alitretinoin and Colorectal-Neoplasms

The prognosis of advanced colorectal carcinoma (CC) is poor. Established chemotherapy shows only limited efficacy but significant side effects. We investigated how far a combination of tamoxifen (TAM), 9-cis-retinoic acid (CRA) and the fluoroquinolone ciprofloxacin (CIP) synergize to inhibit proliferation and promote apoptosis of CC cells in vitro. The CC cell lines LOVO, CC-531 and SW-403 were incubated with TAM, CRA and CIP (10(minus;4)-10(minus;6) M) as single agents and in combination. Cell proliferation was assessed by bromodeoxyuridin incorporation. Apoptosis was quantified immunohistochemically and by FACS analysis after staining with propidium iodide. Changes in the expression of caspase 3, bax, bcl-2 and p21cip/waf were assessed by quantitative Western blotting. CRA and TAM monotherapy was moderately effective. Their combination enhanced apoptosis from 60% to more than 80% in all cell types. Apoptosis was paralleled by inhibition of proliferation and further potentiated by addition of CIP. The combination effectively up-regulated caspase 3 and bax and down-regulated bcl-2 and p21cip/waf. Combinations of biomodulaters act synergistically to inhibit proliferation and promote apoptosis in CC cells. Due to their known safety profile, this justifies clinical trials for colorectal cancer using combinations of these biological response modifiers.

Topics: Alitretinoin; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; bcl-2-Associated X Protein; Blotting, Western; Bromodeoxyuridine; Carcinoma; Caspase 3; Caspases; Cell Division; Cell Line, Tumor; Cell Separation; Ciprofloxacin; Colonic Neoplasms; Colorectal Neoplasms; Cyclin-Dependent Kinase Inhibitor p21; Cyclins; DNA; Down-Regulation; Enzyme-Linked Immunosorbent Assay; Flow Cytometry; Humans; Immunohistochemistry; Indicators and Reagents; Kinetics; Prognosis; Propidium; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Tamoxifen; Time Factors; Tretinoin

Chemotherapy of advanced stages of colorectal carcinoma is unsatisfactory. Retinoids inhibit cell growth and induce apoptosis in a variety of human malignancies. We compared the effect of the synthetic retinoid adapalene (ADA) and 9-cis-retinoic acid (CRA) on carcinoma cell lines in vitro. Colon carcinoma cell lines CC-531, HT-29 and LOVO as well as human foreskin fibroblasts were exposed to different concentrations of ADA and CRA for 3-72 hr. Proliferation was assessed by BrdU incorporation and apoptosis by FACS analysis. Breakdown of DeltaPsi(m) was determined by JC-1 staining and activity of caspases 3 and 8, by a colorimetric assay. Quantitative Western blots were performed to detect changes in bax, bcl-2 and caspase-3. Both retinoic derivatives suppressed DNA synthesis and induced apoptosis in all tested cell lines time- and dose-dependently. While the natural retinoid CRA showed moderate antiproliferative and proapoptotic effects only at the highest concentration (10(-4) M), the synthetic retinoic ADA was significantly more effective, showing remarkable effects even at 10(-5) M. ADA and CRA disrupt DeltaPsi(m) and induce caspase-3 activity in responsive tumor cells. Quantitative Western blots showed a shift of the bax:bcl-2 ratio toward proapoptotic bax in ADA-treated cells. Our results clearly indicate the superiority of ADA compared to CRA. Therefore, we suggest that ADA may be far more suitable as an adjunctive therapeutic agent for treatment of colon cancer in vivo.

Topics: Adapalene; Alitretinoin; Antineoplastic Agents; Apoptosis; bcl-2-Associated X Protein; Caspase 3; Caspases; Cell Division; Colorectal Neoplasms; Humans; Naphthalenes; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Tretinoin; Tumor Cells, Cultured