Gene expression and cancer Flashcards
What causes cancer?
Cancer is caused by damage to the genes that regulate mitosis and the cell cycle, leading to unrestrained cell growth
What is a tumour?
A tumour is a group of abnormal cells that develops and constantly expands in size due to unrestrained cell growth
Why is cancer considered a destructive disease?
Cancer is destructive because it disrupts normal cell function, leading to uncontrolled growth that can damage tissue and organs
What are two main types of tumours?
The two main types of tumours are benign tumours, (non - cancerous) and malignant tumours (cancerous)
What effects do benign and malignant tumours have on the body?
Benign tumours tend to have localised effects
Malignant tumours are more likely to be life threatening as abnormal tissue replaces normal tissue
How does the structure of benign and malignant tumours differ?
Benign tumours: surrounded by a capsule of dense tissue, allowing it to remain as a compact tissue
How does the cell nucleus differ in benign and malignant tumours?
Benign tumours: The cell nucleus has a relatively normal appearance
Malignant tumours: The cell nucleus is often larger and darker due to an abundance of DNA
What does the DNA analysis of tumours reveal about cancer cells?
Cancer cells are from a single mutant cell. Initial mutations cause uncontrolled mitosis, nd further mutations in later generations that can lead to abnormal growth and appearance
What are the main two types of genes, involved in cancer?
The two main types are tumour suppressor genes and oncogenes
What are oncogenes?
Oncogenes are mutated forms of proto oncogenes that can become permanently activated, leading to uncontrolled cell division and tumour formation
How do proto oncogenes normally function?
Proto - oncogenes stimulate cell division when growth factors attach to a receptor on the cell surface membrane, activating genes that cause DNA replication and cell division
What causes a proto oncogene to become an oncogene?
Mutations that lead to either:
1) Permanent activation of the receptor protein on the cell membrane, causing continuous cell division
2) Excessive production of growth factors
Are oncogenes mutations inherited or acquired?
Most mutations involving oncogenes are acquired, although a few cancers result from inherited mutations
What is the function of tumour suppressor genes?
Tumour suppressor genes slow cell division, repair DNA errors and trigger apoptosis (programmed cell death), maintaining normal cell division rates and preventing tumour formation
What happens when a tumour suppressor gene is mutated?
The gene becomes inactivated, stopping its inhibition of cell division, leading to uncontrolled cell growth and potential tumour formation
How do mutated tumour suppressor cells behave?
Mutated cells are structurally and functionally different. Mosrt die, but some survive, clone themselves and form tumours
How does a tumour suppressor gene compare to a proto oncogene?
Tumour suppressor genes inhibit cell division, while proto - oncogenes promote it. Their roles are opposite
What is the most common type of abnormal DNA methylation involved in cancer developemnt?
Hypermethylation (increased methylation)
What is hypomethylation and how does it contribute to cancer?
Hypomethylation is reduced methylation. It occurs in oncogenes, leading to their activation and the formation of tumours
How does hypermethylation lead to cancer?
1) Hypermethylation occurs in the promoter region of tumour suppressor gene
2) The tumour suppressor gene becomes inactivated
3) Transcription of the gene is inhibited
4) The gene is silenced, preventing it from slowing cell division
5) This leads to increased cell division and tumour formation
How does oestrogen affect breast cancer risk after menopause?
After menopause, fat cells in the breast produce more oestrogens, which can trigger breast cancer
How do tumours influence oestrogen levels in breast cancer?
1) Tumours increase local oestrogen production
2) This higher oestrogen concentration promotes tumour growth
3) White blood cells drawn to the tumour also increase oestrogen production, further enhancing tumour development
Why does the risk of breast cancer increase after menopause despite reduced ovarian oestrogen production?
Fat cells in the breast produce more oestrogens post - menopause, which can trigger and promote breast cancer development
What is the relationship between oestrogen and tumour progression in breast cancer?
Oestrogen promotes tumour growth, and tumours themselves amplify oestrogen production, creating a feedback loop that accelerates cancer progression
How does oestrogen activate a gene?
Oestrogen binds to a gene, promoting transcription and activating it
What happens if oestrogen activate a gene that control cell division and growth?
The gene becomes activated, leasing to continued cell division, which can result in tumour formation
How does oestrogen influence proto oncogenes in breast tissue?
Oestrogen causes proto oncogenes in breast tissue to mutate into oncogenes
What is the result of oestrogen converting proto - oncogenes into oncogenes in breast tissue?
This process leads to breast cancer
Why is oestrogen considered a risk factor for tumour formation in breast tissue?
Oestrogen promotes the transcription of genes that control cell growth, potentially causing uncontrolled division and tumour formation
