title: Antitumor activity of HER1/EGFR tyrosine kinase inhibitor erlotinib, alone and in combination with CPT-11 (irinotecan) in human colorectal cancer xenograft models.
abstract: Erlotinib (Tarceva, OSI-774) is a potent, orally available, small-molecule inhibitor of HER1/EGFR tyrosine-kinase activity. In this study, the antitumor activity of erlotinib was evaluated in two human colorectal tumor xenograft models (LoVo and HCT116) in athymic mice. When erlotinib was administered as monotherapy, significant tumor growth inhibition (TGI) was seen in the LoVo model at both 100 mg/kg [TGI > 100%, P < 0.001; 6/10 partial regressions (PRs)] and 25 mg/kg (TGI = 79%, P < 0.001) doses. However, the HCT116 xenograft model was not responsive to any dose of erlotinib tested. The differential response to erlotinib of these two tumor models was not a result of differences in HER1/EGFR expression levels since these were similar in both cell lines. However, it was demonstrated that resistance to erlotinib in the HCT116 model may be a result of persistent activation of ERK in these tumors. Based on the single agent activity of erlotinib in LoVo tumors, a combination study with CPT-11 (Camptosar, irinotecan) was performed. CPT-11 at the optimal dose of 60 mg/kg or a lower dose of 15 mg/kg resulted in significant TGI (TGI > 100%, P < 0.001, and TGI = 93%, P < 0.001, respectively) in LoVo-bearing mice. Combination treatment with erlotinib (25 mg/kg) and CPT-11 (15 mg/kg) produced significantly greater antitumor activity (TGI > 100%, P < 0.001; 10/10 PRs) than either agent alone (P < 0.05), with no increase in toxicity. These data indicate that erlotinib can enhance the antitumor activity of CPT-11, without enhanced toxicity, in the LoVo human colorectal tumor xenograft model.
authors.affiliation: Department of Oncology, Hoffmann-La Roche Inc., 340 Kingsland Street, Nutley, NJ 07110, USA. Jianping.chen@roche.com
authors.forename: Jianping
authors.initials: J
authors.lastname: Chen
authors.forename: Melissa
authors.initials: M
authors.lastname: Smith
authors.forename: Kenneth
authors.initials: K
authors.lastname: Kolinsky
authors.forename: Violeta
authors.initials: V
authors.lastname: Adames
authors.forename: Nila
authors.initials: N
authors.lastname: Mehta
authors.forename: Luke
authors.initials: L
authors.lastname: Fritzky
authors.forename: Mohammad
authors.initials: M
authors.lastname: Rashed
authors.forename: Eric
authors.initials: E
authors.lastname: Wheeldon
authors.forename: Michael
authors.initials: M
authors.lastname: Linn
authors.forename: Brian
authors.initials: B
authors.lastname: Higgins
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use*; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000627:therapeutic use; D045744:Cell Line, Tumor; D017690:Cell Transplantation; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D066246:ErbB Receptors / Q000037:antagonists & inhibitors*; D000069347:Erlotinib Hydrochloride; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D000077146:Irinotecan; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D051058:Oncogene Protein v-akt / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use*; D011799:Quinazolines / Q000627:therapeutic use*; D014183:Transplantation, Heterologous
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D050760:Cyclin-Dependent Kinase Inhibitor p27; D000077146:Irinotecan; D000069347:Erlotinib Hydrochloride; D066246:ErbB Receptors; D051058:Oncogene Protein v-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D002166:Camptothecin