Myeloma-derived macrophage inhibitory factor regulates bone marrow stromal cell-derived IL-6 via c-MYC

BET Inhibitor JQ1 Selectively Reduce Tregs by Upregulating STAT3 and Suppressing PD-1 Expression in Patients with Multiple Myeloma

Multiple myeloma (MM) stands as a prevalent hematological malignancy, primarily incurable, originating from plasma cell clones. MM's progression encompasses genetic abnormalities and disruptions in the bone marrow microenvironment, leading to tumor proliferation, immune dysfunction, and compromised treatment outcomes. Emerging evidence highlights the critical role of regulatory T cells (Tregs) in MM progression, suggesting that targeting Tregs could enhance immune functionality and treatment efficacy. In this study, a notable increase in Treg proportions within MM patients' bone marrow (BM) compared to healthy individuals is observed. Additionally, it is found that the bromodomain and extraterminal domain (BET) inhibitor JQ1 selectively diminishes Treg percentages in MM patients' BM and reduces TGF-β1-induced Tregs. This reduction occurs via inhibiting cell viability and promoting apoptosis. RNA sequencing further indicates that JQ1's inhibitory impact on Tregs likely involves upregulating STAT3 and suppressing PD-1 expression. Collectively, these findings suggest JQ1's potential to modulate Tregs, bolstering the immune response in MM and introducing a promising avenue for MM immunotherapy.

Research progress of the chemokine/chemokine receptor axes in the oncobiology of multiple myeloma (MM)

BACKGROUND

The incidence of multiple myeloma (MM), a type of blood cancer affecting monoclonal plasma cells, is rising. Although new drugs and therapies have improved patient outcomes, MM remains incurable. Recent studies have highlighted the crucial role of the chemokine network in MM's pathological mechanism. Gaining a better understanding of this network and creating an overview of chemokines in MM could aid in identifying potential biomarkers and developing new therapeutic strategies and targets.

PURPOSE

To summarize the complicated role of chemokines in MM, discuss their potential as biomarkers, and introduce several treatments based on chemokines.

METHODS

Pubmed, Web of Science, ICTRP, and Clinical Trials were searched for articles and research related to chemokines. Publications published within the last 5 years are selected.

RESULTS

Malignant cells can utilize chemokines, including CCL2, CCL3, CCL5, CXCL7, CXCL8, CXCL12, and CXCL13 to evade apoptosis triggered by immune cells or medication, escape from bone marrow and escalate bone lesions. Other chemokines, including CXCL4, CCL19, and CXCL10, may aid in recruiting immune cells, increasing their cytotoxicity against cancer cells, and inducing apoptosis of malignant cells.

CONCLUSION

Utilizing anti-tumor chemokines or blocking pro-tumor chemokines may provide new therapeutic strategies for managing MM. Inspired by developed CXCR4 antagonists, including plerixafor, ulocuplumab, and motixafortide, more small molecular antagonists or antibodies for pro-tumor chemokine ligands and their receptors can be developed and used in clinical practice. Along with inhibiting pro-tumor chemokines, studies suggest combining chemokines with chimeric antigen receptor (CAR)-T therapy is promising and efficient.

Long Non-Coding RNA LOC339059 Attenuates IL-6/STAT3-Signaling-Mediated PDL1 Expression and Macrophage M2 Polarization by Interacting with c-Myc in Gastric Cancer

Background: Long non-coding RNA (lncRNA) was identified as a novel diagnostic biomarker in gastric cancer (GC). However, the functions of lncRNAs in immuno-microenvironments have not been comprehensively explored. In this study, we explored a critical lncRNA, LOC339059, that can predict the clinical prognosis in GC related to the modulation of PD-L1 and determined its influence upon macrophage polarization via the IL-6/STAT3 pathway. Methods: To date, accumulating evidence has demonstrated that the dysregulation of LOC339059 plays an important role in the pathological processes of GC. It acts as a tumor suppressor, regulating GC cell proliferation, migration, invasion, tumorigenesis, and metastasis. A flow cytometry assay showed that the loss of LOC339059 enhanced PDL1 expression and M2 macrophage polarization. RNA sequencing, RNA pull-down, RNA immunoprecipitation, Chip-PCR, and a luciferase reporter assay revealed the pivotal role of signaling alternation between LOC339059 and c-Myc. Results: A lower level of LOC339059 RNA was found in primary GC tissues compared to adjacent tissues, and such a lower level is associated with a poorer survival period (2.5 years) after surgery in patient cohorts. Moreover, we determined important immunological molecular biomarkers. We found that LOC339059 expression was correlated with PD-L1, CTLA4, CD206, and CD204, but not with TIM3, FOXP3, CD3, C33, CD64, or CD80, in a total of 146 GC RNA samples. The gain of LOC339059 in SGC7901 and AGS inhibited biological characteristics of malignancy, such as proliferation, migration, invasion, tumorigenesis, and metastasis. Furthermore, our data gathered following the co-culture of THP-1 and U937 with genomic GC cells indicate that LOC339059 led to a reduction in the macrophage cell ratio, in terms of CD68+/CD206+, to 1/6, whereas the selective knockdown of LOC339059 promoted the abovementioned malignant cell phenotypes, suggesting that it has a tumor-suppressing role in GC. RNA-Seq analyses showed that the gain of LOC339059 repressed the expression of the interleukin family, especially IL-6/STAT3 signaling. The rescue of IL-6 in LOC339059-overexpressing cells reverted the inhibitory effects of the gain of LOC339059 on malignant cell phenotypes. Our experiments verified that the interaction between LOC339059 and c-Myc resulted in less c-Myc binding to the IL-6 promoter, leading to the inactivation of IL-6 transcription. Conclusions: Our results establish that LOC339059 acts as a tumor suppressor in GC by competitively inhibiting c-Myc, resulting in diminished IL-6/STAT3-signaling-mediated PDL1 expression and macrophage M2 polarization.

Lessons in aging from Myc knockout mouse models

Despite MYC being among the most intensively studied oncogenes, its role in normal development has not been determined as Myc-/- mice do not survival beyond mid-gestation. Myc ± mice live longer than their wild-type counterparts and are slower to accumulate many age-related phenotypes. However, Myc haplo-insufficiency likely conceals other important phenotypes as many high-affinity Myc targets genes continue to be regulated normally. By delaying Myc inactivation until after birth it has recently been possible to study the consequences of its near-complete total body loss and thus to infer its normal function. Against expectation, these "MycKO" mice lived significantly longer than control wild-type mice but manifested a marked premature aging phenotype. This seemingly paradoxical behavior was potentially explained by a >3-fold lower lifetime incidence of cancer, normally the most common cause of death in mice and often Myc-driven. Myc loss accelerated the accumulation of numerous "Aging Hallmarks", including the loss of mitochondrial and ribosomal structural and functional integrity, the generation of reactive oxygen species, the acquisition of genotoxic damage, the detrimental rewiring of metabolism and the onset of senescence. In both mice and humans, normal aging in many tissues was accompaniued by the downregulation of Myc and the loss of Myc target gene regulation. Unlike most mouse models of premature aging, which are based on monogenic disorders of DNA damage recognition and repair, the MycKO mouse model directly impacts most Aging Hallmarks and may therefore more faithfully replicate the normal aging process of both mice and humans. It further establishes that the strong association between aging and cancer can be genetically separated and is maintained by a single gene.

Identification of potential resistance mechanisms and therapeutic targets for the relapse of BCMA CAR-T therapy in relapsed/refractory multiple myeloma through single-cell sequencing

BACKGROUND

BCMA CAR-T is highly effective for relapsed/refractory multiple myeloma(R/R-MM) and significantly improves the survival of patients. However, the short remission time and high relapse rate of MM patients treated with BCMA CAR-T remain bottlenecks that limit long-term survival. The immune microenvironment of the bone marrow (BM) in R/R-MM may be responsible for this. The present study aims to present an in-depth analysis of resistant mechanisms and to explore potential novel therapeutic targets for relapse of BCMA CAR-T treatment via single-cell RNA sequencing (scRNA-seq) of BM plasma cells and immune cells.

METHODS

This study used 10X Genomic scRNA-seq to identify cell populations in R/R-MM CD45⁺ BM cells before BCMA CAR-T treatment and relapse after BCMA CAR-T treatment. Cell Ranger pipeline and CellChat were used to perform detailed analysis.

RESULTS

We compared the heterogeneity of CD45⁺ BM cells before BCMA CAR-T treatment and relapse after BCMA CAR-T treatment. We found that the proportion of monocytes/macrophages increased, while the percentage of T cells decreased at relapse after BCMA CAR-T treatment. We then reclustered and analyzed the alterations in plasma cells, T cells, NK cells, DCs, neutrophils, and monocytes/macrophages in the BM microenvironment before BCMA CAR-T treatment and relapse after BCMA CAR-T treatment. We show here that the percentage of BCMA positive plasma cells increased at relapse after BCMA CAR-T cell therapy. Other targets such as CD38, CD24, SLAMF7, CD138, and GPRC5D were also found to be expressed in plasma cells of the R/R-MM patient at relapse after BCMA CAR-T cell therapy. Furthermore, exhausted T cells, TIGIT⁺NK cells, interferon-responsive DCs, and interferon-responsive neutrophils, increased in the R/R-MM patient at relapse after BCMA CAR-T cell treatment. Significantly, the proportion of IL1β^hi Mφ, S100A9^hi Mφ, interferon-responsive Mφ, CD16^hi Mφ, MARCO ^hi Mφ, and S100A11^hi Mφ significantly increased in the R/R-MM patient at relapse after BCMA CAR-T cell therapy. Cell-cell communication analysis indicated that monocytes/macrophages, especially the MIF and APRIL signaling pathway are key players in R/R-MM patient at relapse after BCMA CAR-T cell therapy.

CONCLUSION

Taken together, our data extend the understanding of intrinsic and extrinsic relapse of BCMA CAR-T treatment in R/R-MM patient and the potential mechanisms involved in the alterations of antigens and the induced immunosuppressive microenvironment, which may provide a basis for the optimization of BCMA CAR-T strategies. Further studies should be performed to confirm these findings.

The immune suppressive tumor microenvironment in multiple myeloma: The contribution of myeloid-derived suppressor cells

Myeloid derived suppressors cells (MDSC) play major roles in regulating immune homeostasis and immune responses in many conditions, including cancer. MDSC interact with cancer cells within the tumor microenvironment (TME) with direct and indirect mechanisms: production of soluble factors and cytokines, expression of surface inhibitory molecules, metabolic rewiring and exosome release. The two-way relationship between MDSC and tumor cells results in immune evasion and cancer outgrowth. In multiple myeloma (MM), MDSC play a major role in creating protumoral TME conditions. In this minireview, we will discuss the interplay between MDSC and MM TME and the possible strategies to target MDSC.

Cellular senescence in cancers: relationship between bone marrow cancer and cellular senescence

INTRODUCTION

There are many factors and conditions that lead to cellular senescence. Replicative senescence and Hayflick phenomenon are the most important causes of cellular senescence. Senescent cells also lead to wound healing conditions resulting from injury and toxic conditions.

MATERIAL AND METHODS

When a cell becomes senescent, it stops replication and begins to leak inflammatory signals before growth. It also alters the extracellular matrix and behavior of neighbor cells and even motivates them. This review was conducted to determine the association between senescence and bone marrow cancer.

RESULTS

The results showed that senescent cells have a short life span due to their self-destructive nature or natural removal from the body by the immune system. These signals are effective to a certain extent in regenerating the damaged cells when present in a transient state. Cellular senescence can decrease the risk of all cancers, including bone marrow cancer, ensuring that cells with significant DNA injury are prevented from replication.

CONCLUSION

However, senescent cells increase in number as they age, which is very harmful over time. These cells extend into an older tissue for longer periods of time and form longer clusters in older tissues. Therefore, cellular senescence significantly contributes to aging.

A 3D-Bioprinted Multiple Myeloma Model

Multiple myeloma (MM) is a malignancy of plasma cells accounting for ≈12% of hematological malignancies. In this study, the fabrication of a high-content in vitro MM model using a coaxial extrusion bioprinting method is reported, allowing formation of a human bone marrow-like microenvironment featuring an outer mineral-containing sheath and the inner soft hydrogel-based core. MM cells are mono-cultured or co-cultured with HS5 stromal cells that can release interleukin-6 (IL-6), where the cells show superior behaviors and responses to bortezomib in 3D models than in the planar cultures. Tocilizumab, a recombinant humanized anti-IL-6 receptor (IL-6R), is investigated for its efficacy to enhance the chemosensitivity of bortezomib on MM cells cultured in the 3D model by inhibiting IL-6R. More excitingly, in a proof-of-concept demonstration, it is revealed that patient-derived MM cells can be maintained in 3D-bioprinted microenvironment with decent viability for up to 7 days evaluated, whereas they completely die off in planar culture as soon as 5 days. In conclusion, a 3D-bioprinted MM model is fabricated to emulate some characteristics of the human bone marrow to promote growth and proliferation of the encapsulated MM cells, providing new insights for MM modeling, drug development, and personalized therapy in the future.

Integrated analysis of fibroblasts molecular features in papillary thyroid cancer combining single-cell and bulk RNA sequencing technology

BACKGROUND

Papillary thyroid cancer (PTC) is the most common pathological type of thyroid cancer with a high incidence globally. Increasing evidence reported that fibroblasts infiltration in cancer was correlated with prognostic outcomes. However, fibroblasts related study in thyroid cancer remains deficient.

METHODS

Single-cell sequencing data of PTC were analyzed by Seurat R package to explore the ecosystem in PTC and identify fibroblasts cluster. The expression profiles and prognostic values of fibroblast related genes were assessed in TCGA dataset. A fibrosis score model was established for prognosis prediction in thyroid cancer patients. Differentially expressed genes and functional enrichment between high and low fibrosis score groups in TCGA dataset were screened. The correlation of immune cells infiltration and fibrosis score in thyroid cancer patients was explored. Expression levels and prognostic values of key fibroblast related factor were validated in clinical tissues another PTC cohort.

RESULTS

Fibroblasts were highly infiltrated in PTC and could interact with other type of cells by single-cell data analysis. 34 fibroblast related terms were differentially expressed in thyroid tumor tissues. COX regression analysis suggested that the constructed fibrosis score model was an independent prognostic predictor for thyroid cancer patients (HR = 5.17, 95%CI 2.31-11.56, P = 6.36E-05). Patients with low fibrosis scores were associated with a significantly better overall survival (OS) than those with high fibrosis scores in TCGA dataset (P = 7.659E-04). Specific immune cells infiltration levels were positively correlated with fibrosis score, including monocytes, M1 macrophages and eosinophils.

CONCLUSION

Our research demonstrated a comprehensive horizon of fibroblasts features in thyroid cancer microenvironment, which may provide potential value for thyroid cancer treatment.

Member Domain 3 (LRIG3) Activates Hypoxia-Inducible Factor-1 α/Vascular Endothelial Growth Factor (HIF-1α/VEGF) Pathway to Inhibit the Growth of Bone Marrow Mesenchymal Stem Cells in Glioma

Member domain 3 (LRIG3) of the LRIG gene family is down-regulated in several cancers. However, its role in bone marrow mesenchymal stem cells (BMSCs) in gliomas and the related mechanisms is unknown. The qRT-PCR assessed LRIG3 mRNA level. Rat BMSCs were randomly assigned into glioma group (BMSCs cultured in glioma microenvironment); LRIG3 overexpression group; and si-LRIG3 inhibitor group followed by analysis of LRIG3 expression, cell proliferation, PCNA and Ki-67 apoptosis, TNF-α; and HIF-1α/VEGF mRNA level. LRIG3 mRNA expression was decreased in gliomas patients (P < 0.05). BMSCs cultured in glioma microenvironment showed decreased LRIG3, increased cell proliferation, decreased PCNA, Ki-67 and TNF-α secretion as well as elevated HIF-1α and VEGF level (P < 0.05). Transfection of LRIG3 siRNA further promoted the above changes. Conversely, LRIG3 plasmid transfection significantly promoted its expression in glioma BMSCs (P < 0.05), inhibited cell proliferation, promoted PCNA, Ki-67, and TNF-α secretion, and increased HIF-1α and VEGF level (P < 0.05). LRIG3 in rat BMSCs cultured in the glioma microenvironment is decreased. Down-regulation of LRIG3 inhibits TNF-α secretion by activating HIF-1α/VEGF pathway regulating BMSCs proliferation and apoptosis.

Allosteric Site on SHIP2 Identified Through Fluorescent Ligand Screening and Crystallography: A Potential New Target for Intervention

Src homology 2 domain-containing inositol phosphate phosphatase 2 (SHIP2) is one of the 10 human inositol phosphate 5-phosphatases. One of its physiological functions is dephosphorylation of phosphatidylinositol 3,4,5-trisphosphate, PtdIns(3,4,5)P₃. It is therefore a therapeutic target for pathophysiologies dependent on PtdIns(3,4,5)P₃ and PtdIns(3,4)P₂. Therapeutic interventions are limited by the dearth of crystallographic data describing ligand/inhibitor binding. An active site-directed fluorescent probe facilitated screening of compound libraries for SHIP2 ligands. With two additional orthogonal assays, several ligands including galloflavin were identified as low micromolar Ki inhibitors. One ligand, an oxo-linked ethylene-bridged dimer of benzene 1,2,4-trisphosphate, was shown to be an uncompetitive inhibitor that binds to a regulatory site on the catalytic domain. We posit that binding of ligands to this site restrains L4 loop motions that are key to interdomain communications that accompany high catalytic activity with phosphoinositide substrate. This site may, therefore, be a future druggable target for medicinal chemistry.

Cellular senescence and hematological malignancies: From pathogenesis to therapeutics

Cellular senescence constitutes a permanent state of cell cycle arrest in proliferative cells induced by different stresses. The exploration of tumor pathogenesis and therapies has been a research hotspot in recent years. Cellular senescence is a significant mechanism to prevent the proliferation of potential tumor cells, but it can also promote tumor growth. Increasing evidence suggests that cellular senescence is involved in the pathogenesis and development of hematological malignancies, including leukemia, myelodysplastic syndrome (MDS) and multiple myeloma (MM). Cellular senescence is associated with functional decline of hematopoietic stem cells (HSCs) and increased risk of hematological malignancies. Moreover, the bone marrow (BM) microenvironment has a crucial regulatory effect in the process of these diseases. The senescence-associated secretory phenotype (SASP) in the BM microenvironment establishes a protumor environment that supports the proliferation and survival of tumor cells. Therefore, a series of therapeutic strategies targeting cellular senescence have been gradually developed, including the induction of cellular senescence and elimination of senescent cells. This review systematically summarizes the emerging information describing the roles of cellular senescence in tumorigenesis and potential clinical applications, which may be beneficial for designing rational therapeutic strategies for various hematopoietic malignancies.

miR-451a suppression of IL-6R can inhibit proliferation and increase apoptosis through the JAK2/STAT3 pathway in multiple myeloma

The IL-6R/JAK2/STAT3 pathway mediated by interleukin-6 (IL-6) plays an important role in the occurrence and development of multiple myeloma (MM), which is associated with decreased microRNA-451a. However, the biological function of microRNA-451a in MM remains unclear. The bone marrow (BM) of patients with MM was sampled, and the plasma cells were enriched. BM miR-451a, IL-6 and IL-6R levels and Ki-67 expression intensity were evaluated using reverse transcription-quantitative PCR, ELISA and flow cytometry, respectively. U266 cell proliferation, viability and apoptosis were measured using BrdU, CCK-8 and Annexin V/propidium iodide assays, respectively. Total and phospo-(p-)JAK2 and p-STAT3 levels were measured by western blotting. Dual-luciferase reporter assays were performed to validate the predicted target binding sites. miR-451a expression was low in patients with MM and was associated with the Revised International Staging System (R-ISS) stage. IL-6 concentrations were significantly higher in patients with MM than in normal controls and were inversely associated with miR-451a levels (r=-0.96, P<0.0001). IL-6R levels were positively correlated with the R-ISS stage. miR-451a was downregulated, and IL-6R was upregulated in myeloma cell lines. Treatment with an miR-451a mimic inhibited viability and induced apoptosis in U266 cells. p-JAK2 and p-STAT3 levels were significantly lower in mimic-treated U266 cells than in control cells. Thus, miR-451a was shown to regulate myeloma cell proliferation and apoptosis via the IL-6R/JAK2/STAT3 pathway and may be used to predict patient prognosis.

Pathogenic Mechanisms of Myeloma Bone Disease and Possible Roles for NRF2

Osteolytic bone lesions are one of the central features of multiple myeloma (MM) and lead to bone pain, fractures, decreased quality of life, and decreased survival. Dysfunction of the osteoclast (OC)/osteoblast (OB) axis plays a key role in the development of myeloma-associated osteolytic lesions. Many signaling pathways and factors are associated with myeloma bone diseases (MBDs), including the RANKL/OPG and NF-κB pathways. NRF2, a master regulator of inflammatory signaling, might play a role in the regulation of bone metabolism via anti-inflammatory signaling and decreased reactive oxygen species (ROS) levels. The loss of NRF2 expression in OCs reduced bone mass via the RANK/RANKL pathway and other downstream signaling pathways that affect osteoclastogenesis. The NRF2 level in OBs could interfere with interleukin (IL)-6 expression, which is associated with bone metabolism and myeloma cells. In addition to direct impact on OCs and OBs, the activity of NRF2 on myeloma cells and mesenchymal stromal cells influences the inflammatory stress/ROS level in these cells, which has an impact on OCs, OBs, and osteocytes. The interaction between these cells and OCs affects the osteoclastogenesis of myeloma bone lesions associated with NRF2. Therefore, we have reviewed the effects of NRF2 on OCs and OBs in MBDs.

A Novel Aurora Kinase Inhibitor Attenuates Leukemic Cell Proliferation Induced by Mesenchymal Stem Cells

Acute myeloid leukemia (AML) mesenchymal stem cells (MSCs) play an essential role in protecting leukemic cells from chemotherapeutic agents through activating a wide range of adhesion molecules and cytokines. Thus, more attention should be paid to attenuate the protection of leukemic cells by MSCs. By examining the gene expression files of MSCs from healthy donors and AML patients through high-throughput microarrays, we found that interleukin (IL)-6 was an important cytokine secreted by AML MSCs to protect leukemic cells, contributing to disease progression. Strikingly, Aurora A (AURKA) was activated by IL-6, offering a new target to interfere with leukemia. Importantly, a novel AURKA inhibitor, PW21, showed excellent AURKA kinase inhibitory activities and attenuated the interaction of leukemic cells and the microenvironment. PW21 inhibited MSC-induced cell proliferation, colony formation, and migration, and it induced cell apoptosis. Mechanically, PW21 could inhibit IL-6 secreted by MSCs. Moreover, we found that PW21 displayed a strong anti-leukemia effect on non-obese diabetic (NOD)-severe combined immunodeficiency (SCID) and murine MLL-AF9 leukemic models. PW21 significantly prolonged the survival of leukemic mice and eliminated the leukemic progenitor cells. AURKA inhibitor PW21 could provide a new approach for treatment of leukemia through blocking the protection by the leukemic microenvironment in clinical application.

Bone Marrow Senescence and the Microenvironment of Hematological Malignancies

Senescence is the irreversible arrest of cell proliferation that has now been shown to play an important role in both health and disease. With increasing age senescent cells accumulate throughout the body, including the bone marrow and this has been associated with a number of age-related pathologies including malignancies. It has been shown that the senescence associated secretory phenotype (SASP) creates a pro-tumoural environment that supports proliferation and survival of malignant cells. Understanding the role of senescent cells in tumor development better may help us to identify new treatment targets to impair tumor survival and reduce treatment resistance. In this review, we will specifically discuss the role of senescence in the aging bone marrow (BM) microenvironment. Many BM disorders are age-related diseases and highly dependent on the BM microenvironment. Despite advances in drug development the prognosis particularly for older patients remains poor and new treatment approaches are needed to improve outcomes for patients. In this review, we will focus on the relationship of senescence and hematological malignancies, how senescence promotes cancer development and how malignant cells induce senescence.

Hepatocyte Growth Factor: A Microenvironmental Resource for Leukemic Cell Growth

Chronic lymphocytic leukemia (CLL) is characterized by the progressive expansion of B lymphocytes CD5+/CD23+ in peripheral blood, lymph-nodes, and bone marrow. The pivotal role played by the microenvironment in disease pathogenesis has become increasingly clear. We demonstrated that bone marrow stromal cells and trabecular bone cells sustain survival of leukemic B cells through the production of hepatocyte growth factor (HGF). Indeed the trans-membrane kinase receptor for HGF, c-MET, is expressed on CLL cells and STAT3 TYR⁷⁰⁵ or AKT phosphorylation is induced after HGF/c-MET interaction. We have further observed that c-MET is also highly expressed in a peculiar type of cells of the CLL-microenvironment showing nurturing features for the leukemic clone (nurse-like cells: NLCs). Since HGF treatment drives monocytes toward the M2 phenotype and NLCs exhibit features of tumor associated macrophages of type 2 we suggested that HGF, released either by cells of the microenvironment or leukemic cells, exerts a double effect: (i) enhances CLL cells survival and (ii) drives differentiation of monocytes-macrophages to an oriented immune suppressive phenotype. We here discuss how paracrine, but also autocrine production of HGF by malignant cells, may favor leukemic clone expansion and resistance to conventional drug treatments in CLL, as well as in other hematological malignancies. Novel therapeutic approaches aimed to block HGF/c-MET interactions are further proposed.