Cancer is
fundamentally a disease of regulation of tissue growth. In order
for a normal cell to transform into a cancer cell, genes which
regulate cell growth and differentiation must be altered.
Genetic changes can occur at many levels, from gain or loss of
entire chromosomes to a mutation affecting a single DNA
nucleotide. There are two broad categories of genes which are
affected by these changes. Oncogenes may be normal genes which
are expressed at inappropriately high levels, or altered genes
which have novel properties. In either case, expression of these
genes promotes the malignant phenotype of cancer cells. Tumor
suppressor genes are genes which inhibit cell division,
survival, or other properties of cancer cells. Tumor suppressor
genes are often disabled by cancer-promoting genetic changes.
Typically, changes in many genes are required to transform a
normal cell into a cancer cell.
There is a diverse classification scheme for the various genomic
changes which may contribute to the generation of cancer cells.
Most of these changes are mutations, or changes in the
nucleotide sequence of genomic DNA. Aneuploidy, the presence of
an abnormal number of chromosomes, is one genomic change which
is not a mutation, and may involve either gain or loss of one or
more chromosomes through errors in mitosis.
Large-scale mutations involve the deletion or gain of a portion
of a chromosome. Genomic amplification occurs when a cell gains
many copies (often 20 or more) of a small chromosomal locus,
usually containing one or more oncogenes and adjacent genetic
material. Translocation occurs when two separate chromosomal
regions become abnormally fused, often at a characteristic
location. A well-known example of this is the Philadelphia
chromosome, or translocation of chromosomes 9 and 22, which
occurs in chronic myelogenous leukemia, and results in
production of the BCR-abl fusion protein, an oncogenic tyrosine
kinase.
Small-scale mutations include point mutations, deletions, and
insertions, which may occur in the promoter of a gene and affect
its expression, or may occur in the gene's coding sequence and
alter the function or stability of its protein product.
Disruption of a single gene may also result from integration of
genomic material from a DNA virus or retrovirus, and such an
event may also result in the expression of viral oncogenes in
the affected cell and its descendants.
Pathophysiology Epigenetics >>
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Cancer
Classification
1. Nomenclature
2. Adult cancers
3. Childhood cancers
Signs and symptoms
Diagnosis
1. Investigation
2. Biopsy
Treatment
1. Surgery
2. Radiation therapy
3. Chemotherapy
4. Targeted therapies
5. Immunotherapy
6. Hormonal therapy
7. Symptom control
8. Complementary and alternative
9. Treatment trials
Prognosis
1. Emotional impact
Causes
1. Chemical carcinogens
2. Ionizing radiation &
Infectious diseases
3. Hormonal imbalances
& Immune system dysfunction
4. Heredity & Other causes
Pathophysiology
1. Epigenetics
2. Oncogenes
3. Tumor suppressor genes
4. Cancer cell biology
4.1 Clonal evolution
4.2 Biological properties of cancer cells
Prevention
1. Modifiable ("lifestyle") risk factors
2. Diet
3. Vitamins
4. Chemoprevention
5. Genetic testing
6. Vaccination
7. Screening
Epidemiology
History
Research |
