EGFR isoforms and gene regulation in human endometrial cancer cells

Lina Albitar,Gavin Pickett,Jason A Wilken,Kimberly K Leslie,Nita J Maihle,Marilee Morgan

doi:10.1186/1476-4598-9-166

Abstract

BackgroundEpidermal growth factor (EGF) and its receptor (EGFR) constitute a principal growth-promoting pathway in endometrial cancer cells. Pre-clinical studies were undertaken to compare the expression of EGFR isoforms and the downstream effects of activating or blocking EGFR function in Ishikawa H cells, derived from a moderately differentiated type I endometrioid adenocarcinoma, or in Hec50co cells, derived from a poorly differentiated type II adenocarcinoma with papillary serous sub-differentiation.ResultsWe investigated whether EGFR mutations are present in the tyrosine kinase domain (exons 18-22) of EGFR and also whether EGFR isoforms are expressed in the Ishikawa H or Hec50co cell lines. Sequence of the EGFR tyrosine kinase domain proved to be wild type in both cell lines. While both cell lines expressed full-length EGFR (isoform A), EGFR and sEGFR (isoform D) were expressed at significantly lower levels in Hec50co cells compared to Ishikawa H cells. Analysis of gene expression following EGF vs. gefitinib treatment (a small molecule EGFR tyrosine kinase inhibitor) was performed. Early growth response 1, sphingosine kinase 2, dual specificity phosphatase 6, and glucocorticoid receptor DNA binding factor 1 are members of a cluster of genes downstream of EGFR that are differentially regulated by treatment with EGF compared to gefitinib in Ishikawa H cells, but not in Hec50co cells.ConclusionsType I Ishikawa H and type II Hec50co endometrial carcinoma cells both express EGFR and sEGFR, but differ markedly in their responsiveness to the EGFR inhibitor gefitinib. This difference is paralleled by differences in the expression of sEGFR and EGFR, as well as in their transcriptional response following treatment with either EGF or gefitinib. The small cluster of differently regulated genes reported here in these type I vs. type II endometrial cancer-derived cell lines may identify candidate biomarkers useful for predicting sensitivity to EGFR blockade.

Highlights

Epidermal growth factor (EGF) and its receptor (EGFR) constitute a principal growth-promoting pathway in endometrial cancer cells
epidermal growth factor receptor (EGFR) isoforms in Ishikawa H and Hec50co cells Detection of EGFR isoforms in Ishikawa H and Hec50co cells was conducted initially by Reverse transcriptase polymerase chain reaction (RT-PCR)
By these same methods the 3.0 kb sEGFR transcript appeared to be expressed at higher levels in the Hec50co cells relative to the Ishikawa H cells

Summary

Introduction

Epidermal growth factor (EGF) and its receptor (EGFR) constitute a principal growth-promoting pathway in endometrial cancer cells. New therapies using the rationale that cancer cells express or amplify certain signaling proteins, such as the epidermal growth factor receptor (EGFR) family of tyrosine kinase receptors, are under investigation, as described below. The well-differentiated Ishikawa H cell line responds more robustly to EGFR activation and is more sensitive to receptor inhibition compared to Hec50co cells, which are relatively resistant. Cell cycle regulatory events in response to the EGFR tyrosine kinase inhibitor gefitinib are blunted in Hec50co cells compared to Ishikawa H cells [13] The reason these poorly differentiated cells do not respond as well to inhibition of EGFR activity is an interesting question that may have bearing on resistance to tyrosine kinase inhibitors in the clinical setting

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