CD44

Overview

CD44 is a multifunctional transmembrane glycoprotein and cell surface receptor broadly expressed across mammalian tissues, where it plays central roles in cell adhesion, migration, proliferation, and survival. It functions primarily as a receptor for hyaluronic acid (hyaluronan), a major component of the extracellular matrix, as well as for other ligands including osteopontin, collagens, and matrix metalloproteinases. Through these interactions, CD44 mediates intracellular signaling cascades — notably the PI3K/Akt and JAK2/STAT3 pathways — that govern fundamental cellular processes including epithelial-to-mesenchymal transition (EMT), stem cell maintenance, and immune modulation. CD44 exists in multiple isoforms generated by alternative splicing of up to 10 variant exons, allowing context-dependent expression across cell types and disease states.

In oncology, CD44 is widely recognized as a cancer stem cell (CSC) marker, often co-expressed with other stemness-associated proteins such as epithelial cell adhesion molecule (EPCAM). Its overexpression has been documented across a broad spectrum of malignancies — including liver cancer, colorectal cancer, bladder cancer, breast cancer, and prostate cancer, among others — where it is associated with tumor aggressiveness, therapy resistance, and metastatic potential. Because of its consistent surface overexpression on tumor cells and immunological relevance, CD44 has also emerged as a high-value target for receptor-mediated drug delivery systems, particularly those utilizing hyaluronic acid as a targeting ligand.

Recent Publications Focus

Below is a summary of the newest research publications targeting CD44 (sorted by publication date).

Recent studies have established CD44 as a critical marker of cancer stem cell populations and a key driver of therapeutic resistance across multiple cancer types. In triple-negative breast cancer, CD44 expression is necessary for cancer stem cell multipotency and self-renewal, with high levels associated with invasive phenotypes [42397497]. Similarly, in hepatocellular carcinoma, CD44 serves as a stemness marker whose downregulation correlates with reduced tumorigenic potential, particularly through the alpha-fetoprotein-PI3K/Akt pathway that sustains cancer stem cell properties [41651174]. These findings position CD44 not merely as a passive marker but as a functional regulator of cancer stemness, making it an attractive therapeutic target.

The hyaluronic acid-CD44 axis has emerged as a dominant strategy for targeted drug delivery to CD44-overexpressing tumors. Multiple studies employed hyaluronic acid conjugation to direct nanoparticles toward CD44+ cancer cells, including systems co-delivering paclitaxel and piperine for ovarian cancer [42011733] and biodegradable polymersomes encapsulating gemcitabine and copper peroxide for triple-negative breast cancer [41780685]. CD44-targeted chitosan nanoparticles have also been engineered to restore mitochondrial homeostasis in diabetic kidney disease by delivering ginsenoside Rg1 [41707746]. These delivery platforms demonstrate superior cellular uptake and tumor accumulation compared to non-targeted controls, highlighting CD44's utility as an actionable target in cancer and metabolic disease contexts.

CD44 functions as a critical signaling hub in tumor-stroma crosstalk and immune regulation. Endotrophin, a collagen VI fragment, was identified as an ETP receptor that activates STAT3 signaling through CD44 in hepatocellular carcinoma, promoting epithelial-mesenchymal transition and sorafenib resistance [41671381]. In gastric cancer, serglycin engages CD44 to promote LAG3+ regulatory T cell differentiation through a glycolysis-dependent cascade that suppresses oxidative modification and ubiquitin-mediated degradation of LAG3, thereby enhancing immunosuppression [41734377]. Additionally, CD44 participates in a CD44/PD-L1 axis that mediates pro-fibrotic macrophage activation in pulmonary fibrosis, suggesting CD44 targeting as a complementary strategy to PD-1/PD-L1 blockade [42048160]. These findings underscore CD44's role in both tumor cell properties and immunologic dysfunction.

Beyond cancer, CD44 has been recognized as a dynamic hub in age-dependent cell-cell communication networks across tissues. Transcriptomic analysis of cell-cell communication patterns across mouse organs spanning post-natal development through aging revealed that CD44, along with ITGB1, undergoes highly dynamic changes in predicted ligand-receptor interactions across timepoints and organs, suggesting a central role as a coordinating node in developmental and age-related shifts in intercellular communication [41860844]. Additionally, CD44+ plasmacytoid dendritic cells participate in hepatocyte crosstalk that restores antibacterial immunity in cirrhosis [42385859], expanding CD44's relevance to infectious disease and organ-specific immune homeostasis.