Nucleic Acid Sensing Machinery: Targeting Innate Immune System for Cancer Therapy

Nucleic acid sensing is an essential strategy employed by the innate immune system to detect both pathogen-derived nucleic acids and self-DNA released by host apoptotic or necrotic cells. The presence of nucleic acids that gain access to the cytoplasm is perceived by mammalian cells as "stranger" or "danger" signals that trigger a myriad of immunological responses. Recent publications have highlighted the importance of nucleic acid sensing machinery as mediator of innate and adaptive immunity, and cGAS, STING and RIG-I agonists have been validated as immunooncology agents in cancer therapy.

The crucial role of cGAS and STING in eliciting innate and adaptive immune responses provides a scientific rationale for using cGAMP and STING agonists both in human preventive vaccine and immunotherapy settings. Thus, search for natural and synthetic STING agonists and development of cyclic dinucleotides (CDNs)-based adjuvants were strongly intensified. Furthermore, with their ability to induce tumour cell death and lymphocyte cross priming, RIG-I ligands are among the most promising molecules for the development of new immunostimulatory adjuvants in cancer vaccines.

This work focuses on relevant recent patents (2010-2017) that entail the use of nucleic acid sensing machinery to elicit innate and adaptive immune responses, highlighting a new approach in immune-mediated cancer therapy. Several patents describe compositions and methods that may be used as immuno-oncology agents for the treatment of cancer patients. cGAS and/or STING pathways modulating compounds alone or in combination with pharmaceutical compositions are discussed. New approaches to improve DNA-vaccine induced adaptive immunity for cancer therapy through increasing the level of plasmid-mediated activation of innate immune signalling pathways are also discussed. In addition, a targeted selection of very recent clinical studies describing the employment of innate immunity targeting compounds is reported.

It is highly relevant to deepen the study of the nucleic acid-sensing mechanisms to develop new pharmacological approaches to engage these pathways within the tumour microenvironment. Indeed, further clarification will be functional to develop advanced anticancer strategies or to design new vaccine formulations.