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4.4: Uncontrolled Cell Divisions Create Tumors including Cancers

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    Uncontrolled Cell Divisions Create Tumors including Cancers

    Tumors, including cancers, are caused by abnormal cells that multiply continuously. If the abnormal cells continue to divide unstopped, they can damage the tissues around them, spread to other parts of the body (malignancy), and even result in death. In healthy cells, the tight regulation mechanisms of the cell cycle prevent this from happening (cell cycle checkpoints), while failures of cell cycle control can cause unwanted and excessive cell division. Failures of cell cycle control may be caused by inherited genetic abnormalities (genetic predispositions) that compromise the function of certain cell cycle “stop” and “go” signals. Cell cycle checkpoints may also be compromised due to exposures to environmental factors that mutate cellular DNA causing dysfunction in those "stop" and "go" signals controlling the cell cycle. Often, a combination of both genetic predisposition and environmental factors lead to cancer. Environmental factors causing DNA mutations that may lead to cancers can include:

    • exposures to mutagenic chemicals (e.g. chemicals in cigarette smoke, pollutants, etc.)
    • radiation (e.g. X-rays, ultraviolet light)
    • some viruses (e.g. human papilloma virus [HPV])

    Microscopic image of Cancer Tissue

    Above: Light microscope image of a tissue cross-section from a patient with a type of basal cell cancer. The growth of abnormal cells is bracketed on either side, but the overall shape of the cancer tissue is roughly circular.

    The process of a cell escaping its normal control system and becoming cancerous may actually happen throughout the body quite frequently. Fortunately, certain cells of the immune system are capable of recognizing cells that have become cancerous and destroying them. However, in certain cases the cancerous cells remain undetected and continue to proliferate. If the resulting tumor does not pose a threat to surrounding tissues, it is said to be benign and can usually be easily removed. If capable of causing damage to surrounding tissues and spreading through the blood and/or lymph, the tumor is considered malignant and the patient is diagnosed with cancer.

    Attributions

    This page titled 4.4: Uncontrolled Cell Divisions Create Tumors including Cancers is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Rosanna Hartline.