IGFBP4 and cancer: The results showed that sh-circNOX4 CAFs secreted a decreasing panel of cytokines, including interleukin-6 (IL-6), chemokine C–C motif ligand 2 (CCL2), TGF-β2 and insulin-like growth factor binding protein 4 (IGFBP-4), which are reported as niche characteristic genes that facilitate cancer cell migration, invasion, and colonization in the metastatic process [26] (Fig. 6A and Fig. S8A).