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Role of Ubc13 in Breast Cancer Metastasis

ABSTRACT: We recently found that Ubc13 controls breast cancer metastasis. However, the underlying molecular mechanisms remain elusive. In order to gain a better understanding of the signaling pathways controlled by Ubc13 in metastasis, we performed a gene array analysis on xenografts derived from orthotopically implanted MDA-MB-231 LM2 cells, which preferentially metastazize to lung in NOD/SCID mice. MDA-MB-231 LM2 cells were infected with lentivial shRNA constructs targeting either GFP (Control) or Ubc13 (ubc13). The resulting Control or Ubc13-silenced cells were implanted into fat pads of six weeks old female virgin NOD/SCID mice. After eight weeks, tumors were excised, followed by collagenase/hyaluronidase digestion to establish single cell suspension, from which epithelial cells were enriched by depleting mouse cells of hematopoietic, endothelial, and fibroblast origin (CD45, TER119, CD31 and BP-1). The enrihced epithelial cells (three Control and three Ubc13-KD cells) were lysed in TRIZOL to extract RNA, which were then used to run microarray.

ORGANISM(S): Homo sapiens

SUBMITTER: Poidinger Michael

PROVIDER: S-ECPF-GEOD-55649 | biostudies-other |

REPOSITORIES: biostudies-other

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Project description:BackgroundThe prognosis for patients with breast tumor metastases to brain is extremely poor. Identification of prognostic molecular markers of the metastatic process is critical for designing therapeutic modalities for reducing the occurrence of metastasis. Although ubiquitously present in most human organs, large-conductance calcium- and voltage-activated potassium channel (BKCa) channels are significantly upregulated in breast cancer cells. In this study we investigated the role of KCNMA1 gene that encodes for the pore-forming alpha-subunit of BKCa channels in breast cancer metastasis and invasion.MethodsWe performed Global exon array to study the expression of KCNMA1 in metastatic breast cancer to brain, compared its expression in primary breast cancer and breast cancers metastatic to other organs, and validated the findings by RT-PCR. Immunohistochemistry was performed to study the expression and localization of BKCa channel protein in primary and metastatic breast cancer tissues and breast cancer cell lines. We performed matrigel invasion, transendothelial migration and membrane potential assays in established lines of normal breast cells (MCF-10A), non-metastatic breast cancer (MCF-7), non-brain metastatic breast cancer cells (MDA-MB-231), and brain-specific metastatic breast cancer cells (MDA-MB-361) to study whether BKCa channel inhibition attenuates breast tumor invasion and metastasis using KCNMA1 knockdown with siRNA and biochemical inhibition with Iberiotoxin (IBTX).ResultsThe Global exon array and RT-PCR showed higher KCNMA1 expression in metastatic breast cancer in brain compared to metastatic breast cancers in other organs. Our results clearly show that metastatic breast cancer cells exhibit increased BKCa channel activity, leading to greater invasiveness and transendothelial migration, both of which could be attenuated by blocking KCNMA1.ConclusionDetermining the relative abundance of BKCa channel expression in breast cancer metastatic to brain and the mechanism of its action in brain metastasis will provide a unique opportunity to identify and differentiate between low grade breast tumors that are at high risk for metastasis from those at low risk for metastasis. This distinction would in turn allow for the appropriate and efficient application of effective treatments while sparing patients with low risk for metastasis from the toxic side effects of chemotherapy.

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Role of Ubc13 in Breast Cancer Metastasis

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