Transgelin: a potentially useful diagnostic marker differentially expressed in triple-negative and non-triple-negative breast cancers.

Triple negative (TN) (estrogen receptor [ER], progesterone receptor [PR] and HER2-) are highly aggressive, rapidly growing, hormone-unresponsive tumors diagnosed at later stage that affect younger women with shorter overall survival. Most TN tumors are of the basal type. For the remainder, identification of target markers for effective treatment strategies remains a challenge. Transgelin (TGLN) is a 22-kd actin-binding protein of the calponin family. It is one of the earliest markers of smooth muscle differentiation. TGLN has been shown to have important biologic activities including regulating muscle fiber contractility, cell migration, and tumor suppression. We examined TGLN expression in the different molecular subtypes of breast cancer. TGLN expression was examined as a function of tumor size, grade, histologic type, lymph node status, patients' age and overall survival, ER, PR, HER2, and Ki-67 in 101 tumors that included 35 luminal A, 28 luminal B, 4 HER2, and 34 TN types. TGLN positivity (defined as 2+ or 3+) was associated with more aggressive tumors (10% of grade I/II tumors were TGLN+ versus 53% of grade III tumors; P < .001), high Ki-67 count, and low ER and PR expression (P < .001) but not with tumor size, age, or lymph node metastasis. TN (n = 34) tumors were 7.7 times more likely to be TGLN+ than non-TN (n = 67) tumors (77% versus 10%, respectively; P < .001). TGLN may be an excellent diagnostic marker of TN tumors and could be useful in stratification of patients. TGLN may also prove a potential target for future treatment strategies.