Mechanisms of acquired resistance to insulin-like growth factor 1 receptor inhibitor in MCF-7 breast cancer cell line.

Abstract

The purpose of this study was to clarify the mechanism of acquired resistance to the insulin-like growth factor-1 receptor (IGF-1R) tyrosine kinase inhibitor NVP-AEW541. We developed an acquired resistant model by continuously exposing MCF-7 breast cancer cells to NVP-AEW541 (MCF-7-NR). MCF-7 and MCF-7-NR were comparatively analyzed for cell signaling and cell growth. While phosphorylation of Akt was completely inhibited by 3 μM NVP-AEW541 in both MCF-7 and MCF-7-NR, phosphorylation of S6K remained high only in MCF-7-NR, suggesting a disconnection between Akt and S6K in MCF-7-NR. Consistently, the mTOR inhibitor everolimus inhibited phosphorylation of S6K and cell growth equally in both lines. Screening of both lines for phosphorylation of 42 receptor tyrosine kinases with and without NVP-AEW541 showed that Tyro3 phosphorylation remained high only in MCF-7-NR. Protein expression of Tyro3 was found to be higher in MCF-7-NR than in MCF-7. Gene silencing of Tyro3 using siRNA resulted in reduced cell growth and cyclin D1 expression in both lines. While Tyro3 expression was inhibited by NVP-AEW541 and everolimus in MCF-7, it was reduced only by everolimus in MCF-7-NR. These findings suggested that cyclin D1 expression was regulated in a S6K/Tyro3-dependent manner in both MCF-7 and MCF-7-NR, and that the disconnection between IGF-1R/Akt and S6K may enable MCF-7-NR to keep cyclin D1 high in the presence of NVP-AEW541. In summary, acquired resistance to NVP-AEW541 appears to result from IGF-1R/Akt-independent activation of S6K and expression of Tyro3 and cyclin D1.

• Authors: Roudy Chiminch Ekyalongo, Toru Mukohara, Yu Kataoka, Yohei Funakoshi, Hideo Tomioka, Naomi Kiyota, Yutaka Fujiwara, Hironobu Minami
• Journal: Investigational new drugs (Invest New Drugs) Vol. 31 Issue 2 Pg. 293-303 (Apr 2013) ISSN: 1573-0646 [Electronic] United States
• PMID: 22828916 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Immunosuppressive Agents
• NVP-AEW541
• Pyrimidines
• Pyrroles
• Everolimus
• Receptor, IGF Type 1
• Ribosomal Protein S6 Kinases
• Sirolimus

Topics

• Antineoplastic Combined Chemotherapy Protocols
• Apoptosis (drug effects)
• Blotting, Western
• Breast Neoplasms (drug therapy, metabolism, pathology)
• Cell Proliferation (drug effects)
• Drug Resistance, Neoplasm (drug effects)
• Drug Synergism
• Everolimus
• Female
• Humans
• Immunosuppressive Agents (pharmacology)
• Phosphorylation (drug effects)
• Pyrimidines (pharmacology)
• Pyrroles (pharmacology)
• Receptor, IGF Type 1 (antagonists & inhibitors, metabolism)
• Ribosomal Protein S6 Kinases (antagonists & inhibitors, metabolism)
• Sirolimus (analogs & derivatives, pharmacology)
• Tumor Cells, Cultured