Activity 3.1.3 When Cells Lose Control
Introduction
Healthy cells that make up the body’s tissues constantly grow, divide, and replace
themselves. For example, the surface layer of the skin is completely replaced every few
weeks, blood cells are replaced approximately every 120 days, and the epithelial cells that
line the surface of the gut are replaced approximately every five days. Normally cell division
is an orderly process, but sometimes the cells lose control; the result is cancer. Although
there are many different types of cancer, all cancer cells share one important characteristic:
they are abnormal cells in which the processes that regulate normal cell division are
damaged. To understand cancer, you need to understand how cells normally reproduce.
Before a cell divides, the cell makes a copy of its DNA, through a process called DNA
replication. These copies are then distributed to two daughter cells when the original cell is
signaled to divide. The entire process is called the cell cycle. Throughout the cell cycle, there
are checkpoints that ensure the cell can continue in its cycle. For example, there are
checkpoints to make sure the DNA is not damaged and it is okay for the cell to undergo DNA
replication and cell division. When normal cells have irreparable damage to their DNA or
have no further role in the body, the cell undergoes apoptosis, or cell death. This process
stops damaged cells from multiplying. How is it then that cancer cells divide even though they
have damaged DNA?
Regulation of the cell cycle is a very complex process that involves regulator genes. All
cancers involve the malfunction of these genes that regulate the cell cycle. There are two
main types of genes that are involved with cancer: oncogenes and tumor suppressor genes.
All cancers express alterations in one or more of these genes. You will explore the role of
these genes during this activity.
As you read about in the Family Bulletin about Mike Smith, a biopsy of Mike’s bone tumor
was necessary to confirm the diagnosis of osteosarcoma. A biopsy is a procedure performed
to remove tissue or cells from the body for examination under a microscope. Pathologists
look for the characteristic set of features that indicate whether or not a tumor is cancerous. In
this activity, you will investigate biopsy results to examine how cancer cells divide and will
compare these mutated cells with normal cells.
Equipment
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Computer with Internet access
 Forceps
Laboratory journal
 Distilled water
Activity 3.1.3 SR Sheet
 Latex or nitrile exam gloves
Microscope
 Safety goggles
2 Microscope slides
CellServ’s “Visualization of Normal & Transformed Cells-Kit 1”
o Coverslip with IMR-90
o Stain #2
o Coverslip with L929 cells
o Permount (mounting medium)
o Stain #1
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Medical Interventions Activity 3.1.3 When Cells Lose Control – Page 1
Procedure
Part I: Normal Cells Versus Cancer Cells
1. Obtain a Student Response Sheet from the teacher.
2. Answer Questions 1-4 on the Student Response Sheet as you watch the video “Cancer
and the Cell Cycle” found at Emory University’s CancerQuest website:
http://www.cancerquest.org/images/FLV/fullDocumentary/English/fullDocInterfaceE
ng.swf
3. Brainstorm how you think mutations occur in proto-oncogenes and tumor suppressor
genes that can lead to cancer.
4. Investigate how a proto-oncogene becomes an oncogene as you view the Annenberg
Media’s animation “How a Proto-oncogene Becomes an Oncogene” found at:
http://www.learner.org/courses/biology/archive/animations/hires/a_cancer2_h.html
5. Answer question 5 on the Student Response Sheet.
6. Answer Question 6 on the Student Response Sheet as you watch the Annenberg Media’s
animation “p53’s Role in the Cell” about how one particular tumor suppressor gene works,
found at:
http://www.learner.org/courses/biology/archive/animations/hires/a_cancer3_h.html
7. In one to two, well-crafted paragraphs in your laboratory journal, summarize the process
in which normal cells become cancer cells. Your paragraph(s) must include each of the
terms listed below. Underline each term in your paragraph(s):
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Cell cycle
Regulated
Cell division
Apoptosis
Metastasis
Mutations
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Blood vessels
Signals
Proto-oncogenes
Oncogenes
Tumor Suppressor Genes
Part II: Cancer Cell Microscopy
Cell culture is the term used to denote the growing of cells in vitro (meaning outside the body)
in specially designed containers and under precise conditions. Although both normal and
cancer cells can be cultured in vitro in the laboratory, their growth patterns and morphology
(or structure) are very different. Now that you are familiar with the mutations that cause a
normal cell to become cancerous, you will now investigate how these changes affect how
normal and cancer cells grow in culture.
8. Take notes as your teacher presents the Understanding Cancer – Cancer Detection and
Diagnosis presentation, from the National Cancer Institute at the National Institutes of
Health, available at
http://www.cancer.gov/cancertopics/understandingcancer/cancer.
9. Read the following facts about some characteristics of normal versus cancer cells grown
in vitro:
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Medical Interventions Activity 3.1.3 When Cells Lose Control – Page 2
o Normal cells pass through a limited number of cell divisions before they die; this is
called replicative senescence. Alternatively, cancer cells can proliferate indefinitely in
culture.
o Normal cells, when placed on a tissue culture dish, will proliferate until the surface of
the dish is covered by a single layer of cells just touching each other. Their close
proximity will trigger them to stop replicating, a phenomenon called contact inhibition.
Cancer cells do not exhibit contact inhibition. Once cancer cells cover the surface of
the dish, the cells will continue dividing and pile up on top of each other.
o Normal cells have distinct shapes common to that particular cell type. Cancer cells
undergo morphological changes and will exhibit various shapes.
o Normal cells require specific nutrients that must be supplied to them in their tissue
culture medium. Cancer cells can grow under less stringent conditions, and can
usually grow on simple culture medium.
o Normal cells have the normal set of chromosomes. Cancer cells often have an
abnormal number of chromosomes and the chromosomes often have an abnormal
structure.
In PBS, you looked at chromosomes from HeLa cells, the first human cell line successfully
grown in a laboratory. You might have found that the number of chromosomes you counted in
the cell spreads differed from the normal number of human chromosomes in a cell. You also
might have noticed that many of the chromosomes were abnormal. Remember that the HeLa
cell line was actually derived from cancer cells taken from Henrietta Lack’s cervix. The HeLa
cell line was unique at the time for its uncanny ability to easily multiply at a rapid rate in
medium.
10. Answer Conclusion question 1.
11. Working with a partner, obtain a coverslip with IMR-90 cells and a coverslip with L929
cells from your teacher. Be very careful; the coverslips are very fragile.
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The IMR-90 cells were grown from normal human lung fibroblasts.
The L929 cells were grown from transformed subcutaneous mouse cells, derived
from an areolar and adipose tissue biopsy.
12. Determine which side of the coverslip the cells are affixed to, by matching up the
coverslips to the picture below. When the coverslips are in this orientation, the cells are on
the surface facing you:
13. Obtain stain #1, stain #2, forceps and distilled water from your teacher.
14. Gently grasp an edge of one of the coverslips with forceps and dip the coverslip into stain
#1 for 1 second. Repeat once more. Be careful not to drop or break the coverslip.
15. Allow excess stain to drain by touching the edge of the coverslip to the stain container.
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Medical Interventions Activity 3.1.3 When Cells Lose Control – Page 3
16. Transfer the coverslip immediately to stain #2 and dip for 1 second. Repeat once more.
Do not over-stain the coverslip.
17. Remove any residual stain on the coverslip by rinsing the coverslip with distilled water for
a few seconds.
18. Allow the coverslip to dry. You may gently blow on the coverslip to help speed up the
process. Make sure the coverslip is completely dry. Also make sure the underside of the
coverslip is dry.
19. Mount the coverslip to a microscope slide. To mount the coverslip, add 1-2 drops of
Permount to the microscope slide in the area where the coverslip is to be mounted.
20. Place the coverslip with the cell side down onto the Permount.
21. Apply gentle pressure to the coverslip to evenly distribute the Permount between the
coverslip and slide. Be careful to avoid getting air bubbles and getting Permount on the
top of the coverslip.
22. Allow the Permount to dry (which can take up to 48 hours).
23. Repeat steps 13 – 21 for the other coverslip.
24. Observe the IMR-90 normal cells under 100X total magnification. Pay careful attention to
the shapes, growth patterns, and cell distribution.
25. Draw a circle in your laboratory journal to represent your field of view.
26. Draw what you see under the microscope within the circle in your laboratory journal.
27. Switch to high power (400X total magnification) and draw your observations in your
laboratory journal. Look for the following (if present):
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Nuclear and nucleolar shapes
Chromosomes
Giantism: giant cell characterized as a larger than normal cell
Multinuclearity: the presence of more than one nucleus
Abnormal cell shape
Nuclear blebbing: an irregular bulge protruding from the nucleus
28. Observe the L929 tumor cells under 100X total magnification. Pay careful attention to the
shapes, growth patterns, and cell distribution.
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Medical Interventions Activity 3.1.3 When Cells Lose Control – Page 4
29. Draw your observations in your laboratory journal.
30. Switch to high power (400X total magnification) and draw your observations in your
laboratory journal. Look for the characteristics outlined in step 26.
31. Answer the remaining Conclusion questions.
Conclusion
1.
Explain why HeLa cells have an abnormal number or structure of chromosomes.
2.
If you were inspecting tissue taken from a tumor biopsy, what characteristics would you
look for that would indicate the presence of cancer cells? Describe three distinct
morphological differences you would expect to see between normal cells and cancer
cells.
3.
Describe the genetic mutations that you think occurred in the cancer cells that were
responsible for the phenotypic differences between the normal and cancer cells you
observed.
4.
Why is cancer such a difficult disease to study?
5.
How can studying genes give us more information about cancer?
WEB PORTFOLIO:
1) In a short paragraph describe what cancer is.
2) In one to two well-crafted paragraphs, summarize the process in which normal cells
become cancer cells. Your paragraph(s) must include each of the terms listed below.






Cell cycle
Regulated
Cell division
Apoptosis
Metastasis
Mutations





Blood vessels
Signals
Proto-oncogenes
Oncogenes
Tumor Suppressor Genes
3) A picture of the slide with a short description of what you observed
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Medical Interventions Activity 3.1.3 When Cells Lose Control – Page 5