Preliminary insights into methylation patterns in Agent Orange exposed thyroid cancers: a pilot study.

Area of Science:

• Environmental Health
• Oncology
• Epigenetics

Background:

• US military personnel during the Vietnam War were exposed to Agent Orange, a defoliant contaminated with 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD).
• Agent Orange exposure is associated with an increased risk of thyroid cancer among Vietnam-era Veterans.
• The molecular mechanisms underlying this increased thyroid cancer risk are not well understood.

Purpose of the Study:

• To investigate differential DNA methylation profiles in thyroid tumors from Agent Orange-exposed compared to unexposed Vietnam-era US Veterans.
• To explore potential epigenetic mechanisms linking Agent Orange exposure to thyroid cancer development.

Main Methods:

• Retrospective case-case study of 44 Veterans with differentiated thyroid cancer (23 exposed, 21 unexposed).
• Genome-wide DNA methylation profiling using the Infinium Methylation EPICv2 array.
• Linear regression models adjusted for age, VA location, and cell type proportions; gene set enrichment analysis.

Main Results:

• Agent Orange exposure was associated with differential methylation at 309 CpGs (nominal p < 0.001) in thyroid tumors.
• No significant CpGs were detected after multiple comparison adjustment.
• Top associations included CpGs in cancer-related genes (CELF2, OTX2, SSR1, EBF1); hedgehog signaling and anti-folate resistance pathways were enriched.

Conclusions:

• This exploratory study identified differentially methylated loci potentially linked to thyroid cancer in Agent Orange-exposed Veterans.
• Further research with larger cohorts and biomarker assessment is needed to confirm these findings.
• In vitro models are required to elucidate the mechanisms connecting Agent Orange exposure, DNA methylation, and thyroid cancer.