Indole-3-carbinol enhances doxorubicin-induced apoptosis through suppression of NF-B in B-cell precursor acute lymphoblastic leukemia cell line NALM-6

Doxorubicin is a chemotherapeutic agent still in widespread use in hematologic malignancies. A side effect of anthracyclines such as doxorubicin is the activation of nuclear factor-κB (NF-κB), a potent inducer of antiapoptotic genes, which may blunt the therapeutic efficacy of the drugs. In this study, the effect of indole -3-carbinol (I3C) on the activation NF-κB and the anti-apoptotic genes whose expression is regulated by NF-κB was assessed in NALM-6 cells. NALM-6 cells were preincubated with various concentrations of I3C and then treated with doxorubicin. Cellular DNA content assay and Annexin V-FITC staining were performed by flowcytometry for evaluation of apoptosis. For assessing the effect of I3C on the expression of XIAP, survivin, and nuclear p65 proteins, NALM-6 cells were pretreated with I3C and then incubated with doxorubicin. Whole-cell and nuclear extracts were prepared for Western blot analysis. A paired t - test was conducted to evaluate the results. DNA histogram analysis of NALM-6 cells indicates a combination of I3C with doxorubicin significantly escalated the percentages of sub-G1 population cells compared with doxorubicin -only treated group (P< 0.05). Annexin V-FITC staining also showed that cotreatment of NALM-6 cells with I3C and doxorubicin significantly increased the proportion of Annexin-V positive cells in comparison with the doxorubicin treated cells (P <0.05). The western blot analysis indicated I3C significantly inhibits both doxorubicin -induced nuclear translocation of p65 and the expression of doxorubicin-induced NF-κB target. Our results indicated that using natural non-toxic inhibitors of NF- κB such as I3C in combination with anthracyclines might be a rational combination therapy for BCP-ALL cells in which NF- κB is constitutively active.