RAS-driven oncogenesis is supported by downstream antioxidant programs
MOLECULAR & CELLULAR ONCOLOGY
Authors: Lim, Jonathan K. M.; Leprivier, Gabriel; Sorensen, Poul H.
Abstract
In our recent study, we demonstrated that oncogenic RAS (rat sarcoma)-mediated transformation and tumorigenesis are supported by transcriptional induction of a crucial antioxidant component, SLC7A11 (solute carrier family 7 member 11), otherwise known as XCT, a gene encoding the cystine/glutamate transporter. Our data highlight that this promotes the biosynthesis of glutathione, in turn allowing RAS transformed cells to mitigate tumorigenesis-linked oxidative stress.
SLC7A11 Overexpression in Glioblastoma Is Associated with Increased Cancer Stem Cell-Like Properties
STEM CELLS AND DEVELOPMENT
Authors: Polewski, Monika D.; Reveron-Thornton, Rosyli F.; Cherryholmes, Gregory A.; Marinov, Georgi K.; Aboody, Karen S.
Abstract
System x(c)(-) is a sodium-independent electroneutral transporter, comprising a catalytic subunit xCT (SLC7A11), which is involved in importing cystine. Certain cancers such as gliomas upregulate the expression of system x(c)(-), which confers a survival advantage against the detrimental effects of reactive oxygen species (ROS) by increasing generation of the antioxidant glutathione. However, ROS have also been shown to function as targeted, intracellular second messengers in an array of physiological processes such as proliferation. Several studies have implicated ROS in important cancer features such as migration, invasion, and contribution to a cancer stem cell (CSC)-like phenotype. The role of system x(c)(-) in regulating these ROS-sensitive processes in glioblastoma multiforme (GBM), the most aggressive malignant primary brain tumor in adults, remains unknown. Stable SLC7A11 knockdown and overexpressing U251 glioma cells were generated and characterized to understand the role of redox and system x(c)(-) in glioma progression. SLC7A11 knockdown resulted in higher endogenous ROS levels and enhanced invasive properties. On the contrary, overexpression of SLC7A11 resulted in decreased endogenous ROS levels as well as decreased migration and invasion. However, SLC7A11-overexpressing cells displayed actin cytoskeleton changes reminiscent of epithelial-like cells and exhibited an increased CSC-like phenotype. The enhanced CSC-like phenotype may contribute to increased chemoresistance and suggests that overexpression of SLC7A11 in the context of GBM may contribute to tumor progression. These findings have important implications for cancer management where targeting system x(C)(-) in combination with other chemotherapeutics can reduce cancer resistance and recurrence and improve GBM patient survival.