Ovarian cancer is one of the most deadly female cancers. In early stages, women with this cancer have few symptoms, so it is often overlooked until later stages when it’s more difficult to treat. Doctors usually treat ovarian cancer with chemotherapy drugs or by surgically removing the cancerous tissues. However, ovarian cancer often returns, so researchers want to find more effective treatments.
Scientists have shown ovarian cancer patients often have an abundance of a protein called epidermal growth factor receptor, or epidermal protein for short. This protein is found on the surface of sticky cells called epithelial cells that coat surfaces of your body like your skin and digestive tract.
Scientists have found high amounts of epidermal protein can cause epithelial cells to replicate uncontrollably, a common characteristic of cancer cells. Sometimes, these epithelial cells can become less sticky and move away from their original location in the body. When cells spread to other parts of the body, this is called metastasis, another common characteristic of cancer cells. Therefore, scientists hypothesize high amounts of epidermal protein could help ovarian cancer emerge and progress.
Because of this potential link, scientists have focused on the epidermal protein to treat ovarian cancer. Doctors usually treat this protein using molecules specially designed to attach to it, called antibodies. Antibodies block other molecules from attaching to the epidermal protein, which stops the cancerous epithelial cells from replicating. Scientists think this treatment should work, but it has stopped working for many people over time, so it doesn’t slow the spread of ovarian cancer permanently.
A team of researchers from Italy recently developed a treatment for ovarian cancer that targets the epidermal protein in a new way. The team used a virus to inject a light-sensitive chemical into ovarian cancer cells, then hit the cells with a laser light, a method called photo-dynamic therapy. The laser light causes cells to create reactive oxygen chemicals, which kill tumor cells, destroy tumor blood supplies, and trigger the patient’s immune system to respond.
Photo-dynamic therapy can be toxic to healthy cells, so it must be delivered only to tumor cells, and not other cells of the body. Therefore, the researchers engineered the virus with a molecule in its tail that only attaches to cells with the epidermal protein on their surface. The engineered virus uses hand-like fibers to “grab” on to the epidermal protein on the outside of the cancer cells. Once attached, the virus injects the light-sensitive chemicals into the cells.
The scientists tested whether the engineered virus combined with photo-dynamic therapy could successfully kill ovarian cancer cells. First, they measured the presence of the light-sensitive chemical in two types of ovarian cancer cells. They treated the cells with the chemical for 1.5 hours and stained them with dye to locate the light-sensitive chemical under a microscope.
They found more light-sensitive chemicals in cells that received the engineered virus than in cells that were treated with the chemical alone. They also found the chemical was delivered to an internal part of the cell called the mitochondria, known to be an effective location to kill cells using this therapy.
Next, they treated the ovarian cancer cells with the engineered virus and laser light to activate the light-sensitive chemicals. The scientists measured the percentage of living ovarian cancer cells after they were given the treatment, using a method called a cytotoxicity assay. They found more ovarian cancer cells died with increasing doses of the treatment. The percentage of living ovarian cancer cells decreased from 71% down to 1%, demonstrating the treatment was effective in killing ovarian cancer cells.
Finally, the scientists used a method to measure the amount of a specific protein expressed in cells, called a western blot. They measured the amount of epidermal protein in ovarian cancer cells that received the virus and laser light treatment. They found less epidermal protein in ovarian cancer cells that received the treatment than in those that did not.
Researchers have previously proposed that inhibiting epidermal proteins could have antitumor effects in treating other cancers. These scientists concluded their study is a good first step in demonstrating an engineered virus treatment is effective in killing ovarian cancer cells. However, the team only tested their treatment on cancer cells grown in a dish in a lab. They suggested further studies should see if this treatment is effective in animals like mice, and test whether it is toxic to healthy cells.