trans-IV restriction: a new configuration for metal bis-cyclam complexes as potent CXCR4 inhibitors

The chemokine receptor CXCR4 is implicated in multiple diseases including inflammatory disorders, cancer growth and metastasis, and HIV/AIDS. CXCR4 targeting has been evaluated in treating cancer metastasis and therapy resistance. Cyclam derivatives, most notably AMD3100 (Plerixafor™), are a common motif in small molecule CXCR4 antagonists. However, AMD3100 has not been shown to be effective in cancer treatment as an individual agent. Configurational restriction and transition metal complex formation increases receptor binding affinity and residence time. In the present study, we have synthesized novel trans-IV locked cyclam-based CXCR4 inhibitors, a previously unexploited configuration, and demonstrated their higher affinity for CXCR4 binding and CXCL12-mediated signaling inhibition compared to AMD3100. These results pave the way for even more potent CXCR4 inhibitors that may provide significant efficacy in cancer therapy.

Nanoparticle-mediated blockade of CXCL12/CXCR4 signaling enhances glioblastoma immunotherapy: Monitoring early responses with MRI radiomics

The limited therapeutic efficacy of checkpoint blockade immunotherapy against glioblastoma is closely related to the blood-brain barrier (BBB) and tumor immunosuppressive microenvironment, where the latter is driven primarily by tumor-associated myeloid cells (TAMCs). Targeting the C-X-C motif chemokine ligand-12/C-X-C motif chemokine receptor-4 (CXCL12/CXCR4) signaling orchestrates the recruitment of TAMCs and has emerged as a promising approach for alleviating immunosuppression. Herein, we developed an iRGD ligand-modified polymeric nanoplatform for the co-delivery of CXCR4 antagonist AMD3100 and the small-molecule immune checkpoint inhibitor BMS-1. The iRGD peptide facilitated superior BBB crossing and tumor-targeting abilities both in vitro and in vivo. In mice bearing orthotopic GL261-Luc tumor, co-administration of AMD3100 and BMS-1 significantly inhibited tumor proliferation without adverse effects. A reprogramming of immunosuppression upon CXCL12/CXCR4 signaling blockade was observed, characterized by the reduction of TAMCs and regulatory T cells, and an increased proportion of CD8+T lymphocytes. The elevation of interferon-γ secreted from activated immune cells upregulated PD-L1 expression in tumor cells, highlighting the synergistic effect of BMS-1 in counteracting the PD-1/PD-L1 pathway. Finally, our research unveiled the ability of MRI radiomics to reveal early changes in the tumor immune microenvironment following immunotherapy, offering a powerful tool for monitoring treatment responses. STATEMENT OF SIGNIFICANCE: The insufficient BBB penetration and immunosuppressive tumor microenvironment greatly diminish the efficacy of immunotherapy for glioblastoma (GBM). In this study, we prepared iRGD-modified polymeric nanoparticles, loaded with a CXCR4 antagonist (AMD3100) and a small-molecule checkpoint inhibitor of PD-L1 (BMS-1) to overcome physical barriers and reprogram the immunosuppressive microenvironment in orthotopic GBM models. In this nanoplatform, AMD3100 converted the "cold" immune microenvironment into a "hot" one, while BMS-1 synergistically counteracted PD-L1 inhibition, enhancing GBM immunotherapy. Our findings underscore the potential of dual-blockade of CXCL12/CXCR4 and PD-1/PD-L1 pathways as a complementary approach to maximize therapeutic efficacy for GBM. Moreover, our study revealed that MRI radiomics provided a clinically translatable means to assess immunotherapeutic efficacy.

[Research Progress on the Application Strategies of Plerixafor in the Peripheral Blood Stem Cell Mobilization for Autologous Transplantation--Review]

Plerixafor, an analog of C-X-C motif chemokine receptor 4 (CXCR4), which allows the release of stem cells from the bone marrow into peripheral blood (PB) by disrupting the interaction of CXCR4 with stromal cell-derived factor-1 (SDF-1), is effective in mobilization for peripheral blood stem cells (PBSC). Due to its market approval has not been long and its high price in China, the clinical application of plerixafor is still very limited. The clinicians are actively seeking the optimal use of plerixafor to improve the success rate of PBSC collection and reduce the cost. This article reviews the latest research progress related to plerixafor application, in order to summarize the optimal use of plerixafor in autologous hematopoietic stem cell transplantation (auto-HSCT).

Stromal cell-derived factor-1 downregulation contributes to neuroprotection mediated by CXC chemokine receptor 4 interactions after intracerebral hemorrhage in rats

AIM

Stromal cell-derived factor-1 (SDF-1) and CXC chemokine receptor 4 (CXCR4) have a substantial role in neuronal formation, differentiation, remodeling, and maturation and participate in multiple physiological and pathological events. In this study, we investigated the role of SDF-1/CXCR4 in neural functional injury and neuroprotection after intracerebral hemorrhage (ICH).

METHODS

Western blot, immunofluorescence and immunoprecipitation were used to detect SDF-1/CXCR4 expression and combination respectively after ICH. TUNEL staining, Lactate dehydrogenase assay, Reactive oxygen species assay, and Enzyme-linked immunosorbent assay to study neuronal damage; Brain water content to assay brain edema, Neurological scores to assess short-term neurological deficits. Pharmacological inhibition and genetic intervention of SDF-1/CXCR4 signaling were also used in this study.

RESULTS

ICH induced upregulation of SDF-1/CXCR4 and increased their complex formation, whereas AMD3100 significantly reduced it. The levels of TNF-α and IL-1β were significantly reduced after AMD3100 treatment. Additionally, AMD3100 treatment can alleviate neurobehavioral dysfunction of ICH rats. Conversely, simultaneous SDF-1/CXCR4 overexpression induced the opposite effect. Moreover, immunoprecipitation confirmed that SDF-1/CXCR4 combined to initiate neurodamage effects.

CONCLUSION

This study indicated that inhibition of SDF-1/CXCR4 complex formation can rescue the inflammatory response and alleviate neurobehavioral dysfunction after ICH. SDF-1/CXCR4 may have applications as a therapeutic target after ICH.

A highly selective and sensitive fluorescence probe based on BODIPY-cyclen for hydrogen sulfide detection in living cells and serum

Hydrogen sulfide (H2S) is a multifunctional gaseous signaling molecule that plays a vital role in several biological processes. In the present study, a BODIPY-based fluorescent probe called 8-[4-((1,4,7,10-tetraazacyclododecane)methyl)phenyl]-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a, 4a-diaza-s-indacene (BA-Cyclen)-Cu was designed and synthesized; this probe is a Cu(Ⅱ) complex that uses Cu(Ⅱ) decomplexation to achieve the sensitive and rapid detection of aqueous H2S via the "turn-on" mode. We observed that BA-Cyclen-Cu exhibited good membrane permeability, low toxicity, and lysosome-targeting ability, facilitating H2S detection in living cells. Furthermore, we demonstrated the potential biological applications of the probe by measuring exogenous H2S originating from Na2S and GYY4137, a slow-release donor, and endogenous H2S generated via the catalysis of cystathionine-β-synthase in both normal (H9c2) and cancerous (U87) cells. Moreover, BA-Cyclen-Cu was successfully used to detect exogenous H2S by the external standard method in fetal bovine serum, the serum of a healthy person, and the serum of a patient with liver cancer.

Tuning the Softness of the Pendant Arms and the Polyazamacrocyclic Backbone to Chelate the 203Pb/212Pb Theranostic Pair

A series of macrocyclic ligands were considered for the chelation of Pb2+: 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO4S), 1,4,7-tris[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (DO3S), 1,4,7-tris[2-(methylsulfanyl)ethyl]-10-acetamido-1,4,7,10-tetraazacyclododecane (DO3SAm), 1,7-bis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane-4,10-diacetic acid (DO2A2S), 1,5,9-tris[2-(methylsulfanyl)ethyl]-1,5,9-triazacyclododecane (TACD3S), 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetrazacyclotridecane (TRI4S), and 1,4,8,11-tetrakis[2-(methylsulfanyl)ethyl]-1,4,8,11-tetrazacyclotetradecane (TE4S). The equilibrium, the acid-mediated dissociation kinetics, and the structural properties of the Pb2+ complexes formed by these chelators were examined by UV-Visible and nuclear magnetic resonance (NMR) spectroscopies, combined with potentiometry and density functional theory (DFT) calculations. The obtained results indicated that DO4S, DO3S, DO3SAm, and DO2A2S were able to efficiently chelate Pb2+ and that the most suitable macrocyclic scaffold for Pb2+ is 1,4,7,10-tetrazacyclododecane. NMR spectroscopy gave insights into the solution structures of the Pb2+ complexes, and 1H-207Pb interactions confirmed the involvement of S and/or O donors in the metal coordination sphere. Highly fluxional solution behavior was discovered when Pb2+ was coordinated to symmetric ligands (i.e., DO4S and DO2A2S) while the introduction of structural asymmetry in DO3S and DO3SAm slowed down the intramolecular dynamics. The ligand ability to chelate [203Pb]Pb2+ under highly dilute reaction conditions was explored through radiolabeling experiments. While DO4S and DO3S possessed modest performance, DO3SAm and DO2A2S demonstrated high complexation efficiency under mild reaction conditions (pH = 7, 5 min reaction time). The [203Pb]Pb2+ complexes' integrity in human serum over 24 h was appreciably good for [203Pb][Pb(DO4S)]2+ (80 ± 5%) and excellent for [203Pb][Pb(DO3SAm)]2+ (93 ± 1%) and [203Pb][Pb(DO2A2S)] (94 ± 1%). These results reveal the promise of DO2A2S and DO3SAm as chelators in cutting-edge theranostic [203/212Pb]Pb2+ radiopharmaceuticals.

Electronic Structure and Reactivity of Mononuclear Nonheme Iron-Peroxo Complexes as a Biomimetic Model of Rieske Oxygenases: Ring Size Effects of Macrocyclic Ligands

We report the macrocyclic ring size-electronic structure-electrophilic reactivity correlation of mononuclear nonheme iron(III)-peroxo complexes bearing N-tetramethylated cyclam analogues (n-TMC), [FeIII(O2)(12-TMC)]+ (1), [FeIII(O2)(13-TMC)]+ (2), and [FeIII(O2)(14-TMC)]+ (3), as a model study of Rieske oxygenases. The Fe(III)-peroxo complexes show the same δ and pseudo-σ bonds between iron and the peroxo ligand. However, the strength of these interactions varies depending on the ring size of the n-TMC ligands; the overall Fe-O bond strength and the strength of the Fe-O2 δ bond increase gradually as the ring size of the n-TMC ligands becomes smaller, such as from 14-TMC to 13-TMC to 12-TMC. MCD spectroscopy plays a key role in assigning the characteristic low-energy δ → δ* LMCT band, which provides direct insight into the strength of the Fe-O2 δ bond and which, in turn, is correlated with the superoxo character of the iron-peroxo group. In oxidation reactions, reactivities of 1-3 toward hydrocarbon C-H bond activation are compared, revealing the reactivity order of 1 > 2 > 3; the [FeIII(O2)(n-TMC)]+ complex with a smaller n-TMC ring size, 12-TMC, is much more reactive than that with a larger n-TMC ring size, 14-TMC. DFT analysis shows that the Fe(III)-peroxo complex is not reactive toward C-H bonds, but it is the end-on Fe(II)-superoxo valence tautomer that is responsible for the observed reactivity. The hydrogen atom abstraction (HAA) reactivity of these intermediates is correlated with the overall donicity of the n-TMC ligand, which modulates the energy of the singly occupied π* superoxo frontier orbital that serves as the electron acceptor in the HAA reaction. The implications of these results for the mechanism of Rieske oxygenases are further discussed.

Synthesis and in vitro cytotoxic activity of dye-linker-macrocycle conjugates with variable linker length and components

The study investigated the structure-activity relationship of newly synthesized dye-linker-macrocycle (DLM) conjugates and the effect of each component on various biological properties, including cytotoxicity, cellular uptake, intracellular localization, interaction with DNA and photodynamic effects. The conjugates were synthesized by combining 1,8-naphthalimide and thioxanthone dyes with 1,4,7,10-tetraazacyclododecane (cyclen) and 1-aza-12-crown-4 (1A12C4) using alkyl linkers of different lengths. The results revealed significant differences in biological activity among the various series of conjugates. Particularly, 1A12C4 conjugates exhibited notably higher cytotoxicity compared to cyclen conjugates. Conjugation with 1A12C4 proved to be an effective strategy for increasing cellular uptake and cytotoxicity of small-molecule conjugates. In addition, the results highlighted the critical role of linker length in modulating the biological activity of DLM conjugates. It became clear that the choice of each component (dye, macrocycle and linker) could significantly alter the biological activity of the conjugates.

A Bridge too Far? Comparison of Transition Metal Complexes of Dibenzyltetraazamacrocycles with and without Ethylene Cross-Bridges: X-ray Crystal Structures, Kinetic Stability, and Electronic Properties

Tetraazamacrocycles, cyclic molecules with four nitrogen atoms, have long been known to produce highly stable transition metal complexes. Cross-bridging such molecules with two-carbon chains has been shown to enhance the stability of these complexes even further. This provides enough stability to use the resulting compounds in applications as diverse and demanding as aqueous, green oxidation catalysis all the way to drug molecules injected into humans. Although the stability of these compounds is believed to result from the increased rigidity and topological complexity imparted by the cross-bridge, there is insufficient experimental data to exclude other causes. In this study, standard organic and inorganic synthetic methods were used to produce unbridged dibenzyl tetraazamacrocycle complexes of Co, Ni, Cu, and Zn that are analogues of known cross-bridged tetraazamacrocycles and their transition metal complexes to allow direct comparison of molecules that are identical except for the cross-bridge. The syntheses of the known tetraazamacrocycles and the new transition metal complexes were successful with high yields and purity. Initial chemical characterization of the complexes was conducted by UV-Visible spectroscopy, while cyclic voltammetry showed more marked differences in electronic properties from bridged versions. Direct comparison studies of the unbridged and bridged compounds' kinetic stabilities, as demonstrated by decomposition using high acid concentration and elevated temperature, showed that the cyclen-based complex stability did not benefit from cross-bridging. This is likely due to poor complementarity with the Cu²⁺ ion while cyclam-based complexes benefited greatly. We conclude that ligand-metal complementarity must be maintained in order for the topological and rigidity constraints imparted by the cross-bridge to contribute significantly to complex robustness.

A Cyclen-Functionalized Cobalt-Substituted Sandwich-Type Tungstoarsenate with Versatility in Removal of Methylene Blue and Anti-ROS-Sensitive Tumor Cells

Oxidative degradation by using reactive oxygen species (ROS) is an effective method to treat pollutants. The synthesis of artificial oxidase for the degradation of dyes is a hot spot in molecular science. In this study, a nanoscale sandwich-type polyoxometalate (POM) on the basis of a tetra-nuclear cobalt cluster and trivacant B-α-Keggin-type tungstoarsenate {[Co(C₈H₂₀N₄)]₄}{Co₄(H₂O)₂[HAsW₉O₃₄]₂}∙4H₂O (abbreviated as CAW, C₈H₂₀N₄ = cyclen) has been synthesized and structurally examined by infrared (IR) spectrum, ultraviolet–visible (UV–Vis) spectrum, X-ray photoelectron spectrum (XPS), single-crystal X-ray diffraction (SXRD), and bond valence sum (Σs) calculation. According to the structural analysis, the principal element of the CAW is derived from modifying sandwich-type polyanion {Co₄(H₂O)₂ [HAsW₉O₃₄]₂}^8– with four [Co(Cyclen)]²⁺, in which 1,4,7,10-tetraazacyclododecane (cyclen) is firstly applied to modify POM. It is also demonstrated that CAW is capable of efficiently catalyzing the production of ROS by the synergistic effects of POM fragments and Co–cyclen complexes. Moreover, CAW can interfere with the morphology and proliferation of sensitive cells by producing ROS and exhibits ability in specifically eliminating methylene blue (MB) dyes from the solution system by both adsorption and catalytic oxidation.

Self-Assembly of Intelligent Nanoplatform for Endogenous H2S-Triggered Multimodal Cascade Therapy of Colon Cancer

The specific in situ generation and activation of therapeutic agents with high spatiotemporal precision is expected to revolutionize cancer treatment. Here, we develop an intelligent nanoplatform (termed as NP-Cu), which is constructed by assembling photosensitizer chlorin e6 (Ce6), hypoxia-responsive prodrug banoxantrone (AQ4N) with clickable dibenzocyclooctyne (DIBO) functionalized lysine (D-K), and cyclen-Cu²⁺ complex, for improving combination anticancer therapy. Cyclen-Cu²⁺ complex-induced photodynamic therapy (PDT) quenching in NP-Cu can be effectively and selectively activated by tumor-overproduced hydrogen sulfide (H₂S). More importantly, the reaction of endogenous H₂S with Cu²⁺ can generate photothermal agent copper sulfide (CuS) for photothermal therapy (PTT). Furthermore, with the activation of PTT and PDT, intracellular hypoxic stress is amplified to trigger AQ4N-associated chemodynamic therapy (CDT), leading to light-enhanced cascade therapy of PDT, PTT and CDT. Therefore, we present a simple and practical strategy for developing pathological stimuli responsive combination therapy, which has the potential of advancing precision cancer medicine.

Plerixafor on a WHIM - Promise or Fantasy of a New CXCR4 Inhibitor for This Rare, but Important Syndrome?

Warts, Hypogammaglobulinemia, Infections and Myelokathexis (WHIM) is a primary immunodeficiency syndrome. Patients with WHIM syndrome are more susceptible to human papillomavirus (HPV) infections and commonly present to a dermatologist with recalcitrant to treatment warts. Other cardinal features of WHIM syndrome include recurrent sinopulmonary bacterial infections, neutropenia/lymphopenia, low levels of immunoglobulins (IgG, IgA, IgM) and myelokathexis. Research demonstrated that truncating gain-of-function mutations of the C-X-C chemokine receptor type 4 gene (CXCR4) are responsible for this disease. Plerixafor, a specific small molecule antagonist of CXCR4, is currently used for peripheral blood hematopoietic stem cell (HSC) mobilization in stem cell transplant recipients. It has recently shown promise for the treatment of WHIM syndrome in phase I/II clinical trials. In this paper we review the emerging patient clinical data for this medication and highlight the role of CXCR4 in other important skin diseases including keratinocyte carcinomas, psoriasis and cutaneous T-cell lymphoma.

[A Single-Center Analysis of the Use of G-CSF Combined with Plerixafor to Mobilize Peripheral Blood Hematopoietic Stem Cell from Healthy Related Donors in Allogeneic Hematopoietic Stem Cell Transplantation]

OBJECTIVE

To study the effect and safety of G-CSF combined with Plerixafor on the mobilization of peripheral blood hematopoietic stem cells from healthy related donors of allogeneic hematopoietic stem cell transplantation (allo-HSCT).

METHODS

It was analyzed retrospectively that the data of peripheral blood hematopoietic stem cells from 33 (observation group) related donors mobilized by G-CSF plus Plerixafor in Hebei Yanda Lu Daopei Hospital from April 2019 to April 2021. Bone marrow and peripheral blood hematopoietic stem cells (PBSCs) of these donors were respectively collected on the fourth and fifth day of G-CSF-induced mobilization. Following the administration of Plerixafor on the night of the fifth day, PBSCs were collected on the sixth day once again. 46 donors using "G-CSF only" mobilization method in the same period were randomly selected as the control and respectively analyzed the differences of CD34+ cell counts on the fifth and the sixth day in two groups. And the donors' adverse reaction to Plerixafor in the form of questionnaire was also observed. Then it was compared that the patients who underwent allo-HSCT in "G-CSF+Plerixafor" group and "G-CSF only" group in terms of acute GVHD at grade I-IV or III-IV, CMV reactivation and EBV reactivation.

RESULTS

CD34+ cells count (M±Q) among PBSCs collected on the fifth and the sixth day in the observation group were (1.71±1.02)×10⁶/kg and (4.23±2.33)×10⁶/kg, respectively. CD34+ cell counts on the sixth day was significantly higher than that of the fifth day (P<0.001); While the counterparts in the control group were (2.47±1.60)×10⁶/kg and (1.87±1.37)×10⁶/kg, respectively. By statistical analysis, CD34+ cell counts on the sixth day was significantly less than that of the fifth day (P<0.001). The adverse reaction to Plerixafor for the donors in the study were all grade 1 or 2 (mild or moderate) according to CTCAE 5.0 and disappeared in a short time. The patients who underwent allo-HSCT in the "G-CSF+Plerixafor" group and "G-CSF only" group were not statistically significant in terms of acute GVHD at grade I-IV or III-IV, CMV reactivation and EBV reactivation (P>0.1).

CONCLUSION

The cell mobilization program of G-CSF combined with Plerixafor is safe and effective for being applied to allo-HSCT. The addition of Plerixafor can significantly increase the number of CD34 postive cells in the PBSC collection. Key words　　; ;

Plerixafor strategies for autologous hematopoietic cell transplant mobilization: A comparison of efficacy and cost

Addition of plerixafor (P) to granulocyte colony stimulating factor (G-CSF) during peripheral blood mobilization of hematopoietic stem cells (HSC) increases the number of patients meeting collection goals prior to autologous stem cell transplant (aSCT). However, use of P is not universal among transplant centers due to cost. This study aims to compare clinical and financial impacts of using an algorithm-based P mobilization strategy versus use in all patients. This was a single center, retrospective analysis of adult patients with myeloma or amyloidosis receiving aSCT who received apheresis of their HSC between 3/1/2017 and 3/1/2019. Patients prior to 3/1/2018 were classified as receiving P "per algorithm" and those after this date were classified as "up-front" P. For the per-algorithm group, P was given for a pre-apheresis CD34+ cell count of <20 cells/μL on mobilization day 5 and patients returned on day 6 for apheresis. Of the 129 patients included, 55 received P per-algorithm and 74 received up-front P. There was a reduction in median number of apheresis days (1.5 vs 1 day, p < 0.001) and an increase in median number of CD34+ cells collected (6.6 vs 8.5 × 10⁶ cells/kg, p < 0.001) with up-front P. Up-front P increased drug cost but reduced apheresis costs, which resulted in a net savings of $121 per patient in total mobilization costs. These findings suggest that use of up-front P for mobilization significantly reduces apheresis days and increases HSC collection yield without increasing overall cost per patient.

Stem Cell Mobilization in Multiple Myeloma: Comparing Safety and Efficacy of Cyclophosphamide +/- Plerixafor versus Granulocyte Colony-Stimulating Factor +/- Plerixafor in the Lenalidomide Era

Growth factor and chemotherapy-based stem cell mobilization strategies are commonly used to treat patients with multiple myeloma. We retrospectively compared 398 patients mobilized between 2017 and 2020 using either cyclophosphamide (4 g/m²) plus granulocyte colony-stimulating factor (G-CSF) or G-CSF alone, with on demand plerixafor (PXF) in both groups. Although total CD34⁺ yield was higher after chemomobilization compared with G-CSF +/- PXF (median, 13.6 × 10⁶/kg versus 4.4 × 10⁶/kg; P < .01), achievement of ≥2 × 10⁶ CD34⁺ cells (95% versus 93.7%; P = .61) and rates of mobilization failure (5% versus 6.3%; P = .61) were similar. Fewer patients required PXF with chemomobilization (12.3% versus 49.5%; P < .01), and apheresis sessions were fewer (median, 1 [range, 1 to 4] versus 2 [range, 1 to 5]). The rate of complications, including neutropenic fever, emergency department visits, and hospitalizations, was higher after chemomobilization (30% versus 7.4%; P < .01). Previous use of ≤6 cycles of lenalidomide did not impair cell yield in either group. The median cost of mobilization was 17.4% lower in the G-CSF +/- PXF group (P = .01). Between group differences in time to engraftment were not clinically significant. Given similar rates of successful mobilization, similar engraftment time, and less toxicity and lower costs compared with chemomobilization, G-CSF with on-demand PXF may be preferable in myeloma patients with adequate disease control and limited lenalidomide exposure.

Single-dose MGTA-145/plerixafor leads to efficient mobilization and in vivo transduction of HSCs with thalassemia correction in mice

We have developed an in vivo hemopoietic stem cell (HSC) gene therapy approach without the need for myelosuppressive conditioning and autologous HSC transplantation. It involves HSC mobilization and IV injection of a helper-dependent adenovirus HDAd5/35++ vector system. The current mobilization regimen consists of granulocyte colony-stimulating factor (G-CSF) injections over a 4-day period, followed by the administration of plerixafor/AMD3100. We tested a simpler, 2-hour, G-CSF-free mobilization regimen using truncated GRO-β (MGTA-145; a CXCR2 agonist) and plerixafor in the context of in vivo HSC transduction in mice. The MGTA-145+plerixafor combination resulted in robust mobilization of HSCs. Importantly, compared with G-CSF+plerixafor, MGTA-145+plerixafor led to significantly less leukocytosis and no elevation of serum interleukin-6 levels and was thus likely to be less toxic. With both mobilization regimens, after in vivo selection with O6-benzylguanine (O6BG)/BCNU, stable GFP marking was achieved in >90% of peripheral blood mononuclear cells. Genome-wide analysis showed random, multiclonal vector integration. In vivo HSC transduction after mobilization with MGTA-145+plerixafor in a mouse model for thalassemia resulted in >95% human γ-globin+ erythrocytes at a level of 36% of mouse β-globin. Phenotypic analyses showed a complete correction of thalassemia. The γ-globin marking percentage and level were maintained in secondary recipients, further demonstrating that MGTA145+plerixafor mobilizes long-term repopulating HSCs. Our study indicates that brief exposure to MGTA-145+plerixafor may be advantageous as a mobilization regimen for in vivo HSC gene therapy applications across diseases, including thalassemia and sickle cell disease.

CXCR4 inhibition in human pancreatic and colorectal cancers induces an integrated immune response

Inhibition of the chemokine receptor CXCR4 in combination with blockade of the PD-1/PD-L1 T cell checkpoint induces T cell infiltration and anticancer responses in murine and human pancreatic cancer. Here we elucidate the mechanism by which CXCR4 inhibition affects the tumor immune microenvironment. In human immune cell-based chemotaxis assays, we find that CXCL12-stimulated CXCR4 inhibits the directed migration mediated by CXCR1, CXCR3, CXCR5, CXCR6, and CCR2, respectively, chemokine receptors expressed by all of the immune cell types that participate in an integrated immune response. Inhibiting CXCR4 in an experimental cancer medicine study by 1-wk continuous infusion of the small-molecule inhibitor AMD3100 (plerixafor) induces an integrated immune response that is detected by transcriptional analysis of paired biopsies of metastases from patients with microsatellite stable colorectal and pancreatic cancer. This integrated immune response occurs in three other examples of immune-mediated damage to noninfected tissues: Rejecting renal allografts, melanomas clinically responding to anti-PD1 antibody therapy, and microsatellite instable colorectal cancers. Thus, signaling by CXCR4 causes immune suppression in human pancreatic ductal adenocarcinoma and colorectal cancer by impairing the function of the chemokine receptors that mediate the intratumoral accumulation of immune cells.

Phase 1 study of combinatorial sorafenib, G-CSF, and plerixafor treatment in relapsed/refractory, FLT3-ITD-mutated acute myelogenous leukemia patients

Stroma-leukemia interactions mediated by CXCR4, CD44, VLA4, and their respective ligands contribute to therapy resistance in FLT3-ITD-mutated acute myelogenous leukemia (AML). We conducted a phase 1 study with the combination of sorafenib (a FLT3-ITD inhibitor), plerixafor (a SDF-1/CXCR4 inhibitor), and G-CSF (that cleaves SDF-1, CD44, and VLA4). Twenty-eight patients with relapsed/refractory FLT3-ITD-mutated AML were enrolled from December 2010 to December 2013 at three dose levels of sorafenib (400, 600, and 800 mg twice daily) and G-CSF and plerixafor were administered every other day for seven doses starting on day one. Sorafenib 800 mg twice daily was selected for the expansion phase. While no dose-limiting toxicities (DLT) were encountered in the four-week DLT window, hand-foot syndrome and rash were seen beyond the DLT window, which required dose reductions in most patients. The response rate was 36% (complete response (CR) = 4, complete remission with incomplete platelet recovery (CRp) = 4, complete remission with incomplete hematologic recovery (CRi) = 1, and partial response (PR) = 1) for the intention to treat population. Treatment resulted in 58.4 and 47 mean fold mobilization of blasts and CD34 /38- stem/progenitor cells, respectively, to the circulation. Expression of the adhesion molecules CXCR4, CD44, and VLA4 on circulating leukemia cells correlated negatively with the mobilization of CD34+/38-, CD34+/38-/123+ "progenitor" cells (all P ≤ .002). Mass cytometry analysis of sequential samples from two patients demonstrated resistance emerging early on from sub-clones with persistent Akt and/or ERK signaling. In conclusion, the strategy of combined inhibition of FLT3 kinase and stromal adhesive interactions has promising activity in relapsed/refractory, FLT3-ITD-mutated AML, which warrants further evaluation in the front-line setting.

Neutralization of CXCL12 attenuates established pulmonary hypertension in rats

AIMS

The progressive accumulation of cells in pulmonary vascular walls is a key pathological feature of pulmonary arterial hypertension (PAH) that results in narrowing of the vessel lumen, but treatments targeting this mechanism are lacking. The C-X-C motif chemokine 12 (CXCL12) appears to be crucial in these processes. We investigated the activity of two CXCL12 neutraligands on experimental pulmonary hypertension (PH), using two complementary animal models.

METHODS AND RESULTS

Male Wistar rats were injected with monocrotaline (MCT) or were subjected to SU5416 followed by 3-week hypoxia to induce severe PH. After PH establishment, assessed by pulsed-wave Doppler echocardiography, MCT-injected or SU5416 plus chronic hypoxia (SuHx) rats were randomized to receive CXCL12 neutraligands chalcone 4 or LIT-927 (100 mg/kg/day), the C-X-C motif chemokine receptor 4 (CXCR4) antagonist AMD3100 (5 mg/kg/day), or vehicle, for 2 or 3 weeks, respectively. At the end of these treatment periods, echocardiographic and haemodynamic measurements were performed and tissue samples were collected for protein expression and histological analysis. Daily treatment of MCT-injected or SuHx rats with established PH with chalcone 4 or LIT-927 partially reversed established PH, reducing total pulmonary vascular resistance, and remodelling of pulmonary arterioles. Consistent with these observations, we found that neutralization of CXCL12 attenuates right ventricular hypertrophy, pulmonary vascular remodelling, and decreases pulmonary artery smooth muscle cell (PA-SMC) proliferation in lungs of MCT-injected rats and SuHx rats. Importantly, CXCL12 neutralization with either chalcone 4 or LIT-927 inhibited the migration of PA-SMCs and pericytes in vitro with a better efficacy than AMD3100. Finally, we found that CXCL12 neutralization decreases vascular pericyte coverage and macrophage infiltration in lungs of both MCT-injected and SuHx rats.

CONCLUSION

We report here a greater beneficial effect of CXCL12 neutralization vs. the conventional CXCR4 blockade with AMD3100 in the MCT and SuHx rat models of severe PH, supporting a role for CXCL12 in the progression of vascular complications in PH and opening to new therapeutic options.

Effect of the CXCR4 antagonist plerixafor on endogenous neutrophil dynamics in the bone marrow, lung and spleen

Treatment with the CXCR4 antagonist, plerixafor (AMD3100), has been proposed for clinical use in patients with WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome and in pulmonary fibrosis. However, there is controversy with respect to the impact of plerixafor on neutrophil dynamics in the lung, which may affect its safety profile. In this study, we investigated the kinetics of endogenous neutrophils by direct imaging, using confocal intravital microscopy in mouse bone marrow, spleen, and lungs. Neutrophils are observed increasing their velocity and exiting the bone marrow following plerixafor administration, with a concomitant increase in neutrophil numbers in the blood and spleen, while the marginated pool of neutrophils in the lung microvasculature remained unchanged in terms of numbers and cell velocity. Use of autologous radiolabeled neutrophils and SPECT/CT imaging in healthy volunteers showed that plerixafor did not affect GM-CSF-primed neutrophil entrapment or release in the lungs. Taken together, these data suggest that plerixafor causes neutrophil mobilization from the bone marrow but does not impact on lung marginated neutrophil dynamics and thus is unlikely to compromise respiratory host defense both in humans and mice.

Major Improvement in Wound Healing Through Pharmacologic Mobilization of Stem Cells in Severely Diabetic Rats

Current therapeutic strategies for diabetic foot ulcer (DFU) have focused on developing topical healing agents, but few agents have controlled prospective data to support their effectiveness in promoting wound healing. We tested a stem cell mobilizing therapy for DFU using a combination of AMD3100 and low-dose FK506 (tacrolimus) (AF) in streptozocin-induced type 1 diabetic (T1DM) rats and type 2 diabetic Goto-Kakizaki (GK) rats that had developed peripheral artery disease and neuropathy. Here, we show that the time for healing back wounds in T1DM rats was reduced from 27 to 19 days, and the foot wound healing time was reduced from 25 to 20 days by treatment with AF (subcutaneously, every other day). Similarly, in GK rats treated with AF, the healing time on back wounds was reduced from 26 to 21 days. Further, this shortened healing time was accompanied by reduced scar and by regeneration of hair follicles. We found that AF therapy mobilized and recruited bone marrow-derived CD133⁺ and CD34⁺ endothelial progenitor cells and Ym1/2⁺ M2 macrophages into the wound sites, associated with enhanced capillary and hair follicle neogenesis. Moreover, AF therapy improved microcirculation in diabetic and neuropathic feet in GK rats. This study provides a novel systemic therapy for healing DFU.

EMA Recommendation for the Pediatric Indications of Plerixafor (Mozobil) to Enhance Mobilization of Hematopoietic Stem Cells for Collection and Subsequent Autologous Transplantation in Children with Lymphoma or Malignant Solid Tumors

On March 28, 2019, the Committee for Medicinal Products for Human Use adopted a positive opinion recommending the marketing authorization for the medicinal product plerixafor. The marketing authorization holder for this medicinal product is Genzyme Europe B.Th. The adoption was for an extension of the existing adult indication in combination with granulocyte colony-stimulating factor (G-CSF) to pediatric patients (aged 1 year to <18 years) to enhance mobilization of hematopoietic stem cells to the peripheral blood for collection and subsequent autologous transplantation in children with lymphoma or solid malignant tumors. This treatment is indicated either preemptively, when circulating stem cell count on the predicted day of collection after adequate mobilization with G-CSF (with or without chemotherapy) is expected to be insufficient with regard to desired hematopoietic stem cells yield, or in children who previously failed to collect sufficient hematopoietic stem cells. The efficacy and safety of plerixafor were evaluated in an open label, multicenter, phase I/II, dose-ranging, and randomized controlled study (DFI12860) in pediatric patients with solid tumors, including neuroblastoma, sarcoma, Ewing sarcoma, or lymphoma, who were eligible for autologous hematopoietic stem cell transplantation. Forty-five patients (aged 1 year to <18 years) were randomized, 2:1, using 0.24 mg/kg of plerixafor plus standard mobilization (G-CSF with or without chemotherapy) versus control (standard mobilization alone). The primary analysis showed that 80% of patients in the plerixafor arm experienced at least a doubling of the peripheral blood (PB) CD34+ count, observed from the morning of the day preceding the first planned apheresis to the morning prior to apheresis, versus 28.6% of patients in the control arm (p = .0019). The median increase in PB CD34+ cell counts from baseline to the day of apheresis was 3.2-fold in the plerixafor arm versus by 1.4-fold in the control arm. The observed safety profile in the pediatric population was consistent with that in adults, with adverse events mainly related to injection site reactions, hypokalemia, and increased blood bicarbonate. Importantly, plerixafor exposure did not seem to negatively affect transplant efficiency. This article summarizes the scientific review of the application leading to regulatory approval in the European Union. IMPLICATIONS FOR PRACTICE: This review of the marketing authorization of plerixafor will raise awareness of pediatric indication granted for this medicinal product.

Results from a multicenter, noninterventional registry study for multiple myeloma patients who received stem cell mobilization regimens with and without plerixafor

Plerixafor plus granulocyte-colony stimulating factor (G-CSF) enhances the mobilization of hematopoietic stem cells (HSCs) for collection and subsequent autologous hematopoietic stem cell transplantation (HSCT) in patients with multiple myeloma (MM). This international, multicenter, noninterventional registry study (NCT01362972), evaluated long-term outcomes for MM patients who received plerixafor versus other mobilization regimens. The comparisons were: G-CSF + plerixafor (G-CSF + P) versus G-CSF-; G-CSF + P versus G-CSF + chemotherapy (G-CSF + C); and G-CSF + P + C versus G-CSF + C. Propensity score matching was used to balance groups. Primary outcome measures were progression free survival (PFS), overall survival (OS), and cumulative incidence of relapse (CIR) after transplantation. After propensity matching, 77 versus 41 patients in the G-CSF + P versus G-CSF cohorts, 129 versus 129 in the G-CSF + P versus G-CSF + C cohorts, and 117 versus 117 in the G-CSF + P + C versus G-CSF + C cohorts were matched, respectively. Propensity score matching resulted in a smaller sample size and imbalances were not completely overcome. For both PFS and OS, the upper limits of the hazard ratio 95% confidence intervals exceeded prespecified boundaries; noninferiority was not demonstrated. CIR rates were higher in the plerixafor cohorts. G-CSF + P remains an option for the mobilization of HSCs in poor mobilizers with MM with no substantial differences in PFS, OS, and CIR in comparison with other regimens.

Chemokine Receptor Antagonists in Combination with Morphine as a Novel Strategy for Opioid Dose Reduction in Pain Management

INTRODUCTION

Although opioids are widely prescribed for pain, in many circumstances, they have only modest efficacy. Preclinical studies have shown that chemokines, immune mediators released during tissue injury and inflammation, can desensitize opioid receptors and block opioid analgesia by a process termed "heterologous desensitization." The present studies tested the hypothesis that in evoked pain, certain chemokine receptor antagonists (CRAs), given with a submaximal dose of morphine, would result in enhanced morphine potency.

METHODS

Three rodent pain assays were used: incisional pain in rats, the cold-water tail flick test in rats, and the formalin test in mice. The FDA-approved, commercially available CRAs, maraviroc and AMD3100, were used. They block the chemokine receptors and ligands, CCR5/CCL5 (RANTES) and CXCR4/CXCL4 (SDF-1α), respectively.

RESULTS

In the incisional pain assay, it was found that the combination of a single CRA, or of both CRAs, with morphine significantly shifted the morphine dose-response curve to the left, as much as 3.3-fold. In the cold-water tail flick and formalin tests, significant increases of the antinociceptive effects of morphine were also observed when combined with CRAs.

CONCLUSIONS

These results support the potential of a new "opioid-sparing" approach for pain treatment, which combines CRAs with reduced doses of morphine.

Macrophage Exclusion after Radiation Therapy (MERT): A First in Human Phase I/II Trial using a CXCR4 Inhibitor in Glioblastoma

PURPOSE

Preclinical studies have demonstrated that postirradiation tumor revascularization is dependent on a stromal cell-derived factor-1 (SDF-1)/C-X-C chemokine receptor type 4 (CXCR4)-driven process in which myeloid cells are recruited from bone marrow. Blocking this axis results in survival improvement in preclinical models of solid tumors, including glioblastoma (GBM). We conducted a phase I/II study to determine the safety and efficacy of Macrophage Exclusion after Radiation Therapy (MERT) using the reversible CXCR4 inhibitor plerixafor in patients with newly diagnosed glioblastoma.

PATIENTS AND METHODS

We enrolled nine patients in the phase I study and an additional 20 patients in phase II using a modified toxicity probability interval (mTPI) design. Plerixafor was continuously infused intravenously via a peripherally inserted central catheter (PICC) line for 4 consecutive weeks beginning at day 35 of conventional treatment with concurrent chemoradiation. Blood serum samples were obtained for pharmacokinetic analysis. Additional studies included relative cerebral blood volume (rCBV) analysis using MRI and histopathology analysis of recurrent tumors.

RESULTS

Plerixafor was well tolerated with no drug-attributable grade 3 toxicities observed. At the maximum dose of 400 μg/kg/day, biomarker analysis found suprathreshold plerixafor serum levels and an increase in plasma SDF-1 levels. Median overall survival was 21.3 months [95% confidence interval (CI), 15.9-NA] with a progression-free survival of 14.5 months (95% CI, 11.9-NA). MRI and histopathology support the mechanism of action to inhibit postirradiation tumor revascularization.

CONCLUSIONS

Infusion of the CXCR4 inhibitor plerixafor was well tolerated as an adjunct to standard chemoirradiation in patients with newly diagnosed GBM and improves local control of tumor recurrences.

Impact of CD34+ pre-counting and plerixafor on autologous peripheral blood stem cell collection in Japanese university hospitals in eight years

OBJECTIVE

Over the past decade, there have been two major advancements in autologous peripheral blood stem cell (PBSC) collection, namely enumeration of CD 34+ cells for apheresis prediction and use of plerixafor to assist mobilization of PBSC. This study aimed to investigate changes in the efficacy of PBSC collection from two Japanese university hospitals over an eight-year period.

STUDY DESIGN AND METHODS

A series of 399 PBSC collection procedures from 239 patients with solid malignant tumors (ST, n = 42), malignant lymphoma (ML, n = 91), multiple myeloma (MM, n = 99), and others (amyloidosis and leukemia, n = 7) from two university hospitals from 2011 to 2018 were retrospectively analyzed. We also analyzed the effects of CD34+ pre-counting and plerixafor administration in improving CD34+ cell yield.

RESULTS

Using CD34+ pre-count as a reference, the frequency of apheresis was reduced and the yield of CD34+ cells increased in patients with ST. When administrating plerixafor, especially with a CD34+ pre-count <20/μL, the yield of CD34+ cells was significantly increased in patients with ML (p = 0.02) and MM (p = 0.03).

CONCLUSIONS

We verified that CD34+ cell counting and plerixafor administration contributed to effective PBSC collections in our hospitals for the eight-year study period. In patients with ST, CD34+ pre-count threshold for starting apheresis was ≥10/μL. CD34+ pre-count (<20/μL) was useful to select appropriate patients for plerixafor administration among the patients with ML and MM.

An Agonist of the CXCR4 Receptor Strongly Promotes Regeneration of Degenerated Motor Axon Terminals

The activation of the G-protein coupled receptor CXCR4 by its ligand CXCL12α is involved in a large variety of physiological and pathological processes, including the growth of B cells precursors and of motor axons, autoimmune diseases, stem cell migration, inflammation, and several neurodegenerative conditions. Recently, we demonstrated that CXCL12α potently stimulates the functional recovery of damaged neuromuscular junctions via interaction with CXCR4. This result prompted us to test the neuroregeneration activity of small molecules acting as CXCR4 agonists, endowed with better pharmacokinetics with respect to the natural ligand. We focused on NUCC-390, recently shown to activate CXCR4 in a cellular system. We designed a novel and convenient chemical synthesis of NUCC-390, which is reported here. NUCC-390 was tested for its capability to induce the regeneration of motor axon terminals completely degenerated by the presynaptic neurotoxin α-Latrotoxin. NUCC-390 was found to strongly promote the functional recovery of the neuromuscular junction, as assayed by electrophysiology and imaging. This action is CXCR4 dependent, as it is completely prevented by AMD3100, a well-characterized CXCR4 antagonist. These data make NUCC-390 a strong candidate to be tested in human therapy to promote nerve recovery of function after different forms of neurodegeneration.

Coordination Behavior of 1,4-Disubstituted Cyclen Endowed with Phosphonate, Phosphonate Monoethylester, and H-Phosphinate Pendant Arms

Three 1,4,7,10-tetraazacyclododecane-based ligands disubstituted in 1,4-positions with phosphonic acid, phosphonate monoethyl-ester, and H-phosphinic acid pendant arms, 1,4-H4do2p, 1,4-H2do2pOEt, and 1,4-H2Bn2do2pH, were synthesized and their coordination to selected metal ions, Mg(II), Ca(II), Mn(II), Zn(II), Cu(II), Eu(III), Gd(III), and Tb(III), was investigated. The solid-state structure of the phosphonate ligand, 1,4-H4do2p, was determined by single-crystal X-ray diffraction. Protonation constants of the ligands and stability constants of their complexes were obtained by potentiometry, and their values are comparable to those of previously studied analogous 1,7-disubstitued cyclen derivatives. The Gd(III) complex of 1,4-H4do2p is ~1 order of magnitude more stable than the Gd(III) complex of the 1,7-analogue, probably due to the disubstituted ethylenediamine-like structural motif in 1,4-H4do2p enabling more efficient wrapping of the metal ion. Stability of Gd(III)-1,4-H2do2pOEt and Gd(III)-H2Bn2do2pH complexes is low and the constants cannot be determined due to precipitation of the metal hydroxide. Protonations of the Cu(II), Zn(II), and Gd(III) complexes probably takes place on the coordinated phosphonate groups. Complexes of Mn(II) and alkali-earth metal ions are significantly less stable and are not formed in acidic solutions. Potential presence of water molecule(s) in the coordination spheres of the Mn(II) and Ln(III) complexes was studied by variable-temperature NMR experiments. The Mn(II) complexes of the ligands are not hydrated. The Gd(III)-1,4-H4do2p complex undergoes hydration equilibrium between mono- and bis-hydrated species. Presence of two-species equilibrium was confirmed by UV-Vis spectroscopy of the Eu(III)-1,4-H4do2p complex and hydration states were also determined by luminescence measurements of the Eu(III)/Tb(III)-1,4-H4do2p complexes.

Chemokine receptor 4 (CXCR4) blockade enhances resistance to bacterial internalization in RAW264.7 cells and AMD3100, a CXCR4 antagonist, attenuates susceptibility to Brucella abortus 544 infection in a murine model

We investigated the involvement of chemokine receptor type 4 (CXCR4) signaling on the outcome of Brucella (B.) abortus 544 infection in murine macrophages and in a mouse model. CXCR4 manipulation were first evaluated for Brucella invasion and intracellular survival efficiency, mitogen-activated protein kinases (ERK1/2, JNK, p38α) activation and generation of nitric oxide (NO), and then in the splenic bacterial proliferation and cytokine production in BALB/c mice. CXCR4 blockade is involved in the successful control of Brucella invasion, reduction of ERK1/2 phosphorylation and inhibition of nitric oxide release from macrophages. Furthermore, using a reported CXCR4-specific antagonist AMD3100 resulted in splenomegaly but attenuated Brucella proliferation in these organs with elevated serum levels of MCP-1, TNF and IL-12. These findings provide insights on the contribution of CXCR4 signaling in the phagocytic pathway and immune modulation during B. abortus infection.

Radiation-Induced CXCL12 Upregulation via Histone Modification at the Promoter in the Tumor Microenvironment of Hepatocellular Carcinoma

Tumor cells can vary epigenetically during ionizing irradiation (IR) treatment. These epigenetic variegations can influence IR response and shape tumor aggressiveness. However, epigenetic disturbance of histones after IR, implicating in IR responsiveness, has been elusive. Here, we investigate whether altered histone modification after IR can influence radiation responsiveness. The oncogenic CXCL12 mRNA and protein were more highly expressed in residual cancer cells from a hepatoma heterotopic murine tumor microenvironment and coculture of human hepatoma Huh7 and normal IMR90 cells after radiation. H3K4 methylation was also enriched and H3K9 methylation was decreased at its promoter region. Accordingly, invasiveness and the subpopulation of aggressive CD133+/CD24- cells increased after IR. Histone demethylase inhibitor IOX1 attenuated CXCL12 expression and the malignant subpopulation, suggesting that responses to IR can be partially mediated via histone modifications. Taken together, radiation-induced histone alterations at the CXCL12 promoter in hepatoma cells are linked to CXCL12 upregulation and increased aggressiveness in the tumor microenvironment.

Tumor Angiogenic Inhibition Triggered Necrosis (TAITN) in Oral Cancer

CXCR4 is a chemokine receptor crucial in tumor progression, although the angiogenic role of CXCR4 in oral squamous cell carcinoma (OSCC) has not been investigated. Here we show that CXCR4 is crucial for tumor angiogenesis, thereby supporting tumor survival in OSCC. Immunohistochemistry on human clinical specimens revealed that CXCR4 and a tumor vasculature marker CD34 were co-distributed in tumor vessels in human OSCC specimens. To uncover the effects of CXCR4 inhibition, we treated the OSCC-xenografted mice with AMD3100, so-called plerixafor, an antagonist of CXCR4. Notably, we found a unique pathophysiological structure defined as tumor angiogenic inhibition triggered necrosis (TAITN), which was induced by the CXCR4 antagonism. Treatment with AMD3100 increased necrotic areas with the induction of hypoxia-inducible factor-1α in the xenografted tumors, suggesting that AMD3100-induced TAITN was involved in hypoxia and ischemia. Taken together, we demonstrated that CXCR4 plays a crucial role in tumor angiogenesis required for OSCC progression, whereas TAITN induced by CXCR4 antagonism could be an effective anti-angiogenic therapeutic strategy in OSCC treatment.

Proteomic Profiling of Signaling Networks Modulated by G-CSF/Plerixafor/Busulfan-Fludarabine Conditioning in Acute Myeloid Leukemia Patients in Remission or with Active Disease prior to Allogeneic Stem Cell Transplantation

To characterize intracellular signaling in peripheral blood (PB) cells of acute myeloid leukemia (AML) patients undergoing pretransplant conditioning with CXCR4 inhibitor plerixafor, granulocyte colony-stimulating factor (G-CSF), and busulfan plus fludarabine (Bu+Flu) chemotherapy, we profiled 153 proteins in 33 functional groups using reverse phase protein array. CXCR4 inhibition mobilized AML progenitors and clonal AML cells, and this was associated with molecular markers of cell cycle progression. G-CSF/plerixafor and G-CSF/plerixafor/Bu+Flu modulated distinct signaling networks in AML blasts of patients undergoing conditioning with active disease compared to nonleukemic PB cells of patients in remission. We identified AML-specific proteins that remained aberrantly expressed after chemotherapy, representing putative chemoresistance markers in AML.

Characterization, Dynamics, and Mechanism of CXCR4 Antagonists on a Constitutively Active Mutant

The G protein-coupled receptor (GPCR) CXCR4 is a co-receptor for HIV and is involved in cancers and autoimmune diseases. We characterized five purine or quinazoline core polyamine pharmacophores used for targeting CXCR4 dysregulation in diseases. All were neutral antagonists for wild-type CXCR4 and two were biased antagonists with effects on β-arrestin-2 only at high concentrations. These compounds displayed various activities for a constitutively active mutant (CAM). We use the IT1t-CXCR4 crystal structure and molecular dynamics (MD) simulations to develop two hypotheses for the activation of the N1193.35A CAM. The N1193.35A mutation facilitates increased coupling of TM helices III and VI. IT1t deactivates the CAM by disrupting the coupling between TM helices III and VI, mediated primarily by residue F872.53. Mutants of F872.53 in N1193.35A CXCR4 precluded constitutive signaling and prevented inverse agonism. This work characterizes CXCR4 ligands and provides a mechanism for N1193.35A constitutive activation.

Defining the in vivo characteristics of acute myeloid leukemia cells behavior by intravital imaging

The majority of acute myeloid leukemia (AML) patients have a poor response to conventional chemotherapy. The survival of chemoresistant cells is thought to depend on leukemia-bone marrow (BM) microenvironment interactions, which are not well understood. The CXCL12/CXCR4 axis has been proposed to support AML growth but was not studied at the single AML cell level. We recently showed that T-cell acute lymphoblastic leukemia (T-ALL) cells are highly motile in the BM; however, the characteristics of AML cell migration within the BM remain undefined. Here, we characterize the in vivo migratory behavior of AML cells and their response to chemotherapy and CXCR4 antagonism, using high-resolution 2-photon and confocal intravital microscopy of mouse calvarium BM and the well-established MLL-AF9-driven AML mouse model. We used the Notch1-driven T-ALL model as a benchmark comparison and AMD3100 for CXCR4 antagonism experiments. We show that AML cells are migratory, and in contrast with T-ALL, chemoresistant AML cells become less motile. Moreover, and in contrast with T-ALL, the in vivo exploratory behavior of expanding and chemoresistant AML cells is unaffected by AMD3100. These results expand our understanding of AML cells-BM microenvironment interactions, highlighting unique traits of leukemia of different lineages.

Plerixafor for the Treatment of WHIM Syndrome

WHIM syndrome (warts, hypogammaglobulinemia, infections, and myelokathexis), a primary immunodeficiency disorder involving panleukopenia, is caused by autosomal dominant gain-of-function mutations in CXC chemokine receptor 4 (CXCR4). Myelokathexis is neutropenia caused by neutrophil retention in bone marrow. Patients with WHIM syndrome are often treated with granulocyte colony-stimulating factor (G-CSF), which can increase neutrophil counts but does not affect cytopenias other than neutropenia. In this investigator-initiated, open-label study, three severely affected patients with WHIM syndrome who could not receive G-CSF were treated with low-dose plerixafor, a CXCR4 antagonist, for 19 to 52 months. Myelofibrosis, panleukopenia, anemia, and thrombocytopenia were ameliorated, the wart burden and frequency of infection declined, human papillomavirus-associated oropharyngeal squamous-cell carcinoma stabilized, and quality of life improved markedly. Adverse events were mainly infections attributable to the underlying immunodeficiency. One patient died from complications of elective reconstructive surgery. (Funded by the National Institutes of Health.).

Forkhead box C1 boosts triple-negative breast cancer metastasis through activating the transcription of chemokine receptor-4

The transcription factor forkhead box C1 (FOXC1) has recently been proposed as a crucial regulator of triple-negative breast cancer (TNBC) and associated with TNBC metastasis. However, the mechanism of FOXC1 in TNBC development and metastasis is elusive. In this study, overexpression of FOXC1 in MDA-MB-231 cells significantly enhanced, whereas knockdown of FOXC1 in BT549 cells significantly reduced, the capabilities of TNBC cell invasion and motility in vitro and metastasis to the lung in vivo, when compared to their respective control cells. Mechanistic studies revealed that FOXC1 increased the expression of CXC chemokine receptor-4 (CXCR4), probably through transcriptional activation. AMD3100, an inhibitor of CXCR4, could block cell migration. In a zebrafish tumor model, AMD3100 could suppress cell invasion and metastasis. In addition, overexpressing CXCR4 in FOXC1-knockdown BT549 cells increased the capabilities of TNBC cell invasion and motility. In contrast, inhibition of CXCR4 with either AMD3100 or siRNA in MDA-MB-231 cells overexpressing FOXC1 reduced the capabilities of invasion and motility. Taken together, our results reveal a potential mechanism for FOXC1-induced TNBC metastasis.

The optimal time to inject bone mesenchymal stem cells for fracture healing in a murine model

BACKGROUND

Bone marrow is an important source of stem cells, which can promote bone fracture healing.

METHODS

We investigated the optimal time to inject bone marrow mesenchymal stem cells (BMSCs) in a C57 murine unilateral, transverse, femur fracture model. BMSCs transfected with red fluorescent protein (RFP-BMSCs) were injected via the tail vein on day 1, 7, or 14 post-fracture. AMD3100 (inhibitor of stromal cell-derived factor 1 [SDF-1]) was also injected before RFP-BMSCs in one group for comparison; a control group received saline injections. RFP-BMSC migration and fracture healing were evaluated by in vivo fluorescence assay. Micro-CT was performed and mechanical testing and histological analysis. Chemokine levels were evaluated by quantitative real-time PCR and western blotting.

RESULTS

Following injection on day 7 post-fracture, RFP-BMSCs more frequently homed to the fracture site and remained for a longer duration. Bone volume and bone mineral density were increased when BMSCs were injected on day 7 post-fracture (P < 0.05). The mechanical properties of fractured femurs were improved following day-7 BMSC injection. Histology confirmed that BMSC injection improved the formation of new bones.

CONCLUSIONS

Chemokines that induce BMSC migration were highly expressed, and protein levels of osteogenesis-related factors were increased. Seven days after fracture may be the optimal time for injection of BMSCs to promote fracture healing. Additionally, the SDF-1/CXCR4 pathway may play an important role in fracture healing following BMSC injection.

Upregulation of CXCR4 through promoter demethylation contributes to inflammatory hyperalgesia in rats

AIM AND METHODS

Chronic pain associated with inflammation is a common clinical problem, and the underlying mechanisms yet are incompletely defined. DNA methylation has been implicated in the pathogenesis of chronic pain. However, the specific genes regulated by DNA methylation under inflammatory pain condition remain largely unknown. Here, we investigated how chemokine receptor CXCR4 expression is regulated by DNA methylation and how it contributes to inflammatory pain induced by complete Freund's adjuvant (CFA) in rats.

RESULTS

Intraplantar injection of CFA could not only induce significant hyperalgesia in rats, but also significantly increase the expression of CXCR4 mRNA and protein in the dorsal root ganglion (DRG). Intrathecal injection of CXCR4 antagonist AMD3100 significantly relieved hyperalgesia in inflammatory rats in a time- and dose-dependent manner. Bisulfite sequencing and methylation-specific PCR demonstrate that CFA injection led to a significant demethylation of CpG island at CXCR4 gene promoter. Consistently, the expression of DNMT3b was significantly downregulated after CFA injection. Online software prediction reveals three binding sites of p65 in the CpG island of CXCR4 gene promoter, which has confirmed by the chromatin immunoprecipitation assay, CFA treatment significantly increases the recruitment of p65 to CXCR4 gene promoter. Inhibition of NF-kB signaling using p65 inhibitor pyrrolidine dithiocarbamate significantly prevented the increases of the CXCR4 expression.

CONCLUSION

Upregulation of CXCR4 expression due to promoter demethylation followed by increased recruitment of p65 to promoter of CXCR4 gene contributes to inflammatory hyperalgesia. These findings provide a theoretical basis for the treatment of chronic pain from an epigenetic perspective.

A role for the CXCR4-CXCL12 axis in the little skate, Leucoraja erinacea

The interaction between C-X-C chemokine receptor type 4 (CXCR4) and its cognate ligand C-X-C motif chemokine ligand 12 (CXCL12) plays a critical role in regulating hematopoietic stem cell activation and subsequent cellular mobilization. Extensive studies of these genes have been conducted in mammals, but much less is known about the expression and function of CXCR4 and CXCL12 in non-mammalian vertebrates. In the present study, we identify simultaneous expression of CXCR4 and CXCL12 orthologs in the epigonal organ (the primary hematopoietic tissue) of the little skate, Leucoraja erinacea. Genetic and phylogenetic analyses were functionally supported by significant mobilization of leukocytes following administration of Plerixafor, a CXCR4 antagonist and clinically important drug. Our results provide evidence that, as in humans, Plerixafor disrupts CXCR4/CXCL12 binding in the little skate, facilitating release of leukocytes into the bloodstream. Our study illustrates the value of the little skate as a model organism, particularly in studies of hematopoiesis and potentially for preclinical research on hematological and vascular disorders.

Phase I and Biomarker Study of Plerixafor and Bevacizumab in Recurrent High-Grade Glioma

Purpose: Although antiangiogenic therapy for high-grade glioma (HGG) is promising, responses are not durable. Correlative clinical studies suggest that the SDF-1α/CXCR4 axis may mediate resistance to VEGFR inhibition. Preclinical data have demonstrated that plerixafor (a reversible CXCR4 inhibitor) could inhibit glioma progression after anti-VEGF pathway inhibition. We conducted a phase I study to determine the safety of plerixafor and bevacizumab in recurrent HGG.Patients and Methods: Part 1 enrolled 23 patients with a 3 × 3 dose escalation design to a maximum planned dose of plerixafor 320 μg/kg subcutaneously on days 1 to 21 and bevacizumab 10 mg/kg intravenously on days 1 and 15 of each 28-day cycle. Cerebrospinal fluid (CSF) and plasma samples were obtained for pharmacokinetic analyses. Plasma and cellular biomarkers were evaluated before and after treatment. Part 2 enrolled 3 patients and was a surgical study to determine plerixafor's penetration in tumor tissue.Results: In Part 1, no dose-limiting toxicities were seen at the maximum planned dose of plerixafor + bevacizumab. Treatment was well tolerated. After plerixafor 320 μg/kg treatment, the average CSF drug concentration was 26.8 ± 19.6 ng/mL. Plerixafor concentration in resected tumor tissue from patients pretreated with plerixafor was 10 to 12 μg/g. Circulating biomarker data indicated that plerixafor + bevacizumab induces rapid and persistent increases in plasma SDF-1α and placental growth factor. Progression-free survival correlated with pretreatment plasma soluble mesenchymal-epithelial transition receptor and sVEGFR1, and overall survival with the change during treatment in CD34⁺ progenitor/stem cells and CD8 T cells.Conclusions: Plerixafor + bevacizumab was well tolerated in HGG patients. Plerixafor distributed to both the CSF and brain tumor tissue, and treatment was associated with biomarker changes consistent with VEGF and CXCR4 inhibition. Clin Cancer Res; 24(19); 4643-9. ©2018 AACR.

Rapid immune reconstitution of SCID-X1 canines after G-CSF/AMD3100 mobilization and in vivo gene therapy

Hematopoietic stem-cell gene therapy is a promising treatment of X-linked severe combined immunodeficiency disease (SCID-X1), but currently, it requires recipient conditioning, extensive cell manipulation, and sophisticated facilities. With these limitations in mind, we explored a simpler therapeutic approach to SCID-X1 treatment by direct IV administration of foamy virus (FV) vectors in the canine model. FV vectors were used because they have a favorable integration site profile and are resistant to serum inactivation. Here, we show improved efficacy of our in vivo gene therapy platform by mobilization with granulocyte colony-stimulating factor (G-CSF) and AMD3100 before injection of an optimized FV vector incorporating the human phosphoglycerate kinase enhancerless promoter. G-CSF/AMD3100 mobilization before FV vector delivery accelerated kinetics of CD3+ lymphocyte recovery, promoted thymopoiesis, and increased immune clonal diversity. Gene-corrected T lymphocytes exhibited a normal CD4:CD8 ratio and a broad T-cell receptor repertoire and showed restored γC-dependent signaling function. Treated animals showed normal primary and secondary antibody responses to bacteriophage immunization and evidence for immunoglobulin class switching. These results demonstrate safety and efficacy of an accessible, portable, and translatable platform with no conditioning regimen for the treatment of SCID-X1 and other genetic diseases.

MicroRNA-381 Favors Repair of Nerve Injury Through Regulation of the SDF-1/CXCR4 Signaling Pathway via LRRC4 in Acute Cerebral Ischemia after Cerebral Lymphatic Blockage

BACKGROUND/AIMS

Acute cerebral ischemia is a manifestation of cerebral vascular insufficiency and has a high mortality. However, the therapy for acute cerebral ischemia is still limited. This study aimed to investigate the effect of microRNA-381 (miR-381) on the repair of nerve injury in rats with acute cerebral ischemia after cerebral lymphatic blockage (CLB) by targeting leucine-rich repeat C4 protein (LRRC4) through the Stromal cell-derived factor-1/CXC chemokine receptor-4 signaling pathway.

METHODS

Rat models of CLB and middle cerebral artery occlusion (MCAO) were established, and 56 Wistar rats were divided into sham, MCAO, CLB + MCAO, CLB + MCAO + miR-381 inhibitor, CLB + MCAO + miR-381 mimic, CLB + MCAO + AMD3100 and CLB + MCAO + miR-381 mimic + AMD3100 groups. Modified neurological severity score (mNSS was used to determine nerve injury, TTC staining to measure infarction volume, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining and flow cytometry to evaluate cell apoptosis, immunofluorescence to measure BrdU-positive cell number, enzyme-linked immunosorbent assay (ELISA) to determine contents of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10), nerve growth factor (NGF) and neurite outgrowth inhibitor -A (Nogo-A), Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blotting to evaluate expression of miR-381, LRRC4, SDF-1, CXCR4, pERK, Slit2 and vascular endothelial growth factor (VEGF).

RESULTS

LRRC4 was a target gene of miR-381. Compared with the results in the CLB + MCAO group, mNSS, infarction volume, apoptosis rate and TNF-α, IL-1β, IL-6 and Nogo-A contents as well as LRRC4 expression in the CLB + MCAO + miR-381 inhibitor and CLB + MCAO + AMD3100 groups were increased (those in the CLB + MCAO + AMD3100 group > those in the CLB + MCAO + miR-381 mimic + AMD3100 group), while BrdU-positive cell number, contents of NGF and IL-10, and expression of SDF-1, CXCR4, pERK, Slit2 and VEGF in brain tissues were decreased (those in the CLB + MCAO + AMD3100 group < those in the CLB + MCAO + miR-381 mimic + AMD3100 group). The results in the CLB + MCAO + mimic group were opposite of those in the CLB + MCAO + miR-381 inhibitor and CLB + MCAO + AMD3100 groups.

CONCLUSION

Taken together, we concluded that up-regulation of miR-381 promoted nerve injury repair in acute cerebral ischemia rats after CLB by negatively regulating LRRC4 through activating the SDF-1/CXCR4 signaling pathway.

Modeling Idiopathic Pulmonary Fibrosis in Humanized Severe Combined Immunodeficient Mice

Idiopathic pulmonary fibrosis (IPF) is a fibrotic lung disease of unknown etiopathogenesis with limited therapeutic options. IPF is characterized by an abundance of fibroblasts and loss of epithelial progenitors, which cumulates in unrelenting fibrotic lung remodeling and loss of normal oxygenation. IPF has been challenging to model in rodents; nonetheless, mouse models of lung fibrosis provide clues as to the natural progression of lung injury and remodeling, but many have not been useful in predicting efficacy of therapeutics in clinical IPF. We provide a detailed methodologic description of various iterations of humanized mouse models, initiated by the i.v. injection of cells from IPF lung biopsy or explants specimens into severe combined immunodeficiency (SCID)/beige or nonobese diabetic SCID γ mice. Unlike cells from normal lung samples, IPF cells promote persistent, nonresolving lung remodeling in SCID mice. Finally, we provide examples and discuss potential advantages and pitfalls of human-specific targeting approaches in a humanized SCID model of pulmonary fibrosis.

CXCR4 antagonist AMD3100 enhances the response of MDA-MB-231 triple-negative breast cancer cells to ionizing radiation

Radiation therapy (RT) is one of the primary modalities for triple-negative breast cancer (TNBC) treatment. However, due to the pro-metastatic potential of radiation and the intrinsic radiation resistance of some tumors, many patients experience RT failure, which leads to cancer relapse and distant metastasis. This preclinical study evaluated the efficacy of the antagonist of the SDF-1 receptor CXCR4, AMD3100, as a radiosensitizer in TNBC models. The combined effect of ionizing radiation and AMD3100 was determined in vitro by surviving fraction, cell cycle distribution, Bax and Bcl-2 expression, and apoptosis assays in a TNBC cell line (MDA-MB-231). For in vivo studies, human xenograft athymic nude mice were used. Treatment of TNBC cells with AMD3100 significantly augmented cellular radiosensitivity. Radiosensitivity was enhanced specifically through increased Bax expression, reduced Bcl-2 expression, prolonged G2-M arrest, and increased apoptosis. Combined treatment with AMD3100 and irradiation also enhanced tumor growth delay, with an enhancement factor ranging from 1.5 to 1.8. These findings support the evaluation of antagonists of the SDF-1 receptor CXCR4, such as AMD3100, as potent radiosensitizers in TNBC.

Dual-Nuclide Radiopharmaceuticals for Positron Emission Tomography Based Dosimetry in Radiotherapy

Improvement of the accuracy of dosimetry in radionuclide therapy has the potential to increase patient safety and therapeutic outcomes. Although positron emission tomography (PET) is ideally suited for acquisition of dosimetric data because PET is inherently quantitative and offers high sensitivity and spatial resolution, it is not directly applicable for this purpose because common therapeutic radionuclides lack the necessary positron emission. This work reports on the synthesis of dual-nuclide labeled radiopharmaceuticals with therapeutic and PET functionality, which are based on common and widely available metal radionuclides. Dual-chelator conjugates, featuring interlinked cyclen- and triazacyclononane-based polyphosphinates DOTPI and TRAP, allow for strictly regioselective complexation of therapeutic (e.g., 177 Lu, 90 Y, or 213 Bi) and PET (e.g., 68 Ga) radiometals in the same molecular framework by exploiting the orthogonal metal ion selectivity of these chelators (DOTPI: large cations, such as lanthanide(III) ions; TRAP: small trivalent ions, such as GaIII ). Such DOTPI-TRAP conjugates were decorated with 3 Gly-urea-Lys (KuE) motifs for targeting prostate-specific membrane antigen (PSMA), employing Cu-catalyzed (CuAAC) as well as strain-promoted (SPAAC) click chemistry. These were labeled with 177 Lu or 213 Bi and 68 Ga and used for in vivo imaging of LNCaP (human prostate carcinoma) tumor xenografts in SCID mice by PET, thus proving practical applicability of the concept.

Incidence of Second Primary Malignancies after Autologous Transplantation for Multiple Myeloma in the Era of Novel Agents

The advent of novel agents for multiple myeloma (MM) is cause for a re-examination of the incidence of second primary malignancies (SPMs). We examined the SPM rate in MM patients who were enrolled in the prospective observational CALM (Collaboration to Collect Autologous Transplant outcome in Lymphoma and Myeloma) study. Between 2008 and 2012, 3204 patients with MM underwent a first autologous hematopoietic stem cell transplantation. Plerixafor was used as a mobilizing agent for patients with poor (or potentially poor) stem cell mobilization as defined by the respective centers. A total of 135 patients developed SPMs, with a cumulative incidence of 5.3% (95% confidence interval, 4.4 to 6.3) at 72 months. Ninety-four patients developed solid tumors, 30 developed hematologic malignancies, and 11 developed an SPM of an unknown type. The cumulative incidence of known hematologic and solid malignancies were 1.4% and 3.6%, respectively, at 72 months. In a univariate analysis, use of radiotherapy, type of induction regimen, hematopoietic stem cell dose, poor mobilizer status, plerixafor use, and sex did not influence the cumulative incidence of SPMs. Only age over 65 years was statistically associated with an increased incidence. Overall, the incidence of SPMs was comparable to earlier estimations of SPMs in MM.