CD44

CD44 Full Name

CD44 molecule (Indian blood group)

CD44 Introduction

CD44 is a ubiquitously expressed, transmembrane glycoprotein that serves as the principal cell-surface receptor for Hyaluronic Acid (HA), a major component of the extracellular matrix. A defining feature of CD44 is its remarkable structural diversity; through extensive alternative splicing of ten variable exons, the gene produces dozens of isoforms ranging from the standard form (CD44s) to larger variant isoforms (CD44v). Biologically, CD44 acts as more than just an adhesion molecule; it is a dynamic signaling hub. Upon binding to hyaluronan, the cytoplasmic tail of CD44 interacts with ERM proteins (Ezrin, Radixin, Moesin), linking the plasma membrane to the actin cytoskeleton. This linkage coordinates essential cellular processes including cell migration, lymphocyte activation, and hematopoiesis (homing).

Figure 1. CD44 protein and gene structure. (Source: Chen C, et al. 2018)

The clinical relevance of CD44 is most profound in oncology, where it is widely recognized as a key marker for Cancer Stem Cells (CSCs). While normal tissues primarily express the standard CD44s isoform, malignant tumors often switch to expressing specific variant isoforms (such as CD44v6) which are highly oncogenic. This upregulation confers survival advantages to tumor cells, protecting them from oxidative stress and apoptosis. Furthermore, the interaction between CD44 and hyaluronan facilitates the invasion of cancer cells into the surrounding matrix and their subsequent metastasis to distant organs. Beyond cancer, CD44 is also implicated in chronic inflammatory diseases like rheumatoid arthritis, where it mediates the influx of inflammatory cells into the synovium.

Alternate Names for CD44

H-CAM

• 1. Chen C, et al. The biology and role of CD44 in cancer progression: therapeutic implications. J Hematol Oncol. 2018 May 10;11(1):64.
  2. Hassn Mesrati M, et al. CD44: A Multifunctional Mediator of Cancer Progression. Biomolecules. 2021 Dec 9;11(12):1850.