presented by:
Vasoya Sanjay M.

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Cancer Vaccine
INTRODUCTION
For many years, the treatment of cancer was focused primarily on surgery, chemotherapy, and radiation. However, as researchers learn more about how the body fights cancer on its own, therapies are being developed that harness the potential of the body's defense system in this fight, including efforts to prevent some forms of cancer.
The body's defense system - called the immune system - consists of a network of specialized cells and tissues that fight infection and disease. Therapies that use the immune system to fight or prevent cancer are called biological therapies.
Vaccine development is one of the most promising and exciting fields in cancer research; numerous approaches are being studied to developed effective cancer vaccines. The aim of this form of therapy is to teach the patient's immune system to recognize the antigens expressed in tumor cells, but not in normal tissue, to be able to destroy these abnormal cells leaving the normal cells intact. In other words, is an attempt to teach the immune system to recognize antigens that escaped the immunologic surveillance and are ‘tolerated’ by it, therefore able to survive and, in time, disseminate. However each research group developing a cancer vaccine, uses a different technology, targeting different antigens, combining different carriers and adjuvants, and using different immunization schedules.
Unlike the vaccine you might receive for the flu, most cancer vaccines aren't intended to prevent you from getting cancer. Rather, the majority of cancer vaccines being studied aim to condition your body to recognize cancer cells as invaders. Vaccines may be used to attack cancer cells in several different ways. In one method, the vaccine consists of cancer cells that are inactivated, usually through radiation, and injected into your body. These cancer cells can't grow and form new cancer, but they still carry the signals that activate your immune system to attack cancer in your body. Some vaccines are made of cells from your own cancer. Still others are made of cells from your immune system (dendritic cells). Scientists manipulate these cells to recognize cancer cells and then inject the manipulated cells into your body. Once in your body, the manipulated cells target the cancer cells, as well as recruit other cells in your immune system to join the fight.
What is a vaccine?18
A vaccine is a substance designed to stimulate the immune system to launch an immune response. This response is directed against specific targets, or antigens, that are part of the vaccine. An antigen is any substance that the immune system recognizes as foreign.
Vaccines can be made using specific types of molecules from viruses or cells, including molecules from bacterial cells or human cells. These molecules may contain a single antigen or several different antigens. Carbohydrates (sugars), proteins, and peptides (pieces of proteins) are among the types of molecules that have been used to make vaccines. Molecules of DNA or RNA that contain genetic instructions for one or more antigens can also be used as vaccines.
In addition, whole viruses or cells, or parts of viruses or cells that contain different types of molecules, can be used to make vaccines. The flu vaccine, for example, is made using inactive whole flu viruses. If whole human cells are used as vaccines, they are usually treated with enough radiation to keep them from dividing (growing and multiplying) or enough to kill them.
It has been more than 100 years since the first reported attempts to activate a patient's immune system to eradicate developing
cancers. Although a few of the subsequent vaccine studies demonstrated clinically significant treatment effects, active immunotherapy has not yet become an established cancer treatment modality. Two recent advances have allowed the design of more specific cancer vaccine approaches: improved molecular biology techniques and a greater understanding of the mechanisms involved in the activation of T cells.
These advances have resulted in improved systemic antitumor immune responses in animal models. Because most tumor antigens recognized by T cells are still not known, the tumor cell itself is the best source of immunizing antigens.
For this reason, most vaccine approaches currently being tested in the clinics use whole cancer cells that have been genetically modified to express genes that are now known to be critical mediators of immune system activation. In the future, the molecular definition of tumor-specific antigens that are recognized by activated T cells will allow the development of targeted antigen-specific vaccines for the treatment of patients with cancer.
The immune system and cancer 19
Researchers used to think that the immune system prevented cancer from growing and spreading by constantly looking to see if cancer cells are present and killing them once they are found. It was thought that the growth and spread of cancer resulted from a breakdown of the immune system. In a broken-down immune system, effective anti-cancer immune responses could not occur.
However, this theory of immune system control over cancer growth has now been shown to be only partially correct. Researchers now know that strong immune responses against cancer cells are hard to generate, and they are studying ways to strengthen the ability of the immune system to fight cancer.
Part of the problem is that the immune system has the job of knowing the difference between normal cells and cancer cells. To keep us healthy, the immune system must be able to ignore or “tolerate” normal cells and recognize and attack abnormal ones.
To the immune system, cancer cells differ from normal cells in very small, subtle ways. Therefore, the immune system largely tolerates cancer cells rather than attacking them. Although tolerance is essential to keep the immune system from attacking normal cells, tolerance of cancer cells is a problem. Therapeutic cancer vaccines must not only provoke an immune response but stimulate the immune system strongly enough to overcome its usual tolerance of cancer cells.
Another reason cancer cells may not stimulate a strong immune response is that they have developed ways to evade the immune system. Scientists now understand some of the ways in which cancer cells do this. For example, they may shed certain types of molecules that inhibit the ability of the body to attack cancer cells. As a result, cancers become less "visible" to the immune system.
Researchers are now using these advances in knowledge in their efforts to design more effective cancer vaccines. They have developed several strategies for stimulating immune responses against cancers, including the following:
 Identify unusual or unique cancer-related molecules that are rarely present on normal cells and use these so-called “tumor antigens” as vaccines.
 Intervene to make tumor antigens more visible to the immune system. This can be done in several ways:
 Alter the structure of a tumor antigen slightly (that is, make it look more foreign) and give the altered antigen as a vaccine. One way to alter an antigen is modify the gene needed to make it. This can be done in the laboratory.
• Put the gene for a tumor antigen into a viral vector (a harmless virus) and use the virus as a vehicle to deliver the gene to cancer cells or to normal cells. Cells infected with the viral vector will make much more tumor antigen than uninfected cancer cells and may be more visible to the immune system. Cells can also be infected with the viral vector in the laboratory and then given to patients as a vaccine. In addition, patients can be infected (that is, vaccinated) with the viral vector as another way to get virus-infected cells inside the body.
 Put genes for other molecules that normally help stimulate the immune system into a viral vector along with a tumor antigen gene.