To put it simply, cancer cells are cells gone rogue, meaning that they no longer respond to many of the signals that control normal processes of cell growth and death. What causes it, and how does it happen?
Cancer cells originate within tissues from normal cells when a series of mutations leads them to continue to grow and divide out of control. In this way, cancer cells achieve a sort of immortality. Uncontrolled growing and division have a severe impact on the normal functioning of organs or tissues affected by cancer. Moreover, unlike normal cells that remain in the region where they originated, cancer cells have the ability to both invade nearby tissues and spread to distant areas of the body (other differences between normal and cancer cells are presented in Table 1). This makes the spreading of “immortality” even worse.
|Normal Cell||Cancer Cell|
|Grows when needed||Grows uncontrollable|
|Stays within tissue boundaries||Can invade nearby tissues|
|Sticks to nearby cells||May spread to other regions of the body|
|Has a defined lifespan||Can be immortal|
Types of cancer
Any type of cells in the body can become cancerous, start to divide uncontrollably and thus cause tumor formation. This is how cancer cells damage our organism – fast and significant growth of tumors seriously disturb and may cause lethal damage to it. Because of the great number of initial cell source types, a hundred distinct types of tumors can form which will vary considerably in their behavior and response to treatment.
The names of the tumors are derived from the type of cell from which the tumor arises. For example, the most common tumors which originate from the malignancies of epithelial cells are called carcinomas; followed by sarcomas, which are malignancies of connective tissues, such as bone, cartilage, muscle; leukemia or lymphomas arise from blood-forming or immune system cells, respectively. Determining the tissue of the cancerous cells’ origin allows to select the best treatment option.
It is important to mention that tumors are also classified according to their malignancy. Having a tumor does not necessarily mean having cancer. In this case, two types of tumors are distinguished – benign and malignant. Therefore, when a patient is diagnosed with a tumor, it is important to first determine which of these two types it belongs to.
A benign tumor, such as a common skin wart, remains in the same place where it originates, neither invades nor spreads to surrounding tissues and distant body sites. Although cells proliferate incessantly, they do not spread uncontrollably and such tumors, almost in all cases, can be removed by the surgery.
Whereas a malignant tumor (properly referred to as cancer) is capable of metastasizing – invading surrounding normal tissues and spreading throughout the body via the circulatory or lymphatic systems. Those metastatic tumors are no longer localized, meaning they can spread elsewhere in the body and can no longer be controlled. This cancer ability not only complicates its timely detection, but also makes it difficult to select the optimal treatment strategy.
Prevention and regular health checks to identify newly formed tumors plays a key role in the successful treatment of cancer.
How exactly does cancer develop?
As mentioned above, the process begins with a change (mutation) in a single tissue cell, leading to its abnormal proliferation (uncontrollable growth and division). This is the first stage of the cancer development process, which is called tumor initiation.
This uncontrolled cell proliferation further results in the formation of a population of clonally derived tumor cells, in other words, primary cancer. Once a cancer forms, its cells don't remain stable but continue to mutate. These new mutations allow cancer to adapt and evade the damaging effects of various treatments, and that’s how cancer resistance to chemotherapy and targeted therapy drugs develops. Recent advances in science and medicine make it possible to determine the key mutations in a particular tumor and thus select the successful treatment strategy by circumventing the developed resistance to certain drugs.
What causes cancer, and is it possible to avoid it?
Mutations in cancer cells can form due to heredity (determined by genetics) but more often, they are caused by carcinogens (cancer-causing substances) in the environment (including radiation, chemicals, viruses, and etc.).
All carcinogens can be classified into two main categories – initiating agents and tumor promoters. Radiation and many chemical carcinogens are generally referred to as initiating agents since they act by damaging DNA and inducing mutations within the cell. Some of the initiating agents that contribute to human cancers include solar ultraviolet radiation (the major cause of skin cancer), carcinogenic chemicals in tobacco smoke, and aflatoxin (a potent liver carcinogen produced by some molds that contaminate improperly stored supplies of peanuts and grains).
Another type of carcinogen are tumor promoters. They contribute to cancer development by stimulating cell proliferation rather than by inducing mutations. Some of the tumor promoters’ examples could be hormones (usually used during various hormone therapies, forcing specialists to carefully assess potential damage and benefit to the patient) and viruses. For example, the hormone estrogen can stimulate the proliferation of cells of the uterine endometrium. Thus exposure to excess estrogen significantly increases the likelihood that a woman will develop endometrial cancer. Another example could be Hepatitis B and hepatitis C viruses, both of which can cause liver cancer.
The table below shows examples of carcinogens found in the environment and the cancers they can cause. Although it is difficult to avoid all carcinogens in the environment, it is worth trying to minimize contact with them by using protective equipment when working in areas where certain types of carcinogens are present and by using organic products which are almost free of preservatives.
|Carcinogens||Cancer Site||Found in|
|Asbestos||Mesothelioma, Lungs||Roof and floor tiles|
|Benzene||Blood and lymph nodes||Petroleum, paints, detergent, rubber|
|Beryllium||Lungs||Missile fuel, nuclear reactor|
|Chromium||Lungs||Preservatives, pigments, paints|
|Ethylene oxide||Blood||Ripening agent for fruits|
|Nickel||Nose, Lungs||Batteries, ferrous alloys|
|Radon||Lungs||High gasses concentrations in, mines, cellars|
|Vinyl chloride||Liver||Gasses in refrigerators, glues|
|Smoke||Lungs, Colon||Cigars, air pollution, car smoke|
|Formaldehyde||Nose, Pharynx||Solutions used in hospitals/laboratories|
|Soot||Skin||Soot in chimneys|
|Ionizing radiation||Bone marrow||Radiology procedures|
|Hepatic virus - B,C||Liver||Unprotected sex, none-sterile needles and syringes|
|HPV/Herpes viruses||Cervix, skin, head/neck||Multiple sexual partners|
|Helico-bacteria pylori||Stomach||Chronic bacterial infection|
There are several types of cancer treatment strategies (the most popular ones are shortly described in Table 3). The types of treatment that patients receive depend on the type of cancer they have and how advanced it is. Treatment has to be personalized to every patient in order to achieve the best results. For this reason, all relevant factors have to be taken into consideration.
|Biomarker Testing for Cancer Treatment||Biomarker testing is a way to look for genes, proteins, and other substances (called biomarkers or tumor markers) that can provide information about cancer. Biomarker testing can help doctors choose a cancer treatment.|
|Chemotherapy||Chemotherapy is a type of cancer treatment that uses drugs to kill cancer cells.|
|Hormone Therapy||Hormone therapy is a treatment that slows or stops the growth of breast and prostate cancers that use hormones to grow.|
|Hyperthermia||Hyperthermia is a type of treatment in which body tissue is heated to as high as 45 °C to help damage and kill cancer cells with little or no harm to normal tissue.|
|Immunotherapy||Immunotherapy is a type of cancer treatment that helps your immune system fight cancer.|
|Photodynamic Therapy||Photodynamic therapy uses a drug activated by light to kill cancer and other abnormal cells.|
|Radiation Therapy||Radiation therapy is a type of cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors.|
|Stem Cell Transplant||Stem cell transplants are procedures that restore stem cells that grow into blood cells in people who have had theirs destroyed by high doses of chemotherapy or radiation therapy.|
|Surgery||Surgery is a procedure in which a surgeon removes cancer from the patient body.|
|Targeted Therapy||Targeted therapy is a type of cancer treatment that targets the changes in cancer cells that help them grow, divide, and spread.|
Nowadays, healthy nutrition and lifestyle are considered increasingly important components of successful cancer treatment. A variety of unproven methods, such as avoiding products with large amounts of carbohydrates, have been routinely recommended to fight cancer. The results of such experiments usually show little success. Various studies documented that different tumor types demonstrate different sensitivity to the deprivation of amino acids, such as asparagine, arginine, methionine, glutamine, and cysteine, or the major energy source glucose. It is still not entirely clear which nutrients or vitamins for different diseases are cancer-causing or cancer-fighting. Therefore, unless a doctor has advised a specific diet tailored to a specific tumor, the most common recommendation is to eat a generally healthy diet, maintain physical activity, and allow enough time for sleep and rest.