By Sarah Garcia
As the ocean’s top predator and one of the world’s most magnificent and mysterious creatures, sharks have earned quite a reputation—so much so that they have an entire week of television dedicated to them.
Among the shark’s incredible features: a sophisticated immune system and a specialized organ which provides them with a natural cancer shield. Within this may lie a potential cancer cure, according to decades-long research conducted at Mote Marine Laboratory and Aquarium in Sarasota.
Drs. Carl Luer and Cathy Walsh have spent years studying sharks, skates and rays — a group of fishes called elasmobranchs — and the potential cancer treatment link in humans.
Unique to their subclass, sharks and other elasmobranchs have a special organ called the epigonal organ, which is responsible for producing immune cells similar to bone marrow in humans. In the lab, shark immune cell-derived compounds produced by cells of the epigonal organ have been proven to inhibit the growth of certain types of human cancer cell lines, while leaving healthy, non-cancer cells relatively unaffected.
“We wanted to know how this substance works — what possible pathways it activates inside the cells to kill them in a selective way,” Dr. Walsh said. “A lot of substances can destroy cells, but a substance that works through a specific mechanism will have more therapeutic potential.” The proteins from the epigonal cell cultures induce cell death through a specialized mechanism called programmed cell death, or apoptosis.
While Walsh and Luer’s research uncovered that the immune cells were able to attack the cancer cell lines, they have not yet been able to isolate which protein the cells produce that elicits this response.
In the early 2000’s the Mote team partnered with colleagues at Moffitt Cancer Center, including Dr. Clay Smith, who worked at the center at the time. They planned to continue cultivating the shark immune cells, and then test the substance on cancer cells in Moffitt’s labs. However, funding was limited and the project never really took off.
Drs. Luer and Walsh have continued their studies nonetheless, and know just what it will take to push their research to the next level, hoping to eventually bring it to clinical trial.
“After isolating the active protein(s), next steps include testing in animal models and synthesizing the proteins in the laboratory rather than relying on natural sources for tissue used in the cell cultures that produce the proteins,” Dr. Walsh says. “Additional efforts are underway to transform the epigonal cells into a continuous cell line that can be frozen and regenerated to provide a steady supply of bioactive proteins.”