Genetic and phenotypic changes associated with the acquisition of tumorigenicity in human bladder cancer

There has been a general lack of human paired cell lines that both reproduc e the in vivo spectrum of tumor progression of bladder cancer and have some of the genetic changes associated with progression in human tumor tissue. T24, a cell line established from an invasive human transitional cell carci noma (TCC) of the bladder, has been used extensively in bladder cancer rese arch. However, a significant limitation of this cell line is its lack of tu morigenicity when injected into immunocompromised mice. This characteristic was used to our advantage as we sought to characterize T24T, a highly tumo rigenic variant that could then be used to elucidate the genes responsible for human bladder tumor progression. In culture, T24T has a faster doubling time, reaches a higher cell density in monolayer culture, and is more moti le than T24 at higher cell densities. T24T is able to form colonies in soft agar, whereas T24 is not, and expresses HRAS, a gene associated with incre ased aggressiveness in human TCC, at higher levels than T24. Most important ly, T24T forms solid tumors when injected subcutaneously in SCID mice both with and without Matrigel (Sigma, St. Louis, MO), whereas T24 does not. Cyt ogenetically, the 2 cell lines contain at least 5 shared structural anomali es, as determined by detailed karyotyping. Interestingly, T24T has acquired 4 new structural changes, 3 of which [add(10)(p12), i(10)(q10), -15] have been observed in loss of heterozygosity (LOH) studies of tumor progression in human TCC. It appears that the T24/T24T model may be an excellent tool f or the study of human TCC progression because of its relationship with know n karyotypic changes associated with human bladder cancer progression. We a re currently taking advantage of these paired cell lines to identify genes involved in human TCC progression. (C) 2000 Wiley-Liss, Inc.