2/M phase of the cell cycle, internucleosomal DNA fragmentation, poly (ADP-ribose) polymerase cleavage, Bcl-2 modulation and Bax up-regulation, without any significant alterations in the levels of Bcl-xL, CD95/Fas or Fas-L proteins.

CONCLUSION

Drug resistance modulator PSC 833 abolished the P-gp-mediated multidrug-resistance to paclitaxel and paclitaxel-induced apoptosis in human myeloid leukemia (HL-60/VCR) cells in vitro. Furthermore, PSC 833 alone induced apoptosis in parental drug-sensitive leukemia cells, but not in both multidrug-resistant sublines studied.

Resistance of human multidrug-resistant neoplastic cell lines to paclitaxel-induced-radiosensitization is reduced by the non-immunosuppressive cyclosporine analog SDZ PSC 833

The non-immunosuppressive cyclosporine analog SDZ PSC 833 abolished the resistance of human multidrug resistant (MDR-1, P-gp) human promyelocyte leukemia HL-60/VCR cells in vitro to paclitaxel-induced cell cycle- and viability alterations, as well as resistance to paclitaxel-induced radiosensitization. Furthermore, SDZ PSC 833 abolished also the resistance of human multidrug-resistant ovarian A2780/ADR cells to paclitaxel-induced cell cycle alterations and reduced its resistance to paclitaxel-induced radiosensitization. In these multidrug-resistant ovarian carcinoma cells the supra-additive interaction between paclitaxel and SDZ PSC 833 pre-exposure and subsequent irradiation appeared at slightly higher paclitaxel concentrations (40-100 nM) compared to those required for a similar interaction in the parental drug sensitive A2780 cells (40-80 nM paclitaxel).