SummaryMalignant tumor cells can escape CD8 + cytotoxic T cell killing by downregulating class I major histocompatibility complex (MHC) expression. Stable class I MHC surface expression requires loading of the heavy chain/light chain dimer with antigenic peptide, which is delivered to class I MHC molecules in the endoplasmic reticulum by the presumed peptide transporter, encoded by the transporter associated with antigen presentation (TAP) 1 and 2 genes. We have investigated whether loss of class I MHC expression frequently observed in different cancers could result from interference with TAP function. A polyclonal antiserum, raised against a bacterial glutathione S-transferase/human TAP-1 fusion protein, was used for the immunohistochemical analysis of TAP-1 expression in 76 cervical carcinomas. Results showed loss of TAP-1 expression in neoplastic cells in 37 out of 76 carcinomas. Immunohistochemical double staining procedures in combination with HLA-specific antibodies revealed congruent loss at the single cell level of TAP-1 and HLA-A/B expression in 28 out of 37 carcinomas. The remaining samples expressed HLA(-A) in the absence of TAP-1 (n = 6) or showed loss of HLA(-A/B) while TAP-1 was expressed (n = 3). These data strongly indicate that inhibition of peptide transport by downregulation of TAP-1 is a potential strategy of malignant cells to evade immune surveillance.T he transporter associated with antigen presentation (TAP) is encoded by the TAP-I and -2 genes (1, 2), located within the class II MHC region. Their products share structural properties with members of the superfamily of ATP-binding transporters (2, 3) and their function is to translocate antigenic peptide from the cytosol into the endoplasmic reticulum (Elk). There, class I H chain, L chain (B2-microglobulin), and peptide assemble into a complex which is then transported to the cell surface. Mutant cell lines (4, 5) or mice (6) lacking TAP-1 and/or -2 genes do not present antigen to CD8 + Tcells and show strongly reduced levels of surface class I MHC molecules, indicating that peptide should be considered the essential third subunit of the class I complex (7-9). Upon viral infection or malignant cell transformation, the ensuing alternations in gene expression result in the generation of novel sets of peptides available for binding to class I MHC products. These are potential targets for CD8 + CTLs Besides deprivation of H and/or L chains, the loss of peptide could also result in reduced class I MHC surface expression. Downregulation of class I MHC expression has been found in a substantial number of cervical carcinomas, containing human papilloma-virus type 16 DNA (21,22 that show loss of class I MHC surface expression, a posttranscriptional regulation has been postulated (23). Loss of TAP function and the consequent failure to produce stable class I MHC molecules could be an explanation. Therefore in this study, class I MHC and TAP-1 expression were examined in 76 carcinomas of the uterine cervix by immunohistochemistry with class I H chai...

Aims-Chromosomal gains and losses were surveyed by comparative genomic hybridisation (CGH) in a series of colorectal adenomas and carcinomas, in search of high risk genomic changes involved in colorectal carcinogenesis. Methods-Nine colorectal adenomas and 14 carcinomas were analysed by CGH, and DNA ploidy was assessed with both flow and image cytometry. Results-In the nine adenomas analysed, an average of 6.6 (range 1 to 11) chromosomal aberrations were identified. In the 14 carcinomas an average of 11.9 (range 5 to 17) events were found per tumour. In the adenomas the number of gains and losses was in balance (3.6 v 3.0) while in carcinomas gains occurred more often than losses (8.2 v 3.7). Frequent gains involved 13q, 7p, 7q, 8q, and 20q, whereas losses most often occurred at 18q, 4q, and 8p. Gains of 13q, 8q, and 20q, and loss of 18q occurred more often in carcinomas than in adenomas (p = 0.005, p = 0.05, p = 0.05, and p = 0.02, respectively). Aneuploid tumours showed more gains than losses (mean 9.3 v 4.9, p = 0.02), in contrast to diploid tumours where gains and losses were nearly balanced (mean 3.1 v 4.1, p = 0.5).Conclusions-The most striking diVerence between chromosomal aberrations in colorectal adenomas and carcinomas, as detected by CGH, is an increased number of chromosomal gains that show a nonrandom distribution. Gains of 13q and also of 20q and 8q seem especially to be involved in the progression of adenomas to carcinomas, possibly owing to low level overexpression of oncogenes at these loci. (J Clin Pathol 1998;51:901-909)

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Summary In previous studies we have shown down-regulation of class I major histocompatibility complex (MHC) expression in a significant proportion of primary cervical carcinomas, which was found to be strongly correlated with loss of expression of the transporter associated with antigen presentation (TAP). By contrast, class II MHC expression was frequently up-regulated on neoplastic keratinocytes in these malignancies. In order to investigate whether these changes are associated with biological behaviour of the tumours, 20 cervical carcinomas were analysed for MHC (HLA-A, HLA-B/C, HLA-DR) and TAP-1 expression in the primary tumours and in lymph node metastases by immunohistochemistry. The results showed a significant increase in the prevalence of HLA-A and HLA-B/C down-regulation in metastasised neoplastic cells as compared with the primary tumour (P = 0.01). In all cases this was accompanied by loss of TAP-I expression. Up-regulated HLA-DR expression was found exclusively in primary tumours and was absent in the corresponding metastases (P= 0.002). These data are consistent with the hypothesis that loss of TAP-1 and the consequent down-regulation of class I MHC expression provides a selective advantage for neoplastic cervical cells during metastasis. Furthermore, the lack of class II MHC expression in metastasised cells either reflects a different local lymphokine production or indicates that these cells may have escaped CD4+ cytotoxic T-lymphocyte (CTL)-mediated killing.

Summary Cervical intraepithelial neoplasia (CIN) grades I to III lesions (n = 94) and squamous cell carcinomas of the uterine cervix (n = 27) were analysed for MHC class I and II expression and presence of HPV genotypes.MHC class I and II expression was studied by immunohistochemistry and HPV typing was performed by general primer-and type-specific primer mediated PCR (GP/TS PCR). Both A central role in the antigen-specific immune response is played by the major histocompatibility complex (MHC), which are cell surface proteins that act as restricting elements in the recognition of antigen by T-cells. MHC class I (MHC-I) present endogenous antigen to cytotoxic T-lymphocytes (CTLs). Low levels or lack of MHC-I surface expression can consequently render aberrant cells non-immunogenic to CTLs, and may provide a way for cells to escape immune surveillance. MHC-1 alterations have been described in human cancer of different sites of the body (see review RuizCabello et al., 1991).Generally, MHC class II (MHC-II) surface expression is restricted to specialised antigen presenting cells (APCs), that present mainly opsonised exogenous antigen to T-helper cells. Recognition leads to activated T-cells, which can stimulate B-cell, CTL proliferation and MHC non-restricted killing by natural killer (NK) cells or activated macrophages. Occasionally, other cells like neoplastic epithelial cells have been described to express MHC-II, which could assist in the onset of the cellular immune response (Ostrand-Rosenberg et al., 1991).Infections with specific human papillomavirus (HPV) types are strongly associated with the development of cervical cancer, with HPV types 16 and 18 as the most predominant types (Zur Hausen, 1989 (Connor & Stern, 1990;Glew et al., 1992), suggesting that changes in the presentation of viral tumour antigens to the cellular immune system can occur. However, to get insight whether altered MHC-I and -II expression is related to the development of cervical cancer from its premalignant lesions, it is necessary to study dysplastic cervical lesions (CIN) for the MHC-I and -II status.Tumour virus based mechanisms have been described that specifically influence MHC-I cell surface expression (Signas et al., 1982;Schrier et al., 1983). Similar mechanisms could exist for HPV affecting antigen presentation of the infected cells. However, little is known about MHC alterations in CIN lesions in relation to the presence of different HPV genotypes.Therefore in this study expression of MHC-I and -II was investigated in CIN lesions of different grades and cervical carcinomas. HPV typing was carried out by a combined general primer-mediated (GP-) and type-specific (TS-) polymerase chain reaction (PCR) strategy (van den Brule et al., 1991;Walboomers et al., 1992). In addition, HPV RNA in situ hybridisation (RISH) was applied to some HPV 16 PCR positive lesions, in order to localise cells containing transcriptionally active HPV 16 in relation to altered MHC expression. The results indicate that MHC-I and -II alterations are also...