HOPX and neoplasm: Tdiff also express other transcription factors that regulate cell growth, cell cycle progression, differentiation and apoptosis: LITAF; MYBL1 (34); LYAR; HOPX (35); ASCL2, a transcription factor shown to promote Tfh and is regulated by ID2 (36, 37); and BHLHE40 (38), a transcription factor implicated in the maintenance of effector & memory CD8+ TRM and tumor-infiltrating lymphocyte (TIL) fitness and functionality (39, 40).