title: Different histological types of non-small cell lung cancer have distinct folate and DNA methylation levels.
abstract: Aberrant DNA methylation is a commonly observed epigenetic change in lung cancer. Folate has been suggested to play a role in the homeostasis of DNA methylation and has also been implicated in cancer chemotherapy. We investigated a possible role for folate in DNA methylation by measuring folate concentrations in tumors and adjacent normal tissues from 72 non-small cell lung cancer (NSCLC) patients. These were compared to DNA methylation levels and to clinicopathological features. Folate concentrations were determined as the sum of 5,10-methylenetetrahydrofolate and tetrahydrofolate. The MethyLight assay was used to quantitate methylation in promoter regions of P16(CDKN2A), APC, CDH13, RARB, RASSF1, RUNX3, and MYOD1. Methylation of LINE-1 repeats was used as a surrogate for global methylation. Folate levels in tumors correlated positively with LINE-1, CDH13, and RUNX3 methylation. Folate concentrations and methylation of LINE-1, RASSF1, and RUNX3 were significantly higher in adenocarcinoma compared to squamous cell carcinoma (SCC). Two sets of array-based data retrieved from the Gene Expression Omnibus consistently showed that expression of FOLR1, a folate transport enzyme, and GGH, an enzyme that prevents folate retention, were higher and lower, respectively, in adenocarcinomas compared to SCC. This was independently validated by quantitative RT-PCR in 26 adenocarcinomas and 13 SCC. Our results suggest that folate metabolism plays a role in aberrant DNA methylation in NSCLC. The histological subtype differences in folate concentration and DNA methylation observed here were associated with distinct expression patterns for folate metabolizing enzymes. These findings may have clinical applications for histology-directed chemotherapy with fluoropyrimidine and anti-folates in NSCLC.
authors.affiliation: Division of Translational and Clinical Oncology, Molecular and Cellular Targeting Translational Oncology Center, Cancer Research Institute, Kanazawa University, Kanazawa, Japan.
authors.forename: Mingji
authors.initials: M
authors.lastname: Jin
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Kawakami
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Fukui
authors.forename: Sayaka
authors.initials: S
authors.lastname: Tsukioka
authors.forename: Makoto
authors.initials: M
authors.lastname: Oda
authors.forename: Go
authors.initials: G
authors.lastname: Watanabe
authors.forename: Teiji
authors.initials: T
authors.lastname: Takechi
authors.forename: Toshinori
authors.initials: T
authors.lastname: Oka
authors.forename: Toshinari
authors.initials: T
authors.lastname: Minamoto
mesh_terms: D000230:Adenocarcinoma / Q000737:chemistry / Q000235:genetics; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015820:Cadherins / Q000235:genetics; D002289:Carcinoma, Non-Small-Cell Lung / Q000737:chemistry* / Q000235:genetics*; D002294:Carcinoma, Squamous Cell / Q000737:chemistry / Q000235:genetics; D050677:Core Binding Factor Alpha 3 Subunit / Q000235:genetics; D019175:DNA Methylation; D005260:Female; D005492:Folic Acid / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D020084:Long Interspersed Nucleotide Elements; D008175:Lung Neoplasms / Q000737:chemistry* / Q000235:genetics*; D008297:Male; D008875:Middle Aged
chemical_list: D015820:Cadherins; D050677:Core Binding Factor Alpha 3 Subunit; C099972:H-cadherin; C493729:Runx3 protein, human; D005492:Folic Acid