PHD PROJECT
Study of breast cancer cell plasticity : Identification of the factors involved
in reprogramming of non-tumorigenic cells into cancer stem cells.
The goal of this project is to identify the mechanisms driven radiatio-induced cell
reprogramming of non-tumorigenic cells into cells with cancer stem cell phenotype.
Thi projet will follow 2 axes: (i) a study of the soluble factors (growth
factors/Cytokines/chemokynes and microvessicles) involved in the reprogramming
process and (ii) a study of intracellular cell signaling and epigenetic modifications
driven the reexpression of factors involved in cancer stem cell phenotype.
Study of breast cancer cell plasticity.
While cancer cell population has been though to be clonal, there is increasing
evidence for the "cancer stem cell (CSC) hypothesis", which holds that cancers are
driven by a cellular component that has stem cell properties, including self-renewal,
tumorigenicity and multi-lineage differentiation capacity. Researchers and oncologists
see in this model an explanation as to why cancer may be so difficult to cure, as well
as a promising ground for novel therapeutic strategies.
Breast cancer stem cells have been for the first time prospectively identified by Al-
Hajj in 2003 (Al-Hajj, PNAS 2003). Since then, research effort has been focused on
the identification of cancer stem cells by different molecular markers and the
phenotypic characterization of these cells. Several markers have been proposed to
identify a “purer” population of Breast CSCs, CD44high/CD24-/low, ALDH1+, low
proteasome activity. Increasing pre-clinical and translational evidence suggests that
CSCs can mediate tumor metastasis (Guler et al Mod Pathol 2013; Leth-Larsen et al
Mol Med 2013; Wei et al Trans Med 2012) and are resistant to conventional anti-
cancer therapeutics that contributes to recurrence. These findings have led to the
proposal that targeting CSCs in combination with conventional or other targeted
therapies may be required to eradicate cancer and efforts are underway to identify
compounds that target this subpopulation (Cufi et al Oncotarget 2012;
Gangopadhyay et al Clin Breast Cancer 2012; Prud’homme Curr Pharm Des 2012).
However, we and others have recently challenged this assumption by demonstrating
that CSCs could rise from a non-CSCs tumoral population after exposition to radiation
therapy, chemotherapies or histone deacetylase inhibitors (Lagadec et al., Stem cells
2012 ; Debeb BG et al., Stem Cells 2012). These findings represent a divergence
from the unidirectional hierarchical model of CSCs and raise the possibility that
approaches to solely target CSCs will not be sufficient as therapeutic elimination of
CSCs may be followed by their regeneration from residual non-CSCs allowing tumor
regrowth and clinical relapse. These observations may indeed hold great promise
with regard to improving cancer treatment in general; if the net outcome of
established anticancer therapies is always a fine balance between CSC killing and
CSC generation, then preventing the latter process using targeted therapies could
dramatically shift this balance to cell killing, even at much lower total radiation
doses.