Researchers identify racial differences in breast cancer immune microenvironment

Roswell Park Comprehensive Cancer Center researchers have identified significant differences in the immune microenvironment of breast cancer tumors between African-American and white women, shedding light on the ways in which race can influence cancer development and outcomes. The findings, to be presented at the 2018 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, are based on based on a comprehensive review of data from The Cancer Genome Atlas (TCGA), the world's largest public database containing genetic information about various different types of tumors.

Ahmed Elkhanany, MD, a Roswell Park clinical fellow, is lead author and Kazuaki Takabe, MD, PhD, FACS, Alfiero Foundation Endowed Chair in Breast Oncology, is senior author of the study, "Racial disparity in breast cancer immune microenvironment" (abstract 1081), to be presented in a poster session on Saturday, June 2, from 8 a.m. to 11:30 a.m. CDT in McCormick Place, Poster Hall A.

Although white women have the highest incidence of breast cancer in the United States, African-American women are more likely than women of any other ethnic group to die of the disease. While unequal access to high-quality screening and cancer treatment likely contributes to the higher mortality rate among African-Americans, the reasons for this racial disparity in breast cancer go beyond access to care. The biology of various breast tumors, particularly those that are not influenced by hormones such as estrogen and progesterone, differs between African-American and white women. African-American women are also more likely than white women to develop hormone-negative breast cancer, a disease type that is unresponsive to hormone therapy drugs and thus more difficult to treat.

Using the TCGA data and an algorithm that allows for in-depth analysis of various cell types in complex tissue samples, Dr. Takabe and his team found significant differences in the tumor immune microenvironment in African-American and white women that may contribute to racial disparities in the development and progression of breast cancer.

Specifically, tumors from African-American breast cancer patients contained significantly higher numbers of regulatory T cells than tumors from white patients. This difference was present in most breast cancer subtypes but most notable in triple-negative breast cancer, which is three times more likely to develop in African-Americans than whites.

"Knowing that triple-negative breast cancers tend to attract immune cells, we hypothesized that the immune cells that attracted by tumors in African-American women may be different than what we see in women of other ethnicities," says Dr. Takabe. "In the current study, we found that the tumors of African-American women attract regulatory T-cells that calm down our killer lymphocytes and inhibit the body's ability to defend against cancer."

"Regulatory T cells cause the immune system to 'calm down,' which essentially decreases the body's ability to mount an immune response to cancer cells, allowing tumors to grow," adds Dr. Elkhanany. "This finding explains why African-American women who develop certain types of breast cancer tend to have poor outcomes, and we can now use this information to develop novel therapies as well as personalize breast cancer treatment in the future."

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