As a medical writer aiming to keep abreast of new developments, I recently read a report on the genetic analysis of lung tumours with interest, especially having worked in cancer genetics as a research scientist. In this Nature article, the authors analysed a sample of lung adenocarcinomas and identified 26 genes that were highly mutated, including some not previously associated with lung cancer and some known to be mutated in other cancers.
1 These genes will no doubt be the subject of further study, paving the way for possible new targets of therapy in the future.
This work is one example of an increasing view in the modern post-genomic era of cancer not simply as an anatomically-defined disease, but as a collection of diseases owing to particular dysfunctional genes.
2, 3 So to a clinician, a patient does not merely present with lung cancer or breast cancer, but a cancer of mutated genes x, y and z. Hand-in-hand with this view is the increasing trend for developing targeted therapies, where a drug no longer strikes tumours by virtue of their rapid growth, taking a host of other, healthy tissues with them, but hones in on the abnormality specifically expressed in the cancerous cells. Herceptin, which targets the HER2 receptor that is over-expressed in 20-30% of breast cancers,
4 and Glivec, inhibitor of the aberrant kinase expressed by the
BCR-ABL gene that causes chronic myeloid leukaemia,
5 are only two examples that have made a great impact on our quest for effective therapies.
We know that some breast cancers show HER2 over-expression but others do not, and that genes can be mutated in some lung tumours but not in others, illustrating the fact that different faulty genes contribute to tumour development in different individuals.
1 Furthermore, evidence suggests that the mutational status of certain genes can affect a tumour’s sensitivity to chemotherapy or radiotherapy.
6 Our understanding of the roles played by different genes is ever-expanding thanks to basic bench research, be it with
in vitro systems,
in vivo models, using single-celled organisms or more evolved animals. Together with the rapidly developing technologies for genetic profiling, it may one day become possible to determine the genetic basis for every patient’s cancer and tailor a cocktail of therapies just for them.
7 We may never find that elusive “cure” for cancer, but using our best efforts to understand its causes and progression, we may be able to tame it into something we can control and live with.
8 References 1. Ding L
et al. Somatic mutations affect key pathways in lung adenocarcinoma. Nature 2008; 455: 1069-1075.
2. Geddes L. Cancer special: living with the enemy. New Scientist; 22 October 2008. Available online at:
www.newscientist.com [accessed January 2009].
3. Dong LM
et al. Genetic susceptibility to cancer: the role of polymorphisms in candidate genes. JAMA 2008; 299: 2423-2436.
4. Roche Products Ltd. Herceptin Summary of Product Characteristics (Date of revision: September 2008). Available online at:
www.emc.medicines.org.uk [accessed January 2009].
5. Novartis Pharmaceuticals UK Ltd. Glivec Summary of Product Characteristics (Date of revision: November 2007). Available online at:
www.emc.medicines.org.uk [accessed January 2009].
6. Weichselbaum RR
et al. An interferon-related gene signature for DNA damage resistance is a predictive marker for chemotherapy and radiation for breast cancer. PNAS 2008; 105: 18490-18495.
7. Ley TJ
et al. Molecular sequencing of cytogenetically normal acute myeloid leukaemia genome. Nature 2008; 456: 66-72.
8. Aldhous P. Cancer special: old killer, new hope. New Scientist; 22 October 2008. Available online at:
www.newscientist.com [accessed January 2009].
Ellen