Wednesday, Jul 11, 1979
South San Francisco, Calif. -- July 11, 1979 --Genentech, Inc., today announced the successful bacterial production of human growth hormone (hGH) using molecular biological techniques. Genentech's announcement of hGH production follows the company's success in producing human insulin and somatostatin using similar technology. This announcement follows the formal communication of Genentech's research results to the scientific community at the Mile's Symposium on July 11, 1979, in a research paper delivered by Genentech's Dr. David Goeddel.
Human growth hormone is a protein hormone produced in the pituitary gland at the base of the brain mediating both growth and stature. It is currently used in the treatment of "hypopituitary dwarfism," a children's disease in which the pituitary malfunctions and secretes insufficient amounts of hGH for normal growth, and results in dwarfism. Hypopituitary dwarfism is currently treated by administering hGH extracted from the pituitaries of human cadavers. Although this is a rare disease, hGH supplies are now so limited that many suffering from hypopituitary dwarfism are unable to receive treatment.
The successful bacterial production of hGH will enable the production of sufficient quantities of hGH to treat all those hypopituitary patients who could benefit from its administration.
In addition to being efficacious for dwarfism, hGH may have value in treating diffuse gastric bleeding, burns, bone disintegration, bone fractures, and other diseases. Supplies of hGH have been so limited that research has been restricted in these areas, but now adequate supplies of hGH produced by microbial sources will enable clinicians to investigate these important therapeutic uses.
The molecular biological techniques involve combining the genes of different organism to form a hybrid molecule. Genes are composed of DNA (deoxyribonucleic acid), which contain the chemical record in which genetic information is encoded. Scientists at Genentech inserted the gene carrying the genetic information for hGH (along with the necessary control mechanism) into a special plasmid. Plasmids (normal bacterial cell constituents) are circular pieces of DNA into which new pieces of DNA can be inserted using recombinant DNA techniques.
The plasmid with the hGH gene was inserted into a special bacterial strain. Once inside the bacteria, the hGH DNA is used a a template to produce the hGH protein.
At Genentech, a scientific team led by David Goeddel, Ph.D., and Peter Seeburg, Ph.D., achieved the production of hGH in bacteria. Synthetic DNA fragments used in the project were made by Keiichi Itakura, Ph.D., and coworkers at the City of Hope National Medical Center in Duarte, California.
The hGH achievement goes beyond the work done earlier by Genentech on human somatostatin and insulin in three important aspects:
Genentech's research efforts on hGH production were funded by AB Kabi, a Swedish pharmaceutical firm, which is the world's leading supplier of hGH produced through pituitary extraction. Genentech and Kabi will be marketing the hGH produced as a result of this collaborative effort.
"The development of human growth hormone further demonstrates the viability of using the new molecular biology and recombinant DNA technology to produce products with practical application," said Robert Swanson, president of Genentech.
"Testing and refinement of the production process, and FDA approval, is needed before hGH will be available. It is Genentech's goal to make hGH and other products produced by genetically engineered microorganisms safely available to the people who need them in the shortest possible time," Swanson said.
Genentech, a privately financed corporation, was organized solely to develop commercial application of molecular genetic technology. Genentech announced its first product -- the hormone somatostatin--in late 1977, and its second product -- human insulin -- in late 1978.
Human growth hormone is polypeptide (protein) made in the pituitary, which is composed of 191 amino acids with two internal disulfides bonds.
In a series of biochemical processes, organisms, including simple bacteria, translate the genetic information contained in DNA into polypeptides. The general steps are DNA---------------messenger RNA-----------------polypeptide.
Scientists synthesized several DNA fragments which were joined enzymatically to form a DNA segment coding for about 12% of the hGH polypeptides. They then extracted hGH messenger RNA from human pituitaries and converted in enzymatically to DNA in vitro. This DNA segment was joined enzymatically with the synthetic DNA segment to form the complete gene coding for hGH. Using enzymes, the hGH DNA was stitched into circular DNA plasmids. The newly-constructed plasmids were introduced into a strain of E. Coli in accordance with the NIH guidelines for recombinant DNA work.
Once inside the bacteria, the newly-inserted hGH gene was expressed, and the bacteria produced hGH identical to the natural substance as determined by several biochemical methods.
Insulin is a protein hormone composed of two chains of amino acids: an "A" chain and a "B" chain linked together by two disulfide bonds. The "A" chain is composed of 21 amino acids and the "B" chain of 30 amino acids, each arranged in a uniquely ordered sequence.
Proteins are made by translating the genetic information which is carried in a cell's genes. Scientists synthesized in the laboratory genes for the two insulin "A" and "B" chains. This was accomplished by chemically linking together small pieces of DNA sequence and then joining them in a specific manner to form complete genes.
Once the genes were synthesized, they were stitched into circular DNA strands called "plasmids" using special enzymes to perform the molecular surgery. Plasmids are rings of DNA which are found within the cell. The newly constructed plasmids containing the transplanted genetic material were introduced into a benign E. coli bacterial strain.
Once inside the bacteria, the genes were "switched-on" by the bacteria to translate the code into either the "A" chain or the "B" chain proteins found in insulin. The process is the same as that used by bacteria to produce its own proteins. When the cells produced sufficient amounts of the "A" and "B"chains, they were harvested to isolate these proteins from the bacteria and purify it. The two chains were then combined chemically in the laboratory to form the complete Insulin molecule which is identical to that produced by the human body.