DNA methylation changes associated with risk factors in tumors of the upper aerodigestive tract

Cancers of the upper aerodigestive tract (UADT) are common forms of malignancy associated with tobacco and alcohol exposures, although human papillomavirus and nutritional deficiency are also important risk factors. While somatically acquired DNA methylation changes have been associated with UADT cancers, what triggers these events and precise epigenetic targets are poorly understood. In this study, we applied quantitative profiling of DNA methylation states in a panel of cancer-associated genes to a case-control study of UADT cancers. Our analyses revealed a high frequency of aberrant hypermethylation of several genes, including MYOD1, CHRNA3 and MTHFR in UADT tumors, whereas CDKN2A was moderately hypermethylated. Among differentially methylated genes, we identified a new gene (the nicotinic acetycholine receptor gene) as target of aberrant hypermethylation in UADT cancers, suggesting that epigenetic deregulation of nicotinic acetycholine receptors in non-neuronal tissues may promote the development of UADT cancers. Importantly, we found that sex and age is strongly associated with the methylation states, whereas tobacco smoking and alcohol intake may also influence the methylation levels in specific genes. This study identifies aberrant DNA methylation patterns in UADT cancers and suggests a potential mechanism by which environmental factors may deregulate key cellular genes involved in tumor suppression and contribute to UADT cancers.

[Cancer mortality trends in Brazilian state capitals, 1980-2004]

OBJECTIVE

Cancer mortality rates began to decline in developed countries in the 1990s, but their behavior in developing countries is less well-known. An earlier study on cancer mortality in Brazil showed a declining mortality trend for cancer as a whole. however the quality of data results raised some criticism t. The population of state capitals comprises about a quarter of the total Brazilian population and for these cities mortality data available have a better quality than for the entire country, enabling analyses of trends in cancer rates based on more accurate data.

METHODS

Mortality and population data were collected from government databases (SIM/DATASUS and IBGE, respectively). Age-adjusted (world standard) and age-specific mortality rates were calculated for both genders . Linear regression was used to investigate changes in trends.

RESULTS

For all cancers as a whole mortality rates declined throughout the study period for both men and women (-4.6% and -10.5%, respectively). For both genders , the cancer that decreased most was stomach cancer. Among men, lung cancer death rates presented a slight reduction, while prostate cancer rates increased. Among women, "uterus, site unspecified' presented a downward trend, while lung cancer rates increased. The trend for breast cancer remained stable, and cervix uterus rates showed a slight increase at the end of the period.

CONCLUSION

As already seen in developed countries, all cancer mortality rates tended to decline in Brazilian state capitals over the period 1980-2004, a tendency largely due to a decline in stomach cancer death rates for both genders.

[Mortality by industrialization-related leukemias]

OBJECTIVE

To analyze the spatial distribution of mortality by leukemia in the population, looking for clusters, and to establish an association with the level of industrialization.

METHOD

The study was carried out in 43 state regions of the state of São Paulo, Brazil, in the period between 1991 and 1995. It was created an Index of Industrialization-Related Leukemia (IIRL) based on number of manufactures and industrial jobs per 100,000 inhabitants, fiscal aggregated value, diversity of industry activities and presence of manufactures that poses potential risk exposure for leukemia. IIRL was classified in five categories. Standardized leukemia mortality rates were established for each region, classified in five categories, plotted in five different colors and compared to the IIRL map.

RESULTS

The most industrialized regions in the state of São Paulo are Campinas, Piracicaba, Jundiaí, Sorocaba and São Paulo. There was no relationship between mortality by any leukemia type and industrialization. The region of Jales showed the highest standardized mortality rates by leukemia.

CONCLUSIONS

Mortality by leukemia had a homogeneous distribution in the state of São Paulo and no association with the level of industrialization. However, aspects related to the epidemiological method applied--ecological study, mortality by leukemia as a parameter to study a disease which prognosis has changed in the last decades--limit the results interpretation.

[Cancer mortality in Brazil 1980-1995: regional patterns and time trends]

PURPOSE

To analyze the distribution and time-series trends of cancer mortality in the Northern, Northeastern, Central Western, Southern and Southeastern Brazilian geographic regions from 1980 to 1995.

METHODS

Deaths according to year, age, gender and municipality of residence, were ascertained from the Ministry of Health. Age-adjusted rates were calculated for specific cancer sites by gender in the five Brazilian geographic regions.

RESULTS

Lung and breast cancers were, respectively in males and females, the main causes of cancer deaths in the Brazilian population. Overall cancer mortality rates for whole country declined among males (-0.3%) and females (-4.8%). But, rates were on increase for cancers of prostate (38.3%), lung (10.5%) and, more recently, colorectal (14.5% from 1989 to 1995) in males, and for lung (26.7%), breast (9.9%) and colorectal (10.2% from 1989 to 1995) in females. Mortality rates by lung and other tobacco related cancers were higher in the Southern and Southeastern. Females in the Northern and Northeastern had more expressive mortality rates by cervical cancer than other regions, and an inverse trend was observed for breast cancer.

CONCLUSIONS

Mortality rates by all cancers were heterogeneous in Brazil. The risk of death by cancer was higher in the Southern and Southeastern regions, but was decreasing in these regions, the more developed in the country. The other regions, less developed, had lower mortality rates by cancer, but the rates were on increase. From 1991 to 1995, it was observed the stability of mortality rates from tobacco related cancers, fact less perceived among females.