CD229 (Ly9) a Novel Biomarker for B-Cell Malignancies and Multiple Myeloma

Genetic analysis from multiple cohorts implies causality between 2200 druggable genes, telomere length, and leukemia

BACKGROUND

Clinical therapeutic targets for leukemia remain to be identified and the causality between leukemia and telomere length is unclear.

METHODS

This work employed cis expression quantitative trait locus (eQTL) for 2,200 druggable genes from the eQTLGen Consortium and genome-wide association studies (GWAS) summary data for telomere length in seven blood cell types from the UK Biobank, Netherlands Cohort as exposures. GWAS data for lymphoid leukemia (LL) and myeloid leukemia (ML) from FinnGen and Lee Lab were used as outcomes for discovery and replication cohorts, respectively. Robust Mendelian randomization (MR) findings were generated from seven MR models and a series of sensitivity analyses. Summary-data-based MR (SMR) analysis and transcriptome-wide association studies (TWAS) were further implemented to verify the association between identified druggable genes and leukemia. Single-cell type expression analysis was employed to identify the specific expression of leukemia casual genes on human bone marrow and peripheral blood immune cells. Multivariable MR analysis, linkage disequilibrium score regression (LDSC), and Bayesian colocalization analysis were performed to further validate the relationship between telomere length and leukemia. Mediation analysis was used to assess the effects of identified druggable genes affecting leukemia via telomere length. Phenome-wide MR (Phe-MR) analysis for assessing the effect of leukemia causal genes and telomere length on 1,403 disease phenotypes.

RESULTS

Combining the results of the meta-analysis for MR estimates from two cohorts, SMR and TWAS analysis, we identified five LL causal genes (TYMP, DSTYK, PPIF, GDF15, FAM20A) and three ML causal genes (LY75, ADA, ABCA2) as promising drug targets for leukemia. Univariable MR analysis showed genetically predicted higher leukocyte telomere length increased the risk of LL (odds ratio [OR] = 2.33, 95 % confidence interval [95 % CI] 1.70-3.18; P = 1.33E-07), and there was no heterogeneity and horizontal pleiotropy. Evidence from the meta-analysis of two cohorts strengthened this finding (OR = 1.88, 95 % CI 1.06-3.05; P = 0.01). Multivariable MR analysis showed the causality between leukocyte telomere length and LL without interference from the other six blood cell telomere length (OR = 2.72, 95 % CI 1.88-3.93; P = 1.23E-07). Evidence from LDSC supported the positive genetic correlation between leukocyte telomere length and LL (rg = 0.309, P = 0.0001). Colocalization analysis revealed that the causality from leukocyte telomere length on LL was driven by the genetic variant rs770526 in the TERT region. The mediation analysis via two-step MR showed that the causal effect from TYMP on LL was partly mediated by leukocyte telomere length, with a mediated proportion of 12 %.

CONCLUSION

Our study identified several druggable genes associated with leukemia risk and provided new insights into the etiology and drug development of leukemia. We also found that genetically predicted higher leukocyte telomere length increased LL risk and its potential mechanism of action.

T cell-redirecting therapies in hematological malignancies: Current developments and novel strategies for improved targeting

T cell-redirecting therapies (TCRTs), such as chimeric antigen receptor (CAR) or T cell receptor (TCR) T cells and T cell engagers, have emerged as a highly effective treatment modality, particularly in the B and plasma cell-malignancy setting. However, many patients fail to achieve deep and durable responses; while the lack of truly unique tumor antigens, and concurrent on-target/off-tumor toxicities, have hindered the development of TCRTs for many other cancers. In this review, we discuss the recent developments in TCRT targets for hematological malignancies, as well as novel targeting strategies that aim to address these, and other, challenges.

Targeting cancer stem cells in multiple myeloma

Multiple myeloma (MM) is a hematological malignancy of bone marrow (BM) plasma cells with excessive clonal expansion and is associated with the overproduction of light-chain or monoclonal immunoglobulins (Igs). MM remains incurable, with high rates of relapses and refractory disease after first-line treatment. Cancer stem cells (CSCs) have been implicated in drug resistance in MM; however, the evidence for CSCs in MM is not adequate, partly due to a lack of uniformity in the definitions of multiple myeloma stem cells (MMSCs). We review advances in understanding MMSCs and their role in drug resistance to MM therapies. We also discuss novel therapeutic strategies to overcome MMSC-mediated relapses and drug resistance.

A review: Mechanisms and molecular pathways of signaling lymphocytic activation molecule family 3 (SLAMF3) in immune modulation and therapeutic prospects

The signaling lymphocytic activation molecule (SLAM) family participates in the modulation of various innate and adaptive immune responses. SLAM family (SLAMF) receptors include nine transmembrane glycoproteins, of which SLAMF3 (also known as CD229 or Ly9) has important roles in the modulation of immune responses, from the fundamental activation and suppression of immune cells to the regulation of intricate immune networks. SLAMF3 is mainly expressed in immune cells, such as T, B, and natural killer cells. It has a unique molecular structure, including four immunoglobulin-like domains in the extracellular domain and two immunoreceptor tyrosine-based signaling motifs in the intracellular structural domains. These unique structures have important implications for protein functioning. SLAMF3 is involved in pathogenesis of various disease, particularly autoimmune diseases and cancer. However, despite its potential clinical significance, a comprehensive overview of the current paradigm of SLAMF3 research is lacking. This review summarizes the structure, functional mechanisms, and therapeutic implications of SLAMF3. Our findings highlight the significance of SLAMF3 in both physiological and pathological contexts, and underline its dual role in autoimmunity and malignancies, and including disease progression and prognosis. The review also proposes that future studies on SLAMF3 should explore its context-specific inhibitory and stimulatory effects, expand on its potential in disease mapping, investigate related signaling pathways, and explore its value as a drug target. Research in these areas related to SLAMF3 can provide more precise directions for future therapeutic strategies.

SLAM Family Receptors in B Cell Chronic Lymphoproliferative Disorders

The signaling lymphocytic activation molecule (SLAM) receptor family (SLAMF) consists of nine glycoproteins that belong to the CD2 superfamily of immunoglobulin (Ig) domain-containing molecules. SLAMF receptors modulate the differentiation and activation of a wide range of immune cells. Individual SLAMF receptors are expressed on the surface of hematopoietic stem cells, hematopoietic progenitor cells, B cells, T cells, NK cells, NKT cells, monocytes, macrophages, dendritic cells, neutrophils, and platelets. The expression of SLAMF receptors was studied during normal B cell maturation. Several SLAMF receptors were also detected in cancer cell lines of B-lymphoid origin and in pathological B cells from patients with B cell chronic lymphoproliferative disorders (B-CLPD), the most frequent hematological malignancies in adults. This review summarizes current knowledge on the expression of SLAMF receptors and their adaptor proteins SAP and EAT-2 in B-CLPD. Several SLAMF receptors could be regarded as potential diagnostic and differential diagnostic markers, prognostic factors, and targets for the development of novel drugs for patients with B-CLPD.

Utility of CD229 as novel marker in measurable residual disease assessment in multiple myeloma-An evidence-based approach

INTRODUCTION

CD229 has been found to be a useful plasma cell (PC) gating marker in multiple myeloma (MM). This study analyses the expression profile of CD229 on various bone marrow compartments namely, PC, non-PC and hematogones (HGs) using Multiparameter flow cytometry (MFC). Furthermore, it evaluates the ability of CD229 to delineate normal PC (NPC) from aberrant PC (APC) in measurable residual disease assessment (MRD) in MM.

METHODS

Bone marrow aspirates from patients diagnosed with MM (per standard IMWG criteria) were collected in EDTA and processed for MFC using a single tube 14-color antibody panel as per standard operating procedure.

RESULTS

A total of 74 patients with a diagnosis of MM (26 treatment naïve and 48 on therapy) were evaluated. The expression of CD229 was homogenous on both the PC and HG compartments as compared to CD138 and CD38. On comparing the expression of individual markers, it was found to be statistically significant between PC, HGs and non-PC for all three markers (p < 0.001). APC showed lower median expression of CD38 and higher median expression of CD138 and CD229 as compared to NPC and was found to be statistically significant for all markers (p < 0.001). In terms of differential expression on NPC and APC; CD38 was found to be the most aberrantly expressed (70%; 52/74) followed by CD229 (7%; 5/74) and CD138 (5%; 4/74).

CONCLUSIONS

CD229 can be used for the identification of PC and due to relatively homogenous expression; it can be used as a suitable marker for targeted therapies. However, precise discrimination of NPC from APC cannot be reliably achieved with CD229, limiting its utility as a useful marker of diagnostic relevance and MRD assessment in MM.