A general outline on cancer, features of cancer cells and genetics of cancer

1. Cancer
Is a collection of related genetic disease
characterised by uncontrolled growth of abnormal
cells resulting in the formation of tumors
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2. A General Outline
• It is not an inherited disease
• Cancer cells proliferate uncontrollably
• Cancer is said to be monoclonal
• One of the primary reasons why a greater number of cells do not give
rise to cancerous tumors is that malignant transformation requires
more than a single genetic alteration
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3. Basic Properties of a Cancer Cell..
1. Lossofgrowthcontrol
2. Donotremainasasinglelayer(monolayer)ofcellsbutpileuptoformclumps
3. Notresponsivetothetypesofsignalsthatcausetheirnormalcounterpartstoceasegrowthanddivision
4. Theycontinuetogrowintheabsenceofstimulatorygrowthsignalsthatarerequiredbynormalcells
becausetheircellcycledoesnotdependontheinteractionbetweengrowthfactorsandtheirreceptors,
whicharelocatedatthecellsurface
5. areseeminglyimmortalbecausetheycontinuetodivideindefinitelydueto presenceoftelomerasein
cancercells
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4. Basic Properties of a Cancer Cell
6. Cancercellsaregeneticallyunstableandoftenhavehighlyaberrantchromosomecomplements,acondition
termedaneuploidy asaresultofdefectsinthemitoticcheckpointorthepresenceofanabnormalnumberof
centrosomes
7. Failtoelicittheapoptoticresponseevenwhentheirchromosomecontentbecomeshighlyderanged.
8. Cancercellsoftendependonglycolysis,whichisananaerobicmetabolicpathway.Theendproductofglycolysisis
lacticacid,whichissecretedintothetumor’smicroenvironment,whereitmaypromotetumorgrowth.
9. Highmetabolicrequirementsandaninadequatebloodsupplywithinthetumorisovercomebythisglycolysis.
10. Underconditionsofhypoxia(reducedo2),cancercellsactivateatranscriptionfactorcalledhifthatinducesthe
formationofnewbloodvesselsandpromotesthemigratorypropertiesofthecells,whichmaycontributetothe
spreadofthetumor.
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5. Causes of Cancer
• Carcinogenicsubstancesalterthegenome
• Thesechemicalsmaybemutagenicormaybeturnedintomutagenicbycellular enzymes
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Carcinogenic substances Type of cancer
ionizing radiation
soot
cigarette smoke Lung cancer
ultraviolet radiation Skin cancer
viruses DNA tumor viruses & RNA tumor viruses,
stomach-dwelling bacterium Helicobacter pylori,
Asbestos inhaling mesothelioma
Animal fat and alcohol Colon cancer

6. Types
• Based on formation of tumors
•Solid Tumors: masses of tissues
•Some cancers like leukemia of blood do not form tumors
• Based on spreading
• Malignant cancers:malignant tumors tend to metastasize, that is, to spawn cells that
break away from the parent mass, enter the lymphatic or vascular circulation, and
spread to distant sites in the body where they establish lethal secondary tumors
(metastases)
• Benign cancers:the growth of the tumor remains localized, the disease can usually be
treated and cured by surgical removal of the tumor
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7. Tumor-Suppressor Genes
• Act as cell’s brake; they encode proteins that restrain cells
growth and prevent cells from becoming malignant.
• The first tumour suppressor gene studied was associated with
retinoblastoma cancer
• Eg: TP53 gene, APC and RB gene [Retinoblastoma]
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8. Oncogenes
• Encode proteins that promote the loss of growth
control and the conversion of a cell to a
malignant state
• Act as accelerators of cell proliferation
• Lead to genetic instability
• Prevent a cell from becoming a victim of
apoptosis, or promote metastasis
• Cells possess a variety of genes, now referred to
as protooncogenes, that have the potential to
subvert the cell’s own activities and push the cell
toward the malignant state. Eg: RAS
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9. Strategies to combat cancer
• Conventional Approaches to combating cancer, namely, surgery, chemotherapy, and radiation, are not usually
successful
• Targeted therapies:
• [i] it can be targeted to attack only cancer cells, leaving normal cells unscathed
• [ii] it can be targeted to a particular protein whose inactivation leaves the cancer cells unable to grow or survive
• [iii] it can be targeted to the cancer cells of a particular
• The anticancer strategies are divided into three groups:
• A. those that depend on antibodies or immune cells to attack tumor cells,
• B. those that inhibit the activity of cancer-promoting proteins
• C. those that prevent the growth of blood vessels that nourish the tumor
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