| Objective:Although the diagnosis and treatment of nasopharyngeal carcinoma are continuing to make progress, but early diagnosis and prognosis judgement is lacking of effective means and the 5-year survival rate of patients is to be further improved; So we need break out the pathogenesis of nasopharyngeal carcinoma and find a new target to improve its early diagnosis and overall treatment. In this study, to explore the biological activity of ectopic expression of IgM and its possible molecular mechanisms, the effect of anti-human IgM antibody on the tumorigenesis, apoptosis and the expression of IgM, gp96 protein of human nasopharyngeal carcinoma HNE-1 cell xenografts in nude mice were evaluated. Methods:Nasopharyngeal carcinoma HNE-1 cells were cultured, and the animal model of human nasopharyngeal carcinoma was established by transplanting human nasopharyngeal carcinoma HNE-1 cells into right flank subcutis of Balb/c-nu/nu nude mice. Then the 15 mice were randomly divided into experimental group (intraperitoneal injection of anti-human IgM antibody,1.5mg /nude mouse/3d,5 times), the IgG control group (intraperitoneal injection of IgG) and the PBS control group (intraperitoneal injection of PBS); while observing the situation of nude mice, weighing the weight of nude mice, measuring the long diameter and short diameter of by slide gaud on a regular basis (every four days), and eventually drawing tumor growth curve, calculating tumor volume=tumor longest diameter×shortest diameter2/2. Finally, mice were observed 1 week after intraperitoneal injection of 5 times, and then the mice were killed, the tumors were took and weighed, and the tumor growth inhibition ratio was calculated. The change of the tumor and organs of nude mice were observed by hematoxylin and eosin stain. The apoptosis of human nasopharyngeal carcinoma HNE-1 cell in the transplanted tumor tissues of nude mice were assessed by TUNEL, and the apoptotic index were calculated by the image analysis system. The expression of IgM and gp96 protein were measured by immunohistochemistry (SP method), and the average optical density were determinated by the image analysis system. Results:(1) Animal model of human nasopharyngeal carcinoma HNE-1 cell xenografts was successfully constructed in nude mice. Nasopharyngeal carcinoma xenografts in situ were established in each of these three groups and the rate of tumor formation was 100%. The tumors were confirmed as nasopharyngeal carcinoma by biopsy, and nude mice of three groups survived in the experimental period. (2) Food and drink of nude mice was normal, mental state of nude mice was good, without dying and the action was free in three groups. The pathological section examination of heart, liver, spleen, lung, kidney had no obvious difference. (3) The transplanted tumor volume of the experimental group was (26.73±16.51) mm3, significantly lower than those of the IgG control group (204.97±151.88) mm3 and the PBS control group (230.16±167.78) mm3 (P<0.05). No significantly difference was found in body weight of nude mice in the experimental group (21.10±2.35) g, the IgG control group (20.70±3.29) g and PBS control group (20.01±2.22) g (P>0.05). The weight of human nasopharyngeal carcinoma HNE-1 cell xenografts were (0.09±0.07) g in experimental group, significantly lower than those of IgG control group (0.35±0.10) g and the PBS control group (0.38±0.08) g (P<0.05), and the tumor growth inhibition ratio were 74.45% and 76.84%. (4) The apoptosis of human nasopharyngeal carcinoma HNE-1 cell in the transplanted tumor tissues of nude mice were assessed by TUNEL. The tumor cell apoptosis index of experimental group was (1.50±0.76)%, significantly higher than those of IgG control group (0.49±0.15)% and the PBS control group (0.42±0.20)%(P<0.05). (5) The result of immunohistochemistry technique (SP method) to determine the expression of IgM and gp96 protein in implanted tumor of mice showed that the expression of IgM protein was (0.01±0.01) in experimental group, which was much lower than the IgG control group (0.06±0.03) and PBS control group (0.05±0.03), and significant difference was found (P<0.05). Meanwhile, the expression of gp96 protein in experimental group(0.05±0.01) dropped dramatically, the difference between experimental group and IgG control group (0.01±0.03) and PBS controls group (0.11±0.02) was statistically significant (P<0.05). Conclusions:(1)Anti-human IgM antibody had obvious inhibitory effects on the growth of human nasopharyngeal carcinoma HNE-1 cells xenografts in nude mice, which suggested that IgM ectopic expressed in nasopharyngeal carcinoma has a role of growth factor. (2)Anti-human IgM antibody can inhibit the expression of IgM protein, suggesting that anti-human IgM antibody may inhibit the tumor growth by blocking the biological activity of IgM protein. (3)Anti-human IgM antibody has obvious inhibitory effects on the expression of gp96 protein, suggesting that its mechanism may be related to the inhibition of IgM expression. (4)Anti-human IgM antibody can promote apoptosis of human nasopharyngeal carcinoma HNE-1 cell in the transplanted tumor tissues of nude mice, and the apoptosis of tumor cells may be via the inhibition of the expression of IgM and gp96 protein.
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