HLA antigens in colorectal tumours--low expression of HLA class I antigens in mucinous colorectal carcinomas

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.

Combination of NK Cells and Cetuximab to Enhance Anti-Tumor Responses in RAS Mutant Metastatic Colorectal Cancer

The ability of Natural Killer (NK) cells to kill tumor targets has been extensively studied in various hematological malignancies. However, NK cell therapy directed against solid tumors is still in early development. Epidermal Growth Factor Receptor (EGFR) targeted therapies using monoclonal antibodies (mAbs) such as cetuximab and panitumumab are widely used for the treatment of metastatic colorectal cancer (mCRC). Still, the clinical efficacy of this treatment is hampered by mutations in RAS gene, allowing tumors to escape from anti-EGFR mAb therapy. It is well established that NK cells kill tumor cells by natural cytotoxicity and can in addition be activated upon binding of IgG₁ mAbs through Fc receptors (CD16/FcγRIIIa) on their surface, thereby mediating antibody dependent cellular cytotoxicity (ADCC). In the current study, activated Peripheral Blood NK cells (PBNK) were combined with anti-EGFR mAbs to study their effect on the killing of EGFR^+/- cancer cell lines, including those with RAS mutations. In vitro cytotoxicity experiments using colon cancer primary tumors and cell lines COLO320, Caco-2, SW620, SW480 and HT-29, demonstrated that PBNK cells are cytotoxic for a range of tumor cells, regardless of EGFR, RAS or BRAF status and at low E:T ratios. Cetuximab enhanced the cytotoxic activity of NK cells on EGFR⁺ tumor cells (either RAS^wt, RAS^mut or BRAF^mut) in a CD16 dependent manner, whereas it could not increase the killing of EGFR^- COLO320. Our study provides a rationale to strengthen NK cell immunotherapy through a combination with cetuximab for RAS and BRAF mutant mCRC patients.

Effects of fumonisin B1 on HLA class I antigen presentation and processing pathway in GES-1 cells in vitro

Fumonisin B1 (FB1) is a food-borne mycotoxin produced by genus Fusarium and was classified as possible carcinogen to humans by the International Agency for Research on Cancer (IARC). Human leukocyte antigen (HLA) class I antigen presentation pathway plays an important role in immunosurveillance. Defects in HLA class I antigen presentation pathway can down-regulate the expression of HLA class I antigen on the surface of nucleated cells that will confer a survival advantage to randomly mutant cells and may lead to malignant transformation. In the present study, we analyzed the effects of FB1 on the expression of HLA class I heavy chain (classical HLA-A, -B and -C genes included), beta2-microglobulin (β2m), LMP2 and TAP1 genes in human gastric epithelial immortalized GES-1 cells in vitro using semi-quantitative Reverse Transcription Polymerase Chain Reaction (RT-PCR), Western blot and immunocytochemical methods in dose- and time-effect studies. Our results revealed that FB1 have an effect on HLA class I antigen presentation pathway via the decreased expression of HLA class I heavy chain and/or defects of LMP2 and TAP1 expression. However, the importance of this effect in carcinogenesis needs further investigation.

Host response to colorectal cancer

It has long been established that inflammation and immunity play critical roles in the pathogenesis, control and eventual metastasis of cancers. With the advent of more sophisticated animal models and immunohistochemical techniques a greater understanding of the immune system and its interactions has occurred. Individual immune cells are dynamic structures that have variable behaviour controlled by complex interactions in the tumour microenvironment. In the setting of colorectal cancer it was first observed that peritumoral inflammatory infiltrates were associated with improved prognosis. Immunohistochemistry has shown the individual cells types within these infiltrates. It now appears that an adaptive immune response, differentiated along the T-helper 1 pathway controls tumour invasion and metastasis. Furthermore, the immune system exerts selection pressure leading to the evolution of tumour cell variants that can induce tolerance and disable adaptive immunity. These tumour cells then use the mechanisms of innate immunity to facilitate further growth, angiogenesis, invasion and eventual metastasis. These issues are investigated with particular relevance to colorectal cancer. Using the immune response to defeat CRC has been under intense investigation but has so far been unsuccessful. Nevertheless, researchers remain optimistic that immunotherapy will play an important role in the treatment of this common disease.

HLA-A, -B, -C expression in colon carcinoma mimics that of the normal colonic mucosa and is prognostically relevant

Whether human leukocyte antigen (HLA)-A, -B, -C expression has any predictive value on the prognosis of human malignancies remains controversial. Herein, monoclonal antibodies with preferential reactivity for HLA-A, HLA-B, and HLA-C (HCA2, HC10, and L31) were used to stain an archival collection of 291 formalin-fixed/paraffin-embedded tissues, comprising neoplastic lesions from stages II and III colon carcinoma patients (n=165), and the uninvolved, morphologically normal mucosae from a subset (n=126) of these patients. Marked staining variability was detected not only in the tumors as in previous studies, but also in the normal paired mucosae. HLA-A, -B, -C expression was similar in approximately two thirds of the available 126 normal/neoplastic pairs, confirming in vivo our previous observation that most tumor cells mimic the HLA phenotypes of their normal counterparts. Both up and down-regulation occurred in the remaining third of the pairs, but did not coincide with high and low expression, respectively, conventionally evaluated on the tumor lesion only. Remarkably, a "paired" evaluation, but not high or low expression in the tumor, was predictive of the clinical outcome. Deviations from the expression in the normal paired mucosa (both increases and decreases) of HCA2-reactive class I molecules (possibly HLA-A), and down-regulation of L31-reactive class I molecules (possibly HLA-C), particularly in tumors from stage II patients, correlated with poor 5-year overall and disease-free survival, hazard risk ranging from 2 to 6, approximately. Thus, a paired immunohistochemical comparison reveals a novel immune evasion strategy that may impact on the prognosis of colon carcinoma.

Mechanisms of immune evasion by tumors

In the past decade, basic studies in animal models have begun to elucidate the physiological barriers which impede a successful antitumor immune response. These barriers operate at a number of levels, and involve the tumor, the tumor microenvironment and various components of the innate and adaptive immune systems. In this review, we discuss the multiple mechanisms by which tumors evade an immune response, with an emphasis on clinically relevant strategies to overcome these inhibitory checkpoints.

Human Leukocyte Antigen and Antigen Processing Machinery Component Defects in Astrocytic Tumors

PURPOSE

To determine the frequency of abnormalities in human leukocyte antigen (HLA) and antigen processing machinery (APM) component expression in malignant brain tumors. This information may contribute to our understanding of the immune escape mechanisms used by malignant brain tumors because HLA antigens mediate interactions of tumor cells with the host's immune system.

EXPERIMENTAL DESIGN

Eighty-eight surgically removed malignant astrocytic tumors, classified according to the WHO criteria, were stained in immunoperoxidase reactions with monoclonal antibody recognizing monomorphic, locus-specific, and allospecific determinants of HLA class I antigens, beta2-microglobulin, APM components (LMP2, LMP7, TAP1, TAP2, calnexin, calreticulin, and tapasin), and HLA class II antigens.

RESULTS

HLA class I antigens were lost in approximately 50% of the 47 glioblastoma multiforme (GBM) lesions and in approximately 20% of the 18 grade 2 astrocytoma lesions stained. Selective HLA-A2 antigen loss was observed in approximately 80% of the 24 GBM lesions and in approximately 50% of the 12 grade 2 astrocytoma lesions stained. HLA class I antigen loss was significantly (P < 0.025) correlated with tumor grade. Among the APM components investigated, tapasin expression was down-regulated in approximately 20% of the GBM lesions analyzed; it was associated, although not significantly, with HLA class I antigen down-regulation and tumor grade. HLA class II antigen expression was detected in approximately 30% of the 44 lesions analyzed.

CONCLUSION

The presence of HLA antigen defects in malignant brain tumors may provide an explanation for the relatively poor clinical response rates observed in the majority of the T cell-based immunotherapy clinical trials conducted to date in patients with malignant brain tumors.

Does the immune system see tumors as foreign or self?

Given the vast number of genetic and epigenetic changes associated with carcinogenesis, it is clear that tumors express many neoantigens. A central question in cancer immunology is whether recognition of tumor antigens by the immune system leads to activation (i.e., surveillance) or tolerance. Paradoxically, while strong evidence exists that specific immune surveillance systems operate at early stages of tumorigenesis, established tumors primarily induce immune tolerance. A unifying hypothesis posits that the fundamental processes of cancer progression, namely tissue invasion and metastasis, are inherently proinflammatory and thus activating for innate and adaptive antitumor immunity. To elude immune surveillance, tumors must develop mechanisms that block the elaboration and sensing of proinflammatory danger signals, thereby shifting the balance from activation to tolerance induction. Elucidation of these mechanisms provides new strategies for cancer immunotherapy.

Immunology and immunotherapy of colorectal cancer

This review critically discusses data on immunology of colorectal cancer, starting from pathology and molecular biology, and then considering the molecular characterisation of colon cancer antigens and the clinical trials of immunotherapy. A careful evaluation of histopathological studies on intra-epithelial infiltration by T cells in primary tumours, together with the analysis of HLA expression by colorectal cancer cells, suggest that anti-tumour T cell immune responses may take place in vivo in those patients, influencing prognosis and shaping the tumour immunological profile. Moreover, the molecular characterisation of tumour antigens expressed by colorectal carcinomas, together with improved understanding of mechanisms of the immune response and more sensitive methods for the in vivo detection of T cell responses, are now allowing researchers to design new and more effective vaccination protocols, with encouraging preliminary results. By drawing together the experimental evidence from different research fields, this review provides support for the concept that colorectal carcinoma is immunogenic and may reasonably be considered as a target for immunotherapy, and attempts to address critical issues and envisage future developments in this challenging research field.

Down-regulation of HLA-A expression correlates with a better prognosis in colorectal cancer patients

To evaluate the prognostic impact of human leukocyte antigen class I (HLA-I) expression on immune surveillance in colorectal cancer, we studied 88 curatively resected tumors for HLA-A and HLA-B/C expression and correlated these data to clinical and histopathological parameters. HLA-A was normal (all tumor cells had HLA expression) in 32%, reduced (HLA-negative and -positive tumor cells coexisted) in 56%, or absent (no tumor cells expressed HLA) in 12% of evaluable cases. HLA-B/C was normal in 47%, reduced in 47%, and absent in 7% of the cases. Considering both markers, total HLA-I expression was normal in 27%, reduced in 63%, absent in 7%, and could not be evaluated in 3% of the cases due to absent HLA-A expression in tumor and normal cells. Down-regulation of HLA-A expression significantly correlated with a lower tumor stage (p = 0.005), mucinous tumors (p = 0.05), a lower incidence of recurrences (p = 0.03), and a longer disease-free survival (p = 0.02). Down-regulation of HLA-B/C expression correlated with a lower tumor stage (p < 0.001) and a longer disease-free survival (p = 0.04). In multivariate analysis, HLA-A down-regulation was the only prognostic factor correlated with a longer disease-free survival (p = 0.02). Six tumors were negative for HLA-A and -B/C and did not recur during follow-up. Therefore, we analyzed microsatellite instability (MSI) in these cases. Three of these six tumors indeed showed down-regulation of MLH-1, MSH-2, or MSH-6, indicating a MSI-high phenotype. Beta-2-microglobulin protein expression was lost in five of six of the HLA-I-negative cases, but frame shift mutations in three repetitive sequences in beta2-microglobulin were absent. In contrast, loss of MLH-1, MSH-2, and MSH-6-protein expression was only observed in two of nine matched controls with reduced or normal HLA-A and -B/C expression. Our data showed that HLA-I was down-regulated in 72% of colorectal cancers and provided independent prognostic information for a longer disease-free survival. The better prognosis may be caused by elimination of HLA-negative cells by natural killer cells or by an attenuated tumor aggressiveness, as is seen in tumors with a MSI-high phenotype.

HLA-DBR 1 alleles and the susceptibility of Iranian patients with breast cancer

Breast cancer is considered a major malignancy among women worldwide. The contribution of genetic elements to the onset of familial breast cancer has already been established. The current study investigate the alfele frequency of HLA-DRB 1 in 36 primary operable female breast cancer patients from southern Iran by polymerase chain reaction using sequence specific primers (PCR-SSP). Results were compared with those of 36 female control subjects. Statistical analysis was performed and P values were determined for each character. Our results indicated that the frequency of HLA-DRB 1*12 allele is significantly higher in the patient group (p<0.03) compared to the control group. In addition, HLA-DRB1*11 appeared to be as the most frequent allele in the control group (29.2%) and had approximately the same distribution among the patient group (22.5%).

High frequency of altered HLA class I phenotypes in laryngeal carcinomas

The exact frequency of HLA class I losses in human tumors is unknown. We have previously shown that primary breast and colorectal carcinomas frequently lose HLA class I molecules (88% and 73%, respectively). Now we report that this phenomenon is also a frequent event in laryngeal carcinomas. Of a total of 76 laryngeal carcinomas analyzed, 66% of the tumors showed an alteration in HLA class I phenotype. These altered HLA phenotypes were classified as total HLA loss (10.52%) (phenotype I); HLA-A locus-specific loss (13.15%) (phenotype IIIa); HLA-B locus-specific loss (10.52%) (phenotype IIIb); HLA allelic loss (27.63%) (phenotype IV); and HLA-A and B locus loss (3.9%). Comparison of histopathological parameters with HLA expression showed that poorly differentiated tumors had the lowest levels of HLA class I expression (p < 0.05).

Molecular basis for lack of expression of HLA class I antigens in human small-cell lung carcinoma cell lines

HLA class I molecules present antigenic peptides to cytotoxic T lymphocytes and thus play an important role in immune surveillance of cells infected with virus or altered by malignant transformation. Immunochemical studies have demonstrated a marked deficiency or lack of expression of class I molecules on the surface of many different types of tumor cells. It is likely that this allows these cells to escape immune surveillance. In the present study, we examined the molecular basis for lack of expression of class I antigens in small-cell lung carcinoma cell lines. Our results demonstrate that these cell lines also lacked products of MHC-encoded proteasome subunit LMP2 and the putative peptide transporter TAP1. In contrast, LMP7 and TAP2 genes were expressed in these cell lines. Pulse-chase experiments showed that class I molecules were unstable and thus not transported to the cell surface from endoplasmic reticulum. Our results suggest that antigenic peptides were not available for binding to class I alpha chains due to lack of TAP1 and LMP2 gene products. Investigations of the regulatory mechanisms of TAP1 and LMP2 genes showed that the tumor cells lacked trans -regulatory nuclear protein(s), which binds to the interferon-gamma (IFN-gamma) response element (ISRE) in the TAP1, LMP2 bidirectional intergenic promoter. Treatment of tumor cells with IFN-gamma induced ISRE-binding nuclear protein(s) and resulted in expression of TAP1 and LMP2 genes with a concomitant increase in cell-surface expression of class I molecules. Our data provide credence for a role of TAP and LMP genes in immune response.

Markedly decreased expression of TAP1 and LMP2 genes in HLA class I-deficient human tumor cell lines

HLA class I antigens of the human major histocompatibility complex play an important role in immune response. These molecules present foreign antigenic peptides to cytotoxic T lymphocytes and thereby play a role in the immune surveillance of cells infected with virus or other intracellular pathogens or altered by malignant transformation. A marked deficiency or lack of expression of these antigens has been reported in a variety of human neoplasms. In the present study, we examined the expression of class I alpha chain, beta 2-microglobulin, TAP (TAP1 and TAP2) and LMP (LMP2 and LMP7) genes in a number of human tumor cell lines including small-cell lung carcinoma, hepatocellular carcinoma, colon adenocarcinoma and basophilic leukaemia. These cell lines were deficient in expression of both class I alpha chain and beta 2-microglobulin gene products. In addition, these cell lines lacked the products of MHC-encoded proteasome subunit LMP2 as well as the putative peptide transporter TAP1 genes. In contrast, TAP2 and LMP7 genes were expressed in these cell lines. Treatment of cells with gamma-IFN markedly enhanced the expression of class I alpha chain, beta 2-microglobulin, TAP1 and LMP2 genes with a concomitant increase in cell-surface expression of class I molecules. The upregulation of TAP1 and LMP2 expression is associated with increased class I expression, suggesting that endogenous antigens, e.g. tumor antigens, could be presented by class I molecules following treatment of tumor cells with gamma-IFN.

Identification of mRNAs that show modulated expression during colon carcinoma cell differentiation

To investigate the working hypotheses that stem cells or their early descendants are prime targets for neoplastic transformation, and that the degree to which a neoplasm retains the immature phenotype is an important determinant of tumor aggressiveness, we have identified several mRNAs that are downregulated during the in vitro differentiation of HT29-D4 colon carcinoma cells. These genes include heat-shock cognate protein Hsc70, adenylosuccinate lyase, B23/nucleophosmin, alpha-tubulin, and a novel gene designated DS-1. The DS-1 mRNA has a length of approximately 0.9 kb and is downregulated 4.7-fold upon differentiation. From the DS-1 cDNA, a protein of 206 amino acids with a molecular mass of 24 kDa and an isoelectric point of 10.9 can be deduced. An antiserum directed against a synthetic peptide detected a minor band of the expected size in Western blots, as well as a major band of lower size that may represent a processed form of the protein.

Is mucinous carcinoma of the colorectum a distinct genetic entity?

Mucinous carcinomas are defined on the basis of the amount of the mucus component in the tumour mass. Apart from this quantitative criterion, a number of clinicopathological parameters (such as localisation, prevalence in different countries and age groups, association with HNPCC and inflammatory processes) and genetic alterations (e.g. frequency of mutation in Ki-ras and p53 genes, level of MUC2 expression) differentiate these tumours from the non-mucinous ones. Since a different set of genetic lesions implies different inducing agents, these observations suggest that there may be a 'mucinous pathway of carcinogenesis'. Further identification of genetic changes characteristic of the mucinous phenotype will help to understand the aetiology of these tumours and possibly establish markers for detection of the high-risk group.

A reassessment of the role of B7-1 expression in tumor rejection

Introduction of the B7-1 gene into murine tumor cells can result in rejection of the B7-1 transductants and, in some cases, systemic immunity to subsequent challenge with the nontransduced tumor cells. These effects have been largely attributed to the function of B7-1 as a costimulator in directly activating tumor specific, major histocompatibility class I-restricted CD8+ T cells. We examined the role of B7-1 expression in the direct rejection as well as in the induction of systemic immunity to a nonimmunogenic murine tumor. B-16 melanoma cells with high levels of B7-1 expression did not grow in C57BL/6 recipient mice, while wild-type B-16 cells and cells with low B7-1 expression grew progressively within 21 d. In mixing experiments with B7-1hi and wild-type B-16 cells, tumors grew out in vivo even when a minority of cells were B7-1-. Furthermore, the occasional tumors that grew out after injection of 100% B-16 B7-1hi cells showed markedly decreased B7-1 expression. In vivo antibody depletions showed that NK1.1 and CD8+ T cells, but not CD4+ T cells, were essential for the in vivo rejection of tumors. Animals that rejected B-16 B7-1hi tumors did not develop enhanced systemic immunity against challenge with wild-type B-16 cells. These results suggest that a major role of B7-1 expression by tumors is to mediate direct recognition and killing by natural killer cells. With an intrinsically nonimmunogenic tumor, this direct killing does not lead to enhanced systemic immunity.

Major histocompatibility proteins, anti-Hu antibodies, and paraneoplastic encephalomyelitis in neuroblastoma and small cell lung cancer

BACKGROUND

Patients with neuroendocrine-related tumors and paraneoplastic encephalomyelitis (PEM) or paraneoplastic sensory neuronopathy (PSN) develop high titers of antibodies, called anti-Hu, against neuronal proteins expressed in their tumors, usually small cell lung cancer (SCLC). These tumors appear to be more indolent than those not associated with anti-Hu antibodies. The aims of this study were to determine 1) if patients with neuroblastoma (NB) also have anti-Hu antibodies, 2) the correlation between antibody titer and survival, and 3) if coexpression of Hu antigens and major histocompatibility proteins (MHC) by the tumor correlates with the development of anti-Hu associated PEM/PSN:

METHODS

Using immunohistochemistry and Western blot analysis, the sera of 109 patients with NB whose neurologic condition was concealed at the time of the study were examined for the presence of anti-Hu antibodies. The expression of Hu antigens and MHC proteins in 50 nonselected NB and 26 SCLC (16 known to be from seropositive and 10 from seronegative patients) was examined using immunohistochemistry.

RESULTS

Four Stage 4 NB patients were seropositive and had longer survival (median 86 months) than 71 seronegative patients in the same age group and with the same tumor stage (median survival, 28.5 months). Seventy-eight percent of NB and all SCLC expressed Hu antigens. Overall, 17 of 20 tumors from seropositive patients expressed both Hu and MHC Class I proteins, but only 4 of 30 tumors from seronegative patients expressed both proteins (P < 0.0001).

CONCLUSIONS

1) Some patients with NB develop anti-Hu antibodies; a search for that type of tumor is indicated in seropositive children, 2) most NBs and SCLCs express Hu antigens but only a few are associated with anti-Hu antibodies, and 3) Class I MHC expressed by some Hu antigen-bearing tumors may play a role in the development of anti-Hu associated PEM/PSN:

Loss of major histocompatibility complex-encoded transporter associated with antigen presentation (TAP) in colorectal cancer

Presentation of endogenous antigenic peptides to cytotoxic T lymphocytes (CTLs) is mediated by the major histocompatibility complex (MHC) class I molecules. These antigenic peptides derived from the cytoplasmic protein pool are transported by the recently described MHC-encoded transporters (TAP1 and TAP2) into a pre-Golgi region where they take part in the assembly of MHC class I molecules. Using an affinity-purified polyclonal antibody (AK1.7) for TAP1, we analyzed 81 colorectal carcinomas, 32 adenomas, and the respective nonneoplastic mucosa. Loss of the transporter molecule (TAP1) was observed in 14% (11 of 81) of the carcinomas, either complete (7 of 11) or focal (4 of 11), whereas adenomas and normal mucosa were always positive. This study adds further information to the understanding of the mechanisms related to the defective presentation of the MHC class I molecules by tumor cells.

Expression of MHC class I antigen in Morris rat hepatoma and normal liver

Expression of major histocompatibility complex (MHC) class I antigen in Morris rat hepatoma 7777 and normal rat liver tissues was studied by immunohistochemical techniques, Western blot and radiobinding assay. It was found that hepatoma tissue displayed a pattern of enhanced MHC class I antigen expression compared with normal liver. This phenomenon may represent an uncommon pattern of MHC class I antigen expression of liver tumor. The influence of enhanced MHC class I antigen expression on the development and spread of tumors as well as the possible mechanisms of this enhancement are discussed.

Differences in MHC and TAP-1 expression in cervical cancer lymph node metastases as compared with the primary tumours

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 analyzed 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-1 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.

Increased tumorigenicity after differentiation of colon cancer cell line: absence of association with mucin synthesis

BACKGROUND/AIMS

Postconfluence differentiation followed by a decrease in mucin synthesis has been described for the colonic adenocarcinoma cell line Caco-2. Because the onset of differentiation usually heralds the end of proliferation, we expected Caco-2 would be more tumorigenic in the exponential phase. Thus, we compared tumorigenicity, clonigenicity, and mucin synthesis in the exponential and stationary growth phases.

METHODS

We estimated mucin synthesis in Caco-2 cells by measuring the amount of high-molecular-weight [3H]glucosamine-labeled glycoprotein released into the culture medium and in the cytosolic fraction. Colony forming efficiency in soft agar and tumorigenicity in nude mice were assessed.

RESULTS

Cells in the exponential phase synthesized significantly more mucin compared with stationary phase cells. Pretreatment with benzyl-GalNAc reduced production in both phases but did not change clonigenicity. Colonies did not grow from cells seeded in the exponential phase. The average weight of xenografts raised from postconfluence cells was twice that of xenografts raised from cells in the exponential phase.

CONCLUSIONS

Neither exponential cell growth nor increased mucin production predicts clonigenicity and tumorigenicity. It is speculated that a stable process takes place in Caco-2 cells after confluence which makes them more clonigenic in vitro and enhances tumor growth in vivo.

HLA expression by benign and malignant prostatic epithelium: augmentation by interferon-gamma

Chronic prostatitis is a poorly understood entity that is characterized by lymphocytic infiltration of benign prostatic epithelium. Previously, we and others have shown that prostatic epithelium involved by prostatitis is phenotypically different from uninvolved epithelium. In addition, we have shown that malignant prostatic epithelium is rarely, if ever, infiltrated by lymphocytes. We now report that benign prostatic epithelium expresses HLA-DR only in the presence of lymphocytic inflammation, and that benign epithelium without chronic prostatitis and malignant prostatic epithelium do not express HLA-DR. In order to determine whether HLA-DR expression is inducible on malignant prostatic epithelium and therefore, at least theoretically, susceptible to immune regulation, we studied the DU-145 cell line in culture under various conditions. DU-145 cells did not express HLA-DR under routine culture conditions. However, the addition of interferon-gamma (100 to 6000 U/ml.) resulted in HLA-DR expression by DU-145 cells at 24 hours with maximal expression by 72 hours. In contrast, other cytokines (tumor necrosis factor, interleukin-1, interleukin-2) had no effect on HLA-DR expression. These investigations show that interferon-gamma induces HLA-DR expression on the DU-145 prostatic adenocarcinoma cell line, raising the theoretical possibility that malignant prostatic cells may be induced in vivo to express HLA-DR and thus become susceptible to immune regulation.

Expression of beta 2-microglobulin by premalignant epithelium

Many human tumors express low amounts of HLA class I molecules relative to the normal cells from which they are derived. From experimental work it is clear that the malignant behavior of a tumor cell may depend on its MHC class I expression. Therefore, it is of obvious interest to study the HLA class I expression of human tumors in their various stages. We have studied the HLA class I expression by the cells in premalignant epithelial lesions and invasive carcinoma of the bladder and uterine cervix using immunoperoxidase staining for beta 2-microglobulin of paraffin-embedded tissue. We here assume that beta 2-microglobulin expression by malignant and premalignant cells equals HLA class I expression. Thirty-two of the 36 invasive tumors expressed less overall beta 2-microglobulin than cells from the normal epithelium. In contrast, approximately two-thirds of 34 premalignant bladder epithelia and 47 premalignant cervix epithelia displayed higher overall beta 2-microglobulin expression than the normal epithelium. Thus, a systematic large-scale elimination of HLA class I high-expressing tumor cell variants may take place only after the tumor penetrates the basement membrane.

Prognostic factors in colorectal cancer

The prognostic power of the extent of tumour invasion is indisputable; Dukes' classification has repeatedly been proven to be strongly correlated with patient survival. Modifications have led only to confusion, resulting in caution being required in the classification of patients with Dukes' A tumours. In the UK, the American tumour node metastasis and Australian clinicopathological systems are frequently considered too complex for routine clinical use. Meanwhile, Jass's classification may be complicated by observer variation between pathologists, and recent evidence suggests that it offers no advantage over that of Dukes. All the conventional staging systems also fail to take the skill of the surgeon into account when determining outcome. Attempts at quantifying tumour structure have not heralded the expected major advance. For instance, the expense and uncertain prognostic value of tumour DNA content assessed by flow cytometry are likely to restrict widespread use of this technique. It may soon be possible, however, to provide optimum treatment for patients based on individual tumour doubling times. Classification using knowledge of how a small number of cells in the tumour have the ability to invade locally, enter blood vessels and metastasize would also provide important prognostic information on which treatment could be based. Until then, the ease of use and high prognostic power of Dukes' classification ensure that, after 60 years, it is still the 'gold standard' against which all other prognostic classifications in colorectal cancer should be assessed.

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.

Sporadic loss of leucocyte-function-associated antigen-3 (LFA-3) in colorectal carcinomas

Leucocyte-function-associated antigen-3 (LFA-3) is a cell surface glycoprotein involved in T-cell/target cell interaction. The expression of LFA-3 on the cell surface was found to be inevitably associated with the expression of HLA molecules. Loss of LFA-3 or HLA proteins on tumour cells might result in ineffective T-cell/target cell interaction and a failure of immunological tumour surveillance. Immunohistochemistry revealed that LFA-3 is expressed in normal colonic epithelium; however, in a minor fraction of colonic adenomas and in 50.3% of colorectal carcinomas LFA-3 expression was reduced or even absent. To investigate whether the presence or absence of LFA-3 in colorectal carcinomas influences the relapse rate and time of tumour-related death, 149 patients who underwent putatively curative surgery were surveyed for a maximum of 65 months (mean 48 months). In contrast to the prognostic role of tumour stage and grade, the presence versus absence of LFA-3 was not correlated with recurrence or survival. Regarding survival and growth of residual tumour cells after potentially curative resection of the initial tumour burden, we conclude that the status of LFA-3 expression in colorectal carcinoma seems to be irrelevant in vivo.

Identification of locus-specific DNA-binding factors for the regulation of HLA class-I genes in human colorectal cancer

The expression of HLA class-I mRNA in human colorectal cancer cell lines was studied. Locus-specific down-regulation of HLA class-I mRNA could be demonstrated in some of the human colorectal lines. This transcriptional suppression of HLA mRNA, however, was not a result of genetic alterations in the HLA structural genes. The transcription of the HLA class-I genes in the HLA-deficient cell lines could be induced by the addition of human recombinant gamma-IFN. In this report, we have employed these human colorectal cell lines to study locus-specific transcriptional regulation of HLA class-I gene expression. Our results demonstrate that the locus-specific suppression of HLA gene expression in human colorectal cell lines is mediated by the loss of certain DNA-binding transcription factors which act in a locus-specific manner. Our conclusion is further supported by experiments which showed that exogenously introduced HLA-CAT DNA constructs were also regulated in a locus-specific fashion when assayed by in vitro functional assays using these human colorectal cell lines.

Frequency of abnormal expression of HLA-A,B,C and HLA-DR molecules, invariant chain, and LFA-3 (CD58) in colorectal carcinoma and its impact on tumor recurrence

HLA-A,B,C and HLA-DR molecules are involved in cognate LFA-3 (CD58) in antigen-independent T-cell/target-cell interaction. T-cell-mediated host-versus-tumor response might therefore depend on the presence of both types of molecules on the surface of the target cell. To investigate whether presence or absence of these molecules in colorectal carcinoma influences the recurrence rate, 149 patients who underwent curative surgery were surveyed for a maximum of 65 months (mean, 48 months). As determined by immunohistochemistry, aberrant reduction of HLA-A,B,C determinants was observed in 34.9 and a complete loss in 8.7% of the tumor specimens. An induction of HLA-DR molecules was found in 55.0 and of the HLA-DR-associated invariant chain (Ii) in 81.9%. An abnormal reduction of LFA-3 was detected in 43.6%, while a complete loss of this structure was observed in 6.7%. Reduction/loss of HLA-A,B,C was correlated with reduction/loss of LFA-3 (p = 0.03). In contrast to the prognostic role of tumor stage and grade, the presence vs. absence of all these structures was not correlated with the recurrence rate. We conclude that, although encoded on different chromosomes, an abnormal reduction/loss of HLA-A,B,C and LFA-3 might be the consequence of one transacting down-regulating signal. However, the resulting deviant immunophenotypes do not profoundly influence survival and growth potential of residual tumor cells.

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.

Class II (HLA-DR, -DP, and -DO) antigens on intestinal epithelia in ulcerative colitis, Crohn's disease, colorectal cancer and normal small intestine

Class II antigens in involved colonic epithelia of ulcerative colitis (UC), Crohn's disease (CD), colorectal cancer, and epithelia of normal small intestine were investigated using an immunoperoxidase method. Ten normal colonic mucosa served as normal controls. Ten specimens were studied for each group. Normal colonic epithelia did not express class II antigens. In colonic diseases; (1) with regard to the frequency and extent of class II antigens on epithelia. HLA-DR antigens were the most highly and greatly expressed, followed by HLA-DP and then HLA-DQ antigens. (2) The extent of HLA-DR and -DP, but not HLA-DQ, expression on epithelia of UC and colorectal cancer seemed to be positively correlated with the degree of mononuclear cell infiltration in the lesion. (3) The extent of class II antigen expression on colonic epithelia in CD was not related to the degree of mononuclear cell infiltration in the lesion. (4) The extent of HLA-DR and -DP expression on epithelia of colorectal cancer seemed to be positively correlated with increasing undifferentiation. In the normal small intestine, where HLA-DR antigens were physiologically expressed on epithelia. HLA-DQ antigens were not expressed. The heterogeneity among colonic diseases, and between the physiological and pathological status, may reflect differences in immunoregulation.

Immunohistochemical detection of major histocompatibility complex antigens and quantitative analysis of tumour-infiltrating mononuclear cells in renal cell cancer

In order to investigate the anti-tumour immune responsiveness of patients with renal cell cancer (RCC), we examined 30 such patients for the degree of expression of major histocompatibility complex (MHC) class I and class II antigens on RCC and the populations of tumour-infiltrating mononuclear cells (TIM). Normal renal tubular cells expressed class I but not class II antigens. Most of the tumour cells expressed class I antigens in 25 (83%) cases, but the proportion of such cells was reduced in five cases, three of which were of granular cell type histologically. Class II antigens were detected in all specimens with class I positivity. Various numbers of TIM were detected in 25 cases, being composed mainly of T cells and a smaller number of macrophages. Examination for the phenotype of T cells showed that CD8-positive cells were the dominant population. B cells were not detected. Quantitative analysis revealed that the numbers of TIM were significantly lower in cases showing class I reduction than in those with normal class I expression. Therefore, it was clear that class I antigens were preserved in RCC cells in most cases. Furthermore, a higher rate of reduction of class I antigens was observed in cases of granular cell type, which has been reported to have a worse prognosis than the clear cell type. The present data suggest that degree of the expression of MHC class I antigen on RCC might influence the host immune responsiveness against it.

Histocompatibility antigen expression in pulmonary carcinomas as indication of differentiation and of special subtypes

In 70 human carcinomas of the lung the expression of histocompatibility antigens (HLA) was investigated by using monoclonal antibodies in frozen sections. The immunmoreactive tumor volume was determined morphometrically. The tumor types showed a different pattern of HLA expressions. In squamous cell carcinomas (SQC) and small cell carcinomas (SCC) the HLA-A,B,C expression varied in a great range from 0% to 100% of positive tumor volume. For the most part, HLA-DR was not demonstrable. In adenocarcinomas (AC) and large cell carcinomas two different populations were observed. One showed a pattern of HLA expression as seen in SQC. Electron microscopically these AC (type 1) (AC/1) were characterized by intracytoplasmic mucin granules indicating a phenotypical relationship to goblet cells. The other--nearly 50% of adenocarcinomas and one third of large cell carcinomas--expressed both HLA antigens homogeneously in the total tumor volume. Electron microscopically the characteristics of type II pneumocytes and Clara cells were seen in tumor cells of these AC (type II) (AC/II), consisting in lamellar bodies and apically located electron-dense granules. In SQC and AC/I a significant correlation was found between grades of differentiation and mitotic activity on the one side, and expression of HLA-A,B,C on the otrher. The loss of HLA-A,B,C expression seemed to be an indication of a lower grade of differentiation; the smalles expression of HLA-A,B,C occurred in SCC.

Expression of HLA class I antigens in human tumors and their involvement in tumor growth

A decreased expression of major histocompatibility complex (MHC) class I antigens is a common feature of many experimental and human tumors and can often be correlated with malignancy grade. In fact, reduction of class I antigens is associated in most tumors with an enhanced ability to elude immune surveillance. Loss of HLA-A,B,C antigens ranges from a decrease in the percentage of A,B,C-positive cells to selective loss of particular antigens and total loss of class I molecule expression. In man, this has been documented in melanomas, carcinomas, lymphomas, neuroblastoma and acute leukemias. The reduction in membrane antigens is generally associated with a parallel fall in immunoprecipitable intracellular proteins and the corresponding mRNAs in the absence of structural changes in the coding genes. The literature concerning the above mentioned topics is reviewed and discussed.

Colonic lymphoid cell subsets and epithelial HLA-DR antigens in familial polyposis coli

Although there has been some evidence suggesting that immunological mechanisms are involved in the pathophysiology of familial polyposis coli (FPC), there has not been any report as to whether there is any abnormality of lymphoid cell subsets as background, whether polyps (adenomas) show different lymphoid cell subsets from the normal mucosa, or whether HLA-DR antigens are expressed on the epithelia of adenomas. Lymphoid cell subsets (CD5, CD4, CD8, IgA1, IgA2, IgM, IgD, IgG, and IgE positive cells) in the lamina propria, and HLA-DR antigens on the epithelia were studied in 7 patients with FPC. From each patient, 2 specimens were obtained from both the normal (non-polypoid) area and the polyp. Normal colonic mucosa, taken from 15 patients with conventional polyps or colorectal cancer, served as the normal control mucosa. Lymphoid cell subsets and HLA-DR antigens were identified by indirect immunoperoxidase staining using mouse anti-human monoclonal antibodies. In the normal area of FPC, lymphoid cell subsets were similar to those of normal control mucosa except for an increase in IgD positive (IgD+) cells. However, definite alterations were observed in the polyp. There were significant increases in the number of CD4+ and IgG+ cells, and in the sum of five classes of Ig+ cells compared to the normal area or normal control mucosa. HLA-DR antigens were not expressed in the normal control mucosa or in the normal areas, and only on the epithelia of the polyp in 5 out of 7 specimens (71%). These results clearly demonstrate that immunological reactions are involved in FPC polyps.

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.

Tumor-infiltrating lymphocytes and histocompatibility antigens in primary intracranial germinomas

Subpopulations of tumor-infiltrating lymphocytes (TIL's) and the major histocompatibility complex (MHC) antigens of neoplastic cells were examined in three intracranial germinomas by an immunohistochemical method using monoclonal antibodies. About 70% to 80% of TIL's were T lymphocytes which were either infiltrating diffusely or in clusters, whereas 20% to 30% of TIL's were B lymphocytes which tend to cluster in tumor tissues. Examination of T lymphocyte phenotypes revealed both the cytotoxic/suppressor and helper/inducer T lymphocytes, as in other tumors. However, the existence of a considerable number of B lymphocytes in the TIL population was uncommon and seemed to be a characteristic feature of the intracranial germinoma, which might suggest a difference of host immune response to this neoplasm as compared to other tumors. On examination of the MHC antigens, no MHC class I or II antigens in the neoplastic cells were stained, while positive staining for both antigens was seen in the TIL and stroma tissues. From these findings, it was suggested that the degree of TIL infiltration might not be correlated with the expression of MHC antigens in neoplastic cells in cases of primary intracranial germinoma.