Epidemiology of Cancer Flashcards
3 top cancers males (incidence)
prostate
lung
colon
3 top killer cancers (males)
lung
prostate
colon
3 top cancers females (incidence)
breast
lung
colon
3 top cancer killers females
lung
breast
colon
2 reasons why cancer more common in old
accumulation mutations
decline in immunity
unique age demographic
Hodgkins lymphoma?
30
unique age demographic
ALL
12ish
4 well known chemical carcinogens
polycyclic aromatic hydrocarbons
aromatic amines
nitrosamines / amides
aflatoxins
“activation” by microsomal enzymes
large family of microsomal enzymes (p450) that oxidize lipophilic compounds and allow their excretion - oxidation at carbon atoms can form epoxides and at nitrogen and sulfur atoms, can yield products which are mutagenic
chemical carcinogenesis - import of microsomal enzymes?
microsomal enzymes metabolize into active forms
the active metabolite is strong electrophile
these electrophyillic species can chemically modify proteins, RNA, and DNA
which bases can be attacked by electrophiles?
all 4
AMES TEST
measures the abilty of a chemical (in the presence of cytochrom p450 enzymes) to mutagenize salomenella (back to histadine+)
what percent of chemicals shown to be carcinogenic in animal testing are mutagens?
90% produce mutations in chromosomal DNA
Potency of mutagen parallels its
carcinogenicity
are mutagens prevelant
YES! we consume about 1g per day!
principles of cancer learned from animals? (7)
the effect of a chemical is generally dose dependent
specific carcinogen –> specific cancer
carcinogenesis requires time
carcinogenesis requires cell proliferation (tissue with rapid division more susceptible)
mutations are stably transmitted to daughter cells
stem cell is the at risk cell - a fully differentiated cell can never become malignant
malignant cell = stem cell that fails to differentiate normally
cancer develops in two stages
- initiation - caused by mutagen - irreversible
2. promotion - caused by chemical which is not mutagenic - is reversible
promoter of cancer?
often irritants that cause inflammation and cell proliferation
somatic theory of cancer?
cancer cells contain mutations in specific genes that participte in cell growth and differentiation - patients with defect in DNA repair are prone
The environment plays a major role in causing cancer - 3 takeaways?
- significant variation in the incidence of specific cancer seen regionally in countries
- larger variation in incidence between countries
- migrants adopt the risk of country they moved to
* 80% caused by env.
what are carcinogens?
highly reactive chemicals that cause mutations in DNA
What is a major promoter of cancer?
inflammation e.g. ulcerative colitis cholecysitits osteomyelitis hepatitis pancreatitis schistosomiasis (bladder cancer)
