The present study was conducted to investigate the direct action of hypoxanthine, which has been reported to be present in pig follicular fluid, on spontaneous meiotic resumption of pig denuded oocytes in vitro. No oocytes, which were surrounded by a cumulus and some membrana granulosa cells directly adjacent to it from healthy antral follicles, underwent germinal vesicle breakdown (GVBD) when they were cultured in serum-supplemented 199 with or without 4 mM hypoxanthine. On the other hand, 81% of denuded oocytes prepared from such cumulus-oocyte-granulosa cell complexes showed GVBD after 24 h of culture. Hypoxanthine inhibited significantly this spontaneous resumption of meiosis in denuded oocytes. The inhibitory action of hypoxanthine was dose dependent at concentrations of 1-6 mM and was reversible following subsequent culture of the oocytes in hypoxanthine-free medium. However, premature chromosome condensation was observed in oocytes cultured in hypoxanthine-supplemented medium, and the oocytes released from the influence of hypoxanthine completed GVBD and reached the second metaphase slightly faster than those freshly isolated from the follicle. These results suggest that hypoxanthine inhibits spontaneous meiotic resumption of pig oocytes in vitro. However, the inhibitory action of hypoxanthine does not prevent all events involved in GVBD from occurring.
The development of an early tumor detection marker for oral cancer is an obvious need due to the high recurrence rate and poor survival rate. Based on our previous report that overexpression of heterogeneous nuclear ribonucleoprotein (hnRNP) B1 protein was found in 100% of squamous cell carcinomas of human lung, we applied the same immunohistochemical method, using anti-hnRNP B1 antibody, to human oral squamous cell carcinoma (OSCC). Seven human tissue sections of OSCC showed strong staining with anti-hnRNP B1 antibody, and hnRNP B1 protein of 37 kDa was identified in protein fractions isolated from six of the cancerous tissue sections, while it was not found in adjacent noncancerous tissue. Moreover, three non-homogeneous (nodular) leukoplakia sections showed significant anti-hnRNP B1 staining. The results suggest that this antibody detects precancerous lesions as well as advanced lesions (stages I to IV) of OSCC. We also present positive results of cytodiagnosis for two smear specimens. All of the above results indicate that hnRNP B1 is a new and useful marker for early detection of OSCC.
Key words: Oral precancerous lesion -Oral leukoplakia -Cytodiagnosis -Biomarker -ChemopreventionRecently we reported that overexpression of heterogeneous nuclear ribonucleoprotein (hnRNP) B1 of 37 kDaand not hnRNP A2, as had previously been believed-is a good biomarker for the detection of human lung cancer. 1) hnRNP B1 is identical to hnRNP A2 with the addition of 12 amino acids at the N-terminus, a difference probably deriving from alternative splicing.2) hnRNP A2/B1 protein is a major component of the hnRNP core complex in mammalian cell nuclei, and is involved in RNA splicing in nuclei, as well as in mRNA transport from nucleus to cytoplasm.3) In a study on the expression of hnRNP B1 in both human lung cancer cell lines and human lung cancer tissue, we found that cancer cells showed significant positive staining of hnRNP B1 with anti-hnRNP B1 antibody, and that squamous cell carcinomas showed 100% positive staining.1) These results encouraged us to see whether molecular diagnosis of human lung cancer with antihnRNP B1 could be extended to human oral squamous cell carcinoma (OSCC).Success in early detection of oral cancer is of great value, since human oral cancer has a high recurrence rate and is associated with cosmetic disruption in the advanced stage. Although various tumor markers, such as carcinoembryonic antigen (CEA), 4) squamous cell carcinoma-antigen (SCC), 5) glutathione S-transferase-π (GST-π), 6, 7) and cytokeratins, 8,9) are currently being used as diagnostic aids for OSCC, all these markers have proved to be insufficiently sensitive and reliable for the early detection of OSCC and prediction of its recurrence. Thus, the establishment of a new tumor marker with increased specificity and sensitivity for early lesion of OSCC is a high priority.We first found that anti-hnRNP B1 antibody stained cancer cells of seven human tissue sections of OSCC. Next, by western blotting we detected a protein band (37 kDa) of h...
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