CROSS-RESISTANCE AND COLLATERAL SENSITIVITY BETWEEN CYTOTOXIC DRUGS AND RADIATION IN 2 HUMAN BLADDER CELL-LINES

The (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) test was employed as a means of studying the cross resistance and collateral se nsitivities of two bladder cell lines able to grow in the presence of several antineoplastic drugs and/or despite the effects of radiotherap y, This cross resistance and collateral sensitivities were investigate d in the context of two antineoplastic drugs (i.e. doxorubicin (an ant hracycline) and vinorelbine (a Vinca alkaloid)) and radiotherapy. The results show that cell lines able to grow in the presence of anticance r drugs develop a significant degree of resistance to antineoplastic c ompounds and may also develop resistance to radiotherapy, On the other hand, most cell lines treated first with radiotherapy develop a signi ficant degree of resistance towards ionizing radiation and may also di splay increased sensitivity towards anticancer drugs. If these results obtained in vitro are clinically relevant, they may have important ap plications in the treatment of patients. Nevertheless, it will be nece ssary to validate the results on extensive series of chemo- and/or rad ioresistant cell lines exhibiting different mechanisms of resistance.