[Impaired expression of cell-cycle regulatory proteins in seborrheic keratosis]

Seborrheic keratosis (SK) is a benign skin tumor of unknown etiology and pathogenesis. Many details remain unclear despite that there have been a number of studies of cell-cycle abnormalities.

to investigate the expression of the cell-cycle regulatory proteins p53 and p16 and the cell proliferation marker Ki-67 in SK.

The investigation used intraoperative SK material obtained from 130 patients. Tumors were removed from UV-exposed parts of the body in 63 (48%) patients and from the places that were more often closed in 67 (51.5%). An immunohistochemical (IHC) study was performed using monoclonal antibodies to p53, p16, and Ki-67.

A positive reaction with monoclonal antibodies to p53 was recorded in 66 (50.7%) SK samples. In 92.1% of cases, the expression of p53 was found in SK located at the sites that were most exposed to UV radiation (p=0.00001). A positive reaction with monoclonal antibodies to p16 was observed in all SK cases as cytoplasmic staining of more than 50% of the tumor cells: a strong staining in 63 SK samples (overexpression) and a weak staining in 67 SK ones. The level of p16 expression correlated with age (R=0.21; p=0.019) and SK location at the sites exposed to increased insolation (R=0.35; p=0.000038). Overexpressions of p53 and p16 were significantly more commonly recorded in irritated SK. The tumor proliferative activity by the level of Ki-67 expression was low (3.0 to 11.3%). The largest number (8.5±4.8%) of proliferating cells was recorded in irritated SK (p=0.0000001).

The found disorders in the expression of cell-cycle regulatory proteins in SK are suggestive of tumor suppressor activation and keratinocyte senescence. There may be malignant tumor transformation in irritated SK in terms of the significant increase in the expression of p53, p16 in the presence of high cell proliferative activity.