Understanding Cancer Genes and Genetic Risk

An estimated 170,000 Australians were diagnosed with cancer in 2025, highlighting the significant impact of this disease. While many factors contribute to cancer development, genetics play a crucial role. But how do genes influence cancer risk, and what can be done to mitigate that risk?

How DNA Mutations Lead to Cancer

DNA, often called the “instruction manual for life,” provides the blueprint for our cells. This manual is comprised of genes, sections of DNA that instruct cells to make proteins. Proteins are essential for normal cell function, acting as the “cogs and gears” that keep everything running smoothly.

Cancer arises when DNA mutations – mistakes in this instruction manual – occur. Cells have proteins dedicated to identifying and repairing these mutations. Still, if a mutation remains uncorrected, it can lead to cells producing too much or too little of a certain protein, or a protein that doesn’t function correctly.

A common pathway to cancer involves mutations in genes responsible for repairing DNA. For example, mutations in the BRCA1 gene can impair DNA repair mechanisms. If a cell with a BRCA1 mutation accumulates further mutations, it can begin to divide uncontrollably and resist normal cell death, ultimately becoming cancerous.

Inherited vs. Acquired Mutations

There are two primary types of DNA mutations:

• Germline Mutations: These occur in egg or sperm cells and can be passed down to children.
• Somatic Mutations: These occur in any other cell type and are not inheritable.

Inheriting a mutated gene, like BRCA1, means that every cell in the body carries one copy of the faulty gene. While a functional copy of the gene remains, the overall risk of developing cancer is significantly increased.

The Impact of Inherited Mutations

Studies indicate a clear correlation between inherited mutations and cancer risk. For instance, women with an inherited BRCA1 mutation have a 65% chance of developing breast cancer and a 39% chance of developing ovarian cancer by age 70 [2]. In contrast, women with no family history of breast cancer have a 9-12.5% chance of developing the disease by age 75. Similar increased risks are observed for men with BRCA1 or BRCA2 mutations, particularly for breast and prostate cancer.

Other “cancer genes” have been identified, such as TP53, which plays a role in killing abnormal cells. Mutations in TP53 are associated with Li-Fraumeni syndrome, a condition that carries a 90% lifetime risk of developing some form of cancer [2].

What Can Be Done About Cancer Genes?

While you cannot change your genes, you can take steps to reduce your cancer risk. Adopting a healthy lifestyle – avoiding smoking, limiting alcohol consumption, exercising regularly, maintaining a balanced diet, and practicing sun safety – is crucial.

If you have a family history of cancer, consulting your doctor is recommended. They can assess your risk and discuss the possibility of genetic testing and counseling. For individuals with inherited genetic mutations, earlier and more frequent cancer screenings or preventative surgeries may be advised. Early detection remains key to effective cancer treatment.

Advances in Genomic Screening in Australia

Australia is at the forefront of genomic screening initiatives. Monash University’s DNA Screen program has partnered with Cancer Australia to advance the Australian Cancer Plan [1]. A recent national pilot program offered genomic screening to young adults (aged 18-40) for genes linked to hereditary breast and ovarian cancer, Lynch syndrome, and familial hypercholesterolaemia [3]. The program demonstrated high public engagement and clinical uptake, identifying individuals who may not have been eligible for government-funded testing based on current criteria.

This research highlights the feasibility of population-based genomic screening and its potential to improve cancer prevention and early detection efforts in Australia.