SDF-1/CXCR4 and VLA-4 interaction regulates homing in Waldenstrom macroglobulinemia

Different extramedullary disease shown in chemokine receptor 4 targeted PET/CT with [68Ga]Ga-pentixafor in patients with Waldenström macroglobulinemia and smoldering disease

INTRODUCTION

It is important to distinguish Waldenström macroglobulinemia from smoldering Waldenström macroglobulinemia (sWM), because only patients with Waldenström macroglobulinemia require treatment, however the distinction can be clinically complex. The aim of this study is to investigate whether [68Ga]Ga-pentixafor PET/CT shows different characteristics in sWM and Waldenström macroglobulinemia patients and therefore can help to differentiate Waldenström macroglobulinemia and sWM.

RESULTS

Thirty-seven patients with newly diagnosed Waldenström macroglobulinemia and 11 sWM patients were analyzed [35 men and 13 women; 64.3 ± 10.7 (range, 29-87) years old]. The SUVmax of bone marrow disease, lymph nodes, and other extramedullary diseases on [68Ga]Ga-pentixafor were significantly higher than those on 2-[18F]FDG PET/CT (P < 0.05). On [68Ga]Ga-pentixafor PET/CT, patients with Waldenström macroglobulinemia had more lymph node regions involved, significantly higher incidence of involvement in more than three lymph node regions, larger nodal disease, and higher incidence of other extramedullary disease when compared with sWM patients (P < 0.05). Waldenström macroglobulinemia patients showed significantly higher total lesions uptake, total lesion volume, and SUVmax of extramedullary disease than sWM patients did (P < 0.05). None of the visual or semiquantitative indexes in 2-[18F]FDG PET/CT showed significant difference between Waldenström macroglobulinemia and sWM patients.

CONCLUSION

[68Ga]Ga-pentixafor PET/CT had better diagnostic performance than 2-[18F]FDG PET/CT in Waldenström macroglobulinemia. Patients with Waldenström macroglobulinemia presented with more extensive extramedullary disease shown in [68Ga]Ga-pentixafor PET/CT than sWM patients did.

Bing–Neel Syndrome and Coexisting Pituitary Macroadenoma in a Patient with Waldenström Macroglobulinemia Revealed by 18F-FDG and 68Ga-Pentixafor PET/CT

A 63-year-old man presenting with peripheral neuropathies was diagnosed of Waldenström’s macroglobulinemia, and Bing–Neel syndrome was subsequently confirmed via cerebrospinal fluid examinations. Besides involvement in bone marrow, lymph nodes, as well as the thoracic and sacral nerve root, 68Ga-Pentixafor PET/CT detected active tracer uptake in bilateral choroid plexus, which was negative in 18F-FDG PET/CT, possibly suggesting the involvement of Bing–Neel syndrome. The coexisting pituitary macroadenoma was FDG-avid but negative in 68Ga-Pentixafor PET/CT. After six cycles of chemotherapy, the follow-up PET/CT showed complete remission of the previous disease, including the high uptake of 68Ga-Pentixafor in choroid plexus. However, the hypermetabolic pituitary macroadenoma remained unchanged.

Biclonal lymphoplasmacytic lymphoma/Waldenström macroglobulinemia associated with POEMS syndrome: A case report and literature review

Due to its unique clinical, immunological and molecular genetic characteristics, biclonal lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM) with polyneuropathy, organomegaly, endocrinopathy, monoclonal protein and skin changes (POEMS) syndrome is extremely rare in clinical practice, and there is no standard treatment for patients afflicted with this condition. In the present case report, a rare case of double LPL/WM with POEMS syndrome is described. The patient, a 65-year-old male, exhibited significant renal impairment and polylymphadenopathy. The patient was treated with rituximab and his symptoms were resolved following two courses of treatment. A review of the literature was performed, comparing the present case with previous cases. It is hoped that this case report will enable clinicians to gain a better understanding of this disease.

Blurry Vision as a Presentation of Waldenström's Macroglobulinemia: A Case Report With Review of Current Management

A patient was diagnosed with Waldenström’s macroglobulinemia (WM) after the initial findings of anemia and ophthalmological findings of retinal hemorrhage. Upon further workup, the patient was found to have an IgM predominant monoclonal gammopathy on serum protein electrophoresis (SPEP) and urine protein electrophoresis (UPEP). This highlights the need for open communication between different specialties, streamlining rapid and accurate diagnosis. Also highlighted are the unique pathophysiological changes involved in the development of WM. A patient’s primary complaint was blurry vision. After the patient was noted to have a monoclonal gammopathy on SPEP, bone marrow biopsy was performed. The bone marrow biopsy findings were consistent with lymphoplasmacytic lymphoma (LPL). The patient received plasmapheresis and chemotherapy. The disease course is described. The patient saw rapid improvement in all lab abnormalities after the beginning of the appropriate therapy of plasmapheresis and chemotherapy. Remission is common with WM. Regular follow-up with this patient is important.

Semi-quantitative measurements of chemokine receptor 4-targeted 68Ga-pentixafor PET/CT in response assessment of Waldenström macroglobulinemia/lymphoplasmacytic lymphoma

Purpose

⁶⁸Ga-pentixafor PET/CT was reported to have a high sensitivity in detecting tumor involvement of Waldenström macroglobulinemia/lymphoplasmacytic lymphoma (WM/LPL) in our previous study. We aimed to further investigate the semi-quantitative measurements of ⁶⁸Ga-pentixafor PET/CT in response assessment in WM/LPL.

Methods

Fifteen patients with WM/LPL were recruited in a prospective cohort study and underwent both ⁶⁸Ga-pentixafor and ¹⁸F-FDG PET/CT at baseline and post-treatment. PET/CT-based responses were analyzed with semi-quantitative assessments of metabolic tumor volume (MTV) and total lesions glycolysis/uptake (TLG_FDG and TLU_CXCR4), and the correlation between PET/CT-based response and clinical response, monoclonal protein and IgM response was analyzed.

Results

After chemotherapy, 5 patients had complete response or very good partial response, 8 had partial response or minimal response and 2 had progressive disease. In quantitative analysis, ⁶⁸Ga-pentixafor PET/CT-based response (measured in ∆TLU_CXCR4%, ∆MTV_CXCR4%, ∆SUVpeak%) showed a significant direct correlation with clinical response, monoclonal protein and IgM response (p < 0.01). However, ¹⁸F-FDG PET/CT-based response was independent from clinical response (p > 0.05).

Conclusions

The semi-quantitative measurements of ⁶⁸Ga-pentixafor PET/CT outperformed ¹⁸F-FDG PET/CT in response assessment of WM/LPL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-021-00852-0.

Chemokine Receptor 4-Targeted 68Ga-Pentixafor PET/CT in Response Assessment of Waldenström Macroglobulinemia/Lymphoplasmacytic Lymphoma: Comparison to 18F-FDG PET/CT

PURPOSE

68Ga-pentixafor PET/CT was reported to have a high sensitivity in detecting tumor involvement of Waldenström macroglobulinemia/lymphoplasmacytic lymphoma (WM/LPL) in our previous study. We aimed to further investigate its value in response assessment in WM/LPL.

PATIENTS AND METHODS

Fifteen patients with WM/LPL were recruited in a prospective cohort study and underwent both 68Ga-pentixafor and 18F-FDG PET/CT at baseline and posttreatment. PET/CT-based responses were analyzed with visual assessments and compared with clinical response.

RESULTS

At baseline, all of the 15 patients had a positive 68Ga-pentixafor PET/CT scan, whereas 18F-FDG PET/CT was positive in 11/15 patients. After chemotherapy, the overall response rate was 86.7% (13/15), and 68Ga-pentixafor PET/CT showed different degree of tumor response from baseline in these patients. In the 2 patients with progressive disease, 68Ga-pentixafor PET/CT detected new lesions or remarkable increase of 68Ga-pentixafor uptake in tumor involvements. However, 18F-FDG PET/CT failed to detect the improvement of disease in 6/13 patients and missed disease progression in 1 of the 2 patients.

CONCLUSIONS

68Ga-pentixafor PET/CT outperformed 18F-FDG PET/CT in response assessment of WM/LPL.

Pleiotropic Roles of CXCR4 in Wound Repair and Regeneration

Wound healing is a multi-step process that includes multiple cellular events such as cell proliferation, cell adhesion, and chemotactic response as well as cell apoptosis. Accumulating studies have documented the significance of stromal cell-derived factor-1 (SDF-1)/C-X-C chemokine receptor 4 (CXCR4) signaling in wound repair and regeneration. However, the molecular mechanism of regeneration is not clear. This review describes various types of tissue regeneration that CXCR4 participates in and how the efficiency of regeneration is increased by CXCR4 overexpression. It emphasizes the pleiotropic effects of CXCR4 in regeneration. By delving into the specific molecular mechanisms of CXCR4, we hope to provide a theoretical basis for tissue engineering and future regenerative medicine.

Flow cytometry detection of CD138 expression continuum between monotypic B and plasma cells is associated with both high IgM peak levels and MYD88 mutation and contributes to diagnosis of Waldenström macroglobulinemia

BACKGROUND

Differential diagnosis of Waldenström macroglobulinemia (WM) with other indolent B-cell malignancies is still a challenge. Here, we propose an original and simple analysis of routine flow cytometry (FCM) unraveling the characteristic ongoing plasma cell (PC) differentiation of WM tumor B-cells.

METHODS

FCM analysis of both B-cells and PC was performed on a series of 77 patients with IgM peak. MYD88 and CXCR4 mutations were studied using an allele-specific PCR and by high throughput sequencing.

RESULTS

Twenty seven (35%), 46 (58%) and 4 (5%) patients were classified as WM, IgM monoclonal gammopathy of undetermined significance (MGUS) or other B-NHL respectively. MYD88 mutation was found in 25/27 WM (93%) and in 29/46 MGUS (63%). Using FCM, monotypic B-cells were found in 27/27 WM (100%) and 34/46 MGUS (74%). Monotypic CD138pos/CD38pos PCs were detected in 23/27 WM (85%) and 25/46 MGUS (54%). Highlighting the ongoing PC differentiation of WM tumor B-cells by FCM, we evidenced a CD138 expression continuum between monotypic B-cells and PCs. This pattern remained absent in control samples and was significantly associated with higher IgM peaks (p = 6.10^-5 ) and MYD88 mutations (p = 10^-3 ) in both WM and MGUS cases.

CONCLUSIONS

FCM exploration of both B-cells and PC led to identify a CD138 expression continuum as an objective marker of ongoing PC differentiation of WM tumor cells and was strongly associated with increased IgM peak levels and MYD88 mutations. This approach could contribute to place FCM at the forefront of WM diagnosis.

CXCR4 S338X clonality is an important determinant of ibrutinib outcomes in patients with Waldenström macroglobulinemia

CXCR4 S338X clonality ≥25% is associated with lower very good partial response and shorter progression-free survival to ibrutinib. CXCR4 S338X clonality assessment represents a novel biomarker to predict outcomes to ibrutinib in Waldenström macroglobulinemia patients.

Preliminary evidence of imaging of chemokine receptor-4-targeted PET/CT with [68Ga]pentixafor in non-Hodgkin lymphoma: comparison to [18F]FDG

BACKGROUND

In order to study the CXCR4 expression with [⁶⁸Ga]pentixafor PET in different types of non-Hodgkin lymphoma, we performed a retrospective study to describe the [⁶⁸Ga]pentixafor PET/CT imaging in a spectrum of lymphomas and to compare it with [¹⁸F]FDG PET/CT.

RESULTS

Twenty-seven patients with newly diagnosed non-Hodgkin lymphoma were recruited retrospectively. [⁶⁸Ga]pentixafor PET showed increased radioactivity in lymphoplasmacytic lymphoma (n = 8), marginal zone lymphoma (n = 4), diffuse large B cell lymphoma (n = 3), follicular lymphoma (n = 2), mantle cell lymphoma (n = 1), unclassified indolent B cell lymphoma (n = 3), and enteropathy associated T cell lymphoma (n = 3). However, peripheral T cell lymphoma, not otherwise specified (n = 1), and NK/T cell lymphoma (n = 2) were not avid for [⁶⁸Ga]pentixafor. In comparison to [¹⁸F]FDG PET, [⁶⁸Ga]pentixafor PET demonstrated more extensive disease and higher radioactivity in lymphoplasmacytic lymphoma and marginal zone lymphoma.

CONCLUSION

CXCR4 expression varies in different types of non-Hodgkin lymphoma. Overexpression of CXCR4 was detected with [⁶⁸Ga]pentixafor PET/CT in lymphoplasmacytic lymphoma, marginal zone lymphoma, diffuse large B cell lymphoma, follicular lymphoma, mantle cell lymphoma, unclassified indolent B cell lymphoma, and enteropathy associated T cell lymphoma. The uptake of [⁶⁸Ga]pentixafor was higher than [¹⁸F]FDG in lymphoplasmacytic lymphoma and marginal zone lymphoma.

Zebrafish In Vivo Models of Cancer and Metastasis

Metastasis, the dispersal of cancer cells from a primary tumor to secondary sites within the body, is the leading cause of cancer-related death. Animal models have been an indispensable tool to investigate the complex interactions between the cancer cells and the tumor microenvironment during the metastatic cascade. The zebrafish (Danio rerio) has emerged as a powerful vertebrate model for studying metastatic events in vivo. The zebrafish has many attributes including ex-utero development, which facilitates embryonic manipulation, as well as optically transparent tissues, which enables in vivo imaging of fluorescently labeled cells in real time. Here, we summarize the techniques which have been used to study cancer biology and metastasis in the zebrafish model organism, including genetic manipulation and transgenesis, cell transplantation, live imaging, and high-throughput compound screening. Finally, we discuss studies using the zebrafish, which have complemented and benefited metastasis research.

Increased glutathione utilization augments tumor cell proliferation in Waldenstrom Macroglobulinemia

Metabolic reprogramming is a hallmark of cancer cells. In Waldenstrom Macroglobulinemia (WM), the infiltration of IgM-secreting lymphoplamacytic cells into the bone marrow (BM) could shift the homeostasis of proteins and metabolites towards a permissive niche for tumor growth. Here, we investigated whether alerted metabolic pathways contribute to the pathobiology of WM and whether the cytokine composition of the BM promotes such changes. Metabolomics analysis on WM patients and normal donors' serum samples revealed a total of 75 metabolites that were significantly altered between two groups. While these metabolites belonged to amino acids, glucose, glutathione and lipid metabolism pathways, the highest number of the differentially expressed metabolites belonged to glutathione metabolism. Proteomics analysis and immunohistochemical staining both confirmed the increased protein levels mediating glutathione metabolism, including GCLC, MT1X, QPCT and GPX3. Moreover, treatment with IL-6 and IL-21, cytokines that induce WM cell proliferation and IgM secretion, increased gene expression of the amino acid transporters mediating glutathione metabolism, including ASCT2, SLC7A11 and 4F2HC, indicating that cytokines in the WM BM could modulate glutathione metabolism. Glutathione synthesis inhibition using Buthionine sulphoximine (BSO) significantly reduced WM cells proliferation in vitro, accompanied with decreased NFκB-p65 and MAPK-p38 phosphorylation. Moreover, BSO treatment significantly reduced the tumor growth rate in a WM xenograft model, further highlighting the role of glutathione metabolism in promoting tumor growth and proliferation. In summary, our data highlight a central role for glutathione metabolism in WM pathobiology and indicate that intervening with the metabolic processes could be a potential therapy for WM patients.

TLR-mediated activation of Waldenström macroglobulinemia B cells reveals an uncoupling from plasma cell differentiation

Waldenström macroglobulinemia (WM) is a rare malignancy in which clonal B cells infiltrate the bone marrow and give rise to a smaller compartment of neoplastic plasma cells that secrete monoclonal immunoglobulin M paraprotein. Recent studies into underlying mutations in WM have enabled a much greater insight into the pathogenesis of this lymphoma. However, there is considerably less characterization of the way in which WM B cells differentiate and how they respond to immune stimuli. In this study, we assess WM B-cell differentiation using an established in vitro model system. Using T-cell-dependent conditions, we obtained CD138+ plasma cells from WM samples with a frequency similar to experiments performed with B cells from normal donors. Unexpectedly, a proportion of the WM B cells failed to upregulate CD38, a surface marker that is normally associated with plasmablast transition and maintained as the cells proceed with differentiation. In normal B cells, concomitant Toll-like receptor 7 (TLR7) activation and B-cell receptor cross-linking drives proliferation, followed by differentiation at similar efficiency to CD40-mediated stimulation. In contrast, we found that, upon stimulation with TLR7 agonist R848, WM B cells failed to execute the appropriate changes in transcriptional regulators, identifying an uncoupling of TLR signaling from the plasma cell differentiation program. Provision of CD40L was sufficient to overcome this defect. Thus, the limited clonotypic WM plasma cell differentiation observed in vivo may result from a strict requirement for integrated activation.

CXCL12/CXCR4 signal transduction in diseases and its molecular approaches in targeted-therapy

Chemokines are small molecules called "chemotactic cytokines" and regulate many processes like leukocyte trafficking, homing of immune cells, maturation, cytoskeletal rearrangement, physiology, migration during development, and host immune responses. These proteins bind to their corresponding 7-membrane G-protein-coupled receptors. Chemokines and their receptors are anti-inflammatory factors in autoimmune conditions, so consider as potential targets for neutralization in such diseases. They also express by cancer cells and function as angiogenic factors, and/or survival/growth factors that enhance tumor angiogenesis and development. Among chemokines, the CXCL12/CXCR4 axis has significantly been studied in numerous cancers and autoimmune diseases. CXCL12 is a homeostatic chemokine, which is acts as an anti-inflammatory chemokine during autoimmune inflammatory responses. In cancer cells, CXCL12 acts as an angiogenic, proliferative agent and regulates tumor cell apoptosis as well. CXCR4 has a role in leukocyte chemotaxis in inflammatory situations in numerous autoimmune diseases, as well as the high levels of CXCR4, observed in different types of human cancers. These findings suggest CXCL12/CXCR4 as a potential therapeutic target for therapy of autoimmune diseases and open a new approach to targeted-therapy of cancers by neutralizing CXCL12 and CXCR4. In this paper, we reviewed the current understanding of the role of the CXCL12/CXCR4 axis in disease pathology and cancer biology, and discuss its therapeutic implications in cancer and diseases.

VLA-4 phosphorylation during tumor and immune cell migration relies on its coupling to VEGFR2 and CXCR4 by syndecan-1

When targeted by the tumor-promoting enzyme heparanase, cleaved and shed syndecan-1 (Sdc1) then couples VEGFR2 (also known as KDR) to VLA-4, activating VEGFR2 and the directed migration of myeloma cells. But how VEGFR2 activates VLA-4-mediated motility has remained unknown. We now report that VEGFR2 causes PKA-mediated phosphorylation of VLA-4 on S988, an event known to stimulate tumor metastasis while suppressing cytotoxic immune cells. A key partner in this mechanism is the chemokine receptor CXCR4, a well-known mediator of cell motility in response to gradients of the chemokine SDF-1 (also known as CXCL12). The entire machinery necessary to phosphorylate VLA-4, consisting of CXCR4, AC7 (also known as ADCY7) and PKA, is constitutively associated with VEGFR2 and is localized to the integrin by Sdc1. VEGFR2 carries out the novel phosphorylation of Y135 within the DRY microswitch of CXCR4, sequentially activating Gα_iβγ, AC7 and PKA, which phosphorylates S988 on the integrin. This mechanism is blocked by a syndecan-mimetic peptide (SSTN_VEGFR2), which, by preventing VEGFR2 linkage to VLA-4, arrests tumor cell migration that depends on VLA-4 phosphorylation and stimulates the LFA-1-mediated migration of cytotoxic leukocytes.

CXCR4-targeted PET imaging using 64Cu-AMD3100 for detection of Waldenström Macroglobulinemia

Objective:  Waldenström Macroglobulinemia (WM) is a rare B-cell malignancy characterized by secretion of immunoglobulin M and cancer infiltration in the bone marrow. Chemokine receptor such as CXCR4 and hypoxic condition in the bone marrow play crucial roles in cancer cell trafficking, homing, adhesion, proliferation, survival, and drug resistance. Herein, we aimed to use CXCR4 as a potential biomarker to detect hypoxic-metastatic WM cells in the bone marrow and in the circulation by using CXCR4-detecting radiopharmaceutical.Methods: We radiolabeled a CXCR4-inhibitor (AMD3100) with ⁶⁴Cu and tested its binding to WM cells with different levels of CXCR4 expression using gamma counter in vitro. The accumulation of this radiopharmaceutical tracer was tested in vivo in subcutaneous and intratibial models using PET/CT scan. In addition, PBMCs spiked with different amounts of WM cells ex vivo were detected using gamma counting.Results: In vitro, ⁶⁴Cu-AMD3100 binding to WM cell lines demonstrated a direct correlation with the level of CXCR4 expression, which was increased in cells cultured in hypoxia with elevated levels of CXCR4, and decreased in cells with CXCR4 and HIF-1α knockout. Moreover, ⁶⁴Cu-AMD3100 detected localized and circulating CXCR4^high WM cells with high metastatic potential.Conclusions: In conclusion, we developed a molecularly targeted system, ⁶⁴Cu-AMD3100, which binds to CXCR4 and specifically detects WM cells with hypoxic phenotype and metastatic potential in the subcutaneous and intratibial models. These preliminary findings using CXCR4-detecting PET radiopharmaceutical tracer indicate a potential technology to predict high-risk patients for the progression to WM due to metastatic potential.

CXCR4 mutations affect presentation and outcomes in patients with Waldenström macroglobulinemia: A systematic review

Introduction: The genomic landscape of Waldenström macroglobulinemia (WM) is characterized by recurrent MYD88 (MYD88^L265P) and CXCR4 mutations (CXCR4^MUT), detected in 90% and 30% of cases, respectively. The role of CXCR4^MUT in clinical features and outcomes to therapy in WM patients is evolving. Areas covered: We performed a systematic review aimed at evaluating the prevalence of CXCR4^MUT in WM patients, and at assessing differences in clinical features and outcomes to therapy between WM patients with and without CXCR4^MUT. Seventeen studies were included in our analysis. The pooled prevalence of CXCR4^MUT in WM patients was 31%; 34% in MYD88^L265P and 5% in MYD88^WT patients. CXCR4^MUT were associated with higher serum IgM levels and higher risk of hyperviscosity than CXCR4^WT patients. Very good partial response (VGPR) and progression-free survival (PFS) rates to ibrutinib, with and without rituximab, appeared lower in CXCR4^MUT than in CXCR4^WT patients. Response and PFS rates were not affected by CXCR4^MUT status on patients treated with proteasome inhibitors. Expert opinion: Our systematic review shows that WM patients with CXCR4^MUT have specific clinical features and have lower response and PFS rates to BTK inhibitors. Our findings support standardization of CXCR4 testing and development of CXCR4-directed therapy.

68Ga-Pentixafor PET/CT for Imaging of Chemokine Receptor 4 Expression in Waldenström Macroglobulinemia/Lymphoplasmacytic Lymphoma: Comparison to 18F-FDG PET/CT

¹⁸F-FDG PET/CT has some limitations in the evaluation of Waldenström macroglobulinemia/lymphoplasmacytic lymphoma (WM/LPL), an indolent B-cell lymphoma that primarily involves the bone marrow. Because there is a high level of chemokine receptor 4 expression in the B cells of WM/LPL patients, we performed a prospective cohort study to evaluate the performance of ⁶⁸Ga-pentixafor, which targets chemokine receptor 4 in WM/LPL, and to compare it with the performance of ¹⁸F-FDG. Methods: Seventeen patients with WM/LPL were recruited. All patients underwent both ⁶⁸Ga-pentixafor PET/CT and ¹⁸F-FDG PET/CT. A positive PET/CT result was defined as the presence of focal lesions with positive PET results or diffuse bone marrow patterns (uptake > liver). The rates of positive results for PET/CT scans of bone marrow, lymph nodes, and other extramedullary involvement were statistically compared. Results: ⁶⁸Ga-pentixafor PET/CT had a higher rate of positive results than ¹⁸F-FDG PET/CT (100% vs. 58.8%; P = 0.023) in the recruited WM/LPL patients. The sensitivities of ⁶⁸Ga-pentixafor PET/CT and ¹⁸F-FDG PET/CT for detecting bone marrow involvement were 94.1% and 58.8%, respectively (P = 0.077). In terms of detecting lymph node involvement, ⁶⁸Ga-pentixafor PET/CT had a significantly higher rate of positive results than ¹⁸F-FDG PET/CT (76.5% vs. 11.8%; P = 0.003). In addition, ⁶⁸Ga-pentixafor detected more paramedullary and central nervous system involvement than ¹⁸F-FDG. Conclusion: ⁶⁸Ga-pentixafor might be a promising imaging agent for the assessment of WM/LPL.

Characteristics of Waldenström Macroglobulinemia in Korean Patients According to Mutational Status of MYD88 and CXCR4: Analysis Using Ultra-Deep Sequencing

BACKGROUND

Little is known about the mutational frequency of myeloid differentiation factor 88 (MYD88) and C-X-C chemokine receptor type 4 (CXCR4) and the corresponding characteristics in Asian individuals afflicted with Waldenström macroglobulinemia (WM). We investigated the characteristics of WM according to mutational status of MYD88/CXCR4, and attempted to determine the lineage commitment among hematopoietic cells by MYD88^L265P single-cell sequencing on bone marrow (BM) smear slides.

MATERIALS AND METHODS

CXCR4 mutations (muts) were detected using ultra-deep sequencing using target capture. Mutational burden of MYD88 was assessed using real-time polymerase chain reaction. Single-cell sequencing for MYD88 was performed on lymphocytes, plasmacytoid lymphocytes, plasma cells, and neutrophils using laser microdissection.

RESULTS

Among 31 patients, the frequencies of MYD88/CXCR4 muts were as follows: MYD88 wild type (WT) CXCR4^WT (6 patients, 19.4%), MYD88^L265PCXCR4^WT (19 patients, 61.4%), MYD88^L265PCXCR4^mut (6 patients, 19.4%; 1 frameshift and 5 nonsense muts). Immunoglobulin M levels of MYD88^L265CXCR4^WT patients were significantly higher than those of MYD88^WTCXCR4^WT patients (P = .024). Tumor burden in BM was highest in patients with MYD88^L265PCXCR4^mut (82.0%), followed by MYD88^L265PCXCR4^WT (52.8%) and MYD88^WTCXCR4^WT (14.2%) (P < .001). The quantity of MYD88-mutated DNA tended to correlate with tumor burden in BM (correlation coefficient 0.647; P = .009). MYD88^L265P was detected in plasma cells, plasmacytoid lymphocytes, and lymphocytes but not neutrophils.

CONCLUSION

The frequency of MYD88/CXCR4 muts in Korean and Caucasian patients with WM was similar, however 5 of the 6 CXCR4 muts were nonsense-a proportion higher than reported frequencies in Caucasian individuals. Ultra-deep sequencing was capable of detecting CXCR4 muts not detectable using Sanger sequencing, suggesting a possible replacement of the B-cell sorting.

How Recent Advances in Biology of Waldenström's Macroglobulinemia May Affect Therapy Strategy

PURPOSE OF REVIEW

Waldenström macroglobulinemia (WM) is a rare lymphoproliferative disorder. Up to now, therapeutic choice was not influenced by the biological characteristics of the disease. Here, we will review how recent advances in biology in WM may affect therapy strategy.

RECENT FINDINGS

Recently, WM has been described as a new oncogenic model. MyD88 mutation has been described as a key driver mutation and has functional consequences which could be targeted. Other mutations, such as CXCR4 or TP53, have been reported. These mutations are associated with different clinical presentation, prognosis, and treatment response. Mutational status may influence therapeutic choice in some patients but additional data are required. New targeted therapies are on development.

Homing Genes Expression in Fucosyltransferase VI-Treated Umbilical Cord Blood CD133+ Cells which Expanded on Protein-Coated Nanoscaffolds

Umbilical cord blood (UCB)-derived hematopoietic stem cells (HSCs) are considered because of their self-renewing, differentiating, proliferating, and readily available properties. Moreover, HSCs' homing to the hematopoietic microenvironment is an important step in their transplantation process. But low content of progenitor cells in one unit of UCB and defect in the bone marrow (BM) homing limit their applications. Hence, we decided to correct this deficiency with ex vivo incubation of CD133+ cells using fucosyltransferase VI and GDP-fucose. Then C-X-C chemokines receptor-4 (CXCR4), very late activation antigen-4 (VLA4), very late activation antigen-5 (VLA5), lymphocyte function-associated antigen-1 (LFA-1), and E-cadherin (E-cad) genes expressions were investigated with the goal of homing evaluation. The purity of MACS isolated CD133+ cells and confirmation of fucosylation were done by flow cytometry, and the viability of cells seeded on protein-coated poly L-lactic acid (PLLA) scaffold was proven via MTT assay. Scanning electron microscopy (SEM), CFU assays, and expression assays of CXCR4, VLA4, VLA5, LFA-1 and E-cad by real-time PCR were performed, too. Flow cytometry data showed that isolated cells were suitable for fucosyltransferase VI (FT-VI) incubation and expansion on nanoscaffolds. MTT, CFU assays, and SEM micrographs demonstrated fibronectin (FN)-collagen-selectin (FCS)-coated scaffold serve as best environment for viability, clonogenicity, and cell attachment. High levels of homing genes expression were also observed in cells seeded on FCS-coated scaffolds. Also, CXCR4 flow cytometry analysis confirmed real-time data. FCS-PLLA scaffolds provided optimal conditions for viability of FT-VI-treated CD133+ cells, and clonogenicity with the goal of improving homing following UCB-HSCs transplantation.

Working Toward a Genomic Prognostic Classification of Waldenström Macroglobulinemia: C-X-C Chemokine Receptor Type 4 Mutation and Beyond

Waldenström macroglobulinemia is a rare indolent B-cell lymphoma. Whole-exome sequencing studies have improved our knowledge of the Waldenström macroglobulinemia mutational landscape. The MYD88 L265P mutation is present in nearly 90% of patients with Waldenström macroglobulinemia. CXCR4 mutations are identified in approximately 30% of MYD88L265P cases and have been associated with ibrutinib resistance in clinical trials. Mutations in CD79B, ARID1a, or TP53 were described at lower frequency. Deciphering the earliest initiating lesions and identifying the molecular alterations leading to disease progression currently represent important goals in the future to identify the most relevant targets for precision therapy in Waldenström macroglobulinemia.

Detection of MYD88 and CXCR4 mutations in cell-free DNA of patients with IgM monoclonal gammopathies

Liquid biopsyis being integrated into cancer diagnostics with profound therapeutic implications. However, its role in Waldenström's Macroglobulinemia (WM) and IgM monoclonal gammopathies is still unclear. In this study, we evaluated the role of peripheral blood (PB) cell-free DNA (cfDNA) in characterizing the mutational status of MYD88 and CXCR4 of patients with IgM monoclonal gammopathies. Paired bone marrow (BM) tumor DNA (tDNA) and PB cfDNA samples from 98 patients (9 MGUS, 45 with WM in remission, 44 with smoldering WM, newly diagnosed or relapsed WM) and 10 controls with non-IgM monoclonal gammopathies were analyzed. Regarding MYD88^L265P mutation, 76 patients had paired tDNA and cfDNA informative samples. Among patients with WM in remission, 65% harbored the MYD88^L265P mutation, whereas the corresponding percentage among smoldering/newly diagnosed or relapsed WM was 92%. The overall concordance rate was 94% (72/76). For CXCR4 mutations, 65 patients had paired informative tDNA and cfDNA samples. The overall concordance rate was 90% (59/65). All controls had wild-type MYD88 and CXCR4. In conclusion, PB cfDNA is a useful, minimally invasive, cost-effective, and time-effective tool for the identification of the presence of MYD88 and CXCR4 mutations in patients with IgM monoclonal gammopathies avoiding unnecessary BM assessment.

The importance of the genomic landscape in Waldenström's Macroglobulinemia for targeted therapeutical interventions

The Literature has recently reported on the importance of genomics in the field of hematologic malignancies, including B-cell lymphoproliferative disorders such as Waldenström's Macrolgobulinemia (WM). Particularly, whole exome sequencing has led to the identification of the MYD88L265P and CXCR4C1013G somatic variants in WM, occurring in about 90% and 30% of the patients, respectively. Subsequently, functional studies have demonstrated their functional role in supporting WM pathogenesis and disease progression, both in vitro and in vivo, thus providing the pre-clinical evidences for extremely attractive targets for novel therapeutic interventions in WM. Of note, recent evidences have also approached and defined the transcriptome profiling of WM cells, revealing a signature that mirrors the somatic aberrations demonstrated within the tumor clone. A parallel research field has also reported on microRNAs (miRNAs), highlighting the oncogenic role of miRNA-155 in WM. In the present review, we focus on the latest reports on genomics and miRNAs in WM, providing an overview of the clinical relevance of the latest acquired knowledge about genomics and miRNA aberrations in WM.

Role of Bruton's tyrosine kinase in B cells and malignancies

Bruton’s tyrosine kinase (BTK) is a non-receptor kinase that plays a crucial role in oncogenic signaling that is critical for proliferation and survival of leukemic cells in many B cell malignancies. BTK was initially shown to be defective in the primary immunodeficiency X-linked agammaglobulinemia (XLA) and is essential both for B cell development and function of mature B cells. Shortly after its discovery, BTK was placed in the signal transduction pathway downstream of the B cell antigen receptor (BCR). More recently, small-molecule inhibitors of this kinase have shown excellent anti-tumor activity, first in animal models and subsequently in clinical studies. In particular, the orally administered irreversible BTK inhibitor ibrutinib is associated with high response rates in patients with relapsed/refractory chronic lymphocytic leukemia (CLL) and mantle-cell lymphoma (MCL), including patients with high-risk genetic lesions. Because ibrutinib is generally well tolerated and shows durable single-agent efficacy, it was rapidly approved for first-line treatment of patients with CLL in 2016. To date, evidence is accumulating for efficacy of ibrutinib in various other B cell malignancies. BTK inhibition has molecular effects beyond its classic role in BCR signaling. These involve B cell-intrinsic signaling pathways central to cellular survival, proliferation or retention in supportive lymphoid niches. Moreover, BTK functions in several myeloid cell populations representing important components of the tumor microenvironment. As a result, there is currently a considerable interest in BTK inhibition as an anti-cancer therapy, not only in B cell malignancies but also in solid tumors. Efficacy of BTK inhibition as a single agent therapy is strong, but resistance may develop, fueling the development of combination therapies that improve clinical responses. In this review, we discuss the role of BTK in B cell differentiation and B cell malignancies and highlight the importance of BTK inhibition in cancer therapy.

Unraveling the heterogeneity of IgM monoclonal gammopathies: a gene mutational and gene expression study

Immunoglobulin M (IgM) monoclonal gammopathies show considerable variability, involving three different stages of presentation: IgM monoclonal gammopathy of undetermined significance (IgM-MGUS), asymptomatic Waldenström's macroglobulinemia (AWM), and symptomatic WM (SWM). Despite recent findings about the genomic and transcriptomic characteristics of such disorders, we know little about the causes of this clinical heterogeneity or the mechanisms involved in the progression from indolent to symptomatic forms. To clarify these matters, we have performed a gene expression and mutational study in a well-characterized cohort of 69 patients, distinguishing between the three disease presentations in an attempt to establish the relationship with the clinical and biological features of the patients. Results showed that the frequency of genetic alterations progressively increased from IgM-MGUS to AWM and SWM. This means that, in contrast to MYD88 p.L265P and CXCR4 WHIM mutations, present from the beginning of the pathogenesis, most of them would be acquired during the course of the disease. Moreover, the expression study revealed a higher level of expression of genes belonging to the Toll-like receptor (TLR) signaling pathway in symptomatic versus indolent forms, which was also reflected in the disease presentation and prognosis. In conclusion, our findings showed that IgM monoclonal gammopathies present higher mutational burden as the disease progresses, in parallel to the upregulation of relevant pathogenic pathways. This study provides a translational view of the genomic basis of WM pathogenesis.

Waldenstrom's Macroglobulinemia: An Update

Waldenstrom Macroglobulinemia is a rare lymphoproliferative disorder with distinctive clinical features. Diagnostic and prognostic characterisation in WM significantly changed with the discovery of two molecular markers: MYD88 and CXCR4. Mutational status of these latter influences both clinical presentation and prognosis and demonstrated therapeutic implications. Treatment choice in Waldenstrom disease is strictly guided by patients age and characteristics, specific goals of therapy, the necessity for rapid disease control, the risk of treatment-related neuropathy, disease features, the risk of immunosuppression or secondary malignancies and potential for future autologous stem cell transplantation. The therapeutic landscape has expanded during the last years and the approval of ibrutinib, the first drug approved for Waldenstrom Macroglobulinemia, represents a significant step forward for a better management of the disease.

Waldenstrom's Macroglobulinemia: An Update

Waldenstrom Macroglobulinemia is a rare lymphoproliferative disorder with distinctive clinical features. Diagnostic and prognostic characterisation in WM significantly changed with the discovery of two molecular markers: MYD88 and CXCR4. Mutational status of these latter influences both clinical presentation and prognosis and demonstrated therapeutic implications. Treatment choice in Waldenstrom disease is strictly guided by patients age and characteristics, specific goals of therapy, the necessity for rapid disease control, the risk of treatment-related neuropathy, disease features, the risk of immunosuppression or secondary malignancies and potential for future autologous stem cell transplantation. The therapeutic landscape has expanded during the last years and the approval of ibrutinib, the first drug approved for Waldenstrom Macroglobulinemia, represents a significant step forward for a better management of the disease.

The role of G protein-coupled receptors in lymphoid malignancies

B cell lymphoma consists of multiple individual diseases arising throughout the lifespan of B cell development. From pro-B cells in the bone marrow, through circulating mature memory B cells, each stage of B cell development is prone to oncogenic mutation and transformation, which can lead to a corresponding lymphoma. Therapies designed against individual types of lymphoma often target features that differ between malignant cells and the corresponding normal cells from which they arise. These genetic changes between tumor and normal cells can include oncogene activation, tumor suppressor gene repression and modified cell surface receptor expression. G protein-coupled receptors (GPCRs) are an important class of cell surface receptors that represent an ideal target for lymphoma therapeutics. GPCRs bind a wide range of ligands to relay extracellular signals through G protein-mediated signaling cascades. Each lymphoma subgroup expresses a unique pattern of GPCRs and efforts are underway to fully characterize these patterns at the genetic level. Aberrations such as overexpression, deletion and mutation of GPCRs have been characterized as having causative roles in lymphoma and such studies describing GPCRs in B cell lymphomas are summarized here.

Coinhibition of the deubiquitinating enzymes, USP14 and UCHL5, with VLX1570 is lethal to ibrutinib- or bortezomib-resistant Waldenstrom macroglobulinemia tumor cells

The survival of Waldenstrom macroglobulinemia (WM) tumor cells hinges on aberrant B-cell receptor (BCR) and MYD88 signaling. WM cells upregulate the proteasome function to sustain the BCR-driven growth while maintaining homeostasis. Clinically, two treatment strategies are used to disrupt these complementary yet mutually exclusive WM survival pathways via ibrutinib (targets BTK/MYD88 node) and bortezomib (targets 20 S proteasome). Despite the success of both agents, WM patients eventually become refractory to treatment, highlighting the adaptive plasticity of WM cells and underscoring the need for development of new therapeutics. Here we provide a comprehensive preclinical report on the anti-WM activity of VLX1570, a novel small-molecule inhibitor of the deubiquitinating enzymes (DUBs), ubiquitin-specific protease 14 (USP14) and ubiquitin carboxyl-terminal hydrolase isozyme L5 (UCHL5). Both DUBs reside in the 19 S proteasome cap and their inhibition by VLX1570 results in rapid and tumor-specific apoptosis in bortezomib- or ibrutinib-resistant WM cells. Notably, treatment of WM cells with VLX1570 downregulated BCR-associated elements BTK, MYD88, NFATC, NF-κB and CXCR4, the latter whose dysregulated function is linked to ibrutinib resistance. VLX1570 administered to WM-xenografted mice resulted in decreased tumor burden and prolonged survival (P=0.0008) compared with vehicle-treated mice. Overall, our report demonstrates significant value in targeting USP14/UCHL5 with VLX1570 in drug-resistant WM and carries a high potential for clinical translation.

Guideline for the diagnosis, treatment and response criteria for Bing-Neel syndrome

Bing Neel syndrome is a rare disease manifestation of Waldenström's macroglobulinemia that results from infiltration of the central nervous system by malignant lymphoplasmacytic cells. In this guideline we describe the clinical symptoms, as well as the appropriate laboratory and radiological studies, that can aid in the diagnosis. The presentation of Bing Neel syndrome may be very diverse, and includes headaches, cognitive deficits, paresis, and psychiatric symptoms. The syndrome can present in patients with known Waldenström's macroglobulinemia, even in the absence of systemic progression, but also in previously undiagnosed patients. Diagnostic work-up should include cerebral spinal fluid analysis with multiparameter flow cytometry to establish B-cell clonality, protein electrophoresis and immunofixation for the detection and classification of a monoclonal protein as well as molecular diagnostic testing for immunoglobulin gene rearrangement and mutated MYD88. MRI of the brain and spinal cord is also essential. The second challenge is to expand our knowledge of prognosis and treatment outcome. Prospective clinical trials on Bing Neel syndrome patients that employ uniform treatment along with appropriate laboratory cerebral spinal fluid assessments and standardized MRI protocols will be invaluable, constituting a significant step forward in delineating treatment outcome for this intriguing disease manifestation.

Future therapeutic options for patients with Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a rare lymphoma characterized by the accumulation of IgM-producing lymphoplasmacytic cells. Although WM patients can experience prolonged remissions, the disease invariably recurs. Therefore, novel treatments associated with higher success rates and lower toxicity profiles are needed. The discovery of recurrent mutations in the MYD88 and CXCR4 genes has unraveled potential therapeutic targets in WM patients. As a result of these findings and based on the design and execution of a prospective clinical trial, the FDA granted approval to ibrutinib, an oral Bruton tyrosine kinase (BTK) inhibitor, to treat patients with symptomatic WM. The present review focuses on potential therapies that could change the landscape of treatment of patients with WM, specifically focusing on inhibitors or antagonists or the proteasome, BTK, CD38, BCL2 and the CXCR4 and MYD88 genes themselves. Novel agents with novel mechanisms of action should be evaluated in the context of carefully designed clinical trials.

Waldenström macroglobulinemia: biology, genetics, and therapy

Waldenström macroglobulinemia (WM) is a distinct clinicopathologic entity characterized by the presence of a lymphoplasmacytic lymphoma, a non-Hodgkin lymphoma, and IgM monoclonal gammopathy. WM is an indolent, uncommon malignancy mostly affecting the elderly. Patient outcomes have modestly improved since the introduction of rituximab to conventional cytotoxic chemotherapy more than 20 years ago. However, the pivotal discovery of the somatic MYD88 L265P mutation, harbored by most patients with WM, and the somatic CXCR4 WHIM mutations, similar to germline CXCR4 mutations seen in the warts, hypogammaglobulinemia, immunodeficiency, and myelokathexis (WHIM) syndrome, present in approximately one-third of patients with WM, has fundamentally changed our understanding of this disease and expanded the potential therapeutic targets. Within this new paradigm, ibrutinib emerged as a promising new drug. Ibrutinib targets Bruton’s tyrosine kinase, a downstream protein in the B-cell receptor pathway that is overactivated by the MYD88 L265P mutation. A seminal Phase II trial of ibrutinib in previously treated WM patients showed impressive response rates and confirmed the effects of MYD88 L265P and CXCR4 WHIM mutations in response to therapy. Ibrutinib is the first and only US Food and Drug Administration–approved drug specifically for the treatment of WM. However, before ibrutinib can be established as the standard of care for WM, long-term data regarding efficacy and safety are required. Further research to address ibrutinib resistance and cost-effectiveness is also imperative before ibrutinib can gain widespread acceptance. This review will cover the present pathophysiologic understanding of WM in light of the recent MYD88 and CXCR4 discovery, as well as current and emergent treatment regimens with focus on ibrutinib.

Transcriptome sequencing reveals a profile that corresponds to genomic variants in Waldenström macroglobulinemia

Whole-genome sequencing has identified highly prevalent somatic mutations including MYD88, CXCR4, and ARID1A in Waldenström macroglobulinemia (WM). The impact of these and other somatic mutations on transcriptional regulation in WM remains to be clarified. We performed next-generation transcriptional profiling in 57 WM patients and compared findings to healthy donor B cells. Compared with healthy donors, WM patient samples showed greatly enhanced expression of the VDJ recombination genes DNTT, RAG1, and RAG2, but not AICDA Genes related to CXCR4 signaling were also upregulated and included CXCR4, CXCL12, and VCAM1 regardless of CXCR4 mutation status, indicating a potential role for CXCR4 signaling in all WM patients. The WM transcriptional profile was equally dissimilar to healthy memory B cells and circulating B cells likely due increased differentiation rather than cellular origin. The profile for CXCR4 mutations corresponded to diminished B-cell differentiation and suppression of tumor suppressors upregulated by MYD88 mutations in a manner associated with the suppression of TLR4 signaling relative to those mutated for MYD88 alone. Promoter methylation studies of top findings failed to explain this suppressive effect but identified aberrant methylation patterns in MYD88 wild-type patients. CXCR4 and MYD88 transcription were negatively correlated, demonstrated allele-specific transcription bias, and, along with CXCL13, were associated with bone marrow disease involvement. Distinct gene expression profiles for patients with wild-type MYD88, mutated ARID1A, familial predisposition to WM, chr6q deletions, chr3q amplifications, and trisomy 4 are also described. The findings provide novel insights into the molecular pathogenesis and opportunities for targeted therapeutic strategies for WM.

Ibrutinib in Waldenström macroglobulinemia: latest evidence and clinical experience

Ibrutinib is an oral Bruton's tyrosine kinase (BTK) inhibitor, which has recently gained approval by the United States (US) Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of patients with symptomatic Waldenström macroglobulinemia (WM). Herein, we review the role of BTK in the pathophysiology of WM, and present the results of the preclinical and clinical studies that led to the initial investigation and later approval of ibrutinib in WM. We also discuss aspects associated with ibrutinib therapy in WM patients, especially focusing on genomic profiling and the impact on response to ibrutinib, and the management of adverse events.

Genetic aberrations in small B-cell lymphomas and leukemias: molecular pathology, clinical relevance and therapeutic targets

Small B-cell lymphomas and leukemias (SBCLs) are a clinically, morphologically, immunophenotypically and genetically heterogeneous group of clonal lymphoid neoplasms, including entities such as chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), mantle cell lymphoma (MCL), follicular lymphoma (FL), lymphoplasmacytic lymphoma (LPL), marginal zone lymphoma (MZL) and hairy cell leukemia (HCL). The pathogenesis of some of these lymphoid malignancies is characterized by distinct translocations, for example t(11;14) in the majority of cases of MCL and t(14;18) in most cases of FL, whereas other entities are associated with a variety of recurrent but nonspecific numeric chromosomal abnormalities, as exemplified by del(13q14), del(11q22), and +12 in CLL, and yet others such as LPL and HCL that lack recurrent or specific cytogenetic aberrations. The recent surge in next generation sequencing (NGS) technology has shed more light on the genetic landscape of SBCLs through characterization of numerous driver mutations including SF3B1 and NOTCH1 in CLL, ATM and CCND1 in MCL, KMT2D and EPHA7 in FL, MYD88 (L265P) in LPL, KLF2 and NOTCH2 in splenic MZL (SMZL) and BRAF (V600E) in HCL. The identification of distinct genetic lesions not only provides greater insight into the molecular pathogenesis of these disorders but also identifies potential valuable biomarkers for prognostic stratification, as well as specific targets for directed therapy. This review discusses the well-established and recently identified molecular lesions underlying the pathogenesis of SBCLs, highlights their clinical relevance and summarizes novel targeted therapies.

The Addition of the BTK Inhibitor Ibrutinib to Anti-CD19 Chimeric Antigen Receptor T Cells (CART19) Improves Responses against Mantle Cell Lymphoma

PURPOSE

Responses to therapy with chimeric antigen receptor T cells recognizing CD19 (CART19, CTL019) may vary by histology. Mantle cell lymphoma (MCL) represents a B-cell malignancy that remains incurable despite novel therapies such as the BTK inhibitor ibrutinib, and where data from CTL019 therapy are scant. Using MCL as a model, we sought to build upon the outcomes from CTL019 and from ibrutinib therapy by combining these in a rational manner.

EXPERIMENTAL DESIGN

MCL cell lines and primary MCL samples were combined with autologous or normal donor-derived anti-CD19 CAR T cells along with ibrutinib. The effect of the combination was studied in vitro and in mouse xenograft models.

RESULTS

MCL cells strongly activated multiple CTL019 effector functions, and MCL killing by CTL019 was further enhanced in the presence of ibrutinib. In a xenograft MCL model, we showed superior disease control in the CTL019- as compared with ibrutinib-treated mice (median survival not reached vs. 95 days, P < 0.005) but most mice receiving CTL019 monotherapy eventually relapsed. Therefore, we added ibrutinib to CTL019 and showed that 80% to 100% of mice in the CTL019 + ibrutinib arm and 0% to 20% of mice in the CTL019 arm, respectively, remained in long-term remission (P < 0.05).

CONCLUSIONS

Combining CTL019 with ibrutinib represents a rational way to incorporate two of the most recent therapies in MCL. Our findings pave the way to a two-pronged therapeutic strategy in patients with MCL and other types of B-cell lymphoma. Clin Cancer Res; 22(11); 2684-96. ©2016 AACR.

Clonal architecture of CXCR4 WHIM-like mutations in Waldenström Macroglobulinaemia

CXCR4(WHIM) somatic mutations are distinctive to Waldenström Macroglobulinaemia (WM), and impact disease presentation and treatment outcome. The clonal architecture of CXCR4(WHIM) mutations remains to be delineated. We developed highly sensitive allele-specific polymerase chain reaction (AS-PCR) assays for detecting the most common CXCR4(WHIM) mutations (CXCR4(S338X C>A and C>G) ) in WM. The AS-PCR assays detected CXCR4(S338X) mutations in WM and IgM monoclonal gammopathy of unknown significance (MGUS) patients not revealed by Sanger sequencing. By combined AS-PCR and Sanger sequencing, CXCR4(WHIM) mutations were identified in 44/102 (43%), 21/62 (34%), 2/12 (17%) and 1/20 (5%) untreated WM, previously treated WM, IgM MGUS and marginal zone lymphoma patients, respectively, but no chronic lymphocytic leukaemia, multiple myeloma, non-IgM MGUS patients or healthy donors. Cancer cell fraction analysis in WM and IgM MGUS patients showed CXCR4(S338X) mutations were primarily subclonal, with highly variable clonal distribution (median 35·1%, range 1·2-97·5%). Combined AS-PCR and Sanger sequencing revealed multiple CXCR4(WHIM) mutations in many individual WM patients, including homozygous and compound heterozygous mutations validated by deep RNA sequencing. The findings show that CXCR4(WHIM) mutations are more common in WM than previously revealed, and are primarily subclonal, supporting their acquisition after MYD88(L265P) in WM oncogenesis. The presence of multiple CXCR4(WHIM) mutations within individual WM patients may be indicative of targeted CXCR4 genomic instability.

Cell adhesion manipulation through single cell assembly for characterization of initial cell-to-cell interaction

BACKGROUND

Cell-to-cell interactions are complex processes that involve physical interactions, chemical binding, and biological signaling pathways. Identification of the functions of special signaling pathway in cell-to-cell interaction from the very first contact will help characterize the mechanism underlying the interaction and advance new drug discovery.

METHODS

This paper reported a case study of characterizing initial interaction between leukemia cancer cells and bone marrow stromal cells, through the use of an optical tweezers-based cell manipulation tool. Optical traps were used to assemble leukemia cells at different positions of the stromal cell layer and enable their interactions by applying a small trapping force to maintain the cell contact for a few minutes. Specific drug was used to inhibit the binding of molecules during receptor-ligand-mediated adhesion.

RESULTS AND CONCLUSIONS

Our results showed that the amount of adhesion molecule could affect cell adhesion during the first few minutes contact. We also found that leukemia cancer cells could migrate on the stromal cell layer, which was dependent on the adhesion state and activation triggered by specific chemokine. The reported approaches provided a new opportunity to investigate cell-to-cell interaction through single cell adhesion manipulation.

Genomic Landscape of CXCR4 Mutations in Waldenström Macroglobulinemia

PURPOSE

Whole-genome sequencing has revealed MYD88 L265P and CXCR4 mutations (CXCR4(mut)) as the most prevalent somatic mutations in Waldenström macroglobulinemia. CXCR4 mutation has proved to be of critical importance in Waldenström macroglobulinemia, in part due to its role as a mechanism of resistance to several agents. We have therefore sought to unravel the different aspects of CXCR4 mutations in Waldenström macroglobulinemia.

EXPERIMENTAL DESIGN

We have scanned the two coding exons of CXCR4 in Waldenström macroglobulinemia using deep next-generation sequencing and Sanger sequencing in 98 patients with Waldenström macroglobulinemia and correlated with SNP array landscape and mutational spectrum of eight candidate genes involved in TLR, RAS, and BCR pathway in an integrative study.

RESULTS

We found all mutations to be heterozygous, somatic, and located in the C-terminal domain of CXCR4 in 25% of the Waldenström macroglobulinemia. CXCR4 mutations led to a truncated receptor protein associated with a higher expression of CXCR4. CXCR4 mutations pertain to the same clone as to MYD88 L265P mutations but were mutually exclusive to CD79A/CD79B mutations (BCR pathway). We identified a genomic signature in CXCR4(mut) Waldenström macroglobulinemia traducing a more complex genome. CXCR4 mutations were also associated with gain of chromosome 4, gain of Xq, and deletion 6q.

CONCLUSIONS

Our study panned out new CXCR4 mutations in Waldenström macroglobulinemia and identified a specific signature associated to CXCR4(mut), characterized with complex genomic aberrations among MYD88L265P Waldenström macroglobulinemia. Our results suggest the existence of various genomic subgroups in Waldenström macroglobulinemia.