Circular RNA circFGFR1 Functions as an Oncogene in Glioblastoma Cells through Sponging to hsa-miR-224-5p

Recently, increased studies have shown the important regulatory role of circular RNA (circRNA) in cancer progression and development, including glioblastoma (GBM). However, the function of circRNAs in glioblastoma is still largely unclear. Here, we state that circFGFR1 is elevated in glioma cells, resulting in aggravated glioma aggravated malignancy. The upregulation of circFGFR1 also promotes glioma growth in mouse xenograft models. Furthermore, CXCR4 level in glioma cells is positively correlated with circFGFR1 level, and higher CXCR4 expression is found in circFGFR1 overexpression groups. The effect of circFGFR1 on glioma malignancy is abolished in CXCR4 knockout cells. Then, RIP, RNA pull-down, and luciferase reporter assay results showed that hsa-miR-224-5p directly binds to circFGFR1 and CXCR4 mRNA. The CXCR4 3 ′ -untranslated region (UTR) activated luciferase activity was reduced with hsa-miR-224-5p transfection, while it is reversed when cotransfected with circFGFR1, indicating that circFGFR1 acts as a hsa-miR-244-5p sponge to increase CXCR4 expression. The hsa-miR-224-5p expression is negatively corrected with the glioma malignancy through inhibiting CXCR4 level. Besides, the circFGFR1-induced regulation in glioma malignancy is also abrogated in hsa-miR-224-5p knockout cells. Taken together, our findings suggest that circFGFR1 plays a critical role in the tumorigenic behaviors in glioma cells by upregulating CXCR4 expression via sponging to hsa-miR-224-5p. These findings provide a new perspective on circRNAs during GBM development.

Investigating CXCR4 expression of tumor cells and the vascular compartment: A multimodal approach

The C-X-C chemokine receptor 4 (CXCR4) is G protein-coupled receptor that upon binding to its cognate ligand, can lead to tumor progression. Several CXCR4-targeted therapies are currently under investigation, and with it comes the need for imaging agents capable of accurate depiction of CXCR4 for therapeutic stratification and monitoring. PET agents enjoy the most success, but more cost-effective and radiation-free approaches such as ultrasound (US) imaging could represent an attractive alternative. In this work, we developed a targeted microbubble (MB) for imaging of vascular CXCR4 expression in cancer. A CXCR4-targeted MB was developed through incorporation of the T140 peptide into the MB shell. Binding properties of the T140-MB and control, non-targeted MB (NT-MB) were evaluated in MDA-MB-231 cells where CXCR4 expression was knocked-down (via shRNA) through optical imaging, and in the lymphoma tumor models U2932 and SuDHL8 (high and low CXCR4 expression, respectively) by US imaging. PET imaging of [18F]MCFB, a tumor-penetrating CXCR4-targeted small molecule, was used to provide whole-tumor CXCR4 readouts. CXCR4 expression and microvessel density were performed by immunohistochemistry analysis and western blot. T140-MB were formed with similar properties to NT-MB and accumulated sensitively and specifically in cells according to their CXCR4 expression. In NOD SCID mice, T140-MB persisted longer in tumors than NT-MB, indicative of target interaction, but showed no difference between U2932 and SuDHL8. In contrast, PET imaging with [18F]MCFB showed a marked difference in tumor uptake at 40–60 min post-injection between the two tumor models (p<0.05). Ex vivo analysis revealed that the large differences in CXCR4 expression between the two models are not reflected in the vascular compartment, where the MB are restricted; in fact, microvessel density and CXCR4 expression in the vasculature was comparable between U2932 and SuDHL8 tumors. In conclusion, we successfully developed a T140-MB that can be used for imaging CXCR4 expression in the tumor vasculature.

FLT3 Inhibitor Quizartinib Facilitates Proliferation and CXCL12-Induced Chemotaxis in Quizartinib Resistant FLT3/ITD + Hematopoietic Cells By Increasing RUNX1

RUNX1 generally functions as a tumor suppressor in the hematopoietic system. However, RUNX1 expression is significantly elevated in human AML cells with FLT3/ITD mutations, promotes leukemogenesis induced by FLT3/ITD (Behrens et al. JEM 2017) and enhances the resistance of FLT3/ITD + cells to type-II FLT3 inhibitor quizartinib (Hirade et al IJH 2016). We previously reported that RUNX1 expression is higher in CXCR4-low FLT3/ITD + cells compared to Cxcr4-high FLT3/ITD + cells, even though Cxcr4 expression is trans-activated by RUNX1. This difference in RUNX1 expression level was associated with divergent response to CXCL12 in FLT3/ITD + cells harboring different CXCR4 expression levels that were exposed to quizartinib (Fukuda S. et al. ASH 2019). Our data also demonstrated that RUNX1 expression is down-regulated following withdrawal of quizartinib in FLT3/ITD + cells that became refractory to quizartinib (Hirade et al. IJH 2016), suggesting that RUNX1 expression may be up-regulated by quizartinib in FLT3/ITD + cells. Since RUNX1 regulates proliferation of FLT3/ITD + AML cells, the present study investigated association between RUNX1 expression levels and proliferation of quizartinib resistant FLT3/ITD + cells that are exposed to quizartinib. In the sensitive FLT3/ITD + Ba/F3 cells, RUNX1 protein expression was transiently up-regulated but eventually down-regulated by 5 nM quizartinib, coincident with decline in the viable cells. In contrast, RUNX1 expression was up-regulated by quizartinib and remained elevated in the resistant FLT3/ITD + Ba/F3 cells. Since RUNX1 enhances proliferation of FLT3/ITD + cells, we next examined whether proliferation FLT3/ITD + cells that acquired resistance to quizartinib is facilitated by quizaritinib as a result from quizartinib-mediated up-regulation of RUNX1, using the Cxcr4-low and Cxcr4-high FLT3/ITD + cells that acquired resistance to quizartinib. Although CXCL12 barely enhanced the proliferation of refractory FLT3/ITD + Ba/F3 cells, 5 nM quizartinib significantly increased the proliferation of both Cxcr4-low and Cxcr4-high FLT3/ITD + Ba/F3 cells that acquired resistance to quizartinib compared to those without quizartinib. This increase in the proliferation of Cxcr4-low and Cxcr4-high FLT3/ITD + Ba/F3 cells coincided with the elevation in RUNX1 and CXCR4 protein expression. Moreover, the resistant Cxcr4-low FLT3/ITD + Ba/F3 cells proliferated significantly faster than Cxcr4-high FLT3/ITD + cells, with concomitant higher expression of RUNX1 in Cxcr4-low FLT3/ITD + cells than in Cxcr4-high FLT3/ITD + cells. Likewise, type-I FLT3 inhibitor gilteritinib significantly enhanced proliferation of Cxcr4-low and Cxcr4-high FLT3/ITD + Ba/F3 cells that acquired resistance to gilteritinib. Knocking down Runx1 using shRNAs significantly decreased the enhanced proliferation induced by quizartinib in refractory FLT3/ITD + Ba/F3 cells, coincident with reduction in CXCR4 expression. Since CXCR4 expression level was elevated by quizartinib in the FLT3/ITD + cells refractory to quizartinib, we next examined CXCL12-induced migration in quizartinib-resistant FLT3/ITD + cells following exposure to quzartinib. Pre-incubating the quizartinib resistant Cxcr4-low or Cxcr4-high FLT3/ITD + Ba/F3 cells with 5 nM quizartinib for 72 hours significantly enhanced their migration to 100 ng/ml of Cxcl12 compared to those without quizartinib, coincident with elevation in RUNX1 levels. Surprisingly, migration of CXCR4-low FLT3/ITD + cells to CXCL12 was significantly elevated compared to CXCR4-high cells, with concomitant higher expression of RUNX1 in Cxcr4-low FLT3/ITD + cells than in Cxcr4-high FLT3/ITD + cells. Silencing Runx1 using shRNAs significantly decreased migration to CXCL12 in refractory Cxcr4-low FLT3/ITD + Ba/F3 cells. These data indicate that the FLT3 inhibitor itself can facilitate the proliferation and migration to CXCL12 in FLT3/ITD + cells that are refractory to FLT3 inhibitors by up-regulating RUNX1. The results implicate that FLT3 inhibitors may worsen the disease progression in the patients that became refractory to FLT3 inhibitors by facilitating proliferation and migration to CXCL12 of the resistant FLT3/ITD + AML cells. In this regard, targeting RUNX1 may represent additional strategy to eradicate resistant FLT3/ITD + AML cells, in which their proliferation and migration are supported by FLT3 inhibitors. Disclosures No relevant conflicts of interest to declare.

CXCL12/CXCR4 Axis Drives Mitochondrial Trafficking in Tumor Myeloma Microenvironment

Mesenchymal stromal cells (MSCs) within the protective microenvironment of multiple myeloma (MM) promote tumor growth, confer chemoresistance and support metabolic needs of plasma cells (PCs) also transferring mitochondria. In this scenario, heterocellular communication and dysregulation of critical signaling axes are among the major contributors to progression and treatment failure. As metabolic rewiring is involved in the regulation of MSC phenotype, we first analyzed metabolic profile of healthy control (HC-) and MM-MSCs. NAD +/NADH ratio was decreased in MM-MSCs (n=8) as compared with HC-MSCs (n=4, p&lt;0.05), meanwhile ATP/ADP ratio was not significantly different between the two groups. This led us to analyze whether MM-MSCs were much prone in transferring mitochondria than HC-MSCs. We first labeled HC- and MM-MSCs with Mitotracker Red CMXRos before co-culture with MM cells. After 24h of coculture, we quantified mitochondria transfer by flow cytometry. The obtained values were significantly higher in MM cells co-cultured with MM-MSCs (n=10) as compared to PCs co-cultured with HC-MSCs (n=5, p&lt;0.01). In the cell-to-cell contact the gap junction-forming protein CX43 has been found critical for mitochondria uptake in lung and brain injury and it also can regulate CXCL12 secretion by MSCs. We found that MM-MSCs showed a significantly up-regulated CXCL12 expression as compared to HC-MSCs (p&lt;0.001). Therefore, we co-cultured HS-5 cells with myeloma cell lines and observed that significantly increased CXCL12-CX43 colocalization in healthy MSCs. To evaluate the selective PC-induced activation of CXCL12 expression via CX43 in MSCs, we co-cultured HS-5 cells with MM cell lines and exposed cocultures to ioxynil octanoate (IO), a selective inhibitor of CX43-based gap junctions. We found that the up-regulation of CXCL12 induced by MM cells was reverted by exposition to the CX43 inhibitor, thereby indicating that CX43 activated by PCs regulates CXCL12 production in MSCs. Given that CX43 is involved in mitochondria trafficking, we subsequently cocultured MM cells with HS-5 in presence or not of IO. Our data showed that mitochondrial transfer was abolished by CX43 inhibitor. Given that MM PCs induced increased CX43 and CXCL12 colocalization in HS-5 cells, we supposed that CXCL12/CXCR4 signaling could regulate mitochondria trafficking throughout this axis. For this reason, we analyzed the kinetic of mitochondria uptake of several HMCLs and related their CXCR4 expression with the percentage of transferred mitochondria. Our data demonstrated that HMCLs with higher expression of CXCR4 had also higher percentage of transferred mitochondria both in time lapse and flow cytometry. The correlation between CXCR4 expression and the percentage of mitochondria uptake in HMCLs was also confirmed in primary myeloma PCs. Furthermore, plerixafor, a selective inhibitor of CXCR4, significantly reduced mitochondrial transfer from MSCs to myeloma PCs further establishing mechanistically that CXCR4/CXCL12 is directly involved in mitochondrial trafficking. Next, we investigated whether combination of plerixafor with bortezomib or carfilzomib interferes with mitochondrial transfer from MSCs to PCs. Interestingly, we found that the proteasome inhibitors promoted mitochondrial transfer while their combination with plerixafor inhibited mitochondria trafficking. Moreover, intracellular expression of CXCR4 in myeloma PCs from BM biopsy specimens demonstrated higher CXCR4 colocalization with CD138+ cells of non-responder patients to bortezomib compared with responder patients, suggesting that CXCR4 mediated chemoresistance in MM. In conclusion, we have shown that MM-MSCs are relatively low dependent on mitochondria metabolism and are inclined to transfer mitochondria to MM tumor cells. Furthermore, tumor PCs increase the expression of CX43 in MSCs leading to an increased levels of CXCL12 and stimulation of its corresponding receptor expressed on MM cells. The resulting CX43/CXCL12/CXCR4 interplay enhances mitochondrial trafficking from MSCs to myeloma PCs and can protect cancer cells against anti-myeloma agents. Understanding pro-tumorigenic phenotype of MSCs and mechanisms of adhesion and heterocellular communication favoring their interaction with cancer PCs, will allow to manipulate critical pathways, including CXCL12/CXCR4 axis, thus improving disease outcome. Disclosures Di Raimondo: Pfizer: Honoraria; AbbVie: Honoraria; Bristol Myers Squibb: Honoraria; Jazz Pharmaceutical: Honoraria; Janssen Pharmaceuticals: Honoraria; Amgen: Honoraria.

Immunophenotypic and Single-Cell Transcriptional Profiling of CD34+ Hematopoietic Stem and Progenitor Cells Mobilized with Motixafortide (BL-8040) and G-CSF Versus Plerixafor and G-CSF Versus Placebo and G-CSF: A Correlative Study of the Genesis Trial

Background: CD34 expression remains the most common immunophenotypic cell surface marker defining human hematopoietic stem and progenitor cells (HSPCs). Recently, use of multicolor fluorescence-activated cell sorting (mFACS) and single-cell RNA sequencing (scRNA seq) has illustrated the heterogenous nature of CD34+ HSPCs, with immunophenotypically and transcriptionally distinct subsets ranging from primitive hematopoietic stem cells (HSCs) capable of long-term multilineage potential to differentiated, lineage-committed progenitors. Meanwhile, the addition of CXCR4 inhibitors (CXCR4i) to G-CSF (G) has increased mobilization of CD34+ HSPCs for stem cell transplantation (SCT). Yet, the effect of CXCR4i +/- G on mobilization of specific immunophenotypic and transcriptional CD34+ HSPC subsets is not well-characterized. Motixafortide (M) is a novel cyclic peptide CXCR4i with a low receptor off rate and extended in vivo action vs plerixafor (Px). M was recently evaluated in the phase 3, double blind, placebo controlled GENESIS Trial as an HSPC mobilizer prior to autologous SCT (ASCT) in multiple myeloma (MM). Methods: GENESIS Trial patients were prospectively randomized (2:1) to receive either M+G or placebo (P)+G for HSPC mobilization. Demographically similar patients undergoing mobilization with Px+G prior to ASCT for MM were prospectively enrolled on a parallel tissue banking protocol. All patients received G (10 mcg/kg) on days 1-5 (and 6-8 if needed). Patients also received either M (1.25 mg/kg) or P on day 4 (and 6 if needed); or Px (0.24 mg/kg) on day 4 (and 5-7 if needed). Apheresis began day 5 (and 6-8 if needed). HSPCs were purified from apheresis product on day 5 via CD34+ immunomagnetic selection. CD34+ HSPC subset profiling was performed via mFACS and scRNA seq. CXCR4 expression and receptor occupancy was evaluated by antibody binding capacity of 12G5 and 1D9 clones. Results: Demographics were similar between the M+G (n=24), P+G (n=13) and Px+G (n=14) cohorts. By mFACS, M+G mobilized a 5.5 fold higher absolute number (#) of HSCs, multipotent progenitors (MPP) and common myeloid progenitors (CMP) vs P+G (p&lt;0.0001); and a 2.6 fold higher # of these subsets vs Px+G (p=0.0327) (Figure 1A). M+G mobilized a 10.5 fold higher absolute # of primitive HSCs vs P+G (p&lt;0.0001) and a 1.1 fold higher # vs Px+G (p=0.7876) (Figure 1B). M+G and Px+G mobilized a 7-8 fold higher # of plasmacytoid dendritic cell precursors vs P+G (p-values &gt;0.05). 1D9 binding to CXCR4 on CD34+ HSPCs was similar between all 3 arms (p-values 0.45-0.75). 12G5 binding (which competes with CXCR4i's for binding to CXCR4) was significantly lower with M+G (MFI:11) vs P+G (MFI:74; p&lt;0.0001) and Px+G (MFI:271; p&lt;0.0001). By scRNA seq, UMAP clustering identified 3 transcriptionally similar HSC sub-clusters (HSC-I, -II and -III) mobilized by all 3 regimens; and 1 distinct HSC-PL cluster mobilized by P+G expressing heat shock protein genes (HSPA1 A/B) (Figure 1C). Differentially expressed genes (DEGs) of HSCs I-III included CD52, FTH1, HLA-E, KLF2 and LMNA. AVP was unique to HSC-I while EGR1, JUN and ZFP36 were unique to HSC-III. MPPs clustered into 3 sub-clusters (MPP-I, -II and -III). MPP-I clustered closely to HSC-II/III with low expression of genes of differentiation. MPP-II expressed DEGs (PLEK) on a continuum toward megakaryocyte-erythroid progenitors (MEP-I/II), which expressed DEGs of erythroid differentiation (HBD/HBB). MPP-I and -II contained cells from all 3 regimens. However, MPP-III was specific to M+G with DEGs (MT-ATP8, HIST1H1) associated with monocyte, lymphocyte and NK cell differentiation. Conclusions: Extended CXCR4i with M+G mobilized significantly higher #s of combined CD34+ HSCs, MPPs and CMPs vs Px+G and P+G (p-values &lt;0.05). Additionally, M+G mobilized a 10.5 fold higher # of immunophenotypically primitive CD34+ HSCs capable of broad multilineage hematopoietic reconstitution vs P+G (p&lt;0.0001) and similar #s vs Px+G. CXCR4 expression on CD34+ HSPCs by 1D9 binding was similar across all arms. Whereas, 12G5 binding was much lower with M+G vs P+G and Px+G, consistent with extended CXCR4 receptor occupancy by M. All regimens mobilized transcriptionally similar HSC-I-III subsets. However, lack of CXCR4i (M or Px) resulted in mobilization of more-differentiated HSCs (HSC-PL subset). Whereas extended CXCR4i with M+G (but not Px+G) mobilized a unique MPP-III subset with DEGs related to leukocyte differentiation. Figure 1 Figure 1. Disclosures Crees: BioLineRx Ltd.: Research Funding. Retting: BioLineRx Ltd.: Research Funding. Jayasinghe: WUGEN: Consultancy; MMRF: Consultancy. Vainstein: BioLineRx LTD: Current Employment. Sorani: BioLineRx LTD: Current Employment. Ickowicz: BioLineRx Ltd.: Current Employment. Shemesh-Darvish: BioLineRx LTD: Current Employment. Kadosh: BioLineRx Ltd.: Current Employment.

Reduced CXCR4 expression in associated with extramedullary and predicts poor survival in newly diagnosed multiple myeloma

Multiple myeloma (MM), a bone marrow-resident hematological malignancy of plasma cells, has remained largely incurable despite the advancement of novel therapies in recent years. Because of the heterogeneity of myeloma cells, risk stratification of MM is important for making therapeutic regimens. Nevertheless, no immunohistochemical (IHC) predictive and prognostic marker of MM has been constructed yet. Herein, the prognostic value of C-X-C motif chemokine receptor 4 (CXCR4) expression in 48 newly diagnosed MM patients was explored using IHC. Correlations between CXCR4 expression and clinical features of MM were analyzed. CXCR4-positive patients significantly outperformed CXCR4- negative patients in both 3-year estimated overall survival (93.8% vs 45.8%) and progression-free survival (57.1% vs 40.9%). The incidence of extramedullary lesions in CXCR4-negative patients increased significantly compared with CXCR4-positive patients. Plasma cells that reduce CXCR4 expression have poor prognosis and increase the incidence of extramedullary lesions.

ATP Inhibits Breast Cancer Migration and Bone Metastasis through Down-Regulation of CXCR4 and Purinergic Receptor P2Y11

ATP released by bone osteocytes is shown to activate purinergic signaling and inhibit the metastasis of breast cancer cells into the bone. However, the underlying molecular mechanism is not well understood. Here, we demonstrate the important roles of the CXCR4 and P2Y11 purinergic receptors in mediating the inhibitory effect of ATP on breast cancer cell migration and bone metastasis. Wound-healing and transwell migration assays showed that non-hydrolysable ATP analogue, ATPγS, inhibited migration of bone-tropic human breast cancer cells in a dose-dependent manner. BzATP, an agonist for P2X7 and an inducer for P2Y11 internalization, had a similar dose-dependent inhibition on cell migration. Both ATPγS and BzATP suppressed the expression of CXCR4, a chemokine receptor known to promote breast cancer bone metastasis, and knocking down CXCR4 expression by siRNA attenuated the inhibitory effect of ATPγS on cancer cell migration. While a P2X7 antagonist A804598 had no effect on the impact of ATPγS on cell migration, antagonizing P2Y11 by NF157 ablated the effect of ATPγS. Moreover, the reduction in P2Y11 expression by siRNA decreased cancer cell migration and abolished the impact of ATPγS on cell migration and CXCR4 expression. Similar to the effect of ATPγS on cell migration, antagonizing P2Y11 inhibited bone-tropic breast cancer cell migration in a dose-dependent manner. An in vivo study using an intratibial bone metastatic model showed that ATPγS inhibited breast cancer growth in the bone. Taken together, these results suggest that ATP inhibits bone-tropic breast cancer cells by down-regulating the P2Y11 purinergic receptor and the down-regulation of CXCR4 expression.

Investigation of spleen CXCR4 expression by [68Ga]Pentixafor PET in a cohort of 145 solid cancer patients

Background The chemokine receptor CXCR4 is frequently overexpressed and associated with adverse prognosis in most hematopoietic malignancies and solid cancers. Recently, CXCR4 molecular imaging using the CXCR4-specific positron emission tomography (PET) tracer Pentixafor ([68Ga]Pentixafor) has become a well-established method to non-invasively measure CXCR4 expression in vivo. In previous Pentixafor imaging studies, highly variable CXCR4 tracer uptake to the spleen was observed. Results We investigated the hypothesis that enhanced spleen [68Ga]Pentixafor uptake and thus CXCR4 expression in patients with solid tumors would indicate an activated spleen state and/or an association with clinical and prognostic features and survival parameters. In this retrospective study, [68Ga]Pentixafor-PET images and patient records of 145 solid tumor patients representing 27 cancer entities were investigated for an association of spleen [68Ga]Pentixafor uptake and clinical characteristics and outcome. Based on this assessment, we did not observe differences in clinical outcomes, measured by progression-free survival, overall survival and remission status neither within the entire cohort nor within subgroups of adrenal cancer, desmoplastic small round cell tumor, neuroendocrine tumors, non-small cell lung cancer, small cell lung cancer and pancreatic adenocarcinoma patients. No tumor entity showed especially high levels of spleen [68Ga]Pentixafor uptake compared to others or a control cohort. However, when investigating laboratory parameters, there was a positive correlation of high spleen [68Ga]Pentixafor uptake with leukocyte and/or platelet counts in neuroendocrine tumors, non-small cell lung cancer and small cell lung cancer. Conclusion Spleen [68Ga]Pentixafor uptake was not associated with stage of disease and clinical outcomes in solid tumor patients. We identified positively associated platelet and/or leukocyte counts with spleen [68Ga]Pentixafor uptake in neuroendocrine tumors, non-small cell lung cancer and small cell lung cancer, suggesting that splenic CXCR4 expression could possibly play a role in systemic immunity/inflammation in some types of solid tumors or a subgroup of patients within solid tumor entities.