title: Combination chemotherapy of paclitaxel and cisplatin induces apoptosis with Bcl-2 phosphorylation in a cisplatin-resistant human epidermoid carcinoma cell line.
abstract: OBJECTIVE
  Paclitaxel (Taxol, TXL) is an antimicrotubule agent that stabilizes microtubules, arrests the cell cycle at the G(2)/M phase and induces apoptosis. In vitro drug sensitivity assays have shown that the combination of TXL and CDDP is more effective in CDDP-resistant ovarian carcinoma cell lines, with different cytotoxicities depending on the sequence of drug exposure. CDDP also shows poor results in human epidermoid carcinoma particularly of the head and neck region.
  
  
  METHODS
  We investigated the effects and the molecular mechanisms of combination chemotherapy with TXL and CDDP in the CDDP-resistant cell line A431/CDDP2, and in its parental human epidermoid cell line A431/P. Drug sensitivity was determined using the MTS assay and cell cycle perturbation was analyzed using flow cytometry. DNA fragmentation was then analyzed and the protein levels of caspase-3 and Bcl-2, and phosphorylated of Bcl-2 were determined by Western blotting.
  
  
  RESULTS
  In the drug sensitivity assay, exposure to CDDP prior to TXL was more effective than exposure TXL prior to CDDP in A431/P cells. In A431/CDDP2 cells, exposure to TXL prior to CDDP was more effective than exposure to CDDP prior to TXL. Exposure to TXL arrested the cells in the G(2)/M phase in both cell lines. In A431/CDDP2 cells, exposure to TXL prior to CDDP arrested the cells in the G(2)/M phase, an effect caused by either CDDP or TXL. Analysis of DNA fragmentation showed similar results to the drug sensitivity assay. Expression of caspase-3 protein active form was detected following exposure to TXL only and to the TXL/CDDP combination in both A431/P and A431/CDDP2 cells, but phosphorylation of Bcl-2 protein was detected only following exposure to TXL and only in A431/CDDP2 cells.
  
  
  CONCLUSIONS
  These results indicate that exposure to TXL prior to CDDP plays a key role in circumventing CDDP resistance by phosphorylating Bcl-2 protein in the human epidermoid carcinoma cell line A431/CDDP2.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Biopathological Science, Graduate School of Medicine and Dentistry, Okayama University Graduate Schools, 2-5-1 Shikata-Cho, 700-8525, Okayama, Japan. ssawada@md.okayama-u.ac.jp
authors.forename: Seiji
authors.initials: S
authors.lastname: Sawada
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mese
authors.forename: Akira
authors.initials: A
authors.lastname: Sasaki
authors.forename: Norie
authors.initials: N
authors.lastname: Yoshioka
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Matsumura
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000473:pathology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology*; D053938:DNA Fragmentation; D019008:Drug Resistance, Neoplasm; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D017239:Paclitaxel / Q000494:pharmacology*; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D019253:Proto-Oncogene Proteins c-bcl-2; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D017239:Paclitaxel; D002945:Cisplatin