ID: 152: IL23A (p19) expression and subcellular location in cancer cell lines under endoplasmic reticulum stress conditions

Abstract

IL23A, or p19, forms part of heterodimeric cytokine IL-23, and is known to be upregulated under conditions of endoplasmic reticulum (ER) stress in lymphocytes and antigen presenting cells. The purpose of our study was first to verify whether ER stress induction is confined to the p19 subunit only, or whether other subunits of the IL12-/IL-23 family (p35, EBI3, p40, p28) are also upregulated. Second, we wondered also whether the ER-stress-induced upregulation of p19 is restricted to cells of immune lineage or reflects a more generalized pathway that can be activated also in non-myeloid cancer cell lines. We used QPCR to assess kinetics and extent of upregulation of the 5 subunits in the lung epithelial cell line A549 under ER stress conditions, assessed p19 upregulation in HEK293, Hela, A549, Du145 MCF-7, PC3, HT29 and U937 cell lines by ER stress, and analysed the subcellular location of p19 in ER-stressed A549, Du145 and U937 cells. Thapsigargin-induced upregulation of p19 mRNA but not of the other subunits was observed independent of cell type, and was not reflected in enhanced levels of IL-23 secretion measured by ELISA. Immunofluorescence microscopy revealed perinuclear location of p19 in Du145, A549 and U937 cells. Sucrose gradient centrifugation to isolate nuclei of ER-stressed A549 cells revealed that a fraction of p19 was associated with the nucleus. ER stress-induced p19 upregulation is seen in cancer cell and may reflect a novel biological function of p19 independent from its role as composing subunit of the cytokine IL-23.