Dual role of G-quadruplex in translocation renal cell carcinoma: Exploring plausible Cancer therapeutic innovation

G-quadruplex in cancer energy metabolism: A potential therapeutic target

In recent years, energy metabolism in cancer has received increasing attention as an important component of tumor biology, and the functions of transcription factors, mitochondria, reactive oxygen species (ROS) and the autophagy-lysosomal system in which have been elucidated. G-quadruplex (G4) is a molecular switch that regulates gene transcription or translation. As an anticancer target, the effect of G4 on cancer cell proliferation, apoptosis, cycle and autophagy has been recognized. The energy metabolism system is a unified whole composed of transcription factors, metabolic regulators, metabolites and signaling pathways that run through the entire cancer process. However, the role of G4 in this complex metabolic network has not been systematically elucidated. In this review, we analyze the close correlation between G4 and transcription factors, mitochondria, ROS the autophagy-lysosomal system and suggest that G4 can exert a marked effect on cancer energy metabolism by regulating the above mentioned key regulatory elements. The anticancer effects of some G4 ligands through regulation of energy metabolism have also been summarized, confirming the clear involvement of G4 in energy metabolism. Although much more research is needed, we propose that G4 may play a critical role in the complex energy metabolism system of cancer, which is a promising target for anticancer strategies focusing on energy metabolism.

Chimerism: A whole new perspective in gene regulation

The diversity of molecular entities emerging from a single gene are recognized. Several studies have thus established the cellular role(s) of transcript variants and protein isoforms. A step ahead in challenging the central dogma towards expanding molecular diversity is the identification of fusion genes, chimeric transcripts and chimeric proteins that harbor sequences from more than one gene. The mechanisms for generation of chimeras largely follow similar patterns across all levels of gene regulation but also have interdependence and mutual exclusivity. Whole genome and RNA-seq technologies supported by development of computational algorithms and programs for processing datasets have increasingly enabled the identification of fusion genes and chimeric transcripts, while the discovery of chimeric proteins is as yet more subtle. Earlier thought to be associated with cellular transformation, the contribution of chimeric molecules to normal physiology is also realized and found to influence the expression of their parental genes and regulate cellular pathways. This review offers a collective and comprehensive overview of cellular chimeric entities encompassing the mechanisms involved in their generation, insights on their evolution, functions in gene regulation and their current and novel clinical applications.

Why to target G-quadruplexes using peptides: Next-generation G4-interacting ligands

Guanine-rich oligonucleotides existing in both DNA and RNA are able to fold into four-stranded DNA secondary structures via Hoogsteen type hydrogen-bonding, where four guanines self-assemble into a square planar arrangement, which, when stacked upon each other, results in the formation of higher-order structures called G-quadruplexes. Their distribution is not random; they are more frequently present at telomeres, proto-oncogenic promoters, introns, 5'- and 3'-untranslated regions, stem cell markers, ribosome binding sites and so forth and are associated with various biological functions, all of which play a pivotal role in various incurable diseases like cancer and cellular ageing. Several studies have suggested that G-quadruplexes could not regulate biological processes by themselves; instead, various proteins take part in this regulation and can be important therapeutic targets. There are certain limitations in using whole G4-protein for therapeutics purpose because of its high manufacturing cost, laborious structure prediction, dynamic nature, unavailability for oral administration due to its degradation in the gut and inefficient penetration to reach the target site because of the large size. Hence, biologically active peptides can be the potential candidates for therapeutic intervention instead of the whole G4-protein complex. In this review, we aimed to clarify the biological roles of G4s, how we can identify them throughout the genome via bioinformatics, the proteins interacting with G4s and how G4-interacting peptide molecules may be the potential next-generation ligands for targeting the G4 motifs located in biologically important regions.