No evidence for the involvement of XMRV or MCV in the pathogenesis of breast cancer.

BACKGROUND: The aetiology of breast cancer remains elusive. A viral aetiology has been proposed, but to date no virus has been conclusively demonstrated to be involved. Recently, two new viruses, namely Merkel cell polyomavirus (MCV) and xenotropic murine leukaemia virus-related virus (XMRV) have been identified and implicated in the pathogenesis of Merkel cell carcinoma (MCC) and familial form of prostate cancer, respectively. METHODS: We examined 204 samples from 58 different cases of breast cancer for presence of MCV or XMRV by PCR. Samples consisted of both malignant and non-malignant tissues. Additionally, we included 6 cases of MCC and 12 cases of prostate cancer as potential controls for MCV and XMRV, respectively. RESULTS: All of the breast cancer samples examined were negative for both MCV and XMRV. However, 4/6 MCC and 2/12 prostate cancer samples were found to be positive for MCV and XMRV, respectively. Sequence analysis of the amplified products confirmed that these sequences belonged to MCV and XMRV. CONCLUSION: We conclude that there is no evidence for the involvement of MCV or XMRV in the pathogenesis of breast cancer. What role these viruses have in the pathogenesis of MCC and prostate carcinomas remains to be demonstrated.

Molecular and kinetic features of transitional cell carcinomas of the bladder: biological and clinical implications.

Molecular and kinetic analyses have contributed to our understanding of the biology of transitional cell carcinomas (TCC) of the bladder. The concordant pattern of X-chromosome inactivation of multiple TCCs appearing at different times and at different sites and concordant genetic abnormalities in a subset of muscle-invasive TCC strongly support a monoclonal origin and a homogeneous tumor cell selection throughout the neoplasm. However, topographic intratumor heterogeneity results from the accumulation of genetic lesions in tumor suppressor genes, predominantly neurofibromatosis (NF)-1-defective in the superficial compartment and tumor protein p53 (TP53)-defective in the deep one, with lower proliferation and down-regulation of apoptosis in the latter. TCCs follow the general concept of multistep carcinogenesis and proceed through two distinct genetic pathways responsible for generating different TCC morphologies. These are the inactivation of cyclin-dependent kinase inhibitors (p15, p16, and p21WAF/CIP1) in low-grade TCC and early TP53-mediated abnormalities in high-grade TCC. TCC progression correlates with genetic instability and accumulation of collaborative genetic lesions mainly involving TP53, retinoblastoma (RB)-1, and growth factors. Distinctive genetic (low incidence of RB-1 and NF-1 abnormalities) and kinetic (slower cell turnover) profiles also correlate with a "single-file" infiltration pattern and poor survival in muscle-invasive TCCs. The underlying molecular changes of carcinoma in situ involve multiple and more extensive deletions (normally TP53-defective) than coexistent invasive TCC, suggesting an independent genetic evolution, while low-grade dysplasia is mainly polyclonal and shows a low rate of gene deletions.

Critical analysis of histologic criteria for grading atypical (dysplastic) melanocytic nevi.

Low concordance in grading atypical (dysplastic) melanocytic nevi (AMN) has been reported, and no systematic evaluation is available. We studied 123 AMN with architectural and cytologic atypia (40 associated with atypical-mole syndrome), classified according to standard criteria by 3 independent observers. Histologic variables included junctional and dermal symmetry, lateral extension, cohesion and migration of epidermal melanocytes, maturation, regression, nuclear features, nuclear grade, melanin, inflammatory infiltrate location, and fibroplasia. AMN (43 junctional and 80 compound) were graded mild (31), moderate (61), and severe (31). AMN-severe correlated with 3 or more nuclear abnormalities (especially pleomorphism, heterogeneous chromatin, and prominent nucleolus) and absence of regression, mixed junctional pattern, and suprabasilar melanocytes on top of lentiginous hyperplasia. AMN-severe diagnostic accuracy was 99.5% using these criteria, but only the absence of nuclear pleomorphism differentiated AMN-mild from AMN-moderate. No architectural features distinguishing AMN-mild from AMN-moderate were selected as significant by the discriminant analysis. AMN from atypical-mole syndrome revealed subtle architectural differences, but none were statistically significant in the discriminant analysis. Histologic criteria can reliably distinguish AMN-severe but fail to differentiate AMN-mild from AMN-moderate. AMN from atypical-mole syndrome cannot be diagnosed using pathologic criteria alone.

Down-regulation of Epstein-Barr virus nuclear antigen 1 in Reed-Sternberg cells of Hodgkin's disease.

AIMS: To demonstrate Epstein-Barr virus (EBV) encoded nuclear antigen 1 (EBNA-1) gene expression in EBV associated disorders using a new monoclonal antibody (1H4-1) on routinely processed tissues. METHODS: The pressure cooker antigen retrieval method was used for the immunohistochemical demonstration of EBNA-1 gene expression in formalin fixed, EBV positive tissues from Hodgkin's disease, infectious mononucleosis, HIV associated non-Hodgkin's lymphomas, post-transplant lymphomas, and undifferentiated nasopharyngeal carcinoma (NPC). EBV encoded EBNA-2, latent membrane protein 1 (LMP-1) and BZLF-1 gene expression was also examined using commercially available monoclonal antibodies. RESULTS: Of the 34 EBER in situ hybridisation positive cases of Hodgkin's disease examined, none expressed EBNA-1 in the Reed-Sternberg cells. These cells were nevertheless strongly LMP-1 positive in all cases. Strong EBNA-1 staining was seen in all cases of EBER positive HIV associated non-Hodgkin's lymphoma (five of five), nasopharyngeal carcinoma (five of five), infectious mononucleosis (three of three), and post-transplant lymphoma (one of one). These cases also expressed LMP-1, EBNA-2 and BZLF-1, but at differing levels. CONCLUSION: The pressure cooker antigen retrieval procedure is a sensitive and reliable adjunct to immunohistochemistry, especially with antibodies which are otherwise ineffective on routinely processed tissues. The EBNA-1 gene is not expressed at detectable levels in the malignant cells of Hodgkin's disease, but is consistently expressed in other EBV associated disorders. This finding has important implications for the role of EBNA-1 in the biology of EBV.

An orf virus sequence showing homology to the 14K 'fusion' protein of vaccinia virus.

The nucleotide sequence of a region of DNA 30 kb from the right end of the orf virus genome has been determined. Examination of the sequences revealed an open reading frame encoding a 10K peptide with significant amino acid homology to the 14K 'fusion' protein reported in vaccinia virus. The orf virus sequence has a 31% identity with the vaccinia virus protein, but a higher level of homology of core predicted residues. The secondary structure of both proteins is also similar. The occurrence of the TAAAT sequence upstream from the initiation codon indicates that the sequence is likely to be transcribed late in infection.