Optimal Cutting Temperature Compound Research Articles

High Incidence of Thymic Epithelial Tumors in E2F2 Transgenic Mice

In virtually all human tumors, genetic and epigenetic alterations have been found which affect the INK4/-CYCLIN D/RB pathway, which regulates cell cycle entry and exit in normal cells. E2F transcription factors are important downstream components of this pathway, which act by controlling the expression of genes involved in DNA replication and cell cycle progression. To determine whether E2F2 deregulation promotes proliferation and tumorigenesis in vivo, we generated E2F2 transgenic mice, in which the Emu and murine pim1 promoter (pp) direct high expression of E2F2 in thymic epithelial cells. Emu-pp-E2F2 mice start to develop cytokeratin- and ER-TR4-positive cortical thymomas from the age of 20 weeks, and within 1 year, nearly all mice succumb to gross thymic epithelial tumors. General thymic morphology is largely maintained, but T cell development is perturbed in thymomas, with proportionately less CD4(+)CD8(+) double-positive thymocytes. In the first 3 months, E2F2 transgenic thymi exhibit only mild epithelial hyperplasia, and thereafter thymomas arise stochastically, probably following additional mutations. Interestingly, Emu-pp-E2F1 mice do not display cortical thymomas. These data argue that E2F2 promotes unscheduled cell division and oncogenic transformation of thymic epithelial cells.

Demarcation of nonmelanoma skin cancer margins in thick excisions using multispectral polarized light imaging.

More than a million cases of nonmelanoma skin cancers are diagnosed every year. Treatment of cancer patients could benefit greatly if a real-time, noninvasive, reliable, and cost-effective technique for delineating tumor margins were available. A novel multispectral dye-enhanced polarized light imaging technique that enables rapid imaging of large tumor fields is described. A tunable monochromatic light source and a CCD camera were employed as the imaging device. Linear polarizers were introduced into both the incident and collected light pathways in order to limit the measurement volume to the superficial tissue layers. To enhance the tumor contrast in the image, aqueous solutions of toluidine blue or methylene blue were topically applied to fresh thick skin excisions for several minutes. Then the specimens were rinsed in saline solution. Images were acquired before and after staining at the selected wavelengths. The two sets of wavelengths corresponding to the hemoglobin Soret absorption band and to the absorption bands of the dyes were used to demarcate the areas of enhanced hemoglobin and dye absorption, respectively. The resulting images demonstrate that staining significantly enhances contrast of the tumor in the image and enables reliable delineation of cancer. Locations and shapes of tumor lobules revealed by polarized light images closely correspond to those found in Mohs frozen sections for 41 specimens out of 45. The study demonstrates that the suggested technique has significant potential as a guidance tool in tumor excision surgery.

The Use of Optimal Cutting Temperature Compound Can Inhibit Amplification by Polymerase Chain Reaction

Optimal cutting temperature (OCT) is a widely used embedding medium for tissues for histopathologic analysis. This investigation examined the effects that OCT storage can have upon the ability to perform subsequent molecular biological analyses. Tumor material was dissected into small pieces and stored at approximately 20 degrees C both with and without OCT. DNA and RNA were then extracted from the tissue fragments and analyzed by the polymerase chain reaction (PCR), using primer sets designed to amplify a range of product sizes, and also by reverse transcriptase-PCR (RT-PCR). The storage of pathological specimens in OCT compound was found to affect significantly and irreversibly the ability to amplify DNA in the PCR, particularly as the size of the amplified fragment increased. This effect appeared to occur as a result of greater degradation of DNA extracted from tissue embedded in OCT compared to DNA extracted from tissue stored without OCT. RNA quality appeared unaffected, which may be because of the extraction protocol employed. Our results suggest that OCT-embedded frozen-tissue samples may be used for RNA isolation for subsequent RT-PCR and for the in vitro amplification of DNA targets of approximately < 300 base pairs only. We strongly advise against the routine storage of any tissue biopsy material in OCT if molecular analyses may be required.