Hypoxia-Driven TGFß Modulation of Side Population Cells in Breast Cancer: The Potential Role of ERα.

Epithelial-to-mesenchymal transition (EMT) is known to be important in regulating the behaviour of cancer cells enabling them to acquire stem cell characteristics or by enhancing the stem cell characteristics of cancer stem cells, resulting in these cells becoming more migratory and invasive. EMT can be driven by a number of mechanisms, including the TGF-ß1 signalling pathway and/or by hypoxia. However, these drivers of EMT differ in their actions in regulating side population (SP) cell behaviour, even within SPs isolated from the same tissue. In this study we examined CoCl2 exposure and TGF-ß driven EMT on SP cells of the MDA-MB-231 and MCF7 breast cancer cell lines. Both TGF-ß1 and CoCl2 treatment led to the depletion of MDA-MB-231 SP. Whilst TGF-ß1 treatment significantly reduced the MCF7 SP cells, CoCl2 exposure led to a significant increase. Single cell analysis revealed that CoCl2 exposure of MCF7 SP leads to increased expression of ABCG2 and HES1, both associated with multi-drug resistance. We also examined the mammosphere forming efficiency in response to CoCl2 exposure in these cell lines, and saw the same effect as seen with the SP cells. We suggest that these contrasting effects are due to ERα expression and the inversely correlated expression of TGFB-RII, which is almost absent in the MCF7 cells. Understanding the EMT-mediated mechanisms of the regulation of SP cells could enable the identification of new therapeutic targets in breast cancer.

Epithelial-to-mesenchymal transition: what is the impact on breast cancer stem cells and drug resistance.

There is increasing interest in cancer stem cells (CSCs) and their role in cancer progression. Recently, CSCs have been identified in brain, skin, and intestinal tumors and it has been suggested that these CSCs are responsible for tumor growth and metastasis. In breast cancer fatality is often due to the development of metastatic disease (MBC). Almost 30% of early breast cancer patients eventually develop MBC and in 90% of these multi-drug resistance (MDR) occurs. This could be attributed to the presence of breast cancer stem cells (BCSCs). Epithelial-to-mesenchymal transition (EMT) is a process known to contribute to metastasis in cancer and it is mainly characterized by loss of E-cadherin expression. The TGF-ß signaling pathway has an established role in promoting EMT by down-regulating E-cadherin via a number of transcription factors, such as Twist, Snail and Slug. EMT has also been reported to produce cells with stem cell-like properties. Definition of the exact molecular mechanisms that are involved in the generation of stem cells through EMT could lead to the identification of new potential therapeutic targets and enable the development of more efficient strategies for particular patient groups. In this review we discuss what is known about the relationship between EMT, BCSCs and MDR.

Asymmetric dimethyloarginin (ADMA) concentration in the aqueous humor of patients with exfoliation syndrome or exfoliative glaucoma.

BACKGROUND: Asymmetric dimethyloarginin or dimethylarginin (ADMA) is a marker and maker of oxidative stress. It is elevated in several pathological conditions, such as hyperhomocysteinemia and endothelial dysfunction, which have also been reported in patients with exfoliation syndrome (XFS), or exfoliative glaucoma (XFG). We evaluated ADMA levels in the aqueous humor of XFS and XFG patients. METHODS: This study included 48 aqueous samples; 16 from cataract patients with XFS, 16 from cataract patients with XFG and 16 from age-matched cataract control patients. ADMA levels were determined employing a commercial ELISA kit. RESULTS: ADMA concentration was significantly greater in XFG patients (0.398 ± 0.026 µM) compared to either XFS (0.168 ± 0.028 µM; p < 0.0001) or normal cataract controls (0.245 ± 0.025 µM; p = 0.0002). In contrast, no significant difference was detected for ADMA levels in the aqueous of XFS patients as compared to normal controls (p = 0.0477). CONCLUSIONS: Aqueous humor ADMA concentration is significantly elevated in XFG patients supporting the view that oxidative stress plays a key role in XFG pathobiology. The lower level of this marker in XFS suggests that the development of XFG is a prerequisite for ADMA elevation.