Genetic causes of esophageal cancer

The primary reason esophageal cancer develops is an accumulation of genetic mutations that disrupt the normal regulation of cell growth and death. Most of these mutations are acquired during a person's lifetime due to environmental and lifestyle factors like smoking, alcohol consumption, and chronic acid reflux. A small number of cases are due to inherited mutations passed down through families.

Acquired Genetic Mutations

Most esophageal cancer cases result from gene mutations that occur within a person's lifetime. These changes are not inherited but are driven by external factors that cause chronic damage and inflammation. The specific genes affected often differ between the two main types of esophageal cancer.

Genes in Esophageal Adenocarcinoma (EAC)

EAC is the most common type of esophageal cancer in the U.S. and is strongly associated with gastroesophageal reflux disease (GERD) and Barrett's esophagus. The genetic pathway to this cancer involves an accumulation of mutations that allow cells to grow out of control.

• TP53: This is the most frequently mutated gene in EAC. It is a tumor suppressor gene often called the "guardian of the genome" because it triggers DNA repair or programmed cell death (apoptosis) in damaged cells. A mutated TP53 gene loses this crucial function, allowing cells with DNA damage to continue dividing.

• ERBB2 (HER2): The ERBB2 gene is an oncogene that, when amplified, leads to an overproduction of the HER2 protein on the cell surface. This protein drives cell growth and division. Cancers with this amplification are considered HER2-positive, and they can be treated with targeted therapies like trastuzumab (Herceptin).

• CDKN2A: This tumor suppressor gene acts as a brake on the cell cycle. Mutations or inactivation of CDKN2A allow cells to divide without regulation, contributing to uncontrolled growth.

Genes in Esophageal Squamous Cell Carcinoma (ESCC)

ESCC is linked to smoking, alcohol consumption, and a poor diet. It is the most prevalent type of esophageal cancer worldwide.

• TP53: Similar to EAC, TP53 is the most commonly mutated gene in ESCC, with mutations seen in a large majority of cases. Its loss of function is a central driver of the disease.

• CCND1: The CCND1 gene encodes a protein that helps cells progress through the cell cycle. Amplification of this gene is a frequent event in ESCC, leading to an over-expression of its protein product and excessive cell division.

• NOTCH1: This gene is involved in regulating cell differentiation. Mutations in NOTCH1 are frequently found in ESCC and contribute to the uncontrolled proliferation of squamous cells.

Inherited Genetic Mutations

While most cases are not hereditary, a small number of people are born with inherited mutations that significantly increase their risk of developing esophageal cancer. These germline mutations are present in every cell of the body and can be passed down through families.

• RHBDF2: Mutations in the RHBDF2 gene cause a rare inherited condition called Tylosis with esophageal cancer (Howel-Evans syndrome), which leads to a very high lifetime risk of developing ESCC.

• BLM and FANC genes: Rare inherited mutations in genes like BLM (Bloom syndrome) and FANC (Fanconi anemia) impair a cell's ability to repair DNA damage. This accumulation of unrepaired damage makes individuals more susceptible to various cancers, including ESCC.

• Familial Barrett's Esophagus: Some families have a genetic predisposition to developing Barrett's esophagus and, subsequently, EAC. While the specific genes involved are still being investigated, this familial clustering points to an underlying inherited genetic component.