Cancer: An Overview Flashcards
what are chemoreceptors?
long strand-like filaments on cancerous cells that are “looking” for nutrient-filled blood & oxygen
cancer results from a breakdown of…
normal regulatory mechanisms that govern cell behavior
in cancer cells ______ in an uncontrolled manner
proliferate
uncontrolled proliferation is caused from
mutation in genes which are responsible for cell cycle regulation
Cancer has the ability to…
-spread throughout the body
-interfere w/ the normal function of tissues and organs
list the 3 different types of tumors
- tumor
- benign tumor
- malignant tumor
define a tumor
any abnormal proliferation of cells
define a benign tumor
abnormal proliferating cells that remain:
- in their original location
- do NOT invade surrounding normal tissue
- do NOT spread to distant body sites
define a malignant tumor
capable of invading surrounding normal tissue and spreading throughout the body through the circulatory system
what types of tumor are considered cancer?
ONLY malignant tumors
list the 3 basic types of cancers
- carcinomas
- sarcomas
- leukemias & lymphomas
carcinomas comprise ___ % of human cancers
90
define carcinomas
malignancies of epithelial cells
explain why carcinomas are the most common types of human cancers
epithelial tissues are found on the surface of the skin and line the hollow organs; b/c of location, production rate, and volume of cells most cancers are seen here
sarcomas are ____ ____ in humans
very rare
describe sarcomas
they are solid tumors of connective tissues such as:
bone
muscle
cartilage
fibrous tissue
sarcomas are _____ to treat
difficult
leukemias & Lymphomas comprise ___ % of human cancers
7
leukemias arise from…
blood-forming cells
lymphomas arise from..
cells of the immune systems
tumors are further classified according to..
-tissue of origin
-type of cell involved
give some examples of tissues of origin for tumors
-lung
-breast
-colon
-liver
list an example of how to classify a cancer based on the type of cell involved
fibrosarcoma from fibroblasts
(found below the epithelium & basal lamina (our glue))
normal tissue is a _________ of cells in which different __ ________ have been __________.
composite
x chromosomes
inactivated
what are the 4 different types of growth patterns?
- hypertrophy
- hyperplasia
- dysplasia
- neoplasia
describe the growth pattern known as hypertrophy
-increase in cell size
-normal organization
describe the growth pattern known as hyperplasia
-increase in cell #
-normal organization
-could be the beginning of benign tumor
describe the growth pattern known as dysplasia
-disorganized growth
-involves the basal layer
-is known as a benign tumor
describe the growth pattern known as neoplasia
-disorganized growth
-net increase in the # of dividing cells
-known as a malignant tumor
-cells are beginning to migrate
what is an example of tumor progression?
colon carcinoma
describe how colon carcinoma is an example of tumor progression
proliferation of colon epithelial cells give rise to a small benign adenoma or polyp -> clonal selection leads to growth of adenomas and has the potential to proliferate
list the 8 characteristics of cancer
- density-dependent inhibition
- reduced dependence on growth factors
- abnormal or blocked differentiation
- reduction cell adhesion
- angiogenesis
- protease secretion & metastasis
- resistance to apoptosis
- capacity of unlimited replication
describe density dependent inhibition
normal cells become quiescent when optimal density is reached; however, tumor cells will continue to proliferate
describe reduced dependence on growth factors
cancer cells exhibit autocrine growth stimulation causing the cells to produce their own growth factors promoting their proliferation
describe abnormal or blocked differentiation
hematopoietic stem cells produce different cells by several rounds of differentiation…in leukemic cells differentiation is block at a stage where the cell can continue proliferating
describe reduced cell adhesion
cells are less restrained from other cells facilitating metastasis
describe angiogenesis
cancer cells recruiting their own blood supply
describe protease secretion & metastasis
malignant cells secrete proteases that digest extracellular matrix allowing for the cells to invade any underlying structures
describe capacity for unlimted replication
caused as a result of telomerase expression
(causes the signal for apoptosis to be overridden)
describe focus assay
- detects conversion of normal cells into tumor cells in culture
- transformed cells display growth properties of tumor cells
list 5 carcinogens that cause cancer
- UV radiation
- chemical toxins
- mutagens
- tumor promoters
- viruses
list some chemical toxins that cause cancer
- tobacco
- asbestos
- benzenes
- aflatoxin (produced by molds)
list some tumor promoters
- phorbol esters
- endocrine disruptors
- hormones
explain what occurs with tumor viruses in permissive cells
- virus replication
- cell lysis
- release of progeny virus particles
explain what occurs with viruses in non-permissive cells
- virus replication
(some cells are permanently transformed)
tumor viruses are typically expressed ____ _____ in _________ ____ producing ______ ______ which leads to _________ cells.
more highly
inappropriate cells
altered proteins
unregulated
list an example of a DNA genome virus
Hepatitis B virus
list an example of a RNA genome virus
Hepatitis C virus
few retroviruses contain genes that are potent carcinogens. what is known to be the prototype of these highly oncogenic viruses
Rous Sarcoma Virus (RSV)
describe the mechanism by which RSV leads to cell transformation
virus picks up a gene that is homologous to our gene. It inserts these homologous genes into our genome causing cell transformation
list 3 genetic sources of cancer
- oncogenes
- tumor suppressor genes
- DNA repair genes
oncogenes aka
accelerators
tumor suppressor genes are aka
brakes
DNA repair genes are AKA
mechanics
oncogenes when mutated…
induce viral or cellular transformation
when mutated tumor suppressor genes…
cannot arrest proliferation
DNA repair genes when mutated….
cannot repair DNA errors
oncogenes result from…
-single point mutations
-chromosomal translocations
-amplifications
-translocations
give an example of a common oncogene that can cause cancer..
rasK (colon, lung, pancreatic, and thyroid carcinomas)
describe how RAS mutation can lead to cancer
Rat sarcoma virus (RAS) is a g-protein that is activated by binding to GTP. A RAS mutation compromises this binding site so hydrolysis can not occur. Now the cell believes their is an active supply of GF which causes the cell to proliferate uncontrollably
Ras and Raf oncogenes constitutively activate what pathway
ERK MAP kinase pathway
describe what occurs in the translocation of c-myc
the proto-oncogene is translocated from chromosome 8 (c-myc) to chromosome 14(IgH)
the translocation of c-myc results in…
abnormal expression of c-myc causing the transcription factor to respond to GFs
translocation of c-myc causes what type of cancer?
Burkitt’s Lymphoma (malignancy in B cell production)
describe the normal activation of PDGF oncogene
PDFG binds to the PDGFr to dimerize
describe the abnormal activation of PDGF oncogene
tel/PDGF oncogene encodes for a fusion protein where the extra cellular domain of the normal receptor is replaced by Tel transcription factor. this helix-loop-helix causes dimerization of PDGFr in the absence of PDFG. causes the continuous activation of protein kinase
name a translocation of an oncogene that results in a fusion protein
irel/urg (b-cell lymphoma)
proteins encoded by tumor suppressor genes act as..
brakes that slow down cell cycle progression
what is an example of a prototype of a tumor suppressor gene?
Rb (retinoblastoma)
what is the target of tumor suppressor genes?
cdk4,6/ cyclin D
explain the mechanism of Rb, E2F, Ras pathway
an unphosphorylated Rb binds to the E2F transcription factor preventing:
- transcription of genes necessary for DNA replication
- passage through G1 checkpoint into S phase
when cells are stimulated by GFs the Ras pathway is activated. a phosphorylated Rb cannot bind to E2F. E2F goes on to activate gene transcription, triggering onset of S phase.
normally Rb is then dephosphorylated and can inhibit E2F again
in Rb development that is hereditary the first mutation is present in the
germ line
in nonhereditary Rb the first mutation occurs in
somatic cells
list characteristics of retinoblastomas in the eye
- displaced retina
- thickening of the optic nerve due to tumor proliferation
what is involved in the oncogenes that lead to cell survival
- GF
- GFR
- PI 3-kinase
- Akt and Bcl-2
what do oncogenes target
Akt inhibiting Bcl-2
Bcl-2 is
anti-apoptotic
bcl-2 functions as
an oncogene by promoting cell survival
how does Bcl-2 promote cell survival?
by inhibiting the release of cytochrome c from the mitochondria which normally causes apoptosis
