Mechanism Of Anti-human IgM Antibody On The Growth Inhibition Of Human Nasopharyngeal Carcinoma HNE-1Cell Xenograft In Nude Mice

Objective: With the progress of examination methods andtreatments, the five years survival rate of nasopharyngeal carcinoma (NPC)has raised to a certain extent. However, the NPC is a pathogenic diseaseresulting from many combination factors, its pathogenesis remains unclear. Sothe early diagnosis is still difficult and the treatment effect is still not ideal. Inour previous studies[1,2], we found that the immunoglobulin (Ig) M is widelyexpressed in head and neck tumors, including NPC. With the intervention ofanti-human IgM antibodies, it could significantly inhibit the growth of humanNPC HNE-1cell xenograft in nude mice. We suspected that IgM has a growthfactor-like role, but the exact mechanism is still not clear. This study was onthe basis of our preliminary studies, obtaining transplanted tumor tissue ofhuman NPC HNE-1cells in nude mice, through detecting the expression ofSurvivin, proliferating cell nuclear antigen(PCNA), angiopoietin-2(Ang-2)and the transplanted tumor microvessel density(MVD), to further explore thepossible mechanisms of anti-human IgM antibodies inhibiting the growth ofhuman NPC HNE-1cell xenograft in nude mice, so as to providing theoreticbasis for pathogenesis research of NPC and application of anti-human IgMantibodies to clinic therapy. Methods: Taking tumor tissue of transplanting human NPC HNE-1cells in Balb/c-nu/nu nude mice embedded in paraffin andcutting into4μm thick slices. The expression of Survivin, PCNA, Ang-2weremeasured by immunohistochemical SABC method, and the average opticaldensities were determinated by the image analysis system. We captured theimages in Olympus BH2microscope with double-blind method. There wasfive slices of each indicator and five pictures were collected in each slice. Weused the Image-pro Plus6.0software for semiquantitative immunohisto-chemical analysis of the picture, recording an average optical density.Meanwhile, we detected the expression of tumor microvessel marked withCD31by immunohistochemical streptavidin-Alkaline Phosphatase (SAP)method, and counted MVD. All the results expressed in (x±s). We usedSPSS16.0for windows software for statistical analysis and P<0.05indicatedstatistical significance. Result:(1) The expression of Survivin: Survivin wasdetected in the three groups, the mean optical density value of Survivin was(0.153±0.009) in experiment group,(0.221±0.019) in IgG control group,(0.246±0.021) in PBS control group, respectively. Positive expression ofSurvivin in the experimental group was significantly lower than those in theIgG control group and PBS control group, the difference was statisticallysignificant (P<0.05).(2) The expression of PCNA: PCNA was detected in thethree groups, the mean optical density value of PCNA was (0.084±0.025) inexperiment group,(0.149±0.016) in IgG control group,(0.163±0.018) inPBS control group, respectively. Positive expression of PCNA in the experimental group was significantly lower than those in the IgG controlgroup and PBS control group, the difference was statistically significant(P<0.05).(3) The expression of Ang-2: The expression of Ang-2was detectedin the three groups, the mean optical density value of Ang-2was (0.121±0.021) in experiment group,(0.188±0.013) in IgG control group,(0.196±0.005) in PBS control group, respectively. Positive expression of Ang-2in theexperimental group was significantly lower than those in the IgG controlgroup and PBS control group, the difference was statistically significant(P<0.05).(4)The MVD value of anti-human IgM antibody treatment groupwas (12.54±0.47), significantly lower than IgG control group (16.95±0.21)and PBS control group (17.17±0.47), the difference was statisticallysignificant (P<0.05).(5) The MVD was positively correlated with theexpression of Survivin and Ang-2protein in xenograft tissues of human NPCHNE-1cell in nude mice (r=0.754,0.696respectively, P=0.001，0.004respectively). Conclusion:(1) Anti-human IgM antibody can significantlyinhibit the expression of Survivin in xenograft tissues of human NPC HNE-1cell in nude mice.(2) Anti-human IgM antibody can significantly inhibit theexpression of PCNA in xenograft tissues of human NPC HNE-1cell in nudemice.(3) Anti-human IgM antibody can significantly inhibit the expression ofAng-2in xenograft tissues of human NPC HNE-1cell in nude mice.(4)Anti-human IgM antibody can significantly inhibit the expression ofmicrovessel (MVD)/angiogenesis in oxenograft tissues of human NPC HNE-1 cell in nude mice. The mechanism may be related to the inhibition of Ang-2and Survivin expression.(5) The mechanism of Anti-human IgM antibody onthe growth inhibition of human NPC HNE-1cell xenograft in nude mice maybe related to the promotion of apoptosis and the inhibition of cell proliferationand angiogenesis.