Question

Imunalogy
Compare the stages of carcinogenesis and the different aspects of cancer-related genes.

Define and give examples of proto-oncogenes.

Describe the role of oncogenes.

Describe the characteristics of the major body defenses against cancer.

Answer 1

Compare the stages of carcinogenesis and the different aspects of cancer-related genes.

The process of carcinogenesis may be divided into at least three stages:1) initiation,2) promotion, and 3) progression.

The first stage of carcinogenesis, initiation, resulting from an irreversible genetic alteration, mostly mutations, transversions, transitions, and/or small deletions in DNA.

The reversible stage of promotion does not involve changes in the structure of DNA but rather in the expression of the genome mediated through promoter-receptor interactions.

The final irreversible stage of progression is characterized by karyotypic instability and malignant growth. Critical molecular targets during the stages of carcinogenesis include proto-oncogenes, cellular oncogenes, and tumor suppressor genes, alterations in both alleles of the latter being found only in the stage of progression.

Define and give examples of proto-oncogenes.

A normal gene which, when altered by mutation, becomes an oncogene that can contribute to cancer. Proto-oncogenes may have many different functions in the cell. Proto-oncogenes signals cell division and regulate programmed cell death

Example of proto oncogene:-

• Ras.     Ras associated with colorectal cancer
• HER2. HER2 associated with breast cancer.
• Myc.     associated with a type of cancer called Burkitt's lymphoma.
• Cyclin D. associated with B cell lymphocytic leukemia,testicular and ovarian cancer

Describe the role of oncogenes.

Oncogenes are a structurally and functionally heterogeneous group of genes, whose protein products act pleiotropically and affect multiple complex regulatory cascades within the cell. They disregulate cell proliferation, growth, and differentiation, as well as control of the cell cycle and apoptosis

Describe the characteristics of the major body defenses against cancer.

Immune response in the body is followed by a suppressive counter response which is characterized by the expression of so-called “immune checkpoint” receptors or by the attraction of regulatory immune cells.

This counter response prevents excessive inflammation and tissue damage once an infection has been cleared from the body. However, tumors can harness this mechanism to protect themselves against destruction by the immune system. One reason the immune system usually does not attack normal cells is that the surface of normals cells carries proteins that signal to circulating immune cells (T-cells) that the cell bearing them is normal and should not be attacked. These are called checkpoint proteins. Sometimes cancer cells develop the ability to produce one or more of these checkpoint proteins and thus escape from attack. Newer types of cancer drugs called checkpoint inhibitors can block the signal and allow the immune system to attack the cancer.