Bladders from BBN-treated mice showed progression from submucosal inflammation (P1) to squamous metaplasia/focal CIS (P2) to poorly differentiated, invasive cancer (P3). mRNA levels for the inducible cyclooxygenase, COX-2, were elevated three to fourfold at all time points in BBN-treated mice compared to controls.
A total of 876 women were followed by colposcopy examination where biopsies were taken from the visible lesions or from suspicious areas and histopathology diagnosed 459 as normal or benign cases, 325 as CIN1, 36 as CIN2, 25 as CIN3/CIS, and 31 as invasive cancer.
Analysis of several tumor pairs involving a CIS and an invasive cancer provided evidence that the chromosome 9 alteration may in some cases be involved in the progression of CIS to more invasive tumors, in addition to its role in the initiation of T(a) tumors.