Cancer Essay

Question 1

What does obesity increase and what is the consequence for cells (4)

Answer 1

Increase production of pro-inflammatory cytokines, sex steroids and insulin-like growth factor 1

Results in chronic low grade inflammation

Question 2

Chronic low grade inflammation consequence on cells (2)

Answer 2

Promotes proliferation of tumour cells an discourages apoptosis

Question 3

Lifestyle factors that lead to obesity and are also associated with cancer (4)

Answer 3

Low physical activity
High meat intake
Low fruit and veg intake
Low fibre intake

Question 4

How may physical activity protect against colorectal cancer?

Answer 4

Reduction of insulin resistance

Question 5

Oesophageal cancer and obesity

Answer 5

Promoted by gastric reflux in obese individuals

Question 6

Fibre cancer intro

Answer 6

World cancer research fund has reported a 10% decreased risk in colorectal cancer per 10g/day

Question 7

Fibre protective mechanisms (4)

Answer 7

Larger stool size and smaller surface area to volume ratio exposes fewer caring end to the colon
Larger stools result in a reduced transit times
Less carcinogens spend less time in the colon
Products of bacterial fermentation produces anti-tumour agents

Question 8

Albert fibre supplement intervention (3)

Answer 8

Study on men who previously had colorectal tumour removed
High fibre supplementation compared against low fibre supplement
However there were no benefits of fibre supplements

Question 9

Folate or fibre debate (4)

Answer 9

Studies that have reported a reduced risk have come from dietary sources
Therefore no effect can be attributed specifically to fibre
Fibre intake is strongly correlated with folate intake
Studies have shown that serum folate is associated with a lower risk for colon cancer but not rectal cancer

Question 10

Folate cancer mechanism (4)

Answer 10

Plays an important role in DNA synthesis, methylation and repair
Abnormal methylation has been linked to abnormal gene expression
And cancers at several sites
Folate may also reduce HPV proliferation in cells

Question 11

Red meat cancer relationship

Answer 11

Meta-analysis of cohort studies showed a 15% increased risk per 50g/d

Question 12

Red meat cancer mechanism (4)

Answer 12

Generation of potentially carcinogenic N-nitroso compounds
Some meats are cooked at high temp results in the production of heterocyclic amines
And polycyclic aromatic hydrocarbons
Red meat contains haem iron and free iron can lead to the production of free radicals

Question 13

Epic study fibre cancer (3)

Answer 13

Largest study ever conducted
On the relationship between diet and cancer
Findings suggest that dietary fibre is protective

Question 14

Non nutrient components of plant foods that may be protective against cancer (5)

Answer 14

Flavonoids
Isothiocynates  
Allium
Indoles
Phenols

Question 15

Plant foods protection apart from fibre (2)

Answer 15

Some fruit and veg are high in fibre

However they are also high in other components that may protect against cancer

Question 16

CARET trial (3)

Answer 16

Examined the effects of carotene and retinol supplementation ok lung cancer risk
Trial was stopped early due to no benefit and increased mortality
Excess beta carotene promotes cell proliferation if initiation has already occurred

Question 17

Plants and antioxidants (4)

Answer 17

Strong evidence that foods which are rich in antioxidants are protective against many cancers
E.g green leafy veg and citrus fruits
Harder to establish if the benefits are specifically due to antioxidants

Question 18

Issues with interventions (4)

Answer 18

Extremely high doses
Fail to promote dietary behaviour
Lack of considerations of the interactions between nutrients
Lack of consideration of the non nutrient components of fruit and veg

Question 19

African Americans v rural Africans intro oKeefe (5)

Answer 19

Intake from animal products much higher in African Americas than rural Africans in SA
While fibre intake much high in RAs
Colon cancer is also much more prevalent in AAs then RAs
This suggest dietary factors play a role in cancer risk
It’s been observed that AAs have greater mucosal proliferation
Which is a biomarker of cancer risk

Question 20

AAs v RAs intervention (4)

Answer 20

AAs fed high fibre low fat African style diet
Dietary change resulted in marked changes in mucosal biomarkers of cancer risk
Such as increased bacterial fermentation
And suppressed secondary bike acid synthesis

Question 21

Bjelakovic antioxidant meta analysis (2)

Answer 21

Conducted a meta analysis examining the effects of antioxidant supplements on GI cancer
The results from high quality studies found a significantly greater risk of death from AOX supplants

Question 22

Obesity and breast cancer (3)

Answer 22

Premenopausal women at less risk with high BMI
Postmenopausal women at more risk with high BMI
Central adiposity increase risk in all women

Question 23

Obesity breast cancer mechanism (3)

Answer 23

Beyond menopause production of progesterone and oestrogens stops

Increase in androgens
Androgen converted to most carcinogenic oestrogen (17b-oestradiol) in adipose tissue

Strong correlation between oestradiol and BMI Postmenopausal

Question 24

Isothiocynates protective mechanism (3)

Answer 24

Activate phase II metabolism
Of the metabolism of carcinogens
This results in the removal of carcinogens

Question 24

Indoles protective mechanism (3)

Answer 24

Activate both phase I and phase II
Of the metabolism of carcinogens
This results in the removal of carcinogens

Question 24

Allium protective mechanism (3)

Answer 24

Inhibit cell proliferation
Inhibit tumour growth
Which inhibits tumour growth

Question 25

Cancer intro control of cell division (3)

Answer 25

Controlled by proto-oncogenes and anti-oncogenes
Proto-oncogenes produce proteins that stimulate cell division at a low level
Anti-oncogenes produce proteins that prevent cell division

Question 26

Cancer intro - cancer development (3)

Answer 26

Damage to oncogenes is termed carcinogenesis
Most damaged DNA can be repaired
Cancer often depends on loss of DNA repair genes

Question 27

Cancer three steps (5)

Answer 27

Disordered expression of these genes leads to generation of transformed cell
Which is first step of cancer
Followed by proliferation
And finally integration into tissue and spreading to other organs
Some nutrients have the ability to induce or prevent carcinogenesis