Canadian Association of Pathologists-Association canadienne des pathologistes National Standards Committee for High Complexity Testing/Immunohistochemistry: guidelines for the preparation, release, and storage of unstained archived diagnostic tissue sections for immunohistochemistry.

OBJECTIVES: Formalin-fixed, paraffin-embedded unstained archived diagnostic tissue sections are frequently exchanged between clinical laboratories for immunohistochemical staining. The manner in which such sections are prepared represents a type of preanalytical variable that must be taken into account given the growing importance of immunohistochemical assays, especially predictive and prognostic tests, in personalized medicine. METHODS: Recommendations were derived from review of the literature and expert consensus of the Canadian Association of Pathologists-Association canadienne des pathologists National Standards Committee for High Complexity Testing/Immunohistochemistry. RESULTS: Relevant considerations include the type of glass slide on which to mount the unstained sections; the thickness of the tissue sections; the time from slide preparation to testing; the environment, particularly the temperature at which the unstained sections will be maintained prior to testing; the inclusion of on-slide positive control tissue where possible; and whether patient identifier(s) should be included on slide labels. CONCLUSIONS: Clear communication between requesting and releasing laboratories will facilitate the proper preparation of unstained sections and also ensure that applicable privacy considerations are addressed.

Cytotoxic activities of nucleoside and nucleobase analog drugs in malignant mesothelioma: characterization of a novel nucleobase transport activity.

This study was designed to evaluate the cytotoxic activity of several nucleoside and nucleobase analog drugs as possible new agents for treatment of malignant mesothelioma and to identify factors responsible for the clinical variation of nucleoside analog drug response in chemotherapy of mesothelioma. Three human mesothelioma cell lines (MSTO-211H, H2452 and H2052) were tested for gemcitabine sensitivity and nucleoside transport activity. MSTO-211H, H2452 and H2052 exhibited differences in sensitivity to gemcitabine, nucleoside transport rates and hENT1 site densities. In H2052 cells, gemcitabine, 5-fluoro-2'-deoxyuridine, clofarabine and cladribine were most active with IC(50) values of 46, 43, 240 and 490 nM, respectively, whereas 5-fluorouracil was the least cytotoxic drug tested. In H2052 cells, the combination of gemcitabine and fludarabine or cladribine resulted in synergistic cytotoxic response. In nucleobase transport studies, hypoxanthine and 6-mercaptopurine but not 5-fluorouracil was transported into H2052 cells by a novel purine-specific, sodium-independent nucleobase transport activity. In summary differences in nucleoside analog drug transport activities are likely to contribute to the observed clinical variation in nucleoside analog response in patients and for the first time a correlation between nucleobase drug sensitivities and transport activities was shown. A novel combination of gemcitabine and fludarabine or cladribine had synergistic cytotoxic activity against the least sensitive mesothelioma cell line. These drug combinations merit further evaluation as effective therapeutic regimens in patients with aggressive mesothelioma.