PRESENTATION ON

ROLE OF VIRUSES IN CANCERPRODUCTION

DURGESH SIROHI(M.Sc Ist Sem.)

Cancer Types of cancer Sign & symptoms Viruses & Cancer Hepatitis B virus Hepatitis C virus Human papilloma virus Epstein-Barr virus Human T-Lymphotropic virus Conclusion

Cancer known medically as a malignant neoplasm, is a broad group of various diseases, all involving unregulated cell growth.

In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body.

The cancer may also spread to more distant parts of the body through the lymphatic system or blood streams.

The unregulated proliferation and loss of differentiation results in invasive growth that forms unorganised cell masses. This state is called Anaplasia.

2 major type of tumors w.r.t growth pattern are- BENIGN & MALIGNANT OR CANCEROUS TUMORS.

Benign – here the tumor cells remain in place to form a compact mass.

Malignant – here the tumors can actively spread throughout the body.

Not all tumors are cancerous.

Benign tumors do not grow uncontrollably, do not invade neighboring tissues, and do not spread throughout the body.

A benign tumor is a tumor that lacks the ability to metastasize.

The term "benign" implies a mild and non progressive disease.

Common examples of benign tumors include moles and uterine fibroids.

certain cells suddenly abandon their normal growth pattern and begin to reproduce uncontrollably –they become cancerous.

As these cells multiply, they form a lump, or primary tumor. From this tumor, cancer cells often travel through the lymphatic system or the bloodstream to other parts of the body, and form tumor there as well.

This spreading and clumping of cancerous cells is known as metastasis.

The main categories of cancer includes Carcinoma - cancer that begins in the skin or in

tissues that line or cover internal organs. Sarcoma - cancer that begins in bone, cartilage, fat,

muscle, blood vessels, or other connective or supportive tissue.

Leukemia - cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood.

Lymphoma and myeloma - cancers that begin in the cells of the immune system.

Central nervous system cancers - cancers that begin in the tissues of the brain and spinal cord.

Carcinoma

Sarcoma

Cancer symptoms are changes in the body caused by the presence of cancer. They are usually caused by the effect of a cancer on the part of the body where it is growing, although the disease can cause more general symptoms such as weight loss or tiredness. It is advisable that anyone experiencing unusual symptoms that are not normal for them for more than a few weeks should seek medical attention.

The presence of an unusual lump in the body. Changes in a mole on the skin. A persistent cough or hoarseness. A change in bowel habits, such as unusual

diarrhea or constipation. Difficulty in swallowing or continuing indigestion. Any abnormal bleeding, including bleeding from

the vagina, or blood in urine or faeces. A persistent sore or ulcer. Difficulty passing urine. Skin changes such as an unexplained rash.

ROLE OF VIRUSES IN CANCER

Viruses have played an essential role in cancer biology research over the past several decades. At first, viruses were utilized as valuable laboratory research tools for understanding cell cycle controls and carcinogenesis, the origins and development of cancer. The use of viruses allowed researchers to unreveal the genetics, mechanisms, and controls governing the processes of normal cell growth and differentiation. Viruses were also used to determine the role of aberrant cell growth or proliferation - processes characteristic of cancerous tissues.

A virus that can cause cancer is called an oncovirus.

Cancer-causing viruses function much as non-carcinogenic viruses do, invading the living cells of the host and using its DNA-synthesizing proteins and mechanisms in order to produce more copies of itself. Then, the virus disrupts an integral cell-cycle control mechanism in order to render the infected cell and its progeny cancerous, or "hyper-proliferative." Uncontrolled cell replication or proliferation is the basis for oncogenesis.

Some viruses can also play a role in converting normal host cells into tumor cells. These viruses are capable of viral transformation, that is, they transform normal cells into malignant cells.

In fact, five viruses, hepatitis B virus (HBV), hepatitis C virus (HCV), human papilloma virus (HPV), Epstein-Barr virus (EBV), and human T-lymphotropic virus type I (HTLV-I) are thought to contribute to over 15% of the world's cancers. Up to 80% of these human viral-associated cancers are cervical cancer (associated with HPV) and liver cancer (associated with HBV and HCV).

Hepatitis B is an infectious inflammatory illness of the liver caused by the hepatitis B virus (HBV) that affects hominoidea, including humans. Originally known as "serum hepatitis", the disease has caused epidemics in parts of Asia and Africa, and it is endemic in China. About a third of the world population has been infected at one point in their lives, including 350 million who are chronic carriers.

Hepatitis B virus is an hepadnavirus—hepa from hepatotropic (attracted to the liver) and dnabecause it is a DNA virus—and it has a circular genome of partially double-stranded DNA.

• Hepatitis B viruses cannot be spread by holding hands, sharing eating utensils or drinking glasses, kissing, hugging, coughing, sneezing, or breastfeeding.

• The virus is transmitted by exposure to infectious blood or body fluids such as semen and vaginal fluids, while viral DNA has been detected in the saliva, tears, and urine of chronic carriers.

The acute illness causes liver inflammation, vomiting, jaundice and, rarely death. Chronic hepatitis B may eventually cause liver cancer.

The infection is preventable by vaccination.

Hepatitis C is an infectious disease affecting primarily the liver, caused by the hepatitis C virus (HCV).

The hepatitis C virus (HCV) is a small, enveloped, single-stranded, positive-sense RNA virus.It is a member of the hepacivirus genus in the family Flaviviridae.

The infection is often asymptomatic, but chronic infection can lead to scarring of the liver and ultimately to cirrhosis, which is generally apparent after many years. In some cases, those with cirrhosis will go on to develop liver failure, liver cancer .

HCV is spread primarily by blood-to-blood contact associated with intravenous drug use, poorly sterilized medical equipment and transfusions.

Human papillomavirus (HPV) is a virus from the papillomavirus family that is capable of infecting humans.

Like all papillomaviruses, HPVs establish productive infections only in keratinocytes of the skin or mucous membranes.

HPV cause no symptoms in most people, some types can cause warts (verrucae), while others can –in a minority of cases – lead to cancers of the cervix, vulva, vagina, penis, oropharynx and anus.

HPV can cause normal cells on infected skin to turn abnormal. Most of the time, we cannot see or feel these cell changes. In most cases, the body fights off HPV naturally and the infected cells then go back to normal. But in cases when the body does not fight off HPV, HPV can cause visible changes in the form of genital warts or cancer. Warts can appear within weeks or months after getting HPV. Cancer often takes years to develop after getting HPV.

The Epstein–Barr virus (EBV), also called human herpesvirus 4 (HHV-4), is a virus of the herpes family, and is one of the most common viruses in humans.

It is best known as the cause of infectious mononucleosis (glandular fever). It is also associated with particular forms of cancer, such as Hodgkin's lymphoma, Burkitt's lymphoma, nasopharyngeal carcinoma, and central nervous system lymphomas associated with HIV. There is evidence that infection with the virus is associated with a higher risk of certain autoimmune diseases.

Infection with EBV occurs by the oral transfer of

saliva.

When infection with EBV occurs during adolescence or teenage years, it causes infectious mononucleosis 35 to 50 percent of the time.

EBV has been implicated in several diseases that include

infectious mononucleosis

Burkitt's lymphoma

Hodgkin lymphoma

nasopharyngeal carcinoma

multiple sclerosis

Human T-cell Lymphotropic Virus or Human T-lymphotropic virus Type 1 (HTLV-I), also called the Adult T-cell lymphoma virus type 1, a virus that has been implicated in several kinds of diseases including HTLV-I-associated myelopathy, Strongyloidesstercoralis hyper-infection, and a virus cancer link for leukemia. Between one in twenty and one in twenty-five infected persons are thought to develop cancer as a result of the virus.

It was the first identified human retrovirus.

Infection with HTLV-I, like infection with other retroviruses, probably occurs for life and can be inferred when antibodies against HTLV-1 are detected in the serum.

Motor and sensory changes in the extremities

Spastic gait in combination with weakness of the lower limbs

Clonus

Bladder dysfunction and bladder cancer

Transmission of HTLV-I is believed to occur by sexual contact, from mother to child via breastfeeding, and through exposure to contaminated blood, either through blood transfusion or sharing of contaminated needles. The importance of the various routes of transmission is believed to vary geographically.

In Japan, the geographic clustering of infections suggest that the virus is more dependent on mother-to-child transmission.

In the Caribbean, the geographic distribution of the virus is more uniform, and it is more common among those with many sexual partners, indicating that sexual transmission is more common.

Viruses are thought to play a role in cancer development both indirectly and directly. Indirectly, the viruses may induce immunosuppression so that cancer cells are not removed by immune responses, as in the case of HIV/AIDS, or they may cause long term damage to tissues resulting in large scale cell regeneration which increases the chances of natural mutation in proto-oncogenesand tumor suppressor genes, as in the case of HBV and HCV. Directly, by integrating into the host cell's chromosomes, some viruses may alter the normal function of the proto-oncogenes and tumor suppressor genes, as is seen with HPV and HBV.

However, most virus-associated cancers have long latency periods of several decades and only a small percentage of the people infected with the virus actually develop the cancer. This indicates other factors promoting changes in cellular genes are also involved.

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