CANCER CELLS DO NOT UNDERGO APOPTOSIS

 

WHAT IS APOPTOSIS?

As you read this, millions of your cells are dying to ensure your survival.  The health of multicellular organisms depends not only on the ability of cells to grow and divide, but also self-destruct when they are no longer needed or become damaged.  This programmed cell death is known as apoptosis.

http://www.bio.miami.edu/~cmallery/255/255hist/mcb1.19.apoptosis.jpg

 

WHAT HAPPENS DURING APOPTOSIS?

 

1.  Intracellular material is degraded.

2.  The cell breaks into fragments surrounded by membrane.

3.  The membrane is "tagged" with a "destroy me" signal that attracts macrophages which engulf the fragments and complete the destruction. 

 

 http://219.221.200.61/ywwy/zbsw(E)/edetail13.htm

WHY DO CELLS UNDERGO APOPTOSIS?

 

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1.  The cell has been damaged beyond repair.

 

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2.  The cell has outlived its usefulness.

    EX: Shut down of cytotoxic T-cells during the immune response occurs by apoptosis

Recall that during the immune response, Helper T-cells stimulate the proliferation of B-cells and T-cells allowing for the production of antibodies and cytotoxic T-cells.  The cytotoxic T-cells destroy infected body cells.  When all traces of the pathogen have been removed from the body, suppressor T-cells shut the cell-mediated and humoral responses off.  However, millions of cytotoxic T-cells are still circulating looking for infected body cells.  The body removes these cells by programmed apoptosis and subsequent by ingestion by macrophages thus leaving only memory B and T-cells behind from the encounter.

 

 

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3.  The cell has become senescent (shows deterioration associated with aging).

   

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4.  The death of the cell is necessary for the organism to reach its final form during embryonic development.

        EX: Formation of digits in humans

    By the fourth week of human embryonic development, limb buds appear as outpockets from the body wall.  By six-weeks, the terminal (end) portion of the limb buds flatten to form handplates and footplates (figure A).  Forty-eight days after fertilization, select cells within the interdigital spaces of the hand and footplates undergo apoptosis allowing the digits to separate (figure B).  Digit separation is complete by fifty-six days after fertilization (figure C).

 

 

Langman's Medical Embryology 7th Edition

T.W Sandler 1995  

  If the cells in the interdigital space fail to undergo apoptosis, the fetus will be born with webbed hands and/or webbed feet.  The medical term for this condition is syndactyly.  There are many degrees of syndactlyl ranging from complete (no digit separation), to incomplete (partial digit separation).  Sometimes there is only a thin layer of skin remaining in the interdigital space. 

                                        

http://newborns.stanford.edu/images/syndactylyDAClark.jpg

                                                                                                         

Syndactyly occurs in 2-3 of every 10,000 live births.  It can be associated with genetic disorders or may occur sporatically without any other conditions.  

 

Cancer not do die.  They are immortal.

 

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