Recently, it was observed that nestin is preferentially expressed in basal ⁄ myoepithelial cells of the mammary gland, and that this intermediate filament may be used as a myoepithelial marker. However, the clinical and prognostic implications of nestin as a marker for breast cancer are still unclear. We examined mastectomy specimens from 150 breast cancers and matching, adjacent non-cancerous tissues using immunohistochemistry and western blotting. Overall, triple-negative breast cancers -that is, breast cancers that do not express estrogen receptors (ER), progesterone receptors (PR), or human epidermal growth factor receptor 2 (HER2 ⁄ neu) -had higher expression rates for nestin than the other breast cancers (57.14% vs 9.30%; P < 0.001). In triple-negative breast cancers, significantly increased nestin expression rates were observed in patients with lymph node metastasis compared with those without node metastasis (25.00% vs 76.92%; P = 0.032). A similar phenomenon was observed for invasive ductal carcinomas compared with ductal carcinoma in situ (16.67% vs 73.33%; P = 0.046). Nestin expression was also found to be significantly related to ER, PR, and P53 expression (P < 0.05). Nestin expression was associated with both shorter breast cancer-specific survival and poor relapse-free survival in the lymph node-positive group (P = 0.028 and P = 0.012 respectively). After Cox regression was carried out, nestin was not shown to be an independent prognostic factor for breast cancer. These findings substantiate the possibility of using nestin as a marker for triple-negative breast cancer. Triple-negative breast cancer progression is associated with nestin; however, the underlying mechanisms of this relationship require further investigation. (Cancer Sci 2010; 101: 815-819) B reast carcinoma is the most common malignancy in women and is the second leading cause of cancer death in women.(1) Over the last 30 years, deaths from breast cancer have approximately tripled in Japan, which historically has had a low incidence of breast cancer.(2) According to the World Health Organization, more than 1.2 million people will be diagnosed with breast cancer each year worldwide.Breast cancer is a heterogeneous disease embracing several different phenotypes with consistently different biological characteristics.(3) Hormonal therapies (tamoxifen, anti-estrogens) and adjuvant chemotherapy (trastuzumab [Herceptin]) have benefited millions of patients with breast cancer.(4,5) Their success, however, is limited to a subset of patients whose tumors express estrogen receptors (ER), progesterone receptors (PR), human epidermal growth factor receptor 2 (HER2 ⁄ neu), tumor protein 53 (P53), and so on.(6) Therefore, the status of these proteins has prognostic ramifications for breast cancer.Nestin, a primeval protein marker for neural stem cells, is also expressed in follicle stem cells and their immediate, differentiated progeny.(7) It has recently received attention as a marker for newly formed endothelial cells. In their study, Teranishi...
