CXCR4 blockade improves leukemia eradication by allogeneic lymphocyte infusion

Can GCSF-stimulated donor lymphocyte infusions improve outcomes for relapsed disease following allogeneic hematopoietic cell transplantation? A systematic review and meta-analysis

Donor lymphocyte infusions (DLI) can produce graft-versus tumor effects to treat relapse after allogeneic hematopoietic cell transplantation, however, durable responses remain uncommon. A systematic review and meta-analysis are needed to clarify whether DLI collected after stimulation with granulocyte colony-stimulating factor (GCSF; G-DLI) can improve clinical outcomes. Sixteen studies (4 controlled) involving 585 patients were identified in a systematic search up to 17 September 2020. A meta-analysis demonstrated no significant difference in the risk of all-cause mortality (RR: 0.94, 95% CI 0.52-1.68, p = 0.82; n = 3 studies) or relapse-related mortality (RR: 0.72, 0.44-1.18, p = 0.19; n = 3 studies) between G-DLI and conventional DLI (C-DLI) groups. G-DLI products had similar mean CD3+ cells compared to C-DLI products, but median CD34+ cells/kg were increased. No improvement in disease progression, complete response rates, or risk of developing GVHD was observed with G-DLI, however, greater non-relapse mortality was observed compared to C-DLI. Alternative approaches to enhancing graft-versus-tumor effects are needed.

Mesenchymal Stem Cells With Cancer-Associated Fibroblast-Like Phenotype Stimulate SDF-1/CXCR4 Axis to Enhance the Growth and Invasion of B-Cell Acute Lymphoblastic Leukemia Cells Through Cell-to-Cell Communication

Background: Bone marrow mesenchymal stem cells (BM-MSCs) are the stromal cells in the leukemia microenvironment, and can obtain cancer-associated fibroblast (CAF)-like phenotype under certain conditions to further promote leukemia progression. However, the mechanism of MSCs with CAF-like phenotype interacting with leukemia cells in B-cell acute lymphoblastic leukemia (B-ALL) and promoting the progression of B-ALL remains unclear. Methods: Mesenchymal stem cells with CAF-like phenotype were obtained by treating MSCs with recombinant human transforming growth factor-β (rhTGF-β), hereafter referred to as TGF-β conditioned MSCs. In vivo mouse model experiments, in vitro transwell chamber experiments, three-dimensional (3D) cell culture models, lentiviral transfection and other experimental methods were used to investigate the possible mechanism of the interaction between TGF-β conditioned MSCs and leukemia cells in promoting the growth, migration and invasion of B-ALL cells. Results: Compared with untreated MSCs, TGF-β conditioned MSCs significantly promoted the growth and proliferation of leukemia cells in mice, and increased the expression of CXCR4 in tumor tissues. In vitro cell experiments, TGF-β conditioned MSCs obviously promoted the migration and invasion of Nalm-6/RS4;11 cells, which were effectively blocked by the CXCR4 inhibitor AMD3100, thereby inhibiting the secretion of MMP-9 in TGF-β conditioned MSCs and inhibiting the activation of the PI3K/AKT signaling pathway in leukemia cells. Further, findings were made that the interaction between TGF-β conditioned MSCs and leukemia cells were mediated by the interaction between the integrin receptor α5β1 on the surface of leukemia cells and the increased expression of fibronectin on TGF-β conditioned MSCs. AMD3100 could weaken such effect by reducing the expression of integrin α5β1 on leukemia cells. Further regulation of integrin β1 could effectively interfere with the interaction between TGF-β conditioned MSCs and leukemia cells. Conclusion: Mesenchymal stem cells with CAF-like phenotype could be a key factor in promoting the growth and invasion of B-ALL cells, and the SDF-1/CXCR4 axis might be a significant factor in mediating the communication of MSCs with CAF-like phenotype and leukemia cells. To prevent the progression of B-ALL cells, blocking the SDF-1/CXCR4 axis with AMD3100 or targeting integrin β1 might be a potential therapeutic strategy.

Posttransplant blockade of CXCR4 improves leukemia complete remission rates and donor stem cell engraftment without aggravating GVHD

Allogeneic hematopoietic cell transplantation (allo-HCT) is a promising therapeutic option for hematological malignancies, but relapse resulting predominantly from residual disease in the bone marrow (BM) remains the major cause of treatment failure. Using immunodeficient mice grafted with laboratory-generated human B-ALL, our previous study suggested that leukemia cells within the BM are resistant to graft-versus-leukemia (GVL) effects and that mobilization with CXCR4 antagonists may dislodge leukemia cells from the BM, enabling them to be destroyed by GVL effects. In this study, we extended this approach to patient-derived xenograft (PDX) and murine T-ALL and AML models to determine its clinical relevance and effects on GVHD and donor hematopoietic engraftment. We found that posttransplant treatment with the CXCR4 antagonist AMD3100 significantly improved the eradication of leukemia cells in the BM in PDX mice grafted with B-ALL cells from multiple patients. AMD3100 also significantly improved GVL effects in murine T-ALL and AML models and promoted donor hematopoietic engraftment in mice following nonmyeloablative allo-HCT. Furthermore, posttransplant treatment with AMD3100 had no detectable deleterious effect related to acute or chronic GVHD. These findings provide important preclinical data supporting the initiation of clinical trials exploring combination therapy with CXCR4 antagonists and allo-HCT.

Role of CXCR4 in the progression and therapy of acute leukaemia

CXCR4 is expressed on leukaemia cells and haematopoietic stem cells (HSCs), and its ligand stromal-derived factor 1 (SDF-1) is produced abundantly by stromal cells in the bone marrow (BM). The SDF-1/CXCR4 axis plays important roles in homing to and retention in the protective BM microenvironment of malignant leukaemia cells and normal HSCs. CXCR4 expression is regulated by multiple mechanisms and the level of CXCR4 expression on leukaemia cells has prognostic indications in patients with acute leukaemia. CXCR4 antagonists can mobilize leukaemia cells from BM to circulation, which render them effectively eradicated by chemotherapeutic agents, small molecular inhibitors or hypomethylating agents. Therefore, such combinational therapies have been tested in clinical trials. However, new evidence emerged that drug-resistant leukaemia cells were not affected by CXCR4 antagonists, and the migration of certain leukaemia cells to the leukaemia niche was independent of SDF-1/CXCR4 axis. In this review, we summarize the role of CXCR4 in progression and treatment of acute leukaemia, with a focus on the potential of CXCR4 as a therapeutic target for acute leukaemia. We also discuss the potential value of using CXCR4 antagonists as chemosensitizer for conditioning regimens and immunosensitizer for graft-vs-leukaemia effects of allogeneic haematopoietic stem cell transplantation.

The biological role of the CXCL12/CXCR4 axis in esophageal squamous cell carcinoma

Esophageal cancer is the eighth most common malignant tumor and the sixth leading cause of cancer-related death worldwide. Esophageal squamous cell carcinoma (ESCC) is the main histological type of esophageal cancer, and accounts for 90% of all cancer cases. Despite the progress made in surgery, chemotherapy, and radiotherapy, the mortality rate from esophageal cancer remains high, and the overall 5-year survival rate is less than 20%, even in developed countries. The C-X-C motif chemokine ligand 12 (CXCL12) is a member of the CXC chemokine subgroup, which is widely expressed in a variety of tissues and cells. CXCL12 participates in the regulation of many physiological and pathological processes by binding to its specific receptor, C-X-C motif chemokine receptor type 4 (CXCR4), where it causes embryonic development, immune response, and angiogenesis. In addition, increasing evidence indicates that the CXCL12/CXCR4 axis plays an important role in the biological processes of tumor cells. Studies have shown that CXCL12 and its receptor, CXCR4, are highly expressed in ESCC. This abnormal expression contributes to tumor proliferation, lymph node and distant metastases, and worsening prognosis. At present, antagonists and imaging agents against CXCL12 or CXCR4 have been developed to interfere with the malignant process and monitor metastasis of tumors. This article summarizes the structure, function, and regulatory mechanism of CXCL12/CXCR4 and its role in the malignancy of ESCC. Current results from preclinical research targeting CXCL12/CXCR4 are also summarized to provide a reference for the clinical diagnosis and treatment of ESCC.

TCR Redirected T Cells for Cancer Treatment: Achievements, Hurdles, and Goals

Adoptive T cell therapy (ACT) is a rapidly evolving therapeutic approach designed to harness T cell specificity and function to fight diseases. Based on the evidence that T lymphocytes can mediate a potent anti-tumor response, initially ACT solely relied on the isolation, in vitro expansion, and infusion of tumor-infiltrating or circulating tumor-specific T cells. Although effective in a subset of cases, in the first ACT clinical trials several patients experienced disease progression, in some cases after temporary disease control. This evidence prompted researchers to improve ACT products by taking advantage of the continuously evolving gene engineering field and by improving manufacturing protocols, to enable the generation of effective and long-term persisting tumor-specific T cell products. Despite recent advances, several challenges, including prioritization of antigen targets, identification, and optimization of tumor-specific T cell receptors, in the development of tools enabling T cells to counteract the immunosuppressive tumor microenvironment, still need to be faced. This review aims at summarizing the major achievements, hurdles and possible solutions designed to improve the ACT efficacy and safety profile in the context of liquid and solid tumors.

Bone marrow mesenchymal stem cells in microenvironment transform into cancer-associated fibroblasts to promote the progression of B-cell acute lymphoblastic leukemia

Bone marrow microenvironment is essential for leukemia cells to survive and escape the killing effect of chemotherapeutics. Cancer-associated fibroblasts (CAFs) are the dominant stromal cells in tumor microenvironment (TME), but their role in B-cell acute lymphoblastic leukemia (B-ALL) remains unclear. Here, RT-PCR and Western blotting in bone marrow mononuclear cells revealed higher proportions of CAFs markers α-SMA and FAP in the newly diagnosed and relapsed B-ALL patients. In vitro experiments, bone marrow mesenchymal stem cells (BM-MSCs) acquired a CAFs phenotype after co-culture with leukemia cells, which produced high level of tumor-promoting growth factors and reduced the daunorubicin (DNR)-induced damage to B-ALL cells. As for its mechanism, CAFs activation was mediated by TGF-β up-regulation in the co-culture system, and TGF-β triggered MSCs conversion into CAFs relying on the SDF-1/CXCR4 pathway. Further LY2109761 and AMD3100 effectively decreased the activation of CAFs through inhibiting TGF-β receptor and CXCR4. Comparative experiments with MSCs and transformed CAFs prompted that CAFs had more obvious effect than MSCs on stimulating leukemia progression through accelerating leukemia cell migration and invasion. These results clarified the important role of CAFs in B-ALL progression and the possible mechanisms of CAFs activation in leukemia microenvironment, which might provide a theoretical basis for B-ALL patients to find more effective targeted therapies targeting the bone marrow microenvironment.

Combination of PET and CXCR4-Targeted Peptide Molecule Agents for Noninvasive Tumor Monitoring

Precision medicine is emphasizing not only at individual but also at disease molecule level in modern medicine. Therefore, target-specific molecular agents are crucial for precise diagnosis and treatment. We developed a peptide agent that binds a critical chemokine receptor-CXCR4 and could be used to detect tumor status. Confocal images showed binding of the peptide agent to human osteosarcoma cells. Clinical gold-standard molecular imaging agent PET showed tumors had high glucose metabolism, CT showed that these xenograft tumors were calcified and displayed hypervascularity. Peptide imaging demonstrated that these tumors were CXCR4 positive. However, Western blot protein analysis revealed a discordance between the tumor and the CXCR4 targeted agent, suggesting that small changes in peptide sequences have profound effect on binding to their targets. We also demonstrated the molecular screening by modifying the peptide sequence and thereby altering the binding properties of the agent. In conclusion, this study demonstrates that small molecule peptide agents can be used as an additional diagnostic tool for precision medicine.