Immunoprecipitation of cell lysates with RAP-5 does not specifically detect ras oncogene product p21

Immunohistochemical Detection of Interferon-γ: Fake or Fact?

Immunohistochemistry is a widely accepted tool to investigate the presence and immunolocalization of cytokines in tissue sections at the protein level. We have tested the specificity and reproducibility of IFNγ immunohistochemistry on tissue sections with a large panel of anti-IFNγ antibodies. Thirteen different commercially available anti-IFNγ antibodies, including seven advertised and/or regularly applied for immunohistochemistry/-cytochemistry, were tested using a three-step streptavidin–biotin–peroxidase technique and a two-step immunofluorescence (FACS) analysis. Immunoenzyme double staining was used to identify the IFNγ-positive cells. Serial cryostat sections were used of human reactive hyperplastic tonsils, rheumatoid synovium, and inflammatory abdominal aortic aneurysms, known to possess a prominent Th1-type immune response. In vitro phorbol myristate acetate/ionomycin-stimulated T-cells served as positive control; unstimulated cells served as negative control. Cultured T-cells were used adhered to glass slides (immunocytochemistry), in suspension (FACS), or snap-frozen and sectioned (immunohistochemistry). Immunocytochemistry and FACS analysis on stimulated cultured T-cells showed positive staining results with 12 of 13 anti-IFNγ antibodies. However, immunohistochemistry of sectioned stimulated T-cells was negative with all. Unstimulated cells were consistently negative. IFNγ immunohistochemical single- and double staining analysis of the tissue sections showed huge variations in staining patterns, including positivity for smooth muscle cells ( n = 8), endothelial cells ( n = 4), extracellular matrix ( n = 4), and CD138+ plasma cells ( n = 12). Specific staining of T-cells, as the sole positive staining, was not achieved with any of the 13 antibodies. IFNIFNγ-immunohistochemistry appears unreliable because of lack of specificity to stain T-cells in situ. In fact, depending on the type of anti-IFNγ antibody used, a variety of different cell constituents were nonspecifically stained. Consequently, data based on IFNγ-immunohistochemistry must be interpreted with great caution.

Expression of p21 ras protein as a prognostic factor in papillary thyroid cancer

We studied the expression of p21, the ras encoded protein, in primary tumour of 45 patients with papillary thyroid cancer (PTC). Patients were grouped according to outcome so that one group (31 patients) had a good outcome and the other (14 patients) a fatal outcome, after a follow-up of at least 5 years. The presence of p21 ras protein was assessed by immunohistochemistry with a specific monoclonal antibody (MAb Y-13259). The results were correlated with the outcome, with the expression of proliferating cell nuclear antigen (PCNA)/cyclin (as a marker of cell proliferation) and with other well established prognostic factors for PTC (age, grading, extension and tumour size; Endocrinol Metab Clin North Am 1990, 19, 545-576). p21 staining in tumours of living patients was negative in 15, weakly positive (1+) in 10 and strongly positive (2+ or more) in 6 patients. In tumours from deceased patients, p21 staining was negative in 1, weakly positive in 2 and strongly positive in the remaining 11 patients (P < 0.001, chi 2). PCNA immunostaining was increased in 63.6% (7/11) of the tumours from deceased patients compared to 17.8% (5/28) of the tumours of living patients, but no direct correlation was found between p21 and PCNA expression. Among the other prognostic factors studied, only age > or = 40 years was a significant predictor of poor outcome. The survival curve of patients with strongly positive p21 staining was similar to that of patients aged > or = 40 years at the time of diagnosis. The combination of p21 > or = 2+ and age > or = 40 was superior to age alone (P < 0.05) as a prognostic indicator of poor outcome. In conclusion, our results indicate that the p21 product of the ras (proto)oncogene is differently expressed in PTC, in relation to the degree of aggressiveness. Regardless of the pathogenetic role of the ras oncogene in thyroid tumorigenesis, our data indicate that the expression of the p21 ras protein may be regarded as a prognostic indicator in PTC. Furthermore, overexpression of p21 ras protein is associated with patients in the older age groups, and might contribute to the poor prognosis of elderly patients.

Immunodetection of the p21-ras products in human normal and preneoplastic tissues and solid tumors: a review

Immunohistochemical detection of p21-ras to identify and characterize preneoplastic or neoplastic lesions in human tissues is reviewed. Information concerning the commercially available antibodies is presented. Antibodies DWP, Ras-10, Y13-259, YA6-172, NCC-001, and NCC-004 are fully documented with respect to their behavior in appropriate specificity tests and appear to be reliable reagents. After reviewing the data we have identified three groups of tissues or organs with respect to positive immunostaining for p21-ras as the significant criterion of malignancy. These three groups comprise (1) tissues for which no definite conclusion could be drawn (colon, lung, bladder, ovary, and neural and odontogenic tissues) despite occasional claims to the contrary, (2) tissues for which conclusions were negative (pancreas and stomach), and (3) tissues for which p21-ras staining positively discriminated malignant from normal tissues (liver, uterus, and salivary gland). Immunohistochemically detectable levels of products from a mutated ras gene could be demonstrated in a fraction of the samples from colon, lung, and bladder carcinomas, as well as in some histologically normal tissues adjacent to a colon carcinoma. The possibility that a higher relative intensity of the immunostaining reaction for p21-ras might discriminate malignant tissues from normal tissues or benign lesions in breast, pancreas, stomach, lung, uterus, or thyroid samples is suggested. Further studies now appear warranted and a strategy is proposed to validate the conclusions reached thus far.

Ras p21 in breast tissue: associations with pathology and cellular localisation

Immunocytochemistry with monoclonal antibody Y13-259 demonstrated p21 ras in paraffin sections of breast tissue from 171 women: 85 with invasive breast carcinoma, 14 with non-invasive carcinoma and 72 with benign changes only. Many different tissue elements contributed to ras expression. Semiquantitative assessment showed that intensity of immunostaining in the normal epithelium of large ducts, small extralobular ducts and terminal duct lobular units (TDLU) was usually exceeded by that of myoepithelial cells. Vascular smooth muscle and apocrine epithelium also stained strongly, but the flat epithelial cells lining cysts did not express detectable p21 ras. There was a progressive increase from normal epithelium through epithelial hyperplasia of usual type and atypical hyperplasia to carcinoma in situ, without further increase in invasive carcinoma. Expression in carcinomas was inversely related to oestrogen receptor content but independent of the prognosis-associated variables of size, histological type, vascular invasion or lymph node metastasis.

Ras gene product expression in blood and marrow smears of patients with acute leukemia: importance of fixation

Activation of ras protooncogenes by any of several possible mutations in codons 12, 13 or 61 has been demonstrated in a variety of human malignancies, including acute non-lymphoblastic leukemia (ANLL). In situ staining for the ras gene product, p21, has been demonstrated in carcinomas of several sites. High levels of p21 expression have been associated with histologic anaplasia in prostate cancer and regional lymph node metastasis in breast cancer. We examined 16 marrow aspirates and blood smears from patients with acute leukemia, predominantly ANLL, and eight controls. Marrow aspirates or blood were smeared on glass slides and fixed immediately in 10% buffered formalin. p21 was examined with avidin-biotin linked immunoperoxidase visualization. Particular attention must be paid to antibody selection and fixation protocol to demonstrate p21, owing to its rapid degradation ex vivo. Three of 16 patients exhibited occasional high p21 expression primarily in leukemic blasts, but in no case were more than 10% of blast cells positive. Normal reticuloendothelial and myeloid cells occasionally exhibited mild to moderately heavy staining, but megakaryocytes, erythroid precursors, lymphocytes and plasma cells were consistently negative. Most patients, 5 normal volunteers and 3 patients with non-malignant disease, exhibited no reactivity, or only a faint blush. These data suggest that while point mutation and concomitant activation of c-N-ras occurs regularly in ANLL, high levels of ras p21 expression are rarely found with this technique.