p53 nuclear immunostaining and gene mutations in non-small-cell lung cancer and their effects on patient survival

p53 gene mutations are known to occur in about half of all non-small-cell lung cancer (NSCLC) cases. Mutations of the p53 gene usually but not always lead to an increased half life of the p53 protein, and result in a nuclear accumulation of protein which can be detected by immunohistochemistry (IHC). Controversy still exists as to whether the presence of an aberration of the p53 gene or protein is a poor prognostic indicator in patients with NSCLC.

DNA samples and paraffin blocks were obtained from 129 patients of 143 consecutive patients who underwent a pulmonary resection during a 22-month period from July 1991 to April 1993. Mutations of the p53 gene occurring at exons 5-8 were detected by a polymerase chain reaction (PCR)/single strand conformation polymorphism (SSCP) assay, while the nuclear accumulation of the p53 protein was detected by immunohistochemistry.

Of the patients studied, 35% had mutations and 54% showed overexpression, when we defined a positive case as being one in which more than 10% of the tumor cell nuclei were stained. There was a 59.5% concordance between the p53 gene mutations and p53 immunopositivity. p53 immunopositivity in adenocarcinoma and any p53 abnormality (i.e. p53 immunopositivity and/or mutation) in adenocarcinoma were a poor prognostic indicator. However, Cox's proportional hazards model indicated that the stage was the only significant prognostic factor.

p53 immunopositivity and mutations of the p53 gene are frequently seen in NSCLC. They are considered to be mutually related but may sometimes represent a different aspect of p53 abnormality. p53 alteration may be a poor prognostic indicator only in a subset of patients with NSCLC, especially for adenocarcinoma.