Texas study links breast cancer with circadian rhythm

For years, doctors have associated the BRCA1 and BRCA2 gene mutations with an increased risk of breast cancer. But researchers at Texas A&M University have now identified another gene that may have an impact on breast cancer—associated with the body’s circadian rhythm.

At the Texas A&M College of Veterinary Medicine & Biomedical Sciences (CVM) professor Weston Porter and his team have found that Period 2 (Per2), a regulatory mechanism within each cell’s peripheral clock, plays a crucial function in mammalian mammary gland development and that when suppressed, Per2 leads to severely disrupted gland development in mice.

Circadian rhythm is controlled by the suprachiasmatic nucleus (SCN) in the brain’s anterior hypothalamus. In addition to coordinating our sleep patterns, the SCN coordinates the other peripheral clocks in our body, which run on a 24-hour cycle that corresponds with each day.

Their finding—that Per2 has a crucial function outside of timekeeping in mammalian mammary gland development where Per2plays a role in cell differentiation and identity—describes a potentially important role for Per2 in breast cancer. Per2 expression is lost in a large percentage of mammary tumors, which suggests it may have protective effects.

In addition to disruption of the developing mammary gland, Porter also saw the same defect in transplant studies, showing that it is Per2, and not just the central clock itself, that is responsible for the lack of mammary ductal growth in the developing gland.

Their next step is to revisit studies that correlate working a night shift with an increased risk of breast cancer.

Professor Weston Porter said, “We discovered that these glands have what we call a kind of a bipotent phenotype; they’re actually halfway to cancer. They’ve already have many of the characteristics you would see in a premalignant cell. Right now, we are investigating how our findings relate to humans. There are studies out there showing a relationship between decreased levels of Per2 and certain types of breast cancer, which are more invasive. So, we believe that there is a direct relationship.”