Contrary to popular belief, cancer doesn’t just grow at its periphery, but uniformly throughout its entire mass, researchers from the University of Cologne and the Centre for Genomic Regulation (CRG) in Barcelona have found. This discovery, published in the journal eLife, contradicts long-held beliefs about how the disease proliferates and expands.
Dr. Donate Weghorn, a co-author of the study from CRG, asserts, “We’re debunking the notion that a tumor has a ‘two-speed’ growth pattern, with rapid cell division at the periphery and slower activity within the core. Our research shows that every region of the tumor has equal growth activity and the potential to develop harmful mutations.”
These findings hold significant implications for understanding tumor evolution. As Prof. Johannes Berg, another co-author of the study from the University of Cologne, explains, “The continuous cycle of cell death and regeneration throughout the tumor provides cancer numerous opportunities for evolutionary breakthroughs, such as evading immune detection.”
For the past half-century, it has been theorized that cancer grows faster at the edge due to certain advantages. For instance, peripheral cells have easy access to nutrients and oxygen from neighboring healthy tissues and can dispose of waste more efficiently.
As the tumor grows, its center becomes increasingly distanced from surrounding blood vessels, receiving less oxygen and nutrients. These central cells also face greater mechanical pressure, hindering their ability to multiply.
However, this study refutes the above notion, showing that cancer growth is not confined to the edges. The researchers made this discovery using spatial genomics, a method that examines the genetic information of cells in their exact locations within a tissue. By analyzing data from previous studies, the researchers mapped the mutations across different parts of liver tumors in both two and three dimensions.
The researchers evaluated the mutations in each sample and established a method to determine the direction and spread of these mutations. They found that the angles between parent cells and their mutated offspring were evenly distributed in all directions, indicating uniform growth throughout the tumor.
The study also investigated how mutations were dispersed within the tumor. The researchers found that mutations were spread out, suggesting that cell division was happening across the entire tumor.
To further validate their findings, the researchers used computer simulations to create virtual tumors with surface growth and volume growth and compared the mutation patterns in these simulated tumors with those in real ones. The real tumors’ mutation patterns aligned with the volume growth simulations rather than the surface growth ones.
The study, however, had its limitations. It focused primarily on liver cancer, so the findings may not be applicable to all cancer types. Also, the study mainly provides insights into the early stages of tumor growth, which may not fully depict the behavior of larger or metastatic cancers.
Dr. Berg concluded, “Our research focuses on early-stage tumor growth. However, exploring later-stage mutations can give us more insight into why these mutations often undermine many therapeutic strategies.”
