The effects of food preservation on gastric cancer-inducing gene expression

1. The Effects of Food Preservation
on Gastric Cancer-Inducing Gene
Expression
Cathy Quan

2. This experiment uses mutant C. elegans as a model organism to study gene
expression.
Purpose
The purpose of this experiment is to identify the possible correlation
between the chance of being diagnosed with stomach cancer and the amount
of preserved vegetables consumed in a diet.
Introduction

3. Independent Variable: salinity, acidity, and alcohol levels (the preservation
solution)
Dependent Variable: the population count of the C. elegans
Constants: temperature, type of petri dish, starting amount of C. elegans,
incubation time, amount of solution added
Control: petri dish with no added solution
Hypothesis
If multiple fermentation environments are modeled, with different salinity,
acidity and alcohol levels, then that of higher salinity, acidity and alcohol
levels (simulating fermented vegetables) will stimulate the growth of the
mutant C. elegans
Introduction

4. • Gastric (stomach) cancer is the fifth
most common cancer in the world
• Gastric cancer can be caused by
multiple factors, including H. pylori
bacterial infection, excessive salt
intake, smoking, genetic predisposition
• Asian populations have abnormally
high gastric cancer rates
• Asian diet heavily consists of
preserved vegetables
Background

5. Preservation Methods
•Pickling — soaking vegetables in brine or
marinade, which is a vinegar
•Fermentation — soaking vegetables in beer
or another form of alcohol
•Compression — heavily salting the
vegetables, then placing them in large jars
and weighing them down (reduce moisture)
•Many preserved vegetables go through
multiple of the aforementioned processes
• ex. Suan Cai (“Chinese Sauerkraut”,
“Chinese kimchi”) — boiled, sun-dried,
heavily salted and compressed, and then
pickled
Background

6. H. pylori
• H. pylori bacteria grows in the organs involved in the
digestive system
• Attack the stomach lining to find protection from the
immune system; may lead to stomach infections
• H. pylori infections can cause stomach ulcers, and if
not treated properly, stomach cancer
Background

7. Caenorhabditis Elegans (C. elegans)
• Microscopic nematode (roundworm) that
grows to about 1 mm in length
• Feeds on microorganisms (E. coli)
• Easy to study − small, non-complex,
easily cultivated, many mutations
• Two sexes: self-fertilizing
hermaphrodites and males
Mutant C. Elegans
• cup-5 gene − homologue for the muc-1 in
humans, prevents apoptosis in cancer
cells
• trf-1 (Telomeric Repeat Binding Factor) gene
− involved in innate immune response
Background

8. Materials
•Mutant C. elegans strains containing
genes:
• cup-5
• trf-1
• Wild type C. elegans strain (N2)
•E. coli (as food for the C. elegans)
•Petri dishes
•Nematode growth agar
•Salt
•Vinegar
•Alcohol (rice wine)
•Microscope
•Inoculation Loop
•Pipette
•Scalpel

9. Procedures (for each trial)
1. Set up 24 agar plates, using Nematode growth agar
2. Create liquid fermentation solutions (salt, vinegar, rice wine)
3. Drop different mixtures of each fermentation solution into their respective Petri dishes
and spread them across the surface
•none
•salt
•vinegar
•alcohol
•salt & vinegar
•salt & alcohol
•vinegar & alcohol
•salt & vinegar & alcohol
4. Spread E.coli onto each of the 24 Petri dishes
5. Chunk the C. elegans and parafilm the plates
6. Return to lab after a few days for results, take pictures of Petri dishes under
microscope

10. • The chunks of mutant strains which were exposed to higher salinity
vegetables had higher estimated population counts than those which weren’t
exposed
• The mutant strains generally had much higher population counts than the
wild-type strain
• The plates containing vinegar and/or alcohol had the most noticeable
population growth
Results
Figure 1: Average Population Count of C. Elegans in Different Environments

11. Results
Figure 3: Average Population Count of C. Elegans in Different Environments

12. Results
Figure 2: Sample Pictures of C. Elegans Populations Exposed to Different Test Environments

13. Conclusion
•Hypothesis was supported
•Mutant strains that were exposed to higher salinity vegetables had higher
estimated population counts in total
Limitations
•Could not use actual cancer cells (did not have access to a BSL-2 lab)
•Could not manipulate acidity of environment to a pH of 2 to match the
stomach, inhospitable environment for C. elegans
•Minor equipment issues
Conclusion and Discussion

14. Error Analysis
• Systematic Errors
•Mold growth
•Sterilization
• Random Errors
•Estimation of population counts
•C. elegans distribution wasn’t perfectly even, many clusters
•Different sections had different population concentrations
•Microscope clarity
Conclusion and Discussion
even vs. uneven population distribution
mold growth in N2 strain

15. Applications
•Results from this experiment can be applied to other studies regarding stomach
cancer
•Evidence supports the claim that preserved foods, can likely lead to fatal cancers
•May help to bring awareness regarding the risk of eating too much preserved
vegetables, especially among Asian cultures
Future Research
•More trials conducted to see if a direct correlation can be developed between the
type of preservation solution and the population count of the nematodes
•Further studied by testing on actual cancer cells within a manipulated acidic
environment (to simulate a stomach environment), rather than just C. elegans
Conclusion and Discussion

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