p53 is the most frequently altered gene in human cancer and therefore represents an ideal target for cancer therapy. Several amino terminal p53-derived synthetic peptides were tested for their antiproliferative effects on breast cancer cell lines MDA-MB-468 (mutant p53), MCF-7 (overexpressed wild-type p53), and MDA-MB-157 (null p53). p53(15)Ant peptide representing the majority of the mouse double minute clone 2 binding site on p53 (amino acids 12-26) fused to the Drosophila carrier protein Antennapedia was the most effective. p53(15)Ant peptide induced rapid, nonapoptotic cell death resembling necrosis in all breast cancer cells; however, minimal cytotoxicity was observed in the nonmalignant breast epithelial cells MCF-10-2A and MCF-10F. Bioinformatic/biophysical analysis utilizing hydrophobic moment and secondary structure predictions as well as circular dichroism spectroscopy revealed an alpha-helical hydrophobic peptide structure with membrane disruptive potential. Based on these findings, p53(15)Ant peptide may be a novel peptide cancer therapeutic because it induces necrotic cell death and not apoptosis, which is uncommon in traditional cancer therapy.

The use of molecular biomarkers in epidemiologic studies has been advanced as a way to improve risk assessments for occupational and environmental exposures to toxic agents. We have used the detection of two cancer-related, molecular biomarkers of vinyl chloride exposure (mutant ras-p21 and mutant p53) to examine workers with equivalent cumulative exposures that would be above or below the current permissible workplace exposure limit for vinyl chloride for differences in the presence of these biomarkers. Workers with cumulative exposures above the current permissible exposure limit (equivalent of > 40 ppm-years) have a statistically significantly increased occurrence of both biomarkers in comparison to unexposed controls (p < 10(-3)). Although workers with cumulative exposures of < 10 ppm-years, i.e., well below the current limit, do not have a statistically significantly increased occurrence of these biomarkers (p > 0.05), workers with cumulative exposures of 10 to 40 ppm-years, i.e., still below the current limit, are found to have a statistically significant increase (p < 0.05). This suggests that the current exposure limit may not be adequately protective and illustrates the potential utility of molecular biomarkers in the refinement of risk assessments for toxic exposures.

We assessed the ability of cryptophycin 52 (LY355703), a novel antimicrotubule, to induce growth arrest and apoptosis in prostate cancer cell lines and investigated potential molecular mechanisms of death. LNCaP (androgen-dependent) and DU-145 (androgen-independent) cells accumulated in G(2)-M phase of the cell cycle and progressively acquired sub-G(0)-G(1) DNA content after 48 h of exposure to cryptophycin 52 (1-10 pM). Induction of apoptosis was confirmed by DNA ladder formation and detection of cytoplasmic nucleosomes. PC-3 (androgen-independent) cells were less responsive to cryptophycin 52-induced death. Apoptosis was associated with proteolytic processing and activation of the caspase-3-like subfamily proteins caspase-3 and caspase-7 and cleavage of the caspase substrate poly(ADP-ribose) polymerase. The pan-caspase inhibitor BOC-Asp(OMe)-fluoromethylketone effectively reduced cryptophycin 52-induced caspase-3-like protease activity and apoptosis in DU-145 cells. In contrast, BOC-Asp(OMe)-fluoromethylketone did not inhibit apoptosis induction in LNCaP cells by cryptophycin 52, even though both cryptophycin 52-induced caspase-3-like activity and staurosporine-induced death were blocked under identical conditions. Cryptophycin 52 induced phosphorylation of c-raf1 and bcl-2 and/or bcl-x(L) to comparable levels in all cell lines studied, and LNCaP cells overexpressing bcl-2 were more resistant to cryptophycin 52-induced apoptosis. Up-regulation of p53, bax, and p21 expression was induced in wild-type p53-expressing LNCaP cells only after cryptophycin 52 exposure. A sustained increase in c-Jun NH(2)-terminal kinase phosphorylation was also observed, the levels of which strongly correlated with apoptosis. We conclude that apoptosis induced by cryptophycin 52 in prostate cancer cells is androgen status independent, cell type specific for caspase requirement, modulated by the bcl-2 family, linked to but not dependent on p53, and strongly correlated with c-Jun NH(2)-terminal kinase phosphorylation. Cryptophycin 52-induced apoptosis in prostate cancer cells is therefore associated with multiple cell line-specific alterations in apoptosis-associated proteins and pathways.

Recent evidence suggests that the development of skin lesions from arsenic exposure may be mediated by increases in the expression of various growth factors, including transforming growth factor-alpha (TGFα). To investigate this association in humans, levels of total urinary arsenic and urinary TGFα were determined in 41 individuals with and without arsenic-associated skin lesions from Bangladesh who have chronic exposure to arsenic in their drinking water. After adjusting for age and sex, total urinary arsenic was found to be correlated with urinary TGFα (R 2 = 0.37; p < 0.0001), particularly in those individuals with arsenic-associated skin lesions (R 2 = 0.70; p < 0.0001). Stratification of the cohort into quartiles based on urinary TGFα levels demonstrated a trend of increasing odds ratios for the presence of arsenic-associated skin lesions with increasing urinary TGFα, although this was not significant (p = 0.15). These results suggest that urinary TGFα may be a useful biomarker for the epidermal effects of arsenic exposure.

Animal models suggest that dioxins have a negative effect on the level of expression of the epidermal growth factor receptor in cells. In vivo the level of expression in tissue of the epidermal growth factor receptor can be monitored by assaying for the extracellular domain in blood using an enzyme linked immunosorbent assay. We have determined the levels of the extracellular domain of the epidermal growth factor receptor in the plasma of 30 individuals: 10 with high blood dioxin levels (TEQ range = 318-673 ppt), 10 with medium blood dioxin levels (TEQ range = 16-60 ppt), and 10 with low background blood dioxin levels (TEQ range = 3-10 ppt). The levels of the epidermal growth factor receptor extracellular domain were lower in the high blood dioxin group (mean +/- SD = 45 +/- 26 fmol/ml) and the medium blood dioxin group (mean +/- SD = 41 +/- 23 fmol/ml) compared with the low blood dioxin group (mean +/- SD = 73 +/- 43 fmol/ml). These results suggest that the extracellular domain of the epidermal growth factor receptor may be a marker of the biological effect of dioxin exposure.