EGF and PDGF receptors in endometrial cancer

Abstract

Despite its relatively good long term survival compared to other cancers in the female, endometrial carcinoma still kills 20% of those women who develop the disease worldwide. Abnormalities in growth factor receptors have been shown to be important in both the prognosis and probably the malignant transformation of the two other oestrogen-dependent cancers, breast and ovary, which suggests that similar defects may occur in endometrial cancer. In this thesis, two of these growth factor receptors, those for the epidermal and platelet-derived growth factors, are studied in endometrial cancer at the levels of the gene and expression of the proteins on the cell surface, in an attempt to detect abnormalities which might be implicated in carcinogenesis. No amplification or rearrangement of the EGFR gene was detected on 13 tumour samples initially, or of the EGF, PDGF α- and β-subunit receptor genes subsequently on a mixture of tumour samples and cell from endometrial cancer cell lines. The size of the EGF and PDGF receptor proteins and the activation of their tyrosine kinase domains was assessed in an oestrogen responsive (Ishikawa) and an oestrogen independent (HEC-1-A) endometrial cancer cell line. Functioning receptors for EGF were demonstrated in both cell lines but no PDGF receptors were detected. EGF-binding studies were carried out and appropriate affinity constants and receptor numbers obtained in both cell lines. The growth of Ishikawa and HEC-1-A cells in culture was studied but because of the rapid growth of both lines in the absence of serum no meaningful mitogenic effects were shown by any growth factor or steroid. Phorbol ester and TGF-β inhibited the growth of HEC-1-A and Ishikawa cells, respectively. Of particular interest was that, despite the reported sensitivity of Ishikawa cells to oestrogen, no consistent stimulation was observed. The growth of both cell lines in the absence of serum suggested that the cells might be secreting growth factors and conditioned medium was obtained from long term, large scale cultures. The medium was concentrated and passed through a size exclusion column and the fractions assayed for DNA synthesis and competition for EGF-binding to Swiss 3T3 cells. No consistent effect on either of these assays was shown and no further investigation was undertaken.