Investigating the in vitro steatotic mixture effects of similarly and dissimilarly acting test compounds using an adverse outcome pathway-based approach.

Within the EuroMix project, we have previously developed an adverse outcome pathway (AOP)-based in vitro assay toolbox to investigate the combined effects of liver steatosis-inducing compounds in human HepaRG hepatocarcinoma cells. In this study, we applied the toolbox to further investigate mixture effects of combinations, featuring either similarly acting or dissimilarly acting substances. The valproic acid structural analogs 2-propylheptanoic acid (PHP) and 2-propylhexanoic acid (PHX) were chosen for establishing mixtures of similarly acting substances, while a combination with the pesticidal active substance clothianidin (CTD) was chosen for establishing mixtures of dissimilarly acting compounds. We first determined relative potency factors (RPFs) for each compound based on triglyceride accumulation results. Thereafter, equipotent mixtures were tested for nuclear receptor activation in transfected HepG2 cells, while gene expression and triglyceride accumulation were investigated in HepaRG cells, following the proposed AOP for liver steatosis. Dose addition was observed for all combinations and endpoints tested, indicating the validity of the additivity assumption also in the case of the tested mixtures of dissimilarly acting substances. Gene expression results indicate that the existing steatosis AOP can still be refined with respect to the early key event (KE) of gene expression, in order to reflect the diversity of molecular mechanisms underlying the adverse outcome.

Cell adhesion molecules and their relation to (cancer) cell stemness.

Despite decades of search for anticancer drugs targeting solid tumors, this group of diseases remains largely incurable, especially if in advanced, metastatic stage. In this review, we draw comparison between reprogramming and carcinogenesis, as well as between stem cells (SCs) and cancer stem cells (CSCs), focusing on changing garniture of adhesion molecules. Furthermore, we elaborate on the role of adhesion molecules in the regulation of (cancer) SCs division (symmetric or asymmetric), and in evolving interactions between CSCs and extracellular matrix. Among other aspects, we analyze the role and changes of expression of key adhesion molecules as cancer progresses and metastases develop. Here, the role of cadherins, integrins, as well as selected transcription factors like Twist and Snail is highlighted, not only in the regulation of epithelial-to-mesenchymal transition but also in the avoidance of anoikis. Finally, we briefly discuss recent developments and new strategies targeting CSCs, which focus on adhesion molecules or targeting tumor vasculature.