Effects of the combination of ionizing radiation and radio-enhancing molecules in breast cancer models
The proposed program aims to evaluate the efficacy of molecules enhancing the effects of radiotherapy, in in vitro and in vivo models of breast cancer. Two types of molecules, namely an inhibitor of mitochondrial genome maintenance and an inhibitor of the Base Excision Repair pathway, will be tested for radiopotentiation efficacy in the models.
The proposed inhibitors, whether targeting mitochondrial genome maintenance or the BER pathway, are already being investigated in vitro, both in the laboratory and by collaborators. We have shown that inhibition of the mechanisms targeted leads to an impairment in DNA damage repair following genotoxic stress. During this project, we will evaluate the effects of inhibitors on DNA damage repair induced by irradiation of different types (conventional, ultra-high dose rate, even extreme dose rate) and the associated mechanisms.
Variability in response to therapeutic combinations is frequently observed when moving from in vitro to in vivo models. We will therefore evaluate the inhibitors on cell line models well characterized in the laboratory, and corresponding to different breast cancer subtypes. On the other hand, the studies will be completed by a validation of the effects observed in vitro on a murine model of breast cancer. This xenograft model, developed in immunocompetent animals, will enable us to monitor the clinical, histological and immune response of the animals and their tumors, in order to confirm the interest of the molecules for therapeutic application in support of radiotherapy.
The proposed program will benefit from the laboratory's collaborations with physicists and chemists, and IRCM's experimental facilities and platforms (irradiation, animal experimentation, microscopy, cytometry, etc.).
Scaling of cytoskeletal organization in relation to cell size and function
Each cell type, defined by its function and state, is characterized by a specific size range. Indeed, cell size within a specific cell type displays a narrow distribution that can vary from as much as several orders of magnitude between smaller cells, such as red blood cells, and large muscle cells. Interestingly, this size characteristic is essentially maintained during the life cycle of an individual and highly conserved among mammals. Altogether, these features suggest that maintaining “the right size” for a given cell could play an important role in performing its function.
The actin cytoskeleton, that can form different stable while dynamic intracellular architectures, plays a major role in the structural plasticity of cells in response to changes in shape and size. Our recent work suggests that actin networks developed within a cell scale with the actual size and volume of the cell. However, how cells adapt the turnover and organization of their numerous structures assembled from a limiting pool of actin monomers remains to be understood.
In this project, we thus propose to study the organization and dynamics of actin networks in selected cell types displaying distinct sizes. In particular, our study will focus on characterizing the impact of such networks organization/dynamics on different cellular functions such as cell migration or adaptability to environmental cues. The feedback between cytoskeletal architecture dynamics, cell size and function will also be addressed by perturbing the organization and dynamics of the actin cytoskeleton in these cells.
ROLE OF UNFOLDED PROTEIN RESPONSE IN MAINTAINING THE SPERMATOGONIAL STEM CELL POOL IN THE ADULT MOUSE
Adverse conditions (oxidative stress, imbalanced lipid, glucose or calcium levels, or inflammation) induce the accumulation of abnormal proteins resulting in ER stress. The Unfolded Stress Response (UPR) is activated to restore cellular homeostasis, but severe or chronic stress results in apoptotic cell death. Uncontrolled UPR signaling promotes many human diseases (diabetes, Parkinson's, Alzheimer's, liver disease, cancer...), but nothing is known about its implication in adult male sterility. Spermatozoa production relies on Spermatogonial Stem Cells (SSC) which are maintained by self-renewal throughout life. We have shown that the clonogenic activity of SSC is drastically impaired after ER stress through differentiation entry. An HTS screen has highlighted 2 of the 3 UPR branches as being involved in the clonogenic activity of SSC in vitro. The role of these 2 UPR pathways will be further investigated in SSC cultures of mice to determine whether they are involved in the induction of cell death or in the balance between self renewal and differentiation. In treated SSC cultures, cell death, cell cycle, induction of differentiation and synergy between UPR pathways will be analyzed. As the effect of each pathway is mediated by transcriptional factors, the target genes will be characterized by RNAseq in order to identify the gene networks controlled by UPR effectors and involved in the fate of SSC. For the most relevant pathway, an in vivo study will confirm the role of the UPR effector in CSS property.