Lecture 8: Tumour Markers Flashcards
Cancer cells present the following properties
1.spherical morphology
2.expression of fetal antigens, growth-factor independence
3.lack of contact inhibition, anchorage-independence
4.growth to high density.
Early stages of cancer
Progressive changes
In the early stages, the abnormally proliferating cells are usually restricted to the area in which the cancer originated.
Progressive changes in the cancer cells may allow them to escape from the primary site (metastasis), and cause damage to the body on a larger scale.
Cause of cancer
Cancer arises from the mutation of a normal gene.
What are mutated genes causing cancer called?
Mutated genes that cause cancer are called oncogenes.
A factor which brings about a mutation is called ____
A factor which brings about a mutation is called a mutagen.
A mutagen is mutagenic.
Any agent that causes cancer is called a carcinogen and is described as carcinogenic.
Benign vs malignant tumours
Benign tumours do not spread from their site of origin, but can crowd out (squash) surrounding cells eg brain tumour, warts.
Malignant tumours undergo metastasis. They interfere with neighbouring cells and can block blood vessels, the gut, glands, lungs etc.
Process of metastasis
To form a secondary tumour, a tumour cell needs to leave the vessel system and invade tissue. The cell must attach itself to a vessel’s wall.
Once this is done, it can work its way through the vessel and enter the tissue.
Normal cell division vs cancer cells
- DNA is replicated properly.
- Chemical signals start and stop the cell cycle.
- Cells communicate with each other, so they don’t become overcrowded.
1.Mutations occur in the DNA when it is replicated.
2. Chemical signals that start and stop the cell cycle are ignored.
3. Cells do not communicate with each other and tumours form.
What is a tumour marker?
anything present in or produced by cancer cells or other cells of the body in response to cancer or certainbenign conditions that provides information about a cancer, such as howaggressiveit is, whether it can be treated with atargeted therapy, or whether it is responding to treatment.
Examples of macro-molecular tumour markers
Polypeptide
Protein
Nucleic acid
Enzyme
Hormone
Describe tumour markers for sensitivity and specificity
Produced exclusively by a cancer cell as a response to tumuor development
Sensitivity
Not exclusively by a cancer cell, but has enough to be distinguished from production by a normal tissue cell
Specificity
An ideal tumour marker characteristics
High sensitivity
High specificity
Can be qualified
Safe
Convenience
Low price
2 Types of TM:
Describe what it is and its function
- Circulating tumour markers
- can be found in the blood, urine, stool, or other bodily fluids of some patients with cancer. Circulating tumour markers are used to:
1.estimateprognosis
2.detect cancer that remains after treatment (residual disease) or that has returned after treatment
3.assess the response to treatment
4.monitor whether a cancer has become resistant to treatment
2.Tumour tissue markers
-found in the actual tumours themselves, typically in a sample of the tumour that is removed during a biopsy.
Tumour tissue markers are used to:
1.diagnose,stage, and/or classify cancer
2.estimate prognosis
3.select an appropriate treatment (eg, treatment with atargeted therapy)
Tumour marker in oncology
1.Screening
2.Diagnosis
3.Staging
4.Prognosis
Screening: downsides of tumour markers
Tumour markers play a limited role for Tumour screening, because….
1.relatively low sensitivity
2.lack of specificity and relation to Tumour size
Inappropriate for the detection of small cancers
In some cases, Tumour markers can be equal to other examinations envisioned for screening
PSA & prostate cancer
calcitonin & medullary thyroid cancer
Staging: tumour markers importance
The tumour markers and medical imaging are complementary in the pre-therapeutic and post-therapeutic staging
Prognosis and tumour markers
The pre-therapeutic level of certain tumour marker can contribute a prognostic factor because of links with…
Metabolic activity
tumour size
Invasion