title: Bcl-x(L) confers multi-drug resistance in several squamous cell carcinoma cell lines.
abstract: Carboplatin (CBDCA) alone or in combination with irradiation and other chemotherapeutic agents has been used for the treatment of oral squamous carcinoma. However, there are some limitations for such therapy because of inherent or acquired resistance to CBDCA. To gain some insights into the association of CBDCA resistance with Bcl-2 family level or p53 status, we established eight carcinoma cell lines, consisting of two resistant (MIT8, MIT16), two sensitive (MIT6, MIT7), and four intermediate lines. All of the five cell lines with p53 mutation belonged to the resistant approximately intermediate group, whereas two of three other lines with wild-type p53 were in the sensitive group. Interestingly, both of the two resistant cell lines showed elevated levels of Bcl-x(L), almost double that of sensitive line (MIL5), whereas either Bcl-2 or Bax-alpha level did not correlate with the CBDCA-resistance. To further verify the association between the Bcl-x(L) level and the drug resistance, two transformants (x(L)-3, x(L)-6) overexpressing Bcl-x(L) in the CBDCA-sensitive cell line MIT7 were established using the gene transfer method. Both clones showed resistance to multiple chemotherapeutic agents, including CBDCA, actinomycin D, etoposide, and mitomycin C. Moreover, MIT8 and MT16 also displayed cross-resistance to these agents. These findings suggest that Bcl-x(L) may function as one of the key components conferring multiple drug-resistance in squamous cell carcinomas.
authors.affiliation: Department of Oral & Maxillofacial-Surgery, Tokyo Medical University Hospital, 6-7-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Noutomi
authors.forename: H
authors.initials: H
authors.lastname: Chiba
authors.forename: M
authors.initials: M
authors.lastname: Itoh
authors.forename: H
authors.initials: H
authors.lastname: Toyota
authors.forename: J
authors.initials: J
authors.lastname: Mizuguchi
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D015153:Blotting, Western; D016190:Carboplatin / Q000627:therapeutic use*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004354:Drug Screening Assays, Antitumor / Q000379:methods; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D009062:Mouth Neoplasms / Q000188:drug therapy* / Q000235:genetics; D018807:Polymorphism, Single-Stranded Conformational; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014162:Transfection; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein
chemical_list: D000970:Antineoplastic Agents; C494811:BCL2L1 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D016190:Carboplatin