Self-DNA Detection in Genome Maintenance and Cancer

Background Most cancers, either during their development, or during chemotherapy, undergo genotoxic stress and chromosomal instability.

While much is known about how classic DNA repair and DNA damage checkpoint machineries respond to such defects, and how these modulate carcinogenesis and chemotherapy, recent work has implicated another player – the innate immune system.

Because innate immune signalling can both have important cell-intrinsic effects and regulate immune responses, understanding its response to genotoxic stress may transform our view of cancer development and treatment particularly with the advances being made through immunotherapy.

A major trigger for innate immune responses is DNA-dependent activation of the cyclic GMP-AMP synthase cGAS, leading to inflammation, senescence and apoptosis.

Under unperturbed conditions, chromosomal self-DNA appears to be shielded from activating cGAS, but this is negated in response to genotoxic stress.

Although the mechanistic basis underlying this phenomenon is not yet understood, my recent work showed that the chromatin organization of chromosomal DNA inhibits cGAS, thereby potentially preventing cGAS activation during normal growth.

Aims The main purpose of this research plan is to understand how chromatin inhibits cGAS, how this inhibition is relieved in cancer and in response to genotoxic stress, and to reveal the consequences of cGAS activation by self-DNA. Aim 1: Reveal how cGAS activation is controlled by chromatin. Aim 2: Reveal how genotoxic stress activates cGAS.

Aim 3: Reveal how cGAS controls cell fate following genotoxic stress. Methods I will apply biochemistry, structural analysis and cell biology to this problem.

A unique system of cell-free extracts will be used to investigate cGAS response to self-DNA in a physiological but biochemically tractable environment. Cell culture, automated imaging, and gene editing will reveal cell fates and in vivo mechanisms.

Ionising radiation and taxanes will be used as sources of genotoxic stress, both with direct relevance to cancer treatment. How the results of this research will be used.

I hope to establish a comprehensive understanding of how cGAS orchestrates the response to genotoxic stress, and establish model systems to dissect other innate immune pathways.

In collaboration, I subsequently plan to apply these findings to revealing the role of cGAS activation by self-DNA in cancer development and treatment.

The deep mechanistic understanding that I aim to establish should prove valuable to develop approaches for manipulating the cGAS pathway during cancer therapy, as well as utilising it as a biomarker for tumour responses during therapy.