Stable expression of CD1a molecule in human epithelial cell lines shows temperature-dependent expression and affects cell morphology and growth.

Abstract

The human CD1a molecule is a transmembrane protein which shares structural similarities with HLA class I molecules. It has restricted tissue distribution in normal individuals, and is a useful diagnostic marker for certain disease states such as Langerhans cell histiocytosis. In order to investigate the function of this molecule, a cDNA fragment encoding the CD1a molecule was cloned into several EUKARYOTIC expression vectors which were then used to establish human epithelial cell lines stably expressing the membrane-bound CD1a molecule. Human keratinocytes (HaCaT) and epithelial cells (HeLa) stably expressing CD1a were established by retroviral-mediated gene transfer and DNA transfection, respectively. Expression and localization of the CD1A molecule were then confirmed by Northern blot analysis and immunofluorescence methods. CD1a expression appears to have profound effects on cellular growth and morphology. Both stably CD1a-expressing HeLa and HaCaT cells showed increased doubling times, and up to 20% of CD1a-expressing cells showed altered cell morphology. Clonogenicity experiments demonstrated a reduction in colony size and plating efficiency was augmented in CD1a-positive cells when compared with vector-transfected/infected controls. Our findings suggest that CD1A expression may act as a negative growth regulator in these cells in vitro. Furthermore, lower temperatures greatly enhanced the expression of CD1a at both the protein and mRNA levels in a time-dependent fashion. Since the physiological skin temperatures lie well below the core temperature, this observation may have important implications in the study of Langerhans cells in vitro.