Epigenetic Alteration of the Cancer-Related Gene TGFBI in B Cells Infected with Epstein–Barr Virus and Exposed to Aflatoxin B1: Potential Role in Burkitt Lymphoma Development

SIMPLE SUMMARY: Endemic Burkitt lymphoma is an aggressive pediatric cancer whose etiological factors include Epstein–Barr virus (EBV) infection and malaria or environmental carcinogen exposures, such as aflatoxin B1 (AFB1). As evidence suggests B cell methylome remodeling to be a transformation mechanism shared by both EBV and AFB1, the identification of a common molecular signature compromising cell fate could reveal an essential driver of lymphomagenesis and provide a relevant target for novel therapies. We, therefore, explored the genome-wide DNA methylation profiles associated with both endemic Burkitt lymphoma and AFB1 exposure and identified a shared signature affecting the expression of a putative tumor suppressor, TGFBI, whose reduced expression has already been investigated in several cancers, but whose implication in lymphoma has not been evidenced so far. Further research clarifying the functional consequence of TGFBI suppression on B cell fate and the impact on tumor microenvironment reshaping is warranted. ABSTRACT: Burkitt lymphoma (BL) is a malignant B cell neoplasm that accounts for almost half of pediatric cancers in sub-Saharan African countries. Although the BL endemic prevalence is attributable to the combination of Epstein–Barr virus (EBV) infection with malaria and environmental carcinogens exposure, such as the food contaminant aflatoxin B1 (AFB1), the molecular determinants underlying the pathogenesis are not fully understood. Consistent with the role of epigenetic mechanisms at the interface between the genome and environment, AFB1 and EBV impact the methylome of respectively leukocytes and B cells specifically. Here, we conducted a thorough investigation of common epigenomic changes following EBV or AFB1 exposure in B cells. Genome-wide DNA methylation profiling identified an EBV–AFB1 common signature within the TGFBI locus, which encodes for a putative tumor suppressor often altered in cancer. Subsequent mechanistic analyses confirmed a DNA-methylation-dependent transcriptional silencing of TGFBI involving the recruitment of DNMT1 methyltransferase that is associated with an activation of the NF-κB pathway. Our results reveal a potential common mechanism of B cell transformation shared by the main risk factors of endemic BL (EBV and AFB1), suggesting a key determinant of disease that could allow the development of more efficient targeted therapeutic strategies.