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Studies have shown a link between greater rates and risks of breast cancer in women that work night shifts, such that this type of work has been labeled a probable carcinogen. It has been suggested that the disruption of circadian genes- PER and CRY - could be partly responsible for this increased breast cancer risk. The suprachiasmatic nucleus (SCN) in the brain is the central circadian pacemaker; however, how and if Triple-negative breast cancer (TNBC) cells, an aggressive type of breast cancer that is characterized by the absence of estrogen receptors (ER), progesterone receptors (PR), as well as HER-2 growth factor receptors, express particular circadian clock genes when disconnected from the “master clock” is not extensively researched nor understood. This study’s goal was to answer the following questions: do triple-negative breast cancer cells (TNBCs) express circadian genes? Do TNBCs exhibit rhythmic circadian gene expression in vitro? Are TNBCs and the circadian genes responsive to external red-light exposure at a wavelength shown to alter mitochondrial function? Cells were cultured in vitro, exposed or not exposed to red light, and then harvested at 6-hour time intervals for 24 hours. The harvested cells endured RNA isolation, followed by cDNA synthesis and PCR to amplify circadian genes PER1, PER2, PER3, CRY1, CRY2. The expression level was compared to constitutively expressed reference genes to determine whether circadian rhythmicity is present in TNBC cells growing in vitro.