Discovery of a small molecule that selectively destabilizes Cryptochrome 1 and enhances life span in p53 knockout mice.

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 U2OS Bmal1-dLuc cells. 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-transformed p53 null fibroblast cells. Systemic repetitive administration of M47 increased the median lifespan of p53-/- mice by ~25%. Collectively our data suggest that M47 is a promising molecule to treat forms of cancer depending on the p53 mutation.

Cryptochrome deletion in p53 mutant mice enhances apoptotic and anti-tumorigenic responses to UV damage at the transcriptome level.

Previous studies have demonstrated that deletion of cryptochrome (Cry) genes protects p53-/- mutant mice from the early onset of cancer and extends their median life-span by about 1.5-fold. Subsequent in vitro studies had revealed that deletion of Crys enhances apoptosis in response to UV damage through activation of p73 and inactivation of GSK3ß. However, it was not known at the transcriptome-wide level how deletion of Crys delays the onset of cancer in p53-/- mutant mice. In this study, the RNA-seq approach was taken to uncover the differentially expressed genes (DEGs) and pathways following UV-induced DNA damage in p53-/- and p53-/-Cry1-/-Cry2-/- mouse skin fibroblasts. Gene set enrichment analysis with the DEGs demonstrated enrichment in immune surveillance-associated genes regulated by IFN-γ and genes involved in TNFα signaling via NF-κB. Furthermore, protein network analysis enabled identification of DEGs p21, Sirt1, and Jun as key players, along with their interacting partners. It was also observed that the DEGs contained a high ratio of non-coding transcripts. Collectively, the present study suggests new genes in NF-κB regulation and IFN-γ response, as well as non-coding RNAs, may contribute to delaying the onset of cancer in p53-/-Cry1-/-Cry2-/- mice and increasing the life-span of these animals compared to p53-/- mice.

Opposite Carcinogenic Effects of Circadian Clock Gene BMAL1.

The circadian clock confers daily rhythmicity on many biochemical and physiological functions and its disruption is associated with increased risks of developing obesity, diabetes, heart disease and cancer. Although, there are studies on the role of Bmal1 in carcinogenesis using germline, conditional or tissue-specific knockouts, it is still not well understood how BMAL1 gene affects cancer-related biological events at the molecular level. We, therefore, took an in vitro approach to understand the contribution of BMAL1 in this molecular mechanism using human breast epithelial cell lines by knocking out BMAL1 gene with CRISPR technology. We preferred epithelial cells over fibroblasts as the most of cancers originate from epithelial cells. After obtaining BMAL1 knockouts by targeting the gene at two different sites from non-tumorigenic MCF10A and invasive tumorigenic MDA-MB-231 cells, we analysed apoptosis and invasion properties of the cell lines as representative events in tumor development. BMAL1 disruption sensitized both cell lines to a bulky-DNA adduct forming agent (cisplatin) and a double-strand break-inducing agent (doxorubicin), while it enhanced the invasive properties of MDA-MB-231 cells. These results show that the disruption of clock genes may have opposing carcinogenic effects.