NASHVILLE (AP) - State Sen. Mark Green, one of the leading contenders for Tennessee governor in 2018, says he is re-thinking financial ties to a company run by a prominent GOP donor who settled a federal fraud case involving the military health care program.

The donor, Andy Miller Jr., has been a major backer of tea party candidates and issues in recent years. He bankrolled a 2011 trip to Europe for six state lawmakers billed as a "fact-finding mission" about the dangers of radical Islam and was a major supporter of former GOP Rep. Jeremy Durham, who was recently expelled from the Legislature.

Green, a former Army physician whose military background has been featured heavily in his political campaigns, said he is reevaluating his investment in Miller's company, Diatech Oncology of Franklin. The Clarksville Republican said he was inspired to invest in the company because of his own fight against colon cancer, but declined to say how much mon ey is involved.

Green, who is has long been eying a bid to succeed term-limited Gov. Bill Haslam called reassessing the investment "the right thing to do."

Federal prosecutors in Florida announced last month that Miller, his brother Tracy and their company, Healthmark Investment Trust, agreed to pay $7.8 million to settle federal allegations that a company called QMedRx Inc., in which they had partial ownership, violated the federal Anti-Kickback Statute that bans the exchange of anything of value for government business. The settlement did not include an admission of wrongdoing on their part.

The case was part of a larger effort to prosecute compound pharmacies submitting improper claims to TRICARE, the health care program for members of the U.S. military and their families around the world.

Green said he invested in Diatech because the company "has the potential to save hundreds of thousands of peoples' lives."

"I jump at the opportunity to hav e that kind of research done and figured out," Green said. "A lot of my investments are in the health care sector and cancer. ... Heck, if I don't make any money out of it, I'm advancing the research in a disease that potentially could save people."

But to Nashville attorney Bob Tuke, a former Marine who served in Vietnam, there is little question about what Green should do.

"As a veteran, I don't appreciate anyone that rips off federal government care for veterans," said Tuke.

A former Democratic candidate for the U.S. Senate, Tuke said it makes little difference that the company investigated in Florida is a separate entity from the one operating in Tennessee when the common denominator is Miller.

"There shouldn't be any investment with him personally, anything he's associated with at all," Tuke said. "Period."

Miller did not return phone calls and text messages seeking comment. But he told The Tennessean last month that Healthmark is a minority owner of the Florida company and that the case was settled to avoid the uncertainty and cost of protracted litigation.

The Millers have been major backers of politicians with tea party leanings, including perennial congressional candidate Joe Carr and Durham, who last month became the first sitting member to be ousted from the Legislature in 36 years over allegations of a series sexual harassment incidents at the state Capitol complex.

Carr in December paid $2,250 to settle a Federal Election Commission probe into a $200,000 loan made from his campaign to Life Watch Pharmacy, another company owned by Miller. Carr had failed to report the loan for which he received $9,564 in interest when he was running against U.S. Sen. Lamar Alexander in 2014 GOP primary.

The Tennessean first reported that Durham's campaign spending included loans to Life Watch Pharmacy, and that the lawmaker was also an investor in Diatach Oncology. A state campaign finance probe is also underway into a more than $190,000 discrepancy between Durham's bank records and his re-election account.

Green, who has written a memoir about a night he spent at the bedside of Saddam Hussein after the former Iraqi leader's capture in 2003, declined to specify how much money he has invested in Diatach other than that "it's no huge amount." The senator said his campaign has not spent any campaign funds on Miller's companies.

"Tragically my money sits in a checking account with no interest bearing," he said. "My campaign account is not investing in anything."