Gonzalez Regimen (PDQ®): Complementary and alternative medicine - Health Professional Information [NCI] - History
The Gonzalez regimen was developed by Dr. Nicholas Gonzalez, who became interested in the use of pancreatic enzymes and dietary protocols as a possible treatment for cancer as a second-year medical student when he learned of a cancer treatment approach developed by a Texas dentist, William Donald Kelley, D.D.S. Dr. Kelley's approach espoused, among other things, the use of pancreatic enzymes administered orally as anticancer agents. Reviewed in [2,3,4,5] The use of enzymes as a treatment for cancer was originally proposed nearly a century ago  and then resurfaced in the work of Dr. Max Gerson in the 1940s. The Gonzalez regimen was developed from these earlier theories and approaches.
A key concept underlying the original use of pancreatic enzymes for cancer treatment is the trophoblastic theory of cancer. When a human egg is fertilized by sperm, the early cell divisions produce a small ball of cells, which give rise to the blastocyst (preimplantation embryo). The blastocyst possesses a surrounding layer of cells known as the trophectoderm, which is made of individual cells called trophoblasts. Responsible for protecting the developing blastocyst and for mediating its attachment to the wall of the uterus, trophoblasts create the placenta. During the process of attaching the blastocyst to the uterine wall, trophoblasts express invasive qualities similar to those found in cancer cells. Trophoblasts, however, cease their invasive activity once the placenta is in place and functioning and then differentiate into other cell types.
When Scottish embryologist Dr. John Beard  first observed the invasive activity of trophoblasts in 1902, he speculated on the similarities between these cells and cancer cells. In addition, he observed that trophoblast invasiveness begins to decline at about the same time that the pancreas in the developing fetus begins to function. He also theorized that maternal pancreatic enzymes might play a role in containing trophoblastic invasiveness in the uterus. These considerations led to his proposal that cancer cells, like trophoblasts, arise from primordial germ cells. Dr. Beard also thought that some of these primordial cells—carrying latent capacities for invading tissues—could escape and spread throughout the body of the developing fetus. He thought it was possible that pancreatic enzymes modulated the degree of trophoblastic invasiveness in the uterus, he suggested that these same enzymes play a role in either limiting or eliminating cancerous cells elsewhere in the body. Reviewed in  Dr. Beard worked before the advent of molecular biology and human genetics. Although unable to experimentally establish that pancreatic enzymes had anticancer effects, he published papers and a book about his theory between 1902 and 1911. Other scientists of the time raised significant objections to the trophoblastic theory of cancer, and it was never broadly accepted. Reviewed in