Researchers from the Wellcome Sanger Institute, the University of Cambridge, Cambridge University Hospitals NHS Foundation Trust, Great Ormond Street Hospital for Children NHS Trust and the UCL Great Ormond Street Institute of Child Health studied the genomes of tumours from multiple sites in two patients with the condition. In both cases the tumours within a patient arose separately from each other, with their origins in embryonic development. Their findings, published in the New England Journal of Medicine, may be relevant for treating other types of bilateral tumours.
Neuroblastoma is a highly aggressive childhood cancer. About 100 children each year in the UK are affected. It develops from specialised nerve cells - neuroblasts - left behind from a baby's development in the womb*.
Neuroblastoma most commonly occurs in one of the adrenal glands above the kidneys. There are several different types of neuroblastoma, with some more aggressive than others. In rare cases, bilateral tumours occur, for example in both adrenal glands.
Similarly to the evolution of species, individual cells in the body are subject to forces of mutation and selection as they grow. These ‘somatic mutations’ are passed from one cell to another as it divides**. Over a lifetime, different mutations accumulate in the DNA of different cells. By comparing the patterns of somatic mutations between tumour cells and healthy cells, it is possible to trace their evolutionary history.
In this new study, researchers at the Wellcome Sanger Institute extensively sequenced the genomes of bilateral neuroblastoma. Evolutionary genomics showed that the neuroblastoma tumours in an individual arose independently at the very earliest stages of life, within a few cell divisions after fertilization. Both children in the study had inherited a genetic mutation that predisposed them to cancer.
Tim Coorens, first author of the study from the Wellcome Sanger Institute, said: “Thanks to advances in sequencing technologies and developments in analysis methods, it has recently become possible to trace the origin of childhood cancer right back to the embryo. It’s a paradigm shift in how we think about tumours, and how they are related to each other before they became tumours. The parallel evolution of independent tumours was an unexpected and fascinating finding, which reveals the very origin of neuroblastoma within the first few divisions of the fertilised egg.”
Understanding if tumours within a patient are independent or not is vital information for clinicians when deciding the best treatment options. It is usually assumed that tumours at multiple sites are metastatic disease that spread from an original primary tumour. A tumour that has metastasised and spread from one site to another is more aggressive – and requires more intensive treatment – than one that remains within a tissue microenvironment.
Professor John Anderson, senior author of the study from the UCL Great Ormond Street Institute of Child Health and Great Ormond Street Hospital for Children NHS Foundation Trust, said: “This is the first time we’ve been able to prove that bilateral neuroblastoma tumours can be independent entities. It is essential for each patient that clinicians can make the distinction between an aggressive tumour that is spreading, and a set of more benign tumours that are localised. If tumours haven’t metastasised, we can consider less intensive treatments, with fewer side effects.”
The researchers suspect that other types of bilateral tumours may also have similar patterns of development, and so their findings are important more widely for analysing and treating such cancers.
Mark Brider, Children with Cancer UK CEO, said: “Neuroblastoma is one of the most common childhood tumours with around 100 children diagnosed in the UK each year. Yet, it also has one of the lowest survival rates – in its high-risk form, the survival rate is sadly around just 50%.
“We welcome these findings as an important step towards the development of kinder, safer, and more personalised, treatments for children with neuroblastoma which will help reduce the long-term, and often life-limiting, side effects of current aggressive treatments."
Dr Sam Behjati, lead author of the study from the Wellcome Sanger Institute and Addenbrooke’s Hospital, Cambridge, said: “We are in a world now where genome sequencing tumours is a part of healthcare. It is becoming an important tool in the clinic for treating childhood cancers. Using genomics to analyse a tumour’s origins can give us detailed insight into what we are dealing with and how to tackle it.”
*https://www.nhs.uk/conditions/neuroblastoma/
** https://www.ncbi.nlm.nih.gov/books/NBK21894/
Professor David Rowitch at University of Cambridge, who was not part of the study commented, “This major finding allows researchers to trace the cell origins of paediatric cancers to their very roots. This information will help doctors tailor therapies for children’s cancer based on a deep understanding of biology.”
Publication:
“Lineage-Independent Tumors in Bilateral Neuroblastoma” Tim H.H. Coorens et. al. N Engl J Med 2020;383:1860-5. DOI: 10.1056/NEJMoa2000962 http://www.nejm.org/doi/full/10.1056/NEJMoa2000962