| Research Abstract |
Immunohistochemical analysis of estrogen receptor was carried out in salivary adenoid cystic carcinoma and ameloblastoma. In addition, we have tested the presence or absence the antitumor activity of the antiestrogen, tamoxifen, using the DMBA rat submandibular gland tumor model.
In these specimens, in agreement with the results seen with the breast cancer tissue used as positive control, strongly-stained cells, in which the ER-immunoreactivity was located in the cell nucleus, were detected. Accordingly, the cases were classed as ER-positive or ER-negative by scoring them on the basis of the visually estimated percentage of tumor cells showing positive nuclear staining, followed by an evaluation using a 10% cut-off level. In human tumors, ER immunoreactivity was positive in 5 (41.7% of total cases ; 3 female and 2 male) of 12 cases of salivary ACC, 11(50% of total cases ; 6 female and 5 male) of 22 cases of ameloblastoma, and one case (female) ot malignant ameloblastoma. The metastatic tumors, which had obtained from the patients with ER positive tumors, showed also immunoreactivity in a large proportion of the tumor cells.
In separate experiments, the antitumor effects of tamoxifen, an antiestrogen drug, on DMBA-induced ER-positive submandibular gland tumor in rats were studied. Submandibular gland tumors appeared from about 3 months after transplantation of DMBA pellet to female rats, and more than half of them were ER positive. Tamoxifen inhibited the growth of DMBA-induced ER-positive submandibular gland tumors in rats. Thus, this anti-tumor agent might have clinical potential for use against ER-positive salivary adenoid cystic carcinomas.
These results, showing ER expression in human salivary adenoid cystic carcinomas and malignant ameloblastoma, suggest that the presence of this receptor is one of the most useful tools for predicting the response to endocrine therapy for these tumors with poor prognosis
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