Role of radio-induced cell plasticity in the radioresistance of breast cancers

Par sa complexité cellulaire et moléculaire, le cancer est un véritable défi médical et scientifique. Au sein de l'hétérogénéité cellulaire intra-tumorale qui le compose, les cellules souches cancéreuses (CSC) ont des propriétés fonctionnelles, tumorigénique, d'auto-renouvèlement et de différenciation. Elles s’opposent aux non-CSC et ont un rôle certain dans la résistance thérapeutique. La mise en évidence récente d'un potentiel de plasticité cellulaire des non-CSC en CSC modifie le paradigme. Elle soutient que les états de CSC ou de non-CSC pourraient être transitoires et réversibles, influencé par du « stress » tel que les traitements anti-cancéreux. Ainsi, pour comprendre si les récidives locorégionales post-radiothérapie des cancers du sein (CS) sont dues à une résistance innée ou acquise d'un état de CSC mammaires (bCSC), nous avons tracé le devenir cellulaire des différentes populations après RT par une technique de "lineage tracing". Nous avons objectivé que l'enrichissement en bCSC après RT provient du contingent de non-CSC, qui se reprogramme en ibCSC, avec un pic à 5 jours. Les propriétés fonctionnelles des ibCSC ont été validées in vitro puis in vivo. L'analyse transcriptomique par RNAseq de chacun des états, puis à l'échelle de la cellule unique par scRNAseq couplé à une technique de CITE-seq, ont permis de révéler les modifications d'expressions géniques traduisant cette plasticité radio-induite. Utilisant des algorithmes bio-informatiques d’analyse du pseudo-temps, nous avons observés que les ibCSC retournent à un état comparable à l'état de CSC d’origine. Nos résultats montrent le rôle majeur de la plasticité cellulaire dans l'échappement à la RT des CS.Due to its complexity, cancer is a real medical and scientific challenge. Within the intra-tumoral cellular heterogeneity that composes it, cancer stem cells (CSC) have functional, tumorigenic, self-renewal and differentiation properties. They oppose non-CSCs and have a definite role in innate therapeutic resistance. The recent demonstration of the cellular plasticity potential of non-CSCs destabilizes the concept of CSC. It argues that the CSC or non-CSC could be a transient and reversible state, influenced by "stresses" such as cancer treatments. Thus, to understand whether locoregional recurrences after breast cancer (BC) radiation therapy are due to innate or acquired resistance of a mammary CSC state (bCSC), we have traced the cellular fate of different cell populations after RT using a "lineage tracing" technique. We objectified that the enrichment in bCSC after RT comes from the non-CSC contingent, which reprograms into ibCSC, with a peak at 5 days. The functional properties of ibCSCs were validated in vitro and then in vivo. Transcriptomic analysis by RNAseq of each of the states, then at the single cell level by scRNAseq coupled with a CITE-seq technique, revealed the changes in gene expression reflecting this radio-induced plasticity. Supported by bioinformatics algorithms for pseudo-time analysis, we observed that ibCSC went back to the native CSC state. Our results show the major role of cellular plasticity in the RT escape of BC

Is post mastectomy radiotherapy contributive in pN0-1mi breast cancers patients? Results of a French multi-centric cohort

San Antonio Breast Cancer Symposium, San Antonio, TX, DEC 05-09, 201

Is post mastectomy radiotherapy contributive in pN0-1mi breast cancers patients? Results of a French multi-centric cohort

San Antonio Breast Cancer Symposium, San Antonio, TX, DEC 05-09, 201

Transcriptomic Analysis of Breast Cancer Stem Cells and Development of a pALDH1A1:mNeptune Reporter System for Live Tracking

International audienceMany solid cancers are hierarchically organized with a small number of cancer stem cells (CSCs) able to regrow a tumor, while their progeny lacks this feature. Breast CSC is known to contribute to therapy resistance. The study of those cells is usually based on their cell-surface markers like CD44high /CD24low/neg or their aldehyde dehydrogenase (ALDH) activity. However, these markers cannot be used to track the dynamics of CSC. Here, a transcriptomic analysis is performed to identify segregating gene expression in CSCs and non-CSCs, sorted by Aldefluor assay. It is observed that among ALDH-associated genes, only ALDH1A1 isoform is increased in CSCs. A CSC reporter system is then developed by using a far red-fluorescent protein (mNeptune) under the control of ALDH1A1 promoter. mNeptune-positive cells exhibit higher sphere-forming capacity, tumor formation, and increased resistance to anticancer therapies. These results indicate that the reporter identifies cells with stemness characteristics. Moreover, live tracking of cells in a microfluidic system reveals a higher extravasation potential of CSCs. Live tracking of non-CSCs under irradiation treatment show, for the first time, live reprogramming of non-CSCs into CSCs. Therefore, the reporter will allow for cell tracking to better understand the implication of CSCs in breast cancer development and recurrence