Prognostic impact of resistance to bortezomib and/or lenalidomide in carfilzomib-based therapies for relapsed/refractory multiple myeloma: The Kyoto Clinical Hematology Study Group, multicenter, pilot, prospective, observational study in Asian patients

Background

Combinatory strategies with carfilzomib (CFZ), a second‐generation proteasome inhibitor, plus dexamethasone (DEX) with or without lenalidomide (LEN) have shown promising efficacy for patients with relapsed/refractory multiple myeloma (RRMM) in pivotal clinical trials. However, their effects on patients who were resistance to bortezomib (BTZ) and/or LEN have not been fully evaluated in a daily practice setting.

Aims

To evaluate the real‐world efficacy and safety of CFZ‐based treatments; that is, CFZ with LEN plus DEX (KRD therapy) and CFZ with DEX (KD therapy), in Asian patients, we conducted a multicenter pilot prospective observational study in the Kyoto Clinical Hematology Study Group.

Methods and Results

All 50 patients with RRMM enrolled in this study were treated with CFZ‐based treatments between 2017 and 2019. KRD and KD were administered to 31 and 19 patients, respectively. The overall response rates (ORRs) were 80.6% with KRD and 73.7% with KD. Two‐year progression‐free survival (PFS) and overall survival (OS) were 58.5% and 79.7% with KRD, and 23.1% and 52.6% with KD. By multivariate analysis, refractoriness to BTZ and to LEN were identified as independent unfavorable factors for both PFS and OS. The common non‐hematologic AEs included hypertension (42.0%), fever (24.0%), fatigue (24.0%), and infection (16.0%). No serious heart failure was observed. This study is registered as UMIN000025108.

Conclusion

This study suggests the need of the development of novel CFZ‐containing strategy which can overcome the refractoriness to BTZ and/or LEN, while both KRD and KD were shown to be mostly feasible in Asian patients in a daily practice setting.

Expression of activated integrin β7 in multiple myeloma patients

Multiple myeloma (MM) is still extremely difficult to cure, and new therapeutic drugs are needed. We recently found that integrin β7 is constitutively activated in MM cells, and chimeric antigen receptor (CAR) T cells targeting activated integrin β7 have a significant anti-MM effect. In this study, we performed flow cytometry analysis of the expression of activated integrin β7 in bone marrow cells from 137 symptomatic MM patients. In 60/137 (44%) MM patients, activated integrin β7 was detected in most MM cells (> 80% of MM cells were in the positive gate). Activated integrin β7 was highly expressed in MM cells even in heavily treated patients. It also showed high expression in many CD38^lo/^-CD138^-CD19⁺B cells, which reportedly include clonotypic B cells, in the bone marrow of MM patients. Taken together, these results suggest that CAR T-cell therapy targeting activated integrin β7 has the potential to benefit many patients with relapsed or refractory MM.

Plateau is a prognostic factor of lenalidomide therapy for previously treated multiple myeloma

The plateau phase emerging during the treatment of multiple myeloma (MM) is known to last steadily for a certain period, even without treatment. Therefore, the treatment started at plateau phase is expected to be associated with a better outcome. In this study, this hypothesis was evaluated retrospectively for previously treated MM patients in Kansai Myeloma Forum database who received lenalidomide (LEN) with or without dexamethasone for the first time. Disease stability index (DSI) was defined as (maximum - minimum values of M protein during the 90 days before the start of LEN) divided by M-protein values at the start of LEN. The patients were classified into three groups: stable (S), DSI ≤ 0.25; increasing (I), DSI > 0.25 with increasing M protein; decreasing (D), DSI > 0.25 with decreasing M protein. In univariate analysis of 352 patients, DSI group "I", non-IgG type, serum albumin<3.5 g/dL, and age≥70 were statistically significant prognostic factors for both progression-free survival and overall survival. In multivariate analysis, the former 3 risk factors were statistically significant for poor overall survival. Thus, DSI is an independent prognostic factor for the treatment with LEN for previously treated MM.

Outcomes of ixazomib/lenalidomide/dexamethasone for multiple myeloma: A multicenter retrospective analysis

OBJECTIVES

This study aimed to investigate real-world data of ixazomib plus lenalidomide and dexamethasone (IRd) therapy for patients with relapsed and refractory multiple myeloma (RRMM).

METHODS

We retrospectively analyzed 122 patients treated with IRd at 16 centers from May 2017 to January 2019 by using the Kansai Myeloma Forum database.

RESULT

At the start of IRd, the median age was 72 years, 66.7% of patients had IgG type, and the median number of prior therapies was 4, comprising bortezomib (85.4%) and lenalidomide (89.3%)-based regimens. Disease progression and adverse events accounted for treatment discontinuation in 46 and 32 patients, respectively. The median overall survival (OS) was not reached, and the median progression-free survival (PFS) was 11.9 months. Sensitivity to bortezomib did not affect the PFS, whereas lenalidomide-refractory patients had significantly lower PFS than lenalidomide-sensitive patients, who were comparable to TOURMALINE-MM1 study. The patients with IgG type had significantly better PFS and OS than those with non-IgG type.

CONCLUSION

This study presents the largest real-world data of patients treated with IRd in Asia. However, in real clinical practice, the patient background is different from the TOURMALINE-MM1 study, and IRd showed poor efficacy, especially in the non-IgG type and lenalidomide-refractory patients with RRMM.

Durable Remission of Chemotherapy-Refractory Myeloid Sarcoma by Azacitidine

Myeloid sarcoma is a rare disease entity of extramedullary myeloid neoplasm that can occur both as an initial isolated myeloid sarcoma without leukemic cell invasion in the peripheral blood and bone marrow, and as the secondary lesion of acute and chronic myeloid leukemias, myelodysplastic syndrome and chronic myeloproliferative neoplasms. Due to its rarity and its frequent emergence as the recurrent lesion after intensive systemic therapy, including allogeneic hematopoietic stem cell transplantation, the standard treatment has not been established for myeloid sarcoma. In this report, we presented an 84-year-old female patient with isolated myeloid sarcoma which progressed to myelodysplastic syndrome and systemic myeloid sarcoma despite various types of conventional anti-leukemic chemotherapies. However, the patient got a durable partial response by the monotherapy of azacitidine, a hypomethylating agent. She received thirteen courses of azacitidine therapy without progression. We discuss the possibility that hypomethylating agents are the novel effective and feasible therapeutic options for myeloid sarcoma, even in cases refractory to or relapsed after intensive systemic treatment. We also discuss the possible future development of hypomethylating agent-containing combinatory therapeutic strategy for myeloid sarcoma, given its direct anti-leukemic effect and immunomodulatory effect.

Efficacy and safety of romiplostim in refractory aplastic anaemia: a Phase II/III, multicentre, open-label study

A previous dose-finding study has suggested that romiplostim is effective in patients with refractory aplastic anaemia (AA) and 10 µg/kg once weekly was recommended as a starting dose. In this Phase II/III, multicentre, open-label study, romiplostim was administered subcutaneously at a fixed dose of 10 µg/kg once weekly for 4 weeks (weeks 1-4) followed by weekly doses (5, 10, 15 and 20 µg/kg) titrated by platelet response for up to 52 weeks (weeks 5-52). A total of 31 patients with AA who were refractory to immunosuppressive therapy (IST) and thrombocytopenia (platelet count of ≤30 × 10⁹ /l) were enrolled. The primary efficacy endpoint of the proportion of patients achieving any haematological (platelet, neutrophil and erythrocyte) response at week 27 was 84% [95% confidence interval (CI) 66-95%]. Trilineage response was 39% (95% CI 22-58%) at week 53. The most common treatment-related adverse events (AEs) were headache and muscle spasms (each 13%). All AEs were mild or moderate except for three patients with Grade 3 hepatic AEs; no AEs necessitated romiplostim discontinuation. Two patients developed cytogenetic abnormalities, of whom one returned to normal karyotype at last follow-up. High-dose romiplostim is effective and well tolerated in the treatment of patients with AA refractory to IST.

Retrospective multi-center study of Adolescent and Young Adult (AYA) Multiple Myeloma in Kansai Myeloma Forum registry

We retrospectively analyzed the clinical features and outcomes in a real-world cohort of adolescents and the young adult (AYA) patients (age between 16 and 39 years) with symptomatic multiple myeloma (MM) registered with the Kansai Myeloma Forum. 26 patients had been diagnosed as symptomatic MM out of 3284 patients. The prevalence of AYA-MM was 0.8% in this cohort. 81% of the patients was received stem cell transplantation, which may improve outcome. Anemia and hypercalcemia might be prognostic factors, however International Staging System failed to predict overall survival. Five patients developed late-onset adverse events which were serious and life-threatening. The 5-year overall survival was 71.0%. We need to develop the new strategy to overcome AYA-MM.

Second primary malignancy after rituximab-containing immunochemotherapy for diffuse large B cell lymphoma

Extended post-therapy long-term survival of patients with diffuse large B cell lymphoma (DLBCL) may also lead to an increase of late adverse events. We retrospectively investigated the frequency and clinical manifestation of second primary malignancy (SPM) after rituximab-containing immunochemotherapy in patients with DLBCL treated at seven institutes belonging to the Kyoto Clinical Hematology Study Group (KOTOSG) from the perspective of the existence of past or synchronous cancer history. In a median follow-up period of 899 days, 69 SPMs were observed in 58 of 809 patients. The most frequent SPM was gastric cancer, followed by lung cancer and colorectal cancer. The cumulative incidence of SPM increased steadily over time and was not significantly influenced by the presence or absence of past or synchronous cancer history. Our study suggests the need for careful attention to SPM in patients with DLBCL in daily practice.

Retrospective analysis of plasmacytoma in Kansai Myeloma Forum Registry

We retrospectively analyzed 51 patients with solitary plasmacytoma diagnosed from October 2002 to September 2018 from a cohort of 3575 patients with plasma cell dyscrasias registered in the Kansai Myeloma Forum. Twenty-seven patients had solitary bone plasmacytoma (SBP) and 24 had extramedullary plasmacytoma (EMP), with prevalence of 0.8% and 0.7%, respectively. The most frequent M protein was IgG (40%) in SBP, whereas non-secretory proteins were most frequent (50%) in EMP. Five-year overall survival was 78.2% in SBP and 80.8% in EMP (P = 0.894). Among patients with SBP, 44% progressed to MM with a median time of 10.5 months (2.4-93.3 months), whereas 8% of EMP patients progressed to MM with a median time of 18.6 months (13.0-24.2 months). The most frequent treatment was radiotherapy (41%) or observation (41%) in SBP, and chemotherapy (54%) in EMP. No statistically significant difference was observed upon univariate analysis of prognostic factors including age, sex, performance status, and IgG M protein. Our results suggest that there are biological differences between SBP and EMP in real-world settings.

Treatment-free remission after first-line dasatinib discontinuation in patients with chronic myeloid leukaemia (first-line DADI trial): a single-arm, multicentre, phase 2 trial

BACKGROUND

A previous dasatinib discontinuation (DADI) trial showed that 31 (49%) of 63 patients with chronic-phase chronic myeloid leukaemia who were treated with second-line or subsequent dasatinib could discontinue the drug safely. However, the safety and efficacy of discontinuing first-line dasatinib remains unclear. In this trial (the first-line DADI trial) we aimed to assess molecular relapse-free survival at 6 months after discontinuation of dasatinib in patients with chronic myeloid leukaemia who had been treated with first-line dasatinib and had maintained deep molecular response for at least 1 year.

METHODS

The first-line DADI trial was a single-arm, multicentre, phase 2 trial done at 23 hospitals in Japan. Patients with newly diagnosed chronic-phase chronic myeloid leukaemia without hepatosplenomegaly and extramedullary mass, who received at least 24-month dasatinib treatment and had a sustained deep molecular response (defined as BCR-ABL1/ABL1 international scale ≤0·0069% in at least four successive samples spanning a 12 month period) were enrolled. Other eligibility criteria were an age of 15 years or older, an Eastern Cooperative Oncology Group performance status score of 0-2, and no primary organ dysfunction. The primary outcome was molecular relapse-free survival (also known as treatment-free remission) after discontinuation of dasatinib at 6 months and was analysed in all patients who completed the 12-month consolidation phase. Safety was assessed in all patients who received treatment. This study closed early due to accrual and is registered with the UMIN Clinical Trials Registry (UMIN000011099).

FINDINGS

Between Sept 20, 2013 and July 12, 2016, 68 patients who had a deep molecular response after receiving first-line dasatinib for at least 24 months were enrolled and assigned to the consolidation phase. Nine patients were excluded during the consolidation phase and one patient was excluded after study completion because of meeting exclusion criteria. 58 patients discontinued dasatinib and were assessed. 32 (55%) of 58 patients had treatment-free remission at 6 months after dasatinib discontinuation, and median follow-up was 23·3 months (IQR 11·7-31·0). Treatment-free remission at 6 months was 55·2% (95% CI 43·7-69·6). No non-haematological adverse events worse than grade 2 occurred before dasatinib discontinuation. The most common haematological adverse event was anaemia (14 [21%] of 68 treated patients); three (4%) of 68 treated patients had grade 3 neutropenia and one (1%) had grade 4 lymphopenia.

INTERPRETATION

Our findings suggest that dasatinib could be safely discontinued after first-line treatment in patients with chronic myeloid leukaemia who had received at least 36 months of therapy and sustained deep molecular response; however, further confirmation in larger trials is needed.

FUNDING

Epidemiological and Clinical Research Information Network.

Significance of FLT3-tyrosine kinase domain mutation as a prognostic factor for acute myeloid leukemia

The prognostic significance of FLT3-tyrosine kinase domain (TKD) mutations remains unknown. To investigate the prognostic impact of FLT3-TKD, 676 de novo acute myeloid leukemia (AML), we retrospectively analyzed cases and conducted a review of the literature. Of the 676 de novo AML cases, 34 (5.0%) were FLT3-TKD-positive; both FLT3-TKD and FLT3-ITD were noted in only two cases (0.3%). Although no significant differences in relapse-free survival (RFS) were noted, FLT3-TKD-positive cases showed better prognoses than FLT3-ITD-positive cases (FLT3-TKD versus FLT3-ITD, p = 0.152). For overall survival (OS), although FLT3-TKD-positive cases showed prognoses similar to those for FLT3-WT cases, their prognoses were significantly better than those of FLT3-ITD-positive cases (FLT3-TKD versus FLT3-ITD, p = 0.032). Moreover, the 5-year OS for FLT3-TKD-positive cases was 46.1%, indicating that this as an intermediate prognosis group. Although no reports from Asia have indicated a frequency of FLT3-TKD-positive cases > 10%, several reports from Europe and the United States have indicated frequencies > 10%. This suggests the possibility that FLT3-TKD-positive cases are less common in Asia than in Europe and the United States. We anticipate that in the future, the appearance of targeting agents, such as FLT3 inhibitors, will improve the prognosis of FLT3-TKD-positive AML relative to that of FLT3-WT AML.

Prediction of delayed platelet engraftment after autologous stem cell transplantation for B-cell non-Hodgkin lymphoma

Delayed platelet engraftment (DPE) is occasionally observed despite prompt neutrophil engraftment after autologous peripheral blood stem cell transplantation (auto-PBSCT). To identify risk factors for DPE and to develop a simple and clinically applicable system for predicting the time required for platelet recovery, we conducted a multi-institutional retrospective study in 144 patients with B-cell non-Hodgkin lymphoma who underwent auto-PBSCT. In a median observation period of 930 days (range: 25-5272 days), 139 patients successfully achieved platelet engraftment (≥50.0 × 10⁹/L). The median duration for platelet engraftment was 19 days, and 130 patients had platelet engraftment within 40 days after auto-PBSCT; however, the other 14 patients failed to achieve platelet engraftment within 60 days. These 14 patients with DPE required a significantly greater number of apheresis procedures and had a lower pre-apheresis absolute lymphocyte count (PA-ALC) compared to those without DPE. Importantly, multivariate analysis revealed that the number of transplanted CD34⁺ cells (≤2.0 × 10⁶/kg), number of required apheresis procedures (≥3 days), and PA-ALC (≤1.0 × 10⁹/L) were independently associated with a longer time for platelet engraftment after auto-PBSCT. By incorporating these three independent factors as variables, we generated a new scoring system for prediction of the time and probability for platelet engraftment after auto-PBSCT.

Combined rituximab, bendamustine, and dexamethasone chemotherapy for relapsed or refractory indolent B-cell non-Hodgkin lymphoma and mantle cell lymphoma: a multicenter phase II study

This multicenter phase II study (UMIN000008145) aims to investigate the efficacy and safety of six cycles of combination therapy (RBD) comprising rituximab, bendamustine, and dexamethasone (DEX) for relapsed or refractory (RR) indolent B-cell non-Hodgkin lymphoma (B-NHL) and mantle cell lymphoma (MCL). Although the initial study protocol comprised 20 mg/body DEX on days 1 and 2, and 10 mg/body on days 3-5 [high-dose (HD-) DEX group], the dose of DEX was later decreased to 8 mg/body on days 1 and 2 [low-dose (LD-) DEX group] due to frequent cytomegalovirus (CMV) antigenemia and recurrent retinitis. We enrolled 33 patients, and LD-DEX and HD-DEX were administered in 15 and 18 patients, respectively. The overall response and the 3-year progression-free survival rates were 88% and 75.5%, respectively. The leading adverse event was myelosuppression. Incidence of grade 3-4 leukocytopenia, neutropenia, and lymphocytopenia was 55%, 67%, and 91%, respectively. The most frequent nonhematological adverse events were CMV antigenemia and rash (33% and 30%, respectively). Incidence of CMV antigenemia over 10/100,000 white blood cells was significantly lower with LD-DEX than that with HD-DEX (P = 0.0127). In conclusion, RBD showed significant effectiveness for RR indolent B-NHL and MCL.

Immunosuppressive therapy with rabbit antithymocyte globulin therapy for acquired aplastic anemia: a multi-institutional retrospective study in Japanese adult patients

We retrospectively analyzed efficacy and safety of therapy with rabbit antithymocyte globulin (rATG) in combination with cyclosporine A (CsA) in 30 Japanese adult patients with acquired aplastic anemia (AA) in the Kyoto Clinical Hematology Study Group. The median observation period was 31 months and the median age of the patients was 54 years. The objective response rates (ORRs) to rATG plus CsA increased over time until 18 months after the start of treatment; the rate of achievement of better than partial response at 18 months was 66.7%. The 2-year overall survival (OS) rate was 79% in all patients. In eight patients aged ≥ 75 years old, the ORR was 62.5% and the 2-year OS rate of 50% was not significantly inferior to that in patients aged ≤ 74 years old. The overall mortality rate was 16.7% in our cohort, while the mortality rate in patients aged ≥ 75 years old was 37.5%, which was higher than that in patients aged ≤ 74 years old (9.1%), although the difference was not statistically significant. Collectively, rATG combined with CsA is an effective and feasible treatment for AA, while patients should be appropriately selected.

Clinical effects of recombinant thrombomodulin and defibrotide on sinusoidal obstruction syndrome after allogeneic hematopoietic stem cell transplantation

Sinusoidal obstruction syndrome (SOS) is a lethal complication after hematopoietic stem cell transplantation (HSCT). Defibrotide (DF) is the only drug internationally recommended for SOS treatment in Western countries. Recombinant human soluble thrombomodulin (rhTM), which is promising for the treatment of patients with disseminated intravascular coagulation, is also reported to be potentially effective for SOS. To clarify the safety and efficacy of DF and rhTM, we conducted a retrospective survey of these agents in Japan. Data from 65 patients who underwent allogeneic HSCT and received DF (n  =  24) or rhTM (n  =  41) for SOS treatment were collected. The complete response rates for SOS on day 100 were 50% and 54% in the DF and rhTM groups, respectively. The 100-day overall survival rates were 50% in the DF group, and 48% in the rhTM group. Several severe hemorrhagic adverse events were observed in one patient in the DF group and five patients in the rhTM group. The main causes of death were SOS-related death, and no patient died of direct adverse events of DF or rhTM. Our results suggest that rhTM, as well as DF, can be effective as a novel treatment option for SOS.

Retrospective analysis of primary plasma cell leukemia in Kansai Myeloma Forum registry

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The prevalence of pPCL was 1.2%.

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Treatment with novel agents and transplantation may yield a better prognosis.

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Hypercalcemia at diagnosis was suggested to predict worse outcomes.

We retrospectively analyzed twenty-six patients with primary plasma cell leukemia (pPCL) registered from May 2005 until April 2015 by the Kansai Myeloma Forum. Twenty patients received novel agents (bortezomib or lenalidomide), and their median survival of was 34 months. The median survival of patients who underwent autologous stem cell transplantation (SCT) was 40 months, those undergoing allogeneic SCT 55 months, and those undergoing both types of SCT (auto–allo) 61 months; whereas for those who did not undergo SCT it was 28 months (p = 0.845). The only statistically significant risk factor identified by multivariate analysis was hypercalcemia.

Chromosomal abnormality variation detected by G-banding is associated with prognosis of diffuse large B-cell lymphoma treated by R-CHOP-based therapy

Diffuse large B-cell lymphoma (DLBCL), which is the most prevalent disease subtype of non-Hodgkin lymphoma, is highly heterogeneous in terms of cytogenetic and molecular features. This study retrospectively investigated the clinical impact of G-banding-defined chromosomal abnormality on treatment outcomes of DLBCL in the era of rituximab-containing immunochemotherapy. Of 181 patients who were diagnosed with DLBCL and treated with R-CHOP or an R-CHOP-like regimen between January 2006 and April 2014, metaphase spreads were evaluable for G-banding in 120. In these 120 patients, 40 were found to harbor a single chromosomal aberration type; 63 showed chromosomal abnormality variations (CAVs), which are defined by the presence of different types of chromosomal abnormalities in G-banding, including 19 with two CAVs and 44 with ≥3 CAVs; and 17 had normal karyotypes. No specific chromosomal break point or numerical abnormality was associated with overall survival (OS) or progression-free survival (PFS), but the presence of ≥3 CAVs was significantly associated with inferior OS rates (hazard ratio (HR): 2.222, 95% confidence interval (CI): 1.056-4.677, P = 0.031) and tended to be associated with shorter PFS (HR: 1.796, 95% CI: 0.965-3.344, P = 0.061). In addition, ≥3 CAVs more frequently accumulated in high-risk patients, as defined by several conventional prognostic indices, such as the revised International Prognostic Index. In conclusion, our results suggest that the emergence of more CAVs, especially ≥3, based on chromosomal instability underlies the development of high-risk disease features and a poor prognosis in DLBCL.

Effects of Prophylactic Foscarnet on Human Herpesvirus-6 Reactivation and Encephalitis in Cord Blood Transplant Recipients: A Prospective Multicenter Trial with an Historical Control Group

Cord blood transplantation (CBT) is a distinct risk factor for human herpesvirus-6 (HHV-6) reactivation and HHV-6 encephalitis. In a prospective multicenter trial we investigated the effects of prophylactic foscarnet (90 mg/kg i.v. infusion from days 7 to 27 after CBT) on the occurrence of HHV-6 reactivation, HHV-6 encephalitis, and acute graft-versus-host disease (aGVHD) in CBT recipients. Between 2014 and 2016, 57 patients were included in a foscarnet-prophylaxis group. Outcomes were compared with an historical control group who received CBT between 2010 and 2014 (standard-treatment group, n = 63). The cumulative incidence of high-level HHV-6 reactivation, defined as plasma HHV-6 DNA ≥ 10⁴ copies/mL, at 60 days after CBT was significantly lower in the foscarnet-prophylaxis group than in the standard-treatment group (18.3% versus 57.3%, P < .001). Multivariate analysis revealed that myeloablative preconditioning and standard treatment were significant risk factors for high-level HHV-6 reactivation. The cumulative incidence of HHV-6 encephalitis at 60 days after CBT was not different between the groups (foscarnet-prophylaxis group, 12.4%; standard-treatment group, 4.9%; P = .14). The cumulative incidences of grades II to IV and grades III to IV aGVHD at 60 days after CBT were not different between the groups (grades II to IV aGVHD: foscarnet-prophylaxis group, 42.0%; standard-treatment group, 40.5%; P = .96; grades III to IV aGVHD: foscarnet-prophylaxis group, 14.5%; standard-treatment group, 14.5%; P = 1.00). In the setting of this study foscarnet significantly suppressed systemic HHV-6 reactivation in CBT recipients but failed to prevent the development of HHV-6 encephalitis. Suppression of HHV-6 reactivation by foscarnet did not show any effects against the incidence of aGVHD.

High-risk follicular lymphomas harbour more somatic mutations including those in the AID-motif

We investigated clinical and genetic characteristics of high-risk follicular lymphoma (FL), that lacked evidence of large cell transformation at diagnosis, in the rituximab era. First, we retrospectively analysed the clinical features of 100 patients with non-transformed FL that were consecutively treated with rituximab-containing therapies in a discovery cohort. The presence of either peripheral blood and/or bone involvement was associated with short progression-free survival. This was confirmed in a validation cohort of 66 FL patients. Then, whole exome sequencing was performed on randomly selected 5 high- and 9 standard-risk FL tumours. The most common mutational signature was a CG > TG substitution-enriched signature associated with spontaneous deamination of 5-methylcytosine at CpG, but mutations in WA and WRC(Y) motifs (so-called activation-induced cytidine deaminase (AID) motifs) were also enriched throughout the whole exome. We found clustered mutations in target sequences of AID in the IG and BCL2 loci. Importantly, high-risk FLs harboured more somatic mutations (mean 190 vs. 138, P = 0.04), including mutations in WA (33 vs. 22, P = 0.038), WRC (34 vs. 22, P = 0.016) and WRCY motifs (17 vs. 11, P = 0.004). These results suggest that genomic instability that allows for emergence of distinct mutations through AID activity underlies development of the high-risk FL phenotype.

Epigenetic repression of miR-375 is the dominant mechanism for constitutive activation of the PDPK1/RPS6KA3 signalling axis in multiple myeloma

Cytogenetic/molecular heterogeneity is the hallmark of multiple myeloma (MM). However, we recently showed that the serine/threonine kinase PDPK1 and its substrate RPS6KA3 (also termed RSK2) are universally active in MM, and play pivotal roles in myeloma pathophysiology. In this study, we assessed involvement of aberrant miR-375 repression in PDPK1 overexpression in MM. An analysis of plasma cells from 30 pre-malignant monoclonal gammopathies of undetermined significance and 73 MM patients showed a significant decrease in miR-375 expression in patient-derived plasma cells regardless of the clinical stage, compared to normal plasma cells. Introduction of miR-375 reduced PDPK1 expression in human myeloma cell lines (HMCLs), indicating that miR-375 is the dominant regulator of PDPK1 expression. In addition, miR-375 introduction also downregulated IGF1R and JAK2 in HMCLs. CpG islands in the MIR375 promoter were pathologically hypermethylated in all 8 HMCLs examined and in most of 58 patient-derived myeloma cells. Treatment with SGI-110, a hypomethylating agent, and/or trichostatin A, a histone deacetylase inhibitor, increased miR-375 expression, but repressed PDPK1, IGF1R and JAK2 in HMCLs. Collectively, these results show the universal involvement of overlapping epigenetic dysregulation for abnormal miR-375 repression in MM, which is likely to contribute to myelomagenesis and to subsequent myeloma progression by activating oncogenic signalling pathways.