Immunohistochemical study of the expression of cell cycle regulating proteins at different stages of bladder cancer

Abstract

Purpose. The cell cycle is known to be deregulated in cancer. We therefore analyzed the expression of the cell cycle related proteins p21, p27, p16, Rb, and L-myc by immunohistochemical staining of bladder tumors.

Methods. The tissue material consisted of bladder tumors from three groups of patients; group 1, 23 patients with recurrent stage Ta (non-invasive) tumors; group 2, 22 patients presenting at their first admission with T2–4 (muscle invasive) tumors; group 3, 24 patients who experienced disease progression from Ta or T1 (invasive in connective tissue) to a higher stage. By immunohistochemical staining the protein expression was compared to allelic deletions of the corresponding genes. The allelic deletions were detected by PCR-based microsatellite analyses.

Results. We detected a significant reduction in the expression levels of the cell cycle related proteins p21^waf1 (P=0.002), p27^kip1 (P=0.03), Rb (P=0.00002), and L-myc (P=0.00000007) in muscle invasive tumors compared to noninvasive tumors. Tumors presenting as muscle invasive at first diagnosis had significantly lower levels of p16/CDKN2A (P=0.01) when compared to muscle invasive tumors that followed Ta or T1 precursor lesions. We found no general correlation between allelic deletion of a gene and its immunohistochemical protein expression, indicating that the remaining allele may be capable of encoding a normal or even increased protein level.

Conclusions. Our results support the hypothesis that bladder tumors with invasion at first diagnosis differ from those in which invasion follow superficial tumors. This difference is reflected as a different level in cell cycle related protein expression. The data also indicate that allelic deletions of cell cycle related genes do not correlate with an altered level of protein expression.