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R-DNA TECHNOLOGY

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CERVICAL CANCER

 

The cervix is a part of
the human female reproductive system. It is the lower  part of the uterus.

 

The cervical canal is
lined with a layer of columnar cells. The outer region, or the ecto-cervix is
made of a number of layers of cells, topped with flat cells.

The two types of cells
meet at the squamo-columnar junction.

 

Almost 99% of the times,
the causative agent is Human Papilloma Virus (HPV) that causes abnormalities in
the epithelium, which can lead to cancer of the cervix.

HPV is a virus that has
numerous strains, many of which are more likely to cause pre-cancerous changes
in the cervical lining, mainly in the transformation zone, which is the usual
region for the cancer to begin.

 

CAUSES OF CERVICAL CANCER

 

 

Almost all types of
cervical cancers are caused by long-lasting infection with any of the
infectious strains of HPV. There are certain cases, where people with HPV do
not develop cancer.

 

A type of HPV called
“high-risk” HPV has been shown to cause cancers of the cervix as well as cancer
of penis in men. HPV’s are also found to cause cancers of the mouth, throat and
anus in both sexes.

 

HPV infection is spread
through sexual contact or skin-to-skin contact. It is a common infection that
usually is resolved on its own. In a few women, the infection stays for a long
period of time, thus causing cancer due to certain changes in the cells.

 

 

DIAGNOSIS

 

The changes in the
epithelial cells can be detected by cervical cancer screening or otherwise
called, Pap testing or Pap smear testing.

In this test, a surface
sample of cells from the cervix is taken and tested for its appearance.

The abnormally appearing
cells that are not cancerous but may be pre-cancerous, are called Dysplasia.

This can be identified at the time of Pap test, and is called Squamous
Intraepithelial Lesion (SIL).

Cervical
Intra-epithelial Neoplasia (CIN) are the precancerous changes that are observed
in biopsies.

 

After detection of
abnormal cells in the Pap smear test, a colonoscopy procedure is employed that
uses a microscope to examine the surface of cervix, after which a small tissue
sample is taken to test for cancer. This procedure is called biopsy.

 

Another procedure,
called Conization, is the process of removing a cone-shaped portion of the
cervix, around the canal. This is done using a loop of wire that is heated by current
, called Loop Electrosurgical Excision Procedure or LEEP, which is performed
with local anesthesia. When general anesthesia is used, the procedure is called
“Cold knife Conization”.

 

Additional tests like
X-rays, CT-scan, MRI, Cystoscopy and Proctoscopy may be necessary.

 

 

STAGES OF CERVICAL CANCER

 

 

Determining the stage of
cancer helps the doctor to give the best treatment plan to the patient.

 

Cervical cancer is classified
from stage I to stage IV, with many sub-categories.

 

Stage
0:  This stage is not considered as true cancer
and the abnormal cells are present only on the surface of the cervix.

 

Stage
I:  The tumor is present in a trace quantity and
has not spread to any other parts of the body.

 

Stage
II:  Here, the cancer has spread to regions beyond
the cervix and even the uterus, but hasn’t reached the pelvic region yet.

 

Stage
III: The
tumors have spread to the pelvic region and lower regions of the vagina, maybe
even causing blockage in the ureters.

 

Stage
IV:  This stage is said to be the most advanced
stage. The tumors would be found in the bladders, rectum and even other areas
of the whole body.

 

 

TREATMENT

 

Different forms of
treatments are available for cervical cancer, such as surgery, radiation
therapy, chemotherapy, immunotherapy, etc. depending upon the extremity of
spreading of tumors.

 

Surgery is used to
remove the tumor causing cancer, mainly in the early stages of tumors.

Hysterectomy is suggested for older women, wherein their uterus is removed.

Pelvic exenteration
removes the uterus, lymph nodes that surround it along with other organs near
the cancerous tumor.

 

Radiation therapy uses
radiation to shrink the cancer. It can be an external therapy or
brachytherapy,that follows the procedure of inserting a radioactive source near
the tumor.

Radiotherapy is used for
treatment combining it with chemotherapy, mainly for higher stages of cancer.

 

Side effects of
radiotherapy:

Fatigue, diarrhea,
nausea, irritation in radiated area, menstrual changes etc.

 

Side effects of
chemotherapy are similar, and it includes hair loss, loss of appetite, mouth
sores, etc.

 

SYMPTOMS

 

The most common signs or
symptoms of cervical cancer include abnormal vaginal bleeding, especially after
menopause; increased vaginal discharge and pelvic pain.

 

RISK FACTORS

 

Apart from HPV, there
are other factors that have been found to have an effect on epithelial cells to
turn cancerous.

They include:

1. Smoking
habits

2.HIV infection

3.Suppression
of the immune system

4.Obesity

5.Excessive
usage of oral contraceptives

6.Four, or more
full term pregnancies

7.Conceiving
and a full-term pregnancy before the age of 17

8.Family
history of cervical cancer

 

PREVENTION

 

Cervical cancer can be
prevented with vaccination and other detection techniques to observe the
changes in the cervix.

Vaccines are now
available against the common strains of HPV.

Gardasil and Gardasil 9
are the common vaccines used. Gardasil has proven to be very effective against
the four most common HPV types, i.e, 6,11,16 and 18.

Gardasil 9 is an
advanced version, that is effective against nine types of HPV.

(6,11,16,18,31,33,45,52,58)

Vaccination must be
taken before any sexual activity for its complete effectiveness.

Gardasil is also recommended
for males, through age 9 to 25.

 

 

 

 

GENETICS OF HPV &
CERVICAL CANCER

 

 

Human Papillomavirus (HPV)
is a small and Un-enveloped DNA virus that normally affects mucosal cells.

The genome of an HPV has
6 early, or E Genes, that control the viral genes and their behavior. They also
have 2 late, or L genes, that instruct for the virus shell.

 

E6 an E7 are the 2 most
important genes, which must be turned on, if the cancer ahs to develop. If they
turn off, the suicide machinery is activated by the cell, and the cell kills
itself, thus preventing cancer. This property is associated only with high-risk
strains of HPV.

 

Normally,
p53 protein stops cell-growth of the cells that have damaged DNA. But E6 binds
to p53, thus inactivating it. Hence, mutated cells begin to grow and divide.

 

E7
generally tends to promote the growth of cells that do not posses p53, and
kills the cells that do.

Another
protein called Rb protein is present in the cells. This generally slows down
the growth of cells that have damaged DNA. E7 binds to Rb protein, thus
inhibiting the protein from performing its role, leading to cancer.

 

CONCLUSION

 

Cervical cancer is
considered to be the 3rd most common cancer in women, across the
world.

The rates do vary in
many places, ranging from less than 1 to even more than 60 cases per 1 lakh
women.

Delayed diagnosis
leading to poorer outcomes is common in developing countries, and it has become
one of the leading causes of death (cancer related)

 

Compiled
by-

Nandana
Shankar

RA1611014010035

B.tech
Genetic Engineering