Fig 5. MYC is required in cancer cell lines for cytotoxic killing by diMF.

(A) Lethal effect of diMF on a variety human cancer cells that overexpress MYC. Cells were treated with 0.1% DMSO (□) or 6 μM diMF ($■$) for 3 days. Cell viability was assayed by trypan blue exclusion assay. (B) Depletion of MYC in human cancer cell lines by RNAi. The indicated human cancer cell lines were transfected with either control siRNA (lanes 1, 3, 5, and 7) or MYC siRNA (lanes 2, 4, 6, and 8). Extracts were prepared 3 days after siRNA transfection and Western analysis used to examine levels of MYC and β-ACTIN protein. (C) Depletion of MYC alone fails to elicit cell death. The indicated cancer cell lines were transfected with either control siRNA or MYC siRNA. Cell viability was determined by the trypan blue exclusion assay 4 days after transfection. (D) Suppression of diMF cytoxicity by RNAi-depletion of MYC. The indicated cancer cell lines were transfected with either control siRNA or MYC siRNA and then exposed to 6 μM diMF starting 24-hours after transfection. Cell viability was determined by the trypan blue exclusion assay at day 4 after transfection. For data in A, C, and D, each data point represents the average of 3 independent experiments with data collected in triplicate (n = 9). Error bars represent the standard deviation. The pairwise comparisons were done using two tailed, unpaired t-tests. The symbol * indicates p<0.01 compared to DMSO for A and compared to control RNAi groups in C and D.