lOMoARcPSD|51648332
lOMoARcPSD|51648332
Cancer is the second leading cause of death in the United States. In 2018, an estimated 609,640 people
died from cancer, while another 1,735,350 people are predicted to be newly diagnosed with cancer in the
United States alone. However, the overall death rates and the 5-year survival rates have improved since the
1990s.
Cancer can affect all ages and can originate in almost any organ. In terms of diagnoses, skin cancer is the
most common type in the United States. When evaluated by gender, prostate cancer is the most common
type in men, while breast cancer is the most common in women. However, the highest rate of mortality in
both men and women is lung cancer. This module will look at the cell cycle and proliferation, differentiation,
terminology of cancer, cancer cell characteristics, etiology, diagnostics, and treatments for cancer.
Cancer is the unregulated growth of abnormal cells. Most often, cancer cells showcase patterns of altered cell
differentiation and growth. This process is termed neoplasia, meaning “new growth.” The new growth itself is
referred to as a neoplasm. Whereas normal tissue growth responds with hypertrophy and hyperplasia, a
neoplasm’s growth lacks normal regulatory controls over cell growth and division. Neoplasms serve no
purpose, do not respond to appropriate cellular signaling stimuli, and continue to grow primarily at the host’s
expense.
Normal tissue renewal and repair requires:
1. Proliferation, a process of cell division, is an adaptive process for new cell growth to replace old cells or
when additional cells are needed. Neoplasms tend to have genetic abnormalities that cause excessive and
uncontrolled proliferation that is unregulated by normal growth-regulating stimuli.
2. Differentiation is the process by which cells become more specialized with each mitotic division.
3. Apoptosis eliminates senescent (old), damaged, or unwanted cells through a process of controlled cell
death.
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, lOMoARcPSD|51648332
Both the beginning (proliferation) and end stages (apoptosis) of a cell lifecycle are carefully regulated.
Proto-oncogenes encode proteins that signal for the cell to proliferate through a tightly regulated
process. Conversely, tumor suppressor genes encode proteins that inhibit cell growth and signal (when
necessary) for
apoptosis. For instance, should a particular cell growth become unregulated, which if left unregulated could
lead to tumor formation, the tumor suppressor genes will initiate apoptotic events to eliminate the potential
tumor cells. As each type of gene regulates either the initiation of cell growth (proto-oncogenes) or cell death
(tumor suppressor genes), dysregulation in either can lead to unregulated growths and ultimately cancer.
The cell cycle is the process by which a cell duplicates its genetic information and divides between two
genetically identical daughter cells, as shown in Figure 2.1.
The cell cycle is divided into four phases:
1. G1 (gap 1): DNA synthesis stops while the cell enlarges and both RNA and protein synthesis begins.
2.
S phase: DNA synthesis occurs, producing two separate sets of chromosomes, one for each daughter
cell.
3. G2 (gap 2): DNA synthesis again stops while RNA/protein synthesis continues. These first three phases
are referred to as interphase.
Located at the end of each of these phases (G1, S-phase, and G2) are cell cycle checkpoints. Checkpoints are a
means of molecular surveillance used to ensure the cell is ready to proceed to the next phase. If not, the cycle
is halted and allowed to complete its replication or even repair any DNA damage (when detected), thereby
ensuring all the genetic information is passed on correctly.
4.
M phase: consists of mitosis (dividing up the DNA) and cytoplasmic division. Continually dividing cells,
like the skin’s squamous epithelium, continue to cycle from one mitotic division to the next, while some
cells go into a resting state known as G0. A resting phase (G0) may occur when nutrients or growth factors are
unavailable or when highly specialized cells first leave the cell cycle. Cells in G0 may then re-enter the cell
cycle when nutrients become available, or the cell receives stimuli via growth factors, hormones, or other
signals that trigger cell growth, such as blood loss or tissue injury. Notably, highly specialized and terminally
differentiated cells, like neurons, may permanently stay in G0.
Downloaded by Benjamin Luca ()
, lOMoARcPSD|51648332
Cell proliferation is the process of increasing cell numbers by mitotic cell division. In normal tissues, the
number of new cells being produced is equivalent to the number of cells dying or being shed. Thus,
tissue/organ structure and function are maintained.
However, in most cases of cancer, the equilibrium of new vs old (or removed) cells becomes unregulated
and unbalanced. When considering cell proliferation, human cells fall within one of two major categories:
gametes (ovum and sperm) and somatic (non- reproductive) cells. Gametes are haploid, having only one set
of chromosomes from one parent. They are designed for sexual fusion. After fusion, a diploid cell containing
both sets of chromosomes is formed. These are the somatic cells that proceed to form the rest of the body.
Of the 200 various cells that proliferate, they can be divided into three large groups: (1) well-differentiated
neurons and cells of skeletal and cardiac muscles that rarely divide and reproduce; (2) progenitor or parent
cells that continue to divide and reproduce, such as blood, skin, and liver cells; (3) undifferentiated stem cells
that can enter the cell cycle and produce large numbers of progenitor cells if needed. The cells vary greatly in
their rates of reproduction. White blood cells and cells that line the GI tract live only several days and
therefore must be replaced continuously. In most tissues, cell reproduction is
Downloaded by Benjamin Luca ()
lOMoARcPSD|51648332
Cancer is the second leading cause of death in the United States. In 2018, an estimated 609,640 people
died from cancer, while another 1,735,350 people are predicted to be newly diagnosed with cancer in the
United States alone. However, the overall death rates and the 5-year survival rates have improved since the
1990s.
Cancer can affect all ages and can originate in almost any organ. In terms of diagnoses, skin cancer is the
most common type in the United States. When evaluated by gender, prostate cancer is the most common
type in men, while breast cancer is the most common in women. However, the highest rate of mortality in
both men and women is lung cancer. This module will look at the cell cycle and proliferation, differentiation,
terminology of cancer, cancer cell characteristics, etiology, diagnostics, and treatments for cancer.
Cancer is the unregulated growth of abnormal cells. Most often, cancer cells showcase patterns of altered cell
differentiation and growth. This process is termed neoplasia, meaning “new growth.” The new growth itself is
referred to as a neoplasm. Whereas normal tissue growth responds with hypertrophy and hyperplasia, a
neoplasm’s growth lacks normal regulatory controls over cell growth and division. Neoplasms serve no
purpose, do not respond to appropriate cellular signaling stimuli, and continue to grow primarily at the host’s
expense.
Normal tissue renewal and repair requires:
1. Proliferation, a process of cell division, is an adaptive process for new cell growth to replace old cells or
when additional cells are needed. Neoplasms tend to have genetic abnormalities that cause excessive and
uncontrolled proliferation that is unregulated by normal growth-regulating stimuli.
2. Differentiation is the process by which cells become more specialized with each mitotic division.
3. Apoptosis eliminates senescent (old), damaged, or unwanted cells through a process of controlled cell
death.
Downloaded by Benjamin Luca ()
, lOMoARcPSD|51648332
Both the beginning (proliferation) and end stages (apoptosis) of a cell lifecycle are carefully regulated.
Proto-oncogenes encode proteins that signal for the cell to proliferate through a tightly regulated
process. Conversely, tumor suppressor genes encode proteins that inhibit cell growth and signal (when
necessary) for
apoptosis. For instance, should a particular cell growth become unregulated, which if left unregulated could
lead to tumor formation, the tumor suppressor genes will initiate apoptotic events to eliminate the potential
tumor cells. As each type of gene regulates either the initiation of cell growth (proto-oncogenes) or cell death
(tumor suppressor genes), dysregulation in either can lead to unregulated growths and ultimately cancer.
The cell cycle is the process by which a cell duplicates its genetic information and divides between two
genetically identical daughter cells, as shown in Figure 2.1.
The cell cycle is divided into four phases:
1. G1 (gap 1): DNA synthesis stops while the cell enlarges and both RNA and protein synthesis begins.
2.
S phase: DNA synthesis occurs, producing two separate sets of chromosomes, one for each daughter
cell.
3. G2 (gap 2): DNA synthesis again stops while RNA/protein synthesis continues. These first three phases
are referred to as interphase.
Located at the end of each of these phases (G1, S-phase, and G2) are cell cycle checkpoints. Checkpoints are a
means of molecular surveillance used to ensure the cell is ready to proceed to the next phase. If not, the cycle
is halted and allowed to complete its replication or even repair any DNA damage (when detected), thereby
ensuring all the genetic information is passed on correctly.
4.
M phase: consists of mitosis (dividing up the DNA) and cytoplasmic division. Continually dividing cells,
like the skin’s squamous epithelium, continue to cycle from one mitotic division to the next, while some
cells go into a resting state known as G0. A resting phase (G0) may occur when nutrients or growth factors are
unavailable or when highly specialized cells first leave the cell cycle. Cells in G0 may then re-enter the cell
cycle when nutrients become available, or the cell receives stimuli via growth factors, hormones, or other
signals that trigger cell growth, such as blood loss or tissue injury. Notably, highly specialized and terminally
differentiated cells, like neurons, may permanently stay in G0.
Downloaded by Benjamin Luca ()
, lOMoARcPSD|51648332
Cell proliferation is the process of increasing cell numbers by mitotic cell division. In normal tissues, the
number of new cells being produced is equivalent to the number of cells dying or being shed. Thus,
tissue/organ structure and function are maintained.
However, in most cases of cancer, the equilibrium of new vs old (or removed) cells becomes unregulated
and unbalanced. When considering cell proliferation, human cells fall within one of two major categories:
gametes (ovum and sperm) and somatic (non- reproductive) cells. Gametes are haploid, having only one set
of chromosomes from one parent. They are designed for sexual fusion. After fusion, a diploid cell containing
both sets of chromosomes is formed. These are the somatic cells that proceed to form the rest of the body.
Of the 200 various cells that proliferate, they can be divided into three large groups: (1) well-differentiated
neurons and cells of skeletal and cardiac muscles that rarely divide and reproduce; (2) progenitor or parent
cells that continue to divide and reproduce, such as blood, skin, and liver cells; (3) undifferentiated stem cells
that can enter the cell cycle and produce large numbers of progenitor cells if needed. The cells vary greatly in
their rates of reproduction. White blood cells and cells that line the GI tract live only several days and
therefore must be replaced continuously. In most tissues, cell reproduction is
Downloaded by Benjamin Luca ()
