Cancer: Molecular Biology Comes of Age

by National Cancer Institute

(Page 5 of 9)

1952 - 1971

Unlocking the Genetic Code: The New Era of Molecular Biology and Medicine

Molecular biology-the study of living systems at the molecular level-revolutionized both medicine and cancer research. The opening volley of that revolution was sounded in 1953 when James Watson and Francis Crick unveiled their model of the structure of DNA (deoxyribonucleic acid), the cellular material carrying genetic information. The genetic code was soon broken, and many discoveries followed. As knowledge of DNA's structure and functioning grew, so did basic knowledge of the cell. During the 1950s researchers observed and named many structures, or organelles, within the cell, including ribosomes and lysosomes. Cancer researchers discovered much of the new information on cells.

Surgery and Radiotherapy: Progress in the "Conventional" Treatments

While chemotherapies were being tested and "magic bullets" to eliminate cancer sought, advances were being made in the other treatments for cancer-surgery and radiotherapy. These older methods, often with the addition of chemotherapy, remained the major treatments for all but a small proportion of cancer patients.

A National Chemotherapy Program

Mounting successes in chemotherapy encouraged the search for more and better drug treatments. In 1955 Congress appropriated funds for a national effort, and NCI undertook a National Chemotherapy program devoted to testing chemicals that might be effective against cancer.

Viral Oncology, Another Research Frontier

When first suspected of causing cancer, viruses were thought to exist but had never been seen. As microscopes improved, viruses became visible and their structure was revealed. Tiny particles of either ribunocleic acid, they were wrapped in a sheath of protein. In the 1960s and 1970s, viral oncology was one of the most fertile cancer research areas, due in part to a major NCI virus program. One DNA virus was found and linked to human cancer, and an RNA virus was then sought. Discoveries made en route to the 1979 discovery of an RNA human virus proved as important as isolating the virus itself.

The NCI Chemotherapy Program Continues

Over 500,000 chemicals were tested on laboratory animals in NCI's chemotherapy program. Several hundred of these chemicals were tested in clinical trials. By the late 1970s, some 45 chemicals had been found effective against 29 forms of cancer. After a time, researchers found that combinations of drugs were more effective against cancer than those given singly. Childhood leukemia was one of the first cancers that could be cured in this manner. Emil Frei and Emil Freireich made particular contributions in developing the leukemia treatment. A four-drug combination developed by Vincent DeVita raised the cure rate of Hodgkin's Disease from nearly hopeless to 80 percent.

Case Study of a Carcinogen: Smoking and Lung Cancer

Known and used in the New World before the time of Columbus, tobacco was suspected of being a possible carcinogen as early as the 18th century. As cigarette smoking became popular in the 20th century, the incidence of lung cancer began to rise with increased consumption of tobacco. By the mid-1960s, the inescapable correlation led the United States Surgeon General to issue a public report on smoking and health.

A Link with Environmental Pollutants?

The search for chemical causes of cancer coincided with the public's growing awareness of damage being done to the environment in general. A connection seemed possible between the increasing incidence of cancer and industrial pollution of the environment.

Tracking Down the Causes of Cancer

As new cancer treatments and improved techniques for early diagnosis evolved, research continued on the most basic riddle, the cause of cancer. One area of study, chemical carcinogens, was linked to cancer in the 18th century, a link confirmed in 1915 when cancer was induced in lab rabbits. In the 1950s and 1960s, the role of chemical carcinogens and possible carcinogenic mechanisms were further scrutinized. James and Elizabeth Miller showed that many chemical carcinogens are really pre-carcinogens, able to cause cancer only when metabolized. They are thought to damage DNA, producing cancer-generating errors in the genetic code.

A Discovery that Opens Many Doors

In 1970 two researchers working independently made a discovery that would alter cancer research and all biology. Howard Temin and David Baltimore discovered an enzyme, reverse transcriptase, which explained the mechanism by which RNA viruses convert their genetic information into DNA, making genetic engineering possible.

A National Cancer Program Enacted

No less a goal than the conquest of cancer motivated a public and private campaign to create a national program in the late 1960s. Enactment of the National Cancer Act in 1971 created a National Cancer Program administered by the National Cancer Institute. Its Director was to report directly to the President. Enlightened philanthropist Mary Lasker and businessman Benno Schmidt played major roles in spear-heading the public campaign in the support of this legislation.

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.