Anticancer agents Flashcards
LO
Describe the processes that can lead to cancer formation
- viral and cellular oncogenes
- chromosomal aberrations
- mutagenesis
Explain the molecular basis of action of current anticancer agents, with particular emphasis on
- new agents against specific molecular targets
- cytotoxic agents targeted at DNA replication
What is selective toxicity and how is it involved with cancer therapy?
The use of chemical agents that are toxic to an invading organism or cell, which do not affect the host.
This is clearly a problem for developing anti-cancer drugs as the diseased cells have similarproperties to normal cells (especially those in bone marrow, hair, GI mucosa and skin).
We need to look for “windows of opportunity” where cancer cells are especially vulnerable
PTEN is an important tumour suppressor gene
Want only green cells to be used in therapy
Helps find drug targets that only effects cancerous cells
What two things lead to tumour cells?
Inhibition of tumour suppressor gene and the activation of oncogene leads to tumour cells
What is precision medicine and how is it used?
Precision medicine patients with tumours that share the same genetic change receive the drug that targets that change, no matter the type of cancer
Tell me about Transcriptomic profiling and how it is used in cancer therapy
defines 2 major subgroups of MYCN non-amplified Neuroblastomas for precision prognosis and therapy stratification
Stats for cancer in the UK
Don’t need to learn but useful information to be aware of
What are the two important mechanisms for maintaining cell growth and how are they effected in tumours?
Organs and tissues are maintained at appropriate size.
Control mechanisms: 2 important cellular processes must balance each other perfectly – proliferation and apoptosis.
Normal cells have a balance between proliferation and apoptosis. In tumour cells there is more proliferation and less apoptosis which means the cell number increases. This difference +oncogene and -TSG
Invasions and Metastasis leads to a malignant cancerous cell
What is proliferation?
Proliferation refers to the growth and reproduction of cells.
What is apoptosis?
Apoptosis (cell suicide) is the mechanism by which old or damaged cells normally self-destruct.
Tell me about the processes involved in normal cells developing into cancerous cells
Neoplasia excess proliferation, without relation to normal growth and repair. Growth may be fast, but rarely exceeds that in the fastest growing tissues.
Benign proliferate locally and retain tissue characteristics, defined boundary.
Malignant not encapsulated, ill-defined edge, projections extend into surrounding tissues, less well differentiated than the cells of origin.
Spread by invading surrounding tissues – carried to other parts of the body) metastases (secondary tumours)
Compare a malignant verses benign tumour
Explain the differences between the Karyotypes of cancerous vs normal chromosomes
Karyotype illustrating structural abnormalities in cancer
Different chromosome numbers
Normal has only one colour whereas cancerous have multiple
What is a mutation and what are they used to define?
A mutation is a change in the normal base pair sequence
Commonly used to define DNA sequence changes that alter protein function
What are the two main types of mutation
Germline mutation
Somatic mutation
Whats a germline mutation?
A change in the DNA sequence that can be inherited from either parent
Every cell in the body has this mutation
Whats a somatic mutation?
A change in the DNA sequence in cells other than sperm or egg
The mutation is present in the cancer cell and its offspring, but not in the patient’s healthy cells
This only happens in the tumour cells
If you have cancer, its usually because someone in your family has had cancer? True or false
False
Whats the importance of somatic DNA changes in human cancer?
Only 5 –10% of cancer cases have a clear hereditary component,
e.g., BRCA1 and BRCA2 in breast cancer
Even in those cases where susceptibility is clearly inherited, somatic changes are required for cancer to develop
Tell me about Hereditary predisposition and cancer
Some families are more susceptible to getting certain cancers. Remember you can’t inherit cancer it’s just that you are maybe more susceptible to getting it.
Who can get breast cancer and what mutations are involved in this cancer?
5-10% cases have BRCA1/BRCA2 mutations
10-20% cases have family history, no BRCA1/BRCA2 mutations
Most cases have no BRCA1/BRCA2 mutations, family clusters of cases persist
Origins of cancer
What are the four levels of tumour heterogeneity?
What are the two types of cancer genes?
Tumour suppressor genes (checkpoints)
Oncogenes
Explain the role of tumour suppressor genes and oncogenes in cancer
ASPP2 knockdown cooperates with oncogenic RAS activation to promote invasion
A model for colon cancer
Explain how the P53 gene acts as an important TSG?
Which of the following is not a tumour suppressor gene?
- Rb
- p53
- APC
- RAS
- BRCA
RAS
This is an important oncogene
Snapshot of Ras signalling
Whats the overview of what happens in Ras signalling
EGFR upon activation can cause Ras from GDP –> RAS GTP
RAS is the active form which causes downstream signalling of Rat and PI3K
Tell me about the KRAS gene and what a mutation in this gene can lead to?
The KRAS gene codes for a signalling molecule
Mutations in KRAS are present in many cancers, including pancreatic cancer, colon cancer.
You have to look for the mutations by comparing healthy DNA sequence with tumour DNA sequence
Tell me how a heterozygous mutation would be identified?
KRAS mutations, how common?
This pattern of mutations across the gene is like that of other members of the Ras family and has the signature of an oncogene – clusters of mutations which only occur in specific regions of the gene. This means the protein will still function but, in this case, will encourage inappropriate cell growth as the protein is permanently “switched on”, or activated.
Whats the impact of KRAS mutations?
What does the gene help with, when is it activated. inactivated?
KRAS helps to transmit external growth signals to the cell nucleus, driving normal cell growth. It is:
- Activated when it binds GTP
- Inactivated or “switched off” when GTP is hydrolysed to GDP
What does a mutated KRAS gene encode?
The mutated gene encodes proteins with reduced GTPase activity. These proteins are locked into a GTP active state – continuously sending cell growth signals.
What is the difference between this two histogram?
The key difference between KRAS and RB1 is the range and frequency of mutations.
RB1 has 194 different mutations many of which truncate the encoded protein. For example, 88 (28%) are nonsense substitutions which result in the protein being truncated. 53 (17%) are deletions that cause a frameshift and truncate the protein.
Tell me about mutations in tumour suppressor genes and what could occur if they stop functioning?
TSG as a brake – to stop it working you can cut the brake cable anywhere and it will stop functioning. In the case of an oncogene or accelerator, there are only a limited number of ways for it to become stuck “on”. Therefore the oncogene KRAS has a limited number of gene regions which can acquire mutations (and still function albeit inappropriately) and why a TSG such as RB1 has so many different regions of acquired mutations.
Mutations can also be caused by Carcinogens
Name the different carcinogens and what is included under each one?
Ionising radiation
- X Rays, UV light
Chemicals
- tar from cigarettes
Virus infection
- HPV for cervical cancer
- Epstein-Barr Virus for lymphoma and Nasopharyngeal carcinoma
- Helicobacter Pylori implicated in gastric carcinoma
- Hepatitis B virus, strong association with Liver Cancer
Whats the common herbal medicine that may cause liver cancer mutations?
List of IARC Group 1 carcinogens
Whats the main cancer caused by UV radiation?
Tell me about the type of mutations and what could happen
Malignant melanoma;
UV-light-induced mutations leave a typical signature of C>T or G>A mutations.
if these DNA changes occur in critical genes such as BRAF, this can lead to inappropriate and sometimes aggressive cell growth and therefore the development of malignant melanoma.
Whats the typical cancer caused by tobacco smoke?
Why does cancer arise from smoking and what mutations occur?
Lung cancer;
Tobacco smoke contains more than 60 mutagens that bind and chemically modify DNA. These brand the lung cancer genome with characteristic mutational patterns.
Research has shown that the tobacco smoke carcinogens polycyclic aromatic hydrocarbons (PAH) and the nicotine-derived nitrosamines cause G>T mutations
Give an example of a biological factor which can cause cancer?
What happens in this example?
Whats been developed to help combat this?
HPV is a cause of cervical cancer;
When HPV enters cells of the cervix proteins made by the virus activate and inactivate oncogenes and tumour suppressor genes respectively. It is like a machine for turning on lots of cancer genes. The image shows a lesion in a human cervical epithelium infected with human papilloma virus (HPV16). Early viral proteins (green) bind to and re-organise the keratin filaments (red) towards the edge of the cell. Cell nuclei are stained with Dapi (blue).
Vaccination against HPV dramatically reduces cases of cervical cancer. An HPV vaccine is available, and vaccination and screening programmes are being introduced in the UK.
What cancer is obesity associated with?
Bowel and stomach cancer
Viral and cellular oncogens
Gene amplification
For the following chromosomal rearrangements or translocations, how are the proto-oncogenes expressed?
Tell me some hallmarks of cancer and some of the emerging hallmarks and enabling characteristics
What are some of the therapeutics that target the hallmarks of cancer?
Give an example of a chromosomal rearrangement or translocation
Tell me about the philadelphia chromosome and in what cases it is usually identified in
The Philadelphia chromosome is a reciprocal translocation involving chromosomes 9 and 22 that is commonly identified in all cases of chronic myelogenous leukemia (CML) and 10% of acute lymphotic leukaemia (ALL)
The break points of the translocation create a fusion of two genes: ABL1 on chromosome 9 and BCR on chromosome 22
What does this Bcr-Abl FISH flourescence imaging show?
Red is a PCR gene
Green is an ABL gene
The yellow/ white colour shows fusion (shows translocation event)
Tell me about the regulation of the c-Abl and Bcr-Abl tyrosine kinases
Tell me about the drug Gleevec/Glivec (Imatinib; STI 571, CGP57148B)
Gleevec is a brand-name prescription medication. It’s used to treat certain types of blood cancers in adults and children. Gleevec is also used to treat a type of skin cancer and a type of gastrointestinal cancer.
Whats an important mutation for resistance amplification and overexpression?
State some major imatinib resistance mutations
T315I
E255K
H396P
What binds to the active form of Abl and overcomes 14 of 15 of the imatinib-resistant mutants?
Activity of imatinib mesylate and the second-generation tyrosine kinase inhibitors nilotinib and dasatinib against a selection of BCR-ABL1 mutants found in patients with CML. All concentrations are shown in nanomoles per millilitre and represent IC50 values.
Tell me about some third generation Bcr-Abl inhibitors
What is EGFR used as a target for?
Explain how it is used as a target
EGFR is used as a target for cancer therapy because it is commonly expressed at a high level in a variety of solid tumours and it has been implicated in the control of cell survival, proliferation, metastasis and angiogenesis.
What else can be used as targeted therapy?
Monoclonal antibodies
The relative frequencies of the various mechanisms of acquired resistance
Tell me the different EGFR mutations which are associated with drug resistance and drug sensitivity
Response rates to second and third generation EGFR TKIs in clinical trials
Tell me about the drug Vemurafenib and what process it inhibits
Mechanisms of acquired resistance to BRAF-V600E inhibition that led to reactivation of the MAP kinase pathway.
Tell me this pathway
What individual(s) recieved the nobel prize for their discovery of cancer therapy by inhibitor of negative immune regulation
Name some checkpoints that regulate T cell antigen recognition.
What two are particuarly important
Where does checkpoint blockade function?
PD-1 or PD-L1 blockade stimulates what?
anti-tumour T cell response
Broad anti-tumour efficacy of anti-PD-L1/ PD-1 inhibitors: overall response rates
What is better than chemo in melanoma?
Tell me about Bevacizumab (Avastin)
Targeted therapy in lung cancer
Potential algorithm for incorporating chemotherapies, immunotherapy, and targeted therapies into the management of NSCLC in the future
What are the different stages of the cell cycle?
G1 phase: cell prepares for DNA synthesis
S phase: cell generates complete copy of genetic material
G2 phase: cell prepares for mitosis
M phase: replicated DNA is condensed and segregated into chromosomes
G0 phase: resting state
Tell me about alkylating agents and their roles
Tell me about cis-platin
Cisplatin is a chemotherapy medication used to treat a number of cancers. These include testicular cancer, ovarian cancer, cervical cancer, breast cancer, bladder cancer, head and neck cancer, esophageal cancer, lung cancer, mesothelioma, brain tumors and neuroblastoma. It is given by injection into a vei
What does methotrexate inhibit and why is this the case?
Inhibits dihydrofolate reductase
It has a very similar structure to folic acid (bar the methyl group attachment) and folic acid are competitive inhibits of absorption
Tell me about Taxol
Its an anticancer chemotherapy drug
Tell me the following about the topoisomerase II, etopside
- Chemical nature
- Mechanism of action
- Cell cycle specificity
- Toxicity
1. CHEMICAL NATURE: semi-synthetic alkaloid derived from podophyllotoxin
2. ACTION: Binds to tubulin but this is not believed to be important for the therapeutic effect. May stimulate topoisomerase II to cleave DNA
3. CELL CYCLE SPECIFICITY: Greatest lethality seen in S and G2 phases
4. TOXICITY: Leukopenia, nausea and vomiting more common with oral administration, alopecia
Tell me about strand cleavage in bleomycin
Timeline depicting the historical milestones in the development of therapies for NSCLC
