A new breast cancer research study ( free to read ) in a mouse model of breast cancer metastasis recently explored these relationships with profound results. For this new breast cancer research study, investigators took breast cancer cells and injected them with the firefly luciferase gene so that they would glow and be easily tracked. These breast cancer cells were then injected into two groups of mice. One group of mice was placed in an over-crowded environment that prevented them from moving freely for 2 hours per day for 20 days in order to induce chronic stress. The second group of mice (control group) remained in their more expansive home conditions without the stress-inducing restraint. The growth and spread of these breast cancer cells was monitored in addition to changes in sympathetic nerve system function and immune function. The breast cancer researchers reported that
Chronic stress caused nearly a 40-fold increase in the metastasis of breast cancer cells from the primary tumor. The stressful conditions resulted in a 37-fold increase in metastasis to the lungs and a 67% increase in the spread of breast cancer cells to lymph nodes.
Chronic stress induced an infiltration of macrophages, a specific immune system cell type, into the primary breast cancer tumors by 53% on average.
Chronic stress enhanced the expression of pro-inflammatory genes, genes involved in the promotion of breast cancer metastasis, and some growth factor genes involved in breast cancer progression. Additionally, genes with a protective function were reduced by chronic stress.
Treatment with the beta-blocker drug propranolol blocked stress-induced breast cancer metastasis in stressed mice, but had no effect in non-stressed, control mice.
Furthermore, treatment with propranolol suppressed the invasion of primary breast cancer tumors by immune system macrophages.
Treatment of mice with a drug designed to directly inhibit macrophage function successfully reduced breast cancer metastasis.
These are important and exciting breast cancer research results that show us two important things. First, this new breast cancer research shows us that chronic stress increases breast cancer metastasis and does so by altering the sympathetic nervous system, enhancing the recruitment of immune cells to the breast cancer tumor, and increasing the production of growth and inflammatory factors that promote breast cancer metastasis. Secondly, this new breast cancer research shows that drugs that block the stress-induced effects on the sympathetic nervous system and drugs that directly block macrophage function can successfully suppress breast cancer metastasis. These results might open new avenues in breast cancer treatment that can proactively target and suppress breast cancer metastasis.
Natural ways to reduce chronic stress can also be an important aspect to breast cancer treatment plans. Regular exercise has many benefits and has been reported to help reduce stress. Additionally, practices like breathing exercises and meditation have been reported to reduce chronic stress. Reducing chronic stress naturally or blocking physiological pathways involved in stress with new breast cancer treatments might help reduce breast cancer progression and metastasis.