This blog will provide you information about Carcinogenesis. It also explain what is carcinogen and its types. This elaborate about the Stages of Cancer. The article also contains TNM cancer staging system. It will also inform about cancer stage grouping. It will also provide awareness about the Stages of cancer, Causes of cancer, Treatment of Carcinogenesis and Types of Cancer.
1.What is Carcinogenesis?
Carcinogenesis is the process by which normal, healthy cells transform into cancer cells. Most current theory of carcinogenesis characterize it as a multi-step process involving initiation, promotion, progression. In simple words Carcinogenesis’s basically the production or development of cancer. We can call it Oncogenesis. The doctors treating cancer are called as Oncologists. We will discuss the causes, Stages, Treatment and Types of Carcinogenesis in this blog.
Carcinogen:
Carcinogens are defined as agents capable of initiating the development of malignant TUMOURs by including cellular genetic changes. The transformation of a normal cell to a malignant cell is thought to be due to successive and cumulative exposures to carcinogens and other factors over the course of decades. Carcinogens may be natural, or artificial. Carcinogens work by interacting with a cell’s DNA and inducing genetic mutations. Examples include home and workplace chemicals, environmental or medical radiations, smoke, and even some viruses and medications.
2.Types of Carcinogens:
Pro-carcinogens
Co-carcinogen
Direct acting Carcinogens
1: Pro-carcinogens:
A chemical substance that does not itself cause cancer but which can convert by enzymatic action to another substance that can cause cancer. Example: Drug etc.
2: Co-carcinogens:
An agent that aggravates the carcinogenic effects of another substance. It is not cancer causing itself but it enhances the carcinogenic effects of any other substance.
Example: Co-carcinogens present in tobacco smoke includes decane, undecane, pyrene, etc.
3: Direct-acting Carcinogen:
Those which do not require metabolic activation or any molecular activation or any molecular modification in order to induce DNA damage are termed direct-acting carcinogens. Example: UV radiations, alkylating agents, etc.
All these types of carcinogens lead to the cause of cancer by using biological, chemical and physical processes and transform normal cells into cancer cells.
Lets discuss the stages, causes, types and treatment of Carcinogenesis.
3. Stages of Cancer:
Staging is a way to describe a cancer. The cancer’s stage tells you where a cancer is located and its size, how far it has grown into nearby tissues, and if it has spread to nearby lymph nodes or other parts of the body. Before starting any cancer treatment, doctors may use physical exams, imaging scans, and other tests to determine a cancer’s stage. Staging will not complete until all the tests are finished.
TNM staging system for cancer?
Doctors use the TNM staging system for most types of cancer. The TNM system uses letters and numbers to describe the size TUMOUR (T), lymph nodes (N), whether or not the cancer has spread or metastases (M). Each letter and number tell you something about the cancer. The specific definitions for each category are different for each type of cancer staged using this system.
TUMOUR (T):
The letter T and the number after it describe the TUMOUR by answering these questions:
How large is the primary TUMOUR?
Does it go into other tissues or organs in the same area?
Where is it located?
Node (N):
The letter N and the number after it describe if cancer has affected the lymph nodes. The lymph nodes are small, bean-shaped organs that help fight infection. They are a common spot where cancer first spreads. This part of the staging system answers these questions:
Has the TUMOUR spread to the lymph nodes?
If so, which lymph nodes and how many?
Lymph nodes near where the cancer starts, are called regional lymph nodes. Lymph nodes in other parts of the body are called distant lymph nodes. The N category only refers to lymph nodes near the cancer (regional lymph nodes). Distant lymph nodes elsewhere in the body are includes in the “M” category
After the letter N, there will be a number from 0 (zero) to 3. N0 means there are no lymph nodes with cancer. Most often, the more lymph nodes with cancer, the larger the number. But for some TUMOURs, the location of the lymph nodes with cancer may determine the “N” category.
Metastasis (M):
The letter M and the number after it describes if the cancer has spread. It answers these questions:
Has the cancer spread to other parts of the body?
If so, where and how much?
If cancer has not spread, the stage is M0 and the cancer has spread to other parts of the body, it is stage M1.
Lets discuss the important information about Carcinogenesis. This includes its stages, causes, treatment and types of Carcinogenesis.
4.What is cancer stage grouping?
The information collected to determine the TNM stage is used to give a cancer stage specific to you. Most types of cancer have four stages: stage I (1) to IV (4). Some cancers also have a stage 0 (zero). Here is a general description of cancer stage groupings.
Stage 0.
This stage describes cancer in-situ. In situ means “in place.” Stage 0 cancers are still located in the place they started. They have not spread to nearby tissues so this stage of cancer is often curable. Surgery can usually remove the entire TUMOUR.
Stage I .
This stage is usually a cancer that has not grown deeply into nearby tissues. It also has not spread to the lymph nodes or other parts of the body. We can call it early-stage cancer.
Stage II and Stage III.
In general, these 2 stages are cancers that have grown more deeply into nearby tissue. They may have also spread to lymph nodes but not to other parts of the body.
Stage IV.
This stage means that the cancer has spread to other organs or parts of the body.
This segment contains information about stages of carcinogenesis, we will discuss the causes, treatment and types of Carcinogenesis in detail.
5. Causes of Cancer:
Rapid advances in recent cancer studies have made it possible to theorize on carcinogenic risk factors. So we can divide risk factor into environmental factors and genetic factors. It has long been known that the incidence of cancer differs according to the region, occupation, eating habits, and lifestyles.
1. Environmental Factors
Various environmental factors have been shown to be carcinogenic risk factors. These factors include those whose carcinogenic effects can be avoided by altering lifestyles such as a smoking habit, and can be said to be directly linked with cancer prevention.
2. Physical factors
● Ionized radiation
It is well known that ionized radiation may cause gene mutation or chromosome aberration. So the results of an epidemiological survey of carcinogenesis in atomic bomb victims show increased incidence of leukemia, lung cancer, etc. in the population. With respect to the timing of carcinogenesis, while the incidence of leukemia was high between 5–20 years after the exposure to atomic-bomb radiation, that of lung cancer is still high even now, more than 50 years since the exposure.
● Ultraviolet light
Ultraviolet light is an environmental factor that associates with skin cancer. Ultraviolet radiation may modify DNA base pairs so it results in the formation of pyrimidine dimers. Moreover, ultraviolet light contributes to the production of a reactive oxygen species, which directs cells toward carcinogenesis.
3. Chemical factors
• Benzo [a] pyrene
Smoking is most clearly associated with the increased risk of cancer. Smoking-associated cancers include lung cancer, head and neck cancer such as laryngeal and pharyngeal cancers, esophageal cancer, bladder cancer, pancreatic cancer as well as uterine cervix cancer. Concerning the carcinogenic substances in tobacco smoke, benzo [a] pyrene is thought to have great significance. It is known that benzo [a] pyrene may cause characteristic point mutation in the p53 gene, a TUMOUR suppressor gene, which is considered to be one of the mechanisms of carcinogenesis due to tobacco smoke.
• Ethyl alcohol
Heavy drinking is also associated with the incidence of head and neck cancer. It is associated with gastrointestinal cancer. Furthermore, in patients with esophageal cancer who consume a large amount of alcohol and tobacco, the incidence of p53 gene abnormalities is 90% or higher.
• Heterocyclic amine
Heterocyclic amine is known to be a carcinogenic substance in overcooked meat and fish. In epidemiological surveys, intake of overcooked meat and fish is also said to be associated with the occurrence of breast cancer and colon cancer.
4. Biological factors
Biological carcinogenic factors include various viruses.
Genetic Factors
Carcinogenesis is sporadically observed, but sometimes concentrates in certain families. The causes of such familial neoplastic diseases were unknown for many years, however, in recent aggressive studies on cancer-related genes. The Rb1 gene which Is responsible for retinoblastoma was identified in 1986, and subsequently, a succession of genes responsible for hereditary neoplastic syndrome have been identified. These genes include DNA repair genes, cell cycle genes, genes responsible for tissue organization, signal transduction genes, etc.
Abnormalities of such genes also represent carcinogenic risk factors.
DNA copying errors Random errors occurs in DNA every-time cell copies its DNA to make new cells. This routine process occurs millions of times in everybody but usually does no harm. Cancer can occur when an error effects an important gene than an unimportant gene. 2/3 cancer mutations occur due to these errors in DNA copying. Some individuals are born with germline mutation which means the errors inherit from one generation to another generation. For example: 75% of pancreatic cancer mutations occurs by DNA copying errors. 5% of pancreatic cancer mutations are in inheritance. 20% of pancreatic cancer mutations due to other environmental factors.
Cell cycle genes
● Rb1 gene Retinoblastoma is a malignant neoplastic disease occurring in 1 in 15,000 individuals. Bilateral retinoblastoma is always considered to be hereditary.
● p53 gene in Li Fraumeni syndrome effects various organs. Leading to the manifestation of breast cancer, soft tissue TUMOUR, brain TUMOUR, etc. In 1990, the disease was proved to be an autosomal dominant hereditary disease associated with inherited mutation in the p53 gene.
This segment explains the stages and causes of carcinogenesis, now we will get through Treatment and Types of cancer.
6. Treatment of Cancer:
There are many options to treat Cancer. Here are some types of treatment of Cancer which are discus below:
Hormone therapy
It is a cancer treatment that slows or stops the growth of cancer that uses hormones to grow. We can also call it hormonal therapy, hormone treatment, or endocrine therapy.
Cancer surgery
Cancer surgery is a procedure to remove the TUMOUR, as well as nearby tissues containing cancer cells. There are many reasons to go for surgery:
I. To remove some or all cancer cells.
ii. To relieve cancer side effects.
Bone marrow transplant (BMT)
It is a special therapy for patients with certain cancers or other diseases. A bone marrow transplant involves taking cells that in the bone marrow (stem cells). Filtering those cells, and giving them back either to the donor (patient) or to another person. Once the transplant is finished, you’ll need to stay in hospital for a few weeks while you wait for the stem cells to settle in your bone marrow and start producing new blood cells. During this period, you may feel weak, and experience vomiting, diarrhea, a loss of appetite.
How is bone marrow transplant performed?
A stem cell transplant remain in use after chemotherapy and radiation is complete so the stem cells are delivered into your bloodstream, usually through a tube called a central venous catheter. The process is similar to getting a blood transfusion. The stem cells travel through the blood into the bone marrow. Also, it needs a donor.
Chemotherapy
It is a drug treatment that uses powerful chemicals to kill fast-growing cells in your body. Chemotherapy is most often used to treat cancer. Since cancer cells grow and multiply much more quickly than most cells in the body. Many different chemotherapy drugs are available.
People get more than one type of chemotherapy at a time. The chemotherapy itself stays in the body within 2 -3 days of treatment but there are short-term and long-term side effects that patients may experience.
Targeted therapy
Is a type of cancer treatment that uses drugs or other substances to precisely identify and attack certain types of cancer cells? A targeted therapy can be used by itself or in combination with other treatments. Such as traditional or standard chemotherapy, surgery, or radiation therapy. A targeted therapy can be used by itself or in combination with other treatments, such as traditional or standard chemotherapy, surgery, or radiation therapy. They survive for three or four years after diagnosis.
Radiation therapy
Kills cancer cells or slows their growth by damaging their DNA. Radiation therapy (also called radiotherapy) is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink TUMOURs.
What is the radiation treatment for cancer?
Radiation therapy is a type of cancer treatment that uses beams of intense energy to kill cancer cells. Radiation therapy uses X-rays, but protons or other types of energy also can be in use. The term “radiation therapy” most often refers to external beam radiation therapy.
Immunotherapy
Type of cancer treatment that helps your immune system and so it boosts the body’s natural defense to fight cancer. It uses substances made by the body or in a laboratory to improve how your immune system works to find and destroy cancer cells, 15-20% of patients achieve durable results with immunotherapy, is the success rate. How long can you stay on immunotherapy?
Many people stay on immunotherapy for up to two years so It can take weeks or months to start working, depending on how your immune system and the cancer respond. Each treatment takes about 30 to 90 minutes. Depending on the drug used, you’ll receive a dose every 2 to 3 weeks until the cancer shows signs of improvement or you have certain side effects.
We will discuss the Types of carcinogenesis, after understand the causes, stages and Treatment of cancer.
7. Types of Cancer:
Following are some common types of Cancer:
Lung cancer
Lung cancer (pulmonary carcinoma) is the most common cancer in the world, both in terms of cases (1.6 million cases; 12.7% of total cancer cases) and deaths (1.4 million deaths; 18.2% of total cancer deaths). It is cause by tobacco smoke. Risk estimates for lung cancer in the United States indicate that tobacco smoke is responsible for 90% of lung cancers. Tobacco smoke is a complex mixture of more than 5,300 identified chemicals. Most of these compounds cause DNA damage by forming DNA adducts or by inducing other alterations in DNA so the DNA damages are subject to error-prone DNA repair or can cause replication errors.
Such errors in repair or replication can result in mutations in TUMOUR suppressor genes or oncogenes leading to cancer.
Breast cancer
Breast cancer is the second most common cancer [(1.4 million cases, 10.9%), but ranks 5th as cause of death (458,000, 6.1%)]. Increased risk of breast cancer is associated with persistently elevated blood levels of estrogen so Estrogen appears to contribute to breast carcinogenesis by three processes;
(1) The metabolism of estrogen to genotoxic, mutagenic carcinogens,
(2) The stimulation of tissue growth,
(3) The repression of phase II detoxification enzymes that metabolize
Colon cancer
Colorectal cancer is the third most common cancer [1.2 million cases (9.4%), 608,000 deaths (8.0%)] Tobacco smoke may be responsible for up to 20% of colorectal cancers in the United States In addition, substantial evidence implicates bile acids as an important factor in colon cancer. Twelve studies indicate that the bile acids deoxycholic acid (DCA) or lithocholic acid (LCA) induce production of DNA-damaging reactive oxygen species or reactive nitrogen species in human or animal colon cells. Studies reported that bile acids cause programmed cell death (apoptosis) so that increased apoptosis can result in selective survival of cells that are resistant to induction of apoptosis. Colon cells with reduced ability to undergo apoptosis in response to DNA damage would tend to accumulate mutations so as such cells may give rise to colon cancer.
Stomach cancer
Stomach cancer is the fourth most common cancer [990,000 cases (7.8%), 738,000 deaths (9.7%)]. Infection is the main causative factor in stomach cancer. Chronic gastritis (inflammation) caused by H. pylori is often long-standing if not treated. Infection of gastric epithelial cells with H. pylori results in increased production of reactive oxygen species (ROS). ROS cause oxidative DNA damage including the major base alteration 8hydroxydeoxyguanosine (8-OHdG) so 8-OHdG resulting from ROS is increased in chronic gastritis.
The altered DNA base can cause errors during DNA replication that have mutagenic and carcinogenic potential. Thus H. pylori-induced ROS appear to be the major carcinogens in stomach cancer because they cause oxidative DNA damage leading to carcinogenic mutations. Diet is thought to be a contributing factor in stomach cancer. In Japan where very salty pickled foods are popular, the incidence of stomach cancer is high. Preserved meat such as bacon, sausages, and ham increase the risk while a diet high in fresh fruit and vegetables may reduce the risk. The risk also increases with age.
Hepatitis B and C virus
Hepatitis B virus (HBV) and Hepatitis C virus (HCV) are viruses that cause acute or chronic liver disease. They are in the report as “known human carcinogens”. It studies in humans show that chronic hepatitis B and hepatitis C infections cause liver cancer.
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