Cancer: A Genetic Disease
Cancer is fundamentally a disease of the genes. It occurs when changes (mutations) in genes that control cell growth and division lead to uncontrolled cell proliferation. These genetic changes can be inherited or acquired during a person's lifetime.
Our cells have sophisticated mechanisms to repair DNA damage and prevent cancer. However, when multiple mutations accumulate in critical genes, these safety mechanisms can fail, allowing cancer to develop.
Genes → Proteins → Cell Behavior
How Cancer Develops Genetically
The Multi-Step Process of Carcinogenesis
Initial Mutation
DNA damage in proto-oncogenes or tumor suppressor genes
Clonal Expansion
One cell with advantage replicates more
Additional Mutations
Accumulation of more genetic changes
Invasion
Cells break through tissue barriers
Metastasis
Spread to distant organs
Key Concepts:
- Cancer requires multiple mutations (typically 5-10)
- These mutations affect different cellular pathways
- The process can take years or decades to complete
- Not all mutations lead to cancer - some are neutral
Why Understanding Matters:
- Helps in early detection and prevention
- Guides development of targeted therapies
- Enables personalized medicine approaches
- Informs about inherited cancer risks
Key Categories of Cancer Genes
Proto-oncogenes
Normal genes that promote cell growth and division. When mutated, they become oncogenes that drive uncontrolled cell proliferation.
Tumor Suppressors
Genes that slow down cell division, repair DNA mistakes, or tell cells when to die. When inactivated, cells grow uncontrollably.
DNA Repair Genes
Genes that fix mistakes made when DNA is copied. When these don't work, mutations accumulate in other genes faster.
Important Cancer Genes in Detail
Select a gene to learn more
How Cancer-Causing Mutations Occur
Sources of Mutations
Inherited Mutations
About 5-10% of cancers are caused by inherited mutations passed down in families. These are present in all cells from birth. Examples include BRCA1/2 mutations that increase breast cancer risk.
Environmental Factors
Carcinogens like tobacco smoke, UV radiation, certain chemicals, and viruses can damage DNA. These cause acquired mutations in affected cells only.
Replication Errors
Each time a cell divides, it copies its DNA. Random mistakes happen in about 1 in 1,000,000 bases. Normally repaired, but occasional errors persist.
Types of Genetic Changes
Point Mutations
Single base changes that can alter protein function. Example: The RAS oncogene commonly has point mutations at codon 12.
Mutant: GAT (Aspartic acid)
Gene Amplifications
Extra copies of a gene lead to overproduction of its protein. Example: HER2 is amplified in 20-30% of breast cancers.
Cancer cell: 50+ copies of HER2
Chromosomal Translocations
Parts of chromosomes swap places, creating fusion genes. Example: BCR-ABL in chronic myeloid leukemia.
Chromosome 9 (ABL) and 22 (BCR)
Applying Genetic Knowledge in Cancer Care
Genetic Testing
Identifies inherited cancer risk mutations (like BRCA) to guide prevention and screening strategies for patients and their families.
Tumor Profiling
Sequencing tumor DNA to identify mutations that can guide treatment selection (like EGFR inhibitors for EGFR-mutated lung cancer).
Targeted Therapies
Drugs designed to specifically block the effects of cancer-causing mutations while sparing normal cells.
Test Your Knowledge
Cancer Genetics Quiz
Answer these questions to check your understanding of cancer genetics concepts.
