In vitro differential sensitivity of melanomas to phenothiazines is based on the presence of codon 600 BRAF mutation.
The panel of 60 human cancer cell lines (the NCI-60) assembled by the National Cancer Institute for anticancer drug discovery is a widely used resource. We previously sequenced 24 cancer genes in those cell lines. Eleven of the genes were found to be mutated in three or more of the lines. Using a pharmacogenomic approach, we analyzed the relationship between drug activity and mutations in those 11 genes (APC, RB1, KRAS, NRAS, BRAF, PIK3CA, PTEN, STK11, MADH4, TP53, and CDKN2A). That analysis identified an association between mutation in BRAF and the antiproliferative potential of phenothiazine compounds. Phenothiazines have been used as antipsychotics and as adjunct antiemetics during cancer chemotherapy and more recently have been reported to have anticancer properties. However, to date, the anticancer mechanism of action of phenothiazines has not been elucidated. To follow up on the initial pharmacologic observations in the NCI-60 screen, we did pharmacologic experiments on 11 of the NCI-60 cell lines and, prospectively, on an additional 24 lines. The studies provide evidence that BRAF mutation (codon 600) in melanoma as opposed to RAS mutation is predictive of an increase in sensitivity to phenothiazines as determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt assay (Wilcoxon P = 0.007). That pattern of increased sensitivity to phenothiazines based on the presence of codon 600 BRAF mutation may be unique to melanomas, as we do not observe it in a panel of colorectal cancers. The findings reported here have potential implications for the use of phenothiazines in the treatment of V600E BRAF mutant melanoma.
Ikediobi
Ogechi N
ON
Genomics and Bioinformatics Group, Laboratory of Molecular Pharmacology, National Cancer Institute, Bethesda, Maryland, USA. ikediobio@pharmacy.ucsf.edu
Reimers
Mark
M
Durinck
Steffen
S
Blower
Paul E
PE
Futreal
Andrew P
AP
Stratton
Michael R
MR
Weinstein
John N
JN
D019943:Amino Acid Substitution; D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003062:Codon / Q000235:genetics*; D004354:Drug Screening Assays, Antitumor; D018698:Glutamic Acid / Q000235:genetics; D006801:Humans; D008545:Melanoma / Q000188:drug therapy* / Q000473:pathology; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D010640:Phenothiazines / Q000627:therapeutic use*; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D015203:Reproducibility of Results; D014633:Valine / Q000235:genetics; D018631:ras Proteins / Q000378:metabolism
D000970:Antineoplastic Agents; D003062:Codon; D050505:Mutant Proteins; D010640:Phenothiazines; D018698:Glutamic Acid; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf; D018631:ras Proteins; C031637:phenothiazine; D014633:Valine