Lesson 8 of 9 / Mutation, cell division and cancer
Cancer develops through several changes
How does a local growth gain access to other tissues?
I can describe accumulation of mutations, angiogenesis and metastasis in cancer development.
I can explain multi-step cancer development, angiogenesis and metastasis.Syllabus
Syllabus 8876, Core 2(j). Explain multi-step cancer development, angiogenesis and metastasis.
About 5 min
Make a guess. You are not marked.
New blood vessels grow into a tumour. Has the cancer spread to other organs?
Show the answer
That is angiogenesis, not metastasis.
Angiogenesis feeds the tumour. Metastasis is cells forming a secondary tumour elsewhere.
The key idea
Cancer commonly develops as mutations accumulate in a cell lineage. Further changes can support blood supply, invasion and spread to distant sites.
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
A cell can acquire a mutation and pass it to its descendants. Additional changes in some descendants may weaken normal controls further or confer a growth advantage. Over successive divisions, a lineage can accumulate changes associated with uncontrolled proliferation.
As a tumour grows, access to oxygen and nutrients can become limiting. Angiogenesis is the formation of new blood vessels, stimulated by signals from the tumour and its environment. This can support further growth; it does not mean tumour cells themselves become red blood cells.
Malignant cells can invade nearby tissue and enter blood or lymphatic vessels. Some survive transport, leave the circulation and establish growth at another site. This spread and establishment of secondary tumours is metastasis.
Angiogenesis and metastasis are different processes. A new vessel supplies a growing mass; a metastatic cell forms a new growth elsewhere. Not every abnormal growth has acquired the capacity to invade or metastasise, and the sequence is a simplified framework rather than an identical timetable for all cancers.
Step by step
- 1
Accumulate changes
Descendant cells can inherit and add mutations over multiple divisions.
- 2
Support growth
New vessels can supply oxygen and nutrients.
- 3
Spread and establish
Invasive cells can travel and found secondary growths.
Worked example
Distinguish supply from spread
A tumour releases signals that cause nearby vessels to grow towards it. Does this observation alone demonstrate metastasis?
One way to explain it
No. It supports angiogenesis. Metastasis would require evidence that tumour cells spread from the original site and establish growth elsewhere.
Why this answer works
- Name the process actually observed.
- State the additional evidence needed for the stronger claim.
Watch out for this
A student says: "A tumour is metastatic as soon as any new blood vessel forms nearby." What is wrong with this?
Show the answer
Angiogenesis supports blood supply. Metastasis requires tumour-cell spread and establishment at another site.
Check your understanding
Which event specifically indicates metastasis?
Show the answer
Cells from a primary tumour establish a secondary tumour elsewhere.
Spread and establishment at another site define the process.
Quick recall
How does a local growth gain access to other tissues?