Cancer Vaccines Are Proving Their Mettle
Shots for pancreas, head-and-neck and cervical tumors appear effective, studies find
TUESDAY, April 17, 2007 (HealthDay News) -- Vaccines against deadly pancreatic and head and neck cancers are showing real promise and may one day become an important part of treatment, researchers report.
Researchers are also confirming that cervical cancer vaccines are both highly effective and long-lasting, according to two other studies.
All of the new findings were presented Tuesday at the American Association of Cancer Research's annual meeting in Los Angeles.
In one report, a team led by Andrew Lepisto, a postdoctoral researcher in the department of immunology at the University of Pittsburgh School of Medicine, presented the results of a phase I trial of a vaccine for pancreatic cancer.
In that trial, Lepisto's team gave an immune cell-based vaccine to 12 cancer patients who underwent surgery for pancreatic cancer, one of the deadliest malignancies, because it is often caught too late
"Patients who are eligible for surgery represent about 20 percent of all pancreatic cancer patients," Lepisto said during a teleconference. The five-year survival rate after surgery is only about 20 percent, he added.
"The goal of the vaccine was to raise a strong immune response to prevent the cancer from coming back," Lepisto explained.
"We found that if we did the surgery and followed up with the vaccine, we extended patient's lives from a 20 percent five-year survival rate to over 42 percent," he said. "There are five patients who are long-term survivors."
Lepisto is planning to use the five surviving patients to understand how the immune vaccine extended their lives.
Another study was led by Sanjay K. Srivastava, an assistant professor in the department of pharmacology at the University of Pittsburgh School of Medicine. His team found that an extract of triphala -- the dried and powdered fruits of three plants -- caused pancreatic cancer cells to die in mice.
"Our results demonstrate that triphala has strong anticancer properties given its ability to induce apoptosis [natural, programmed cell death] in pancreatic cancer cells without damaging normal pancreatic cells," Srivastava said in a prepared statement. "With follow-up studies, we hope to demonstrate its potential use as a novel agent for the prevention and treatment of pancreatic cancer," he added.
In a third presentation, a team at the University of Pittsburgh School of Medicine say they've developed a vaccine that uses parts of the immune system to target p53, which is a protein that suppresses tumor growth. The scientists used the vaccine to treat head and neck cancer cells.
"In cancer, p53 is either mutated or altered," Theresa Whiteside, a professor of pathology, immunology and otolaryngology, said during the teleconference. By targeting the unchanged parts of altered p53 cells with a vaccine that activates the immune process, her team was able to produce killer cells that destroyed tumor cells. The vaccine also boosted the supply of immune "helper cells," which help the killer cells do their job.
"We can generate killer cells and helper cells in patients with head and neck cancer," Whiteside said. "On the basis of this study, we have initiated a phase I clinical trial in patients with head and neck cancer," she said.
In two other presentations, researchers presented data on the benefit of widely publicized vaccines that prevent most cervical cancer. The vaccines do so by preventing infection with the major strains of human papillomavirus (HPV), thought to be the cause of most cervical malignancies.
In the first report, Dr. Stanley Gall, a professor of obstetrics and gynecology at the University of Louisville, and colleagues reported that a new HPV vaccine made by GlaxoSmithKline was safe and effective.
"The vaccine was 100 percent effective in preventing precancerous lesions from HPV types 16 and 18 for up to five to six years," Gall said during the teleconference. These types of HPV account for about 72 percent of all cervical cancers, he said.
Overall, the vaccine showed 68 percent efficacy regardless of the type of cancer-causing HPV virus, Gall said. "The protection goes beyond what is expected from a vaccine that is targeted to type 16 and 18 alone," he said. "It protected against type 45 and 31 and also extended protection up to five years," he said.
In the other report, Dr. Darron R. Brown, a professor of medicine and infectious disease, at the Indiana University School of Medicine, and colleagues showed that the currently available vaccine, Gardasil, made by drug giant Merck, is 99 percent to 100 percent effective in preventing cervical cancer from HPV types 16 and 18. The study involved more than 12,000 women.
"In addition, 241 women who received Gardasil five years ago are still 100 percent protected from HPV 16 and 18 and have high sustained antibody levels," Brown said during the teleconference. "This is very encouraging," he said.
For more information on cancer vaccines, visit the American Cancer Society.