43P - Influence of chromosomal instability on cGAS/STING activation and metastatic behavior of lung and colorectal cancer cells

Background

Although metastases are primarily responsible for tumor related deaths and are thought to be associated with chromosomal instability (CIN), understanding whether and how CIN promotes metastasis is still unknown. Recent findings suggest that CIN drives metastasis through activation of the cGAS-STING (cyclic GMP-AMP synthase-stimulator of interferon genes) pathway via induction of epithelial-mesenchymal transition (EMT).

Methods

To test the hypothesis of the cGAS/STING pathway being a CIN transducer and trigger of metastasis, we selected 12 cell lines derived from primary tumors and metastases of lung and colorectal cancer with high, intermediate, and low metastatic potential in a large-scale xenograft model (Jin et al., Nature, 2020). Table: 43P

Metastatic potential	Lung cancer	Colorectal cancer
Primary tumor	Metastases	Primary tumor
MSS	MSI
High	A549	NCI-H650	HT29	HCT-116
Intermediate	NCI-H23	NCI-H1568	SW-480	RKO
Low	NCI-H1793	NCI-H2009	SW-948	SW-48

CIN levels, micronucleus (MN) formation and whole chromosome gains or losses of all cell lines were determined by immunofluorescence microscopy, genome-wide SNP genotyping and flow cytometry. The impact of MN rupture-induced cGAS/STING pathway activation on metastasis was assessed by analyzing the processing of NF-kB2/p100, translocation of RelB to the nucleus and expression of epithelial versus mesenchymal markers as a readout for EMT.

Results

75% of the cell lines harbored a high frequency of chromosome gains and losses, what however did not clearly correlate with formation of cGAS-positive MN. More importantly, the abundance of cGAS-positive MN did not correlate with non-canonical NF-kB signaling, EMT and metastatic potential. Primary tumor-derived lung cancer cell lines expressed more mesenchymal markers than those isolated from metastases, with the extent of EMT being dependent on non-canonical NF-kB signaling.

Conclusions

Our findings indicate a higher complexity of the interaction of CIN, cGAS/STING and NF-kB signaling and EMT than previously assumed and lead to the conclusion that metastasis formation cannot - at least in a cell line model - be exclusively explained by CIN-induced cGAS/STING-signaling.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Mildred-Scheel-Stipendium of the Deutsche Krebshilfe.

Disclosure

All authors have declared no conflicts of interest.