Abstract
NVP-AEW541, a specific ATP-competitive inhibitor of the insulin-like growth factor-1 receptor (IGF1R) tyrosine kinase, has been reported to interfere with tumor growth in various tumor transplantation models. We have assessed the efficacy of NVP-AEW541 in repressing tumor growth and tumor progression in the Rip1Tag2 transgenic mouse model of pancreatic β-cell carcinogenesis. In addition, we have tested NVP-AEW541 in Rip1Tag2;RipIGF1R double-transgenic mice which show accelerated tumor growth and increased tumor malignancy compared with Rip1Tag2 single-transgenic mice. Previously, we have shown that high levels of IGF-2, a high-affinity ligand for IGF1R, are required for Rip1Tag2 tumor cell survival and tumor growth. Unexpectedly, treatment of Rip1Tag2 mice with NVP-AEW541 in prevention and intervention trials neither did affect tumor growth nor tumor cell proliferation and apoptosis. Yet, it significantly repressed progression to tumor malignancy, that is, the rate of the transition from differentiated adenoma to invasive carcinoma. Treatment of Rip1Tag2;RipIGF1R double-transgenic mice resulted in moderately reduced tumor volumes and increased rates of tumor cell apoptosis. Sustained expression of IGF-2 and of the IGF-2-binding form of insulin receptor (IR-A) in tumor cells suggests a compensatory role of IR-A upon IGF1R blockade. The results indicate that inhibition of IGF1R alone is not sufficient to efficiently block insulinoma growth and imply an overlapping role of IGF1R and insulin receptor in executing mitogenic and survival stimuli elicited by IGF-2. The reduction of tumor invasion upon IGF1R blockade on the other hand indicates a critical function of IGF1R signaling for the acquisition of a malignant phenotype.
Highlights
Mounting evidence from cell culture experiments, animal models, and correlative studies in patients with cancer clearly show that the insulin-like growth factor (IGF)/IGF-1 receptor (IGF1R) system plays a central role in many cancer types [1, 2]
In repressing proliferation and survival of insulinoma cells, we first tested the ability of AEW541 to induce apoptosis in the cultured insulinoma cell lines bT2 and bT-IGF1R, which have been derived from tumors of RT2 and RT2; RipIGF1R mice, respectively
Much lower levels of AEW541 are required to reduce viability of bT-IGF1R cells compared with bT2 cells (Fig. 1B), as determined by DNA integrity measurements using propidium iodide (PI), indicating a stringent dependence of bT-IGF1R cells on functional IGF1R signaling
Summary
Mounting evidence from cell culture experiments, animal models, and correlative studies in patients with cancer clearly show that the insulin-like growth factor (IGF)/IGF-1 receptor (IGF1R) system plays a central role in many cancer types [1, 2]. Interfering with this system has emerged as a promising strategy to treat a variety of human cancers [3,4,5]. IGFs (IGF-1 and IGF-2) exert their biologic function mainly by Authors' Affiliations: 1Institute of Biochemistry and Genetics, Department of Biomedicine, University of Basel; and 2Disease Area Oncology, Novartis Institutes for BioMedical Research, Novartis Pharma AG, Basel, Switzerland. García-Echeverría: Oncology Drug Discovery and Preclinical Research, Sanofi, Vitry-sur-Seine, France
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