Globally, breast cancer is ubiquitous and regarded as a leading cause of death amongst other causes of death. It plays a role in several aberrant genes seen in the tumorigenesis pathway, thus making it heterogenic. An example of this gene is the HDAC1 gene, which is a multifunctional protein and plays a role in gene expression regulation. Using the CRISPR/Cas9 system, a remarkable gene editing approach essential in identifying and validating genomic targets with the potential to be tumoricidal, the role of HDAC1 was investigated in a breast cancer cell line, MCF-7.