Using DNA Microarray Technology in Cancer Diagnosis

DNA microarray technology is a powerful tool that scientists and doctors can use to help predict the course of a disease for a person that has been diagnosed with cancer. The diagnosis of cancer has generally been done by taking a biopsy of a tumor and looking at the cells under a microscope to come up with the diagnosis.

Now scientists and doctors can use DNA microarray technology to classify cancers based on the genetic sequence in a cell from the tissue taken from the biopsy and get a better diagnosis. Only looking at the appearance of cancer cells can be misleading because the treatment used to treat one cancer may work with one patient but not another. Therefore, along with histopathological examination to determine the prognosis of cancer in a patient, knowing the genetic sequence can help develop more personalized treatment plans for a person that has cancer. This technology is very useful because scientists can classify cancers based on the functions of the genes in the cancerous cell(s).

DNA microarray is made up of a slide, or similar to a computer chip, that has a sequence of DNA placed on it by a robot. This sequence will later be used to match with another sequence of genetic material to analyze the expression of the genes. Before the expression of the genes can be determined, the robot will place the DNA sequence in a grid formation, which is spaced in a pattern of regularly spaced horizontal and vertical lines. After that the DNA sequence is placed on the microarray chip by the robot, a tissue sample, usually a blood sample, is taken from the patient that has been diagnosed with cancer.

The tissue sample is placed in a solution that allows for the cancerous cells to be broken down so the DNA and RNA can be separated. As a result, RNA molecules that are bonded together, specifically the messenger RNA (mRNA), can be collected. Once the mRNA is collected, a scientist can bind a fluorescent dye to the mRNA and the mRNA can be placed on the microarray chip by a robot. The mRNA is a copy of the DNA and, therefore, is complimentary to the DNA it was copied from. Thus, once the mRNA is placed onto the chip, the mRNA that was expressed from the DNA will bind onto the DNA that it is complementary to.

As a result, the mRNA that binds with the DNA on the chip will give off a fluorescent dye that can be analyzed by a computer. The brighter the color that is present on the computer screen, the more active the gene is and the less color, or even no color, means that a gene is not being expressed.

Being able to look at the expression patterns and levels, referred to as the brightness from the fluorescent dye, allows scientists to be able to determine which genes are being active in a cancerous cell. Therefore, personalized treatment plans can be developed for each individual patient.

Reference

Machine Learning in DNA Microarray Analysis for Cancer Classification https://crpit.com/confpapers/CRPITV19Cho.pdf