Lesson 9 of 9 / Mutation, cell division and cancer
Cancer develops through multiple steps
Why does an increased risk not mean cancer is inevitable?
In this lesson: Explain risk factors, mutation accumulation, angiogenesis and metastasis.
About 7 min
The key ideaCancer develops through accumulated changes and selection within cell populations; invasion and spread require additional capabilities.
Explore the idea
Distinguish growth, supply and spread
A lineage can inherit earlier changes and acquire further ones over successive divisions. The drawing does not imply one mutation is enough.
Explanation
Inherited variants can predispose a person to cancer by reducing the number of further changes needed. Chemical carcinogens and ionising radiation can damage DNA, increasing mutation risk. Reduced immune surveillance can allow abnormal cells or cancer-associated infections to persist more readily. Risk factors change probability rather than guaranteeing a particular cancer.
A cell acquiring a growth or survival advantage can produce a larger clone, within which additional changes may arise. Multiple alterations affecting proliferation, repair, survival and interactions with surrounding tissue can accumulate over time. This is a multistep process, not one fixed sequence identical in every tumour.
As a tumour grows, angiogenesis supplies new blood vessels that support delivery of oxygen and nutrients and removal of wastes. This can permit further growth. The vessels do not mean the tumour has become a separate organism; it depends on host resources.
Metastasis involves cells leaving a primary tumour, invading surrounding tissue, entering blood or lymph, surviving transport, leaving the circulation and establishing secondary growth elsewhere. A secondary tumour derives from the original cancer lineage, not from every nearby normal cell becoming the original tissue type.
Step by step
- 1
Separate risk from outcome
Avoid deterministic claims about exposure.
- 2
Follow clonal progression
Additional changes occur within expanding populations.
- 3
Track physical spread
Distinguish local growth, invasion and distant colonisation.
Worked example
Work through the evidence
Why does finding a carcinogen exposure in someone without cancer not disprove its risk effect?
One way to explain it
A risk factor raises probability across comparable populations; individuals may not accumulate all necessary changes or may remove damaged cells. It is not a guarantee for every exposed person.
Why this answer works
- Probability is a population-level claim.
- Other genetic and environmental factors can influence outcome.
Is this true? "Angiogenesis and metastasis mean the same thing."
Angiogenesis is new blood-vessel formation; metastasis is establishment of cancer growth at a distant site.