Targeting p53 via JNK Pathway: A Novel Role of RITA for Apoptotic Signaling in Multiple Myeloma

The low frequency of p53 alterations e.g., mutations/deletions (∼10%) in multiple myeloma (MM) makes this tumor type an ideal candidate for p53-targeted therapies. RITA is a small molecule which can induce apoptosis in tumor cells by activating the p53 pathway. We previously showed that RITA strongly activates p53 while selectively inhibiting growth of MM cells without inducing genotoxicity, indicating its potential as a drug lead for p53-targeted therapy in MM. However, the molecular mechanisms underlying the pro-apoptotic effect of RITA are largely undefined. Gene expression analysis by microarray identified a significant number of differentially expressed genes associated with stress response including c-Jun N-terminal kinase (JNK) signaling pathway. By Western blot analysis we further confirmed that RITA induced activation of p53 in conjunction with up-regulation of phosphorylated ASK-1, MKK-4 and c-Jun. These results suggest that RITA induced the activation of JNK signaling. Chromatin immunoprecipitation (ChIP) analysis showed that activated c-Jun binds to the activator protein-1 (AP-1) binding site of the p53 promoter region. Disruption of the JNK signal pathway by small interfering RNA (siRNA) against JNK or JNK specific inhibitor, SP-600125 inhibited the activation of p53 and attenuated apoptosis induced by RITA in myeloma cells carrying wild type p53. On the other hand, p53 transcriptional inhibitor, PFT-α or p53 siRNA not only inhibited the activation of p53 transcriptional targets but also blocked the activation of c-Jun suggesting the presence of a positive feedback loop between p53 and JNK. In addition, RITA in combination with dexamethasone, known as a JNK activator, displays synergistic cytotoxic responses in MM cell lines and patient samples. Our study unveils a previously undescribed mechanism of RITA-induced p53-mediated apoptosis through JNK signaling pathway and provides the rationale for combination of p53 activating drugs with JNK activators in the treatment of MM

Suppressing miRNA-15a/-16 expression by interleukin-6 enhances drug-resistance in myeloma cells

The bone marrow microenvironment facilitates the survival, differentiation, and proliferation of myeloma (MM) cells. This study identified that microRNA-15a and -16 expressions tightly correlated with proliferation and drug sensitivity of MM cells. miRNA-15a/-16 expression in MM cells was significantly increased after treatment with cytotoxic agents. The interaction of bone marrow stromal cells (BMSC) with MM cells resulted in decreased miRNA-15a/-16 expression and promoted the survival of the MM cells. Interleukin-6 (IL-6) produced by BMSCs suppressed the expression of miRNA-15a and 16 in a time- and dose- dependent pattern, with the suppression on miRNA-15a being more significant than on miRNA-16. miRNA-15a-transfected MM cells were found to be arrested in G1/S checkpoint, and the transfected MM cells had decreased growth and survival. In conclusion, our data suggest that via suppressing miRNA-15a and -16 expressions, IL-6 secreted by BMSCs promotes drug-resistance in myeloma cells

Critical Role of AKT in Myeloma-induced Osteoclast Formation and Osteolysis

Abnormal osteoclast formation and osteolysis are the hallmarks of multiple myeloma (MM) bone disease, yet the underlying molecular mechanisms are incompletely understood. Here, we show that the AKT pathway was up-regulated in primary bone marrow monocytes (BMM) from patients with MM, which resulted in sustained high expression of the receptor activator of NF-κB (RANK) in osteoclast precursors. The up-regulation of RANK expression and osteoclast formation in the MM BMM cultures was blocked by AKT inhibition. Conditioned media from MM cell cultures activated AKT and increased RANK expression and osteoclast formation in BMM cultures. Inhibiting AKT in cultured MM cells decreased their growth and ability to promote osteoclast formation. Of clinical significance, systemic administration of the AKT inhibitor LY294002 blocked the formation of tumor tissues in the bone marrow cavity and essentially abolished the MM-induced osteoclast formation and osteolysis in SCID mice. The level of activating transcription factor 4 (ATF4) protein was up-regulated in the BMM cultures from multiple myeloma patients. Adenoviral overexpression of ATF4 activated RANK expression in osteoclast precursors. These results demonstrate a new role of AKT in the MM promotion of osteoclast formation and bone osteolysis through, at least in part, the ATF4-dependent up-regulation of RANK expression in osteoclast precursors

Minor clone of del(17p) provides a reservoir for relapse in multiple myeloma

The deletion of chromosome 17p (del(17p)) is considered a crucial prognostic factor at the time of diagnosis in patients with multiple myeloma (MM). However, the impact of del(17p) on survival at different clonal sizes at relapse, as well as the patterns of clonal evolution between diagnosis and relapse and their prognostic value, has not been well described. To address these issues, we analyzed the interphase fluorescence in situ hybridization (iFISH) results of 995 newly diagnosed MM (NDMM) patients and 293 patients with MM at their first relapse. Among these patients, 197 had paired iFISH data at diagnosis and first relapse. Our analysis of paired iFISH revealed that a minor clone of del(17p) at relapse but not at diagnosis was associated with poor prognosis in MM (hazard ratio for median overall survival 1.64 vs. 1.44). Fifty-six and 12 patients developed one or more new cytogenetic abnormalities at relapse, mainly del(17p) and gain/amp(1q), respectively. We classified the patients into six groups based on the change patterns in the clonal size of del(17p) between the two time points. Patients who did not have del(17p) during follow-up showed the best outcomes, whereas those who acquired del(17p) during their disease course, experienced compromised survival (median overall survival: 61.3 vs. 49.4 months; hazard ratio =1.64; 95% confidence interval: 1.06-2.56; P<0.05). In conclusion, our data confirmed the adverse impact of a minor clone of del(17p) at relapse and highlighted the importance of designing optimal therapeutic strategies to eliminate high-risk cytogenetic abnormalities (clinicaltrials gov. identifier: NCT04645199)

LILRB4 represents a promising target for immunotherapy by dual targeting tumor cells and myeloid-derived suppressive cells in multiple myeloma

Multiple myeloma (MM) remains an incurable hematological malignancy. Despite tremendous advances in the treatment, about 10% of patients still have very poor outcomes with median overall survival less than 24 months. Our study aimed to underscore the critical mechanisms pertaining to the rapid disease progression and provide novel therapeutic selection for these ultra-high-risk patients. We utilized single-cell transcriptomic sequencing to dissect the characteristic bone marrow niche of patients with survival of less than two years (EM24). Notably, an enrichment of LILRB4high pre-matured plasma-cell cluster was observed in the patients in EM24 compared to patients with durable remission. This cluster exhibited aggressive proliferation and drug-resistance phenotype. High-level LILRB4 promoted MM clonogenicity and progression. Clinically, high expression of LILRB4 was correlated with poor prognosis in both newly diagnosed MM patients and relapsed/refractory MM patients. The ATAC-seq analysis identified that high chromosomal accessibility caused the elevation of LILRB4 on MM cells. CRISPR-Cas9 deletion of LILRB4 alleviated the growth of MM cells, inhibited the immunosuppressive function of MDSCs, and further rescued T cell dysfunction in MM microenvironment. The more infiltration of myeloid-derived suppressive cells (MDSCs) was observed in EM24 patients as well. Therefore, we innovatively generated a TCR-based chimeric antigen receptor (CAR) T cell, LILRB4-STAR-T. Cytotoxicity experiment demonstrated that LILRB4-STAR-T cells efficaciously eliminated tumor cells and impeded MDSCs function. In conclusion, our study elucidates that LILRB4 is an ideal biomarker and promising immunotherapy target for high-risk MM. LILRB4-STAR-T cell immunotherapy is promising against tumor cells and immunosuppressive tumor microenvironment in MM

Detection of recurrent cytogenetic aberrations in multiple myeloma: A comparison between MLPA and iFISH

Multiple myeloma (MM) is a genetically heterogeneous disease with diverse clinical characteristics and outcomes. Recently, multiplex ligation-dependent probe amplification (MLPA) has emerged as an effective and robust method for the detection of cytogenetic aberrations in MM patients. In the present study, MLPA analysis was applied to analyze cytogenetics of CD138 tumor cells of 59 MM samples, and its result was compared, retrospectively, with the interphase fluorescence in situ hybridization (iFISH) data. We firstly established the normal range of each of the 42 diagnostic probes using healthy donor samples. A total of 151 aberrations were detected in 59 patient samples, and 49/59 cases (83.1%) harbored at least one copy number variation. Overall, 0–7 aberrations were detected per case using MLPA, indicating the heterogeneity and complexity of MM cytogenetics. We showed the high efficiency of MLPA and the high congruency of the two methods to assess cytogenetic aberrations. Considering that MLPA analysis is not reliable when the aberration only exits in a small population of tumor cells, it is essential to use both MLPA and iFISH as complementary techniques for the diagnosis of MM

Phase I study of the Syk inhibitor sovleplenib in relapsed or refractory mature B-cell tumors

Sovleplenib (HMPL-523) is a selective spleen tyrosine kinase (Syk) inhibitor with antitumor activity in preclinical models of B-cell malignancy. We conducted a dose-escalation and dose-expansion phase I study of sovleplenib in patients with relapsed/refractory mature Bcell tumors. Dose escalation followed a 3+3 design; patients received oral sovleplenib (200-800 mg once daily [q.d.] or 200 mg twice daily [b.i.d.], 28-day cycles). During dose expansion, patients were enrolled into four cohorts per lymphoma classification and treated at the recommended phase 2 dose (RP2D). Overall, 134 Chinese patients were enrolled (dose escalation, n=27; dose expansion, n=107). Five patients experienced dose-limiting toxicities: one each of amylase increased (200 mg q.d.), febrile neutropenia (800 mg q.d), renal failure (800 mg q.d.), hyperuricemia and blood creatine phosphokinase increased (200 mg b.i.d.) and blood bilirubin increased and pneumonia (200 mg b.i.d.). RP2D was determined as 600 mg (>65 kg) or 400 mg (≤65 kg) q.d. The primary efficacy end point of independent review committee–assessed objective response rate in indolent B-cell lymphoma was 50.8% (95% CI, 37.5–64.1) in 59 evaluable patients at RP2D (follicular lymphoma: 60.5%, marginal zone lymphoma: 28.6%, lymphoplasmacytic lymphoma/Waldenström macroglobulinemia, 0%). The most common (≥10% patients) grade ≥3 treatment-related adverse events in the doseexpansion phase were decreased neutrophil count (29.9%), pneumonia (12.1%) and decreased white blood cell count (11.2%). Pharmacokinetic exposures increased doseproportionally with ascending dose levels from 200–800 mg, without observed saturation. Sovleplenib showed antitumor activity in relapsed/refractory B-cell lymphoma with acceptable safety. Further studies are warranted