Thiol redox modulation of doxorubicin mediated cytotoxicity in cultured AIDS-related Kaposi's sarcoma cells

Abstract

The chemotherapeutic, doxorubicin, is currently used empirically in the treatment of AIDS- related Kaposi's sarcoma (AIDS-KS). Although often employed in a chemotherapeutic cocktail (doxorubicin, bleomycin, vincristine) single-agent therapy has recently been attempted with liposome encapsulated doxorubicin. Although doxorubicin's mechanism of action against AIDS-KS is unknown, we hypothesized that doxorubicin's ability to undergo redox cycling is associated with its clinical efficacy. The current study was conducted to investigate the effects of doxorubicin on selected xenobiotic-associated biochemical responses of three cellular populations: KS lesional cells, nonlesional cells from the KS donors, and fibroblasts obtained from HIV- aged matched men. Our results show that during doxorubicin challenge, there are strong positive correlations between cellular glutathione (GSH) levels and viability (r = 0.94), NADPH levels and viability (r = 0.93), and GSH and NADPH levels (r = 0.93), and demonstrate that as a consequence of their abilities to maintain cellular thiol redox pools HIV- donor cells are significantly less susceptible to doxorubicin's cytotoxic effects relative to AIDS-KS cells. Additional studies further supported the contribution of reduced thiols in mediating doxorubicin tolerance. While pretreatment with the GSH precursor, N-acetylcysteine was cytoprotective for all cell groups during doxorubicin challenge, GSH depletion markedly enhanced doxorubicin's cytotoxic effects. Studies to investigate the effects of a hydroxyl scavenger and iron chelator during doxorubicin challenge showed moderate cytoprotection in the AIDS-KS cells but deleterious effects in the HIV control cells. Inactivation of the longer lived membrane generated ROI in the cytoprotective deficient AIDS-KS cells, as well as an impairment of endogenous defenses in the HIV- donor control cells, may account for these scavenger and chelator associated findings. In summary, our findings show that doxorubicin mediates, at least in part, its AIDS-KS cellular cytotoxic effects by a redox related mechanism, and provides a biochemical rationale for doxorubicin's clinical efficacy in AIDS-KS treatment.

DNA damage detected with γH2AX in endometrioid adenocarcinoma cell lines

“…Several groups reported that inhibiting DOX-induced intracellular oxidative stress by the overexpression of antioxidant enzymes prevented apoptosis in tumor cells (17), and that depleting endogenous antioxidants (e.g. glutathione) made tumor cells more susceptible to DOX (18,19). However, there are other studies that did not support the role of oxidative stress as the sole factor responsible for tumor cell apoptosis induced by DOX (20,21).…”

Doxorubicin Induces Apoptosis in Normal and Tumor Cells via Distinctly Different Mechanisms

“…Several groups reported that inhibiting DOX-induced intracellular oxidative stress by the overexpression of antioxidant enzymes prevented apoptosis in tumor cells (20,21), and that depleting endogenous antioxidants (e.g. glutathione) made tumor cells more susceptible to DOX (22,23). However, other studies did not support the role of oxidative stress in tumor cell apoptosis induced by DOX and other chemotherapeutic agents (24,25).…”

Members of the glutathione and ABC-transporter families are associated with clinical outcome in patients with diffuse large B-cell lymphoma

“…[9][10][11][12][13]23,26 L-buthionine-S-sulphoximine (BSO), a GCL inhibitor, which depletes intracellular GSH levels, has been shown to sensitize cells to treatment with alkylators and anthracyclines. 13 Overexpression of GPX1 and other antioxidant enzymes has been shown to suppress apoptosis in cancer cell lines and tumor xenograft models, [14][15][16][17][18] including in the setting of doxorubicin treatment. [14][15][16] In lymphoma, the oncogene BCL2, overexpressed in 50% of DLBCLs, is known to inhibit apoptosis, and has been shown to do so in part through the antioxidant pathway and GPX1.…”

“…13 Overexpression of GPX1 and other antioxidant enzymes has been shown to suppress apoptosis in cancer cell lines and tumor xenograft models, [14][15][16][17][18] including in the setting of doxorubicin treatment. [14][15][16] In lymphoma, the oncogene BCL2, overexpressed in 50% of DLBCLs, is known to inhibit apoptosis, and has been shown to do so in part through the antioxidant pathway and GPX1. 18 To our knowledge, only one prior study has suggested that GPX1 overexpression did not have a significant protective effect on doxorubicin-induced apoptosis.…”

“…Overexpression of GPX1 and other antioxidant enzymes, as well as depletion of intracellular GSH, have been shown to suppress anthracyclineinduced apoptosis in several experimental systems, including cancer cell lines and tumor xenografts. [14][15][16][17][18] Previous clinical studies have examined GPX1 function 19 and genetic polymorphisms 20 as they relate to susceptibility to lymphoma but not response to therapy. A cDNA microarray-based study of tumor samples from a patient population with DLBCL 21 found increased expression of antioxidant defense enzymes, including GPX1, to be associated with a better prognosis in this disease.…”