Rodent model of reproductive tract leiomyomata. Establishment and characterization of tumor-derived cell lines.

Uterine myometrial tumors are the most commonly found gynecological neoplasm in women. The underlying causes of uterine leiomyomata are poorly understood, a result in part of the absence of a good animal model system in which to study these tumors. This report describes a novel rat model (Eker rat) in which spontaneous gynecological smooth muscle tumors arise with a high frequency. Leiomyomas are the predominant reproductive tract tumor that arise in these animals, although leiomyosarcomas have also been observed. Cell lines have been established from both the benign and malignant lesions. All of the lines express smooth muscle-specific actin, and leiomyoma-derived cell lines express desmin. Two of the cell lines are tumorigenic in nude mice, and the lines are variable for expression of estrogen and progesterone receptors. These lines are the first rodent tumor-derived lines to be established from leiomyomata and are the only lines available from a hereditary form of these tumors. Together with Eker rats that spontaneously develop leiomyomata, they constitute an in vitro/in vivo model system for gaining insights into the mechanism of transformation of uterine smooth muscle cells and the role of steroid hormones and hormone receptors in myometrial tumorigenesis.