Introductory Chapter: Gene Profiling in Cancer in the Era of Metagenomics and Precision Medicine

Abstract

According to the central dogma of molecular biology, the entire process of producing proteins in cells is defined as gene expression, which includes replication of the DNA, DNA transcription into mRNA, and mRNA translation into proteins [1]. Although DNA is the same in all cell types of an organism, each cell expresses only a part of its genes each time, which equates to the ability of the cell to modify the expression of its genome and thus changes its functions [2]. Gene expression profiling is a process in which the genes expressed in a cell can be measured at a specific time [3]. This method simultaneously calculates the levels of thousands of genes leading to the presentation of the expression pattern of the cell’s genes [4]. Therefore, through gene expression profiling, we can discover the functions of a cell at a particular time, which constitutes an important application of this method in cancer cells. A cancer cell is defined as each cell of a tissue in which there is a loss of the standard controlling mechanisms of cell division, resulting in its uncontrolled multiplication, leading to the accumulation of transformed somatic cells, which contain many genetic alterations and epigenetic modifications. These cells have the ability to filter into adjacent tissues, creating metastasis. Metastatic cells impede the physiologic functioning of the vital organs and destroy the physiological tissues resulting in death [5].