Syndecan-1 (CD138) (CD138)

Syndecan-1 (CD138) is a type I transmembrane heparan sulfate proteoglycan that acts as a multifaceted mediator of cell-cell and cell-matrix interactions [8, 9, 12]. It is primarily expressed on the surface of mature plasma cells and various epithelial tissues, where it functions as a co-receptor for several growth factors, including hepatocyte growth factor (HGF) and fibroblast growth factors (FGF), thereby regulating signaling pathways essential for cell survival and proliferation [5, 10, 12]. In malignancies like multiple myeloma, CD138 is significantly upregulated and plays a critical role in promoting tumor growth, angiogenesis, and adhesion within the bone marrow niche [8, 11, 23]. It also undergoes proteolytic shedding from the cell surface, producing soluble CD138 (sCD138) which can facilitate metastasis and serve as a prognostic biomarker for disease severity [8, 11, 19]. Due to its high expression on malignant plasma cells, CD138 has emerged as a major therapeutic target in hematology and oncology [10, 11]. Investigational therapies include antibody-drug conjugates (ADCs) like indatuximab ravtansine, which deliver potent cytotoxic agents directly to tumor cells, as well as chimeric antigen receptor (CAR) T-cell therapies [3, 4, 15]. Despite its promise, therapeutic development is challenged by the expression of CD138 on healthy epithelial cells, which can lead to off-target effects in the skin and gastrointestinal tract [2, 12, 15].

Other names

Syndecan-1SDC1SYND1CD138 antigenHeparan sulfate proteoglycan fibroblast-type

Drugs targeting CD138 primarily utilize antibody-drug conjugates (ADCs) to deliver cytotoxic payloads, such as maytansinoid DM4, directly to the intracellular compartment of cancer cells following receptor-mediated endocytosis [3, 5, 10]. Other mechanisms include the induction of antibody-dependent cellular cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC) by monoclonal antibodies, and the direct cytotoxic activity of engineered CAR-T cells against CD138-expressing malignant cells [1, 13, 14, 15]. Some agents also work by blocking CD138-mediated growth factor signaling and preventing the shedding of the CD138 extracellular domain [2, 5, 8].