MMSA-1 expression pattern in multiple myeloma and its clinical significance

Involvement of ZDHHC9 in lung adenocarcinoma: regulation of PD-L1 stability via palmitoylation

Palmitoylation is a post-translational modification occurring on cysteine residues, which process is catalyzed by a family of zinc finger Asp-His-His-Cys (DHHC) domain-containing (ZDHHC) protein acyltransferases. As a family member, ZDHHC9 plays a crucial role in varied malignancies by regulating protein stability via protein substrate palmitoylation. Based on the bioinformatic analysis of GEO gene microarray GSE75037 (|log₂ fold change|> 1, P < 0.05), ZDHHC9 was defined as a significantly upregulated gene in lung adenocarcinoma (LUAD), which was also confirmed in our collected clinical specimens. It is necessary to explore the biological function of ZDHHC9 in LUAD cells. The follow-up functional experiments revealed that ZDHHC9 deficiency inhibited proliferation, migration, and invasion, while stimulated apoptosis in HCC827 cells. Besides, these malignant phenotypes could be accelerated by ZDHHC9 overexpression in A549. Moreover, we revealed that ZDHHC9 knockdown could promote PD-L1 protein degradation by reducing its palmitoylation level. The reduction of PD-L1 protein level could enhance anti-tumor immunity and inhibit the growth of LUAD cells. Therefore, our study uncovers the tumor-promoting role of ZDHHC9 in LUAD via regulating PD-L1 stability through palmitoylation, highlighting ZDHHC9 as a novel therapeutic target for LUAD.

Protein palmitoylation and cancer

Protein S-palmitoylation is a reversible post-translational modification that alters the localization, stability, and function of hundreds of proteins in the cell. S-palmitoylation is essential for the function of both oncogenes (e.g., NRAS and EGFR) and tumor suppressors (e.g., SCRIB, melanocortin 1 receptor). In mammalian cells, the thioesterification of palmitate to internal cysteine residues is catalyzed by 23 Asp-His-His-Cys (DHHC)-family palmitoyl S-acyltransferases while the removal of palmitate is catalyzed by serine hydrolases, including acyl-protein thioesterases (APTs). These enzymes modulate the function of important oncogenes and tumor suppressors and often display altered expression patterns in cancer. Targeting S-palmitoylation or the enzymes responsible for palmitoylation dynamics may therefore represent a candidate therapeutic strategy for certain cancers.

Current treatment options of T cell-associated immunotherapy in multiple myeloma

Multiple myeloma (MM) is a complex disease and is presently an incurable malignant plasma cell tumor. Although the introduction of proteasome inhibitor and the immunomodulators markedly improved the effect of myeloma therapy, most patients still suffer from relapse even with an initially effective therapy. Accumulating evidence suggests that immunotherapy is a promising option in treating MM. And T cell plays crucial role through inducing sustained immune response in vivo in the immunotherapy of tumors. In this article, we will discuss progress of several T cell-based immunotherapies with insight into how they eradicate myeloma cells and their disadvantages.

A novel multi-epitope vaccine from MMSA-1 and DKK1 for multiple myeloma immunotherapy

The identification of novel tumour-associated antigens is urgently needed to improve the efficacy of immunotherapy for multiple myeloma (MM). In this study, we identified a membrane protein MMSA-1 (multiple myeloma special antigen-1) that was specifically expressed in MM and exhibited significantly positive correlation with MM. We then identified HLA-A*0201-restricted MMSA-1 epitopes and tested their cytotoxic T lymphocyte (CTL) response. The MMSA-1 epitope SLSLLTIYV vaccine was shown to induce an obvious CTL response in vitro. To improve the immunotherapy, we constructed a multi-epitope peptide vaccine by combining epitopes derived from MMSA-1 and Dickkopf-1 (DKK1). The effector T cells induced by multi-epitope peptide vaccine-loaded dendritic cells lysed U266 cells more effectively than MMSA-1/DKK1 single-epitope vaccine. In myeloma-bearing severe combined immunodeficient mice, the multi-epitope vaccine improved the survival rate significantly compared with single-epitope vaccine. Consistently, multi-epitope vaccine decreased the tumour volume greatly and alleviated bone destruction. The frequencies of CD4⁺ and CD8⁺ T cells was significantly increased in mouse blood induced by the multi-epitope vaccine, indicating that it inhibits myeloma growth by changing T cell subsets and alleviating immune paralysis. This study identified a novel peptide from MMSA-1 and the multi-epitope vaccine will be used to establish appropriate individualized therapy for MM.