Cancer therapy and treatment Flashcards
What are the conventional cancer therapies?
- Surgery (remove or debulk local tumour)
- Radiotherapy (local and regional)
- Chemotherapy (systematic treatment for metastatic disease, combinations of drugs with different site of action needed for effective treatment)
Why is hormone therapy effective in breast cancer?
Tamoxifen inhibits ER
Change in one abnormal condition triggers apoptosis
Tailored therapy to molecular changes in individual cancer
What is radiation dependent on?
Expression of wild type p53
True of certain drugs that inhibit topoisomerases (camptothecin, etoposide)
Taxol= spindle poison, damage reported via p53
How can chemotherapy lead to drug resistance?
Unstable cancer cells can evolve mdr overexpression (membrane channel secretion protein) Secretes drugs outside the cancer cells
What are the targets for therapy?
Growth factors and receptors/ signalling molecules/ cell cycle proteins/ pro-angiogenesis and pro-apoptotic molecules
What are angiostatic agents?
Anti-angiogenesis, block vessel growth to keep tumour small
Kill normal cells so unlikely to require resistance, effective in mouse models, clinical trial dramatic results but some variation
Examples of cancer drug success
Imatinib/ Glivec
Herceptin
Vemurafenib
Panitumumab/ Cetuximab
What is Imatinib?
Small molecule inhibitor bcr/abl fusion protein in chronic myeloid leukaemia
90% patients enter remission but gene still detectable in bone marrow so will eventually come back
Intrinsic mutability of cells contain range of drug-resistant sub-clones before treatment is selected
What is Herceptin?
Monoclonal antibody to HER-2/ neu receptor protein, (EGF family receptor) only effective in HER-2 overexpressing breast cancers
What is Vemurafenib?
Small molecule drug inhibitor of the mutant BRAF in melanomas (RAS pathway)
What is Panitumumab?
Monoclonal antibodies to the EGF receptor in colorectal cancer- only effective without K-ras mutation
What is immunotherapy?
Stimulates patient immune system to recognise and destroy cancer cells
What are the immune checkpoint inhibitors?
Ipilimumab targets CTLA-4 (inactivates)
Pembrolizumab targets PD-1, PD-L1 (T cells)- monoclonal antibodies block reaction to free T cells
Boosts the immune system repsonse against melanoma cells and other cancers (defective mismatch repair in colorectal cancers)
How may cancer cells evade host defences?
Downregulation of MHC class 1 on tumour cells (doesn’t present antigens)= safe from CTL attack
Induction of CTL non-responsiveness to tumour Ag (PD-1)
Release of immunosuppressive factors from tumour- TGF beta
What is synthetic lethality?
Using genomic instability for tumour selective drugs
BRCA 1/2
Have defective DNA d/s strand repair (homologous recombination)
Susceptible to drugs that block other major DNA repair pathway
What drug is used in BRCA mutations?
Olaparib= PARP inhibitor (Poly ADP Ribose Polymerase)
Kills BRCA 1/2 cancers
How does synthetic lethality work?
Two genes- mutation in either gene not lethal, bothy mutated= cell death
Disables base excision repair in s/s brake repair so causes cell death (knocks out compensating pathway)
How does drug resistance occur?
- Overexpression of mdr (membrane channel secretion protein that exports drugs)
- mutation or amplification of the target protein or other proteins in the same signalling pathway
- Mutation in cell death pathway
How are appropriate therapies selected?
Tumour profiling- Genomic (DNA copy number changes and Next Generation Sequencing/ NGS), transcriptomic and proteomic analysis, mRNA micro array
Inform about molecular abnormalities that may respond to tailored therapies
Changes in RNA expression
What are the 2000Orignal Hallmarks of cancer?
- Self-sufficiency in growth signalling (cell cycle control)
- Evading apoptosis (death pathways)
- Limitless replicative potential (immortalisation)
- Insensitivity to anti-growth signals (signalling pathways)
- Sustained angiogenesis (cytokines)
- Tissue invasion and metastasis (adhesion, proteolysis and movement)
What are the emerging hallmarks in the 2011 version?
- Deregulating cellular energetics increased Fluoro-deoxy glucose in PET scan
- Avoiding immune destruction (escape surveillance and checkpoints)
What are the enablers in the 2011 version?
- Genomic instability and mutations
- Tumour-promoting inflammation
