Your Cancer Risk Guide

When scientists at Stanford University looked around for a good way to grow a cancer vaccine, they realized they could do no better than the plant that has caused more cancers than you can count. They were not trying to develop a cancer vaccine such as Gardasil, which gives the body immunity against an infectious agent (in this case, the papillomavirus) that can trigger cancer (in this case, cervical). That’s all well and good, but the true grail is a therapeutic vaccine, one that would prompt the body’s immune system to attack cancer cells and only cancer cells, or that would consist of antibodies that do so.

The theory rests on the fact that the surface of malignant cells are studded with molecules that can prime the immune system’s T cells, for instance, to attack the cancer cells, or act as homing signals that lure antibodies to munch up and destroy the cells.

A bunch of such cancer vaccines are in development, but they face a serious problem. Everyone is likely to need a different vaccine, because everyone’s cancer cells are probably slightly different on the molecular level. Growing the antibodies according to the usual recipe means using animal cells, which is expensive (thousands of dollars per patient), time consuming (months) and possibly risky (they might contain viruses or other contaminants that are not exactly what you want to inject into cancer patients). So biologist Ronald Levy of Stanford University and colleagues decided to investigate plants as vaccine factories.

This evening, they are announcing in the advance online issue of the Proceedings of the National Academy of Sciences that they have grown an injectable cancer vaccine in genetically-engineered plants, tested it in 16 cancer patients and found it to be safe (tests of whether it works come next). Fully aware of the irony here, Levy and his team used tobacco plants to grow the vaccine, which would act against follicular B-cell lymphoma. This chronic, incurable form of non-Hodgkin’s lymphoma strikes some 16,000 people in the United States each year. For all its horrors, however, follicular B-cell lymphoma just may be tailor-made for a cancer vaccine: all of the malignant cells are the descendants of a single bad actor and have an identical molecule on their surface. But the molecular signature of one patient’s cancer cells is slightly different from every other patient’s; hence the need for potentially expensive personalized vaccines.

When it comes to developing a cancer vaccine, Dr. Lee Riley admits he’s not a patient man.

That’s why the St. Luke’s Hospital cancer surgeon and researcher has turned his focus from liver cancer and melanoma to the most common cancer affecting women: breast cancer.

The way Riley sees it, the larger pool of candidates could shorten the time it takes to determine what works and what doesn’t — from 20 years to two.

”I don’t want to take baby steps,” he said.

Most breast cancer vaccine studies nationwide focus on women with advanced disease, but Riley’s will look at women in the early stages of the disease. They represent about half of all breast cancer diagnoses, he said, and may stand to benefit more from early treatment.

Riley wants to enroll 10-20 women, zap their tumors with high-energy radio waves, then inject the tumor with an approved immune system stimulant.

The hope is to turn cells inside the tumor into an arsenal of cancer fighters that continue to kill for years, much like a tetanus shot works to fend off bacterial infections for 10 years or more.

When used in cancer research, the term vaccine is not the same as a vaccine against polio or the flu, for example, which can prevent a healthy person from getting sick. Cancer vaccines are designed to prevent recurrence.

Many are under development across the country, including more than 30 against advanced breast cancers, one against melanoma at Lehigh Valley Hospital and one that shows such promise against a specific kind of lung cancer that the major drug company GlaxoSmithKline is sponsoring a multi-center trial enrolling thousands of patients.

Yet vaccines that effectively treat existing tumors appear to be a long way off. None has been approved by the U.S. Food & Drug Administration, according to Jill O’Donnell-Tormey, executive director of the Cancer Research Institute, a nonprofit organization that supports and coordinates immuno-therapy research against cancer. Even Gardasil, the so-called cervical cancer vaccine approved by the FDA in 2006, works by preventing certain types of viral infections that can lead to cervical cancer.

At St. Luke’s, the breast cancer study will test the effects of several already-approved immune system stimulants on a patient’s tumor and two lymph nodes: the ‘’sentinel” node into which the tumor drains and another.

The goal is to find the stimulant - or combination - that produces enough of an immune system reaction to fight cancer cells but not turn the immune system against healthy cells.