PRRX2 as a novel TGF-ß-induced factor enhances invasion and migration in mammary epithelial cell and correlates with poor prognosis in breast cancer.

TGF-ß and cancer progression share a multifaceted relationship. Despite the knowledge of TGF-ß biology in the development of cancer, several factors that mediate the cancer-promoting role of TGF-ß continue to be identified. This study aimed to identify and characterise novel factors potentially related to TGF-ß-mediated tumour aggression in breast cells. We treated the human mammary epithelial cell line MCF10A with TGF-ß and identified TGF-ß-dependent upregulation of PRRX2, the gene encoding paired-related homeobox 2 transcription factor. Overexpression of PRRX2 enhanced migration, invasion and anchorage-independent growth of MCF10A cells and induced partial epithelial mesenchymal transition (EMT), as determined by partial fibroblastoid morphology of cells, upregulation of EMT markers and partially disrupted acinar structure in a three-dimensional culture. We further identified PLAT, the gene encoding tissue-type plasminogen activator (tPA), as the highest differentially expressed gene in PRRX2-overexpressing MCF10A cells, and demonstrated direct binding and transactivation of the PLAT promoter by PRRX2. Furthermore, PLAT knockdown inhibited PRRX2-mediated enhanced migration and invasion, suggesting that tPA may mediate PRRX2-induced migration and invasion. Finally, the significant correlation of PRRX2 expression with poor survival in 118 primary breast tumour samples (P = 0.027) and the increased PRRX2 expression in metaplastic breast carcinoma samples, which is pathogenetically related to EMT, validated the biological importance of PRRX2-enhanced migration and invasion and PRRX2-induced EMT. Thus, our data suggest that upregulation of PRRX2 may be a mechanism contributing to TGF-ß-induced invasion and EMT in breast cancer. © 2016 Wiley Periodicals, Inc.

Frequent alterations of HER2 through mutation, amplification, or overexpression in pleomorphic lobular carcinoma of the breast.

Mutations in HER2 gene have been identified in a small subset of breast cancer cases. Identification of HER2 mutation has therapeutic implications for breast cancer, but whether a subgroup of breast cancer with a higher frequency of HER2 mutation exists, remains unknown. We analyzed HER2 mutation and pathologic factors on 73 formalin-fixed, paraffin-embedded samples, including 21 pleomorphic invasive lobular carcinoma (p-ILC) cases, 3 pleomorphic lobular carcinoma in situ (p-LCIS) cases, and 49 classic invasive lobular carcinoma (c-ILC) cases. Mutations were identified through direct sequencing. HER2 overexpression and amplification were determined through immunohistochemistry and fluorescent in situ hybridization. Six mutations were identified, including five in the 24 p-ILC or p-LCIS (p-ILC/p-LCIS) cases (20.8 %) and one in the 49 c-ILC cases (2.0 %), and the difference in frequency was significant (p = 0.013). Eight of the 24 (33.3 %) p-ILC/p-LCIS cases exhibited HER2 amplification or overexpression (amplification/overexpression), which was significantly higher than in the c-ILC cases (1/49, 2 %). Mutation and amplification/overexpression were mutually exclusive. HER2 mutations were identified more frequently in the p-ILC/p-LCIS cases with extensive apocrine change (p = 0.018). Combined HER2 alterations through mutation or amplification/overexpression were more frequently identified in p-ILC/p-LCIS cases without estrogen receptor expression. The high frequency (54.1 %, 13/24) of combined HER2 alterations in the p-ILC/p-LCIS cases suggests a crucial role of HER2 in the pathogenesis of p-ILC/p-LCIS. Because of the reported responsiveness of HER2 mutation to anti-HER2 therapy, p-ILC patients without HER2 amplification/overexpression should receive HER2 mutation analysis to identify this therapeutically relevant target.

Fibrillin-1, a novel TGF-beta-induced factor, is preferentially expressed in metaplastic carcinoma with spindle sarcomatous metaplasia.

TGF-ß induces epithelial-mesenchymal transition (EMT), which is involved in tumour progression. This study aims to identify and characterise novel factors potentially related to TGF-ß-mediated tumour aggression in breast cancer. We treated the human mammary epithelial cell line MCF10A with TGF-ß and observed TGF-ß-dependent upregulation of FBN1, involving demethylation of CpG sites, in MCF10A cells undergoing EMT. The biological importance of fibrillin-1, encoded by FBN1, was evaluated through immunohistochemistry on 225 breast cancer specimens of various subtypes. Fibrillin-1 expression was observed only in metaplastic carcinoma of the breast (MCB) (51.7%), and the expression was observed in spindle sarcomatous metaplasia (SSM), but not in other metaplasia, including matrix-producing, pleomorphic, and squamous metaplasia, and carcinomatous components of both MCB and non-MCB. Fibrillin-1 expression was also restricted to the SSM of non-mammary carcinosarcomas of various organs. Overall, fibrillin-1 expression was enriched in MCB and non-mammary carcinosarcoma with SSM (93.7% and 93.3%, respectively), but not in MCBs and non-mammary carcinosarcoma without SSM. FBN1 knockdown in MDA-MB-231 cells with high FBN1 expression did not compromise migration, invasion, and tumourigenesis, and did not alter the expression of other EMT-related markers. In conclusion, fibrillin-1 is a novel TGF-ß-induced marker. Fibrillin-1 expression in SSM, but not in other metaplasia and carcinomatous components, in both MCBs and non-mammary carcinosarcomas, together with the inability of FBN1-knockdown to compromise migration and invasion, indicates that fibrillin-1 is a marker induced solely in spindle metaplasia during EMT and does not induce EMT nor lead to tumour aggressiveness.