Scientists have demonstrated how cancer cells influence neighboring cells to create a favorable niche for the tumor to grow. Understanding this can inform future early-stage cancer therapies [1]
Cancer is a disease of aging. With the exception of childhood cancers, most of which stem from inherited genetic errors, adult cancers tend to occur later in life. It can take years or even decades from an initial mutation for tumors to appear and spread. Most cells with cancerous mutations fail to grow into tumors, but a small number eventually prevails, leading to disease.
One of the key factors that determines the fate of a pre-cancerous cell is its communication with the immediate environment, or stroma, which can either block or support tumor growth [2]. A recent study published in Nature by Erik C. Cardoso and colleagues dissects this relationship in detail in the context of lung adenocarcinoma (LUAD), pointing to the exciting possibility of treating cancers long before they are detected.
Lung cancer often starts with mutations in AT2 cells
The authors focused on LUAD, the most common type of lung cancer, to test how normal lung stem cells become cancer-promoting cells after acquiring cancer-causing mutations. They genetically engineered mice in which a mutation in a critical KRAS gene can be triggered after the animals receive treatment with a drug called tamoxifen. The mutation then only appears in the lungs.
KRAS mutations occur in approximately a third of LUAD cases in patients; however, a single KRAS mutation is not enough to trigger cancer growth, and other changes within the mutant cells and their environment are required [3]. Understanding the exact steps of this process is critical in creating effective treatments.
The first steps in cancer growth are similar to tissue response to injury
Alveolar type II (AT2) cells act as stem cells in the lungs, replacing injured or lost cells of the inner lining, but they also frequently give rise to LUAD. The authors found that when AT2 cells acquire a KRAS mutation, they first enter a transitional “repair-like” state that resembles the lung’s normal response to injury. In this transitional state, AT2 cells carrying mutations begin sending molecular messages that alter nearby fibroblasts and immune cells, gradually creating a microenvironment that supports tumor formation. The authors describe this as the creation of a tumor-permissive niche.
In one of the main findings of the study, the authors identified a signaling molecule called amphiregulin (AREG), which is produced in large amounts by the mutant AT2 cells after they entered the regenerative-like transitional state. AREG activates EGFR signaling in nearby fibroblasts. EGFR is a well-known growth receptor frequently involved in cancer biology.
Non-malignant cells support the tumors and allow them to grow
Fibroblasts are connective tissue cells that normally help maintain lung structure and assist with wound repair. In the mutant environment, however, they are reprogrammed into abnormal fibrotic fibroblasts. These fibroblasts begin expressing genes associated with scarring, wound healing, and extracellular matrix remodeling. Essentially, the lung tissue starts to act as though it has been chronically injured, even though there was no actual wound.
The study also examined immune cells, particularly alveolar macrophages. Macrophages are immune cells that normally help clean debris and fight infection in the lungs. The researchers found that local macrophages are also reprogrammed by the developing tumor environment, adopting a hybrid state with inflammatory and immunosuppressive features. Instead of fighting abnormal cells, these altered macrophages were found to help support tumor development.
Early cancer develops in stages
Interestingly, the sequence of events mattered. First, mutant AT2 cells that have acquired a KRAS mutation enter a regenerative-like state and produce AREG. Second, AREG activates fibroblasts through EGFR signaling. Next, activated fibroblasts remodel the tissue and alter macrophages. Finally, the immune system becomes progressively more supportive of tumor growth, creating a self-reinforcing cycle.
To further test whether this signaling network is truly necessary for tumor formation, the authors blocked different parts of the pathway. When they inhibited EGFR signaling using gefitinib, fibroblast reprogramming was greatly reduced. Macrophage activation was also decreased, and the mutant epithelial cells lost many of their abnormal regenerative features.
They also genetically deleted AREG from the mutant AT2 cells. This had striking effects. Tumor formation dropped significantly, fibrotic fibroblasts were reduced, and immune remodeling was impaired. Without AREG, the mutant cells were much less capable of building a tumor-supportive environment.
Mutant KRAS inhibition breaks up tumor-stoma interactions
Another important aspect of the study was reversibility. The abnormal microenvironment was not permanently fixed at early stages. When the researchers inhibited mutant KRAS signaling using a KRAS-specific inhibitor, many of the abnormal cell states were reversed. Fibroblasts lost their fibrotic characteristics, macrophage remodeling decreased, and epithelial cells regained more normal identities. This suggests that the early tumor-supportive niche remains plastic and potentially treatable before advanced cancer develops.
Similarities in human cancer tissues
The team then investigated whether these findings also apply to human lung cancer. They analyzed single-cell sequencing data from patients with early-stage lung adenocarcinoma. Similar populations of regenerative-like tumor cells were identified in human tumors, and these cells also express high levels of AREG. In addition, human tumors were found to contain fibroblasts with fibrotic gene signatures similar to those seen in mice.
To further validate the results, the researchers created human lung organoids using primary human AT2 cells engineered to express mutant KRAS. These organoids reproduced many of the same features seen in mice. The human mutant cells entered transitional regenerative states, expressed AREG, and induced fibrotic changes in surrounding fibroblasts. Once again, EGFR inhibition blocked these effects.
Key takeaways
Overall, the paper argues that cancer initiation is not simply a matter of mutant cells growing uncontrollably. Instead, the earliest stages of cancer involve active cooperation between mutant epithelial cells, fibroblasts, and immune cells. Mutant cells effectively “educate” their surroundings to support future tumor growth.
The findings are clinically important because they identify a potentially vulnerable window before full cancer develops. Current lung cancer treatments are often given after tumors are already advanced and resistant to therapy. This work suggests that interrupting early communication between mutant cells and their microenvironment — especially the AREG-EGFR signaling pathway — could prevent tumors from establishing supportive niches in the first place.
Literature
[1] Cardoso, E. C., Lee, H., England, F. J., Cho, H., Lu, R., Varankar, S. S., … & Lee, J. H. (2026). Early fibrotic niches establish tumour-permissive microenvironments. Nature, 1-11.
[2] Yuan, S., Stewart, K. S., Yang, Y., Abdusselamoglu, M. D., Parigi, S. M., Feinberg, T. Y., … & Fuchs, E. (2022). Ras drives malignancy through stem cell crosstalk with the microenvironment. Nature, 612(7940), 555-563.
[3] Guerra, C., Mijimolle, N., Dhawahir, A., Dubus, P., Barradas, M., Serrano, M., … & Barbacid, M. (2003). Tumor induction by an endogenous K-ras oncogene is highly dependent on cellular context. Cancer cell, 4(2), 111-120.
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