Cancer is caused by uncontrolled cell growth and can be benign or malignant. Malignant cancer cells can invade nearby tissues and spread via the bloodstream to other parts of the body. Cancers are caused by factors like radiation, chemicals, viruses, and genetic mutations. There are several types of cancer named according to the affected tissue. Diagnosis involves techniques like biopsy, endoscopy, and imaging tests. Treatment options include chemotherapy, radiation therapy, immunotherapy, surgery, and others. Retroviruses can cause cancer and AIDS - they contain RNA that is converted to DNA and incorporated into the host cell genome, causing the cell to continuously produce new virus particles.

1. CANCER
&
RETROVIRUS

2. CANCER
Canceris one of themost common disease in theworld.
The division of normalcells is precisely controlled. Newcells
are only formed for growth or to replace dead ones.
Cancerous cells justcontinueto divide giving rise to mass of
cells called tumors.
Tumors are of two types:-
• Benign tumor
• Malignant tumor

3. Benign tumor
Non cancerous
They lack ability to invade neighbour tissueor metastasize.
Malignant tumor
Cancerous
 Invade neighbouringtissue
 They may spread to other location in the body through blood,
& wheneverthey get lodged in thebody, they start newtumor.
This property is called metastasis.

4. Causes of Cancer
 Transformationof normal cells into cancerous cells may be
induced by physical, chemical or biological agents.These agents
are calledcarcinogens.
 Ionizingas wellas non ionizingradiations cause DNA damage
leading to transformationof cancerous cells.
 The chemicalcarcinogens present in tobacco smoke is the
major cause of lung cancer.
 Cancercausing viruses called oncogenic viruses have genes
called viral oncogenes.

5. Categories of Cancer
 Carcinoma: Cancerthatbegins in the skin or in tissuesthatline
or cover internalorgans.
 Sarcoma: Cancer thatbegins in bone, cartilage, fat, muscle,
blood vessels, or other connective or supportive tissue.
 Leukemia:Cancerthatstarts in blood-forming tissuesuch as the
bone marrow & causes large numbers of abnormal blood cells to
be produced & enter theblood.
 Lymphoma & myeloma: Cancers thatbegin in the cells of the
immunesystem.

6.  Centralnervous system cancers: Cancers thatbegin in the tissues
of the brain& spinal cord.

7. Cancer detection & diagnosis
 Biopsy:A small tissue is surgically removed& examined
undera microscope for the presence of cancer cells.

8.  Endoscopy: A flexible plastic tubewitha tiny camera on the
end is insertedinto thebody cavities & organs.
 Diagnosticimaging:Radiography, CT (computed
tomography), MRI (magneticresonance imaging) are useful
to detect cancers of internalorgans.
 Blood test:Some tumors release substancescalled tumor
makers, which can be detected in theblood.

9. Treatment of cancer
 Chemotherapy:Chemotherapyis theuse of drugsthat
either kill cancercells orpreventthecells from dividing.

10. Radiationtherapy: Radiationtherapy is theuse of certain
types of high energyradiation to kill cancer cells & shrink
tumors.

11. Biological therapy / Immunotherapy:It is treatmentwith
substances thathelpthe body’s immunesystem fightcancer
or other diseases, or decrease the side effectsof cancer
treatment.
Surgery: Surgical removal of the damaged tissues or organs is
also a treatmentoption for cancer.

12. Retrovirus
• A retrovirus implies thatreplication is backward compared to
thecentral dogma of molecular biology.
• The genomeof a retrovirus is single-strandedRNA.
• Once it infects thecell, the RNA strand is used as templateto
make double-stranded DNA.
• Retrovirus have been linked to cancer & AIDS.
• Retrovirus thatcause tumor include Rocus sarcoma virus &
Mouse mammary tumor virus.
• AIDS is caused by a retrovirus called HIV.

14. Life cycle of Retrovirus

15.  Whenthey infectcells, theirRNA is turned into DNA by
reverse transcriptase.
 This newDNA is thenincorporated into thehost cellgenome
by an integraseenzyme, at which point retroviral DNA is referred
to as aprovirus.
 The host cellthentreats the viral DNA as part of its own
genome.
 Newviral RNAis produced by theinfectedcell.
 Finally,newviruses are produced which can infectother cells.

16. REFENCES
• Wikipedia
• Biology textbook NCERT
• cancer.about.com
• www.medicinenet.com
• dictionary.reference.com