ico-oncogenetica

Oncogenetics

Uncontrolled cell growth creating malignant tumours 

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Cancer happens when normal cells start to grow uncontrollably, creating a malignant tumour. Around 1 in 3 people will develop cancer in their lifetime. It is the second most common cause of death in Europe, and the most common among those aged between 45 and 60.

Cancer can occur in any part of the body, changing its normal functioning. Its name is generally associated with the organ where it has originated and it can cause metastasis in other parts of the body.

The organs most often affected by this disease in men are the lungs, the prostate, the colon, the rectum, the stomach and the liver, while in women it is the breast, the colon, the rectum, the cervix and the stomach.

Various causes of cancer have been discovered, including genetic factors, lifestyle factors, such as smoking, diet and exercise, factors involving certain types of infections or exposure to chemical substances and radiation.

All tumours are genetic since sporadic mutations are detected in the tumour. However, only 5 to 10% of tumours are hereditary.

There are over 200 known types of familial cancer. Carriers of a pathogenic variant in a gene associated with different types of hereditary cancer have an increased risk of developing cancer and passing it on to their children.

Over the last ten years, research has identified pathogenic variants in many genes associated with hereditary cancer. Some of these genes can play an important role in various types of cancer and in most cases various genes can cause cancer.

Sistemas Genómicos, in collaboration with the National Centre for Cancer Research (CNIO), has developed a complete panel of 111 genes, making it possible to study all of the most important genes associated with hereditary cancer so that one simple laboratory process can provide quick and precise results.

How might I know if I’m at risk of hereditary cancer?
  • If there have been diagnoses of cancer at an early age in your family: breast or ovarian cancer, bowel cancer or endometrial cancer.
  • If various family members are diagnosed with the same kind of cancer across various generations on the same branch of the family tree:
    • 2 or more cases of breast, ovarian, prostate or pancreatic cancer
    • 2 or more cases of bowel, endometrial, ovarian, stomach or pancreatic cancer
    • 2 or more cases of pancreatic cancer or melanoma
  • If a rare cancer is detected at any age:
    • ovarian cancer
    • breast cancer in a male
    • bowel cancer with microsatellites instability
    • 10 or more gastrointestinal polyps detected
  • If a pathogenic variant is detected in a family member with cancer.  

Various studies have shown that between 5 and 10% of tumour in the breast and ovaries have a hereditary component. The main susceptibility genes are BRCA1 and BRCA2. These high-penetrance genes are inherited through the dominant autosomal mode.

According to the NCCN, a high risk should be suspected in the following cases:

  • Breast cancer before the age of 50
  • Ovarian cancer
  • Breast cancer in males or family members with breast cancer in males
  • Triple-negative breast cancer
  • Association with pancreatic or prostate cancer
  • Two or more family members with breast cancer under the age of fifty
  • Detection of a pathogenic variant in the BRCA1 or BRCA2 gene in a family member

People diagnosed with breast or ovarian cancer who have had a mutation detected on the BRCA1 and BRCA2 genes are at a high risk of developing another kind of cancer in the future.

However, 15 other genes have been described as having a high and medium penetrance associated with breast and ovarian cancer, such as RAD51C, TP53, PTEN, STK11, CHEK2, PALB2, BRIP1, ATM, CDH1, XRCC2, MRE11A, NBN, RAD51D.

If it is confirmed that there is a mutation on the BRCA1 or BRCA2 gene or a mutation of another gene associated with a risk of breast cancer, your doctor may have other options to help you reduce your risk, taking preventative measures, detecting cancer early on or improving your treatment.

Bowel cancer is hereditary in 5% of patients.

Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome is characterised by an increased risk of suffering from both colon cancer and other types of cancer such as endometrial, ovarian, stomach or small intestine. HNPCC is diagnosed clinically by following the Amsterdam or Bethesda clinical criteria; however, there are families that do not meet these criteria and have mutations in some of the associated genes.

Familial adenomatous polyposis (FAP) is a hereditary disease that primarily appears as many sessile or pedunculated polyps of various sizes with a tubular adenomatous structure, hairy or mixed, that cover the gastrointestinal mucous membrane and are considered premalignant. From a genetic perspective, there is a huge dominant autosomal hereditary pattern and it is caused by mutations on the APC gene.

MYH-associated polyposis (MAP) is inherited via recessive autosomal pattern. People with MUTYH biallelic mutations are prone to multiple adenomas. MUTYH biallelic mutations have been found in people diagnosed with bowel cancer below the age of 50 that have not had many polyps or none at all. The frequency of duodenal polyposis is between 4% and 25% in people with MUTYH biallelic mutations.

There are other types of polyposis: hamartomatous, juvenile, Peutz-Jeghers syndrome.

Diffuse gastric cancer (DGC) is part of a common group of gastric cancers and is characterised by the appearance of a poorly differentiated adenocarcinoma that infiltrates the stomach wall, making it rigid. Hereditary gastric cancers make up for 1% of these cancers, appearing before the age of 40. From a genetic perspective, there is a huge dominant autosomal hereditary pattern and it is caused by mutations on the CDH1 gene.

Familial Prostate Cancer It is estimated that between 5% and 10% of cases of Prostate Cancer (PCa) are mainly due to high-risk inherited genetic factors or susceptibility genes for this type of neoplasia. High-risk families are deemed to be those that have three or more close family members affected by Prostate Cancer, the presence of the pathology across three or more generations or early-age diagnosis in at least two affected close family members. It is associated with the HOXB13, CHEK2 and BRCA2 genes.

Familial Pancreatic Cancer (FPC) is found in families with at least two close family members with confirmed exocrine pancreatic cancer. FPC inheritance is mainly dominant autosomal with a heterogeneous phenotype. The main gene involved is yet to be discovered although germline mutations have been detected in the BRCA2, PALB2 and ATM genes.

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