Figure 7. RKIP inhibits NICD-induced EMT in hypoxia.

(A–D) RKIP-overexpressing H1299 cells (A, B) or RKIP-depleted H1299 cells (C, D) were incubated under hypoxic conditions (1% O₂) for the indicated times. (A, C) Total cell extracts (30 μg) were subjected to western blot analysis to examine the expression of each noted protein at the indicated times. (B, D) Expression of each protein was quantified and represented graphically. Data indicates the mean values ± S.D. of three independent experiments. *p < 0.05. (E) Schematic illustration of RKIP-mediated regulation of Notch1. human Notch receptor 1 (hNotch1) contains two large regions: NEC (Notch extracellular subunits) and NICD (Notch intracellular domain). NICD consists of many motifs, including epidermal growth factor-like repeats (EGFR), Lin12 Notch repeats (LNR), a RAM23 domain (RAM), and Ankyrin repeats (ANK). NICD released by γ-secretase is translocated into the nucleus to activate the translation of EMT-related genes, subsequently promoting cell invasion and metastasis. When RKIP is overexpressed, tumor metastasis is blocked by RKIP-mediated inhibition of Notch1 activation.