Allele-specific PCR for detecting the deafness-associated mitochondrial 12S rRNA mutations.

Mutations in mitochondrial 12S rRNA (MT-RNR1) are the important causes of sensorineural hearing loss. Of these mutations, the homoplasmic m.1555A>G or m.1494C>T mutation in the highly conserved A-site of MT-RNR1 gene has been found to be associated with both aminoglycoside-induced and non-syndromic hearing loss in many families worldwide. Since the m.1555A>G and m.1494C>T mutations are sensitive to ototoxic drugs, therefore, screening for the presence of these mutations is important for early diagnosis and prevention of deafness. For this purpose, we recently developed a novel allele-specific PCR (AS-PCR) which is able to simultaneously detect these mutations. To assess its accuracy, in this study, we employed this method to screen the frequency of m.1555A>G and m.1494C>T mutations in 200 deafness patients and 120 healthy subjects. Consequently, four m.1555A>G and four m.1494C>T mutations were identified; among these, only one patient with the m.1494C>T mutation had an obvious family history of hearing loss. Strikingly, clinical evaluation showed that this family exhibited a high penetrance of hearing loss. In particular, the penetrances of hearing loss were 80% with the aminoglycoside included and 20% when excluded. PCR-Sanger sequencing of the mitochondrial genomes confirmed the presence of the m.1494C>T mutation and identified a set of polymorphisms belonging to mitochondrial haplogroup A. However, the lack of functional variants in mitochondrial and nuclear modified genes (GJB2 and TRMU) in this family indicated that mitochondrial haplogroup and nuclear genes may not play important roles in the phenotypic expression of the m.1494C>T mutation. Thus, other modification factors, such as environmental factor, aminoglycosides or epigenetic modification may have contributed to the high penetrance of hearing loss in this family. Taken together, our data showed that this assay is an effective approach that could be used for detection the deafness-associated MT-RNR1 mutations.

Plasma adrenomedullin levels and nasopharyngeal carcinoma prognosis.

BACKGROUND: Adrenomedullin has been identified as a tumor growth factor. However, few studies have reported its relationship with cancer survival. We evaluated the prognostic value of pretreatment plasma adrenomedullin levels in nasopharyngeal carcinoma (NPC). METHODS: Plasma adrenomedullin levels of 258 NPC patients and 100 healthy controls were determined using enzyme-linked immunosorbent assay. Adverse event was defined as tumor progression or death from any cause during 5-year follow-up. The relationships between plasma adrenomedullin levels and 5-year mortality, adverse event, tumor-free survival and overall survival were evaluated using multivariate analysis. RESULTS: Pretreatment plasma adrenomedullin levels were substantially higher in patients than in healthy subjects and were correlated highly with tumor classification, lymph node classification and tumor node metastasis stage positively. Adrenomedullin was identified as an independent predictor of 5-year mortality, adverse event, tumor-free survival and overall survival. Based on receiver operating characteristic curve analysis, pretreatment plasma adrenomedullin level had high predictive value for 5-year mortality and adverse event and had high diagnostic value for NPC. CONCLUSIONS: Adrenomedullin may be a reliable biomarker for predicting the long-term prognosis of patients with NPC and also has potential diagnostic utility for NPC.