Relationship between diurnal rhythm of cell cycle and interferon receptor expression in implanted-tumor cells

Whether the diurnal rhythm of cell cycle is associated with that of interfe ron-alpha/beta receptor (IFNAR) expression was investigated in implanted-tu mor cells. The expression of IFNAR mRNA significantly increased when the pr oportion of tumor cells in DNA synthesis (S) phase increased in vitro, A di urnal rhythm was observed for cell cycle distribution in implanted-tumor ce lls. The specific binding of interferon-alpha to receptor and IFNAR mRNA in creased when the proportion of tumor cells in S phase increased in vivo. Th e time-dependent expression of IFNAR was supported by that of transcription factor level induced by interferon-p, The present result suggests that the rhythm of IFNAR expression is closely related to that of cell cycle distri bution in implanted-tumor cells. (C) 2001 Elsevier Science Inc. All rights reserved.