healthy life healthy lifestyle 820000 people get sick and 650000 die in a year. How does lung cancer, the "first killer" of cancer, come into being?

820000 people get sick and 650000 die in a year. How does lung cancer, the "first killer" of cancer, come into being?

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It can also adjust the pH value of the blood, filter out small thrombus formed in the vein, adjust the concentration of biological substances and drugs in the blood, participate in water metabolism, produce a variety of hormones, etc., or replace cells that die as a result of aging and injury. when the body no longer needs more daughter cells, some cells have genetic mutations. Causing these cells to produce unbearable, these cancer cells do not have the function of normal cells and do not repair damage like platelets. But it can plunder the nutrition of normal cells, and cancer cells need more nutrients for their growth; they can also invade the boundaries of surrounding normal cells and transfer to all parts of the body through blood vessels or lymphatic vessels, leading to the occurrence of lung cancer if the inner wall cells of the main bronchus and lungs. Not all genetic mutations cause cancer, and over time the cancer cells that have mutated this gene keep dividing.

The lung is an important organ in the respiratory system. It is located in the chest near the spine and consists of the right lung and the left lung.

Between our exhalation and inhalation, the lungs transport oxygen through the alveolar wall to the blood. at the same time, carbon dioxide leaves the blood into the alveoli and is excreted through the lungs.

What many people do not know is that the function of the lung is not only breathing, it can also adjust the pH value of the blood, filter out small thrombus formed in the vein, adjust the concentration of biological substances and drugs in the blood, participate in water metabolism, produce a variety of hormones, and so on. At the same time, the lung is also one of the main places for the human body to produce platelets, which can synthesize 10 million platelets per hour, accounting for about 50% of the total platelet production.

It is such a powerful and important organ that is often targeted by cancer. National cancer statistics released by the National Cancer Center in 2022 show that:

Lung cancer is the most common cancer in China and the leading cause of cancer death.

The number of cancer cases in China in 2016-incidence, the red box is the data of lung cancer

The number of cancer deaths in China in 2016-mortality, the red box is the data of lung cancer

Picture source: reference [1]

Because of the lack of understanding and understanding of cancer, many people are confused after diagnosis, "Why do I have lung cancer?" "how did lung cancer come to me?"

Where do cancer cells come from and where do they go?

Our human body contains trillions of cells, and these cells will experience apoptosis and death, in order to maintain the growth and repair of the body, the cells will divide.

In general, mother cells divide into two daughter cells, which can be used to build new body tissues or to replace cells that die as a result of aging and injury. When the body no longer needs more daughter cells, cell division terminates.

However, it is in the process of cell division that some cells have genetic mutations and their genetic factors are abnormal, causing these cells to produce "superpowers" that the human body cannot bear:It does not wither and die like normal cells, and it can replicate and accumulate itself indefinitely.This kind of cell is cancer cell.

So, what are the consequences of the wanton growth of cancer cells?

820000 people get sick and 650000 die in a year. How does lung cancer, the

The most direct point.If the cancer cells are in the primary site, over time, they will squeeze out the space and oppress the tissue or nerves in the area.

In addition, these cancer cells do not have the function of normal cells:

  • Will not resist the invasion of bacteria or viruses like white blood cells and T cells.
  • It doesn't transport nutrients and carbon dioxide like red blood cells.
  • Nor will it repair the damage like platelets.

But it can rob normal cells of nutrients: cancer cells need more nutrients to grow than ordinary cells, and cancer cells absorb nutrients very quickly in order to divide continuously.

Cancer cells make use of the characteristics of their own infiltration and metastasis, they can also invade the boundaries of surrounding normal cells and transfer to all parts of the body through blood vessels or lymphatic vessels. If they are allowed to develop, the nutritional supply of normal cells in the body can not keep up. Various functions that maintain the operation of the human body will also be abolished.

This is why it is said that cancer cells are "selfish, regardless of human life or death".

Three key conditions lead to the occurrence of lung cancer

If there is a genetic mutation in the inner wall cells of the main bronchus and lungs, and the following three conditions are met at the same time, then lung cancer may occur.

Key condition 1: disease-causing gene mutation

Not all gene mutations cause cancer, but one or two key gene mutations contain pathogenic factors, and the cancer cells that have mutated over time continue to divide and form cancer.

For example, the EGFR gene mutation is one of the most common mutations in non-small cell lung cancer. It is estimated that EGFR mutations account for 40% to 50% of adenocarcinoma (a type of lung cancer) in the Chinese population.

EGFR is a gene that plays an important role in the process of cell growth, proliferation and differentiation. For example, when we have a wound, EGFR will stimulate cell growth and help the wound heal. After performing its function, we will temporarily rest and wait for the next call. However, when EGFR has a genetic mutation, it can not stop, will continue to stimulate cell growth, proliferation, differentiation, and eventually lead to the occurrence of cancer.


Key condition 2: cancer cells escape the supervision of the immune system

The body's immune system itself has the ability to defend against disease. when the pathogenic factors are found, the immune system will mobilize various cells in the body to launch attacks to prevent the occurrence or deterioration of the disease.

But cunning cancer cells in order to avoid the attack of the immune system, can pretend to be normal cells, or pretend to be harmless, to escape the supervision of the immune system, this small number of cancer cells will continue to proliferate and eventually form cancer.

For example, many patients with lung cancer, tumor cells PD-L1 positive more than 50%, this is a way of camouflage cancer cells.

Normal cells in the body express PD-L1 to prevent themselves from being accidentally injured by the immune system, and cancer cells have also learned this trick to express PD-L1 in large quantities. When the PD-L1 protein on the cancer cell binds to the PD-1 protein on the immune cell, it releases the signal that "I am a good cell, beg to let go", which can inhibit the activity of the immune cell, and the immune cell thinks it is one of its own, so it releases the cancer cell.

PD-L1 on cancer cells binds to PD-1 on T cells


Key condition 3: cumulative time

Unlike lung cancer in children, primary lung cancer in adults does not occur suddenly.

It is a long process from the birth of the first cancer cell to the discovery and perception of cancer, which takes about 10 to 20 years.

At the beginning, the tumor grows slowly, but once the malignant transformation forms, it accelerates growth:

One cancer cell can split and proliferate into two, two into four, four into eight, and eight into sixteen.

This growth process of cancer cells is called exponential growth, and the doubling time is getting shorter and shorter, and the longer the tumor is, the faster it is.

A schematic diagram of the evolution of cancer

Six high risk factors promote the occurrence of lung cancer

As we get older, the number of cell divisions in the body increases, and so does the probability of genetic mutation, which is why people with a high incidence of cancer are generally elderly.

But,In many cases, some external factors will induce and accelerate gene mutation.

For example, once inhaled carcinogens, it will directly or indirectly damage lung cells, causing genetic mutations or changes in chromosome structure and number, thus inducing lung cancer.

In addition, inhaling fine particles in air pollution, or chronic lung disease, can also cause lung damage. Lung cells have to divide and proliferate constantly in order to repair these injuries. As the number of division and proliferation increases, the probability of gene mutation is also increasing, resulting in lung cancer.

The high risk factors of lung cancer can be classified into the following six points:

1. Smoking and passive smoking

  • Long-term heavy smoking is the most important carcinogenic factor of lung cancer. the greater the amount of smoking and the longer the smoking time, the higher the risk of lung cancer.
  • Passive smoking is also a risk factor for lung cancer, mainly in women.

two。 Radiation factor

  • Natural stone materials containing radon and other radioactive elements, such as granite, brick sand, cement and gypsum. Radioactive particles that decay radon can cause radiation damage to the human respiratory system and cause lung cancer.
  • High dose of ionizing radiation is also a pathogenic factor of lung cancer.

3. Occupational exposure history

  • In industrial production and mining areas, there are carcinogens such as asbestos, chromium, nickel, copper, tin, arsenic, radioactive substances and so on. Long-term exposure to the above carcinogens can increase the risk of lung cancer.

4. Air pollution

  • Outdoor pollution: such as industrial exhaust, automobile exhaust, haze and so on contain Class A carcinogens identified by the World Health Organization.
  • Indoor micro-environmental pollution: soot from indoor coal burning, soot from kitchen cooking, carcinogens released from indoor decoration materials, etc.

5. Heredity and gene

  • Family aggregation: there is a phenomenon of family aggregation in patients with lung cancer. if there are patients with lung cancer in the family, their relatives have an increased risk of developing lung cancer.
  • Gene mutation: abnormal structure and function of EGFR mutation gene, ALK fusion gene and other genes are closely related to the occurrence of lung cancer.

6. Lung disease

  • The American Cancer Society lists tuberculosis as one of the risk factors for lung cancer. The risk of lung cancer in patients with pulmonary tuberculosis is 10 times higher than that in normal people.
  • Some chronic lung diseases (such as chronic obstructive pulmonary disease, sarcoidosis, idiopathic pulmonary fibrosis, scleroderma), viral infection, mycotoxin (Aspergillus flavus) and so on may also be related to the occurrence of lung cancer.

Although lung cancer is the "first killer" of cancer death, it is a kind of cancer that can be prevented.For the above people with high risk factors, lung cancer screening is recommended from the age of 50. Low-dose spiral CT (LDCT) test is recommended. The screening frequency should be carried out according to the CT results and doctor's advice.

References:

[1] Zheng RS, Zhang SW, Zeng HM, Wang SM, Sun KX, Chen R, Li L, Wei WQ, He J. Cancer incidence and mortality in China, 2016 [J]. JNCC, 2022, 2 (1): 1-9. DOI: https://doi.org/10.1016/j.jncc.2022.02.002.

[2] Lefran ç ais, E., Ortiz-Mu ñ oz, G., Caudrillier, A.Et al.The lung is a site of platelet biogenesis and a reservoir for haematopoietic progenitors.Naturefive hundred and forty four105 Mel 109 (2017).

[3] Wikipedia: https://en.wikipedia.org/wiki/Lung_cancer

[4] Wikipedia: https://en.wikipedia.org/wiki/Cancer

[5] National Institutes of Health: https://www.cancer.gov/about-cancer/understanding/what-is-cancer

[6] take a deep breath: pineapple deciphers lung cancer. Li Zhizhong. Beijing。 Tsinghua University Press, 2018

[7] recognize lung cancer. Wu Yilong. Beijing。 People's Health Publishing House, 2008.

[8] Xiaohe Medical Code. Lung cancer entry. Https://www.xiaohe-jiankang.com/disease/1103

Content editor: Duffy

Medical examination: Li Xing, Su Bangjie

Content production: Xiaohe Medical Code