Discover new types of cell division

(Researchers at the University of Wisconsin Carbone Cancer Center have discovered a new form of cell division in human cells.

They believe that this new form of division serves as a mechanism to hinder nature in the process of faulty cell division, preventing some cells from the path to cancer.

"If we can promote this new type of cell division, which we call klerokinesis, we can prevent some cancers from developing," said lead researcher Dr. Mark Burkard. Professor of hematology-oncology at the UW School of Medicine and Public Health School faculty said.

Burkard presented this discovery on December 17 at the annual meeting of the American Society for Cell Biology in San Francisco.

As a doctor examining breast cancer patients, Burkard studies cancers, in which cells contain too many chromosomes, a condition called polyploidy.

About 14% of breast cancers and 35% of pancreatic cancers have three or more sets of chromosomes, instead of the usual two. Many other cancers have cells that contain chromosomal defects, not too much or too little.

"Our goal in the laboratory is to find ways to develop new treatment strategies for breast cancer due to polyploid status , " Burkard said. The original goal of this study was to create human cells with more chromosomes. But after following the accepted formulas, the researchers unexpectedly observed new forms of cell division.

So far, Burkard and most cell biologists today have adopted a last-century hypothesis developed by the German biologist Theodor Boveri, who studied the sea urchin eggs. Boveri surmised that faulty cell division led to cells with abnormal chromosomal sets, and then uncontrolled cell growth identified cancer characteristics. With evidence accumulated over the years, most scientists have accepted this hypothesis.

Normal cell division is at the center of an organism's ability to grow from a single fertilized egg into a fully developed individual. More than one million million divisions must have place to take place. In each division, a mother cell becomes two daughter cells. Even in a fully grown adult, many types of cells often regenerate through cell division.

The basic process of self-replicating cells begins with a synthesis stage, when a copy is made up of cellular components, including chromosomes containing DNA in the nucleus. Then, in mitosis, two sets of chromosomes are separated in opposite directions, while still in the same cell. Finally, during cell division, a cell is divided into two daughter cells, at the end of the mitosis process.

Burkard and his team created cells with too many chromosomes - to mimic cancer. Scientists prevent cell division with a chemical and wait to see what happens.

"We expect to recover a number of cells with abnormal chromosomes," Burkard explained.

The researchers found that, instead of abnormal appearance, daughter cells are normal most of the time. Contrary to Boveri's hypothesis, abnormal cell division rarely has a long-term negative impact on human cells.

So the group decided to see how human cells restore normal chromosome sets by following up with a microscope. This microscope is capable of recording video images.

"We started with two kernels in one cell," Burkard said. "To our great surprise, we saw bulging cells on one side into two cells without needing to pass through the cell division."

Each cell in the two new cells inherits an intact nucleus containing a complete set of chromosomes. Separation occurs, erratically, in a slower growth phase than at the end of mitosis.

Scientists have done some additional experiments to ascertain that the division they observed was different from cell division.

"We have had a hard time convincing ourselves because this type of cell division has never appeared in any textbook ," Burkard said.

Over time, they discovered that only 90% of daughter cells had recovered a normal chromosome supplement. Burkard wants to push statistics to 99%.

"If we can push the cells towards this new form of cell division, we can be able to keep normal cells and reduce the incidence of cancer," he said.

Burkard thinks that among all the cell division rings an organism undergoes, every time during cell division can fail. And that new form of division is a containment mechanism that allows cells to recover from errors and normal development.

The team named this new cell division type klerokinesis to distinguish it from cell division. Burkard was supported by Dr. William Brockliss to name the cell division; klero is a Greek prefix meaning "allocated inheritance".

The project collaborators include Dr. Beth Weaver, UW assistant professor of cell biology and regeneration, Dr. Alka Choudhary, Robert Lera; Dr. Melissa Martowicz and Dr. Jennifer Laffin.