T98G Glioblastoma cells: a tumor model to investigate the circadian regulation of clock gene expression and phospholipid synthesis

LUCAS G. SOSA-ALDERETE; PAULA M. WAGNER; LUCAS GORNÉ ; MARIO E. GUIDO.

Conferencia; International Conference on the Bioscience of Lipids; 2015

Circadian clocks present even in immortalized cell lines, can be synchronized by different ambient signals ( light, food, glucocorticoids, etc. ) (Fig. 1) and temporarily regulate diverse physiological processes. The disruption of circadian rhythms may lead to metabolic disorders or higher cancer risk through failures in cell division control. Here we investigated whether the immortalized human glioblastoma T98G cells subject to proliferation (P) in the presence of serum, or maintained quiescent (Q) (Table 1) keep a functional clock, after synchronization, regulating gene expression and phospholipid (PL) metabolism under a circadian base. We examined the expression of clock genes (Bmal1, Per1, Rev-Erbα) (Fig. 2 and 3) and PL synthesizing enzyme genes (choline kinase α: Chokα and CTP:phosphoethanolamine cytidylyltransferase 2:Pcyt-2) (Fig. 4), and the metabolic labeling of PLs (Fig 5). For this, cells grown in 10% FBS-DMEM for 2-3 days were synchronized with a 20 min shock of dexamethasone (Dex, 100 nM) (time 0). Then, cells maintained with (P) or without FBS-DMEM (Q) for 48 h were collected at different times for further assays. Results showed that Bmal1, Per1, Rev-Erbα, Chokα and Pcyt-2 exhibited different temporal expression profiles, phases and amplitudes depending on the proliferative condition tested (Table 2). Cell cultures also displayed a circadian oscillation in the labeling of 32P-PLs mainly when kept arrested. Overall, the temporal control of gene expression and metabolism persists in quiescent tumor cells and became more disorganized as proliferation progresses.