Because TNBC lacks hormone receptors (estrogen receptor and progesterone receptor) and human epidermal growth factor receptor 2 (HER2) 3, therapies targeting these receptors are not an option, and cytotoxic chemotherapy agents such as fluorouracil (5-FU) 4, cisplatin (CDDP) 5, and paclitaxel (PXT) 6 are used as first-line treatments. Compared with other types of breast cancer, TNBC shows a shorter survival time, higher rate of mortality within five years after diagnosis, and higher rate of distant metastasis 2. Triple-negative breast cancer (TNBC) accounts for 15–20% of all breast cancer cases 1. These results suggest that 5-FU–induced cell migration is mediated by αB-crystallin in the BL2 subtype of TNBC. Thus, 5-FU increased cell motility in cell lines with high, but not low, αB-crystallin expression. In addition, the cell motility of MDA-MB-231 cells overexpressing αB-crystallin was significantly higher than that of MDA-MB-231 cells harboring a control vector. Also, cell motility was not increased by 5-FU treatment in HCC1806 cells harboring stealth siRNA targeting CRYAB. A wound healing assay revealed that 5-FU significantly increased cell motility in HCC1806 cells, but not in MDA-MB-231 cells, which have low αB-crystallin expression. Here, we evaluated the effect of fluorouracil (5-FU), a typical chemotherapy for the treatment of TNBC, on cell motility by utilizing a cell line with high αB-crystallin expression (HCC1806). We therefore hypothesized that αB-crystallin is associated with increased cell motility in the BL2 subtype after treatment with chemotherapy. Research has shown that αB-crystallin ( CRYAB) is more highly expressed in the basal-like subtypes than in the other subtypes and is associated with brain metastasis in TNBC patients. Among triple-negative breast cancer (TNBC) subtypes, the basal-like 2 (BL2) subtype shows the lowest survival rate and the highest risk of metastasis after treatment with chemotherapy.

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