HHLA2 (B7H7/B7-H5/B7y), a newly defined B7 family member (Zhao et al., 2013), is a co-inhibitory molecule expressed in multiple cancers, including lung, breast and pancreatic cancers as well as melanoma, and osteosarcoma and shows limited expression in normal tissues. The gene discussed is HHLA2; the disease is osteosarcoma.