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  • Rights: The University of Waikato
    Published 29 July 2008 Referencing Hub media
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    Hayley Reynolds (Auckland Bioengineering Institute) and Associate Professor Rod Dunbar (University of Auckland) explain the effect of UV on melanocytes1.

    Acknowledgements:
    Dr Roger Uren
    Henry Cavillones
    Ed Tarwinski
    Carita Bonita
    Sunny Ripert
    American Society of Clinical Oncology

    Transcript

    HAYLEY REYNOLDS
    A melanoma2 is cancer3 of the skin. There are three different types of skin cancer, but melanoma is the most aggressive and it’s the most serious. It can spread very quickly throughout the body, and it’s a cancer of the pigment4 cells in the skin, which are called melanocytes.

    DR ROD DUNBAR
    These are the cells that would normally contribute to skin pigmentation5, so different ethnic groups have different skin colour – that’s because their cells called melanocytes make different levels of pigment. Those cells are also the same cells that respond to ultraviolet light, and induce the tanning response. So in fairer skin people, particularly you notice, when exposed to UV light6 over time, the skin colour changes, and that is because the cells inside the skin – the melanocytes – make more pigment in response to UV, and this is probably a protective response to prevent UV damaging the cells lower down.

    These melanocytes are sitting in the middle of the skin, if you look at it in cross section, effectively between the epidermis7 and the dermis8. And they usually sit on their own, and they have long finger-like projections, like a tree branch almost, that push out into the gaps between cells. And this then allows them to make pigment and to push it into other cells.

    In many of us, there are collections of melanocytes, which are the moles and freckles. In some cases, these collections of melanocytes can become cancerous, and what that means is that the cells there don't just collect as a group, but they also start to grow, and when cells divide, as in any part of the body, the collection starts to look bigger and bigger and bigger, and so one of the first signs of a melanoma developing is a mole9 that changes in size.

    The other thing that melanoma cells do, as they start to grow, is they start to burrow into the skin. It is a common thing in cancer that the cells start to lose the normal relationships with their neighbours. Normally, cells are very tightly constrained to a neighbourhood – as if you can't move out of a certain number of blocks of your city. When cells start to turn cancerous, one of the things that makes them so dangerous is that they start to roam in other parts of the body. And they can arrive in parts of the body where they grow very very well, and they start to disrupt the function of that part of the body.

    1. melanocytes: Cells in the epidermis of the skin and elsewhere that produce melanin.
    2. melanoma: A cancer of a particular type of skin cell, called a melanocyte. Melanocytes are responsible for skin colour. The cancer usually appears on the skin, but may affect the eye and membranes (for example, the lining of the nose, the meninges of the brain or the lining of the anus).
    3. cancer: The term for a group of more than 100 diseases in which abnormal cells divide and multiply uncontrollably.
    4. pigment: Any fine, insoluble, dry, solid particles used to give colour. In biology, the dye-like material produced generally in the superficial parts of animals that gives colour to skin, eyes and hair.
    5. pigment: Any fine, insoluble, dry, solid particles used to give colour. In biology, the dye-like material produced generally in the superficial parts of animals that gives colour to skin, eyes and hair.
    6. UV (ultra violet) light: Light that is invisible to the human eye and at a wavelength between 300–400 nanometres. UV light is what causes sun burn and can cause some types of cancer.
    7. epidermis: The outer layer of cells on a plant. The surface layer of the two main layers that make up the skin in animals contains basal cells, squamous cells and melanocytes.
    8. dermis: The inner layer of the two main layers that make up the skin. Contains the roots of hairs, glands (that make sweat, which helps regulate body temperature, and sebum, which is an oily substance that helps keep the skin from drying out), blood vessels, lymph vessels and nerves.
    9. mole: 1. A pigmented spot on the skin that contains a cluster of melanocytes. Also called a nevus. 2. (mol) One of the SI base units, the mole is defined as being the amount of substance that contains as many elementary entities as there are atoms in exactly 12 g of carbon-12.
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      melanocytes

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    2. Cells in the epidermis of the skin and elsewhere that produce melanin.

      pigment

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    4. Any fine, insoluble, dry, solid particles used to give colour. In biology, the dye-like material produced generally in the superficial parts of animals that gives colour to skin, eyes and hair.

      dermis

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    6. The inner layer of the two main layers that make up the skin. Contains the roots of hairs, glands (that make sweat, which helps regulate body temperature, and sebum, which is an oily substance that helps keep the skin from drying out), blood vessels, lymph vessels and nerves.

      melanoma

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    8. A cancer of a particular type of skin cell, called a melanocyte. Melanocytes are responsible for skin colour. The cancer usually appears on the skin, but may affect the eye and membranes (for example, the lining of the nose, the meninges of the brain or the lining of the anus).

      UV (ultra violet) light

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    10. Light that is invisible to the human eye and at a wavelength between 300–400 nanometres. UV light is what causes sun burn and can cause some types of cancer.

      mole

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    12. 1. A pigmented spot on the skin that contains a cluster of melanocytes. Also called a nevus.

      2. (mol) One of the SI base units, the mole is defined as being the amount of substance that contains as many elementary entities as there are atoms in exactly 12 g of carbon-12.

      cancer

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    14. The term for a group of more than 100 diseases in which abnormal cells divide and multiply uncontrollably.

      epidermis

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    16. The outer layer of cells on a plant. The surface layer of the two main layers that make up the skin in animals contains basal cells, squamous cells and melanocytes.