MR1 and breast cancer: In this study, we selected the shortest splicing form of MR‐1, MR‐1S (NM‐001077399.1), which is the only one with cancer effects.[8] It consists of three different exons and encodes a 15.6 kDa protein with 142 amino acids (aa), without homology to any known protein.[53] Clinical data shows that MR‐1 is overexpressed in gastric cancer and pancreatic ductal adenocarcinoma, and is significantly correlated with clinical staging and poor survival rate.[11, 13] Preliminary laboratory studies focused on liver cancer and breast cancer.