Week 8: Questions

Question 1

What is the leading cause of death in Canada? What percentage of Canadians die from this cause?

Answer 1

Cancer is the leading cause of death in Canada with 28.2% of all deaths

Question 2

What are the most common types of cancer in Canada (except for non-melanoma skin cancer)?

Answer 2

Prostate cancer with 20%, lung cancer with 13%, breast cancer with 25% and colorectal cancer with 10%

Question 3

What percentage of Canadians will develop cancer during their lifetime?

Answer 3

44% of men and 43% of woman

Question 4

What percentage of Canadians diagnosed with lung cancer are still alive five years after diagnosis? What are the percentages for breast cancer and prostate cancer?

Answer 4

For lung cancer, it is low at 22%, prostate is 91% and breast is 89%

Question 5

Distinguish between a benign and a malignant tumor.

Answer 5

Benign: harmless, doesn’t spread or continue to grow

Malignant: cell growth that continues in an uncontrolled manner, resulting in cancer

Question 6

Define the terms metastasis and angiogenesis. Explain why a cancerous tumor that displays these processes may be harmful or deadly.

Answer 6

Metastasis: When individual cancer cells leave a tumor, enter the bloodstream and develop tumors at new sites.

Full Process:
1. A small tumor is confined to its place of origin
2. Tumor cells break through the basal lamina, which is a fibrous boundary layer
3. Tumor cells invade local blood vessels
4. Tumor cells travel through the bloodstream to other places in the body
5. Tumors cells adhere in new locations, forming new tumors

Angiogenesis: successful tumors secrete chemical signals that cause blood vessels to sporut from the circulatory system - results in heavy cells receiving less oxygen and good molecules

1. Successful tumors secrete chemical signals
2. Chemical signals initiate the growth of blood vessels
3. Blood vessels connect tumors to the blood supply, resulting in tumor growth

Question 7

How Do Cancer Cells Differ from Normal Cells?

Answer 7

Normal:
Communicate with one another using chemical signals (division, migration, differentiation and specialization)

Have special morphologies or shapes

Attach to other cells in orderly manner to form tissues and organs

Stop dividing at certain density

Cancer:

Do not behave in orderly manner sine they are damaged

Ignore chemical signals

Do not stop dividing

Lose characteristics unique to the tissue (tumor initialized in lung will feature cells that don’t look or function like lung cells)

Lose physical connection to tissue or organ and secrete enzymes called proteases that break down other cells

Question 8

Cancer cells are immortal. Explain why this is so.

Answer 8

Cancer cells multiply even after they reach a certain density, as a concequence, they pile up on top of eachother

There is also no limit of how many times they can divide so they are really immortal.

Question 9

What is the role of growth factors?

Answer 9

Many normal cells require signal molecules that are called growth factors in order to grow.

They also respond to another type of signal molecule which is called a growth inhibitor which prevents cell division

In general, a growth factor is a signal molecule that enables normal cells to divide.

Question 10

Cells divide, differentiate, or die. What is cell differentiation?

Answer 10

Cells divide to produce two identical daughter cells. Cells stop dividing to specialize in structure and function, a process called differentiation. Once differentiated, some cells may divide again under certain conditions.

Question 11

In general, what is the purpose of a checkpoint in the cell cycle?

Answer 11

Specialized proteins called “cell cycle regulators” or “checkpoint proteins” regulate the progression from one phase of the cell cycle to the next.

The progression through these checkpoints is a strictly regulated process that usually works without errors.

When errors do occur, they can have catastrophic consequences, including the development of cancer.

Question 12

Apoptosis is programmed cell death, in which normal cells die if their DNA is damaged or if they have reached the end of their life span. Cancer cells do not die on schedule, even if they are damaged or old. What are the consequences of the failure of normal cells to undergo apoptosis?

Answer 12

If regular cells do not undergo apoptosis, it may lead to uncontrolled cell division and subsequently lead to the development of a tumor.

Question 13

G1

Answer 13

G1:
Phase Events & Checkpoint items

First Gap Phase: The newly divided cell enters this phase right after completing cell division (or mitosis). During G1, the cell increases in size and prepares to replicate its DNA

G1-Checkpoint: Rest or Divide?

Toward the end of G1, the cell has to be sufficiently healthy to replicate its DNA. If the DNA is undamaged and enough resources are available for the cell to keep growing and divide, growth signals will stimulate the cell to proceed to the DNA synthesis, or S, phase. Otherwise, either the cell dies or it enters a resting state, also referred to as G0 phase.

Checklist summary:
✓ No DNA damage
✓ Sufficient resources

S:
Phase Events & Checkpoint Items

Synthesis Phase: The cell replicates its DNA. At the end of this phase, the cell has two complete sets of chromosomes.

S-Checkpoint: DNA OK?

Throughout the S phase, DNA is continuously monitored for replication errors. If DNA synthesis progresses without errors, growth signals will stimulate the cell to proceed to G2, during which the cell matures.

Checklist summary:
✓ No errors during DNA replication

G2:
Phase Events & Checkpoint Items
​​
Second Gap Phase: The cell continues to grow and prepares for division.

G2-Checkpoint: Fully Equipped?

To proceed to the next phase, all chromosomes have to be fully replicated and contain no other types of damage. Only then can it enter mitosis, or M phase, and divide.

Checklist summary:
✓ DNA without damage
✓ Chromosome set complete
✓ Enough cell components

M:
Phase Events & Checkpoint Item

Mitosis: In this last phase of the cell cycle, the cell stops growing and divides into two daughter cells, each with the same number of chromosomes.

M-Checkpoint: Are Any Sister Chromatids Unattached?

For mitosis to proceed correctly, the two copies in a duplicated chromosome (each called a sister chromatid) should both be attached to the mitotic spindle. If they are, mitosis continues: The two sister chromatids separate, becoming two chromosomes. The two identical sets of chromosomes move to opposite ends of the dividing cell.

Checklist summary:
✓ All sister chromatids attached to mitotic spindle

Question 14

What would happen if the cell continued through the cell cycle after failing one of the checkpoint items?

Answer 14

Failures in these checkpoints could lead to the accumulation of damage, which may lead to mutations.

When errors do occur, they can have catastrophic consequences, including the development of cancer.

Question 15

Make sure that you understand the difference between proto-oncogenes and oncogenes and can explain why cancer cells result from several mutations, in which one tumor suppressor gene is disabled and several oncogenes are activated.

Answer 15

Proto-oncogene: A gene that encodes for a protein that regulates cell division

Oncogene: A gene that tells the cell to divide in the absence of normal instructions to do so

Tumor Supressor: A gene that encodes for a protein that tells a cell not to divide
- Cancer cells result from an accumulation of several mutations
- Atleast one tumor suppressor must be disabled and severeal oncogenes activated
- In cancer cells, proto-oncogenes and tumor supressor genes are not balanced

Question 16

What is the role of a normal proto-oncogene in the normal cell cycle? How does the role of a mutant oncogene differ from the role of a proto-oncogene?

Answer 16

It’s a cell gene encoded to urge cells to go ahead and divide. Think of it like a car accelerator and they control cell division quite precisely

A mutant oncogene is different as it is essentially a car accelerator stuck on “go”

So it encourages cell division continuously without the instructions that a proto-oncogene has.

Question 17

How does a tumor suppressor gene function in the normal cell cycle? What happens if a tumor suppressor gene is disabled?

Answer 17

A tumor supressor gene acts as the cars breaks and it decides if the cell should not divide, it works hand in hand with the proto-oncogene.

If it gets disabled, it allows cell devision to continue even if it does not require to which may lead to the development of mutations

Question 18

What is a Philadelphia chromosome? How does this chromosome cause CML (chronic myelogenous leukemia)?

Answer 18

Scientists discovered that only patients with CML had an unsual small chromosome in their cells

Two chromosomes (number 9 and 22) had exchanged pieces with eachother.

This chromosome had actually repositioned 2 proto-oncogenes, abl and bcr, next to eachotehr in way that made them permanently stuck on, which led to out of control cell division.

Question 19

Risks Associated with Cancer

Answer 19

Smoking
Smokers are 40 times more likely to develop lung cancer
Smoking is responsible for 30% of cancer deaths
80-90% of lung cancer is due to smoking

Diet and Exercise
35% of deaths related to diet
Too many saturated fats, red meats, few fruits and veggies and not enough fiber
Cancer in colon and rectum are 10x higher where consumption of meats and fats are significant
Exercise can reduce breast or prostate cancer
Lack of exercise in childhood is responsible for 5% of the above cancers

Alcohol
Mouth, throat, liver, larynx and esphagus cancer is associated with heavy drinking
May also be associated with breast cancer
A smoker is 6x more likely to get esophageal cancer
6x more for a drinker too
If both smoking and drinking are combined, its 40x more likely to develop esophageal cancer

Radiation
Most dangerous is ultraviolet irradiation
Responsible for 90% of skin cancers
Melanoma is leading type of cancer among young adults

Infection
Bacteria (helicobacter pylori) is associated with stomach cancer
Flatworms associated with bladder and liver cancer

Human papillomavirus (HPV) is responsible for the world’s cancers of the genitals and anus
Its a sexually transmitted disease
Prevalence in developing nations is 15% and developed is 7%
HPV is responsible for 80-90% of cervical cancer
Cervical cancer is the 2nd most common cancer affecting woman
Rarity in the USA is due to Pap Test, which is a method used to detect cervical cancer by collecting and examining cervical cells

Workplace Carcinogens and Pollution
Scrotal cancer amoung chimney sweepers
40 materials are associated with increases of particular cancers
Responsible for 5% of cancer deaths in the US
2% of all cancer can be attributed to air, water, soil pollution

Inheritance
5-10% of acners may be inherited mutation
Mutations in these 2 genes: BRCA-1 and BRCA-2 account for 90% of all hereditary breast cancers
A woman with BRCA-genes faces a 84% of developing breast cancer by 70
BRCA are supposed to repair DNA and act as tumor suppressor

Age
75-79 is the most common age of developing cancer

Poverty
All cancers except breast, prostate, colon and Rectum are higher in the poor

Reasons may be: smoking, poor nutrition, exposure to carcinogens in workplace and exposure to infectious agents maybe by lack of clean water
They also cannot afford medical screenings so early treatment and prevention isn’t possible

Question 20

Are Canadian men and women equally likely to carry defective versions of the BCRA-1 and BCRA-2 gene? Explain your answer.

Answer 20

Yes because even though these genes only induce ovarian and breast cancer which men cannot develop, men can still carry these genes and give them to their offspring

Question 21

Canadian Guidlines for Breast Cancer Vs. American

Answer 21

Canadian:
If you are 40 to 49 years old, talk to your doctor about your risk for breast cancer, along with the benefits and limitations of having a mammogram.

If you are 50 to 74 years old, have a mammogram every 2 years.

If you are 75 or older, talk to your doctor about whether having a mammogram is right for you.

American:
Yearly mammogram for women starting at age 40

Clinical breast exam for women once every 3 years (age 20 - 30) and annually (40 years and over)

Optional breast self-exam for woman starting at age 20.

Question 22

What is a false positive result to a Pap test? What is a false negative result to a Pap test? Which of these might result in unnecessary follow-up procedures or treatment?

Answer 22

A Pap test may suggest cervical cell abnormalities when there are none (called a false positive).

A Pap test may not detect cervical cell abnormalities even though they are present (called a false negative).

A false positive may result in unnecessary follow-ups

Question 23

Cancer Treatments

Answer 23

Surgery
Performed on more than 50% of all patients
Biopsies
Most successful when tumor is locaized and not spread or metastasized

Radiation Therapy
Kills cancer cells that cannot be surgically removed or shrink a tumor for surgery
External; tumor is bombarded with a focused beam of X-rays
Internal; localized radiation is placed near tumor

Chemotherapy
Generally used to treat cancers that have spread from the primary tumor
Uses drugs that impair the ability of cells to replicate
Drugs can be taken orally or injected
May produce side effects since drugs target all cells undergoing mitosis
Chemo can cause anemia, weakened immune system, hair loss and nausea.\

New Treatments
Immunotherapy; patient’s immune system is used to fight cancer
Some act to fight cancer directly, some help boost immune system so therapy could work better
Antibodies and molecules from immune system are created in lab and administered to patients to target specific cancers like breast cancer

Angiogeneis inhibitors; drugs that stop growth of blood vessels
They inhibit the eability to tumors to attach to the circulatory system and obtain nutrients and oxygen necessary for growth

Chemoprevention
The action of natural or manufactured materials used ot prevent or halt cancer development

Diet rich in fruits, veggies, fiber and low in sat. fat decrease risk of cancer such as colon and rectum

Researchers found that the phytochemical “dithiolethione” found in vegetables such as broccoli, cabbage, cauliflower inhibit the development of tumors in the lung, colon, mammary gland, and bladder when tested on animals.

Also interferes with cancer formatiom since it actiavtes liver enzymes that in turn detoxify carinogens

Question 24

Can you reduce your cancer risk to zero? Why or why not?

Answer 24

No because scientists say that even if we remove all external possibilities, we still 20-25% of cancers
It’s a complex disease that occurs in our cells so there is really no way that we can 100% remove the chances of it occurring.
Things such as getting older are inevitable which will rise chances of cancer happening.