BackgroundHead and Neck Squamous Cell Carcinoma (HNSCC) tumors are often resistant to therapies. Therefore searching for predictive markers and new targets for treatment in clinically relevant in vitro tumor models is essential. Five HNSCC-derived cell lines were used to assess the effect of 3D culturing compared to 2D monolayers in terms of cell proliferation, response to anti-cancer therapy as well as expression of EMT and CSC genes.MethodsThe viability and proliferation capacity of HNSCC cells as well as induction of apoptosis in tumor spheroids cells after treatment was assessed by MTT assay, crystal violet- and TUNEL assay respectively. Expression of EMT and CSC markers was analyzed on mRNA (RT-qPCR) and protein (Western blot) level.ResultsWe showed that HNSCC cells from different tumors formed spheroids that differed in size and density in regard to EMT-associated protein expression and culturing time. In all spheroids, an up regulation of CDH1, NANOG and SOX2 was observed in comparison to 2D but changes in the expression of EGFR and EMT markers varied among the cell lines. Moreover, most HNSCC cells grown in 3D showed decreased sensitivity to cisplatin and cetuximab (anti-EGFR) treatment.ConclusionsTaken together, our study points at notable differences between these two cellular systems in terms of EMT-associated gene expression profile and drug response. As the 3D cell cultures imitate the in vivo behaviour of neoplastic cells within the tumor, our study suggest that 3D culture model is superior to 2D monolayers in the search for new therapeutic targets.Electronic supplementary materialThe online version of this article (10.1186/s12935-019-0733-1) contains supplementary material, which is available to authorized users.

The rapid accumulation of knowledge on apoptosis regulation in the 1990s was followed by the development of several experimental anticancer- and anti-ischaemia (stroke or myocardial infarction) drugs. Activation of apoptotic pathways or the removal of cellular apoptotic inhibitors has been suggested to aid cancer therapy and the inhibition of apoptosis was thought to limit ischaemia-induced damage. However, initial clinical studies on apoptosis-modulating drugs led to unexpected results in different clinical conditions and this may have been due to co-effects on non-apoptotic interconnected cell death mechanisms and the ‘yin-yang’ role of autophagy in survival versus cell death. In this review, we extend the analysis of cell death beyond apoptosis. Upon introduction of molecular pathways governing autophagy and necrosis (also called necroptosis or programmed necrosis), we focus on the interconnected character of cell death signals and on the shared cell death processes involving mitochondria (e.g. mitophagy and mitoptosis) and molecular signals playing prominent roles in multiple pathways (e.g. Bcl2-family members and p53). We also briefly highlight stress-induced cell senescence that plays a role not only in organismal ageing but also offers the development of novel anticancer strategies. Finally, we briefly illustrate the interconnected character of cell death forms in clinical settings while discussing irradiation-induced mitotic catastrophe. The signalling pathways are discussed in their relation to cancer biology and treatment approaches.

Colony forming or clonogenic assay is an in vitro quantitative technique to examine the capability of a single cell to grow into a large colony through clonal expansion. Clonogenic activity is a sensitive indicator of undifferentiated cancer stem cells. Here, we described the colony forming ability of the isolated breast cancer stem cells from the total population of cancer cells using double-layered, soft agarose-based assay. This method demonstrates that cancer stem cells can survive and generate colony growth in an anchorage-independent culture model. The 0.005% crystal violet solution is used in this assay to visualize the generated colonies.