Subcellular localization of accumulated p53 in ovarian cancer cells.

Inactivation of the tumor suppressor gene p53 is frequently associated with ovarian cancer. Accumulation of stabilized p53 protein is a common feature in this tumor type. Underlying mutations in the p53 core region can lead to loss of the normal conformational state or loss of residues necessary for DNA binding and transcriptional regulation. Five HPV-free ovarian cancer cell lines established in our laboratory with and without immunocytochemically detectable p53 expression were selected for the correlation of subcellular localization of aberrant p53 and the type of gene mutation. The expression level regarding staining intensity and proportion of cells accumulating p53 was characterized employing an immunoreactive score. Two cell lines with point missense mutations in the core region showed strong nuclear or nuclear plus cytoplasmic staining. One cell line with exclusive staining of the cytoplasm contained a deletion of the major nuclear localization signal. Among two cell lines without p53 accumulation, one contained a microdeletion resulting in a frame shift, the other carried the wild-type sequence. The MDM2 oncogene was not amplified and its gene product was not overexpressed. In ovarian cancer, inactivated p53 can accumulate in both major cell compartments depending on the type of the underlying mutation.