43. Triple Negative Breast Cancer, Stem Cells and African Ancestry

Jiagge, E et al. 2018

In many respects, women of African ancestry fare worse than other populations when diagnosed with breast cancer. For example, mortality rates are higher than those of white Americans, and some types of breast cancer that are harder to treat are especially common in women of African ancestry.

In this paper, the authors summarize previous studies about triple negative breast cancer, breast cancer stem cells and breast cancer in African American women. These three topics have one thing in common: an association with breast cancer virulence. By looking at previous targeted studies, they looked at how these topics are connected.

The summaries:

Triple Negative Breast Cancer and African Ancestry

Researchers have looked at socioeconomic factors that may explain disparities in breast cancer outcomes for women of African ancestry. Studies examined effects of inadequate health care, lack of insurance coverage and delayed treatment, for example.

But to understand why African American women develop triple negative breast cancer (TNBC) more frequently, scientists look at tumor biology. TNBC means the tumor is not reliant on hormone receptors and is affected by a receptor called HER2/Neu. TNBC is less common than hormone-positive breast cancer, and we have fewer tools to treat TNBC. 

By looking at the cellular and genetic levels, studies have found several different tumor subtypes that could help in pinpointing possible treatments. Research also has shown that basal-like subtypes are more common among the African American women, and those may explain the connection to TNBC.

Breast Cancer Stem Cells and TNBC

Stem cells are found throughout the body, and they are the key to self-renewal. Mammary stem cells are responsible for generating glands in the breast, and sometimes during this process, a mammary cancer stem cell may develop. These, too, can redevelop, unlike cancer cells that do not have breast cancer stem cells.

Being able to identify these cells and interfere with their progress is an exciting prospect for researchers working on precise treatments.  For now, these cells may play a role in how easily cancer moves from the breast to other parts of the body.

Most stem cell research in humans has been based on specimens from white, European and Asian patient populations. Using donor samples from the Komen Tissue Bank, researchers wanted to see how these stem cell patterns appeared in tumors from women of African ancestry. They found elevations of some markers in those samples compared to white women’s.  Other studies found different levels of other proteins and receptors among specimens from the groups.

Why this review is important:

By using previous studies of TNBC, breast cancer stem cells and disparities in mortality rates for women of African ancestry, the authors suggest additional genetic studies to uncover why virulent patterns of breast cancer are more common in this population.