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Published on: February 17, 2012
Regulation of DCIS to invasive breast cancer progression by Singleminded-2s (SIM2s)
K C Scribner1, F Behbod, W W Porter
1Department of Integrative Biosciences, College of Veterinary Medicine, Texas A&M University, College Station, TX, USA.
Abstract:
Singleminded-2s (SIM2s) is a member of the bHLH/PAS family of transcription factors and a key regulator of mammary epithelial cell differentiation. SIM2s is highly expressed in mammary epithelial cells and downregulated in human breast cancer. Loss of Sim2s causes aberrant mouse mammary ductal development, with features suggestive of malignant transformation, whereas overexpression of SIM2s promotes precocious alveolar differentiation in nulliparous mouse mammary glands, suggesting that SIM2s is required for establishing and enhancing mammary gland differentiation. To test the hypothesis that SIM2s regulates tumor cell differentiation, we analyzed SIM2s expression in human primary breast ductal carcinoma in situ (DCIS) samples and found that SIM2s is lost with progression from DCIS to invasive ductal cancer (IDC). Using a MCF10DCIS.COM progression model, we have shown that SIM2s expression is decreased in MCF10DCIS.COM cells compared with MCF10A cells, and reestablishment of SIM2s in MCF10DCIS.COM cells significantly inhibits growth and invasion both in vitro and in vivo. Analysis of SIM2s-MCF10DCIS.com tumors showed that SIM2s promoted a more differentiated tumor phenotype including the expression of a broad range of luminal markers (CSN2 (β-casein), CDH1 (E-cadherin), and KER18 (keratin-18)) and suppressed genes associated with stem cell maintenance and a basal phenotype (SMO (smoothened), p63, SLUG (snail-2), KER14 (keratin-14) and VIM (vimentin)). Furthermore, loss of SIM2s expression in MCF10DCIS.COM xenografts resulted in a more invasive phenotype and increased lung metastasis likely due to an increase in Hedgehog signaling and matrix metalloproteinase expression. Together, these exciting new data support a role for SIM2s in promoting human breast tumor differentiation and maintaining epithelial integrity.
Insights
Singleminded-2s (SIM2s) loss promotes breast cancer progression and invasion. Restoring SIM2s expression enhances tumor differentiation and epithelial integrity, suggesting its role in suppressing breast cancer development.
Area of Science:
- Molecular Biology
- Cancer Biology
- Cellular Differentiation
Background:
- Singleminded-2s (SIM2s) is a transcription factor crucial for mammary epithelial cell differentiation.
- SIM2s is downregulated in human breast cancer, and its loss is linked to aberrant mammary gland development and malignant transformation.
- Previous studies suggest SIM2s is essential for establishing and enhancing mammary gland differentiation.
Purpose of the Study:
- To investigate the role of SIM2s in regulating human breast tumor cell differentiation and progression.
- To analyze SIM2s expression changes during the transition from ductal carcinoma in situ (DCIS) to invasive ductal cancer (IDC).
- To determine the functional impact of SIM2s re-expression on breast cancer cell growth, invasion, and metastasis.
Main Methods:
- Analysis of SIM2s expression in human primary breast DCIS and invasive ductal cancer (IDC) samples.
- Utilized the MCF10DCIS.COM cell line model for studying breast cancer progression.
- Assessed the effects of SIM2s re-expression on MCF10DCIS.COM cell growth, invasion, and tumor phenotype in vitro and in vivo.
- Examined the expression of differentiation markers, stem cell-associated genes, and signaling pathways (Hedgehog, MMPs) in SIM2s-expressing tumors.
Main Results:
- SIM2s expression is lost during the progression from DCIS to IDC.
- Re-establishing SIM2s in MCF10DCIS.COM cells significantly inhibited growth and invasion.
- SIM2s expression promoted a differentiated tumor phenotype, upregulating luminal markers and suppressing stem cell/basal markers.
- Loss of SIM2s in xenografts led to increased invasiveness and lung metastasis, associated with elevated Hedgehog signaling and matrix metalloproteinase expression.
Conclusions:
- SIM2s plays a critical role in promoting human breast tumor differentiation.
- SIM2s functions to suppress breast cancer progression, invasion, and metastasis.
- Restoration of SIM2s may represent a potential therapeutic strategy for breast cancer by enhancing differentiation and maintaining epithelial integrity.
