Cancer: Innovative Approaches

by National Cancer Institute

(Page 9 of 9)

1992

POTENTIAL SOLUTIONS TO THE PROBLEM of cancer seem limited only by the imagination. In some promising new therapies, the body's internal weapons are trained on cancerous growths. In other treatments, no less a powerful element than light is employed to eradicate the invaders. Still other research focuses on stopping the tumor's blood supply.

Blocking the Pathways of Cancer

Prodded by growth-promoting oncogenes, freed from the restraints of suppressor genes, cancer cells move through a series of steps in their quest to establish tumors. Through the mechanisms of metastasis, invasion and angiogenesis, the renegade cells undertake an "arduous marathon." In 1992 researchers began testing methods to foil metastases, using drugs to block necessary enzymes in the cancer cells and others that arrest the growth of new tumors.

To metastasize, or spread, cancer cells detach themselves from the tumor and leak into nearby blood vessels. These roving cells move through the circulatory system until they find a suitable place to breach the vessel wall again and invade the surrounding tissues. The human body produces its own defense, the non-metastatic 23 (nm23) tumor suppressor gene, the presence of which has proved a powerful predictor of survival among breast cancer patients.

Immunotherapy: The Body's Own Weapons

Researchers have also harnessed the body's own complex immune system to defend against cancer. By linking monoclonal antibodies to lethal toxins derived from plants or bacteria, researchers such as Ellen Vitetta and Ira Pastan realized the dream of a "magic bullet": the tailor-made antibody delivers its deadly cargo directly to its target cell.

Harnessing the Immune System

In 1993 Gary Nabel treated patients with melanoma by injecting genes encased in fat droplets into tumors.The gene he used coded for a protein which arouses the immune system. When the cancer cells incorporated the gene and began producing the telltale protein, immune cells attacked. These experiments demonstrated the possible uses of direct gene transfer in human cancer treatment.

Taking Aim With Light

Photodynamic therapy employs a photosensitizing agent injected into the body to make cells ultrasensitive to light. The agent quickly passes through normal cells, but lingers in cancerous ones. The treated cancer cells are then exposed to light from a laser, which destroys them while doing little damage to the normal cells in the area.

Survival Tactics

1993 - 1997

STRATEGIES AIMED AT KEEPING CANCER FROM OCCURRING, progressing or recurring remain invaluable weapons. By the early 1990s, more than forty chemoprevention trials tested the power of assorted vitamins, minerals and drugs against cancer. New fronts in the war against cancer have opened as health care professionals increasingly focus on the special needs of at-risk populations and cancer survivors.

Lifestyle Factors

NCI has established many links between lifestyle and cancer and relays this information to the public. Programs like the wide-ranging Bionutrition and Cancer Prevention Research Initiative, launched in 1993, use the latest technologies to plumb the connection, with an eye toward reshaping public health practices. Epidemiological research indicates that a third of cancer deaths are linked to diet, and study after study proves that regular exercise offers protection from some kinds of cancer.

Screening

Evidence from many studies shows that screening for cancer before any symptoms appear increases the chances of successful treatment. In 1993 NCI launched a 16-year screening trial, enlisting more than 74,000 men a nd women, to evaluate selected biological markers as possible early-warning systems for prostate, lung, colorectal and ovarian cancers.

Controlling Environment

In addition to pursuing a healthier lifestyle, sound prevention practices mean minimizing exposure to dangerous, everyday carcinogens. Stopping tobacco use offers the best opportunity for cancer prevention, and a 1993 EPA report confirmed that the danger goes beyond smokers. Secondhand exposure to cigarette smoke, a Class A human carcinogen, results in approximately 3,000 deaths a year.

Cancer Vaccines

The idea of "immunizing" people against cancer by injecting substances that rouse the body's anticancer defenses has intrigued researchers for more than a century. Many cancer vaccines being developed and tested aim to prevent already-treated cancer from recurring or to protect high-risk individuals. Other potential vaccines mark tumor cells for destruction or force them to produce self-destructive cytokines. A vaccine tested by Jeffrey Schlom combined an antigen-producing gene found in many types of cancer with a vaccinia virus, an established immune stimulant. While still experimental, human cancer vaccines remain a real possibility.

Laser capture microdissection

Laser capture microdissection is a new technique that allows researchers to capture tumor cells in seconds, while the cell still expresses genes as it would inside the body.

The Promise of P53

By 1996 the p53 tumor suppressor gene and the powerful protein it encodes emerged as the darling of the biochemical world. Mutated or crippled versions of p53 had been implicated in 52 human cancers. Thousands of scientists have focused their research on this gene, hoping to use p53 as a tool for early diagnosis; as a guideline for varying treatment of cancer patients with disabled copies of p53 and those with working copies; and as a method of tracking a tumor back to its origin-the corruption of a cell by a specific carcinogen. The discovery of germline mutations of p53 in families with an inherited predisposition to multiple cancers (Li-Fraumeni syndrome) provided further insight into the functions of this gene.

Surviving and Thriving

In 1997, 7.5 million living Americans had a history of cancer. Women have especially benefitted from recent medical advances: 5-year survival rates for ovarian, breast and uterine cancers detected in early stages exceed 80 percent. Cancer survivors deal with unique issues such as long-term physical, psychological and social side effects of treatment, the economic costs of medical care and recovery, and the possibility of future malignancies. Past survivorship research consisted mainly of laboratory studies and focused on children, who live the longest with both the blessings and the curses of potentially toxic therapies. Organizations such as the NCI's Office of Cancer Survivorship and the National Coalition for Cancer Survivors now actively promote clinical research on the realities of surviving cancer for both children and adults.

Special Populations

By conducting community-based research, scientists hope to identify factors that increase or decrease the risk of cancer in an individual or group of people. Community research has already linked factors such as cigarette smoking and exposure to certain viruses or bacteria with cancer; scientists are also exploring possible connections based on racial variations, genetics and diet. Studying attitudes toward cancer and the perceived risk of developing cancer in selected groups of people may also aid in education and prevention efforts.

About the Author

www.nci.nih.gov
The National Cancer Institute's research programs are extensive and contain many innovative initiatives. I invite you to explore our Web site to find out more about the exciting work being conducted here at NCI and by NCI-supported scientists throughout the country.