Human tumor antigens, immunosurveillance, and cancer vaccines

Combination of pioglitazone and dendritic cell to optimize efficacy of immune cell therapy in CT26 tumor models

Introduction

The maturation faith of dendritic cells is restrained by the inflammatory environment and cytokines, such as interleukin-6 and its downstream component. Therefore, introducing the suitable antigen to dendritic cells is crucial. However, reducing the severity of the suppressive tumor microenvironment is indispensable. The present study examined the combination therapy of lymphocyte antigen 6 family member E (LY6E) pulsed mature dendritic cells (LPMDCs) and pioglitazone against colorectal cancer (CRC) to elevate the effectiveness of cancer treatment through probable role of pioglitazone on inhibiting IL-6/STAT3 pathway.

Methods

Dendritic cells were generated from murine bone marrow and were pulsed with lymphocyte antigen 6 family member E peptide to assess antigen-specific T-cell proliferation and cytotoxicity assay with Annexin/PI. The effect of pioglitazone on interleukin (IL)-6/STAT3 was evaluated in vitro by real-time polymerase chain reaction (PCR). Afterward, the CRC model was established by subcutaneous injection of CT26, mouse colon carcinoma cell line, in female mice. After treatment, tumor, spleen, and lymph nodes samples were removed for histopathological, ELISA, and real-time PCR analysis.

Results

In vitro results revealed the potential of lysate-pulsed dendritic cells in the proliferation of double-positive CD3-8 splenocytes and inducing immunogenic cell death responses, whereas pioglitazone declined the expression of IL-6/STAT3 in colorectal cell lines. In animal models, the recipient of LPMDCs combined with pioglitazone demonstrated high tumor-infiltrating lymphocytes. Elevating the IL-12 and interferon-gamma (IFN-γ) levels and prolonged survival in lysate-pulsed dendritic cell and combination groups were observed.

Conclusion

Pioglitazone could efficiently ameliorate the immunosuppressive feature of the tumor microenvironment, mainly through IL-6. Accordingly, applying this drug combined with LPMDCs provoked substantial CD8 positive responses in tumor-challenged animal models.

Pan-Cancer Survey of Tumor Mass Dormancy and Underlying Mutational Processes

Tumor mass dormancy is the key intermediate step between immune surveillance and cancer progression, yet due to its transitory nature it has been difficult to capture and characterize. Little is understood of its prevalence across cancer types and of the mutational background that may favor such a state. While this balance is finely tuned internally by the equilibrium between cell proliferation and cell death, the main external factors contributing to tumor mass dormancy are immunological and angiogenic. To understand the genomic and cellular context in which tumor mass dormancy may develop, we comprehensively profiled signals of immune and angiogenic dormancy in 9,631 cancers from the Cancer Genome Atlas and linked them to tumor mutagenesis. We find evidence for immunological and angiogenic dormancy-like signals in 16.5% of bulk sequenced tumors, with a frequency of up to 33% in certain tissues. Mutations in the CASP8 and HRAS oncogenes were positively selected in dormant tumors, suggesting an evolutionary pressure for controlling cell growth/apoptosis signals. By surveying the mutational damage patterns left in the genome by known cancer risk factors, we found that aging-induced mutations were relatively depleted in these tumors, while patterns of smoking and defective base excision repair were linked with increased tumor mass dormancy. Furthermore, we identified a link between APOBEC mutagenesis and dormancy, which comes in conjunction with immune exhaustion and may partly depend on the expression of the angiogenesis regulator PLG as well as interferon and chemokine signals. Tumor mass dormancy also appeared to be impaired in hypoxic conditions in the majority of cancers. The microenvironment of dormant cancers was enriched in cytotoxic and regulatory T cells, as expected, but also in macrophages and showed a reduction in inflammatory Th17 signals. Finally, tumor mass dormancy was linked with improved patient survival outcomes. Our analysis sheds light onto the complex interplay between dormancy, exhaustion, APOBEC activity and hypoxia, and sets directions for future mechanistic explorations.

Assessment of tumor-associated immune cells in laryngeal squamous cell carcinoma

PURPOSE

This study investigated the characteristics of tumor-associated immune cells (TAICs) in laryngeal squamous cell carcinoma (LSCC) and their correlation with clinicopathological variables.

METHODS

The immune cell infiltrates of 71 specimens of stages I-IV LSCC were examined. The density of TAICs expressing CD3, CD4, CD8, CD68, and CD163 was assessed using immunohistochemical staining and image analysis in peritumoral and intratumoral regions.

RESULTS

Higher densities of CD3+ and CD8+ cell and lower densities of CD68+ and CD163+ cell infiltrations were found in early tumor stages than in late tumor stages. A higher percentage of patients with strong CD3+ and CD8+ immune cell infiltration and weak CD68+ cell infiltration in both tumor regions presented with T1 stage tumors compared with T4 stage tumors. Further, strong CD68+ cells infiltration in both regions was observed in a greater number of patients who had a relapse, while a weak CD3+ cells infiltration in both regions was found in a greater number of patients with nodal lymphatic metastasis. The univariate analysis showed that a high density of peritumoral CD3+ and CD8+ immune cells in both regions was significantly associated with a favorable overall survival (OS) (P = 0.004; P = 0.006; P = 0.042). In contrast, a high density of intratumoral CD68+ cells and peritumoral CD163+ cells was significantly associated with poor OS durations (P = 0.026; P = 0.030). The multivariate analysis demonstrated that a high density of peritumoral CD163+ cells correlated with poor OS after adjusting for tumor stage, recurrence, and nodal lymphatic metastasis (P = 0.034). This study found different patterns of TAIC infiltration in LSCC. The density and location of TAICs infiltration correlated with the clinicopathological characteristics of LSCC.

CONCLUSION

A combined analysis of the density of TAICs and their location may help predict patient survival and response to checkpoint inhibitors.

Integrative Analyses of Colorectal Cancer Show Immunoscore Is a Stronger Predictor of Patient Survival Than Microsatellite Instability

Microsatellite instability in colorectal cancer predicts favorable outcomes. However, the mechanistic relationship between microsatellite instability, tumor-infiltrating immune cells, Immunoscore, and their impact on patient survival remains to be elucidated. We found significant differences in mutational patterns, chromosomal instability, and gene expression that correlated with patient microsatellite instability status. A prominent immune gene expression was observed in microsatellite-instable (MSI) tumors, as well as in a subgroup of microsatellite-stable (MSS) tumors. MSI tumors had increased frameshift mutations, showed genetic evidence of immunoediting, had higher densities of Th1, effector-memory T cells, in situ proliferating T cells, and inhibitory PD1-PDL1 cells, had high Immunoscores, and were infiltrated with mutation-specific cytotoxic T cells. Multivariate analysis revealed that Immunoscore was superior to microsatellite instability in predicting patients' disease-specific recurrence and survival. These findings indicate that assessment of the immune status via Immunoscore provides a potent indicator of tumor recurrence beyond microsatellite-instability staging that could be an important guide for immunotherapy strategies.

Minimal residual disease in cancer therapy--Small things make all the difference

Minimal residual disease (MRD) is a major hurdle in the eradication of malignant tumors. Despite the high sensitivity of various cancers to treatment, some residual cancer cells persist and lead to tumor recurrence and treatment failure. Obvious reasons for residual disease include mechanisms of secondary therapy resistance, such as the presence of mutant cells that are insensitive to the drugs, or the presence of cells that become drug resistant due to activation of survival pathways. In addition to such unambiguous resistance modalities, several patients with relapsing tumors do not show refractory disease and respond again when the initial therapy is repeated. These cases cannot be explained by the selection of mutant tumor cells, and the precise mechanisms underlying this clinical drug resistance are ill-defined. In the current review, we put special emphasis on cell-intrinsic and -extrinsic mechanisms that may explain mechanisms of MRD that are independent of secondary therapy resistance. In particular, we show that studying genetically engineered mouse models (GEMMs), which highly resemble the disease in humans, provides a complementary approach to understand MRD. In these animal models, specific mechanisms of secondary resistance can be excluded by targeted genetic modifications. This allows a clear distinction between the selection of cells with stable secondary resistance and mechanisms that result in the survival of residual cells but do not provoke secondary drug resistance. Mechanisms that may explain the latter feature include special biochemical defense properties of cancer stem cells, metabolic peculiarities such as the dependence on autophagy, drug-tolerant persisting cells, intratumoral heterogeneity, secreted factors from the microenvironment, tumor vascularization patterns and immunosurveillance-related factors. We propose in the current review that a common feature of these various mechanisms is cancer cell dormancy. Therefore, dormant cancer cells appear to be an important target in the attempt to eradicate residual cancer cells, and eventually cure patients who repeatedly respond to anticancer therapy but lack complete tumor eradication.

Age-related increase in IL-17 activates pro-inflammatory signaling in prostate cells

BACKGROUND

A close relationship between aging, inflammation, and prostate cancer is widely accepted. Aging is accompanied by a progressive increase in pro-inflammatory cytokines, including interleukin 17 (IL-17), a key pro-inflammatory cytokine that becomes dysregulated with age. However, the contribution of IL-17 to age-related prostate tumorigenesis remains unclear. The aim of this study was to investigate the role of age-related IL-17 dysregulation in prostate tumorigenesis.

METHODS

Serum and splenic T-lymphocytes from young GPAT-1 knock-out aging-mimic T cell mice as well as young and aged wild-type mice were collected. shRNA was used to knock down the IL-17 receptor in LNCaP prostate cancer cells and RWPE-1 non-transformed prostate epithelial cells, which were then exposed to the mouse sera or conditioned media from stimulated T-lymphocytes. NF-κB activation, NF-κB target gene expression, and cell proliferation were all measured in these cells by luciferase assay, qPCR, Western blot analysis, and MTT assay, respectively.

RESULTS

T-lymphocyte-secreted IL-17 from aging-mimic mice induced NF-κB activity and target gene expression in LNCaP and RWPE-1 cells. It also promoted proliferation of these cells.

CONCLUSION

Aging-mimic T cell mice produce increased levels of IL-17, which stimulates the pro-inflammatory NF-κB pathway in prostate epithelial cells. NF-κB increases inflammation, carcinogenesis and metastatic potential in the prostate. These findings provide evidence that the dysregulation of cytokine production seen in aged T cells may directly contribute to the increased risk for prostate cancer in the elderly.

Immunotherapeutic approaches for cancer therapy: An updated review

In spite of specific immune effector mechanisms raised against tumor cells, there are mechanisms employed by the tumor cells to keep them away from immune recognition and elimination; some of these mechanisms have been identified, while others are still poorly understood. Manipulation or augmentation of specific antitumor immune responses are now the preferred approaches for treatment of malignancies, and traditional therapeutic approaches are being replaced by the use of agents which potentiate immune effector mechanisms, broadly called "immunotherapy". Cancer immunotherapy is generally classified into two main classes including active and passive methods. Interventions to augment the immune system of the patient, for example, vaccination or adjuvant therapy, actively promote antitumor effector mechanisms to improve cancer elimination. On the other hand, administration of specific monoclonal antibodies (mAbs) against different tumor antigens and adoptive transfer of genetically-modified specific T cells are currently the most rapidly developing approaches for cancer targeted therapy. In this review, we will discuss the different modalities for active and passive immunotherapy for cancer.

Skewed T-helper (Th)1/2- and Th17/T regulatory‑cell balances in patients with renal cell carcinoma

The characterization of CD4⁺ T-cell subsets reflects the immune status and is important in the maintenance of tumorigenesis and homeostasis. To identify changes in the balance of T helper (Th)1, Th2, Th17 and regulatory T cells (Treg) in individuals with renal cell carcinoma (RCC), the present study investigated a total of 131 patients with RCC and 36 healthy volunteers. The number of CD4⁺ T-bet⁺ cells, CD4⁺ GATA binding protein 3⁺ cells, CD4⁺ RAR-related orphan receptor γt⁺ cells, CD4⁺ CD25^hi CD127^lo CD45RA⁻ cells and CD4⁺ CD25^hi CD127^lo CD45RA⁺ cells, defined as Th1, Th2, Th17, activated and naïve Treg cells, respectively, were detected in the peripheral blood using flow cytometric analysis. In addition, tumor-infiltrating forkhead box P3 (Foxp3)⁺ cells were examined using immunohistochemistry. Compared with healthy volunteers, a significant decrease in the peripheral percentages of Th1, activated and naïve Treg cells was observed in patients with RCC, while those of the Th2 and Th17 cells were increased. In particular, as the tumor stage and grade progressed, the levels of Th1, activated and naïve Treg cells in the peripheral blood decreased; however, the levels of Th2 and Th17 cells increased. Furthermore, the number of tumor-infiltrating Foxp3⁺ cells increased with increasing tumor stage. These results demonstrated that the balance of Th1 and Th2 cells was skewed towards the Th2 profile and the balance of Th17 and Treg cells was skewed towards the Th17 profile in the peripheral blood of patients with renal cell carcinoma (RCC) and Treg cells were recruited to the tumor sites. Therefore, dysfunctional host anti-tumor immunity was observed in patients with RCC, with a skewed Th1/Th2 and Th17/Treg balance.

A cellular automaton model for tumor dormancy: emergence of a proliferative switch

Malignant cancers that lead to fatal outcomes for patients may remain dormant for very long periods of time. Although individual mechanisms such as cellular dormancy, angiogenic dormancy and immunosurveillance have been proposed, a comprehensive understanding of cancer dormancy and the “switch” from a dormant to a proliferative state still needs to be strengthened from both a basic and clinical point of view. Computational modeling enables one to explore a variety of scenarios for possible but realistic microscopic dormancy mechanisms and their predicted outcomes. The aim of this paper is to devise such a predictive computational model of dormancy with an emergent “switch” behavior. Specifically, we generalize a previous cellular automaton (CA) model for proliferative growth of solid tumor that now incorporates a variety of cell-level tumor-host interactions and different mechanisms for tumor dormancy, for example the effects of the immune system. Our new CA rules induce a natural “competition” between the tumor and tumor suppression factors in the microenvironment. This competition either results in a “stalemate” for a period of time in which the tumor either eventually wins (spontaneously emerges) or is eradicated; or it leads to a situation in which the tumor is eradicated before such a “stalemate” could ever develop. We also predict that if the number of actively dividing cells within the proliferative rim of the tumor reaches a critical, yet low level, the dormant tumor has a high probability to resume rapid growth. Our findings may shed light on the fundamental understanding of cancer dormancy.

Surgery, wound healing, and metastasis: recent insights and clinical implications

BACKGROUND

Surgery-induced acceleration of tumour growth has been observed since several centuries.

METHODS

We reviewed recent insights from in vitro data, animal experimentation, and clinical studies on how surgery-induced wound healing or resection of a primary cancer influences the tumour-host ecosystem in patients harbouring minimal residual or metastatic disease.

RESULTS

Most of the growth factors, chemokines, and cytokines orchestrating surgical wound healing promote tumour growth, invasion, or angiogenesis. In addition, resection of a primary tumour may accelerate synchronous metastatic growth. In the clinical setting, indirect evidence supports the relevance of the above findings. Randomized clinical trials are underway comparing resection versus observation in metastatic breast and colon cancer with asymptomatic primary tumours.

CONCLUSIONS

In depth knowledge of how surgical intervention alters the tumour-host-metastasis communicating ecosystems could have important implications for clinical decision making in patients with synchronous metastatic disease and for the design and timing of multimodality treatment strategies.

Regulation of tumor dormancy and role of microenvironment: a mathematical model

Herein, a mathematical model of a molecular control system for the regulation of secondary tumors is formulated and analyzed to explore how secondary tumors can be controlled by a primary tumor with/without a surgery and the microenvironment. This control system is composed of fibroblast growth factor-2 (FGF2), urokinase-type plasminogen activator (uPA), plasmin, transforming growth factor-beta (TGFβ), latent TGFβ (LTGFβ), and tumor density. The control of secondary tumors by primary tumors was first modeled by Boushaba, Nilsen-Hamiton and Levine in [46]. The model is based on the idea that the vascularization of a secondary tumor can be suppressed by inhibitors from a larger primary tumor. The emergence of tumors at secondary sites 5-7 cm from a primary site was observed after surgical removal of the primary tumor in silico. The model supports the notion that the fate of secondary tumors after surgery depends on the distance from the primary tumor and the surrounding microenvironment. As such, the primary tumor did not influence the growth of remote secondary tumors, but it could effectively suppress the growth of the secondary tumors if they were too close to the primary tumor, even after it was removed. Thus, the model predicts the emergence of secondary tumors after the excision of the primary tumor when the distance between these tumors is in the "distance window." It also predicts that the growth behaviors of the secondary tumors depend on the local microenvironment. Based on these findings, we propose several treatment options for better clinical outcomes.

Tumor immunotherapy using adenovirus vaccines in combination with intratumoral doses of CpG ODN

The combination of viral vaccination with intratumoral (IT) administration of CpG ODNs is yet to be investigated as an immunotherapeutic treatment for solid tumors. Here, we show that such a treatment regime can benefit survival of tumor-challenged mice. C57BL/6 mice bearing ovalbumin (OVA)-expressing EG.7 thymoma tumors were therapeutically vaccinated with adenovirus type 5 encoding OVA (Ad5-OVA), and the tumors subsequently injected with the immunostimulatory TLR9 agonist, CpG-B ODN 1826 (CpG), 4, 7, 10, and 13 days later. This therapeutic combination resulted in enhanced mean survival times that were more than 3.5× longer than naïve mice, and greater than 40% of mice were cured and capable of resisting subsequent tumor challenge. This suggests that an adaptive immune response was generated. Both Ad5-OVA and Ad5-OVA + CpG IT treatments led to significantly increased levels of H-2 K(b)-OVA-specific CD8+ lymphocytes in the peripheral blood and intratumorally. Lymphocyte depletion studies performed in vivo implicated both NK cells and CD8+ lymphocytes as co-contributors to the therapeutic effect. Analysis of tumor infiltrating lymphocytes (TILs) on day 12 post-tumor challenge revealed that mice treated with Ad5-OVA + CpG IT possessed a significantly reduced percentage of regulatory T lymphocytes (Tregs) within the CD4+ lymphocyte population, compared with TILs isolated from mice treated with Ad5-OVA only. In addition, the proportion of CD8+ TILs that were OVA-specific was reproducibly higher in the mice treated with Ad5-OVA + CpG IT compared with other treatment groups. These findings highlight the therapeutic potential of combining intratumoral CpG and vaccination with virus encoding tumor antigen.

Histopathologic-based prognostic factors of colorectal cancers are associated with the state of the local immune reaction

PURPOSE

The prognosis of patients with colorectal cancer has sometimes proved uncertain; thus, the prognostic significance of immune criteria was compared with that of the tumor extension criteria using the American Joint Committee on Cancer/International Union Against Cancer-TNM (AJCC/UICC-TNM) staging system.

PATIENTS AND METHODS

We studied the intratumoral immune infiltrates in the center of the tumor and in the invasive margin of 599 specimens of stage I to IV colorectal cancers from two independent cohorts. We analyzed these findings in relation to the degree of tumor extension and to the frequency of recurrence.

RESULTS

Growth of the primary tumor and metastatic spread were associated with decreased intratumoral immune T-cell densities. Sixty percent of patients with high densities of CD8(+) cytotoxic T-lymphocyte infiltrate presented with stage Tis/T1 tumor, whereas no patients with low densities presented with such early-stage tumor. In patients who did not relapse, the density of CD8 infiltrates was inversely correlated with T stage. In contrast, in patients whose tumor recurred, the number of CD8 cells was low regardless of the T stage of the tumor. Univariate analysis showed that the immune score was significantly associated with differences in disease-free, disease-specific, and overall survival (hazard ratio [HR], 0.64, 0.60, and 0.70, respectively; P < .005). Time-dependent receiver operating characteristic curve analysis illustrated the predictive accuracy of the immune parameters (c-index = 65.3%, time-dependent c-index [Cτ] = 66.5%). A final stepwise model for Cox multivariate analysis supports the advantage of the immune score (HR, 0.64; P < .001; Cτ = 67.9%) compared with histopathologic features in predicting recurrence as well as survival.

CONCLUSION

Assessment of CD8(+) cytotoxic T lymphocytes in combined tumor regions provides an indicator of tumor recurrence beyond that predicted by AJCC/UICC-TNM staging.

Nanoparticle delivery systems in cancer vaccines

Therapeutic strategies that involve the manipulation of the host's immune system are gaining momentum in cancer research. Antigen-loaded nanocarriers are capable of being actively taken up by antigen-presenting cells (APCs) and have shown promising potential in cancer immunotherapy by initiating a strong immunostimulatory cascade that results in potent antigen-specific immune responses against the cancer. Such carrier systems offer versatility in that they can simultaneously co-deliver adjuvants with the antigens to enhance APC activation and maturation. Furthermore, modifying the surface properties of these nanocarriers affords active targeting properties to APCs and/or enhanced accumulation in solid tumors. Here, we review some recent advances in these colloidal and particulate nanoscale systems designed for cancer immunotherapy and the potential for these systems to translate into clinical cancer vaccines.

Biomolecular network reconstruction identifies T-cell homing factors associated with survival in colorectal cancer

BACKGROUND & AIMS

Colorectal cancer is a complex disease involving immune defense mechanisms within the tumor. Herein, we used data integration and biomolecular network reconstruction to generate hypotheses about the mechanisms underlying immune responses in colorectal cancer that are relevant to tumor recurrence.

METHODS

Mechanistic hypotheses were formulated on the basis of data from 108 patients and tested using different assays (gene expression, phenome mapping, tissue-microarrays, T-cell receptor [TCR] repertoire).

RESULTS

This integrative approach revealed that chemoattraction and adhesion play important roles in determining the density of intratumoral immune cells. The presence of specific chemokines (CX3CL1, CXCL10, CXCL9) and adhesion molecules (ICAM1, VCAM1, MADCAM1) correlated with different subsets of immune cells and with high densities of T-cell subpopulations within specific tumor regions. High expression of these molecules correlated with prolonged disease-free survival. Moreover, the expression of certain chemokines associated with particular TCR repertoire and specific TCR use predicted patient survival.

CONCLUSIONS

Data integration and biomolecular network reconstruction is a powerful approach to uncover molecular mechanisms. This study shows the utility of this approach for the investigation of malignant tumors and other diseases. In colorectal cancer, the expression of specific chemokines and adhesion molecules were found as being critical for high densities of T-cell subsets within the tumor and associated with particular TCR repertoire. Intratumoral-specific TCR use correlated with the prognosis of the patients.

Tumor immunogenicity and responsiveness to cancer vaccine therapy: the state of the art

Despite enormous effort, promising pre-clinical data in animal studies and over 900 clinical trials in the United States, no cancer vaccine has ever been approved for clinical use. Over the past decade a great deal of progress has been in both laboratory and clinical studies defining the interactions between developing tumors and the immune system. The results of these studies provide a rationale that may help explain the failure of recent therapeutic cancer vaccines in terms of vaccine principles, in selecting which tumors are the most appropriate to target and instruct the design and implementation of state-of-the-art cancer vaccines.

Polymorphisms of pro-inflammatory genes and prostate cancer risk: a pharmacogenomic approach

In this paper, we consider the role of the genetics of inflammation in the pathophysiology of prostate cancer (PCa). This paper is not an extensive review of the literature, rather it is an expert opinion based on data from authors' laboratories on age-related diseases and inflammation. The aim is the detection of a risk profile that potentially allows both the early identification of individuals at risk for disease and the possible discovery of potential targets for medication. In fact, a major goal of clinical research is to improve early detection of age-related diseases, cancer included, by developing tools to move diagnosis backward in disease temporal course, i.e., before the clinical manifestation of the malady, where treatment might play a decisive role in preventing or significantly retarding the manifestation of the disease. The better understanding of the function and the regulation of inflammatory pathway in PCa may help to know the mechanisms of its formation and progression, as well as to identify new targets for the refinement of new treatment such as the pharmacogenomics approach.

Dormancy of metastatic melanoma

Metastatic dormancy of melanoma has not received sufficient attention, most likely because once detectable, metastasis is almost invariably fatal and, understandably, the focus has been on finding ways to prolong life of patients with overt recurrences. Nevertheless, analysis of the published clinical and experimental data on melanoma indicates that some aspect of melanoma biology imitate traits recently associated with dormancy in other solid cancers. Among them the ability of some melanomas to disseminate early during primary tumor progression and once disseminated, to remain undetected (dormant) for years. Comparison of cutaneous and uveal melanoma indicates that, in spite of being of the same origin, they differ profoundly in their clinical progression. Importantly for this discussion, between 40 and 50% of uveal melanoma remain undetected for longer than a decade, while less than 5% of cutaneous melanoma show this behavior. Both types of melanoma have activating oncogene mutations that provide autonomous pro-proliferative signals, yet the consensus is that those are not sufficient for tumor progression. If that is the case, it is possible to envision that signals from outside the tumor cell, (microenvironment) shape the fate of an individual disseminated cell, regardless of an oncogene mutation, to progress or to pause in a state of dormancy. To stimulate further debate and inquiry we describe here a few examples of potential signals that might modify the fate of disseminated cell and provide brief description of the current knowledge on dormancy in other cancers. Our hope is to convince the reader that disseminated melanoma cells do enter periods of prolonged dormancy and that finding ways to induce it, or to prolong it, might mean an extension of symptoms-free life for melanoma patients. Ultimately, understanding the biology of dormancy and the mechanisms of dormant cell survival, might allow for their specific targeting and elimination.

Depletion of endogenous tumor-associated regulatory T cells improves the efficacy of adoptive cytotoxic T-cell immunotherapy in murine acute myeloid leukemia

Tumor-induced immune suppression can permit tumor cells to escape host immune resistance. To elucidate host factors contributing to the poor response of adoptively transferred tumor-reactive cytotoxic T lymphocytes (CTLs), we used a systemic model of murine acute myeloid leukemia (AML). AML progression resulted in a progressive regulatory T-cell (Treg) accumulation in disease sites. The adoptive transfer of in vitro-generated, potently lytic anti-AML-reactive CTLs failed to reduce disease burden or extend survival. Compared with non-AML-bearing hosts, transferred CTLs had reduced proliferation in AML sites of metastases. Treg depletion by a brief course of interleukin-2 diphtheria toxin (IL-2DT) transiently reduced AML disease burden but did not permit long-term survival. In contrast, IL-2DT prevented anti-AML CTL hypoproliferation, increased the number of transferred CTLs at AML disease sites, reduced AML tumor burden, and resulted in long-term survivors that sustained an anti-AML memory response. These data demonstrated that Tregs present at AML disease sites suppress adoptively transferred CTL proliferation, limiting their in vivo expansion, and Treg depletion before CTL transfer can result in therapeutic efficacy in settings of substantial pre-existing tumor burden in which antitumor reactive CTL infusion alone has proven ineffective.

Tricks tumors use to escape from immune control

Tumor escape from the host immune system has been a major problem in immunotherapy of human malignancies. Human tumors are known to develop escape strategies, which might differ among tumors of the same histology. This suggests that host-tumor interactions create the tumor microenvironment that is unique for every tumor. Recent advances in cancer immunology allow for a better understanding of the mechanisms tumors use to execute immune escape and of the relationship the tumor establishes with immune cells. It is now feasible to obtain an "immune signature" of the tumor, that is to define the genetic, molecular and functional profiles of immune cells in the tumor microenvironment. This knowledge might be critically important for the personalized selection of available therapies and thus for clinical outcome.

Anaplastic lymphoma kinase: an oncogene for tumor vaccination

The immune system contributes both to the maintenance of cancer in an equilibrium state and to the elimination of tumor cells. Specific antitumor vaccination could increase the intensity or modulate the quality of this immune response against transformed cells. Antitumor vaccination strategies rely upon the identification of one or multiple antigens that can serve to stimulate the immune system. This review will focus particularly on cancer vaccination strategies based on the use of DNA molecules and on the search for antigens that are required for the growth of tumor cells and that cannot be easily down-regulated by the cancer cells (oncoantigens). In addition, we will summarize some results on clinical trials that are currently exploiting selected antigens against tumors and on the recently identified anaplastic lymphoma kinase as a potential oncoantigen for selected types of human cancers.

Dendritic cells: a critical player in cancer therapy?

Cancer immunotherapy seeks to mobilize a patient's immune system for therapeutic benefit. It can be passive, that is, transfer of immune effector cells (T cells) or proteins (antibodies), or active, that is, vaccination. Early clinical trials testing vaccination with ex vivo generated dendritic cells (DCs) pulsed with tumor antigens provide a proof-of-principle that therapeutic immunity can be elicited. Yet, the clinical benefit measured by regression of established tumors in patients with stage IV cancer has been observed in a fraction of patients only. The next generation of DC vaccines is expected to generate large numbers of high avidity effector CD8 T cells and to overcome regulatory T cells and suppressive environment established by tumors, a major obstacle in metastatic disease. Therapeutic vaccination protocols will combine improved DC vaccines with chemotherapy to exploit immunogenic chemotherapy regimens. We foresee adjuvant vaccination in patients with resected tumors but at high risk of relapse to be based on in vivo targeting of DCs with fusion proteins containing anti-DCs antibodies, antigens from tumor stem/propagating cells, and DC activators.

Immunity, ageing and cancer

Compromised immunity contributes to the decreased ability of the elderly to control infectious disease and to their generally poor response to vaccination. It is controversial as to how far this phenomenon contributes to the well-known age-associated increase in the occurrence of many cancers in the elderly. However, should the immune system be important in controlling cancer, for which there is a great deal of evidence, it is logical to propose that dysfunctional immunity in the elderly would contribute to compromised immunosurveillance and increased cancer occurrence. The chronological age at which immunosenescence becomes clinically important is known to be influenced by many factors, including the pathogen load to which individuals are exposed throughout life. It is proposed here that the cancer antigen load may have a similar effect on "immune exhaustion" and that pathogen load and tumor load may act additively to accelerate immunosenescence. Understanding how and why immune responsiveness changes in humans as they age is essential for developing strategies to prevent or restore dysregulated immunity and assure healthy longevity, clearly possible only if cancer is avoided. Here, we provide an overview of the impact of age on human immune competence, emphasizing T-cell-dependent adaptive immunity, which is the most sensitive to ageing. This knowledge will pave the way for rational interventions to maintain or restore appropriate immune function not only in the elderly but also in the cancer patient.

An HLA-DR-degenerate epitope pool detects insulin-like growth factor binding protein 2-specific immunity in patients with cancer

Recent studies have shown the importance of helper CD4 T cells in initiating and sustaining tumor-specific CD8 T-cell immunity. This has paved the way for identifying MHC class II epitopes that could be incorporated into class I-based vaccines. In this study, the goal was to identify an HLA-DR-degenerate epitope pool derived from insulin-like growth factor binding protein 2 (IGFBP-2). IGFBP-2, a regulator of insulin-like growth factor action, is overexpressed in the majority of breast and ovarian cancers. Using algorithms, we predicted 29 HLA-DR1-binding epitopes. Binding assays targeting 15 different HLA-DRs revealed that 10 epitopes were degenerate, binding to at least four different HLA-DR variants. An IFN-gamma enzyme-linked immunosorbent spot assay was used to assess immunity to these 10 epitopes in 48 patients with either breast or ovarian cancer and 18 controls. Elevated T-cell immunity in patients was detected in 4 of the 10 epitopes (IGFBP2.17, IGFBP2.22, IGFBP2.249, and IGFBP2.293). The cumulative T-cell frequency of these four epitopes was elevated in patients relative to controls. All four peptides are naturally processed and presented to CD4 T-cells. The degenerate pool of peptides covers nearly 80% of patients and may be useful for augmenting CD4 T-cell immunity in patients undergoing immunization.

Taming cancer by inducing immunity via dendritic cells

Immunotherapy seeks to mobilize a patient's immune system for therapeutic benefit. It can be passive, i.e. transfer of immune effector cells (T cells) or proteins (antibodies), or active, i.e. vaccination. In cancer, passive immunotherapy can lead to some objective clinical responses, thus demonstrating that the immune system can reject tumors. However, passive immunotherapy is not expected to yield long-lived memory T cells that might control tumor outgrowth. Active immunotherapy with dendritic cell (DC)-based vaccines has the potential to induce both tumor-specific effector and memory T cells. Early clinical trials testing vaccination with ex vivo-generated DCs pulsed with tumor antigens provide a proof-of-principle that therapeutic immunity can be elicited. Yet, there is a need to improve their efficacy. The next generation of DC vaccines is expected to generate large numbers of high-avidity effector CD8(+) T cells and to overcome regulatory T cells. Therapeutic vaccination protocols will combine improved ex vivo DC vaccines with therapies that offset the suppressive environment established by tumors.

Models, mechanisms and clinical evidence for cancer dormancy

Patients with cancer can develop recurrent metastatic disease with latency periods that range from years even to decades. This pause can be explained by cancer dormancy, a stage in cancer progression in which residual disease is present but remains asymptomatic. Cancer dormancy is poorly understood, resulting in major shortcomings in our understanding of the full complexity of the disease. Here, I review experimental and clinical evidence that supports the existence of various mechanisms of cancer dormancy including angiogenic dormancy, cellular dormancy (G0-G1 arrest) and immunosurveillance. The advances in this field provide an emerging picture of how cancer dormancy can ensue and how it could be therapeutically targeted.