Cancer is the second largest killer in the UK. Mutations arise in the genetic information in the cell which leads to uncontrolled growth and division of cells. Unhampered by normal restraints they eventually invade surrounding tissues and spread in the body. Certain mutations in the human genome seem to be linked to cancers. They seem to drive cancer growth. For example the BRAF, MEK and EGFR mutations are common mutations found in melanoma skin cancer.
A new multi-gene test is being introduced which will look for 46 known gene mutations. Drugs can then be given to patients that inhibit or attack the gene mutation. At the moment chemotherapy [drug treatment] is usually non specific and attacks all dividing cells so normal cells as well as cancer cells are harmed. This is leads to side effects such as nausea and hair loss. Being able to detect the exact mutation can lead to being able to provide drugs that target that mutation for example MEK and BRAF inhibitors have been used. Doctors will be able to predict what drugs will work more accurately and chemotherapy should have less side effects. Certain genes such as the BRCA 1 and BRCA 2 genes have been shown to be associated with aggressive forms of breast cancer and now prostate cancer. This is extremely useful as cancers picked up on screening are often relatively harmless -‘the pussy cat type’ rather than the ‘tiger’ and treatment may cause more harm than leaving alone so being able to differentiate and pick out the killers is important. See previous blog on breast cancer screening- //medicalschoolinterviewstheknowledge.wordpress.com/2012/11/04/topical-issues-of-the-week-breast-screening-pussy-cats-and-tiger-cancers
Cancer cells are extremely hard to eliminate. Unlike bacterial cells cancer cells are of course very like our normal cells so substances that kill them effectively are usually toxic -they kill normal cells too. They often contain several, some times hundreds of mutations and have the ability to form further mutations as they multiply uncontrollably. So when we attack one mutation new mutations form which eventually renders the treatment useless.
It is estimated that we have millions of cells with mutations. It is thought we often have a few cancerous cells. Thankfully our immune system can recognise cancer cells. When normal cells turn into cancer cells, some of the antigens on their surface change. These cells, like many body cells, constantly shed bits of protein from their surface into the circulatory system. Often, tumour antigens are among the shed proteins. These shed antigens prompt action from immune defenders, including cytotoxic T cells, natural killer cells, and macrophages. Patrolling cells of the immune system provide continuous body wide surveillance, catching and eliminating cells that undergo malignant transformation. Tumours develop when this immune surveillance breaks down or is overwhelmed.