No abstract

Cells expressing oncogenic c-Myc are sensitized to TNF superfamily proteins. c-Myc also is an important factor in determining whether a cell is sensitive to TRAIL-induced apoptosis, and it is well established that the mitochondrial pathway is essential for apoptosis induced by c-Myc. We investigated whether c-Myc action on the mitochondria is required for TRAIL sensitivity and found that Myc sensitized cells with defective intrinsic signaling to TRAIL. TRAIL induced expression of antiapoptotic Mcl-1 and cIAP2 through activation of NF-kappaB. Both Myc and the multikinase inhibitor sorafenib block NF-kappaB. Combining sorafenib with TRAIL in vivo showed dramatic efficacy in TRAIL-resistant tumor xenografts. We propose the combination of TRAIL with sorafenib holds promise for further development.

Oxidation of endogenous macromolecules can generate electrophiles capable of forming mutagenic adducts in DNA. The lipid peroxidation product malondialdehyde, for example, reacts with DNA to form M 1 G, the mutagenic pyrimidopurinone adduct of deoxyguanosine. In addition to free radical attack of lipids, DNA is also continuously subjected to oxidative damage. Among the products of oxidative DNA damage are base propenals. We hypothesized that these structural analogs of malondialdehyde would react with DNA to form M 1 G. Consistent with this hypothesis, we detected a dose-dependent increase in M 1 G in DNA treated with calicheamicin and bleomycin, oxidizing agents known to produce base propenal. The hypothesis was proven when we determined that 9-(3-oxoprop-1-enyl)adenine gives rise to the M 1 G adduct with greater efficiency than malondialdehyde itself. The reactivity of base propenals to form M 1 G and their presence in the target DNA suggest that base propenals derived from oxidative DNA damage may contribute to the mutagenic burden of a cell.