Thrombopoietin receptor agonist for treating bone marrow aplasia following anti-CD19 CAR-T cells-single-center experience.

Anti CD-19 chimeric antigen receptor T (CAR-T) cells demonstrate effective early anti-tumor response; however, impaired hematopoietic recovery is observed in about 30% of patients with prolonged cytopenia appearing as an unmet need for optimal treatment. All adult patients given commercially available anti CD-19 CAR-T for diffuse large B cell lymphoma (DLBCL) were screened at 21-28 days after CAR-T infusion for cytopenia. In case of severe persistent cytopenia, patients were given TPO receptor agonists. Initial dose of eltrombopag was 50 mg/day and gradually increased to a maximal dose of 150 mg/day. Romiplostim was given as subcutaneous injection once a week for 2 doses (125 mcg). Response was defined as transfusion independency along with resolution of severe neutropenia (ANC > 500 /microL) and/or platelets > 20,000/microL for three consecutive values on different days. TPO receptor agonists were tapered down when response was met. From May 2019 to December 2021, 93 patients were eligible (74%, tisagenlecleucel and 26%, axicabtagene ciloleucel). The median age was 69 (range, 19-85) years. Six patients (6.5%) (tisagenlecleucel, n = 4 or axicabtagene ciloleucel, n = 2) demonstrated prolonged severe cytopenia and were treated with TPO receptor agonists (eltrombopag, n = 4; romiplastim, n = 1, both drugs, n = 1). Median time from CAR-T infusion to initiation of TPO receptor agonist was 43 (range, 21-55) days. All patients were transfusion-dependent and were given daily GCSF prior to TPO receptor agonist administration. Response to TPO receptor agonists was seen in all 6 patients. Median time from TPO receptor agonist initiation to resolution of cytopenia was 22 (range, 8-124) days for Hb, 27 (range, 6-38) days for platelets, and 29 (range, 7-61) days for neutrophils. A complete resolution of all blood counts (ANC > 500 /microL and platelets > 20,000/microL and hemoglobin > 8 gr/dL) was seen in 5/6 patients. No toxicity was observed during the therapy course. This paper supports further investigation of TPO receptor agonists in the treatment of persistent cytopenia following CAR-T cell therapy.

Polatuzumab-based regimen or CAR T cell for patients with refractory/relapsed DLBCL-a matched cohort analysis.

Polatuzumab (Pola)-based regimens and chimeric antigen receptor T (CAR T) cells provide superior outcome compared to conventional chemoimmunotherapy in patients with relapsed/refractory diffuse large B cell lymphoma (R/R DLBCL). Choosing between these strategies remains controversial. The efficacy of CAR T versus Pola-rituximab(R) /Pola-bendamustine(B)-R in R/R DLBCL patients after failing ≥2 lines of treatment was compared in a retrospective, 'real-world' study. Propensity score matching, for age, lymphoma category (de-novo/transformed), number of prior lines, Eastern Cooperative Oncology Group performance status and lactate dehydrogenase level, was applied to control for differences in patients' characteristics. Response rate, progression-free survival (PFS) and overall survival (OS) were analyzed. A total of 82 patients, treated with CAR T (n=41) or Pola-based regimens (n=41), were included. No treatment-related deaths occurred with CAR T vs. 3 (7.3%) with Pola. The overall and complete response rates were 83% and 58% with CAR T vs. 66% and 44% with Pola-based-regimens (p=0.077 and p=0.18, respectively). At a median follow-up of 9 months (range 1-19.2) and 16 months (range 0.7-25.3) for the CAR T and Pola arm respectively, the median PFS has not been reached for CAR T vs. 5.6 months for Pola (95% CI 3.6-7.6, p=0.014). Median OS has not been reached for CAR T vs. 10.8 months (95% CI 2.2-19.4) for Pola (p=0.026). To conclude, in a real-world setting, treatment with CAR T achieved superior PFS and OS compared to Pola-based regimens in patients with R/R DLBCL.

Haematological patients' perception of home transfusions: Effect of the COVID-19 pandemic.

BACKGROUND AND OBJECTIVES: The COVID-19 pandemic has led to a growing interest in hospital-at-home programmes, including home transfusion services. We studied whether the pandemic had influenced patients' perception of home transfusions. MATERIALS AND METHODS: We conducted a survey among haematology patients who receive transfusions in the hospital day care facility. Patients were asked about the burden of day care transfusions and whether they would prefer receiving home transfusions. The survey was conducted during the COVID-19 pandemic, and the results were compared with a survey performed before the pandemic (baseline). RESULTS: Sixty patients were included in the COVID-19 cohort and 31 patients in the baseline cohort. There was a non-significant decrease in the proportion of patients willing to receive home transfusions during the pandemic compared with baseline (35% vs. 47%, respectively, p = 0.28). More patients in the COVID-19 cohort were afraid to receive home transfusions (60% compared with 48% at baseline, p = 0.29), and fewer patients believed that hospital transfusion impaired their quality of life (19% compared with 36% at baseline, p = 0.09). These unexpected results may be partly attributed to the shorter time needed to arrive at the hospital during the pandemic and a greater fear of having transfusion-related adverse effects at home. CONCLUSIONS: Our results show that the pandemic did not increase the willingness of patients to receive home transfusions, with a non-significant drift towards refusal of home transfusions. Patients' opinions should be taken into consideration when planning for future home transfusion services, by creating a comprehensive approach to patients' needs.

BNT162b2 COVID-19 vaccine is significantly less effective in patients with hematologic malignancies.

Patients with hematologic malignancies have an increased risk of severe COVID-19 infection. Vaccination against COVID-19 is especially important in these patients, but whether they develop an immune response following vaccination is unknown. We studied serologic responses to the BNT162b2 vaccine in this population. A lower proportion of patients were seropositive following vaccination (75%) than in a comparison group (99%; p < 0.001), and median (interquartile range [IQR]) antibody titers in patients were lower (90 [12.4-185.5] and 173 [133-232] AU/ml, respectively; p < 0.001). Older age, higher lactate dehydrogenase, and number of treatment lines correlated with lower seropositivity likelihood and antibody titers, while absolute lymphocyte count, globulin level, and time from last treatment to vaccination correlated with higher seropositivity likelihood and antibody titers. Chronic lymphocytic leukemia patients had the lowest seropositivity rate followed by indolent lymphoma. Patients recently treated with chemo-immunotherapy, anti-CD20 antibodies, BCL2, BTK or JAK2 inhibitors had significantly less seropositive responses and lower median (IQR) antibody titers (29%, 1.9 [1.9-12] AU/ml; 0%, 1.9 [1.9-1.9] AU/ml; 25%, 1.9 [1.9-25] AU/ml; 40%, 1.9 [1.9-92.8] AU/ml; and 42%, 10.9 [5.7-66.4] AU/ml, respectively; p < 0.001). Serological response to BNT162b2 vaccine in patients with hematologic malignancies is considerably impaired, and they could remain at risk for severe COVID-19 infection and death.

Management and Outcome of Venous Thrombosis in Patients with Myeloproliferative Neoplasms: Data from the Israeli MPN Working Group.

The BCR-ABL-negative myeloproliferative neoplasms (MPN) are associated with high incidence of venous thrombosis and a significant rate of recurrent events, but there is no consensus regarding their management. In this retrospective study, we analyzed 96 patients with MPN-related venous thrombosis. The index venous thrombosis occurred at a median age of 58 years (IQR 37-71), with 58% of the events involving unusual sites. Patients who were on antiplatelet agents at the time of index thrombosis tended to be older than patients who were not receiving antiplatelets at the time of index thrombosis. The majority of index thromboses occurring after the diagnosis of MPN had uncontrolled blood counts at the time of event and were not receiving antithrombotic agents. Following the thrombotic episode, 75% of patients received long-term anticoagulation. At a median follow-up of 3.4 years, the recurrence rate was 14%. Thrombophilia was significantly more prevalent among patients with recurrent thrombosis compared to patients without recurrence (p < 0.01). Patients who developed a recurrent event early were more likely to have thrombophilia (either inherited or antiphospholipid antibodies), and controlled blood counts, and were likely to receive anticoagulation at the time of recurrence compared to patients with later recurrences. Thrombophilia may contribute to venous thrombosis recurrence, especially early after the index venous thrombosis. Suboptimal anticoagulation and blood count control are factors associated with late venous thrombosis recurrence.

Frontline treatment with the combination obinutuzumab ± chlorambucil for chronic lymphocytic leukemia outside clinical trials: Results of a multinational, multicenter study by ERIC and the Israeli CLL study group.

In recent years, considerable progress has been made in frontline therapy for elderly/physically unfit patients with CLL. The combination of obinutuzumab and chlorambucil (O-Clb) has been shown to prolong progression free survival (PFS, median PFS-31.5 months) and overall survival (OS) compared to chlorambucil alone. More recently, obinutuzumab given in combination with either ibrutinib or venetoclax improved PFS but not OS when compared to O-Clb. In this retrospective multinational, multicenter co-operative study, we evaluated the efficacy and safety of frontline treatment with O ± Clb in unfit patients with CLL, in a "real-world" setting. Patients with documented del (17p13.1)/TP53 mutation were excluded. A total of 437 patients (median age, 75.9 years; median CIRS score, 8; median creatinine clearance, 61.1 mL/min) were included. The clinical overall response rate was 80.3% (clinical complete and partial responses in 38.7% and 41.6% of patients, respectively). Median observation time was 14.1 months and estimated median PFS was 27.6 months (95% CI, 24.2-31.0). In a multivariate analysis, high-risk disease [del (11q22.3) and/or IGHV-unmutated], lymph nodes of diameter > 5 cm, obinutuzumab monotherapy and reduced cumulative dose of obinutuzumab, were all independently associated with shorter PFS. The median OS has not yet been reached and estimated 2-year OS is 88%. In conclusion, in a "real-world" setting, frontline treatment with O-Clb achieves PFS comparable to that reported in clinical trials. Inferior outcomes were noted in patients with del (11q22.3) and/or unmutated IGHV and those treated with obinutuzumab-monotherapy. Thus, O-Clb can be still considered as legitimate frontline therapy for unfit CLL patients with low-risk disease.

Timing of BNT162b2 vaccine prior to COVID-19 infection, influence disease severity in patients with hematologic malignancies: Results from a cohort study.

The COVID-19 pandemic continues to pose challenges to the treatment of hemato-oncology patients. Emergence of COVID-19 variants, availability of vaccine boosters and antiviral treatments could impact their outcome. We retrospectively studied patients with hematologic malignancies and confirmed COVID-19 during the Omicron outbreak. Of 116 evaluated patients, 16% developed severe or critical COVID-19. Diagnosis of chronic lymphocytic leukemia (CLL) was significantly associated with severe COVID-19 (p = 0.01). The vaccine effectiveness was related to the timing of the vaccine, with patients who received a mRNA vaccine within 7-90 days prior to COVID-19 being less likely to develop severe disease compared to all other patients (p = 0.019). There was no correlation between disease severity and antiviral therapies. Importantly, 45% of patients undergoing active hematological treatment had to interrupt their treatment due to COVID-19. In conclusion, patients with hematologic malignancies are at a considerable risk for severe COVID-19 during the Omicron outbreak, with patients with CLL being the most vulnerable. mRNA vaccines have the potential to protect hematological patients from severe COVID-19 if administered within the previous 3 months. Hematological treatment interruption is a frequent adverse outcome of COVID-19 infection.

Lymphoproliferative disease detected by breast cancer screening.

OBJECTIVE: To determine the rate of lymphoproliferative disease (LPD) in women undergoing routine breast cancer screening (BCS). BCS can reveal pathologies other than carcinoma that involve the breast and lymph tissue. The few studies that have described cases in which BCS led to the diagnosis of LPD were based on small series and focused on imaging rather than clinical characteristics. SETTING AND METHODS: A multi-center retrospective study in Israel, investigating LPD rate and characteristics among women diagnosed with LPD via BCS. RESULTS: Thirty-four patients out of 14,400 consecutive women undergoing BCS at Tel Aviv Sourasky Medical Center during the study period were diagnosed with LPD, suggesting a diagnosis rate of 0.24%. The enlarged cohort (n = 45), including 11 patients that were retrieved from the databases of three other centers, demonstrates a predominant histological diagnosis of non-aggressive LPD (n = 33). Thirty-four (76%) had a suspicious axillary lymph node, and 11 had a breast lesion. The median maximal lesion size was 1.95 cm (range 0.8-6.5). Disease was localized in 60% of patients (stage 1 and 1E). Univariate analysis revealed that lymphocyte count was inversely associated with aggressive histology. At median follow-up of 39 months, all but three patients were alive. These three had been diagnosed with non-aggressive LPD which had never been treated and died from unrelated causes. CONCLUSIONS: The LPD detection rate via BCS was 2.36 per 1000 screens. The majority of LPDs were non-aggressive. Nearly a third were aggressive, most detected at an early stage, and the clinical outcome was generally favorable.

Hereditary thrombotic thrombocytopenic purpura and COVID-19: Impacts of vaccination and infection in this rare disease.

Introduction: Severe COVID-19 is associated with an important increase of von Willebrand factor and mild lowering of ADAMTS13 activity that may, in the presence of a strong inflammatory reaction, increase the risk of acute thrombotic thrombocytopenic purpura (TTP). Although acute episodes of immune-mediated TTP associated with COVID-19 or SARS-CoV-2 vaccination have been reported, data about clinical evolution of hereditary TTP (hTTP) during the pandemic are scarce. Method: We conducted a survey among adult patients of the International Hereditary TTP Registry about SARS-CoV-2 vaccination, COVID-19, and occurrence of acute hTTP episodes. Results: Of 122 adult hTTP patients invited to participate, 86 (70.5%) responded. Sixty-five had been vaccinated (75.6%), of which 14 had received in addition a booster, resulting in 139 individual vaccine shots. Although vaccinations in patients on plasma prophylaxis were done within 1 week of the last plasma infusion, all 23 patients treated with plasma on demand were vaccinated without prior plasma infusions. One patient on uninterrupted weekly plasma infusions presented within 3 days from his second vaccination with neurological symptoms and computed tomography scan 9 days later showed subacute ischemic/hemorrhagic frontal lobe infarction. A second male patient developed acute myocarditis after his second dose of mRNA-1273 vaccine. Twelve (14%) patients had COVID-19, associated with an acute hTTP episode in three of them: one patient had a transient ischemic attack, one a stroke, and a pregnant woman was hospitalized to intensify plasma treatment. Discussion: The risk of an acute episode triggered by COVID-19 seems higher than following vaccination in hTTP patients, who can be safely vaccinated against SARS-CoV-2.

Thrombotic and bleeding complications in patients with chronic lymphocytic leukemia and severe COVID-19: a study of ERIC, the European Research Initiative on CLL.

BACKGROUND: Patients with chronic lymphocytic leukemia (CLL) may be more susceptible to COVID-19 related poor outcomes, including thrombosis and death, due to the advanced age, the presence of comorbidities, and the disease and treatment-related immune deficiency. The aim of this study was to assess the risk of thrombosis and bleeding in patients with CLL affected by severe COVID-19. METHODS: This is a retrospective multicenter study conducted by ERIC, the European Research Initiative on CLL, including patients from 79 centers across 22 countries. Data collection was conducted between April and May 2021. The COVID-19 diagnosis was confirmed by the real-time polymerase chain reaction (RT-PCR) assay for SARS-CoV-2 on nasal or pharyngeal swabs. Severe cases of COVID-19 were defined by hospitalization and the need of oxygen or admission into ICU. Development and type of thrombotic events, presence and severity of bleeding complications were reported during treatment for COVID-19. Bleeding events were classified using ISTH definition. STROBE recommendations were used in order to enhance reporting. RESULTS: A total of 793 patients from 79 centers were included in the study with 593 being hospitalized (74.8%). Among these, 511 were defined as having severe COVID: 162 were admitted to the ICU while 349 received oxygen supplementation outside the ICU. Most patients (90.5%) were receiving thromboprophylaxis. During COVID-19 treatment, 11.1% developed a thromboembolic event, while 5.0% experienced bleeding. Thrombosis developed in 21.6% of patients who were not receiving thromboprophylaxis, in contrast to 10.6% of patients who were on thromboprophylaxis. Bleeding episodes were more frequent in patients receiving intermediate/therapeutic versus prophylactic doses of low-molecular-weight heparin (LWMH) (8.1% vs. 3.8%, respectively) and in elderly. In multivariate analysis, peak D-dimer level and C-reactive protein to albumin ratio were poor prognostic factors for thrombosis occurrence (OR = 1.022, 95%CI 1.007‒1.038 and OR = 1.025, 95%CI 1.001‒1.051, respectively), while thromboprophylaxis use was protective (OR = 0.199, 95%CI 0.061‒0.645). Age and LMWH intermediate/therapeutic dose administration were prognostic factors in multivariate model for bleeding (OR = 1.062, 95%CI 1.017-1.109 and OR = 2.438, 95%CI 1.023-5.813, respectively). CONCLUSIONS: Patients with CLL affected by severe COVID-19 are at a high risk of thrombosis if thromboprophylaxis is not used, but also at increased risk of bleeding under the LMWH intermediate/therapeutic dose administration.

Acquired thrombotic thrombocytopenic purpura: A rare disease associated with BNT162b2 vaccine.

BACKGROUND: In December 2020 the Israeli Health Ministry began a mass vaccination campaign with the BNT162b2 vaccine. This was an important step in overcoming the severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) pandemic. Autoimmune phenomenon have been described after receiving vaccinations. PATIENTS/METHODS: Here we describe a case series of patients who developed acquired Thrombotic Thrombocytopenic Purpura, a rare autoimmune disease, within several days of receiving the BNT162b2 vaccine. CONCLUSIONS: A disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) activity should be evaluated in patients with history of aTTP before and after any vaccination, especially the SARS-CoV-2 vaccination, and immunosuppression treatment should be considered before vaccination in cases of low ADAMTS13 activity. Patients should be closely monitored after the vaccine for clinical situation and laboratory data. Post vaccination thrombocytopenia assessment should include immune thrombocytopenic purpura, vaccine-induced immune thrombotic thrombocytopenia and acquired thrombotic thrombocytopenic purpura.

Outcome of relapsed/refractory diffuse large B-cell lymphoma patients treated with polatuzumab vedotin-based therapy: real-life experience.

The efficacy of polatuzumab vedotin in relapsed/refractory diffuse large B-cell lymphoma outside clinical study are undetermined. This retrospective study examined the efficacy and safety of polatuzumab vedotin administered in real life settings. Forty-seven patients, 31 with de-novo DLBCL and 16 with transformed lymphoma, treated with polatuzumab-based regimen in 14 Israeli centers between June 2018 and November 2019, were included. Median age was 66.1 years (60.4-78.8) and median number of prior lines was 3 (2-7). The overall response rate was 61% (n = 29), including 40% complete responses (n = 19) and 21% (n = 10) partial responses. The median overall survival and progression-free survival were 8.3 months and 5.6 months, respectively. An ECOG PS ≥2 predicted a decreased overall survival (p = 0.045). Primary refractory vs relapsed disease (p = 0.005) and transformed vs de-novo DLBCL (p = 0.039) were associated with shorter PFS (p = 0.027). Our data show that polatuzumab-based regimen is an effective and tolerable treatment in relapsed/refractory DLBCL.

COVID-19 severity and mortality in patients with CLL: an update of the international ERIC and Campus CLL study.

Patients with chronic lymphocytic leukemia (CLL) may be more susceptible to Coronavirus disease 2019 (COVID-19) due to age, disease, and treatment-related immunosuppression. We aimed to assess risk factors of outcome and elucidate the impact of CLL-directed treatments on the course of COVID-19. We conducted a retrospective, international study, collectively including 941 patients with CLL and confirmed COVID-19. Data from the beginning of the pandemic until March 16, 2021, were collected from 91 centers. The risk factors of case fatality rate (CFR), disease severity, and overall survival (OS) were investigated. OS analysis was restricted to patients with severe COVID-19 (definition: hospitalization with need of oxygen or admission into an intensive care unit). CFR in patients with severe COVID-19 was 38.4%. OS was inferior for patients in all treatment categories compared to untreated (p < 0.001). Untreated patients had a lower risk of death (HR = 0.54, 95% CI:0.41-0.72). The risk of death was higher for older patients and those suffering from cardiac failure (HR = 1.03, 95% CI:1.02-1.04; HR = 1.79, 95% CI:1.04-3.07, respectively). Age, CLL-directed treatment, and cardiac failure were significant risk factors of OS. Untreated patients had a better chance of survival than those on treatment or recently treated.

Prevalence of Paroxysmal Nocturnal Hemoglobinuria Clones in Myeloproliferative Neoplasm Patients: A Cross-Sectional Study.

INTRODUCTION: The myeloproliferative neoplasms (MPN) are clonal diseases that confer an increased risk of thrombohemorrhagic complications. Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal disease associated with an increased thrombotic risk. Small PNH clones are prevalent in aplastic anemia and myelodysplastic syndrome patients, but their prevalence in MPN patients is unknown. PATIENTS AND METHODS: Consecutive patients with MPN followed up at a single center were recruited. PNH clones were analyzed in erythrocytes and white blood cells by flow cytometry. RESULTS: PNH clones were detected in 2% of patients and were more common in JAK2 V617F positive patients. We could not detect any differences in clinical manifestations or complications in patients either with or without PNH clones because of the small patient numbers. CONCLUSION: The prevalence of PNH clones in MPN is similar to that described in myelodysplastic syndromes. Whether PNH clones influence MPN phenotype and complications should be studied prospectively in larger patient cohorts and over long-term follow-up.

Treatment and prognosis of stage I follicular lymphoma in the modern era - does PET matter?

Follicular lymphoma (FL) is the most common subtype of indolent non-Hodgkin lymphoma. Patients with stage I disease are usually treated with radiotherapy (RT). In previous studies, mostly from the pre positron emission tomography-computed tomography (PET-CT) era, the 5 year progression-free survival (PFS) and overall survival (OS) rates of stage I disease were 60-80% and 80-93%, respectively. This study retrospectively evaluated the outcome of stage I FL which was treated with involved field RT in the PET-CT era between 2002 and 2015. Ninety-one patients were enrolled. Five year PFS and OS rates were 73% and 97%, respectively. Relapse occurred in 19 (21%) patients, 74% occurring outside the radiation field. In conclusion, PET-CT staging of clinical stage I FL may contribute to the improved prognosis in patients treated with RT compared to historical cohorts, possibly due to better identification of "genuine" stage I disease.

Ruxolitinib treatment for myelofibrosis: Efficacy and tolerability in routine practice.

Ruxolitinib has been shown in two randomized clinical trials to be effective in alleviating systemic symptoms and reducing spleen size in patients with myelofibrosis (MF). We retrospectively evaluated efficacy and tolerability of ruxolitinib in a cohort of unselected MF patients treated in routine clinical practice. One hundred and two patients who began ruxolitinib therapy were identified in 13 participating centers. Ninety three of the patients receiving ruxolitinib for at least 3 months were evaluated for treatment efficacy and toxicity. Median age at ruxolitinib initiation was 67 years. Indications for treatment were constitutional symptoms (15%), symptomatic splenomegaly (6%) or both (76%). Two patients received ruxolitinib for other indications. The median initial ruxolitinib dose was 30mg/day. Median duration of therapy was 11 months. Eighty two patients (88.2%) responded to therapy, 76 (84.4%) patients had improvement in constitutional symptoms and 60 patients (70.6%) had reduction in spleen length. While on ruxolitinib, 30% of patients had grade 3-4 anemia and 12.9% of patients had grade 3-4 thrombocytopenia. Thirteen patients (14%) discontinued therapy. This analysis of a cohort of MF patients treated with ruxolitinib in routine clinical practice demonstrates the efficacy and tolerability of this drug outside of a highly monitored clinical trial setting.

The proliferation arrest of primary tumor cells out-of-niche is associated with widespread downregulation of mitotic and transcriptional genes.

In recording the changes acquired in gene expression profile during culture of fresh bone marrow samples from patients with multiple myeloma or acute myeloid leukemia, the most remarkable finding in both instances was widespread downregulation of mitotic and transcriptional genes (e.g. MKI67, CCNB1, ASPM, SGOL1, DLGAP5, CENPF, BUB1, KIF23, KIF18a, KIF11, KIF14, KIF4, NUF2, KIF1, AE2FB, TOP2A, NCAPG, TTK, CDC20, and AURKB), which could account for the ensuing proliferation arrest. Many of these genes were also underexpressed in leukemic cells from the blood or myeloma cells from an extramedullary site compared with their expression in the aspirates. Taken together, our results exhibited mitotic and transcriptional gene subsets where their expression appears to be coordinated and niche dependent. In addition, the genes induced during culture specified a variety of angiogenic factors (e.g. interleukin-8 and CXCL-5) and extracellular matrix proteins (e.g. osteopontin and fibronectin) probably released by the tumor cells while generating their favored microenvironment.

Multiple myeloma cells recruit tumor-supportive macrophages through the CXCR4/CXCL12 axis and promote their polarization toward the M2 phenotype.

Multiple myeloma (MM) cells specifically attract peripheral-blood monocytes, while interaction of MM with bone marrow stromal cells (BMSCs) significantly increased monocyte recruitment (p<0.01). The CXCL12 chemokine, produced by both the MM and BMSCs, was found to be a critical regulator of monocyte migration. CXCL12 production was up-regulated under MM-BMSCs co-culture conditions, whereas blockage with anti-CXCR4 antibodies significantly abrogated monocyte recruitment toward a MM-derived conditioned medium (p<0.01). Furthermore, elevated levels of CXCL12 were detected in MM, but not in normal BM samples, whereas malignant MM cells often represented the source of increased CXCL12 in the BM. Blood-derived macrophages effectively supported MM cells proliferation and protected them from chemotherapy-induced apoptosis. Importantly, MM cells affected macrophage polarization, elevating the expression of M2-related scavenger receptor CD206 in macrophages and blocking LPS-induced TNFα secretion (a hallmark of M1 response). Of note, MM-educated macrophages suppressed T-cell proliferation and IFNγ production in response to activation. Finally, increased numbers of CXCR4-expressing CD163+CD206+ macrophages were detected in the BM of MM patients (n=25) in comparison to MGUS (n=11) and normal specimens (n=8). Taken together, these results identify macrophages as important players in MM tumorogenicity, and recognize the CXCR4/CXCL12 axis as a critical regulator of MM-stroma interactions and microenvironment formation.