Kinome expression profiling to target new therapeutic avenues in multiple myeloma

Threonine and tyrosine kinase promotes multiple myeloma progression by regulating regucalcin expression

Multiple myeloma (MM) is a malignant proliferative disorder of plasma cells and remains an incurable disease. Threonine and tyrosine kinase (TTK) is a dual-specific protein kinase that targets serine/threonine and tyrosine residues for phosphorylation. Its elevated expression has been linked to unfavorable outcomes in several types of cancer. Although the role of TTK in MM are still incompletely understood. In this research, we assessed TTK mRNA and protein expression levels in 51 MM patients and 30 healthy donors using qRT-PCR and western blotting. The impact of TTK expression on MM cell apoptosis, proliferation, and the cell cycle were assessed through CCK-8 assay, flow cytometry, and western blotting. Our findings revealed a significant overexpression of TTK in multiple myeloma patients and cell lines. TTK knockdown promoted apoptosis and G0/G1 phase arrest while inhibiting proliferation in MM cells, whereas TTK overexpression reduced apoptosis and G0/G1 phase arrest, enhancing proliferation in MM cells. Next, we identified regucalcin (RGN) as a downstream target of TTK through proteomic analysis. In NDMM, the expression of RGN was decreased. Cell function experiments showed that RGN knockdown significantly promoted MM cell proliferation, inhibited apoptosis and reduced cell cycle arrest, and reversed the increased apoptosis, weakened proliferation, and enhanced cell cycle arrest caused by TTK knockdown. Finally, a xenograft mouse model showed that TTK significantly promotes MM development. In summary, we demonstrated that the TTK-RGN axis regulates cell apoptosis, G0/G1 phase arrest, and proliferation in MM, highlighting TTK as a potential target for therapeutic intervention in this cancer.

Understanding mechanisms of resistance to FLT3 inhibitors in adult FLT3-mutated acute myeloid leukemia to guide treatment strategy

The presence of FLT3 mutations, including the most common FLT3-ITD (internal tandem duplications) and FLT3-TKD (tyrosine kinase domain), is associated with an unfavorable prognosis in patients affected by acute myeloid leukemia (AML). In this setting, in recent years, new FLT3 inhibitors have demonstrated efficacy in improving survival and treatment response. Nevertheless, the development of primary and secondary mechanisms of resistance poses a significant obstacle to their efficacy. Understanding these mechanisms is crucial for developing novel therapeutic approaches to overcome resistance and improve the outcomes of patients. In this context, the use of novel FLT3 inhibitors and the combination of different targeted therapies have been studied. This review provides an update on the molecular alterations involved in the resistance to FLT3 inhibitors, and describes how the molecular monitoring may be used to guide treatment strategy in FLT3-mutated AML.

Cancer testis antigens: Emerging therapeutic targets leveraging genomic instability in cancer

Cancer care has witnessed remarkable progress in recent decades, with a wide array of targeted therapies and immune-based interventions being added to the traditional treatment options such as surgery, chemotherapy, and radiotherapy. However, despite these advancements, the challenge of achieving high tumor specificity while minimizing adverse side effects continues to dictate the benefit-risk balance of cancer therapy, guiding clinical decision making. As such, the targeting of cancer testis antigens (CTAs) offers exciting new opportunities for therapeutic intervention of cancer since they display highly tumor specific expression patterns, natural immunogenicity and play pivotal roles in various biological processes that are critical for tumor cellular fitness. In this review, we delve deeper into how CTAs contribute to the regulation and maintenance of genomic integrity in cancer, and how these mechanisms can be exploited to specifically target and eradicate tumor cells. We review the current clinical trials targeting aforementioned CTAs, highlight promising pre-clinical data and discuss current challenges and future perspectives for future development of CTA-based strategies that exploit tumor genomic instability.

FHND004 inhibits malignant proliferation of multiple myeloma by targeting PDZ-binding kinase in MAPK pathway

Inhibitors of Epidermal growth factor receptor tyrosine kinase (EGFR-TKIs) are producing impressive benefits to responsive types of cancers but challenged with drug resistances. FHND drugs are newly modified small molecule inhibitors based on the third-generation EGFR-TKI AZD9291 (Osimertinib) that are mainly for targeting the mutant-selective EGFR, particularly for the non-small cell lung cancer (NSCLC). Successful applications of EGFR-TKIs to other cancers are less certain, thus the present pre-clinical study aims to explore the anticancer effect and downstream targets of FHND in multiple myeloma (MM), which is an incurable hematological malignancy and reported to be insensitive to first/second generation EGFR-TKIs (Gefitinib/Afatinib). Cell-based assays revealed that FHND004 and FHND008 significantly inhibited MM cell proliferation and promoted apoptosis. The RNA-seq identified the involvement of the MAPK signaling pathway. The protein chip screened PDZ-binding kinase (PBK) as a potential drug target. The interaction between PBK and FHND004 was verified by molecular docking and microscale thermophoresis (MST) assay with site mutation (N124/D125). Moreover, the public clinical datasets showed high expression of PBK was associated with poor clinical outcomes. PBK overexpression evidently promoted the proliferation of two MM cell lines, whereas the FHND004 treatment significantly inhibited survival of 5TMM3VT cell-derived model mice and growth of patient-derived xenograft (PDX) tumors. The mechanistic study showed that FHND004 downregulated PBK expression, thus mediating ERK1/2 phosphorylation in the MAPK pathway. Our study not only demonstrates PBK as a promising novel target of FHND004 to inhibit MM cell proliferation, but also expands the EGFR kinase-independent direction for developing anti-myeloma therapy.

Therapeutic potential of targeting polo-like kinase 4

Polo-like kinase 4 (PLK4), a highly conserved serine/threonine kinase, masterfully regulates centriole duplication in a spatiotemporal manner to ensure the fidelity of centrosome duplication and proper mitosis. Abnormal expression of PLK4 contributes to genomic instability and associates with a poor prognosis in cancer. Inhibition of PLK4 is demonstrated to exhibit significant efficacy against various types of human cancers, further highlighting its potential as a promising therapeutic target for cancer treatment. As such, numerous small-molecule inhibitors with distinct chemical scaffolds targeting PLK4 have been extensively investigated for the treatment of different human cancers, with several undergoing clinical evaluation (e.g., CFI-400945). Here, we review the structure, distribution, and biological functions of PLK4, encapsulate its intricate regulatory mechanisms of expression, and highlighting its multifaceted roles in cancer development and metastasis. Moreover, the recent advancements of PLK4 inhibitors in patent or literature are summarized, and their therapeutic potential as monotherapies or combination therapies with other anticancer agents are also discussed.

Phosphorylation of PBK at Thr9 by CDK5 correlates with invasion of prolactinomas

CONTEXT

Prolactinomas are the most prevalent functional pituitary neuroendocrine tumors (PitNETs), and they are invasive to surrounding anatomic structures. The detailed mechanisms of invasion are not yet clear.

OBJECTIVE

We explored the role of PBK phosphorylation in the proliferation and invasion of prolactinomas and its possible mechanism.

RESULTS

We report that PBK directly binds to and is phosphorylated at Thr9 by cyclin-dependent kinase 5 (CDK5), which promotes GH3 cell EMT progression and proliferation. Phosphorylation of PBK at Thr9 (pPBK-T9) by CDK5 enhances the stability of PBK. p38 is one of the downstream targets of PBK, and its phosphorylation is reduced as pPBK-T9 increases in vivo and in vitro. Furthermore, we found that pPBK-T9 is highly expressed in invasive PitNETs and was significantly correlated with invasion by univariate and multivariate analyses.

CONCLUSIONS

Phosphorylation of PBK at Thr9 by CDK5 promotes cell proliferation and EMT progression in prolactinomas.

The important regulatory roles of circRNA‑encoded proteins or peptides in cancer pathogenesis (Review)

Circular RNAs (circRNAs) represent a class of RNA molecules characterized by their covalently closed structures. There are three types of circRNAs, namely exonic circRNAs, exon‑intron circRNAs and circular intronic RNAs. To date, four distinct mechanisms have been unveiled through which circRNAs exert their functional influence, including serving as microRNA (miRNA) sponges, interacting with RNA binding proteins (RBPs), modulating parental gene transcription and acting as templates for translation. Of note, among these mechanisms, the miRNA/RBP sponge function has been the most investigated one. Recent research has uncovered the presence of various proteins or peptides encoded by circRNA. CircRNAs are translated independent of the 5' cap and 3' polyA tail, which are typical elements for linear RNA translation. Some unique elements, such as internal ribosome entry sites and N‑methyladenosine modifications, facilitate the initiation of translation. These circRNA‑encoded proteins or peptides participate in diverse signalling pathways and act as important regulators in carcinogenesis by influencing cell proliferation, migration, apoptosis and other key processes. Consequently, circRNA‑encoded proteins or peptides have great potential as therapeutic targets for anticancer drugs. The present comprehensive review aimed to systematically summarize the current understanding of circRNA‑encoded proteins or peptides and to unveil their roles in carcinogenesis.

TTK/MPS1 inhibitor OSU-13 targets the mitotic checkpoint and is a potential therapeutic strategy for myeloma

Despite substantial recent advances in treatment, multiple myeloma (MM) remains an incurable disease, with a shortage of treatment options for patients with high-risk disease, warranting the need for novel therapeutic targets and treatment approaches. Threonine and tyrosine kinase (TTK), also known as monopolar spindle 1 (MPS1), is a kinase essential for the mitotic spindle checkpoint whose expression correlates to unfavorable prognosis in several cancers. Here, we report the importance of TTK in MM, and the effects of the TTK inhibitor OSU-13. Elevated TTK expression correlated with amplification/ gain of 1q21 and decreased overall and event-free survival in MM. Treatment with OSU-13 inhibited TTK activity efficiently and selectively at a similar concentration range to other TTK inhibitor clinical candidates. OSU-13 reduced proliferation and viability of primary human MM cells and cell lines, especially those with high 1q21 copy numbers, and triggered apoptosis through caspase 3 and 7 activation. In addition, OSU-13 induced DNA damage and severe defects in chromosome alignment and segregation, generating aneuploidy. In vivo, OSU-13 decreased tumor growth in mice with NCI-H929 xenografts. Collectively, our findings reveal that inhibiting TTK with OSU-13 is a potential therapeutic strategy for MM, particularly for a subset of high-risk patients with poor outcome.

Combined inhibition of Wee1 and Chk1 as a therapeutic strategy in multiple myeloma

Multiple myeloma (MM) is a hematological malignancy characterized by an abnormal clonal proliferation of malignant plasma cells. Despite the introduction of novel agents that have significantly improved clinical outcome, most patients relapse and develop drug resistance. MM is characterized by genomic instability and a high level of replicative stress. In response to replicative and DNA damage stress, MM cells activate various DNA damage signaling pathways. In this study, we reported that high CHK1 and WEE1 expression is associated with poor outcome in independent cohorts of MM patients treated with high dose melphalan chemotherapy or anti-CD38 immunotherapy. Combined targeting of Chk1 and Wee1 demonstrates synergistic toxicities on MM cells and was associated with higher DNA double-strand break induction, as evidenced by an increased percentage of γH2AX positive cells subsequently leading to apoptosis. The therapeutic interest of Chk1/Wee1 inhibitors' combination was validated on primary MM cells of patients. The toxicity was specific of MM cells since normal bone marrow cells were not significantly affected. Using deconvolution approach, MM patients with high CHK1 expression exhibited a significant lower percentage of NK cells whereas patients with high WEE1 expression displayed a significant higher percentage of regulatory T cells in the bone marrow. These data emphasize that MM cell adaptation to replicative stress through Wee1 and Chk1 upregulation may decrease the activation of the cell-intrinsic innate immune response. Our study suggests that association of Chk1 and Wee1 inhibitors may represent a promising therapeutic approach in high-risk MM patients characterized by high CHK1 and WEE1 expression.

Chronic Kidney Disease Transdifferentiates Veins into a Specialized Immune-Endocrine Organ with Increased MYCN-AP1 Signaling

Most patients with end-stage renal disease (ESRD) and advanced chronic kidney disease (CKD) choose hemodialysis as their treatment of choice. Thus, upper-extremity veins provide a functioning arteriovenous access to reduce dependence on central venous catheters. However, it is unknown whether CKD reprograms the transcriptome of veins and primes them for arteriovenous fistula (AVF) failure. To examine this, we performed transcriptomic analyses of bulk RNA sequencing data of veins isolated from 48 CKD patients and 20 non-CKD controls and made the following findings: (1) CKD converts veins into immune organs by upregulating 13 cytokine and chemokine genes, and over 50 canonical and noncanonical secretome genes; (2) CKD increases innate immune responses by upregulating 12 innate immune response genes and 18 cell membrane protein genes for increased intercellular communication, such as CX3CR1 chemokine signaling; (3) CKD upregulates five endoplasmic reticulum protein-coding genes and three mitochondrial genes, impairing mitochondrial bioenergetics and inducing immunometabolic reprogramming; (4) CKD reprograms fibrogenic processes in veins by upregulating 20 fibroblast genes and 6 fibrogenic factors, priming the vein for AVF failure; (5) CKD reprograms numerous cell death and survival programs; (6) CKD reprograms protein kinase signal transduction pathways and upregulates SRPK3 and CHKB; and (7) CKD reprograms vein transcriptomes and upregulates MYCN, AP1, and 11 other transcription factors for embryonic organ development, positive regulation of developmental growth, and muscle structure development in veins. These results provide novel insights on the roles of veins as immune endocrine organs and the effect of CKD in upregulating secretomes and driving immune and vascular cell differentiation.

Maternal embryonic leucine zipper kinase in tumor cell and tumor microenvironment: Emerging player and promising therapeutic opportunities

Maternal embryonic leucine zipper kinase (MELK) is a member of the AMPK (AMP-activated protein kinase) protein family, which is widely and highly expressed in multiple cancer types. Through direct and indirect interactions with other proteins, it mediates various cascades of signal transduction processes and plays an important role in regulating tumor cell survival, growth, invasion and migration and other biological functions. Interestingly, MELK also plays an important role in the regulation of the tumor microenvironment, which can not only predict the responsiveness of immunotherapy, but also affect the function of immune cells to regulate tumor progression. In addition, more and more small molecule inhibitors have been developed for the target of MELK, which exert important anti-tumor effects and have achieved excellent results in a number of clinical trials. In this review, we outline the structural features, molecular biological functions, potential regulatory mechanisms and important roles of MELK in tumors and tumor microenvironment, as well as substances targeting MELK. Although many molecular mechanisms of MELK in the process of tumor regulation are still unknown, it is worth affirming that MELK is a potential tumor molecular therapeutic target, and its unique superiority and important role provide clues and confidence for subsequent basic research and scientific transformation.

Identification of potential biomarkers in cancer testis antigens for glioblastoma

OBJECTIVE

To screen and validate cancer testis antigens (CTAs) as potential biomarkers and explore their molecular mechanisms in glioblastoma (GBM).

METHODS

Ribonucleic acid sequencing (RNA-seq) and bioinformatics analyses were utilized to screen the highly expressed CTAs in GBM. Correlation analysis was used to identify potential biomarkers associated with tumor purity and prognosis. Immunohistochemistry was applied for detection of protein expression. Protein-protein interaction (PPI) network construction, functional enrichment analysis, and binding domain prediction were performed to investigate the underlying molecular mechanisms of GBM.

RESULTS

A total of 8 highly expressed CTAs were identified in GBM. One of them was PDZ-binding kinase (PBK). PBK messenger RNA (mRNA) was most highly expressed in GBM and associated with tumor purity and prognosis, PBK protein expression was also significantly increased in GBM tissues and correlated with p53 expression. Functional enrichment analysis revealed that the PBK related genes were predominantly enriched in cell cycle pathway with 38 genes enriched. The proteins encoding by these 38 genes were performed by binding domain prediction analysis, which demonstrated 15 proteins interacting with PBK. Most of these proteins were up regulated in GBM.

CONCLUSION

PBK is highly expressed in GBM. It may serve as a potential biomarker for GBM targeting therapy and the cell cycle modulator by interacting with certain key molecules of cell cycle in GBM.

Developing mRNA signatures as a novel prognostic biomarker predicting high risk multiple myeloma

Background

Multiple myeloma (MM) remains an essentially incurable disease. This study aimed to establish a predictive model for estimating prognosis in newly diagnosed MM based on gene expression profiles.

Methods

RNA-seq data were downloaded from the Multiple Myeloma Research Foundation (MMRF) CoMMpass Study and the Genotype-Tissue Expression (GTEx) databases. Weighted gene coexpression network analysis (WGCNA) and protein-protein interaction network analysis were performed to identify hub genes. Enrichment analysis was also conducted. Patients were randomly split into training (70%) and validation (30%) datasets to build a prognostic scoring model based on the least absolute shrinkage and selection operator (LASSO). CIBERSORT was applied to estimate the proportion of 22 immune cells in the microenvironment. Drug sensitivity was analyzed using the OncoPredict algorithm.

Results

A total of 860 newly diagnosed MM samples and 444 normal counterparts were screened as the datasets. WGCNA was applied to analyze the RNA-seq data of 1589 intersecting genes between differentially expressed genes and prognostic genes. The blue module in the PPI networks was analyzed with Cytoscape, and 10 hub genes were identified using the MCODE plug-in. A three-gene (TTK, GINS1, and NCAPG) prognostic model was constructed. This risk model showed remarkable prognostic value. CIBERSORT assessment revealed the risk model to be correlated with activated memory CD4 T cells, M0 macrophages, M1 macrophages, eosinophils, activated dendritic cells, and activated mast cells. Furthermore, based on OncoPredict, high-risk MM patients were sensitive to eight drugs.

Conclusions

We identified and constructed a three-gene-based prognostic model, which may provide new and in-depth insights into the treatment of MM patients.

The BLM helicase is a new therapeutic target in multiple myeloma involved in replication stress survival and drug resistance

Multiple myeloma (MM) is a hematologic cancer characterized by accumulation of malignant plasma cells in the bone marrow. To date, no definitive cure exists for MM and resistance to current treatments is one of the major challenges of this disease. The DNA helicase BLM, whose depletion or mutation causes the cancer-prone Bloom's syndrome (BS), is a central factor of DNA damage repair by homologous recombination (HR) and genomic stability maintenance. Using independent cohorts of MM patients, we identified that high expression of BLM is associated with a poor outcome with a significant enrichment in replication stress signature. We provide evidence that chemical inhibition of BLM by the small molecule ML216 in HMCLs (human myeloma cell lines) leads to cell cycle arrest and increases apoptosis, likely by accumulation of DNA damage. BLM inhibition synergizes with the alkylating agent melphalan to efficiently inhibit growth and promote cell death in HMCLs. Moreover, ML216 treatment re-sensitizes melphalan-resistant cell lines to this conventional therapeutic agent. Altogether, these data suggest that inhibition of BLM in combination with DNA damaging agents could be of therapeutic interest in the treatment of MM, especially in those patients with high BLM expression and/or resistance to melphalan.

Transcriptional profiles define drug refractory disease in myeloma

Identifying biomarkers associated with disease progression and drug resistance are important for personalized care. We investigated the expression of 121 curated genes, related to immunomodulatory drugs (IMiDs) and proteasome inhibitors (PIs) responsiveness. We analyzed 28 human multiple myeloma (MM) cell lines with known drug sensitivities and 130 primary MM patient samples collected at different disease stages, including newly diagnosed (ND), on therapy (OT), and relapsed and refractory (RR, collected within 12 months before the patients' death) timepoints. Our findings led to the identification of a subset of genes linked to clinical drug resistance, poor survival, and disease progression following combination treatment containing IMIDs and/or PIs. Finally, we built a seven-gene model (MM-IMiD and PI sensitivity-7 genes [IP-7]) using digital gene expression profiling data that significantly separates ND patients from IMiD- and PI-refractory RR patients. Using this model, we retrospectively analyzed RNA sequcencing (RNAseq) data from the Mulltiple Myeloma Research Foundation (MMRF) CoMMpass (n = 578) and Mayo Clinic MM patient registry (n = 487) to divide patients into probabilities of responder and nonresponder, which subsequently correlated with overall survival, disease stage, and number of prior treatments. Our findings suggest that this model may be useful in predicting acquired resistance to treatments containing IMiDs and/or PIs.

Inhibition of the Protein Arginine Methyltransferase PRMT5 in High-Risk Multiple Myeloma as a Novel Treatment Approach

Multiple myeloma (MM) is an incurable clonal plasma cell malignancy. Subsets of patients have high-risk features linked with dismal outcome. Therefore, the need for effective therapeutic options remains high. Here, we used bio-informatic tools to identify novel targets involved in DNA repair and epigenetics and which are associated with high-risk myeloma. The prognostic significance of the target genes was analyzed using publicly available gene expression data of MM patients (TT2/3 and HM cohorts). Hence, protein arginine methyltransferase 5 (PRMT5) was identified as a promising target. Druggability was assessed in OPM2, JJN3, AMO1 and XG7 human myeloma cell lines using the PRMT5-inhibitor EPZ015938. EPZ015938 strongly reduced the total symmetric-dimethyl arginine levels in all cell lines and lead to decreased cellular growth, supported by cell line dependent changes in cell cycle distribution. At later time points, apoptosis occurred, as evidenced by increased AnnexinV-positivity and cleavage of PARP and caspases. Transcriptome analysis revealed a role for PRMT5 in regulating alternative splicing, nonsense-mediated decay, DNA repair and PI3K/mTOR-signaling, irrespective of the cell line type. PRMT5 inhibition reduced the expression of upstream DNA repair kinases ATM and ATR, which may in part explain our observation that EPZ015938 and the DNA-alkylating agent, melphalan, have combinatory effects. Of interest, using a low-dose of mTOR-inhibitor, we observed that cell viability was partially rescued from the effects of EPZ015938, indicating a role for mTOR-related pathways in the anti-myeloma activity of EPZ015938. Moreover, PRMT5 was shown to be involved in splicing regulation of MMSET and SLAMF7, known genes of importance in MM disease. As such, we broaden the understanding of the exact role of PRMT5 in MM disease and further underline its use as a possible therapeutic target.

PLK4 inhibitor plus bortezomib exhibits a synergistic effect on treating multiple myeloma via inactivating PI3K/AKT signaling

OBJECTIVE

The anti-tumor effect of polo-like kinase 4 (PLK4) inhibitor has been explored in several neoplasms, while its synergy with bortezomib in multiple myeloma (MM) remains elusive. Hence, the present study aimed to investigate the effect of PLK4 inhibitor on the sensitivity of MM to bortezomib treatment and its underlying mechanism.

METHODS

MM cell lines (RPMI-8226 and U266) were cultured in different concentrations of CFI-400945 (PLK4 inhibitor), bortezomib, or their combination. Subsequently, 740 Y-P (PI3K activator) was added in the combination of CFI-400945 and bortezomib. Besides, cell viability and apoptosis were measured by CCK-8 reagent and TUNEL apoptosis kit, separately; meanwhile, western blot was carried out for detecting PLK4, p-PI3K, PI3K, p-AKT, and AKT.

RESULTS

CFI-400945 and bortezomib decreased the cell viability in dose-dependent manners in MM cell lines, respectively. The combination of different concentrations of CFI-400945 and bortezomib reduced cell viability compared with monotherapy in MM cell lines (all P < 0.05). Interestingly, 200 nM CFI-400945 and 4 nM bortezomib showed the maximum synergy in MM cell lines. Furthermore, 200 nM CFI-400945 plus 4 nM bortezomib showed a better effect on decreasing cell viability and promoting cell apoptosis than CFI-400945 or bortezomib monotherapy in MM cells cell lines (all P < 0.05). Moreover, 740 Y-P alleviated the effect of bortezomib and CFI-400945 on PI3K/AKT signaling, cell viability, and apoptosis in MM cell lines.

CONCLUSIONS

PLK4 inhibitor plus bortezomib shows synergy in decreasing cell viability and enhancing cell apoptosis via repressing PI3K/AKT signaling in MM.

Gene expression profiling as a prognostic tool in multiple myeloma

Multiple myeloma (MM) is an aggressive plasma cell malignancy with high degrees of variability in outcome, some patients experience long remissions, whilst others survive less than two years from diagnosis. Therapy refractoriness and relapse remain challenges in MM management, and there is a need for improved prognostication and targeted therapies to improve overall survival (OS). The past decade has seen a surge in gene expression profiling (GEP) studies which have elucidated the molecular landscape of MM and led to the identification of novel gene signatures that predict OS and outperform current clinical predictors. In this review, we discuss the limitations of current prognostic tools and the emerging role of GEP in diagnostics and in the development of personalised medicine approaches to combat drug resistance.

Clarifying the molecular mechanism of tomentosin‑induced antiproliferative and proapoptotic effects in human multiple myeloma via gene expression profile and genetic interaction network analysis

Multiple myeloma (MM) is an aggressive B cell malignancy. Substantial progress has been made in the therapeutic context for patients with MM, however it still represents an incurable disease due to drug resistance and recurrence. Development of more effective or synergistic therapeutic approaches undoubtedly represents an unmet clinical need. Tomentosin is a bioactive natural sesquiterpene lactone extracted by various plants with therapeutic properties, including anti‑neoplastic effects. In the present study, the potential antitumor activity of tomentosin was evaluated on the human RPMI‑8226 cell line, treated with increasing tomentosin concentration for cytotoxicity screening. The data suggested that both cell cycle arrest and cell apoptosis could explain the antiproliferative effects of tomentosin and may result in the inhibition of RPMI‑8226 cell viability. To assess differentially expressed genes contributing to tomentosin activity and identify its mechanism of action, a microarray gene expression profile was performed, identifying 126 genes deregulated by tomentosin. To address the systems biology and identify how tomentosin deregulates gene expression in MM from a systems perspective, all deregulated genes were submitted to enrichment and molecular network analysis. The Protein‑Protein Interaction (PPI) network analysis showed that tomentosin in human MM induced the downregulation of genes involved in several pathways known to lead immune‑system processes, such as cytokine‑cytokine receptor interaction, chemokine or NF‑κB signaling pathway, as well as genes involved in pathways playing a central role in cellular neoplastic processes, such as growth, proliferation, migration, invasion and apoptosis. Tomentosin also induced endoplasmic reticulum stress via upregulation of cyclic AMP‑dependent transcription factor ATF‑4 and DNA damage‑inducible transcript 3 protein genes, suggesting that in the presence of tomentosin the protective unfolded protein response signaling may induce cell apoptosis. The functional connections analysis executed using the Connectivity Map tool, suggested that the effects of tomentosin on RPMI‑8226 cells might be similar to those exerted by heat shock proteins inhibitors. Taken together, these data suggested that tomentosin may be a potential drug candidate for the treatment of MM.

Phosphocatalytic Kinome Activity Profiling of Apoptotic and Ferroptotic Agents in Multiple Myeloma Cells

Through phosphorylation of their substrate proteins, protein kinases are crucial for transducing cellular signals and orchestrating biological processes, including cell death and survival. Recent studies have revealed that kinases are involved in ferroptosis, an iron-dependent mode of cell death associated with toxic lipid peroxidation. Given that ferroptosis is being explored as an alternative strategy to eliminate apoptosis-resistant tumor cells, further characterization of ferroptosis-dependent kinase changes might aid in identifying novel druggable targets for protein kinase inhibitors in the context of cancer treatment. To this end, we performed a phosphopeptidome based kinase activity profiling of glucocorticoid-resistant multiple myeloma cells treated with either the apoptosis inducer staurosporine (STS) or ferroptosis inducer RSL3 and compared their kinome activity signatures. Our data demonstrate that both cell death mechanisms inhibit the activity of kinases classified into the CMGC and AGC families, with STS showing a broader spectrum of serine/threonine kinase inhibition. In contrast, RSL3 targets a significant number of tyrosine kinases, including key players of the B-cell receptor signaling pathway. Remarkably, additional kinase profiling of the anti-cancer agent withaferin A revealed considerable overlap with ferroptosis and apoptosis kinome activity, explaining why withaferin A can induce mixed ferroptotic and apoptotic cell death features. Altogether, we show that apoptotic and ferroptotic cell death induce different kinase signaling changes and that kinome profiling might become a valid approach to identify cell death chemosensitization modalities of novel anti-cancer agents.

The Significance of mRNA in the Biology of Multiple Myeloma and Its Clinical Implications

Multiple myeloma (MM) is a genetically complex disease that results from a multistep transformation of normal to malignant plasma cells in the bone marrow. However, the molecular mechanisms responsible for the initiation and heterogeneous evolution of MM remain largely unknown. A fundamental step needed to understand the oncogenesis of MM and its response to therapy is the identification of driver mutations. The introduction of gene expression profiling (GEP) in MM is an important step in elucidating the molecular heterogeneity of MM and its clinical relevance. Since some mutations in myeloma occur in non-coding regions, studies based on the analysis of mRNA provide more comprehensive information on the oncogenic pathways and mechanisms relevant to MM biology. In this review, we discuss the role of gene expression profiling in understanding the biology of multiple myeloma together with the clinical manifestation of the disease, as well as its impact on treatment decisions and future directions.

RNA-Sequencing-Based Transcriptomic Score with Prognostic and Theranostic Values in Multiple Myeloma

Multiple myeloma (MM) is the second most frequent hematological cancer and is characterized by the clonal proliferation of malignant plasma cells. Genome-wide expression profiling (GEP) analysis with DNA microarrays has emerged as a powerful tool for biomedical research, generating a huge amount of data. Microarray analyses have improved our understanding of MM disease and have led to important clinical applications. In MM, GEP has been used to stratify patients, define risk, identify therapeutic targets, predict treatment response, and understand drug resistance. In this study, we built a gene risk score for 267 genes using RNA-seq data that demonstrated a prognostic value in two independent cohorts (n = 674 and n = 76) of newly diagnosed MM patients treated with high-dose Melphalan and autologous stem cell transplantation. High-risk patients were associated with the expression of genes involved in several major pathways implicated in MM pathophysiology, including interferon response, cell proliferation, hypoxia, IL-6 signaling pathway, stem cell genes, MYC, and epigenetic deregulation. The RNA-seq-based risk score was correlated with specific MM somatic mutation profiles and responses to targeted treatment including EZH2, MELK, TOPK/PBK, and Aurora kinase inhibitors, outlining potential utility for precision medicine strategies in MM.

Targeting the methyltransferase SETD8 impairs tumor cell survival and overcomes drug resistance independently of p53 status in multiple myeloma

Background

Multiple myeloma (MM) is a malignancy of plasma cells that largely remains incurable. The search for new therapeutic targets is therefore essential. In addition to a wide panel of genetic mutations, epigenetic alterations also appear as important players in the development of this cancer, thereby offering the possibility to reveal novel approaches and targets for effective therapeutic intervention.

Results

Here, we show that a higher expression of the lysine methyltransferase SETD8, which is responsible for the mono-methylation of histone H4 at lysine 20, is an adverse prognosis factor associated with a poor outcome in two cohorts of newly diagnosed patients. Primary malignant plasma cells are particularly addicted to the activity of this epigenetic enzyme. Indeed, the inhibition of SETD8 by the chemical compound UNC-0379 and the subsequent decrease in histone H4 methylation at lysine 20 are highly toxic in MM cells compared to normal cells from the bone marrow microenvironment. At the molecular level, RNA sequencing and functional studies revealed that SETD8 inhibition induces a mature non-proliferating plasma cell signature and, as observed in other cancers, triggers an activation of the tumor suppressor p53, which together cause an impairment of myeloma cell proliferation and survival. However, a deadly level of replicative stress was also observed in p53-deficient myeloma cells treated with UNC-0379, indicating that the cytotoxicity associated with SETD8 inhibition is not necessarily dependent on p53 activation. Consistent with this, UNC-0379 triggers a p53-independent nucleolar stress characterized by nucleolin delocalization and reduction of nucleolar RNA synthesis. Finally, we showed that SETD8 inhibition is strongly synergistic with melphalan and may overcome resistance to this alkylating agent widely used in MM treatment.

Conclusions

Altogether, our data indicate that the up-regulation of the epigenetic enzyme SETD8 is associated with a poor outcome and the deregulation of major signaling pathways in MM. Moreover, we provide evidences that myeloma cells are dependent on SETD8 activity and its pharmacological inhibition synergizes with melphalan, which could be beneficial to improve MM treatment in high-risk patients whatever their status for p53.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01160-z.

Second-Generation Antimitotics in Cancer Clinical Trials

Mitosis represents a promising target to block cancer cell proliferation. Classical antimitotics, mainly microtubule-targeting agents (MTAs), such as taxanes and vinca alkaloids, are amongst the most successful anticancer drugs. By disrupting microtubules, they activate the spindle assembly checkpoint (SAC), which induces a prolonged delay in mitosis, expected to induce cell death. However, resistance, toxicity, and slippage limit the MTA's effectiveness. With the desire to overcome some of the MTA's limitations, mitotic and SAC components have attracted great interest as promising microtubule-independent targets, leading to the so-called second-generation antimitotics (SGAs). The identification of inhibitors against most of these targets, and the promising outcomes achieved in preclinical assays, has sparked the interest of academia and industry. Many of these inhibitors have entered clinical trials; however, they exhibited limited efficacy as monotherapy, and failed to go beyond phase II trials. Combination therapies are emerging as promising strategies to give a second chance to these SGAs. Here, an updated view of the SGAs that reached clinical trials is here provided, together with future research directions, focusing on inhibitors that target the SAC components.

CHEK1 and circCHEK1_246aa evoke chromosomal instability and induce bone lesion formation in multiple myeloma

BACKGROUND

Multiple myeloma (MM) is still incurable and characterized by clonal expansion of plasma cells in the bone marrow (BM). Therefore, effective therapeutic interventions must target both myeloma cells and the BM niche.

METHODS

Cell proliferation, drug resistance, and chromosomal instability (CIN) induced by CHEK1 were confirmed by Giemsa staining, exon sequencing, immunofluorescence and xenograft model in vivo. Bone lesion was evaluated by Tartrate-resistant acid phosphatase (TRAP) staining. The existence of circCHEK1_246aa was evaluated by qPCR, Sanger sequencing and Mass Spectrometer.

RESULTS

We demonstrated that CHEK1 expression was significantly increased in human MM samples relative to normal plasma cells, and that in MM patients, high CHEK1 expression was associated with poor outcomes. Increased CHEK1 expression induced MM cellular proliferation and evoked drug-resistance in vitro and in vivo. CHEK1-mediated increases in cell proliferation and drug resistance were due in part to CHEK1-induced CIN. CHEK1 activated CIN, partly by phosphorylating CEP170. Interestingly, CHEK1 promoted osteoclast differentiation by upregulating NFATc1 expression. Intriguingly, we discovered that MM cells expressed circCHEK1_246aa, a circular CHEK1 RNA, which encoded and was translated to the CHEK1 kinase catalytic center. Transfection of circCHEK1_246aa increased MM CIN and osteoclast differentiation similarly to CHEK1 overexpression, suggesting that MM cells could secrete circCHEK1_246aa in the BM niche to increase the invasive potential of MM cells and promote osteoclast differentiation.

CONCLUSIONS

Our findings suggest that targeting the enzymatic catalytic center encoded by CHEK1 mRNA and circCHEK1_246aa is a promising therapeutic modality to target both MM cells and BM niche.

Genome-wide identification of potential biomarkers in multiple myeloma using meta-analysis of mRNA and miRNA expression data

Multiple myeloma (MM) is a plasma cell malignancy with diverse clinical phenotypes and molecular heterogeneity not completely understood. Differentially expressed genes (DEGs) and miRNAs (DEMs) in MM may influence disease pathogenesis, clinical presentation / drug sensitivities. But these signatures overlap meagrely plausibly due to complexity of myeloma genome, diversity in primary cells studied, molecular technologies/ analytical tools utilized. This warrants further investigations since DEGs/DEMs can impact clinical outcomes and guide personalized therapy. We have conducted genome-wide meta-analysis of DEGs/DEMs in MM versus Normal Plasma Cells (NPCs) and derived unified putative signatures for MM. 100 DEMs and 1,362 DEGs were found deranged between MM and NPCs. Signatures of 37 DEMs ('Union 37') and 154 DEGs ('Union 154') were deduced that shared 17 DEMs and 22 DEGs with published prognostic signatures, respectively. Two miRs (miR-16-2-3p, 30d-2-3p) correlated with survival outcomes. PPI analysis identified 5 topmost functionally connected hub genes (UBC, ITGA4, HSP90AB1, VCAM1, VCP). Transcription factor regulatory networks were determined for five seed DEGs with ≥ 4 biomarker applications (CDKN1A, CDKN2A, MMP9, IGF1, MKI67) and three topmost up/ down regulated DEMs (miR-23b, 195, let7b/ miR-20a, 155, 92a). Further studies are warranted to establish and translate prognostic potential of these signatures for MM.

Targeting RFWD2 as an Effective Strategy to Inhibit Cellular Proliferation and Overcome Drug Resistance to Proteasome Inhibitor in Multiple Myeloma

The potential to overcome resistance to proteasome inhibitors is greatly related with ubiquitin-proteasome system during multiple myeloma (MM) treatment process. The constitutive photomorphogenic 1 (RFWD2), referred to an E3 ubiquitin ligase, has been identified as an oncogene in multiple cancers, yet important questions on the role of RFWD2 in MM biology and treatment remain unclear. Here we demonstrated that MM patients with elevated RFWD2 expression achieved adverse outcome and drug resistance by analyzing gene expression profiling. Moreover, we proved that RFWD2 participated in the process of cell cycle, cell growth and death in MM by mass spectrometry analysis. In vitro study indicated that inducible knockdown of RFWD2 hindered cellular growth and triggered apoptosis in MM cells. Mechanism study revealed that RFWD2 controlled MM cellular proliferation via regulating the degradation of P27 rather than P53. Further exploration unveiled that RFWD2 meditated P27 ubiquitination via interacting with RCHY1, which served as an E3 ubiquitin ligase of P27. Finally, in vivo study illustrated that blocking RFWD2 in BTZ-resistant MM cells overcame the drug resistance in a myeloma xenograft mouse model. Taken together, these findings provide compelling evidence for prompting that targeting RFWD2 may be an effective strategy to inhibit cellular proliferation and overcome drug resistance to proteasome inhibitor in MM.

PBK/TOPK promotes chemoresistance to oxaliplatin in hepatocellular carcinoma cells by regulating PTEN

Oxaliplatin (OXA) resistance limits the efficiency of treatment for hepatocellular carcinoma (HCC). Studies have shown that the PDZ-binding kinase (PBK) plays important roles in tumors. However, the role of PBK in HCC is still a problem. In this study, we explored whether PBK is involved in the chemoresistance to OXA in HCC. Expressions of PBK in six HCC cell lines and one human hepatocytes line were determined by real-time quantitative PCR and western blot analysis. SNU-182 and HepG2 cells were chosen to induce OXA resistance. PBK was silenced or overexpressed in OXA-resistant and sensitive cell lines. Then, cell proliferation, migration, and invasion were measured by cholecystokinin-8 assay and Transwell assay, respectively. The Cancer Genome Atlas dataset showed that PBK is highly expressed in HCC and signifies poor prognosis to patient with HCC. Results showed that expression of PBK in HCC cells was significantly higher than that in THLE2 cells, and it was further increased in OXA-resistant HCC cells. Silencing of PBK promoted the sensitivity of drug-resistant HCC cells to OXA. Overexpression of PBK relieved the apoptosis induced by OXA and promoted the migration and invasion of OXA-sensitive HCC cells. Thus, this study revealed that high PBK expression is correlated with OXA resistance in HCC cells, which may provide a promising therapeutic target for treating HCC.

Multi-omics tumor profiling technologies to develop precision medicine in multiple myeloma

Multiple myeloma (MM), the second most common hematologic cancer, is caused by accumulation of aberrant plasma cells in the bone marrow. Its molecular causes are not fully understood and its great heterogeneity among patients complicates therapeutic decision-making. In the past decades, development of new therapies and drugs have significantly improved survival of MM patients. However, resistance to drugs and relapse remain the most common causes of mortality and are the major challenges to overcome. The advent of high throughput omics technologies capable of analyzing big amount of clinical and biological data has changed the way to diagnose and treat MM. Integration of omics data (gene mutations, gene expression, epigenetic information, and protein and metabolite levels) with clinical histories of thousands of patients allows to build scores to stratify the risk at diagnosis and predict the response to treatment, helping clinicians to make better educated decisions for each particular case. There is no doubt that the future of MM treatment relies on personalized therapies based on predictive models built from omics studies. This review summarizes the current treatments and the use of omics technologies in MM, and their importance in the implementation of personalized medicine.

Multi-omics tumor profiling technologies to develop precision medicine in multiple myeloma

Multiple myeloma (MM), the second most common hematologic cancer, is caused by accumulation of aberrant plasma cells in the bone marrow. Its molecular causes are not fully understood and its great heterogeneity among patients complicates therapeutic decision-making. In the past decades, development of new therapies and drugs have significantly improved survival of MM patients. However, resistance to drugs and relapse remain the most common causes of mortality and are the major challenges to overcome. The advent of high throughput omics technologies capable of analyzing big amount of clinical and biological data has changed the way to diagnose and treat MM. Integration of omics data (gene mutations, gene expression, epigenetic information, and protein and metabolite levels) with clinical histories of thousands of patients allows to build scores to stratify the risk at diagnosis and predict the response to treatment, helping clinicians to make better educated decisions for each particular case. There is no doubt that the future of MM treatment relies on personalized therapies based on predictive models built from omics studies. This review summarizes the current treatments and the use of omics technologies in MM, and their importance in the implementation of personalized medicine.

Tissue Treg Secretomes and Transcription Factors Shared With Stem Cells Contribute to a Treg Niche to Maintain Treg-Ness With 80% Innate Immune Pathways, and Functions of Immunosuppression and Tissue Repair

We used functional -omics angles and examined transcriptomic heterogeneity in CD4⁺Foxp3⁺ regulatory T cells (Treg) from spleen (s-Treg), lymph nodes (LN-Treg), intestine (int-Treg), and visceral adipose tissue (VAT-Treg), and made significant findings: 1) Five new shared Treg genes including NIBAN, TNFRSF1b, DUSP4,VAV2, and KLRG1, and 68 new signatures are identified. Among 27 signaling pathways shared in four tissue Treg, 22 pathways are innate immune pathways (81.5%); 2) s-Treg, LN-Treg, int-Treg, and VAT-Treg have zero, 49, 45, and 116 upregulated pathways, respectively; 3) 12, 7, and 15 out of 373 CD markers are identified as specific for LN-Treg, int-Treg, and VAT-Treg, respectively, which may initiate innate immune signaling; 4) 7, 49, 44, and 79 increased cytokines out of 1176 cytokines are identified for four Treg, respectively, suggesting that Treg have much more secretory proteins/cytokines than IL-10, TGF-β, and IL-35; 5) LN-Treg, int-Treg, and VAT-Treg have 13 additional secretory functions more than s-Treg, found by analyzing 1,706 secretomic genes; 6) 2, 20, 25, and 43 increased transcription factors (TFs) out of 1,496 TFs are identified four Treg, respectively; 7) LN-Treg and int-Treg have increased pyroptosis regulators but VAT-Treg have increased apoptosis regulators; 8) 1, 15, 19, and 31 increased kinases out of 661 kinome are identified for s-Treg, LN-Treg, int-Treg, and VAT-Treg, respectively; 9) comparing with that of s-Treg, LN-Treg, int-Treg, and VAT-Treg increase activated cluster (clusters 1–3) markers; and decrease resting cluster (clusters 4–6) markers; and 10) Treg promote tissue repair by sharing secretomes and TFs AHR, ETV5, EGR1, and KLF4 with stem cells, which partially promote upregulation of all the groups of Treg genes. These results suggest that stem cell-shared master genes make tissue Treg as the first T cell type using a Treg niche to maintain their Treg-ness with 80% innate immune pathways, and triple functions of immunosuppression, tissue repair, and homeostasis maintenance. Our results have provided novel insights on the roles of innate immune pathways on Treg heterogeneity and new therapeutic targets for immunosuppression, tissue repair, cardiovascular diseases, chronic kidney disease, autoimmune diseases, transplantation, and cancers.

DNA Repair Expression Profiling to Identify High-Risk Cytogenetically Normal Acute Myeloid Leukemia and Define New Therapeutic Targets

Cytogenetically normal acute myeloid leukemias (CN-AML) represent about 50% of total adult AML. Despite the well-known prognosis role of gene mutations such as NPM1 mutations of FLT3 internal tandem duplication (FLT3-ITD), clinical outcomes remain heterogeneous in this subset of AML. Given the role of genomic instability in leukemogenesis, expression analysis of DNA repair genes might be relevant to sharpen prognosis evaluation in CN-AML. A publicly available gene expression profile dataset from two independent cohorts of patients with CN-AML were analyzed (GSE12417). We investigated the prognostic value of 175 genes involved in DNA repair. Among these genes, 23 were associated with a prognostic value. The prognostic information provided by these genes was summed in a DNA repair score, allowing to define a group of patients (n = 87; 53.7%) with poor median overall survival (OS) of 233 days (95% CI: 184-260). These results were confirmed in two validation cohorts. In multivariate Cox analysis, the DNA repair score, NPM1, and FLT3-ITD mutational status remained independent prognosis factors in CN-AML. Combining these parameters allowed the identification of three risk groups with different clinical outcomes in both training and validation cohorts. Combined with NPM1 and FLT3 mutational status, our GE-based DNA repair score might be used as a biomarker to predict outcomes for patients with CN-AML. DNA repair score has the potential to identify CN-AML patients whose tumor cells are dependent on specific DNA repair pathways to design new therapeutic avenues.