In vitro effects of the BH3 mimetic, (-)-gossypol, on head and neck squamous cell carcinoma cells.
OBJECTIVE
Bcl-xL overexpression is common in head and neck squamous cell carcinomas (HNSCC) and correlates with resistance to chemotherapy. Thus, a nonpeptidic, cell-permeable small molecule that mimics the BH3 domain of proapoptotic proteins may inhibit Bcl-xL function and have therapeutic potential for HNSCC by overcoming drug-resistance. (-)-Gossypol, the levorotatory isomer of a natural product isolated from cottonseeds and roots, was recently discovered to bind to the BH3 binding groove of Bcl-xL and Bcl-2.


METHODS
We investigated the in vitro effects of (-)-gossypol on HNSCC cell lines as well as on fibroblast and keratinocyte cultures by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell survival assays and assessed the results with respect to Bcl-2 family protein expression.


RESULTS
We observed dose-dependent growth inhibition of 10 HNSCC cell lines at biologically achievable doses (2.5-10 micromol/L). (-)-Gossypol doses required to inhibit the growth of human fibroblast cell lines by 50% were 2- to 10-fold higher than for HNSCC cell lines. To inhibit human oral keratinocyte growth by 50%, (-)-gossypol concentrations were 2-to 3-fold higher than for HNSCC cell lines.


CONCLUSIONS
There is a direct correlation between Bcl-xL-to-Bcl-xS ratios and sensitivity to (-)-gossypol. This agent induced apoptosis in a much higher proportion of cells with wild-type p53. Importantly, cell lines resistant to cisplatin were very sensitive to (-)-gossypol. These results demonstrate that (-)-gossypol has potent antitumor activity in HNSCC in vitro. This agent may be developed as a novel therapeutic agent for HNSCC, either alone or in combination with existing chemotherapeutic agents.
Oliver
Christopher L
CL
Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, Michigan 48109-0312, USA.
Bauer
Joshua A
JA
Wolter
Keith G
KG
Ubell
Mathew L
ML
Narayan
Ajita
A
O'Connell
Kathleen M
KM
Fisher
Susan G
SG
Wang
Shaomeng
S
Wu
Xihan
X
Ji
Min
M
Carey
Thomas E
TE
Bradford
Carol R
CR
D017209:Apoptosis; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D005347:Fibroblasts / Q000378:metabolism; D006072:Gossypol / Q000737:chemistry* / Q000494:pharmacology*; D006258:Head and Neck Neoplasms / Q000188:drug therapy* / Q000473:pathology; D006801:Humans; D020287:In Situ Nick-End Labeling; D020128:Inhibitory Concentration 50; D010446:Peptide Fragments / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051020:bcl-X Protein
C494811:BCL2L1 protein, human; C474007:Bax protein (53-86); D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D013778:Tetrazolium Salts; D013844:Thiazoles; D016159:Tumor Suppressor Protein p53; D051020:bcl-X Protein; C022616:thiazolyl blue; D006072:Gossypol