Stem cells and cancer cells have enough molecular similarities that the former can be used to trigger immunity against the latter.
With much of his early career dictated by US Navy interests, Carl June drew inspiration from malaria, bone marrow transplantation, and HIV in his roundabout path to a breakthrough in cancer immunotherapy.
April 1, 2014|
COURTESY OF UNIVERSITY OF PENNSYLVANIAIn 1971, as Carl June geared up to graduate from his San Francisco Bay–area high school, the Vietnam War raged on. He had been accepted to Stanford University, Caltech, and others, but with the risk of being drafted into the already decade-long war, June opted to attend the United States Naval Academy (USNA) in Annapolis, Maryland, “with the rationale that it would make me an officer, rather than going in as an enlisted person into the rice paddies,” he says.
A year earlier, the school had launched its premed program. With a knack for biology, June jumped on the opportunity, joining 15 others in the second USNA premed class. More good fortune struck when the U.S. pulled its troops out of Vietnam in 1973, “so when I graduated there was no longer a war, which I was happy about,” June recalls. Rather than sending him overseas, the Navy gave June a full ride to medical school at Baylor College of Medicine in Texas, where he completed the required coursework in three years. He then jetted off to Geneva, Switzerland, to join a lab conducting research on malaria vaccines at the World Health Organization for the fourth year of his scholarship. “My last year [of med school] was really a transformative year for me,” he says. Although June went on to train as a leukemia oncologist—and never got a PhD—that year in Geneva showed him he was a lab scientist at heart.
To repay the Navy’s subsidizing his extensive education, which included almost three years at the Fred Hutchinson Cancer Research Center in Seattle as an oncology fellow, June spent an additional 12 years in the service. His research throughout that time was dictated in large part by the interests of the US Navy, which did not include cancer research. But every step of the journey ended up providing a critical clue in his current work developing immunotherapies for cancer, June says. “It turned out to be a huge blessing in disguise.”
“Up until then, it was just a handful of what people regarded as kooks or zealots doing this. And then all of a sudden people believed in it.”
In 2010, decades of work culminated in the long-term remissions of refractory leukemia in two of three people. June’s team extracted and genetically modified the patients’ T cells to target a B-lymphocyte antigen, then reinfused the cells back into the bloodstream. When June and his colleagues reported that the patients were still cancer-free a year later, “it ignited a firestorm,” June says. “Up until then, it was just a handful of what people regarded as kooks or zealots doing this. And then . . . all of a sudden people believed in it. The cancer field now sees this as a viable option for therapy.”
Here, June talks about how treating HIV and cancer are really two sides of the same coin; how diverse research fields and diverse comrades have taught him lifelong lessons; and how his career path changed when cancer struck his own family.
Radiation calls. Following his medical training at Baylor, and then a four-year residency at the National Naval Medical Center in Bethesda, June headed off to Seattle in 1983 to the Fred Hutchinson Cancer Research Center, where he specialized in bone-marrow transplants. “The Navy back then was interested in having bone-marrow transplantation,” June recalls, “ because it was one way to treat radiation casualties,” such as those caused by exposure during submarine reactor accidents.
Growing T cells. June moved to Seattle just as monoclonal antibody technology was first becoming widely available. By chance, his predecessor at the Hutchinson Center had been working on antibodies against CD28, a surface molecule expressed on T cells that serves as coreceptor for T-cell activation. “I began working with those, and with my mentors Paul Martin, John Hansen, and Jeffrey Ledbetter, we found that they had really amazing effects on T cells,” June says. The anti-CD28 antibodies mimicked a natural ligand that served as the long-predicted “signal 2” necessary to initiate T-cell proliferation (signal 1 being a foreign antigen). “It turned out to be the key to make T cells grow,” he says. “So basically by being in the right place at the right time, I found out by luck that we could make T cells grow really efficiently. . . . We had the first very robust and physiologic T-cell culture system.”
A lab of his own. In 1986, June returned to Bethesda, where, in his own lab at the Naval Medical Research Institute (NMRI), his research was once again dictated by Navy needs. This time, it was infectious disease, “which is still a main problem . . . that the military faces overseas,” June says. Specifically, he began to study how to restore the immune systems of HIV patients, and because he’d been working with CD28, he knew just what to do: grow them some new T cells. With postdoc Bruce Levine, June developed beads coated in anti-CD28 antibodies to bind T cells from the blood of HIV patients, which, along with anti-CD3 serving as a surrogate for “signal 1,” spurred the cells’ proliferation. The researchers then separated the beads, which contain iron, from the cells using a magnet and reinfused the cells into the patients. “We studied people who had T-cell depletion from HIV and used what we had learned in the lab to grow [their] T cells,” June says. “And we found, lo and behold, their T-cell counts went up, and their immune function got better.”
An immunology CAR show. Having proved that this so-called adoptive T-cell transfer strategy was safe and effective, June and others began to wonder if they could modify the T cells ex vivo to make them even more potent when transferred back into patients. In 1991, Arthur Weiss of the University of California, San Francisco, developed the first-ever chimeric antigen receptor (CAR), called CD4-zeta, as a tool for studying T-cell activation, and the nearby biotech company Cell Genesys thought that it might have potential for treating HIV. The extracellular domain of the CAR bound an HIV envelope protein, while the internal zeta chain mediated T-cell activation. The company called upon June to insert the CAR into patients’ T cells, and together the collaborators launched the first human CAR trials, engineering the T cells of HIV patients to express CD4-zeta before reinfusing the cells into the blood. It worked: the researchers documented the long-term persistence of the gene-modified T cells, and once again, the patients’ immune function improved.
Out of the Navy. June finished his obligation to the Navy in 1996, and a few years later accepted a position at the University of Pennsylvania in Philadelphia (Penn), where he finally dove headfirst into cancer research. And he used the same exact approach he had taken to studying HIV. In 2001, June teamed up with Penn’s David Porter to test adoptive T-cell transfer treatment of cancer in the clinic. The first trials, conducted with leukemia patients, were simple: using the same beads he and Levine had invented at NMRI, the researchers took patients’ T cells, grew them in the lab, reinfused them, then watched as the patients’ T-cell counts climbed and their immune function improved. “What we had learned in HIV, how to efficiently grow cells, gave us a big advantage over the people who had only a cancer background,” June says.
Making it real. Just as with HIV, the next step was to make the T-cell therapy even more effective by modifying the cells ex vivo. June’s postdoc Michael Milone developed a CAR that targets CD19, a B cell–specific surface protein that’s expressed on cancerous cells in about half of leukemia cases, but not expressed on other cell types. After some promising animal studies, the researchers treated their first three patients. “It’s been kind of a dream since 2010, when we first started the leukemia trials,” June says. “In the first few days after we treated, we saw quite a striking antileukemia effect. . . . At first I was nervous, and I’m sure David Porter was too. We would wake up every day kind of pinching ourselves to see, did these things really happen and would the patients relapse tomorrow, for instance? But three years out now, they haven’t.” At the American Society of Hematology meeting last December, June and his team reported on an additional 56 patients from trials in pediatric acute lymphoblastic leukemia (ALL), adult ALL, and chronic lymphocytic leukemia, who showed an overall response rate of 72 percent , with many experiencing complete remission. “We’re continuing to see very potent activity and it’s very exciting.”
Let the good times roll. For years, adoptive T-cell therapy “was purely academic; there was no interest from the pharmaceutical field,” June says. But that’s all changed now. Novartis was the first to join the field in August 2012, when the company licensed the intellectual property invented in June’s lab from The University of Pennsylvania. Next came Kite Pharma, which is partnering with the National Cancer Institute on CAR therapies developed by Steven Rosenberg’s group. Most recently, Juno Therapeutics announced in January 2014 that it had raised $145 million to advance T-cell immunotherapies for cancer, drawing on technologies developed at the Memorial Sloan Kettering Cancer Center and the Fred Hutchinson Cancer Research Center, among others. “It’s an amazing turnaround,” June says. “It’s gone from this small group of academic scientists doing this in academic boutique settings to where this is now a very substantial investment by the pharmaceutical and biotechnology industries.”
What’s next? “The main science question now facing the field is: ‘Can this, and how can this kind of technology be applied to the more common solid cancers?’” June says. To address these cancers, another one of June’s former postdocs, Carmine Carpenito, designed a CAR with a high affinity for mesothelin, a human protein that is overexpressed in a variety of cancers. With Penn’s Yangbing Zhao, June is now testing the CAR—introduced to cells via nonpermanent mRNA expression—in patients with pancreatic cancer and mesothelioma. “We’ve seen in pilot studies signs of activity that are encouraging, and other centers are just getting underway as well,” June says. “There will be trials in virtually any cancer you can name within the next year or so.”
HIV roots. Through it all, June has continued the HIV research that he began during his time in the Navy. Taking inspiration from a patient in Berlin who was functionally cured of HIV in 2008 after receiving a bone marrow transplant from a donor with a mutation in the HIV coreceptor gene CCR5, June, his postdoc Elena Perez, and their colleagues designed zinc-finger nucleases to knock out CCR5 in patients’ T cells. With Penn infectious disease specialist Pablo Tebas, they have completed a Phase 1 trial that “looks really promising,” says June, who points out the similarities between the approaches he has taken to treat cancer and to treat HIV. “There’s been cross-pollination both ways. It’s the same principle of engineering the immune system: in the case of cancer we do it so the immune system will reject the tumor, and in the case of HIV one major approach is to make the immune system so it can’t be infected.”
Life on the field. While he excelled academically, June valued his time as a defensive lineman on the high school football team, where he got to interact with a diverse group of people. “It was a very useful thing,” he says. “There, I saw the entire population and not just people who could do well in academics. And some people who grow up in a very elite, rarefied environment never do; they have no idea what the average person’s like.” And he was pretty good, being scouted for the Naval Academy’s football team out of high school. But at just 205 pounds, he didn’t make the cut for the Division I team. “They played Notre Dame that year; they played Michigan,” he recalls. “I would have gotten slaughtered.”
Who needs a PhD? Although he has spent most of his career in the lab, June never did get a PhD. “[The Navy wasn’t] interested in training PhDs; they wanted medical officers,” June says. And in the end, he found, it didn’t really matter. “You don’t need more than one degree is my feeling.” He told his two grown sons to figure out whether they wanted to work in the lab or the clinic, and choose either an MD or a PhD track based on that. They each followed his advice and came to opposite conclusions: one son, a biomechanical engineer, is now an assistant professor at Montana State University, while the other became a rheumatologist and recently accepted an assistant professorship at Penn State University. “And I’m very proud of both of them,” June says.
From the heart. When June’s first wife was diagnosed with ovarian cancer in late 1995, he gained a whole new perspective on the disease. “I’m trained as a leukemia oncologist, but until you actually see someone firsthand, from the other side of the bed, having cancer and the side effects and all that . . .” he trails off. “It really helped me. I learned a lot about translational medicine.” The experience motivated him to shift his research focus from the basic work he’d been doing on signal transduction and growing T cells in culture to actually getting these therapies into patients. “My wife died in 2001, and we treated our first leukemia patient [that same year].”