21. Genes and Cancer
Viruses
Chemicals Radiation
Heredity
Chemicals (e.g., from smoking), radiation, viruses, and Chromosomes
heredity all contribute to the development of cancer by are DNA
triggering changes in a cellās genes molecules
22. Oncogenes or tumor genes are genes with potential properties for the
induction of neoplastic transformation
(either in natural or experimental conditions)
(Duesberg 1980)
Normal cellular genes with the potential to become oncogenes
are called proto-oncogenes
24. Proto-Oncogenes and Normal Cell Growth
Normal Growth-Control Pathway
Growth factor
Receptor
Signaling enzymes
Transcription
factors
Cell nucleus DNA
Cell proliferation
Oncogenes are related to normal genes called proto-oncogenes that encode components of the cellās normal
growth-control pathway. Some of these components are growth factors, receptors, signaling enzymes, and
transcription factors. Growth factors bind to receptors on the cell surface, which activate signaling enzymes
inside the cell that, in turn, activate special proteins called transcription factors inside the cellās nucleus. The
activated transcription factors āturn onā the genes required for cell growth and proliferation.
25. Normal cell Normal
genes
regulate
cell growth
Oncogenes
Cancer cell accelerate
cell growth
and division
Oncogenes are genes whose PRESENCE in
Mutated/damaged oncogene certain forms and/or overactivity can
stimulate the development of cancer.
26. Oncogenes or tumor genes are genes with potential properties for the
induction of neoplastic transformation
(either in natural or experimental conditions)
(Duesberg 1980)
The word oncogene comes from the word āonkos ā meaning tumor
29. When an oncogene becomes activated it might
cause cancer
Proto-oncogene -> oncogene -> other steps -> cancer
30. Activation of Oncogenes
1. Mutation
a. Insertional mutagenesis
b. Point mutagenesis
2. Amplification
3. Translocation
31. Mutation : A mutation is a permanent change in
the DNA sequence of a gene. Mutations in a
gene's DNA sequence can alter the amino acid
sequence of the protein encoded by the gene.
33. Activation of oncogenes
1b. Mutagenesis of oncogenes
Altered polypeptides produced by mutant oncogenes could be
related to the origin of some human tumors
39. Activation of oncogenes
3. Translocation
A chromosome translocation is a chromosome A karyotype is the number and appearance
abnormality caused by rearrangement of parts of chromosomes in the nucleus of a
between nonhomologous chromosomes. A gene eukaryote cell
fusion may be created when the translocation
joins two otherwise separated genes, the
occurrence of which is common in cancer.
45. Tumor Suppressor Genes
Tumor suppressor genes are normal genes whose ABSENCE
can lead to cancer
i.e. Tumor suppressor genes protect the cell
46. Tumor Suppressor Genes - Tumor suppressor genes are normal genes whose ABSENCE can lead to cancer
i.e. Tumor suppressor genes protect the cell
Normal cell Normal
genes
prevent
cancer
Remove or inactivate
tumor suppressor genes
Cancer cell Damage to
both genes
leads to
cancer
Mutated/inactivated If a pair of tumor suppressor genes are either
tumor suppressor genes lost from a cell or inactivated by mutation,
their functional absence might allow cancer
to develop
47. Tumor Suppressor Genes
Act Like a Brake Pedal
Tumor Suppressor
Gene Proteins
Growth factor
Receptor
Signaling
enzymes Transcription
factors
Cell nucleus DNA
Cell proliferation
Tumor suppressor genes are a family of normal genes that instruct cells to produce proteins that restrain cell growth and division. Since tumor
suppressor genes code for proteins that slow down cell growth and division, the loss of such proteins allows a cell to grow and divide in an
uncontrolled fashion. Tumor suppressor genes are like the brake pedal of an automobile. The loss of a tumor suppressor gene function is like
having a brake pedal that does not function properly, thereby allowing the cell to grow and divide continually.
49. p53 Tumor Suppressor Protein
Triggers Cell Suicide
p53 protein
Normal cell Excessive DNA damage Cell suicide
(Apoptosis)
One particular tumor suppressor gene codes for a protein called āp53ā that can trigger cell suicide (apoptosis). In cells
that have undergone DNA damage, the p53 protein acts like a brake pedal to halt cell growth and division. If the damage
cannot be repaired, the p53 protein eventually initiates cell suicide, thereby preventing the genetically damaged cell
from growing out of control.
55. Oncogenes or tumor genes are genes with potential properties for the
induction of neoplastic transformation either in natural
or experimental conditions
(Duesberg 1980)
Tumor suppressor genes are normal genes whose ABSENCE
can lead to cancer
56. āNever, never, never give upā
Winston Churchill
1966
Nobel prize in
Physiology and medicine