Global challenges Study Guide

Cancer is a disease characterised by the uncontrolled growth and division of cells. Normally, cells in the human body grow, divide, and die in a regulated manner following a set programme. This tightly controlled process ensures that new cells are produced only when needed, replacing old or damaged ones, and maintaining healthy tissues and organs. However, when a cell undergoes specific changes, often due to damage to its DNA or other cellular mechanisms, it can lose this control. These altered cells begin to divide repeatedly without stopping, ignoring the signals that normally halt cell division. This leads to an accumulation of abnormal cells, forming a mass called a tumour. Tumours can be benign or malignant. Benign tumours are non-cancerous; they typically grow slowly and do not spread to other parts of the body. Malignant tumours, on the other hand, are cancerous. Cells from malignant tumours can invade surrounding tissues and, critically, can break away from the primary tumour and travel through the bloodstream or lymphatic system to form secondary tumours in other parts of the body. This process is known as metastasis. The uncontrolled growth and spread of these abnormal cells disrupt the normal functioning of organs and systems, leading to the various symptoms and health problems associated with cancer.

Stem cells are undifferentiated cells that have the remarkable capacity to develop into many different cell types. In medicine, their potential lies in replacing damaged tissues or organs, offering new treatments for a range of conditions from Parkinson's disease to spinal cord injuries. The primary benefit is their ability to differentiate into specialized cells, which means they could potentially repair or regenerate tissues that have been damaged by disease or trauma. For example, stem cells could be used to regenerate heart muscle after a heart attack, or to produce new pancreatic cells for people with type 1 diabetes. However, the use of stem cells, particularly embryonic stem cells, carries significant ethical and practical risks. Ethical concerns often revolve around the source of embryonic stem cells, as their collection typically involves the destruction of an embryo. There are also practical risks such as the potential for stem cells to grow uncontrollably, leading to tumour formation, or the risk of immune rejection if the cells are not from the patient themselves or a compatible donor. Furthermore, the long-term effectiveness and safety of many stem cell therapies are still under investigation, and some treatments are very expensive and not widely available. Advancements in induced pluripotent stem cells (iPSCs), which are adult cells re-programmed to an embryonic-like state, offer a way to bypass some ethical concerns associated with embryonic stem cells by using a patient's own cells, thereby also reducing the risk of immune rejection. A balanced perspective requires weighing the immense potential for treating debilitating diseases against these ethical dilemmas and practical safety considerations.