• Cachexia

    Loss of body weight and muscle mass, and weakness that may occur in patients with cancer, AIDS, or other chronic diseases. [NCI]

  • Cancer incidence rate

    The number of new cancers of a specific site/type occurring in a specified population during a year. Usually expressed as the number of cancers per 100,000 population at risk. [Multilingual Cancer Glossary]

  • Cancer stem cells

    Cells that divide to replenish a population of cancer cells. They are the cells that survive a therapeutic treatment that destroys the vast majority of the tumour. Cancer stem cells (CSCs) divide to produce cells that make up the returning tumour and are often the cells that leave the primary tumour, survive in the blood stream, and metastasize to distant organs. Also called tumour initiating cells. [Adapted from: Nguyen, D.H. (2016). Systems Biology of Tumour Physiology: Rethinking the Past, Defining the Future, Chapter 2, Cellular plasticity, cancer stem cells, and cells-of-origin. Springer.]

  • Carcinogen

    A carcinogen is an agent with the capacity to cause cancer in humans. Carcinogens may be natural, such as aflatoxin, which is produced by a fungus and sometimes found on stored grains, or manmade, such as asbestos or tobacco smoke. Carcinogens work by interacting with a cell’s DNA and inducing genetic mutations. [NHGRI]

  • Cell Death

    If a cell has an error in its DNA that cannot be repaired, it may undergo programmed cell death (apoptosis). Apoptosis is a common process throughout life that helps the body get rid of cells it doesn’t need. Cells that undergo apoptosis break apart and are recycled by a type of white blood cell called a macrophage. Apoptosis protects the body by removing genetically damaged cells that could lead to cancer, and it plays an important role in the development of the embryo and the maintenance of adult tissues. [From]

  • Cell Division

    There are two types of cell division: mitosis and meiosis. Most of the time when people refer to “cell division,” they mean mitosis, the process of making new body cells. Meiosis is the type of cell division that creates egg and sperm cells. Mitosis is a fundamental process for life. During mitosis, a cell duplicates all its contents, including its chromosomes, and splits to form two identical daughter cells. Because this process is so critical, the steps of mitosis are carefully controlled by a number of genes. When mitosis is not regulated correctly, health problems such as cancer can result. The other type of cell division, meiosis, ensures that humans have the same number of chromosomes in each generation. It is a two-step process that reduces the chromosome number by half—from 46 to 23—to form sperm and egg cells. When the sperm and egg cells unite at conception, each contributes 23 chromosomes so the resulting embryo will have the usual 46. Meiosis also allows genetic variation through a process of DNA shuffling while the cells are dividing. [From]

  • Cell Plasticity

    The potential of a differentiated cell (a cell that has matured to have a specific function and identify) to de-differentiate back into a stem-like state and then to differentiate into a new state. The premise is that a cell’s identity and function are not permanently fixed after a cell has differentiated. Within a tumour, neighbouring cells change from one shape to another in ways that normal cells do not. [Adapted from: Nguyen, D.H. (2016). Systems Biology of Tumour Physiology: Rethinking the Past, Defining the Future, Chapter 2, Cellular plasticity, cancer stem cells, and cells-of-origin. Springer.]

  • Chromatin

    Chromatin is a substance within a chromosome consisting of DNA and protein. The DNA carries the cell’s genetic instructions. The major proteins in chromatin are histones, which help package the DNA in a compact form that fits in the cell nucleus. Changes in chromatin structure are associated with DNA replication and gene expression. [NHGRI]

  • Chromosome

    Thread-like structures located inside the cell nucleus. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure. Except for sperm and eggs, all human cells contain 46 chromosomes (23 pairs). [Adapted from NCI; NHGRI]

  • Co-stimulatory signal

    The second stimulation required for T-cells to become fully activated (also called Signal 2). [Patient Resource LLC]

  • Cohort study

    A research study that compares a particular outcome (such as lung cancer) in groups of individuals who are alike in many ways but differ by a certain characteristic (for example, female nurses who smoke compared with those who do not smoke). [NCI]

  • Complementary and alternative medicine

    Forms of treatment that are used in addition to (complementary) or instead of (alternative) standard treatments. These practices generally are not considered standard medical approaches. Standard treatments go through a long and careful research process to prove they are safe and effective, but less is known about most types of complementary and alternative medicine. Complementary and alternative medicine may include dietary supplements, megadose vitamins, herbal preparations, special teas, acupuncture, massage therapy, magnet therapy, spiritual healing, and meditation. Also called CAM. [NCI]

  • Confidence interval

    It is impossible to study every single person in a given population, so researchers select a sample or sub-group of the population. This means that the researcher can only estimate the parameters (i.e. characteristics) of a population, the estimated range being calculated from a set of sample data. Therefore, a confidence interval is a way to measure how well your sample represents the population you are studying. The probability that the confidence interval includes the true value within a population is called the confidence level of the confidence interval. You can calculate a confidence interval for any confidence level you like, but the most commonly used value is 95%. A 95% confidence interval tells us that we can be 95% certain that the true rate lies somewhere between the lower and upper limits of the confidence interval. (Adapted from

  • CRISPR-Cas9

    A laboratory tool used to change or “edit” pieces of a cell’s DNA. CRISPR-Cas9 uses a specially designed RNA molecule to guide an enzyme called Cas9 to a specific sequence of DNA. Cas9 then cuts the strands of DNA at that point and removes a small piece, causing a gap in the DNA where a new piece of DNA can be added. CRISPR-Cas9 is a breakthrough in science that will have important uses in many kinds of research. In cancer research, it may help to understand how cancer forms and responds to treatment as well as new ways to diagnose, treat, and prevent it. [NCI]

  • CTLA-4 (cytotoxic T lymphocyte associated antigen 4)

    A protein receptor found on the surface of T-cells. This protein is part of the CTLA-4 checkpoint pathway, which can shut down an immune system response in its early stages. Certain cancer cells have the ability to turn on this checkpoint, which stops the immune response against the cancer cells. [Patient Resource LLC]

  • Cytokines

    Proteins released by immune cells to communicate with other immune cells. Certain cytokines, such as interferon and interleukin, help regulate specific immune system functions. [Patient Resource LLC]

  • Cytotoxicity

    Refers to the ability of certain chemicals or mediator cells to destroy living cells by inducing either accidental cell death (necrosis) or programmed cell death (apoptosis). Given this information, the ability to accurately measure cytotoxicity can prove to be a very valuable tool in identifying compounds that might pose certain health risks to humans. Furthermore, by determining the cytotoxicity levels of cancer cells themselves, new drugs can be developed to hinder the proliferation of cancer cells by disrupting their genetic material or by blocking the nutrients that the cells need to survive. [Adapted from :]