Loss of polymorphic A and B locus HLA antigens in colon carcinoma

Tumor Antigenicity and a Pre-Existing Adaptive Immune Response in Advanced BRAF Mutant Colorectal Cancers

Simple Summary

BRAF mutant metastatic CRCs (BRAF-mCRCs) are considered a unique clinical entity characterized by a dismal prognosis and that do not respond efficiently to both standard chemotherapy and to orally selective inhibitors of BRAF^V600E. In this study, the gene expression profiles of 89 immunotherapy-naïve BRAF-CRCs were generated using the PanCancer IO 360 gene expression panel to improve the knowledge of the mechanisms involved in tumor-suppressive immune functions in BRAF-mCRCs. A significant fraction of BRAF-mCRCs shows a hot/inflamed profile and may be potential candidates for responding to immunotherapy. Only a partial overlap between these hot signatures and the presence of microsatellite instability (MSI) was observed, demonstrating that MSI tumors showed a not differential expression of MHC Class I antigen presentation pathway compared with microsatellite-stable tumors. The analysis of gene expression profiles is a promising strategy both for immune profiling of primary tumors before any treatment and for following the evolution of metastatic disease during therapy.

Abstract

The main hypothesis of this study is that gene expression profiles (GEPs) integrating both tumor antigenicity and a pre-existing adaptive immune response can be used to generate distinct immune-related signatures of BRAF mutant colorectal cancers (BRAF-CRCs) to identify actionable biomarkers predicting response to immunotherapy. GEPs of 89 immunotherapy-naïve BRAF-CRCs were generated using the Pan-Cancer IO 360 gene expression panel and the NanoString nCounter platform and were correlated with microsatellite instability (MSI) status and with CD8+ tumor-infiltrating lymphocyte (TIL) content. Hot/inflamed profiles were found in 52% of all cases, and high scores of Tumor Inflammation Signature were observed in 42% of the metastatic BRAF-CRCs. A subset of MSI tumors showed a cold profile. Antigen Processing Machinery (APM) signature was not differentially expressed in MSI tumors compared with MSS cases. By contrast, the APM signature was significantly upregulated in CD8+ BRAF-CRCs versus CD8− tumors. Our study demonstrates that a significant fraction of BRAF-CRCs may be a candidate for immunotherapy and that the simultaneous analysis of MSI status and CD8+ TIL content increases accuracy in identifying patients who can potentially benefit from immune checkpoint inhibitors. GEPs may be very useful in expanding the spectrum of patients with BRAF-CRCs who can benefit from immune checkpoint blockade.

HLA class I loss in colorectal cancer: implications for immune escape and immunotherapy

T cell-mediated immune therapies have emerged as a promising treatment modality in different malignancies including colorectal cancer (CRC). However, only a fraction of patients currently respond to treatment. Understanding the lack of responses and finding biomarkers with predictive value is of great importance. There is evidence that CRC is a heterogeneous disease and several classification systems have been proposed that are based on genomic instability, immune cell infiltration, stromal content and molecular subtypes of gene expression. Human leukocyte antigen class I (HLA-I) plays a pivotal role in presenting processed antigens to T lymphocytes, including tumour antigens. These molecules are frequently lost in different types of cancers, including CRC, resulting in tumour immune escape from cytotoxic T lymphocytes during the natural history of cancer development. The aim of this review is to (i) summarize the prevalence and molecular mechanisms behind HLA-I loss in CRC, (ii) discuss HLA-I expression/loss in the context of the newly identified CRC molecular subtypes, (iii) analyze the HLA-I phenotypes of CRC metastases disseminated via blood or the lymphatic system, (iv) discuss strategies to recover/circumvent HLA-I expression/loss and finally (v) review the role of HLA class II (HLA-II) in CRC prognosis.

MHC/HLA Class I Loss in Cancer Cells

In this chapter I describe Tumour Immune Escape mechanisms associated with MHC/HLA class I loss in human and experimental tumours. Different altered HLA class-I phenotypes can be observed that are produced by different molecular mechanisms. Experimental and histological evidences are summarized indicating that at the early stages of tumour development there is an enormous variety of tumour clones with different MHC class I expression patterns. This phase is followed by a strong T cell mediated immune-selection of MHC/HLA class-I negative tumour cells in the primary tumour lesion. This transition period results in a formation of a tumour composed only of HLA-class I negative cells. An updated description of this process observed in a large variety of human tumors is included. In the second section I focus on MHC/HLA class I alterations observed in mouse and human metastases, and describe the generation of different tumor cell clones with altered MHC class I phenotypes, which could be similar or different from the original tumor clone. The biological and immunological relevance of these observations is discussed. Finally, the interesting phenomenon of metastatic dormancy is analyzed in association with a particular MHC class I negative tumor phenotype.

PNA: A Marker of Neoplastic Progression and Differentiation in the Gastrointestinal Tract

We examined 35 cases of stomach carcinoma and 40 cases of colonic carcinoma with PNA associated with peroxidase (peanut agglutinin, lectin which binds to the terminal disaccharide galactose β (1, 3)-N-acetil-galacto-samine).

In this way evaluation of the functional aspects of the normal-neoplastic sequence was undertaken. This method was carried out for histological and ultrastructural investigations. The results obtained in both cases showed a different reactivity in the evolution of neoplastic disease: in fact, positivity in dysplasia is finely granular intracytoplasmic, whereas in well-differentiated neoplastic transformation such a reactivity is preferentially localized along the cellular membranes, with restoration of gross positivity in the cytoplasm for the poorly-differentiated neoplasm. We therefore believe PNA to be a marker not only of neoplastic progression but of differentiation as well: we also hypothesize it to reveal glycoprotein groups with possible antigenic power, involved in immunologic interactions between tumor and host.

Antibodies for transplantation

The use of antibodies in transplantation has become a clinical reality. Antibodies have been used to both dampen the recipient's immune response and to obscure the immunogenicity of the donor graft. Traditionally, antibodies have been administered to the transplant recipient to transiently inactivate the host's T cells, the lymphocytes responsible for recognizing and attacking foreign proteins, cells, and tissues. Antibodies can also be used to eliminate any highly immunogenic passenger cells from a donor graft prior to transplantation, and antibodies can mask or conceal antigens present on donor cells that might trigger rejection.

Comparative expression of major histocompatibility complex (MHC) antigens on CD5+ and CD5- B cells in patients with chronic lymphocytic leukaemia (CLL)

The aim of this study was to investigate the expression of major histocompatibility complex (MHC) antigens on CD5+ and CD5- B cells of 13 patients with chronic lymphocytic leukaemia (CLL). This was carried out using a series of monoclonal antibodies (MAbs) against polymorphic and monomorphic class I and class II antigens, as well as to the transferrin receptor and assessed by flow cytometry and direct and indirect immunofluorescence. The expression of these molecules was assessed as mean fluorescent intensity (MFI). The results showed that cells from all 13 individuals expressed monomorphic class I antigens. The number of cases expressing polymorphic HLA-Bw6, -Bw4, -B7, -B27 and -A2 class I antigens on CD5- B cells was 11 (85%), 6(46%), 2(15%), 1(8%), 3 (23%), respectively, which was consistent with the expected population frequency distributions of these antigens. For each of the class I antigens on CD5+ and CD5- B cells, the ratio of the MFI was greater than 1 in 12 of 13 cases. For the transferrin receptor (CD71), this ratio was also almost always greater than 1. These results indicate that, unlike solid tumours where the loss or abnormal expression of class I and II antigens is a frequent event, the expression of class I antigens in CLL patients seems to be normal. This indicates that the loss of these antigens cannot provide the leukaemic cells with a selective advantage to escape immunological detection.

Loss of antigen-presenting molecules (MHC class I and TAP-1) in lung cancer

Presentation of endogenous antigenic peptides to cytotoxic T lymphocytes is mediated by the major histocompatibility complex (MHC) class I molecules. For the stable assembly of MHC class I complex it is necessary that the antigenic peptide is transported by the MHC-encoded transporters TAP-1 and TAP-2 into a pre-Golgi region. T-cell-mediated host-vs-tumour response might therefore depend on the presence of these molecules on tumour cells. The presence of MHC class I antigens and TAP-1 was studied in a series of 93 resection specimens of non-small-cell lung carcinomas (NSCLCs) by immunohistochemical methods using antibodies against the assembled class I molecule, beta 2-microglobulin (beta 2-m), heavy-chain A locus, A2 allele and TAP-1 protein. Eighty-six patients were included in the survival analysis. Total loss of class I molecule was observed in 38% of the cases and was usually accompanied by loss of beta 2-m and of heavy chain A locus. Selective loss of A locus was seen in 8.3% and of A2 allele in 27% of the cases. TAP-1 loss was always combined with beta 2-m and/or heavy chain A locus loss. No correlation was found between the expressional status of any of the above molecules, including the selective A2 allelic loss and histological type, degree of differentiation, tumoral stage, nodal stage and survival. Our findings suggest that loss of antigen-presenting molecules (including both MHC class I alleles and TAP-1) is a frequent event in lung cancer. However, the immunophenotypic profile of MHC class I and TAP-1 seems to be unrelated in vivo to the phenotype, growth or survival of NSCLC.

Lymphocyte subset infiltration patterns and HLA antigen status in colorectal carcinomas and adenomas

Fifty eight large bowel adenocarcinomas and 20 adenomas were studied immunohistochemically, using fresh frozen tissue sections, with regard to lymphocyte subpopulations (CD3, CD4, CD8, CD19, and CD20) in the inflammatory infiltrate and to expression of human leucocyte antigens (HLA-ABC, HLA-A2, and HLA-DR). The findings were related to differentiation and Duke's stage of carcinoma. The inflammatory infiltrate was found to have a phenotype that remained constant irrespective of the intensity of the inflammation. CD4 and CD3 positive cells predominated with fewer CD8 positive cells and a scanty diffuse CD19/20 positive cell population. CD19/20 follicular aggregates were common at the advancing margin of the carcinomas. There was no significant association with Duke's stage, differentiation or HLA status. HLA changes (ABC loss, A2 loss, and DR gain) were associated with differentiation, being more common and more extensive in poorly differentiated carcinomas. HLA-A2 loss was also associated with stage of progression of carcinoma. Inflammation associated with adenomas was found to have a similar phenotype to that associated with carcinomas. HLA changes in adenomas were uncommon, being seen in only one of our 20 cases.

Expression of MHC class I and class II antigens in primary breast carcinomas and synchronous nodal metastases

Expression of the major histocompatibility (MHC) class I and class II antigens was studied by immunohistochemistry in a series of 70 primary breast carcinomas and in nodal metastases. In particular, the expression of class I (HLA A-B-C) and class II (DP, DQ and DR) molecules was compared in: a) primary breast cancers devoid of nodal metastases (n = 36) and tumors exhibiting metastatic deposits (n = 34) at the time of surgery, and b) primary breast carcinomas and their corresponding synchronous axillary nodal metastases. Reduced or absent HLA A-B-C antigen expression was seen in approximately 54.3% of primary breast carcinomas, whereas a partial or complete induction of class II products was observed in 18.5% (DQ), 30% (DP) or 48.5% (DR) of the same cases. An almost complete overlap of antigen expression was observed in breast tumors in which no metastases were found by histological examination of axillary nodes and in neoplasms showing histologically-diagnosed synchronous metastases. The reactivity for class I and class II antigens in nodal metastases roughly paralleled that exhibited by corresponding primary tumors. A discordant expression was seen in 11 cases (32%) stained for HLA A-B-C and in 8 (24%), 7 (21%) and 6 (18%) cases assayed for DP, DQ and DR products, respectively. When a discordant expression was detected, either decreased or increased staining patterns were observed in metastases. The finding of overlapping MHC antigenic profiles in the majority of primary breast tumors and nodal metastases casts doubts on the hypothesis that loss of MHC antigens can play an important role in the seeding and growth of metastatic breast carcinoma cells.

KBF1 (p50 NF-kappa B homodimer) acts as a repressor of H-2Kb gene expression in metastatic tumor cells

Downregulation of major histocompatibility complex class I expression is causally related to high malignancy and low immunogenicity of certain murine tumors. In this study, we have analyzed the roles of the nuclear factors KBF1/p50 and p65 in regulation of class I expression in high and low metastatic tumor cells. Low class I-expressing cells show at higher levels of KBF1/p50 and NF-kappa B (p50/p65) binding activity than high class I-expressing cells. However, an excess of KBF1 over NF-kappa B is observed in low expressing cells, while an excess of NF-kappa B over KBF1 is observed in high expressing cells. Stable transfection of a p65 expression vector into low class I-expressing cells activated H-2 transcription and cell surface expression, while stable transfection of p50 expression vector into high expressing cells suppressed H-2Kb transcription and cell surface expression. Our studies suggest that KBF1 has the potential of downregulating class I gene expression, whereas dimers containing the p65 subunit are activators of class I gene expression.

Effect of anti-CD3 antibody on the generation of interleukin-2-activated lymphocytes from tumor tissues of gastrointestinal cancer

BACKGROUND

The efficiency of anti-CD3 antibody (OKT3) for adoptive immunotherapy using lymphokine-activated killer (LAK) cells generated from tumor-infiltrating lymphocytes (TIL), regional lymph node lymphocytes (RLNL), and peripheral blood lymphocytes (PBL) was investigated.

METHODS

TIL, RLNL, and PBL derived from 39 patients with gastrointestinal cancers (16 gastric cancers, 17 colorectal cancers, and 6 esophageal cancers) were cultured for 4 weeks with 200 U/ml of recombinant interleukin-2. To one group, solid-phase 10 micrograms/ml OKT3 was added during the initial culture period (day 2 or 4). Cytotoxicity against K562 cells (NK-like activity) and Daudi cells (LAK activity) and the phenotypes of effector cells generated after culturing for 2-3 weeks were studied.

RESULTS

Proliferative responses were significantly increased by OKT3 in each type of effector cell (P less than 0.01); in particular, TIL expanded more by OKT3 than PBL and RLNL (P less than 0.01). The population of CD8+ CD11b- cytotoxic T-cells in OKT3-stimulated groups was significantly larger than that in unstimulated groups (P less than 0.01), whereas no differences were observed with CD4+ cells (helper/inducer T-cells) and CD8+ CD11b+ cells (suppressor T-cells). OKT3 enhanced the NK-like activity of TIL and PBL but did not affect their LAK activity. OKT3 suppressed the NK and LAK activity of RLNL.

CONCLUSIONS

OKT3 stimulation did not significantly enhance the LAK activity, but the authors propose that OKT3 could be an effective addition to adoptive immunotherapy using TIL due to an increased proliferation and generation of a large cytotoxic T-cell population.

Loss of HLA class-I alleles, heavy chains and beta 2-microglobulin in colorectal cancer

Using immunohistochemical methods, we have analysed colorectal biopsies of normal mucosa, metaplastic polyps (5 cases), adenomas (15 cases) and adenocarcinomas (70 cases) with 13 monoclonal antibodies (MAbs) to allelic products of the HLA-A, B, C loci. Nine of the 70 carcinomas showed total loss of HLA Class-I molecules due to an underlying defect regarding not only the expression of beta 2-microglobulin (beta 2-m), but also the heavy chains of HLA A, B and C loci, or both. Much commoner was a loss of one or more Class-I alleles as follows: A1/Aw36 (completely lost in 4 of 29 cases and focally lost in another 2), A2 (in 1 of 37 cases), A3 (in 2 of 14 cases), A1 1/28/31/33 (in 3 of 11 cases), B7 (in 3 of 13 and focally in 1 other case), B17 (in 1 case), Bw4 (in 8 of 45 and focally in another 6), Bw6 (in 9 of 62 and focally in another 3). Focal selective loss (Bw6 and a combined A1-Bw6), was observed in 2 adenomas. Normal colonic mucosa, as well as stromal and lymphoid cells present between the neoplastic glands, were studied in each case as a control. A particular allele was only considered to be lost by the malignant cells if it was still expressed on these adjacent tissues.

Loss of monomorphic and polymorphic HLA antigens in metastatic breast and colon carcinoma

MHC class I antigens are intimately involved in intercellular communication, and recognition by cytotoxic T cells. Thus tumour cells that fail to express them may be at a growth or metastatic advantage. A series of ten colorectal and ten breast carcinomas, and their respective lymph node metastases, were examined immunohistologically using monoclonal antibodies (mAb) against both monomorphic and A2 polymorphic determinants, and beta-2-microglobulin (beta 2m). Four colon polypoid adenomas stained positively throughout, but 6/10 primary tumours had partial or complete loss of expression of monomorphic determinants using mAb W6/32: two node and the liver metastasis showed less, four more expression. Similar results were seen for beta 2m. HLA-A2 expression was absent or reduced in 4/4 colon tumours and all their metastases. Among the breast tumours, W6/32 staining was absent or reduced in 2/10, and node deposits showed two with less reactivity than their primary. Beta 2m staining was reduced or absent in 8/10 primaries and all the node metastases; in every case in which beta 2m was detected in the primary tumour their corresponding lymph node metastasis showed a decreased expression. HLA-A2 expression was absent or reduced in 3/4 primary breast carcinomas, and all their metastases. These results show that individual human colon and breast carcinomas often have a reduced HLA class I antigen expression, which apparently confers a metastatic advantage.

HLA antigen expression and malignant mesothelioma

The expression of HLA antigens by a tumor may determine its progression and metastatic potential by influencing the immune response to that tumor. The upregulation of HLA antigen expression on some cell types by interferons (IFNs) may contribute to their antitumor activity. Malignant mesothelioma (MM) is a tumor that has a poor prognosis and is unaffected by conventional therapy, although immunotherapy has not been adequately assessed. In this study, we have examined the constitutive and IFN-inducible expression of class I and class II HLA antigens on MM cell lines using indirect immunofluorescence and Northern blotting. All MM cell lines constitutively expressed class I, but not class II, surface antigen, and all three class I loci (HLA-A, HLA-B, and HLA-C) were expressed. The MM cell lines were heterogeneous in their response to the IFNs. Treatment with IFN-alpha marginally increased class I surface expression, but not class II. Class I mRNA was, however, clearly increased in all cell lines after IFN-alpha treatment, suggesting that class I surface antigen was already maximally expressed. IFN-gamma increased class I mRNA expression in all but one cell line and induced DR expression on three of the cell lines. DQ-beta, but not DQ-alpha, mRNA was inducible in the same three cell lines, but DQ surface antigen was never demonstrable.(ABSTRACT TRUNCATED AT 250 WORDS)

Application of isoelectric focusing for studies of major histocompatibility complex class I antigen expression on human carcinomas and sarcomas

By one-dimension isoelectric focusing we analysed the major histocompatibility complex class I antigen expression on human tumours. Blood lymphocytes of the patients, processed in parallel, served as a basis for comparison. The prerequisite for the analysis is the preparation of metabolically active tumour cell suspensions devoid of significant leucocyte contamination. The method was found to be suitable for study of the expression of HLA alleles on ex vivo tumour cells and allowed the detection of changes imposed by in vitro treatment with interferon gamma and tumour necrosis factor alpha.

Loss of MHC class-I expression in cervical carcinomas

The expression of MHC class-I antigens was analysed in 67 cervical carcinoma biopsies; 16% of the biopsies showed complete or heterogeneous loss of HLA expression as judged by reactivity with antibodies recognizing monomorphic determinants of the class-I heavy chain bound to beta 2 microglobulin (beta 2m). In addition, other biopsies showed a loss in expression of particular allelic products: 23% for HLA-A2; 17% for HLA-A3; 23% for HLA-Bw4 and 19% for HLA-Bw6. Three biopsies showed changes at 2 alleles, 2 of which were at both HLA-A and -B loci. Down-regulation of class-I expression may be virally mediated and HPV DNA is frequently found in cervical carcinomas. However, there appeared to be no direct correlation between the detection of HPV 16 or 18 DNA in these tumours and changes in HLA expression. There was also no correlation with the expression of the oncofoetal antigen 5T4. Our results show that a significant proportion (at least 30%) of the cervical carcinomas showed some alteration in MHC class-I expression. Such changes may allow tumours to evade immune surveillance with more rapid progression. There was, however, no correlation with tumour type, degree of differentiation or stage of disease at presentation.

Reduction of major histocompatibility complex class I antigens on invasive and high-grade transitional cell carcinoma

We examined immunohistologically the expression of major histocompatibility complex (MHC) class I and II antigens, which play important roles in immune reactions, on transitional cell carcinoma (TCC). When stained with monoclonal antibody W6/32 against class I antigens, reduced staining was observed in 34 of 46 TCCs and was virtually absent in 15 of these. The cases showing reduced staining were much more frequent (29 of 34) in high- to moderate-grade than in low-grade TCC. Furthermore, class I antigens were reduced in 18 of 19 invasive TCCs, but in 16 of 27 superficial TCCs. Thus, the reduction of class I antigens was correlated significantly with a decreased degree of tumour cell differentiation and the presence of invasion. Class II antigens on TCC showed variable expression and were not related to tumour grade or stage.

Selective and non-selective loss of immunoregulatory molecules (HLA-A,B,C antigens and LFA-3) in transitional cell carcinoma

The expression of the major histocompatibility complex (MHC) class I and II antigens and lymphocyte function-associated antigen-3 (LFA-3) was investigated using immunohistochemical staining of bladder tissue sections from 18 patients with transitional cell carcinoma (TCC) and two normal bladder specimens. The expressions of HLA-A,B,C antigens varied greatly between different tumours. Complete loss was observed in one of 18 cases. Moderate to strong expression of HLA-A,B,C antigens was observed in 10 of 18 cases with the remaining seven cases showing either weak expression or expression on only a proportion of the tumour cells. Selective loss of HLA-Bw6 was seen in one of 18 cases. In many cases heterogenous and often focal expression of HLA-D products was seen. In one case tumour cells not expressing HLA-DR antigens were adjacent to strongly HLA-DR expressing non-neoplastic bladder epithelium, indicating a lack of inducible HLA-DR in the tumour cells. LFA-3 was undetectable in two of 18 cases with the remaining 16 cases showing moderate to strong expression of the molecule. These findings indicate that a substantial proportion of bladder tumours have one or more of a wide range of different alterations in the expressions of immunoregulatory molecules that could contribute to escape from immune surveillance.

MHC restricted and non-restricted killer lymphocytes

Cytotoxic lymphocytes are either MHC-restricted (cytotoxic T-cells) or nonrestricted (natural killer NK-cells), although cells of the monocyte/macrophage lineage are also cytotoxic, and lymphocytes or phagocytic cells expressing Fc-receptors for immunoglobulin can function as antibody-dependent killer cells (referred to as antibody-dependent cellular cytotoxicity: ADCC). Antigen-specific T-lymphocytes recognise their target antigen in the context of MHC class I components, focusing their attack only against those cells expressing the relevant antigen specificity on their cell surface. A more primitive and alternative mechanism exists whereby NK-cells, classified as large granular lymphocytes (LGL), are able to kill in a non-specific manner, not requiring prior sensitisation to antigen. Both antigen-specific T-cells and LGL mediate their cytotoxicity through the release of cytotoxic molecules at the target-effector cell interface. LGL also have a regulatory role in the immune system through the release of cytokines, and can be distinguished from T-lymphocytes by the expression of distinct phenotypic markers (CD16+, CD56+) and they lack CD3 antigen expression or rearranged alpha/beta or gamma/delta T-cell receptor gene products. Cytotoxic activity is positively regulated by interleukin-2 (IL-2) and interferon (IFN), whilst prostaglandins and transforming growth factor-beta (TGF beta) diminish activation and effector pathways. Cytotoxicity mediated by NK- and T-cell populations are principally involved in the defence against microbial infections and neoplasia; the abrogation of cytotoxicity either by direct interaction of 'suppressor factors' with effector cells, or indirectly by reducing cytokine production can inevitably lead to the proliferation of the disease.

Lacking prognostic significance of beta 2-microglobulin, MHC class I and class II antigen expression in breast carcinomas

To evaluate the impact of MHC antigen expression on the survival of patients with cancer, 77 human breast carcinomas were investigated for the expression of beta 2-microglobulin (beta 2m), HLA-A,B,C and HLA-DR. Thirty-one benign breast tumours were stained for comparison. The results for the carcinomas were related to the survival data of the cancer patients. The expression of beta 2m, HLA-A,B,C and HLA-DR was significantly lower in malignant tumours compared to the benign lesions. Whereas all benign tumours were positive for beta 2m and HLA-A,B,C and 28/31 positive for HLA-DR the following positivity rates were found in carcinomas: 74/77 for beta 2m, 57/77 for HLA-A,B,C and 10/77 for HLA-DR. The follow-up (median 45 months) of 66 cancer patients for overall survival and of 65 patients for disease-free survival revealed no influence of beta 2m, HLA-A,B,C or HLA-DR expression on the prognosis of this cancer. In conclusion, experimental data indicating the importance of MHC antigens in anti-tumour responses are not confirmed by the analysis of cancer patient survival data.

Expression of MHC class I and class II antigens in colonic carcinomas

Malignant and non-malignant ('normal') colonic tissues from patients with colonic carcinoma were examined for the expression of MHC class I and class II antigens by immunoenzymatic staining using monoclonal antibodies. The amount of class I antigen as detected by 2 monoclonal antibodies, FMC 16 or W6/32 was clearly diminished in 11 of 14 tumours when compared to the amount present on 'normal' colonic tissue from the same individual. The loss of class I antigen did not correlate with tumour stage or differentiation. The reactivities of FMC 16 and W6/32 with these tissues were not identical, which indicates that the 2 monoclonal antibodies may recognize different epitopes on the HLA class I molecule. Class II antigens were absent from 'normal' colonic epithelium but were present on 20 of 28 tumours, with DR being detected more often than DP, and DQ found only on 4 of 28 tumours. When present, staining for class II antigens was heterogeneous within the tumour, in that all tumour cells did not stain equally. DR and DP antigens were found more often on moderately or poorly differentiated adenocarcinomas and on stage B, C and D tumours in that order of frequency. Thus tumours with a better prognosis were less likely to express DR and DP. The expression of DQ was unrelated to staging or differentiation.

Selective changes in expression of HLA class I polymorphic determinants in human solid tumors

Analysis of surgical biopsies with monoclonal antibodies (mAbs) to framework determinants of major histocompatibility complex class I antigens has shown that malignant transformation is frequently associated with a marked loss of these cell surface molecules. The present study sought to determine whether more selective losses of major histocompatibility complex class I expression occur. Multiple specimens from 13 different types of primary and metastatic tumors were tested utilizing mAb BB7.2, which recognizes a polymorphic HLA-A2 epitope. In each case, expression of HLA-A,B,C molecules was determined by testing with mAb W6/32 directed to a framework HLA class I determinant. We have found that in HLA-A2-positive patients (identified by reactivity of their normal tissues with mAb BB7.2), HLA-A2 products are not detectable or are reduced in their expression in 70-80% of endometrial, colorectal, mammary, and renal tumors; in 40-60% of soft-tissue, skin, ovary, urinary bladder, prostate, and stomach tumors; and in 25-30% of melanomas and lung carcinomas tested. All tumors expressed the framework HLA-A,B,C determinant. The HLA-A2 epitope recognized by mAb BB7.2 is located in a portion of the HLA-A2 molecule postulated to react with the T-cell receptor. Immune surveillance to tumors is thought to depend on cytotoxic T cells, which require corecognition of polymorphic HLA class I epitopes, and on natural killer cells, which are, on the contrary, activated by the absence of HLA class I antigens. The selective loss of an HLA class I polymorphic epitope shown in this study may explain the mechanism by which tumor cells escape both T-cell recognition and natural killer cell surveillance.

Loss of HLA-A,B,C allele products and lymphocyte function-associated antigen 3 in colorectal neoplasia

The expression of HLA-A,B,C antigens and lymphocyte function-associated antigen 3 in human colorectal adenomas and adenocarcinomas was studied by immunohistochemistry. None of 10 adenomas and only 1 of 30 carcinomas had lost expression of all HLA-A,B,C molecules. On the other hand, focal loss of an HLA-B product was seen in 2 of the adenomas, and complete losses of tumor cell HLA-A2 (in 7 of 13 cases), HLA-Bw4 (in 4 of 13 cases), and HLA-A3 (in 1 of 6 cases) were seen in the carcinomas. No complete losses of HLA-A1 (in 6 cases) or HLA-Bw6 (in 22 cases) occurred in the carcinomas. In addition, 1 of 20 adenocarcinomas totally lacked lymphocyte function-associated antigen 3. Because a loss of tumor cell HLA-A,B,C antigen or lymphocyte function-associated antigen 3 could be selected for through an advantage in escape from cytotoxic T-lymphocyte attack, our results suggest that immunoselection may be a more important mechanism in tumor progression than has previously been assumed.