Reticulocalbin-2 (RCN2, also named as ERC-55), is a 55-kDa Ca2+-binding protein containing six EF-hands, which was identified to be localized in endoplasmic reticulum. RCN2 is belonging to Reticulocalbin (RCN) family, the family members could play oncogenic roles in human malignancies and facilitate tumor cell proliferation and metastasis. Recently, studies on RCN2 functions mainly focused on its role in differentiation and endocrine regulation in mouse. Another study has suggested that RCN2 could be a potential tumor-associated antigen for mammary cancer immunological prevention. Up to now, the experimental evidence uncovering the role of RCN2 in cancer is very limited.