TGFB1 and esophageal squamous cell carcinoma: revealed that Maelstrom (MAEL) could promote the recruitment of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) to tumor sites via activation of Akt1/RelA/IL-8 signaling pathway, and TGF-β secreted by PMN-MDSCs could upregulate MAEL by inducing Smad2/Smad3 phosphorylation to further promote ESCC progression (94).