Expression of the ets-1 proto-oncogene in human breast carcinoma: differential expression with histological grading and growth pattern.

The proto-oncogene, ets-1, is a transcription factor known to control the expression of a number of genes and has been postulated to play a role in cell growth, differentiation and tumour invasion. We examined 137 cases of breast carcinoma by immunohistochemistry and compared the degree of Ets-1 expression among the different histological types of invasive carcinomas. Ets-1 was not expressed in the normal breast epithelium nor in noninvasive carcinomas. Among the 137 breast carcinoma cases, 104 (83.2%) showed positive staining for the Ets-1 protein. Histologically, invasive ductal carcinomas expressed immunopositivity with intense staining for Ets-1 in the tumour cells. Ets-1 expression correlated with Bloom-Richardson grading in invasive ductal carcinoma (p<0.01). However, there was no correlation between Ets-1 expression and lymph node metastasis, "t" classification or TNM staging. In situ hybridization confirmed the presence of Ets-1 mRNA in breast carcinomas. The expression of Ets-1 mRNA was detected in two of three different kinds of cultured human breast carcinoma cell lines and one of three human breast carcinoma tissues by the reverse transcription polymerase chain reaction method. These findings suggest that ets-1 is overexpressed in ductal cells of the breast that have undergone malignant conversion and that ets-1 is one of the factors associated with tumour growth and histological differentiation of breast carcinomas.