In other words, whenever scientists have fallen for the illusion that there was a single, simple key to what causes cancer, this hope has been dashed. In the case of breast cancer, some studies indicated that over one hundred genes were involved. However, with the decoding of the complete human genome in 2003, when scientists looked deeper into which genes differed within malignant cells compared with normal cells from the same patients, they found that many genes differed. This led to the idea that identifying the small number of genes involved in a specific type of cancer would allow one to correct the damage caused by the mutated gene, thereby halting the process of malignant growth. In the 1990s the discovery of the role of specific mutations in the development of colorectal cancer led to the new notion that “cancer is a genetic disease.” This meant that every cancer begins with a mutation that the body’s proof-reading machinery fails to correct and that goes on to develop into a full-fledged cancer. So, the question remains, what causes most cancers? Most cancers do not have a single, potent cause even remotely comparable to cigarette smoking. However, lung cancer – the main cancer caused by cigarette smoking – appears to be an exception. Rather than exposure to chemicals in the environment – which most of us are exposed to at extremely low levels – cigarette smoking is by far the source of the most important exposure to chemicals, and this habit accounts for roughly one-third of all cancers in the U.S. Certainly, some occupational exposures that cause cancer were identified, but these accounted for relatively few cases in the general population, and these exposures were reduced over time as a result of regulation in the workplace. But, aside from cervical cancer and liver cancer, these hopes have not been borne out.Īnother explanation that gained wide adherence in the 1980's and 1990's was the idea that chemicals in the environment played a major role in causing cancer. The finding of cancer genes derived from viruses in human cancers led to the idea that viruses would turn out to cause many cancers. In addition to recounting advances in treatment, the film tells the parallel story of the evolution of ideas about what causes cancer, and here too, it delivers an enlightening, if humbling, lesson. In spite of the progress that has been made, for many of the most common cancers - such as lung, colon, pancreas, esophagus, and ovary – treatment has changed little over the past decades. These, and other discoveries, were only achieved through a process of painstaking effort and overcoming many failures and false leads.
0 kommentar(er)
