P53 is a tumor-suppressor gene that codes for a multi-functional DNA-binding protein involved in cell cycle arrest, DNA repair, differentiation, and apoptosis. The P53 gene is mutated in approximately 50% of human cancers and in germline DNA of families with inherited cancer syndromes. The role of P53 mutations in the program of carcinogenic genetic alterations differs among tumor sites ranging from the earliest mutations that can be detected in premalignant cells to mutations that trigger malignant transformation of a benign neoplasm. P53 mutations can cause expression of abnormal proteins or result in complete absence of P53 expression. For these reasons the role of P53 genetic disruption has different implications in different tumor types and may vary depending on the effect of the mutation on P53 protein function. Immunohistochemical detection of P53, commonly used as a surrogate for identification of a mutant gene, has imperfect sensitivity and specificity, further complicating correlations between P53 gene status and clinical outcomes. The presence of P53 mutations has been shown to affect prognosis of some cancers. The identity of P53 mutations can be used to determine tumor clonality. The detection of P53 mutations suggests the severity of premalignant lesions. Evolving technology for more accurate identification of P53 mutations, better understanding of the function of mutant P53 protein, and more detailed analysis of individual tumor types may expand the relevance of P53 gene analysis for clinical outcomes and therapeutic response.
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