High insulin levels may drive worse breast cancer outcomes for Black women
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Key takeaways:
- Tumor samples from Black women with triple-negative breast cancer expressed higher levels of insulin receptor signaling than those from white women.
- Insulin resistance may play a role in breast cancer outcomes.
BOSTON — Tumor samples from Black women diagnosed with triple-negative breast cancer expressed higher levels of insulin signaling than samples from white women, suggesting hyperinsulinemia may play a role in disease outcomes, data show.
Triple-negative breast cancer, an aggressive form of the disease that tends to grow and spread more quickly, accounts for about 10% to 15% of all breast cancers, according to Alexis Engel, BA, a medical student at the Icahn School of Medicine at Mount Sinai. Black women have higher rates of triple-negative breast cancer as well as a greater risk for death from breast cancer compared with white women, Engel said.
“Black women have worse outcomes when diagnosed with triple-negative breast cancer than white women,” Engel told Healio before a presentation at ENDO 2024. “In studies that have controlled for access to treatment and other health-related disparities, which can also play a role, Black women still had worse outcomes. We conducted this study to try and understand what is going on.”
For the cross-sectional study, researchers analyzed tumor samples from 45 Black and 48 white women newly diagnosed with triple-negative breast cancer, using immunohistochemistry analysis. Researchers quantified the breast cancer expression of insulin receptor signaling (n = 92), as well as insulin-like growth factor I (n = 92), phosphorylated Erk (pERK; n = 91) and forkhead transcription factor O subfamily member 3a (FOXO3a; n = 90), all downstream receptors of the insulin receptor signaling pathway. Researchers categorized the intensity of expression ranging from none (zero) to intense (3). Scores of zero and 1 were considered negative and scores of 2 and 3 were considered positive.
“We collected tumor samples from Black and white women with triple-negative breast cancer, looking at the expression of different proteins in the tumors,” Engel said. “We wanted to see if the tumors from Black women had more signs of sensitivity to insulin than white women.”
Researchers observed positive insulin receptor staining for 64% of tumors, with insulin receptor expression more prevalent in tumors from Black women (P = .003). Positive staining was also associated with higher BMI, waist circumference and fasting insulin (P for all < .05).
Engel noted that positive IGF-I receptor, FOXO3a and PERK staining were not associated with any age or metabolic parameters.
“We found that insulin receptor signaling was higher among Black women, which would indicate that Black women are responding to insulin to a greater degree than white women,” Engel told Healio. “This is despite the fact that, at baseline, Black and white women had similar fasting insulin levels.”
Engel said the observed signaling patterns could be related to overall levels of insulin resistance, noting that Black women overall have higher rates of diabetes, obesity and insulin resistance; research is ongoing.
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Engel AJ, et al. RF17-03. Presented at: ENDO annual meeting; June 1-4, 2024; Boston.
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