title: Chemoresistant colorectal cancer cells, the cancer stem cell phenotype, and increased sensitivity to insulin-like growth factor-I receptor inhibition.
abstract: 5-Fluorouracil (5FU) and oxaliplatin are standard therapy for metastatic colorectal cancer (CRC), but the development of chemoresistance is inevitable. Because cancer stem cells (CSC) are hypothesized to be chemoresistant, we investigated CSC properties in newly developed chemoresistant CRC cell lines and sought to identify targets for therapy. The human CRC cell line HT29 was exposed to increasing doses of 5FU (HT29/5FU-R) or oxaliplatin (HT29/OxR) to achieve resistance at clinically relevant doses. Western blotting and flow cytometry were done to determine molecular alterations. The insulin-like growth factor-I receptor (IGF-IR) monoclonal antibody (mAb) AVE-1642 was used to inhibit signaling in vitro and in vivo using murine xenograft models. HT29/5FU-R and HT29/OxR showed 16- to 30-fold enrichment of CD133(+) cells and 2-fold enrichment of CD44(+) cells (putative CRC CSC markers). Resistant cells were enriched 5- to 22-fold for double-positive (CD133(+)/CD44(+)) cells. Consistent with the CSC phenotype, resistant cells exhibited a decrease in cellular proliferation in vitro (47-59%; P < 0.05). Phosphorylated and total IGF-IR levels were increased in resistant cell lines. HT29/5FU-R and HT29/OxR cells were approximately 5-fold more responsive to IGF-IR inhibition relative to parental cells (P < 0.01) in vitro. Tumors derived from HT29/OxR cells showed significantly greater growth inhibition in response to an IGF-IR mAb than did parental cells (P < 0.05). Chemoresistant CRC cells are enriched for CSC markers and the CSC phenotype. Chemotherapy-induced IGF-IR activation provided for enhanced sensitivity to IGF-IR-targeted therapy. Identification of CSC targets presents a novel therapeutic approach in this disease.
authors.affiliation: Department of Surgical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77230-1402, USA.
authors.forename: Nikolaos A
authors.initials: NA
authors.lastname: Dallas
authors.forename: Ling
authors.initials: L
authors.lastname: Xia
authors.forename: Fan
authors.initials: F
authors.lastname: Fan
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gray
authors.forename: Puja
authors.initials: P
authors.lastname: Gaur
authors.forename: George
authors.initials: G
authors.lastname: van Buren
authors.forename: Shaija
authors.initials: S
authors.lastname: Samuel
authors.forename: Michael P
authors.initials: MP
authors.lastname: Kim
authors.forename: Sherry J
authors.initials: SJ
authors.lastname: Lim
authors.forename: Lee M
authors.initials: LM
authors.lastname: Ellis
mesh_terms: D000071916:AC133 Antigen; D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D017209:Apoptosis / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000473:pathology; D019008:Drug Resistance, Neoplasm; D005472:Fluorouracil / Q000494:pharmacology; D006023:Glycoproteins / Q000032:analysis; D019073:HT29 Cells; D006801:Humans; D018960:Hyaluronan Receptors / Q000032:analysis; D008297:Male; D051379:Mice; D014411:Neoplastic Stem Cells / Q000187:drug effects*; D010455:Peptides / Q000032:analysis; D010641:Phenotype; D017526:Receptor, IGF Type 1 / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000502:physiology; D015398:Signal Transduction
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; C497483:CD44 protein, human; D006023:Glycoproteins; D018960:Hyaluronan Receptors; C000606023:PROM1 protein, human; D010455:Peptides; C000606024:Prom1 protein, mouse; D017526:Receptor, IGF Type 1; D005472:Fluorouracil