Human colorectal tumour infiltrating lymphocytes express activation markers and the CD45RO molecule, showing a primed population of lymphocytes in the tumour area

Image analyzer-based assessment of tumor-infiltrating T cell subsets and their prognostic values in colorectal carcinomas

To find useful tools to evaluate the prognosis in colorectal carcinoma (CRC) patients, we investigated the prognostic values of tumor-infiltrating T lymphocyte subsets according to intratumoral subsites as well as clinical or molecular characteristics. Immunohistochemistry for CD8, CD45RO, and FOXP3 was performed, and densities of the T cell subsets in each tissue microarray core (cells/mm2) were measured by image analysis. In the training set (n = 218) of CRC, T cell subset densities in the invasion front were more strongly associated with patient outcome than those in the tumor center. In the validation set (n = 549), T cell subset densities in the invasion front were evaluated. Univariate analysis showed that all three T cell subset densities were significantly associated with longer progression free survival and overall survival time (p < 0.001). In multivariate analysis, a high CD45RO density correlated independently with longer progression free survival (p = 0.011) and overall survival time (p = 0.007) in CRC patients, regardless of tumor location or adjuvant chemotherapy status. Our results showed that CD45RO density in the invasion front was the only independent prognostic factor regarding CRC. However, CD8 and FOXP3 densities were also independent prognostic factors in certain clinical settings. Thus, image analysis of tissue microarray cores in the invasion front of CRC could be used as a valid method for evaluating the prognostic significance of T cell subset densities.

Interleukin 21 up-regulates perforin-mediated cytotoxic activity of human intra-epithelial lymphocytes

Human intra-epithelial lymphocytes (IELs) are predominantly T-cell receptor-alphabeta(+) (TCR-alphabeta(+)) CD8(+) CD45RO(+) memory T cells located between intestinal epithelial cells. They respond to a greater extent to stimulation with interleukin (IL)-15 than to CD3/TCR triggering, suggesting that they react to the cytokine milieu in their local environment rather than to cognate antigen. A newly described member of the gammac cytokine family, IL-21, has potent antitumor effects. As IELs resemble lymphocytes infiltrating neoplastic lesions, their response to IL-21 may be relevant in vivo. Here, IL-21 was shown to increase perforin-mediated cytotoxicity and serine esterase release by IELs. This IL-21-mediated up-regulation occurred without changes in IEL survival or cell division. Interestingly, the effects of IL-21 occurred without increased phosphorylation of signal transducer and activator of transcription (STAT)1, STAT3, STAT4, STAT5, extracellular signal-regulated kinase (ERK), or p38. IL-21 had no effect on Fas ligand (FL)- or tumour necrosis factor-alpha (TNF-alpha)-mediated cytotoxicity, but it down-regulated IL-15-stimulated expression of CD25 and CD94, indicating that it has both positive and negative actions. This functional profile is unique to human IELs, emphasizing that they are a distinct compartment of lymphocytes and that IL-21 may promote their role in tumour immunosurveillance.

T cell infiltrate predicts long-term survival following resection of colorectal cancer liver metastases

BACKGROUND

While tumor infiltrating lymphocytes (TIL) have been shown to independently predict survival in primary colorectal cancer, the prognostic implications of TIL in resectable colorectal cancer liver metastases (CRCLM) have not been previously defined. This study examines the correlation between TIL numbers and survival following hepatic resection.

METHODS

We studied patients who survived <or=2 or >or=10 years following CRCLM resection. Immunohistochemistry was performed on tissue microarrays (TMAs) to determine the number of T cells within CRCLM. Correlation between TIL frequency and <or=2 or >or=10 year survival was determined while controlling for established prognostic factors.

RESULTS

Of 162 patients, 104 survived <or=2 years and 58 survived >or=10 years. Independent correlates of 10-year survival following CRCLM resection included a high number of CD8 T cells, a low number of CD4 T cells, and a clinical risk score of <or=2 (P < 0.001). Among 10-year survivors, 31% of patients had a high number of CD8 T cells compared with 8% for <or=2 year survivors (P < 0.01). Surprisingly, only 22% of 10-year survivors had a high number of CD4 T cells, in contrast to 69% of those who died within 2 years (P < 0.001). The combination of CD8 and CD4 T cell counts was a more powerful predictor of survival than either marker alone.

CONCLUSIONS

CRCLM T cell number is an independent correlate of long-term survival following liver resection. We conclude that CRCLM TIL analysis represents a potentially powerful prognostic tool which will require further validation prior to broad application.

Phenotype and function of dendritic cells and T-lymphocyte polarization in the human colonic mucosa and adenocarcinoma

AIM

To evaluate the status of activation of the intestinal dendritic cells (DCs) and T lymphocytes (T cells) from surgical specimens of human colon and adenocarcinoma, and the potential effect of administration of interleukin 2 (IL-2).

METHODS

Patients undergoing colectomy for cancer were randomized to receive subcutaneous IL-2 (12million UI/day) (treated group; n=10) for 3days before operation or no treatment (control group, n=10). DCs and T cells were isolated and purified from the lamina propria (LP) of segments of normal colon and adenocarcinoma of both groups. Cell phenotype was determined by expression of membrane receptors. Interaction between DC and T cells was assesses by a mixed leukocyte reaction using naïve T cells co-cultured with DCs. CD4+ T-cell polarization was studied by intracellular staining with monoclonal antibodies for interleukin-4 and interferon-gamma.

RESULTS

CD4+ T cells were significantly less in tumour than in LP (p<0.05) in both treated and control groups. IL-2 did not modify the number of any of the T-cell subsets analysed. In contrast, T cells isolated from LP and neoplasm of treated patients produced more interferon-gamma and less interleukin-4 (p<0.05 vs. controls). IL-2 administration significantly increased (p<0.05) the number of mature, myeloid and plasmocytoid DCs compared to controls. Allogeneic naïve T cells were polarized toward a Th1 type of response which appeared to be mediated by IL-2 activated DCs.

CONCLUSIONS

systemic IL-2 treatment may have immunomodulatory properties on intestinal DC maturation and drive a Th1 mediated anti-neoplastic response.

Dissection of spontaneous cytotoxicity by human intestinal intraepithelial lymphocytes: MIC on colon cancer triggers NKG2D-mediated lysis through Fas ligand

Human intestinal intraepithelial lymphocytes (IELs), which are T-cell receptor alphabeta+ CD8+ T cells located between epithelial cells (ECs), are likely to participate in the innate immune response against colon cancer. IELs demonstrate spontaneous cytotoxic (SC) activity specifically directed against EC tumours but not against other solid tumour types. The aim of this study was to dissect out the mechanism of SC activity, focusing on the interaction of NKG2D on IELs with its ligands [major histocompatibility complex (MHC) class I chain-related protein (MIC) and UL16 binding protein (ULBP)] found mainly on EC tumours. A novel series of events occurred. The NKG2D-MIC/ULBP interaction induced Fas ligand (FasL) production and FasL-mediated SC activity against HT-29 cells and MIC-transfectants. Tumour necrosis factor-alpha and interferon-gamma, produced independently of this interaction, promoted SC activity. The immune synapse was strengthened by the interaction of CD103 on IELs with E-cadherin on HT-29 cells. Neither T-cell receptor nor MHC class I was involved. While the HT-29 cells were destroyed by soluble FasL, tumour necrosis factor-alpha and interferon-gamma, the IELs were resistant to the effects of these mediators and to FasL expressed by the HT-29 cells. This unidirectional FasL-mediated cytotoxicity of IELs against HT-29 cells, triggered through NKG2D, is unique and is likely to be a property of those CD8+ tumour-infiltrating lymphocytes that phenotypically resemble IELs.

Tumor infiltrating T lymphocytes in colorectal cancer: Tumor-selective activation and cytotoxic activity in situ

OBJECTIVE

To examine whether tumor-selective infiltration, activation, and cytotoxic activity of tumor infiltrating T lymphocytes (TIL) can be demonstrated in situ in colorectal cancer samples.

SUMMARY BACKGROUND DATA

Recent studies indicated a correlation between the presence of TIL and an improved prognosis in colorectal cancer. However, tumor-selective activation and cytotoxic activity of CD8 TIL in situ in colorectal cancer patients have not yet been examined.

METHODS

Tumor samples from 49 patients and corresponding normal mucosa samples from 23 patients with colorectal cancer (UICC stages II-IV) were examined for TIL. Two-color fluorescence immunohistochemistry and multicolor flowcytometric (FACS) analysis were used for quantification of CD8 T cells and measurement of their activation status (CD69-expression) and cytotoxic activity (CD107a-expression) in situ. Presence of tumor antigen-reactive T cells in tumor, blood, and bone marrow was evaluated by IFN-gamma Elispot analysis.

RESULTS

While absolute numbers of CD8 T cells were similar, CD4 T helper cells were significantly increased in tumor tissue compared with normal mucosa. There was a significantly higher proportion of activated and cytotoxically active CD8 TIL in colorectal cancer compared with normal mucosa. Increased activation, cytotoxic activity, and functional reactivity of TIL were correlated with the presence of functional tumor antigen-reactive T cells in the blood and bone marrow. The proportion of activated TIL decreased significantly with higher tumor stage.

CONCLUSIONS

Tumor-selective activation and cytotoxic activity of CD8 TIL and tumor-selective migration of CD4 T helper cells were demonstrated in colorectal cancer for the first time. Our data support the immunogenicity of colorectal cancer and suggest clinical significance of tumor-specific immune responses.

The immunogenicity of colorectal cancers with high-degree microsatellite instability

BACKGROUND

High-degree microsatellite instability (MSI-H) is a feature of approximately 15% of sporadic colorectal cancers. Patients with MSI-H cancers have been reported to have a better prognosis than those with non-MSI-H cancers. The MSI-H subset is also characterised by a dense infiltrate of intra-epithelial lymphocytes and the hypothesis that the latter represents an efficacious immune response contributing to improved outcome is very attractive.

METHODS

Data for this review were identified by searches of MEDLINE, PubMed, and cross references from relevant articles using the search terms 'microsatellite instability', 'colorectal cancer' and 'immunology', 'immune response' or 'immunogenicity'.

RESULTS

A total of 38 articles were identified by the search criteria and a further 95 articles by cross-referencing. The relevance of the articles to be interviewed was established by hand searching. Out of a total of 133 articles identified, 47 articles were rejected due to lack of relevance. A total of 86 articles were included in the review, pertaining to microsatellite instability in colorectal cancer, and immune mechanisms in colorectal cancer.

CONCLUSION

It is suggested that this distinct group of colorectal cancers may have inherent immunogenic properties and that further elucidation of these may be invaluable to the development of successful immunotherapy.

Characterization of NKR+ T-cell subsets in human bone marrow: implications for immunosurveillance of neoplasia

In addition to hematopoietic progenitors, human bone marrow contains mature T/NK lymphocytes. Valpha24Vbeta11 NKT-cells, a subset of NK receptor+ (NKR+) T-cells in humans, are rare in bone marrow, suggesting the presence of other NKR+ T-cells which may contribute to tumor surveillance. NKR+/- T-cells were examined in blood (PB), and bone marrow from donors (DM) and patients with active hematopoietic malignancy (PM), or in remission (PR). T-cells in PR & PM were enriched for CD56+ and CD57+ subsets, compared to DM. All marrow NKR+/- T-cell subsets were more activated than PB. PM and, surprisingly, PR marrow contained more activated cells than DM. CD8+ cells were significantly increased in all patient marrows and there was evidence of the formation of an effector/memory pool in malignant marrow. These data suggest that NKR+ T-cell enrichment in human bone marrow that has been exposed to neoplastic transformation is compatible with a role in localized tumor surveillance/eradication.

Selective infiltration of CCR5+CXCR3+ T lymphocytes in human colorectal carcinoma

T cell infiltration in colorectal cancer is associated with a favorable prognosis, suggesting an occurrence of a certain degree of anti-tumor immunity. T helper type 1 (Th1) and Th2 cells are now known to selectively express CC-chemokine receptor 5 (CCR5)/CXC-chemokine receptor 3 (CXCR3) and CCR4, respectively. To clarify the mechanism of T cell infiltration, we examined in situ expression of these chemokine receptors and their respective chemokine ligands in 40 cases of human colorectal cancer. Immunohistochemistry showed a predominant accumulation of T cells expressing CCR5 and CXCR3 mainly along the invasive margin, whereas those expressing CCR4 were rare. Flow cytometric analysis showed that more than half of CD8(+) T cells and a fraction of CD4(+) cells isolated from fresh tumor tissues co-expressed CCR5 and CXCR3, and CD8(+) T cells and CD4(+) cells predominantly produced interferon-gamma (IFN-gamma) over interleukin-4 (IL-4) after in vitro stimulation. RANTES/CCL5, a ligand of CCR5, was localized within infiltrating CD8(+) T cells in a granular pattern, whereas IP-10/CXCL10, a ligand of CXCR3, was localized in cancer cells and macrophages along the invasive margin. These data were consistent with an active recruitment of T cells expressing CCR5 or CXCR3 into the invasive margin of colorectal cancer. With the previous clinicopathological studies showing a favorable prognostic impact of T cell infiltration in colorectal cancer, our study supports the occurrence of a certain level of Th1-shifted cellular immune responses in human colorectal cancer.

Fas ligand and tumour counter-attack in colorectal cancer stratified according to microsatellite instability status

Expression of membrane-bound Fas ligand (FasL) by colorectal cancer cells may allow the development of an immune-privileged site by eliminating incoming tumour-infiltrating lymphocytes (TILs) in a Fas-mediated counter-attack. Sporadic colorectal cancer can be subdivided into three groups based on the level of DNA microsatellite instability (MSI). High-level MSI (MSI-High) is characterized by the presence of TILs and a favourable prognosis, while microsatellite-stable (MSS) cancers are TIL-deficient and low-level MSI (MSI-Low) is associated with an intermediate TIL density. The purpose of this study was to establish the relationship between MSI status and FasL expression in primary colorectal adenocarcinoma. Using immunohistochemistry and a selected series of 101 cancers previously classified as 31 MSI-High, 30 MSI-Low, and 40 MSS, the present study sought to confirm the hypothesis that increased TIL density in MSI-High cancers is associated with low or absent membrane-bound FasL expression, while increased FasL in MSS cancers allows the killing of host TILs. TUNEL/CD3 double staining was also used to determine whether MSS cancers contain higher numbers of apoptotic TILs in vivo than MSI-High or MSI-Low cancers. Contrary to the initial hypothesis, it was found that MSI-High cancers were associated with higher FasL expression (p = 0.04) and a stronger intensity of FasL staining (p = 0.007). In addition, mucinous carcinomas were independently characterized by increased FasL expression (p = 0.03) and staining intensity (p = 0.0005). Higher FasL expression and staining intensity did not correlate with reduced TIL density or increased numbers of apoptotic TILs. However, consistent with the hypothesis that curtailment of the host anti-tumour immune response contributes to the poor prognosis in MSS cancers, it was found that apoptotic TILs were most abundant in MSS carcinomas and metastatic Dukes' stage C or D tumours (p = 0.004; p = 0.046 respectively). This study therefore suggests that MSS colorectal cancers are killing incoming TILs in an effective tumour counter-attack, but apparently not via membrane-bound FasL.

Prognostic value of the CD4+/CD8+ ratio of tumour infiltrating lymphocytes in colorectal cancer and HLA-DR expression on tumour cells

The purpose of this study was to clarify whether HLA-DR expression of colorectal tumour cells or the CD4+/CD8+ ratio of the tumour infiltrating lymphocytes is significantly associated with the prognosis of colorectal cancer. Using flow cytometry, we studied the tumour cell expression of the HLA class II in 70 enzymatically dissociated colorectal cancers and the phenotype of tumour infiltrating lymphocytes (TILs) in 41 cases. There was no trend in 5-year survival between three levels (low, medium, high) of HLA-DR expression on the tumour cells. Patients with low CD4+/CD8+ ratios had a better clinical course, with significantly higher 5-year survival, p=0.046, independent of the Dukes stage and age. Our results have implications for tumour immunology; colorectal cancer cells might be a target for cytotoxic T-lymphocytes, however the tumour cells are not able to initiate an immune response. Stimulation of the immune system could possible be obtained using dendritic cells cultured in vitro and loaded with tumour antigens.

A basal membrane-like structure surrounding tumour nodules may prevent intraepithelial leucocyte infiltration in colorectal cancer

Epithelial tumours consist of an epithelial compartment and a stromal compartment, which are sometimes separated by a basal membrane-like structure. We sought to determine whether these factors have prognostic value in 84 curatively resected stage II and III colorectal cancer by immunohistochemically staining tumours for leucocytes (CD45) and extracellular matrix, and to assess the presence of a basal membrane-like structure. Leucocyte infiltration was also assessed in hematoxylin-eosin (HE) stained sections. Most leucocytes were located in the tumour stroma. A relatively high intraepithelial leucocyte infiltration was significantly correlated with a lower level of tumour recurrence (P=0.03) and a longer disease-free survival (P=0.05), whereas leucocytes located in the tumour stroma (P=0.92) or at the advancing margin (p=0.06) were not. Intraepithelial leucocyte infiltration was also significantly correlated with leucocyte infiltration in the tumour stroma (P=0.02) and at the advancing tumour margin (P=0.005), and as assessed in HE-stained tumour sections (P=0.05), but each of these parameters on its own did not have a prognostic value in predicting disease-free survival. Moreover, the presence of a basal membrane-like structure surrounding the tumour epithelium was inversely correlated with the number of intraepithelial leucocytes (P=0.05), suggesting that this membrane-like structure functions as a barrier to intraepithelial leucocyte infiltration. We conclude that leucocytes must be in the direct vicinity of tumour cells to affect tumour growth. The presence of an extracellular matrix barrier seems to prevent this interaction.

Survival in human colorectal cancer correlates with expression of the T-cell costimulatory molecule OX-40 (CD134)

BACKGROUND

The T-cell costimulatory molecule OX-40 (CD134) is expressed on activated CD4(+) ("helper") T cells. Such cells have been detected in human cancers, and engagement of OX-40 improves colon cancer immunity in an animal model.

METHODS

Sections of primary colon cancers, normal margins, mesenteric lymph nodes, and metastases were stained for OX-40 by immunohistochemistry. Cancer registry data were reviewed.

RESULTS

High levels of OX-40 positive tumor-infiltrating lymphocytes were found in 15 of 72 primary tumors. Thirty-one cases had prominent lymphocytic infiltrates expressing OX-40 at the invasive margin of the tumor. Overall, 50% of primary tumors showed high expression of OX-40. Nearly all mesenteric lymph nodes expressed OX-40, whether tumor was present or not. Normal margins of colon did not show high levels of OX-40. High OX-40 expression in the primary tumor correlated with better survival (mean survival high OX-40, 47 months, low OX-40, 35 months, P <0.05), although this correlation was not stage-independent.

CONCLUSIONS

High levels of OX-40 positive lymphocytes are present in half of primary colon cancers, and this expression in primary tumors significantly correlates with better survival. This correlation with survival and our previous preclinical research suggest a basis for an OX-40 immunotherapy trial.

Mature dendritic cells make clusters with T cells in the invasive margin of colorectal carcinoma

Dendritic cells (DCs) take up tumour-specific antigen and migrate to regional lymph nodes to generate anti-tumour immunity. Although DC infiltration within human tumour tissue has been reported, the subset distribution has not been fully investigated. This study used immunohistochemistry to investigate DC subset distribution in colorectal adenocarcinoma. DCs expressing CD83, which are considered to be mature DCs, were present mainly in the invasive margin of cancer stroma. CD83(+) DCs in the invasive margin formed clusters with lymphocytes, the majority of which were CD45RO(+) T cells. The number of CD4(+) T cells was greater than that of CD8(+) T cells in these DC-lymphocyte clusters. The elongated cytoplasmic processes of CD83(+) DCs engulfed CD4(+) T cells. DCs that express CD1a were located throughout tumour tissue. Although the number of CD1a(+) DCs was almost the same as that of CD83(+) DCs in the invasive margin of cancer stroma, CD1a(+) DCs were mostly scattered and rarely formed clusters with lymphocytes. DCs that expressed both CD1a and CD83 were rare. Moreover, about 20% of lymphocytes in DC-lymphocyte clusters were positive for Ki-67, and CD83(+) DCs were attached to Ki-67(+) cells. CD83(+) DCs were also present in T-cell areas that had a distinctive structure involving the presence of B-cell lymphoid follicles. These results suggest that in the invasive margin of the colorectal cancer stroma, mature CD83(+) DCs form clusters with T cells to promote T-cell activation for the generation of tumour-specific immunity.

Biased activation of human T lymphocytes due to low extracellular pH is antagonized by B7/CD28 costimulation

As T cell response to tumor-associated antigens may be impaired by the acidic microenvironment typical of solid tumors, we assessed the effect of extracellular pH (pH(e)) on the activation and proliferation of human T lymphocytes and generation of the cytotoxic response. T lymphocytes stimulated with anti-CD3 mAb or PHA at low pH(e) were unable to secrete IL-2 and IFN-gamma and their ability to progress through the cell cycle was impaired. T lymphocytes also displayed up-regulation of IFN-gammaR2 chain and CTLA-4 expression, rendering them sensitive to negative regulatory signals. Agonistic mAb against CD28, but not against CD2, completely restored cytokine production and cell cycle progression, but down-regulated IFN-gammaR2 and CTLA-4 expression. The anti-CD28mAb rescued the CTL response of allogeneic anti-tumor cultures generated at low pH(e). Following anti-CD28 mAb treatment, T cells synthesized cyclooxygenase-2 (Cox-2) protein, which is involved in the early phases of T cell activation. This rescue of T cell activation was independent of the inducible 6-phosphofructo-2-kinase (iPFK-2) pathway, which stimulates proliferation in hypoxic and acidic conditions. The restoration of proliferative and cytotoxic T cell responses by CD28-triggering provides insight into the mechanisms by which B7 enhances the T cell anti-tumor response in vivo.

Inhibition of activated/memory (CD45RO(+)) T cells by oxidative stress associated with block of NF-kappaB activation

Impaired immune responses in cancer patients have been associated with oxidative stress. Increased levels of reactive oxygen species released from activated, tumor-infiltrating macrophages or granulocytes may therefore constitute a hurdle for effective immunotherapy against cancer. In this study, we investigated functional consequences and molecular events in T cells exposed to low levels of oxidative stress. We observed that cytokine production of human PBMC, upon stimulation with an HLA-A*0201-restricted influenza peptide and nonspecific receptor cross-linking, was reduced after exposure to micromolar levels of H2O2. Functional impairment as measured by IFN-gamma release occurred earlier and at lower doses of exogenously added H2O2 than required to induce apoptosis. This suggests that there is a dose window of oxidative stress leading to T cell unresponsiveness in the absence of apoptosis. The reduction of Th1 cytokines, induced by H2O2, was predominantly observed in memory/effector (CD45RO(+)) T cells and correlated with a block in NF-kappaB activation. IL-10 production was more profoundly influenced by low doses of H2O2 than IFN-gamma, TNF-alpha, and IL-2. The influence of H2O2 on production of IL-10 was not significantly different between memory/activated and naive T cells. These observations suggest that Th1 and Th2 cytokines are differently regulated under conditions of oxidative stress. Taken together, these findings may explain why Ag-experienced, CD45RO(+), T cells found in the tumor milieu are functionally suppressed.

An acidic microenvironment inhibits antitumoral non-major histocompatibility complex-restricted cytotoxicity: implications for cancer immunotherapy

Local immunosuppression may explain the failure of an effective immune response against solid tumors. Although it is well known that the interstitial pH is significantly lower in solid tumors than in normal tissue, only a few studies in the mouse system have investigated the influence of this acidic milieu on the anti-tumoral cytotoxic response. Here the authors report the suppression of human non-major histocompatibility complex (MHC)-restricted cytotoxicity against tumor cells by an acidic extracellular pH (pHe). Unstimulated peripheral blood mononuclear cells, lymphokine-activated killer (LAK) cells, and natural killer cell clones were used as effector cells. According to pH measurements in solid tumors, representative pH values of 7.2 to 5.3 were chosen during the cytotoxic assays. Target cell lysis was measured using two nonradioactive fluorometric methods, namely two-color flow cytometry and a modified calcein-release assay, which allowed cell-mediated cytotoxicity to be measured and compared with that in adherent targets. Using K562, Daudi, or Raji as suspended target cell lines, the cytotoxic activity of unstimulated peripheral blood mononuclear cells and of LAK cells was markedly reduced by a decreasing pHe. An extracellular pH of 5.8 to 5.3 resulted in a nearly complete loss of the cytotoxic response. This pHe-dependent impairment of the killing activity could also be shown for killer cells stimulated with interleukins-7 and -12, phytohemagglutinin, or lipopolysaccharide. The lytic potential of homogeneous natural killer cell clones as effectors was also strictly influenced by the surrounding pH. The pHe dependence of the non-MHC-restricted killer cell functions against tumor cells seems to be a general phenomenon, because the cytolytic activity of LAK cells against six human adherent tumor cell lines (HeLa, HepG2, LS174T, LS174Te, MCF-7, and RT112) was also clearly reduced under acidic conditions. To initiate the killing process, adhesion molecules play an important role in recognition and binding of the target cell. However, flow cytometric analysis revealed that the expression pattern of relevant adhesion molecules was unaffected by acidic pHe. In conclusion, these data clearly indicate an inhibition of non-MHC-restricted cytotoxicity against tumor cells by an acidic pHe, which may contribute to the failure of immunosurveillance against solid tumors. Consequently, efforts to enhance the anti-tumoral cytotoxicity by immunotherapies may have limited success.

Functional down-regulation of beta1 and beta2 integrins of lamina propria lymphocytes (LPL) and tumor-infiltrating lymphocytes (TIL) in colorectal cancer patients

Integrins play an important role in various lymphocyte functions. In this study, we isolated lamina propria lymphocytes (LPL) and tumor-infiltrating lymphocytes (TIL) from normal and malignant tissues in patients with colorectal cancer, and examined the expression of beta1 and beta2 integrins on these lymphocytes quantitatively with two-color flow cytometry. Both LPL and TIL expressed a lower level of common beta1 chain (CD29) in CD4 and CD8 subpopulations than did peripheral blood lymphocytes (PBL). Among the associated alpha chains, the expression levels of alpha1 (CD49a) and alpha2 (CD49b) were slightly higher, whereas those of alpha4 (CD49d) and alpha6 (CD49f) were markedly reduced in LPL and TIL. No significant differences were observed in expressions of any alpha1 integrin chains between these two lymphocytes populations. Similarly, both alphaL (CD11a) and beta2 (CD18) were down-regulated in TIL and LPL with CD8+ cytotoxic phenotype, but not in those with CD4+ phenotype. CD8+ TIL expressed a slightly but significantly higher level of alphaLbeta2 than did CD8+ LPL. CD8+ LPL and CD8+ TIL consistently showed significantly decreased binding to purified ICAM-1, VCAM-1 and HT29 colon cancer cells as compared with CD8+ PBL. Although CD8+ TIL showed a slightly higher level of adhesion to these substrates than did CD8+ LPL, the level was much lower than that in PBL. The expression pattern and functional down-regulation of these integrins may be one of the reasons why TIL cannot eradicate the cancer cells in colorectal cancer.

Characterisation of tumour infiltrating lymphocytes and correlations with immunological surface molecules in colorectal cancer

Using flow cytometry, we studied the phenotype of tumour infiltrating lymphocytes (TILs) in 41 enzymatically dissociated colorectal cancers and compared this to the expression of HLA class I and II and CD80 on tumour cells. We studied the possible enzymatic damage to various surface markers after enzymatic dissociation. The reproducibility of flow cytometric determinations obtained from TILs was good (kappa value: 0.79). The median CD4+/CD8+ ratio was 2.2. Approximately 43-45% (median of cells in each tumour) of both the CD4(+)- and the CD8(+)-TILs expressed HLA class II; 14.2% of the CD4(+)-TILs expressed CD25 and none of the CD8(+)-TILs expressed CD25. CD3-/CD16+/CD56(+)-TILs were very infrequent. Expression of HLA class II did not correlate with any lymphocyte surface markers. Since TILs are "turned off" rather than stimulated when tumour cells express HLA class II but not CD80, the lack of correlations could be due to anergy.

FasL is more frequently expressed in liver metastases of colorectal cancer than in matched primary carcinomas

Colorectal carcinoma cells have recently been shown to express Fas ligand (FasL). This ligand could allow the tumour cells to evade activated tumour-infiltrating lymphocytes (TILs) by inducing their apoptosis and would thus promote tumour survival and possibly metastasis formation. To test this hypothesis in vivo we analysed the expression of FasL mRNA and protein in paired tissue samples of normal colonic mucosa (N), primary colorectal carcinomas (T) and their metastases (M) from a total of 21 patients by four different methods. Additionally, the presence and activation status of infiltrating lymphocytes, which might contribute to the total amount of FasL in the tissue, was determined by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) in the same samples. The frequency of FasL detection was 30-40% in T and was 60-100% in M, depending on the sensitivity of the method. Simultaneously, the amount of CD25 mRNA, used as a measure of the number of activated TILs, was in 90% of patients lower in M than in T. The increased frequency of FasL detection in liver metastases was therefore not due to the presence of activated TILs. We conclude that metastasizing subpopulations of colorectal tumour cells express FasL more frequently than the primary carcinomas and may be able to eliminate activated TILs in vivo via Fas/FasL-induced apoptosis or other hitherto unknown mechanisms.

Can immunotherapy by gene transfer tip the balance against colorectal cancer?

Gene therapy, in particular the transfer of genes encoding immunostimulatory molecules (cytokines and costimulatory molecules) as well as selectively cytotoxic enzymes and DNA vaccination, has the potential of enhancing cell mediated immune responses against tumours including those of colorectal origin. Genes can be transferred using viral vectors either to cultured tumour cells in vitro that can be returned to the patient as a "cancer vaccine", or directly to tumour cells in vivo. Vaccination with DNA constructs expressing specific tumour antigens characteristic of colorectal neoplasia can trigger immune recognition and destruction of tumour cells. The aim is to tip the balance from protumour to antitumour mechanisms by generating a local immune response and systemic antitumour immune memory to destroy metastases. Studies in murine models, combined with human studies, show that such approaches could become an adjunct to current treatments for human colorectal cancer in the near future.

Crohn's disease and ulcerative colitis mucosal T cells are stimulated by intestinal epithelial cells: implications for immunosuppressive therapy

BACKGROUND

Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory diseases, and their pathogenesis is attributed, in part, to alterations of the mucosal immune system. This study was designed to define the possible contribution of epithelial cells to the activation of lamina propria T lymphocytes (LPTs) in CD and UC.

METHODS

LPTs isolated from CD, UC, and control surgical specimens were cocultured with freshly isolated allogeneic or autologous epithelial cells or epithelial cell lines. Resulting T-cell proliferation was evaluated by tritiated thymidine incorporation on day 5.

RESULTS

When intestinal epithelial cells were used to stimulate mucosal T-cell proliferation, CD and UC LPTs were less responsive than control LPTs (p < 0.05 and p < 0.03, respectively). This difference between inflamed and control T cells was consistently observed by using a variety of different intestinal epithelial cell types.

CONCLUSIONS

CD and UC mucosal T cells are hyporesponsive to activation by intestinal epithelial cells when compared with control LPTs. Elucidating the mechanism underlying the differential activation of CD and UC LPTs may help to better understand the immunopathogenesis of these conditions.

T cell receptor-zeta and granzyme B expression in mononuclear cell infiltrates in normal colon mucosa and colon carcinoma

BACKGROUND

Whereas the presence of a lymphoid infiltrate has been associated with a favourable prognosis in colorectal carcinoma, the proliferative and cytotoxic responses of freshly isolated tumour infiltrating lymphocytes are frequently impaired. In mice, tumour induced immune suppression has been associated with a decreased expression of the zeta-chain of the T cell receptor (TCR)-CD3 complex, and loss of mRNA for granzyme B.

AIM

To compare the expression of TCR-zeta and granzyme B in lymphocytes infiltrating normal colonic mucosa and Duke's A and D colorectal carcinomas.

SPECIMENS

Paraffin wax embedded normal (n = 10) and malignant colonic mucosa (seven Dukes's A, nine Dukes's D).

METHOD

Immunohistochemistry.

RESULTS

The numbers of TCR-zeta + lymphocytes decreased from normal mucosa to Dukes's D carcinomas. In contrast, granzyme B+ lymphocytes were more frequent in Dukes's A carcinomas than in normal mucosa, but disappeared from advanced stage tumours. Granzyme B expressing cells were mainly CD3- (natural killer/lymphokine activated killer cells) in normal mucosa, but CD3+ in tumours, indicating the presence of activated cytotoxic T lymphocytes. In vitro culture of tumour infiltrating lymphocytes rapidly restored the expression of both molecules.

CONCLUSION

The frequency of TCR-zeta + and granzyme B+ lymphocytes is decreased in advanced stage colorectal carcinomas. The restoration of expression during in vitro stimulation suggests the presence of tumour derived suppressive factors in situ.

High incidence of interleukin 10 mRNA but not interleukin 2 mRNA detected in human breast tumours

Despite the presence of a lymphocytic infiltrate in solid cancers, the failure for tumour growth to be contained suggests an inadequate immune response to the tumour. Poor cytotoxicity exerted by tumour-infiltrating lymphocytes (TILs) against tumour cells in vitro, combined with continued tumour growth in vivo, suggests deficiencies in TIL function or numbers. Various theories have been postulated to explain how tumour cells may escape immunosurveillance and control. One of the many hypotheses is the failure of production of cytokines, which are necessary for T cells to mediate their function. Thus, the expression of cytokine mRNA in human breast tumour sections was investigated by reverse transcriptase polymerase chain reaction (RT-PCR) with cytokine-specific primers. A relatively consistent finding was detection of interleukin (IL) 10 mRNA among the tumours. No IL-2 and little IL-4 mRNA was detected in the tumours. IL-6 and IL-10 mRNA was detected in only one and two of the normal breast tissues respectively. IL-2, IL-4 and tumour necrosis factor (TNF)-alpha mRNA was not detected in any of the normal breast tissues. The reduced function of TILs may be related to IL-10, which has known inhibitory effects on T-cell activation.

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.

Selected eicosanoids increase the proliferation rate of human colon carcinoma cell lines and mouse colonocytes in vivo

Eicosanoids have been implicated in colon carcinogenesis, but their role remains unclear. The levels of PGE2 are elevated in colon cancer tissues and in blood draining colon tumors. The effect of eicosanoids on the proliferation of colonic cells is unknown. We studied the effect of several prostaglandins (PGs) and leukotriene (LT)B4 on the proliferation rate of the human colon adenocarcinoma cell lines SW1116 and HT-29 and of 16,16-dimethyl PGE2 (dmPGE2) on the colon of BALB/c mice. PGs E2, F2 alpha, I2, the methyl ester of PGE2, dmPGE2, and LTB4 (10(-10), 10(-8), 10(-6) M), administered for up to 72 h, stimulated cell proliferation in SW1116 cells and all but PGF2 alpha and PGI2 stimulated proliferation in HT-29 cells. The proliferative effect was time- and concentration-dependent. However, in SW1116 cells the response to PGs was 'bell-shaped', being maximal at 10(-8) M, with the 10(-10) and 10(-6) M concentrations being less effective. In HT-29 cells, the addition of methyl groups to the PGE2 molecule increased the proliferative effect. None of these eicosanoids affected the distribution of these cells in the cell cycle or their rate of programmed cell death (apoptosis). dmPGE2 stimulated 3.6-fold the proliferation of colonocytes in normal BALB/c mice. This was determined by bivariate flow cytometric analysis of the expression of proliferating cell nuclear antigen (PCNA) in virtually pure populations of mouse colonocytes. dmPGE2 did not alter the cell cycle distribution of these cells. We conclude that several PGs as well as LTB4 stimulate the proliferation of human colon carcinoma cells in vitro, while dmPGE2 has a similar effect on mouse colonocytes in vivo. These findings raise the possibility that eicosanoids may contribute to colonic carcinogenesis by stimulating the proliferation rate of tumor cells in the colon.

Lymphocytes infiltrating colorectal cancer have low proliferative capacity but can secrete normal levels of interferon gamma

Significant numbers of infiltrating mononuclear cells are commonly observed in solid tumours, although their role in restricting tumour growth is not clear. Tumour-infiltrating lymphocytes (TIL) from 38 patients with colorectal cancer, in parallel with peripheral blood lymphocytes (PBL), were assayed to determine their ability to proliferate in response to concanavalin A (ConA), interleukin-2 (IL-2), ConA+IL-2, phorbol 12-myristate 13-acetate (PMA)+ionomycin ionomycin (IOM), and staphylococcal enterotoxin B(SEB). These reagents were selected to give a range of weak to strong proliferative responses either via or independent of the T cell receptor. Proliferation of TIL was significantly lower than that of PBL in all cultures: ConA (P < 0.001), IL-2 (P = 0.002), ConA+IL-2 (P < 0.001), PMA+IOM (P < 0.001), SEB (P = 0.002). In addition to the low proliferative capacity of TIL, production of cytokines by TIL may also play a role in control of tumour growth. We have assayed IFN gamma production in the supernatants from 16 paired TIL and PBL cultures, and tumour necrosis factor alpha (TNF alpha) in 6 paired cultures. TNF alpha concentrations were significantly lower in TIL cultures than in PBL cultures stimulated with ConA (P < 0.05), but no different in control or IL-2 stimulated cultures. IFN gamma levels did not significantly differ between PBL and TIL cultures, indicating that despite the restricted proliferative capacity of TIL, these cells remain capable of secreting significant amounts of IFN gamma.

Freshly isolated tumour-infiltrating T-lymphocytes have a high cytotoxic potential, as measured by their ability to induce apoptosis in the target cell

To test if freshly isolated tumour-infiltrating lymphocytes (TIL) can induce apoptosis in a target cell, we have combined two previously described methods. Because TIL predominantly are T-lymphocytes, we have applied a redirected approach. When the target cells that express anti-human-CD3 monoclonal antibodies in their membranes bind to the T cell receptor-associated CD3-complex, signals are generated, which activate T cell effector mechanisms. This approach circumvents problems with MHC-restriction and allows for functional testing of all T cells, irrespective of their clonal specificity. In order to assay for induction of DNA fragmentation, we have labelled the target cell nuclei with [3H]thymidine. Upon harvesting fragmented DNA are washed away. Electrophoretic analysis of the fragmented DNA demonstrated the characteristic 'ladder' pattern, consistent with apoptosis. This rapid and simple assay monitors the capacity of different T cells to induce apoptosis in the target cell. It depends on intercellular interactions and clearly discriminates between different T cell subsets. With this assay we demonstrate the functional integrity of the cytotoxic effector arm of freshly isolated TIL.

Differential effects of cyclic adenosine 3',5'-monophosphate on T cell cytotoxicity

We have investigated natural killer cell and T cell cytotoxicity using different assays and report a dual effect of cyclic adenosine 3',5'-monophosphate (cAMP) on T cell cytotoxicity depending on the activation status of the effector cell and the test system in question. cAMP enhanced the capacity of pre-activated T cells to induce DNA fragmentation in the target cell, while it inhibited spontaneous T cell cytotoxicity and natural killer cell cytotoxicity in conventional assays based on 51Cr release. The enhancement was most likely mediated by the cAMP-dependent protein kinase type II (cAKII), which is the particular isoform in T cells associated with the centrosome and the microtubule organizing center (MTOC). We show the complete co-localization of the cAKII with the centrosome after conjugate formation. Furthermore, the reorganization of the MTOC following conjugate formation brings the type II kinase into close proximity with the T lymphocyte membrane are engaged in the effector-target interaction. Functional studies utilizing different cAMP-analog combinations further substantiate the involvement of the type II kinase.

Limited heterogeneity in the T-cell receptor V-gene usage in lymphocytes infiltrating human colorectal tumours

The presence of T lymphocytes in solid tumours may reflect an ongoing immune response against the transformed cells. We have used polymerase chain reaction (PCR) technology to investigate the T-cell receptor variable-region gene (V-gene) usage in freshly isolated tumour-infiltrating lymphocytes (TILs) to look for a possible oligoclonality of T cells in the tumour area. We used 19 different V beta-family-specific primers. Peripheral blood lymphocytes and lamina propria lymphocytes from the same patients were also tested by PCR. Our results demonstrate a limited heterogeneity in the V-gene usage of TILs from seven patients with colorectal cancers, suggesting a local antigen-driven immune response at the tumour site.