The T98G glioblastoma as a cell model to investigate the circadian clock function in human tumor cells

LUCAS G. SOSA ALDERETE AND MARIO E. GUIDO

Tunuyán-Mendoza

Congreso; XII Latin American Symposium on Chronobiology; 2013

The circadian timing system generates oscillations in many physiological processes and behavior allowing the organism to adapt to the daily changes in environment. Circadian clocks (CC) are present in most tissues examined and even in immortalized cell lines. The disruption of the biological clock may lead to diverse pathologies; however, little is known about the activity of CC in tumor cells. To this aim, T98G cells derived from a human glioblastoma were used to investigate potential rhythmic responses under non-proliferative (quiescent) and proliferative conditions. We first optimized a protocol to obtain quiescent and proliferative cells able to be synchronized by extracellular signals: dexamethasone (DEX). Cells were grown for 48 h in 10% FBS-DMEM to reach ~50-70% of confluence and then treated with DEX. After synchronization (SYN), cells were maintained both in serum free DMEM for 24 h (non-proliferative) and 4 % FBS-DMEM (proliferative) and collected at different times from 0 to 48 h. Results indicate that the mRNA for the clock gene Bmal1 displayed a temporal oscillation both in quiescent and proliferative cells with the highest expression at 24 h and 40 h after SYN, respectively. In addition, Per1 and choline kinase alpha (CK), a clock controlled gene (ccg) encoding for a regulatory phospholipid synthesizing enzyme, showed also a temporal variation but only in non-proliferative cells with a peak at 16 h post SYN. After 24 h, the mRNA for both genes showed a damped temporal oscillation profile. Our results strongly suggest that T98G cells synchronized by DEX and maintained only under non-proliferative conditions keep the intrinsic molecular clock functional allowing the cells to preserve the circadian rhythmicity in the expression of clock and ccg.