To date, only one spliced isoform has been reported; this isoform contains six EF-hand motifs (calcium-binding motifs) and an HDEL sequence, an ER retention signal, on its C terminus.21 An increasing number of reports indicate upregulation of RCN1 in cancer patients and multiple tumor types, including breast cancer,22 colorectal cancer,23 kidney cancer24 and liver cancer,25 but the underlying mechanism remains unclear. Here, RCN1 is linked to cancer.