Public Health & StudyDisease &Epidemics Exam 3

What is Cancer? What Symptoms Do You
Think Of?

Tumors
• Pain
• Fatigue
• Organ Dysfunction

What is Cancer?

A disease caused by an uncontrolled division of abnormal cells in a
part of the body.

What Is A Cell?

The cell is the smallest structure of the body capable of performing all
of the processes that define life.

Cells are the “Basic Building Blocks”

There are a few basic types
• But they mostly share the same core
architecture
• They can be assembled into a huge
array of final structures by combining
different types in different ways

Cells

Some cells are found all over the
body: Epithelial cells
• Some cells travel while others stay
put: Blood cells
• Each of the organs in the body
consists of specialized cells that
carry out the organ’s functions

What Do Cells Do?

Activities to keep themselves alive:
• Transport in oxygen and glucose
• Get rid of waste products—CO2 and others
• Specialized jobs:
• Form a barrier
• Attack invading germs
• Contract muscle
• Form a filter to let certain chemicals or elements in or keep them out
• Conduct electrical signals

What Do You Do?

You bring in the nutrients: eating and drinking
• You ultimately get rid of the waste: urine, feces, exhalation

Heart & blood
vessels

pump &
pipe system to
move blood around
your body, taking
blood w/ oxygen
from your lungs and
glucose & other
nutrients from your
GI tract to your cells
that need those
things to survive,
take waste to
kidneys/liver, take
CO2 to lungs

Lungs

blood that
has given most of its
oxygen to other cells
in the body comes in
and gets oxygenate

Kidneys

Filter blood
to get out other
waste products from
cells

GI Tract 

digests food into glucose, vitamins,
other nutrients, that get delivered into
bloodstream so cells can do their job, gets rid
of waste products from cells doing their job

Brain 

Mastermind
all the activities that
get your cells what
they need and keep
you safe (alive!)

Nerves

Conduct
signals around your
body that make you
breathe, digest
(cells are ☺!) move
around etc

Pancreas

Make a chemical (hormone) that
helps you nourish your cells with glucose from
the food you eat

The Basics

Everything comes down to cell function or dysfunction
• Cells do specialized jobs
• Cells have all sorts of gates and barriers to keep things out or bring
things in
• Our bodies have a pretty tight range of normal and everything is a
thermostat working to keep us within it
• This normal is maintained by signals including hormones and nerves

Homeostasis

the ability of a
system to regulate its internal
environment through
maintaining a stable, relatively
constant set of properties such
as temperature and pH.

• Various components work
together as a system to maintain
homeostasis

Homeostasis is involved in every organ system of the body.
• No one organ system of the body acts alone
• Ex. Regulation of body temperature cannot occur without the cooperation of
the integumentary system (skin), nervous system, musculoskeletal system,
and cardiovascular system at a minimum.

Thermostats

Temperature
• Nutrients and Vitamins
• Energy/Glucose
• Fluid
• PH
• Cell growth/death

Five Critical Components

A sensor that measures the value of the regulated variable.
• A “set point,” although this is usually not a point but a range of
normal values.
• An error detector that compares the actual value of the regulated
variable with the set point. The result of this comparison is an error
signal that is interpreted by the controller.
• The controller interprets the error signal and determines what the
effectors should do
• The effectors directly raise or lower the value of the regulated
variable.

Why Is This Important?

Nearly (?) any medical condition can be traced back to failure at some
point in the homeostatic control system
• Inability to detect a change in the external environment
• Failure of initiating a feedback loop
• Failure to enact a response to return to the setpoint
• Failure in the setpoint itself.
• A return to health requires re-stabilization of the internal
environment of the body without causing further harm and doing so
promptly to avoid the death of cells from dysregulation, and
irreparable failure of organ systems.

Aging

is an example of disease as a result of homeostatic imbalance.
• As an organism ages, weakening of feedback loops gradually results in
an unstable internal environment.
• This lack of homeostasis increases the risk for illness and is
responsible for the physical changes associated with aging.

What is the homeostatic
process that is disrupted?-Diabetes

Blood glucose (sugar) level

Why was that process
important/what was it
doing?-Diabetes

Glucose (carried by blood to different organs & tissues) is the main source of
energy your cells use to function

What causes the
disruption?-Diabetes

Type II: The pancreas doesn’t produce enough insulin AND/OR cells of the
body don’t respond to the insulin normally, so they don’t take in the sugar
they need for energy. Strongly genetic (40% chance with 1 T2D parent, 70%
chance with both parents). Example of a modifiable risk factor: Physical
inactivity. Aerobic & resistance exercise both increase insulin sensitivity

What happens because of
the disruption? (Signs,
symptoms, sequelae)?-Diabetes

Symptoms: Polydipsia, polyuria, polyphagia. Your kidneys are trying to get rid
of the excess sugar by peeing it out. Losing fluids through excessive urination
makes you thirsty. You feel hungry because your cells are starving! Gradual in
Type II

Sequelae: High levels of glucose remain circulating in the blood. Since
blood goes everywhere in the body and high glucose levels are
inflammatory to cells, this is why the sequelae can be so widespread:
nerve damage, kidney damage, heart disease, eye damage etc.

Can Also Help You Understand Treatments

Insulin
• Metformin: reduces absorption of
glucose from the intestines, decreases
release of glucose stores from liver,
and helps cells be more insulin
sensitive
• (GLP-1s are more complex, but
essentially do the same: decrease
glucose release from liver, increase
insulin sensitivity)

What is the homeostatic
process that is disrupted?-Chronic stress

Blood cortisol level

Why was that process
important/what was it
doing?-Chronic stress

Cortisol normally helps regulate how your body uses glucose for energy,
regulates blood pressure, regulates inflammation, helps control your sleep-
wake cycle. In normal stress, it helps you stay vigilant after the release of
adrenaline

What causes the
disruption?-Chronic stress

Chronic activation of the HPA axis due to chronic stress keeps cortisol levels in
blood high over long periods of time

What happens because of
the disruption? (Signs,
symptoms, sequelae)?

Increases risk of high blood pressure, diabetes, cancer, immune system
dysfunction, etc

Which of the following is not true about cells?

Some organs are made of cells, while others are made of tissues

The set point in any given homeostatic system is generally a single value 

False, it is most often a range of normal values

Regulation of blood glucose is important because

-Blood glucose is the source of energy for your body’s cells

-Elevated blood glucose is inflammatory to many cells and tissues in the long term

-Dysregulation of blood glucose level can lead to death, especially in Type 1 diabetes

Elevated cortisol levels in the body are always bad for your health

False

Onco-

cancer

•Oncologist
• Oncogene

Carcino-

cancer

• Carcinogenic

-Oma

swelling or tumor
• Mesothelioma
• Lymphoma

-Emia

in blood (not necessarily cancer)
• Leukemia (cancer)
• Septicemia (not cancer)

Malignant

cancerous, capable of invading and destroying nearby tissue and spreading to other
parts of body

Benign

not capable of this (but can still cause trouble)

Leukemia

is a cancer in the blood cells where cancer cells circulate in
the body and behave to some extent like healthy cells. Eventually they
displace healthy cells, preventing their normal function.

Not All Cancers Form Tumors

Cancer cells do not always form a compact tumor.

Ends in -oma

(carcinoma, sarcoma, lymphoma): tumor

Ends in –emia

(leukemia): “in the blood,”
not tumor

What is the homeostatic
process that is disrupted? -Cancer

Regulation of cell division/reproduction

Why Do Cells Reproduce?

Worn out or injured cells must be replaced (blood, skin)
• Particular types of cells must increase in response to environmental
changes (Can you think of an example from last module?)
• Growth of organisms or parts of organisms (hair, nails, bones, nerves)

Cell Reproduction

The length of the cell cycle is highly variable, even within the cells of a
single organism.
• In humans, the frequency of cell turnover ranges from a few hours in
early embryonic development to an average of two to five days for
epithelial cells and to an entire human lifetime for some specialized
cells, such as cortical neurons or cardiac muscle cells
(remember this when we talk about cancer treatment!)

How Do Cells Reproduce Normally?

• Cells normally divide only when they
receive the proper signals from growth
factors that circulate in the bloodstream
or from a cell they directly contact.
• When a cell receives the message to
divide, it goes through the cell cycle,
which includes several phases for the
division to be completed.
• Checkpoints along each step of the
process make sure that everything goes
the way it should.

Apoptosis

The death of cells which occurs as a
normal and controlled part of an
organism's growth or development.
• During apoptosis, the cell shrinks
and pulls away from its neighbors.
Then the cell shrinks and breaks
apart

It is used during early development to
eliminate unwanted cells (for example,
those between the fingers of a
developing hand)
• In adults, apoptosis is used to rid the
body of cells that have been damaged
beyond repair.

Why was that process
important/what was it
doing? -Cancer

Replication allows for growth, repair/replacement of worn out or
injured cells, and response to external environment. Apoptosis
keeps this process in check and happening in an orderly fashion

How Does It Happen?

Active oncogenes are expressed • OR tumor suppressor genes are
lost.

oncogenes

genes that cause a cell to become
cancerous.

Proto-oncogenes

are normal genes that, when mutated in certain
ways, become oncogenes

proto-oncogenes

The genes that code for the positive cell-cycle regulators are called

Tumor Suppressor Genes

are genes that code for regulators that,
when activated, can prevent the cell from undergoing uncontrolled
division.
• p53 is the best known of these. Mutated p53 genes have been
identified in more than 50% of all human tumor cells.
• Tumor suppressor genes can initiate apoptosis if there is a problem
detected in the cell reproduction process

cancer

is actually many different
diseases caused by a common
mechanism: uncontrolled cell growth

What causes the
disruption? (Cellular level,
Risk Factors, Exposures, etc)

Mutations that cause an oncogene to promote unregulated cell
division or turn off a tumor suppressor gene, so that it cannot stop
unregulated cell division

What Happens Next?

Cancer cells divide and produce more cancer cells, either in the form
of a mass (tumor) or circulating (leukemia)
• Some cancer cells are able to invade normal tissue, enter the
bloodstream, and metastasize to a remote site in the body—lymph
nodes, other organs, etc

So Why Is That A Problem?

Space
• Specialized Functions
• Spreading to other body parts to interfere with
space and specialized functions there

Symptoms

• Some depend on the type of cell that is over-dividing
• Some depend on the physical location of the tumor
• Some are common to most cancers

Chemotherapy

Interfere with the activities cells use to keep themselves alive:
• Transport in oxygen and glucose (Stop tumors from growing blood vessels, interfere with
cells ability to use oxygen and glucose)
• Reproduce (Attack enzymes or other processes that help in cell division)

• Targets rapidly dividing cells
• Some normal cells do divide
quickly, including cells in hair
follicles, nails, the mouth,
digestive tract, and bone
marrow.
• Chemotherapy also can
unintentionally harm these
other types of rapidly dividing
cells, causing chemotherapy
side effects.

Radiation Therapy

-Use radiation to make small breaks in the DNA inside cells. This
damage can keep cancer cells from growing and dividing and cause
them to die
• Can be delivered externally or internally (radioembolization)

Immunotherapy

• As part of its normal
function, the immune
system detects and
destroys abnormal cells
and most likely prevents or
curbs the growth of many
cancers.
• Immunotherapy enhances
& targets this response

Which of the following is a reason for cell reproduction?

Worn or injured cells must be replaced

Some types of cells must increase in response to environmental changes

Growth of organisms or parts of organisms

The life span of most types of cells in the human body is 3 months

False 

Which of the following can lead to the development of cancer?

Activation of oncogenes

Inactivation of tumor suppressor genes

Because all cancers have the same underlying disruption to homeostasis, they all have the same risk factors and causative exposures

False

Cancer

is actually many different
diseases caused by a common
mechanism: uncontrolled cell
growth.

What Causes Lung Cancer?

• Smoking (accounts for over 80% of cases)*
• Exposure to harmful substances such as asbestos, radon, arsenic, chromium, and
diesel exhaust
• Air pollution, particularly particulate matter and ozone
• Genetics: family history of lung cancer and certain genetic mutations can make
individuals more susceptible to lung cancer.
• Weakened immune system
• Age: Lung cancer risk increases with age *As with all risk factors we will
discuss, not everyone who is exposed
to these risk factors will develop lung
cancer. However, reducing exposure
to these factors can significantly lower
the risk.

What Causes Breast Cancer?

Genetic Factors: inherited gene mutations, such as BRCA1 and BRCA2
• Family history of breast cancer, especially in multiple generations or
at a young age.
• Hormonal Factors:
• Early menstruation and late menopause
• Use of hormone replacement therapy (HRT)
• Dense breasts, which have more hormone-producing tissue
• Lifestyle Factors: Obesity, Physical inactivity, Smoking, Alcohol
consumption

Why Do The Risk Factors Differ?

Some factors
• Kind of cell: how active is it? What signals does it respond to, etc
• Route of exposure to carcinogens
• Hormone sensitivity
• Some factors we haven’t identified

What Causes Cancer?

Mutations in response to environmental exposures to carcinogens
• Long exposure to a carcinogen. For example, someone who uses tobacco, and
has used tobacco for many years is more likely to have cancer than someone
who’s never used tobacco.
• Extensive exposure to a carcinogen. For example, someone who is exposed to
silica dust daily at work, if not wearing a proper respirator or other
protections.
• Genetic (inherited) mutations. About 5% to 12% of cancers are
inherited, meaning people are born with genetic mutations that
cause cancer.
• Random mistakes in normal DNA replication may result in cancer-
causing mutations (one of the reasons cancer increases w/ age)

Generally cannot pinpoint 1 cause for any
case

• It is impossible to determine the initial cause for most specific
cancers.
• In a few cases, only one cause exists: for example, the virus HHV-8
causes all Kaposi’s Sarcomas.
• For most other cancers, we use epidemiology to estimate likely
causes
• For example, men who currently smoke tobacco develop lung cancer at a rate
14x that of men who have never smoked tobacco
• The chance of lung cancer in a current smoker being caused by smoking is
about 93%; there is a 7% chance that the smoker's lung cancer was caused by
radon gas or some other, non-tobacco cause

Genetics

Only about 5-10% of cancers are caused by mutations that are
inherited from a person’s parents.
• In families with an inherited cancer-causing mutation, multiple family
members will often develop the same type of cancer. These cancers
are called “familial” or “hereditary” cancers

The remaining 90-95% of cancers are caused by mutations that
happen during a person’s lifetime as a natural result of aging and
exposure to environmental factors, such as tobacco smoke and
radiation.
• These cancers are called “non-hereditary” or “spontaneous” cancers.
• About 30% of sporadic cancers do have some hereditary component
that is currently undefined, while the majority, or 70% of sporadic
cancers, have no hereditary component

BRCA

stands for Breast Cancer genes. BRCA1 and BRCA2 are genes
that help repair damaged DNA and regulate the cell cycle
• Mutations in BRCA1 and BRCA2 can significantly increase the risk of
developing certain cancers
• Women with BRCA mutations have a 50-80% lifetime risk of developing breast
cancer, compared to the general population risk of 12-13%.
• Women with BRCA mutations have a 30-60% lifetime risk of developing
ovarian cancer, compared to the general population risk of 1.5%.
• BRCA mutations may also increase the risk of pancreatic cancer, prostate
cancer, and melanoma.

Mutagens

An agent, such as radiation or a chemical substance, which causes
genetic mutations
• Many mutagens are carcinogens
• Some carcinogens are not mutagens.
• Ex. estrogen. Which is thought to promote cancers through their stimulating
effect on the rate of cell division. Faster rates of division increasingly leave
fewer opportunities for repair enzymes to repair damaged DNA during DNA
replication, increasing the likelihood of a genetic mistake

Tobacco Use

• Tobacco use is strongly linked to an increased
risk for many kinds of cancer
• Smoking cigarettes is the leading cause of the
following types of cancer:
• Acute myelogenous leukemia
• Bladder cancer
• Cervical Cancer
• Esophageal cancer
• Kidney cancer
• Lung cancer
• Oral cavity (mouth/tongue) cancer
• Pancreatic cancer
• Stomach cancer
• Cigarette smoking is estimated to cause about
30% of all cancer deaths in the United States.

Quitting smoking allows
new, healthy cells to
actively replenish the
damaged cells in the lining
of our airways leading to a
reduction (return towards
baseline) in the risk of lung
cancer

Viruses and Bacteria

Examples of cancer-causing viruses
and bacteria include:
• Human papillomavirus (HPV) increases
the risk for cancers of the cervix, penis,
vagina, anus, and oropharynx
• Hepatitis B and Hepatitis C increase the
risk for liver cancer
• Epstein-Barr virus increases the risk for
Burkitt Lymphoma
• We have two vaccines that can
prevent these cancers: Hep B and
HPV

Viruses

• It is thought that when the virus infects a cell, it inserts a part of its
own DNA near the cell growth genes, causing cell division.
• The group of changed cells that are formed from the first cell dividing
all have the same viral DNA near the cell growth genes.
• The group of changed cells are now special because one of the
normal controls on growth has been lost

Bacteria

Helicobacter pylori increases the risk for gastric cancer.
• Infection with H. pylori produces high levels of reactive oxygen species
that damage DNA and increase the risk of cancer

Radiation

There are two main types of radiation linked with an increased risk of
cancer:
• Ultraviolet radiation: non-melanoma skin cancers
• Ionizing radiation
• Sources: radon gas, medical tests such as X-rays and CT scans, occupational exposures
• Associated with leukemia, thyroid cancer, breast cancer

Immunosuppressive Medications

• Immunosuppressive medicines such as those used post-organ-
transplant are linked to an increased risk of cancer because they
lower the body's ability to keep cancer from forming.
• The risk of cancer, especially cancer caused by a virus, is higher in the
first 6 months after organ transplant, but the risk lasts for many years.

Environmental Exposures

Aflatoxins
• Aristolochic Acids
• Arsenic
• Asbestos
• Benzene
• Benzidine
• Beryllium
• 1,3-Butadiene
• Cadmium
• Coal Tar and Coal-Tar Pitch
• Coke-Oven Emissions
• Crystalline Silica (respirable size)
• Erionite
• Ethylene Oxide
• Formaldehyde
• Hexavalent Chromium Compounds
• Indoor Emissions from the Household Combustion of Coal
• Mineral Oils: Untreated and Mildly Treated
• Nickel Compounds
• Radon
• Secondhand Tobacco Smoke (Environmental Tobacco Smoke)
• Soot
• Strong Inorganic Acid Mists Containing Sulfuric Acid
• Thorium
• Trichloroethylene
• Vinyl Chloride
• Wood Dust

Diet

It is hard to study the effects of diet on cancer because a person's diet
includes foods that may protect against cancer and foods that may
increase the risk of cancer.
• It is also hard for people who take part in the studies to keep track of
what they eat over a long period of time
• Some studies have shown that a diet high in fat, proteins, calories,
and red meat increases the risk of colorectal cancer, but other studies
have not shown this.
• It is not known if a diet low in fat and high in fiber, fruits, and
vegetables lowers the risk of colorectal cancer.

Diabetes

Some studies show that diabetes may slightly increase the risk of having the following types of
cancer:
• bladder cancer
• breast cancer in women
• colorectal cancer
• endometrial cancer
• liver cancer
• lung cancer
• oral cancer
• Ovarian cancer
• pancreatic cancer
• Diabetes and cancer share some of the same risk factors, such as being older, having obesity,
smoking, physical inactivity. Therefore, it is hard to know whether the risk of cancer is increased
more by diabetes or by these risk factors.
• Studies are being done to see how medicine that is used to treat diabetes affects cancer risk.

Scientific Process

Science may be characterized by an attitude toward the world, an
attitude that gets us asking particular kinds of questions, but the
systematic approach to answering these questions requires the
participation of other people working with the same basic assumptions
about how we can engage with the world to understand it better.

Hypothesis

is a suggested solution for an unexplained occurrence
that does not fit into current accepted scientific theory.
The basic idea of a hypothesis is that there is no pre-determined
outcome.
• There either is or isn’t a difference between two groups

Public Health Paradigm

Five Step Process
• Defining the health problem
• Identifying associated risk factors
• Developing and testing community-level interventions to control or deter
perceived threats to public health
• Implementing interventions to improve population health
• Monitoring the interventions to determine their efficacy
(Schneider, 2006)

Three Types of Error

• Random
• Confounding
• Bias

Random errors

in the data. All
data contain random errors, because no
measurement system is perfect.
• The magnitude of random errors depends partly
on the scale on which something is measured
(errors in molecular-level measurements would
be on the order of nanometers, whereas errors
in human height measurements are probably on
the order of a centimeter or two) and partly on
the quality of the tools being used.
• Can’t be eliminated entirely

Bias

refers to systematic errors in any type of epidemiologic study
that result in an incorrect estimate of the association between
exposures and outcomes.
• Systematic (in contrast to random error)meaning that they
disproportionately affect the data in one direction only—so, for
example, we would always underestimate or always overestimate a
measure

Information bias

results from systematic differences in the way data
on exposure or outcome are obtained from the various study groups

Observer bias

occurs when there are systematic differences in the
way information is collected for the groups being studied. Observer
bias may occur as a result of the investigator's prior knowledge of the
hypothesis under investigation or knowledge of an individual's
exposure or disease status. Such information may result in differences
in the way information is collected, measured or interpretation by the
investigator for each of the study groups.

Loss to follow-up

is a particular problem associated with cohort
studies. Bias may be introduced if the individuals lost to follow-up
differ with respect to the exposure and outcome from those persons
who remain in the study.
• Selection bias occurs when the two groups being compared differ
systematically. That is, there are differences in the characteristics
between those who are selected for a study and those who are not
selected, and where those characteristics are related to either the
exposure or outcome under investigation.

Recall bias

may occur when the information provided on exposure is
different between the cases and controls.

Confunding 

involves the possibility that an observed association is
due, totally or in part, to the effects of differences between the study
groups (other than the exposure under investigation) that could affect
their risk of developing the outcome being studied.

In order for a variable to be considered as a confounder

1. The variable must be independently associated with the
outcome (i.e. be a risk factor).
2. The variable must be associated with the exposure under
study in the source population.
3. It should not lie on the causal pathway between exposure and
disease.

The effects of confounding can result in

• An observed difference between study populations when no real difference
exists.
• No observed difference between study populations when a true association
does exist.

The practice of evidence-based public health

(EBPH) is an integration
of science-based interventions with community preferences for
improving population health (CDC)
• The development, implementation, and evaluation of effective
programs and policies in public health through application of
principles of scientific reasoning, including systematic uses of data
and information systems and appropriate use of behavioral science
theory and program planning models.

Key components

• Making decisions based on the best available scientific evidence
• Using data and information systems systematically
• Applying program planning frameworks
• Engaging the community in decision making
• Conducting sound evaluation
• Disseminating what is learned.

Key steps

• Evidence generation
• Evidence synthesis
• Evidence communication and policy recommendation