Leucine zipper/EF hand-containing transmembrane-1 (LETM1) is a mitochondrial inner membrane protein that is a potential biomarker of prognosis of several cancers, such as colorectal cancer, esophageal squamous cell carcinoma, breast cancer, lung non-small cell carcinoma, and gastric adenocarcinoma [23–27]. Here, LETM1 is linked to cancer.