Reovirus
Introduction:
There are many new science discoveries being made daily. One of the newest discoveries is the reovirus cancer treatment. "Reovirus is a naturally occurring oncolytic virus in clinical trials" (Prestwich 2009, 13). A Reovirus is a virus with a double strand of DNA and is associated with plant and animal infections. Reoviruses are highly resistant to physical and chemical inactivation, along with low ph. Reoviruses can remain infective in enviroments for long periods of time. Reoviruses have been proven to kill cancer cells and cancer stem cells. Although this treatment may only treat certain types of cancers, the technology and treatment will open many other doors of medical research for additional innovative treatments in the future of cancer research and development. With this recent discovery currently in clinical trials, future cancer treatments may be more effective, less invasive and less painful for cancer patients.
Findings:
Before reoviruses, the previous cancer treatments include chemotherapy, laser therapy, radiation therapy, and cryosurgery. As with most treatments, each treatment has its flaws and side effects. Chemotherapy, often referred to as "chemo" is a cancer treatment that uses drugs to kill cancer. Chemo is used to kill cancer cells, stop cancer from spreading, or slow growth of cancer cells. "But while chemotherapy can shrink tumors, they often grow back and become resistant, or refractory to the treatment" (Loe 2011, 22). "To combat this resistance, doctors often cautiously combine chemotherapy with other treatments that have different mechanisms for attacking and killing cancer cells" (Loe 2011, 23). Chemo can be given in many ways like in a cream or pill you can swallow. In chemotherapy you can experience anemia, changes in appetite, bleeding problems, constipation, diarrhea, fatigue, hair loss, infections, memory changes, mouth throat pains, nausea, vomiting, pain in general, sexual fertility problems, skin and nail changes, swelling, and urination changes. These are just possible side effects. There are many different kinds of chemotherapy today and this treatment affects each patient differently.
Radiation therapy uses high energy radiation to shrink tumors and kill cancer. In radiation therapy, there are different types of radiation that can be used to treat the cancer including x-rays, gamma rays, and charged particles. Radiation therapy can be applied in many ways. It can be delivered externally by a machine outside the body, internally where the radioactive material is inside the body by the cancer cells, and directly through the blood stream. The side effects of radiation therapy are diarrhea, fatigue, mouth and throat pain, sickness, and vomiting.
Another type of treatment being utilized today is laser therapy. Laser stands for Light Amplification by Stimulated Emission of Radiation. It is a high intensity light focused into a narrow beam. Lasers are used to focus on tiny areas and are also used to make small incisions, like a scalpel. Laser therapy uses high intensity light to treat illness and cancers. Laser therapy is more commonly applied to superficial cancer. Superficial cancers are cancers on the surface of the body and cancers lining the internal organs.
Lasers also treat symptoms of cancer such as bleeding or obstructions in the body like tumors. Laser therapy can be given alone but is commonly used with other treatments because it is more successful that way. Laser therapy is given through a flexible endoscope which is a thin lighted tube used to look at tissues inside the body. The endoscope is equipped with thin optic fibers that provide light. Then the endoscope is inserted into the body where ever the cancer is and the laser precisely cuts the tumor.
The advantage of laser therapy is the preciseness of the laser rather than scalpels so there is less damage to tissue. This in turn is less painful for the patient. The bleeding, swelling, and scarring are far less with laser surgery as well. Laser therapy patients also heal quicker from laser surgery than others and are less likely to get infections. The drawback to the laser therapy is only certain doctors are qualified to do the surgery because it requires special training. Laser therapy is also extremely expensive compared to the other treatments and requires bulky equipment. Lastly, the effects of laser therapy are not long term so doctors may have to repeat the therapy several times for the full benefit of it.
The final method of cancer treatment is cryosurgery. Cryosurgery is the treatment of using extreme cold to destroy cancer cells. Cryosurgery can be applied internally or externally. When applied externally, liquid nitrogen is placed directly in contact with the cancer cells by using a spray or cotton swab. When applied internally, doctors use a hollow instrument called a cryoprobe to circulate liquid nitrogen or argon gas to the tumor. The doctors use an MRI or ultrasound to guide them through the body and monitor the freezing of cancer cells. The only downfall to this treatment is the long term effectiveness of keeping the cancer permanently away. These types of cancer treatments may be used by itself or as a combination depending on the physician, the stage of cancer, and the patient’s tolerance to the treatments.
The newest treatment is the reovirus. "Reovirus is a virus with no known associated disease" (Loe 2011, 25). Reoviruses can be found in nature everywhere. "Exposure to reovirus is common in humans, with half of all children by the age of twelve having been exposed and nearly 100 percent testing positive by adulthood" (Loe 2011, 26). When infected by the reovirus, there are usually no symptoms or very mild symptoms. Reoviruses weren't always known for killing cancer. They were at first just a common virus. "The link to reovirus’ cancer-killing ability was established after it was discovered that it reproduces well in various cancer cell lines including those found in blood cancers" (Calgary 2006, 32).The reovirus is an oncolytic virus meaning that it can kill cancer cells. "Oncolytic viruses can exert their antitumor activity via direct oncolysis or activation of antitumor immunity" (Errington 2008, 16).
Oncolysis is the destruction of tumor cells because of a treatment, usually chemotherapy or radiation therapy. "[The virus has been proven effective against] lymphoid, colon, ovarian, breast, pancreatic, brain, lung, head and neck, and other cancer cells" (Denoon 2010, 19). The reovirus kills cancer cells by infecting them and attacking the cancer cells the way regular viruses attack regular cells. "The study shows that reovirus infected cancer cells secrete proteins which, even when isolated, result in the death of cancer cells"(Philomena 2011, 1). The reovirus cannot always be applied to a patient because the body will protect itself from the virus. "Normal human cells are protected from reovirus infection by a protein called PKR" (Philomena 2011, 2). PKR stands for protein kinase RNA activated, this protein is used in your body as a viral defense. "However a cellular signaling protein (Ras), which can block PKR activity, is abnormally activated in many types of cancer and provides a window of opportunity for reovirus infection" (Philomena 2011, 3). From here, doctors would inject the virus into the patient. This allows the virus to go through the blood stream and not just attack the cancerous area but any other places where cancer cells are. "When introduced to the blood, the reovirus enters cancer cells, replicates within them and ultimately kills them" (Calgary 2006, 31).
This is a tremendous discovery since cancer cells can spread and wrap around organs and other vital body parts. The virus will attack the cancer cells only, leaving the healthy cells intact. A reovirus is not only effective against cancer cells, but also cancer stem cells. Cancer stem cells are like mother cancer cells. These cancer stem cells produce more cancer cells. If you only kill the cancer cells in a treatment, the cancer stem cells will continue to produce more and more cancer cells. This is why the reovirus is a very effective treatment. In a recent clinical study, the virus was used to attack the cancer stem cells that were left behind from autologous stem cell transplant. This transplant usually follows after high doses of chemo therapy.
An autologous stem cell transplant is where some of the cancer patient's stem cells are taken prior to high dose chemotherapy and later after the chemotherapy are placed back into the patient using an IV. The stem cells are taken out because during a high dose of chemotherapy, the bone marrow is destroyed or severely damaged. This transplant is effective for the patient because there is no risk of rejection in the stem cells. There is possible rejection when the bone marrow transplant is obtained from a donor. "However, it has been estimated that as many as 30 percent of these autologous stem cell transplants are contaminated by cancer cells, and there is a risk that they may contribute to clinical relapse of the cancer by reintroducing cancer cells back into the body" (Calgary 2006, 30).
Reoviruses are very helpful in this situation, because they can be used to kill the cancer cells in the autologous stem cell transplant. The reovirus is natural so it does not need genetic modification as other treatments. The reovirus is deadly to cancer in its natural state while other treatments nay or may not be effective. And all other cancer treatments have harmful side effects to patients. Like in chemotherapy, it may kill the cancer cells but it may also damage the patient's healthy cells. The reovirus works to kill cancer cells and leaves healthy cells unharmed. The reoviruses effectiveness is dependent on your immune system. If the cancer does not block most PKR activity, then the proteins will attack the reovirus as its' fighting the cancer. One disadvantage to the reovirus is that it is not available for all types of cancers.
As of this point, only two-thirds of all cancers may possibly use this as a treatment option. It only works on two thirds because only two thirds have an activated Ras pathway in their cells. An activated Ras pathway is a pathway that is activated in cells by Ras, a signaling protein. Through this path is where the reovirus penetrates the cancer cells. Once it goes inside the cell, it replicates within the cell causing it to burst and release more viruses to infect the cells, eventually killing the whole cancer. Reoviruses also promote antitumor immunity. The reovirus promotes antitumor immunity by enhancing and developing a strong helper T cell response which restricts tumor growth. "These reovirus oncotherapy-initiated antitumor immune responses represent an anticancer therapeutic entity that can maintain a long-term cancer-free health even after discontinuation of therapy" (Gujar 2010, 12).
This has been successful in a recent study. "Recently reovirus-based oncotherapy has been successfully implemented for the treatment of prostate cancer" (Gujar 2011, 4). In this study, the reovirus prevented a tumor and created immunity to that tumor which was prostate cancer. "Such reovirus-initiated antiprostate cancer immunity represents a clinically valuable entity that can promote long-term cancer-free health even after discontinuation of the primary oncotherapy" (Gujar 2011, 9).
Conclusion:
If the reovirus passes all clinical trials and is passed by the medical industry as a conventional cancer treatment, many physicians and patients will benefit from this new treatment. This treatments is very accessible. The reovirus is a common virus found everywhere in nature. It is oncolytic, meaning it can kill cancer cells. It has the ability to treat two thirds of cancers. It attacks cancers by infecting them through an activated Ras pathway and then replicates within the cell causing it to burst, infecting the cells around it. The virus also kills cancer stem cells and can help provide antitumor immunity to the body. The reovirus is applied in a single injection to where the cancer is.
The reovirus is better than laser, chemotherapy, radiation therapy, and cryosurgery. It is better because it requires no genetic modification and is natural. This causes the reovirus to have little to no side effects. Patients will recover from treatment much quicker than today's converntional methods of cancer treatments. Another bonus to the reovirus is it kills cancer cells while leaving normal cells unharmed. This is a tremendous breakthrough for cancer research. Patient's healthy cells will stay intact while cancer cells are destroyed. Due to this new discovery and treatment, the reovirus is the most innovative and cutting edge technology to treat cancer at this time.