Targeted liposomal doxorubicin/ceramides combinations: The importance to assess the nature of drug interaction beyond bulk tumor cells.

One of the major assets of anticancer nanomedicine is the ability to co-deliver drug combinations, as it enables targeting of different cellular populations and/or signaling pathways implicated in tumorigenesis and thus tackling tumor heterogeneity. Moreover, drug resistance can be circumvented, for example, upon co-encapsulation and delivery of doxorubicin and sphingolipids, as ceramides. Herein, the impact of short (C6) and long (C18) alkyl chain length ceramides on the nature of drug interaction, within the scope of combination with doxorubicin, was performed in bulk triple-negative breast cancer (TNBC) cells, as well as on the density of putative cancer stem cells and phenotype, including live single-cell tracking. C6- or C18-ceramide enabled a synergistic drug interaction in all conditions and (bulk) cell lines tested. However, differentiation among these two ceramides was reflected on the migratory potential of cancer cells, particularly significant against the highly motile MDA-MB-231 cells. This effect was supported by the downregulation of the PI3K/Akt pathway enabled by C6-ceramide and in contrast with C18-ceramide. The decrease of the migratory potential enabled by the targeted liposomal combinations is of high relevance in the context of TNBC, due to the underlying metastatic potential. Surprisingly, the nature of the drug interaction assessed at the level of bulk cancer cells revealed to be insufficient to predict whether a drug combination enables a decrease in the percentage of the master regulators of tumor relapse as ALDH+/high putative TNBC cancer stem cells, suggesting, for the first time, that it should be extended further down to this level.

The cancer stem cell phenotype as a determinant factor of the heterotypic nature of breast tumors.

Gathering evidence supports the existence of a population of cells with stem-like characteristics, named cancer stem cells (CSC), which is involved not only in tumor recurrence but also in tumorigenicity, metastization and drug resistance. Several markers have been used to identify putative CSC sub-populations in different cancers. Notwithstanding, it has been acknowledged that breast CSC may originate from non-stem cancer cells (non-SCC), interconverting through an epithelial-to-mesenchymal transition-mediated process, and presenting several deregulated canonical and developmental signaling pathways. These support the heterogeneity that, directly or indirectly, influences fundamental biological features supporting breast tumor development. Accordingly, CSC have increasingly become highly relevant cellular targets. In this review, we will address the stemness concept in cancer, setting the perspective on CSC and their origin, by exploring their relation and regulation within the tumor microenvironment, in the context of emerging therapeutic targets. Within this framework, we will discuss nucleolin, a protein that has been associated with angiogenesis and, more recently, with the stemness phenotype, becoming a common denominator between CSC and non-SCC for multicellular targeting.

Targeting cancer stem cells and non-stem cancer cells: the potential of lipid-based nanoparticles.

Background Cancer stem cells (CSCs) have been described as a relevant contributor to tumorigenicity, metastasis, tumor recurrence and drug resistance, making this cell population a relevant target in solid tumors. METHODS: This has stimulated the development of different therapeutic strategies often targeting surface markers (CD44, epithelial cell adhesion molecule (EpCAM), aldehyde dehydrogenase (ALDH) and nucleolin) and/or signaling pathways that are aberrantly activated and contribute to CSCs proliferation and survival. RESULTS: There are a variety of signaling pathways often involved in physiological processes of cell function that aberrantly regulate CSCs, including Notch, Hedgehog, Wnt, PI3K/Akt, JAK/STAT and Ras/ERK signaling pathways. The inhibition of these pathways usually depletes CSC population and increases tumor sensitivity to chemotherapy. However, the recognition of the potential of cells to interconvert in response to environmental stimulus, turned both CSCs and non-stem cancer cells into two relevant therapeutic targets. Therefore, the use of drug combinations is increasingly needed. These drugs with different mechanisms of action often characterized by distinct pharmacokinetics profiles and, as such, will present distinct biodistribution patterns, following systemic administration. To synchronize pharmacokinetics, one can encapsulate synergistic drug combinations into lipid-based nanoparticles, assuring tumor delivery of the selected drug ratio. CONCLUSION: This review will focus on the multiple strategies to target CSCs, as well as on the potential of lipid-based nanoparticles to target both CSCs and non-stem cancer cells.