Pharmacological modulation of the circadian clock as a novel strategy to treat glioblastoma

WAGNER PAULA; GUIDO, MARIO E.

Congreso; SAIB; 2022

All living organisms have adapted through evolution to the day/night cycles and most mammals have developed a circadian timing system to adjust their physiology and behavior to the 24 h light/dark cycle. This biological timekeeping regulates diverse cellular processes in organs, tissues, and even in individual cells, including tumor cells. Nowadays, it is known that the cellular clock is composed of the transcripcional machine and the metabolic/cytosolic oscillator. On the whole, these oscillators work together to maintain the cellular homeostasis. However, modern life with hyper caloric diets, nocturnal shift work, prolonged artificial illumination, etc. have severely altered the temporal organization of behavior and physiological processes and can cause metabolic disorders and an increased risk of cancer. In particular, glioblastoma (GBM) is the most common and aggressive type of brain tumor accounting for 80% of primary malignant tumors of the central nervous system. Due to its great resistance to conventional therapies, it is necessary new chemotherapeutic approaches considering the impact of the circadian clock on tumor biology. Previous results from our laboratory evidenced metabolic oscillations in T98G cells from GBM in ROS levels and glycerophospholipids metabolism as well as a marked temporal drug susceptibility when treated with Bortezomib (proteasome inhibitor). In addition, a strong interaction between the metabolic oscillator and the transcriptional circadian machinery was observed in T98G cells that had decreased expression of the molecular activator Bmal1. Here, we investigate how the metabolic/cytosolic oscillator disruption can be used as a novel therapeutic strategy for the treatment of GBM using selective pharmacological inhibitors of casein kinases 1δ and 1ϵ (PF670462) and glycogen synthase kinase 3α/β (CHIR99021). These kinases determined the speed at which the cellular circadian clock runs due to their role in phosphorylation of clock proteins. The results showed a cytotoxic effect of these inhibitors in T98G with an IC50 of 1.5 uM and 8.6 uM when cells were treated with PF670462 or CHIR99021, respectively. Moreover, wound healing assays revealed that the wound closure was delayed in CHIR-treated cells as compared with control cells. Alterations on redox oscillations and temporal susceptibility to Bortezomib were also observed when cells were treated with these inhibitors. On the other hand, disruption of the molecular clock also evidences cytotoxic effect on tumor survival when T98G cells were treated with SR9009 (REV-ERB agonist) or KL001 (inhibitor of CRY degradation).Overall, our observations suggest that the pharmacological modulation of the cellular circadian clock can be postulated as a novel therapeutic strategy for the treatment of GBM. Understanding and delving into tumor regulation from a chronobiological viewpoint will further help to design new treatments that maximize therapeutic benefits.