Uncontrolled growth is called cancer. It happens when body fails to counterbalance the lavish utilization of nutrients by some cells. Cancer spreads from its origin to multiple other places in the body in a process called metastasis. In other words, cancer keeps claiming an ever-increasing area of the body. If your body were a country, cancer would be the ultimate land-grabber.
By Jamshed Arslan, PhD
In this essay, I would outline the signaling that leads to the start and spread of cancer in the body.
Benign and malignant tumor
The word tumor is used interchangeably with cancer. However, technically, not all tumors are cancers. Tumor is just the word used for swelling of a body part because of abnormal growth. If such growth responds to body’s growth inhibitors, it is referred to as benign tumor; otherwise, it is called malignant tumor or cancer.
Before becoming cancer, the cell was part of your own body and was under the control of ligands such as growth factors and inhibitors. These ligands bind to specific cell receptors to maintain a normal turnover of a cell. Depending on the type of ligand, cell receptors send a cascade of signals to the nucleus. In response, the genes for grow-and-divide, stop-growing or, even, death are transcribed. The cells start becoming cancerous or malignant when they do not respond to the latter two signals.
The incessant cell division can be achieved through various mechanisms. Take the example of glioblastoma, a fast-growing type of tumor of the central nervous system. The glial or supportive cells of the brain and spinal cord generate their own growth signals. One such growth signal in glioblastoma is PDGF, which stimulate nonstop growth of glial cells. Another mechanism is the increased number of receptors on the cell. In this case, even when the growth signals are relatively low, the fact that receptors are overexpressed leads to excessive cell division. Here again, it is the genes that are amplified and transcribe abnormally high number of receptors. Over time, these receptors start signaling independent of the presence of ligand. In other words, cancer cells promote their own selfish “progress” irrespective of any need for such growth.
Tissue invasion and metastasis
Cancerous growth is not linear: one malignant cell divides into two, then to four, eight, and so on, occupying an ever-increasing area. Cells start breaking off from the original tumor mass. For such breaking down of tumor’s original boundaries, malignant cells secrete enzymes like matrix metalloproteinases (MMPs). It is the MMPs that chew off the boundaries of original tumor mass and make the room for undeserved growth of cancer cells. MMPs also destroy protective coverings of blood vessels so that the malignant cells could spread to the rest of the body to initiate a new tumor. Indeed, the spread of cancer is a destructive process.
To multiply ceaselessly, the cancer sends signals to the body to generate new blood vessels. Cancer’s unstoppable thirst for energy makes your body weak. However, from cancer’s perspective, body’s priority should only be such “growth and prosperity” regardless of the cost. Cancer is the most selfish entity in a body!
If cancer can be localized, surgery and radiation are two viable options. Even when a cancer is surgically removed, its remnants or the metastasized cells maintain a rapid growth. Radiation may also hurt normally growing cells. Another common treatment is chemotherapy, which blunts every fast-growing cell in the body by targeting ligands, receptors or any of the signaling molecules. Since hair and gut cells are some of the fastest growing cells in the body, baldness and gut problems are some of the observable effects of chemotherapy. However, such side effects are a small price to pay for the bigger goal of mitigating cancer, which is a fatal ailment.
Lessons from cancer biology
If an institute keeps grabbing more than its fair share, as happens quite frequently in third world countries, it behaves like a cancer. Only the equitable distribution of power can discourage a cancerous growth of any organization in a country. Since not all tumors are malignant, we must be very careful in labeling any entity a cancer. But once recognized, the option of surgery and chemotherapy should be considered despite the side effects. Let’s think.
Pharm D (gold medalist); PhD (Neuropharmacology)
Skilled in basic and clinical research and scientific writing with over a decade of teaching experience.