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

Natural Killer Cell Mechanosensing in Solid Tumors

Natural killer (NK) cells, which are an exciting alternative cell source for cancer immunotherapies, must sense and respond to their physical environment to traffic to and eliminate cancer cells. Herein, we review the mechanisms by which NK cells receive mechanical signals and explore recent key findings regarding the impact of the physical characteristics of solid tumors on NK cell functions. Data suggest that different mechanical stresses present in solid tumors facilitate NK cell functions, especially infiltration and degranulation. Moreover, we review recent engineering advances that can be used to systemically study the role of mechanical forces on NK cell activity. Understanding the mechanisms by which NK cells interpret their environment presents potential targets to enhance NK cell immunotherapies for the treatment of solid tumors.

Determinants of Resistance to Checkpoint Inhibitors

The development of immune checkpoint inhibitors (ICIs) has drastically altered the landscape of cancer treatment. Since approval of the first ICI for the treatment of advanced melanoma in 2011, several therapeutic agents have been Food and Drug Administration (FDA)-approved for multiple cancers, and hundreds of clinical trials are currently ongoing. These antibodies disrupt T-cell inhibitory pathways established by tumor cells and thus re-activate the host’s antitumor immune response. While successful in many cancers, several types remain relatively refractory to treatment or patients develop early recurrence. Hence, there is a great need to further elucidate mechanisms of resistant disease and determine novel, effective, and tolerable combination therapies to enhance efficacy of ICIs.

Intratumoral infiltrating lymphocytes correlate with improved survival in colorectal cancer patients: Independent of oncogenetic features

BACKGROUND

The clinical relevance and prognostic value of tumor-infiltrating lymphocytes (TILs) as an interplay between malignant cells and immune function has been known for decades. On contrary, this potential may be different by T lymphocytes subsets endowed with a different function. Colorectal cancer (CRC) is a heterogeneous disease with different suggested prognostic biomarkers. So, this study was conducted to examine the prognostic value of CD8+ TILs on the survival rate of CRC as an independent factor of oncogenetic tumor features.

METHODS

With respect to this, 281 formalin-fixed, paraffin-embedded tissue samples of Iranian CRC patients were evaluated for clinical features including tumor location, tumor stage, differentiation grade, and mucinous characteristics. Then, using the standard immunohistochemical technique, tumor sections were examined, and CD8+ TILs were counted and identified in two regions of the tumor, including intratumoral (ITCIL TILs) and stromal (S TILs). The prognostic value of CD8⁺ TILs was determined by comparing with parameters, such as diagnostic age, tumor stage, adjuvant therapy, microsatellite instability (MSI) status, KRAS and BRAF mutations, family history, and survival.

RESULTS

The presence of intratumoral tumor cell-infiltrating lymphocytes (ITCIL) CD8+ lymphocytes are significantly associated with differentiation (p = 0.004), tumor, node, and metastases (TNM) stage (p = 0.001), and MSI (p = 0.001). Meanwhile, based on the level of stromal infiltrating lymphocytes (SIL) infiltration, analysis of CRC patients was statistically associated with a location (p = 0.002), TNM stage (p < 0.001), metastasis (p < 0.001), and KRAS mutation (p = 0.031). Also, tumors with severe ITCIL CD8+ lymphocytes have a good prognosis compared with tumors with poor or moderate ITCIL CD8+ lymphocytes.

CONCLUSIONS

These results suggest that intratumor cell-infiltrating CD8- T lymphocytes as an independent prognostic factor that have an antitumor activity as judged by their favorable effect on patients' survival and could potentially be exploited in the treatment of CRC.

Repression of let-7a cluster prevents adhesion of colorectal cancer cells by enforcing a mesenchymal phenotype in presence of liver inflammation

The liver is the most common site of metastasis in patients with colorectal cancer, and colorectal cancer liver metastasis (CRLM) is associated with poor rates of survival. However, CRLM occurs infrequently in livers exhibiting signs of hepatitis or cirrhosis, suggesting a role for inflammation in attenuating CRLM. The molecular mechanisms driving this phenomenon remain unclear. The aim of this study was to confirm the mechanism by which liver inflammation inhibits CRLM. We used BALB/c animal models of inflammatory liver diseases to confirm that liver inflammation inhibits CRLM, and then elucidated the molecular mechanisms governing that process. Out data showed that liver inflammation induces IFN-γ expression, which then downregulates expression of the let-7a cluster through IRF-1 in colorectal cancer cells. Finally, we showed that modulation of let-7a expression regulated the epithelial–mesenchymal transition in colorectal cancer cell lines, and inhibited their capacity to metastasize in vivo. Cumulatively, we clarified the critical role played by the IFN-γ/IRF-1/let-7a cluster/EMT pathway in regulating the spread of circulating colorectal cancer cells to the liver, and highlighted the critical role that the hepatitis microenvironment plays in modulating that process.

Towards the introduction of the 'Immunoscore' in the classification of malignant tumours

The American Joint Committee on Cancer/Union Internationale Contre le Cancer (AJCC/UICC) TNM staging system provides the most reliable guidelines for the routine prognostication and treatment of colorectal carcinoma. This traditional tumour staging summarizes data on tumour burden (T), the presence of cancer cells in draining and regional lymph nodes (N) and evidence for distant metastases (M). However, it is now recognized that the clinical outcome can vary significantly among patients within the same stage. The current classification provides limited prognostic information and does not predict response to therapy. Multiple ways to classify cancer and to distinguish different subtypes of colorectal cancer have been proposed, including morphology, cell origin, molecular pathways, mutation status and gene expression-based stratification. These parameters rely on tumour-cell characteristics. Extensive literature has investigated the host immune response against cancer and demonstrated the prognostic impact of the in situ immune cell infiltrate in tumours. A methodology named ‘Immunoscore’ has been defined to quantify the in situ immune infiltrate. In colorectal cancer, the Immunoscore may add to the significance of the current AJCC/UICC TNM classification, since it has been demonstrated to be a prognostic factor superior to the AJCC/UICC TNM classification. An international consortium has been initiated to validate and promote the Immunoscore in routine clinical settings. The results of this international consortium may result in the implementation of the Immunoscore as a new component for the classification of cancer, designated TNM-I (TNM-Immune). © 2013 The Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

A nodal positivity constant: new perspectives in lymph node evaluation and colorectal cancer

PURPOSE

To date, associations between the number of lymph nodes evaluated, staging, and survival have been examined in the context of large population-based studies conducted by a small number of investigators. Therefore, although high-quality data are available, perspective is lacking.

METHODS

Studies for this paper were identified by searches of Medline, Scopus, PubMed, and manual searching of references from articles, using the search terms ''colorectal cancer'', ''nodal status'' and ''lymph node''.

RESULTS

It is clear that survival benefit increases with the increasing number of lymph nodes harvested. Despite this observation, there has been no significant increase in the proportion of node-positive cancers over the past two decades.

CONCLUSION

The nodal positivity rate for colorectal cancer consistently approximates 40 % across a wide range of studies internationally, a phenomenon that has not previously been recognized in the literature. We review the evidence and introduce the concept of a nodal positivity constant.

Local delivery of recombinant adenovirus expressing hepatitis B virus X protein and interleukin-12 results in antitumor effects via inhibition of hepatoma cell growth and intervention of tumor microenvironment

Hepatocellular carcinoma (HCC) is a typical hypervascular tumor. Our previous studies have demonstrated that hepatitis B virus X protein (HBx) was able to inhibit the growth of HCC cells via inducing apoptosis and inhibiting tumor angiogenesis. Interleukin-12 (IL-12) is a disulfide-linked heterodimeric cytokine with potent immunostimulatory activity and anti-angiogenic properties. In this study, to further investigate the regulatory effect of IL-12 on HBx-mediated intervention of hepatoma microenvironment especially on intervention of neovessels and immune microenvironment, we constructed the recombinant adenovirus expressing HBx and mouse IL-12 named Ad-HBx-mIL-12. HBx-mIL-12 could effectively suppress tumor growth and induce apoptosis in vivo. Moreover, treatment with Ad-HBx-mIL-12 not only induced a massive accumulation of immune cells (CD8(+) T leukocytes, macrophages and dendritic cells) in tumors in situ, also apparently reduced the number of angiogenic blood vessels within tumor tissues. These results suggest that HBx-mIL-12 can not only induce cell cycle arrest and apoptosis in HCC cells, but also effectively shift the tumor microenvironment from pro-oncogenic to antitumor through recruitment of immune cells and inhibiting stromal cell growth, such as vascular endothelial cells.

Colorectal cancer vaccines in clinical trials

This article elucidates current strategies of active immunotherapy for colorectal cancer patients with a focus on T-cell mediated immunotherapy. Poor prognosis of especially stage III and IV colorectal cancer patients emphasizes the need for advanced therapeutic intervention. Here, we refer to clinical trials using either tumor cell-derived vaccines or tumor antigen vaccines with a special interest on safety, induced immune responses, clinical benefit and efforts to improve the clinical impact of these vaccines in the context of colorectal cancer treatment.

Trends in cancer immunotherapy

Modulation of the immune system for therapeutic ends has a long history, stretching back to Edward Jenner's use of cowpox to induce immunity to smallpox in 1796. Since then, immunotherapy, in the form of prophylactic and therapeutic vaccines, has enabled doctors to treat and prevent a variety of infectious diseases, including cholera, poliomyelitis, diphtheria, measles and mumps. Immunotherapy is now increasingly being applied to oncology. Cancer immunotherapy attempts to harness the power and specificity of the immune system for the treatment of malignancy. Although cancer cells are less immunogenic than pathogens, the immune system is capable of recognizing and eliminating tumor cells. However, tumors frequently interfere with the development and function of immune responses. Thus, the challenge for cancer immunotherapy is to apply advances in cellular and molecular immunology and develop strategies that effectively and safely augment antitumor responses.

Extracellular matrix of glioblastoma inhibits polarization and transmigration of T cells: the role of tenascin-C in immune suppression

Dense accumulations of T cells are often found in peritumoral areas, which reduce the efficiency of contact-dependent lysis of tumor cells. We demonstrate in this study that the extracellular matrix (ECM) produced by tumors can directly regulate T cell migration. The transmigration rate of several T cells including peripheral blood primary T cell, Jurkat, and Molt-4 measured for glioma cells or glioma ECM was consistently low. Jurkat cells showed reduced amoeba-like shape formation and delayed ERK activation when they were in contact with monolayers or ECM of glioma cells as compared with those in contact with HepG2 and MCF-7 cells. Phospho-ERK was located at the leading edge of migrating Jurkat cells. Glioma cells, but not MCF-7 and HepG2 cells, expressed tenascin-C. Knocking down the tenascin-C gene using the short hairpin RNA strategy converted glioma cells to a transmigration-permissive phenotype for Jurkat cells regarding ERK activation, transmigration, and amoeba-like shape formation. In addition, exogenous tenascin-C protein reduced the amoeba-like shape formation and transmigration of Jurkat cells through MCF-7 and HepG2 cell monolayers. A high level of tenascin-C was visualized immunohistochemically in glioma tumor tissues. CD3(+) T cells were detected in the boundary tumor area and stained strongly positive for tenascin-C. In summary, glioma cells can actively paralyze T cell migration by the expression of tenascin-C, representing a novel immune suppressive mechanism achieved through tumor ECM.

Regulatory T cells in a spectrum of HPV-induced cervical lesions: cervicitis, cervical intraepithelial neoplasia and squamous cell carcinoma

PROBLEM

Thriving of tumors amidst rich immune infiltrates is an unexplained paradox.

METHOD OF STUDY

Immune markers on lymphocytic infiltrates in HPV-positive cervicitis, cervical intraepithelial neoplasia III (CIN III), squamous cell carcinoma (SCC) and normal cervices were characterized immunohistochemically. Regulatory T cells were enumerated and phenotypically characterized using antibodies to FOXP3.

RESULTS

SCCs had higher numbers of CD4 and CD8 cells; infiltrates expressed more CD25, TGFbeta, and IL10 but had significantly lower IL2 compared with cervicitis and CIN III. Expression of CD25 and IL2 correlated well in cervicitis and CIN III but not in SCC. FOXP3 expression was also higher and ratios of CD4/FOXP3 and CD8/FOXP3 were lower in SCC. A fraction of cervicitis, CIN I, CIN II and CIN III had natural (n) regulatory T cells (Tregs); their lesional distribution was predominantly intraepithelial in cervicitis, while in CIN they were also present in the stroma. The proportion of FOXP3(+) CD25(+); FOXP3(+) CD25(-) and TGFbeta(+) CD25(+) in invasive tumors was 17; 19 and 22 respectively.

CONCLUSION

Cervical tumors are marked by the presence of an immunoregulatory environment, and harbor equal proportions of 'inactive' n Tregs; activated n Tregs; and Tregs operating via TGFbeta. nTregs in cervicitis and CIN may be a potential marker of persistence.

Tumor-specific regulatory T cells in cancer patients

A large body of evidence indicates that the presence of regulatory T cells (Tregs) in tumors is associated with a dampened tumor-specific immune response and a clear negative impact on survival. Many different subsets of Tregs have been identified, which all act through similar or distinct pathways to suppress tumor-specific effector cells. The observation that tumor-infiltrating Tregs are able to recognize tumor-derived antigens and can be expanded by vaccines that primarily aim at reinforcing the effector arm of the antitumor response stresses the need to study Tregs for each type of cancer targeted by immunotherapy. Current protocols enable us to isolate and culture tumor-infiltrating Tregs. Ultimately, this will not only lead to a full comprehension of the specificity and working mechanisms of Tregs but also facilitate the development of successful interventions strategies for the immunotherapy of cancer.

Celecoxib inhibits growth of tumors in a syngeneic rat liver metastases model for colorectal cancer

Introduction

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to reduce the risk of colorectal cancer in cyclooxygenase-2 (COX-2) overexpressing colorectal cancers. The present study was designed to evaluate the inhibitory effects of the COX-2 inhibitor celecoxib on the growth of colorectal cancer liver metastases in a syngeneic rat model, CC531.

Materials and methods

The effects of celecoxib on cell viability in vitro were evaluated by treatment of CC531 tumor cell cultures with celecoxib. In vivo, Wag/Rij rats were inoculated with CC531 tumor cells at two sites in the liver and treated with celecoxib starting one week before, or directly after tumor inoculation. Control rats were inoculated without treatment. Three weeks after tumor inoculation rats were sacrificed. Tumor size, immune cell infiltration, caspase-3 activity, PGE₂ and celecoxib levels were determined.

Results

CC531 tumors did not show COX-2 expression. Tumor growth was significantly inhibited by celecoxib treatment in a dose dependent manner. Immune cell infiltration was decreased after celecoxib treatment, indicating that the immune system was not involved in preventing tumor growth. Tumor caspase-3 levels were only significantly increased if treatment was started before tumor inoculation. Celecoxib serum concentration starting at 0.84 μg/ml significantly inhibited the outgrowth of CC531 liver tumors. In contrast, in vitro concentrations of celecoxib of at least 12 μg/ml were needed to affect tumor cell viability.

Conclusion

These results suggest that the inhibitory effects of celecoxib on tumor growth are not by direct cytotoxicity, but by creating an unfavorable environment for tumor growth.

High number of intraepithelial CD8+ tumor-infiltrating lymphocytes is associated with the absence of lymph node metastases in patients with large early-stage cervical cancer

In a prospective study, we have examined the tumor-specific immune response in a group of 59 patients with human papillomavirus (HPV) 16-positive (HPV16(+))-induced or HPV18(+)-induced cervical cancer. Local antitumor immunity was analyzed by the enumeration of tumor-infiltrating dendritic cells and CD4+, CD8+, and regulatory T cells as well as by calculation of the ratio of CD8+/CD4+ T cells and CD8+/regulatory T cells. Systemic tumor-specific immunity was assessed by determination of the HPV E6- and/or E7-specific T-cell response in the blood of these patients. Finally, these variables were evaluated with respect to known histopathologic prognostic variables, including the absence (LN-) or presence (LN+) of lymph node metastases. Stratification according to the lymph node status of patients revealed a significantly stronger CD8+ T-cell tumor infiltration, a higher CD8+/CD4+ T-cell ratio, and higher CD8+/regulatory T-cell ratio in the group of patients in which the tumor failed to metastasize to the tumor-draining lymph node. Subdivision according to the presence (IR+) or absence (IR-) of circulating HPV-specific T cells disclosed that the highest number of tumor-infiltrating CD8+ T cells was found in the group of LN- patients displaying a concomitant systemic tumor-specific immune response (LN-IR+). CD8+ T-cell infiltration in LN-IR- patients was comparable with that of LN+ patients. In cervical cancer, the absence of lymph node metastases is strongly associated with a better prognosis. Our data indicate that, especially in a subgroup of LN- patients, a strong and effective interaction between immune system and tumor exists. This subgroup of cervical cancer patients may have the best prognosis.

Challenges for cancer vaccine development

The first generation of human cancer vaccines has been tested in phase III clinical trials, but only a few of these have demonstrated sufficient efficacy to be licensed for clinical use. This article reviews some of the mechanisms that could contribute to these limited clinical responses, and highlights the challenges faced for development of future vaccines.

Locoregional therapies of liver metastases in a rat CC531 coloncarcinoma model results in increased resistance to tumour rechallenge

BACKGROUND

Locoregional treatments like photodynamic therapy (PDT), radiofrequency ablation (RFA) or hepatic artery infusion (HAI) of chemotherapeutics may be applied for unresectable colorectal liver metastases. We evaluated the effect of these treatments on the immune response in a rat colon tumour liver metastases model.

METHOD

Wag/Rij rats were inoculated at day 0 with CC531 tumour cells at two sites in the liver. At day 15, one of two tumours was treated with RFA or PDT, or the liver was treated by HAI. Twelve days later (day 27), rats were rechallenged locally with CC531 cells in the liver or systemically with CC531 cells in the femoral vein. At day 42, tumour growth in liver and lungs was determined.

RESULTS

RFA, PDT and HAI were very effective in liver tumour eradication, but following RFA or PDT there was no inhibitory effect on untreated nearby liver tumours. Outgrowth after local rechallenge was, however, significantly inhibited in RFA-, PDT- and HAI-treated rats, whereas all control rats showed outgrowth of a third liver tumour. After systemic rechallenge, control rats developed lung metastases whereas treated rats did not, but this difference was not statistically significant.

CONCLUSION

These results show that following PDT, RFA and HAI resistance to local and possibly systemic tumour rechallenge is increased. This may be partly due to the induction or enhancement of a cellular immune response.

Inhibiting complement regulators in cancer immunotherapy with bispecific mAbs

Although monoclonal antibody (mAb)-mediated immunotherapy of cancer has been proven to be feasible for clinical use, success rates until now have been disappointing. One reason for this might be the overexpression of membrane-bound complement regulatory proteins (mCRPs) by tumour cells. As complement activation is an important effector mechanism induced by therapeutic mAbs, inhibition of complement activation by tumour cells might reduce therapeutic efficacy by decreasing direct complement-mediated lysis as well as complement-dependent cellular cytotoxicity. Modulation of the function of these mCRPs might be achieved with therapeutic bispecific (bi-)mAbs that target a tumour antigen and simultaneously block a major mCRP. Clinical results will probably increase with such bi-mAbs compared with monovalent antitumour mAbs. In this review the feasibility of this approach is discussed.

Four-color staining combining fluorescence and brightfield microscopy for simultaneous immune cell phenotyping and localization in tumor tissue sections

Immune-cell infiltration is frequently seen within human solid tumors. A detailed phenotypic analysis of these cells may aid in the understanding of an antitumor immune response. Standard hematoxylin/eosin and conventional immunohistochemical stainings are helpful, but have major limitations in the number of markers that can be identified and localized per tissue section. Therefore, we developed a combined fluorescence and brightfield microscopic technique by using both immunofluorescence and immunogold-silver methods, thereby discriminating three different leukocyte markers plus one tumor marker simultaneously in a single section. This enabled us to study both phenotype and location of infiltrating immune cells in colorectal tumors. We used a two-step staining in which primary and secondary antibodies were selected for minimal cross-reactivity. Furthermore, the secondary fluorescent antibody conjugates were selected for minimal spectral overlap. For computer-assisted analysis the brightfield microscopy image was combined with the fluorescence microscopy images. This combination of techniques provides a powerful tool for detailed multiparameter microscopic analysis of formalin-fixed, paraffin-embedded tissue sections in general and for tumor-immune cell infiltration in particular.

Natural killer cells infiltrating colorectal cancer and MHC class I expression

A majority of colorectal adenocarcinomas displays diminished MHC class I expression, making them particularly vulnerable for NK cell-mediated killing. Generally, these tumors also show a substantial inflammatory infiltrate. Most inflammatory cells, however, reside in the tumor stroma, where they do not have direct contact with tumor cells in the tumor epithelium. In this study, we investigated the correlation between colorectal tumor MHC class I aberrations and infiltration of NK cells. We studied 88 tumor specimens obtained from 88 colorectal cancer patients for locus-specific HLA aberrations and correlated these data to infiltration of CD4, CD8+ and CD56+ lymphocytes. The lymphocyte markers were individually combined with laminin as a second marker to facilitate quantification in the different tumor compartments, i.e. tumor epithelium and tumor stroma. Locus-specific partial or total HLA class I loss was detected in 72% of the tumors studied. Twenty-eight percent had no HLA loss at all. Mean overall intra-epithelial infiltration of CD56+ lymphocytes was 7 cells/mm(2) compared to 76 cells/mm(2) for CD8 and 19 cells/mm(2) for CD4+ lymphocytes. Locus-specific partial or total loss of tumor cell MHC class I expression was positively correlated with the intra-epithelial infiltration of CD8+ cells (P = 0.01), but not with CD4+ or CD56+ lymphocytes. Triple immunofluorescence staining showed that these cells were CD8 and granzyme-B positive T-lymphocytes. Our data showed that colorectal tumors are sparsely infiltrated by CD56+ cells compared to CD8+ T-cells and that loss of MHC is associated with T-cell infiltration instead of NK cell infiltration. Considering the fact that MHC loss is quite common in colorectal cancer and that, due to local absence of NK cells, it is unlikely that there has been selection for NK-escape variants, improvement of the intra-epithelial infiltration/migration of NK cells may be an important basis for the development of an effective adjuvant NK-based immunotherapy of colorectal cancer.

Prognostic value of tumor-infiltrating dendritic cells in colorectal cancer: role of maturation status and intratumoral localization

The clinical significance of tumor-infiltrating dendritic cells has been reported in a variety of human solid tumors as shown by the correlations found between the presence of tumor-infiltrating dendritic cells and clinical prognosis. In this study, we evaluated whether there is an association between the presence and maturation status of tumor-infiltrating dendritic cells, T lymphocytes, and clinical course in 104 primary tumor samples of patients with colorectal cancer. Dendritic cells were identified with four different markers (S-100, HLA class II, CD208, and CD1a) in double immunohistochemistry, with laminin as second marker to support the exact localization. Tumor-infiltrating dendritic cells showed a distinct infiltration pattern based on their maturation status. CD1a-positive dendritic cells resided in the advancing tumor margins in relatively high numbers, whereas mature CD208-positive dendritic cells were sparsely present in the tumor epithelium but mainly distributed in the tumor stroma and advancing tumor margin. Furthermore, high infiltration of CD1a-positive dendritic cells in the tumor epithelium was significantly correlated to the infiltration of CD4 lymphocytes (P = 0.006). Patients with relatively high numbers of mature CD208-positive infiltrating dendritic cells in the tumor epithelium had a shorter overall survival (P = 0.004). In addition, patients with relatively high numbers of CD1a-positive dendritic cells in the advancing margin of the tumor had a shorter disease-free survival (P = 0.03). We found that tumor-infiltrating dendritic cells had preferential infiltration sites within a tumor, affected local tumor cell-immune cell interactions, and correlated to the clinical prognosis of colorectal cancer patients.

Dendritic cells in colorectal cancer correlate with other tumor-infiltrating immune cells

Dendritic cells (DCs) are the most efficient antigen-presenting cells and play a key role in a cellular antitumor immune response. In this study we investigated the exact localization of DCs within colorectal tumors and their relationship to tumor-infiltrating lymphocytes as well as clinical outcome of the patients. Primary tumor specimens of 104 patients with a diagnosis of colorectal cancer were identified retrospectively and analyzed with the dendritic cell markers S-100 protein and human leukocyte antigens (HLA) class II. The markers were individually combined with laminin as a second marker to facilitate the observation of the different tumor localizations. S-100 or HLA class II positive cells were found in the three different compartments of colorectal tumors: tumor epithelium, tumor stroma, and advancing tumor margin, but mainly present in tumor stroma and advancing tumor margin. S-100-positive tumor-infiltrating DCs in direct contact with tumor cells, i.e., in tumor epithelium, significantly correlated to the intraepithelial infiltration of CD4+ (p=0.02) and CD8+ (p=0.01) lymphocytes. High HLA class II+ cell infiltration in the tumor stroma correlated to a lower intraepithelial infiltration of CD8+ (p=0.02) lymphocytes. High intraepithelial infiltration of S-100-positive DCs suggested increased disease-free survival, but was not statistically significant, while high amounts of HLA class II+ cells in the tumor stroma correlated with an adverse survival outcome. Our results show that the infiltration of DCs in colorectal cancer, depending on both location and type of marker, is correlated with local immune interactions and patient prognosis, suggesting a central role for DCs in controlling local tumor immunity.

The influence of host response on colorectal cancer prognosis

Colorectal cancer (CRC) is a leading cause of cancer-related death worldwide. Several tumor characteristics have been shown to be of prognostic significance, although stage at diagnosis continues to be the most important predictor of survival. Emerging new data suggest that the presence of a host response to CRC may also influence survival and other outcomes in CRC. This review summarizes recent evidence regarding the prognostic significance of the host response to CRC. In retrospective analyses, tumor-associated macrophages and tumor-infiltrating lymphocytes appear to be the elements most significantly associated with improved outcomes in CRC. The presence of other cells, including dendritic cells, natural killer cells, eosinophils, and mast cells, also appears to be associated with increased survival. The influence of the host response to CRC needs confirmation in prospective studies, but in the meantime should be part of risk stratification. Novel approaches to further augmenting this response merit study.

Immunohistochemical detection of melphalan–DNA adducts in colon cancer cells in vitro and human colorectal liver tumours in vivo

Melphalan is a chemotherapeutic drug that exerts its cytotoxic effect mainly through the formation of DNA adducts. We report the specific immunohistochemical detection and visualisation of melphalan-DNA adducts using the monoclonal antibody MP5/73 in cultured tumour cells and solid tumour tissue from colorectal liver metastases from patients treated with melphalan. The human colon cancer cell lines HT29, SW480 and SW1116, and the rat colon cancer cell line CC531 were exposed to different concentrations of melphalan. In addition, tumour samples from 17 patients with colorectal liver metastases treated by isolated hepatic perfusion with high dose melphalan (200mg) were collected. Cell lines and tumour samples were stained with the MP5/73 antibody against melphalan-DNA adducts and cell viability was determined by an MTT assay. Melphalan-DNA adducts could be visualised by immunohistochemistry in both cultured cells and solid tumour tissue. A correlation between melphalan exposure concentration, the subsequent melphalan-DNA adduct staining intensity, and melphalan cytotoxicity existed for each individual cell line, but the level of both parameters independently differed between cell lines. Specific staining for melphalan-DNA adducts also was feasible in the human solid tumour tissue. There was considerable variation in melphalan-DNA adduct staining, staining intensity, and distribution in the tumour stroma and the tumour epithelium among the different patients. Melphalan-DNA adducts appeared to be more intense in tumour cells at the border of the tumour nodules than in tumour cells in the centre. Thus, visualisation of melphalan-DNA adducts by immunohistochemistry allows the study of distribution of melphalan-DNA adducts in solid tumours.

Immune system and prognosis in colorectal cancer: a detailed immunohistochemical analysis

The efficacy of tumor cell-immune cell interactions depends on a number of factors, for example, the expression of HLA-I on tumor cells, the type of immune cell, the accessibility of tumor cells for immune cells and the expression of immunogenic epitopes. We assessed infiltration of CD4+, CD8+, CD56+ and CD57+ cells in the tumor epithelium, tumor stroma and advancing tumor margin of 93 colorectal carcinomas and correlated this to clinicopathological parameters, the expression of HLA-A and HLA-B/C on tumor cells, the presence of a basal membrane (BM)-like structure surrounding tumor nodules and the presence of microsatellite instability/mutator phenotype (absent MLH-1 expression). The median intraepithelial CD4+, CD8+, CD56+ and CD57+ cell infiltrations were 3, 23, 0 and 0 cells/mm(2) tumor, respectively. HLA-A/BC expression by tumor cells was normal in 28/43%, heterogeneous in 59/48% and absent in 13/9% of the cases. A BM-like structure surrounding the tumor nodules was absent, present and thick in 47, 38 and 15% of the cases. Six cases lost MLH1 expression. There was a positive correlation between leukocyte infiltration in the three compartments for CD4+, CD8+, CD56+ (partly) and CD57+ (all P<0.05) cell infiltration. Intraepithelial CD8+ cell infiltration inversely correlated with HLA-A (P=0.04) and HLA-B/C expression (P=0.04). Intraepithelial CD57+ cell infiltration inversely correlated with HLA-B/C expression (P=0.04). Moreover, intraepithelial infiltration of CD8+ and CD57+ cells was inversely correlated to the presence of a BM-like structure (P=0.003 and 0.04, respectively). Uni- and multivariate analyses showed that a lower tumor stage (P=0.004) and marked infiltration of CD8+ (P=0.04) and CD57+ cells (P=0.05) at the advancing tumor margin were independent prognostic factors for a longer disease-free survival. Loss of MLH1 expression was correlated with a significantly higher intraepithelial CD8+ and CD57+ cell infiltration. We conclude that infiltration of CD8+ and CD57+ cells are important prognostic factors in colorectal cancer. However, their interaction with tumor cells is inversely correlated to the presence of HLA-I on tumor cells and a thick BM-like structure around tumor islets. Our data indicate that NK cells might play an important role in the immune surveillance in colorectal cancer patients.

Magnitude and polarization of P53-specific T-helper immunity in connection to leukocyte infiltration of colorectal tumors

The tumor antigen p53 is mutated frequently and overexpressed in colorectal cancer. As a result, patients with this type of cancer commonly display p53-specific T-helper (Th) immunity. Examination of the cytokines produced by these Th-cells showed that a majority of the proliferative p53-specific T cell cultures produced none of the key cytokines (IFNgamma, TNFalpha, IL-4, IL-5 or IL-10), indicating that these p53-specific Th-responses are not polarized. In patients who exhibited p53-specific reactivity against multiple p53-epitopes, non-polarized responses could be found side by side with polarized Th-responses that produced INFgamma or other cytokines such as IL-10. Patients who exhibited p53-specific IFNgamma-producing Th cell-immunity before surgical excision of the tumor displayed higher numbers of tumor infiltrating intraepithelial leukocytes (p = 0.04) than patients lacking such responses, suggesting that the systemic presence of p53-specific Th-cells positively affects local tumor-immunity. Our data concerning the polarization-state of p53-specific Th immunity in colorectal cancer patients support the use of vaccine formulations that induce strong Th1-polarized p53-specific immunity to ensure proper (re-)programming of the anti-tumor response.