The overall objective of this study is to determine what genetic loci are responsible for the initiation and malignant progression of carcinoma of the urinary bladder. Finding such sites would be useful for understanding carcinogenesis at the DNA level, and for monitoring TCC clinically. At the outset, bladder carcinoma apparently arises from areas of hyperplasia, showing increasingly autonomous growth and tissue disorganization. These are typically accompanied at the genetic level by aberrant expression of oncogenes such as ras and myc, and by genomic alterations frequently manifested as karyotypic markers. However, it is difficult to relate these genetic changes to specific clinical properties of interest such as recurrence rates and metastatic ability due to the overall complexity of transformation. To investigate these issues, we will use a rodent urothelial in vivo/in vitro model system which reproduces many features of human TCC. We characterized transformation markers in a series of cell lines generated from bladders of rats chronically treated with carcinogens. Most of the lines displayed high levels of Ha-ras and c-myc gene products extended longevity in culture and anchorage independent growth. But not all were tumorigenic in athymic mice, suggesting that oncogene overexpression may occur early en route to TCC, but that tumorigenicity requires other events as well. In the proposal studies, we will investigate the association of ras, myc and other (proto)oncogenes in the initiation and progression of TCC. First, we will try to determine whether c-myc and Ha-ras overexpression might be due to activating changes in their genes, or increased mRNA stability. Second, we will introduce ras or myc oncogenes into normal urothelial cells to determine the direct phenotypic consequences of their expression in vitro and in vivo. Third, to see whether the activation of certain oncogenes is associated with specific stages of TCC, we will treat rats with carcinogens for timed intervals and determine the temporal sequence in bladder lesions of oncogene overexpression, extended longevity in vitro, anchorage independent growth and tumorigenicity. Parallel experiments will be performed with human bladder material where possible.
