LAUSR

Nasopharyngeal carcinoma (NPC), the most common head and neck cancer, is characterized by distinct geographic distribution and familial aggregation. Multiple risk factors, including host genetics, environmental factor, and EBV infection, have been linked to the development of NPC, particularly in the familial clustering cases. However, the cause of NPC endemicity remains enigmatic due possibly to the complicated interplay between these risk factors. Recently, positive Epstein‐Barr virus (EBV) DNA loads at nasopharyngeal (NP) cavity has been found to reflect NPC development and applied in NPC screening. To examine whether the increased NP EBV loads could aggregate in the families and be affected by host genetics and environmental factor, EBV loads were obtained by 510 NP brushing samples from eligible unaffected individuals, who have two or more relatives affected with NPC, in 116 high‐risk NPC families. The correlation of relative pairs was estimated using S.A.G.E. (version 6.4, 2016), and host heritability of NP EBV loads was calculated with variance component models using SOLAR (version 8.4.2, 2019). In result, significant correlations of EBV loads were observed between parent‐offspring pairs and sibling‐sibling pairs (P < .001), but not in distant kin relationship pairs. Interestingly, after excluding the shared environmental factor within families, host genetics contributes significantly to NP EBV loads with a heritability of 56.41% (P = 1.00 × 10−7), and its effect was slightly elevated (68.86%, P = 3.40 × 10−6) in families with more NPC cases (≥3). These findings indicate that additional host‐genetic variants involved in the EBV local NP mucosal behavior may be especially important for the development of NPC.