TNFRSF9 and neoplasm: Refractory effector T cells in the TME can be revitalized to regain their anti-tumor activities, i.e., the ability to restrain tumor growth, by stimulating T cell costimulatory receptors, such as those belonging to the tumor necrosis factor receptor superfamily (TNFRSF), i.e., CD40, 4-1BB, and OX40 [31,32].