4.6: Activity 5

Integrated Human Anatomy and Physiology Lab Manual I: Fundamentals of Structure and Movement · LibreTexts

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    Calculating Mitotic Index: A Key Tool in Cancer Research

    Objective

    Understand the mitotic index and learn how to calculate it as a tool to assess cell division, which is crucial in cancer research.

    As mentioned in the background information section, cancer comprises many different diseases caused by a common mechanism: uncontrolled cell growth. Despite the redundancy and overlapping levels of cell-cycle control, errors do occur. One of the critical processes monitored by the cell-cycle checkpoint surveillance mechanism is the proper replication of DNA during the S phase. Even when all of the cell-cycle controls are fully functional, a small percentage of replication errors (mutations) will be passed on to the daughter cells. If changes to the DNA sequence occur within a coding portion of a gene and are not corrected, a gene mutation results. Cancers start when a gene mutation gives rise to a faulty protein that plays a key role in cell reproduction.

    Three cell scenarios: normal, increased division, and decreased apoptosis leading to tumors.
    Figure \(\PageIndex{1}\): Cell Division and Apoptosis. In an adult organism, normal cell division is balanced by apoptosis (programmed cell death) to maintain a constant cell number in homeostasis. An increase in cell division or a decrease in apoptosis leads to a rise in the number of cells and tumor formation. (CC BY 4.0; via OpenStax).

    The Mitotic Index (MI) is a measure of the proportion of dividing cells. An elevated mitotic index (higher cellular proliferation rate) indicates more cells are dividing and is an important prognostic factor predicting both overall survival and response to chemotherapy in most cancer types. This happens due to the self-sufficiency of growth signals, insensitivity to anti-growth signals, and limitless replicative potential. The mitotic index may be elevated during processes that promote division, such as normal growth or cellular repair.
    MI can be determined by analyzing micrographs and counting the relative number of dividing versus non- dividing cells.

    • Percentage of cells in mitosis = total number of cells in all phases of mitosis x 100/total number of cells.
    • Mitotic index = total number of cells in all phases of mitosis/total number of cells.

    If you were to compare the mitotic indices of healthy tissue and tumor tissue, what differences would you expect to observe? Write proposed hypothesis.

    Table \(\PageIndex{1}\): Hypothetical data for calculating percentage of cells in mitosis and mitotic index
    Percent cells in each phase Calculate
    Tissue Type Interphase Prophase Metaphase Anaphase Telophase Percent of cells in mitosis Mitotic Index
    Normal lung 19 0 0 1 0    
    Cancerous lung 15 1 3 1 0    
    Normal stomach 18 0 0 1 1    
    Cancerous stomach 15 2 1 1 1    
    Normal ovary 17 0 1 2 0    
    Cancerous ovary 11 2 2 3 2    

    Analysis

    1. Why is the mitotic index an important parameter in cell biology? Discuss its relevance in understanding cell proliferation and tissue growth.
    2. What are some limitations of using the mitotic index as a sole indicator of tumor behavior? Discuss other factors that should be considered in conjunction with the mitotic index for a comprehensive assessment of cancer.
    3. What does the data show about the rate of cell division in cancerous tissue compared to normal tissue?
    4. Which type of cancer is the fastest growing? Explain your answer, using relevant data to support your claim.

    This page titled 4.6: Activity 5 was last modified on Tue, 01 Sep 2026 01:45:40 GMT and is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Lakshmikanta Sengupta and Susmita Sengupta.