Interactions -MD2B4 Flashcards
What does clonal mean?
genetic changes are inherited when cells divide
what is progression in relation to tumorigenesis
‘cellular evaluation’ - progressive accumulation of genetic changes resulting in tumour progression from normal cells to benign tumour to malignant to metastatic tumour
name some hallmarks of cancer (10)
resisting cell death evading growth suppressors activating invasion metastasis sustained proliferative signalling avoiding immune destruction tumour-promoting inflammation genome instability and mutation introducing angiogenesis enabling replicative immmortality deregulating cellular energetics
what are the 3 DNA methylation changes that can be detected in cancer cells?
- gene-specific hypo- and hyper- methylation
- global hypomethylation across the genome
- increased incidence of mutations
what is the impact of gene-specific hypomethylation?
the gene is transcribed
removal of methylation = activation of oncogenes
give an example of the impact of gene-specific hypomethylationq
BCL-2 oncogene is hypomethylated and over transcribed in human B-cell chronic lymphocytic leukemia and breast cancer
what is the impact of gene-specific hypermethylation?
the gene is supressed
methylation = suppression of tumour genes
give an example of the impact of gene-specific hypermethylation
DNA repair: MGMT, MLH1, BRCA1 -suppressed and no longer expressed and so there is dysregulation in DNA repair leading to cancer
Apoptosis and survival
GSTP1 is methylated in >90% of prostate cancers
what are the impacts of genome-wide hypomethylation?
it happens early on and progresses over time - detected in all cancer types
hypomethylation of repetitive regions causes genome instability (deletion, insertion…)
what happens to cytosine when its methylated?
it is methylated to form 5-methylcytosine which is unstable
it can undergo spontaneous deamination and forms a thymine base
so methylation gives rise to a spontaneous mutation converting cytosine to thymine
what happens to methylation as cancer progresses?
global methylation decreases
gene-specific hypermethylation at CpG islands in promotors occurs
alteration and dysregulation of histone modifications
why are epigenetic mistakes clinically relevant?
epigenetic mistakes change and progress over time
significant clinical implications
used for detection, classification, prognosis, and treatment
what are common features of a tumour cell population?
heterogenous
0.1-0.8% of of the tumour cells are made up of cancer stem cells (cancer-initiating cells)
what are the capabilities of cancer stem cells?
drug resistant
self-renewal
differentiation
tumorigenicity when transplanted into animal host
what do cancer stem cells differentiate into?
self renewing cells and differentiated cells that make up the bulk of the tumour
what mechanisms can cacncer stem cells origionate through?
de-differentiation of somatic or differentiated cancer cells
mutations and epigenetic changes in normal stem cells or progenitor cells
what are the most commonly mutated classes of genes in cancer?
epigenetic regulators
how is epigenetics used in early cancer diagnosis?
detection of CpG island hypermethylation in biological fluids and serums
example: GSTP1 in urine specimens of patients with putative prostate cancer
how is epigenetics used in cancer prognosis?
hypermethylation of specific genes
whole DNA methylome profiles
Histone modification map
how is epigenetics used in tumour response predictions
CpG island hypermethylation as a marker of response to chemotherapy, hormone therapy and targeted therapy
example: MGMT in patients with glioma and temozolomide treatment -predicts outcomes/response to treatment
how is epigenetics used in follow up cancer appointments?
detection of CpG island hypermethylation in biological fluids and serum
e.g., p15 methylation in acute myeloid leukemia - reoccurance
what are Epidrugs?
small-molecule inhibitors that target epigenetic machinery
are dna methylation and histone modifications reversible?
yes
unlike mutations which are not
what are the main classes of epidrugs?
DNA methyltransferase inhibitors (DNMTi)
histone deacetyltransferase inhibitors (HDACi)
histone acetyltransferase inhibitors (HATi)
The aim is to activate tumour suppressor genes, deactivate oncogenes, prevent proliferation and trigger apoptosis in cancer cells
alter active site of enzymes to inhibit them
what is the role of DNMT inhibitors?
aberrant DNA hypermethylation
reactivate the hypermethylated genes, leading to their activation and cancer cells reprogramming that ultimately lead to proliferation arrest and cell death
what is the role of HDCAis inhibitors in cancer?
reverse transcriptional repression of multiple genes involved in cell cycle progression, differentiation aand apoptosis
what are the role of HDAC inhibitors
reverses transcriptional repression of multiple genes involved in cell cycle progression, differentiation and apoptosis
4 different classes
vorinostat is FDA approved for the treatment of cutaneous t cell lymphoma
name 2 biomedical non modifiable risk factors
genetic susceptibility
hormonal factors in females
name some lifestyle risk factors for cancer
smoking alcohol physical inactivity chronic infections diet
name some environmental risk factors for cancer
sunlight - skin/melanoma
radiation - leukaemia, breast, thyroid
occupational exposure - nasal cavity
pollution - skin, lung, bladder
what is absolute risk
the chance that a person will develop a disease during a given time
general indicator as to how many people are at risk in general populaiton
what is relative risk?
compares the risk of disease between 2 groups of people
compares one group with a certain risk factor for a disease to another groups risk
what is incidence and how is it calculated
estimates how many people will be diagnosed with cancer within certain time period
identify nimber of people diagnosed over a range of years, place numbers in statistical model to predict further incidence
given as a rate
can be age adjusted
what is prevalence
estimates how many people have or have had cancer (ALL people with cancer)
shown as a percentage
what are non-modifiable risk factors?
unmodifiable intrinsic risk factors - unavoidable spontaneous mutations that arise because of random errors in DNA replication
occur in different organisms at diffferent rates
what are the two types of non-intrinsic risk factors?
exogenous - modifiable/external- carcinogens, viruses, lifestyle factors
endogenous - partially modifiable - immune, metabolism, DNA damage responses, hormone levels
half of all cancers are in people over 70, true/false
true
what do faulty BRCA genes increase the risk of?
BRCA1 and 2: breast, ovarian, pancreatic and prostate
what are BRCA1 and BRCA 2 genes?
Tumour suppressor genes
mutations means that cells can grow out of control and lead to cancer develpoment
only 1 in 400 have the fault
~70% in every 100 women with a faulty BRCA1/2 gene will develop by aged 80
true/false
true
what is another term for lynch syndome?
non-polyposis colon cancer (HNPXX)
INCREASES RISK OF BOWEL CANCER
70 in 100 people with Lynch syndrome will develop bowel cancer
most will develop before aged 50
what does Li fraumeni syndrome increase the risk of? and what gene?
TP53 gene. - tumour supressor
breast
bone
brain
what are the 5 key modifiable risk factors?
tobacco use alcohol consumption excess body weight physical activity healthy eating
how many cancer cases arise from modifiable risk factors?
~1/2
what is primary cancer prevention?
addresses the cause so the disease does not occur e.g., avoid certain behaviours/activities
what is secondary cancer prevention
identified the disease before the onset of symptoms and keeps it from becoming more extensive e.g., screening
what is tertiary cancer prevention?
reduces complications and progression of disease once it has become clinically apparant
rank the top 5 cancer risk factors
- smoking
- excess body weight
- drinking alcohol
- UV radiation
- physical inactivity
how many cases of cervical cancer are modifiable?
100%
what causes 19% of all cancers?
smoking
what does excess body weight affect?
inflammation in the body cell and blood vessel growth cells' ability to live longer levels of hormones that can fuel cell growth factors that regulate cell growth the ability of cancer cells to spread
how does alcohol raise cancer risk?
alcohol is converted to acetaldehyde that can damage DNA inside cells
alcohol can act as an irritant
cells that are damaged mah try and repair themselves which may lead towards DNA changes
lead to oxidative stress - ROS
liver damage
combination of alcohol and smoking on cancer risk
alchohol may help other harmful chemicals such as those in tobacco smoke, enter the cells lining the upper digestive tract
alcohol may also slow down the bodies ability to break down and get rid of some harmful chemicals
what are the three main groups of UV radiation
UVA
UVB
UVC
which UV rays have the most energy but arent a risk factor?
UVC
Which form of UV radiation causes skin cancers?
UVB
what reduces the risk of 13 different cancers?
exercise
what are the 5 types of observational study?
cohort case-study cross-sectional gene-wide association gene-environemnt §
what is a cohort study
group of people with something in common
usually an exposure or involvement in a defined populaiton group
study to obtain additional evidence to refute or support the existence of an association between suspected cause and diseases
cohort is identified prior to to appearance of disease being investigated
groups observed for defined period of time
what is a prospective cohort study?
2 groups - exposed and unexposed
both free from condition from the outset
observed for specifc period of time
long duration
funding for long period
drop out
what is a reterospective cohort study?
outcomes have all occured before the start of the investigation
investigator goes back to the past to select the study group and traces them forward through time
what is an ambi-directional cohort study?
combines prospective and reterospective
cohort is identified from past records and assesses the date for the outcome. same cohort is followed up pprospectively into the future for further assessment of outcome
what is relative risk?
incidence risk among exposed group/incidence risk among non-exposed group
what is attributable risk?
incidence risk among an exposed group minus the incidence risk among non exposed group
what is bioavailability?
proportion of administered drug which reaches the systemic ciruclation unchanged and therefore available for distribution to the site of action
what method of drug adminiistration acheives 100% bioavailability?
intravenous injection
all the drug reaches the systemic circualtion unchanged
which method of drug admiinistration always acheives less than 100% bioavailability?
oral route common, safe, convenient, economical exposure to pH, enzymes, gut activity exposure to first pass metabolism absorption depejds on rates of GI transit requires patient compliance
which methods of drug administration avoids first pass metabolism?
mucosal routes sublingual, buccal - spray under tounge nasal, eye, vaginal, rectal rapid transit to systemic circulation drug stability- pH in mouth is neutral compared to stomach
also inhalation routes
what is pharmacokinetics
study of drug movement within the body - what the body does to the drug
what is pharmacodynamics?
study of drug effects and mechanisms of action - what the drug does to the body
what are the 4 phases of pharmacokinetics (ADME)
- ABSORPTION
- DISTRIBUTION
- METABOLISM
- EXCRETION
Describe the absorption phase of pharmakokinetics
Drug must cross the GI tract and avoid metabolism by liver
Most drug absorption occurs via passive diffusion
Rate = permeability x SA x concentration difference
what factors affect GI drug absorption rate?
surface area/blood flow
GI motility - e.g., laxatives = rapid transit so less exposuer and absorption
Malabsoptive states - e.g., coeliac disease - reduces/impairs absorption
food type - meal composition - fat intake delays gastric emptying
lipid solubility of drug can increase absorption rate
what is first pass metabolsim?
The extent of drug metabolism occuring before the drug enters the systemic circulation
desribe the process of first pass metabolism
after absorption, orally administered drugs enter the portal system
drugs can be rapidly metabolised by enxymes in the liver
this reduces the level of drug reaching thr systemic circulation so has major affect on bioavailability
swallowed drug > digestive system > hepatic portal system > liver > rest of body
what is the drug distribution phase?
process of drug being transferred ffrom systemic circulation to the tissues
what is rate and distribution of drugs determined by?
ability of drug to pass through tissue membrane
lipid solubility of drug
binding of drug to plasma proteins
active transport of some drugs across cell membranes
presence of other drugs in the body
perfusion rate limitations
what is the effect of drugs binding to plasma proteins?
drugs can bind reversibly to plasma proteins
only non-protein bound drug molecules go on to traverses membranes to gain access
changes in protein binding can lead to changes in drug distribution
how much of the total drug plama must constitute of protein bound drugs
90%
E.G., warfarin used to treat coagulation disorders/risks - around 99% of this is protein bound - stays in blood so low distribution level
what increases drug half life dramatically?
high-protein-binding
what is the risk of protein dispalcement with co-admisitered drugs?
warfarin is usually 99% protein bound but if the pateint also takes aspirin which is a high protein binder, the asprin will displace the warfarin from the plasma proteins and therefore increasing the level of unbound protein in the blood. the effective concentration of warfarin increases and this toxicity can lead to excessive bleeding as its a drug that helps prevent blood clots
where is the main sight of drug metabolism?
liver
what are the 2 phases of drug metabolism?
phase 1: oxidation, reduction, hydrolysis, demethylation. products are more chemicslly reactive and more toxic than the parent drug, Cytochrome p450 enzymes are important
phase 2: conjugation, sulphonation, glucuronidation, acetylation. conjugates are often chemically polar and readily cleared by the kidney. retains them longer in the bloodstream
what are the effects of drug activity on drug metabolism?
Conversion of drugs to inactive compounds by liver; promotes excretion of converted drug molecules by kidneys
pro-drugs - inactive pro-drugs can undergo metabolism in the liver following ingestion to become pharmacologically active
active metabolites - e.g., codeine (inactive) is converted to morphine (active) in the liver
what are the features of pro-drugs
altered absorption kinetics
prevent adverse effects
improve distribution post ingestion
what factors affect drug metabolism?
liver disease
advancing age
genetic polymorphisms in drug metabolising enzymes
competition between drugs for the same metabolising enzymes
where is the major route of drug excretion?
kidney via urine
also via GI - bile
foecal drug excretion
what are minor routes of drug excretion?
lungs, sweat, tears, saliva, breast milk
what is rate of elimination?
amount of drug eliminated from the body per unit time
what is first order kinetics in drug elimination?
drug concentration is decreased exponentially
natural logarithm of drug concentration and time is linear
rate of elimination is proportional to the amount of drug in the body
how can drug half life be determined?
elimination curve
what is the half life of paracetamol?
~2 hours
what is the half life of chloroquine?
~6 WEEKS
how long does it usually take for drugs to be absent from the body?
after 5 half lives have elapsed?
what is half life of a drug?
meausre of the presence of the drug in the body rather than the duration of the action of the drug
the half life of the same drug remains the same no matter the dosage given
what are the 4 types of pharmacolgical actions of drugs?
- via direct effects of cellular receptor function
- via action on ion channels
- via action of membrane transport processes
- via enzyme inhibition
which receptors have fast responses and which are slow
cell membranes - fast responses
cell cytoplams - slower responses
what is a receptor agonist?
an agonist is a moleucle that binds to a recptors and activates it
can be partial - doesnt have the same extent of biological reponse
what is a receptor antagonist?
competitive antagonists compete for the same binding sites as the agonist
non-competitive antagonists alter the receptor binding site to reduce agonist activity
give 2 examples of receptor antagnonists
atenolol - therapeutic competitive inhibitor of the Beta-1 adrenergic receptor and is used to treat hypertension and cardiac arrhythmia
ketamine - therapuetic non-compeititve antagonist of the neuronal N-methyl-D-aspartate receptor and is used as an anaesthetic
what is the affect of drugs targetting ion channels
ion channels influnce the movement of ions into and out of cells across membranes
influences polarisaion of excitable cells and influences intracellular signallign cascades
drugs acting on ion channels affect neural transmission and muscle contractility
what are examples of ion channels inhibitors
sodium channel blockers - local anaesthesia e.g., lidocaine
calcium channel blockers -slow heart rate e.g., verapamil
what is the effect of drugs targeting transporters?
transporters mediate the movement of specific endogenous signlaling molecules and nutrients in and out of cells
so targetting this can cause accumulation or prevention
what is an example of drug targeting of transporters?
selective serotonin reuptake inhibitor (SSRI) anti-depressant drug, sertaline, blocks neironal serortonin transporter (SERT) leading to retention or serotonin in the nrual post-synaptic cleft.
what are examples of drug targeting enzymes?
ACE inhibitors - ramirpil blocks ACE
NSAIDs - iburpofen
what is the importance of the P450 isoenzyme? - drug -drug interactions
introduction of the P450 enzykmes by one drug can increase the rate of metabolism of another resulting in lower plamsa concentrations and reduced effects
upon withdrawal plasma concentrations of the other drug increase and toxicity can occur
what are common important drugs affected by P450 enzymes?
Ciclosporin Oral contraceptives Warfarin Phenytoin - epilepsy drug Acetylcholinesterase inhibitors Theophyline - asthma Statins
COWPATS
What is pharmacogenetics?
Individual responses to drugs can vary
genetic polymorphisms exist in drug metabolising enzyme genes especially in cytochrome p450 enzymes
some can lack enzymes and so drugs have no effect
some can have extra copies and so are rapid metabolisers - enhanced effect
opens up the field of personalised medication
what proportion of > 65 year olds take at least one medication?
4 in 5
what percentage of older people take >4 medications simultaneously?
36%
what percentage of admissions for older adults are due to adverse drug reactions?
5-12%
what is an adverse drug reaction
undesirbale effect of a drug beyond its anticipated therapeutic effects
what are ADRs related to? (DoTS classification)
Dose
Time-course
Susceptibility
what is the theraputic index?
theraputic window - stay between to get deisred repsonse
what are some examples of drug sensitivity in older adults?
reduced receptor responses renal clearane reduced altered immune response slower gastric emptying reduced plasma albumin altered liver metabolism
what is the problem with drug disocovery?
attrition remains high
small moleucle drug approvals remain constant
new drug candidates must represent a significant advantage over standard of care
disease models fail to refelct complexity of human disease
cure vs disease control
lack of effective biomarker research
what is precision medicine?
not a one size fits all approach
takes into account individual variability
more accurate prediction about the treatment and prevention strategies for a particualer disease or group of people
what are advantages of precision medicine?
wider availability of doctors to use patients genetic and other molcular infomation as part of routine medical care
ability to predict whcih treatments will work best
improved approahces for preventing, diagnosing and treating a wide range of diseases
what are commercial challenges of precision medicine?
unlike traditional medicines where manuacturers can earn more selling these products to a large population, pprecsion medicine doesnt provide this opportunity
manufacturers often charge a lot of moneyy for their products like with orphan medications (rare diseases and some cancers)
what is an explanatory trial?
‘as-treated’ analysis
analyses only those who completed follow-up and complied with treatments
compares the physiological effects of the treatments
what is a pragmatic trial?
‘intention to treat’ analysis
Intention-to-treat analysis is a method for analyzing results in a prospective randomized study where all participants who are randomized are included in the statistical analysis and analyzed according to the group they were originally assigned, regardless of what treatment (if any) they received
as treated vs intention to treat
as treated - larger sizes of effect
intention - smalller effect sizes
what are key ethical issues in clinical trials?
clinician has to provide the best treatment for each individual patient
scientific integrity requires treatment to be chosen at random
clinical equipose: reasonable uncertainty about which treatment including non-treatment is better so randomisation dies not deny any patient the best treatment
what is informed consent? - what should be explained to patients before the trial
patient is invited to be in a trial
what the alternative treatments are
the treatment is allocated at random
patient can withdraw at any time
information should be given verbally and in writing with time to make a deicison
how many cells do we carry?
~3.72x10^23
what are the objectives of a cancer treatment?
> destroy/kill ALL cancer cells - possible complete cure
> destroy/kill MOST cancer cells - prolonging survival time
> destroy/kill SOME cancer cells - eliminating symptoms or preserving QOL
what are the categories of tumour rersponse (treatment efficacy)
> complete response: dissapearance of all signs of disease
partial response: reduction of tumour volume by at last 30%
stable disease: no significant change
disease progression: increase in tumour volume by at least 20% or new metastasis
what is meant by overall survival?
survival time from the start of treatment
what is disease-free survival?
survival time prior to tumour relapse after radical treatment
what is progression free survival?
survival time prior to tumour progression
how do you assess if one treatment is better than the other?
estimaet effects from sample of data and provide survival curves
estimate confidence interval around the estimate to rerlect uncertainty
what are methods of traditional cancer treatment?
radiation
surgery
chemotherapy
what are new methods of cancer therapy?
targeted drug therapy
precision medicine
what is chemotherapy?
administration of chemical agents to destroy cancer cells
aim to cure where possible and palliate where cure is impossible
what is neoadjuvent chemeotherapy?
administered prior ro surgery to facilitate resection (shrinking) and prevent mestastasis
what is adjuvent chemotherapy?
administered post operatively
debulking to kill micro-metastases
reduce risk of distant replapse
increase disease-free survival
what is palliative chemotherapy?
improving the qualtiy of the patients life by controlling symptoms prolonging life in a patient where cure isn’t possible
what is salvage chemotherapy?
potentially curative, high dose regimen given to a patient who has failed or recurred following a prior curativ regimen
what are antimetabolites? - mechanism of chemotherapy
limit the synthesis of nucleic acid precursors (needed for DNA replication)
e.g., methotrexate inhibits dihydrofolate reductase - reduces the synthesis of folate which is necessary for purine and pyrimidine production
what are topoisomerase enzymes? - mechanism of chemotherapy
they participate in the winding and unwinding of DNA and are inhibited by anthracyclines snd camptothecins
what agents cause stucutral damage to mature DNA?
alkylating agents, platinum derivatives
what do vinca alkyloids and taxanes do - chemotherapy mechanisms?
disturb function of mitotic spindle
what chemotharpeutic mechanism involves hormones?
homonal agents - block proliferation if hormone responsive cells
what is the mechanism of action for alkylating agents?
target DNA, produce alkylation through the formation of intermediates
not cell cycle phase specific - just damage DNA wherever they are in the cycle, causing cell death
e.g., cisplatin, carboplatin
what is the mechanism of action for antimetabolites?
interfere with DNA synthesis
structural analogues or inhibit sseveral enzymes
s-phase specific
e.g., methotrexate
what is the mechanism of action for mitotic spindle agents
bind to microtubular proteins inhibiting microtubule assembly, thereby interupting the mitosis phase of cell division
M phase speicific
e.g., docetaxel
What is the mechanism of action for topoisomerase inhibitors?
DNA topoisomerase 1 and 2 are essential enzymes for transcription, replication and mitosis - moduare the structure for winding of DNA
e.g., Topo 1 INHIBITORS
what do all mechanisms of action for chemotherspy have in common?
targeting DNA replication machinery and ability of cells to divide
the problem is that this is the mechanism of all growing cells in our body, not just cancer
what are the principles of combination chemotherapy?
> use drugs active as a single agent
use drugs with different mechanisms of action
use drugs with different mechanisms of resistance
use drugs with different side-effects
be aware of drug-drug interactions
is survival increased with combination therapy?
overall survival is significantly increased
what is category one cancer based on effectivness of chemotherapy?
evidence that single or combination of drugs alone or other therapeutic modalites will result in cure - deifined by a normal lifespan and prolongation of survival in most patients
germ cell, leukaemia, lymphoma
what is category two cancer based on effectivness of chemotherapy?
average survival is prolongued when chemotherapy is used in adjuvent to local surgery or radiotherapy in the early stages of disease
e.g., breast, colorectal, ovarian
what is category three cancer based on effectivness of chemotherapy?
evidnece that a single drug or combination will produce clinically useful responsievness in more than 20% of patients. may be of short duration
e.g., lung, bladder, prostate, stomach, cervical
what is category four cancer based on effectivness of chemotherapy?
tumours where locsl control mayu be improved bt uusing chemotherapy before, during or after surgery/radiotherapy
e.g., head and neck
what is category five cancer based on effectivness of chemotherapy?
tumours for which there are no effective drugs
objective response occur in less than 20% of patients
e.g., liver, melanoma, pancreatic, brain, thyriod
what is meant by a complete response to treatment? (chemo)
dissapearance of all target lesions
what is meant by a partial response to treatment? (chemo)
at least 30% decrease in the sum of the longest diameter of targeted lesions
what is meant by a stable disease (chemo)?
neither sufficient shrinkage to qualify for PR or significant enough increase to qualify for PD
what is meant by progressive disease (chemo)?
at least 20% increase in the sum of the LD of the targeted lesions
what are methods of chemotherapy delivery?
IV or oral
straight to site where needed:
local drug application - intra-arterial (hepatic infusion)
- intra-pertoneal (ovarian cancer)
- intra-pleural (pleural metastasis)
what is mucositis
common complication of cancer chemotherapy
begins 5-10 days post initiation of treatment and lasts 1-2 weeks
causes mucosal lining of the mouth to atrophy and break down, forming ulcers and sores
oral pain
burning
ulceration
difficulty eating, drinking, speaking
what is the problem with cytotoxic drugs?
drug resistance
resistance is often due to mutation or altered expression of genes whos products mediate:
> transport o a drug into/out of a cell
> metabilism and therefore intracellular concentration of the drug
> structure of the target protein (structural/enxyme) to which the drug binds to cause cytotoxicity
> protection from apoptosis
what are features of cancer stem cells?
quiescent, increased expression of anti-apoptotic proteins and increased activity of pro-survival pathways
what does the MDR1 gene encode? - multidrug resistance gene
P-glycoprotein (PGP): mediates transport of certain drugs out of the cell therefore reducing intracellular concentration and cytotoxicity
overexpression of PGP achieved through incresded expression of its mRNA with or without MDR1 gene amplification
what are processes of multi-drug resistance
increased drug efflux decreased drug influx tumour microenvironment drug targets - mutations, feedback activation drug metabolism - detoxifying gene regulation
resistance can be intrnsic or aquired
epigeneitc alterations can cause resistance - reversible by epigenetic modification?
how can drug resistance be overcome?
platinum drugs targeting resistance mechsanisms
more of drug in a way thats less toxic
more specific agents - pairing with drugs thhat are not resistant
drug resistance is also affected by the microenvironment
what are the characteristics of radical radiotherapy?
preserves normal anatomy
acute morbidity
less severe
localised disease
high dose therapy delivered in daily fractions over 7 weeks
e.g., larangeal carcinoma when patients are not fit to undergo radical surgery
what are the characteristics of adjuvent radiotherapy?
administered as an addition to potentially curative surgery
eradicate microscopic residual disease remaining in the tumour bed
used to reduce local relapse rates following partial masectomy
what are the characteristics of palliative radiotherapy?
control of distressing symptoms
not curative
improve QOL
relive pain
what is external beam radiation?
x-rays, gamma rays and electron beams from linear accelerators
high-intensity electron beams have greater penetration, less scatter, delivers high enerft to deep seated tumours while sparing nomral tissues
planned using CT scan to create 3D image
computor profeamme designs radiation beams that follow the shape of the tumour
what is brachytherapy?
internal radiotherapy
use of radioactive sources implanted directly into a tumour or body cavity to deliver localised radiotheapy
examples: iridium-192 needles or wires implanted into tumours of the breast, tounge, floor of mouth
sealed caesium -137 radioactive sources into the vagina, rectum to treat cancer of the vagina, cervix, uterus, rectum, animals
pellets of iodine-125 to treat prostate cancer
major disadvantage is staff handling radioactive sources
how is thyriod cancer treated?
Radioisotope
iodine-131
specific transport protein that allows uptake of this iodine in the thyriod and it will stay in that region
what is proton therapy
form of radiotherapy that uses protons instead of x-rays
high energy proton beams target tumours morre precisely
less damage to healthy tissues
what molecular mechanisms contribute to radioresistant phenotypes
evasion of apoptosis
altered mitochondrial and energy metabolism
inflammation
altered cell cycle
what are some early effects of radiotherapy (2-3 weeks)?
tiredness, lack of energy, depression
specific local effects related to area beign treated: skin- erythema, bowel - diarrhoea, bladder - urine frequency/dysuria, scalp - hair loss, mouth - mucositis
what are some late effects of radiotherapy?
loss of stem cell recovery
damage to small blood vessels resulting in occlusion
skin - fibrosis
bowel - stricture, perforation
bladder - fibrosis. haematuria
rare induction of second malignancy - leukaemia (3 yrs), solid tumour (10-30 yrs) post exposure
what are the 3 types of surgical oncology?
surgery for prevention - familial cancer, liver transplant
surgery for cancer cure - total eraditcation of primary tumour, regional lymphatics
surgery for palliation - surivice longer, better QOL, reduce occlusion of lumen
what is a tumour margin?
rim of normal tissue surrounding the tumour
sent off to pathology to ensure a good tumour margin and all tumour is removed
what is a lumpectomy?
proceudre used for breast cancer
minimal mutilation when cancer is detected early - small scar
lymph node disection and removal of breast required when cancer has spread
(mastectomy)
what are the main types of damage caused by ioinsing radiation?
base and sugar damage
single stand breaks
double strand breaks
covalent intra or inter strand cross linking
what factors affect the tumours response to radiation
where the cell is in the cell cycle what type of tumour how fast is it growing type of microenvironment dosage of radiotherapy
what are therapeutic vaccines?
modified tumour cells, tumour associated antigens, dendritic cells, oncolytiic viruses
what are different methods of immunotherapy?
therapeutic vaccines immune system modulators monoclonal antibodies adoptive t cell transfer immune checkpoint inhibitors
how are dendritic cells involved in immunotherapy?
they generate cytotoxic T cells which kill cancer cells by recognising specific antigens produced in the cell
cancer cells produce antigens that are seen as foreign and are presented as peptides that can be recognised by cytotoxic T cells
how are dendritic cell vaccines created for vaccine therapy?
- take blood from cancer patient
- remove monocytes (give rise to dendritic cells)
- stimulate with various factors in vitro
- they become dendritic cells
- feed the cells specific peptides (tumour antigens) or tumour lysate
- inject back into patient as a vaccine to induce a T cell immune repsonse agasint the tumour
how are dentritic cells used in treatment of prostate cancer?
Sipuleucel -T
use a fusion protein which is a combination of an antigen thats present in prostate cancer - prostatic acid phosphatase)- and granulocyte macrophage colony stimulating factor - stimulated dendritic cells
introduce into activiated dendritic cells int he patient and give them back as therapy
(take cells, modify, replace)
very expensive
how much longer is survival when using dendritic cells/sipuleucel-T in prostate cancer?
4 months longer
what are key mediators of cell communication in the tumour microenvironment?
cytokiines