Researchers isolate compound that obstructs cell growth in multiple myeloma and other cancers fueled by certain proteins (5/15/2008)

Extract of coconut shrinks tumors by killing cancer cells

A natural compound extracted from the milk of coconuts has proven effective in curbing the uncontrolled growth of certain cancer tumors, according to researchers at Mayo Clinic.

A recently published study by Drs. A. Keith Stewart and Rodger E. Tiedemann of the Mayo Clinic Cancer Center indicates that a substance called kinetin riboside, prevents new cell growth in tumors controlled by cyclin D proteins. (Cyclin D proteins are members of the cyclin family of proteins related to cell division.) Kinetin riboside is found in minute quantities in coconut milk and other natural plants and is related to the hormones that govern root growth in plants.

The results of the study were published in the May 1, 2008, issue of the Journal of Clinical Investigation. The journal is published by the American Society for Clinical Investigation, founded in 1908 to recognize important advances in medical research. "Cyclin D is like the gas pedal for cell progression," Stewart said. "In cancer cells, too much cyclin is produced and overwhelms the cell, causing it to grow too quickly. Kinetin riboside appears to switch that process off."

Three closely related proteins called cyclin D1, D2 and D3 are found in all proliferating cell types and collectively control the progression of cells through their cell cycle. Since D-cyclin proteins are essential to cell division, they are implicated in certain types of cancer.

After screening more than 4,000 drugs and natural compounds for their ability to control cyclin, the study narrowed the possibilities to about 30. Eventually, Stewart and Tiedemann focused on only one-kinetin riboside-as a way to control the cyclin D proteins.

Kinetin riboside works by rapidly binding itself to the cyclin gene and switching off the normal progression of cell division. Laboratory tests on mice demonstrated some cancer cells died as a result of the process, causing tumors to shrink in size. Healthy body cells remained unaffected.

The Mayo study focused on cells found in multiple myeloma tumors, but Cyclin D1 and D2 is important in the progression of many other cancers, including breast, prostate, colon, parathyroid adenoma, certain lymphomas and melanoma.

"Kinetin riboside not only stops myeloma cells from growing, it kills large numbers of the tumor cells as well," Tiedemann says. "Its effectiveness in controlling cyclin holds the promise of a therapy for a number of different cancers."

The researchers are now focusing on developing modified versions of the compound that offer the same benefits but possess specific characteristics that make it more desirable for the development of clinical drugs.

More than 60,000 Americans have been diagnosed with multiple myeloma. An estimated 15,000 new cases are reported each year and it accounts for a disproportionate 2 percent of all cancer deaths. The research was partially funded by the Multiple Myeloma Research Foundation and The Leukemia & Lymphoma Society.

Note: This story has been adapted from a news release issued by the Mayo Clinic

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