(First of two parts)
A normal cell in the human body will go about its function, dividing into exact copies of itself in the process of mitosis until a mechanism called “contact inhibition” tells the cell (or by now the group of cells) to stop multiplying, as most of the space to grow may have been covered.
One of the cells may have a little defect, a mistake in its DNA when it multiplied, and it recognizes it within itself.
It knows that it has to be corrected, that it needed to “die” so that it can be replaced by a healthy cell and at the same time avoid multiplying itself and the defect. A mechanism called apoptosis activates within that cell which triggers its death, resolving the mistake.
The human body creates and replaces roughly 100 billion new cells per day, and a tiny percentage of those cells have mistakes, mutations. Thus regulatory mechanisms such as apoptosis, correcting these mutations, are relatively common.
To avoid confusion, one probably heard of meiosis which is different from mitosis. Basically cells undergoing mitosis creates a genetically identical clone of itself (somatic cells) while cells undergoing meiosis divides into genetically unique cells from the mother cell. Meiosis is exclusive for the gametes – the sperm and egg cells – and are the basis of reproduction / passing genes to offspring.
Going back, in cases where the (somatic) cell that had defects fail to eliminate itself, perhaps the mutation it acquired stops the mechanism of apoptosis and / or contact inhibition, it proceeds to multiply, forming into a bunch of abnormal cells – this is called a Neoplasm. These cells may multiply indefinitely and form lumps or circulate in the body. For lumps, when they get large enough to be noticed they may be called tumors.
The word tumor and neoplasm are often used interchangeably, but in the strictest sense, not all tumors turn out to be cancers and not all cancers have tumors (like cancers of the blood, i.e. leukemia). However in day to day vocabulary, the word tumor is used more than neoplasm.
Now these tumors may be differentiated into three types. Benign tumors are those that do not usually cause damage to their surroundings and are more often confined.
Fun fact, moles are actually benign tumors. Potentially malignant tumors classified as carcinoma in situ, are localized tumors. They may not cause damage now as they are more often confined in a capsule, but they have the potential to break away from that and become life threatening. The third are malignant tumors which are essentially cancer. These are the ones that don’t stop dividing, keep on mutating, invade other tissues and organs and endanger the organism.
When they are untreated or they become unresponsive to treatment, cancer has been proven to kill the organism. Note that some benign tumors have the potential to turn into cancers.
Basically cancers are a large family of diseases that involve abnormal cell growth with the potential to invade or spread to other parts of the body. Since the year 2000, a peer-reviewed article published in the journal Cell by the cancer researchers Douglas Hanahan and Robert Weinberg, identified the six (6) hallmarks of cancer. These hallmarks are still very much cited today in cancer studies.
Cancer cells stimulate their own growth, they have self-sufficiency in growth signals.
They resist inhibitory signals that might otherwise stop their growth, they are insensitive to anti-growth signals.
They resist their programmed cell death, they evade the mechanism of apoptosis.
They can multiply indefinitely.
They stimulate the growth of blood vessels to supply nutrients to themselves (sustained angiogenesis)
They invade local tissue and spread to distant sites (tissue invasion and metastasis).
This is why cancer cells are aptly named immortal cells because they refuse to die and they refuse to be stopped until the organism they are growing upon has died.
Introspective Review on the Causes of Cancer
“The greatest risk of getting cancer is being alive” and “The only way to avoid cancer is to never be born”.
These are humorous albeit dark phrases blurted out in the medical community but very much true to the science of cancer.
According to the Seminars in Cancer Biology published in Elsevier, it is identified that the basic cause of sporadic (non-familial) cancers is DNA damage and genomic instability. The rest may be from inherited genetic mutations (passed down from family) and Carcinogenic substances. The most popular of these carcinogens is tobacco smoke.
Carcinogens are various substances that promote the formation of cancer or carcinogenesis. Basically they increase one’s risks of getting cancer. For risk factors however, it is not generally possible to prove what caused a particular cancer (at least for now) because the various causes do not have specific fingerprints. For example, if a person who smokes heavily develops lung cancer, then it was most likely caused by the tobacco use, but since everyone has a small chance of developing lung cancer (even without family history) as a result of air pollution, radiation, and the random “misfortune” of DNA damage and genomic instability in cells, the cancer may have developed due to one of those reasons and not strictly from heavy tobacco use.
Everyone can get cancer. It’s only a matter of when. Nobody is exempt. When one has a family history of cancer it simply increases the risk of getting cancer. When one has a lifestyle of indulging in carcinogens, or they have no choice but to work exposed to it, it simply increases the risk of getting cancer. Without a family history of cancer or without all the risk factors – with the way things go in the human body, every single person has a risk of getting cancer.
This is where the absurdity of cancer lies – A human being who came from a cancer stricken family tree, who have lived a risky lifestyle and is exposed to many carcinogens may die of old age or other diseases without getting cancer, while another who came from a healthy family tree and have lived healthily may get cancer and die from it.
A controversial study published in Science / American Association of the Advancement of Science in 2017 titled “Stem cell divisions, somatic mutations, cancer etiology, and cancer prevention” stated
“Most textbooks attribute cancer-causing mutations to two major sources: inherited and environmental factors. A recent study highlighted the prominent role in cancer of replicative (R) mutations that arise from a third source: unavoidable errors associated with DNA replication”
These random unavoidable errors in DNA replication has been dubbed in the study as “bad luck” and it caused quite the controversy for being “insensitive” due to the fact that cancer patients and cancer survivors, while true that they didn’t choose to get sick, may be attributed as unlucky and this didn’t help with their overall morals and esteem. Due to this nature of cancer, it can be a sensitive topic in some spiritual cultures in which they attribute it to karma or punishment for past lives or bad deeds. However those attributions are obviously an untrue association to what is really happening. While it may be said that how the study is written may sound defeatist, it still holds true that decreasing risks such as switching to and maintaining a healthy lifestyle and identifying risk factors, such as family history, actually helps in avoiding cancer as much as possible. The study also emphasized that knowing these unavoidable causes early on may help in the identification of these mutations – paving the way for early treatment.
Alcohol, drugs, an unhealthy diet, obesity, and especially smoking are cancer risk factors. Many substances and chemicals are carcinogenic, such as asbestos which is known to specifically cause mesothelioma. Diseases caused by infection and inflammation may predispose to cancer. Whatever the cause of cancer may be, prudent choices against modifiable cancer risk factors ultimately help in preventing and/or combating the disease regardless of luck or misfortune.