Tr. Yeager et Ca. Reznikoff, METHOTREXATE RESISTANCE IN HUMAN UROEPITHELIAL CELLS WITH P53 ALTERATIONS, The Journal of urology, 159(2), 1998, pp. 581-585
Purpose: Bladder cancers are frequently treated with combination chemo
therapy that includes methotrexate (MTX). The development of drug resi
stance is a common problem in treatment of bladder cancers. We tested
if the status of p53 and/or pRb affects the development of MTX resista
nce in bladder epithelial cell lines. Materials and Methods: We used t
wo isogeneic sets of cell lines in which we manipulated the status of
p53 and/or pRb by transformation with Human Papillomavirus (HPV) E6 an
d/or E7 or with a transdominant TP53 mutant (Tp53(143)). One series of
isogeneic origin was derived from normal human uroepithelial cells (H
UC), and the other was derived from a human transitional cell carcinom
a (TCC). Cell lines with p53 and/or pRb alterations were cultured for
six months while increasing the MTX concentration in each line, as res
istance developed. Results: Two cell lines with both pRb and p53 alter
ations, alpha E6/E7-HUC and alpha E7-HUCp53mu, acquired the greatest r
esistance (750 nM) to MTX. One line with p53 loss, EG-TCC#10, acquired
intermediate resistance (500 nM), while two lines, alpha E7-HUC and E
7-TCC#10, with altered pRb but wildtype p53, showed low levels of MTX
resistance (125 nM and 80 nM, respectively). Two clear mechanisms of M
TX resistance were identified. All five MTX resistant cell lines showe
d altered uptake of MTX. In addition, two of five MTX resistant cell l
ines, both with altered p53, showed dihydrofolate reductase (DHFR) amp
lification. Conclusions: p53 alteration increases the risk for develop
ment of drug resistance by both DHFR amplification and altered MTX tra
nsport in transformed human bladder epithelial cell lines.