Cancer arises from changes in a cell’s DNA. These genetic alterations lead to uncontrolled cell growth and division, a hallmark of cancer. Such changes affect specific genes, often called cancer genes, which regulate cell behavior. Understanding these genetic shifts provides insight into how normal cells become cancerous.
Understanding Cancer Genes
Two main gene categories are involved in cancer: proto-oncogenes and tumor suppressor genes. Proto-oncogenes promote cell growth and division, acting like an accelerator pedal. When these genes undergo mutations, they become oncogenes, continuously active and driving uncontrolled cell proliferation. This is a “gain-of-function” mutation, increasing the gene’s activity.
Conversely, tumor suppressor genes regulate cell growth, repair DNA damage, and trigger programmed cell death (apoptosis), acting like a brake pedal. Mutations in tumor suppressor genes lead to their inactivation, meaning they lose their ability to control cell division or initiate cell death. This represents a “loss-of-function” mutation, as the gene’s protective function is diminished or eliminated. Both types of mutations, when accumulated, contribute to the complex process of cancer development.
How Cancer Genes Cause Disease
Mutated cancer genes disrupt cell cycle regulation, leading to uncontrolled proliferation. Oncogenes, when activated, constantly signal cells to grow and divide, overriding the body’s natural controls. For instance, a mutated HER2 gene can cause cells to produce excessive HER2 protein, leading to uncontrolled growth in certain cancers. This unchecked growth allows rapid accumulation of abnormal cells, forming a tumor.
Concurrently, inactivated tumor suppressor genes fail to halt abnormal cell division or repair DNA errors. The TP53 gene, for example, normally helps repair damaged DNA and initiates cell death if damage is irreparable; however, a mutation in TP53 allows cells with damaged DNA to continue dividing. This failure in the body’s quality control mechanisms permits cells with accumulating genetic changes to survive and multiply. Over time, multiple genetic changes in both oncogenes and tumor suppressor genes accumulate, pushing cells towards a cancerous state.
Inherited Versus Acquired Mutations
Cancer-linked genetic mutations are categorized as inherited (germline) or acquired (somatic). Inherited mutations are present in every cell of the body from birth, passed down from a parent. These mutations can significantly increase a person’s lifetime risk of developing certain cancers, though they do not guarantee cancer will develop. For example, mutations in the BRCA1 and BRCA2 genes are well-known inherited mutations that elevate the risk of breast and ovarian cancers.
Acquired mutations, also known as somatic mutations, occur during a person’s lifetime and are found only in specific cells, often within the tumor itself. These mutations can arise from various factors, including random errors during cell division, exposure to environmental carcinogens like tobacco smoke or UV radiation, or simply as a result of aging. Most cancers are believed to be caused by these acquired genetic changes, which accumulate over time and contribute to cancer development. While an inherited mutation starts a cell with one genetic flaw, acquired mutations add further damage, accelerating the progression toward cancer.
Testing for Cancer Genes
Genetic testing plays a significant role in understanding and managing cancer risk. Individuals may undergo testing to assess their inherited risk for certain cancers, especially if they have a strong family history of the disease. Identifying an inherited mutation can inform proactive screening strategies and preventive measures. For those already diagnosed with cancer, genetic testing of tumor tissue can guide treatment decisions by revealing specific mutations that may respond to targeted therapies.
The testing process involves collecting a sample, such as blood or saliva for inherited mutations, or tumor tissue for acquired mutations. Results provide valuable information for individuals and their families regarding cancer risk and management strategies. Genetic counseling is offered alongside testing to help individuals understand the implications of their results and make informed decisions about their health.
Targeting Cancer Genes in Treatment
Understanding specific cancer gene mutations has led to the development of “precision medicine” or “targeted therapy.” This approach focuses on developing drugs that specifically interact with the proteins produced by mutated genes or the pathways they control, rather than broadly attacking all rapidly dividing cells like traditional chemotherapy. These therapies aim to block the abnormal signals that drive cancer growth, leading to more effective treatments with fewer side effects.
For instance, if a tumor has a specific gene mutation that causes it to produce too much of a particular growth-promoting protein, a targeted therapy drug might be designed to block that protein’s activity. This prevents the cancer cells from receiving the signals they need to grow and divide uncontrollably. Examples include drugs that inhibit specific enzymes called tyrosine kinases, which are overactive in cancer cells, or monoclonal antibodies designed to attach to and disrupt cancer-promoting proteins on cell surfaces. This tailored approach allows for more personalized and less toxic treatment strategies.