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48 Cards in this Set
- Front
- Back
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What is the difference between a benign and a malignant tumor?
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Benign: a single, clustered mass
Malignant: cells with the ability to invade neighboring tissue |
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How do most cancers originate?
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From a single cell resulting from many mutations.
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Are cancers genetically stable or unstable?
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Unstable.
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Is cancer often caused by a single mutation?
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No, most often cancer requires multiple mutations.
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How does chromosomal translocation contribute to cancer?
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By de-regulating gene expression or by creating fusion proteins (ex. Bcr-Abl)
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What is an oncogene?
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An oncogene is a mutated proto-oncogene, which normally promotes healthy cell growth.
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How does an oncogene work?
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Oncogenes promote uncontrolled cell growth.
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What is tumor suppressor gene?
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Tumor supressor genes control growth by not allowing cells to replicate with damaged DNA.
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How does a tumor suppressor gene work?
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Tumor suppressor genes recognize DNA damage prior to replication, and either promote DNA repair, senescence, or apoptosis.
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Compare oncogenes and tumor suppressor genes.
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The cancer contributing mutation in tumor suppressor genes is loss-of-function, whereas in oncogenes it is a gain-of-function mutation. In tumor suppressor genes, both copies need to me mutated to have an effect. Only one copy needs to be mutated to have an effect in oncogenes.
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How can a mutation causing changes in the gene contribute to cancer?
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Changes in the coding region of a gene can lead to the production of a faulty protein, like a proliferation regulator that is always on.
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How can a mutation causing changes in levels of expression of a protein contribute to cancer?
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An increase in the expression of a proliferation protein like Ras could contribute to cancer.
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Explain gene amplification.
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Gene amplification is when a normally functioning protein is greatly overproduced.
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Describe Rb.
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Retinoblastoma tumor suppressor gene; sequesters E2F protein so that it can't initiate cell proliferation.
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Describe p53.
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The guardian of the genome, it does not allow replication to occur if there is DNA damage.
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Describe Ras.
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Ras is a proto-oncogene which is attached to the membrane and bound to GDP in its inactive form. In its active form, it is bound to GTP and transmits signals for cell proliferation.
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Describe two general mechanisms by which viruses can cause cancer.
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Viral DNA can integrate into the host DNA and cause mutations, such as the inhibition of tumor suppressor genes or the induction or oncogenes. Viral proteins can also interact directly with cellular proteins either to promote or inhibit control of proliferation.
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How are epigenetics relevant to cancer?
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Methylation of tumor suppressor genes can contribute to cancer.
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What is a genetic predisposition to cancer?
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When you inherit precursor genes with defects in DNA repair; they do not necessarily cause cancer, but gives you a greater probability of it.
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What types of cells are chemotherapeutic agents aimed at stopping?
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Rapidly proliferating cells.
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Are chemotherapeutic agents specific to cancer cells?
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No, they target healthy cells as well, especially fast growing ones like bone marrow, mucous membranes, and hair follicles.
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What are alkylating agents?
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Chemotherapy drugs that add alkyl groups to electronegative compounds under normal cellular conditions.
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What are 3 mechanisms of action of alkylating agents?
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Cross linking of DNA strands, abnormal base pairing, and making DNA strand breaks.
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What are anthracycline antibodies?
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Anthracycline antibiodies are chemotherapy agents first intended to be antibiotics, but were discovered to affect human cells too much to be effective.
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What are 3 mechanisms of action of anthracyte antibodies?
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Inhibiting DNA synthesis by intercalating between base pairs, inhibiting the topoisomerase II enzyme, and creating oxygen radicals.
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What are antimetabolites?
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Antimetabolites are drugs that have similarity to metabolites involved in normal nucleic acid synthesis and interfere with the formation of biomolecules in the cell (S - phase).
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What is the mechanism of action of antimetabolites?
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Mimic enzyme substrates and block enzyme function, which can interfere with DNA replication or RNA metabolism.
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What is the mode of action of plant alkyloids?
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They stop cell division by blocking microtubule function.
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What is the difference in the mode of action of vinca alkaloids and taxanes?
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Vinca alkyloids prevent microtubule formation, taxanes prevent microtubule disassembly.
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On what phase of the cell cycle do plant alkyloids act?
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Mitosis, or M - phase.
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How do topoisomerase inhibitors work?
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They interfere with transcription, DNA replication, chromosome separation, and repair mechanisms by either not allowing topoisomerases to relieve helical strain on unwinding DNA or by creating permanent double strand cuts in DNA.
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Which cancer drugs act at any phase of the cell cycle?
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Alkylating agents and anthracycline antibodies.
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Which cancer drugs act specifically on the S phase?
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Antimetabolites and topoisomerase inhibitors.
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Which cancer drugs act specifically on Mitosis?
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Plant alkyloids.
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Which cancer drugs act specifically on the G-2 phase?
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Topoisomerase inhibitors.
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What is molecular targeted therapy?
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Therapy targeting molecules that are unique or overexpressed in cancer cells, the goal being a more specific drug with fewer side effects.
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Why is signal transduction an important target for chemotherapy?
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It is essential for proliferation.
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What is the role of the HER receptor family in normal cell growth and in cancer?
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The HER receptor normally forms a dimer, which transmits a signalling pathway for proliferation. In cancer, HER is overproduced, and cell growth is rapid and uncontrolled.
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What does herceptin do?
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It binds to the HER monomer, preventing dimerization and subsequent signal transduction and proliferation.
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How does Gleevec work?
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It binds to the Brc-Abl ATP binding site. Brc-Abl is a continuously active tyrosine kinase, but when bound by Gleevec is unable to phosphorylate substrates and cause proliferation.
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What is angiogenesis?
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The process of growing new blood vessels.
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How does chemotherapy target angiogenesis? What is an example?
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By preventing blood supply to a tumor, the tumor is effectively starved to death. Avastin.
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Describe hormone responsive breast cancer.
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Tumors depend on hormonal stimulation for growth. In hormone receptor positive breast cancer, estrogen or progesterone receptors are overproduced.
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Describe hormone therapy, and name 3 treatment strategies.
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Hormone therapy blocks the ability of the hormone to turn on and stimulate cancer cells. This is done by blocking the receptors, down-regulating the receptors, or lowering hormone synthesis.
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Explain siRNA therapy.
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siRNA therapy targets specific mRNA for destruction, so as to not make the defective protein.
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Explain epigenetic therapy.
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Epigenetic therapy would inhibit methylation, and subsequent silencing, of tumor suppressor genes.
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What is the main mechanism of drug resistance?
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Cancer cells are genetically unstable and prone to random mutation, which could confer resistance on the cells.
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How does drug resistance affect chemotherapy?
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Due to the possibility of mutations causing resistance, chemotherapy drugs are often administered as a cocktail of multiple drugs.
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