Globular C1q Receptor (gC1qR/p32/HABP1) Suppresses the Tumor-Inhibiting Role of C1q and Promotes Tumor Proliferation in 1q21-Amplified Multiple Myeloma

The numerous facets of 1q21+ in multiple myeloma: Pathogenesis, clinicopathological features, prognosis and clinical progress (Review)

Multiple myeloma (MM) is a malignant neoplasm characterized by the clonal proliferation of abnormal plasma cells (PCs) in the bone marrow and recurrent cytogenetic abnormalities. The incidence of MM worldwide is on the rise. 1q21+ has been found in ~30-40% of newly diagnosed MM (NDMM) patients.1q21+ is associated with the pathophysiological mechanisms of disease progression and drug resistance in MM. In the present review, the pathogenesis and clinicopathological features of MM patients with 1q21+ were studied, the key data of 1q21+ on the prognosis of MM patients were summarized, and the clinical treatment significance of MM patients with 1q21+ was clarified, in order to provide reference for clinicians to develop treatment strategies targeting 1q21+.

The role of proliferating stem-like plasma cells in relapsed or refractory multiple myeloma: Insights from single-cell RNA sequencing and proteomic analysis

The management and comprehension of relapsed or refractory multiple myeloma (RRMM) continues to pose a significant challenge. By integrating single-cell RNA sequencing (scRNA-seq) data of 15 patients with plasma cell disorders (PCDs) and proteomic data obtained from mass spectrometry-based analysis of CD138+ plasma cells (PCs) from 144 PCDs patients, we identified a state of malignant PCs characterized by high stemness score and increased proliferation originating from RRMM. This state has been designated as proliferating stem-like plasma cells (PSPCs). NUCKS1 was identified as the gene marker representing the stemness of PSPCs. Comparison of differentially expressed genes among various PC states revealed a significant elevation in LGALS1 expression in PSPCs. Survival analysis on the MMRF CoMMpass dataset and GSE24080 dataset established LGALS1 as a gene associated with unfavourable prognostic implications for multiple myeloma. Ultimately, we discovered three specific ligand-receptor pairs within the midkine (MDK) signalling pathway network that play distinct roles in facilitating efficient cellular communication between PSPCs and the surrounding microenvironment cells. These insights have the potential to contribute to the understanding of molecular mechanism and the development of therapeutic strategies involving the application of stem-like cells in RRMM treatment.

The C1q and gC1qR axis as a novel checkpoint inhibitor in cancer

Understanding at the molecular level of the cell biology of tumors has led to significant treatment advances in the past. Despite such advances however, development of therapy resistance and tumor recurrence are still unresolved major challenges. This therefore underscores the need to identify novel tumor targets and develop corresponding therapies to supplement existing biologic and cytotoxic approaches so that a deeper and more sustained treatment responses could be achieved. The complement system is emerging as a potential novel target for cancer therapy. Data accumulated to date show that complement proteins, and in particular C1q and its receptors cC1qR/CR and gC1qR/p33/HABP1, are overexpressed in most cancer cells and together are involved not only in shaping the inflammatory tumor microenvironment, but also in the regulation of angiogenesis, metastasis, and cell proliferation. In addition to the soluble form of C1q that is found in plasma, the C1q molecule is also found anchored on the cell membrane of monocytes, macrophages, dendritic cells, and cancer cells, via a 22aa long leader peptide found only in the A-chain. This orientation leaves its 6 globular heads exposed outwardly and thus available for high affinity binding to a wide range of molecular ligands that enhance tumor cell survival, migration, and proliferation. Similarly, the gC1qR molecule is not only overexpressed in most cancer types but is also released into the microenvironment where it has been shown to be associated with cancer cell proliferation and metastasis by activation of the complement and kinin systems. Co-culture of either T cells or cancer cells with purified C1q or anti-gC1qR has been shown to induce an anti-proliferative response. It is therefore postulated that in the tumor microenvironment, the interaction between C1q expressing cancer cells and gC1qR bearing cytotoxic T cells results in T cell suppression in a manner akin to the PD-L1 and PD-1 interaction.

p32/OPA1 axis-mediated mitochondrial dynamics contributes to cisplatin resistance in non-small cell lung cancer

Cisplatin resistance is a major obstacle in the treatment of non-small cell lung cancer (NSCLC). p32 and OPA1 are the key regulators of mitochondrial morphology and function. This study aims to investigate the role of the p32/OPA1 axis in cisplatin resistance in NSCLC and its underlying mechanism. The levels of p32 protein and mitochondrial fusion protein OPA1 are higher in cisplatin-resistant A549/DDP cells than in cisplatin-sensitive A549 cells, which facilitates mitochondrial fusion in A549/DDP cells. In addition, the expression of p32 and OPA1 protein is also upregulated in A549 cells during the development of cisplatin resistance. Moreover, p32 knockdown effectively downregulates the expression of OPA1, stimulates mitochondrial fission, decreases ATP generation and sensitizes A549/DDP cells to cisplatin-induced apoptosis. Furthermore, metformin significantly downregulates the expressions of p32 and OPA1 and induces mitochondrial fission and a decrease in ATP level in A549/DDP cells. The co-administration of metformin and cisplatin shows a significantly greater decrease in A549/DDP cell viability than cisplatin treatment alone. Moreover, D-erythro-Sphingosine, a potent p32 kinase activator, counteracts the metformin-induced downregulation of OPA1 and mitochondrial fission in A549/DDP cells. Taken together, these findings indicate that p32/OPA1 axis-mediated mitochondrial dynamics contributes to the acquired cisplatin resistance in NSCLC and that metformin resensitizes NSCLC to cisplatin, suggesting that targeting p32 and mitochondrial dynamics is an effective strategy for the prevention of cisplatin resistance.

PRUNE1 (located on chromosome 1q21.3) promotes multiple myeloma with 1q21 Gain by enhancing the links between purine and mitochondrion

Patients with multiple myeloma (MM) with chromosome 1q21 Gain (1q21+) are clinically and biologically heterogeneous. 1q21+ in the real world actually reflects the prognosis for gain/amplification of the CKS1B gene. In this study, we found that the copy number of prune exopolyphosphatase 1 (PRUNE1), located on chromosome 1q21.3, could further stratify the prognosis of MM patients with 1q21+. Using selected reaction monitoring/multiple reaction monitoring (SRM/MRM) analysis, liquid chromatography-tandem mass spectrometry (LC-MS/MS), transmission electron microscopy (TEM), confocal fluorescence microscopy, calculation of adenosine triphosphate (ATP), intracellular reactive oxygen species (ROS) and mitochondrial oxygen consumption rates (OCRs), we demonstrated for the first time that PRUNE1 promotes the proliferation and invasion of MM cells by stimulating purine metabolism, purine synthesis enzymes and mitochondrial functions, enhancing links between purinosomes and mitochondria. SOX11 was identified as a transcription factor for PRUNE1. Through integrated analysis of the transcriptome and proteome, CD73 was determined to be the downstream target of PRUNE1. Furthermore, it has been determined that dipyridamole can effectively suppress the proliferation of MM cells with high-expression levels of PRUNE1 in vitro and in vivo. These findings provide insights into disease-causing mechanisms and new therapeutic targets for MM patients with 1q21+.

The G allele of SNP rs3922 reduces the binding affinity between IGF2BP3 and CXCR5 correlating with a lower antibody production

Effective vaccines that function through humoral immunity seek to produce high-affinity antibodies. Our previous research identified the single-nucleotide polymorphism rs3922G in the 3'UTR of CXCR5 as being associated with nonresponsiveness to the hepatitis B vaccine. The differential expression of CXCR5 between the dark zone (DZ) and light zone (LZ) is critical for organizing the functional structure of the germinal center (GC). In this study, we report that the RNA-binding protein IGF2BP3 can bind to CXCR5 mRNA containing the rs3922 variant to promote its degradation via the nonsense-mediated mRNA decay pathway. Deficiency of IGF2BP3 leads to increased CXCR5 expression, which results in the disappearance of CXCR5 differential expression between DZ and LZ, disorganized GCs, aberrant somatic hypermutations, and reduced production of high-affinity antibodies. Furthermore, the affinity of IGF2BP3 for the rs3922G-containing sequence is lower than that for the rs3922A counterpart, which may explain the nonresponsiveness to the hepatitis B vaccination. Together, our findings suggest that IGF2BP3 plays a crucial role in the production of high-affinity antibodies in the GC by binding to the rs3922-containing sequence to regulate CXCR5 expression.

Single-Cell Transcriptomes Combining with Consecutive Genomics Reveal Clonal Evolution and Gene Regulatory Networks in Relapsed and Refractory Multiple Myeloma

This study attempted to investigate how clonal structure evolves, along with potential regulatory networks, as a result of multiline therapies in relapsed/refractory multiple myeloma (RRMM). Eight whole exome sequencing (WES) and one single cell RNA sequencing (scRNA-seq) were performed in order to assess dynamic genomic changes in temporal consecutive samples of one RRMM patient from the time of diagnosis to death (about 37 months). The 63-year-old female patient who suffered from MM (P1) had disease progression (PD) nine times from July 2017 [newly diagnosed (ND)] to Aug 2020 (death), and the force to drive branching-pattern evolution of malignant PCs was found to be sustained. The mutant-allele tumor heterogeneity (MATH) and tumor mutation burden (TMB) initially exhibited a downward trend, which was then upward throughout the course of the disease. Various somatic single nucleotide variants (SNVs) that had disappeared after the previous treatment were observed to reappear in later stages. Chromosomal instability (CIN) and homologous recombination deficiency (HRD) scores were observed to be increased during periods of all progression, especially in the period of extramedullary plasmacytoma. Finally, in combination with WES and scRNA-seq of P1-PD9 (the nineth PD), the intro-heterogeneity and gene regulatory networks of MM cells were deciphered. As verified by the overall survival of MM patients in the MMRF CoMMpass and GSE24080 datasets, RUNX3 was identified as a potential driver for RRMM.

Circulating C1q levels in health and disease, more than just a biomarker

C1q is the recognition molecule of the classical pathway of the complement system. By binding to its targets, such as antigen-bound immunoglobulins or C-reactive protein, C1q contributes to the innate defense against infections. However, C1q also plays several other roles beyond its traditional role in complement activation. Circulating levels of C1q are determined in routine diagnostics as biomarker in several diseases. Decreased C1q levels are present in several autoimmune conditions. The decreased levels reflect the consumption of C1q by complement activation and serves as a biomarker for disease activity. In contrast, increased C1q levels are present in infectious and inflammatory diseases and may serve as a diagnostic biomarker. The increased levels of C1q are still incompletely understood but are suggested to modulate the adaptive immune response as C1q is known to impact on the maturation status of antigen-presenting cells and C1q impacts directly on T cells leading to decreased T-cell activity in high C1q conditions. In this review, we provide a comprehensive overview of the current literature on circulating levels of C1q in health and disease, and discuss how C1q can both protect against infections as well as maintain tolerance by regulating adaptive immunity.

Computational Insights into the Interaction between Cytoadherence Receptor gC1qR and the DBLβ12 Domain of a Plasmodium falciparum PfEMP1 Ligand

Human receptor gC1qR is a 32 kD protein that mediates the cytoadherence of Plasmodium falciparum-infected erythrocytes (IEs) to human brain microvascular endothelial cells (HBMEC) and platelets. The cytoadherence of IEs to gC1qR has been associated with severe malaria symptoms. The cytoadherence to gC1qR is mediated by the Duffy binding-like β12 (DBLβ12) domain of Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1), PFD0020c. Here, we report the structural insights into the binding of the DBLβ12 domain of PfEMP1 with the human receptor gC1qR using computational methods. A molecular model of the DBLβ12 domain was generated and used for protein-protein docking with the host receptor gC1qR. The protein-protein docking revealed that the DBLβ12 asymmetrically interacts with two subunits of the gC1qR trimer at the solution face of gC1qR. A total of 21 amino acid residues of DBLβ12 interact with 26 amino acid residues in the gC1qR trimer through 99 nonbonding interactions and 4 hydrogen bonds. Comparative analysis of binding sites on the DBL domain fold for the two receptors gC1qR and ICAM1 showed that the two sites are distinct. This is the first study that provides structural insights into DBLβ12 binding with its receptor gC1qR and may help in designing novel antisevere malaria interventions.