ecdysterone and Adenocarcinoma

The p75(NTR) functions as a tumor suppressor in prostate epithelial cells, where its expression declines with progression to malignant cancer. Previously, we showed that treatment with the nonsteroidal anti-inflammatory drug, indomethacin, induced p75(NTR) expression in the T24 cancer cell line leading to p75(NTR)-mediated decreased survival. Utilizing the indole moiety of indomethacin as a pharmacophore, we identified in rank-order with least efficacy, ketorolac, etodolac, indomethacin, 5-methylindole-3-acetic acid, indole-3-carbinol, and 3,3'-diindolylmethane (DIM) exhibiting greatest activity for induction of p75(NTR) levels and inhibition of cell survival. Prostate (PC-3, DU-145) and bladder (T24) cancer cells were more sensitive to DIM induction of p75(NTR)-associated loss of survival than breast (MCF7) and fibroblast (3T3) cells. Transfection of the PC-3 prostate cell line with a dominant-negative form of p75(NTR) before DIM treatment significantly rescued cell survival demonstrating a cause and effect relationship between DIM induction of p75(NTR) levels and inhibition of survival. Furthermore, siRNA knockdown of the p38 mitogen-activated protein kinase (MAPK) protein prevented induction of p75(NTR) by DIM in the PC-3 prostate cell line. DIM treatment induced phosphorylation of p38 MAPK as early as within 1 minute. Collectively, we identify DIM as an indole capable of inducing p75(NTR)-dependent apoptosis via the p38 MAPK pathway in prostate cancer cells.

Topics: 3T3 Cells; Adenocarcinoma; Animals; Anti-Inflammatory Agents, Non-Steroidal; Anticarcinogenic Agents; Apoptosis; Brassicaceae; Breast Neoplasms; Cell Line, Tumor; Ecdysterone; Female; Humans; Indoles; Male; Mice; Neoplasm Proteins; Nerve Tissue Proteins; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Prostatic Neoplasms; Protein Processing, Post-Translational; Receptors, Nerve Growth Factor; Recombinant Fusion Proteins; RNA, Small Interfering; Signal Transduction; Transfection

The CDK inhibitor p21waf is a principal mediator of p53 function but can also be transactivated by many p53-independent stimuli leading to cell growth arrest or differentiation. In order to study the function of p21waf in a p53-deficient environment, we established an inducible expression of p21waf in the p53-null lung cancer cell line H1299, based on the muristerone-regulated system. Overexpression of p21waf led cells to growth arrest which after several days became irreversible and the arrested cells acquired a senescent phenotype as judged by cell shape, the senescence-associated beta-gal marker and inhibition of colony formation. The effect of p21waf overexpression, in the absence of p53, on the cytotoxicity caused by irradiation, doxorubicin and taxol was studied. Expression of p21waf provided protection against the cytotoxic effect of radiation and doxorubicin but not of taxol. These results are relevant to treatment of cancer when p53 is inactive.

Topics: Adenocarcinoma; Cellular Senescence; Cyclin-Dependent Kinase Inhibitor p21; Cyclin-Dependent Kinases; Cyclins; Doxorubicin; Drug Resistance; Ecdysterone; Gene Expression Regulation, Neoplastic; Humans; Lung Neoplasms; Radiation Tolerance; Tumor Cells, Cultured