P53 EXPRESSION IN HUMAN CARCINOMAS - COULD FLOW-CYTOMETRY BE AN ALTERNATIVE TO IMMUNOHISTOCHEMISTRY

Several studies have shown that p53 expression has important clinical implications as an indicator of prognosis and response to chemotherapy or radiotherapy in different human tumor types. Determination of p53 expression by immunohistochemistry (IHC) has been incorporated into ro utine practice and its reliability has been consolidated. However, flo w cytometric (FCM) analysis might represent an important objective and rapid approach. In the present study we determined p53 expression by IHC and FCM on a series of 118 human solid tumors. IHC determination w as performed on histological sections and FCM analysis on cell suspens ions. Low correlation coefficients (r(s) from 0.22 to 0.57) were obser ved between IHC and FCM data from individual tumors. By considering th e IHC approach as the gold standard, high sensitivity and low specific ity were found for FCM in detecting p53 expression. The FCM analysis o f p53 expression and DNA content showed p53-positive cells in all cell cycle phases. Moreover, in most breast, lung, and colon aneuploid tum ors (77%), p53-positive cells were detected only in the subpopulations with abnormal DNA content. In conclusion, FCM-p53 expression cannot b e used alternatively to IHC determination, and its clinical relevance remains to be validated. Nevertheless, FCM may provide important infor mation about p53 protein expression in the different subpopulations an d cell cycle phases.