HHLA2 and neoplasm: Studies on the mechanisms of other tumors have found that B7-H7 may exert pro-tumor effects by activating the Janus kinase (JAK)/signal transducer and activator of transcription (STAT), PI3K/Akt, and epidermal growth factor receptor (EGFR)/mitogen-activated protein kinase (MAPK)/ERK pathways (12, 22, 23).