PTGER4 and laryngotracheoesophageal cleft: Research showed that LC patients had increased tumor necrosis factor alpha (TNF-α), interferon gamma (INF-γ), and interleukin 8 (IL-8) along with an upregulation of prostaglandin E receptor 4 (EP4); however, in general, proinflammatory cytokines have not been recognized as an independent LC marker [32,33].