HOUSTON, Feb. 9 (Xinhua) -- Polyploid cells in the liver can protect the liver against cancer, said researchers from the U.S. University of Texas (UT) Southwestern on Friday.

Researchers of the Children's Medical Center Research Institute (CRI) at UT Southwestern developed new methods to transiently and reversibly alter ploidy for the first time, which led to the finding, the university said in a press release.

"This was an important advance because it allowed us to separate the effects of ploidy from the effects of genes that change ploidy," said Hao Zhu, assistant professor at CRI.

"Using these techniques, we were able to show polyploid liver cells protected the liver against cancer formation in the mouse," said Hao, who is also a cancer research scholar at Cancer Prevention Research Institute of Texas (CPRIT).

Polyploid cells carry two or more sets of chromosomes. Most human cells are diploid, meaning they have two sets of chromosomes -- one set inherited from each parent.

Although rare in most human tissues, these cells are prevalent in the hearts, blood, and livers of mammals. Polyploidization also increases significantly when the liver is exposed to injury or stress from fatty liver disease or environmental toxins that could cause liver cancer later in life.

In humans, cancer develops when genes that suppress cancer, known as tumor suppressors, are lost and when mutations or genes that promote cancer, known as oncogenes, are gained or activated.

"We found polyploidy in liver cells did not strongly affect the activity of some oncogenes, but it did protect against the loss of tumor suppressor genes," said Zhu, who is also an assistant professor of Pediatrics and Internal Medicine at UT Southwestern.

"When normal diploid cells lose one or both copies of tumor suppressor genes, cancers can form. Polyploid cells, which carry additional copies of important tumor suppressor genes, are better protected and more resistant to cancer formation because they have these extra copies of the genome," said Zhu.

Future work in the Zhu's lab will focus on the role of polyploidy in a variety of chronic liver diseases that frequently lead to liver cancer.

UT Southwestern, one of the premier academic medical centers in the United States, integrates pioneering biomedical research with exceptional clinical care and education.

UT Southwestern is based in Dallas, about 380 km northwest of Houston, and its physicians provide medical care in about 70 specialties to more than 100,000 hospitalized patients and oversee approximately 2.2 million outpatient visits a year.