Immunotherapy and immunoescape in colorectal cancer

The current role of dendritic cells in the progression and treatment of colorectal cancer

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related deaths worldwide. Dendritic cells (DCs) constitute a heterogeneous group of antigen-presenting cells that are important for initiating and regulating both innate and adaptive immune responses. As a crucial component of the immune system, DCs have a pivotal role in the pathogenesis and clinical treatment of CRC. DCs cross-present tumor-related antigens to activate T cells and trigger an antitumor immune response. However, the antitumor immune function of DCs is impaired and immune tolerance is promoted due to the presence of the tumor microenvironment. This review systematically elucidates the specific characteristics and functions of different DC subsets, as well as the role that DCs play in the immune response and tolerance within the CRC microenvironment. Moreover, how DCs contribute to the progression of CRC and potential therapies to enhance antitumor immunity on the basis of existing data are also discussed, which will provide new perspectives and approaches for immunotherapy in patients with CRC.

Immune subtype identification and multi-layer perceptron classifier construction for breast cancer

Introduction

Breast cancer is a heterogeneous tumor. Tumor microenvironment (TME) has an important effect on the proliferation, metastasis, treatment, and prognosis of breast cancer.

Methods

In this study, we calculated the relative proportion of tumor infiltrating immune cells (TIICs) in the breast cancer TME, and used the consensus clustering algorithm to cluster the breast cancer subtypes. We also developed a multi-layer perceptron (MLP) classifier based on a deep learning framework to detect breast cancer subtypes, which 70% of the breast cancer research cohort was used for the model training and 30% for validation.

Results

By performing the K-means clustering algorithm, the research cohort was clustered into two subtypes. The Kaplan-Meier survival estimate analysis showed significant differences in the overall survival (OS) between the two identified subtypes. Estimating the difference in the relative proportion of TIICs showed that the two subtypes had significant differences in multiple immune cells, such as CD8, CD4, and regulatory T cells. Further, the expression level of immune checkpoint molecules (PDL1, CTLA4, LAG3, TIGIT, CD27, IDO1, ICOS) and tumor mutational burden (TMB) also showed significant differences between the two subtypes, indicating the clinical value of the two subtypes. Finally, we identified a 38-gene signature and developed a multilayer perceptron (MLP) classifier that combined multi-gene signature to identify breast cancer subtypes. The results showed that the classifier had an accuracy rate of 93.56% and can be robustly used for the breast cancer subtype diagnosis.

Conclusion

Identification of breast cancer subtypes based on the immune signature in the tumor microenvironment can assist clinicians to effectively and accurately assess the progression of breast cancer and formulate different treatment strategies for different subtypes.

Parvovirus-Based Combinatorial Immunotherapy: A Reinforced Therapeutic Strategy against Poor-Prognosis Solid Cancers

Resistance to anticancer treatments poses continuing challenges to oncology researchers and clinicians. The underlying mechanisms are complex and multifactorial. However, the immunologically "cold" tumor microenvironment (TME) has recently emerged as one of the critical players in cancer progression and therapeutic resistance. Therefore, TME modulation through induction of an immunological switch towards inflammation ("warming up") is among the leading approaches in modern oncology. Oncolytic viruses (OVs) are seen today not merely as tumor cell-killing (oncolytic) agents, but also as cancer therapeutics with multimodal antitumor action. Due to their intrinsic or engineered capacity for overcoming immune escape mechanisms, warming up the TME and promoting antitumor immune responses, OVs hold the potential for creating a proinflammatory background, which may in turn facilitate the action of other (immunomodulating) drugs. The latter provides the basis for the development of OV-based immunostimulatory anticancer combinations. This review deals with the smallest among all OVs, the H-1 parvovirus (H-1PV), and focuses on H-1PV-based combinatorial approaches, whose efficiency has been proven in preclinical and/or clinical settings. Special focus is given to cancer types with the most devastating impact on life expectancy that urgently call for novel therapies.

Synchronous nodal metastatic risk in screening detected and endoscopically removed pT1 colorectal cancers

BACKGROUND

The population screening campaigns have resulted in increasing the prevalence of endoscopically resected colorectal cancers (CRCs) invading the submucosa (pT1). Synchronous nodal involvement occurs in less than 15 % of these tumors. Histologic criteria currently used for selecting patients needing resection are imprecise and most patients could have been simply followed-up. Tumor infiltrating lymphocytes (TILs) and mismatch repair (MMR) status impact on CRC prognosis. To identify patients requiring completion surgery, the value of histologic variables, TILs and MMR status as risk factors of nodal metastasis was investigated in screening detected and endoscopically removed pT1 CRCs.

METHODS

In 102 endoscopically resected pT1 CRCs, the cancer phenotype, CD3+ and CD8+ TILs, and MMR status were assessed. Univariate and multivariate analyses were used to evaluate the correlation with nodal metastasis.

RESULTS

Positive resection margin, evidence of vascular invasion and tumor budding, wide area of submucosal invasion, and high number of CD3+ TILs were associated with nodal metastasis in univariate analyses. Vascular invasion was statistically independent in multivariate analysis. Evidence of neoplastic cells in the vessels and/or at the excision border featured 5 out of 5 metastatic tumors and 13 out of 97 non-metastatic ones.

CONCLUSIONS

Completion surgery should be recommended only in pT1 CRC with vascular invasion or with tumor cells reaching the margin. In all other cases, the treatment choice should result from a multidisciplinary discussion on the patient-centered evaluation of the risk-benefit ratio.

Cancer stem cells as targets for DC-based immunotherapy of colorectal cancer

The therapy of colorectal cancer (CRC) patients is often unsuccessful because of the presence of cancer stem cells (CSCs) resistant to conventional approaches. Dendritic cells (DC)-based protocols are believed to effectively supplement CRC therapy. Our study was aimed to assess how the number and properties of CSCs isolated from tumor tissue of CRC patients will affect the biological characteristics of in vitro modified DCs. Similar procedures were conducted with the using of CRC HCT116 and HT29 cell lines. We found that the detailed configuration of CSC-like markers significantly influenced the maturation and activation of DCs after stimulation with cancer cells lysates or culture supernatants. This basic stimulatory effect was enhanced by LPS that is normally present in CRC CSCs niche. The increased number of CD29+ and CD44+ CSCs presented the opposite impact on treated DCs as showed by many significant correlations. The CD133+ CSCs seemed to impair the functions of DCs. The more CD133+ CSCs in tumor sample the lower number of activated DCs evidenced after stimulation. Moreover, our results showed superiority of the spherical culture model over the adherent one since spherical HCT116 and HT29 cells presented similar influence on DCs properties as CRC patients cancer cells. We concluded that the DCs features may depend directly on the properties of CSCs affected by progression status of tumor.

The Clinicopathological and Prognostic Implications of FoxP3+ Regulatory T Cells in Patients with Colorectal Cancer: A Meta-Analysis

Background and Objective: Forkhead box P3 (FoxP3) is known as the specific marker for regulatory T lymphocytes (Tregs), which are responsible for self-tolerance and disturb the antitumor immunity. However, the prognostic implication of tumor-infiltrating FoxP3⁺ Tregs in patients with colorectal cancer (CRC) still remains controversial. The aim of this present study was to investigate the prognostic role of FoxP3⁺ Tregs in CRC through meta-analysis. Methods: PubMed, Embase and Web of Science were searched for relevant articles up to December 12, 2016. Pooled hazard ratio (HR) and 95% confidence interval (CI) were calculated to explore the prognostic value of FoxP3⁺ Tregs in CRC. Odds ratio (OR) was calculated to investigate the correlation between FoxP3⁺ Tregs and pathological parameters. Results: A total of 18 studies comprising 3,627 patients with CRC were enrolled in our meta-analysis. The combined HR for FoxP3⁺ Tregs on cancer-specific survival was 0.70 (95% CI = 0.62-0.80, P < 0.001). High FoxP3⁺ Tregs level was also associated with favorable prognosis on overall survival (HR = 0.76, 95% CI = 0.58-1.01, P = 0.058), with P-value very close to the statistical threshold. Yet, there was no correlation between FoxP3⁺ Tregs infiltration and disease-free survival (HR = 0.83, 95% CI = 0.63-1.09, P = 0.182). Moreover, FoxP3⁺ Tregs infiltration was significantly correlated with pT stage (OR = 0.50, 95% CI = 0.39-0.65, P < 0.001), tumor grade (OR = 0.77, 95% CI = 0.61-0.98, P = 0.032), lymphatic invasion (OR = 0.25, 95% CI = 0.07-0.89, P = 0.033) and vascular invasion (OR = 0.67, 95% CI = 0.52-0.86, P = 0.001). Conclusion: The present meta-analysis suggests that high FoxP3⁺ Tregs infiltration is inclined to indicate favorable prognosis and is associated with the pathogenesis of CRC. Immunotherapy targeting Tregs in patients with CRC should be further investigated.

Immune Checkpoint Modulation in Colorectal Cancer: What's New and What to Expect

Colorectal cancer (CRC), as one of the most prevalent types of cancer worldwide, is still a leading cause of cancer related mortality. There is an urgent need for more efficient therapies in metastatic disease. Immunotherapy, a rapidly expanding field of oncology, is designed to boost the body's natural defenses to fight cancer. Of the many approaches currently under study to improve antitumor immune responses, immune checkpoint inhibition has thus far been proven to be the most effective. This review will outline the treatments that take advantage of our growing understanding of the role of the immune system in cancer, with a particular emphasis on immune checkpoint molecules, involved in CRC pathogenesis.

Dendritic cell defects in the colorectal cancer

Colorectal cancer (CRC) results from the accumulation of both genetic and epigenetic alterations of the genome. However, also the formation of an inflammatory milieu plays a pivotal role in tumor development and progression. Dendritic cells (DCs) play a relevant role in tumor by exerting differential pro-tumorigenic and anti-tumorigenic functions, depending on the local milieu. Quantitative and functional impairments of DCs have been widely observed in several types of cancer, including CRC, representing a tumor-escape mechanism employed by cancer cells to elude host immunosurveillance.

Understanding the interactions between DCs and tumors is important for comprehending the mechanisms of tumor immune surveillance and escape, and provides novel approaches to therapy of cancer. This review summarizes updated information on the role of the DCs in colon cancer development and/or progression.

Defective generation and maturation of dendritic cells from monocytes in colorectal cancer patients during the course of disease

Colorectal cancer (CRC) is the second-leading cause of cancer-related deaths in Western countries. Today, the role of the host’s immune system in controlling the progression and spread of solid tumors is broadly established. Tumor immunosurveillance escape mechanisms, such as those involving dendritic cells (DCs), the most important antigen-presenting cells, are likewise recognized processes involved in cancer. The present study evaluates the ability of CRC patients to generate DCs in vitro from circulating monocytes at both pre- and post-operative timepoints; the results are correlated with the stage of disease to shed light on the systemic immune statuses of CRC patients. Our data showed that patients’ DCs had lower co-stimulatory molecule expression and were less able to present antigens to allogeneic T cells compared to healthy controls’ (HC) DCs. Furthermore altered cytokine secretion, such as increased IL-10 and reduced IL-12 and TNF-α, was observed. At the post-operative timepoints we observed a recovery of the patients’ ability to generate immature DCs, compared to HCs, but the maturational capacity remained affected. Our study conclusively highlights the persistently impaired in vitro generation of fully mature and functional DCs, which appears to be more altered during advanced stages. This work sheds light on a dendritic cell-based tumor immune escape mechanism that could be useful for the development of more effective immunotherapeutic strategies.

Autologous dendritic cell based adoptive immunotherapy of patients with colorectal cancer-A phase I-II study

Dendritic cell-based active immunotherapies of cancer patients are aimed to provoke the proliferation and differentiation of tumor-specific CD4(+) and CD8(+) T-lymphocytes towards protective effector cells. Isolation and in vitro differentiation of circulating blood monocytes has been established a reasonable platform for adoptively transferred DC-based immunotherapies. In the present study the safety and tolerability of vaccination by autologous tumor cell lysates (oncolysate)- or carcinoembriogenic antigen (CEA)-loaded DCs in patients with colorectal cancer was investigated in a phase I-II trial. The study included 12 patients with histologically confirmed colorectal cancer (Dukes B2-C stages). Six of the patients received oncolysate-pulsed, whereas the other six received recombinant CEA-loaded autologous DCs. The potential of the tumor antigen-loaded DCs to provoke the patient's immune system was studied both in vivo and in vitro. The clinical outcome of the therapy evaluated after 7 years revealed that none of the six patients treated with oncolysate-loaded DCs showed relapse of colorectal cancer, whereas three out of the six patients treated with CEA-loaded DCs died because of tumor relapse. Immunization with both the oncolysate- and the CEA-loaded autologous DCs induced measurable immune responses, which could be detected in vivo by cutaneous reactions and in vitro by lymphocyte proliferation assay. Our results show that vaccination by autologous DCs loaded with autologous oncolysates containing various tumor antigens represents a well tolerated therapeutic modality in patients with colorectal cancer without any detectable adverse effects. Demonstration of the efficacy of such therapy needs further studies with increased number of patients.

Quantification of blood dendritic cells in colorectal cancer patients during the course of disease

Colorectal cancer is a malignancy with poor prognosis that might be associated with defective immune function. The aim of the present study was to investigate circulating dendritic cells in colorectal cancer patients, in order to contribute to elucidate tumor-escape mechanisms and to point out a possible correlation with the clinical condition of the disease. Therefore, we enumerated ex vivo myeloid and plasmacytoid dendritic cells, through multicolor flow cytometry, in 26 colorectal patients and 33 healthy controls. Furthermore we performed several analyses at determined time points in order to define the immunological trend of cancer patients after surgery and other conventional treatments. At the pre-operative time point the absolute number of plasmacytoid dendritic cells in cancer patients was significantly reduced in comparison to controls, this result being mainly referred to stage III-IV patients. The number of myeloid dendritic cells did not show any significant difference compared to healthy controls; interestingly the expression of the tolerogenic antigen CD85k was significantly higher on cancer patients' myeloid dendritic cells than controls'. At the following samplings, circulating dendritic cell absolute number did not show any difference compared to controls. Conclusively the impairment of the number of circulating dendritic cells may represent one of the tumor escape mechanisms occurring in colorectal cancer. These alterations seem to be correlated to cancer progression. Our work sheds light on one of dendritic cell-based tumor immune escape mechanisms. This knowledge may be useful to the development of more effective immunotherapeutic strategies.

Influence of the oncolytic parvovirus H-1, CTLA-4 antibody tremelimumab and cytostatic drugs on the human immune system in a human in vitro model of colorectal cancer cells

Introduction

Tumor-directed and immune-system-stimulating therapies are of special interest in cancer treatment. Here, we demonstrate the potential of parvovirus H-1 (H-1PV) to efficiently kill colorectal cancer cells and induce immunogenicity of colorectal tumors by inducing maturation of dendritic cells (DCs) alone and also in combination with cytostatic drugs in vitro. Using our cell culture model, we have additionally investigated the effects of anti-CTLA-4 (cytotoxic T-lymphocyte-associated antigen 4) receptor antibody tremelimumab on this process.

Materials and methods

Colon carcinoma cell lines were treated with different concentrations of cytostatic drugs or tremelimumab or were infected with H-1PV in different multiplicities of infection (MOIs), and viability was determined using MTT assays. Expression of CTLA-4 in colon carcinoma cell lines was measured by FACScan™. For the coculture model, we isolated monocytes using adherence, and differentiation into immature DCs (iDCs) was stimulated using interleukin-4 and granulocyte-macrophage colony-stimulating factor. Maturation of iDCs into mature DCs (mDCs) was induced by a cytokine cocktail. SW480 colon carcinoma cells were infected with H-1PV or treated with cytostatic drugs. Drug treated and H-1PV-infected SW480 colon carcinoma cells were cocultured with iDCs and expression of maturation markers was measured using FACScan™. Cytokine measurements were performed using enzyme-linked immunosorbent assay.

Results

Colon carcinoma cells SW480 were potently infected and killed by H-1PV. CTLA-4 expression in SW480 cells increased after infection with H-1PV and also after treatment with cytostatic drugs. Tremelimumab had no influence on viability of the colon carcinoma cell line. There was no maturation of iDCs after coculture with SW480; instead, H-1PV-infected or drug pretreated SW480 induced maturation. Cytokine production was higher for H-1PV-infected cells but was not significantly enhanced by tremelimumab treatment alone or in combination. Addition of tremelimumab did not interfere with the maturation process as measured by markers of maturation as well as by determination of cytokine levels.

Conclusion

By enhancing both cell death and immunogenicity of tumors, H-1PV is of special interest for tumor-directed therapy. These features make it a promising candidate for clinical application in human colorectal cancer. As tremelimumab does not significantly interfere with this process, an interesting therapeutic combination of active enhancement of tumor immunogenicity and independent masking of the CTLA-4 silencing process on tumor cells is highlighted.

Review article: antitumoural immunity in colorectal cancer - current and potential future implications in clinical practice

BACKGROUND

Most of the current research in gastrointestinal oncology is focused on biology of cancer itself, but there is growing interest in the patient's immune system response and its relation with cancer cells.

AIM

To review the impact of the antitumoural immune response on epidemiology, prognosis and treatment of colorectal cancer.

METHODS

Search of the literature published in English using the PubMed database.

RESULTS

The role of the immune system in the antitumoural immunosurveillance is clearly supported by the increased incidence of colorectal cancer and adenomatous polyps in immunosuppressed patients. Moreover, the degree of infiltration of the tumours by the immune cells has been shown to be a strong prognostic factor of both disease recurrence and survival. The immune system plays an important role in the chemotherapy-induced cell death. New therapeutic strategies targeting the antitumoural immunity are being currently investigated with promising results.

CONCLUSION

Better knowledge of antitumoural immune system can have a major impact on patients' management in daily clinical practice. Colorectal cancer screening is an important issue in immunosuppressed patients, and recommendations should be refined for selected high-risk patients. The use of an immune score to guide the therapeutic strategies in the adjuvant setting should be supported. Further and larger clinical trials are necessary to accelerate the development of innovative immune therapies.

Synergistical toll-like receptors activated dendritic cells induce antitumor effects against carcinoembryonic antigen-expressing colon cancer

PURPOSE

Dendritic cell (DC)-based cancer vaccine represents a promising immunotherapy against cancer. There has been recent evidence which have suggested that toll-like receptor (TLR) ligands may be critical for DC preparation; this was usually omitted in the past. Our study is designed to investigate if the vaccination of synergistical toll-like receptors activated DCs can induce more potent cytotoxic T Lymphocytes (CTL) responses and antitumor activity in carcinoembryonic antigen (CEA) transgenic mouse tumor models.

METHODS

We involved combination of TLR3 and TLR7/8 ligands in culture protocol of DCs. The DCs' surface molecules expression, IL-12 secretion and proliferation capacity of lymphocytes were tested. We also investigate the CTL activity against MC38-CEA colon tumor cells and the prophylactic and therapeutic effects of DC vaccination in subcutaneous mouse colon tumor models.

RESULTS

Compared with conventionally generated DCs, we showed synergistic TLR-activated DCs exhibited higher surface molecule expression, significantly higher secretion of IL-12 and more potent proliferating capacity of lymphocytes. Synergistic TLR-activated DCs were also able to induce lymphocytes possessing the specific cytotoxicity against MC38-CEA cells in vitro. Vaccination with CEA epitope pulsed TLR-activated DCs elicited antigen-specific preventive effect on MC38-CEA tumors, but failed to cure the tumor-bearing mice, that may be due to the suboptimal epitope selected and host immunosuppression.

CONCLUSIONS

Our results have proved that combined activation of TLRs can lead to better maturation status of DCs and also induce more effective antitumor immune responses against colon cancer, suggesting this may be a potential strategy to develop more powerful DC cancer vaccines.

Assessment of activity of an adhesion molecule CD134 and CD137 in colorectal cancer patients

Epidemiological studies prove that incidence of colorectal cancer is increasing. The first line therapy of colorectal cancer is surgical resection of the primary tumor and elimination of regional and remote metastases. THE AIM OF THE STUDY was to determine expression of adhesion molecules CD134 and CD137 in the peripheral blood in colorectal cancer patients, depending on clinical cancer stage, size and invasion of the tumor.

MATERIAL AND METHODS

The study enrolled 72 patients with primary colorectal adenocarcinoma. An average patient age was 64.55 years. Clinical tumor stage was assessed using two scales: Dukes: A and Astler-Coller scale. Expression of adhesion molecules was determined in the peripheral blood collected on the day of the procedure and 10 days after the procedure.

RESULTS

An average activity of CD134 molecules (12.66%) was significantly higher than that of CD137 (6.26%) (p<0.001). Clinical tumor stage was assessed on Dukes scale and was unrelated to CD134 activity, while activity of CD137 was related to clinical cancer stage.

CONCLUSIONS

CD137 activity is directly proportional to colorectal cancer stage. Surgical resection of the tumor results in increased CD134 and CD137 expression. Long term studies, enrolling larger groups of patients, including their subdivision to colon and rectal cancer, are required to utilize CD134 and CD137 in immune therapy of colorectal cancer.

Determination of the activity of CD134 (OX-40) and CD137 (4-1BB) adhesive molecules by means of flow cytometry in patients with colorectal cancer metastases to the liver

Colorectal carcinoma (CRC) is one of the most common reasons of mortality in patients diagnosed with neoplasms. In nearly 20% of patients with colorectal carcinoma metastatic lesions are diagnosed. In general, survival of patients with metastatic lesions to the liver and other organs is poor. Conventional therapy of colorectal carcinoma is based on the surgical excision of the tumor, chemotherapy, and radiotherapy.

THE AIM OF THE STUDY

was to determine the expression of CD134 and CD137 molecules inside the tumor, at the border of the tumor, in the healthy tissue, and peripheral blood, considering patients with colorectal carcinoma metastases to the liver.

MATERIAL AND METHODS

The study group comprised 39 patients subject to surgical treatment at the Department of General and Gastroenterological Surgery, due to colorectal carcinoma with liver metastases. CD134 and CD137 adhesive molecule levels were determined inside the tumor, at the border of the tumor, and in the healthy margins of the surgical incision. Additionally, the authors evaluated the peripheral blood level of the above-mentioned molecules on the day of the surgical procedure, and 10 days, thereafter.

RESULTS

The mean CD134 levels were the highest inside the tumor, significantly decreasing towards the direction of healthy tissues. The average peripheral blood molecule levels were four-fold higher on the day of the surgical procedure, as compared to values obtained on the tenth postoperative day. This dependency also concerned the remaining statistical measures.The mean CD137 levels showed no significant difference, regardless their location. The authors observed significant, peripheral blood, CD137 level differences, considering the day of the surgical procedure and tenth postoperative period. The mean CD137 peripheral blood level was several times higher on the day of the surgical procedure, as compared to the postoperative period.

CONCLUSIONS

The determination of the activity of CD134 and CD137 molecules might create opportunities to plan treatment and predict prognosis in case of colorectal carcinoma. Proper immuno-therapeutic management which is based on the expression of the above-mentioned molecules might help determine the risk of metastases, preventing from their development. In advanced cases treatment of liver metastases might be possible.

Low molecular weight hyaluronan preconditioning of tumor-pulsed dendritic cells increases their migratory ability and induces immunity against murine colorectal carcinoma

We have recently shown that systemic administration of low molecular weight hyaluronan (LMW HA) significantly reduces colorectal carcinoma (CRC) growth in vivo. The elicited response is partially mediated by activated dendritic cells (DC). To potentiate the ability of DC loaded with whole tumor lysate (DC/TL) to induce immunity against CRC in mice, we aimed to study the effects of preconditioning DC with LMW HA for therapeutic vaccination. LMW HA improved maturation of ex vivo generated DC, increased IL-12, decreased IL-10 production, and enhanced a MLR activity in vitro. Although TNF-α showed a similar capacity to mature DC, preconditioning of DC/TL with LMW HA increased their ability to migrate in vitro toward CCL19 and CCL-21 in a CD44- and a TLR4-independent manner; this effect was superior to Poly(I:C), LPS, or TNF-α and partially associated with an increase in the expression of CCR7. Importantly, LMW HA dramatically enhanced the in vivo DC recruitment to tumor-regional lymph nodes. When these LMW HA-treated CRC tumor lysate-pulsed DC (DC/TL/LMW HA) were administered to tumor-bearing mice, a potent antitumor response was observed when compared to DC pulsed with tumor lysate alone and matured with TNF-α. Then, we showed that splenocytes isolated from animals treated with DC/TL/LMW HA presented a higher proliferative capacity, increased IFN-γ production, and secreted lower levels of the immunosuppressive IL-10. Besides, increased specific CTL response was observed in DC/TL/LMW HA-treated animals and induced long-term protection against tumor recurrence. Our data show that LMW HA is superior to other agents at inducing DC migration; therefore, LMW HA could be considered a new adjuvant candidate in the preparation of DC-based anticancer vaccines with potent immunostimulatory properties.

Immune Cells in Colorectal Cancer: Prognostic Relevance and Role of MSI

There is growing evidence that both local and systemic inflammatory responses play an important role in the progression of a variety of solid tumors. Colorectal cancer (CRC) results from the cumulative effect of sequential genetic alterations, leading to the expression of tumor-associated antigens possibly inducing a cellular anti-tumor immune response. It is well recognized that cytotoxic lymphocytes (CTLs) constitute one of the most important effector mechanisms of anti-tumor-immunity. However, their potential prognostic influence in CRC remains controversial. In addition, other key players like natural killer cells, tumor associated macrophages and regulatory T cells play an important role in the immune attack against CRC and need further investigation. This review will mainly focus on the role of the adaptive immune system in CRC and particularly in regard to microsatellite instability.

Combinatorial therapy for liver metastatic colon cancer: dendritic cell vaccine and low-dose agonistic anti-4-1BB antibody co-stimulatory signal

BACKGROUND

The combination of dendritic cell (DC) vaccine and 4-1BB ligation may be a suitable choice of immunotherapy for incurable cancer. However, at anti-tumor effector doses over 100 μg, 4-1BB Ab ligation is toxic to CD4(+) T cells, thus limiting its therapeutic use.

MATERIALS AND METHODS

A liver metastatic colon cancer model was established by hepatic injection of CT26 cells into Balb/c mice. Intraperitoneal administration of 1 × 10(6)/200 μL/mouse therapeutic-DCs (tumor lysate pulsed-DCs, P-DCs) began on d 7 after tumor cell inoculation. A P-DC injection was performed twice within a 1-wk interval. Agonistic anti 4-1BB Ab was intraperitoneally injected on d 7, 9, and 11 after tumor cell inoculation. Animals were sacrificed on d 21, and tumor growth was determined by weighing the liver with the tumor.

RESULTS

In the 20 μg 4-1BB ligation group, significant induction of CD3(+)CD8(+) T cells was observed without toxicity to CD3(+)CD4(+) T cells. DC vaccine treatment induced tumor antigen-specific Th1 cytokine (IL-2 and IFN-γ) secretion from the splenic lymphocytes. Ligation of 4-1BB reduced the DC vaccine-related IL-10 secretion and regulatory T cell population. Compared with anti-tumor effect of DC vaccine or 20 μg 4-1BB Ab alone, the combination therapy significantly increased the tumor rejection power to the level observed with higher doses of 4-1BB Ab alone. The combination therapy did not induce high-dose 4-1BB-related toxicity with CD4(+) T cell reduction, but did significantly induce tumor antigen-specific IFN-γ secreting effector CD8(+) cytotoxic T cells.

CONCLUSIONS

The data from our study reveal the value of using a DC vaccine combined with as little as 20 μg 4-1BB Ab as an improved immunotherapeutic for cancer.

Reversal of gastrointestinal carcinoma-induced immunosuppression and induction of antitumoural immunity by a combination of cyclophosphamide and gene transfer of IL-12

Immunotherapy-based strategies for gastrointestinal carcinomas (GIC) have been exploited so far, but these approaches have to face strong mechanisms of immune escape induced by tumours. We previously demonstrated that sub-therapeutic doses of an adenovirus expressing IL-12 genes (AdIL-12) mediated a potent antitumour effect against subcutaneous (s.c.) colorectal carcinomas (CRC) in mice pre-treated with low doses of cyclophosphamide (Cy). In our study we used this combination to assess its impact on the immunosuppressive microenvironment. In s.c. CRC model we demonstrated that non-responder mice failed to decrease Tregs in tumour, spleen and peripheral blood. Reconstitution of Tregs into tumour-bearing mice treated with combined therapy abolished the antitumoural effect. In addition, Cy + AdIL-12 modified Tregs functionality by inhibiting the in vitro secretion of IL-10 and TGF-β and their ability to inhibit dendritic cells activation. Combined treatment decreased the number of myeloid-derived suppressor cells (MDSCs) in comparison to non-treated mice and, interestingly, administration of Tregs restored splenic MDSCs population. Furthermore, combined therapy potently generated specific cytotoxic IFN-γ-secreting CD4+ T cells able to eradicate established CRC tumours after adoptive transfer. Finally, we evaluated the combination on disseminated CRC and pancreatic carcinoma (PC). Cy + AdIL-12 were able to eradicate liver metastatic CRC (47%) and PC tumour nodules (40%) and to prolong animal survival. The results of this study support the hypothesis that Cy + AdIL-12 might be a valid immunotherapeutic strategy for advanced GIC.

Delivery of immunostimulatory monoclonal antibodies by encapsulated hybridoma cells

Immunostimulatory monoclonal antibodies are immunoglobulins directed toward surface proteins of immune system cells that augment the immune response against cancer in a novel therapeutic fashion. Exogenous administration of the recombinant humanized immunoglobulins is being tested in clinical trials with agents of this kind directed at a variety of immune-controlling molecular targets. In this study, the encapsulation of antibody-producing hybridoma cells was tested in comparison with the systemic administration of monoclonal antibodies. Hybridomas producing anti-CD137 and anti-OX40 mAb were encapsulated in alginate to generate microcapsules containing viable cells that secrete antibody. Immobilized cells in vitro were able to release the rat immunoglobulin produced by the hybridomas into the supernatant. Microcapsules were implanted by injection into the subcutaneous tissue of mice and thereby provided a platform for viable secreting cells, which lasted for more than 1 week. The pharmacokinetic profile of the rat monoclonal antibodies following microcapsule implantation was similar to that attained following an intraperitoneal administration of the purified antibodies. The rat-mouse hybridoma cells did not engraft as tumors in immunocompetent mice, while they lethally xenografted in immunodeficient mice, if not microencapsulated. The antitumor therapeutic activity of the strategy was studied on established CT26 colon carcinomas resulting in complete tumor eradication in an elevated fraction of cases and strong tumor-specific CTL responses with either anti-CD137 or anti-OX40 producing hybridomas, thus offering proof of the concept. This form of administration permitted combinations of more than one immunostimulatory monoclonal antibody to exploit the synergistic effects such as those known to be displayed by anti-CD137 and anti-OX40 mAb.

Targeted immunotherapy for colorectal cancer: monoclonal antibodies and immunotoxins

Colorectal cancer (CRC) is a major health concern worldwide. It is the third most frequently diagnosed cancer and the second leading cause of cancer death. There currently are a number of treatment options for CRC, however many of them have failed to demonstrate desired therapeutic benefit. Therefore, significant efforts are being directed towards the development of new biological therapies with improved efficacy. Immunotherapy is an emerging treatment modality for a variety of cancers. Several promising treatments have already been approved by the US FDA and are being tested in clinical trials. Antibodies have been proved to be useful in cancer therapy due to their ability to recognize tumor-associated antigens expressed at higher density on malignant cells in comparison with those that are normal. Antibodies can be used as a single therapy or in combination with other therapies. A large variety of monoclonal antibodies have been developed. However, only a very few are able to kill a sufficient number of malignant cells and cause tumor regression. Hence, it is often necessary to arm the antibody with a cytotoxic agent to enhance the efficacy of the anti-tumor activity. This review provides a brief overview of some of the current agents being employed in targeted immunotherapy for CRC.

Expression of calreticulin is associated with infiltration of T-cells in stage IIIB colon cancer

AIM: To investigate the correlation between expression of calreticulin and infiltration of lymphocytes in stage IIIB colon cancer.

METHODS: Sixty-eight pathologically-confirmed specimens were obtained from stage IIIB (T3N1M0) colon cancer patients who underwent radical resection between January 1999 and May 2002 at the Cancer Center of Sun Yat-Sen University, Guangzhou, China. Immunohistochemical analysis was performed to show infiltration of lymphocytes and expression of calreticulin in colon cancer. Association between calreticulin expression, infiltration of lymphocytes, and 5-year survival rate of patients was assessed.

RESULTS: The expression level of calreticulin was lower in cancer nest than in its adjacent normal epithelium since 61.8% (42/68) of the samples were stained with calreticulin in colon cancer. The expression of calreticulin in colon cancer was associated with the infiltration of CD45RO+ cells rather than with that of CD3+ cells. In addition, the stronger expression of calreticulin and the higher infiltration of CD3+ and CD45RO+ cells in colon cancer were associated with the higher 5-year survival rate of patients.

CONCLUSION: Expression of calreticulin is associated with infiltration of T-cells, which implies that a low expression level of molecular marker may represent a new mechanism underlying immune escape in colon cancer.

Invasive front of colorectal cancer: Dynamic interface of pro-/anti-tumor factors

Tumor-host interaction at the invasive front of colorectal cancer represents a critical interface encompassing a dynamic process of de-differentiation of colorectal carcinoma cells known as epithelial mesenchymal transition (EMT). EMT can be identified histologically by the presence of “tumor budding”, a feature which can be highly specific for tumors showing an infiltrating tumor growth pattern. Importantly, tumor budding and tumor border configuration have generated considerable interest as additional prognostic factors and are also recognized as such by the International Union Against Cancer. Evidence seems to suggest that the presence of tumor budding or an infiltrating growth pattern is inversely correlated with the presence of immune and inflammatory responses at the invasive tumor front. In fact, several tumor-associated antigens such as CD3, CD4, CD8, CD20, Granzyme B, FOXP3 and other immunological or inflammatory cell types have been identified as potentially prognostic in patients with this disease. Evidence seems to suggest that the balance between pro-tumor (including budding and infiltrating growth pattern) and anti-tumor (immune response or certain inflammatory cell types) factors at the invasive front of colorectal cancer may be decisive in determining tumor progression and the clinical outcome of patients with colorectal cancer. On one hand, the infiltrating tumor border configuration and tumor budding promote progression and dissemination of tumor cells by penetrating the vascular and lymphatic vessels. On the other, the host attempts to fend off this attack by mounting an immune response to protect vascular and lymphatic channels from invasion by tumor buds. Whereas standard pathology reporting of breast and prostate cancer involves additional prognostic features, such as the BRE and Gleason scores, the ratio of pro- and anti-tumor factors could be a promising approach for the future development of a prognostic score for patients with colorectal cancer which could complement tumor node metastasis staging to improve the clinical management of patients with this disease.

Indoleamine 2,3-dioxygenase in lung allograft tolerance

BACKGROUND

Indoleamine 2,3-dioxygenase (IDO), an enzyme involved in the degradation of tryptophan (Try) to kynurenine (Kyn), is thought to suppress T-cell activity. Although a few experimental studies have suggested a role for IDO in graft acceptance, human data are scarce and inconclusive. We sought to establish whether, in lung transplant recipients (LTRs), plasma IDO activity mirrors the level of graft acceptance.

METHODS

We measured the plasma Kyn/Try ratio, reflecting IDO activity, by high-performance liquid chromatography (HPLC) in 90 LTRs, including 26 patients who were still functionally/clinically stable for >36 post-transplant months (stable LTRs) and 64 LTRs with bronchiolitis obliterans syndrome (BOS, Grades 0-p to 3). Twenty-four normal healthy controls (NHCs) were also included.

RESULTS

The Kyn/Try ratio in stable LTRs resembled that observed in NHCs, whereas, unexpectedly, patients with BOS, who had lower counts of peripheral CD4(+) T-regulatory cells and tolerogenic plasmacytoid dendritic cells than stable LTRs, showed an increased plasma Kyn/Try ratio compared with both NHCs and stable LTRs. IDO expression by in vitro-stimulated peripheral blood mononuclear cells (PBMC) did not vary between BOS and stable LTRs. Furthermore, BOS patients displayed signs of chronic systemic inflammation (increased plasma levels of interleukin-8 and tumor necrosis factor-alpha) and higher T-cell activation (increased frequency of peripheral interferon-gamma-producing clones).

CONCLUSIONS

Our results suggest that, in vivo, in lung transplantation, plasma IDO activity does not reflect the degree of lung graft acceptance, but instead is correlated with the degree of chronic inflammation.

Immunotherapy for liver tumors: present status and future prospects

Increasing evidence suggests that immune responses are involved in the control of cancer and that the immune system can be manipulated in different ways to recognize and attack tumors. Progress in immune-based strategies has opened new therapeutic avenues using a number of techniques destined to eliminate malignant cells. In the present review, we overview current knowledge on the importance, successes and difficulties of immunotherapy in liver tumors, including preclinical data available in animal models and information from clinical trials carried out during the lasts years. This review shows that new options for the treatment of advanced liver tumors are urgently needed and that there is a ground for future advances in the field.

Immunotherapy for gastrointestinal cancer: current status and strategies for improving efficacy

BACKGROUND

Despite improvement in conventional strategies for treating gastrointestinal (GI) carcinoma, large numbers of patients still suffer from incurable or progressive disease.

OBJECTIVE

Here we consider the prospects for circumventing limitations and maximising the efficacy of different immunotherapies.

METHODS

We summarise different cancer vaccines and targeted drugs and highlight the scientific rationale of using immunotherapy for targeting GI cancers, in addition to the potential strategies for improving immunotherapeutic efficacy.

RESULTS/CONCLUSION

Many cancer vaccines and antibody-directed therapies have been tested in early phase clinical trials and demonstrated proof of concept and safety. As yet few have been properly evaluated for clinical efficacy; although adoptive transfer of tumour-associated-antigen-specific T cells has shown dramatic clinical responses in some patients. The recognition of a role for T regulatory cells in limiting anti-tumour immunity has provided momentum for developing strategies to over-ride such immunoinhibitory effects. There is some evidence that conventional therapies may work by influencing these negative factors and allowing expression of immune control mechanisms. An important developing area for clinical evaluation is the testing of combined conventional and immunotherapeutic modalities which may provide for synergy; thereby circumventing the limitations of individualised treatments and generating additional clinical benefits.