P-0014 - Insulin receptor activation confers resistance to lapatinib inhibition in HER2-positive gastric cancer

Date 28 June 2014
Event World GI 2014
Session Poster Session
Topics Anti-Cancer Agents & Biologic Therapy
Gastric Cancer
Translational Research
Presenter Lian Liu
Citation Annals of Oncology (2014) 25 (suppl_2): ii14-ii104. 10.1093/annonc/mdu165
Authors L. Liu1, Z. Zhang1, J. Li2
  • 1Fudan University Shanghai Cancer Center, Shanghai/CN
  • 2Fudan University Cancer Hospital, Shanghai/CN

Abstract

Introduction

HER2 gene amplification and/or over-expression was reported in about 20% gastric cancers. Anti-HER2 therapies (including monoclonal antibody trastuzumab and kinase inhibitor lapatinib) are effective in HER2 positive (HER2+) gastric cancer in both preclinical and clinical settings. However, only moderate efficacy was shown in clinical trials. It was reported that there was widespread potential for growth-factor-driven resistance to anti-cancer kinase inhibitors, including lapatinib. An shRNA screening of 80 cancer-related growth factors and corresponding receptors showed that insulin receptor (InsR) knockdown enhanced the toxicity of lapatinib in HER2 positive gastric cancer cells. We further examined the influence of InsR on resistance to lapatinib in HER2 positive gastric cancer cells.

Methods

Growth inhibition by lapatinib and rescue by insulin stimulation was examined in two HER2+ gastric cancer cell lines (NCI-N87 and SNU-216) by clonal assay and western blotting. OSI906 was an inhibitor of InsR. Synergy between HER2 and InsR was studied by combining lapatinib with OSI906 or with InsR knockdown using InsR specific siRNA. Flow cytometry was used to assess the effect of insulin stimulation on lapatinib induced apoptosis and G1 cell cycle arrest. Immunohistochemistry was done in tissue microarray of 152 gastric cancer samples to evaluate the expression profile of HER2, p-InsR and InsR.

Results

In NCI-N87 and SNU-216, treatment with lapatinib reduced phosphorylation of HER2, EGFR and downstream AKT, leading to decreased cell proliferation. Insulin stimulation could phosphate InsR and re-phosphate downstream AKT inhibited by lapatinib, conferring resistance to lapatinib and resumed cell proliferation. OSI906 could abrogate resistance induced by insulin stimulation by inhibit AKT phosphorylation. Combined treatment with lapatinib and OSI906 or InsR siRNA exhibited stronger inhibition than either treatment alone. Apoptosis and G1 cell cycle arrest induced by lapatinib could be reversed by insulin stimulation. Among 152 gastric cancer samples, HER2 overexpression was found in 27 tumors (17.8%). InsR expression was detected in 28 tumors (18.4%), respectively. Meanwhile, p-InsR was detected in 13 tumors (8.6%). There are significantly more InsR and p-InsR positive cases in patients with HER2+ tumors than in those with HER2‐negative tumors (InsR, 33.3% versus 15.2%, P < 0.05; p-IR 22.2% versus 5.6%, P < 0.05).

Conclusion

These data suggest InsR activation could confer resistance to lapatinib in HER2 positive gastric cancer through bypass activation of common downstream AKT signaling. Combinations of HER2 and InsR inhibitors would be an effective treatment strategy against gastric cancer expressing both HER2 and InsR.