NPC susceptible

By | April 30, 2012

Susceptible population of NPC, nasopharyngeal carcinoma can occur in all age groups, 30-60 years of age but more common, accounting for 75% -90%. Sex ratio of 23.8: 1.
1. Obvious regional
Nasopharyngeal cancer in Europe, the Americas and Oceania are quite rare, the incidence rate were 1 / 10 million or less. Some countries in Africa the incidence of nasopharyngeal carcinoma is slightly higher, about 510/10 million, but more common in Southeast Asia countries and China. Although much higher than the world of nasopharyngeal carcinoma is common, but the national average mortality rate is only 1. 88/10 million 2.49/10 million men, women 1. 27/10 million. In addition to Guangdong, Guangxi, Hunan, Fujian, Jiangxi more than this level, the other provinces and cities at this level are the following. Youyi the Pearl River Delta in Guangdong Province and the Xijiang River counties and cities, especially in Zhaoqing, Foshan, Guangzhou and other places of high incidence. In addition, adjacent to Guangxi and Guangdong and Hunan Shuangpai Cangwu County, nasopharyngeal cancer mortality is also high, up to 9 / 10 million or more. Contiguous to each other in these regions of China constitute the core areas of high incidence of nasopharyngeal carcinoma.
2. Race and the phenomenon of part of the population susceptible
NPC disease has obvious racial differences. Three races in the world, some Mongoloid as nasopharyngeal carcinoma high-risk population, including southern China and Southeast Asia's Chinese, Thai, Singaporean and North American Eskimos so, on the incidence of the Chinese people the highest rate; black people of; and the lowest incidence of white people. High incidence of residents moved to keep after the low-fat high tendency of nasopharyngeal carcinoma.
In the high incidence of Guangdong province, people speak different dialects incidence of different people to speak Cantonese dialect particularly high. In Guangzhou and Hong Kong survey found that residents in Guangzhou and Hong Kong water boat the highest mortality of nasopharyngeal carcinoma: 54.7/10 million men, women 18.8/10 million. Eskimos living in Greenland (which is Mongolian) a higher incidence of the NPC.
3. Familial clustering of Sun Yat-sen Cancer Hospital data show that 21.6% of nasopharyngeal cancer patients with family history, family history of nasopharyngeal carcinoma which accounted for 12.3%. NPC nasopharyngeal carcinoma in first degree relatives was significantly higher than the cumulative incidence of spouse of family, and other tumors no significant difference. Twins with the risk of nasopharyngeal carcinoma have been reported.
Albeck and other reports, 27% of nasopharyngeal carcinoma in Greenland patients with a family history of cancer, mainly in cancer patients among first-degree relatives, and most of nasopharyngeal and parotid gland.
4. Incidence rate is relatively stable
In terms of long-term observation showed high incidence of nasopharyngeal carcinoma or low-incidence areas the incidence is relatively stable. For example, the high incidence of nasopharyngeal carcinoma in Guangdong for 20 years the four areas the incidence of no greater volatility. In low-incidence areas such as Europe, America, Oceania, Asia, Japan, India and other countries over the years the incidence of NPC is always 1 / 10 million or less. The same period was significantly higher lung cancer, cervical cancer has declined markedly. This phenomenon Hint: risk factors of nasopharyngeal carcinoma is relatively stable in nature.
Nasopharyngeal carcinoma may be multifactorial, and its carcinogenesis may involve multiple steps. Pathogenesis of NPC-related factors may include:
1. Genetic susceptibility
Although not a genetic nasopharyngeal cancer, but it is in a susceptible population is quite prominent, and the phenomenon of familial aggregation. Linkage analysis showed that human leukocyte antigen (human leukocyte antigen, HLA) and genes encoding cytochrome p4502El (cytochrome p4502E, CYP2El) may be a genetic risk NPC, the NPC with the majority of their occurrence. Cancer Hospital, Sun Yat-sen in 2002, using the human genome 22 of 382 polymorphic autosomal microsatellite markers in Guangdong Province, Guangzhou dialect pedigree with high incidence of NPC conducted genome-wide scan, the NPC susceptibility gene located in the 4p1511 -q12 region.
Modern molecular genetics and molecular biology study found that high frequency of NPC chromosome loss of heterozygosity (lossof heterozygosity, LOH) are mainly located in the chromosomes Ip, 3p, 9p, 9q, llq, 13q, 14q, 16q, and 19p , and locate the corresponding loss of area LOR minimum (minimal deletion regions, MDRs), suggest the high-frequency deletion region may contain the NPC plays an important role in the pathogenesis of the tumor suppressor gene; NPC amplification of genetic material mainly located in chromosome lq, 2q, 3q, 6p, 6q, 7qll, 8q, l1q13, 12q, 15q, 17q and 20q, that may exist in these regions associated with the development of nasopharyngeal cancer genes.
The above study shows the existence of patients with nasopharyngeal carcinoma chromosome instability and therefore more vulnerable to harmful external factors, "attack" and cause disease.
NPC susceptible population 2. EB virus
The immunological method proved with EB virus capsid antigen (VCA), membrane antigen (MA), early antigen (EA) and nuclear antigen (EBNA) and other specific antigens. EB virus is closely related with the NPC, the main basis that:
(1) in the detection of nasopharyngeal carcinoma patients to the EB virus-associated antibodies (including IgA / VCA, IgA / EA, EBNA, etc.), both antibody positive rate, or the geometric mean antibody titers and other tumors than normal (including head and neck cancer) were significantly increased, and the antibody titers were positively correlated with tumor burden. And the antibody titer can be recovered with the disease gradually decreased; with disease recurrence or deterioration was significantly higher once again.
(2), nasopharyngeal cancer cells could be detected within the markers, such as EB virus EB virus DNA and EBNA.
(3) in vitro using cell lines with EB virus infection in nasopharyngeal epithelial cells and found that infected epithelial growth accelerated mitotic activity are common.
(4) It is reported that EB virus in some of the action of tumor promoters can be induced to teach human embryonic nasopharyngeal undifferentiated carcinoma membrane organization.
Nevertheless, the current lack of EB virus caused a complete animal model of NPC, can not believe that EB virus is the cause of nasopharyngeal carcinoma. Thus, in terms of the incidence of nasopharyngeal carcinoma, EB virus is likely to genetic factors and / or the premise of certain environmental factors can play a role in cancer.
3. Environmental factors
Foreign reports, lived in the United States, Canada, the first generation of Chinese (Guangdong residents more) nasopharyngeal cancer mortality rate 30 times the local whites, the second generation dropped to 15 times, the third generation has not yet have the exact figures, but the general trend is to continue to decline. At the same time, White was born in Southeast Asia, which has increased the incidence of nasopharyngeal carcinoma. Due to the reason some people's blood relations have undergone changes, environmental factors clearly play an important role also. Recent studies have found that the following material and nasopharyngeal carcinoma have a certain relationship:
(1) nitrite rubber: can be induced animal tumors. Which dimethyl sulfoxide and diethyl nitrate nitrate adhesive glue in Guangzhou were higher in the salted fish, salted fish feeding with rats, can induce nasal or sinus cancer. He Hongchao Deng (1972) that the Cantonese nasopharyngeal cancer may be related to a high incidence of children's habits to eat salted fish can be detected in their urine mutagenicity of volatile with nitrite rubber.
(2) aromatic cavity: high incidence of n
asopharyngeal carcinoma within the family, per gram of dust in the 3,4 – benzo Mao broad content of 16.83, significantly higher than the low incidence area families. Similarly, the compound in animal experiments can also be induced "nasopharyngeal" Department of tumors.
NPC susceptible (3) trace elements: a small dose of sulfuric acid in the second sickle nitroso Relief winded process induced from the NPC to promote the role of cancer.

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