14, 15 - Cancer Flashcards
Define cancer
Diseases in which abnormal cells divide w/o control and are able to invade other tissues
When are cancer cells formed?
When normal cells lose normal regulatory mechanisms that control growth, differentiation, and multiplication
What happens to cancer cells?
Lose the specialized characteristics that distinguish one type of cell from another (loss of differentiation)
What is a neoplasm?
New and diseases form of tissue growth
Which neoplasms are cancerous? Which aren’t?
- Benign neoplasms = not cancerous
- Malignant neoplasms = cancerous, can invade other parts of the body and give secondary tumours (metastasis)
How do carcinogenic chemicals cause cancer?
Induce gene mutations or interfere w/ normal cell differentiation
What can initiate carcinogenesis (birth of cancer)?
A chemical or other mutagen (ex: sunlight)
What is an example of a gene that can give rise to cancer?
BRCA1/ BRCA2 – tumour suppressor proteins, mutation causes protein to not function properly or not be made
What are proto-oncogenes?
Genes which code for proteins involved in the control of cell division and differentiation
What can happen if proto-oncogens mutate?
Can disrupt normal cell function and become cancerous; would now be called oncogenes
What does Ras gene code for? What happens if its mutated?
- Codes for Ras protein (cell division signaling) and is self-regulating
- If mutated, is continually active leading to continuous division
What are anti-oncogenes? What happens to them to cause cancer?
- Tumour suppressor genes
- Inactivation causes cancer
What cellular defects can be caused by genetic defects?
- Abnormal signalling pathways; insensitivity to signals
- Abnormalities in cell-cycle regulation
- Evasion of cell death (apoptosis)
- Limitless cell division
- New blood vessels; tissue invasion and metastasis
What are the 5 types of cancer? Which is most common?
1) Carcinoma - epithelial cells; most common
2) Sarcoma - connective tissue
3) Lymphoma and leukemia - hemopoietic cells, bone marrow-derived cells that normally mature in bloodstream (leukemia) or lymphatic system (lymphoma)
4) Germinoma - germ cells; testicle and ovarian cancers
5) Blastoma - resembles embryonic tissue; tumour of primitive, incompletely differentiated cells
What are the mechanisms of cancer cells?
- DNA synthesis or mitosis to produce new cells
- Cell differentiation to produce specialized cells
- Growth factors and cell surface receptors
- Growth inhibitors and cell surface receptors
- Cell cycle and regulation
What are the basis/causes of cancer?
Mutation, chemical, and/or viral
What are the 2 types of mutations in cancer?
1) Germ-line -> mutation present in germ cells, hereditary
2) Somatic -> non-inherited change in genetic structure
What is the multi-stage theory of cancer?
1) Initial mutations
2) Promotion phase (mutated cell proliferation)
3) Small benign tumour forms and develops (malignant phenotype)
4) Primary malignant tumour forms (progression)
5) Cells break off, lodge at remote sites and secondary tumours form (metastasis)
____ was identified as the cause of scrotal cancer
Benzoapyrene (component of soot)
What do oncogenic viruses do?
- Insert themselves into host genome
- DNA viruses produce proteins that interact w/ growth regulatory proteins or tumour suppressor genes and may lead to/promote cancer
- Viral genome may be near regulatory genes, producing mutations
- RNA viruses produce double stranded DNA provirus that is inserted into host genome usually near proto-oncogenes
How is cancer therapy decided?
Based on specific type, location, and stage of cancer
What are the fundamental techniques for cancer therapy? What is involved in each?
- Surgery -> cancer must be in primary tumour stage; must excise entire tumour
- Radiation therapy -> ionizing radiation used to shrink tissues by causing damage to DNA and apoptosis; requires tumour that is localized
- Immunologic therapy -> utilizes immune system to eradicate cancer, boosting levels of lymphocytes to destroy foreign cells, including premalignant and malignant cells
- Chemotherapy
What is chemotherapy used for?
- To reduce size of a tumour prior to surgery
- Sensitize tumours to radiation therapy or destroy microscopic tumours after surgery
What is chemotherapy used with? What types of tumours is it effective against?
- Used w/ surgery or radiation therapy
- Effective against metastasized tumours or residual tumours after therapy
What is the drawback to chemotherapy?
Lack of selectivity (effect both normal and malignant cells)
Which classes of drugs are alkylating agents?
- Nitrogen mustards
- Phosphamide mustards
- Nitrosureas
- Platins
Which classes of drugs are antimetabolite and nucleoside analogs?
DHFR and thymidylate synthase inhibitors
Which classes of drugs are antimitotic agents?
- Vinca alkaloids
- Taxanes
What are the various drug categories used for cancer therapy?
- Alkylating agents
- Antimetabolite and nucleoside analogs
- Antitumour antibiotics
- Antimitotic agents
- Miscellaneous antineoplastic
- Hormone therapy
- Combination therapies
What do alkylating agents do?
- React w/ DNA, preferentially alkylating in N-7 position of guanine
- May alkylate other sides on DNA bases
What do bifunctional alkylating agents do?
Produce inter and intra-strand crosslinks, preventing DNA separation (cytotoxic)