Downregulation of GSTπ expression by tryptanthrin contributing to sensitization of doxorubicin-resistant MCF-7 cells through c-jun NH2-terminal kinase-mediated apoptosis

Abstract

Overexpression of GSTpi and underexpression of Topo II expression are associated with multidrug resistance (MDR) phenotype through nontransporter pathway. Tryptanthrin, a quinazoline derivative, was reported to sensitize resistant cells to doxorubicin by downregulation of MDR1 expression. This study aims to extendedly investigate the effect of tryptanthrin on the role of nontransporter-based genes in determining the MDR response in doxorubicin-resistant MCF-7 cells (MCF-7/adr). Results show that tryptanthrin downregulates GSTpi expression and reduces glutathione S-transferase (GST) activity, but has no effect on Topo II expression. Less production of GSTpi decomposes the protein-protein interactions of GSTpi and c-jun NH2-terminal kinase (JNK). The resulting free-form JNK undergoes phosphorylation upon elevated intracellular doxorubicin accumulation and subsequently activates JNK-mediated apoptosis. In conclusion, in addition to transporter pathway, tryptanthrin reverses MDR partly by modulating GSTpi-related pathway, a nontransporter pathway, in MCF-7/adr cells. It indicates that tryptanthrin may act as a potential chemoadjuvant agent through multiple targets.

Establishment of Paclitaxel-resistant Breast Cancer Cell Line and Nude Mice Models, and Underlying Multidrug Resistance Mechanisms in Vitro and in Vivo

“…We found that GST-π was apparently over-expressed in the MCF-7/TAX cell line which was associated with paclitaxel resistance, simultaneously, in in-vivo experiment, the expression of GST-π was also upregulated in tumor tissues of MDR nude mice model, these demonstrated that the paclitaxelinduced MDR was mediated by GST-π. In adriamycin resistant human myelogenous leukemia (K562/A02) cells and MCF-7 cells (MCF-7/adr), the MDR was both modulated by the alteration of GST-π and activity of GSTrelated enzymes as well (Yu et al, 2009;Song et al, 2011). In brief, it illustrated that the overexpression of GST-π was related to MDR in breast tumors and indicated poor prognosis to chemotherapy.…”

Benzo[b]tryptanthrin Inhibits MDR1, Topoisomerase Activity, and Reverses Adriamycin Resistance in Breast Cancer Cells

“…Additionally, the apoptotic markers, cleaved caspase-3 and cleaved PARP, [30] were monitored by Western blot analysis of HCT15 cells treat- Tryptanthrin was reported to have MDR-reversing effects through down-regulation of the MDR1 gene expression and protein synthesis. [31][32][33] Benzo[b]tryptanthrin has one more benzene ring attached to tryptanthrin (Figure 1). According to the previously reported results, benzo-annulation did not change the topo I inhibition activity, but noticeably enhanced the topo II inhibitory activity and cytotoxicity against HCT15 cells.…”

Modulatory Effects and Action Mechanisms of Tryptanthrin on Murine Myeloid Leukemia Cells

“…Tryptanthrin is a phytochemical found in the medicinal indigo plants such as Polygonum tinctorium and Isatis tinctoria. It was found to possess a wide spectrum of biological and pharmacological activities, including anti-microbial (7-9), immunomodulatory (11-13), antiinflammatory (13-15) and anti-tumor (16)(17)(18)(19) activities. A previous report has shown that tryptanthrin is able to induce both apoptosis and differentiation in the human leukemia HL-60 cells and U-937 cells in vitro (16), however, the underlying action mechanisms remain unclear.…”

“…Reaction mixture containing 40 units of RN ASE OUT TM recombinant ribonuclease inhibitor, 1 M-MLV first strand buffer, 0.5 mM of each dNTP, 10 mM DTT, 0.1g oligo (dT) [12][13][14][15][16][17][18] and 200 units of M-MLV reverse transcriptase was prepared, and 2 g RNA sample was added into 20 l reaction mixture. A negative control using DEPCtreated water instead of RNA sample was used to check if there was any contamination.…”

“…It was first isolated from Strobilanthes cusia as an anti-fungal agent against dermatophytes (7). Tryptanthrin is a weakly basic alkaloid and has been reported to have various biological and pharmacological activities, such as inhibitory activities against a variety of microorganisms and parasites (7)(8)(9)(10), immunomodulatory (11)(12)(13) and anti-inflammatory activities (13)(14)(15), and anti-tumor activity towards human leukemia and breast cancer cell lines in vitro (16)(17)(18). Moreover, the crude ethyl acetate extract and tryptanthrin extracted from the indigo plant Polygonum tinctorium have cancer chemopreventive activity by prevention of azoxymethane-induced intestinal tumor formation in F344 rats (19).…”