Time-dependent changes in proliferation, DNA damage and clock gene expression in hepatocellular carcinoma and healthy liver of a transgenic mouse model

Preservation of circadian rhythm in hepatocellular cancer

Circadian rhythms are controlled at the cellular level by a molecular clock consisting of several genes/proteins engaged in a transcription-translation-degradation feedback loop. These core clock proteins regulate thousands of tissue-specific genes. Regarding circadian control in neoplastic tissues, reports to date have demonstrated anomalous circadian function in tumor models and cultured tumor cells. We have extended these studies by analyzing circadian rhythmicity genome-wide in a mouse model of liver cancer, in which mice treated with diethylnitrosamine at 15 days develop liver tumors by 6 months. We injected tumor-bearing and control tumor-free mice with cisplatin every 2 h over a 24-h cycle; 2 h after each injection mice were sacrificed and gene expression was measured by XR-Seq (excision repair sequencing) assay. Rhythmic expression of several core clock genes was observed in both healthy liver and tumor, with clock genes in tumor exhibiting typically robust amplitudes and a modest phase advance. Interestingly, although normal hepatic cells and hepatoma cancer cells expressed a comparable number of genes with circadian rhythmicity (clock-controlled genes), there was only about 10% overlap between the rhythmic genes in normal and cancerous cells. "Rhythmic in tumor only" genes exhibited peak expression times mainly in daytime hours, in contrast to the more common pre-dawn and pre-dusk expression times seen in healthy livers. Differential expression of genes in tumors and healthy livers across time may present an opportunity for more efficient anticancer drug treatment as a function of treatment time.

Effects and Prognostic Values of Circadian Genes CSNK1E/GNA11/KLF9/THRAP3 in Kidney Renal Clear Cell Carcinoma via a Comprehensive Analysis

Kidney renal clear cell carcinoma (KIRC) is one of the most prevalent and deadly types of renal cancer in adults. Recent research has identified circadian genes as being involved in the development and progression of KIRC by altering their expression. This study aimed to identify circadian genes that are differentially expressed in KIRC and assess their role in KIRC progression. In KIRC, there were 553 differentially expressed rhythm genes (DERGs), with 300 up-regulated and 253 down-regulated DERGs. Functional enrichment analyses showed that DERGs were greatly enriched in the circadian rhythm and immune response pathways. Survival analyses indicated that higher expression levels of CSNK1E were related to shorter overall survival of KIRC patients, whereas lower expression levels of GNA11, KLF9, and THRAP3 were associated with shorter overall survival of KIRC patients. Through cell assay verification, the mRNA level of CSNK1E was significantly up-regulated, whereas the mRNA levels of GNA11, KLF9, and THRAP3 were dramatically down-regulated in KIRC cells, which were consistent with the bioinformatics analysis of KIRC patient samples. Age, grade, stage, TM classification, and CSNK1E expression were all shown to be high-risk variables, whereas GNA11, KLF9, and THRAP3 expression were found to be low-risk factors in univariate Cox analyses. Multivariate Cox analyses showed that CSNK1E and KLF9 were also independently related to overall survival. Immune infiltration analysis indicated that the proportion of immune cells varied greatly between KIRC tissues and normal tissue, whereas CSNK1E, GNA11, KLF9, and THRAP3 expression levels were substantially linked with the infiltration abundance of immune cells and immunological biomarkers. Moreover, interaction networks between CSNK1E/GNA11/KLF9/THRAP3 and immune genes were constructed to explore the stream connections. The findings could help us better understand the molecular mechanisms of KIRC progression, and CSNK1E/GNA11/KLF9/THRAP3 might be used as molecular targets for chronotherapy in KIRC patients in the near future.

Circadian Regulation of Gene Expression and Metabolism in the Liver

Circadian rhythms are approximately 24-hour cycles of variation in physiological processes, gene expression, and behavior. They result from the interplay of internal biological clocks with daily environmental rhythms, including light/dark and feeding/fasting. Note that 24-hour rhythms of liver metabolic processes have been known for almost 100 years. Modern studies reveal that, like metabolism, hepatic gene expression is highly rhythmic. Genetic or environmental changes can disrupt the circadian rhythms of the liver, leading to metabolic disorders and hepatocellular carcinoma. In this review, we summarize the current understanding of mechanisms regulating rhythmic gene expression in the liver, highlighting the roles of transcription factors that comprise the core clock molecular as well as noncanonical regulators. We emphasize the plasticity of circadian rhythms in the liver as it responds to multiple inputs from the external and internal environments as well as the potential of circadian medicine to impact liver-related diseases.

Period circadian regulator 2 suppresses drug resistance to cisplatin by PI3K/AKT pathway and improves chronochemotherapeutic efficacy in cervical cancer

OBJECTIVE

Chronotherapy, a promising therapy, may build up the chemotherapy efficacy through thinking about timing of therapy. Here, we observed the roles of period circadian regulator 2 (PER2) on cervical cancer progression and the therapeutic efficacy of cisplatin (DDP) based on the circadian rhythm of PER2.

METHODS

When Hela/DDP and SiHa/DDP transfected with pcDNA3.1-PER2 and/or treated with human epidermal growth factor (hEGF), viability, apoptosis, migration, and nuclear translocation of NF-κB p65 were detected by CCK-8, flow cytometry, transwell, immunofluorescence and western blot. Furthermore, the expression of circadian rhythm regulators, multidrug resistance, and epithelial-mesenchymal transition (EMT) proteins was detected by western blot. Hela/DDP cells-induced tumor formation in nude mice was constructed. The expression of PER2 was measured at different time point by RT-qPCR. Cisplatin was separately injected into mice with cervical cancer at the highest and lowest expression of PER2. After 5 weeks, tumor volume was measured and tumor proliferation was assessed by immunohistochemistry.

RESULTS

Overexpression of PER2 significantly reduced proliferative and migrated capacities and nuclear translocation of NF-κB p65 as well as enhanced apoptosis in Hela/DDP and SiHa/DDP cells. Meanwhile, its overexpression elevated the expression of circadian rhythm regulators as well as lowered the expression of multidrug resistance proteins and EMT pathway activation by suppressing PI3K/AKT pathway. PER2 was rhythmically expressed in cervical cancer tissues. Compared to cisplatin treatment at the lowest expression of PER2, tumor growth and proliferation of tumor cells were distinctly suppressed in mice treated with cisplatin at the highest expression of PER2.

CONCLUSION

Our findings confirmed the circadian rhythm of PER2 in cervical cancer and its overexpression restrained the resistance to cisplatin in cervical cancer by PI3K/AKT pathway. It may improve cisplatin efficacy through considering the circadian rhythm of PER2.

Does timing matter in radiotherapy of hepatocellular carcinoma? An experimental study in mice

This study investigates whether a chronotherapeutic treatment of hepatocellular carcinoma (HCC) may improve treatment efficacy and mitigate side effects on non-tumoral liver (NTL). HCC was induced in Per2::luc mice which were irradiated at four time points of the day. Proliferation and DNA-double strand breaks were analyzed in irradiated and nonirradiated animals by detection of Ki67 and γ-H2AX. Prior to whole animal experiments, organotypic slice cultures were investigated to determine the dosage to be used in whole animal experiments. Irradiation was most effective at the proliferation peaks in HCC at ZT02 (early inactivity phase) and ZT20 (late activity phase). Irradiation effects on NTL were minimal at ZT20. As compared with NTL, nonirradiated HCC revealed disruption in daily variation and downregulation of all investigated clock genes except Per1. Irradiation affected rhythmic clock gene expression in NTL and HCC at all ZTs except at ZT20 (late activity phase). Irradiation at ZT20 had no effect on total leukocyte numbers. Our results indicate ZT20 as the optimal time point for irradiation of HCC in mice at which the ratio between efficacy of tumor treatment and toxic side effects was maximal. Translational studies are now needed to evaluate whether the late activity phase is the optimal time point for irradiation of HCC in man.

The Expression and Function of Circadian Rhythm Genes in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is among the most common and lethal form of cancer worldwide. However, its diagnosis and treatment are still dissatisfactory, due to limitations in the understanding of its pathogenic mechanism. Therefore, it is important to elucidate the molecular mechanisms and identify novel therapeutic targets for HCC. Circadian rhythm-related genes control a variety of biological processes. These genes play pivotal roles in the initiation and progression of HCC and are potential diagnostic markers and therapeutic targets. This review gives an update on the research progress of circadian rhythms, their effects on the initiation, progression, and prognosis of HCC, in a bid to provide new insights for the research and treatment of HCC.