By Lina carolina 
Researchers from leading institutions including the Francis Crick Institute, University College London (UCL), Gustave Roussy, and Memorial Sloan Kettering Cancer Center (MSK) have made a groundbreaking discovery: the expansion of mutant blood cells, a phenomenon commonly associated with aging, can be found within cancerous tumors. This presence, termed tumour infiltrating clonal haematopoiesis (TI-CH), is directly linked to poorer prognoses for patients, suggesting a complex interplay between the aging process and cancer progression.
The implications of this research are far-reaching, particularly as global populations continue to age. Understanding the biological mechanisms that connect age-related genetic changes to diseases like cancer and cardiovascular disease is paramount for developing effective preventative and therapeutic strategies. This study, published in the prestigious New England Journal of Medicine, sheds critical light on one such connection, revealing how common age-associated cellular changes within the blood can directly influence the trajectory of solid tumors.
The Emergence of Clonal Haematopoiesis of Indeterminate Potential (CHIP)
Clonal haematopoiesis of indeterminate potential (CHIP) is a condition characterized by the accumulation of mutations in blood stem cells over time. This process is influenced by a combination of intrinsic aging mechanisms and external environmental factors, such as exposure to carcinogens or toxins. While CHIP has previously been identified as a risk factor for age-related disorders, including cardiovascular disease, its specific role in the evolution and progression of solid cancers has remained an area of intense investigation.
The current study involved an extensive analysis of over 400 patients with lung cancer, drawn from Cancer Research UK-funded studies TRACERx and PEACE. This cohort was further augmented by data from approximately 49,000 patients with various cancer types at MSK, providing a robust and diverse dataset for analysis.
CHIP and Its Impact on Cancer Prognosis
The initial phase of the research involved analyzing blood samples from patients to identify the presence of CHIP mutations. By correlating this genetic information with clinical data, the scientists observed a significant association: patients with CHIP mutations in their blood lived for a shorter duration, irrespective of their age at diagnosis or the stage of their cancer. This finding underscored the systemic impact of these age-related blood cell mutations.
However, the research team sought to delve deeper, investigating whether these CHIP mutations were not only present in the blood but also actively infiltrating the solid tumors themselves. Through detailed analysis, they discovered that in 42% of patients with CHIP, the specific mutations were indeed found within their lung tumors, a phenomenon they termed tumour infiltrating clonal haematopoiesis (TI-CH). Crucially, it was the presence of TI-CH, rather than CHIP alone, that was strongly associated with a higher risk of cancer relapse and, consequently, cancer-related mortality.
This pivotal finding was further corroborated by the PEACE study, a postmortem investigation that examined metastatic sites – the areas where cancer has spread and is often the primary cause of death. The analysis of metastatic tumors from these sites revealed a frequent presence of TI-CH mutations, reinforcing the link between these infiltrating mutant blood cells and the aggressive nature of advanced cancer.
Differentiating Mutation Impact: Not All Clones Are Equal
To unravel the intricate relationship between TI-CH and poor patient outcomes, the scientists conducted a detailed examination of the cellular composition within lung tumors. Their findings revealed that patients with TI-CH exhibited an expansion of myeloid cells, a specific type of immune cell. Myeloid cells play a critical role in the tumor microenvironment. Unlike other immune cells that are programmed to detect and combat cancer, myeloid cells have been implicated in regulating inflammation and, more concerningly, in supporting tumor growth and dissemination.
The research also highlighted the differential impact of specific mutations. Mutations affecting the TET2 gene, a key regulator of blood cell production, were found to be particularly influential. Across thousands of individuals studied, blood cells carrying TET2 mutations demonstrated a greater propensity to infiltrate tumors. Further investigation, involving the single-cell analysis of hundreds of cells from the tumors of two patients with TI-CH, confirmed that TET2 mutations were predominantly located within myeloid cells, with minimal presence in other immune cell types. This specificity suggests a targeted role for these mutant myeloid cells in cancer progression.
In a significant experimental validation, the research team collaborated with experts in blood cancer and CHIP at the Crick, led by Dominique Bonnet. Together, they developed organoids – miniature, lab-grown models of lung tumors – incorporating TET2-mutant myeloid cells. This experimental approach demonstrated that these TET2-mutant myeloid cells actively remodeled the tumor microenvironment and accelerated the growth of the tumor organoids. This provided direct evidence of the functional contribution of these mutant cells to tumor aggressiveness.
Global Validation and Future Directions
The study’s reach extended beyond lung cancer through a collaboration with researchers at Memorial Sloan Kettering Cancer Center in the United States. By analyzing a substantially larger dataset of over 49,000 patients with diverse cancer types, the findings were rigorously validated. The presence of TI-CH emerged as an independent predictor of shorter survival across multiple cancer types.
Furthermore, the prevalence of CHIP and TI-CH varied depending on the specific cancer. These mutations were found to be more common in cancers that are notoriously difficult to treat, such as lung cancer, head and neck cancers, and pancreatic cancer. This observation suggests that the influence of age-related blood cell mutations might be particularly pronounced in certain aggressive tumor types.
The next critical steps for this line of research involve definitively confirming that CHIP directly contributes to the observed cancer outcomes. Additionally, scientists aim to meticulously detail the exact mechanisms by which CHIP functionally implicates itself in the development of aggressive cancers.
Expert Commentary and Broader Implications
Oriol Pich, a Postdoctoral Project Research Scientist at the Crick’s Cancer Evolution and Genome Instability Laboratory and a lead author of the study, emphasized the significance of the findings. "Our results show that blood cells carrying age-related mutations can infiltrate tumors and impact cancer evolution, leading to worse outcomes for patients," Pich stated. "This is important because CHIP is a natural phenomenon of ageing that is common in patients with cancer."
Charlie Swanton, Deputy Clinical Director at the Crick, Chief Clinician at Cancer Research UK, and Chief Investigator for TRACERx, highlighted the novel aspect of the research. "This is the first time that we’ve been able to see at scale, the interaction of two different types of ‘clonal proliferations’, age-related CHIP and cancer, providing insight into how ageing might impact cancer risk," Swanton commented. "As we start to piece together the picture of the most important mutations which evolve during the ageing process in cells from the bone marrow, and the impact they have in disease, we hope we can start to identify opportunities for intervention and maybe even prevention of some age-related cancers."
The potential for early intervention and prevention is a key implication of this research. If CHIP can be detected early, and its role in promoting cancer progression is further elucidated, it may open avenues for therapeutic strategies aimed at mitigating the risk of aggressive cancer in aging individuals. This could involve therapies that target the expansion or infiltration of mutant myeloid cells, or interventions that bolster the immune system’s ability to counteract their pro-tumorigenic effects.
This extensive research was generously supported by Cancer Research UK and the National Institute of Health and Care Research UCLH Biomedical Research Centre, alongside other dedicated funders. The collaborative nature of the study, spanning multiple leading research institutions, underscores the global effort to unravel complex biological processes that impact human health.