Our results showed that HHLA2 was widely expressed in multiple tumor types and HHLA2 protein expression was detected in 12 commonly diagnosed tumors, including breast cancer, lung cancer, and others, several cancers such as colon and rectum cancer exhibited HHLA2 levels in tumor sites, which is in contrast to a previous study (Janakiram et al., 2015a). Here, HHLA2 is linked to breast cancer.