Effects of recombinant erythropoietin on breast cancer-initiating cells

Inhibition of Notch enhances efficacy of immune checkpoint blockade in triple-negative breast cancer

Aberrant Notch, which is a defining feature of triple-negative breast cancer (TNBC) cells, regulates intercellular communication in the tumor immune microenvironment (TIME). This includes tumor-associated macrophage (TAM) recruitment through Notch-dependent cytokine secretion, contributing to an immunosuppressive TIME. Despite the low response rate of TNBC to immune checkpoint blockade (ICB), here, we report that inhibition of Notch-driven cytokine-mediated programs reduces TAMs and induces responsiveness to sequentially delivered ICB. This is characterized by the emergence of GrB+ cytotoxic T lymphocytes (CTLs) in the primary tumor. A more impressive effect of sequential treatment is observed in the lung where TAM depletion and increased CTLs are accompanied by near-complete abolition of metastases. This is due to (i) therapeutic reduction in Notch-dependent, prometastatic circulating factors released by the primary tumor, and (ii) elevated PD ligand 1 (PD-L1) in lung metastases, rendering them profoundly sensitive to ICB. These findings highlight the potential of combination cytokine inhibition and ICB as an immunotherapeutic strategy in TNBC.

Novel Anti-Cancer Stem Cell Compounds: A Comprehensive Review

Cancer stem cells (CSCs) possess a significant ability to renew themselves, which gives them a strong capacity to form tumors and expand to encompass additional body areas. In addition, they possess inherent resistance to chemotherapy and radiation therapies used to treat many forms of cancer. Scientists have focused on investigating the signaling pathways that are highly linked to the ability of CSCs to renew themselves and maintain their stem cell properties. The pathways encompassed are Notch, Wnt/β-catenin, hedgehog, STAT3, NF-κB, PI-3K/Akt/mTOR, sirtuin, ALDH, MDM2, and ROS. Recent studies indicate that directing efforts towards CSC cells is essential in eradicating the overall cancer cell population and reducing the likelihood of tumor metastasis. As our comprehension of the mechanisms that stimulate CSC activity, growth, and resistance to chemotherapy advances, the discovery of therapeutic drugs specifically targeting CSCs, such as small-molecule compounds, holds the potential to revolutionize cancer therapy. This review article examines and analyzes the novel anti-CSC compounds that have demonstrated effective and selective targeting of pathways associated with the renewal and stemness of CSCs. We also discussed their special drug metabolism and absorption mechanisms. CSCs have been the subject of much study in cancer biology. As a possible treatment for malignancies, small-molecule drugs that target CSCs are gaining more and more attention. This article provides a comprehensive review of the current state of key small-molecule compounds, summarizes their recent developments, and anticipates the future discovery of even more potent and targeted compounds, opening up new avenues for cancer treatment.

Protective potential of sulfated polysaccharides from tropical seaweeds against alkylating- and oxidizing-induced genotoxicity

Sulfated polysaccharides (SPs) from seaweeds are potential bioactive natural compounds, but their DNA protective activity is poorly explored. This article aimed to evaluate the genotoxic/antigenotoxic potentials of a sulfated heterofucan from brown seaweed Spatoglossum schröederi (Fucan A - FA) and a sulfated galactan from green seaweed Codium isthomocladum (3G4S) using in vitro Comet assay (alkaline and oxidative versions) with HepG2 cells. The antioxidant activity of these SPs was evaluated by total antioxidant capacity, radical scavenging, metal chelating, and antioxidant enzyme activity assays. Both SPs were not genotoxic. FA and 3G4S displayed strong antigenotoxic activity against oxidizing chemical (H₂O₂) but not against alkylating chemical (MMS). The DNA damage reduction after a pre-treatment of 72 h with these SPs was 81.42% to FA and 81.38% to 3G4S. In simultaneous exposure to FA or 3G4S with H₂O₂, HepG2 cells presented 48.04% and 55.41% of DNA damage reduction compared with the control, respectively. The antigenotoxicity of these SPs relates to direct antioxidant activity by blockage of the initiation step of the oxidative chain reaction. Therefore, we conclude that FA and 3G4S could be explored as functional natural compounds with antigenotoxic activity due to their great protection against oxidative DNA damage.

Endocrine regulation of cancer stem cell compartments in breast tumors

Cancer cells within breast tumors exist within a hierarchy in which only a small and rare subset of cells is able to regenerate growths with the heterogeneity of the original tumor. These highly malignant cancer cells, which behave like stem cells for new cancers and are called "cancer stem cells" or CSCs, have also been shown to possess increased resistance to therapeutics, and represent the root cause underlying therapy failures, persistence of residual disease, and relapse. As >90% of cancer deaths are due to refractory tumors, identification of critical molecular drivers of the CSC-state would reveal vulnerabilities that can be leveraged in designing therapeutics that eradicate advanced disease and improve patient survival outcomes. An expanding and complex body of work has now described the exquisite susceptibility of CSC pools to the regulatory influences of local and systemic hormones. Indeed, breast CSCs express a plethora of hormonal receptors, which funnel hormonal influences over every aspect of breast neoplasia - be it tumor onset, growth, survival, invasion, metastasis, or therapy resistance - via directly impacting CSC behavior. This article is intended to shed light on this active area of investigation by attempting to provide a systematic and comprehensive overview of the available evidence directly linking hormones to breast CSC biology.

Notch Signaling in Vascular Endothelial Cells, Angiogenesis, and Tumor Progression: An Update and Prospective

The Notch signaling pathway plays an essential role in a wide variety of biological processes including cell fate determination of vascular endothelial cells and the regulation of arterial differentiation and angiogenesis. The Notch pathway is also an essential regulator of tumor growth and survival by functioning as either an oncogene or a tumor suppressor in a context-dependent manner. Crosstalk between the Notch and other signaling pathways is also pivotal in tumor progression by promoting cancer cell growth, migration, invasion, metastasis, tumor angiogenesis, and the expansion of cancer stem cells (CSCs). In this review, we provide an overview and update of Notch signaling in endothelial cell fate determination and functioning, angiogenesis, and tumor progression, particularly in the development of CSCs and therapeutic resistance. We further summarize recent studies on how endothelial signaling crosstalk with the Notch pathway contributes to tumor angiogenesis and the development of CSCs, thereby providing insights into vascular biology within the tumor microenvironment and tumor progression.

Unlocking the Secrets of Cancer Stem Cells with γ-Secretase Inhibitors: A Novel Anticancer Strategy

The dysregulation of Notch signaling is associated with a wide variety of different human cancers. Notch signaling activation mostly relies on the activity of the γ-secretase enzyme that cleaves the Notch receptors and releases the active intracellular domain. It is well-documented that γ-secretase inhibitors (GSIs) block the Notch activity, mainly by inhibiting the oncogenic activity of this pathway. To date, several GSIs have been introduced clinically for the treatment of various diseases, such as Alzheimer's disease and various cancers, and their impacts on Notch inhibition have been found to be promising. Therefore, GSIs are of great interest for cancer therapy. The objective of this review is to provide a systematic review of in vitro and in vivo studies for investigating the effect of GSIs on various cancer stem cells (CSCs), mainly by modulation of the Notch signaling pathway. Various scholarly electronic databases were searched and relevant studies published in the English language were collected up to February 2020. Herein, we conclude that GSIs can be potential candidates for CSC-targeting therapy. The outcome of our study also indicates that GSIs in combination with anticancer drugs have a greater inhibitory effect on CSCs.

Exploring Dysregulated Signaling Pathways in Cancer

Cancer cell biology takes advantage of identifying diverse cellular signaling pathways that are disrupted in cancer. Signaling pathways are an important means of communication from the exterior of cell to intracellular mediators, as well as intracellular interactions that govern diverse cellular processes. Oncogenic mutations or abnormal expression of signaling components disrupt the regulatory networks that govern cell function, thus enabling tumor cells to undergo dysregulated mitogenesis, to resist apoptosis, and to promote invasion to neighboring tissues. Unraveling of dysregulated signaling pathways may advance the understanding of tumor pathophysiology and lead to the improvement of targeted tumor therapy. In this review article, different signaling pathways and how their dysregulation contributes to the development of tumors have been discussed.

Cancer Stem Cells, Quo Vadis? The Notch Signaling Pathway in Tumor Initiation and Progression

The Notch signaling pathway regulates cell proliferation, cytodifferentiation and cell fate decisions in both embryonic and adult life. Several aspects of stem cell maintenance are dependent from the functionality and fine tuning of the Notch pathway. In cancer, Notch is specifically involved in preserving self-renewal and amplification of cancer stem cells, supporting the formation, spread and recurrence of the tumor. As the function of Notch signaling is context dependent, we here provide an overview of its activity in a variety of tumors, focusing mostly on its role in the maintenance of the undifferentiated subset of cancer cells. Finally, we analyze the potential of molecules of the Notch pathway as diagnostic and therapeutic tools against the various cancers.

Serum erythropoietin levels, breast cancer and breast cancer-initiating cells

Background

Cancer is frequently associated with tumor-related anemia, and many chemotherapeutic agents impair hematopoiesis, leading to impaired quality of life for affected patients. The use of erythropoiesis-stimulating agents has come under scrutiny after prospective clinical trials using recombinant erythropoietin to correct anemia reported increased incidence of thromboembolic events and cancer-related deaths. Furthermore, previous preclinical reports indicated expansion of the pool of breast cancer-initiating cells when erythropoietin was combined with ionizing radiation.

Methods

Using four established breast cancer cell lines, we test the effects of recombinant human erythropoietin and the number of breast cancer-initiating cells in vitro and in vivo and study if recombinant human erythropoietin promotes the phenotype conversion of non-tumorigenic breast cancer cells into breast cancer-initiating cells. In a prospective study, we evaluate whether elevated endogenous serum erythropoietin levels correlate with increased numbers of tumor-initiating cells in a cohort of breast cancer patients who were scheduled to undergo radiation treatment.

Results

Our results indicate that recombinant erythropoietin increased the number of tumor-initiating cells in established breast cancer lines in vitro. Irradiation of breast cancer xenografts caused a phenotype conversion of non-stem breast cancer cells into induced breast cancer-initiating cells. This effect coincided with re-expression of the pluripotency factors c-Myc, Sox2, and Oct4 and was enhanced by recombinant erythropoietin. Hemoglobin levels were inversely correlated with serum erythropoietin levels, and the latter were correlated with disease stage. However, tumor sections revealed a negative correlation between serum erythropoietin levels and the number of ALDH1A3-positive cells, a marker for breast cancer-initiating cells.

Conclusions

We conclude that physiologically slow-rising serum erythropoietin levels in response to tumor-related or chemotherapy-induced anemia, as opposed to large doses of recombinant erythropoietin, do not increase the pool of breast cancer-initiating cells.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1100-9) contains supplementary material, which is available to authorized users.

Recombinant human erythropoietin stimulates melanoma tumor growth through activation of initiation factor eIF4E

Recombinant human erythropoietin (EPO) is standard treatment for anemia in cancer patients. Recent clinical trials suggest that EPO may accelerate tumor progression and increase mortality. However, the evidence supporting a growth-promoting effect of EPO has remained controversial. Employing an in vivo model of B16 murine melanoma, we observed that administration of EPO to tumor bearing C57BL/6 mice resulted in pronounced acceleration of melanoma growth. Our in vitro studies demonstrate that B16 murine melanoma cells express EPOR, both at the protein and mRNA levels. Interestingly, expression of EPOR was retained in the established tumors. EPO stimulation of B16 cells enhanced proliferation and protein synthesis rates, and correlated with activation of the receptor associated Janus kinase 2 (Jak2) as well as phosphorylation of extracellular signal–regulated kinase (Erk) 1/2 and Akt kinases. Treatment with EPO and Jak-2 antagonists significantly inhibited EPO-mediated B16 cell proliferation. Moreover, EPO dose-dependently induced the phosphorylation and activation of the translation initiation factor eIF4E as well as the phosphorylation of its repressor, the eIF4E binding protein 4E-BP1. Finally, using eIF4E small interfering RNA (siRNA), we observed that EPO-mediated stimulation of B16 cell proliferation is eIF4E-dependent. Our results indicate that EPO exerts a powerful stimulatory effect on cell proliferation and de novo protein synthesis in melanoma cells through activation of the initiation factor eIF4E.

NOTCH1 is a poor prognostic factor for breast cancer and is associated with breast cancer stem cells

Recently, the human gene NOTCH1 has been found to be implicated in cancer cell metastasis and the maintenance of cancer stem cells. However, for breast cancer in particular, an association between NOTCH1 levels and metastasis has not been determined. In this study, we investigated the expression status and correlation of NOTCH1 with clinically important factors related to metastasis and the cancer stem cell marker ALDH1. NOTCH1 and ALDH1 levels in 115 tumor tissues from primary lesions were determined by immunohistochemical staining. Most tissues were stained positive for both NOTCH1 and ALDH1, and NOTCH1 positivity was significantly associated with ALDH1 levels. NOTCH1 levels were significantly associated with TNM stage, metastasis, and triple-negative breast cancer. Moreover, both univariate and multivariate regression analyses revealed that basal-like features and NOTCH1 positivity were associated with disease-free survival as independent predictors. These analyses indicated that breast cancer patients testing positive for NOTCH1 had shorter disease-free survival. Our findings suggest that NOTCH1 may be involved in metastasis and is closely correlated with breast cancer stem cells.

Combination therapy of RY10-4 with the γ-secretase inhibitor DAPT shows promise in treating HER2-amplified breast cancer

RY10-4, a novel protoapigenone analog, shows potent cytotoxicity against human breast cancer cells. However, breast cancer cell lines overexpressing human epidermal growth factor receptor 2 (HER2), SKBR3 and BT474, showed less sensitivity to RY10-4 when compared to breast cancer cells lines expressing lower levels of HER2, such as MDA-MB-231 and MCF-7 cells. This was associated with aberrant hyperactivity in Notch signaling in cells treated with RY10-4, since treatment with RY10-4 causes an increase in Notch activity by 2-to3.5-fold in SKBR3 and BT474 cell lines. The increase in activity was abrogated with a γ-secretase inhibitor, DAPT, or with Notch1 small-interfering RNA (si-Notch1). Cell proliferation was inhibited more effectively by RY10-4 plus DAPT or si-Notch1 than either agent alone. RY10-4 plus DAPT increases apoptosis in both HER2-overexpressing cell lines by two-fold compared to RY10-4 alone, while DAPT alone has no significant effects on apoptosis. In addition, we previously found RY10-4 could inhibit tumor growth through the PI3K/AKT pathway. Here we report that the combination of RY10-4 and DAPT exhibit additive suppression on AKT phosphorylation, contributing to the anti-cancer effects. In an animal model, this combination therapy inhibits the growth of SKBR3 tumor xenografts in nude mice to a greater extent than treatment with either reagent alone. These results indicate that the aberrant activation of Notch signaling impedes the inhibitory effect of RY10-4 on HER2-amplified cell proliferation. Furthermore, these adverse effects can be prevented by treatment combining RY10-4 with a Notch pathway inhibitor.

Targeting Notch degradation system provides promise for breast cancer therapeutics

Notch receptor signaling pathways play an important role, not only in normal breast development but also in breast cancer development and progression. As a group of ligand-induced proteins, different subtypes of mammalian Notch (Notch1-4) are sensitive to subtle changes in protein levels. Thus, a clear understanding of mechanisms of Notch protein turnover is essential for understanding normal and pathological mechanisms of Notch functions. It has been suggested that there is a close relationship between the carcinogenesis and the dysregulation of Notch degradation. However, this relationship remains mostly undefined in the context of breast cancer, as protein degradation is mediated by numerous signaling pathways as well as certain molecule modulators (activators/inhibitors). In this review, we summarize the published data regarding the regulation of Notch family member degradation in breast cancer, while emphasizing areas that are likely to provide new therapeutic modalities for mechanism-based anti-cancer drugs.

Association between FBP1 and hypoxia-related gene expression in clear cell renal cell carcinoma

Fructose-1,6-bisphosphatase 1 (FBP1) is a rate-limiting enzyme in gluconeogenesis. Recently, the catalytic activity-independent function of FBP1, hypoxia-induced factor (HIF) repression in the nucleus, was identified. The aim of the present study was to investigate the association between FBP1 and hypoxia-related gene expression in clear cell renal cell carcinoma (ccRCC). The protein expression levels of FBP1, HIF-1α, HIF-2α, erythropoietin (EPO) and carbonic anhydrase IX (CA9) were assessed by immunohistochemical staining of ccRCC paraffin blocks from 123 patients using the tissue microarray technique. The expression level of FBP1 was then correlated with various clinicopathological factors, and the protein expression levels of HIF-1α, HIF-2α, EPO and CA9. Clinicopathological factors, including age, gender, T stage and Fuhrman grade, were not significantly different between patients with low and high FBP1 expression in ccRCC (P>0.05). FBP1 protein expression level was significantly correlated with the expression levels of HIF-1α (P=0.005) and EPO (P=0.010), but not significantly correlated with the expression levels of HIF-2α (P=0.123) and CA9 (P=0.513) in ccRCC tissues. The current findings confirm the association between FBP1 and hypoxia-related gene expression, and may facilitate understanding of the mechanisms of ccRCC tumorigenesis.

Targeting the Notch signaling pathway in cancer therapeutics

Despite advances in surgery, imaging, chemotherapy, and radiotherapy, the poor overall cancer-related death rate remains unacceptable. Novel therapeutic strategies are desperately needed. Nowadays, targeted therapy has become the most promising therapy and a welcome asset to the cancer therapeutic arena. There is a large body of evidence demonstrating that the Notch signaling pathway is critically involved in the pathobiology of a variety of malignancies. In this review, we provide an overview of emerging data, highlight the mechanism of the Notch signaling pathway in the development of a wide range of cancers, and summarize recent progress in therapeutic targeting of the Notch signaling pathway.

Erythropoietin promotes breast tumorigenesis through tumor-initiating cell self-renewal

Erythropoietin (EPO) is a hormone that induces red blood cell production. In its recombinant form, EPO is the one of most prescribed drugs to treat anemia, including that arising in cancer patients. In randomized trials, EPO administration to cancer patients has been associated with decreased survival. Here, we investigated the impact of EPO modulation on tumorigenesis. Using genetically engineered mouse models of breast cancer, we found that EPO promoted tumorigenesis by activating JAK/STAT signaling in breast tumor-initiating cells (TICs) and promoted TIC self renewal. We determined that EPO was induced by hypoxia in breast cancer cell lines, but not in human mammary epithelial cells. Additionally, we demonstrated that high levels of endogenous EPO gene expression correlated with shortened relapse-free survival and that pharmacologic JAK2 inhibition was synergistic with chemotherapy for tumor growth inhibition in vivo. These data define an active role for endogenous EPO in breast cancer progression and breast TIC self-renewal and reveal a potential application of EPO pathway inhibition in breast cancer therapy.

Regulation of angiogenesis via Notch signaling in breast cancer and cancer stem cells

Breast cancer angiogenesis is elicited and regulated by a number of factors including the Notch signaling. Notch receptors and ligands are expressed in breast cancer cells as well as in the stromal compartment and have been implicated in carcinogenesis. Signals exchanged between neighboring cells through the Notch pathway can amplify and consolidate molecular differences, which eventually dictate cell fates. Notch signaling and its crosstalk with many signaling pathways play an important role in breast cancer cell growth, migration, invasion, metastasis and angiogenesis, as well as cancer stem cell (CSC) self-renewal. Therefore, significant attention has been paid in recent years toward the development of clinically useful antagonists of Notch signaling. Better understanding of the structure, function and regulation of Notch intracellular signaling pathways, as well as its complex crosstalk with other oncogenic signals in breast cancer cells will be essential to ensure rational design and application of new combinatory therapeutic strategies. Novel opportunities have emerged from the discovery of Notch crosstalk with inflammatory and angiogenic cytokines and their links to CSCs. Combinatory treatments with drugs designed to prevent Notch oncogenic signal crosstalk may be advantageous over λ secretase inhibitors (GSIs) alone. In this review, we focus on the more recent advancements in our knowledge of aberrant Notch signaling contributing to breast cancer angiogenesis, as well as its crosstalk with other factors contributing to angiogenesis and CSCs.

Autocrine/paracrine erythropoietin regulates migration and invasion potential and the stemness of human breast cancer cells

Recent studies suggest that erythropoietin (EPO) has pleiotropic effects in several cell types in addition to hematopoietic cells; however, the role of EPO-mediated cell signaling in nonhematopoietic cells, including in cancer cells, remains controversial. Here, we report our findings of autocrine/paracrine production of EPO by breast cancer cells and its functional significance. We detected a significant level of autocrine/paracrine EPO in the conditioned medium from the culture of SKBR3 breast cancer cells, particularly when the cells were cultured in hypoxia. Through knockdown of EPO and EPO receptor expression and experimental elevation of EPO receptor expression in SKBR3 breast cancer cells, we demonstrated novel roles of autocrine/paracrine EPO-mediated cell signaling in regulating migration and invasion potential and stemness-like properties of breast cancer cells.

Radiation-induced Notch signaling in breast cancer stem cells

PURPOSE

To explore patterns of Notch receptor and ligand expression in response to radiation that could be crucial in defining optimal dosing schemes for γ-secretase inhibitors if combined with radiation.

METHODS AND MATERIALS

Using MCF-7 and T47D breast cancer cell lines, we used real-time reverse transcription-polymerase chain reaction to study the Notch pathway in response to radiation.

RESULTS

We show that Notch receptor and ligand expression during the first 48 hours after irradiation followed a complex radiation dose-dependent pattern and was most pronounced in mammospheres, enriched for breast cancer stem cells. Additionally, radiation activated the Notch pathway. Treatment with a γ-secretase inhibitor prevented radiation-induced Notch family gene expression and led to a significant reduction in the size of the breast cancer stem cell pool.

CONCLUSIONS

Our results indicate that, if combined with radiation, γ-secretase inhibitors may prevent up-regulation of Notch receptor and ligand family members and thus reduce the number of surviving breast cancer stem cells.

Layered signaling regulatory networks analysis of gene expression involved in malignant tumorigenesis of non-resolving ulcerative colitis via integration of cross-study microarray profiles

Background

Ulcerative colitis (UC) was the most frequently diagnosed inflammatory bowel disease (IBD) and closely linked to colorectal carcinogenesis. By far, the underlying mechanisms associated with the disease are still unclear. With the increasing accumulation of microarray gene expression profiles, it is profitable to gain a systematic perspective based on gene regulatory networks to better elucidate the roles of genes associated with disorders. However, a major challenge for microarray data analysis is the integration of multiple-studies generated by different groups.

Methodology/Principal Findings

In this study, firstly, we modeled a signaling regulatory network associated with colorectal cancer (CRC) initiation via integration of cross-study microarray expression data sets using Empirical Bayes (EB) algorithm. Secondly, a manually curated human cancer signaling map was established via comprehensive retrieval of the publicly available repositories. Finally, the co-differently-expressed genes were manually curated to portray the layered signaling regulatory networks.

Results

Overall, the remodeled signaling regulatory networks were separated into four major layers including extracellular, membrane, cytoplasm and nucleus, which led to the identification of five core biological processes and four signaling pathways associated with colorectal carcinogenesis. As a result, our biological interpretation highlighted the importance of EGF/EGFR signaling pathway, EPO signaling pathway, T cell signal transduction and members of the BCR signaling pathway, which were responsible for the malignant transition of CRC from the benign UC to the aggressive one.

Conclusions

The present study illustrated a standardized normalization approach for cross-study microarray expression data sets. Our model for signaling networks construction was based on the experimentally-supported interaction and microarray co-expression modeling. Pathway-based signaling regulatory networks analysis sketched a directive insight into colorectal carcinogenesis, which was of significant importance to monitor disease progression and improve therapeutic interventions.

Notch1 is required for hypoxia-induced proliferation, invasion and chemoresistance of T-cell acute lymphoblastic leukemia cells

Background

Notch1 is a potent regulator known to play an oncogenic role in many malignancies including T-cell acute lymphoblastic leukemia (T-ALL). Tumor hypoxia and increased hypoxia-inducible factor-1α (HIF-1α) activity can act as major stimuli for tumor aggressiveness and progression. Although hypoxia-mediated activation of the Notch1 pathway plays an important role in tumor cell survival and invasiveness, the interaction between HIF-1α and Notch1 has not yet been identified in T-ALL. This study was designed to investigate whether hypoxia activates Notch1 signalling through HIF-1α stabilization and to determine the contribution of hypoxia and HIF-1α to proliferation, invasion and chemoresistance in T-ALL.

Methods

T-ALL cell lines (Jurkat, Sup-T1) transfected with HIF-1α or Notch1 small interference RNA (siRNA) were incubated in normoxic or hypoxic conditions. Their potential for proliferation and invasion was measured by WST-8 and transwell assays. Flow cytometry was used to detect apoptosis and assess cell cycle regulation. Expression and regulation of components of the HIF-1α and Notch1 pathways and of genes related to proliferation, invasion and apoptosis were assessed by quantitative real-time PCR or Western blot.

Results

Hypoxia potentiated Notch1 signalling via stabilization and activation of the transcription factor HIF-1α. Hypoxia/HIF-1α-activated Notch1 signalling altered expression of cell cycle regulatory proteins and accelerated cell proliferation. Hypoxia-induced Notch1 activation increased the expression of matrix metalloproteinase-2 (MMP2) and MMP9, which increased invasiveness. Of greater clinical significance, knockdown of Notch1 prevented the protective effect of hypoxia/HIF-1α against dexamethasone-induced apoptosis. This sensitization correlated with losing the effect of hypoxia/HIF-1α on Bcl-2 and Bcl-xL expression.

Conclusions

Notch1 signalling is required for hypoxia/HIF-1α-induced proliferation, invasion and chemoresistance in T-ALL. Pharmacological inhibitors of HIF-1α or Notch1 signalling may be attractive interventions for T-ALL treatment.

MicroRNA-34a modulates chemosensitivity of breast cancer cells to adriamycin by targeting Notch1

BACKGROUND AND AIMS

MicroRNA-34a (miR-34a) as a tumor suppressor has been reported in many other studies. However, its role in modulating the sensitivity of breast cancer cells to adriamycin (ADR) remains unclear. The aim of this study is to evaluate the role of miR-34a in the sensitivity of breast cancer cells to ADR.

METHODS

The role of miR-34a in breast cancer cells was detected using MTT assay, flow cytometry assay, real-time PCR and Western blot, etc. The association of miR-34a and Notch1 was analyzed by dual-luciferase reporter assay and Notch1-siRNA technology. Real-time PCR assay was performed to test the expression of miR-34a and Notch1 in 38 selective breast cancer tissue samples.

RESULTS

Ectopic overexpression of miR-34a could sensitize MCF-7 breast cancer cells to ADR. MiR-34a mimic could inhibit the luciferase activity of the construct containing wild-type 3' UTR of Notch1 in MCF-7/ADR cells. Notch1-siRNA could partially reverse the effect of miR-34a inhibitor in inducing chemoresistance of MCF-7 cells to ADR. Further, there was an inverse association between Notch1 and miR-34a expression in breast cancer.

CONCLUSION

Dysregulation of miR-34a plays critical roles in the acquired ADR resistance of breast cancer, at least in part via targeting Notch1.

Targeting Notch signaling for cancer therapeutic intervention

The Notch signaling pathway is an evolutionarily conserved, intercellular signaling cascade. The Notch proteins are single-pass receptors that are activated upon interaction with the Delta (or Delta-like) and Jagged/Serrate families of membrane-bound ligands. Association of ligand-receptor leads to proteolytic cleavages that liberate the Notch intracellular domain (NICD) from the plasma membrane. The NICD translocates to the nucleus, where it forms a complex with the DNA-binding protein CSL, displacing a histone deacetylase (HDAc)-corepressor (CoR) complex from CSL. Components of a transcriptional complex, such as MAML1 and histone acetyltransferases (HATs), are recruited to the NICD-CSL complex, leading to the transcriptional activation of Notch target genes. The Notch signaling pathway plays a critical role in cell fate decision, tissue patterning, morphogenesis, and is hence regarded as a developmental pathway. However, if this pathway goes awry, it contributes to cellular transformation and tumorigenesis. There is mounting evidence that this pathway is dysregulated in a variety of malignancies, and can behave as either an oncogene or a tumor suppressor depending upon cell context. This chapter highlights the current evidence for aberration of the Notch signaling pathway in a wide range of tumors from hematological cancers, such as leukemia and lymphoma, through to lung, skin, breast, pancreas, colon, prostate, ovarian, brain, and liver tumors. It proposes that the Notch signaling pathway may represent novel target for cancer therapeutic intervention.

Prognostic significance of erythropoietin in pancreatic adenocarcinoma

BACKGROUND

Erythropoietin (Epo) administration has been reported to have tumor-promoting effects in anemic cancer patients. We investigated the prognostic impact of endogenous Epo in patients with pancreatic ductal adenocarcinoma (PDAC).

METHODOLOGY

The clinico-pathological relevance of hemoglobin (Hb, n = 150), serum Epo (sEpo, n = 87) and tissue expression of Epo/Epo receptor (EpoR, n = 104) was analyzed in patients with PDAC. Epo/EpoR expression, signaling, growth, invasion and chemoresistance were studied in Epo-exposed PDAC cell lines.

RESULTS

Compared to donors, median preoperative Hb levels were reduced by 15% in both chronic pancreatitis (CP, p<0.05) and PDAC (p<0.001), reaching anemic grade in one third of patients. While inversely correlating to Hb (r = -0.46), 95% of sEPO values lay within the normal range. The individual levels of compensation were adequate in CP (observed to predicted ratio, O/P = 0.99) but not in PDAC (O/P = 0.85). Strikingly, lower sEPO values yielding inadequate Epo responses were prominent in non-metastatic M0-patients, whereas these parameters were restored in metastatic M1-group (8 vs. 13 mU/mL; O/P = 0.82 vs. 0.96; p<0.01)--although Hb levels and the prevalence of anemia were comparable. Higher sEpo values (upper quartile ≥ 16 mU/ml) were not significantly different in M0 (20%) and M1 (30%) groups, but were an independent prognostic factor for shorter survival (HR 2.20, 10 vs. 17 months, p<0.05). The pattern of Epo expression in pancreas and liver suggested ectopic release of Epo by capillaries/vasa vasorum and hepatocytes, regulated by but not emanating from tumor cells. Epo could initiate PI3K/Akt signaling via EpoR in PDAC cells but failed to alter their functions, probably due to co-expression of the soluble EpoR isoform, known to antagonize Epo.

CONCLUSION/SIGNIFICANCE

Higher sEPO levels counteract anemia but worsen outcome in PDAC patients. Further trials are required to clarify how overcoming a sEPO threshold ≥16 mU/ml by endogenous or exogenous means may predispose to or promote metastatic progression.

Leukocyte-mediated cell dissemination and metastasis: findings from multiple types of human tumors

Our previous studies revealed that leukocyte infiltration could trigger human breast and prostate tumor invasion through focal disruptions of the tumor capsule, which selectively favors monoclonal proliferation of tumor progenitors or a biologically more aggressive cell clone overlying the focal disruptions. Our current study, involving multiple types of human tumors, further shows that leukocyte infiltration could also trigger tumor metastasis through the following pathways: [1] more leukocytes migrate to focally disrupted tumor capsules, which forms leukocyte aggregates surrounding newly formed tumor cell clusters, [2] the physical movement of leukocytes into proliferating tumor cells disrupts the intercellular junctions and cell-surface adhesion molecules, causing the disassociation of tumor cells from the tumor core, [3] leukocytes are conjoined with some of these tumor cells through plasma membrane fusion, creating tumor cell-leukocyte chimeras (TLCs), and [4] the leukocyte of TLCs impart migratory capacity to associated tumor cell partners, physically dragging them to different tissue sites. Our findings suggest a novel pathway for tumor cell dissemination from the primary sites and the subsequent journey to new sites. Our findings also provide a unique explanation for the cellular mechanism of leukocytes on tumor invasion and metastasis. If confirmed, our hypothesis and technical approach may significantly facilitate early detection and intervention of tumor invasion and metastasis.

The role of erythropoietin and erythropoiesis-stimulating agents in tumor progression

Over the past few decades, understanding of the physiologic function of erythropoietin (EPO) has evolved significantly. EPO binds to erythropoietin receptors (EPOR), initiating signaling that stimulates growth, inhibits apoptosis, and induces the differentiation of erythroid progenitors to increase red blood cell mass. EPO has additionally been shown to exert tissue-protective effects on multiple tissues, suggesting a pleiotropic mechanism of action. Erythropoiesis-stimulating agents (ESA) are used clinically for treating cancer-related anemia [chemotherapy-induced anemia (CIA)]. Recent clinical trials have reported increased adverse events and/or reduced survival in ESA-treated cancer patients receiving chemotherapy, potentially related to EPO-induced cancer progression. Signaling pathways downstream of EPO/EPOR have been shown to influence numerous cellular functions in both normal and tumor cells, including proliferation, apoptosis, and drug resistance. Some studies have reported effects on proliferation, reduced chemotherapy efficacy, reduction of apoptosis, and resistance to selective therapies on cancer cell lines, whereas others have shown null effects. In addition, newer targeted cancer therapies that are directed toward specific signaling pathways may be antagonized by ESAs. This molecular interplay between anticancer agents and potential survival signals triggered by ESAs may have been underestimated and may contribute toward decreased survival seen in certain trials. As more targeted anticancer therapies become available, these types of interactions may mitigate therapeutic efficacy by allowing tumor cells to acquire drug resistance. Therefore, a more complete understanding of the complex pathways involved will allow for the rational use of ESAs for the safe treatment of CIA in oncology patients.

Notch-1 induces epithelial-mesenchymal transition consistent with cancer stem cell phenotype in pancreatic cancer cells

Activation of Notch-1 is known to be associated with the development and progression of human malignancies including pancreatic cancer. Emerging evidence suggest that the acquisition of epithelial-mesenchymal transition (EMT) phenotype and induction of cancer stem cell (CSC) or cancer stem-like cell phenotype are interrelated and contributes to tumor recurrence and drug resistance. The molecular mechanism(s) by which Notch-1 contributes to the acquisition of EMT phenotype and CSC self-renewal capacity has not been fully elucidated. Here we show that forced over-expression of Notch-1 leads to increased cell growth, clonogenicity, migration and invasion of AsPC-1 cells. Moreover, over-expression of Notch-1 led to the induction of EMT phenotype by activation of mesenchymal cell markers such as ZEB1, CD44, EpCAM, and Hes-1. Here we also report, for the first time, that over-expression of Notch-1 leads to increased expression of miR-21, and decreased expression of miR-200b, miR-200c, let-7a, let-7b, and let-7c. Re-expression of miR-200b led to decreased expression of ZEB1, and vimentin, and increased expression of E-cadherin. Over-expression of Notch-1 also increased the formation of pancreatospheres consistent with expression of CSC surface markers CD44 and EpCAM. Finally, we found that genistein, a known natural anti-tumor agent inhibited cell growth, clonogenicity, migration, invasion, EMT phenotype, formation of pancreatospheres and expression of CD44 and EpCAM. These results suggest that the activation of Notch-1 signaling contributes to the acquisition of EMT phenotype, which is in part mediated through the regulation of miR-200b and CSC self-renewal capacity, and these processes could be attenuated by genistein treatment.

Notch signaling proteins: legitimate targets for cancer therapy

Proteins and small peptides (growth factors and hormones) are key molecules in maintaining cellular homeostasis. To that end, Notch signaling pathway proteins are known to play critical roles in maintaining the balance between cell proliferation, differentiation and apoptosis, and thus it has been suggested that Notch may be responsible for the development and progression of human malignancies. Therefore, the Notch signaling pathway proteins may present novel therapeutic targets, which could have promising therapeutic impact on eradicating human malignancies. This review describes the role of Notch signaling pathway proteins in cancer and how its deregulation is involved in tumor development and progression leading to metastasis and the ultimate demise of patients diagnosed with cancer. Further, we summarize the role of several Notch inhibitors especially "natural agents" that could represent novel therapeutic strategies targeting Notch signaling toward better treatment outcome of patients diagnosed with cancer.

Are cancer stem cells radioresistant?

Based on findings that cancer cell clonogens exhibit stem cell features, it has been suggested that cancer stem-like cells are relatively radioresistant owing to different intrinsic and extrinsic factors, including quiescence, activated radiation response mechanisms (e.g., enhanced DNA repair, upregulated cell cycle control mechanisms and increased free-radical scavengers) and a surrounding microenvironment that enhances cell survival mechanisms (e.g., hypoxia and interaction with stromal elements). However, these radiosensitivity features are probably dynamic in nature and come into play at different times during the course of chemo/radiotherapy. Therefore, different molecularly targeted radiosensitization strategies may be needed at different stages of therapy. This article describes potential sensitization approaches based on the dynamics and changing properties of cancer stem-like cells during therapy.

Role of Notch and its oncogenic signaling crosstalk in breast cancer

The Notch signaling plays a key role in cell differentiation, survival, and proliferation through diverse mechanisms. Notch signaling is also involved in vasculogenesis and angiogenesis. Moreover, Notch expression is regulated by hypoxia and inflammatory cytokines (IL-1, IL-6 and leptin). Entangled crosstalk between Notch and other developmental signaling (Hedgehog and Wnt), and signaling triggered by growth factors, estrogens and oncogenic kinases, could impact on Notch targeted genes. Thus, alterations of the Notch signaling can lead to a variety of disorders, including human malignancies. Notch signaling is activated by ligand binding, followed by ADAM/tumor necrosis factor-α-converting enzyme (TACE) metalloprotease and γ-secretase cleavages that produce the Notch intracellular domain (NICD). Translocation of NICD into the nucleus induces the transcriptional activation of Notch target genes. The relationships between Notch deregulated signaling, cancer stem cells and the carcinogenesis process reinforced by Notch crosstalk with many oncogenic signaling pathways suggest that Notch signaling may be a critical drug target for breast and other cancers. Since current status of knowledge in this field changes quickly, our insight should be continuously revised. In this review, we will focus on recent advancements in identification of aberrant Notch signaling in breast cancer and the possible underlying mechanisms, including potential role of Notch in breast cancer stem cells, tumor angiogenesis, as well as its crosstalk with other oncogenic signaling pathways in breast cancer. We will also discuss the prognostic value of Notch proteins and therapeutic potential of targeting Notch signaling for cancer treatment.

Association between pharmaceutical support and basic science research on erythropoiesis-stimulating agents

BACKGROUND

To our knowledge, no prior research has evaluated the association between pharmaceutical industry funding and basic science research results. When erythropoiesis-stimulating agents (ESAs) were licensed to treat chemotherapy-associated anemia, basic science concerns related to potential cancer stimulation were raised. We evaluated associations between pharmaceutical industry support and reported findings evaluating ESA effects on cancer cells.

METHODS

Articles identified in MEDLINE and EMBASE databases (1988-2008) investigating basic science findings related to ESA administration in the solid tumor setting were reviewed. Outcomes included information on erythropoietin receptors (EpoRs), Epo-induced signaling events, cellular function, and qualitative conclusions. Information on study funding (academic investigators with no reported funding from ESA manufacturers [64 studies], academic investigators with grant funding from ESA manufacturers [7 studies], and investigators employed by the ESA manufacturers [3 studies]) was evaluated. Some studies did not include information on each outcome.

RESULTS

Investigators without funding from ESA manufacturers were more likely than academic investigators with such funding or investigators employed by ESA manufacturers to identify EpoRs on solid tumor cells (100%, 60%, and 67%, respectively; P = .009), Epo-induced signaling events (94%, 0%, and 0%, respectively; P = .001), or changes in cellular function (57%, 0%, and 0%, respectively; P = .007) and to conclude that ESAs had potentially harmful effects on cancer cells (57%, 0%, and 0%, respectively; P = .008).

CONCLUSIONS

Researchers who do not have pharmaceutical industry support are more likely than those with pharmaceutical support to identify detrimental in vitro effects of ESAs. The potential for conflicts of interest to affect basic science research should be considered.

Erythropoietin receptor response circuits

PURPOSE OF REVIEW

In 1985-1989, erythropoietin (EPO), its receptor (EPOR), and janus kinase 2 were cloned; established to be essential for definitive erythropoiesis; and initially intensely studied. Recently, new impetus, tools, and model systems have emerged to re-examine EPO/EPOR actions, and are addressed in this review. Impetus includes indications that EPO affects significantly more than standard erythroblast survival pathways, the development of novel erythropoiesis-stimulating agents, increasing evidence for EPO/EPOR cytoprotection of ischemically injured tissues, and potential EPO-mediated worsening of tumorigenesis.

RECENT FINDINGS

New findings are reviewed in four functional contexts: (pro)erythroblast survival mechanisms, new candidate EPO/EPOR effects on erythroid cell development and new EPOR responses, EPOR downmodulation and trafficking, and novel erythropoiesis-stimulating agents.

SUMMARY

As Current Opinion, this monograph seeks to summarize, and provoke, new EPO/EPOR action concepts. Specific problems addressed include: beyond (and before) BCL-XL, what key survival factors are deployed in early-stage proerythroblasts? Are distinct EPO/EPOR signals transduced in stage-selective fashions? Is erythroblast proliferation also modulated by EPO/EPOR signals? What functions are subserved by new noncanonical EPO/EPOR response factors (e.g. podocalyxin like-1, tribbles 3, reactive oxygen species, and nuclear factor kappa B)? What key regulators mediate EPOR inhibition and trafficking? And for emerging erythropoiesis-stimulating agents, to what extent do activities parallel EPOs (or differ in advantageous, potentially complicating ways, or both)?

Targeting Notch signaling pathway to overcome drug resistance for cancer therapy

Chemotherapy is an important therapeutic strategy for cancer treatment and remains the mainstay for the management of human malignancies; however, chemotherapy fails to eliminate all tumor cells because of intrinsic or acquired drug resistance, which is the most common cause of tumor recurrence. Recently, emerging evidences suggest that Notch signaling pathway is one of the most important signaling pathways in drug-resistant tumor cells. Moreover, down-regulation of Notch pathway could induce drug sensitivity, leading to increased inhibition of cancer cell growth, invasion, and metastasis. This article will provide a brief overview of the published evidences in support of the roles of Notch in drug resistance and will further summarize how targeting Notch by "natural agents" could become a novel and safer approach for the improvement of tumor treatment by overcoming drug resistance.

The War on Cancer rages on

In 1971, the "War on Cancer" was launched by the US government to cure cancer by the 200-year anniversary of the founding of the United States of America, 1976. This article briefly looks back at the progress that has been made in cancer research and compares progress made in other areas of human affliction. While progress has indeed been made, the battle continues to rage on.

Radiation resistance of cancer stem cells: the 4 R's of radiobiology revisited

There is compelling evidence that many solid cancers are organized hierarchically and contain a small population of cancer stem cells (CSCs). It seems reasonable to suggest that a cancer cure can be achieved only if this population is eliminated. Unfortunately, there is growing evidence that CSCs are inherently resistant to radiation, and perhaps other cancer therapies. In general, success or failure of standard clinical radiation treatment is determined by the 4 R's of radiobiology: repair of DNA damage, redistribution of cells in the cell cycle, repopulation, and reoxygenation of hypoxic tumor areas. We relate recent findings on CSCs to these four phenomena and discuss possible consequences.

Neoplastic stem cells: current concepts and clinical perspectives

Neoplastic stem cells have initially been characterized in myeloid leukemias where NOD/SCID mouse-repopulating progenitors supposedly reside within a CD34+/Lin- subset of the malignant clone. These progenitors are considered to be self-renewing cells responsible for the in vivo long-term growth of neoplastic cells in leukemic patients. Therefore, these cells represent an attractive target of therapy. In some lymphoid leukemias, NOD/SCID mouse-repopulating cells were also reported to reside within the CD34+/Lin- subfraction of the clone. More recently, several attempts have been made to transfer the cancer stem cell concept to solid tumors and other non-hematopoietic neoplasms. In several of these tumors, the cell surface antigens AC133 (CD133) and CD44 are considered to indicate the potential of a cell to initiate permanent tumor formation in vivo. However, several questions concerning the phenotype, self-renewal capacity, stroma-dependence, and other properties of cancer- or leukemia-initiating cells remain to be solved. The current article provides a summary of our current knowledge on neoplastic (cancer) stem cells, with special emphasis on clinical implications and therapeutic options as well as a discussion about conceptual and technical limitations.

Anaemia: a rare but neglected problem among Finnish patients receiving chemotherapy for solid tumours

GOALS OF THE WORK

Anaemia is very frequently diagnosed among cancer patients. Use of erythropoietins has proved to be effective in reducing the need of transfusions and enhancing patients' quality of life, but may also have detrimental effects in treating nonanemic asymptomatic patients. We assessed the frequency of anaemia and the frequency with which it was diagnosed and treated in different types of solid tumours treated at outpatient chemotherapy policlinics.

MATERIALS AND METHODS

During the study period, altogether 733 consecutive subjects received chemotherapy at the five Finnish University Hospitals. Their data were collected. The physician who was responsible for the chemotherapy treatment was unaware of the survey. The response to anaemia (treated or not, the modality of treatment) were established from patients records; 69% were females, mean age was 61 years (range, 24-92).

RESULTS

The median haemoglobin level was 12.7 g/dL (range, 8.9-15.5 g/dL). About one third of the patients (200/733, 27%) had a value less than 12 g/dL. In only 15% of these cases was there any documentation of response or a possible treatment option for anaemia. On the other hand, only 12% of all patients (N=91) had a haemoglobin value less than 11 g/dL. However, in most of them anaemia had not been considered; in only 25% of cases was an active treatment option selected.

CONCLUSIONS

According to our survey, anaemia was less common in our patients than in the European Cancer Anaemia Survey. Only a minority of chemotherapy patients receiving their treatments as outpatients would need active treatment for their anaemia.

Multicellular tumor spheroids: an underestimated tool is catching up again

The present article highlights the rationale, potential and flexibility of tumor spheroid mono- and cocultures for implementation into state of the art anti-cancer therapy test platforms. Unlike classical monolayer-based models, spheroids strikingly mirror the 3D cellular context and therapeutically relevant pathophysiological gradients of in vivo tumors. Some concepts for standardization and automation of spheroid culturing, monitoring and analysis are discussed, and the challenges to define the most convenient analytical endpoints for therapy testing are outlined. The potential of spheroids to contribute to either the elimination of poor drug candidates at the pre-animal and pre-clinical state or the identification of promising drugs that would fail in classical 2D cell assays is emphasised. Microtechnologies, in the form of micropatterning and microfluidics, are also discussed and offer the exciting prospect of standardized spheroid mass production to tackle high-throughput screening applications within the context of traditional laboratory settings. The extension towards more sophisticated spheroid coculture models which more closely reflect heterologous tumor tissues composed of tumor and various stromal cell types is also covered. Examples are given with particular emphasis on tumor-immune cell cocultures and their usefulness for testing novel immunotherapeutic treatment strategies. Finally, tumor cell heterogeneity and the extraordinary possibilities of putative cancer stem/tumor-initiating cell populations that can be maintained and expanded in sphere-forming assays are introduced. The relevance of the cancer stem cell hypothesis for cancer cure is highlighted, with the respective sphere cultures being envisioned as an integral tool for next generation drug development offensives.

Down-regulation of the fetal stem cell factor SOX17 by H33342: a mechanism responsible for differential gene expression in breast cancer side population cells

Human solid tumors contain rare cancer side population (SP) cells, which expel the fluorescent dye Hoechst 33342 (H33342) and display cancer stem cell characteristics. Transcriptional profiling of cancer SP cells isolated by H33342 fluorescence analysis is a newly emerging approach to discover cancer stem cell markers and aberrant differentiation pathways. Using Affymetrix expression microarrays and quantitative reverse transcription-PCR, we investigated differential gene expression between SP and non-SP (NSP) cells isolated from human mammary carcinoma cell lines. A total of 136 genes were up-regulated in breast cancer SP relative to NSP cells, one of which was the fetal stem cell factor and Wnt/beta-catenin signaling pathway target SOX17. Strikingly, we discovered that SOX17 was down-regulated by H33342 in a dose-dependent manner. In SP cells, which expel H33342, down-regulation of SOX17 was less pronounced than in NSP cells, which retain H33342. As a result of this, SOX17 displayed a 10-20-fold overexpression in cancer SP relative to NSP cells. Similar results were obtained for further stemness-related genes, namely EPC1 and SPRY1. These findings establish a previously unidentified gene-regulatory impact of H33342 as a novel mechanism responsible for differential gene expression in cancer SP cells. This has significant implications for the future interpretation of cancer SP cells.

Evaluating erythropoietin-associated tumor progression using archival tissues from a phase III clinical trial

Despite the prevalence of anemia in cancer, recombinant erythropoietin (Epo) has declined in use because of recent Phase III trials showing more rapid cancer progression and reduced survival in subjects randomized to Epo. Since Epo receptor (EpoR), Jak2, and Hsp70 are well-characterized mediators of Epo signaling in erythroid cells, we hypothesized that Epo might be especially harmful in patients whose tumors express high levels of these effectors. Because of the insensitivity of immunohistochemistry for detecting low level EpoR protein, we developed assays to measure levels of EpoR, Jak2 and Hsp70 mRNA in formalin-fixed paraffin-embedded (FFPE) tumors. We tested 23 archival breast tumors as well as 136 archival head and neck cancers from ENHANCE, a Phase III trial of 351 patients randomized to Epo versus placebo concomitant with radiotherapy following complete resection, partial resection, or no resection of tumor. EpoR, Jak2, and Hsp70 mRNA levels varied >30-fold, >12-fold, and >13-fold across the breast cancers, and >30-fold, >40-fold, and >30-fold across the head and neck cancers, respectively. Locoregional progression-free survival (LPFS) did not differ among patients whose head and neck cancers expressed above- versus below-median levels of EpoR, Jak2 or Hsp70, except in the subgroup of patients with unresected tumors (n = 28), where above-median EpoR, above-median Jak2, and below-median Hsp70 mRNA levels were all associated with significantly poorer LPFS. Our results provide a framework for exploring the relationship between Epo, cancer progression, and survival using archival tumors from other Phase III clinical trials.

Erythroid-Stimulating Agents in Cancer Therapy: Potential Dangers and Biologic Mechanisms

Erythropoietin-stimulating agents (ESAs) were originally designed to replace endogenous erythropoietin in patients with anemia secondary to renal failure. Their use has subsequently been expanded to include patients with anemia of other causes, including cancer patients, in whom deficiency of erythropoietin, per se, is not the primary cause of anemia. Although early studies showed promise of ESA administration in reducing the need for transfusions and improving the quality of life in cancer patients, several large randomized clinical trials have recently shown a potential detrimental effect of ESA administration on tumor progression and survival in these patients. These studies have called into question the safety of ESAs as supportive therapy in patients being treated for oncologic conditions. However, numerous questions remain to be addressed regarding the design of these studies, the effect of various targeted hemoglobin levels, and the potential biologic mechanisms proposed to explain promotion of tumor progression and reduced survival.

Emerging role of Notch in stem cells and cancer

The Notch signaling pathway is known to be responsible for maintaining a balance between cell proliferation and death and, as such, plays important roles in the formation of many types of human tumors. Recently, Notch signaling pathway has been shown to control stem cell self-renewal and multi-potency. As many cancers are thought to be developed from a number of cancer stem-like cells, which are also known to be linked with the acquisition of epithelial-mesenchymal transition (EMT); and thus suggesting an expanding role of Notch signaling in human tumor progression.

Neoplasia: the second decade

This issue marks the end of the 10-year anniversary of Neoplasia where we have seen exciting growth in both number of submitted and published articles in Neoplasia. Neoplasia was first published in 1999. During the past 10 years, Neoplasia has dynamically adapted to the needs of the cancer research community as technologies have advanced. Neoplasia is currently providing access to articles through PubMed Central to continue to facilitate rapid broad-based dissemination of published findings to the scientific community through an Open Access model. This has in part helped Neoplasia to achieve an improved impact factor this past year, demonstrating that the manuscripts published by Neoplasia are of great interest to the overall cancer research community. This past year, Neoplasia received a record number of articles for review and has had a 21% increase in the number of published articles.

Sca-1 identifies the tumor-initiating cells in mammary tumors of BALB-neuT transgenic mice

Cancer stem cells, initiating and sustaining the tumor process, have been isolated in human and murine breast cancer using different cell markers. In the present study, we aimed to evaluate the presence and characteristics of stem/tumor-initiating cells in the model of the mouse mammary neoplasia driven by the activated form of rat Her-2/neu oncogene (BALB-neuT mice). For this purpose, we generated tumor spheres from primary spontaneous BALB-neuT tumors. Tumor sphere cultures were characterized for clonogenicity, self-renewal, and ability to differentiate in epithelial/myoepithelial cells of the mammary gland expressing basal and luminal cytokeratins and alpha-smooth muscle actin. In addition, tumor spheres were more resistant to doxorubicin compared with parental tumor cells. In the attempt to identify a selected marker for the sphere-generating cells, we found that Sca-1(+) cells, present in tumors or enriched in mammospheres, and not CD24(+) or CD29(+) cells, were responsible for the sphere generation in vitro. Moreover, cells from the tumor spheres showed an increased tumor-generating ability in respect to the epithelial tumor cells. Sca-1(+) sorted cells or clonal mammospheres derived from a Sca-1(+) cell showed a superimposable tumor-initiating ability. The data of the present study indicate that a Sca-1(+) population derived from mammary BALB-neuT tumors is responsible for sphere generation in culture and for initiating tumors in vivo.

RNA interference-mediated inhibition of erythropoietin receptor expression suppresses tumor growth and invasiveness in A2780 human ovarian carcinoma cells

Although recombinant human erythropoietin (rHuEpo) has revolutionized the treatment of anemia, recent clinical trials suggested that rHuEpo use may be associated with decreased survival in cancer patients. Although the expression of erythropoietin (Epo) receptor (EpoR) has been demonstrated in various human cancers, the effect of exogenous Epo on the growth and therapy resistance of EpoR-bearing tumor cells is unclear at present. In the current study, we examined the hypothesis that EpoR may contribute to tumor growth independent of Epo in A2780 human ovarian carcinoma cells. A2780 human ovarian carcinoma cells showed high levels of EpoR expression, but lacked expression of Epo mRNA and biologically active Epo protein under both normoxic and hypoxic conditions. Exogenous Epo did not stimulate EpoR-mediated signaling, proliferation, invasiveness, or resistance to cytotoxic drugs in A2780 cells. In contrast, specific inhibition of EpoR expression using a short hairpin RNA (shRNA) expression plasmid resulted in markedly reduced proliferation and invasiveness in vitro. In addition, inhibition of EpoR expression led to abrogated in vivo ovarian cancer cell growth in a tumor xenograft system and resulted in decreased EpoR signaling. Our findings suggest that EpoR may be constitutively active in some cancer cells in the absence of Epo and provide the first evidence for a potential role of an Epo-independent, EpoR-mediated pathway in the growth of some human cancers.

Erythropoietin receptor is expressed in meningiomas and lower levels are associated with tumour recurrence

AIMS

The Epo-EpoR pathway plays a role in tumour growth, metastasis and treatment resistance and is a potential target in oncological treatment. As the EpoR status in human meningiomas is unknown, our aim was to characterize EpoR expression in these tumours.

METHODS

We examined 131 meningioma samples of all WHO grades from 116 patients by immunohistochemistry for EpoR. Among these, 25 meningiomas showed brain invasion and 29 patients had a further tumour recurrence. A group of 20 patients without tumour recurrence served as controls. In 12 cases we were able to compare both the primary and the following recurrent tumours. The presence of EpoR in meningiomas was confirmed by RT-PCR and Western blot.

RESULTS

EpoR was expressed in all meningiomas. Statistical analysis revealed that the mean expression levels of EpoR were significantly lower in primary tumours with known recurrence compared with a recurrence-free control group. Additional matched pair analysis in individual cases showed no significant differences between primary and recurrent tumours. No significant correlation between EpoR expression and WHO grade, age, sex or brain invasion was detected. Using specific primer pairs for RT-PCR, we were able to detect all three known isoforms of EpoR: the full-length isoform EpoR-F, the truncated isoform EpoR-T and the soluble isoform EpoR-S.

CONCLUSIONS

Our results demonstrate the expression of EpoR in meningiomas. Lower EpoR mean levels might be a useful marker for a higher recurrence risk, but further studies are needed to clarify the influence of EpoR on recurrences and the role of the different isoforms.