Cancer Biology, Genetics
The Johns Hopkins University
Dr. Vogelstein is also Clayton Professor of Oncology and Pathology and director of the Ludwig Center for Cancer Genetics and Therapeutics at the Sidney Kimmel Comprehensive Cancer Center of the Johns Hopkins University School of Medicine.
Cancer Genetics and Its Implications for Patients
Throughout his career, Bert Vogelstein has sought to define the genetic changes that drive human cancers. Now that most of these changes have been identified, his work is focused on using what he has learned to develop therapies and diagnostic methods to improve patients’ lives.
Vogelstein demonstrated that a tumor forms when genetic mutations cause a cell to lose its normal growth controls, and that tumors become more dangerous as additional mutations derail more growth-controlling genes. He also found that this process is accelerated by mutations that change how quickly new mutations arise.
By analyzing human tumors, Vogelstein’s team found that most colorectal cancers begin with a mutation in a gene called APC, and then went on to uncover how APC normally regulates colon cell growth. They also characterized mutations in other growth pathways that cause tumors to progress, as well as genes that are important for maintaining genetic stability in the colon.
More recently, Vogelstein’s team analyzed protein-coding genes in many types of human tumors and found that most contained 50 to 100 genetic alterations whose effects could be tied to about a dozen signaling pathways. Identifying those pathways has steered researchers toward potential new approaches to diagnosis and treatment.
In addition, Vogelstein’s group has developed blood tests to identify patients with inherited predispositions to colorectal cancer, as well as a variety of tests for the early detection of cancers. These tests are all based on a technology he and his colleague Kenneth Kinzler invented, called “digital PCR,” that can detect a single mutant gene among tens of thousands of normal copies of the same gene.
Vogelstein’s team is also developing therapies that target the unique vulnerabilities in cancer cells that result from their mutations. For example, in the past year, his team has shown that patients whose tumors contain a specific type of genetic alteration are extraordinarily sensitive to a specific form of immunotherapy. This therapy can result in pronounced regressions of tumors with this defect, even in advanced cancer patients.
Over the past three decades, Bert Vogelstein and his team have uncovered many of the molecular pathways that allow tumor cells to multiply and spread. Along the way, they established a genetic model that has become the paradigm for understanding how cancers originate and develop. Now, they are focused on using this knowledge to save lives.
Vogelstein trained as a pediatric oncologist at Johns Hopkins University School of Medicine, and one of his first patients was a four-year-old with leukemia. “There was this precious little girl with a disease that we knew almost nothing about,” he explains. A feeling of helplessness drove him to the research lab, where he began studying a variety of cancers. Soon, Vogelstein joined a group of scientists at Hopkins who were analyzing colon tumor samples in various stages of progression. He was able to develop an experimental approach that showed the tumors came from a single initiating cell in the normal colon. Since then, Vogelstein has spent much of his life trying to identify the genetic events that cause this single cell to multiply and form a tumor.
Surprisingly, one of the first fruits of his endeavors was TP53 – a gene that was not known to be important in human cancer. Vogelstein and his graduate student Suzanne Baker discovered that TP53 is a tumor suppressor whose protective function goes haywire when it’s mutated. Working with graduate student Janice Nigro, Baker and Vogelstein went on to show that TP53 is inactivated in most types of human cancer – a discovery that stimulated a revolution in cancer research. More than 30,000 mutations of TP53 have since been identified in human cancers.
Vogelstein then joined forces with his former graduate student Kenneth Kinzler, now a professor and colleague at Johns Hopkins, to show that mutations in a gene called APC are the cause of nearly all colorectal tumors. The team also discovered other genes responsible for hereditary colorectal cancers, drastically changing the health management of families afflicted with these disorders.
More recently, Kinzler, Vogelstein, and their colleagues sequenced the first “cancer genome.” The analysis revealed a number of genes that are altered in typical breast, colon, pancreas, and brain tumors, and laid the foundation for understanding the scientific and biomedical implications of the cancer genome. This, in turn, paved the way for so-called precision medicine, in which clinicians look for the characteristics of each person’s cancer and tailor therapies to guide their treatment.
Many of Vogelstein’s current projects are aimed at devising better diagnostics and treatments for cancer patients. His group pioneered the idea that somatic mutations represent uniquely specific biomarkers for cancer patients. This work led to the first FDA-approved DNA mutation-based screening tests. Since then, his group has created powerful technologies to screen for biomarkers in patients, such as “liquid biopsies” that evaluate blood samples to obtain information about underlying tumors and their responses to therapy. More recently, Vogelstein’s group showed that a tumor’s genomic information can be used to guide immunotherapy.
“The challenge now is to transform the revolution in understanding this group of diseases to a revolution in the care of patients,” says Vogelstein. “Though this will take copious effort, medical history suggests it is only a matter of time.”