Immuno-oncology: Is it a New Hope for Cancer Patients?

Abstract

Cancer is the one of the leading causes of death, whose incidences is increasing
day by day due to lack of understanding about its complete mechanism. Therefore, to understand
complete mechanism of cancer, researchers started to move their focus from the cancer
cell to the host and the environment in which the cancer grows, a very important component
of which is the immune system.1,2 The immune system comprises of innate and adaptive
system which provides protection to the body against pathogens. The immune cell receptors
recognize the foreign and activate the complex immune response signaling pathways which
results in the elimination of pathogens.3,4 The first problem with cancer cells is that they arise
from our own cells, so some times unable to recognize as non self. Further, if they recognized,
alters the immune response signaling pathways at various steps which results in failure
of immune response. The cancer cells can avoid recognition and elimination by altering the
immune response signaling pathways at various steps such as disrupting antigen recognition
and presentation mechanisms, down regulates the MHC class I molecules or inhibiting the antigen
processing mechanisms. Additionally, cancer cells may disrupt the pathways which
are involved in controlling T-cell inhibition and activation, or by recruiting regulatory T cells
(Treg) and Myeloid-derived suppressor cells (MDSC) which are immunosuppressive. Further,
cancer cells may release of some of immunosuppressive immune factors such as adenosine and
prostaglandin E2, and the enzyme Indoleamine 2,3-dioxygenase (IDO) which leads to progression
of cancer.