| Head and neck squamous cell carcinoma (HNSCC) is one of the ten most common cancers in the world. It is characterized by local invasion, dissemination to regional lymph nodes and frequent recurrence at the primary sites. Despite great improvements in diagnosis and treatments (including surgery, radiotherapy and chemotherapy), 5-year survival and overall survival of the patients remain unchanged over the past 30 years.It is most frequently found that metastasis of the cervical lymph nodes occurs in patients with HNSCC. The presence of lymph node metastases can not always be detected clinically by means of radiological assessment or ultrasound-guided fine-needle aspiration biopsy. Histopathological examination of the neck dissection thus provides significant information for staging and prognosis. However, most parts of a lymph node are usually left unexamined, which suggests that many metastatic cells are overlooked. In addition, some studies showed that pathologic serial sectioning may improve the identification of lymph node metastases. There are some difficulties and limitations on technique to discover lymph node metastases. Therefore, it is very desirable to search for specific tumor markers to investigate lymph node metastases by molecular biological assay.Loss of heterozygosity (LOH) is one of the molecualr markers in malignant tumors. Ithas been proved that LOH in many chromosomes is closely correlated with the development of HNSCC. Among them, chromosome 9 is the most frequently associated with LOH. We analyzed LOH at D9S171 microsatellite locus in primary rumors and lymph nodes of neck dissection, in order to explore the molecular mechanism of the tumor, and the relationship between LOH and clinical features, as well as a possible method to detect lymph node metastases in patients with laryngeal and hypopharyngeal squamous cell carcinoma.1. ObjectiveTo study the frequency of LOH at D9S171 locus and its clinical relevance in patients with laryngeal and hypopharyngeal squamous cell carcinoma. To evaluate the value of LOH to detect metastases of the cervical lymph nodes.2. MethodsA total of 27 primary tumors, 135 lymph nodes from neck dissection and the corresponding normal tissues was obtained from 27 patients with laryngeal and hypopharyngeal squamous cell carcinoma. All of the subjects were patients in the Second Hospital affiliated to Medical College of Zhejiang University during the period from September 2002 to December 2003. None of patients had previously received irradiation or chemotherapy. All available cases were proven to be squamous cell carcinoma by pathological examination. Genomic DNA was extracted from primary tumor and lymph node tissues using a standard phenol-chloroform method. Polymerase chain reaction (PCR) was carried out to amplfy D9S171 locus. Products were separated on 10% denaturing polyacrylamide gels. Then, gels were stained with silver nitrate. LOH was analysed at D9S171 locus. Chi-square test was adopted for statistical analysis.3. ResultsThe frequency of LOH at D9S171 locus was 62.96% in primary tumors, which was closely correlated with the clinical stage (P<0.01). It was demonstrated that LOH occurred more frequently in patients with lymph node metastases and advanced cases(stage UK IV).LOH was detected in both the primary tumor and the matched lymph nodes. The higher level of LOH (35.6%) was found in lymph nodes of neck dissection, compared with the positive rate of cervical lymph nodes detected by pathological examination (17.0%) (P <0.01); The incidences of both LOH and the node metastases determined by pathological examination were closely correlated with the distribution of the regional lymph nodes, which were the highest in the level II (.P<0.01).4. ConclusionsThe high level of LOH was found in primary tumors. It appears that LOH is closely correlated with tumoregenesis and there may be the mutation of putative tumor suppressor genes near D9S171 locus in laryngeal and hypopharyngeal squamous cell carcinoma. The incidence of LOH a...
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