Yasemin Kubra Akyel

Circadian clocks generate daily rhythms of gene expression that influence physiology, disease, and responses to therapeutics, yet how circadian transcription differs between juvenile and adult organisms remains unresolved. Here, we used genome-wide eXcision Repair sequencing (XR-seq) to quantify transcription-coupled repair as an indirect, high-sensitivity measure of transcription. We profiled the brain, liver, kidney, and testis from juvenile and adult C57BL6/J mice across a 24 h cycle and show that XR-seq enables sensitive circadian transcription mapping. In all organs except the testis, rhythmic transcription phases clustered near dawn and dusk. While core clock gene rhythms are largely preserved between juveniles and adults, rhythms of many clock-controlled genes differ markedly by age. Rhythmic genes are strongly organ-specific yet their overlap between ages is limited, indicating substantial developmental changes in circadian control. Together, these data provide a multi-organ map of juvenile versus adult circadian transcription and indicate that adult therapeutic schedules may not translate to juveniles.

Glioblastoma (GBM) is the most aggressive malignant primary brain tumor in adults, with incidence peaking in later life. It is commonly treated with surgery followed by administration of ionizing radiation and the DNA alkylating agent temozolomide (TMZ). Even though this regimen confers some progression-free survival, there is essentially no cure with the median survival with the standard of care being about 12 months. Currently, several alternative approaches are being developed to improve upon this outcome. We have already shown EdU alone effectively treats GBM, and we now study efficacy of TMZ+EdU combination therapy. TMZ+EdU significantly improves antitumor efficacy compared to either single-agent therapy against GBM cell lines in vitro , against three different orthotopic GBM xenograft models, and against passage-zero patient GBM tumor tissues engrafted within an organotypic brain slice culture (OBSC)-based platform. Together, these data suggest that EdU could be effective alongside standard of care TMZ in patients with GBM. STATEMENT OF SIGNIFICANCE (50-WORD): By simultaneously engaging distinct DNA repair pathways, combination of TMZ and EdU produced unprecedented survival benefits and synergistic effects in preclinical GBM models, offering a promising new avenue in the treatment of GBM.

Essential for survival and reproduction, the circadian timing system (CTS) regulates adaptation to cyclical changes such as the light/dark cycle, temperature change, and food availability. The regulation of energy homeostasis possesses rhythmic properties that correspond to constantly fluctuating needs for energy production and consumption. Adipose tissue is mainly responsible for energy storage and, thus, operates as one of the principal components of energy homeostasis regulation. In accordance with its roles in energy homeostasis, alterations in adipose tissue’s physiological processes are associated with numerous pathologies, such as obesity and type 2 diabetes. These alterations also include changes in circadian rhythm. In the current review, we aim to summarize the current knowledge regarding the circadian rhythmicity of adipogenesis, lipolysis, adipokine secretion, browning, and non-shivering thermogenesis in adipose tissue and to evaluate possible links between those alterations and metabolic diseases. Based on this evaluation, potential therapeutic approaches, as well as clock genes as potential therapeutic targets, are also discussed in the context of chronotherapy.

The circadian timing system controls absorption, distribution, metabolism, and elimination processes of drug pharmacokinetics over a 24-h period. Exposure of target tissues to the active form of the drug and cytotoxicity display variations depending on the chronopharmacokinetics. For anticancer drugs with narrow therapeutic ranges and dose-limiting side effects, it is particularly important to know the temporal changes in pharmacokinetics. A previous study indicated that pharmacokinetic profile of capecitabine was different depending on dosing time in rat. However, it is not known how such difference is attributed with respect to diurnal rhythm. Therefore, in this study, we evaluated capecitabine-metabolizing enzymes in a diurnal rhythm-dependent manner. To this end, C57BL/6J male mice were orally treated with 500 mg/kg capecitabine at ZT1, ZT7, ZT13, or ZT19. We then determined pharmacokinetics of capecitabine and its metabolites, 5′-deoxy-5-fluorocytidine (5′DFCR), 5′-deoxy-5-fluorouridine (5′DFUR), 5-fluorouracil (5-FU), in plasma and liver. Results revealed that plasma C_max and AUC_0-6h (area under the plasma concentration-time curve from 0 to 6 h) values of capecitabine, 5′DFUR, and 5-FU were higher during the rest phase (ZT1 and ZT7) than the activity phase (ZT13 and ZT19) ( p < 0.05). Similarly, C_max and AUC_0-6h values of 5′DFUR and 5-FU in liver were higher during the rest phase than activity phase ( p < 0.05), while there was no significant difference in liver concentrations of capecitabine and 5′DFCR. We determined the level of the enzymes responsible for the conversion of capecitabine and its metabolites at each ZT. Results indicated the levels of carboxylesterase 1 and 2, cytidine deaminase, uridine phosphorylase 2, and dihydropyrimidine dehydrogenase ( p < 0.05) are being rhythmically regulated and, in turn, attributed different pharmacokinetics profiles of capecitabine and its metabolism. This study highlights the importance of capecitabine administration time to increase the efficacy with minimum adverse effects.

Article Invited Speaker Abstracts was published on February 1, 2023 in the journal Turkish Journal of Biochemistry (volume 48, issue s1).

Cryptochromes are negative transcriptional regulators of the circadian clock in mammals. It is not clear how reducing the level of endogenous CRY1 in mammals will affect circadian rhythm and the relation of such a decrease with apoptosis. Here, we discovered a molecule (M47) that destabilizes Cryptochrome 1 (CRY1) both in vitro and in vivo. The M47 selectively enhanced the degradation rate of CRY1 by increasing its ubiquitination and resulted in increasing the circadian period length of U2OSBmal1-dLuccells. In addition, subcellular fractionation studies from mice liver indicated that M47 increased degradation of the CRY1 in the nucleus. Furthermore, M47-mediated CRY1 reduction enhanced oxaliplatin-induced apoptosis in Ras-transformedp53null fibroblast cells. Systemic repetitive administration of M47 increased the median lifespan ofp53^−/−mice by ~25%. Collectively our data suggest that M47 is a promising molecule to treat forms of cancer depending on thep53mutation.

Objective: Gastric cancer is the second leading cause of cancer-related death worldwide. 5-Fluorouracil (5-FU) is one of the most commonly used drugs to treat cancer, but 5-FU and its forms are characterized by wide inter-individual pharmacokinetic variability. ABCC5 and ABCC11 are members of the ABC transporter superfamily and play a role in the efflux of antineoplastic drugs like 5-FU. Methods: The influence of two SNPs in ABCC5 (rs562, T>C) and ABCC11 (rs17822931, G>A) was evaluated based on the pharmacokinetics and toxicity of 5-FU in HER2-negative advanced gastric cancer patients treated with cisplatin and 5-FU (n=18). The genetic variants and plasma 5-FU concentrations were detected by RT-PCR and HPLC, respectively. Results: There was no statistically significant difference between 5-FU AUC0-96 h values and ABCC5 (rs562; T>C), 21.04 ±3.46 vs 16.65 μg.h/mL, p=0,261) and ABCC11 (rs17822931; G>A), 17.04 ±4.39 vs 54 ±3.79 mg.h/L, p=0,564) variants. Similarly, there were no statistically significant differences between the variants and the most frequently observed side effects of diarrhea and mucositis. Conclusion: We recommend investigating the noted SNPs more precisely in a larger study population with more comprehensive evaluation.