The history of the search for a cure for cancer is long and fascinating. See www.pbs.org/show/story-cancer-emperor-all-maladies/ A major issue is that each cancer has its unique characteristics. A breakthrough in treatment of leukemia did not lead to a cure for other cancers, for example.
The idea of using viruses to target cancer cells and engaging the body’s immune system to battle cancer has been around for over a century. Medical science would love to train the immune system’s soldiers to step up to the battle. Now it appears that genetic engineering can provide support for the troops. Part of the problem is that cancer cells are camouflaged as friendly so our lymphocytes usually don’t produce antibodies to fight them.
The idea of infusing cancer cells with viruses so they become recognized as enemy cells has recently realized some success in fighting brain cancer. Infusing a virus into a cancer cell, of course, has risks of causing the disease associated with the virus. This creates a delicate problem. It turns out that the receptor for the poliovirus to enter the cell is present on most tumor cells, but not on normal cells. Somehow scientists at Preston Robert Tisch Brain Tumor Center of Duke University came up with the idea of using genetic engineering to alter the poliovirus by removing the poliovirus’ innate ability to cause disease and splicing in rhinovirus, which causes colds. The result is termed PVS-RIPO, which retains the ability to enter and infect cancer cells, but not normal cells.
PVS-RIPO kills cancer cells, but not normal cells, because its ability to grow (and kill) depends on biochemical abnormalities only present in cancer cells. Safety testing in non-human primates and human patients has shown no nerve cell killing, no ability to cause poliomyelitis, and no ability of PVS-RIPO to change back to wild type poliovirus that can cause poliomyelitis.1
Clinical trials have been promising and have been described on 60 minutes. It is too soon to call it a cure for brain cancer, but the FDA has given PVS-RIPO a breakthrough therapy designation. This status is expected to expedite future trials and yield the support and advice of the FDA at the highest levels. No research on the effectiveness of PVS-RIPO on other cancers has yet been done. A universal cure is the holy grail of cancer research.
The structure of the PVS-RIPO Virus.
The Virus particle consists of a protein shell (blue, red and green shapes) arranged in a symmetric structure. In this image, the particle has been “cracked open,” to reveal the virus genome (yellow, pink), which is surrounded by the protein shell. The PVS-RIPO genetic code is based on the Sabin vaccine (yellow) with a piece of genetic information from a common cold virus spliced in (pink.)1
Across the Atlantic, a team in Germany is utilizing genetic engineering in a different way. Immune soldiers called dentritic cells patrol the body for foreign invaders. Since cancer rogues look so similar to normal cells, the new technology’s goal is to improve the dentritic cells’ ability to recognize cancer cells. Genetic code of the relevant cancer is placed in nanoparticles giving them a negative charge, which causes them to be drawn into the dentritic cells in the spleen, lymph nodes and bone marrow.
Once there a cancer molecule – known as an antigen – is created according to the genetic code and used as a biological mugshot for the dentritic immune cells to search for and fight tumors. The procedure has been tested on mice and shown to trigger a strong immune response.
From tests on three skin cancer patients, the procedure appears safe. More tests are required on this promising approach. Since the bit of genetic code is pertinent to the exact cancer of the patient, the procedure is customized. This should mean it will work to treat cancer anywhere in the body. Further, once the immune cells recognize this type of cancer, the cancer should not reoccur. Because of this, the injections of the genetic codes embedded in the tiny particles are called vaccines.
“The vaccines are fast and inexpensive to produce, and virtually any tumor antigen can be encoded by RNA,” said lead author Prof Ugur Sahin, managing director of Translational Oncology at the University Medical Centre of the Johannes Gutenberg University, Mainz, Germany.3
Will genetic engineering be the holy grail in the long search for a cure for cancer?
Adapted from 1. http://www.cancer.duke.edu/btc/modules/Research3/index.php?