Cancer, Carcinogenesis And Oncogenes

Running head: CANCER: CARCINOGENESIS AND ONCOGENES 1

Cancer: Carcinogenesis and Oncogenes

Student Name

Institution Affiliation

Date

Running head: CANCER: CARCINOGENESIS AND ONCOGENES 2

Cancer: Carcinogenesis and Oncogenes

Introduction

Cancer is the uncontrolled growth of abnormal cells in the body. The cancerous cells can also be

called malignant cells. Normal cells have growth-control genes which regulate their rate of

proliferation. These genes are known as tumor suppressor genes. Malignant cells lack these tumor-

suppressor genes. Subsequently, they multiply endlessly leading to the formation of tumors. There

are several differences between normal and malignant cells as expressed in the table below.

Characteristic

Normal cells

Malignant cells

Appearance

The cells are generally of the

same size, have a moderately

dark nucleus and only

specific number of

chromosomes.

The cells have extremely variable sizes,

have an extremely dark nucleus due to

the excess DNA. They also have an

abnormal number of chromosomes

which are disorganized within the cell.

Growth

These cells stop growing at

some point when the number

of cells required is at

maximum.

These cells never stop growing even

after sufficient number of cells have

been formed. This results in formation

of tumors.

Communication

These cells respond to

signals by neighboring cells

to terminate their

proliferation process.

They do not respond to signals to end

their reproduction. Instead, they

continue proliferating.

Running head: CANCER: CARCINOGENESIS AND ONCOGENES 3

Cell repair and

apoptosis

These cells undergo cell

repair and cell death process

within their lifespan

Malignant cells do not undergo any of

these processes.

Stickiness

Normal cells produce some

secretions to make them stick

to one another hence

facilitating localized growth.

Cancerous cells lack these secretions

hence they do not stick to each other.

Consequently, they can move from one

place to another freely.

Ability to

spread

Owing to their adhesive

character, they do not move

from one body part to

another.

They move from one place to another

through metastasis. This can be through

the lymphatic system, circulation

system or merely floating away to new

locations.

Maturation

They reach maturation at one

point of their growth cycle.

They are undifferentiated cells

(immature). This is because they

proliferate rapidly even before complete

maturation.

Evasion of the

immune system

Normal cells become

destroyed by lymphocytes

once they get damaged.

Cancerous evade the action of white

blood cells by secreting protein

complexes to inactivate the

lymphocytes.

Blood supply

Normal cells undergo

angiogenesis to acquire

Malignant cells undergo angiogenesis

even when it is irrelevant ie when they

ought to stop their proliferation process.

Running head: CANCER: CARCINOGENESIS AND ONCOGENES 4

nutrients for their growth and

proliferation

10.

Energy source

Normal cells obtain their

energy from Kreb’s cycle

and glycolysis. Their

produce their energy in the

presence of oxygen.

Cancerous cells produce most of their

energy in the absence of oxygen.

("Difference between Cancer Cells and Normal Cells | Difference Between," n.d.)

The check points for a normal cell to qualify to be a cancerous cell are:

a) The cell ought to have growth factors that prompt it to continue proliferating even when it

should stop.

b) The cell should have the ability to evade proteins that code for apoptosis to avoid cell death

when the abnormal growth commences.

c) The cell needs to neglect/ avoid the signals of neighboring cells to stop proliferating.

d) The normal cells also need to shed off their adhesive feature so that they can move from

place to place within the body.

Carcinogenesis

Carcinogenesis is the process of the formation of cancerous cells, their development and eventual

spreading out. It occurs in stages which can be studied in two distinct models (Roberts, 2010,

p. 12)

a) TNM staging system

b) Number staging system

Running head: CANCER: CARCINOGENESIS AND ONCOGENES 5

TNM staging system

TNM stands for Tumor, Node, Metastasis staging system. It describes the initial tumor, whether

the cancer cells have spread to the lymph node, and if it has spread to other body parts. The system

also integrates numbers in a specific manner (Tonissen, 2013, p. 38).

 T refers to the size of the primary tumor. It can be ranked from T1 to T2.

 N refers to whether the cancer has gotten to the lymph nodes. It can be ranked from N0 to

N3.

 M refers to whether the cancer has reached other body parts. It can either be M0 or M1.

Examples of these include:

T2N1M0- The cancer has spread to the lymph nodes but not ye to other body parts

T4N3M1- This is symbolic of advanced cancer.

Sometimes letters ‘a’, ‘b’, and ‘c’ can be used to sub divide the categories further. Letter ‘p’ can

also be used before TNM to indicate that these are pathological findings. When letter ‘c’ is used

before TNM, it indicates that those are clinical findings ("Experimental Carcinogenesis," n.d.,

p. 34).

Number Staging System

Conceptually, carcinogenesis can be divided into four stages (Roberts, 2010, p. 16). These are:

a) Initiation

b) Promotion

c) Progression

d) Metastasis

Running head: CANCER: CARCINOGENESIS AND ONCOGENES 6

Initiation

This stage involves the alteration of proto-oncogenes by carcinogens. It can be either spontaneous

or induced. The DNA methylation of promoter gene regions can transcriptionally repress the tumor

suppressor genes. The mutation of the DNA synthesis process due to chemical carcinogens

eventually leads to proliferation of the cells. These cells tend to have a lifespan equal to that of the

organism. Basically, the DNA adduct formation which activates proto-oncogenes and conversely

inactivates tumor suppressor genes is the tumor-initiating event.

Tumor Promotion

This stage is considered to be the longest phase but is reversible. As the rate of proliferation

increases, the probability of the conversion of cells to malignant cells increases. The tumor

promoter can either reduce the rate of malignant conversion or on the other hand speed up the

process Tumor promoters are fundamentally known to be both mutagenic and carcinogenic hence

they can perform both tasks. Carcinogens which display both tumor initiation and promotion

qualities are known to be complete carcinogens. A good example is 4-aminobiphenyl

("Experimental Carcinogenesis," n.d., p. 37).

Malignant conversion and Tumor Progression

This is the stage in which preneoplastic cells are converted to cancerous cells. This only occurs as

a result of further genetic mutation on the cell. It is crucial to note that the level of tumor promoters

must remain constant or increase for this to happen. If not so, the cells form benign lesion (non-

cancerous swellings). The preneoplastic cells are converted to malignant cells which invade the

cellular territories of neighboring cells and tissues.

Running head: CANCER: CARCINOGENESIS AND ONCOGENES 7

Metastasis

In this phase, the cancerous cells move from one point to another point of the body. This can be

through the circulatory system, lymphatic system, and/or simply floating away from one point to

another.

Oncogenes

These are cancer causing genes which result from the mutation in proto-oncogenes. They work

against the tumor suppressor genes by promoting the uncontrollable proliferation of cells. The

form of mutations involved are gain-of-function mutations which increase the expression of the

normal cells(Benz, C.C, Liu, & E.T, 2011, p. 26) . Subsequently, only one copy of the gene needs

to be mutated to initiate cancer.

There are numerous types of oncogenes. These include:

a) HER2/neu

b) Ras

c) Myc

d) Cyclin D

e) hTERT

f) Src

Myc oncogene

This gene is primarily found in the nucleus of a cell. It serves as a signal for cell proliferation after

a series of mechanisms. It acts as a transcriptional factor for the cyclin D gene ("Examples of

Oncogenes and How Mutations Can Lead to the Development of Cancer," n.d.). Excess amounts

of Myc genes can make the cells to multiply uncontrollably. Myc genes can also be activated via

Running head: CANCER: CARCINOGENESIS AND ONCOGENES 8

chromosomal re-arrangement. This is when a strong promoter sequence is located inappropriately

next to the myc protein coding sequence. This in turn leads to production of vast amounts of the

Myc mRNA. Mutant B cells are known to produce excess amounts of Myc proteins. This makes

them proliferate rapidly and form tumors.

Running head: CANCER: CARCINOGENESIS AND ONCOGENES 9

References

Benz, C.C, Liu, & E.T. (2011). Oncogenes. Springer Verlag.

The Difference between Cancer Cells and Normal Cells | Difference Between. (n.d.).

Retrieved August 26, 2017, from http://www.differencebetween.net/science/health/the-

difference-between-cancer-cells-and-normal-cells/

Examples of Oncogenes and How Mutations Can Lead to the Development of Cancer. (n.d.).

Retrieved August 26, 2017, from

http://www.brighthub.com/science/genetics/articles/76140.aspx

Experimental Carcinogenesis. (n.d.). Encyclopedia of Cancer, 1078-1078. doi:10.1007/978-3-

540-47648-1_2061

Roberts, R. (Ed.). (2010). Carcinogenesis. Amsterdam: Elsevier.

Tonissen, K. (2013). Carcinogenesis. Rijeka, Croatia: InTech.

Place new order. It's free, fast and safe

Paper type

Deadline

Page count

550 words

Total price: $ 15.00

Our customers say

Jeff Curtis

USA, Student

"I'm fully satisfied with the essay I've just received. When I read it, I felt like it was exactly what I wanted to say, but couldn’t find the necessary words. Thank you!"

Ian McGregor

UK, Student

"I don’t know what I would do without your assistance! With your help, I met my deadline just in time and the work was very professional. I will be back in several days with another assignment!"

Shannon Williams

Canada, Student

"It was the perfect experience! I enjoyed working with my writer, he delivered my work on time and followed all the guidelines about the referencing and contents."

Cancer, carcinogenesis and oncogenes

Place new order. It's free, fast and safe

Our customers say

Jeff Curtis

Ian McGregor

Shannon Williams