Cancer is an uncontrolled, invasive growth of abnormal cells that divide repeatedly. Cancer cells accumulate at a certain place to form a tumour. The tumour can be either benign or malignant. Benign tumors are non-cancerous growth while malignant tumours are cells that invade and interfere with the functioning of surrounding normal tissue.
Research and testing have showed that there are at least 6 viruses that can cause cancer. Viruses that cause tumour, change cells by integrating their genetic material with the host cells’ DNA, it is a permanent insertion in that the genetic material is never “removed”. DNA tumour viruses can exist as provirus and their viral proteins causes host cells to divide uncontrollably, resulting in a tumour developed. On the other hand, retroviruses are the only RNA tumour viruses that can cause cancer. Retroviruses transcribe (+) sense RNA into DNA, then integrates as a provirus into the host chromosome. The proteins of the provirus transform the host cells into neoplastic ones, where infection leads to the production of new virions by budding, which does not kill the infected cell. Hence, the RNA tumour viruses continue to infect the uninfected cells and after some time, the presence of virus particles ensures transmission of virions to offspring.
Research and testing have showed that there are at least 6 viruses that can cause cancer. Viruses that cause tumour, change cells by integrating their genetic material with the host cells’ DNA, it is a permanent insertion in that the genetic material is never “removed”. DNA tumour viruses can exist as provirus and their viral proteins causes host cells to divide uncontrollably, resulting in a tumour developed. On the other hand, retroviruses are the only RNA tumour viruses that can cause cancer. Retroviruses transcribe (+) sense RNA into DNA, then integrates as a provirus into the host chromosome. The proteins of the provirus transform the host cells into neoplastic ones, where infection leads to the production of new virions by budding, which does not kill the infected cell. Hence, the RNA tumour viruses continue to infect the uninfected cells and after some time, the presence of virus particles ensures transmission of virions to offspring.
http://biology.about.com/library/weekly/aa121400a.htm
An example of a virus that can cause cancer is hepatitis B virus (HBV), which causes the inflammation of the liver.
No comments:
Post a Comment