Viral genetic factors linked to nasopharyngeal cancer

19 February 2019

Dr Alan Chiang (Croucher Scholarship 1994), of the University of Hong Kong, has revealed for the first time that viral genetic factors are intimately linked to the development of nasopharyngeal cancer.

The Epstein-Barr virus (EBV) is a human gamma-herpesvirus that infects more than 90 per cent of adults and is associated with almost all nasopharyngeal cancer cases in Southern Chinese populations. The virus is also found in cancers including gastric carcinoma, Burkitt lymphoma, Hodgkin lymphoma, and other lymphomas.

Nasopharyngeal cancer is so prevalent among young adult males in Guangdong, that it has been dubbed “Guangdong cancer”. There is an incidence rate of one out of 4,000 males aged 20 to 44 in Southern China. The cancer is usually detected in its late stages but the survival rate can be doubled if found early.

Most research has focused on human genetic factors while viral genetic factors linked to the cancer have not been well studied.

Researchers, led by Chiang, compared genomic sequences of EBV isolated from saliva samples of 142 healthy carriers with those from primary tumour biopsies derived from 62 Hong Kong patients with nasopharyngeal cancer. They discovered that healthy carriers harboured five different sub-groups of the virus while the cancer patients predominantly harboured two of the sub-groups.

The specific genetic variants identified with these two sub-groups were found in 97 per cent of nasopharyngeal cancer cases and a sub-set of 40 per cent of population carriers. After assigning a genetic risk factor to each of the EBV variants, comparisons showed that the two EBV variants highly associated with nasopharyngeal cancer cases were more prevalent in Hong Kong Chinese than individuals in other geographic regions and in nasopharyngeal cancer than other EBV-associated cancers.

Dr Alan Chiang, Croucher Scholarship 1994

The research findings have been published in the International Journal of Cancer. A patent on the high-risk Epstein-Barr virus variants was filed in November 2018.

The presence of high-risk variants of the virus in nasopharyngeal cancer and the sub-set of population carriers in Hong Kong indicates an important role for Epstein-Barr virus genetic variations in the pathogenesis of the cancer and explains the high incidence of nasopharyngeal cancer in Hong Kong and other areas where they are endemic.

Chiang believes that adding information on the EBV variants to screening methods used to identify individuals at risk of developing nasopharyngeal cancer could significantly increase the predictive value of such tests.

Dr Alan Kwok-shing Chiang is a clinician-scientist practising in the field of paediatric haematology and oncology. His research interest in Epstein-Barr virus biology and its links to nasal NK/T cell lymphoma affecting the Chinese population dates back to his PhD studies at the Department of Pathology of The University of Hong Kong, for which he was awarded a Croucher Scholarship in 1994.

To view Dr Chiang’s Croucher profile, please click here.