Image from Darryl Leja, NHGRI
Growing cancer cells (purple) surrounded by healthy cells (pink), illustrating a primary tumor spreading to other parts of the body
Through extensive analyses of data from The Cancer Genome Atlas (TCGA), researchers have produced a new resource known as the Pan-Cancer Atlas.
Multiple research groups analyzed data on more than 10,000 tumors spanning 33 types of cancer, including acute myeloid leukemia and diffuse large B-cell lymphoma.
The work revealed new insights regarding cells of origin, oncogenic processes, and signaling pathways.
These insights make up the Pan-Cancer Atlas and are described in 27 papers published in Cell Press journals. The entire collection of papers is available through a portal on cell.com.
The Pan-Cancer Atlas is the final output of TCGA, a joint effort of the National Cancer Institute (NCI) and the National Human Genome Research Institute (NHGRI) to “collect, select, and analyze human tissues for genomic alterations on a very large scale.”
“This project is the culmination of more than a decade of ground-breaking work,” said Francis S. Collins, MD, PhD, director of the National Institutes of Health.
“This analysis provides cancer researchers with unprecedented understanding of how, where, and why tumors arise in humans, enabling better informed clinical trials and future treatments.”
The project focused on genome sequencing as well as other analyses, such as investigating gene and protein expression profiles and associating them with clinical and imaging data.
“The Pan-Cancer Atlas effort complements the over 30 tumor-specific papers that have been published by TCGA in the last decade and expands upon earlier pan-cancer work that was published in 2013,” said Jean Claude Zenklusen, PhD, director of the TCGA Program Office at NCI.
The Pan-Cancer Atlas is divided into 3 main categories—cell of origin, oncogenic processes, and signaling pathways—each anchored by a summary paper that recaps the core findings for the topic. Companion papers report in-depth explorations of individual topics within these categories.
Cell of origin
In the first Pan-Cancer Atlas summary paper, the authors review the findings from analyses using a technique called molecular clustering, which groups tumors by parameters such as genes being expressed, abnormality of chromosome numbers in tumor cells, and DNA modifications.
The analyses suggest that tumor types cluster by their possible cells of origin, a finding that has implications for the classification and treatment of various cancers.
“Rather than the organ of origin, we can now use molecular features to identify the cancer’s cell of origin,” said Li Ding, PhD, of Washington University School of Medicine in St. Louis, Missouri.
“We are looking at what genes are turned on in the tumor, and that brings us to a particular cell type. For example, squamous cell cancers can arise in the lung, bladder, cervix, and some tumors of the head and neck. We traditionally have treated cancers in these areas as completely different diseases, but, [by] studying their molecular features, we now know such cancers are closely related.”
“This new molecular-based classification system should greatly help in the clinic, where it is already explaining some of the similar clinical behavior of what we thought were different tumor types,” said Charles Perou, PhD, of UNC Lineberger Comprehensive Cancer Center in Chapel Hill, North Carolina.
“These findings also provide many new therapeutic opportunities, which can and will be tested in the next phase of human clinical trials.”
Oncogenic processes
The second Pan-Cancer Atlas summary paper presents a broad view of the TCGA findings on the processes that lead to cancer development and progression.
The research revealed insights into 3 critical oncogenic processes—germline and somatic mutations, the influence of the tumor’s underlying genome and epigenome on gene and protein expression, and the interplay of tumor and immune cells.
“For the 10,000 tumors we analyzed, we now know—in detail—the inherited mutations driving cancer and the genetic errors that accumulate as people age, increasing the risk of cancer,” Dr Ding said. “This is the first definitive summary of the genetics behind 33 major types of cancer.”
“TCGA has created a catalogue of alterations that occur in a variety of cancer types,” said Katherine Hoadley, PhD, of University of North Carolina at Chapel Hill.
“Having this catalogue of alterations is really important for us to look, in future studies, at why these alterations are there and to predict outcomes for patients.”
Signaling pathways
The final Pan-Cancer Atlas summary paper details TCGA research on the genomic alterations in the signaling pathways that control cell-cycle progression, cell death, and cell growth. The work highlights the similarities and differences in these processes across a range of cancers.
The researchers believe these studies have revealed new patterns of potential vulnerabilities that might aid the development of targeted and combination therapies.