GPR56 binds transglutaminase 2 to suppress tumor metastasis331 and binds collagen III to regulate cortical development and lamination.332 GPR56 has shown a high expression level in many cancers, such as esophageal cancer,333 glioblastoma,334 human melanoma335 and colon cancer276 as a cancer promoting factor which is different from GPR109A and GPR43. Here, HCAR2 is linked to cancer.