A study of gender-based cytochrome P4501A2 variability: a possible mechanism for the male excess of bladder cancer.

One hypothesis for the well known gender difference in bladder cancer risk is that males and females metabolize carcinogens differently. The caffeine breath test (CBT) was performed on a group of healthy men and women to determine whether there was a gender difference in P4501A2 activity. Results consistent with previous data suggest an elevation of CBT in men were observed, although this increase was not statistically significant. Among women, however, there was a significant difference between nulliparous and parous women(P = 0.03). Parous women had CBT values similar to men, whereas the results of women who had never given birth were lower. Confirming earlier studies, women taking oral contraceptives had low CBT values. Our data suggest an effect of recent caffeine consumption, with heavy coffee drinkers having higher rates of caffeine clearance. Adjustment for other weak effects, such as age, exposure to environment cigarette smoke, history of smoking, recent meat and cruciferous vegetable consumption, and use of alcohol or other medications, did not alter these findings. The finding of a difference between parous and nulliparous women requires further study.

Increased risk of pancreatic cancer in melanoma-prone kindreds with p16INK4 mutations.

BACKGROUND: A gene on chromosome 9p, p16INK4, has been implicated in the pathogenesis of cutaneous malignant melanoma in 19 melanoma-prone families. In 10 of these kindreds mutations that impaired the function of the p16INK4 protein (p16M alleles) cosegregated with the disease. By contrast, in the other nine kindreds the mutation did not alter the function of p16INK4 (p16W alleles). We looked for differences in clinical and genetic epidemiologic features in these two groups of families. METHODS: We compared the median ages at diagnosis of melanoma, number of melanomas, thickness of the tumors, and number of nevi in the kindreds. We estimated prospectively the risks of melanoma or other cancers in families followed for 6 to 18 years and the risks of other cancers since 1925 (the entire period) by comparing the number of cancer cases observed with the number expected. RESULTS: The risk of invasive melanoma was increased by a factor of 75 in kindreds with p16M alleles and a factor of 38 in kindreds with p16W alleles. Although this difference was not significant (P = 0.14), there was a striking difference in the risk of other tumors. In kindreds with p16M alleles, the risk of pancreatic cancer was increased by a factor of 13 in the prospective period (2 cases observed, 0.15 expected; standardized incidence ratio, 13.1; 95 percent confidence interval, 1.5 to 47.4) and by a factor of 22 in the entire period (7 cases observed, 0.32 expected; standardized incidence ratio, 21.8; 95 percent confidence interval, 8.7 to 44.8). In contrast, we found no cases of pancreatic cancer in kindred with p16W alleles. CONCLUSIONS: The development of pancreatic cancer in kindreds prone to melanoma may require a p16M mutation. Genetic factors, such as the kind of mutation found in p16INK4, may explain the inconsistent occurrence of other cancers in these kindreds.