Breast cancer is the second leading cause of death in women, accounting for about 40,000 deaths per year. A specific mutation in the human epidermal growth factor receptor 2 (HER2/Neu) has been shown to lead to a more invasive cancer and poor prognosis. Current research has shown that when HER2/neu is overexpressed, a transcription factor nuclear factor-kappa B (NF-kB) is also overexpressed. NF-kB exists as a dimer made up of five potential proteins. This research is evaluating the role of each of these five proteins in a HER2/neu positive breast cancer cell line NF-639.Using the technique of interference RNA (RNAi), each of the five separate protein’s expression has been blocked to evaluate its role in the function of the transcription factor and any phenotypic changes seen in the cancer cells. Protein levels and mRNA levels were also evaluated to validate the success of the RNAi.