Genetic components in susceptibility to nasopharyngeal carcinoma.

A series of blood samples from more than 200 histologically confirmed Chinese patients with NPC in Singapore were typed for 25 genetically controlled red-cell enzyme and five serum protein systems. A comparable number of patients suspected of having NPC but histologically negative and a series of healthy unrelated Chinese were typed for the same systems. The gene frequencies of NPC patients and controls differed by 4% or more in four of the 11 systems that showed variation; a further system, G6PD deficiency, also showed a significant difference between the two series but was excluded because of possible unreliability of the results from patients. Smaller differences existed in several other systems, including chromosome 6 markers closely linked to HLA. An analysis of differences within dialect groups showed a consistent effect for PGD, but for red-cell acid phosphatase there was a reversal of the difference between patients and controls among the Cantonese. These results need a larger series to confirm their validity. A breakdown of patients into those 30 years of age or older and those under 30 slightly enhanced the differences in gene frequencies. A multivariate analysis, using genetic distance statistics, showed a significant difference between NPC patients and controls, which is evident also when they are compared in the separate dialect groups. The histologically negative patients occupied an intermediate position. The study indicates that etiological factors resulting in clinically and histologically confirmed NPC operate on a genetically distinct subpopulation of Chinese in Singapore.