Page 6 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

1.4 Cancer therapy and immunotherapy 3

are initiated by oncogenic viruses—RNA and DNA viruses—that induce malignant
transformation and prophylactic immunization against some viruses such as EBV,
HPV, and HBV may be a rational strategy for prevention of malignancy [18].
The disrupted immune response can induce tumor growth and prevent effective
antitumor suppression, possibly through a process of “sneaking through” that allows
better growth of micro-tumors rather than large tumors [19].

1.3 Cancer and immune system impairment

Based on investigations, tumors may produce some immunosuppressive factors, such
as alpha-fetoprotein, interleukin-10 (IL-10) and transforming growth factor-β (TGF-
β), which suppress immune responses against tumors and cancer cells themselves
can, therefore, lead to immunosuppression. Hence, scientists have used neutralizing
antibodies against these immunosuppressive factors [6]. Interestingly, patients with
primary immunodeficiency diseases have higher risk to develop cancer.
CSCs are different from normal stem cell and can be identified by the immune
system. The immune system also produces a set of proteins such as complements
with effects against cancer and other immune or inflammatory responses. These pro-
teins released by T cells and are classified as “cytokines.” Cytokines include proteins
such as tumor-necrosis factors, interferons, interleukins, and growth factors. Based
on investigations, vaccination accompany with the complements can cause tumor
lysis. While incompletely defined, several soluble and cellular mediators of tumor
rejection have been described, including complement factors, active macrophages, T
cells, and NK cells. Though T cells need antigen specificity, the molecular and cel-
lular mechanisms of innate immunity can detect the tumor phenotype in the lack of
antigen specificity [20]. Because most TAA are self-proteins, the immune response
cannot detect and destroy them and in patients’ immune tolerance can be created to
TAAs. In addition, the cells of the immune system may not influence tumor microen-
vironment, resulting in slower immune-mediated tumor eradication [19].
Reports have also indicated that genetic elements are as important as environ-
mental carcinogens. Investigations on retrovirus infection between different breeds
of animals have indicated that a unique carcinogen resulted in different consequences
among different breeds, demonstrating the effect of genetic background in the induc-
tion of cancer. Environmental factors may also regulate immune responses [21].

1.4 Cancer therapy and immunotherapy
As previously have been mentioned, tumor cells can express similar antigens to nor-
mal cells, with lower quantity allowing tumor cells to evade immune system attack
by inducing of tolerance. Immunotherapy may damage to the normal tissues and
organs, such as process by the development of autoimmunity induced by anticy-
totoxic T lymphocyte-associated antigen 4 (anti-CTLA-4) or anti-PD1 monoclonal