Loc108167440 suppressed myeloma cell growth by P53-mediated apoptosis

Targeted therapy of multiple myeloma

Multiple myeloma (MM) is a malignant proliferative disease of monoclonal plasma cells (PCs) and is characterized by uncontrolled proliferation of PCs and excessive production of specific types of immunoglobulins. Since PCs are terminally differentiated B cells, the World Health Organization (WHO) classifies MM as lymphoproliferative B-cell disease. The incidence of MM is 6-7 cases per 100,000 people in the world every year and the second most common cancer in the blood system. Due to the effects of drug resistance and malignant regeneration of MM cells in the microenvironment, all current treatment methods can prolong both overall and symptom-free survival rates of patients with MM but cannot cure MM. Both basic and clinical studies have proven that targeted therapy leads to a clear and significant prolongation of the survival of patients with MM, but when the disease recurs again, resistance to the previous treatment will occur. Therefore, the discovery of new targets and treatment methods plays a vital role in the treatment of MM. This article introduces and summarizes targeted MM therapy, potential new targets, and future precision medicine in MM.

Gm40600 promotes CD4+ T-cell responses by interacting with Ahnak

It is important to characterize novel proteins involved in T- and B-cell responses. Our previous study demonstrated that a novel protein, Mus musculus Gm40600, reduced the proliferation of Mus musculus plasmablast (PB)-like SP 2/0 cells and B-cell responses induced in vitro by LPS. In the present study, we revealed that Gm40600 directly promoted CD4+ T-cell responses to indirectly up-regulate B-cell responses. Importantly, we found that CD4+ T-cell responses, including T-cell activation and differentiation and cytokine production, were increased in Gm40600 transgenic (Tg) mice and were reduced in Gm40600 knockout (KO) mice. Finally, we demonstrated that Gm40600 promoted the Ahnak-mediated calcium signalling pathway by interacting with Ahnak to maintain a cytoplasmic lateral location of Ahnak in CD4+ T cells. Collectively, our data suggest that Gm40600 promotes CD4+ T-cell activation to up-regulate the B-cell response via interacting with Ahnak to promote the calcium signalling pathway. The results suggest that targeting Gm40600 may be a means to control CD4+ T-cell-related diseases.

Gm614 Protects Germinal Center B Cells From Death by Suppressing Caspase-1 Transcription in Lupus-Prone Mice

Only a few signaling pathways have been reported in germinal center (GC) B-cell proliferation and death. In this study, we showed that a novel uncharacterized Gm614 protein is highly expressed in GC B cells from lupus-prone mice. Critically, ablation of this GC B-cell-specific Gm614 promoted GC B-cell death and mitigation of autoimmune symptoms, whereas overexpression protected GC B cells from death and exacerbated autoimmune symptoms. We demonstrated that mechanistically, nuclear-localized Gm614 reduced caspase-1 expression in GC B cells by binding with caspase-1 promoter to suppress its activation. Our results suggest that Gm614 protects GC B cells from death by suppressing caspase-1 transcription in autoimmune diseases. This may provide some hints for targeting the cell proliferation involved in autoimmune diseases.

The E3 ubiquitin ligase Itch deficiency promotes antigen-driven B-cell responses in mice

Deficiency of Itch, an E3 ubiquitin ligase, usually induced severe systemic and progressive autoimmune disease. The Itch function is well studied in T cells but not in B cells. We hypothesize that B-cell-specific Itch deficiency promoted antigen-induced B-cell activation and antibody-expressing plasma cell (PC) production. We found that unlike Itch KO, Itch cKO (CD19^cre Itch^f/f ) mice did not demonstrated a significant increase in the sizes of spleens and LNs, antibody level, and base mutation of antibody gene. However, in line with the fact that Itch expression decreased in GC B cells, PCs, and plasmablast (PB)-like SP 2/0 cells, Itch deficiency promoted B-cell activation and antibody production induced by antigens including lipopolysaccharide (LPS) and sheep red blood cells (SRBCs). Mechanistically, we found that Itch deficiency promotes antigen-induced cytokine production because Itch controls the proteins (e.g., eIF3a, eIF3c, eIF3h) with translation initiation factor activity. Altogether, our data suggest that Itch deficiency promotes antigen-driven B-cell response. This may provide hints for Itch-targeted treatment of patients with autoimmune disease.

Hspa13 Promotes Plasma Cell Production and Antibody Secretion

The generation of large numbers of plasma cells (PCs) is a main factor in systemic lupus erythematosus (SLE). We hypothesize that Hspa13, a member of the heat shock protein family, plays a critical role in the control of PC differentiation. To test the hypothesis, we used lipopolysaccharide (LPS)-activated B cells and a newly established mouse line with a CD19^cre-mediated, B cell–specific deletion of Hspa13: Hspa13 cKO mice. We found that Hspa13 mRNA was increased in PCs from atacicept-treated lupus-prone mice and in LPS-stimulated plasmablasts (PBs) and PCs. A critical finding was that PBs and PCs [but not naïve B cells and germinal center (GC) B cells] expressed high levels of Hspa13. In contrast, the Hspa13 cKO mice had a reduction in BPs, PCs, and antibodies induced in vitro by LPS and in vivo by sheep red blood cells (SRCs)- or 4-hydroxy-3-nitrophenylacetyl (NP)-immunization. Accordingly, the Hspa13 cKO mice had reduced class-switched and somatically hypermutated antibodies with defective affinity maturation. Our work also showed that Hspa13 interacts with proteins (e.g., Bcap31) in the endoplasmic reticulum (ER) to positively regulate protein transport from the ER to the cytosol. Importantly, Hspa13 mRNA was increased in B220⁺ cells from patients with multiple myeloma (MM) or SLE, whereas Hspa13 cKO led to reduced autoantibodies and proteinuria in both pristane-induced lupus and lupus-prone MRL/lpr mouse models. Collectively, our data suggest that Hspa13 is critical for PC development and may be a new target for eliminating pathologic PCs.

Gm6377 suppressed SP 2/0 xenograft tumor by down-regulating Myc transcription

PURPOSE

Disturbed process of B-cell differentiation into plasmablasts (PBs)/plasma cells (PCs) is involved in multiple myeloma (MM). New strategies will be required to eliminate the MM cell clone for a long-term disease control. Because of its PB-like characteristics, the mus musculus myeloma SP 2/0 cell line was used in this study to search novel targets for PBs/PCs.

METHODS/PATIENTS

Affymetrix microarrays and RNA-sequencing assays were used to search a novel different molecule (Gm6377) between PBs/PCs and mature B cells. Cell counting kit-8 (CCK8), flow cytometry (FACS), xenograft mouse model, and the luciferase reporter system were used to assess the effect of Gm6377 on SP 2/0 cell proliferation, cell cycle, tumor growth, and Myc promoter activation, respectively.

RESULTS

We found that B cells expressed a high level of Gm6377 mRNA, whereas Gm6377 mRNA was decreased in PCs. In addition, SP 2/0 cells also expressed low levels of Gm6377 mRNA. Critically, Gm6377 overexpression suppressed SP 2/0 cell proliferation but not cell cycle. Furthermore, Gm6377 overexpression suppressed tumor progression in the SP 2/0 xenograft mouse model. Finally, we found that Gm6377 suppressed SP 2/0 cell proliferation by reducing the activation of the Myc promoter.

CONCLUSIONS

These results suggest that Gm6377 suppresses myeloma SP 2/0 cell growth by suppressing Myc. Thus, modulation of Gm6377 may be a potential therapeutic way to treat MM.