PCNA and urothelial carcinoma: Since these 5/6 randomly selected chemotherapy resistant mammary carcinomas and a single neoadjuvantly treated urothelial carcinoma exhibited no IGF1R/PCNA interaction in the post-treatment setting, it is implied that the IGF1R/PCNA negative tumor cells survived radio-chemotherapy (selection) or that chemotherapy resulted in the downregulation of IGF1R/PCNA interaction (modification).