Active Motif's HeLa acid extract (Sodium butyrate treated) was prepared under acidic conditions from cells harvested from a cell culture of the HeLa human epithelial carcinoma cell line that was treated with sodium butyrate. Acid extraction is performed under conditions that are optimized for solubility of histone proteins. Sodium butyrate is a compound that has profound effects on the morphology, growth rate and gene expression of mammalian cultured cells. The primary mechanism of action of sodium butyrate is the inhibition of the activity of histone deacetylases (HDACs) that results in the extensive, although reversible, acetylation of histones. In HeLa cells, butyrate-mediated histone hyperacetylation leads to inhibition of DNA synthesis and arrest in G1, induction of differentiation, and alterations in gene expression. The HeLa cell line was originally derived from cells obtained in 1951 from Henrietta Lacks, a cervical cancer patient who eventually died from her cancer. The HeLa cell line is one of the oldest and most commonly utilized immortal cell lines in scientific research. These cells are highly prolific and easily sustainable, allowing for flexibility in their application in various fields of scientific research, including cancer biology, virology, and human disease. To date, over 60,000 publications across various disciplines have referenced the use of HeLa cells.