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Amoeba could help fight cancers


 

Dictyostelium discoideum

Experiments in a soil-dwelling amoeba have provided insight that could help us treat cancers characterized by PTEN mutations, researchers have reported in PLOS ONE.

The team discovered that this amoeba has two genes that function like the human tumor suppressor PTEN.

And increasing expression of one of these genes compensated for a mutation in the other gene.

If the same method works in humans with mutated PTEN, this finding could have implications for a range of cancers.

PTEN mutations are thought to be involved in nearly half of all leukemia cases, 40% of breast cancer cases, and up to 70% of prostate cancer cases.

“If you look at tumors across the board . . . , you find that PTEN is the most generally mutated gene, and, when you mutate PTEN in mice, you cause tumors,” said study author David Soll, PhD, of the University of Iowa in Iowa City.

He and his colleagues found that the amoeba Dictyostelium discoideum has the gene ptenA, which mutates similarly to the human PTEN gene and causes behavioral defects in the cell.

They also found a close relative of ptenA in the amoeba, called lpten, that performs the same functions of ptenA but to a lesser degree.

The researchers hypothesized that ramping up the presence of lpten could compensate for the mutated ptenA.

They tested this theory by placing lpten in a plasmid behind a powerful promoter designed to overexpress the gene. They then introduced the super-charged lpten into a cell with the mutated ptenA gene.

The team found that the overexpressed lpten gene fully compensated for all of the defects in the ptenA mutant.

If this method works in human cells, it could lead to a new way to treat cancers, the researchers said. They are now aiming to identify a drug that would activate the promoter for one of PTEN’s close relatives.

Once a patient is diagnosed with cancer caused by a PTEN mutation, the patient could take the drug, overexpress the PTEN replacement gene, and potentially stop cancer in its tracks, Dr Soll said.

This research has also led Dr Soll and his colleagues to study other human genes that may be able to step in for the mutated PTEN gene and perform the same tumor-suppressing role. The team is currently studying 2 close relatives of PTEN.

“And nature might have put them there just for that; that’s the curious thing,” Dr Soll said. “Somewhere, there may be a backup system, what we call ‘redundancy,’ that might be the basis for better identifying tumors and possibly creating cancer-fighting drugs. You have another gene which might be able to step in for the broken gene to keep things normal, and that’s what we’re playing with here. It’s very sophisticated.”

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