Multipolar spindles
Encyclopedia
Multipolar spindles are spindle formations characteristic of cancer
cells. Spindle formation is mostly conducted by the aster
of the centrosome
which it forms around itself. In a mitotic cell wherever two asters convene the formation of a spindle occurs.
Mitosis
consists of two independent processes: the intra-chromosomal and the extra-chromosomal (formation of spindle) changes both of these being in total coordination of each other.
In cancer cells, it has been observed that the formation of the spindles comes before when com pared to the chromosome
s. Due to this the prophase
stage is briefer allowing metaphase to occur in advance. Chromosomes then are unable to reach the metaphase
plate and are stranded behind. These chromosomes still have asters attached them and when met with other
asters, multiple spindles are formed.
occurs in these cells, the chromosomes are separated abnormally and results in aneuploidy
of both daughter cells. This can lead to loss of cell viability and chromosomal instability.
. Cancer is defined by uncontrolled cell growth
and malignant cells can undergo cell division
with multipolar spindles because they can group multiple centrosomes into two spindles. These multipolar spindles are often assembled early in mitosis
and rarely seen towards the later stages.
Research has shown possible causes of formation of multipolar spindles. A possible causes of multipolar spindle formation involve regulation of protein kinase
family known as Aurora kinase
. Aurora kinase has two forms which are designated Aurora kinase A and Aurora kinase B. These proteins play a key role in mitosis and are regulated by phosphorylation
and degradation. Deregulation of these proteins can lead to multiple centrosome formation and aneuploidy. In some human cancers, the expression and kinase activity of Aurora kinases have been up-regulated and has been looked into as a possible target for anti-cancer drugs.
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
cells. Spindle formation is mostly conducted by the aster
Aster (cell biology)
An aster is a cellular structure shaped like a star, formed around each centrosome during mitosis in an animal cell. Astral rays, composed of microtubules, radiate from the centrosphere and look like a cloud....
of the centrosome
Centrosome
In cell biology, the centrosome is an organelle that serves as the main microtubule organizing center of the animal cell as well as a regulator of cell-cycle progression. It was discovered by Edouard Van Beneden in 1883...
which it forms around itself. In a mitotic cell wherever two asters convene the formation of a spindle occurs.
Mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
consists of two independent processes: the intra-chromosomal and the extra-chromosomal (formation of spindle) changes both of these being in total coordination of each other.
In cancer cells, it has been observed that the formation of the spindles comes before when com pared to the chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
s. Due to this the prophase
Prophase
Prophase, from the ancient Greek πρό and φάσις , is a stage of mitosis in which the chromatin condenses into a highly ordered structure called a chromosome in which the chromatin becomes visible. This process, called chromatin condensation, is mediated by the condensin complex...
stage is briefer allowing metaphase to occur in advance. Chromosomes then are unable to reach the metaphase
Metaphase
Metaphase, from the ancient Greek μετά and φάσις , is a stage of mitosis in the eukaryotic cell cycle in which condensed & highly coiled chromosomes, carrying genetic information, align in the middle of the cell before being separated into each of the two daughter cells...
plate and are stranded behind. These chromosomes still have asters attached them and when met with other
asters, multiple spindles are formed.
Characterstics
Cells with multipolar spindles are characterized by more than two centrosomes, usually four, and sometimes have a second metaphase plate. The multiple centrosomes segregate to opposite ends of the cell and the spindles attach to the chromosomes haphazardly. When anaphaseAnaphase
Anaphase, from the ancient Greek ἀνά and φάσις , is the stage of mitosis or meiosis when chromosomes move to opposite poles of the cell....
occurs in these cells, the chromosomes are separated abnormally and results in aneuploidy
Aneuploidy
Aneuploidy is an abnormal number of chromosomes, and is a type of chromosome abnormality. An extra or missing chromosome is a common cause of genetic disorders . Some cancer cells also have abnormal numbers of chromosomes. Aneuploidy occurs during cell division when the chromosomes do not separate...
of both daughter cells. This can lead to loss of cell viability and chromosomal instability.
Presence in cancer cells
The presence of multipolar spindles in cancer cells is one of many differences from normal cells which can be seen under a microscopeMicroscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...
. Cancer is defined by uncontrolled cell growth
Cell growth
The term cell growth is used in the contexts of cell development and cell division . When used in the context of cell division, it refers to growth of cell populations, where one cell grows and divides to produce two "daughter cells"...
and malignant cells can undergo cell division
Cell division
Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...
with multipolar spindles because they can group multiple centrosomes into two spindles. These multipolar spindles are often assembled early in mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
and rarely seen towards the later stages.
Research has shown possible causes of formation of multipolar spindles. A possible causes of multipolar spindle formation involve regulation of protein kinase
Protein kinase
A protein kinase is a kinase enzyme that modifies other proteins by chemically adding phosphate groups to them . Phosphorylation usually results in a functional change of the target protein by changing enzyme activity, cellular location, or association with other proteins...
family known as Aurora kinase
Aurora Kinase
Aurora kinases are serine/threonine kinases that are essential for cell proliferation. The enzyme helps the dividing cell dispense its genetic materials to its daughter cells. More specifically, Aurora kinases play a crucial role in cellular division by controlling chromatid segregation...
. Aurora kinase has two forms which are designated Aurora kinase A and Aurora kinase B. These proteins play a key role in mitosis and are regulated by phosphorylation
Phosphorylation
Phosphorylation is the addition of a phosphate group to a protein or other organic molecule. Phosphorylation activates or deactivates many protein enzymes....
and degradation. Deregulation of these proteins can lead to multiple centrosome formation and aneuploidy. In some human cancers, the expression and kinase activity of Aurora kinases have been up-regulated and has been looked into as a possible target for anti-cancer drugs.