Search

International audience; The impact of cancer on lifespan is significantly increasing worldwide. Enhanced activity of drug efflux pumps and the incidences of the tumor microenvironment such as the apparition of a hypoxic gradient inside of the bulk tumor, are the major causes of chemotherapy failure. For instance, expression of Hypoxia-inducible factor (HIF-1α) has been associated with metastasis, resistance to chemotherapy and reduced survival rate. One of the current challenges to fight against cancer is therefore to find new molecules with therapeutic potential that could overcome this chemoresistance. In the present study, we focused on the bioactive plant flavonoid quercetin, which has strong antioxidant and anti-proliferative properties. We examined the efficacy of combined treatments of quercetin and the anti-cancer drugs gemcitabine and doxorubicin, known to specifically act on human pancreatic and hepatic cancer cells, respectively. Moreover, our study aimed to investigate more in-depth the implication of the multidrug transporter MDR1 and HIF-1α n chemoresistance and if quercetin could act on the activity of the drug efflux pumps and the hypoxia-associated effects. We observed that the anti-cancer drugs, were more effective when administered in combination with quercetin, as shown by an increased percentage of dead cells up to 60% in both 2D and 3D cultures. In addition, our results indicated that the combination of anti-cancer drugs and quercetin down-regulated the expression of HIF-1α and increased the expression levels of the regulator of apoptosis p53. Moreover, we observed that quercetin could inhibit the efflux activity of MDR1. Finally, our in vitro study suggests that the efficiency of the chemotherapeutic activity of known anti-cancer drugs might be significantly increased upon combination with quercetin. This flavonoid may therefore be a promising pharmacological agent for novel combination therapy since it potentializes the cytotoxic activity of gemcitabine and doxorubicin on by targeting the chemoresistance developed by the pancreatic and liver cancer cells respectively.

Polycomb group (PcG) proteins are epigenetic regulators that reduce tumor suppressor gene expression and promote cancer cell survival. The aim of the present study was to determine whether a bilberry extract (Antho 50) inhibits the expression of PcG proteins in Jurkat cells and, if so, to determine the underlying mechanism. Apoptotic rates and the formation of reactive oxygen species (ROS) were assessed by flow cytometry, and protein expression by Western blotting. Antho 50 induced apoptosis, augmented ROS formation, increased p73, p21 and cleaved caspase-3 expression levels, and decreased those of p-Akt, survivin, PcG proteins, HDACs, DNMT1 and UHRF1. The antioxidant enzyme PEG-catalase prevented the formation of ROS and apoptosis induced by Antho 50 and also by H2O2. These findings indicate that Antho 50 promotes apoptosis in Jurkat cells, in part, by decreasing the expression levels of PcG proteins, and, hence, the subsequent PcG proteins-dependent pro-survival events via a redox-dependent mechanism.

International audience; The molecular pathways by which flavagline derivatives exert their cytotoxicity against various cancer cell types are well documented, while the mechanisms that prevent their cytotoxic effects on normal cells still have to be clarified. Here we provide the underlying molecular events by which normal skin cells remain unaffected after exposure to the synthetic flavagline FL3. Indeed, the anticancer agent fails to trigger apoptosis of healthy cells and is unable to induce the depolarization of their mitochondrial membrane and the cytosolic release of cytochrome C, in contrast to what is observed for cancer cells. Most importantly, FL3 specifically induces in normal cells, but not in malignant cells, an activation of Bad, without significant mitochondrial and cytosolic redistribution of Bax or Bcl-2. Moreover, gene knockdown of Bad sensitizes the normal fibroblastic cells to FL3 and induces a caspase-3 dependent apoptosis. Bad activation, known to promote survival and block apoptosis, explain therefore the lack of cytotoxicity of FL3 on normal skin cells. Finally, these findings provide new insights into the molecular resistance mechanisms of resistance of healthy cells against FL3 cytotoxicity and identify it as a promising anticancer drug.

The low-density lipoprotein receptor-related protein-1 (LRP-1) is a member of Low Density Lipoprotein Receptor (LDLR) family, which is ubiquitously expressed and which is described as a multifunctional endocytic receptor which mediates the clearance of various extracellular matrix molecules including serine proteinases, proteinase-inhibitor complexes, and matricellular proteins. Several studies showed that high LRP-1 expression promotes breast cancer cell invasiveness, and LRP-1 invalidation leads to cell motility abrogation in both tumor and non-tumor cells. Furthermore, our group has reported that LRP-1 silencing prevents the invasion of a follicular thyroid carcinoma despite increased pericellular proteolytic activities from MMP2 and uPA using a 2D-cell culture model. As the use of 3D culture systems is becoming more and more popular due to their promise as enhanced models of tissue physiology, the aim of the present work is to characterize for the first time how the 3D collagen type I matrix may impact the ability of LRP-1 to regulate the migratory properties of thyroid carcinoma using as a model FTC-133 cells. Our results show that inhibition of LRP-1 activity or expression leads to morphological changes affecting cell-matrix interactions, reorganizations of the actin-cytoskeleton especially by inhibiting FAK activation and increasing RhoA activity and MLC-2 phosphorylation, thus preventing cell migration. Taken together, our results suggest that LRP-1 silencing leads to a decrease of cell migratory capacity in a 3D configuration.

Angiogenesis is now well known for being involved in tumor progression, aggressiveness, emergence of metastases, and also resistance to cancer therapies. In this study, to better mimic tumor angiogenesis encountered in vivo, we used 3D culture of osteosarcoma cells (MG-63) that we deposited on 2D endothelial cells (HUVEC) grown in monolayer. We report that endothelial cells combined with tumor cells were able to form a well-organized network, and that tubule-like structures corresponding to new vessels infiltrate tumor spheroids. These vessels presented a lumen and expressed specific markers as CD31 and collagen IV. The combination of 2D endothelial cells and 3D microtissues of tumor cells also increased expression of angiogenic factors as VEGF, CXCR4 and ICAM1. The cell environment is the key point to develop tumor vascularization in vitro and to be closer to tumor encountered in vivo.

As initiators of the carcinogenic process, cancer stem cells (CSCs) are considered as new targets for anti-cancer therapies. However, these cells are hidden in the cancer bulk and remain relatively insensitive to chemotherapy, which targets their proliferative capacities. Alternatively, growing evidences have pointed out that a differentiation therapy could adversely affect these cells, which consequently should lose their self-renewal properties and become less aggressive. In order to evaluate the differentiation potential of an emerging class of anti-cancer drugs, we used the poorly differentiated teratocarcinomal cell as a model of Oct4-expressing CSC and determined the molecular mechanisms induced by the highly active flavagline FL3. The drug, administrated at sublethal concentration and for long period, was able to downregulate the expression levels of the stemness factors Oct4 and Nanog at both transcriptional and translational levels, concomitantly with a decrease of clonogenicity. The appearance of specific neural markers further demonstrated the differentiation properties of FL3. Interestingly, an expression of active caspase-3 and an upregulation of the expression of the germ cell nuclear factor were observed in treated cells; this suggests that the suppression of Oct4 expression required for the induction of differentiation involves overlapping mechanisms of protein degradation and gene repression. Finally, this study shows that FL3, like all-trans retinoic acid (ATRA), acts as a differentiation inducer of teratocarcinomal cells. Thus, FL3 offers an alternative possibility for cancer treatment since it could target the carcinogenic process by inducing the differentiation of ATRA-resistant and Oct4-expressing CSCs, without toxic side effects on normal cells.