Suppressive role exerted by microRNA-29b-1-5p in triple negative breast cancer through SPIN1 regulation.

Rosa Drago-Ferrante,Christian Scerri,Riccardo Di Fiore,Christian Saliba,Giovanni Tesoriere,Renza Vento,James Degaetano,Antonio Giordano,Godfrey Grech,Daniela Carlisi,Gordon Caruana-Dingli,Joseph Debono,Anna De Blasio,Shawn Baldacchino,Francesca Pentimalli

doi:10.18632/oncotarget.15960

Abstract

MiR-29 family dysregulation occurs in various cancers including breast cancers. We investigated miR-29b-1 functional role in human triple negative breast cancer (TNBC) the most aggressive breast cancer subtype. We found that miR-29b-1-5p was downregulated in human TNBC tissues and cell lines. To assess whether miR-29b-1-5p correlated with TNBC regenerative potential, we evaluated cancer stem cell enrichment in our TNBC cell lines, and found that only MDA-MB-231 and BT-20 produced primary, secondary and tertiary mammospheres, which were progressively enriched in OCT4, NANOG and SOX2 stemness genes. MiR-29b-1-5p expression inversely correlated with mammosphere stemness potential, and miR-29b-1 ectopic overexpression decreased TNBC cell growth, self-renewal, migration, invasiveness and paclitaxel resistance repressing WNT/βcatenin and AKT signaling pathways and stemness regulators. We identified SPINDLIN1 (SPIN1) among predicted miR-29b-1-5p targets. Consistently, SPIN1 was overexpressed in most TNBC tissues and cell lines and negatively correlated with miR-29b-1-5p. Target site inhibition showed that SPIN1 seems to be directly controlled by miR-29b-1-5p. Silencing SPIN1 mirrored the effects triggered by miR-29b-1 overexpression, whereas SPIN1 rescue by SPIN1miScript protector, determined the reversal of the molecular effects produced by the mimic-miR-29b-1-5p. Overall, we show that miR-29b-1 deregulation impacts on multiple oncogenic features of TNBC cells and their renewal potential, acting, at least partly, through SPIN1, and suggest that both these factors should be evaluated as new possible therapeutic targets against TNBC.

Highlights

Despite improved diagnostic skills and breakthroughs in effective treatment, breast cancer continues to be the leading cause of cancer deaths among women worldwide, with breast cancer incidence and death rates generally increasing with age [1]
To assess whether miR-29b-1-5p correlated with triple negative breast cancer (TNBC) regenerative potential, we evaluated cancer stem cell enrichment in our TNBC cell lines, and found that only MDA-MB-231 and BT-20 produced primary, secondary and tertiary mammospheres, which were progressively enriched in OCT4, NANOG and SOX2 stemness genes
In TNBC tissues the analysis was carried out in 21 formalin-fixed, paraffin-embedded (FFPE) cancerous tissues, compared to 6 normal human mammary tissues; in TNBC cell lines the analysis was performed in MDA-MB-231, BT-20, HCC1395 and MDA-MB-468 cells compared to Human Mammary Epithelial Cells (HMECs), www.impactjournals.com/oncotarget a normal human mammary epithelial cell line

Summary

Introduction

Despite improved diagnostic skills and breakthroughs in effective treatment, breast cancer continues to be the leading cause of cancer deaths among women worldwide, with breast cancer incidence and death rates generally increasing with age [1]. Human triple-negative breast cancer (TNBC), which accounts for approximately 10–20% of all breast tumors, refers to forms that do not express estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) [2]. These forms present a very difficult therapeutic challenge as are characterized by high heterogeneity, a aggressive nature and by the lack of targeted therapies [3]. CSCs seem to be the cause of cancer initiation, growth and development, the source for tissue renewal and malignant potential, the crucial component leading to tumor recurrence, therapy resistance, and metastasis [6]

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