PIM2 inhibition as a rational therapeutic approach in B-cell lymphoma

Identification of intratumoral microbiome-driven immune modulation and therapeutic implications in diffuse large B-cell lymphoma

OBJECTIVE

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma, with significant clinical heterogeneity. Recent studies suggest that the intratumoral microbiome may influence the tumor microenvironment, affecting patient prognosis and therapeutic responses. This study aims to identify microbiome-related subtypes in DLBCL and assess their impact on prognosis, immune infiltration, and therapeutic sensitivity.

METHODS

Transcriptomic and microbiome data from 48 DLBCL patients were obtained from public databases. Consensus clustering was used to classify patients into distinct microbiome-related subtypes. Functional enrichment analysis, immune infiltration assessments, and single-cell RNA sequencing were performed to explore the biological characteristics of these subtypes. Drug sensitivity predictions were made using the OncoPredict tool. Hub genes' expression and biological function were validated and inferred in cell lines and independent cohorts of DLBCL.

RESULTS

Two distinct microbiome-related subtypes were identified. Patients in Cluster 1 exhibited significantly better overall survival (P < 0.05), with higher immune infiltration of regulatory T cells and M0 macrophages compared to Cluster 2, which was associated with poorer outcomes. Functional enrichment analysis revealed that genes in Cluster 1 were involved in immune regulatory pathways, including cytokine-cytokine receptor interactions and chemokine signaling, suggesting enhanced anti-tumor immune responses. In contrast, genes in Cluster 2 were enriched in immunosuppressive pathways, contributing to a less favorable prognosis. Single-cell RNA sequencing analysis revealed significant heterogeneity in immune cell populations within the tumor microenvironment. B cells exhibited the most notable heterogeneity, as indicated by stemness and differentiation potential scoring. Intercellular communication analysis demonstrated that B cells played a key role in immune cell interactions, with significant differences observed in MIF signaling between B-cell subgroups. Pseudo-time analysis further revealed distinct differentiation trajectories of B cells, highlighting their potential heterogeneity across different immune environments. Metabolic pathway analysis showed significant differences in the average expression levels of metabolic pathways among B-cell subgroups, suggesting functional specialization. Furthermore, interaction analysis between core genes involved in B-cell differentiation and microbiome-driven differentially expressed genes identified nine common genes (GSTM5, LURAP1, LINC02802, MAB21L3, C2CD4D, MMEL1, TSPAN2, and CITED4), which were found to play critical roles in B-cell differentiation and were influenced by the intratumoral microbiome. DLBCL cell lines and clinical cohorts validated that MMEL1 and CITED4 with important biologically function in DLBCL cell survival and subtype classification.

CONCLUSIONS

This study demonstrates the prognostic significance of the intratumoral microbiome in DLBCL, identifying distinct microbiome-related subtypes that impact immune infiltration, metabolic activity, and therapeutic responses. The findings provide insights into the immune heterogeneity within the tumor microenvironment, focusing on B cells and their differentiation dynamics. These results lay the foundation for microbiome-based prognostic biomarkers and personalized treatment approaches, ultimately aiming to enhance patient outcomes in DLBCL.

Identification of oxidative stress-related hub genes for predicting prognosis in diffuse large B-cell lymphoma

BACKGROUND

Oxidative stress is a cellular characteristic that might induce the proliferation and differentiation of tumor cells and promote tumor progression in diffuse large B-cell lymphoma (DLBCL).

METHODS

The DLBCL gene sequencing dataset, tumor mutation burden data, copy number variation data of Somatic cell mutation data in TCGA were downloaded for data training analysis, along with four DLBCL datasets in GEO for validation analysis. The known oxidative stress related genes (OSRGs) were collected from websites. The weighted gene co-expression network analysis (WGCNA) was conducted on the TCGA DLBCL dataset to obtain gene modules related to oxidative stress and intersected with the known OSRGs to obtain the hub genes, which were used to perform consensus clustering on the samples to obtain new phenotypes. Next, the prognosis related OSRGs were selected through regression analysis algorithms and key genes were identified. These genes were used to establish the prognostic risk model and predictive model, and to compare functional and pathway differences among different risk groups.

RESULTS

Through website search, we obtained 297 known OSRGs, and after intersecting with WGCNA results, we obtained 26 OSRGs. The TCGA-DLBC samples were clustered into 2 subtypes with these genes and there were significant differences in immune infiltration between subtypes. After regression analysis, we obtained a total of four key genes, BMI1, CDKN1A, NOX1, and SESN1. The risk prediction model established with these four genes as variables has accurate prognostic prediction ability. The key genes interact with 65 miRNAs, 57 TFs, 47 RBPs, and 62 drugs, respectively, and are closely related to immune infiltration of the disease. Among them, CDKN1A and SESN1 had the highest variability.

CONCLUSIONS

The key genes involved in oxidative stress could predict the prognosis of DLBCL and potentially become therapeutic targets.

Virtual tissue expression analysis

MOTIVATION

Bulk RNA expression data are widely accessible, whereas single-cell data are relatively scarce in comparison. However, single-cell data offer profound insights into the cellular composition of tissues and cell type-specific gene regulation, both of which remain hidden in bulk expression analysis.

RESULTS

Here, we present tissueResolver, an algorithm designed to extract single-cell information from bulk data, enabling us to attribute expression changes to individual cell types. When validated on simulated data tissueResolver outperforms competing methods. Additionally, our study demonstrates that tissueResolver reveals cell type-specific regulatory distinctions between the activated B-cell-like (ABC) and germinal center B-cell-like (GCB) subtypes of diffuse large B-cell lymphomas (DLBCL).

AVAILABILITY AND IMPLEMENTATION

R package available at https://github.com/spang-lab/tissueResolver (archived as 10.5281/zenodo.14160846).Code for reproducing the results of this article is available at https://github.com/spang-lab/tissueResolver-docs archived as swh:1:dir:faea2d4f0ded30de774b28e028299ddbdd0c4f89).

Unveiling CKS2: A Key Player in Aggressive B-Cell Lymphoma Progression and a Target for Synergistic Therapy

BACKGROUND

The objective of this study was to investigate the expression levels and biological significance of CKS2 in Burkitt cell lymphoma (BL) and diffuse large B-cell lymphoma (DLBCL). Additionally, the potential synergistic anti-tumor effects of CKS2 knockdown in combination with etoposide in BL and DLBCL were explored for the first time.

METHODS

Bioinformatics analysis was utilized to explore the transcriptional levels, prognostic value, and gene function enrichment of CKS2 in BL and DLBCL. Specific shRNA sequences were designed to target CKS2 for the purpose of constructing a lentiviral expression vector, and therapeutic effects were assessed through analyses of cell proliferation, cell cycle distribution, and cell apoptosis.

RESULTS

First, the study examined the increased transcriptional and protein levels of CKS2 in BL and DLBCL through analysis of various databases and immunohistochemistry tests. Elevated CKS2 expression was found to be correlated with a worse prognosis in BL and DLBCL patients, as evidenced by data from the TCGA and GEO databases. Enrichment analysis indicated that CKS2 functions were primarily linked to protein kinase regulatory activity, G1/S phase transition of the cell cycle, and the p53 signaling pathway, among others. Second, stable suppression of CKS2 gene expression in Raji and SUDHL6 cells using shRNA resulted in a significant inhibition of cell proliferation. Moreover, CKS2-shRNA induced G0/G1 cell cycle arrest and apoptosis by activating the p53 signaling pathway in Raji and SUDHL6 cells. Third, the combined treatment of CKS2-shRNA and etoposide exhibited a synergistic effect on the proliferation and apoptosis of Raji and SUDHL6 cells.

CONCLUSIONS

Our findings suggest that CKS2 may play a critical role in the progression of BL and DLBCL and provide evidence for the potential therapeutic application of combining CKS2-shRNA and etoposide agents in the treatment of BL and DLBCL.

Potential role of the P2X7 receptor in the proliferation of human diffused large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of invasive non-Hodgkin lymphoma. 60-70% of patients are curable with current chemoimmunotherapy, whereas the rest are refractory or relapsed. Understanding of the interaction between DLBCL cells and tumor microenvironment raises the hope of improving overall survival of DLBCL patients. P2X7, a member of purinergic receptors P2X family, is activated by extracellular ATP and subsequently promotes the progression of various malignancies. However, its role in DLBCL has not been elucidated. In this study, the expression level of P2RX7 in DLBCL patients and cell lines was analyzed. MTS assay and EdU incorporation assay were carried out to study the effect of activated/inhibited P2X7 signaling on the proliferation of DLBCL cells. Bulk RNAseq was performed to explore potential mechanism. The results demonstrated high level expression of P2RX7 in DLBCL patients, typically in patients with relapse DLBCL. 2'(3')-O-(4-benzoylbenzoyl) adenosine 5-triphosphate (Bz-ATP), an agonist of P2X7, significantly accelerated the proliferation of DLBCL cells, whereas delayed proliferation was detected when administrated with antagonist A740003. Furthermore, a urea cycle enzyme named CPS1 (carbamoyl phosphate synthase 1), which up-regulated in P2X7-activated DLBCL cells while down-regulated in P2X7-inhibited group, was demonstrated to involve in such process. Our study reveals the role of P2X7 in the proliferation of DLBCL cells and implies that P2X7 may serve as a potential molecular target for the treatment of DLBCL.

Bifunctional Inhibitor Reveals NEK2 as a Therapeutic Target and Regulator of Oncogenic Pathways in Lymphoma

Expression of the serine/threonine kinase never in mitosis gene A (NIMA)-related kinase 2 (NEK2) is essential for entry into mitosis via its role in facilitating centrosome separation. Its overactivity can lead to tumorigenesis and drug resistance through the activation of several oncogenic pathways, including AKT. Although the cancer-enabling activities of NEK2 are documented in many malignancies, including correlations with poor survival in myeloma, breast, and non-small cell lung cancer, little is known about the role of NEK2 in lymphoma. Here, in tumors from patients with diffuse large B-cell lymphoma (DLBCL), the most common, aggressive non-Hodgkin lymphoma, we found a high abundance of NEK2 mRNA and protein associated with an inferior overall survival. Using our recently developed NEK2 inhibitor, NBI-961, we discovered that DLBCL cell lines and patient-derived cells exhibit a dependency on NEK2 for their viability. This compromised cell fitness was directly attributable to efficient NEK2 inhibition and proteasomal degradation by NBI-961. In a subset of particularly sensitive DLBCL cells, NBI-961 induced G2/mitosis arrest and apoptosis. In contrast, an existing indirect NEK2 inhibitor, INH154, did not prevent NEK2 autophosphorylation, induce NEK2 proteasomal degradation, or affect cell viability. Global proteomics and phospho-proteomics revealed that NEK2 orchestrates cell-cycle and apoptotic pathways through regulation of both known and new signaling molecules. We show the loss of NEK2-sensitized DLBCL to the chemotherapy agents, doxorubicin and vincristine, and effectively suppressed tumor growth in mice. These studies establish the oncogenic activity of NEK2 in DLBCL and set the foundation for development of anti-NEK2 therapeutic strategies in this frequently refractory and relapse-prone cancer.

Phase 1/2 Study of the Pan-PIM Kinase Inhibitor INCB053914 Alone or in Combination With Standard-of-Care Agents in Patients With Advanced Hematologic Malignancies

BACKGROUND

The Proviral Integration site of Moloney murine leukemia virus (PIM) kinases are implicated in tumorigenesis; the pan-PIM kinase inhibitor, INCB053914, demonstrated antitumor activity in hematologic malignancy preclinical models.

PATIENTS AND METHODS

This phase 1/2 study evaluated oral INCB053914 alone or combined with standard-of-care agents for advanced hematologic malignancies (NCT02587598). In Parts 1/2 (monotherapy), patients (≥18 years) had acute leukemia, high-risk myelodysplastic syndrome (MDS), MDS/myeloproliferative neoplasm, myelofibrosis (MF), multiple myeloma, or lymphoproliferative neoplasms. In Parts 3/4 (combination therapy), patients had relapsed/refractory or newly diagnosed (≥65 years, unfit for intensive chemotherapy) acute myeloid leukemia (AML) or MF with suboptimal ruxolitinib response.

RESULTS

Parts 1/2 (n = 58): 6 patients experienced dose-limiting toxicities (DLTs), most commonly aspartate aminotransferase/alanine aminotransferase-elevated (AST/ALT; each n = 4). Fifty-seven patients (98.3%) had treatment-emergent adverse events (TEAEs), most commonly ALT-elevated and fatigue (36.2% each); 48 (82.8%) had grade ≥3 TEAEs, most commonly anemia (31.0%); 8 (13.8%) had grade ≥3 ALT/AST-elevated TEAEs. Parts 3/4 (n = 39): for INCB053914 + cytarabine (AML; n = 6), 2 patients experienced DLTs (grade 3 maculopapular rash, n = 1; grade 3 ALT-elevated and grade 4 hypophosphatemia, n = 1); for INCB053914 + azacitidine (AML; n = 16), 1 patient experienced a DLT (grade 3 maculopapular rash). Two complete responses were observed (1 with incomplete count recovery). For INCB053914 + ruxolitinib (MF; n = 17), no DLTs occurred; 3 patients achieved best reduction of >25% spleen volume at week 12 or 24.

CONCLUSION

INCB053914 was generally well tolerated as monotherapy and in combinations; TEAEs were most commonly ALT/AST-elevated. Limited responses were observed with combinations. Future studies are needed to identify rational, effective combination strategies.

Patterns of Oncogene Coexpression at Single-Cell Resolution Influence Survival in Lymphoma

Cancers often overexpress multiple clinically relevant oncogenes, but it is not known if combinations of oncogenes in cellular subpopulations within a cancer influence clinical outcomes. Using quantitative multispectral imaging of the prognostically relevant oncogenes MYC, BCL2, and BCL6 in diffuse large B-cell lymphoma (DLBCL), we show that the percentage of cells with a unique combination MYC+BCL2+BCL6- (M+2+6-) consistently predicts survival across four independent cohorts (n = 449), an effect not observed with other combinations including M+2+6+. We show that the M+2+6- percentage can be mathematically derived from quantitative measurements of the individual oncogenes and correlates with survival in IHC (n = 316) and gene expression (n = 2,521) datasets. Comparative bulk/single-cell transcriptomic analyses of DLBCL samples and MYC/BCL2/BCL6-transformed primary B cells identify molecular features, including cyclin D2 and PI3K/AKT as candidate regulators of M+2+6- unfavorable biology. Similar analyses evaluating oncogenic combinations at single-cell resolution in other cancers may facilitate an understanding of cancer evolution and therapy resistance.

SIGNIFICANCE

Using single-cell-resolved multiplexed imaging, we show that selected subpopulations of cells expressing specific combinations of oncogenes influence clinical outcomes in lymphoma. We describe a probabilistic metric for the estimation of cellular oncogenic coexpression from IHC or bulk transcriptomes, with possible implications for prognostication and therapeutic target discovery in cancer. This article is highlighted in the In This Issue feature, p. 1027.

Bioinformatics analysis of the pathogenic link between Epstein-Barr virus infection, systemic lupus erythematosus and diffuse large B cell lymphoma

Epstein-Barr virus (EBV) is a risk factor for diffuse large B-cell lymphoma (DLBCL) and systemic lupus erythematosus (SLE). While prior research has suggested a potential correlation between SLE and DLBCL, the molecular mechanisms remain unclear. The present study aimed to explore the contribution of EBV infection to the pathogenesis of DLBCL in the individuals with SLE using bioinformatics approaches. The Gene Expression Omnibus database was used to compile the gene expression profiles of EBV-infected B cells (GSE49628), SLE (GSE61635), and DLBCL (GSE32018). Altogether, 72 shared common differentially expressed genes (DEGs) were extracted and enrichment analysis of the shared genes showed that p53 signaling pathway was a common feature of the pathophysiology. Six hub genes were selected using protein-protein interaction (PPI) network analysis, including CDK1, KIF23, NEK2, TOP2A, NEIL3 and DEPDC1, which showed preferable diagnostic values for SLE and DLBCL and involved in immune cell infiltration and immune responses regulation. Finally, TF-gene and miRNA-gene regulatory networks and 10 potential drugs molecule were predicted. Our study revealed the potential molecular mechanisms by which EBV infection contribute to the susceptibility of DLBCL in SLE patients for the first time and identified future biomarkers and therapeutic targets for SLE and DLBCL.

Lymphocyte to monocyte ratio predicts survival and is epigenetically linked to miR-222-3p and miR-26b-5p in diffuse large B cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma. 10-20% of the patients present with bone marrow (BM) involvement which predicts a worse survival. This study aimed to determine the prognostic significance of serum miR-222-3p, miR-26b-5p, EBV-miR-BHRF1-2-5p, and EBV-miR-BHRF1-2-3p and correlate their levels to clinical and haematological markers in DLBCL with special emphasis on the lymphocyte-monocyte ratio (LMR) and neutrophil-monocyte ratio. We also studied the role of BM BMI1 and PIM2 proteins in predicting BM infiltration. Serum miRNAs were studied on 40 DLBCL and 18 normal individuals using qRT-PCR. BMI1 and PIM2 proteins were studied on BM biopsies by immunohistochemistry. The results were correlated with clinical and follow-up data. All the studied miRNAs were dysregulated in DLBCL serum samples. BMI1 and PIM2 were expressed in 67% and 77.5% of BM samples, respectively. LMR was significantly associated with disease-free survival (DFS) (P = 0.022), miR-222-3P (P = 0.043), and miR-26b-5p (P = 0.043). EBV-miR-BHRF1-2-3p was significantly correlated to haemoglobin level (P = 0.027). MiR-222-3p, miR-26b-5p, and EBV-miR-BHRF1-2-5p expressions were significantly correlated to each other (P = 0.001). There was no significant correlation between the studied markers and follow-up data. LMR is a simple method for predicting survival in DLBCL. MiR-222-3p and miR-26b-5p may be implicated in an immunological mechanism affecting patients' immunity and accordingly influence LMR. The correlation between miR-222-3p, miR-26b-5p, and EBV-miR-BHRF1-2-5p may indicate a common mechanism among the 3 miRNAs that may explain DLBCL pathogenesis.

An XBP1s-PIM-2 positive feedback loop controls IL-15-mediated survival of natural killer cells

Spliced X-box-binding protein 1 (XBP1s) is an essential transcription factor downstream of interleukin-15 (IL-15) and AKT signaling, which controls cell survival and effector functions of human natural killer (NK) cells. However, the precise mechanisms, especially the downstream targets of XBP1s, remain unknown. In this study, by using XBP1 conditional knockout mice, we found that XBP1s is critical for IL-15-mediated NK cell survival but not proliferation in vitro and in vivo. Mechanistically, XBP1s regulates homeostatic NK cell survival by targeting PIM-2, a critical anti-apoptotic gene, which in turn stabilizes XBP1s protein by phosphorylating it at Thr⁵⁸. In addition, XBP1s enhances the effector functions and antitumor immunity of NK cells by recruiting T-bet to the promoter region of Ifng. Collectively, our findings identify a previously unknown mechanism by which IL-15-XBP1s signaling regulates the survival and effector functions of NK cells.

Targeting Pim kinases in hematological cancers: molecular and clinical review

Decades of research has recognized a solid role for Pim kinases in lymphoproliferative disorders. Often up-regulated following JAK/STAT and tyrosine kinase receptor signaling, Pim kinases regulate cell proliferation, survival, metabolism, cellular trafficking and signaling. Targeting Pim kinases represents an interesting approach since knock-down of Pim kinases leads to non-fatal phenotypes in vivo suggesting clinical inhibition of Pim may have less side effects. In addition, the ATP binding site offers unique characteristics that can be used for the development of small inhibitors targeting one or all Pim isoforms. This review takes a closer look at Pim kinase expression and involvement in hematopoietic cancers. Current and past clinical trials and in vitro characterization of Pim kinase inhibitors are examined and future directions are discussed. Current studies suggest that Pim kinase inhibition may be most valuable when accompanied by multi-drug targeting therapy.

Deep learning-based classifier of diffuse large B-cell lymphoma cell-of-origin with clinical outcome

Diffuse large B-cell lymphoma (DLBCL) is an aggressive form of non-Hodgkin lymphoma with poor response to R-CHOP therapy due to remarkable heterogeneity. Based on gene expression, DLBCL cases were divided into two subtypes, i.e. ABC and GCB, where ABC subtype is associated with poor outcomes. Due to its association with clinical outcome, this classification, also known as cell-of-origin (COO), is an efficient way to predict the response to R-CHOP therapy. Previous COO classification methods have some shortcomings, e.g. limited number of samples in the training dataset. These shortcomings challenge the robustness of methods and make it difficult to implicate these methods at clinical level. To overcome the shortcomings of previous methods, we developed a deep learning-based classifier model on a cohort of 381 DLBCL patients using expression data of 20 genes. We implemented multilayer perceptron (MLP) to train deep learning-based classifier, named MLP-COO. MLP-COO achieved accuracy of 99.70% and 94.70% on training and testing datasets, respectively, with 10-fold cross-validation. We also assessed its performance on an independent dataset of 294 DLBCL patients. On independent dataset, we achieved an accuracy of 95.90% with MCC of 0.917. To show its broader applicability, we used this classifier to predict the clinical outcome using survival data from two large cohorts of DLBCL patients. In survival analysis, MLP-COO recapitulates the survival probabilities of DLBCL patients based on their COO in both cohorts. We anticipate that MLP-COO model developed in this study will benefit in the accurate COO prediction of DLBCL patients and their clinical outcomes.

Bioinformatics Analysis of miRNAs Targeting TRAF5 in DLBCL Involving in NF-κB Signaling Pathway and Affecting the Apoptosis and Signal Transduction

Background

Diffuse large B-cell lymphoma (DLBCL) is an aggressive B-cell lymphoma with high heterogeneity. There is an unmet need to investigate valid indicators for the diagnosis and therapy of DLBCL.

Methods

GEO database was utilized to screen for differentially expressed genes (DEGs) and differential miRNAs in DLBCL tissues. The Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were applied to analyse DEGs. Then multiple databases were searched for related miRNAs within DLBCL, TNF receptor-associated factor 5 (TRAF5) and NF-kappa B (NF-κB) signaling pathways. The KOBAS database was used to assist in the screening of miRNAs of interest and construct the regulatory network of miRNA-mRNA. Finally, the expression level and diagnostic performance of miRNAs were analyzed with GEO datasets, and DEGs were identified from the GEPIA database.

Results

DEGs were significantly concentrated in the NF-κB signaling pathway and cytokine-cytokine receptor interaction, and involved in the process of immune response and protein binding. MiR-15a-5p, miR-147a, miR-192-5p, miR-197-3p, miR-532-5p, and miR-650 were revealed to be targeting TRAF5 and participating in NF-κB signaling pathway and might impact the apoptosis and signal transduction of DLBCL. In the GEPIA database, TRAF5 was significantly overexpressed in DLBCL. The expression of miR-197-3p was upregulated within GEO datasets, while the rest of the miRNAs were downregulated in DLBCL.

Conclusions

Subsets of miRNAs may participate in the NF-κB signaling pathway by co-targeting TRAF5 and could be prospective biomarkers exploring the pathogenesis of DLBCL.

Richter Syndrome: From Molecular Pathogenesis to Druggable Targets

Richter syndrome (RS) represents the occurrence of an aggressive lymphoma, most commonly diffuse large B-cell lymphoma (DLBCL), in patients with chronic lymphocytic leukemia (CLL). Most cases of RS originate from the direct transformation of CLL, whereas 20% are de novo DLBCL arising as secondary malignancies. Multiple molecular mechanisms contribute to RS pathogenesis. B-cell receptor (BCR) overreactivity to multiple autoantigens is due to frequent stereotyped BCR configuration. Genetic lesions of TP53, CDKN2A, NOTCH1 and c-MYC deregulate DNA damage response, tumor suppression, apoptosis, cell cycle and proliferation. Hyperactivation of Akt and NOTCH1 signaling also plays a role. Altered expression of PD-1/PD-L1 and of other immune checkpoints leads to RS resistance to cytotoxicity exerted by T-cells. The molecular features of RS provide vulnerabilities for therapy. Targeting BCR signaling with noncovalent BTK inhibitors shows encouraging results, as does the combination of BCL2 inhibitors with chemoimmunotherapy. The association of immune checkpoint inhibitors with BCL2 inhibitors and anti-CD20 monoclonal antibodies is explored in early phase clinical trials with promising results. The development of patient-derived xenograft mice models reveals new molecular targets for RS, exemplified by ROR1. Although RS still represents an unmet medical need, understanding its biology is opening new avenues for precision medicine therapy.

Follicular Lymphoma Microenvironment Characteristics Associated with Tumor Cell Mutations and MHC Class II Expression

Follicular lymphoma (FL) is a B-cell malignancy with a complex tumor microenvironment that is rich in nonmalignant immune cells. We applied single-cell RNA sequencing to characterize the diverse tumor and immune cell populations of FL and identified major phenotypic subsets of FL T cells, including a cytotoxic CD4 T-cell population. We characterized four major FL subtypes with differential representation or relative depletion of distinct T-cell subsets. By integrating exome sequencing, we observed that somatic mutations are associated with, but not definitive for, reduced MHC expression on FL cells. In turn, expression of MHCII genes by FL cells was associated with significant differences in the proportions and targetable immunophenotypic characteristics of T cells. This provides a classification framework of the FL microenvironment in association with FL genotypes and MHC expression, and informs different potential immunotherapeutic strategies based upon tumor cell MHCII expression.

SIGNIFICANCE

We have characterized the FL-infiltrating T cells, identified cytotoxic CD4 T cells as an important component that is associated with tumor cell-intrinsic characteristics, and identified sets of targetable immune checkpoints on T cells that differed from FLs with normal versus low MHC expression. See related commentary by Melnick, p. 374. This article is highlighted in the In This Issue feature, p. 369.

Identification of Hub Genes and Key Pathways Associated with Follicular Lymphoma

Follicular lymphoma (FL) is the second most prevalent form of non-Hodgkin lymphoma (NHL) and accounts for almost 20% of all NHL cases. Although FL patients' overall survival rates have steadily increased, there is still no accepted standard of care for individuals who experience recurrence or resistance to treatment. Hence, it is needed to evaluate the precise molecular cascades underlying FL to develop efficient diagnostic and treatment approaches. Herein, we aimed to evaluate variations in gene expression profiles, explore the underlying mechanisms, and find new FL targets. In the present study, Gene Expression Omnibus (GEO) database was employed to evaluate microarray datasets including GSE32018 and GSE55267. R software was employed to evaluate differentially expressed genes (DEGs) between FL and noncancer samples. The DEGs were evaluated using GO, KEGG pathway enrichment analysis, and PPI network to evaluate hub genes, which were then, examined using gene function enrichment analysis. According to the obtained results, a total of 190 upregulated and 162 downregulated DEGs were evaluated. Following the generation of PPI networks, 15 hub genes in highly connected upregulated DEGs were selected including FN1, MMP9, CCL2, CD8A, POSTN, CCR5, COL3A1, CXCL12, VCAM1, COL1A2, CCL5, SPARC, TIMP1, CXCL9, and IL18. The GO enrichment evaluation of the underlined hub genes indicated that the immunological response was the most considerably enriched term. Twelve significant cascades were found using the KEGG pathway analysis, most of which were linked to cellular structure and immunity. Our findings suggested that FN1, SPARC, POSTN, MMP9, and VCAM1 genes are potential biomarkers of FL, and cellular immunity contributes to the pathogenesis of FL. Moreover, the unique DEGs and cascades found in the present study may present new perspectives on the molecular basis of FL's underlying mechanisms as well as a new understanding of FL's future precise management.

Identification of FCER1G related to Activated Memory CD4+ T Cells Infiltration by Gene Co-expression Network and Construction of a Risk Prediction Module in Diffuse Large B-Cell Lymphoma

Diffuse large B cell lymphoma (DLBCL) is a group of biologically heterogeneous tumors with different prognoses. The tumor microenvironment plays a vital role in the tumorigenesis and development of DLBCL, and activated memory CD4⁺ T cells are an essential component of immunological cells in the lymphoma microenvironment. So far, there are few reports about activated memory CD4+T cells infiltration and related genes in the DLBCL tumor microenvironment. This study obtained the mRNA expression profile information of the testing GSE87371 dataset and another six validation datasets (GSE53786, GSE181063, GSE10846, GSE32918, GSE32018, GSE9327, GSE3892, TCGA-DLBC) from the GEO and TCGA databases. Weighted Gene Co-expression Network Analysis (WGCNA) screened gene module associated with activated memory CD4⁺ T cells infiltration. CIBERSORT and TIMER (immune cells infiltrating estimation analysis tools) were used to identify the relationship between activated memory CD4⁺ T cells and genes associated with immune infiltrating cells in the tumor microenvironment. The least absolute shrinkage and selection operator (LASSO) built the risk prediction model and verified it using nomogram and Kaplan-Meier analysis. Further functional characterization includes Gene Ontology, KEGG pathway analysis and Gene Set Enrichment Analysis (GSEA) to investigate the role and underlying mechanisms of these genes. These results suggest that the expression of FCER1G can reflect the invasion of activated memory CD4⁺ T cells in DLBCL, which provides a new idea for studying the tumor microenvironment and may become a potential predictive biomarker for the assessment of DLBCL.

High ETV6 Levels Support Aggressive B Lymphoma Cell Survival and Predict Poor Outcome in Diffuse Large B-Cell Lymphoma Patients

The identification of prognostic factors for aggressive B-cell lymphomas still represents an unmet clinical need. We used forward phase protein arrays (FFPA) to identify proteins associated with overall survival (OS) from diagnostic formalin-fixed paraffin-embedded material of diffuse large B-cell lymphoma (DLBCL) patients (n = 47). Univariate Cox regression analysis identified numerous proteins, including immune check-point molecules (PDCD1, PDCD2 and PD1L2) and BCL2 to be significantly associated with OS. However, only ETV6 and PIM2 proteins persisted following multivariate Cox analysis. Independent validation studies by immunohistochemistry and analysis of public gene expression profiles of DLBCL confirmed a prognostic role for high ETV6 and ETV6/PIM2 ratios in DLBCL. ETV6 is a recurrently mutated/deleted gene in DLBCL for which its function in this disease entity is currently unknown. We find that ETV6 is upregulated during oncogenic transformation of germinal center B-cells and that it regulates DLBCL survival, as its acute loss results in marked apoptosis. Fluctuations in survivin (BIRC5) expression levels were associated with this phenomenon. Furthermore, an inverse correlation between ETV6 and BIRC5 expression levels was found and correlated with a response to the BIRC5 inhibitor, YM155. In conclusion, we present evidence for an oncogenic function of ETV6 in DLBCL.

PIM2 and NF-κβ gene expression in a sample of AML and ALL Egyptian patients and its relevance to response to treatment

Background

The relation between PIM2 and the transcriptional factor NF κβ have been controversial in literature. The significance of PIM2 and NF-κβ genes expression on the incidence of acute leukemia (AML and ALL) and its relevance to the response rate was evaluated. Sixty de novo acute leukemia patients were stratified in 2 groups: 30 acute myeloid leukemia (AML) and 30 acute lymphoblastic leukemia (ALL) patients and compared to 30 sex- and age-matched controls. The expression level of PIM2 and NF κβ genes was measured using quantitative real-time polymerase chain reaction (QRT-PCR). The patients were followed with clinical examination and complete blood counts.

Results

The expression level of PIM2 gene was significantly higher in AML patients (P<0.001) compared to the control group. The mean expression level of NF κβ gene was significantly high in AML and ALL patients compared to the healthy control group (P=0.037 and P<0.001; respectively). The overall survival in AML patients was higher in NF κβ gene low expressers compared to high expressers (P=0.047). The number of AML patients who achieved complete remission was significantly higher in PIM2 gene low expressers in comparison to PIM2 gene high expressers (P=0.042).

Conclusion

PIM2 and NF κβ genes might have a role in the pathogenesis of acute leukemia, poor overall survival, and failure of response to induction therapy.

Engineered Fully Human Single-Chain Monoclonal Antibodies to PIM2 Kinase

Proviral integration site of Moloney virus-2 (PIM2) is overexpressed in multiple human cancer cells and high level is related to poor prognosis; thus, PIM2 kinase is a rational target of anti-cancer therapeutics. Several chemical inhibitors targeting PIMs/PIM2 or their downstream signaling molecules have been developed for treatment of different cancers. However, their off-target toxicity is common in clinical trials, so they could not be advanced to official approval for clinical application. Here, we produced human single-chain antibody fragments (HuscFvs) to PIM2 by using phage display library, which was constructed in a way that a portion of phages in the library carried HuscFvs against human own proteins on their surface with the respective antibody genes in the phage genome. Bacterial derived-recombinant PIM2 (rPIM2) was used as an antigenic bait to fish out the rPIM2-bound phages from the library. Three E. coli clones transfected with the HuscFv genes derived from the rPIM2-bound phages expressed HuscFvs that bound also to native PIM2 from cancer cells. The HuscFvs presumptively interact with the PIM2 at the ATP binding pocket and kinase active loop. They were as effective as small chemical drug inhibitor (AZD1208, which is an ATP competitive inhibitor of all PIM isoforms for ex vivo use) in inhibiting PIM kinase activity. The HuscFvs should be engineered into a cell-penetrating format and tested further towards clinical application as a novel and safe pan-anti-cancer therapeutics.

Inhibition of PIM Kinases in DLBCL Targets MYC Transcriptional Program and Augments the Efficacy of Anti-CD20 Antibodies

The family of PIM serine/threonine kinases includes three highly conserved oncogenes, PIM1, PIM2, and PIM3, which regulate multiple pro-survival pathways and cooperate with other oncogenes such as MYC. Recent genomic CRISPR-Cas9 screens further highlighted oncogenic functions of PIMs in diffuse large B cell lymphoma (DLBCL) cells, justifying development of small molecule PIM inhibitors and therapeutic targeting of PIM kinases in lymphomas. However, detailed consequences of PIM inhibition in DLBCL remain undefined. Using chemical and genetic PIM blockade, we comprehensively characterized PIM kinase-associated pro-survival functions in DLBCL and the mechanisms of PIM inhibition-induced toxicity. Treatment of DLBCL cells with SEL24/MEN1703, a pan PIM inhibitor in clinical development, decreased BAD phosphorylation and cap-dependent protein translation, reduced MCL1 expression, and induced apoptosis. PIM kinases were tightly coexpressed with MYC in diagnostic DLBCL biopsies, and PIM inhibition in cell lines and patient-derived primary lymphoma cells decreased MYC levels as well as expression of multiple MYC-dependent genes, including PLK1. Chemical and genetic PIM inhibition upregulated surface CD20 levels in a MYC-dependent fashion. Consistently, MEN1703 and other clinically available pan-PIM inhibitors synergized with the anti-CD20 monoclonal antibody rituximab in vitro, increasing complement-dependent cytotoxicity and antibody-mediated phagocytosis. Combined treatment with PIM inhibitor and rituximab suppressed tumor growth in lymphoma xenografts more efficiently than either drug alone. Taken together, these results show that targeting PIM in DLBCL exhibits pleiotropic effects that combine direct cytotoxicity with potentiated susceptibility to anti-CD20 antibodies, justifying further clinical development of such combinatorial strategies.

Loss of synergistic transcriptional feedback loops drives diverse B-cell cancers

Background

The most common B-cell cancers, chronic lymphocytic leukemia/lymphoma (CLL), follicular and diffuse large B-cell (FL, DLBCL) lymphomas, have distinct clinical courses, yet overlapping “cell-of-origin”. Dynamic changes to the epigenome are essential regulators of B-cell differentiation. Therefore, we reasoned that these distinct cancers may be driven by shared mechanisms of disruption in transcriptional circuitry.

Methods

We compared purified malignant B-cells from 52 patients with normal B-cell subsets (germinal center centrocytes and centroblasts, naïve and memory B-cells) from 36 donor tonsils using >325 high-resolution molecular profiling assays for histone modifications, open chromatin (ChIP-, FAIRE-seq), transcriptome (RNA-seq), transcription factor (TF) binding, and genome copy number (microarrays).

Findings

From the resulting data, we identified gains in active chromatin in enhancers/super-enhancers that likely promote unchecked B-cell receptor signaling, including one we validated near the immunoglobulin superfamily receptors FCMR and PIGR. More striking and pervasive was the profound loss of key B-cell identity TFs, tumor suppressors and their super-enhancers, including EBF1, OCT2(POU2F2), and RUNX3. Using a novel approach to identify transcriptional feedback, we showed that these core transcriptional circuitries are self-regulating. Their selective gain and loss form a complex, iterative, and interactive process that likely curbs B-cell maturation and spurs proliferation.

Interpretation

Our study is the first to map the transcriptional circuitry of the most common blood cancers. We demonstrate that a critical subset of B-cell TFs and their cognate enhancers form self-regulatory transcriptional feedback loops whose disruption is a shared mechanism underlying these diverse subtypes of B-cell lymphoma.

Funding

National Institute of Health, Siteman Cancer Center, Barnes-Jewish Hospital Foundation, Doris Duke Foundation.

The Second-Generation PIM Kinase Inhibitor TP-3654 Resensitizes ABCG2-Overexpressing Multidrug-Resistant Cancer Cells to Cytotoxic Anticancer Drugs

Human ATP-binding cassette (ABC) subfamily G member 2 (ABCG2) mediates the transport of a wide variety of conventional cytotoxic anticancer drugs and molecular targeted agents. Consequently, the overexpression of ABCG2 in cancer cells is linked to the development of the multidrug resistance (MDR) phenotype. TP-3654 is an experimental second-generation inhibitor of PIM kinase that is currently under investigation in clinical trials to treat advanced solid tumors and myelofibrosis. In this study, we discovered that by attenuating the drug transport function of ABCG2, TP-3654 resensitizes ABCG2-overexpressing multidrug-resistant cancer cells to cytotoxic ABCG2 substrate drugs topotecan, SN-38 and mitoxantrone. Moreover, our results indicate that ABCG2 does not mediate resistance to TP-3654 and may not play a major role in the induction of resistance to TP-3654 in cancer patients. Taken together, our findings reveal that TP-3654 is a selective, potent modulator of ABCG2 drug efflux function that may offer an additional combination therapy option for the treatment of multidrug-resistant cancers.

Identification of PLA2G7 as a novel biomarker of diffuse large B cell lymphoma

BACKGROUND

Diffuse large B-cell lymphoma is the most common form of non-Hodgkin lymphoma globally, and patients with relapsed or refractory DLBCL typically experience poor long-term outcomes.

METHODS

Differentially expressed genes associated with DLBCL were identified using two GEO datasets in an effort to detect novel diagnostic or prognostic biomarkers of this cancer type, after which receiver operating characteristic curve analyses were conducted. Genes associated with DLBCL patient prognosis were additionally identified via WCGNA analyses of the TCGA database. The expression of PLA2G7 in DLBCL patient clinical samples was further assessed, and the functional role of this gene in DLBCL was assessed through in vitro and bioinformatics analyses.

RESULTS

DLBCL-related DEGs were found to be most closely associated with immune responses, cell proliferation, and angiogenesis. WCGNA analyses revealed that PLA2G7 exhibited prognostic value in DLBCL patients, and the upregulation of this gene in DLBCL patient samples was subsequently validated. PLA2G7 was also found to be closely linked to tumor microenvironmental composition such that DLBCL patients expressing higher levels of this gene exhibited high local monocyte and gamma delta T cell levels. In vitro experiments also revealed that knocking down PLA2G7 expression was sufficient to impair the migration and proliferation of DLBCL cells while promoting their apoptotic death. Furthmore, the specific inhibitor of PLA2G7, darapladib, could noticeably restrained the DLBCL cell viability and induced apoptosis.

CONCLUSIONS

PLA2G7 may represent an important diagnostic, prognostic, or therapeutic biomarker in patients with DLBCL.

Distinct evolutionary paths in chronic lymphocytic leukemia during resistance to the graft-versus-leukemia effect

Leukemic relapse remains a major barrier to successful allogeneic hematopoietic stem cell transplantation (allo-HSCT) for aggressive hematologic malignancies. The basis for relapse of advanced lymphoid malignancies remains incompletely understood and may involve escape from the graft-versus-leukemia (GvL) effect. We hypothesized that for patients with chronic lymphocytic leukemia (CLL) treated with allo-HSCT, leukemic cell-intrinsic features influence transplant outcomes by directing the evolutionary trajectories of CLL cells. Integrated genetic, transcriptomic, and epigenetic analyses of CLL cells from 10 patients revealed that the clinical kinetics of post-HSCT relapse are shaped by distinct molecular dynamics. Early relapses after allo-HSCT exhibited notable genetic stability; single CLL cell transcriptional analysis demonstrated a cellular heterogeneity that was static over time. In contrast, CLL cells relapsing late after allo-HSCT displayed notable genetic evolution and evidence of neoantigen depletion, consistent with marked single-cell transcriptional shifts that were unique to each patient. We observed a greater rate of epigenetic change for late relapses not seen in early relapses or relapses after chemotherapy alone, suggesting that the selection pressures of the GvL bottleneck are unlike those imposed by chemotherapy. No selective advantage for human leukocyte antigen (HLA) loss was observed, even when present in pretransplant subpopulations. Gain of stem cell modules was a common signature associated with leukemia relapse regardless of posttransplant relapse kinetics. These data elucidate the biological pathways that underlie GvL resistance and posttransplant relapse.

Positive regulation of PFKFB3 by PIM2 promotes glycolysis and paclitaxel resistance in breast cancer

BACKGROUND

Breast cancer (BC) is one of the most common female malignancies in the world. Chemotherapeutic resistance is the major cause of BC therapy failure, leading to tumor recurrence and metastasis. Studies have illustrated the close relationship between glycolysis and BC progression and drug resistance. The key glycolysis regulator, PFKFB3 makes a difference during BC progression and drug resistance. However, the mechanism remains to be unknown.

METHODS

Mass spectrometry analyses were used to found that PIM2 was a potential new binding protein of PFKFB3. Co-immunoprecipitated and western blot were used to verify the interaction between PIM2 and PFKFB3 in BC and the molecular mechanism by which PIM2 phosphorylates PFKFB3 in regulating the protein function. PFKFB3 mutant forms were used to demonstrate the need for PFKFB3 in BC drug resistance.

RESULTS

We identified that PIM2 is a new binding protein of PFKFB3. We used biochemical methods to determine that PIM2 can directly bind and change the phosphorylation of PFKFB3 at Ser478 to enhance PFKFB3 protein stability through the ubiquitin-proteasome pathway. Importantly, phosphorylation of PFKFB3 at Ser478 promoted glycolysis, BC cell growth, and paclitaxel resistance together with PIM2 in vitro and in vivo.

CONCLUSION

Our study demonstrates that PIM2 mediates PFKFB3 phosphorylation thus regulates glycolysis and paclitaxel resistance to promote tumor progression in BC and provides preclinical evidence for targeting PFKFB3 as a new strategy in BC treatment to battle paclitaxel resistance.

HELQ and EGR3 expression correlate with IGHV mutation status and prognosis in chronic lymphocytic leukemia

Background

IGHV mutation status is a crucial prognostic biomarker for CLL. In the present study, we investigated the transcriptomic signatures associating with IGHV mutation status and CLL prognosis.

Methods

The co-expression modules and hub genes correlating with IGHV status, were identified using the GSE28654, by ‘WGCNA’ package and R software (version 4.0.2). The over-representation analysis was performed to reveal enriched cell pathways for genes of correlating modules. Then 9 external cohorts were used to validate the correlation of hub genes expression with IGHV status or clinical features (treatment response, transformation to Richter syndrome, etc.). Moreover, to elucidate the significance of hub genes on disease course and prognosis of CLL patients, the Kaplan–Meier analysis for the OS and TTFT of were performed between subgroups dichotomized by the median expression value of individual hub genes.

Results

2 co-expression modules and 9 hub genes ((FCRL1/FCRL2/HELQ/EGR3LPL/LDOC1/ZNF667/SOWAHC/SEPTIN10) correlating with IGHV status were identified by WGCNA, and validated by external datasets. The modules were found to be enriched in NF-kappaB, HIF-1 and other important pathways, involving cell proliferation and apoptosis. The expression of hub genes was revealed to be significantly different, not only between CLL and normal B cell, but also between various types of lymphoid neoplasms. HELQ expression was found to be related with response of immunochemotherapy treatment significantly (p = 0.0413), while HELQ and ZNF667 were expressed differently between stable CLL and Richter syndrome patients (p < 0.0001 and p = 0.0278, respectively). By survival analysis of subgroups, EGR3 expression was indicated to be significantly associated with TTFT by 2 independent cohorts (GSE39671, p = 0.0311; GSE22762, p = 0.0135). While the expression of HELQ and EGR3 was found to be associated with OS (p = 0.0291 and 0.0114 respectively).The Kras, Hedgehog and IL6-JAK-STAT3 pathways were found to be associating with the expression of hub genes, resulting from GSEA.

Conclusions

The expression of HELQ and EGR3 were correlated with IGHV mutation status in CLL patients. Additionally, the expression of HELQ/EGR3 were prognostic markers for CLL associating with targetable cell signaling pathways.

PIM2 deletion alleviates lipopolysaccharide (LPS)-induced respiratory distress syndrome (ARDS) by suppressing NLRP3 inflammasome

Inflammation has an essential role in regulating the pathogenesis of acute respiratory distress syndrome (ARDS). The serine/threonine kinase PIM2 is highly expressed in human macrophages, and exhibits regulatory role in inflammatory response. However, its effect on ARDS progression has not been investigated and still remains unclear. In the study, we attempted to investigate the potential of PIM2 during ARDS progression, and to reveal the underlying molecular mechanisms. Here, we found that PIM2 expression was dramatically up-regulated in lipopolysaccharide (LPS)-exposed murine macrophages through a dose- and time-dependent manner. Additionally, we found that PIM2 knockdown greatly alleviated LPS-triggered activation of Caspase-1, interleukin (IL)-1β, NOD-like receptor pyrin domain 3 (NLRP3) and apoptosis-associated speck-like protein (ASC) in macrophages, along with suppressed inflammatory response. Importantly, we identified that PIM2 could directly interact with NLRP3. PIM2 over-expression could further promote LPS-triggered inflammation and NLRP3 inflammasome in macrophages. Furthermore, PIM2 knockout significantly alleviated the severity of ARDS in LPS-challenged mice. Evidently decreased inflammatory response and NLRP3 inflammasome were detected in pulmonary tissues of LPS-treated mice with PIM2 deficiency. Together, our findings demonstrated that PIM2 as a promising therapeutic target for ARDS treatment through regulating NLRP3 inflammasome.

MDM2-P53 Signaling Pathway-Mediated Upregulation of CDC20 Promotes Progression of Human Diffuse Large B-Cell Lymphoma

Background

Cell-division cycle 20 (CDC20) is overexpressed in a variety of tumor cells and is negatively regulated by wild-type p53 (wtp53). Our previous study uncovered that CDC20 was upregulated and associated with poor outcome in diffuse large B-cell lymphoma (DLBCL) based on bioinformatics analysis. Dysregulation of the MDM2-p53 is a major mechanism to promote DLBCL. Thus, we hypothesized that CDC20 could be a downstream gene of the MDM2-p53 signaling pathway. However, the clinical significance and mechanistic role of a novel MDM2-p53-CDC20 signaling pathway in DLBCL have still remained unclear.

Materials and Methods

RT-qPCR was performed in MDM2 knocked down (KD) and control (Ctrl) OCI-Ly3/OCI-Ly10 cells to investigate whether CDC20 was a downstream gene of the MDM2-p53 pathway. The effects of CDC20 on cell proliferation, cell cycle and apoptosis were assessed, as well as the role of CDC20 in suppressing tumorigenicity in vivo. Furthermore, we also investigated the roles of CDC20 and MDM2 in progression of DLBCL and the underlying mechanisms.

Results

The results of RT-qPCR revealed that CDC20 was downregulated while TP53 was upregulated in MDM2 KD OCI-Ly3 and OCI-Ly10 cells. It was unveiled that the expression levels of CDC20 and MDM2 were upregulated in DLBCL tissues and cells, and high CDC20 expression was correlated with adverse clinical features and poor outcome. Functional assays showed that downregulation of CDC20 could inhibit proliferation, induce apoptosis and cell cycle arrest in vitro. In addition, inactivation of the MDM2-p53 pathway by downregulation of MDM2 restored wtp53 expression level and reduced CDC20 protein level in OCI-Ly3 and OCI-Ly10 cells. Besides, targeting CDC20 was found to suppress tumorigenesis of DLBCL in vivo.

Conclusion

CDC20 was identified as a key downstream gene of the MDM2-p53 signaling pathway in DLBCL and may be used as a novel target gene to guide therapeutic applications.

Mantle cell lymphoma: insights into therapeutic targets at the preclinical level

INTRODUCTION

Mantle cell lymphoma (MCL) is a chronically relapsing B-cell non-Hodgkin lymphoma characterized by recurrent molecular-cytogenetic aberrations that lead to deregulation of DNA damage response, cell cycle progression, epigenetics, apoptosis, proliferation, and motility. In the last 10 years, clinical approval of several innovative drugs dramatically changed the landscape of treatment options in the relapsed/refractory (R/R) MCL, which translated into significantly improved survival parameters.

AREAS COVERED

Here, up-to-date knowledge on the biology of MCL together with currently approved and clinically tested frontline and salvage therapies are reviewed. In addition, novel therapeutic targets in MCL based on the scientific reports published in Pubmed are discussed.

EXPERT OPINION

Bruton tyrosine-kinase inhibitors, NFkappaB inhibitors, BCL2 inhibitors, and immunomodulary agents in combination with monoclonal antibodies and genotoxic drugs have the potential to induce long-term remissions in majority of newly diagnosed MCL patients. Several other classes of anti-tumor drugs including phosphoinositole-3-kinase, cyclin-dependent kinase or DNA damage response kinase inhibitors have demonstrated promising anti-lymphoma efficacy in R/R MCL. Most importantly, adoptive immunotherapy with genetically modified T-cells carrying chimeric antigen receptor represents a potentially curative treatment approach even in the patients with chemotherapy and ibrutinib-refractory disease.

Fructose-1, 6-bisphosphatase 1 interacts with NF-κB p65 to regulate breast tumorigenesis via PIM2 induced phosphorylation

Rationale: Fructose-1, 6-bisphosphatase 1 (FBP1), a rate-limiting enzyme in gluconeogenesis, was recently shown to be a tumor suppressor and could mediate the activities of multiple transcriptional factors via its non-canonical functions. However, the underlying mechanism of posttranscriptional modification on the non-canonical functions of FBP1 remains elusive.

Methods: We employed immunoaffinity purification to identify binding partner(s) and used co-immunoprecipitation to verify their interactions. Kinase reaction was used to confirm PIM2 could phosphorylate FBP1. Overexpression or knockdown proteins were used to assess the role in modulating p65 protein stability. Mechanistic analysis was involved in protein degradation and polyubiquitination assays. Nude mice and PIM2-knockout mice was used to study protein functions in vitro and in vivo.

Results: Here, we identified Proviral Insertion in Murine Lymphomas 2 (PIM2) as a new binding partner of FBP1, which could phosphorylate FBP1 on Ser144. Surprisingly, phosphorylated FBP1 Ser144 abrogated its interaction with NF-κB p65, promoting its protein stability through the CHIP-mediated proteasome pathway. Furthermore, phosphorylation of FBP1 on Ser144 increased p65 regulated PD-L1 expression. As a result, phosphorylation of FBP1 on Ser144 promoted breast tumor growth in vitro and in vivo. Moreover, the levels of PIM2 and pSer144-FBP1 proteins were positively correlated with each other in human breast cancer and PIM2 knockout mice.

Conclusions: Our findings revealed that phosphorylation noncanonical FBP1 by PIM2 was a novel regulator of NF-κB pathway, and highlights PIM2 inhibitors as breast cancer therapeutics.

HDAC3 functions as a positive regulator in Notch signal transduction

Aberrant Notch signaling plays a pivotal role in T-cell acute lymphoblastic leukemia (T-ALL) and chronic lymphocytic leukemia (CLL). Amplitude and duration of the Notch response is controlled by ubiquitin-dependent proteasomal degradation of the Notch1 intracellular domain (NICD1), a hallmark of the leukemogenic process. Here, we show that HDAC3 controls NICD1 acetylation levels directly affecting NICD1 protein stability. Either genetic loss-of-function of HDAC3 or nanomolar concentrations of HDAC inhibitor apicidin lead to downregulation of Notch target genes accompanied by a local reduction of histone acetylation. Importantly, an HDAC3-insensitive NICD1 mutant is more stable but biologically less active. Collectively, these data show a new HDAC3- and acetylation-dependent mechanism that may be exploited to treat Notch1-dependent leukemias.

Biosystem Analysis of the Hypoxia Inducible Domain Family Member 2A: Implications in Cancer Biology

The expression of HIGD2A is dependent on oxygen levels, glucose concentration, and cell cycle progression. This gene encodes for protein HIG2A, found in mitochondria and the nucleus, promoting cell survival in hypoxic conditions. The genomic location of HIGD2A is in chromosome 5q35.2, where several chromosomal abnormalities are related to numerous cancers. The analysis of high definition expression profiles of HIGD2A suggests a role for HIG2A in cancer biology. Accordingly, the research objective was to perform a molecular biosystem analysis of HIGD2A aiming to discover HIG2A implications in cancer biology. For this purpose, public databases such as SWISS-MODEL protein structure homology-modelling server, Catalogue of Somatic Mutations in Cancer (COSMIC), Gene Expression Omnibus (GEO), MethHC: a database of DNA methylation and gene expression in human cancer, and microRNA-target interactions database (miRTarBase) were accessed. We also evaluated, by using Real-Time Quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR), the expression of Higd2a gene in healthy bone marrow-liver-spleen tissues of mice after quercetin (50 mg/kg) treatment. Thus, among the structural features of HIG2A protein that may participate in HIG2A translocation to the nucleus are an importin α-dependent nuclear localization signal (NLS), a motif of DNA binding residues and a probable SUMOylating residue. HIGD2A gene is not implicated in cancer via mutation. In addition, DNA methylation and mRNA expression of HIGD2A gene present significant alterations in several cancers; HIGD2A gene showed significant higher expression in Diffuse Large B-cell Lymphoma (DLBCL). Hypoxic tissues characterize the “bone marrow-liver-spleen” DLBCL type. The relative quantification, by using qRT-PCR, showed that Higd2a expression is higher in bone marrow than in the liver or spleen. In addition, it was observed that quercetin modulated the expression of Higd2a gene in mice. As an assembly factor of mitochondrial respirasomes, HIG2A might be unexpectedly involved in the change of cellular energetics happening in cancer. As a result, it is worth continuing to explore the role of HIGD2A in cancer biology.

Anti‑survival and pro‑apoptotic effects of meridianin C derivatives on MV4‑11 human acute myeloid leukemia cells

Meridianin C is a marine natural product with anticancer activity. Several meridianin C derivatives (compounds 7a‑j) were recently synthesized, and their inhibitory effects on pro‑viral integration site for Moloney murine leukemia virus (PIM) kinases, as well as their antiproliferative effects on human leukemia cells, were reported. However, the anti‑leukemic effects and mechanisms of action of meridianin C and its derivatives remain largely unknown. The aim of the present study was to investigate the effects of meridianin C and its derivatives on MV4‑11 human acute myeloid leukemia cell growth. The parent compound meridianin C did not markedly affect the viability and survival of MV4‑11 cells. By contrast, MV4‑11 cell viability and survival were reduced by meridianin C derivatives, with compound 7a achieving the most prominent reduction. Compound 7a notably inhibited the expression and activity of PIM kinases, as evidenced by reduced B‑cell lymphoma‑2 (Bcl‑2)‑associated death promoter phosphorylation at Ser112. However, meridianin C also suppressed PIM kinase expression and activity, and the pan‑PIM kinase inhibitor AZD1208 only slightly suppressed the survival of MV4‑11 cells. Thus, the anti‑survival effect of compound 7a on MV4‑11 cells was unrelated to PIM kinase inhibition. Moreover, compound 7a induced apoptosis, caspase‑9 and ‑3 activation and poly(ADP‑ribose) polymerase (PARP) cleavage, but did not affect death receptor (DR)‑4 or DR‑5 expression in MV4‑11 cells. Compound 7a also induced the generation of cleaved Bcl‑2, and the downregulation of myeloid cell leukemia (Mcl)‑1 and X‑linked inhibitor of apoptosis (XIAP) in MV4‑11 cells. Furthermore, compound 7a increased eukaryotic initiation factor (eIF)‑2α phosphorylation and decreased S6 phosphorylation, whereas GRP‑78 expression was unaffected. Importantly, treatment with a pan‑caspase inhibitor (z‑VAD‑fmk) significantly attenuated compound 7a‑induced apoptosis, caspase‑9 and ‑3 activation, PARP cleavage, generation of cleaved Bcl‑2 and downregulation of Mcl‑1 and XIAP in MV4‑11 cells. Collectively, these findings demonstrated the strong anti‑survival and pro‑apoptotic effects of compound 7a on MV4‑11 cells through regulation of caspase‑9 and ‑3, Bcl‑2, Mcl‑1, XIAP, eIF‑2α and S6 molecules.

TRAF3 regulates the oncogenic proteins Pim2 and c-Myc to restrain survival in normal and malignant B cells

TRAF3 is a versatile intracellular adapter protein with multiple context-specific roles. Uniquely in B cells, TRAF3 deficiency enhances survival and increases the risk of transformation, as loss of TRAF3 is observed in several types of B cell cancers. Here, we report a new mechanism for TRAF3 in the restraint of B cell survival. We found that TRAF3 deficiency was associated with induction of the pro-survival kinase Pim2 in mouse primary B cells and human malignant B cell lines. The increase in Pim2 was independent of NF-κB2 activation but was ameliorated with inhibition of STAT3 expression or function. TRAF3 deficiency also led to a Pim2-dependent increase in c-Myc protein levels and was associated with reduced c-Myc ubiquitination. TRAF3-deficient primary B cells were less sensitive to cell death induced by the Pim inhibitors SGI-1776 and TP-3654. Interestingly, human malignant B cell lines with low expression of TRAF3 were more sensitive to Pim inhibition-induced cell death. Combination treatment of TRAF3-deficient B cells and B cell tumor lines with c-Myc inhibitors enhanced their sensitivity to Pim inhibition, suggesting a possible therapeutic strategy. TRAF3 thus suppresses a Pim2-mediated B cell survival axis, which can be a potential target for treatment of B cell malignancies.

Bioinformatic validation identifies candidate key genes in diffuse large-B cell lymphoma

Aim: In this study, four datasets concerning 167 diffuse large B-cell lymphoma (DLBCL) patients versus 56 controls and seven datasets involving 280 germinal center B-cell like (GCB) versus 224 activated B-cell like (ABC) DLBCL were included. Materials & methods: We identified 80 different expression genes (DEGs) for DLBCL versus nontumor and 77 DEGs for GCB versus ABC DLBCL. Results: These DEGs were found to be enriched in cell activity, signal transduction and extracellular region. Then ten central node genes for DLBCL versus nontumor and two hub genes for GCB versus ABC DLBCL were identified. Last, PAICS, IRF4 and PTPN1 were explored to be correlated with poor prognosis in DLBCL patients. Conclusion: Our study has identified critical genes from transcriptional profiles for DLBCL.

Influence of the bispecific antibody IgG subclass on T cell redirection

T cell redirection mediated by bispecific antibodies (BsAbs) is a promising cancer therapy. Dual antigen binding is necessary for potent T cell redirection and is influenced by the structural characteristics of a BsAb, which are dependent on its IgG subclass. In this study, model BsAbs targeting CD19xCD3 were generated in variants of IgG1, IgG2, and IgG4 carrying Fc mutations that reduce FcγR interaction, and two chimeric IgG subclasses termed IgG1:2 and IgG4:2, in which the IgG1- or IgG4-F(ab)2 are grafted on an IgG2 Fc. Molecules containing an IgG2 or IgG4-F(ab)2 domain were confirmed to be the most structurally compact molecules. All BsAbs were shown to bind both of their target proteins (and corresponding cells) equally well. However, CD19xCD3 IgG2 did not bind both antigens simultaneously as measured by the absence of cellular clustering of T cells with target cells. This translated to a reduced potency of IgG2 BsAbs in T-cell redirection assays. The activity of IgG2 BsAbs was fully restored in the chimeric subclasses IgG4:2 and IgG1:2. This confirmed the major contribution of the F(ab)2 region to the BsAb's functional activity and demonstrated that function of BsAbs can be modulated by engineering molecules combining different Fc and F(ab)2 domains. Abbreviations: ADCC: Antibody-dependent cellular cytotoxicity; AlphaScreenTM: Amplified Luminescent Proximity Homogeneous Assay Screening; ANOVA: Analysis of variance; BiTE: bispecific T-cell engager; BSA: bovine serum albumin; BsAb: bispecific antibody; cFAE: controlled Fab-arm exchange; CDC: complement-dependent cellular cytotoxicity; CIEX: cation-exchange; CIR: chimeric immune receptor; DPBS: Dulbecco's phosphate-buffered saline; EC50 value: effective concentration to reach half-maximum effect; EGFR: epidermal growth factor receptor; EI: expansion index (RAt=x/RAt=0); FACS: fluorescence-activated cell sorting; FVD: fixable viability dye; HI-HPLC: hydrophobic interaction HPLC; HI-FBS: heat-inactivated fetal bovine serum; HPLC: high-pressure liquid chromatography; IC50 value: effective concentration to reach half-maximum inhibition; IQ: Inhibition Quotient; IS: immunological synapse; MES: 2-(N-morpholino)ethanesulfonic acid; R-PE: recombinant phycoerythrin; RA: red area in μm2/well; RD: receptor density; RFP: red fluorescent protein; Rg: radius of gyration; RSV: respiratory syncytial virus; SAXS: small-angle x-ray scattering; scFv: single-chain variable fragment; SD: standard deviation; SPR: surface plasmon resonance; WT: wild-type.

CD81 is a novel immunotherapeutic target for B cell lymphoma

The anti-CD81 mAb (5A6) eliminates lymphoma tumor cells from patient follicular biopsy specimens while sparing the imbedded normal B and T lymphocytes. It has equivalent therapeutic effects as rituximab against a xenografted human B cell lymphoma.

The tetraspanin CD81 was initially discovered by screening mAbs elicited against a human B cell lymphoma for their direct antiproliferative effects. We now show that 5A6, one of the mAbs that target CD81, has therapeutic potential. This antibody inhibits the growth of B cell lymphoma in a xenograft model as effectively as rituximab, which is a standard treatment for B cell lymphoma. Importantly, unlike rituximab, which depletes normal as well as malignant B cells, 5A6 selectively kills human lymphoma cells from fresh biopsy specimens while sparing the normal lymphoid cells in the tumor microenvironment. The 5A6 antibody showed a good safety profile when administered to a mouse transgenic for human CD81. Taken together, these data provide the rationale for the development of the 5A6 mAb and its humanized derivatives as a novel treatment against B cell lymphoma.

PIM kinase inhibitor, AZD1208, inhibits protein translation and induces autophagy in primary chronic lymphocytic leukemia cells

The PIM1, PIM2, and PIM3 serine/threonine kinases play a role in the proliferation and survival of cancer cells. Mice lacking these three kinases were viable. Further, in human hematological malignancies, these proteins are overexpressed making them suitable targets. Several small molecule inhibitors against this enzyme were synthesized and tested. AZD1208, an orally available small-molecule drug, inhibits all three PIM kinases at a low nanomolar range. AZD1208 has been tested in clinical trials for patients with solid tumors and hematological malignancies, especially acute myelogenous leukemia. The present study evaluated the efficacy and biological actions of AZD1208 in chronic lymphocytic leukemia (CLL) cells. CLL cells had higher levels of PIM2 protein and mRNAs than did normal lymphocytes from healthy donors. Treatment of CLL lymphocytes with AZD1208 resulted in modest cell death, whereas practically no cytotoxicity was observed in healthy lymphocytes. To determine the mechanism by which AZD1208 inhibits PIM kinase function, we evaluated PIM kinase pathway and downstream substrates. Because peripheral blood CLL cells are replicationally quiescent, we analyzed substrates involved in apoptosis, transcription, and translation but not cell cycle targets. AZD1208 inhibited protein translation by decreasing phosphorylation levels of 4E-binding protein 1 (4E-BP1). AZD1208 induced autophagy in replicationally-quiescent CLL cells, which is consistent with protein translation inhibition. These data suggest that AZD1208 may elicit cytotoxicity in CLL cells through inhibiting translation and autophagy induction.

PIM kinases mediate resistance of glioblastoma cells to TRAIL by a p62/SQSTM1-dependent mechanism

Glioblastoma (GBM) is the most common and aggressive brain tumor and is associated with poor prognosis. GBM cells are frequently resistant to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and finding new combinatorial therapies to sensitize glioma cells to TRAIL remains an important challenge. PIM kinases are serine/threonine kinases that promote cell survival and proliferation and are highly expressed in different tumors. In this work, we studied the role of PIM kinases as regulators of TRAIL sensitivity in GBM cells. Remarkably, PIM inhibition or knockdown facilitated activation by TRAIL of a TRAIL-R2/DR5-mediated and mitochondria-operated apoptotic pathway in TRAIL-resistant GBM cells. The sensitizing effect of PIM knockdown on TRAIL-induced apoptosis was mediated by enhanced caspase-8 recruitment to and activation at the death-inducing signaling complex (DISC). Interestingly, TRAIL-induced internalization of TRAIL-R2/DR5 was significantly reduced in PIM knockdown cells. Phospho-proteome profiling revealed a decreased phosphorylation of p62/SQSTM1 after PIM knockdown. Our results also showed an interaction between p62/SQSTM1 and the DISC that was reverted after PIM knockdown. In line with this, p62/SQSTM1 ablation increased TRAIL-R2/DR5 levels and facilitated TRAIL-induced caspase-8 activation, revealing an inhibitory role of p62/SQSTM1 in TRAIL-mediated apoptosis in GBM. Conversely, upregulation of TRAIL-R2/DR5 upon PIM inhibition and apoptosis induced by the combination of PIM inhibitor and TRAIL were abrogated by a constitutively phosphorylated p62/SQSTM1^S332E mutant. Globally, our data represent the first evidence that PIM kinases regulate TRAIL-induced apoptosis in GBM and identify a specific role of p62/SQSTM1^Ser332 phosphorylation in the regulation of the extrinsic apoptosis pathway activated by TRAIL.

AZD1208, a Pan-Pim Kinase Inhibitor, Has Anti-Growth Effect on 93T449 Human Liposarcoma Cells via Control of the Expression and Phosphorylation of Pim-3, mTOR, 4EBP-1, S6, STAT-3 and AMPK

Overexpression of Pim kinases has an oncogenic/pro-survival role in many hematological and solid cancers. AZD1208 is a pan-Pim kinase inhibitor that has anti-cancer and anti-adipogenic actions. Here, we investigated the effects of AZD1208 on the growth of 93T449 cells, a differentiated human liposarcoma cell line. At 20 µM, AZD1208 was cytotoxic (cytostatic) but not apoptotic, reducing cell survival without DNA fragmentation, caspase activation or increasing cells in the sub G1 phase; known apoptotic parameters. Notably, AZD1208 reduced phosphorylation of signal transducer and activator of transcription-3 (STAT-3) in 93T449 cells. STAT-3 inhibition by AG490, a JAK2/STAT-3 inhibitor similarly reduced cell survival. AZD1208 down-regulated phosphorylation of mammalian target of rapamycin (mTOR) and ribosomal S6 while up-regulated eukaryotic initiation factor-2α (eIF-2α). In addition, AZD1208 induced a LKB-1-independent AMPK activation, which was crucial for its cytostatic effect, as knock-down of AMPK greatly blocked AZD1208s ability to reduce cell survival. AZD1208 had no effect on expression of two members of Pim kinase family (Pim-1 and Pim-3) but inhibited phosphorylation of 4EBP-1, a downstream effector of Pim kinases. Importantly, a central role for Pim-3 in the actions of AZD1208 was confirmed by knock-down, which not only reduced 93T449 cell survival but also led to the inhibition of 4EBP-1, mTOR, eIF-2α and STAT-3, along with the activation of AMPK. In summary, this is the first report demonstrating that AZD1208 inhibits growth of liposarcoma cells and that this activity is mediated through Pim-3 kinase, STAT-3, mTOR, S6 and AMPK expression and phosphorylation pathways.

Gene expression profiles analysis identifies a novel two-gene signature to predict overall survival in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common hematologic malignancy, however, specific tumor-associated genes and signaling pathways are yet to be deciphered. Differentially expressed genes (DEGs) were computed based on gene expression profiles from GSE32018, GSE56315, and The Cancer Genome Atlas (TCGA) DLBC. Overlapping DEGs were then evaluated for gene ontology (GO), pathways enrichment, DNA methylation, protein–protein interaction (PPI) network analysis as well as survival analysis. Seventy-four up-regulated and 79 down-regulated DEGs were identified. From PPI network analysis, majority of the DEGs were involved in cell cycle, oocyte meiosis, and epithelial-to-mesenchymal transition (EMT) pathways. Six hub genes including CDC20, MELK, PBK, prostaglandin D2 synthase (PTGDS), PCNA, and CDK1 were selected using the Molecular Complex Detection (MCODE). CDC20 and PTGDS were able to predict overall survival (OS) in TCGA DLBC and in an additional independent cohort GSE31312. Furthermore, CDC20 DNA methylation negatively regulated CDC20 expression and was able to predict OS in DLBCL. A two-gene panel consisting of CDC20 and PTGDS had a better prognostic value compared with CDC20 or PTGDS alone in the TCGA cohort (P=0.026 and 0.039). Overall, the present study identified a set of novel genes and pathways that may play a significant role in the initiation and progression of DLBCL. In addition, CDC20 and PTGDS will provide useful guidance for therapeutic applications.

Identification of MMP9 as a novel key gene in mantle cell lymphoma based on bioinformatic analysis and design of cyclic peptides as MMP9 inhibitors based on molecular docking

Mantle cell lymphoma (MCL) is an aggressive disease. MCL is associated with poor patient prognosis and limited survival. To identify key genes and explore targeting cyclic peptide inhibitors for the treatment of MCL, we downloaded two gene expression profiles (GSE32018 and GSE9327) from the Gene Expression Omnibus (GEO) database. We screened 84 differentially expressed genes (DEGs). Pathway analysis showed that DEMs were mainly enriched in the ‘Pathway in cancer’, ‘PI3K-Akt signaling pathway’, ‘Cytokine-cytokine receptor interaction’, ‘Rap1 signaling pathway’, ‘NF-κB signaling pathway’ and ‘Leukocyte trans-endothelial migration’. We subsequently constructed a protein-protein interaction (PPI) network of DEGs. In addition, matrix metalloproteinase 9 (MMP9) with a high degree in the PPI network was identified as a hub gene in MCL. Meanwhile in the Molecular Complex Detection (MCODE) analysis, MMP9 was located in the important cluster. Thus, MMP9 can be used as a therapeutic target for MCL and we designed cyclic peptides as MMP9 inhibitors. MMP9 protein structure was gathered from the Protein Data Bank (PDB), with a PDB ID: 1L6J. MMP9 and cyclic peptides were docked using Molecular Operating Environment (MOE) software after structural optimization. It was revealed that cyclic peptide 2 bound deeply in the binding pocket of MMP9 and had interaction with the active-site Zn²⁺ ion in the catalytic domain. Cyclic peptides 1, 2, 4–6 also displayed potential interaction with active residues of MMP9; thus, these cyclic peptides can serve as potential drug candidates to block MMP9 activity and future studies are warranted to confirm their efficacy.

Preclinical characterization of INCB053914, a novel pan-PIM kinase inhibitor, alone and in combination with anticancer agents, in models of hematologic malignancies

The Proviral Integration site of Moloney murine leukemia virus (PIM) serine/threonine protein kinases are overexpressed in many hematologic and solid tumor malignancies and play central roles in intracellular signaling networks important in tumorigenesis, including the Janus kinase-signal transducer and activator of transcription (JAK/STAT) and phosphatidylinositol 3-kinase (PI3K)/AKT pathways. The three PIM kinase isozymes (PIM1, PIM2, and PIM3) share similar downstream substrates with other key oncogenic kinases and have differing but mutually compensatory functions across tumors. This supports the therapeutic potential of pan-PIM kinase inhibitors, especially in combination with other anticancer agents chosen based on their role in overlapping signaling networks. Reported here is a preclinical characterization of INCB053914, a novel, potent, and selective adenosine triphosphate-competitive pan-PIM kinase inhibitor. In vitro, INCB053914 inhibited proliferation and the phosphorylation of downstream substrates in cell lines from multiple hematologic malignancies. Effects were confirmed in primary bone marrow blasts from patients with acute myeloid leukemia treated ex vivo and in blood samples from patients receiving INCB053914 in an ongoing phase 1 dose-escalation study. In vivo, single-agent INCB053914 inhibited Bcl-2-associated death promoter protein phosphorylation and dose-dependently inhibited tumor growth in acute myeloid leukemia and multiple myeloma xenografts. Additive or synergistic inhibition of tumor growth was observed when INCB053914 was combined with selective PI3Kδ inhibition, selective JAK1 or JAK1/2 inhibition, or cytarabine. Based on these data, pan-PIM kinase inhibitors, including INCB053914, may have therapeutic utility in hematologic malignancies when combined with other inhibitors of oncogenic kinases or standard chemotherapeutics.

PIM-2 protein kinase negatively regulates T cell responses in transplantation and tumor immunity

PIM kinase family members play a crucial role in promoting cell survival and proliferation via phosphorylation of their target substrates. In this study, we investigated the role of the PIM kinases with respect to T cell responses in transplantation and tumor immunity. We found that the PIM-2 isoform negatively regulated T cell responses to alloantigen, in contrast to the PIM-1 and PIM-3 isoforms, which acted as positive regulators. T cells deficient in PIM-2 demonstrated increased T cell differentiation toward Th1 subset, proliferation, and migration to target organs after allogeneic bone marrow transplantation, resulting in dramatically accelerated graft-versus-host disease (GVHD) severity. Restoration of PIM-2 expression markedly attenuated the pathogenicity of PIM-2-deficient T cells to induce GVHD. On the other hand, mice deficient in PIM-2 readily rejected syngeneic tumor, which was primarily dependent on CD8+ T cells. Furthermore, silencing PIM-2 in polyclonal or antigen-specific CD8+ T cells substantially enhanced their antitumor response in adoptive T cell immunotherapy. We conclude that PIM-2 kinase plays a prominent role in suppressing T cell responses, and provide a strong rationale to target PIM-2 for cancer immunotherapy.

Intrinsic resistance to PIM kinase inhibition in AML through p38α-mediated feedback activation of mTOR signaling

Although conventional therapies for acute myeloid leukemia (AML) and diffuse large B-cell lymphoma (DLBCL) are effective in inducing remission, many patients relapse upon treatment. Hence, there is an urgent need for novel therapies. PIM kinases are often overexpressed in AML and DLBCL and are therefore an attractive therapeutic target. However, in vitro experiments have demonstrated that intrinsic resistance to PIM inhibition is common. It is therefore likely that only a minority of patients will benefit from single agent PIM inhibitor treatment. In this study, we performed an shRNA-based genetic screen to identify kinases whose suppression is synergistic with PIM inhibition. Here, we report that suppression of p38α (MAPK14) is synthetic lethal with the PIM kinase inhibitor AZD1208. PIM inhibition elevates reactive oxygen species (ROS) levels, which subsequently activates p38α and downstream AKT/mTOR signaling. We found that p38α inhibitors sensitize hematological tumor cell lines to AZD1208 treatment in vitro and in vivo. These results were validated in ex vivo patient-derived AML cells. Our findings provide mechanistic and translational evidence supporting the rationale to test a combination of p38α and PIM inhibitors in clinical trials for AML and DLBCL.

Downregulation of Pim-2 induces cell cycle arrest in the G0/G1 phase via the p53-non-dependent p21 signaling pathway

Pim-2 is a serine/threonine protein kinase that is highly expressed in various types of cancer, with essential roles in the regulation of signal transduction cascades, which promote cell survival and proliferation. The present study demonstrated that Pim-2 was expressed in cells lines derived from hematopoietic tumors and lung cancer. In vitro, downregulation of Pim-2 by short interfering RNA inhibited proliferation and delayed G₀/G₁ cell cycle progression in K562 leukemia, RPMI-8226 multiple myeloma, and H1299 and A549 non-small cell lung carcinoma cell lines. Furthermore, downregulation of Pim-2 resulted in upregulation of cyclin-dependent kinase (CDK) inhibitor p21, irrespective of the p53 status. In addition, the present study revealed that CDK2 and phosphorylated retinoblastoma (pRb) were significantly downregulated. This finding suggested that inhibition of CDK2 and pRb expression via upregulated p21 was involved in the downregulation of Pim-2-induced G₀/G₁ cell cycle arrest in lung cancer and hematopoietic malignancy cells. These results suggested that Pim-2 may serve a role in hematopoietic tumors, lung cancer proliferation and cell cycle progression by regulating the p21 signaling pathway. Downregulation of Pim-2 decreased cancer cell proliferation. Therefore, Pim-2 may be a potential therapy target in clinical cancer therapy.

The oncogenic membrane protein LMP1 sequesters TRAF3 in B-cell lymphoma cells to produce functional TRAF3 deficiency

Loss-of-function mutations in genes encoding the signaling protein tumor necrosis factor receptor-associated factor 3 (TRAF3) are commonly found in human B-cell malignancies, especially multiple myeloma and B-cell lymphoma (BCL). B-cell TRAF3 deficiency results in enhanced cell survival, elevated activation receptor signaling, and increased activity of certain transcriptional pathways regulating expression of prosurvival proteins. A recent analysis of TRAF3 protein staining of ∼300 human BCL tissue samples revealed that a higher proportion of samples expressing the oncogenic Epstein-Barr virus-encoded protein latent membrane protein 1 (LMP1) showed low/negative TRAF3 staining than predicted. LMP1, a dysregulated mimic of the CD40 receptor, binds TRAF3 more effectively than CD40. We hypothesized that LMP1 may sequester TRAF3, reducing its availability to inhibit prosurvival signaling pathways in the B cell. This hypothesis was addressed via 2 complementary approaches: (1) comparison of TRAF3-regulated activation and survival-related events with relative LMP1 expression in human BCL lines and (2) analysis of the impact upon such events in matched pairs of mouse BCL lines, both parental cells and subclones transfected with inducible LMP1, either wild-type LMP1 or a mutant LMP1 with defective TRAF3 binding. Results from both approaches showed that LMP1-expressing B cells display a phenotype highly similar to that of B cells lacking TRAF3 genes, indicating that LMP1 can render B cells functionally TRAF3 deficient without TRAF3 gene mutations, a finding of significant relevance to selecting pathway-targeted therapies for B-cell malignancies.

Mutational profile of primary breast diffuse large B-cell lymphoma

Primary breast lymphoma is a rare form of extra-nodal lymphoid neoplasm. The most common histological type is the diffuse large B-cell lymphoma, which represents 60–80% of all the cases. Our study analyzes the mutational profile of the primary lymphoma of the breast through targeted massive sequencing with a panel of 38 genes in a group of 17 patients with primary breast diffuse large B-cell lymphoma. Seventy-point-five percent of the patients presented with stage IE and 29.5% with stage IIE. 44% of the cases correspond to lymphomas with germinal center phenotype and 33.3% to activated B-cell. The genes with a higher mutational frequency include PIM1 (in 50% of the analyzed samples), MYD88 (39%), CD79B, PRDM1 and CARD11 (17%), KMT2D, TNFIAP3 and CREBBP (11%). The profile of mutant genes involves mostly the NFκB signaling pathway. The high frequency of mutations in PIM1 compared with other lymphomas may have implications in the clinical presentation and evolution of this type of lymphoma.