HCCS is a 79 amino acid protein that may act as a tumor suppressor, promoting the apoptosis of cancer cells. Expressed in leukocytes, lung, spleen, liver, heart, kidney, muscle and uterine cervix, HCCS-1 is down-regulated in cervical cancers. The gene encoding HCCS-1 maps to human chromosome 15q25.1. Encoding more than 700 genes, chromosome 15 is made up of approximately 106 million base pairs and comprises about 3% of the human genome. Angelman and Prader-Willi syndromes are associated with loss of function or deletion of genes in the 15q11-q13 region. Tay-Sachs disease is a lethal disorder associated with mutations of the HEXA gene, which is encoded by chromosome 15. Marfan syndrome is associated with chromosome 15 through the FBN1 gene.