OVER-EXPRESSION OF P53-PROTEIN AND CIGARETTE-SMOKING IN BRONCHIAL-CARCINOMA

A recessive gene on chromosome 17 encodes a protein, known as p53, whi ch normally acts to regulate the cell cycle, its mutation and over-exp ression being amongst the commonest genetic abnormalities in human mal ignant neoplasms. As detected by immunolabelling using the anti-p53 pr otein antibodies PAb1801, DO7 and CM1, over-expression was demonstrabl e in 13 of 59 tissue biopsy specimens from a series of patients with n ewly-diagnosed primary bronchial carcinoma from whom accurate data on smoking history had been obtained prior to bronchoscopy. There was a s tatistically significant relationship between over-expression and tota l exposure to cigarette smoke (p53-positive, median 46 pack-years; p53 -negative, median 32 pack-years; P<0.001) and between over-expression and intensity of exposure (p53-positive, median 20 cigarettes/day; p-5 3 negative, median 14 cigarettes/day; P<0.001), but no difference betw een the two groups in terms of total duration of this exposure (p53-po sitive, median 47 y; p53-negative, median 46 y). These data confirm fi ndings of previous studies suggesting a possible link between cigarett e smoke and those derangements of the structure or function of the p53 -encoding gene which lead to its over-expression by malignant bronchia l tumours. They support, in addition, a specific mutagenic role for th e chemical carcinogens it contains. Over-expression of p53 did not app ear to influence survival.