Association between cigarette smoking and mutation of the p53 gene in squamous-cell carcinoma of the head and neck.

BACKGROUND: Although epidemiologic studies have long associated tobacco and alcohol use with the development of squamous-cell carcinoma of the head and neck, the molecular targets of these carcinogens have yet to be identified. We performed a molecular analysis to determine the pattern of mutations in the p53 gene in neoplasms from patients with squamous-cell carcinoma of the head and neck and a history of tobacco or alcohol use. METHODS: Sequence analysis of the conserved regions of the p53 gene was performed in tumor samples from 129 patients with primary squamous-cell carcinoma of the head and neck. We then used statistical analysis to identify any patient characteristics associated with mutation of the p53 gene. RESULTS: We found p53 mutations in 42 percent of the patients (54 of 129). Fifty-eight percent of the patients who smoked cigarettes and used alcohol (37 of 64; 95 percent confidence interval, 45 to 70 percent), 33 percent of the patients who smoked but abstained from alcohol (13 of 39; 95 percent confidence interval, 19 to 50 percent), and 17 percent of the patients who neither smoked nor drank alcohol (4 of 24, 95 percent confidence interval, 5 to 37 percent) had p53 mutations (P = 0.001). (Two patients used alcohol but did not smoke, and neither had a p53 mutation.) Furthermore, 100 percent of the mutations in the patients who neither drank nor smoked occurred at sites containing cytidine phosphate guanosine dinucleotides (potentially representing endogenous mutations) within the p53 gene (5 of 5 mutations; 95 percent confidence interval, 48 to 100 percent), whereas only 23 percent of those in cigarette smokers consisted of such changes (12 of 53 mutations; 95 percent confidence interval, 12 to 36 percent; P = 0.001). CONCLUSIONS: In our study, a history of tobacco and alcohol use was associated with a high frequency of p53 mutations in patients with squamous-cell carcinoma of the head and neck. Preliminary evidence linked cigarette smoking to p53 mutations at nonendogenous mutation sites. Our findings suggest a role for tobacco in the molecular progression of squamous-cell carcinoma of the head and neck and support the epidemiologic evidence that abstinence from smoking is important to prevent head and neck cancer.

Induction of reversible changes in cell-surface glycoconjugates and lung colonization potential by 13-cis retinoic acid.

Murine squamous carcinoma cells (KLN205) grown in a medium supplemented with the retinoid, 13-cis retinoic acid (RA), had dose-dependent, selective increases in the expression of certain lectin receptors, which correlated with a dramatic decrease in the ability to form pulmonary colonies (P = .0003) (Couch MJ, Pauli BU, Weinstein RS, Coon JS: JNCI, 78:971-977, 1987). These findings suggest a possible relationship between the RA-induced glycoconjugate alterations and the decreased experimental metastatic behavior. We further define the mechanism of RA's action. The finding that RA treatment (5 X 10(-6) M, 5 X 10(-7) M) did not perturb the cell cycle of KLN205 cells provides further proof that the decreased metastatic behavior is not attributable to any inhibition in the rate of growth or to alterations in the cell cycle. Furthermore, since stable subpopulations with variable lectin binding could not be detected, the mechanism of RA's action does not appear to be due to selection of variant tumor-cell subpopulations. Finally, in a series of experiments designed to determine the reversibility of the RA treatment, the RA-induced decrease in metastatic behavior reverted back to a more metastatic state in the same time frame (3 days) as the reversion of the RA-induced changes in cell-surface glycoconjugate expression. This reversion provides further evidence for a close relationship between the RA-induced modulation of tumor cell-surface glycoconjugate expression and the decreased metastatic behavior; it suggests that transient, reversible modulation of the tumor cell surface may play a role in determining metastatic behavior.

Modulation of the metastatic phenotype by 13-cis-retinoic acid.

KLN 205 murine squamous carcinoma cells were grown in medium supplemented with the retinoid 13-cis-retinoic acid (RA) to study the relationship between RA-induced cell surface changes and alterations of the metastatic phenotype. Modulation of the cell surface glycoconjugate expression was measured by flow cytometric analysis of the RA-treated tumor cells stained with fluoresceinated lectins. RA treatment (5 X 10(-6) and 5 X 10(-7) M) altered the glycoconjugate expression of KLN 205 cells in a selective, dose-dependent fashion. Tumor cells grown in RA-supplemented medium for more than 4 days demonstrated greatly increased binding of fluoresceinated Griffonia simplicifolia I lectin, peanut lectin, wheat-germ lectin, concanavalin A, and soybean lectin (P less than .001), but the increased binding of Ulex europaeus lectin was of a much smaller magnitude (P = .02). After 15 days of growth in these noncytotoxic or cytostatic concentrations of RA, malignant KLN 205 cells had a greatly decreased proclivity to metastasize, as measured by the lung colony assay (P = .0003). The RA-induced cell surface glycoconjugate changes preceded the decrease in experimental metastatic potential. Since enzymatic (neuraminidase) alteration of the tumor cell surface to produce glycoconjugate expression similar to that seen in RA-treated cells also reduced the ability of the KLN 205 cells to form lung colonies (P = .0022), it is suggested that RA-induced alteration of the cell surface carbohydrate antigens is related to the decreased experimental metastatic potential seen in tumor cells treated with RA.