Glucose Deprivation Contributes to the Development of KRAS Pathway Mutations in Tumor Cells

Abstract

Tumor progression is driven by genetic mutations, but little is known about the environmental conditions that select for these mutations. Studying the transcriptomes of paired colorectal cancer cell lines that differed only in the mutational status of their KRAS or BRAF genes, we found that GLUT1, encoding glucose transporter-1, was one of three genes consistently upregulated in cells with KRAS or BRAF mutations. The mutant cells exhibited enhanced glucose uptake and glycolysis and survived in low glucose conditions, phenotypes that all required GLUT1 expression. In contrast, when cells with wild-type KRAS alleles were subjected to a low glucose environment, very few cells survived. Most surviving cells expressed high levels of GLUT1 and 4% of these survivors had acquired new KRAS mutations. The glycolysis inhibitor, 3-bromopyruvate preferentially suppressed the growth of cells with KRAS or BRAF mutations. Together, these data suggest that glucose deprivation can drive the acquisition of KRAS pathway mutations in human tumors.Mutations in oncogenes and tumor suppressor genes endow cancer cells with the ability to outgrow their neighboring cells in situ (1). Though numerous studies have identified the downstream effects of such mutations and their biochemical mediators, there is relatively little known about the microenvironmental conditions that provide the selective advantage that allows cells with such mutations to clonally expand. Mutations in KRAS commonly occur in colorectal, pancreatic, and some forms of lung cancer, while BRAF mutations occur commonly in melanomas as well as in colorectal tumors without KRAS mutations (2-4). BRAF and KRAS mutations are mutually exclusive, that is, do not occur in the same tumor, suggesting a common origin and effect. Indeed, KRAS binds to and activates BRAF, thereby activating MAPK signaling pathways (5,6). Despite advances in the molecular delineation of the RAS/ RAF pathway, the specific environmental pressures that drive KRAS and BRAF mutations and how KRAS and BRAF mutations alleviate these pressures are unknown.

Glucose deprivation increases monocarboxylate transporter 1 (MCT1) expression and MCT1-dependent tumor cell migration

“…This and the well-known property of glucose deprivation to promote mutations in TCs 20 prompted us to test whether clonal selection could account for changes in MCT1 and/or CD147 expression. It was ruled out by showing i) that the reintroduction of glucose after a starvation period of 24 h (resulting in increased MCT1 and CD147 protein expression) restored basal protein expression levels (Supplementary Figure 2B), and ii) that the glucose starvation of 2 independent clones isolated from the total SiHa population caused a significant increase in the expression of both proteins (Supplementary Figures 2C-D).…”

L’effet Warburg

“…SYNTHÈSE REVUES de la captation du glucose, de la glycolyse et de la production d'acide lactique, ainsi qu'un dysfonctionnement mitochondrial. De plus, le potentiel prolifératif des cellules transformées par K-Ras requiert une forte concentration en glucose et en glutamine dans le milieu de culture [15].…”

Mutant BRAF Induces DNA Strand Breaks, Activates DNA Damage Response Pathway, and Up-Regulates Glucose Transporter-1 in Nontransformed Epithelial Cells

“…26 However, it is not known whether mutant BRAF is sufficient to up-regulate GLUT1 expression. Therefore, we applied Western blot analysis to demonstrate that expression of GLUT1 significantly increased in cyst108 and RK3E cells expressing BRAF V600E as compared to those cells expressing BRAF WT 36 hours and 48 hours after transfection ( Figure 5, A and C).…”

“…Furthermore, a recent study has demonstrated that BRAF expression is required for the expression of GLUT1, which encodes glucose transporter-1, and glucose deprivation is associated with the development of KRAS pathway mutations in tumor cells. 26 Thus, in this study, we also tried to determine whether mutant BRAF plays a causal role in up-regulating GLUT1 expression in our cellular model.…”