R01CA256188

Probing Cytosolic Nucleic Acid Sensing Pathways in Cancer - Abstract

The ability of mammalian cells to elicit inflammation is central to many processes including embryogenesis, wound healing, tissue regeneration, and cancer metastasis. A major source of inflammatory signaling is the aberrant presence of double-stranded (DS) nucleic acids in the cytoplasm. Mammalian cells have evolved highly conserved mechanisms to detect cytosolic nucleic acids as an anti-viral defense.

In normal cells, cGAS (cyclic GMP-AMP synthase) and its downstream signaling effector STING (stimulator of interferon genes) have been proposed as essential mediators of type I interferon (IFN) signaling and downstream immune activation. However, we have shown that in cancer cells with chromosomal instability (CIN), there is no evidence of type I IFN signaling despite the presence of cytosolic DNA and constitutive activation of cGAS and STING. Instead, cancer cells rewire their signaling downstream of STING to selectively suppress IFN signaling and enable other pro-metastatic pathways such as NF-B.

Three important pieces of evidence bring into question the essentiality of the cGAS-STING pathway in promoting anti-tumor immunity and suggest heretofore unappreciated redundancies and context dependence of nucleic acid sensing in cancer:

1) Chromosomally unstable cancer cells retain IFN-responsiveness to cytosolic dsRNA.
2) Cancer cells with CIN can still elicit a robust, anti-tumor immune response to cytosolic dsDNA, in a manner independent of cGAS-STING and type I IFN.
3) Expression of nucleic acid sensors and downstream inflammatory pathways is highly variable across tumor subpopulations and metastatic cell states - in which a continuum of stem-like to more committed epithelial progenitors is observed.

Together, these findings challenge the current view that cGAS-STING signaling is the universal mediator of inflammation in response to cytosolic dsDNA. Herein, we aim to understand functional redundancies and interactions across cytosolic nucleic acid sensing pathways and how their transcriptional outputs vary with tumor cell differentiation status.

We will systematically interrogate key nucleic acid sensors and their downstream effectors in three syngeneic mouse models characterized by increased metastatic potential and high levels of CIN. We will experimentally manipulate CIN rates to identify cytosolic nucleic acid-dependent, but cGAS-STING-independent mechanisms of immune activation (Aim 1). We will then couple high-throughput single-cell sequencing with combinatorial CRISPR-mediated gene inactivation of key cytosolic nucleic acid sensors and effectors in metastasis-initiating stem cells distinguished by SOX2 expression, versus their more differentiated counterparts, to map the cell state-specific regulatory logic of this pathway (Aim 2).

Unraveling the context-dependence of this extremely important and versatile signaling cascade has the potential to transform our thinking about chronic inflammation in cancer and to reveal therapeutic vulnerabilities in chromosomally unstable cancer cells that are otherwise resistant to cGAS-STING signaling.

Weill Medical College Of Cornell University

TO PROVIDE FUNDAMENTAL INFORMATION ON THE CAUSE AND NATURE OF CANCER IN PEOPLE, WITH THE EXPECTATION THAT THIS WILL RESULT IN BETTER METHODS OF PREVENTION, DETECTION AND DIAGNOSIS, AND TREATMENT OF NEOPLASTIC DISEASES. CANCER BIOLOGY RESEARCH INCLUDES THE FOLLOWING RESEARCH PROGRAMS: CANCER CELL BIOLOGY, CANCER IMMUNOLOGY, HEMATOLOGY AND ETIOLOGY, DNA AND CHROMOSOMAL ABERRATIONS, TUMOR BIOLOGY AND METASTASIS, AND STRUCTURAL BIOLOGY AND MOLECULAR APPLICATIONS.

93.396 - Cancer Biology Research

National Cancer Institute (NCI) [HHS - NIH]

New York United States

State-Wide

Research Project Grant (Parent R01 Clinical Trial Not Allowed) (PA-19-056)

Amendment Since initial award the total obligations have increased 382% from $736,310 to $3,548,978.