Abstract:
BACKGROUND : Due to their high proliferative requirements, tumorigenic cells possess altered metabolic systems
whereby cells utilize higher quantities of glutamine and glucose. These altered metabolic requirements make it of
interest to investigate the effects of physiological non-tumorigenic concentrations of glucose and glutamine on
tumorigenic cells since deprivation of either results in a canonical amino acid response in mammalian cell.
METHODS : The influence of short-term exposure of tumorigenic cells to correlating decreasing glutamine- and
glucose quantities were demonstrated in a highly glycolytic metastatic breast cell line and a cervical carcinoma
cell line. Thereafter, cells were propagated in medium containing typical physiological concentrations of 1 mM
glutamine and 6 mM glucose for 7 days. The effects on morphology were investigated by means of polarizationoptical
transmitted light differential interference contrast. Flow cytometry was used to demonstrate the effects of
glutamine-and glucose starvation on cell cycle progression and apoptosis induction. Fluorometrics were also
conducted to investigate the effects on intrinsic apoptosis induction (mitocapture), reactive oxygen species
production (2,7-dichlorofluorescein diacetate) and acidic vesicle formation (acridine orange).
RESULTS : Morphological data suggests that glutamine-and glucose deprivation resulted in reduced cell density and
rounded cells. Glutamine-and glucose starvation also resulted in an increase in the G2M phase and a sub-G1 peak.
Complete starvation of glutamine and glucose resulted in the reduction of the mitochondrial membrane potential
in both cell lines with MDA-MB-231 cells more prominently affected when compared to HeLa cells. Further, starved
cells could not be rescued sufficiently by propagating since cells possessed an increase in reactive oxygen species,
acidic compartments and vacuole formation.
CONCLUSION : Starvation from glutamine and glucose for short periods resulted in decreased cell density, rounded
cells and apoptosis induction by means of reactive oxygen species generation and mitochondrial dysfunction. In
addition, the metastatic cell line reacted more prominently to glutamine-and glucose starvation due to their highly
glycolytic nature. Satisfactory cellular rescue was not possible as cells demonstrated oxidative stress and depolarized
mitochondrial membrane potential. This study contributes to the knowledge regarding the in vitro effects and
signal transduction of glucose and/or L-glutamine deprivation in tumorigenic cell lines.
