Oxidative stress and inflammation gene expression profiles in mammosphere formation. Response to cisplatin

Abstract

[eng] The key to improve the outcome for breast cancer patients may lie in a better understanding of cancer stem cells (CSCs) biology, a small sub-population of poorly-differentiated, self-renewable and chemoresistant cells within the tumor. In vitro, these CSCs can form floating three-dimensional (3D) spheroids (mammospheres) in a serum-free defined medium and ultra-low attachment plates. Mammospheres can be used not only for drug testing but also for studying CSCs role in breast cancer tumorigenesis. It is known that CSCs utilize redox and inflammation regulatory mechanisms to promote cancer initiation and development. In this regard, our aim was to study the stemness-related, oxidative stress and inflammation gene expression in adherent MCF-7 cultures and mammospheres. Additionally, the effect of the anticancer drug cisplatin (CDDP) on mammosphere forming efficiency and its size was analysed. Following this objective, breast cancer MCF-7 cells were cultured in adherent plates with standard and mammospheres growth medium (DMEM and 3DTM, respectively) and in ultra-low attachment plates with 3DTM to obtain primary mammospheres (MS1). RNA isolation, reverse transcription and real-time quantitative PCR were performed to analyse mRNA expression. In addition, mammosphere assay was carried out with increasing concentrations of CDDP. An increase in oxidative stress and inflammatory related genes were observed in 3DTM adherent culture and mostly notably in MS1, while the relative expression of stemness markers was increased in 3DTM and remained at similar levels in MS1 formation. Moreover, CDDP treatment resulted in a higher formation efficiency of MS1 but with a decrease in mammospheres size. Our resultsindicatesthat mammosphere culture involves the upregulation of CSC specific markers associated with malignant and metastatic phenotype of cancer cells. Moreover, the increase of oxidative stress and inflammation related genes in mammospheres could play an important role in cancer progression and chemoresistance