A novel small molecule agent displays potent anti-myeloma activity by inhibiting the JAK2-STAT3 signaling pathway

The ubiquitin ligase HERC4 suppresses MafA transcriptional activity triggered by GSK3β in myeloma by atypical K63-linked polyubiquitination

MafA and c-Maf are close members of the Maf transcription factor family and indicators of poor prognosis of multiple myeloma (MM). Our previous study finds that the ubiquitin ligase HERC4 induces c-Maf degradation but stabilizes MafA, and the mechanism is elusive. In the present study we find that HERC4 interacts with MafA and mediates its K63-linked polyubiquitination at K33. Moreover, HERC4 inhibits MafA phosphorylation and its transcriptional activity triggered by glycogen synthase kinase 3β (GSK3β). The K33R MafA variant prevents HERC4 from inhibiting MafA phosphorylation and increases MafA transcriptional activity. Further analyses reveal that MafA can also activate the STAT3 signaling but it is suppressed by HERC4. Lastly, we demonstrate that lithium chloride, a GSK3β inhibitor, can upregulate HERC4 and synergizes dexamethasone, a typical anti-MM drug, in inhibiting MM cell proliferation and xenograft growth in nude mice. These findings thus highlight a novel regulation of MafA oncogenic activity in MM and provide the rationale by targeting HERC4/GSK3β/MafA for the treatment of MM.

Targeting the oncogenic transcription factor c-Maf for the treatment of multiple myeloma

Multiple myeloma (MM) is a hematologic malignancy derived from clonal expansion of plasma cells within the bone marrow and it may progress to the extramedullary region in late stage of the disease course. c-Maf, an oncogenic zipper leucine transcription factor, is overexpressed in more than 50% MM cell lines and primary species in association with chromosomal translocation, aberrant signaling transduction and modulation of stability. By triggering the transcription of critical genes including CCND2, ITGB7, CCR1, ARK5, c-Maf promotes MM progress, proliferation, survival and chemoresistance. Notably, c-Maf is usually expressed at the embryonic stage to promote cell differentiation but less expressed in healthy adult cells. c-Maf has long been proposed as a promising therapeutic target of MM and a panel of small molecule compounds have been identified to downregulate c-Maf and display potent anti-myeloma activities. In the current article, we take a concise summary on the advances in c-Maf biology, pathophysiology, and targeted drug discovery in the potential treatment of MM.

Glaucocalyxin A suppresses multiple myeloma progression in vitro and in vivo through inhibiting the activation of STAT3 signaling pathway

Background

Multiple myeloma (MM) is the most common malignant hematological disease in the people worldwide. Glaucocalyxin A (GLA) is a bioactive ent-kauranoid diterpenoid, that is derived from Rabdosia japonica var. GLA has been demonstrated that it had various pharmacological activities, such as anti-coagulation, anti-bacterial, anti-tumor, anti-inflammation, antioxidant activities. Although GLA has effective anti-tumor properties, its effects on multiple myeloma remain unclear. The aim of this study was to examine the possible anti-cancer effects of GLA and their molecular mechanisms on MM cells in vitro and in vivo.

Methods

To evaluate the role of GLA on the proliferation of MM cells in vitro and in vivo, we used MTT method to detect the role of GLA on the proliferation of MM cells. Cell apoptosis and cell cycle assay were evaluated by flow cytometry. Protein expressions in GLA-treated and untreated MM cells were evaluated by western blot analyses. MM xenograft nude mice model was used to investigate the role of GLA on the proliferation of MM cells in vivo. IHC assay was used to examine the role of GLA on the MM xenograft model in vivo.

Results

In the present study, we firstly reported the potent anti-myeloma activity of GLA on MM cells. We found that GLA could induce apoptosis in vitro and in vivo. GLA could inhibit the phosphorylation of the signal transducer and activator of transcription 3 (STAT3) and downregulate interleukin IL-6 induced STAT3 phosphorylation in MM. Overexpression of STAT3 could significantly prevent apoptosis induced by GLA; while knockdown of STAT3 enhanced it. Moreover, GLA could inhibit cell proliferation by inducing the cell cycle arrest. GLA reduced the expression of cell cycle-related proteins CCNB1, CCND1, CCND2, and CCND3 and increased the expression of p21 in MM cell lines. In addition, in the MM xenograft nude mice model, GLA exhibited very good anti-myeloma activity. Administration of GLA almost completely inhibited tumor growth within 19 days without physical toxicity. And the IHC results showed GLA significantly inhibited cell proliferation and interfered STAT3 pathway on MM xenograft model tumor tissues.

Conclusions

Taken together, our present research indicated that GLA inhibits the MM cell proliferation, induces MM cell apoptosis and cell cycle arrest through blocking the activation of STAT3 pathway. Thus, GLA may be a potential therapeutic candidate for MM patients in the future.

Patient similarity network of newly diagnosed multiple myeloma identifies patient subgroups with distinct genetic features and clinical implications

The remarkable genetic heterogeneity of multiple myeloma poses a substantial challenge for proper prognostication and clinical management of patients. Here, we introduce MM-PSN, the first multiomics patient similarity network of myeloma. MM-PSN enabled accurate dissection of the genetic and molecular landscape of the disease and determined 12 distinct subgroups defined by five data types generated from genomic and transcriptomic profiling of 655 patients. MM-PSN identified patient subgroups not previously described defined by specific patterns of alterations, enriched for specific gene vulnerabilities, and associated with potential therapeutic options. Our analysis revealed that co-occurrence of t(4;14) and 1q gain identified patients at significantly higher risk of relapse and shorter survival as compared to t(4;14) as a single lesion. Furthermore, our results show that 1q gain is the most important single lesion conferring high risk of relapse and that it can improve on the current International Staging Systems (ISS and R-ISS).

Astragaloside IV Protects 6-Hydroxydopamine-Induced SH-SY5Y Cell Model of Parkinson's Disease via Activating the JAK2/STAT3 Pathway

Objectives

Astragaloside IV (AS-IV), the main active component of Astragalus membranaceus, bears anti-inflammatory, antioxidant, and neuroprotective activity. Parkinson’s disease (PD) is a common neurodegenerative disease. This study explored the protective effect of AS-IV on the cell model of PD.

Materials and Methods

SH-SY5Y cells were incubated with different concentrations (10, 50, 100, 150, and 200 μM) of 6-hydroxydopamine (6-OHDA) for 0, 3, 6, 12, 24, and 48 h to establish the PD cell model. Different concentrations (0, 25, 50, 100, 150, and 200 μM) of AS-IV or 15 mM JAK2/STAT3 pathway inhibitor SC99 was added for intervention 2 h before 6-OHDA treatment. The viability and morphological damage of 6-OHDA-treated SH-SY5Y cells were measured using MTT assay and Hoechst 33258 staining. The expression of microtubule associated protein 2 (MAP2) was detected by immunofluorescence staining. The levels of inflammation and oxidative stress were measured using ELISA. Apoptosis of 6-OHDA-treated SH-SY5Y cells was detected using flow cytometry, and phosphorylation level of JAK2 and STAT3 were detected using Western blot analysis.

Results

The survival rate of SH-SY5Y cells treated with 100 μM 6-OHDA for 24 h was about 50%. AS-IV (25–100 μM) significantly improved the viability (all p < 0.01), increased MAP2 expression, and repaired the morphological damage induced by 6-OHDA. AS-IV inhibited IL-1β, IL-6, and TNF-α level (all p < 0.05), reduced MDA and ROS content and increased SOD concentration, thereby reducing inflammation and oxidative stress (all p < 0.01) in 6-OHDA-treated SH-SY5Y cells. Moreover, AS-IV decreased apoptosis rate and Bax/Bcl-2 ratio induced by 6-OHDA (all p < 0.05). Mechanically, AS-IV significantly increased the phosphorylation of JAK2 and STAT3 (p < 0.01); the addition of SC99 decreased the cell viability, increased the apoptosis rate, enhanced the levels of inflammatory factors and oxidative stress.

Conclusion

AS-IV enhanced the cell viability, and inhibited apoptosis, inflammation and oxidative stress of 6-OHDA-treated SH-SY5Y cells via activating the JAK2/STAT3 signaling pathway. This study may confer novel insights for the management of PD.

Future of Personalized Therapy Targeting Aberrant Signaling Pathways in Multiple Myeloma

Multiple myeloma (MM) is a genetically complex disease. Identification of mutations and aberrant signaling pathways that contribute to the progression of MM and drug resistance has potential to lead to specific targets and personalized treatment. Aberrant signal pathways include RAS pathway activation due to RAS or BRAF mutations (targeted by vemurafenib alone or combined with cobimetinib), BCL-2 overexpression in t(11:14) (targeted by venetoclax), JAK2 pathway activation (targeted by ruxolitinib), NF-κB pathway activation (treated with DANFIN combined with bortezomib), MDM2 overexpression, and PI3K/mTOR pathway activation (targeted by BEZ235). Cyclin D1 (CCND1) and MYC are also emerging as key potential targets. In addition, histone deacetylase inhibitors are already in use for the treatment of MM in combination therapy, and targeted inhibition of FGFR3 (AZD4547) is effective in myeloma cells with t(4;14) translocation. Bromodomain and extra terminal (BET) protein antagonists decrease the expression of MYC and have displayed promising antimyeloma activity. A better understanding of the alterations in signaling pathways that promote MM progression will further inform the development of precision therapy for patients.

Decoration of Anti-CD38 on Nanoparticles Carrying a STAT3 Inhibitor Can Improve the Therapeutic Efficacy Against Myeloma

STAT3 is an oncoprotein which has been shown to contribute to drug resistance in multiple myeloma (MM). Nonetheless, the clinical utility of STAT3 inhibitors in treating MM has been limited, partly related to some of their pharmacologic properties. To overcome these challenges, our group had previously packaged STAT3 inhibitors using a novel formulation of nanoparticles (NP) and found encouraging results. In this study, we aimed to further improve the pharmacologic properties of these NP by decorating them with monoclonal anti-CD38 antibodies. NP loaded with S3I-1757 (a STAT3 inhibitor), labeled as S3I-NP, were generated. S3I-NP decorated with anti-CD38 (labeled as CD38-S3I-NP) were found to have a similar nanoparticular size, drug encapsulation, and loading as S3I-NP. The release of S3I-1757 at 24 h was also similar between the two formulations. Using Cy5.5 labeling of the NP, we found that the decoration of anti-CD38 on these NP significantly increased the cellular uptake by two MM cell lines (p < 0.001). Accordingly, CD38-S3I-NP showed a significantly lower inhibitory concentration at 50% (IC50) compared to S3I-NP in two IL6-stimulated MM cell lines (p < 0.001). In a xenograft mouse model, CD38-S3I-NP significantly reduced the tumor size by 4-fold compared to S3I-NP on day 12 after drug administration (p = 0.006). The efficacy of CD38-S3I-NP in suppressing STAT3 phosphorylation in the xenografts was confirmed by using immunocytochemistry and Western blot analysis. In conclusion, our study suggests that the decoration of anti-CD38 on NP loaded with STAT3 inhibitors can further improve their therapeutic effects against MM.

Co-culture of ovarian cancer stem-like cells with macrophages induced SKOV3 cells stemness via IL-8/STAT3 signaling

Among recent concepts in the cancer biology field, the tumor microenvironment is highly associated with cancer stem cells, and plays a key role in tumor progression. This study aimed to explore the mechanism that the stemness induction of SKOV3 cell line by macrophages derived from THP-1 cells, which was co-cultured with SKOV3-derived ovarian cancer stem-like cells (OCSLCs). Sphere formation, soft agar colony formation, and expression levels of CD133 and CD44 were assessed to reflect OCSLC properties. ELISA was used to evaluate secretion profile changes in macrophages co-cultured with or without SKOV3-derived OCSLCs. For mechanistic evaluation, rhIL-8, IL-8 neutralizing antibody (IL-8 Ab), signal transducer and activator of transcription 3 (STAT3) shRNA and STAT3 cDNA were used. The results showed that IL-10, VEGF, MMP-9, IL-8 secretion and CD163 and STAT3 expression levels in macrophages co-cultured with OCSLCs were increased compared with those from THP-1 cells, while IL-12 and NO amounts were significantly reduced, reflecting M2 macrophage polarization. Addition of rhIL-8 to THP-1 cell conditioned media promoted M2 macrophage polarization and stemness in SKOV3 cells, which were suppressed by IL-8 Ab addition to co-culture conditioned media. Consistently, overexpression of STAT3 induced M2 macrophage polarization and stemness in SKOV3 cells, which were inhibited by STAT3 knockdown in macrophages from THP-1 cells. Importantly, STAT3 overexpression rescued the effects of IL-8 Ab on M2 macrophage polarization and stemness in SKOV3 cells. These results suggested that stemness induction in SKOV3 cells by macrophages co-cultured with SKOV3-derived OCSLCs involved IL-8/STAT3 signaling.

An inhibitor of cholesterol absorption displays anti-myeloma activity by targeting the JAK2-STAT3 signaling pathway

The activated JAK2-STAT3 signaling pathway is a high risk factor for multiple myeloma (MM), a fatal malignancy of plasma cells. In the present study, SC09, a potential inhibitor of cholesterol absorption, was identified in a STAT3-targeted drug screen. SC09 suppressed the activation of STAT3 in a time-course and concentration-dependent manner but did not affect its family members STAT1 and STAT5. SC09 inhibited STAT3 transcriptional activity and downregulated the expression of STAT3-regulated genes. Further studies showed that SC09 selectively inhibited JAK2 activation but not other kinases including c-Src, ERK, p38 and mTOR that are all associated with STAT3 activation. Moreover, SC09 obviously induced MM cell death in vitro and delayed MM tumor growth in vivo. SC09-induced MM cell death was dependent on the endogenous STAT3 status, and this effect could be attenuated by enforced expression of STAT3. All the results collectively indicated that SC09 blocks the JAK2-STAT3 signaling thus displaying anti-MM activity. Given its well tolerance and anti-MM potency, SC09 is credited for further investigation as a promising drug for MM treatment.

Interferon-stimulated gene 15 induces cancer cell death by suppressing the NF-κB signaling pathway

Interferon-stimulated gene 15 (ISG15) is an important cytokine that has been reported in carcinogenesis. However, we found that ISG15 and de-ISGylase USP18 were induced by several anti-cancer agents, which was confirmed by both RT-PCR and immunoblotting assays. Further studies demonstrated that ectopic ISG15 and USP18 inhibited proliferation of myeloma, leukemia and cervical cancer cells. More importantly, ISG15 and USP18 induced cancer cell apoptosis. This finding was confirmed in a cervical xenograft model in which cervical cancer growth was suppressed by lentiviral ISG15. In the mechanistic study, ISG15 was found to disrupt the NF-κB signaling pathway by downregulating the expression of IKKβ and p65, phosphorylation of p65 and IκBα. Consistent with this finding, ISG15 suppressed the expression of NF-κB recognition element-driving luciferase and decreased the transcription of XIAP and Mcl-1, two typical genes regulated by NF-κB. Therefore, the present study demonstrated that ISG15 induces cancer cell apoptosis by disrupting the NF-κB signaling pathway. This study highlighted a novel role of ISG15 in tumor suppression.

Kinase inhibitors as potential agents in the treatment of multiple myeloma

Recent years have witnessed a dramatic increase in the number of therapeutic options available for the treatment of multiple myeloma (MM) - from immunomodulating agents to proteasome inhibitors to histone deacetylase (HDAC) inhibitors and, most recently, monoclonal antibodies. Used in conjunction with autologous hematopoietic stem cell transplantation, these modalities have nearly doubled the disease's five-year survival rate over the last three decades to about 50%. In spite of these advances, MM still is considered incurable as resistance and relapse are common. While small molecule protein kinase inhibitors have made inroads in the therapy of a number of cancers, to date their application to MM has been less than successful. Focusing on MM, this review examines the roles played by a number of kinases in driving the malignant state and the rationale for target development in the design of a number of kinase inhibitors that have demonstrated anti-myeloma activity in both in vitro and in vivo xenograph models, as well as those that have entered clinical trials. Among the targets and their inhibitors examined are receptor and non-receptor tyrosine kinases, cell cycle control kinases, the PI3K/AKT/mTOR pathway kinases, protein kinase C, mitogen-activated protein kinase, glycogen synthase kinase, casein kinase, integrin-linked kinase, sphingosine kinase, and kinases involved in the unfolded protein response.

The Class I PI3K inhibitor S14161 induces autophagy in malignant blood cells by modulating the Beclin 1/Vps34 complex

S14161 is a pan-Class I PI3K inhibitor that induces blood cancer cell death, but its mechanism is largely unknown. In the present study, we evaluated the role of S14161 in autophagy, an emerging event in cell destination. Multiple myeloma cell lines RPMI-8226, OPM2, KMS11 and leukemia cell line K562 were treated with S14161. The results showed that S14161 induced autophagy as demonstrated by increased LC3-II and decreased p62, which were prevented by autophagy inhibitors including 3-methyladenine and bafilomycin A1. Mechanistic studies showed that S14161 had no effects on Vps34 expression, but increased Beclin 1 and decreased Bcl-2, two major regulators of autophagy. Furthermore, S14161 dissociated the Beclin 1/Bcl-2 complex and enhanced the formation of Beclin 1/Vps34 complex. Moreover, S14161 inhibited the mTORC1 signaling transduction. S14161 downregulated activation of mTOR and its two critical targets 4E-BP1 and p70S6K, suggesting S14161 inhibited protein synthesis. Taken together, these results demonstrated that Class I PI3K regulates autophagy by modulating protein synthesis and the Beclin 1 signaling pathway. This finding helps understanding the roles of PI3K in autophagy and cancer treatment.

A novel STAT3 inhibitor negatively modulates platelet activation and aggregation

The signal transducer and activator of transcription 3 (STAT3) plays a critical role in platelet functions. This study sought to understand the effects of the STAT3 inhibitor SC99 on platelet activation and aggregation. Immunoblotting assays were applied to measure the effects of SC99 on the STAT3 signaling pathway. A ChronoLog aggregometer was used to evaluate platelet aggregation. A flow cytometer was used to evaluate P-selectin expression in the presence of SC99. AlamarBlue and Annexin-V staining were used to evaluate platelet viability and apoptosis, respectively. A fluorescence microscope was applied to analyze platelet spreading. SC99 inhibited the phosphorylation of JAK2 and STAT3 in human platelets but had no effects on the phosphorylation of AKT, p65 or Src, all of which are involved in platelet activation. Further studies revealed that SC99 inhibited human platelet aggregation induced by collagen and thrombin in a dose-dependent manner. SC99 inhibited thrombin-induced P-selectin expression and fibrinogen binding to single platelets. Moreover, SC99 inhibited platelet spreading on fibrinogen and clot retraction mediated by outside-in signaling. SC99 inhibited platelet aggregation in mice but it did not significantly prolong the bleeding time. Taken together, the present study revealed that SC99 inhibited platelet activation and aggregation as a STAT3 inhibitor. This agent can be developed as a promising treatment for thrombotic disorders.

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.

Discovery of monocarbonyl curcumin-BTP hybrids as STAT3 inhibitors for drug-sensitive and drug-resistant breast cancer therapy

Signal transducer and activator of transcription 3 (STAT3) is a well-known antitumor target. Exogenous ROS insult can lead to selective cytotoxicity against cancer cells. A combination of STAT3 inhibition and “oxidation therapy” may be a new strategy to address the multidrug-resistance issue due to their important roles in the survival and drug resistance of cancer cells. Here, a series of novel curcumin-BTP hybrids were designed and evaluated as STAT3 inhibitors with ROS production activity. Compound 6b exerted the best antitumor activity and selectivity for MCF-7 and MCF-7/DOX cells (IC₅₀ = 0.52 μM and 0.40 μM, respectively), while its IC₅₀ value for MCF-10A breast epithelial cells was 7.72 μM. Furthermore, compound 6b suppressed STAT3 phosphorylation, nuclear translocation and DNA-binding activity and the expression of STAT3 specific oncogenes. Increases in the level of IL-6-induced p-STAT3 were also inhibited by 6b without influencing IFN-γ-induced p-STAT1 expression. Additionally, 6b effectively promoted intracellular ROS accumulation, induced cancer cell apoptosis and cell cycle arrest, abolished the colony formation ability of breast cancer cells, and inhibited P-gp expression in MCF-7/DOX cells. Finally, 6b suppressed the growth of implanted human breast cancer in vivo. Our findings highlight that 6b may be a promising therapeutic agent for drug-sensitive and drug-resistant breast cancers.

Natural product pectolinarigenin inhibits osteosarcoma growth and metastasis via SHP-1-mediated STAT3 signaling inhibition

Signal transducer and activator of transcription 3 (STAT3) has important roles in cancer aggressiveness and has been confirmed as an attractive target for cancer therapy. In this study, we used a dual-luciferase assay to identify that pectolinarigenin inhibited STAT3 activity. Further studies showed pectolinarigenin inhibited constitutive and interleukin-6-induced STAT3 signaling, diminished the accumulation of STAT3 in the nucleus and blocked STAT3 DNA-binding activity in osteosarcoma cells. Mechanism investigations indicated that pectolinarigenin disturbed the STAT3/DNA methyltransferase 1/HDAC1 histone deacetylase 1 complex formation in the promoter region of SHP-1, which reversely mediates STAT3 signaling, leading to the upregulation of SHP-1 expression in osteosarcoma. We also found pectolinarigenin significantly suppressed osteosarcoma cell proliferation, induced apoptosis and reduced the level of STAT3 downstream proteins cyclin D1, Survivin, B-cell lymphoma 2 (Bcl-2), B-cell lymphoma extra-large (Bcl-xl) and myeloid cell leukemia 1 (Mcl-1). In addition, pectolinarigenin inhibited migration, invasion and reserved epithelial–mesenchymal transition (EMT) phenotype in osteosarcoma cells. In spontaneous and patient-derived xenograft models of osteosarcoma, we identified administration (intraperitoneal) of pectolinarigenin (20 mg/kg/2 days and 50 mg/kg/2 days) blocked STAT3 activation and impaired tumor growth and metastasis with superior pharmacodynamic properties. Taken together, our findings demonstrate that pectolinarigenin may be a candidate for osteosarcoma intervention linked to its STAT3 signaling inhibitory activity.