Centre For Human Genetics
Genetics is the study of genes, their structure and their functioning. It throws light on the mechanism of certain illnesses, such as cancer, and opens up therapeutic perspectives.
Genetic anomalies and the risk of cancer
The starting point for cancer has always been a mutation of a gene(s).
In hereditary cancers, the anomalies of some genes are present from birth. They form part of your gene pool. In non-hereditary cancers anomalies occur during the course of life. These are known as “acquired” anomalies. Genetics also has an interest in this since the anomalies identified from that time on say a lot about the aggressiveness of the tumour and are predictive of its evolution, enabling a better adapted treatment to be ascertained.
In the case of familial or hereditary disposition, genetic tests are important in identifying the possible presence of the anomaly associated with an increased risk of cancer, as early as possible.
Hereditary cancers represent 5% of all cancers. They are characterised by their early manifestation, that is, around the age of 25 or 30, and become manifest in several people from the same familial branch. The most frequent are breast and colon cancers.
Genetic advisory consultations provide patients suffering from a hereditary cancer or members of their family with all the information on the risk of developing, or passing on the illness, as well as possible preventative measures. In our centre - and this is one of our specificities - genetic advisory consultations are provided for families at risk of breast cancer and colon cancer. They thus benefit from close monitoring, which is intended to detect the occurrence of a possible cancer as quickly as possible.
The most frequent form of hereditary colorectal cancer is Lynch syndrome or HNPCC. Familial polyposis adenomatous syndromes and multiple adenoma syndromes are rarer, as are the various hamartomatous polyposis syndromes. Click here to learn more.
In hereditary breast cancers, the most frequent mutations are those of the BRCA-1 and BRCA-2 genes.
Dans les cancers du sein héréditaires, les mutations les plus fréquentes sont celles des gènes BRCA-1 et BRCA-2.
Représentation schématique d'un arbre généalogique: les carrés illustrent les hommes, les ronds les femmes, la couleur noire le statut clinique de polypose adénomateuse familiale. Le génotype correspondant à la mutation germinale du gène APC, dont les électrophérogrammes accompagnent la généalogie, est représenté par le sigle - : l'allèle normale du gène APC étant associé au caractère +.
Genetic Anomalies and diagnostic interest
Genetics are of diagnostic interest. In some cancers they turn out to be just as efficient as other examinations. This is the case particularly for sarcoma and blood cancers.
The identification of possible genetic anomalies associated with sarcoma enables them to be better differentiated and, meaning the treatment which is most suited can be opted for: genetic modifications are in effect predictive of the evolution of the tumour, of its behaviour. It is therefore important to share, in the context of pluridisciplinary meetings, information provided by genetics and that which results from other examinations (radiology, examination of the diseased tissue under the microscope …).
In blood cancers, genetic factors may play an important role in the emergence of the illness or in its evolution from a dormant form, to a more active form.
These cancers were previously diagnosed by being based principally on the morphology of blood cells.
Analysis of some markers, or antigens, shown on the surface of these cells then allows the diagnosis to be refined. Today the examination of genetic anomalies means that cancers of the blood can be better differentiated, allowing a treatment which is best suited to be chosen, and identifying potential targets within the cancerous cells for new medications. These therapies, which are called “targeted” therapies, act in a specific way on anomalies, without having an effect on the whole body, as is the case with chemotherapy. They are thus better tolerated. Targeted therapies are the subject of international studies in which reference centres, such as ours, take part.
Finally, in blood cancers, genetics enable a residual illness to be detected: cancerous cells which are not identified by standard examinations linger in the body after treatment. It is important to be able to detect these cells, which are known as “residuals” since they sometimes require supplementary treatment.
A necessary complementarity
In our Cancer Centre the progress made in the genetics of cancer is put to good use in the pluridisciplinary meetings in which geneticists and doctors in charge of diagnosis and of cancer treatment take part. This conjunction of knowledge thus allows the most appropriate approach to be determined for the patient, the type of cancer, the extent of its spread and its genetic characteristics.
Research
During the last decade, a great deal of progress has been made in genetics, thanks to the development of DNA chips, a real identity card of the human gene pool, at very high resolution. This tool is now accessible at the centre for genetics and is used in characterising cancers which are at times difficult to categorize.
Research on genetic anomalies associated with certain cancers requires state of the art surgical appliances. Tools at the reference centres today allow the composition of genes to be studied in a very detailed manner.
Advances in knowledge in the area of the genetics of cancers require collaboration with other large international centres. Our Centre for Human Genetics is therefore a part of European associations, which allow a high number of observations to be built up and validated.
Caryotype 24 - couleurs
