DEVELPOMEN TO NEW TREATMENT AND DETAILS OF THE GENETIC CHANGES UNDERLYING THE NEOPLASTIC TRANSFORMATION OF UTERINE SMOOTH MUSCLE

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Leiomyosarcoma constitutes only about 1.3% of uterine malignancies and one-quarter of uterine sarcomas, but it is important because it is an extremely malignant neoplasm with high rates of local recurrence and distant metastasis. The introduction of a new therapy for leiomyosarcoma of the uterus is urgently needed since neither radiotherapy nor chemotherapy is effective. However, the details of the genetic changes underlying the neoplastic transformation of uterine smooth muscle cells have not been fully characterized. Calponin hl, an actin-binding protein capable of inhibiting smooth muscle contraction, is a constitutive element of smooth muscle cells (SMCs). Among smooth muscle neoplasms of the uterus, however, leiomyosarcomas exhibit a reduced expression of calponin h1, as we reported previously. Therefore, the effect of calponin hl was assessed by transfecting its gene into leiomyosarcoma cells. A human calponin h1 cDNA construct was transfected into the human leiomyosarcoma cell l … More ines SKN and SK-LMS-lby electroporation. To confirm the gene transfer and expression of calponin h1 protein in the neomycin-resistant colonies, transfected cells were investigated by Southern blotting, RT-PCR, Western blotting and immunohistochemistry. We observed the morphology of calponin hl-transfected cells and evaluated their proliferative activity and the tumorigenicity by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay, anchorage-independent growth assay, and nude mice tumorigenicity assay. The cellular arrangement of calponin hl-transfected cells came to resemble that seen in cultured normal myometrial smooth muscle cells. The proliferation of human calponin h1-transfected leiomyosarcoma cells was inhibited to 69% of control in SK-LMS-1, and to 70% in SKN. In assays of anchorage-independent growth and nude mice tumorigenicity, growth and tumorigenicity were both significantly reduced in calponin h1-transfected leiomyosarcoma cells. Calponin h1 may function as a tumor suppressor in leiomyosarcoma. Clinically, induction of the normal differentiated phenotype by transferring the calponin h1 gene into poorly differentiated leiomyosarcoma cells may be of potential therapeutic value. Less