Phenotypic and microRNA transcriptomic profiling of the MDA-MB-231 spheroid-enriched CSCs with comparison of MCF-7 microRNA profiling dataset.

Lily Boo,Huynh Ky,Soon Keng Cheong,Han Kiat Ong,Sheau Wei Tan,Kok Gan Chan,Woan Charn Liew,Wan Yong Ho,Wai Fong Yin,Dilan Amila Satharasinghe,Swee Keong Yeap,Norlaily Mohd Ali

doi:10.7717/peerj.3551

Abstract

Breast cancer spheroids have been widely used as in vitro models of cancer stem cells (CSCs), yet little is known about their phenotypic characteristics and microRNAs (miRNAs) expression profiles. The objectives of this research were to evaluate the phenotypic characteristics of MDA-MB-231 spheroid-enriched cells for their CSCs properties and also to determine their miRNAs expression profile. Similar to our previously published MCF-7 spheroid, MDA-MB-231 spheroid also showed typical CSCs characteristics namely self-renewability, expression of putative CSCs-related surface markers and enhancement of drug resistance. From the miRNA profile, miR-15b, miR-34a, miR-148a, miR-628 and miR-196b were shown to be involved in CSCs-associated signalling pathways in both models of spheroids, which highlights the involvement of these miRNAs in maintaining the CSCs features. In addition, unique clusters of miRNAs namely miR-205, miR-181a and miR-204 were found in basal-like spheroid whereas miR-125, miR-760, miR-30c and miR-136 were identified in luminal-like spheroid. Our results highlight the roles of miRNAs as well as novel perspectives of the relevant pathways underlying spheroid-enriched CSCs in breast cancer.

Highlights

There has been a substantial amount of evidence indicating that tumours contain a group of self-renewing cancer cells known as cancer stem cells (CSCs) which are responsible for tumour initiation, progression, and metastasis (Chen, Huang & Chen, 2013)
The capacity of the MDA-MB-231 spheroid cells to be serially passaged demonstrated the self-renewing ability of the cells which is a common property of cells enriched with CSCs properties
When the CD44+/CD24− and ALDH+ expression were compared between the two spheroids, MDA-MB-231 spheroids displayed a higher fraction of cells displaying those markers

Summary

Introduction

There has been a substantial amount of evidence indicating that tumours contain a group of self-renewing cancer cells known as cancer stem cells (CSCs) which are responsible for tumour initiation, progression, and metastasis (Chen, Huang & Chen, 2013). Numerous methods have been proposed in order to isolate and expand the cells to the sufficient amount feasible for research use, these methods comes with their own challenges. The use of ALDEFLOUR assay, a stem cell marker based on enzymatic activity of ALDH1 was proposed to be the reliable tool to isolate CSCs from tumour(Croker et al, 2009). This approach is not recommended as a standalone assay as it requires other marker combinations to further separate the CSCs populations from the tumour. More useful and effective assays are needed to culture CSCs population subtypes

Objectives

Methods

Results

Discussion

Conclusion