Circular RNAs (circRNAs) are a class of non-coding RNAs formed by covalently closed loops through back-splicing and exon-skipping. circRNAs have been confirmed to play a vital role in various biological functions, acting as microRNA sponges and reservoirs, as well as combining with RNA-binding proteins during the progression of multiple cancer types. Therefore, the present review evaluated recent research articles in PubMed that were published between November 2017 and September 2020. Key word search strings included: ‘Circular RNA (circRNA) AND bladder cancer (BC)’, ‘circular RNA (circRNA) AND prostate cancer (PCa)’ and ‘circular RNA (circRNA) AND renal cell cancer (RCC)’. In total, >58 circRNAs were found to be implicated in urological cancers, with several of the circRNAs targeting common carcinogenic pathways, such as the AKT, TGF-β, MAPK, VEGF and even metabolic pathways. circRNAs are important modulators of BC, PCa and RCC. circRNAs are functionally implicated in the pathogenesis of these cancer types, and have been found to act as biomarkers for the diagnosis and prognosis of urological cancer. However, to the best of our knowledge, the functions of circRNAs in tumors of the urinary system remain largely unknown and require further research.

Senescence is a result of cellular stress and is a potential mechanism for regulating cancer. As a member of the mitogen-activated protein kinase family, ERK1/2 (extracellular signal-regulated protein kinase) has an important role in delivering extracellular signals to the nucleus, and these signals regulate the cell cycle, cell proliferation and cell development. Previous studies demonstrated that ERK1/2 is closely associated with cell aging; however other previous studies suggested that ERK1/2 exerts an opposite effect on aging models and target proteins, even within the same cell model. Recent studies demonstrated that the effect of ERK1/2 on aging is likely associated with its target proteins and regulators, negative feedback loops, phosphorylated ERK1/2 factors and ERK1/2 translocation from the cytoplasm to the nucleus. The present review aims to examine the mechanism of ERK1/2 and discuss its role in cellular outcomes and novel drug development.

Angiogenesis plays important roles in development, stress response, wound healing, tumorigenesis and cancer progression, diabetic retinopathy, and age-related macular degeneration. It is a complex event engaging many signaling pathways including vascular endothelial growth factor (VEGF), Notch, transforming growth factor-beta/bone morphogenetic proteins (TGF-β/BMPs), and other cytokines and growth factors. Almost all of them eventually funnel to two crucial molecules, VEGF and hypoxia-inducing factor-1 alpha (HIF-1α) whose expressions could change under both physiological and pathological conditions. Hypoxic conditions stabilize HIF-1α, while it is upregulated by many oncogenic factors under normaxia. HIF-1α is a critical transcription activator for VEGF. Recent studies have shown that intracellular metabolic state participates in regulation of sprouting angiogenesis, which may involve AMP-activated protein kinase (AMPK). Indeed, AMPK has been shown to exert both positive and negative effects on angiogenesis. On the one hand, activation of AMPK mediates stress responses to facilitate autophagy which stabilizes HIF-1α, leading to increased expression of VEGF. On the other hand, AMPK could attenuate angiogenesis induced by tumor-promoting and pro-metastatic factors, such as the phosphoinositide 3-kinase /protein kinase B (Akt)/mammalian target of rapamycin (PI3K/Akt/mTOR), hepatic growth factor (HGF), and TGF-β/BMP signaling pathways. Thus, this review will summarize research progresses on these two opposite effects and discuss the mechanisms behind the discrepant findings.

Some genetic melanocortin-1 receptor (MC1R) variants responsible for human red hair color (RHC-variants) are consequently associated with increased melanoma risk. Although MC1R signaling is critically dependent on its palmitoylation primarily mediated by the ZDHHC13 protein-acyl transferase, whether increasing MC1R palmitoylation represents a viable therapeutic target to limit melanomagenesis in redheads is unknown. Here we identify a specific and efficient in vivo strategy to induce MC1R palmitoylation for therapeutic benefit. We validate the importance of ZDHHC13 to MC1R signaling in vivo by targeted expression of ZDHHC13 in C57BL/6J-MC1RRHC mice and subsequently inhibit melanomagenesis. By identifying APT2 as the MC1R depalmitoylation enzyme, we are able to demonstrate that administration of the selective APT2 inhibitor ML349 treatment efficiently increases MC1R signaling and represses UVB-induced melanomagenesis in vitro and in vivo. Targeting APT2, therefore, represents a preventive/therapeutic strategy to reduce melanoma risk, especially in individuals with red hair.