Differential regulation of hypoxia-induced CXCR4 triggering during B-cell development and lymphomagenesis

Whole-Blood and Peripheral Mononuclear Cell Transcriptional Response to Prolonged Altitude Exposure in Well-Trained Runners

BACKGROUND

Recombinant human erythropoietin (rHuEpo) abuse by athletes threatens the integrity of sport. Due to the overlap in physiological response to rHuEpo and altitude exposure, it remains difficult to differentiate changes in hematological variables caused by rHuEpo or altitude, and therefore, other molecular methods to enhance anti-doping should be explored.

OBJECTIVE

To identify the hematological and transcriptomic response to prolonged altitude exposure typical of practices used by elite athletes.

DESIGN

Longitudinal study.

SETTING

University of Cape Town and Altitude Training Centre in Ethiopia.

PARTICIPANTS AND INTERVENTION

Fourteen well-trained athletes sojourned to an altitude training camp in Sululta, Ethiopia (∼2400-2500 m above sea level) for 27 days. Blood samples were taken before arrival, 24 hours, and 9, 16, and 24 days after arrival at altitude in addition to 24 hours and 6, 13, and 27 days upon return to sea level.

MAIN OUTCOME MEASURES

Blood samples were analyzed for hemoglobin concentration, hematocrit, and reticulocyte percentage. The transcriptomic response in whole blood and peripheral blood mononuclear cells (PBMC) were analyzed using gene expression microarrays.

RESULTS

A unique set of 29 and 10 genes were identified to be commonly expressed at every altitude time point in whole blood and PBMC, respectively. There were no genes identified upon return to sea level in whole blood, and only one gene within PBMC.

CONCLUSIONS

The current study has identified a series of unique genes that can now be integrated with genes previously validated for rHuEpo abuse, thereby enabling the differentiation of rHuEpo from altitude exposure.

Hypoxia and hypoxia-inducible factor signals regulate the development, metabolism, and function of B cells

Hypoxia is a common hallmark of healthy tissues in physiological states or chronically inflamed tissues in pathological states. Mammalian cells sense and adapt to hypoxia mainly through hypoxia-inducible factor (HIF) signaling. Many studies have shown that hypoxia and HIF signaling play an important regulatory role in development and function of innate immune cells and T cells, but their role in B cell biology is still controversial. B cells experience a complex life cycle (including hematopoietic stem cells, pro-B cells, pre-B cells, immature B cells, mature naïve B cells, activated B cells, plasma cells, and memory B cells), and the partial pressure of oxygen (PO₂) in the corresponding developmental niche of stage-specific B cells is highly dynamic, which suggests that hypoxia and HIF signaling may play an indispensable role in B cell biology. Based on the fact that hypoxia niches exist in the B cell life cycle, this review focuses on recent discoveries about how hypoxia and HIF signaling regulate the development, metabolism, and function of B cells, to facilitate a deep understanding of the role of hypoxia in B cell-mediated adaptive immunity and to provide novel strategies for vaccine adjuvant research and the treatment of immunity-related or infectious diseases.

R4 RGS proteins as fine tuners of immature and mature hematopoietic cell trafficking

G-protein-coupled receptors (GPCRs) are the largest and most diverse group of membrane receptors. They are involved in almost every physiologic process and consequently have a pivotal role in an extensive number of pathologies, including genetic, neurologic, and immune system disorders. Indeed, the vast array of GPCRs mechanisms have led to the development of a tremendous number of drug therapies and already account for about a third of marketed drugs. These receptors mediate their downstream signals primarily via G proteins. The regulators of G-protein signaling (RGS) proteins are now in the spotlight as the critical modulatory factors of active GTP-bound Gα subunits of heterotrimeric G proteins to fine-tune the biologic responses driven by the GPCRs. Also, they possess noncanonical functions by multiple mechanisms, such as protein-protein interactions. Essential roles and impacts of these RGS proteins have been revealed in physiology, including hematopoiesis and immunity, and pathologies, including asthma, cancers, and neurologic disorders. This review focuses on the largest subfamily of R4 RGS proteins and provides a brief overview of their structures and G-proteins selectivity. With particular interest, we explore and highlight, their expression in the hematopoietic system and the regulation in the engraftment of hematopoietic stem/progenitor cells (HSPCs). Distinct expression patterns of R4 RGS proteins in the hematopoietic system and their pivotal roles in stem cell trafficking pave the way for realizing new strategies for enhancing the clinical performance of hematopoietic stem cell transplantation. Finally, we discuss the exciting future trends in drug development by targeting RGS activity and expression with small molecules inhibitors and miRNA approaches.

R4 RGS proteins suppress engraftment of human hematopoietic stem/progenitor cells by modulating SDF-1/CXCR4 signaling

Specific R4 RGS members are expressed in human HSPCs and regulated by the SDF-1/CXCR4 axis.

RGS1/13/16 suppress HSPC engraftment, SDF-1 signaling, and key effectors of stem cell trafficking/maintenance.

Homing and engraftment of hematopoietic stem/progenitor cells (HSPCs) into the bone marrow (BM) microenvironment are tightly regulated by the chemokine stromal cell–derived factor-1 (SDF-1) and its G-protein–coupled receptor C-X-C motif chemokine receptor 4 (CXCR4), which on engagement with G-protein subunits, trigger downstream migratory signals. Regulators of G-protein signaling (RGS) are GTPase-accelerating protein of the Gα subunit and R4 subfamily members have been implicated in SDF-1–directed trafficking of mature hematopoietic cells, yet their expression and influence on HSPCs remain mostly unknown. Here, we demonstrated that human CD34⁺ cells expressed multiple R4 RGS genes, of which RGS1, RGS2, RGS13, and RGS16 were significantly upregulated by SDF-1 in a CXCR4-dependent fashion. Forced overexpression of RGS1, RGS13, or RGS16 in CD34⁺ cells not only inhibited SDF-1–directed migration, calcium mobilization, and phosphorylation of AKT, ERK, and STAT3 in vitro, but also markedly reduced BM engraftment in transplanted NOD/SCID mice. Genome-wide microarray analysis of RGS-overexpressing CD34⁺ cells detected downregulation of multiple effectors with established roles in stem cell trafficking/maintenance. Convincingly, gain-of-function of selected effectors or ex vivo priming with their ligands significantly enhanced HSPC engraftment. We also constructed an evidence-based network illustrating the overlapping mechanisms of RGS1, RGS13, and RGS16 downstream of SDF-1/CXCR4 and Gα_i. This model shows that these RGS members mediate compromised kinase signaling and negative regulation of stem cell functions, complement activation, proteolysis, and cell migration. Collectively, this study uncovers an essential inhibitory role of specific R4 RGS proteins in stem cell engraftment, which could potentially be exploited to develop improved clinical HSPC transplantation protocols.

To breathe or not to breathe: Understanding how oxygen sensing contributes to age-related phenotypes

Aging is characterized by a progressive loss of tissue integrity and functionality due to disrupted homeostasis. Molecular oxygen is pivotal to maintain tissue functions, and aerobic species have evolved a sophisticated sensing system to ensure proper oxygen supply and demand. It is not surprising that aberrations in oxygen and oxygen-associated pathways subvert health and promote different aspects of aging. In this review, we discuss emerging findings on how oxygen-sensing mechanisms regulate different cellular and molecular processes during normal physiology, and how dysregulation of oxygen availability lead to disease and aging. We describe various clinical manifestations associated with deregulation of oxygen balance, and how oxygen-modulating therapies and natural oxygen oscillations influence longevity. We conclude by discussing how a better understanding of oxygen-related mechanisms that orchestrate aging processes may lead to the development of new therapeutic strategies to extend healthy aging.

Transcriptomic profile of adverse neurodevelopmental outcomes after neonatal encephalopathy

A rapid and early diagnostic test to identify the encephalopathic babies at risk of adverse outcome may accelerate the development of neuroprotectants. We examined if a whole blood transcriptomic signature measured soon after birth, predicts adverse neurodevelopmental outcome eighteen months after neonatal encephalopathy. We performed next generation sequencing on whole blood ribonucleic acid obtained within six hours of birth from the first 47 encephalopathic babies recruited to the Hypothermia for Encephalopathy in Low and middle-income countries (HELIX) trial. Two infants with blood culture positive sepsis were excluded, and the data from remaining 45 were analysed. A total of 855 genes were significantly differentially expressed between the good and adverse outcome groups, of which RGS1 and SMC4 were the most significant. Biological pathway analysis adjusted for gender, trial randomisation allocation (cooling therapy versus usual care) and estimated blood leukocyte proportions revealed over-representation of genes from pathways related to melatonin and polo-like kinase in babies with adverse outcome. These preliminary data suggest that transcriptomic profiling may be a promising tool for rapid risk stratification in neonatal encephalopathy. It may provide insights into biological mechanisms and identify novel therapeutic targets for neuroprotection.

Cyclosporine a directly affects human and mouse b cell migration in vitro by disrupting a hIF-1 αdependent, o2 sensing, molecular switch

BACKGROUND

Hypoxia is a potent molecular signal for cellular metabolism, mitochondrial function, and migration. Conditions of low oxygen tension trigger regulatory cascades mediated via the highly conserved HIF-1 α post-translational modification system. In the adaptive immune response, B cells (Bc) are activated and differentiate under hypoxic conditions within lymph node germinal centers, and subsequently migrate to other compartments. During migration, they traverse through changing oxygen levels, ranging from 1-5% in the lymph node to 5-13% in the peripheral blood. Interestingly, the calcineurin inhibitor cyclosporine A is known to stimulate prolyl hydroxylase activity, resulting in HIF-1 α destabilization and may alter Bc responses directly. Over 60% of patients taking calcineurin immunosuppressant medications have hypo-gammaglobulinemia and poor vaccine responses, putting them at high risk of infection with significantly increased morbidity and mortality.

RESULTS

We demonstrate that O 2 tension is a previously unrecognized Bc regulatory switch, altering CXCR4 and CXCR5 chemokine receptor signaling in activated Bc through HIF-1 α expression, and controlling critical aspects of Bc migration. Our data demonstrate that calcineurin inhibition hinders this O 2 regulatory switch in primary human Bc.

CONCLUSION

This previously unrecognized effect of calcineurin inhibition directly on human Bc has significant and direct clinical implications.

The CXCR4-CXCL12-Axis Is of Prognostic Relevance in DLBCL and Its Antagonists Exert Pro-Apoptotic Effects In Vitro

In tumor cells of more than 20 different cancer types, the CXCR4-CXCL12-axis is involved in multiple key processes including proliferation, survival, migration, invasion, and metastasis. Since data on this axis in diffuse large B cell lymphoma (DLBCL) are inconsistent and limited, we comprehensively studied the CXCR4-CXCL12-axis in our DLBCL cohort as well as the effects of CXCR4 antagonists on lymphoma cell lines in vitro. In DLBCL, we observed a 140-fold higher CXCR4 expression compared to non-neoplastic controls, which was associated with poor clinical outcome. In corresponding bone marrow biopsies, we observed a correlation of CXCL12 expression and lymphoma infiltration rate as well as a reduction of CXCR4 expression in remission of bone marrow involvement after treatment. Additionally, we investigated the effects of three CXCR4 antagonists in vitro. Therefore, we used AMD3100 (Plerixafor), AMD070 (Mavorixafor), and WKI, the niacin derivative of AMD070, which we synthesized. WK1 demonstrated stronger pro-apoptotic effects than AMD070 in vitro and induced expression of pro-apoptotic genes of the BCL2-family in CXCR4-positive lymphoma cell lines. Finally, WK1 treatment resulted in the reduced expression of JNK-, ERK1/2- and NF-κB/BCR-target genes. These data indicate that the CXCR4-CXCL12-axis impacts the pathogenesis of DLBCL and represents a potential therapeutic target in aggressive lymphomas.

Can Exercise-Induced Modulation of the Tumor Physiologic Microenvironment Improve Antitumor Immunity?

The immune system plays an important role in controlling cancer growth. However, cancers evolve to evade immune detection. Immune tolerance and active immune suppression results in unchecked cancer growth and progression. A major contributor to immune tolerance is the tumor physiologic microenvironment, which includes hypoxia, hypoglucosis, lactosis, and reduced pH. Preclinical and human studies suggest that exercise elicits mobilization of leukocytes into circulation (also known as "exercise-induced leukocytosis"), especially cytotoxic T cells and natural killer cells. However, the tumor physiologic microenvironment presents a significant barrier for these cells to enter the tumor and, once there, properly function. We hypothesize that the effect of exercise on the immune system's ability to control cancer growth is linked to how exercise affects the tumor physiologic microenvironment. Normalization of the microenvironment by exercise may promote more efficient innate and adaptive immunity within the tumor. This review summarizes the current literature supporting this hypothesis.

Hypoxia as a barrier to immunotherapy in pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is a lethal disease with limited response to cytotoxic chemoradiotherapy, as well as newer immunotherapies. The PDA tumor microenvironment contains infiltrating immune cells including cytotoxic T cells; however, there is an overall immunosuppressive milieu. Hypoxia is a known element of the solid tumor microenvironment and may promote tumor survival. Through various mechanisms including, but not limited to, those mediated by HIF-1α, hypoxia also leads to increased tumor proliferation and metabolic changes. Furthermore, epithelial to mesenchymal transition is promoted through several pathways, including NOTCH and c-MET, regulated by hypoxia. Hypoxia-promoted changes also contribute to the immunosuppressive phenotype seen in many different cell types within the microenvironment and thereby may inhibit an effective immune system response to PDA. Pancreatic stellate cells (PSCs) and myofibroblasts appear to contribute to the recruitment of myeloid derived suppressor cells (MDSCs) and B cells in PDA via cytokines increased due to hypoxia. PSCs also increase collagen secretion in response to HIF-1α, which promotes a fibrotic stroma that alters T cell homing and migration. In hypoxic environments, B cells contribute to cytotoxic T cell exhaustion and produce chemokines to attract more immunosuppressive regulatory T cells. MDSCs inhibit T cell metabolism by hoarding key amino acids, modulate T cell homing by cleaving L-selectin, and prevent T cell activation by increasing PD-L1 expression. Immunosuppressive M2 phenotype macrophages promote T cell anergy via increased nitric oxide (NO) and decreased arginine in hypoxia. Increased numbers of regulatory T cells are seen in hypoxia which prevent effector T cell activation through cytokine production and increased CTLA-4. Effective immunotherapy for pancreatic adenocarcinoma and other solid tumors will need to help counteract the immunosuppressive nature of hypoxia-induced changes in the tumor microenvironment. Promising studies will look at combination therapies involving checkpoint inhibitors, chemokine inhibitors, and possible targeting of hypoxia. While no model is perfect, assuring that models incorporate the effects of hypoxia on cancer cells, stromal cells, and effector immune cells will be crucial in developing successful therapies.

Primary non-Hodgkin lymphoma of the right femur and subsequent metastasis to the left femur: A case report and literature review

Non-Hodgkin lymphoma of the bone is rare and typically causes an extensive bone lesion. The present study describes a case of diffuse large B-cell primary non-Hodgkin lymphoma of the bone, which occurred in the right femur, and was initially treated with surgery and chemotherapy. Following a 7-year period of complete remission, a new, similar lesion was identified in the left femur. With both lesions, there was no accompanying destruction of any other bones or organ involvement. Metastasis of PLB to the contralateral side is extremely rare and, to the best of our knowledge, this is the first report of this particular presentation in China or worldwide. We hypothesized that the present situation arose due to mechanisms involving the tumor microenvironment, circulating tumor cells, lymphocyte homing and self-seeding. The present report describes the case in detail, and discusses the possible underlying mechanisms and their potential contribution to the treatment of non-Hodgkin lymphoma, as well as the prevention of metastasis and recurrence, which may be of considerable clinical significance.

A Brake for B Cell Proliferation: Appropriate responses to metabolic stress are crucial to maintain B cell viability and prevent malignant outgrowth

B cell activation is accompanied by metabolic adaptations to meet the increased energetic demands of proliferation. The metabolic composition of the microenvironment is known to change during a germinal center response, in inflamed tissue and to vary significantly between different organs. To sustain cellular homeostasis B cells need to be able to dynamically adapt to changes in their environment. An inability to take up and process available nutrients can result in impaired B cell growth and a diminished humoral immune response. Furthermore, the metabolic microenvironment can affect B cell signaling and provide a means to avoid aberrant proliferation or modulate B cell function. Thus, a better understanding of the intricate interplay between cell signaling and metabolism could provide novel insight into how B cell function is regulated and have implications for the development of vaccines or treatment of autoimmune disorders and B cell derived malignancies.

The role of G protein-coupled receptors in lymphoid malignancies

B cell lymphoma consists of multiple individual diseases arising throughout the lifespan of B cell development. From pro-B cells in the bone marrow, through circulating mature memory B cells, each stage of B cell development is prone to oncogenic mutation and transformation, which can lead to a corresponding lymphoma. Therapies designed against individual types of lymphoma often target features that differ between malignant cells and the corresponding normal cells from which they arise. These genetic changes between tumor and normal cells can include oncogene activation, tumor suppressor gene repression and modified cell surface receptor expression. G protein-coupled receptors (GPCRs) are an important class of cell surface receptors that represent an ideal target for lymphoma therapeutics. GPCRs bind a wide range of ligands to relay extracellular signals through G protein-mediated signaling cascades. Each lymphoma subgroup expresses a unique pattern of GPCRs and efforts are underway to fully characterize these patterns at the genetic level. Aberrations such as overexpression, deletion and mutation of GPCRs have been characterized as having causative roles in lymphoma and such studies describing GPCRs in B cell lymphomas are summarized here.

Effect of mitochondrially targeted carboxy proxyl nitroxide on Akt-mediated survival in Daudi cells: Significance of a dual mode of action

Vicious cycles of mutations and reactive oxygen species (ROS) generation contribute to cancer progression. The use of antioxidants to inhibit ROS generation promotes cytostasis by affecting the mutation cycle and ROS-dependent survival signaling. However, cancer cells select mutations to elevate ROS albeit maintaining mitochondrial hyperpolarization (Δψm), even under hypoxia. From this perspective, the use of drugs that disrupt both ROS generation and Δψm is a viable anticancer strategy. Hence, we studied the effects of mitochondrially targeted carboxy proxyl nitroxide (Mito-CP) and a control ten carbon TPP moiety (Dec-TPP⁺) in the human Burkitt lymphoma cell line (Daudi) and normal peripheral blood mononuclear cells under hypoxia and normoxia. We found preferential localization, Δψm and adenosine triphosphate loss, and significant cytotoxicity by Mito-CP in Daudi cells alone. Interestingly, ROS levels were decreased and maintained in hypoxic and normoxic cancer cells, respectively, by Mito-CP but not Dec-TPP⁺, therefore preventing any adaptive signaling. Moreover, dual effects on mitochondrial bioenergetics and ROS by Mito-CP curtailed the cancer survival via Akt inhibition, AMPK-HIF-1α activation and promoted apoptosis via increased BCL2-associated X protein and poly (ADP-ribose) polymerase expression. This dual mode of action by Mito-CP provides a better explanation of the application of antioxidants with specific relevance to cancerous transformation and adaptations in the Daudi cell line.

Hypoxia and B cells

The ability of cells to sense and adapt to changes in oxygen is mediated by hypoxia-inducible factor (HIF). Immune cells function in physiologically complex and varying environments whereby oxygen, pH, nutrients, metabolites and cytokines are continuously fluctuating. HIF is well known to play an important role in coordinating the adaptation and function of both innate immune cells and T cells in these complex environments. This review summarises recent discoveries concerning how hypoxia and HIF control B cell behaviour, and regulate antibody quality and decisions concerning tolerance. Hypoxia and HIF activation may provide an important context; coordinating metabolism with variable demands for quiescence, rapid proliferation, and differentiation. Understanding when and how HIF is activated during B cell development and response is important as drugs targeting HIF could influence antibody responses, providing novel therapeutic opportunities for vaccine adjuvants and in treating autoimmunity.

Germinal Center Hypoxia Potentiates Immunoglobulin Class Switch Recombination

Germinal centers (GCs) are anatomic sites where B cells undergo secondary diversification to produce high-affinity, class-switched Abs. We hypothesized that proliferating B cells in GCs create a hypoxic microenvironment that governs their further differentiation. Using molecular markers, we found GCs to be predominantly hypoxic. Compared to normoxia (21% O₂), hypoxic culture conditions (1% O₂) in vitro accelerated class switching and plasma cell formation and enhanced expression of GL-7 on B and CD4⁺ T cells. Reversal of GC hypoxia in vivo by breathing 60% O₂ during immunization resulted in reduced frequencies of GC B cells, T follicular helper cells, and plasmacytes, as well as lower expression of ICOS on T follicular helper cells. Importantly, this reversal of GC hypoxia decreased Ag-specific serum IgG1 and reduced the frequency of IgG1⁺ B cells within the Ag-specific GC. Taken together, these observations reveal a critical role for hypoxia in GC B cell differentiation.

Identification and Validation of a Potential Marker of Tissue Quality Using Gene Expression Analysis of Human Colorectal Tissue

Correlative studies have identified numerous biomarkers that are individualizing therapy across many medical specialties, including oncology. Accurate interpretation of these studies requires the collection of tissue samples of sufficient quality. Tissue quality can be measured by changes in levels of gene expression and can be influenced by many factors including pre-analytical conditions, ischemic effects and the surgical collection procedure itself. However, as yet there are no reliable biomarkers of tissue quality at researchers' disposal. The aim of the current study was to identify genes with expression patterns that fluctuated reproducibly in response to typical post-surgical stress (ischemia) in order to identify a specific marker of tissue quality. All tissue samples were obtained from patients with primary colorectal carcinoma (CRC) (N = 40) either via colonoscopy prior to surgery, or by surgical resection. Surgically resected tissue samples were divided into three groups and subjected to cold ischemia for 10, 20 or 45 minutes. Normal colorectal tissue and CRC tissue was analyzed using microarray and quantitative real-time PCR (qPCR). Comparing changes in gene expression between pre- and post-surgical tissue using microarray analysis identified a list of potential tissue quality biomarkers and this list was validated using qPCR. Results revealed that post-operative ischemia significantly alters gene expression in normal and CRC tissue samples. Both microarray analysis and qPCR revealed regulator of G-protein signaling 1 (RGS1) as a potential marker of CRC tissue quality and eukaryotic translation elongation factor 1 alpha 1 (EEF1A1) as a potential reference gene of post-operative tissue quality. Larger studies with additional time points and endpoints will be needed to confirm these results.

Potential role of hypoxia in early stages of Hodgkin lymphoma pathogenesis

A unique feature of the germinal center B cell-derived Hodgkin and Reed/Sternberg cells of classical Hodgkin lymphoma is their lost B cell phenotype and the aberrant expression of factors of other hematopoietic cell types, including ID2 and NOTCH1. As cellular dedifferentiation and upregulation of ID2 and NOTCH1 are typical consequences of a hypoxic response, we wondered whether hypoxia may impose an HRS cell-like phenotype in B cells. Culturing normal B cells or cell lines of germinal center-type diffuse large B-cell lymphoma under hypoxic conditions caused partial downregulation of several B cell markers, ID2 upregulation, and increased NOTCH1 activity. The hypoxic cells acquired further features of Hodgkin and Reed/Sternberg cells, including increased JUN expression, and enhanced NFκB activity. The Hodgkin and Reed/Sternberg cell-expressed epigenetic regulators KDM4C and PCGF2, as well as the phosphatase DUSP1 were partially induced in hypoxic B cells. Inhibition of DUSP1 was toxic for classical Hodgkin lymphoma cell lines. Thus, hypoxia induces key Hodgkin and Reed/Sternberg cell characteristics in mature B cells. We speculate that hypoxic conditions in the germinal center may impose phenotypic changes in germinal center B cells, promoting their survival and initiating their differentiation towards a Hodgkin and Reed/Sternberg cell-like phenotype. These may then be stabilized by transforming events in the Hodgkin and Reed/Sternberg precursor cells.

Hypoxia inducible factor-1α: Its role in colorectal carcinogenesis and metastasis

Tumor growth creates a hypoxic microenvironment, which promotes angiogenesis and aggressive tumor growth and invasion. HIF1α is a central molecule involved in mediating these effects of hypoxia. In colorectal cancer (CRC), hypoxia stabilizes the transcription factor HIF1α, leading to the expression of genes that are involved in tumor vascularization, metastasis/migration, cell survival and chemo-resistance. Therefore, HIF1α is a rational target for the development of new therapeutics for CRC. This article reviews the central role of HIF1α in CRC angiogenesis, metastasis, and progression as well as the strategies to target HIF1α stabilization.

Effect of acute hypoxia on CXCR4 gene expression in C57BL/6 mouse bone marrow-derived mesenchymal stem cells

BACKGROUND

One of the most important stimuli in stem cell biology is oxygen. Chemokine receptor 4 (CXCR4) plays a crucial role in the migration and homing of stem cells. In this study, mesenchymal stem cells (MSCs) were exposed to 1% oxygen to investigate the effect of acute hypoxia on CXCR4 gene expression.

MATERIALS AND METHODS

MSCs were isolated from C57BL/6 mouse bone marrow and were identified and expanded in normoxic culture. Cells were incubated at 37°C under 1% hypoxic conditions for periods of 4, 8, 16, 24, and 48 h. After hypoxia preconditioning, the cells were placed in normoxic condition for 8 h to achieve cellular hypoxia-reoxygenation. To assess the level of CXCR4 gene expression, real-time quantitative reverse transcription-polymerase chain reaction was carried out for each group.

RESULTS

Data from statistical analysis illustrated that exposure of MSCs to acute hypoxic condition down-regulates CXCR4 expression with the maximum under-expression observed in 4 h (0.91 ± 0.107) and 8 h (50 ± 2.98) groups. Moreover, the relative gene expression of CXCR4 was decreased after hypoxia-reoxygenation by more than 80% in 4 h (0.136 ± 0.018) and 24 h (12.77 ± 0.707) groups.

CONCLUSION

The results suggest that CXCR4 expression in MSCs decreases upon acute hypoxic stress. Furthermore, hypoxia-reoxygenated MSCs showed decreased expression of CXCR4, compared to cells subjected to acute hypoxia. This difference could have resulted from the cells being compatible with low oxygen metabolism. In summary, before the therapeutic application of MSCs, it should be regarded as a necessity to optimize the oxygen concentration in these cells, as it is a critical factor in modulating CXCR4 expression.

Development and validation of a gene profile predicting benefit of postmastectomy radiotherapy in patients with high-risk breast cancer: a study of gene expression in the DBCG82bc cohort

PURPOSE

To identify genes predicting benefit of radiotherapy in patients with high-risk breast cancer treated with systemic therapy and randomized to receive or not receive postmastectomy radiotherapy (PMRT).

EXPERIMENTAL DESIGN

The study was based on the Danish Breast Cancer Cooperative Group (DBCG82bc) cohort. Gene-expression analysis was performed in a training set of frozen tumor tissue from 191 patients. Genes were identified through the Lasso method with the endpoint being locoregional recurrence (LRR). A weighted gene-expression index (DBCG-RT profile) was calculated and transferred to quantitative real-time PCR (qRT-PCR) in corresponding formalin-fixed, paraffin-embedded (FFPE) samples, before validation in FFPE from 112 additional patients.

RESULTS

Seven genes were identified, and the derived DBCG-RT profile divided the 191 patients into "high LRR risk" and "low LRR risk" groups. PMRT significantly reduced risk of LRR in "high LRR risk" patients, whereas "low LRR risk" patients showed no additional reduction in LRR rate. Technical transfer of the DBCG-RT profile to FFPE/qRT-PCR was successful, and the predictive impact was successfully validated in another 112 patients.

CONCLUSIONS

A DBCG-RT gene profile was identified and validated, identifying patients with very low risk of LRR and no benefit from PMRT. The profile may provide a method to individualize treatment with PMRT.

Optimization of the therapeutic efficacy of human umbilical cord blood-mesenchymal stromal cells in an NSG mouse xenograft model of graft-versus-host disease

BACKGROUND AIMS

Although in vitro studies have demonstrated the immunosuppressive capacity of mesenchymal stromal cells (MSCs), most in vivo studies on graft-versus-host disease (GVHD) have focused on prevention, and the therapeutic effect of MSCs is controversial. Moreover, optimal time intervals for infusing MSCs have not been established.

METHODS

We attempted to evaluate whether human umbilical cord blood-MSCs (hUCB-MSCs) could either prevent or treat GVHD in an NSG mouse xenograft model by injection of MSCs before or after in vivo clearance. Mice were infused with either a single dose or multiple doses of 5 × 10(5) hUCB-MSCs (3- or 7-day intervals) before or after GVHD onset.

RESULTS

Before onset, hUCB-MSCs significantly improved the survival rate only when repeatedly injected at 3-day intervals. In contrast, single or repeated injections after GVHD onset significantly increased the survival rate and effectively attenuated tissue damage and inflammation. Furthermore, the levels of prostaglandin E2 and transforming growth factor-β1 increased significantly, whereas the level of interferon-γ decreased significantly in all MSC treatment groups.

CONCLUSIONS

These data establish the optimal time intervals for preventing GVHD and show that hUCB-MSCs effectively attenuated symptoms and improved survival rate when administered after the onset of GVDH.

The roles of hypoxia-inducible factors in regulating neural stem cells migration to glioma stem cells and determinating their fates

The mortality of patients with malignant gliomas remains high despite the advancement in multi-modal therapy including surgery, radio- and chemotherapy. Glioma stem cells (GSCs), sharing some characteristics with normal neural stem cells (NSCs), contribute to the cellular origin for primary gliomas and the recurrence of malignant gliomas after current conventional therapy. Accordingly, targeting GSCs proves to be a promising avenue of therapeutic intervention. The specific tropism of NSCs to GSCs provides a novel platform for targeted delivery of therapeutic agents. Tropism and mobilization of NSCs are enhanced by hypoxia through upregulating chemotactic cytokines and activating several signaling pathways. Moreover, hypoxia-inducible factors (HIFs) produced under hypoxic microenvironment of the stem cell niche play critical roles in the growth and stemness phenotypes regulation of both NSCs and GSCs. However, the definite cellular and molecular mechanisms of HIFs involvement in the process remain obscure. In this review, we focus on the pivotal roles of HIFs in migration of NSCs to GSCs and potential roles of HIFs in dictating the fates of migrated NSCs and targeted GSCs.

When oxygen runs short: the microenvironment drives host-pathogen interactions

Pathogens that colonize or infect the human body have to face varying oxygen concentrations within different organs. Inflammation itself promotes oxygen consumption within affected tissues and creates a low oxygen environment. As a consequence, pathogens and the host immune system have to adapt to rapid changes in oxygen availability. Here we summarize recent findings on the adaptation of pathogens, host defense mechanisms and treatment strategies against intracellular pathogens in a low oxygen environment.

The three-layer concentric model of glioblastoma: cancer stem cells, microenvironmental regulation, and therapeutic implications

Tumors arising in the central nervous system are thought to originate from a sub-population of cells named cancer stem cells (CSCs) or tumor initiating cells (TICs) that possess an immature phenotype, combined with self-renewal and chemotherapy resistance capacity. Moreover, in the last years, these cells have been identified in particular brain tumor niches fundamental for supporting their characteristics. In this paper, we report studies from many authors demonstrating that hypoxia or the so called “hypoxic niche” plays a crucial role in controlling CSC molecular and phenotypic profile. We recently investigated the relationship existing between Glioblastoma (GBM) stem cells and their niche, defining the theory of three-concentric layers model for GBM mass. According to this model, GBM stem cells reside preferentially within the hypoxic core of the tumour mass, while more differentiated cells are mainly localized along the peripheral and vascularized part of the tumour. This GBM model provides explanation of the effects mediated by the tumour microenvironment on the phenotypic and molecular regulation of GBM stem cells, describing their spatial distribution in the tumor bulk. Moreover, we discuss the possible clinical implications of the creation of this model for future GBM patient management and novel therapeutic strategies development.

Recruitment of regulatory T cells is correlated with hypoxia-induced CXCR4 expression, and is associated with poor prognosis in basal-like breast cancers

Introduction

Basal-like breast cancers behave more aggressively despite the presence of a dense lymphoid infiltrate. We hypothesised that immune suppression in this subtype may be due to T regulatory cells (Treg) recruitment driven by hypoxia-induced up-regulation of CXCR4 in Treg.

Methods

Immunoperoxidase staining for FOXP3 and CXCL12 was performed on tissue microarrays from 491 breast cancers. The hypoxia-associated marker carbonic anhydrase IX (CA9) and double FOXP3/CXCR4 staining were performed on sections from a subset of these cancers including 10 basal-like and 11 luminal cancers matched for tumour grade.

Results

High Treg infiltration correlated with tumour CXCL12 positivity (OR 1.89, 95% CI 1.22 to 2.94, P = 0.004) and basal phenotype (OR 3.14, 95% CI 1.08 to 9.17, P = 0.004) in univariate and multivariate analyses. CXCL12 positivity correlated with improved survival (P = 0.005), whereas high Treg correlated with shorter survival for all breast cancers (P = 0.001), luminal cancers (P < 0.001) and basal-like cancers (P = 0.040) that were confirmed in a multivariate analysis (OR 1.61, 95% CI 1.02 to 2.53, P = 0.042). In patients treated with hormone therapy, high Treg were associated with a shorter survival in a multivariate analysis (OR 1.78, 95% CI 1.01 to 3.15, P = 0.040). There was a tendency for luminal cancers to show CXCL12 expression (102/138, 74%) compared to basal-like cancers (16/27, 59%), which verged on statistical significance (P = 0.050). Up-regulation of CXCR4 in Treg correlated with the basal-like phenotype (P = 0.029) and tumour hypoxia, as indicated by CA9 expression (P = 0.049).

Conclusions

Our data show that in the setting of hypoxia and CXCR4 up-regulation in Treg, CXCL12 expression may have the negative consequence of enhancing Treg recruitment and suppressing the anti-tumour immune response.

Inherited Syndromes Predisposing to Inflammation and GI Cancer

Cancers arising within the gastrointestinal (GI) tract are commonly associated with an immune component at their inception and later in their maintenance. While many of the immune factors and immune cell types surrounding these lesions have been highlighted, the underlying pre-dispositions in immunesupported carcinogenesis are not well characterised. Inherited Mendelian GI disorders such as polyposis syndromes, while classically due to germline mutations in non-immune genes, commonly demonstrate alterations in key immune and inflammatory genes. In some cases immune based therapies have been shown to provide at least some benefit in animal models of these syndromes. The advent of genome wide association studies has begun to powerfully examine the genetic nature of complex non-Mendelian GI diseases highlighting polymorphisms within immune related genes and their potential to provide the niche in which GI cancers may originate. Here in the role in which Mendelian and non-Mendelian genetics of immune related factors supporting GI malignancy will be presented and discussed.

Variations in Gnai2 and Rgs1 expression affect chemokine receptor signaling and the organization of secondary lymphoid organs

Ligand bound chemoattractant receptors activate the heterotrimeric G protein Gi to stimulate downstream signaling pathways to properly position lymphocytes in lymphoid organs. Here we show how variations the expression of a chemokine receptor and in two components in the signaling pathway, Gα_i2 and RGS1, affects the output fidelity of the signaling pathway. Examination of B cells from mice with varying numbers of intact alleles of Ccr7, Rgs1, Gnai2, and Gnai3 provided the basis for these results. Loss of a single allele of either Gnai2 or Rgs1 affected CCL19 triggered chemotaxis, while loss of a single allele of Ccr7, which encodes the cognate CCL19 receptor, had little effect. Emphasizing the importance of Gnai2, B cells lacking Gnai3 expression responded to chemokines better than did wild type B cells. At an organismal level, variations in Rgs1 and Gnai2 expression affected marginal zone B cell development, splenic architecture, lymphoid follicle size, and germinal center morphology. Gnai2 expression was also needed for the proper alignment of MOMA-1⁺ macrophages and MAdCAM-1⁺ endothelial cells along marginal zone sinuses in the spleen. These data indicate that chemoattractant receptors, heterotrimeric G-proteins, and RGS protein expression levels have a complex inter-relationship that affects the responses to chemoattractant exposure.

CXCL12 (SDF-1)/CXCR4 pathway in cancer

Chemokines, small proinflammatory chemoattractant cytokines that bind to specific G-protein-coupled seven-span transmembrane receptors, are major regulators of cell trafficking and adhesion. The chemokine CXCL12 [stromal cell-derived factor-1 (SDF-1)] binds primarily to CXC receptor 4 (CXCR4; CD184). The binding of CXCL12 to CXCR4 induces intracellular signaling through several divergent pathways initiating signals related to chemotaxis, cell survival and/or proliferation, increase in intracellular calcium, and gene transcription. CXCR4 is expressed on multiple cell types including lymphocytes, hematopoietic stem cells, endothelial and epithelial cells, and cancer cells. The CXCL12/CXCR4 axis is involved in tumor progression, angiogenesis, metastasis, and survival. This pathway is a target for therapeutics that can block the CXCL12/CXCR4 interaction or inhibit downstream intracellular signaling.

Hypoxic tumors and their effect on immune cells and cancer therapy

The abnormal decrease or the lack of oxygen supply to cells and tissues is called hypoxia. This condition is commonly seen in various diseases such as rheumatoid arthritis and atherosclerosis, also in solid cancers. Pre-clinical and clinical studies have shown that hypoxic cancers are extremely aggressive, resistant to standard therapies (chemotherapy and radiotherapy), and thus very difficult to eradicate. Hypoxia affects both the tumor and the immune cells via various pathways. This review summarizes the most common effects of hypoxia on immune cells that play a key role in the anti-tumor response, the limitation of current therapies, and the potential solutions that were developed for hypoxic malignancies.

X-box binding protein 1 contributes to induction of the Kaposi's sarcoma-associated herpesvirus lytic cycle under hypoxic conditions

Kaposi's sarcoma-associated herpesvirus (KSHV), like other herpesviruses, has two stages to its life cycle: latency and lytic replication. KSHV is required for development of Kaposi's sarcoma, a tumor of endothelial origin, and is associated with the B-cell tumor primary effusion lymphoma (PEL) and the plasmablastic variant of multicentric Castleman's disease, all of which are characterized by predominantly latent KSHV infection. Recently, we and others have shown that the activated form of transcription factor X-box binding protein 1 (XBP-1) is a physiological trigger of KSHV lytic reactivation in PEL. Here, we show that XBP-1s transactivates the ORF50/RTA promoter though an ACGT core containing the XBP-1 response element, an element previously identified as a weakly active hypoxia response element (HRE). Hypoxia induces the KSHV lytic cycle, and active HREs that respond to hypoxia-inducible factor 1alpha are present in the ORF50/RTA promoter. Hypoxia also induces active XBP-1s, and here, we show that both transcription factors contribute to the induction of RTA expression, leading to the production of infectious KSHV under hypoxic conditions.

Chemokine signaling in cancer: one hump or two?

Chemokines and their receptors play essential roles in the development and function of multiple tissues. Chemokine expression, particularly CXCL12 and its receptor CXCR4, has prognostic significance in several cancers apparently due to chemokine mediated growth and metastatic spread. These observations provide the rationale for pursuing CXCR4 inhibition for cancer chemotherapy. However, the multiple homeostatic functions of CXCR4 may preclude global inhibition as a therapeutic strategy. Here I review CXCR4 signaling and how it might differ in normal and transformed cells with special emphasis on the role that altered CXCR4 counter-regulation might play in tumor biology. I propose that CXCR4 mediates unique signals in cancer cells as a consequence of abnormal counter-regulation and that this results in novel biological responses. The importance of testing this hypothesis lies in the possibility that targeting abnormal CXCR4 signaling might provide an anti-tumor effect without disturbing normal CXCR4 functions.

CXCR4 expression and biologic activity in acute myeloid leukemia are dependent on oxygen partial pressure

The CXCR4/SDF-1 axis has been studied extensively because of its role in development and hematopoiesis. In acute myeloid leukemia (AML), elevated expression of CXCR4 has been shown to correlate with shortened survival. Hy-poxia increases CXCR4 in several tumor models, but the impact of reduced O(2) partial pressure (pO(2)) on expression and biologic function of CXCR4 in AML is unknown. We determined pO(2) in bone marrows of AML patients as 6.1% (+/-1.7%). At this pO(2), CXCR4 surface and total expression were up-regulated within 10 hours in leukemic cell lines and patient samples as shown by Western blotting, fluorescence-activated cell sorting, and microscopy. Interestingly, hypoxic cells failed to internalize CXCR4 in response to SDF-1, and upon reoxygenation at 21% O(2), surface and total expression of CXCR4 rapidly decreased independent of adenosine triphosphate or proteasome activity. Instead, increased pO(2) led to alteration of lipid rafts by cholesterol depletion and structural changes and was associated with increased shedding of CXCR4-positive microparticles, suggesting a novel mechanism of CXCR4 regulation. Given the importance of CXCR4 in cell signaling, survival, and adhesion in leukemia, the results suggest that pO(2) be considered a critical variable in conducting and interpreting studies of CXCR4 expression and regulation in leukemias.

Hypoxia increases breast cancer cell-induced lymphatic endothelial cell migration

Because tumors are characterized by hypoxic environments, we used a novel in vitro noninvasive magnetic resonance imaging assay to examine the influence of invasive MDA-MB-231 breast cancer cells on the invasion and migration of human dermal lymphatic microvascular endothelial cells (HMVEC-dLy) under normoxic and hypoxic conditions. Nonmalignant immortalized MCF-12A human mammary epithelial cells instead of cancer cells or chambers with HMVEC-dLy alone were used as controls for comparison. HMVEC-dLy cells were labeled with a T(2) contrast agent (Feridex), and their invasion and migration through extracellular matrix under normoxic and hypoxic conditions were monitored using magnetic resonance imaging. A significant increase in the invasion and migration of HMVEC-dLy cells was detected in the presence of cancer cells, which further increased significantly under hypoxic conditions. HMVEC-dLy cells formed interconnecting strands extending toward the cancer cells under normoxic but not under hypoxic conditions. Following reoxygenation, these interconnecting strands, extending from HMVEC-dLy cells toward the cancer cells, were observed. These data demonstrate the importance of hypoxia in lymphatic endothelial cell invasion and migration through extracellular matrix in the presence of cancer cells.

The Italian Network for Tumor Biotherapy (NIBIT): getting together to push the field forward

As for a consolidated tradition, the 5^th annual meeting of the Italian Network for Cancer Biotherapy took place in the Certosa of Pontignano, a Tuscan monastery, on September 20–22, 2007. The congress gathered more than 40 Italian leading groups representing academia, biotechnology and pharmaceutical industry. Aim of the meeting was to share new advances in cancer bio-immunotherapy and to promote their swift translation from pre-clinical research to clinical applications. Several topics were covered including: a) molecular and cellular mechanisms of tumor escape; b) therapeutic antibodies and recombinant constructs; c) clinical trials up-date and new programs; d) National Cooperative Networks and their potential interactions; e) old and new times in cancer immunology, an "amarcord". Here, we report the main issues discussed during the meeting.