When the cells become red. Science of how cancer starts Alina Khaled

Cell life cycle

Every cell in your body follows a strict, almost military code of conduct. It thrives, performs its assigned duties, splits only when necessary, and dies gracefully when its time comes. This process is known as the cell cycle, and it is a carefully choreographed dance controlled by internal checkpoints and molecular signals. When cells become damaged or old, they undergo a form of programmed self-destruction called apoptosis, which is a cellular “retirement plan” that prevents damage to the rest of the body. However, like any complex system, the cell cycle is not foolproof. DNA errors can occur naturally during reproduction or can be caused by external factors such as toxins, radiation, or inflammation. Normally, these cells are repaired before the next division, but if the repair system fails, a mutant cell may infiltrate. Once a cell begins to ignore stop signals or bypass apoptosis, it can begin to multiply uncontrollably, the first spark in a chain reaction that can lead to cancer.

An error has occurred in the DNA code

At the heart of this process lies DNA, the blueprint that determines cell behavior. DNA damage occurs constantly, due to exposure to the environment such as UV radiation, cigarette smoke, or simply due to normal metabolic activity. Cells have an amazing set of repair tools to deal with this, but sometimes the damage occurs in sensitive areas – genes that control growth and division. There are two main categories of these key genes: proto-oncogenes that promote growth when needed and tumor suppressor genes that act as brakes to stop uncontrolled division. When a proto-oncogene mutates, it can become permanently “turned on,” causing cells to continue dividing. When a tumor suppressor gene is damaged, the cell loses its ability to apply the brakes. Most cancers do not arise from a single mutation, but from a gradual accumulation of many mutations, a slow breakdown in cellular control that can take years or even decades to manifest.

The tumor takes shape

When these abnormal cells multiply, they form a tumor, a growing mass that can remain contained or begin to invade surrounding tissue. Benign tumors tend to grow slowly and stay in one place, while malignant tumors go beyond their boundaries, invading nearby organs and disrupting normal function. But what makes a tumor truly dangerous is its ability to create its own lifeline. Once it reaches a certain size, it needs more oxygen and nutrients to survive. It sends chemical signals that trick nearby blood vessels into sprouting new branches toward them, a process called angiogenesis. With a dedicated blood supply, the tumor can grow faster and stronger. It’s no longer just a collection of cells; It is a self-sustaining ecosystem that lives outside the body while challenging its rules.

How does cancer spread?

The most lethal step in cancer development is metastasis, when cancer cells break away from their original site and travel to distant parts of the body. This is not an easy journey, as most cells that enter the bloodstream die along the way, but the few that survive are often the most adaptable and aggressive. They use the circulatory or lymphatic system as highways, settle in new tissues and begin forming colonies. Once they settle in another organ, such as the lungs, liver, or bones, these cells continue to divide and form secondary tumors. This process completely changes the disease, making treatment more complex. Metastasis is the reason why cancer is detected early, before it has spread, and is more treatable. It is not only the growth of the original tumor that poses the greatest threat, but its ability to wander around and seed new tumors elsewhere.

The role of the immune system

Fortunately, the body is not defenseless. Your immune system is constantly monitoring abnormal cells. White blood cells known as T cells and natural killer cells patrol the body, destroying anything that looks suspicious. In many cases, they succeed in eliminating cancer cells before they can form a tumor. But cancer cells are smart. It is developing ways to evade detection by changing surface proteins, mimicking normal cells, or releasing substances that suppress immune activity. For many years, this made treating advanced cancers very difficult. But recently, a new generation of treatments called immunotherapies has emerged, changing the landscape. These treatments work by ‘retaining’ the immune system to recognize cancer cells and attack them again, effectively restarting the body’s natural defences. In some patients, this approach has led to long-term remissions, which were previously thought impossible.

Prevention and hope

While not all cancers are preventable, many risk factors are within our control. Avoiding tobacco, limiting alcohol, maintaining a healthy diet rich in plants, exercising regularly and protecting the skin from excessive sunlight all make measurable differences. Vaccines, such as those for HPV and hepatitis C, can completely prevent some virus-related cancers. Early detection remains one of the most powerful tools. Regular checkups such as mammograms, Pap tests, and colonoscopies detect changes before they become serious. On the treatment side, researchers are moving toward precision medicine, where genetic testing for tumors helps doctors choose treatments tailored to the unique mutations of that cancer. This personalized approach transforms survival outcomes and quality of life for countless patients