title: Effect of simvastatin on cetuximab resistance in human colorectal cancer with KRAS mutations.
abstract: BACKGROUND
  Metastatic colorectal cancer (CRC) patients with v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations are resistant to treatment with cetuximab, a monoclonal antibody that targets the epidermal growth factor receptor. Statins have reported antitumor activity, but it is unknown whether simvastatin can reverse cetuximab resistance in KRAS mutant CRC.
  
  
  METHODS
  Human CRC cell lines with KRAS mutations (LS153, LS174T, DLD1, LoVo, SW403, SW480, SNU175, and LS1034) or with v-raf murine sarcoma viral oncogene homolog B1 (BRAF) mutations (DiFi, SW48, HT29, and RKO) were used to test the effect of cetuximab, simvastatin, and cetuximab plus simvastatin on cell proliferation and apoptosis in vitro. Because BRAF(V600E) mutant may be responsible for cetuximab resistance in KRAS wild-type cells, we measured the growth of xenograft tumors originating from KRAS mutant and BRAF mutant cells in mice treated with cetuximab alone or plus simvastatin (n = 5 mice per treatment group). We used immunoblot assays to study RAS-regulated activation of BRAF protein after simvastatin treatment. All statistical tests were two-sided.
  
  
  RESULTS
  Addition of simvastatin (0.2 μM) to cetuximab (0.03-1.0 μM) reduced cell proliferation of KRAS mutant (P < .001) but not of BRAF mutant CRC cells in vitro. Treatment of KRAS mutant cells with simvastatin reduced BRAF activity and induced apoptosis. Treatment with cetuximab and simvastatin reduced the growth of xenograft tumors originating from KRAS mutant cells compared with cetuximab alone (eg, for tumors originating from DLD1 cells, cetuximab vs cetuximab + simvastatin, mean tumor volume = 49.4 vs 20.2 cm(3), mean difference = 29.2 cm(3), 95% confidence interval = 19.7 to 38.5, P < .001); treatment with cetuximab alone or in combination with simvastatin had no effect on the growth of BRAF mutant tumors.
  
  
  CONCLUSIONS
  Simvastatin may overcome cetuximab resistance in colon cancer cells with KRAS mutations by modulating BRAF activity and inducing apoptosis.
authors.affiliation: Division of Hematology-Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul 135-710, Korea.
authors.forename: Jeeyun
authors.initials: J
authors.lastname: Lee
authors.forename: Inkyoung
authors.initials: I
authors.lastname: Lee
authors.forename: Boram
authors.initials: B
authors.lastname: Han
authors.forename: Joon Oh
authors.initials: JO
authors.lastname: Park
authors.forename: Jiryeon
authors.initials: J
authors.lastname: Jang
authors.forename: Chaehwa
authors.initials: C
authors.lastname: Park
authors.forename: Won Ki
authors.initials: WK
authors.lastname: Kang
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D000068818:Cetuximab; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D005260:Female; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D010957:Plasmids; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras); D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019821:Simvastatin / Q000494:pharmacology; D014162:Transfection; D014183:Transplantation, Heterologous; D018631:ras Proteins / Q000235:genetics*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D019821:Simvastatin; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; D000068818:Cetuximab