Breast Cancer Onset – Insights from Evolutionary Research

From the initial phases of cellular mutations commencing during puberty, leading to their eventual development into breast cancer later in life, this entire progression has long remained enigmatic.

However, a group of scientists at Kyoto University has now unveiled the intricate process through which breast cancer emerges within the mammalian epithelial cells, primarily responsible for milk secretion. Their groundbreaking findings have been documented in the esteemed journal Nature.

In their initial assessment, the research team determined that approximately 20 mutations amass within each epithelial cell on an annual basis until the onset of menopause. Remarkably, following menopause, the mutation rate experiences a significant decline.

“Additionally, our results suggest that estrogen influences mutation accumulation in mammary epithelium, which correlates with our discovery of decreased accumulation after childbirth,” says corresponding author Seishi Ogawa of KyotoU’s Graduate School of Medicine.

With an understanding that 70% of breast cancers are influenced by estrogen, Ogawa’s research team may provide valuable insights into the role of estrogen in the initiation of breast cancer.

Deeper exploration into the genetic interplay among breast cancer, its adjacent lesions, and normal epithelial cells has led to mapping of breast cancer’s translocation-positive expansion. Within this expansion phase, cells originating from various sources and destined to develop into breast cancer make themselves apparent, typically around 30 years of age.

While prior research has predominantly centered on driver mutations – those genetic alterations within already cancerous cells that drive abnormal growth – these discoveries offer a more comprehensive perspective of the process. They unveil the presence of driver mutations and also shed light on their timing and sequence in cancer formation.

“Normal-looking tissues may already contain numerous populations of non-cancer cells—or clones—that have acquired mutations in cancer-related genes,” says co-author author Tomomi Nishimuraof KyotoU’s Graduate School of Medicine.

Following a thorough analysis of the commonalities and distinctions in mutations found within cancerous and non-cancerous lesions arising from these clones, the research team worked on reconstructing an evolutionary tree. This tree was crafted to provide a visual representation of the distinct and specific pattern underlying the evolution of cancer.

“Our study brings us closer to exposing the clinical profile of estrogen-sensitive breast cancer, particularly in pre-menopausal women, potentially aiding cancer risk monitoring and prevention,” adds Ogawa.

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