HCCR-1 (human cervical cancer oncogene 1), also known as HCCR-2 or LETMD1, is a 360 amino acid single-pass membrane protein that is expressed in the kidney, liver, skeletal muscle, heart and brain. It is suggested that HCCR-1 may be involved in tumorigenesis and may function as a negative regulator of the p53 tumor suppressor. Overexpression of HCCR-1 may cause mitochondrial dysfunction that can lead to UVC or staurosporine-induced apoptosis resistance and progression of tumor formation. HCCR-1 is considered a candidate biomarker for breast cancer. Various human tumors including leukemia, lymphoma, and carcinomas of the breast, kidney, ovary, stomach, colon, and uterine cervix have high HCCR-1. Six isoforms exist due to alternative splicing events.