Innate Immune System’s Surprising Role in Cancer Development

Medical News: Scientists at Memorial Sloan Kettering Cancer Center (MSK), New York, have made a surprising discovery. They’ve found that the body's immune system, which usually fights infections, might also inadvertently fuel cancer. This groundbreaking research explored how issues in the MRE11 complex, a key player in DNA repair, lead to persistent immune responses that could contribute to cancer development. Dr. John Petrini, head of the MSK research team, emphasized that these insights shed new light on how cancer may start and suggest fresh approaches to therapy. This Medical News report explores their findings and what they mean for cancer treatment and prevention.


Innate Immune System’s Surprising Role in Cancer Development

Immune System’s Double Role in Health and Cancer
The study, led by postdoctoral fellow Dr. Hexiao Wang, delved into the MRE11 complex's role. This protein group, including MRE11, RAD50, and NBS1, is essential for DNA repair. The team showed that in a mouse model of breast cancer, when this complex is disrupted, the immune system’s innate signaling kicks in to protect the DNA. However, the persistent activation of this immune response, while aimed at protection, can also create an environment that promotes cancer growth. These findings suggest that targeting immune signals may open doors for innovative therapies.
 
Chronic Activation of Immune Pathways and Cancer Risks
In their study, the MSK researchers manipulated the MRE11 complex within mammary organoids (lab-grown mini breast models). The engineered organoids, when implanted into animals and exposed to oncogenes (genes that can turn normal cells into cancerous ones), developed tumors 40% of the time - significantly more than the 5% occurrence seen in normal organoids. Intriguingly, the affected organoids exhibited a heightened expression of interferon-stimulated genes (ISGs), which are typically triggered by viral infections or stress. This activation led to DNA being loosely packed, making specific genes accessible and more likely to drive cancerous changes.
 
DNA Repair Complex and Its Impact on Immune Signaling
The researchers also pinpointed the crucial role of an immune sensor, IFI205. IFI205 responds to damaged DNA and initiates immune signals. When this sensor was removed from the modified organoids, the DNA structure stabilized, and tumor development rates returned to normal. This experiment underscored that IFI205 is at the core of this immune activation and that chronic activation of this immune pathway can become a catalyst for cancer. “Our study shows that when DNA repair mechanisms go awry, the body’s immune response may, counterintuitively, make cancer more likely,” explained Dr. Petrini.
 
Potential Pathways to Future Cancer Treatments
This study adds depth to prior research on the MRE11 complex and its role in maintaining genetic stability, including the work by Dr. Christopher Wardlaw and Dr. Petrini, previously published in Nature Communicat ions.
https://www.nature.com/articles/s41467-022-33535-y
 
That research highlighted how a malfunctioning MRE11 complex results in misplaced DNA fragments that activate immune responses, suggesting that the immune system’s reaction to ongoing DNA damage might contribute to cancer risk. Together, these studies suggest new avenues for treatment, especially in cancer types where this immune-genetic interaction is particularly active.
 
By understanding these underlying genetic and immune system interactions, scientists hope to find methods to counteract the negative effects of immune signaling when DNA is under stress. "When we identify the interactions between MRE11 complex functions and immune responses, we may be able to develop therapies that reduce unwanted immune reactions, thus lowering the likelihood of cancer starting in the first place," Dr. Petrini added.
 
Study Methodology and Key Findings
The MSK study involved examining the cellular mechanisms in organoids derived from mice with a specific mutation in the MRE11 complex. These organoids closely mimicked breast tissue and allowed the team to control the oncogene’s activation in a controlled environment. They found that organoids with the mutated MRE11 complex showed an abnormally high activation of ISGs before they even encountered cancer-driving genes. Additionally, the researchers discovered that gene expression changed drastically across 5,600 genes between the normal and mutated organoids, an indication of widespread genome instability.
 
Through further experiments, they also determined that other immune pathways, such as the cGAS-STING pathway, did not significantly contribute to the immune activation. Instead, IFI205 emerged as the primary driver of this immune signaling, causing chronic immune responses that led to changes in the way DNA is packed and accessed within cells. Without IFI205, these cancer-promoting changes in DNA packaging did not occur, which suggests that future cancer therapies could focus on regulating IFI205’s activity.
 
IFI205’s Role in Immune Signaling and Genome Stability
IFI205 is part of the HIN-200 family, proteins that detect DNA damage and stimulate immune responses. Normally, this protein ensures the DNA remains stable by binding to double-stranded DNA and activating immune signaling only when necessary. But in cases where the MRE11 complex is deficient, as in the mice used in the study, IFI205’s constant activation leads to uncontrolled immune responses, making the genetic environment more susceptible to cancer.
In organoids that lacked IFI205, the DNA remained tightly packed, which reduced the chances of oncogenes turning on. This result suggests that IFI205 may be an actionable target in preventing or slowing down cancer in individuals with genomic instability.
 
Implications and Future Research Directions
The Memorial Sloan Kettering team is excited about these findings, which may lead to innovative cancer prevention strategies. By disrupting IFI205 or modulating its interaction with the MRE11 complex, it may be possible to maintain a stable genome even in individuals with genetic vulnerabilities. "If we can find ways to stabilize the genome, perhaps we can slow down or prevent cancer development even in high-risk patients," said Dr. Petrini.
 
The research has also opened up questions about how other immune sensors might affect cancer progression. With further studies, scientists hope to map these complex interactions and develop targeted treatments that prevent the immune system from accidentally aiding cancer development.
 
Conclusion
In summary, this research from MSK illuminates a previously unknown aspect of our immune system: while it fights infections, it can also create conditions that enable cancer to thrive. By linking the MRE11 complex's role in DNA repair to immune system activation, the study provides a framework for understanding how chronic immune responses can increase cancer risk. The researchers hope that their work will pave the way for treatments that prevent cancer by stabilizing DNA and modulating immune responses.
 
The study findings were published in the peer-reviewed journal: Genes & Development.
https://genesdev.cshlp.org/content/early/2024/10/25/gad.351455.123
 
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