Abstract
Of the 200,000 new cases of breast cancer diagnosed each year in the U.S, ~80% of the cancers are estrogen receptor alpha (ER) positive. Therefore, most first line treatments are endocrine therapies that target the ER. Selective estrogen receptor modulators (SERMs) and selective estrogen receptor down-regulators (SERDs) are used in premenopausal women, and aromatase inhibitors (AIs) are often used in postmenopausal women. Many of these cancers revert to an endocrine resistant, metastatic phenotype after one or more successful first line treatment(s). Patients who present with endocrine refractory disease have no good option for therapy other than chemotherapy regimens, which ultimately fail with high rates of mortality. Interestingly, approximately 25% of patients with endocrine resistant, metastatic disease harbor a mutated ER within the cancer cells, a mutation that was not detected in the primary tumor. During metastasis, some cells from the primary tumor are shed into the bloodstream and undergo hemodynamic shear stress on route to the secondary site of metastasis. Some of these cells, known as circulating tumor cells (CTCs), can seed in secondary organs and produce metastatic lesions. Several studies have recently linked fluid shear stress (FSS) with DNA instability and tumor metastasis. To explore this possibility, we used an
in vitro
model to test the effect of FSS on breast cancer cells, with the ultimate aim of understanding how FSS changes genomic dynamics, possibly leading to increased mutation frequency. We have preliminary results that physiological levels of FSS induce activation of the ATR DNA damage response pathway in both MDA-MB231 and MCF-7 breast cancer cells. Whole exome sequencing results support this data by showing sequential exposure of MCF-7 cells to FSS results in both
de novo
somatic mutations as well as an increase in mutation frequency at several common SNP sites. These data suggest FSS may play a role in downstream genomic instability and mutagenesis. Furthermore, Western blot and migration data of sheared cells show that FSS alters the phenotype of these cells, potentially rendering them more drug resistant and/or metastatically competent. In conclusion, we have shown that FSS may play a direct role in altering genomic instability as well as the phenotypic signature in breast cancer cells, resulting in cells that may be more metastatic and aggressive. The ultimate goal of this research is to utilize this
in vitro
approach to
identify molecular targets that can be pursued to either prevent or delay metastatic breast disease.
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