| OBJECTIVES: Infection with human parvovirus B19 is a global concern and the infection rate is similar among the United States, Europe and Asia, with approximately half of 15-year-old adolescents and over 60% adults being seropositive. Increasing evidences have shown that a growing list of pathologies is now attributed to B19. Some researchers have demonstrated that B19 infection may be important in the pathogenesis of acute lymphoblastic and myeloblastic leukaemia. One study has shown a marked up-regulation of COX-2 expression in RA synoviocytes after incubation with the recombinant protein VP1u, which plays a key role in the carcinogenesis by promoting the proliferation of neoplastic cells and their resistance to apoptosis, as well as angiogenesis, tumor cell invasion and setting up of the metastatic process. However, there has been no report linking parvovirus B19 with colon carcinoma so far. The aim of this study was to evaluate whether parvovirus B19, a common infectious pathogen in humans, also was involved in the carcinogenesis of human colon, and to provide a new clue to the etiology of colon carcinoma.METHODS: A total of 119 paraffin-embedded specimens of colon polyps, adenocarcinomas, carcinoma-adjacent tissues, and normal controls were processed for nested PCR, in situ hybridization and immunohistochemistry detection of B19 DNA and protein. The results of positive rates were analyzed using statistic software. Ten matched cases selected randomly were confirmed by laser capture microdissection of histologically defined tissue components followed by nested PCR amplification of B19 DNA. Then the nested-PCR products were sequenced. The expression of B19 capsid protein and cyclo-oxygenase-2 were studied by the method of immunohistochemistry in 37 cases of colon adenocarcinoma, and then their correlations were analyized by statistics. The expression of cyclo-oxygenase-2 in the colon-cancer cells (Lovo) transfected by inducible vector for VP1u was determined by western-blot analysis.RESULTS: B19 DNA was detected in 94.6% (35/37) of colon adenocarcinomas, 67.6% (25/37) of adjacent non-cancerous tissues,85.6% (30/35) of polyps and 60.0% (6/10) of normal controls by nested PCR, respectively. The results of microdissection showed that neoplastic cells contained B19 DNA (10/10), whereas most of the normal-appearing cells in adjacent tissues were negative for virus (3/10). Analysis of the microdissected material confirmed the presence of viral DNA preferentially located in the colonic neoplastic epithelium. In situ hybridization detected B19 DNA in 81.1% (30/37) of colon adenocarcinomas, 43.2% (16/37) of adjacent non-cancerous tissues, 74.3% (26/35) of polyps and 50.0% (5/10) of normal controls, respectively. B19 capsid protein was found in 78.4% (29/37), 32.4% (12/37) and 57.1% (20/35) of colon adenocarcinomas, tumor-adjacent tissues, and polyps, respectively, but not in normal colons (none of ten). There were significant differences in nested PCR, in situ hybirdization and immunohistochemistry between adenocarcinomas and non-neoplastic adjacent tissues(P = 0.012,P < 0.001,P < 0.001), and between adenocarcinomas and normal controls(P = 0.014,P = 0.017,P < 0.001). Additionally, the statistic analysis showed a weak trend between colon polyps and normal controls by nested-PCR and in situ hybirdization (P = 0.093,P = 0.062), respectively, but no significant differences were detected , nevertheless, a significant diference was found between them by the method of immunohistochemistry ( P = 0.001 ). A significant correlation between the expression of cyclo-oxygenase-2 and capsid protein of B19 was found in the 37 cases of colon adenocarcinoma(P = 0.001,κ=0.539). A time course study revealed that VP1u expression was induced 12 hours post tetracycline exposure and reached plateau after 48 hours, furthermore, the activated VP1u upregulated the expression of cyclo-oxygenase-2 protein. CONCLUSIONS: Parvovirus B19 DNA commonly exist in human colon tissues and its capsid protein is preferentially located in colon polyps and adenocarcinomas lesions. Parvovirus B19 may induce important oncogenic pathways in colon-cancer cells through the upregulation of cyclo-oxygenase-2.
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