Evolution Of Cancer Essay

Cancer is a general term used to describe the abnormal growth of cells which attacks different parts of the body or organs. A tumor, also called neoplasm, can be characterized as an abnormal mass of tissue which may either be solid or fluid-filled. Not only can a tumor becomes cancerous, it can also be benign

(not cancerous), pre-malignant (pre-cancerous), or malignant (cancerous). According to World Health

Organisation (WHO), cancer is the second leading cause of death and around 8.8 million people died of cancer related diseases in 2015. The most common types of cancer affecting men are: prostate, lung, colorectal, stomach and liver cancer and among women, we have the cervical, lung, breast, stomach and colorectal cancer. Also, according

The development of cancer within an individual takes an evolutionary process similar to the evolution of species. In the evolution of species, individuals in a population tend to evolve by mutation and selection.

By mutation, we mean the change in the gene of a cell that can be passed to the offspring, while selection is simply an increase in the diversity of life. Similarly, tumors evolve by mutation and selection. However, these processes act on cells in a tissue caused by carcinogens (a substance capable of causing cancer in living tissue)(Casás-Selves and DeGregori, 2011). A concept that explains the reproducibility of the evolutionary process is known as tumorigenesis. In tumorigenesis, despite the presence of confounding factors (e.g genetic background, micro-environment), each tumor of the same type, or subtype can be seen as an independent realization of the same evolutionary process.

The immune system can be described as the network of cells, tissues and organs that work together to protect the body against infection and illness caused by pathogens. There are two types of

Examples of cells of the innate immune system are macrophages, natural killer (NK) cell, dendritic cells etc., while that of the adaptive system are of two main types called the B cells (e.g. antibodies) and T cells (e.g. Helper

T cells, Cytotoxic T lymphocytes (CTLs)). The primary function of the immune system is to grant protection against cancer, this implies that the immune system is important to cancer patient as it helps fight against cancer. The main response of the immune system to tumors is to destroy the abnormal cells using CTLs. When tumor antigens are presented on major histocompatibility complex (MHC) class

I molecules, the CTLs recognizes the tumor cell as abnormal cells and destroys them. Sometimes, this task can be accomplished with the assistance of the helper T cells. Antibodies can also be generated against tumor cells causing its destruction by the complement system. However, tumor cells can avoid being detected by CTLs by reducing the number of MHC class I molecule on their surface (Green et al.,

2009).

As dangerous and deadly as cancer is to our society, there is still a gap in our understanding of