Since cancer is a disease in which some body cells seem to be "out of control," knowledge of cellular biochemistry is basic to ultimate understanding of the cancerous process. Studies of deoxyribonucleic acid (DNA) and ribonucleic acid (UNA)—the master chemical molecules of life—are providing clues to ways in which viruses, chemicals, and radiation bring about the malignant change within a cell.

Such studies were lent impetus by the report late in 1967 of the success of a team of California biochemists, led by a Nobel laureate, in synthesizing the DNA, or infective core, of a virus.

An electron micrograph of two duplex viral DNA rings

An electron micrograph of two duplex viral DNA rings (X 810,000) synthesized in the test tube. One duplex lies inside the other; each consists of a template of natural virus with a complete synthetic complementary circle.

The synthetic molecule is capable of infecting bacteria, replicating within their cells and giving rise to a new generation of intact, normal virus. Having succeeded in copying one virus, the team believes it should be possible to copy others, including tumor viruses. This could have important implications in terms of a better understanding of cancer causation and control.

In a study of representatives of three known groups of RNA animal tumor viruses, other California scientists found biochemical similarities that match previously observed similarities in structure and method of replication. All of the viruses studied contained single-stranded RNA consisting of two major components. These and other findings suggested that the nucleic acids of all RNA tumor viruses may be very similar in size and structure and probably quite different from the RNA of non-tumor viruses, suggesting that cancer viruses have certain features in common.

A United States investigator and his Swedish collaborators have explored further the inhibitory effect of lymphocytes on the synthesis of DNA of tumor cells. Their experiments carried out in tissue cultures of mouse tumor cells have shown that all lymphocytes inhibit DNA synthesis in the target cells, thus indicating a positive role for these lymphoid cells in the body's immunological response to cancer. Lymphocytes showing greatest inhibitory effect, however, were those obtained from mice pretreated, or sensitized, by inoculation with tumor cells, a further manifestation of immune reaction.

Dr. Arthur Romberg

Dr. Arthur Romberg of Stanford University, head of a research team that in synthesizing the inner core of a virus, achieved the first man-made biologically active DNA.