Dana-Farber Cancer Institute scientists report they have shrunk or slowed the growth of notoriously resistant pancreatic tumors in mice, using a drug routinely prescribed for malaria and rheumatoid arthritis.
The pre-clinical results, which will appear in the April issue of the journal Genes & Development and is currently published on its web site, have already prompted the opening of a small clinical trial in patients with advanced pancreatic cancer, one of the deadliest and hardest-to-treat forms of cancer, said the investigators, led by Alec Kimmelman, MD, PhD, a radiation oncologist at Dana-Farber.
“We are seeing robust and impressive responses in pancreatic cancer mouse models,” said Kimmelman, whose laboratory specializes in studies of pancreatic cancer, the fourth-leading cause of cancer death in the United States. The oral drug, hydroxychloroquine, is inexpensive, widely available, and causes relatively mild side effects, he said. A second, planned clinical trial will combine the drug with radiation.
“While these findings are indeed exciting and a cause for optimism, one needs to be mindful that so far the effects, while impressive, have only been shown in mice,” said Ronald DePinho, MD, director of the Belfer Institute for Applied Cancer Science at Dana-Farber. “I eagerly await to see how the human studies will progress.”
A new treatment avenue would be extremely welcome in pancreatic cancer. The National Cancer Institute estimates that 43,140 people were diagnosed in 2010 and 36,800 died. Despite some recent gains with targeted molecular agents and combination regimens, only about 6 percent of patients live five years, and the median survival is less than six months.
Hydroxychloroquine is a form of the drug chloroquine, which is used to prevent and treat malaria and also prescribed for autoimmune diseases, including lupus and rheumatoid arthritis. These compounds have recently stirred much interest in cancer research, because they inhibit a process called autophagy (from the Greek for “self-eating”) that is elevated in cancer cells.
Autophagy is present in normal cells as well, but at a much lower level. The process enables cells to break down and eliminate proteins, such as damaged cell membranes and worn-out organelles like mitochondria. But it is also a survival strategy. When nutrients are scarce, cells can digest and feed on their own non-critical proteins to avoid starvation.
Cancer cells also use autophagy to outwit chemotherapy treatment. Research has shown that cancer cells can activate this process in response to a variety of cancer treatments, allowing them to survive during the stress of therapy. But, as Kimmelman noted, autophagy can also be a cell-death mechanism. Cancer researchers are intensely studying – and debating – how to manipulate autophagy as a potential method to slow tumors’ growth or make them more sensitive to other therapies.
In their research reported in Genes & Development, Kimmelman and colleagues were stunned to find that autophagy was turned on at all times in pancreatic cancer cell lines – not just under conditions of stress, treatment or starvation. “This was a big surprise,” he said. “These cells weren’t deprived of nutrients; they were swimming in all the nutrients they could ever want.” This suggested that for some unknown reason, pancreas tumors are highly dependent on autophagy, and therefore potentially uniquely good candidates for autophagy-inhibiting treatment.