THE NORMAL STRUCTURE AND FUNCTION OF CD44 AND ITS ROLE IN NEOPLASIA

CD44 is a transmembrane glycoprotein, the variant isoforms of which ar e coded for by alternative splicing, with the most prolific isoform be ing CD44 standard. CD44 is found in a wide variety of tissues includin g the central nervous system, lung, epidermis, liver, and pancreas, wh ereas variant isoforms of CD44 (CD44v) appear to have a much more rest ricted distribution. Variants of CD44 are expressed in tissues during development, including embryonic epithelia. Known functions of CD44 ar e cellular adhesion (aggregation and migration), hyaluronate degradati on, lymphocyte activation, lymph node homing, myelopoiesis and lymphop oiesis, angiogenesis, and release of cytokines. The functions of CD44 are principally dependant on cellular adhesion in one setting or anoth er. The role of CD44 in neoplasia is less well defined, although metas tatic potential can be conferred on non-metastasising cell lines by tr ansfection with a variant of CD44 and high levels of CD44 are associat ed with several types of malignant tumours. The physiological function s of CD44 indicate that the molecule could be involved in the metastat ic spread of tumours. Many studies have investigated the pattern of CD 44 distribution in tumours and some observations suggest that certain cells do not use CD44 in tumorigenesis or in the production of metasta ses. However, the data are extremely conflicting, and further studies are needed to establish the prognostic value of CD44 and its variant i soforms. The precise function of CD44 in the metastatic process and th e degree of involvement in human malignancies has yet to be establishe d fully.