Differentiation of mammary tumors and reduction in metastasis upon Malat1 LncRNA loss

Arun, G., Diermeier, S., Akerman, M., Chang, K. C., Wilkinson, J. E., Hearn, S., Kim, Y., MacLeod, A. R., Krainer, A. R., Norton, L., Brogi, E., Egeblad, M., Spector, D. L. (2016) Differentiation of mammary tumors and reduction in metastasis upon Malat1 LncRNA loss. Cancer Research, 76 (Supple). ISSN 0008-5472

URL: http://cancerres.aacrjournals.org/content/76/6_Sup...
DOI: 10.1158/1538-7445.nonrna15-pr11

Abstract

Genome-wide studies have identified thousands of long non-coding RNAs (lncRNAs) lacking protein-coding capacity. MALAT1 (Metastasis Associated Lung Adenocarcinoma Transcript 1) is among the most abundant and highly conserved nuclear restricted lncRNAs whose expression is mis-regulated in many cancers including breast cancer. RNA-FISH experiments on primary tumor and metastatic nodules from patients with luminal type breast cancer revealed that MALAT1 lncRNA is 4-5 times up regulated in metastatic nodules compared to primary tumors. This strongly suggests that MALAT1 plays an important role in the metastatic progression of luminal breast cancers. We have used the MMTV-PyMT mouse model of luminal B breast cancer to characterize the role of Malat1 in primary breast cancer and its subsequent metastasis. Malat1 lncRNA was knocked down via subcutaneous administration of antisense oligonucleotides (ASOs) at a dose of 125mg/kg/week over a period of 7 weeks after which animals were sacrificed and primary tumors and lungs were removed for molecular and histological analyses. Malat1 ASO treatment resulted in ~60% knockdown in the primary tumor concomitant with a significant reduction in tumor progression rate as well as a change in the differentiation status. Detailed histo-pathological analysis of ASO treated tumors showed an increase in well-differentiated ductular tumors, whereas scrambled ASO treated tumors progressed to solid carcinomas. Most interestingly, a marked decrease was observed in the incidence of lung metastases; ~70% fewer metastatic nodules in Malat1 ASO treated animals than scrambled ASO treated animals. Further, Malat1 ASO treated ex-vivo generated mammary gland organoids from MMTV-PyMT mice, resulted in an inhibition of branching morphogenesis, which recapitulates the invasive process that initiate metastases in vivo. RNA-seq analysis of the primary tumors and tumor derived organoids treated with Malat1 ASO showed up-regulation of genes involved in differentiation and down regulation of genes involved in migration and proliferation. Further, Malat1 knock-down also resulted in aberrant splicing of many genes including critical transcription factors. Together, our data indicates that Malat1 lncRNA regulates critical processes in breast cancer pathogenesis and represents a promising therapeutic target for treatment.

Item Type: Paper
Additional Information: Meeting Abstract
Subjects: diseases & disorders > cancer > cancer types > breast cancer
organs, tissues, organelles, cell types and functions > cell types and functions > cell functions > cell differentiation
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > long non-coding RNA
diseases & disorders > cancer > metastasis
CSHL Authors:
Communities: CSHL labs > Egeblad lab
CSHL labs > Krainer lab
CSHL labs > Spector lab
Depositing User: Matt Covey
Date Deposited: 10 Jun 2016 19:44
Last Modified: 05 Dec 2016 16:56
URI: http://repository.cshl.edu/id/eprint/32832

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