Growth factor expression in normal, benign, and malignant breast tissue.

Several oncogenes seem to encode certain growth factors that may play a part in regulating cell growth in tumours. To assess whether such factors are synthesised endogenously by tumour cells the amounts of messenger RNA for several growth factors known to be synthesised by cancer cells of the breast in vitro were examined in biopsy specimens from 52 malignant and 15 non-malignant tumours of the breast and four samples of normal breast. Transforming growth factor beta messenger RNA was significantly more abundant in breast cancers (32 of 42 (76%) having appreciable amounts) than non-malignant breast tissue (five of 13 (38%) having similar amounts). Transcripts for both transforming growth factor alpha and its receptor, epidermal growth factor receptor, were found more commonly in carcinomas that were negative for oestrogen receptor (64% and 87%, respectively) than in those that were positive (27% and 30%, respectively). Insulin-like growth factor II messenger RNA was present in all 15 samples of non-malignant tissue but was found (in considerably lower amounts) in only 11 of 21 (52%) carcinomas. Epidermal growth factor receptor was also found in all non-malignant breast tissues, compared with 19 of 45 (42%) carcinomas. Platelet derived growth factor A and B chain transcripts coexisted in all normal and benign tissue and most carcinomas. This differing pattern of expression growth factors in tissue from malignant tumours compared with benign tumours and normal breast tissue suggests that some growth factors, particularly transforming growth factors alpha and beta, may have an important role in controlling growth of human breast cancers, particularly those that are hormone independent.