Hypoxia-Induced MALAT1 Promotes the Proliferation and Migration of Breast Cancer Cells by Sponging MiR-3064-5p

Chung-Hsien Shih; Li-Ling Chuang; Mong-Hsun Tsai; Li-Han Chen; Eric Y Chuang; Tzu-Pin Lu; Liang-Chuan Lai

doi:10.3389/fonc.2021.658151

Hypoxia-Induced MALAT1 Promotes the Proliferation and Migration of Breast Cancer Cells by Sponging MiR-3064-5p

Front Oncol. 2021 May 3:11:658151. doi: 10.3389/fonc.2021.658151. eCollection 2021.

Authors

Chung-Hsien Shih¹, Li-Ling Chuang^{2

3}, Mong-Hsun Tsai^{4

5}, Li-Han Chen⁶, Eric Y Chuang^{5

7

8}, Tzu-Pin Lu^{5

9}, Liang-Chuan Lai^{1

5}

Affiliations

¹ Graduate Institute of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
² School of Physical Therapy and Graduate Institute of Rehabilitation Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
³ Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, Taoyuan, Taiwan.
⁴ Institute of Biotechnology, National Taiwan University, Taipei, Taiwan.
⁵ Bioinformatics and Biostatistics Core, Center of Genomic and Precision Medicine, National Taiwan University, Taipei, Taiwan.
⁶ Institute of Fisheries Science, College of Life Science, National Taiwan University, Taipei, Taiwan.
⁷ Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan.
⁸ Collage of Biomedical Engineering, China Medical University, Taichung, Taiwan.
⁹ Institute of Epidemiology and Preventive Medicine, National Taiwan University, Taipei, Taiwan.

Abstract

Hypoxia, a common process during tumor growth, can lead to tumor aggressiveness and is tightly associated with poor prognosis. Long noncoding RNAs (lncRNAs) are long ribonucleotides (>200 bases) with limited ability to translate proteins, and are known to affect many aspects of cellular function. One of their regulatory mechanisms is to function as a sponge for microRNA (miRNA) to modulate its biological functions. Previously, MALAT1 was identified as a hypoxia-induced lncRNA. However, the regulatory mechanism and functions of MALAT1 in breast cancer are still unclear. Therefore, we explored whether MALAT1 can regulate the functions of breast cancer cells through miRNAs. Our results showed the expression levels of MALAT1 were significantly up-regulated under hypoxia and regulated by HIF-1α and HIF-2α. Next, in contrast to previous reports, nuclear and cytoplasmic fractionation assays and fluorescence in situ hybridization indicated that MALAT1 was mainly located in the cytoplasm. Therefore, the labeling of MALAT1 as a nuclear marker should be done with the caveat. Furthermore, expression levels of miRNAs and RNA immunoprecipitation using antibody against AGO2 showed that MALAT1 functioned as a sponge of miRNA miR-3064-5p. Lastly, functional assays revealed that MALAT1 could promote cellular migration and proliferation of breast cancer cells. Our findings provide evidence that hypoxia-responsive long non-coding MALAT1 could be transcriptionally activated by HIF-1α and HIF-2α, act as a miRNA sponge of miR-3064-5p, and promote tumor growth and migration in breast cancer cells. These data suggest that MALAT1 may be a candidate for therapeutic targeting of breast cancer progression.

Keywords: MALAT1; breast cancer; hypoxia; hypoxia inducible factor-1α; long non-coding RNA; miR-3064-5p; microRNA.