STC2 and breast cancer: STC-1 was identified a phagocytosis checkpoint in 2021.11 STC-1 was first discovered in the corpuscles of the stannius of bony fishes,111 and its homologous genes in mammals, STC-1 and STC-2, were subsequently cloned.112 STC-1 is widely expressed in the ovary, prostate, bladder, kidney, adrenal gland, lung, heart, uterus, and pituitary gland in mammals,113 and its expression is upregulated in breast cancer, which potentiates invasiveness of breast cancer via JNK-/c-Jun pathway.114