Backgroud Multiple myeloma (MM) is an incurable plasma cell malignancy in the bone marrow (BM), while immunoglobulin D type of MM (IgD MM) is a very rare but most severe subtype in all MM cases. Therefore, systemic study on IgD MM is purposeful to disclose the recurrent and refractory features in both IgD and other types of MM, and beneficial to the development of potent therapeutic strategy on MM. Methods Agilent SBC-ceRNA microarray chips were employed to examine 3 normal plasma cell samples (NPCs), 5 lgD MM samples and 5 lgG MM samples, respectively. Sanger sequencing, RNase R digestion and qPCR assays were used to detect the existence and expression of circHNRNPU. BaseScope™ RNA ISH assay was performed to test circHNRNPU levels in paraffin-embedded MM tissues. The protein encoded by circHNRNPU was identified by LC-MS/MS, which was named as circHNRNPU_603aa. The function of circHNRNPU_603aa on cellular proliferation and cell cycle was assessed by MTT test, colony formation assay, flow cytometry and MM xenograft mouse model in vivo. RIP-seq, RIP-PCR and WB analysis for ubiquitination were performed to explore the potential mechanism of circHNRNPU_603aa in MM. Exosomes were isolated from the culture supernatant of MM cells by ultracentrifugation and characterized by Transmission Electron Microscope and WB confirmation of exosomes markers Alix and CD9. Results CircHNRNPU was one of the top most abundant and differentially expressed circRNA in IgD MM relative to lgG and NPCs samples. Increased circHNRNPU was associated with poor outcomes in four independent MM patient cohorts. Intriguingly, MM cells secreted circHNRNPU, which encoded a protein named as circHNRNPU_603aa. Overexpressed circHNRNPU_603aa promoted MM cell proliferation in vitro and in vivo, in contrast knockdown of circHNRNPU_603aa by siRNA abrogated these effects. Due to circHNRNPU_603aa including RNA-binding RGG-box region, it regulated SKP2 exon skipping, thereby competitively inhibited c-Myc ubiquitin so as to stabilize c-Myc in MM. MM cells secreted circHNRNPU through exosomes to interfere with various cells in the BM microenvironment. Conclusion Our findings demonstrate that circHNRNPU_603aa is a promising diagnostic and therapeutic marker in both MM cells and BM niche.

Background Multiple myeloma (MM) is a clinically and biologically heterogeneous plasma‐cell malignancy. Despite extensive research, disease heterogeneity and relapse remain a big challenge in MM therapeutics. We tried to dissect this disease and identify novel biomarkers for patient stratification and treatment outcome prediction by applying single‐cell technology. Methods We performed single‐cell RNA sequencing (scRNA‐seq) and variable‐diversity‐joining regions‐targeted sequencing (scVDJ‐seq) concurrently on bone marrow samples from a cohort of 18 patients with newly diagnosed MM (NDMM; n = 12) or refractory/relapsed MM (RRMM; n = 6). We analysed the malignant clonotypes using scVDJ‐seq data and conducted data integration and cell‐type annotation through the CCA algorithm based on gene expression profiling. Furthermore, we identified disease status‐specific genes and modules by comparison of NDMM and RRMM datasets and explored the findings in a larger MM cohort from the MMRF CoMMpass study. Results We found that all the myeloma cells in either diagnosed or relapsed samples were dominated by a major clone, with a few subclones in several samples (n = 5). Next, we investigated the universal transcriptional features of myeloma cells and identified eight meta‐programs correlated with this disease, especially meta‐programs 1 and 8 (M1 and M8), which were the most significant and related to cell cycle and stress response, respectively. Furthermore, we classified the malignant plasma cells into eight clusters and found that the cell numbers in clusters 2/6/7 were exclusively higher in relapsed samples. Besides, we identified several attractive candidates for biomarkers (e.g. SMAD1 and STMN1) associated with disease progression and relapse in our dataset and related to overall survival in the CoMMpass dataset. Conclusions Our data provide insights into the heterogeneity of MM as well as highlight the relevance of intra‐tumour heterogeneity and discover novel biomarkers that might be a potent therapy.

In this open‐label, single‐arm, phase I/II clinical trial, we evaluated the efficacy of anti‐B cell maturation antigen (BCMA) chimeric antigen receptor (CAR)‐T cell (HDS269B) therapy in 49 relapsed/refractory multiple myeloma (RRMM) patients, including 20 with Eastern Cooperative Oncology Group (ECOG) grade 3–4. After HDS269B infusion (9 × 106 CAR+ cells/kg), 17 patients (34.69%, 11 ECOG 0–2, 6 ECOG 3–4) developed cytokine release syndrome [grade 1–2: 14 patients (28.57%); grade 3: 3 patients (6.12%)]. The objective response rate (ORR) was 77%, with a complete response (CR) achieved in 47%. Ongoing response >12 months occurred in 15 patients, and was extended beyond 38 months in one patient. The median progression‐free survival (PFS) and overall survival (OS) were 10 months (95% CI 5.3–14.7) and 29 months (95% CI 10.0–48.0), respectively. The PFS (12 months) and OS (18 months) rates were 41.64% and 62.76%, respectively. In patients with ECOG 0–2 and 3–4, ORR was 79.31% (23/29) and 75.0% (15/20) and PFS were 15 months (95% CI 5.4–24.6) and 4 months (95% CI 0–11.7), respectively. OS was not reached in ECOG 0–2 patients, but was 10.5 months (95% CI 0–22) in ECOG 3–4 patients. Single‐cell sequencing indicated that treatment efficacy might be related to mTORC1 signaling. Thus, HDS269B therapy is safe and effective for RRMM patients, even those with ECOG 3–4.

Secreted proteins provide crucial signals that have been implicated in the development of acute myeloid leukemia (AML) in the bone marrow microenvironment. Here we identify aberrant expressions of inflammatory IL‐17B and its receptor (IL‐17RB) in human and mouse mixed lineage leukemia–rearranged AML cells, which were further increased after exposure to chemotherapy. Interestingly, silencing of IL‐17B or IL‐17RB led to significant suppression of leukemic cell survival and disease progression in vivo. Moreover, the IL‐17B–IL‐17RB axis protected leukemic cells from chemotherapeutic agent–induced apoptotic effects. Mechanistic studies revealed that IL‐17B promoted AML cell survival by enhancing ERK, NF‐κB phosphorylation, and the expression of antiapoptotic protein B‐cell lymphoma 2, which were reversed by small‐molecule inhibitors. Thus, the inhibition of the IL‐17B–IL‐17RB axis may be a valid strategy to enhance sensitivity and therapeutic benefit of AML chemotherapy.—Guo, H.‐Z., Niu, L.‐T., Qiang, W.‐T., Chen, J., Wang, J., Yang, H., Zhang, W., Zhu, J., Yu, S.‐H. Leukemic IL‐17RB signaling regulates leukemic survival and chemoresistance. FASEB J. 33, 9565–9576 (2019). http://www.fasebj.org