Alcohol and Dietary Folate Intake and Promoter CpG Island Methylation in Clear-Cell Renal Cell Cancer

ABSTRACT

We investigated whether alcohol and dietary folate intakes were associated with promoter methylation in clear-cell renal cell carcinoma (ccRCC). The Netherlands Cohort Study with a case-cohort design included 120,852 subjects aged 55–69 yr in 1986. Diet was measured with a food-frequency questionnaire. After 20.3 yr of follow-up, paraffin-embedded tumor blocks were collected. Methylation-specific polymerase chain reaction (MSP) was used to analyze promoter methylation of 11 genes. ccRCC cases were classified into low (0–19% of the genes), intermediate (20–39%), and high (40%+) methylation. Multivariable Cox regression analyses were conducted, stratified according to methylation, including 3980 subcohort members and 297 ccRCC cases. Increasing alcohol intake was associated with decreased ccRCC risk, but was not statistically significant; multivariable adjusted hazard ratio (HR) for ≥30 g alcohol/day versus 0 g/day was 0.78 [95% confidence interval (CI): 0.48–1.24], and P-value for trend was 0.46. In strata according to methylation index, no significant heterogeneity was observed. Dietary folate intake was not associated with ccRCC risk. There was no significant heterogeneity between strata according to methylation index. There was no effect modification of alcohol and dietary folate intake on ccRCC risk, nor in strata according to methylation index. Our findings do not support the hypothesis that alcohol and dietary folate intakes are involved in ccRCC.

Acknowledgment

The authors are indebted to the subjects of this study and further wish to thank the Netherlands Cancer Registry, the Dutch Pathology Registry (PALGA), and all the pathology laboratories that provided tissue samples. They are grateful to Kim van Straeten and Kim Wouters, laboratory technicians, and Zheng Feng at the Department of Pathology, Maastricht University Medical Centre, for all their efforts in the laboratory. Finally, they would like to thank Dr. R. Alexandra Goldbohm for her contributions in the design of the NLCS; Dr. Christine Hulsbergen-van de Kaa, Kjeld van Houwelingen, and Dr. Boukje van Dijk for their work on the initial series of cases from the first 11.3 yr of follow-up; Dr. Arnold Kester for statistical advice; Sacha van de Crommert, Jolanda Nelissen, Jacqueline Spronck, Henny Brants, Conny de Zwart, Marijke Moll, and Annemie Pisters for their assistance with data entry and data management; and Harry van Montfort, Ton van Moergastel, Ellen Dutman, Ralph Meijer, and Ruud Schmeitz for programming assistance.

The results published here are in part based on data generated by the TCGA Research Network: http://cancergenome.nih.gov/.

Funding

The Netherlands Cancer Society (UM 2009–4536).