Induction Of CXCR4 Expression Research Articles

CXCR4 expression of multiple myeloma as a dynamic process: influence of therapeutic agents

Chemokine receptors represent novel targets for treatment of multiple myeloma (MM). However, CXCR4 expression appears to be highly dynamic. This in vitro study investigated the impact of commonly used anti-myeloma agents on CXCR4 expression. Established human myeloma cell lines as well as patient-derived CD138+ plasma cells were exposed to antineoplastic drugs. Cells were analyzed for CXCR4 expression by flow cytometry and direct stochastic optical reconstruction microscopy (dSTORM). In addition, cellular uptake of 68Ga-Pentixafor, a PET radiotracer for noninvasive assessment of CXCR4 expression in vivo, was assessed. CXCR4 expression was highly variable and turned out to be substance, dose and time dependent. Treatment with bortezomib was associated with reduced expression, while dexamethasone and doxorubicin significantly increased expression of CXCR4. Combination of these compounds further increased CXCR4 expression. In conclusion, drugs or combination of drugs can induce CXCR4 expression in myeloma cells. Hence, pretreatment may impact on response to CXCR4-based therapies.

Artemin regulates CXCR4 expression to induce migration and invasion in pancreatic cancer cells through activation of NF-κB signaling

Pancreatic ductal adenocarcinoma (PDAC) is the most lethal human malignant tumor because of the early onset of local invasion and distant metastasis. Perineural invasion is a prominent characteristic of pancreatic adenocarcinoma, which is a multifactorial process that involves various signaling molecules from different signaling pathways. The glial cell line-derived neurotrophic factor family of ligands was reported to be involved in perineural invasion in pancreatic cancer. Artemin is one member of the glial cell line-derived neurotrophic factor family of ligands. Although Artemin has previously been demonstrated to promote invasiveness of pancreatic cancer, the mechanisms remain poorly understood. In this study, we performed an analysis to determine the effects of Artemin on modulating tumor cell metastatic potential and invasion activity and explored its mechanisms in pancreatic cancer. We indicated that Artemin and CXCR4 were overexpressed in cancer tissues and widely expressed in pancreatic cancer cell lines. We observed that activation of ERK1/2 and Akt in Artemin-treated cells led to enhanced nuclear accumulation of NF-κB, which then induced CXCR4 expression. Through regulation of the expression of CXCR4, Artemin functionally promoted the migration and invasion in pancreatic cancer cells. The present study indicated that Artemin induced CXCR4 expression by activating Akt and ERK 1/2/NF-κB signaling, thereby modulating tumor cell metastatic potential and invasion activity in pancreatic cancer by regulating SDF-1α/CXCR4 axis. Artemin might be an effective and potent therapeutic target for pancreatic cancer metastasis, especially in perineural invasion.

NFκB-Mediated Invasiveness in CD133+ Pancreatic TICs Is Regulated by Autocrine and Paracrine Activation of IL1 Signaling.

Tumor-initiating cells (TIC) have been implicated in pancreatic tumor initiation, progression, and metastasis. Among different markers that define this cell population within the tumor, the CD133+ cancer stem cell (CSC) population has reliably been described in these processes. CD133 expression has also been shown to functionally promote metastasis through NF-κB activation in this population, but the mechanism is unclear. In the current study, overexpression of CD133 increased expression and secretion of IL1β (IL1B), which activates an autocrine signaling loop that upregulates NF-κB signaling, epithelial-mesenchymal transition (EMT), and cellular invasion. This signaling pathway also induces CXCR4 expression, which in turn is instrumental in imparting an invasive phenotype to these cells. In addition to the autocrine signaling of the CD133 secreted IL1β, the tumor-associated macrophages (TAM) also produced IL1β, which further activated this pathway in TICs. The functional significance of the TIC marker CD133 has remained elusive for a very long time; the current study takes us one step closer to understanding how the downstream signaling pathways in these cells regulate the functional properties of TICs.Implications: This study demonstrates the important role of tumor- and macrophage-derived IL1β stimulation in pancreatic cancer. IL1 signaling is increased in cells with CD133 expression, leading to increased NF-kB activity, EMT induction, and invasion. Increased invasiveness via IL1β stimulation is mediated by the upregulation of CXCR4 expression. The study highlights the importance of IL1-mediated signaling in TICs. Mol Cancer Res; 16(1); 162-72. ©2017 AACR.

Transmembrane tumor necrosis factor-α promotes the recruitment of MDSCs to tumor tissue by upregulating CXCR4 expression via TNFR2

Myeloid-derived suppressor cells (MDSCs) accumulated in tumor sites promote immune evasion. We found that TNFR deficiency-induced rejection of transplanted tumor was accompanied with markedly decreased accumulation of MDSCs. However, the mechanism(s) behind this phenomenon is not completely understood. Here, we demonstrated that TNFR deficiency did not affect the amount of MDSCs in bone marrow (BM), but decreased accumulation of Gr-1+CD11b+ MDSCs in the spleen and tumor tissues. The chemotaxis of Tnfr−/− MDSCs was prominently decreased in response to both tumor cell culture supernatants and tumor tissue homogenates from Tnfr−/− and wild-type mice, indicating an effect of TNFR signaling on chemokine receptor expression in MDSCs. We used real-time PCR to detect gene expression for several chemokine receptors in MDSCs from BM and found that CXCR4 was the most affected molecule at the transcriptional level in Tnfr−/− MDSCs. Neutralizing CXCR4 in wild-type MDSCs by a specific antibody blocked their chemotactic migration. Interestingly, it was tmTNF-α, but not sTNF-α, that induced CXCR4 expression in MDSCs. This effect of tmTNF-α was totally blocked in TNFR2−/− but not in TNFR1−/− MDSCs, and partially inhibited by PDTC or SB203580, an inhibitor of NF-κB or p38 MAPK pathway, respectively. Adoptive transfer of wild-type MDSCs restored MDSCs accumulation in tumors of Tnfr−/− mice, but this could be partially blocked by treatment with a CXCR4 inhibitor AMD3100. Our data suggest that tmTNF-α upregulates CXCR4 expression that promotes chemotaxis of MDSCs to tumor, and give a new insight into a novel mechanism by which tmTNF-α facilitates tumor immune evasion.

Intranasal Oncolytic Virotherapy with CXCR4-Enhanced Stem Cells Extends Survival in Mouse Model of Glioma.

SummaryThe challenges to effective drug delivery to brain tumors are twofold: (1) there is a lack of non-invasive methods of local delivery and (2) the blood-brain barrier limits systemic delivery. Intranasal delivery of therapeutics to the brain overcomes both challenges. In mouse model of malignant glioma, we observed that a small fraction of intranasally delivered neural stem cells (NSCs) can migrate to the brain tumor site. Here, we demonstrate that hypoxic preconditioning or overexpression of CXCR4 significantly enhances the tumor-targeting ability of NSCs, but without altering their phenotype only in genetically modified NSCs. Modified NSCs deliver oncolytic virus to glioma more efficiently and extend survival of experimental animals in the context of radiotherapy. Our findings indicate that intranasal delivery of stem cell-based therapeutics could be optimized for future clinical applications, and allow for safe and repeated administration of biological therapies to brain tumors and other CNS disorders.

The induction of CXCR4 expression in human osteoblast-like cells (MG63) by CoCr particles is regulated by the PLC-DAG-PKC pathway.

Osteolysis which leads to aseptic loosening of implants is a fundamental problem in joint replacement surgery (arthroplasty) and the leading cause for implant failure and revision surgery. Metal (CoCr) particles separated from implants by wear cause osteolysis and the failure of orthopedic implants, but the molecular mechanism is not clear. The chemokine receptor CXCR4 has been shown to play a pivotal role in periprosthetic osteolysis. The aim of this study was to determine which signal transduction pathway (PLC-DAG-PKC or MAPK/ERK) induces CXCR4 expression in osteoblast-like cells (MG63) cells. MG63 and Jurkat cells were stimulated with different amounts of particles (107 , 106 , and 105 ) for different time periods (30 min to 24 h), in the presence and absence of specific inhibitors (chelerythrine for the PLC-DAG-PKC pathway and PD98059 for the MAPK/ERK pathway). The expression of CXCR4-specific mRNA was determined by real-time polymerase chain reaction (PCR), and the PKC activity was measured by Western Blot using an antibody specific for PKC-related phosphorylation. Real-time PCR data showed that CXCR4 mRNA expression in MG63 cells induced by CoCr particles was significantly diminished by the PKC-specific inhibitor chelerythrine. This effect was not observed with the MAPK/ERK inhibitor PD98059. The involvement of PKC was also confirmed by an intensified phosphorylation pattern after stimulation with CoCr particles. In Jurkat cells, none of the inhibitors exhibited any effect. The induction of CXCR4-specific mRNA expression in MG63 cells after stimulation with CoCr particles is regulated by the PLC-DAG-PKC pathway and not by the MAPK/ERK pathway. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2326-2332, 2017.

Local CXCR4 Upregulation in the Injured Arterial Wall Contributes to Intimal Hyperplasia.

CXCR4 is a stem/progenitor cell surface receptor specific for the cytokine stromal cell‐derived factor‐1 (SDF‐1α). There is evidence that bone marrow‐derived CXCR4‐expressing cells contribute to intimal hyperplasia (IH) by homing to the arterial subintima which is enriched with SDF‐1α. We have previously found that transforming growth factor‐β (TGFβ) and its signaling protein Smad3 are both upregulated following arterial injury and that TGFβ/Smad3 enhances the expression of CXCR4 in vascular smooth muscle cells (SMCs). It remains unknown, however, whether locally induced CXCR4 expression in SM22 expressing vascular SMCs plays a role in neointima formation. Here, we investigated whether elevated TGFβ/Smad3 signaling leads to the induction of CXCR4 expression locally in the injured arterial wall, thereby contributing to IH. We found prominent CXCR4 upregulation (mRNA, 60‐fold; protein, 4‐fold) in TGFβ‐treated, Smad3‐expressing SMCs. Chromatin immunoprecipitation assays revealed a specific association of the transcription factor Smad3 with the CXCR4 promoter. TGFβ/Smad3 treatment also markedly enhanced SDF‐1α‐induced ERK1/2 phosphorylation as well as SMC migration in a CXCR4‐dependent manner. Adenoviral expression of Smad3 in balloon‐injured rat carotid arteries increased local CXCR4 levels and enhanced IH, whereas SMC‐specific depletion of CXCR4 in the wire‐injured mouse femoral arterial wall produced a 60% reduction in IH. Our results provide the first evidence that upregulation of TGFβ/Smad3 in injured arteries induces local SMC CXCR4 expression and cell migration, and consequently IH. The Smad3/CXCR4 pathway may provide a potential target for therapeutic interventions to prevent restenosis. Stem Cells 2016;34:2744–2757

Abstract 4112: Geminin overexpression-dependent recruitment and crosstalk with mesenchymal stem cells enhances aggressiveness in triple-negative breast cancers

Abstract Introduction: Tumor resident mesenchymal stem cells (MSCs) promote cancer progression. Pathways involved in recruitment of MSCs to breast tumor cells remain largely undefined. We aimed at defining the mechanism whereby geminin overexpressing breast tumor cells recruit and interact with MSCs to increase their own aggressiveness. Experimental Procedures: We used co-culturing assay, immunohistochemistry, in vitro invasion assay with or without cytokines neutralization, western blot analysis, immunoprecipitation, immunofluorescence, ELISA, exposure to hypoxic conditions, cytokines receptor inactivation, in vivo orthotopic tumor formation assay in the presence or absence of inhibitors to the proposed signaling pathways, analysis of publically available data sets for the association of selected factors with overall survival, distant metastasis free survival and recurrent free survival to define the mechanism geminin overexpressing cells employ in vivo to recruit and initiate bi-directional interactions with MSCs in order to enhance their own aggressiveness. Results: Here we show that geminin-dependent acetylation of chromatin HMGB1 (Ac-HMGB1) leads to its release to the extracellular space. Extracellular Ac-HMGB1 promotes geminin overexpressing (GemOE) cells survival by binding to RAGE receptors. Extracellular Ac-HMGB1 also triggers expression and activation of RAGE in the non-expressing MSCs leading to induction of CXCR4 expression and migration of MSCs towards SDF1/CXCL12-expressing GemOE cells. Inhibiting c-Abl, RAGE or CXCR4 prevented MSCs recruitment to GemOE cells in vitro and in vivo. Reciprocal interactions between GemOE cells and MSCs elevate the TIC, basal and EMT traits in GemOE cells leading to enhanced aggressiveness. Indeed, faster, larger and more aggressive tumors develop when GemOE cells are co-injected with MSCs in orthotropic tumor model. Concurrently, inhibiting c-Abl and thus geminin function or RAGE or CXCR4 activity in the in vivo model not only suppressed MSCs recruitment to the orthotopic breast tumors, but also led to decrease in TIC, basal and EMT phenotypes in these tumors. Conclusion: We suggest that GemOE generates metastatic tumors in part through recruiting and interacting with MSCs. Citation Format: Theresa Bonner, Suryatheja Ananthula, Janene Nordan, Simran Batth, Gailen D. Marshall, Lauren H. Gardner, Yoshiko Shimizu, Wael M. ElShamy. Geminin overexpression-dependent recruitment and crosstalk with mesenchymal stem cells enhances aggressiveness in triple-negative breast cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4112.

KIT Exon 11 Codons 557-558 Deletion Mutation Promotes Liver Metastasis Through the CXCL12/CXCR4 Axis in Gastrointestinal Stromal Tumors.

KIT mutations, the most prevalent genetic event in gastrointestinal stromal tumors (GIST), are associated with malignant features and poor prognosis. Aggressive GISTs possess a high propensity to spread to the liver. This study aimed to explore the role of KIT mutations in GIST liver metastasis. A total of 170 GISTs were used to determine the association between KIT mutations and liver metastasis. Immunohistochemistry was performed to assess the correlation of KIT mutations with CXCR4 and ETV1 expression. Genetic and pharmacologic methods were used to study the regulation of CXCR4 and ETV1 by KIT mutations. Codons 557 and 558 in KIT exon 11 were deletion hot spots in GISTs. KIT exon 11 deletions involving codons 557-558 were highly associated with liver metastasis. Overexpression of mutant KIT with exon 11 codons 557-558 deletion (KIT Δ557-558) increased GIST cell motility and liver metastasis. Mechanistically, overexpression of KIT Δ557-558 in GIST cells increased ETV1 and CXCR4 expression. CXCR4 knockdown counteracted KIT Δ557-558-mediated cell migration. Moreover, KIT Δ557-558-induced CXCR4 expression could be abolished by silencing ETV1. The chromatin immunoprecipitation assay showed that ETV1 directly bound to the CXCR4 promoter. After ERK inhibitor PD325901 treatment, the upregulation of ETV1 by KIT Δ557-558 was prevented. In addition, KIT exon 11 codons 557-558 deletion enhanced CXCL12-mediated GIST cell migration and invasion. KIT exon 11 557-558 deletion upregulates CXCR4 through increased binding of ETV1 to the CXCR4 promoter in GIST cells, which thus promotes liver metastasis. These findings highlighted the potential therapeutic targets for metastatic GISTs. Clin Cancer Res; 22(14); 3477-87. ©2016 AACR.

Tetramethylpyrazine (TMP), an Active Ingredient of Chinese Herb Medicine Chuanxiong, Attenuates the Degeneration of Trabecular Meshwork through SDF-1/CXCR4 Axis.

BackgroundA traditional Chinese medicine, Tetramethylpyrazine (TMP), has been prescribed as a complementary treatment for glaucoma to improve patient prognosis. However, the pharmacological mechanism of action of TMP is poorly understood. In previous studies, we demonstrated that TMP exerts potent inhibitory effects on neovascularization, suppresses the tumorigenic behavior of glioma cells, and protects neural cells by regulating CXCR4 expression. Here, we further investigated whether the SDF-1/CXCR4 pathway is also involved in the TMP-mediated activity in trabecular meshwork cells.Methodology/Principal FindingsCXCR4 expression was examined by quantitative real-time PCR in trabecular and iris specimens from 54 primary open-angle glaucoma (POAG) patients who required surgery and 19 non-glaucomatous donors. Our data revealed markedly elevated CXCR4 expression in the trabecular meshwork of POAG patients compared with that of controls. Consistently, CXCR4 expression was much higher in glaucomatous trabecular meshwork cells than in normal trabecular meshwork cells. Using RT-PCR and western blot assays, we determined that glaucoma-related cytokines and dexamethasone (DEX) also significantly up-regulated CXCR4 expression in primary human trabecular meshwork (PHTM) cells. Moreover, the TGF-β1-mediated induction of CXCR4 expression in PHTM cells was markedly down-regulated by TMP compared with control treatment (PBS) and the CXCR4 antagonist AMD3100. In addition, TMP could counteract the TGF-β1-induced effects on stress fiber accumulation and expansion of PHTM cells. TMP markedly suppressed the migration of PHTM cells stimulated by TGF-β1 in transwell and scratch wound assays. TMP also suppressed the extracellular matrix (ECM) accumulation induced by TGF-β2.ConclusionsOur findings demonstrate that CXCR4 might be involved in the pathogenetic changes in the trabecular meshwork of patients with POAG. Additionally, TMP might exert its beneficial effects in POAG patients by down-regulating CXCR4 expression.

Abstract 4182: Gemcitabine triggers angiogenesis-promoting molecular signals in pancreatic cancer cells: Therapeutic implications

Abstract Pancreatic tumor microenvironment (TME) is characterized by poor tumor vasculature and extensive desmoplasia that together contribute to poor response to chemotherapy. It was recently shown that targeting of TME to inhibit desmoplastic reaction in a mouse model of pancreatic cancer resulted in increased microvessel density and intratumoral drug concentration, leading to improved therapeutic response. This approach; however, failed to generate a favorable response in a clinical trial. In that regard, we have previously demonstrated that gemcitabine-treatment of pancreatic cancer cells induces CXCR4 expression in a counter-defense mechanism and promotes pancreatic tumor cell invasiveness. The goal of present study was to examine the effect of chemotherapy on endothelial cell growth and migration. Pancreatic cancer cells were treated with gemcitabine or vehicle for 8 h and subsequently incubated in fresh low serum-containing media for next 48 h. Conditioned media was collected from vehicle- (V-CM) and gemcitabine-treated (Gem-CM) pancreatic cancer cells and used for the treatment of human umbilical vein endothelial cells (HUVEC). The data demonstrated stimulatory effects of Gem-CM on endothelial cell proliferation, migration, invasion and capillary-like structure (CLS) formation. Expression analysis of vehicle- and gemcitabine-treated pancreatic cancer cells and their conditioned-media revealed an upregulation of CXCL8/IL8, which is a known regulator of angiogenesis. Currently, we are investigating whether IL8 mediates the effect of Gem-CM on endothelial cells. Together, our findings suggest that gemcitabine triggers angiogenesis-promoting molecular signals in pancreatic cancer cells, which, in light of our previous observations, may hold important clinical and translational significance. Citation Format: Mohammad Aslam Khan, Sanjeev K. Srivastava, Arun Bhardwaj, Seema Singh, James E. Carter, Ajay P. Singh. Gemcitabine triggers angiogenesis-promoting molecular signals in pancreatic cancer cells: Therapeutic implications. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4182. doi:10.1158/1538-7445.AM2015-4182

Abstract 245: Plasminogen Augments Cxcl12/cxcr4-regulated Stem Cell Homing And Contributes To Cardiac Repair After Myocardial Infarction.

Myocardial infarction (MI) is a leading cause of morbidity and mortality worldwide. Bone marrow (BM)-derived stem cells promote tissue repair and regeneration after MI. Thrombolytic treatment with plasminogen (Plg) activators significantly improves the clinical outcome in MI by restoration of cardiac perfusion. In addition to its canonical function, Plg is critical for cardiac repair, wound healing and liver injury, however, the mechanism for Plg-regulated tissue repair remains unclear. Here, we show a novel role of Plg in stem cell-mediated neovascularization and cardiac repair after MI. Our data show that Granulocyte colony-stimulating factor (G-CSF), a stem cell mobilizer, significantly increased neovascularization and decreased infarct size in the infarct area, and improved ejection fraction and LV internal diameter by echocardiogram in wild-type mice. No improvement in tissue repair and heart function was observed in Plg deficient (Plg-/-) mice indicating that Plg is required for stem cell-regulated cardiac repair after MI. In vivo tracking of GFP-expressing BM cells after BM transplantation revealed that in Plg-/- mice, recruitment of BM-derived stem cells (GFP+c-kit+ cells) to the infarcted heart and stem cell-derived vessels and arteries are dramatically decreased (by 11 fold) suggesting that Plg may regulate stem cell homing to the lesion sites and subsequently contribute stem cell-mediated tissue regeneration. Mechanistic studies show that Plg up-regulated CXCR4 expression on stem cell in vivo and in vitro, suggesting Plg may promotes stem cell homing by induction of CXCR4 expression in stem cells. Stem cell migration was enhanced by endogenous Plg in vitro, however, AMD3100, a CXCR4 antagonist, significantly inhibited Plg-regulated stem cell migration. Furthermore, lentiviral reconstitution of CXCR4 expression in BM cells rescued stem cell homing to the infarcted heart in Plg-/- mice, indicating that Plg mediates stem cell homing through regulating CXCR4 expression. These findings identified a novel role of Plg in cardiac repair by promoting stem cell homing to the injured heart after MI. Thus, targeting Plg may offer a new therapeutic strategy for strengthening stem cell-mediated cardiac repair and regeneration after MI.

Hypoxia Promotes Migration and Induces CXCR4 Expression via HIF-1α Activation in Human Osteosarcoma

BackgroundCellular adaptation to a hypoxic microenvironment is essential for tumor progression and is largely mediated by HIF-1α through coordinated regulation of hypoxia-responsive genes. The chemokine SDF-1α and its unique receptor CXCR4 have been implicated in organ-specific metastases of many cancers. In this study, we investigated the response of osteosarcoma cells to hypoxia and the expression of CXCR4 and HIF-1α in human osteosarcoma specimens and explored the roles of CXCR4 and HIF-1α in the cell migration process.Methodology/Principal FindingsWe performed immunohistochemistry, immunocytochemistry, quantitative real-time PCR, Western blots and fluorescent reporter assays to evaluate the correlation between CXCR4 and HIF-1α expression in human osteosarcoma specimens or SOSP-9607 cells under normoxic and hypoxic conditions. Transwell assays were used to assess cell migration under different conditions. Exposure of SOSP-9607 cells to hypoxic conditions resulted in significantly increased migration. When SOSP-9607 cells were subjected to hypoxic conditions, the mRNA and protein levels of CXCR4 were significantly increased in a time-dependent manner. Moreover, siHIF-1α significantly decreased the mRNA and protein levels of CXCR4 under hypoxia, whereas pcDNA-HIF-1α significantly increased the mRNA and protein levels of CXCR4 under normoxia. A luciferase reporter gene study showed that siHIF-1α reduced pGL3-CXCR4 luciferase activity. Furthermore, coexpression of HIF-1α and CXCR4 was significantly higher in patients with distant metastasis compared with those without metastasis.Conclusions/SignificanceThe hypoxia-HIF-1α-CXCR4 pathway plays a crucial role during the migration of human osteosarcoma cells, and targeting this pathway might represent a novel therapeutic strategy for patients suffering from osteosarcoma.

Galectin-1 Upregulates CXCR4 to Promote Tumor Progression and Poor Outcome in Kidney Cancer

Galectin-1, a β-galactoside-binding lectin, is involved in many physiologic and pathologic processes, including cell adhesion, differentiation, angiogenesis, and tumor progression. However, the role of galectin-1 in kidney cancer remains elusive. This study evaluated the role of galectin-1 in the progression and clinical prognosis of renal cell carcinoma. We found significant overexpression of galectin-1 in both kidney cancer cell lines and metastatic tissue specimens from patients with renal cell carcinoma. Knockdown of galectin-1 gene expression in renal cancer cell lines reduced cell invasion, clonogenic ability, and epithelial-mesenchymal transition in vitro; reduced tumor outgrowth in vivo; and inhibited the angiogenesis-inducing activity of these cells in vitro and in vivo. Galectin-1 knockdown decreased CXCR4 expression levels in kidney cancer cells, and restoration of CXCR4 expression in galectin-1-silenced cells rescued cell motility and clonogenic ability. Additional studies suggested that galectin-1 induced CXCR4 expression through activation of nuclear factor-κB (NF-κB). Analysis of patient specimens confirmed the clinical significance and positive correlation between galectin-1 and CXCR4 expression levels and revealed concomitant overexpression of galectin-1 and CXCR4 associated adversely with overall and disease-free survival. Our findings suggest that galectin-1 promotes tumor progression through upregulation of CXCR4 via NF-κB. The coordinated upregulation of galectin-1 and CXCR4 may be a novel prognostic factor for survival in patients with renal cell carcinoma and the galectin-1-CXCR4 axis may serve as a therapeutic target in this disease.

Targeting The Protective Microenvironment In Multiple Myeloma (MM): An Analysis Of The CXCL12/CXCR4-Axis and Its Inhibitors AMD3100 and Nox-A12 Combined With Antimyeloma Substances, Such As Pomalidomide and Carfilzomib

IntroductionThe interaction of malignant plasma cells (PC) with the bone marrow (BM) microenvironment is crucial for MM pathogenesis. The CXCL12/CXCR4-axis plays a key role in this cross-talk.CXCL12 induces homing of normal hematopoietic progenitor cells to the BM and also drives MM cells to their protective niche. The binding of CXCL12 to CXCR4 directly promotes PC survival and facilitates environment-mediated drug resistance, which ultimately renders antimyeloma substances ineffective. Therefore, targeting the CXCL12/CXCR4-axis in combination with the use of new antimyeloma therapeutics represents a promising approach in developing new treatment strategies. MethodsComparative analysis of three different CXCR4 antibody clones (12G5, 44717, 4G10) and their interaction with the CXCR4 inhibitor AMD3100 was performed by flow cytometry. The effect of CXCL12 on CXCR4 expression using the human MM cell lines (MMCLs) U266 and L363, with and without AMD3100, was assessed by flow- and image cytometry. CXCR4 downstream pathways were analysed by western blot. Pomalidomide and the specific proteasome inhibitor carfilzomib were tested in various concentrations, with and without AMD3100, using MMCLs (U266, L363) and BM samples from MM patients (n=4, BM infiltration >50%), with and without M210B4 stroma support. Cell viability was evaluated by trypan blue- and PI/annexin staining. Treatment effects on the expression of CD138, CD38 and CXCR4 were detected by flow- and image cytometry. The combination of carfilzomib with AMD3100 or NOX-A12 is currently being analysed regarding synergistic cytotoxicity and drug resistance. NOX-A12 is a PEGylated mirror-image oligonucleotide (Spiegelmer®) that binds to CXCL12 (stromal cell-derived factor-1, SDF-1) with high affinity, thereby inhibiting CXCL12 signalling on both its receptors, CXCR4 and CXCR7. The effect of NOX-A12 is of eminent interest when compared to AMD3100 and with use of various antimyeloma agents. ResultsAMD3100 treatment of U266 cells reduced CXCR4 expression with the commonly used antibody (ab)-clone 12G5 by 44-fold and with clone 44717 by 5-fold. The binding of the ab-clone 4G10 (FITC- and PE-coupled) was not influenced by AMD3100 at the concentrations tested (20-200 µl/ml), making 4G10 the most reliable for CXCR4 analysis. We also established a protocol for image cytometry that allows imaging of high cell throughputs, assessing viability and the expression of intra- and extracellular CXCR4 with no need for transfection. Human U266 cells showed high extra- and intracellular CXCR4-expression, whereas the lower expression of CXCR4 in L363 cells was confirmed. CXCL12 induced a notable decrease in extracellular CXCR4 and increased intracellular CXCR4 expression, confirming the reliability of our image cytometry protocol. AMD3100 alone inhibited cell proliferation (p<0.01) in U266 monoculture at different time points (t1=24h, t2=3d), although it was not cytotoxic. In terms of CXCR4 expression, CXCL12-induced CXCR4 internalization was inhibited by AMD3100, even after long incubation periods (t=3d). The use of carfilzomib on MMCLs confirmed prior cytotoxic concentrations (20-100nM), whereas L363 cells were even more sensitive than U266 cells. M210B4 co-culture induced CXCR4 expression and tumor cell protection, however was not able to completely induce resistance to carfilzomib: use of 100nM carfilzomib remained substantially cytotoxic, decreasing overall cell numbers, CD138 positive cells and CXCR4-expression in U266 cells. Co-cultivation of MM patient-derived BM cells with M210B4 stroma substantially reduced cell apoptosis as described (Zlei,Engelhardt, Ex Hematol 2007, Udi, Engelhardt, BJH 2013). When primary MM cells were grown without stroma support, AMD3100 did not enhance pomalidomide-induced cytotoxic effects; however, when primary MM cells were co-cultured with M210B4, pomalidomide (100nM) and AMD3100 (50µM) inhibited cell proliferation, and the combination was significantly more effective than AMD3100 alone (p=0.018). ConclusionOur findings stress the importance of CXCL12 and its receptor CXCR4 in MM progression and environment-mediated drug resistance. Analysis of the CXCL12/CXCR4-axis, of its inhibitors AMD3100 and NOX-A12 as well as their combined effects with antimyeloma substances may pave the way to novel therapeutic strategies. Disclosures:No relevant conflicts of interest to declare.

Residual Prostate Cancer Cells after Docetaxel Therapy Increase the Tumorigenic Potential via Constitutive Signaling of CXCR4, ERK1/2 and c-Myc

Despite an increasing prevalence of patients with docetaxel-refractory prostate cancer, little is known about the tumor biology of the docetaxel-resistant residual tumor cells compared with primary tumor cells. In this study, tumorigenic potential was increased in the docetaxel-resistant residual prostate cancer cell lines (DRD, 1G7 and PC3DR) compared with parental cells (DU145 or PC3). Enhanced tumorigenic potential was conferred by oncogenic c-Myc, which was stabilized by constitutively activated ERK1/2 in DRD, 1G7, and PC3DR cells. Constitutively activated ERK1/2 was maintained by CXCR4, which was upregulated in DRD, 1G7, and PC3DR cells. In docetaxel-treated DU145 cells, transiently activated ERK1/2 induced CXCR4 expression by stabilizing c-Myc. Furthermore, constitutive activation of CXCR4, ERK1/2, and c-Myc signaling was evident in clinical tissue samples from human patients with docetaxel-resistant prostate cancer. In DTX-resistant residual prostate cancer cells, the enhanced tumorigenic potential was reduced by ERK1/2 inhibition, or by AMD3100, a CXCR4 antagonist. Thus, docetaxel treatment constitutively activated the CXCR4, ERK1/2, and c-Myc signaling loop in docetaxel-resistant residual prostate cancer cells. Constitutive signaling pathways are viable therapeutic targets for residual prostate tumor cells following acquisition of docetaxel resistance.

An Undesired Effect of Chemotherapy: GEMCITABINE PROMOTES PANCREATIC CANCER CELL INVASIVENESS THROUGH REACTIVE OXYGEN SPECIES-DEPENDENT, NUCLEAR FACTOR κB- AND HYPOXIA-INDUCIBLE FACTOR 1α-MEDIATED UP-REGULATION OF CXCR4

Recently, we have shown that CXCL12/CXCR4 signaling plays an important role in gemcitabine resistance of pancreatic cancer (PC) cells. Here, we explored the effect of gemcitabine on this resistance mechanism. Our data demonstrate that gemcitabine induces CXCR4 expression in two PC cell lines (MiaPaCa and Colo357) in a dose- and time-dependent manner. Gemcitabine-induced CXCR4 expression is dependent on reactive oxygen species (ROS) generation because it is abrogated by pretreatment of PC cells with the free radical scavenger N-acetyl-L-cysteine. CXCR4 up-regulation by gemcitabine correlates with time-dependent accumulation of NF-κB and HIF-1α in the nucleus. Enhanced binding of NF-κB and HIF-1α to the CXCR4 promoter is observed in gemcitabine-treated PC cells, whereas their silencing by RNA interference causes suppression of gemcitabine-induced CXCR4 expression. ROS induction upon gemcitabine treatment precedes the nuclear accumulation of NF-κB and HIF-1α, and suppression of ROS diminishes these effects. The effect of ROS on NF-κB and HIF-1α is mediated through activation of ERK1/2 and Akt, and their pharmacological inhibition also suppresses gemcitabine-induced CXCR4 up-regulation. Interestingly, our data demonstrate that nuclear accumulation of NF-κB results from phosphorylation-induced degradation of IκBα, whereas HIF-1α up-regulation is NF-κB-dependent. Lastly, our data demonstrate that gemcitabine-treated PC cells are more motile and exhibit significantly greater invasiveness against a CXCL12 gradient. Together, these findings reinforce the role of CXCL12/CXCR4 signaling in gemcitabine resistance and point toward an unintended and undesired effect of chemotherapy.

Targeting the CD20 and CXCR4 Pathways in Non-Hodgkin Lymphoma with Rituximab and High-Affinity CXCR4 Antagonist BKT140

Chemokine axis CXCR4/CXCL12 is critically involved in the survival and trafficking of normal and malignant B lymphocytes. Here, we investigated the effect of high-affinity CXCR4 antagonist BKT140 on lymphoma cell growth and rituximab-induced cytotoxicity in vitro and in vivo. In vitro efficacy of BKT140 alone or in combination with rituximab was determined in non-Hodgkin lymphoma (NHL) cell lines and primary samples from bone marrow aspirates of patients with NHL. In vivo efficacy was evaluated in xenograft models of localized and disseminated NHL with bone marrow involvement. Antagonizing CXCR4 with BKT140 resulted in significant inhibition of CD20+ lymphoma cell growth and in the induction of cell death, respectively. Combination of BKT140 with rituximab significantly enhanced the apoptosis against the lymphoma cells in a dose-dependent manner. Moreover, rituximab induced CXCR4 expression in lymphoma cell lines and primary lymphoma cells, suggesting the possible interaction between CD20 and CXCR4 pathways in NHL. Primary bone marrow stromal cells (BMSC) further increased CXCR4 expression and protected NHL cells from rituximab-induced apoptosis, whereas BKT140 abrogated this protective effect. Furthermore, BKT140 showed efficient antilymphoma activity in vivo in the xenograft model of disseminated NHL with bone marrow involvement. BKT140 treatment inhibited the local tumor progression and significantly reduced the number of NHL cells in the bone marrow. Combined treatment of BKT140 with rituximab further decreased the number of viable lymphoma cells in the bone marrow, achieving 93% reduction. These findings suggest the possible role of CXCR4 in NHL progression and response to rituximab and provide the scientific basis for the development of novel CXCR4-targeted therapies for refractory NHL.

Hypoxia induces CXCR4 expression and biological activity in gastric cancer cells through activation of hypoxia-inducible factor-1α

Given the important role of CXCR4 in cancer metastasis, microenvironmental factors that modulate CXCR4 may have an impact on the process of tumor expansion. Hypoxia is a common feature of solid tumors and a significant microenvironmental factor that drives aggressive behavior. CXCR4 is upregulated in several cancer cells under hypoxic conditions, suggesting a relationship between tumor hypoxia and CXCR4. However, the role of hypoxia in regulating CXCR4 in gastric cancer remains poorly understood. KATO III gastric cancer cells were exposed to hypoxia or normoxia. CXCR4 expression in cells transfected with shRNA specific for HIF-1α was investigated by western blotting and flow cytometry. Wound healing, migration and invasion assays were used to assess cell motility and the chemotactic response to CXCL12, a major CXCR4 ligand. CXCR4 expression at the protein level and in the cell membrane was significantly increased in KATOIII cells following exposure to hypoxia. This upregulation of CXCR4 was implicated in increased cell motility and enhanced chemotactic responses (migration and invasion) to CXCL12 treatment in vitro. The increases in CXCR4 expression and metastatic potential in gastric cancer cells exposed to hypoxia were blocked by HIF-1α-specific shRNA. Our results indicate that hypoxia upregulates CXCR4 in gastric cancer cells in a HIF-1α-dependent manner, and that upregulation of CXCR4 plays a role in cancer cell migration and invasion. Thus, disrupting the hypoxia-HIF-1α-CXCR4 axis could be an attractive therapeutic strategy for the treatment of gastric cancer.

Abstract 538: ROS differentially regulates prostate cancer cell survival

Abstract In vitro and in vivo studies have shown that ROS accumulation correlates with increasing aggressiveness of prostate cancer cells, and increased expression of oncogenic molecules, such as CXCR4. CXCR4 is a G-Protein Coupled Receptor that is heavily implicated in the metastatic dissemination of prostate tumor cells to bone marrow. In cancer and other cell models, CXCR4 expression and activity increases in response to hypoxic environments and/or oxidative stress. Cells react by inducing expression of a HIF1α transcription factor, which enhances expression of targeted genes involved in adjusting to oxidative stress and cell survival. HIF1α has been shown to directly induce the expression of CXCR4 in prostate cancer cells. Therefore, generation of ROS in tumor tissues may critically influence CXCR4-mediated expression and functions, ultimately encouraging cancer progression. In this study, we elucidate a mechanism by which ROS induces CXCR4 expression and function in prostate cancer cells. We initially investigated the role of ROS on the phosphorylation of AKT (p-AKT) and ERK1/2 (p-ERK1/2) in DU145 and 22Rv1 prostate cancer cell lines. Using H2O2 as our model of ROS, we found that H2O2 induced a gradual expression of p-AKT and p-ERK1/2 by western blot analysis, which was abrogated by the ROS scavenger N-acetyl cysteine (NAC). It has been shown that PTEN is a negative regulator of AKT and ERK1/2 signaling, and that ROS accumulation inactivates PTEN phosphatase function; hence, we determined whether the increase in p-AKT and p-ERK1/2 expression was due to loss of PTEN function. By performing a phosphatase assay, we found that H2O2 inhibited PTEN catalytic activity compared to untreated cells, while NAC abrogated these effects in both cell lines. The increase in ROS and loss of PTEN has been shown to correlate with CXCR4-mediated function; therefore, we determined the role of H2O2 on CXCR4 expression. We found that H2O2 induced CXCR4 expression in DU145 cells, but not in 22Rv1 cells. Furthermore, we investigated whether ROS-mediated induction of CXCR4 was HIF1α dependent. Interestingly, H2O2 induced expression of HIF1α in DU145 cells, which was abrogated by siRNA for HIF1α. HIF1α expression decreased in 22Rv1 cells, which correlated with apoptosis, as confirmed by Annexin-V analysis. Finally, we observed that the H2O2-mediated increase in CXCR4 enhanced transendothelial invasion and migration in DU145 cells in a CXCR4 dependent manner. Our study suggests that ROS differentially regulates CXCR4 expression and function in prostate cancer cells, suggesting that ROS plays a differential role on heterogeneous tumor mass. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 538. doi:1538-7445.AM2012-538