ABSTRACT
BACKGROUND: To investigate small-nucleolar RNAs (snoRNAs) as reference genes when measuring miRNA expression in tumour samples, given emerging evidence for their role in cancer. METHODS: Four snoRNAs, commonly used for normalisation, RNU44, RNU48, RNU43 and RNU6B, and miRNA known to be associated with pathological factors, were measured by real-time polymerase chain reaction in two patient series: 219 breast cancer and 46 head and neck squamous cell carcinoma (HNSCC). SnoRNA and miRNA were then correlated with clinicopathological features and prognosis. RESULTS: Small-nucleolar RNA expression was as variable as miRNA expression (miR-21, miR-210, miR-10b). Normalising miRNA PCR expression data to these recommended snoRNAs introduced bias in associations between miRNA and pathology or outcome. Low snoRNA expression correlated with markers of aggressive pathology. Low levels of RNU44 were associated with a poor prognosis. RNU44 is an intronic gene in a cluster of highly conserved snoRNAs in the growth arrest specific 5 (GAS5) transcript, which is normally upregulated to arrest cell growth under stress. Low-tumour GAS5 expression was associated with a poor prognosis. RNU48 and RNU43 were also identified as intronic snoRNAs within genes that are dysregulated in cancer. CONCLUSION: Small-nucleolar RNAs are important in cancer prognosis, and their use as reference genes can introduce bias when determining miRNA expression.
Subject(s)
Breast Neoplasms/genetics , MicroRNAs/analysis , RNA, Small Nucleolar/physiology , Breast Neoplasms/mortality , Breast Neoplasms/pathology , Carcinoma/genetics , Carcinoma, Squamous Cell , Female , Head and Neck Neoplasms/genetics , Humans , Neoplasms, Squamous Cell/genetics , Prognosis , RNA, Small Nucleolar/analysis , Squamous Cell Carcinoma of Head and NeckABSTRACT
A method was developed for determining benzylpenicillin and cloxacillin in animal tissues. Samples are extracted with acetonitrile, and the extract is cleaned up on a C18 solid-phase extraction (SPE) cartridge, derivatized, and quantitated by liquid chromatography with UV detection at 325 nm. The method was validated on spiked bovine kidney, liver, and muscle tissues. Kidney was spiked at 0.01, 0.05, and 0.20 mg/kg; liver and muscle were spiked at 0.20 mg/kg. Recoveries were 75-100% , with coefficients of variation of 2-7%. The method was further validated on kidney, liver, and muscle tissues from 2 sheep dosed with Aquacaine G suspension (containing benzylpenicillin). Mean levels of benzylpenicillin in these tissues ranged from 0.02 to 4.06 mg/kg, with coefficients of variation of replicate analyses between 3 and 7%. The limit of detection was approximately 0.005 mg/kg for benzylpenicillin and cloxacillin in kidney, liver, and muscle tissues. This method was used to study the stability of both spiked and incurred residues of benzylpenicillin in ovine liver during storage at -20 degrees C for 3 months. Assuming the rate of loss follows a first-order kinetic decay, the mean half-life of benzylpenicillin in liver is 62 days for spiked tissues and 71 days for tissues with incurred residues.