Center for human genetics

A cancer always starts with a mutation in one or several genes.

In hereditary cancers, abnormalities in certain genes are present from birth. They are part of the genetic heritage. In non-hereditary cancers, the abnormalities occur during life. These are called "acquired" abnormalities. Genetics is also interested in this field because the anomalies identified, once they reveal the aggressiveness of the tumor and predict its evolution, make it possible to determine the most appropriate treatment.

In case of familial or hereditary predisposition, it is important to screen as early as possible, through genetic testing, for the possible presence of the anomaly associated with the increased risk of cancer.

Hereditary cancers represent 5% of all cancers. They are characterized by an early onset, i.e. around 25 or 30 years of age, and occur in several people of the same family branch. The most frequent are breast and colon cancers.

Genetic counseling provides patients with hereditary cancer or their family members with information about the risk of developing or transmitting the disease and possible preventive measures. In our center, and this is one of our specificities, genetic counseling is offered to families at risk of breast and colon cancer. These families benefit from a close follow-up to detect the occurrence of a possible cancer as soon as possible.

The most common form of hereditary colorectal cancer is Lynch syndrome, also known as hereditary non-polyposis colorectal cancer (HNPCC). Less common are familial adenomatous polyposis syndromes and multiple adenoma syndromes, as well as various hamartomatous polyposis syndromes. To learn more, click here.

In hereditary breast cancer, the most frequent mutations are in the BRCA-1 and BRCA-2 genes.

Schematic representation of a family tree: the squares illustrate the males, the circles the females, the black color the clinical status of familial adenomatous polyposis. The genotype corresponding to the germline mutation of the APC gene, whose electropherograms accompany the genealogy, is represented by the sign -, the normal allele of the APC gene being associated with the sign +.

Genetics is diagnostically relevant. In some cancers, it performs at least as well as other tests. This is namely the case for sarcomas and blood cancers.

The identification of possible genetic abnormalities associated with sarcomas allows for better differentiation and, consequently, the choice of the most appropriate treatment: genetic changes are indeed predictive of the evolution of the tumor and its behavior. It is therefore essential to pool the data provided by genetics and those provided by other examinations (radiology, microscopic examination of the diseased tissue, etc.) as part of multidisciplinary meetings.

In blood cancers, genetic factors may play an important role in the occurrence of the disease or in its progression from a dormant to a more active form.

These cancers were previously diagnosed primarily on the basis of blood cell morphology.

The analysis of certain markers, or antigens, expressed on the surface of these cells then allowed the diagnosis to be refined. Today, the examination of genetic abnormalities makes it possible to differentiate blood cancers even better, to choose the most appropriate treatment, and to identify potential targets within the cancer cell for new drugs. These so-called "targeted" therapies act specifically on the abnormalities, without having an effect on the whole body, as is the case with chemotherapy. They are therefore better tolerated. Targeted therapies are the subject of international studies in which reference centers such as ours participate.

Finally, in blood cancers, genetics can be used to detect residual disease: sometimes cancer cells that are not identified by the usual tests persist in the body after treatment. It is important to be able to detect these so-called "residual" cells because they sometimes require additional treatment.

In our institute, the progress made in cancer genetics is put to good use during multidisciplinary meetings in which geneticists and physicians in charge of the diagnosis and treatment of cancers take part. The combination of knowledge allows determining the most appropriate approach according to the patient, the type of cancer, its degree of extension, and its genetic characteristics.

During the last decade, great progress has been made in the field of genetics thanks to the development of DNA chips, a true identity card of the human genetic heritage at very high resolution. This tool is now accessible to the genetics center and used in the characterization of cancers that are sometimes difficult to classify.

Research on genetic anomalies associated with certain cancers requires state-of-the-art equipment. The tools of the reference centers now make it possible to study the composition of genes in great detail.

The advancement of knowledge in the field of cancer genetics implies collaboration with other major international centers. Our Center for Human Genetics is therefore part of European groups, which enables to accumulate a large number of observations and to validate them.