Psychological stress is associated with altered levels of myeloid-derived suppressor cells in breast cancer patients

Stress, metabolism and cancer: integrated pathways contributing to immune suppression

The potential for immune cells to control cancers has been recognized for many decades, but only recently has real excitement begun to spread through the oncology community following clear evidence that therapeutic blockade of specific immune-suppressive mechanisms is enough to make a real difference in survival for patients with several different advanced cancers. However, impressive and encouraging as these new clinical data are, it is clear that more effort should be devoted toward understanding the full spectrum of factors within cancer patients, which have the potential to block or weaken antitumor activity by immune cells. The goal of this brief review is to highlight recent literature revealing interactive stress and metabolic pathways, particularly those mediated by the sympathetic nervous system, which may conspire to block immune cells from unleashing their full killing potential. There is exciting new information regarding the role of neurogenesis by tumors and adrenergic signaling in cancer progression (including metabolic changes associated with cachexia and lipolysis) and in regulation of immune cell function and differentiation. However, much more work is needed to fully understand how the systemic metabolic effects mediated by the brain and nervous system can be targeted for therapeutic efficacy in the setting of immunotherapy and other cancer therapies.

The immunobiology of myeloid-derived suppressor cells in cancer

The tumor microenvironment is a complex and heterogeneous milieu in which multiple interactions occur between tumor and host cells. Immunosuppressive cells which are present in this microenvironment, such as regulatory T (Treg) cells and myeloid-derived suppressor cells (MDSCs), play an important role in tumor progression, via down-regulation of antitumor responses. MDSCs represent a heterogeneous group of cells originated from the myeloid lineage that are in the immature state. These cells markedly accumulate under pathologic conditions, such as cancer, infection, and inflammation, and use various mechanisms to inhibit both adaptive and innate immune responses. These immunosuppressive mechanisms include deprivation of T cells from essential amino acids, induction of oxidative stress, interference with viability and trafficking of T cells, induction of immunosuppressive cells, and finally polarizing immunity toward a tumor-promoting type 2 phenotype. In addition to suppression of antitumor immune responses, MDSCs can also enhance the tumor metastasis and angiogenesis. Previous studies have shown that increased frequency of MDSCs is related to the tumor progression. Moreover, various drugs that directly target these cells or reverse their suppressive activity can improve antitumor immune responses as well as increase the efficacy of immunotherapeutic intervention. In this review, we will first discuss on the immunobiology of MDSCs in an attempt to find the role of these cells in tumor progression and then discuss about therapeutic approaches to target these cells.

Effect of Chronic Psychological Stress on Liver Metastasis of Colon Cancer in Mice

Metastasis to the liver is a main factor in colorectal cancer mortality. Previous studies suggest that chronic psychological stress is important in cancer progression, but its effect on liver metastasis has not been investigated. To address this, we established a liver metastasis model in BALB/c nude mice to investigate the role of chronic stress in liver metastasis. Our data suggest that chronic stress elevates catecholamine levels and promotes liver metastasis. Chronic stress was also associated with increased tumor associated macrophages infiltration into the primary tumor and increased the expression of metastatic genes. Interestingly, β-blocker treatment reversed the effects of chronic stress on liver metastasis. Our results suggest the β-adrenergic signaling pathway is involved in regulating colorectal cancer progression and liver metastasis. Additionally, we submit that adjunctive therapy with a β-blocker may complement existing colorectal cancer therapies.

Tolerance and immune suppression in the tumor microenvironment

The concept of immunological tolerance has guided and permeated much of modern immunology. Ray Owen's ground-breaking observations in twin cattle provided the first mechanistic explanation for tolerance to self-molecules and established tolerance as a beneficial process that protects the host against autoreactivity. However, his studies also opened the door to understanding that tolerance may be detrimental, such as occurs when cancer cells induce tolerance/immune suppression resulting in inhibition of anti-tumor immunity. This article briefly traces the early history of the field of tumor immunology with respect to tolerance, and then focuses on a relatively recently identified population of cells called myeloid-derived suppressor cells (MDSCs). MDSC are instrumental in causing tolerance/immune suppression in individuals with cancer. They are present in most individuals with cancer and because of their potent immune suppressive activity are a major deterrent to natural anti-tumor immunity and a significant obstacle to immunotherapy.

Myeloid-derived suppressor cells in major depression patients suppress T-cell responses through the production of reactive oxygen species

Major depression is closely associated with immune dysregulation. Myeloid-derived suppressor cells (MDSCs) are an important suppressor of immune responses. The aim of this study was to evaluate the possible role of MDSCs in major depression patients. We collected peripheral blood mononuclear cells (PBMCs) from 25 major depression patients and 25 healthy donors, and the frequency of MDSCs was determined by flow cytometric analysis. The proportion of MDSCs was increased in the peripheral blood of major depression patients, when compared with healthy controls. Further functional studies revealed that MDSCs from depression patients suppressed T cell function potently. We examined the reactive oxygen species (ROS) content in MDSCs from 6 major depression patients and 6 healthy controls. The ROS content in depression derived MDSCs was significantly elevated, when compared with those from healthy controls. We also examined the arginase activity and NO content in 5 major depression patients and 5 healthy controls, respectively. But no significant changes were detected between two groups. Administration of a ROS inhibitor completely abrogated the suppressive effect of MDSCs on T cells. In conclusion, our study revealed that MDSCs from depression patients suppress T cell reponses in ROS-dependent manner.

Decreased Cortisol and Pain in Breast Cancer: Biofield Therapy Potential

Breast cancer is one of the leading causes of cancer death among women of all races. Pain is a common symptom associated with cancer; 75–90% of cancer patients experience pain during their illness and up to 50% of that pain is undertreated. Unrelieved pain leads to increased levels of the stress hormone cortisol. The purpose of this study was to examine the impact of bioenergy on fecal cortisol levels for mice injected with murine mammary carcinoma 4T1 in two separate pilot studies. Using a multiple experimental group design, six to eight week old female BALB/c mice were injected with tumor and randomly assigned, in groups of 10, to daily treatment, every other day treatment, and no treatment groups. Five days after tumor cell injection, bioenergy interventions were begun for a period of ten consecutive days. Fecal samples were collected for each study and ELISA analysis was conducted at the end of both studies. For both studies, cortisol levels were decreased in the every other day treatment groups but remained high in the no treatment groups. Future studies utilizing bioenergy therapies on cortisol levels in a murine breast cancer model can begin to describe pain outcomes and therapeutic dose.

Myeloid-Derived Suppressor Cells and Therapeutic Strategies in Cancer

Development of solid cancer depends on escape from host immunosurveillance. Various types of immune cells contribute to tumor-induced immune suppression, including tumor associated macrophages, regulatory T cells, type 2 NKT cells, and myeloid-derived suppressor cells (MDSCs). Growing body of evidences shows that MDSCs play pivotal roles among these immunosuppressive cells in multiple steps of cancer progression. MDSCs are immature myeloid cells that arise from myeloid progenitor cells and comprise a heterogeneous immune cell population. MDSCs are characterized by the ability to suppress both adaptive and innate immunities mainly through direct inhibition of the cytotoxic functions of T cells and NK cells. In clinical settings, the number of circulating MDSCs is associated with clinical stages and response to treatment in several cancers. Moreover, MDSCs are reported to contribute to chemoresistant phenotype. Collectively, targeting MDSCs could potentially provide a rationale for novel treatment strategies in cancer. This review summarizes recent understandings of MDSCs in cancer and discusses promissing clinical approaches in cancer patients.

Myeloid-Derived Suppressor Cells: Critical Cells Driving Immune Suppression in the Tumor Microenvironment

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that suppress innate and adaptive immunity. MDSCs are present in many disease settings; however, in cancer, they are a major obstacle for both natural antitumor immunity and immunotherapy. Tumor and host cells in the tumor microenvironment (TME) produce a myriad of pro-inflammatory mediators that activate MDSCs and drive their accumulation and suppressive activity. MDSCs utilize a variety of mechanisms to suppress T cell activation, induce other immune-suppressive cell populations, regulate inflammation in the TME, and promote the switching of the immune system to one that tolerates and enhances tumor growth. Because MDSCs are present in most cancer patients and are potent immune-suppressive cells, MDSCs have been the focus of intense research in recent years. This review describes the history and identification of MDSCs, the role of inflammation and intracellular signaling events governing MDSC accumulation and suppressive activity, immune-suppressive mechanisms utilized by MDSCs, and recent therapeutics that target MDSCs to enhance antitumor immunity.

Psychosocial telephone counseling for survivors of cervical cancer: results of a randomized biobehavioral trial

PURPOSE

Survivors of cervical cancer experience quality-of-life (QOL) disruptions that persist years after treatment. This study examines the effect of a psychosocial telephone counseling (PTC) intervention on QOL domains and associations with biomarkers.

PATIENTS AND METHODS

We conducted a randomized clinical trial in survivors of cervical cancer, who were ≥ 9 and less than 30 months from diagnosis (n = 204), to compare PTC to usual care (UC). PTC included five weekly sessions and a 1-month booster. Patient-reported outcomes (PROs) and biospecimens were collected at baseline and 4 and 9 months after enrollment. Changes in PROs over time and associations with longitudinal change in cytokines as categorical variables were analyzed using multivariable analysis of variance for repeated measures.

RESULTS

Participant mean age was 43 years; 40% of women were Hispanic, and 51% were non-Hispanic white. Adjusting for age and baseline scores, participants receiving PTC had significantly improved depression and improved gynecologic and cancer-specific concerns at 4 months compared with UC participants (all P < .05); significant differences in gynecologic and cancer-specific concerns (P < .05) were sustained at 9 months. Longitudinal change in overall QOL and anxiety did not reach statistical significance. Participants with decreasing interleukin (IL) -4, IL-5, IL-10, and IL-13 had significantly greater improvement in QOL than those with increasing cytokine levels.

CONCLUSION

This trial confirms that PTC benefits mood and QOL cancer-specific and gynecologic concerns for a multiethnic underserved population of survivors of cancer. The improvement in PROs with decreases in T-helper type 2 and counter-regulatory cytokines supports a potential biobehavioral pathway relevant to cancer survivorship.

A nervous tumor microenvironment: the impact of adrenergic stress on cancer cells, immunosuppression, and immunotherapeutic response

Long conserved mechanisms maintain homeostasis in living creatures in response to a variety of stresses. However, continuous exposure to stress can result in unabated production of stress hormones, especially catecholamines, which can have detrimental health effects. While the long-term effects of chronic stress have well-known physiological consequences, recent discoveries have revealed that stress may affect therapeutic efficacy in cancer. Growing epidemiological evidence reveals strong correlations between progression-free and long-term survival and β-blocker usage in cancer patients. In this review, we summarize the current understanding of how the catecholamines, epinephrine and norepinephrine, affect cancer cell survival and tumor progression. We also highlight new data exploring the potential contributions of stress to immunosuppression in the tumor microenvironment and the implications of these findings for the efficacy of immunotherapies.

Clinical perspective: Linking psychosocial care to the disease continuum in patients with multiple myeloma

OBJECTIVE

A model of psychosocial care specific for patients with multiple myeloma and their caregivers has not yet been proposed. We sought to develop a model of care that considers the specific profile of this disease.

METHOD

The authors, representing a multidisciplinary care team, met in December of 2012 to identify a model of psychosocial care for patients with multiple myeloma and their caregivers. This model was determined by consensus during the meeting and via total agreement following the meeting. The meeting was sponsored by Onyx Pharmaceuticals.

RESULTS

The need for targeted psychosocial care for the multiple myeloma patient and caregiver throughout the disease process is essential to ensure quality of life and optimal treatment outcomes. We propose herein the first known model of care for the treatment of multiple myeloma that engages both the patient and their caregivers.

SIGNIFICANCE OF RESULTS

Innovative partnerships between psychosocial providers and other entities such as pharmaceutical companies can maximize resources for comprehensive program development. This manuscript proposes a model of care that promotes active engagement in therapies for multiple myeloma while engaging the individual patient and their family caregivers. This treatment approach must be evidence based in terms of distress screening tools, comprehensive psychosocial assessments, and, most importantly, in the interventions and measurements of response that clinicians apply to this population.

Experiences of paradox: a qualitative analysis of living with cancer using a framework approach

OBJECTIVES

Life-threatening diseases such as cancer represent unique traumas-compared with singular, time-limited traumatic events-given their multidimensional, uncertain, and continuing nature. However, few studies have examined the impact of cancer on patients as a persistent stressor. The aim of this qualitative study is to explore patients' ongoing experiences of living with cancer and the changes encountered in this experience over time.

METHODS

Written reflections to three open-ended questions collected from 28 patients on their experience of cancer at two time points were analyzed to explore participants' experiences and perspectives over time. Content analysis using a framework approach was employed to code, categorize, and summarize data into a thematic framework.

RESULTS

Data analysis yielded the thematic framework-living with paradox, consisting of four interrelated themes: sources, experiences, resolution of paradox, and challenges with medical culture/treatment. The primary theme concerned moving through a dualistic and complex cancer experience of concurrently negative and positive emotional states across the course of cancer.

CONCLUSIONS

Respondents indicated that cycling through this contradictory trajectory was neither linear, nor singular, nor conclusive in nature, but reiterative across time. Recognition that patients' cancer experience may be paradoxical and tumultuous throughout the cancer trajectory can influence how practitioners provide patients with needed support during diagnosis, treatment, and recovery. This also has implications for interventions, treatment, and care plans, and adequately responding to the diversity of patient's psychosocial, physical, existential, and spiritual experience of illness.

Randomized controlled trial of expressive writing for patients with renal cell carcinoma

PURPOSE

This randomized controlled trial examined the quality-of-life benefits of an expressive writing (EW) intervention for patients with renal cell carcinoma (RCC) and identified a potential underlying mechanism of intervention efficacy.

PATIENTS AND METHODS

Patients (N = 277) with stage I to IV RCC were randomly assigned to write about their deepest thoughts and feelings regarding their cancer (EW) or about neutral topics (neutral writing [NW]) on four separate occasions. Patients completed the Center for Epidemiologic Studies Depression Scale (CES-D), MD Anderson Symptom Inventory (MDASI), Brief Fatigue Inventory (BFI), Pittsburgh Sleep Quality Index (PSQI), Medical Outcomes Study Short Form-36 (SF-36), and Impact of Event Scale (IES) at baseline and 1, 4, and 10 months after the intervention.

RESULTS

The mean age of participants (28% stage IV; 41% female) was 58 years. Multilevel modeling analyses, using a Bonferroni-corrected α = .021 for six outcomes adjusted for the correlation among outcomes, revealed that, relative to the NW group, patients in the EW group reported significantly lower MDASI scores (P = .003) and higher physical component summary scores on the SF-36 (P = .019) at 10 months after the intervention. Mediation analyses revealed that significant group differences for MDASI scores at 10 months were mediated by lower IES scores at 1 month after the intervention in the EW group (P = .042). No significant group differences were observed in the BFI, CES-D, PSQI, and mental component summary of the SF-36.

CONCLUSION

EW may reduce cancer-related symptoms and improve physical functioning in patients with RCC. Evidence suggests that this effect may occur through short-term improvements in cognitive processing.

Breast cancer and coping among women of color: a systematic review of the literature

Breast cancer is the most commonly diagnosed form of cancer for women regardless of race/ethnicity. Women of color are diagnosed at later stages and experience greater mortality than their White counterparts. However, there has been comparatively little research on coping with breast among racial/ethnic minorities at time of diagnosis, during treatment, or in the course of survivorship. This is despite the fact that research has repeatedly shown that distress can impact disease progression and survival. The questions asked of this systematic literature review include: (1) What is known about coping with breast cancer among major racial/ethnic groups? (2) What are the strengths and gaps in research to date? Over 120 peer-reviewed published studies (1980-2012) were reviewed. A total of 33 met criteria for inclusion including 15 quantitative, 17 qualitative, and 1 mixed methods study. The majority of studies were small sample cross-sectional studies. Only five studies were longitudinal, and two randomized-controlled intervention trials sought to improve coping among survivors. The most common topic in both quantitative and qualitative studies was spirituality and coping among African American breast cancer patients. Thirteen studies included Latinas only or in combination with other groups. Only one quantitative and one qualitative study solely addressed the Asian American population exploring coping and adjustment. In the course of this systematic literature review, we elucidate what is known about coping with breast cancer among racial/ethnic minority women and identify priorities for future research.

Peripheral blood mononuclear cells of patients with breast cancer can be reprogrammed to enhance anti-HER-2/neu reactivity and overcome myeloid-derived suppressor cells

Two major barriers in the immunotherapy of breast cancer include tumor-induced immune suppression and the establishment of long-lasting immune responses against the tumor. Recently, we demonstrated in an animal model of breast carcinoma that expanding and reprogramming tumor-sensitized lymphocytes, ex vivo, yielded T memory (Tm) cells as well as activated CD25+ NKT cells and NK cells. The presence of activated CD25+ NKT and NK cells rendered reprogrammed T cells resistant to MDSC-mediated suppression, and adoptive cellular therapy (ACT) of reprogrammed lymphocytes protected the host from tumor development and relapse. Here, we performed a pilot study to determine the clinical applicability of our protocol using peripheral blood mononuclear cells (PBMCs) of breast cancer patients, ex vivo. We show that bryostatin 1 and ionomycin combined with IL-2, IL-7, and IL-15 can expand and reprogram tumor-sensitized PBMCs. Reprogrammed lymphocytes contained activated CD25+ NKT and NK cells as well as Tm cells and displayed enhanced reactivity against HER-2/neu in the presence of MDSCs. The presence of activated NKT cells was highly correlated with the rescue of anti-HER-2/neu immune responses from MDSC suppression. Ex vivo blockade experiments suggest that the NKG2D pathway may play an important role in overcoming MDSC suppression. Our results show the feasibility of reprogramming tumor-sensitized immune cells, ex vivo, and provide rationale for ACT of breast cancer patients.

Chronic psychological stress induces the accumulation of myeloid-derived suppressor cells in mice

Chronic psychological stress has been shown to adversely impact immune system functions and compromise host defenses against various infections. However, the underlying mechanisms remain elusive. Recent studies have demonstrated that myeloid-derived suppressor cells (MDSCs) play an important role in regulating immunity. It is of interest to explore whether or not chronic psychological stress plays immunosuppressive functions partially by inducing MDSCs accumulation. In this work, we report that chronic psychological stress led to the accumulation of CD11b+Gr1+ cells in the bone marrow of BALB/c mice. Repeated β-agonist infusion showed no such effect. However, β-adrenergic blockade, but not glucocorticoids blockade, partially reversed the accumulation of CD11b+Gr1+ cells under the condition of chronic psychological stress, suggesting catecholamines collaborate with other factors to induce the accumulation. Further exploration indicates that cyclooxygenase 2 (COX-2)-prostaglandin E2 (PGE2) loop might act downstream to induce the accumulation. A majority of the accumulated CD11b+Gr1+ cells were Ly6G+Ly6C(low) immature neutrophils, which inhibited cytokine release of macrophages as well as T cell responsiveness. Moreover, the accumulated CD11b+Gr1+ cells under the condition of chronic psychological stress expressed multiple inhibitory molecules. Taken together, our data demonstrate for the first time that chronic psychological stress induces MDSCs accumulation in mice, which can contribute to immunosuppression.

Striking life events associated with primary breast cancer susceptibility in women: a meta-analysis study

Purpose

The association between striking life events, an important stress and acute anxiety disorder, and the occurrence of primary breast cancer is unclear. The current meta-analysis was designed to assess the relationship between striking life events and primary breast cancer incidence in women.

Methods

Systematic computerized searching of the PubMed, ScienceDirect, Embase, and BMJ databases with the combinations of controlled descriptors from Mesh, including breast cancer, breast tumor, cancer of breast, mammary carcinoma, life events, life change events, case–control studies, case-base studies, cohort study, and cohort analysis and identified a total of 307 papers published from January 1995 to April 2012. Following evaluation of methodological quality with the Downs & Black criteria, seven case–control or cohort studies were selected and the association between striking life events and primary breast cancer incidence in women was measured using random effect or fixed-effect odds ratios combined with 95% confidence interval.

Results

The seven studies included in the final meta-analysis included 99,807 women. A meta-analysis showed that the pooled OR for striking life events and breast cancer was 1.51 (95% CI 1.15 - 1.97, P = 0.003), indicating that women with striking life events were at 1.5-fold greater risk of developing breast cancer. The pooled OR for severe striking life events and breast cancer was 2.07 (95% CI 1.06 - 4.03), indicating that women with severe striking life events were at 2-fold greater risk of developing breast cancer.

Conclusions

The current meta-analysis showed significant evidence for a positive association between striking life events and primary breast cancer incidence in women.

Myeloid-derived suppressor cells in breast cancer

Myeloid-derived suppressor cells (MDSCs) are a population of immature myeloid cells defined by their suppressive actions on immune cells such as T cells, dendritic cells, and natural killer cells. MDSCs typically are positive for the markers CD33 and CD11b but express low levels of HLADR in humans. In mice, MDSCs are typically positive for both CD11b and Gr1. These cells exert their suppressive activity on the immune system via the production of reactive oxygen species, arginase, and cytokines. These factors subsequently inhibit the activity of multiple protein targets such as the T cell receptor, STAT1, and indoleamine-pyrrole 2,3-dioxygenase. The numbers of MDSCs tend to increase with cancer burden while inhibiting MDSCs improves disease outcome in murine models. MDSCs also inhibit immune cancer therapeutics. In light of the poor prognosis of metastatic breast cancer in women and the correlation of increasing levels of MDSCs with increasing disease burden, the purposes of this review are to (1) discuss why MDSCs may be important in breast cancer, (2) describe model systems used to study MDSCs in vitro and in vivo, (3) discuss mechanisms involved in MDSC induction/function in breast cancer, and (4) present pre-clinical and clinical studies that explore modulation of the MDSC-immune system interaction in breast cancer. MDSCs inhibit the host immune response in breast cancer patients and diminishing MDSC actions may improve therapeutic outcomes.

Psychosocial stress and inflammation in cancer

Stress-induced immune dysregulation results in significant health consequences for immune related disorders including viral infections, chronic autoimmune disease, and tumor growth and metastasis. In this mini-review we discuss the sympathetic, neuroendocrine and immunologic mechanisms by which psychosocial stress can impact cancer biology. Both human and animal studies have shown the sympathetic and neuroendocrine responses to psychosocial stress significantly impacts cancer, in part, through regulation of inflammatory mediators. Psychosocial stressors stimulate neuroendocrine, sympathetic, and immune responses that result in the activation of the hypothalamic-pituitary-adrenal (HPA)-axis, sympathetic nervous system (SNS), and the subsequent regulation of inflammatory responses by immune cells. Social disruption (SDR) stress, a murine model of psychosocial stress and repeated social defeat, provides a novel and powerful tool to probe the mechanisms leading to stress-induced alterations in inflammation, tumor growth, progression, and metastasis. In this review, we will focus on SDR as an important model of psychosocial stress in understanding neural-immune mechanisms in cancer.

Cancer-related intrusive thoughts predict behavioral symptoms following breast cancer treatment

OBJECTIVE

Behavioral symptoms are common in breast cancer survivors, including disturbances in energy, sleep, and mood, though few risk factors for these negative outcomes have been identified. Our study examined intrusive thoughts as a predictor of lingering symptoms in breast cancer survivors in the year following treatment.

METHOD

Data come from the Moving Beyond Cancer psychoeducational intervention trial, aimed at easing the transition from patient to survivor. Women (n = 558) completed psychosocial questionnaires within 4 weeks posttreatment and again 2, 6, and 12 months later. We examined intrusive thoughts about cancer at the baseline assessment as a predictor of fatigue, sleep problems, pain, breast cancer-specific symptoms, depressive symptoms, negative affect, and quality of life using growth curve modeling, controlling for study condition and other covariates.

RESULTS

Intrusive thoughts were associated with higher levels of all symptoms at baseline and at the 12-month assessment. Intrusive thoughts also influenced the trajectory of pain, depressive symptoms, negative affect, and physical functioning over time; women with higher intrusions at baseline started worse and improved over time, whereas those with lower intrusions remained at a constant, lower level over time. Intrusions were not associated with the trajectory of fatigue, sleep, breast cancer-specific symptoms, or mental functioning; women with higher intrusions at baseline started worse and remained worse over time.

CONCLUSION

Intrusive thoughts are associated with enduring elevations in behavioral symptoms and impaired quality of life in the year after breast cancer treatment and may be a risk factor for poor outcomes.

Immunotherapy of cancer: reprogramming tumor-immune crosstalk

The advancement of cancer immunotherapy faces barriers which limit its efficacy. These include weak immunogenicity of the tumor, as well as immunosuppressive mechanisms which prevent effective antitumor immune responses. Recent studies suggest that aberrant expression of cancer testis antigens (CTAs) can generate robust antitumor immune responses, which implicates CTAs as potential targets for immunotherapy. However, the heterogeneity of tumor cells in the presence and quantity of CTA expression results in tumor escape from CTA-specific immune responses. Thus, the ability to modulate the tumor cell epigenome to homogenously induce expression of such antigens will likely render the tumor more immunogenic. Additionally, emerging studies suggest that suppression of antitumor immune responses may be overcome by reprogramming innate and adaptive immune cells. Therefore, this paper discusses recent studies which address barriers to successful cancer immunotherapy and proposes a strategy of modulation of tumor-immune cell crosstalk to improve responses in carcinoma patients.

On the armament and appearances of human myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSC) have frequently been observed in patients with cancer. This heterogeneous population of myeloid cells can exert potent suppression of lymphocyte function and thereby poses a significant hurdle to natural or therapeutically induced anti-tumor immunity. On the other hand, the natural function of MDSC is not yet well understood and their role in infection, inflammation and autoimmune disease is still puzzling. Understanding MDSC biology will provide the tools necessary for therapeutic targeting of this population, but also permit exploitation of their strong tolerogenic function in the treatment of inflammatory conditions and the prevention of graft rejection.

The Microenvironmental Effect in the Progression, Metastasis, and Dormancy of Breast Cancer: A Model System within Bone Marrow

Despite diagnostic advances, breast cancer remains the most prevalent cancer among women in the United States. The armamentarium of treatment options for metastatic disease is limited and mostly ineffective with regards to eradicating cancer. However, there have been novel findings in the recent literature that substantiate the function of the microenvironment in breast cancer progression and the support of metastasis to tertiary sites such as bone marrow. The uncovered significance of the microenvironment in the pathophysiology of breast cancer metastasis has served to challenge previously widespread theories and introduce new perspectives for the future research to eradicate breast cancer. This paper delineates the current understanding of the molecular mechanisms involved in the interactions between breast cancer cells and the microenvironment in progression, metastasis, and dormancy. The information, in addition to other mechanisms described in bone marrow, is discussed in the paper.

Regulatory dendritic cells in the tumor immunoenvironment

The tumor microenvironment is a pivotal factor in tumorigenesis, and especially in progression, as the pathogenesis of cancer critically depends on the complex interactions between various microenvironmental components. A key component of the tumor immunoenvironment is the infiltration of immune cells, which has been proven to play a dual role in tumor growth and progression. This Janus two-faced function of the tumor immunoenvironment is seen in tumor infiltration by T cells, which correlates with improved patient survival, but also with the homing of multiple subsets of immunoregulatory cells that inhibit the antitumor immune response. Regulatory dendritic cells (regDCs) have recently been shown to be induced by tumor-derived factors and represent a new and potentially important player in supporting tumor progression and suppressing the development of antitumor immune responses. Our recent data reveal that different tumor cell lines produce soluble factors that induce polarization of conventional DCs into regDCs, both in vitro and in vivo. These regDCs can suppress the proliferation of pre-activated T cells and are phenotypically and functionally different from their precursors as well as the classical immature conventional DCs. Understanding the biology of regDCs and the mechanisms of their formation in the tumor immunoenvironment will provide a new therapeutic target for re-polarizing protumorigenic immunoregulatory cells into proimmunogenic effector cells able to induce and support effective antitumor immunity.