By Gilang Cahya 
Researchers from leading international institutions, including the Francis Crick Institute, University College London (UCL), Gustave Roussy, and Memorial Sloan Kettering Cancer Center (MSK), have unveiled a significant discovery linking age-related genetic changes in blood cells to more aggressive cancer and poorer patient prognoses. The study, published in the prestigious New England Journal of Medicine, identifies the presence of "tumour infiltrating clonal haematopoiesis" (TI-CH) as a critical factor associated with increased cancer relapse and mortality. This breakthrough offers a crucial new perspective on how the aging process directly influences the development and progression of solid tumors, a phenomenon with profound implications for an aging global population.
Unraveling the Link Between Aging and Cancer: The Role of Clonal Haematopoiesis
The aging process is intrinsically linked to an accumulation of genetic mutations within our cells. Among these, a condition known as clonal haematopoiesis of indeterminate potential (CHIP) has emerged as a significant area of research. CHIP occurs when blood stem cells acquire mutations over time, influenced by both the natural passage of years and external environmental factors. While CHIP has previously been associated with an elevated risk of age-related disorders such as cardiovascular disease, its direct impact on the evolution of solid cancers has remained largely unexplored until now.
This groundbreaking study, a collaborative effort involving over 400 lung cancer patients from the Cancer Research UK-funded TRACERx and PEACE studies, alongside an extensive dataset of 49,000 patients with various cancer types from MSK, sought to bridge this knowledge gap. The research team meticulously analyzed blood samples to identify individuals with CHIP mutations. The initial findings were striking: the presence of these mutations was correlated with a shorter survival time for patients, irrespective of their age at diagnosis or the stage of their cancer. This observation set the stage for a deeper investigation into the specific mechanisms at play.
Tumour Infiltrating Clonal Haematopoiesis: A New Prognostic Indicator
The subsequent phase of the research focused on determining whether the CHIP-related mutations found in the blood were also present within the cancerous tumors themselves. This infiltration by mutated blood cells was observed in a significant proportion of CHIP-positive patients, specifically in 42% of those studied. The researchers aptly termed this phenomenon "tumour infiltrating clonal haematopoiesis" (TI-CH). Crucially, it was TI-CH, rather than CHIP alone, that emerged as the primary driver of increased risk for cancer relapse and mortality.
This pivotal finding was further corroborated by data from the PEACE study, a comprehensive postmortem investigation that examined metastatic sites—areas where cancer has spread and is often the primary cause of death. The analysis revealed that metastatic tumors at these advanced stages frequently contained TI-CH mutations, underscoring the aggressive nature associated with this phenomenon.
Not All Mutations Are Equal: The Influence of Myeloid Cells and TET2
To understand how TI-CH contributes to poorer patient outcomes, the scientists delved into the cellular composition of lung tumors. They discovered that patients with TI-CH exhibited an expansion of myeloid cells, a specific type of immune cell. While immune cells are generally understood to play a role in fighting cancer, myeloid cells are known to modulate inflammation and can, in certain contexts, actively support tumor progression and metastasis.
The research also highlighted the specific role of mutations in the TET2 gene, a crucial regulator of blood cell production. The study found that when TET2 mutations were present, the affected blood cells were more likely to infiltrate tumors. Further analysis of individual cells from the tumors of two TI-CH patients confirmed that TET2 mutations were predominantly found within myeloid cells, and not in other immune cell populations.
In a significant experimental validation, researchers collaborated with experts in blood cancer and CHIP at the Crick Institute, led by Dr. Dominique Bonnet. They successfully created organoids, essentially miniature lung tumors, incorporating TET2-mutant myeloid cells. This in vitro modeling demonstrated that these mutated myeloid cells actively remodeled the tumor microenvironment and accelerated the growth of the organoids, providing direct evidence of their pro-cancerous role.
Broader Implications: TI-CH in Diverse Cancer Types
The implications of these findings extend beyond lung cancer. In collaboration with researchers at Memorial Sloan Kettering Cancer Center, the team analyzed a vast dataset of over 49,000 patients across a spectrum of cancer types. This large-scale validation confirmed that the presence of TI-CH served as an independent predictor of shorter survival across various malignancies.
However, the prevalence of CHIP and TI-CH varied depending on the cancer type. The study identified these mutations as being more common in cancers that are notoriously difficult to treat, including lung cancer, head and neck cancer, and pancreatic cancer. This observation suggests that TI-CH may be a key factor contributing to the recalcitrance of these aggressive tumors to treatment.
Future Directions and Expert Commentary
The research team has outlined clear next steps for this vital line of inquiry. The immediate focus will be on definitively confirming that CHIP directly contributes to cancer outcomes and on elucidating the precise molecular mechanisms by which CHIP functionally participates in the development of aggressive cancers.
Dr. Oriol Pich, a lead author and Postdoctoral Project Research Scientist at the Crick’s Cancer Evolution and Genome Instability Laboratory, 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," he stated. "This is important because CHIP is a natural phenomenon of ageing that is common in patients with cancer."
Professor Charlie Swanton, Deputy Clinical Director at the Crick and Chief Clinician at Cancer Research UK, highlighted the broader impact of the study. "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," he 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."
This research was made possible through substantial funding from Cancer Research UK and the National Institute of Health and Care Research UCLH Biomedical Research Centre, alongside support from additional philanthropic and governmental bodies. The discovery of TI-CH as a significant factor in cancer progression marks a crucial step forward in understanding the complex interplay between aging and disease, opening new avenues for diagnostic tools and potentially novel therapeutic strategies to combat age-related cancers. The implications for early detection, personalized treatment approaches, and even preventative interventions are profound, offering a glimmer of hope in the ongoing fight against cancer, particularly within an aging demographic.
