All living organisms have a circadian clock, sometimes called a biological clock, that is an important part of maintaining optimal health.   The circadian rhythm is a roughly 24-hour cycle in the biochemical, physiological, or behavioral processes of living things.   Although  circadian rhythms originate from within our bodies, they are synchronized to the environment by external cues, including the day-night cycle caused by the Earth's rotation.  Researchers are looking more closely at the role circadian rhythms play in the development of diseases such as breast cancer and also how factors such as hormones affect this biological clock.

Carla Finkielstein, a molecular biologist at Virgina Tech, has launched a research project to study how changes in circadian rhythms may contribute to the development of breast cancer in women.   According to Finkielstein, "There are a number of epidemiological studies that show women working night shifts have a higher incidence of breast cancer."  The question she asks is:   Can working odd hours actually alter a women's body chemistry--turning healthy cells into cancer cells?

With support from the National Science Foundation, she is using frog embryos to help figure out on a molecular basis the physiological changes in women who work night shifts.   She says studies show that night workers have abnormal levels of specific protein in their cells, which act by turning on and off genes that regulate how cells grow and divide.  Proper timing of cell division is a major factor contributing to the regulation of normal cell growth and is a fundamental process in the development of most cancers.  She explains," Our research explores ways in which the loss of circadian function impairs the death of cells in the cell cycle and leads to the accumulation of damaged, or cancerous, cells."

Where is this leading us, what is the clinical application?   "If we were to generate a panel of markers that we can follow regularly for women who works night shifts, it would enable us to record changes in circadian-controlled genes and thus predict whether a person is at risk of developing breast cancer, " Finkielstein said.   "If we see abnormal changes, all we may need to do is to alter this person's work schedule."

This study reinforces the important role circadian rhythm plays in sex and gender-based research.  In another example,  researchers at Northwestern University who are working in the lab of Dr. Fred Turek have determined that sex differences in hormone status in female mice are critical to better understanding stress or sleep deprivation.  There is growing evidence that circadian rhythm may play a part in other health issues like cardiovascular disease and diabetes.