Nasopharyngeal cancer (NPC) has a very distinct geographic and ethnic distribution, occurring at high rates among ethnic Chinese from southeastern China and at much lower rates among Caucasian populations. While infection with the Epstein Barr virus (EBV) is believed to be necessary for development of the cancer, other factors, both genetic and exogenous, are also thought to be important. To investigate genetic, dietary, occupational, and behavioral factors related to the etiology of NPC, two studies were conducted in Taiwan - a case-control study of approximately 1,000 individuals and a multiplex family study of approximately 3,000 individuals (350 families). To date, our results suggest an association between risk and specific variants of the enzyme CYP2E1 and several DNA repair genes, specific patterns of HLA and KIR genes, and long-term cigarette smoking. High intakes of nitrosamines and nitrite during childhood and weaning also were associated with increased risks. Occupational exposures to wood dusts also appeared to affect risk;in contrast, formaldehyde exposure was not a significant risk factor. Exogenous risk factors identified within our family study were similar to those observed from our case-control study. Evaluation of gene expression profiles from nasopharynx tumor and normal cells suggest that genes involved in DNA repair and in the metabolism of nitrosamines are involved in NPC pathogenesis. Results from our tissue-based expression studies also suggest the possibility of loss-of-heterozygosity on the telomeric end of chromosome 14 in NPC, and that EBV gene expression within NPC tumor cells affect the expression of host genes involved in immune presentation. This suggests a possible mechanism by which EBV manages to evade immune surrveillance in NPC. Uaffected individuals from NPC multiplex families have been shown in our study to have elevated levels of antibodies against EBV compared to the general population. To follow-up on this finding, we have evaluated the value of EBV serology to predict subsequent NPC risk among unaffected individuals from NPC multiplex families. We observed that individual with elevated antibody levels against several EBV markers are at a 4 to 6-fold increased risk of developing NPC within 10 years, but the low specificity of the antibodies evaluated suggest that improvements are required before such serology-based tests can be used clinically.
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