CD44 and esophageal squamous cell carcinoma: In the settings of esophageal squamous cell carcinoma (ESCC), circ_0001821 acts as a miR-423-5p sponge to upregulate BTRC expression, thus inducing IKBA ubiquitination to affect NF-κB signaling and cell proliferation [166]; hsa_circ_0021727 (circ-CD44) promotes proliferation by sponging miR-23b-5p to upregulate the TAB1/NF-κB pathway [167]; ciRS-7 promotes ESCC growth and metastasis through miR-7/HOXB13 induced NF-κB pathway [168]; circCYP24A1 facilitates ESCC progression by interacting with PKM2 to regulate NF-κB signaling [169].