Tumor Cells and the Onset of
Cancer
By: Amie M. Hacker
The Statistics
I. Cancer causes approximately 1/5th of
the deaths in the United States each
year.
a. In 2001, cancer accounted for 553,768 of all
deaths in the U.S. This is 22.9 %
II. Worldwide, between 100 and 350 of
every 100,000 people die of cancer.
Men v. Women (The Statistics
cont…)
I. Breast Cancer is the leading cancer among
white and African American women.
a. Every three minutes a woman in the
United States is diagnosed with breast
cancer.
II. Prostate Cancer is the third most common
cause of death in males.
a. More than 300,000 men lose their lives
each year due to Prostate Cancer.
Background Information of
Cancer
I. Cancer is due to a failure in the
mechanisms that usually control the
growth and production of cells
II. When a cancer is present, normal cell
birth and death rate is disrupted.
III. The losses of cellular regulation gives
rise to most or all cases of cancer. This
is due to genetic damages.
Background cont…
IV. A mutation in two classes of genes is
implicated in the onset of cancer.
a. Proto-oncogenes
b. Tumor-suppressor genes
V. Gene from both of these classes encode
proteins that help regulate cell birth or
cell death.
Proto-oncogenes (Background
cont…)
I. They are activated by mutations to
become oncogenes.
II. This mutation will cause the gene to
become excessively active in growth.
III. This can be caused by either an increase
in gene expression or by the production
of a hyperactive product.
Tumor-suppressor gene
(Background cont…)
I. Under normal conditions, these genes
are used to restrain the growth of cells,
until needed.
II. When tumor-suppressor genes are
damaged, the cells are unrestrained and
have inappropriate growth.
Six Changes that Lead to Cancer
I. Self-sufficient in growth signals
II. Insensitivity to antigrowth signals
III. Evasion of apoptosis
IV. Limitless replicative potential
V. Tissue invasion and metastasis
VI. Sustained antigenesis
Tumors
I. Definitions
a. Tumor
b. Metastasis
c. Benign
d. Malignant
e. Stem cells
Metastic Tumor Cells are
Invasive and Can Spread
I. Especially in older people, tumors are more
frequent, but they do not usually pose a
threat. These are called benign.
II. These tumors may function as normal cells.
III. They have a fibrous capsule.
IV. Benign tumors only become problems when
their size interferes with normal function
Metastic Tumor cont…
I. The picture shows
a benign skull
tumor.
Metastic Tumor cont…
V. Malignant tumors usually divide and
grow more rapidly than normal, fail to
die at normal rate, or invade a nearby
tissue.
a. They may remain localized for a
time period.
b. They may also acquire the ability
to metastasize.
How Metastic Tumors Spread
I. Normal cells are restricted to their place in
the organ or tissue.
II. Physical barriers, such as the basal lamina,
prevent cells from traveling to different areas
of the tissue.
III. Cancer cells are able to degrade the basal
lamina and penetrate other cells and areas of
the tissue.
How Metastic Tumors Spread
cont…
IV. Cancer cells may secrete a protein that
converts the serum protein plasminogen
to the active protease plasmin.
V. As the basal lamina degrades, some of
the tumor cell will enter the blood
stream, but fewer than 1 in 10,000
survive and are able to create a
secondary, metastic tumor.
Cancers Usually Originate From
Proliferating Cells
I. For oncogenic mutations to provoke
cancer, they must occur in dividing
cells.
II. Precursor cells initiate tumor growth.
III. As differentiated cells die, they are
replaced by proliferation of stem cells.
Stem cells are capable of transforming
into tumor cells.
Cancers Usually Originate From
Proliferating Cells cont…
IV. Since stem cell divide throughout the
life time, oncogenic mutations in the
DNA can accumulate and transform
into cancer cells.
Tumor Growth Requires Formation
of New Blood Vessels
I. Tumors require new blood vessels in order to
grow.
a. In the absence of blood, the tumor
can grow into a mass of about 106
cells.
II. Most tumors induce the formation of new
blood vessels. These blood vessels will invade
the tumor and, in turn, nourish it. This is
called angiogenesis.
Tumor Growth cont…
III. Process of Angiogenesis
a. Degradation of the basal lamina
b. Migration of the endothelial cells
into the tumor
c. Division of the endothelial cells
d. Formation of a new basement
membrane
Review and Questions
I. Review
a. What is cancer?
b. Types of Mutations
c. Three ways tumors grow and
cause the onset of cancer
II. Questions?