GROWTH FACTORS AND HUMAN BLADDER CANCER

我们项目的长期目标是研究生长因子的作用

Our project's long-term goal is to investigate the role of growth factors (GFs) and their receptors in normal urothelial homeostasis, and in the induction and maintenance of urothelial malignancy. The bladder's epithelium is in the unique position of being perpetually bathed by pools of naturally occurring mitogens such as epidermal growth factor (EGF), which are excreted in the urine in very high concentrations and in biologically active forms. The continuous exposure of urothelial cells to such substances may result in continuous stimulation, continuous cell division, and eventual loss of growth control. Thus, it is likely that the study of tumor and normal GFs will elucidate the processes which induce and maintain transitional cell carcinoma (TCC). We are: (1) examining growth factor receptors on normal and malignant transitional epithelium; (2) detecting and characterizing GFs produced by human TCC (TCC-GFs); and (3) assessing effects of TCC-GFs and other GFs on normal and malignant urothelium and selected other cells. Initial work is being performed in vitro. Direct and competitive binding assays with radioisotope-labeled ligands are being used to detect and quantitate receptors for EGF on malignant and normal transitional epithelial cells, and to study their binding kinetics. To examine the receptors on fresh urothelium and correlate their distribution on TCC with tumor stage, grade, and prognosis, autoradiography is being utilized. Factor production has been documented by detecting growth-stimulating activity in the culture supernates from TCC cell lines growing in serum-free medium, on the producing cells themselves, other TCC cells, and nontransformed targets. Preliminary sizing has already been performed, and at least two different fractions of growth-stimulating activity have been documented. We plan to characterize other selected chemical and physical properties which will allow us to compare these "activities" with other GFs, including EGF. Active fractions have been tested for their ability to stimulate the growth of normal fibroblasts in soft agar, and these two fractions do contain transforming ability. Biochemical properties of normal growth factors (particularly EGF) and TCC-GFs will be tested, including ability to stimulate DNA synthesis, induce ornithine decarboxylase (ODC) activity, and alter the polyamine requirements of target cells. In addition, because of the recent commercial availability of human EGF, it will now be possible to compare its binding and effects to that of standard (murine) EGF on human urothelial and TCC targets. (J)