Hypoxia-Induced Secretion of TGF-β1 in Mesenchymal Stem Cell Promotes Breast Cancer Cell Progression

Disseminated breast cancer cells have the capacity to metastasise to the bone marrow and reside in a dormant state within the mesenchymal stem cell niche. Research has focussed on paracrine signalling factors, such as soluble proteins, within the microenvironment. However, it is now clear extracellular vesicles secreted by resident mesenchymal stem cells into this microenvironment also play a key role in the initiation of dormancy. Dormancy encourages reduced cell proliferation and migration, while upregulating cell adhesion, thus retaining the cancer cells within the bone marrow microenvironment. Here, MCF7 breast cancer cells were treated with mesenchymal stem cell–derived extracellular vesicles, resulting in reduced migration in two-dimensional and three-dimensional culture, with reduced cell proliferation and enhanced adhesion, collectively supporting cancer cell dormancy.

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Translational disequilibrium as an interference marker to study miRNA and methylation silencing of APRIN, a stem cell regulator in breast cancer microchimerism

Journal of Clinical Oncology ◽

10.1200/jco.2009.27.15_suppl.11109 ◽

2009 ◽

Vol 27 (15_suppl) ◽

pp. 11109-11109

Author(s):

P. Geck ◽

V. Denes ◽

M. Pilichowska ◽

A. Makarovskiy ◽

G. A. Carpinito

Keyword(s):

Breast Cancer ◽

Dna Methylation ◽

Stem Cell ◽

Cell Lines ◽

Cancer Cell ◽

Breast Cancer Cell ◽

Cancer Cell Lines ◽

Breast Cancer Cell Lines ◽

Fetal Microchimerism ◽

Clinical Breast

11109 Background: Gene silencing is universally observed in cancer and involves promoter DNA methylation. We found that a cohesin-related stem cell regulator, APRIN (Pds5B) was silenced in breast cancer clinical samples. Surprisingly, in 40% of these samples DNA methylation was not involved. Furthermore, in some breast cancer cell lines the APRIN protein was silenced without transcript downregulation or promoter methylation. This “translational disequilibrium” has been frequently reported with other proteins, but without mechanistic explanations. Recent results with RNA interference indicate that gene repression through microRNAs (typically mismatched) is mostly translational without transcript degradation. We propose, therefore, that the puzzling translational disequilibrium phenomenon is a new form of epigenetic silencing by miRNA mechanisms. We aim (i) to verify miRNA epigenetics of APRIN silencing in breast cancer cell lines; (ii) to study clinical breast cancer samples for methylation vs. miRNAs mechanisms in APRIN translational disequilibrium; and (iii) to investigate if miRNA silencing of APRIN affects a fetal embryonic stem cell pool in breast cancer (microchimerism). Methods: (i) We used miRNA mimics and miRNA inhibitors in breast cancer cell lines to verify specific miRNA involvement in APRIN silencing. (ii) We used immunohistochemistry with bisulfite converted DNA for methylation and microdissected RNA for microRNA interference studies from 56 clinical breast cancer samples. (iii) We used Y-chromosome markers on microdissected DNA for fetal microchimerism studies. Results: (i) We found that in breast cancer cell lines with APRIN translational disequilibrium a set of microRNAs correlate with APRIN silencing. (ii) We found miRNA related mechanisms in about 35 percent of breast cancer samples where APRIN was silenced and (iii) APRIN may specifically affect stem cells of fetal origin in the mother's mammary gland and contribute to cancer. Conclusions: The novel miRNA-based mechanism maybe a new epigenetic factor of gene silencing in cancer. We experimentally confirmed a set of APRIN specific miRNAs and established preliminary correlations with fetal microchimerism in breast cancer. No significant financial relationships to disclose.

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