TGFB1 and neoplasm: Moreover, GBM is characterized by a highly immunosuppressive environment, with mechanisms such as programmed death-ligand 1 (PD-L1) upregulation, transforming growth factor beta (TGF-β) secretion, and the recruitment of regulatory T cells (Tregs) and tumor-associated macrophages (TAMs), which collectively suppress antitumor immune responses and contribute to resistance to immunotherapy [27,28].