Colorectal Cancer
Copyright ©2006 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Sep 21, 2006; 12(35): 5635-5643
Published online Sep 21, 2006. doi: 10.3748/wjg.v12.i35.5635
Tyrosine kinase of insulin-like growth factor receptor as target for novel treatment and prevention strategies of colorectal cancer
Michael Höpfner, Andreas P Sutter, Alexander Huether, Viola Baradari, Hans Scherübl
Michael Höpfner, Andreas P Sutter, Alexander Huether, Viola Baradari, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Medical Clinic I, Gastroenterology/Infectious Diseases/Rheumatology, Berlin, Germany
Hans Scherübl, Klinik für Gastroenterologie und Gastrointestinale Onkologie, Vivantes-Klinikum Am Urban, Dieffenbachstr. 1, Berlin 10967, Germany
Author contributions: All authors contributed equally to the work.
Correspondence to: Professor Hans Scherübl, Klinik für Gastroenterologie und Gastrointestinale Onkologie, Vivantes-Klinikum Am Urban, Dieffenbachstr. 1, Berlin 10967, Germany. hans.scheruebl@vivantes.de
Telephone: +49-30-69725201 Fax: +49-30-69725205
Received: October 24, 2005
Revised: February 7, 2006
Accepted: February 18, 2006
Published online: September 21, 2006
Abstract

AIM: To investigate the antineoplastic potency of the novel insulin-like growth factor 1 receptor (IGF-1R) tyrosine kinase inhibitor (TKI) NVP-AEW541 in cell lines and primary cell cultures of human colorectal cancer (CRC).

METHODS: Cells of primary colorectal carcinomas were from 8 patients. Immunostaining and crystal violet staining were used for analysis of growth factor receptor protein expression and detection of cell number changes, respectively. Cytotoxicity was determined by measuring the release of the cytoplasmic enzyme lactate dehydrogenase (LDH). The proportion of apoptotic cells was determined by quantifying the percentage of sub-G1 (hypodiploid) cells. Cell cycle status reflected by the DNA content of the nuclei was detected by flow cytometry.

RESULTS: NVP-AEW541 dose-dependently inhibited the proliferation of colorectal carcinoma cell lines and primary cell cultures by inducing apoptosis and cell cycle arrest. Apoptosis was characterized by caspase-3 activation and nuclear degradation. Cell cycle was arrested at the G1/S checkpoint. The NVP-AEW541-mediated cell cycle-related signaling involved the inactivation of Akt and extracellular signal-regulated kinase (ERK) 1/2, the upregulation of the cyclin-dependent kinase inhibitors p21Waf1/CIP1 and p27Kip1, and the downregulation of the cell cycle promoter cyclin D1. Moreover, BAX was upregulated during NVP-AEW541-induced apoptosis, whereas Bcl-2 was downregulated. Measurement of LDH release showed that the antineoplastic effect of NVP-AEW541 was not due to general cytotoxicity of the compound. However, augmented antineoplastic effects were observed in combination treatments of NVP-AEW541 with either 5-FU, or the EGFR-antibody cetuximab, or the HMG-CoA-reductase inhibitor fluvastatin.

CONCLUSION: IGF-1R-TK inhibition is a promising novel approach for either mono- or combination treatment strategies of colorectal carcinoma and even for CRC chemoprevention.

Keywords: Insulin-like growth factor receptor; Tyrosine kinase; Colorectal cancer; Apoptosis; Cell cycle arrest