Paraffin-embedded tissue as a source of RNA for gene expression analysis in oral malignancy

The role of secreted aspartyl proteinases in Candida tropicalis invasion and damage of oral mucosa

Candida virulence attributes include the ability to colonize and invade host tissues, and the secretion of hydrolytic enzymes. Although Candida albicans is regarded as the principal fungi causing infections in humans, other species, particularly Candida tropicalis, are increasingly being recognized as human pathogens. Relatively little is known, however, about the virulence attributes associated with C. tropicalis. The present study aimed to investigate epithelial infection by C. tropicalis using a reconstituted human oral epithelium (RHOE) together with confocal laser scanning microscopy and real-time PCR. A comparison of clinical strains was made in terms of tissue colonization, invasion and C. tropicalis secreted aspartyl proteinase (SAPT) gene expression. All C. tropicalis strains were able to colonize RHOE in a strain-dependent manner. After 12 h of infection, C. tropicalis was found to be highly invasive, with extensive tissue damage occurring after 24 h. Real-time PCR of C. tropicalis SAPT1-4 genes showed that expression was strain-dependent, with SAPT2-4 transcripts being frequently detected and SAPT1 rarely detected. Tissue invasion and damage was not inhibited by the presence of pepstatin A. Accordingly, and given that an increase in infection time was not accompanied with an increase in SAPT gene expression, it can be suggested that the proteinases are not involved in invasion and damage of RHOE by C. tropicalis. In summary, C. tropicalis can be considered as highly invasive with the ability to induce significant tissue damage. These features, however, do not appear to be related to specific SAPT gene expression.

Gene expression in formalin-fixed paraffin-embedded lymph nodes

Elucidation of molecular pathways involved in development of human lymphoma requires efficient methods for tackling gene expression in lymph nodes. Expression studies of transcription factors in these malignancies facilitate understanding the changes occurring in neoplastic transformation and lymphoma development. Excised lymph nodes are routinely fixed in formalin and embedded in paraffin for diagnosis and stored in many hospitals' pathology archives. These tissues represent a precious resource for research since they allow retrospective studies to cover a broad range of human lymphoma even the less frequent types. Reverse transcription polymerase chain reaction (RT-PCR) is a commonly used method for gene expression analysis and a reproducible protocol for RNA isolation from lymph nodes is an inevitable requirement for these studies. However, formalin fixation and paraffin-embedding interfere with the quality of RNA especially when isolated from lymph nodes being the most fragile lymphatic tissues. We present here a simple and fast method for RNA isolation from formalin-fixed paraffin-embedded lymph nodes that can be successfully applied for RT-PCR as well as for quantitative RT-PCR analysis. We tested diverse isolation reagents and combined a range of factors in order to get a high quality RNA for retrospective studies of gene expression in human lymphoma samples. Our modified method of RNA extraction from FFPE provides superior yields and purity based on qPCR data.

Characterization of Candida parapsilosis infection of an in vitro reconstituted human oral epithelium

Oral candidosis is a common problem in immunocompromised patients, and whilst Candida albicans is regarded as the principal cause of infection, other non-Candida albicans Candida (NCAC) species are increasingly being recognized as human pathogens. Relatively little is known about the virulence factors associated with NCAC species, and the aim of this study was to use a reconstituted human oral epithelium (RHOE) to examine epithelial infection withCandida parapsilosis. Strains originating from the oral and vaginal mucosa and from the urinary tract were all shown to colonize RHOE in a strain-dependent manner. Strain differences were found in the colonizing morphology and in the extent of invasion of the RHOE. Low invasion of RHOE was detected for strains after 12 h, whereas extensive tissue damage was evident after 24 h when assessed using histological examination and lactate dehydrogenase activity determination. Tissue damage was reduced in the presence of pepstatin A, although C. parapsilosis invasion of the tissue was not inhibited. Real-time polymerase chain reaction of secreted aspartyl proteinase (SAP) genes (SAPP1-3) showed that expression was strain dependent, with an increased expression generally occurring for Candida infecting RHOE compared with planktonic equivalents. In summary, C. parapsilosis was not highly invasive of RHOE but did induce significant tissue damage, which could relate to specific SAPgene expression.

Characterization of Candida albicans infection of an in vitro oral epithelial model using confocal laser scanning microscopy

INTRODUCTION

Oral candidosis presents as several distinct forms and one of these, chronic hyperplastic candidosis, is distinguished by penetration of the epithelium by Candida. The aim of this study was to use confocal laser scanning microscopy to examine invasion of the oral epithelium by Candida albicans from different oral conditions and to determine whether inherent strain differences exist that could relate to infection type. Reverse transcription-polymerase chain reaction was also used to detect products from virulence gene families.

METHODS

C. albicans (n = 19) was used to infect reconstituted human oral epithelium, which was incubated for 12 h. One half of the reconstituted human oral epithelium was then fixed and stained with concanavalin A-Alexa 594, pan-cytokeratin antibody-Alexa 488 and Hoechst nucleic acid dye. RNA was extracted from the remaining tissue for reverse transcription-polymerase chain reaction targeting secreted aspartyl proteinase, phospholipase and agglutinin-like sequence genes of C. albicans.

RESULTS

Confocal laser scanning microscopy revealed strain-dependent tissue invasion, with differences evident in surface colonization, C. albicans morphology and the extent and pattern of tissue penetration. Hyphae were seen to directly penetrate epithelial cells and migrate between keratinocytes with yeast budding also evident in the reconstituted human oral epithelium. A relationship between 'high tissue invasion' and expression of secreted aspartyl proteinase genes 4-6 was noted. Interestingly, four of the five 'high invaders' originated from chronic hyperplastic candidosis.

CONCLUSIONS

Confocal laser scanning microscopy permitted high resolution analysis of reconstituted human oral epithelium invasion by C. albicans and identified strain differences in the invasion process. Association between extensive hyphal morphology, direct epithelial penetration and high surface colonization were made with the 'highly invasive' strains.

Extraction of RNA from archival tissues and measurement of thrombospondin-1 mRNA in normal, dysplastic, and malignant oral tissues

Thrombospondin-1 (TSP-1) is an extracellular matrix glycoprotein implicated in the regulation of angiogenesis and tumour development. Our objectives were to ascertain the quantity and quality of RNA extracted from archival, formalin-fixed, paraffin embedded, oral tissues and their application in measuring the concentrations of TSP-1 mRNA in these tissues. We compared three techniques of isolation of RNA as well as related experimental variables. TSP-1 mRNA was measured in specimens of normal, dysplastic, and malignant oral tissues by real-time reverse transcriptase polymerase chain reaction (RT-PCR). RNA suitable for analysis by real-time RT-PCR was obtained by the three techniques tested, although the yield varied depending on the protocol used (range 0.2-3.6 microg/mm(3)). The mean (S.D.) concentrations of TSP-1 mRNA relative to 18S were 21.1 (7.2) in normal oral tissues (n=9), 11.0 (8.2) in dysplastic tissue (n=8) and 7.3 (5.3) in carcinomatous tissue (n=17). The difference between normal and carcinomatous specimens was significant (p=0.01). This reduction in expression of TSP-1 mRNA from normal to dysplasia to carcinoma may favour the angiogenic drive that accompanies the development of oral tumours.

Overexpression of inactive arylsulphatase mutants and in vitro activation by light-dependent oxidation with vanadate

Arylsulphatases B (ASB) and A (ASA) are subject to a unique post-translational modification that is required for their function. The modification reaction, conversion of an active-site cysteine into a formylglycine, becomes saturated when these enzymes are overexpressed. We have removed the possibility of in vivo modification by expressing mutants of ASB and ASA in which the active-site cysteine is substituted with a serine. These mutants are expressed much more efficiently when compared with the native enzymes under identical conditions. The purified ASB mutant can then be converted into catalytically active ASB in vitro using vanadate and light.

A simple method for RNA isolation from formalin-fixed and paraffin-embedded lymphatic tissues

Gene activation that lies beneath lymphoid cell differentiation has been one of the most explored issues in immunology in the recent years. However, the analysis of this molecular event in lymphoproliferative diseases is often hampered by the lack of fresh material. Most tissues available for routine histological investigation are formalin fixed and paraffin embedded. Gene expression in such specimens could be analyzed using reverse transcription of mRNA and the polymerase chain reaction (RT-PCR). Therefore we adjusted and established a method for mRNA isolation from such specimens by a combination of previously reported protocols and a modification of the phenol/chloroform extraction method. Given the significance of transcription factors in the human hemopoietic system, we investigated whether mRNA could be successfully isolated from archival tissue for a study on expression of Ikaros family transcription factors in lymphatic tissue. Although quantitative analysis of RNA isolated from archival tissue is probably not feasible due to the unpredictable degree of RNA isolation varying from sample to sample, we show here that screening analysis is possible and simple.

Signal recognition particle receptor (SRPR) is downregulated in a rat model of cyclosporin A-induced gingival overgrowth

Differential display is a powerful technique which can be used to identify those genes whose expression is altered between two or more tissues under investigation. We have applied differential display to a rat model of cyclosporin A-induced gingival overgrowth (CIGO) to identify genes which are differentially expressed as a result of drug treatment. Ten weanling Wistar rats were fed with a pelleted diet containing cyclosporin A (CsA) at 120 mg/kg for 10 d and then 200 mg/kg for a further 30 d prior to culling. Experimental rats were compared with 10 age/sex-matched rats on a control diet. Significant evidence of overgrowth was observed in the interdental papilla between the mandibular first and second molar teeth in the CsA group. Differential display was performed on total cellular RNA extracted from the mandibular buccal gingiva. A cDNA product was isolated which was underexpressed in the overgrowth tissue and demonstrated a 95% sequence homology to the human signal recognition particle receptor (Human Docking Protein). Preliminary studies indicate that this gene is also underexpressed in human CIGO tissue. The method of approach and the potential implications of our findings are discussed.

A comparison of the management of potentially malignant oral mucosal lesions by oral medicine practitioners and oral & maxillofacial surgeons in the UK

This study describes the results of a survey undertaken to assess the management of potentially malignant oral mucosal lesions by oral medicine practitioners and compares their approach with that of oral & maxillofacial surgeons that we have previously described. Significant differences were noted between the two groups in the use of photography to document the lesions and in the use of certain special investigations, which included measurement of serum iron, serum ferritin, serum Vit B12, red cell folate and candidal isolation. The groups also varied in the perceived importance of the age of the patient and anatomical site of the lesion when deciding on the need for further biopsy. There was also significant variation in the use of certain treatment modalities, including excising non-dysplastic and severely dysplastic/carcinoma in-situ lesions and eliminating trauma when treating mild/moderately dysplastic and severely dysplastic/carcinoma in-situ lesions. Significant differences in the frequency and duration of follow-up were noted for non-dysplastic lesions. Finally, the two groups differed significantly when asked to rank the perceived importance of certain factors (the histopathology of the most recent biopsy and the anatomical site of the lesion) when deciding the need to follow-up. Possible reasons for the variation are discussed.