Background: 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-&kappaB (NF-&kappaB), 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-&kappaB and the anti-apoptotic genes whose expression is regulated by NF-&kappaB was assessed in NALM-6 cells.

Materials and Methods: 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.

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-&kappaB target.

Conclusion: Our results indicated that using natural non-toxic inhibitors of NF-&kappaB such as I3C in combination with anthracyclines might be a rational combination therapy for BCP-ALL cells in which NF-&kappaB is constitutively active.