What a disease: cancer. Risks and myths

In the first article about cancer, we told what kind of disease it is and how it develops. After reading, many have a question that affects the development of a malignant tumor. Today, experts at the Solo project of the Atlas biomedical holding will talk about real and mythical factors that increase the risk of cancer.


Illustrations: Michael Kowalski

What does not cause cancer

Let's start with the myths and tell you what factors do not affect the risk of developing a tumor.

• Genetically modified foods
  Genetically modified foods are foods in which one or more genes have been modified. There is a misconception that GM foods affect the human genome. This delusion originates from the scientific work of Séralini, in which there were many inaccuracies and inaccuracies. Repeated studies have not confirmed that genetically modified foods cause cancer.
  
  
• Artificial sweeteners
  The most common sugar substitutes - saccharin and aspartame - in the XX century were considered carcinogenic. Aspartame was associated with the appearance of a brain tumor, and because of saccharin in rats, a bladder tumor developed. But clinical studies have disproved the link between artificial sweeteners and the development of malignant tumors.
  
  
• Dairy Products
  Cow's milk contains insulin-like growth factor (IGF-1), progesterone and estrogen. They were supposed to affect hormone levels in the human body, which may increase the risk of developing cancer. Today there is no reliable data to say exactly how milk consumption affects risk. Dairy products may increase the risk of prostate cancer, but reduce the risk of developing colorectal cancer and bladder cancer. More detailed studies are needed to verify this.
  
  
• Sugar
  Evidence that sugar affects the incidence of malignant tumors, no. Sugar or glucose - fuel for all cells of our body. It is impossible to regulate the level of glucose so that it reaches only healthy cells. However, sugar intake indirectly affects the development of the tumor. Due to the high calorie content, a sweet meal can lead to obesity, which increases the risk of developing malignant tumors.
  
  
• Termination of pregnancy
  Interruption of pregnancy disrupts the normal functioning of the female sex hormones, therefore it has been suggested that abortion may increase the risk of developing breast cancer. But in the course of research it was found that abortion does not affect the risk of developing breast cancer.
  
  
• Microwave Popcorn A microwave
  popcorn package contains a non-stick layer. During preparation, a substance is released from it which, if inhaled, increases the risk of lung cancer. However, the increased risk is fixed only among employees of popcorn factories. In normal life, the risk does not increase, even assuming that a person can only eat popcorn. If you are afraid of harmful effects, do not open the package immediately after cooking, let the popcorn cool down a bit. Then dangerous volatile substances will settle and will not harm the body.

Environmental factors that increase the risk of developing malignant tumors. cancerprogressreport.org

Smoking

Smoking is one of the most significant factors affecting the development of a tumor.

Cigarette - a small factory, in the smoke which contains about 7 thousand chemical compounds. It is proved that 93 of them are hazardous to human health. With each puff solid particles that are contained in the smoke, fall on the surface of the epithelium of the mouth, throat and lungs. The body can not remove them, so the more a person smokes, the more carcinogens deposited in the tissues.

Carcinogenic substances damage the DNA of healthy cells, leading to mutations. Most damage accumulates in the cells of the lungs, larynx, pharynx and oral mucosa, but mutations also occur in the cells of the bladder and liver.



The tar in the composition of tobacco smoke inhibits the work of the immune system, so it is worse to recognize and destroy malignant cells. This is another reason for the high risk of cancer.

You can often hear the delusion that smoking a hookah is not as harmful as regular cigarettes. Hookah contains more carbon monoxide, nicotine and tar. The hookah smoker per hour draws in about 200 times, while one cigarette accounts for 10-13 puffs. Therefore, when smoking a hookah, a person consumes much more harmful substances than when smoking cigarettes.

There is a myth that smoking pipes and cigars is safer than smoking regular cigarettes. But studies show that the harmful effects of cigars and pipes are no different from ordinary cigarettes.



The surrounding tobacco smoke, which other people breathe next to the smoker, also contains dangerous carcinogens. They contribute to the formation of mutations in the cells of the respiratory tract, even in non-smokers.

Every year, worldwide, passive smoking causes about 21,000 cases of fatal lung cancer. To protect yourself and loved ones from smoke, do not allow others to smoke near you in your home, car, or other indoor areas. Children's bodies are especially susceptible to the harmful effects of tobacco smoke, so do not allow smokers to stay near children.

Obesity

Obesity is the second after smoking cause of the development of malignant tumors.

People who are overweight have a higher risk of developing cancer of the esophagus, thyroid, stomach, liver, kidney, brain, pancreas and breast, gall bladder, endometrium, ovaries and colorectal cancer.

There are several mechanisms of influence of excess weight on the development of a tumor:

• People with obesity develop chronic inflammation, which the immune system is constantly fighting. At the same time, special substances are released that damage the DNA of healthy cells that are located next to the focus of inflammation.
• Elevated levels of insulin and insulin-like growth factor (IGF-1) promote the growth of both healthy and tumor tissues.
• Fat cells produce a large amount of the hormone estrogen, which increases the risk of developing breast cancer, endometrium (uterine lining) and ovaries.
• Fat cells synthesize adipose tissue hormones (adipokines), which stimulate cell division and differentiation. The level of these hormones increases with an increase in the amount of adipose tissue in the body.

Obesity and its associated changes in the microflora can affect the inflammatory processes in the body and increase the risk of developing a malignant tumor. Therefore, scientists are also studying the role of intestinal microflora in the development of malignant tumors.

Viruses and infections

Some viruses and bacteria increase the risk of developing a malignant tumor.

Human papillomavirus  is a widespread virus, some types of which lead to cancer. The presence of oncogenic HPV types in the human body increases the risk of developing cancer of the cervix, anus and oropharynx. The most common oncogenic HPV types are 16 and 18.



HPV is transmitted through contact with the skin or mucosa of the genital organs of an infected person. Proper and regular use of a condom reduces the risk of transmitting the virus. If the condom is used irregularly or incorrectly, the likelihood of transmission of the virus increases.

On average, immunity takes 1-2 years to completely get rid of human papillomavirus. During this time benign warts may appear, but most often the virus is asymptomatic. Oncogenic HPV types are different. They stay in the body for a long time and cause cells to divide, which increases the risk of cervical cancer.

Epstein-Barr virus is associated with an increased risk of developing lymphomas and nasopharyngeal cancer. The virus is transmitted through saliva during a kiss, sharing a toothbrush and drinking glasses. Approximately 90% of the population has the Epstein-Barr virus. In most cases, the viral infection is asymptomatic.

Hepatitis B and C virusescan lead to the development of chronic infection, which increases the risk of developing cirrhosis and liver cancer. Human immunodeficiency virus does not belong to oncogenic viruses, but it can cause AIDS, which increases the likelihood of malignant tumors.

Helicobacter pylori is the cause of 90% of all gastric cancers in the world.
As a rule, all the bacteria in the stomach die due to the acidic environment. Helicobacter pylori can move and hide in the mucus that covers the walls of the stomach. The bacterium also secretes ammonia, which neutralizes acid and creates conditions that are favorable for survival. The waste products of Helicobacter pylori damage the cells of the epithelium of the stomach, which provokes the development of ulcers and increases the risk of cancer.

Sedentary lifestyle

The risk of developing endometrial, colon and lung cancer is increased if a person spends most of the time sitting or lying down. Scientists still do not know exactly why this is happening. The probable causes are lack of physical activity, unhealthy diet and excess weight.

In many studies, just sitting down while watching TV is associated with an increased risk of developing certain types of cancer. While watching TV, a person spends fewer calories than when reading books or working at a computer in a sitting position. In addition, scientists assume that watching TV is associated with the consumption of high-calorie and sweet foods, which can lead to excess weight.

Unbalanced nutrition

Scientists were able to establish a link between the development of malignant tumors and the consumption of certain products.

The researchers found that a high intake of red meat cooked at high temperatures is associated with an increased risk of developing colorectal cancer, pancreatic and prostate cancers.

Red meat cooked at high temperatures (more than 150ºС) on the grill, grill or pan, contains heterocyclic amines and polycyclic aromatic hydrocarbons (PAHs). In laboratory studies, these substances were recognized as mutagens: they damage DNA and increase the risk of developing cancer.

Most processed meats contain salts, nitrites and nitrates. When a person eats, for example, a piece of sausage, nitrites and nitrates react with other compounds in the meat and can turn into nitrosamines. Nitrosamines are carcinogens and mutagens that increase the risk of cancer.

Salty foods can damage the lining of the stomach, which causes inflammation and atrophy. This creates favorable conditions for Helicobacter pylori and thereby increases the risk of developing stomach cancer.

Hot drinks are also carcinogenic. Tea, coffee or mate above 65 degrees Celsius increase the risk of esophageal cancer. Scientists suggest that this is due to damage to the epithelium.

Excessive drinking

Excessive use of alcohol increases the risk of developing malignant head and neck tumors, cancer of the esophagus, liver and colorectal cancer.

There are several mechanisms of negative effects of alcohol. First, alcohol acts as an irritant and damages the cells of the mouth and throat. A damaged cell can become malignant as mutations accumulate.

Secondly, the product of alcohol metabolism damages the liver. In the liver, ethanol is metabolized to acetaldehyde. It is a toxic substance that damages the DNA of cells. Also, excessive alcohol consumption leads to inflammation and scarring of the liver, which increases the risk of developing a malignant tumor.

Thirdly, alcohol consumption in women is associated with a high level of estrogen (female sex hormone), which increases the risk of developing breast cancer.

The increased risk does not depend on the type of drink, since ethanol is contained in any kind of alcohol.

Adverse working conditions

Some types of work are associated with an increased risk of developing malignant tumors:

• Agriculture. Due to exposure to sun and agricultural chemicals.
• Construction and painting works. Due to exposure to asbestos, solvents, paint, combustion products of coal, exhaust gases and the sun.
• The production and mining industry is associated with the effects of oil and its products, asbestos, coal combustion products, solvents, sunlight, industrial dust, and also radon gas.
• Increased risk of cancer among workers in the service sector may be associated with passive smoking, exposure to the sun, exhaust fumes.

Some types of cancer are associated with exposure to specific carcinogens. For example, people who work with asbestos have an increased risk of developing lung cancer, colorectal cancer, ovarian cancer, and stomach cancer.

Reproductive and hormonal factors

The risk of developing breast cancer depends on the duration of exposure and the level of female sex hormones - endogenous estrogen and progesterone. The level of these hormones increases during puberty and in the absence of pregnancy.

The early appearance of menstruation, late menopause, late birth of the first child or the absence of pregnancy are signs of prolonged exposure to hormones. Therefore, these reproductive factors suggest an increased risk of developing breast cancer.



Exogenous hormones, which enter the body of a woman from the outside, also increase the risk of developing breast cancer. Exogenous hormones include hormones in oral contraceptives and hormone replacement drugs.

Oral contraceptives reduce the risk of endometrial cancer and ovarian cancer, but may increase the risk of developing breast, cervical and liver cancer. The longer a woman takes oral contraceptives, the lower the risk of developing endometrial cancer and the higher the risk of developing other types of tumors. After stopping oral contraceptives, the risk of developing cancer gradually decreases.

Hormones in oral contraceptives can change the susceptibility of cervical cells to human papillomavirus. Therefore, if there is an oncogenic type of HPV in the body, the risk of developing a malignant tumor increases several times.

Hormone replacement therapy, which is used to prevent diseases during menopause, also increases the risk of developing breast cancer. This is confirmed by a randomized controlled trial in which 16.6 thousand women took part. Among women who took hormone replacement drugs, 245 breast cancer cases were diagnosed; among women taking placebo, 185 cases.

Ultraviolet and ionizing radiation

Ultraviolet radiation and ionizing radiation also increase the risk of developing malignant tumors.

When ultraviolet light affects unprotected skin, DNA damage occurs in cells. If exposure continues for a long time, a sunburn appears on the skin. Red indicates that the body is trying to repair or replace damaged cells. The same thing happens with a normal burn, but there is an important difference. With a burn, something hot does not cause DNA damage, so the cells are gradually replaced by new ones.

When sunburn, DNA damage can be left without recovery, then among the normal cells in the skin will be a cell with a mutation. Such cells divide and continue to accumulate more and more mutations, so they can turn into cells of a malignant tumor.



Ionizing radiation also damages the DNA of cells and can cause cancer. Exposure to ionizing radiation can be encountered during X-ray, fluorography, mammography or computed tomography. These procedures are considered safe for human health, as the benefits of them outweigh the small risk.

In ordinary life, a common source of ionizing radiation is radon gas. Radon secrete natural materials, such as granite, as well as soil and groundwater. Gas enters homes through cracks in floors and walls, accumulates in basements and may be contained in water. Radon is the second cause of lung cancer after smoking.

Environment

Plants and factories, a large number of cars, as well as improper disposal of industrial waste may be associated with an increased risk of cancer.

Scientists at the University of Illinois, USA, found a connection between an unfavorable environmental situation and a high incidence of malignant tumors. A particularly brightly polluted environment is associated with the incidence of lung, prostate and breast cancer.

The reason for the development of malignant neoplasms due to harmful substances of the environment - oxidative stress. Cell DNA is damaged by an oxidation reaction, which leads to the appearance and fixation of mutations in somatic cells.

Medical preparations and procedures

Patients who have undergone radiation therapy, chemotherapy or stem cell transplantation have an increased risk of developing a new malignant tumor.

Heredity

Heredity is a factor that we cannot influence. However, you can correctly assess the risks and carefully consider your health to reduce the likelihood of developing malignant tumors.

Most of the mutations that cause cancer are transmitted in an autosomal dominant manner: with a 50% probability, the hereditary mutation can pass from parent to child.



All nuclear DNA genes are contained in cells in two copies, one from each parent. If the mutation occurred in only one gene, then the second one performs its work. In this case, the person has a predisposition to malignant tumors: if the second gene is damaged, the cell can become malignant.

Many familial cases of cancer are associated with hereditary mutations in tumor suppressor genes. More than 90 genes are known that are reliably associated with hereditary forms of cancer. The risk of developing different types of malignant tumors may depend on several genes, as well as a set of mutations in one gene.

For example, mutations in the BRCA1 and BRCA2 genes multiply the risk of developing breast and ovarian cancer in women. At the same time, about 20 other genes affect the development of hereditary breast and ovarian cancer. In men, this mutation increases the risk of prostate and breast cancer. In both sexes, the presence of these mutations in cells increases the risk of pancreatic cancer and melanoma.

Many familial forms of cancer develop due to unknown mutations: geneticists have yet to identify them.

Indefinite factors

Today, only some of the factors that influence carcinogenesis are known. But not all.

You can live in an ecologically clean area, carefully monitor your health, be physically active, eat right and still have a risk. This suggests that cancer development does not always depend on a person’s actions or lifestyle.

For example, the causes of most somatic mutations that lead to the development of breast or prostate cancer are not known. Although these types of malignant tumors are one of the most common in the world.

Initially, we wanted to talk about risks, prevention and screening in one article, but we collected so much interesting information that we got three separate materials. Today you learned about the factors that increase the risk. Next time atlas tell you how to manage these factors.