p53 and Cancer

p53 mutations have been documented in around 50% of cancers making it the most common genetic event in human malignancies. Located on chromosome 17p13, it encodes a 53 kilodalton modular nuclear phosphoprotein, which functions predominantly as a transcriptional regulator. p53 protein within a cell integrates signals arising from a wide range of cellular stresses and directs cellular responses through several downstream genes via its conserved domain viz N-terminal, SH3-binding, sequence-specific DNA binding, tetramerization and C-terminal.


Under normal circumstances of cell growth, p53 protein has a relatively short half-life, being mainly controlled through an autoregulatory loop in which Mdm-2 binds p53 and targets it for nuclear export and ubiquitin-dependent proteolysis. In times of cellular stress, p53 is phosphorylated by protein kinases at several sites, becomes stabilised, and act via different pathways that ultimately lead to protection through growth arrest or apoptosis of the damaged cell. In the event of p53 protein inactivation via various mechanisms there will be loss of its protective functions, allowing damaged cell to continue in the cell cycle and placing the cell at risk of malignant transformation.

The Role of Genetic Testing in Medical Practice in The 21st Century

The practice of medicine has been revolutionized by the progress made in genetics. Genetic testing has become the gold standard in the diagnosis of many disorders. The decoding of entire human genome by Human Genome Project have improved our understanding and discovery of the genetic basis of many disorders. There are more than 6000 different single gene disorders identified to date. Many more disorders are being identified and characterized everyday with the discovery of the genes involved. The prevention of many genetic disorders is now made possible by preconceptional carrier testing, prenatal diagnosis or preimplantation diagnosis with the availability of various new molecular testing.

However, there is still a gap between the discovery of the genes, the diagnostic testing and the actual prevention of many of these conditions. Majority of the genetic disorders has a variety of mutation mechanisms, which make molecular testing difficult even for the proband. Unless the mutation is characterized in the proband, accurate and rapid prenatal diagnosis may not be possible. Furthermore, variable expressivity and severity of some genetic diseases create dilemma and obviate the benefits of prenatal diagnostic testing, for example the disorders coded by mitochondrial DNA. In addition, many of the conditions are too rare and not cost effective to be carried out by routine molecular diagnostic laboratory. A list of genetic testing available including the laboratories performing the test is available at www.genetests.org. Ethical issues surrounding genetic testing, the availability of treatment and severity of the disease, social and culture peculiarities will continue despite the growing availability of molecular diagnostic testing for many genetic disorders.

Hopefully, the advances in genetic testing will enable the early detection, prevention and effective therapy based on the molecular understanding of many common chronic diseases with complex inheritance such as hypertension, asthma, diabetes, stroke and ischemic heart diseases. Genetic characterization of individuals will also enable pharmaceutical companies to design the best drugs tailored to the genetic make-up of individuals hence achieving the best response with least side effects. The possibility of having one's genome stored in chips for various purposes can also be achieved in future.