Immune signals initiated by chromosomal instability lead to metastasis

Unravelling the intricate relationship between immune cells and cancer cells through STING pathway rewiring.

Introduction

Chromosomal instability (CIN) has long been recognised as a prominent feature of advanced cancers. However, recent research has shed light on the intricate connection between CIN and the STING (Stimulator of Interferon Genes) pathway. Researchers at Memorial Sloan Kettering Cancer Center (MSK) and Weill Cornell Medicine conducted this ground-breaking study, which has provided fascinating insights into the function of the immune system and its interactions with cancer cells. In this article, we will delve into the findings of this study and explore the implications for future cancer treatments.

STING pathway 

The STING pathway plays a crucial role in the response to cellular stress and the innate immunity response to DNA damage and chromosomal instability. Chromosomal instability refers to the increased rate of chromosomal aberrations, such as mutations, rearrangements, and aneuploidy, within a cell population. This instability can lead to genomic alterations that contribute to the initiation and evolution of cancer.

This pathway is activated when the presence of cytosolic DNA is detected, which can be indicative of cellular damage or infection, triggering a cascade of signalling events leading to the production of type I interferons and other inflammatory cytokines.

Many recent studies have revealed an intriguing relationship between chromosomal instability and the STING pathway, including the STING pathway’s ability to be activated by the accumulation of micronuclei resulting from chromosomal instability in cancer cells. This activation can lead to the promotion of anti-tumour immunity and the suppression of tumourigenesis.

The Promise and Limitations of STING Agonist Drugs

STING-agonist drugs have shown great potential in preclinical studies, arousing optimism for their use in cancer therapy. However, clinical trials have yielded disappointing results, with low response rates observed in patients. Dr. Samuel Bakhoum, an assistant member at MSK, highlights the discrepancy between lab findings and clinical outcomes. Only a small fraction of patients demonstrated a partial response, leading researchers to question the underlying reasons for this disparity.

The Sinister Cooperation: CIN and Immune Cells

Chromosomal instability acts as a driver for cancer metastasis, enabling cancer cells to spread throughout the body. The STING pathway, specifically, is where Dr. Bakhoum's team discovered that the immune system has a significant impact on this process. The cooperation between cancer cells with CIN and immune cells is orchestrated by STING, resulting in a pro-metastatic tumour microenvironment. This finding provides a crucial understanding of why STING-agonist drugs have not been effective in clinical trials.

Introducing Contact Tracing: Unravelling Cell-to-Cell Interactions

Researchers utilised a newly developed tool called ContactTracing to examine cell-to-cell interactions and cellular responses within growing tumours. By analysing single-cell transcriptomic data, they gained valuable insights into the effects of CIN and STING activation. The tool's capabilities allowed them to identify patients who could still mount a robust response to STING activation, enabling the selection of better candidates for STING agonist therapy.

STING Inhibition: A Potential Solution

Interestingly, the study suggests that patients with high levels of CIN may actually benefit from STING inhibition rather than activation. Treatment of study mice with STING inhibitors successfully reduced metastasis in models of melanoma, breast, and colorectal cancer. These findings open up new possibilities for personalised medicine, where patients can be stratified based on their tumour's response.

By identifying the subset of patients whose tumours can still mount a strong response to STING activation, doctors could select better candidates for STING agonists. This biomarker-based approach could help figure out which patients would benefit from turning on STING and which would benefit from turning it off. This could lead to more targeted and effective treatments for people with advanced cancer that is caused by chromosomal instability.

Conclusion

Based on the research findings, it can be concluded that chronic activation of the STING pathway, induced by CIN, promotes changes in cellular signalling that hinder anti-tumour immunity and facilitate cancer metastasis. This rewiring of downstream signalling ultimately renders STING-agonist drugs ineffective in advanced cancer patients. However, the study also suggests that STING inhibitors may benefit these patients by reducing chromosomal instability-driven metastasis. The research highlights the importance of identifying biomarkers to determine which patients would benefit from STING activation or inhibition.

Overall, these findings provide valuable insights into the underlying mechanisms of cancer progression and offer potential opportunities for improved treatment strategies for patients with advanced cancer.

The study shown in figure 1, analysed 39,234 single cells within the tumour microenvironment (TME), categorised by cell subtype assignment. It showed that tumour cell rates of CIN were genetically dialled-up or dialled-down. The study also showed CIN-dependent effects on differential abundance at the neighbourhood level, grouped by cell subtype and ranked by mean log2 (FC) within each cell subtype. Node opacity was scaled by the p-value.

Written by Sara Maria Majernikova

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Reference: 

Li, J., Hubisz, M.J., Earlie, E.M. et al. Non-cell-autonomous cancer progression from chromosomal instability. Nature 620, 1080–1088 (2023). https://doi.org/10.1038/s41586-023-06464-z