NKD2 as a Mediator of IFIX Antioncogene-Induced Wnt Signalling and Epithelial–Mesenchymal Transition in Human OSCC

Abstract

The activation of the human interferon-inducible protein X (IFIX) isoform is associated with maintaining a stable cytoskeleton and inhibiting epithelial–mesenchymal transition (EMT). However, the mechanisms and pathways underlying IFIX-mediated oncogenesis are not well understood. In this study, we investigated the effects of IFIX overexpression and knockdown in CAL-27 and SCC-25 oral squamous cell carcinoma (OSCC) cells. We observed significant variations in the expression of E-cadherin, N-cadherin, vimentin and Snail, as well as changes in wingless/integrated (Wnt) signalling. Our results indicated a strong correlation between IFIX and EMT, as evidenced by quantitative reverse-transcription PCR and Western blotting, which revealed that Wnt3a and Wnt4 pathway components were regulated in IFIX-overexpressing or knockdown cells, with naked cuticle 2 (NKD2) showing the strongest positive correlation. Both IFIX overexpression and knockdown modulated NKD2 expression. NKD2 silencing mimicked the phenotypic effects of IFIX knockdown, inhibiting E-cadherin expression and increasing N-cadherin, Snail and vimentin expression. Additionally, silencing NKD2 restored the anticarcinogenic phenotype associated with IFIX overexpression, affecting cell proliferation, invasion and migration. These findings provide mechanistic insights into the antioncogenic effects of IFIX in OSCC, involving the inhibition of Wnt signalling through NKD2, which leads to cancer-inhibiting phenotypic effects, including restricted EMT.