By PAUL ELIAS
AP Biotechnology Writer

SAN FRANCISCO — Despite optimism and enthusiasm, stem cell researchers arriving here Thursday for a conference are rowing hard against strong currents of financial, political and technical turmoil.

There's even talk of trying to temper heightened public expectations that cures for diseases are imminent.

"Many of the technologies we hyped to the general public haven't worked yet," Celgene Corp. President Alan Lewis said Wednesday at a biotechnology trade show in Philadelphia. He also noted that venture capitalists "are very cautious" about investing in stem cell companies because of uncertainty over the field's future.

Still, hope springs eternal among the world's best cloners and stem cell researchers gathering in San Francisco on Thursday to show off their latest breakthroughs at the biggest professional conference on the topic to date.

The more than 1,000 researchers set to attend are excited by the prospect that they can someday coax - on command - stem cells to regenerate into spare body parts to heal the sick and injured.

"Stem cell research is the hottest thing in science right now," said Leonard Zon, president of the International Society for Stem Cell Research, which is hosting the conference dedicated to one of the most controversial issues in science.

Even the most outspoken proponents of the technology concede they are years away from actual drugs based on stem cells.

It's almost certain that the first applications of the work will be simply an unspectacular tool to help researchers gauge an experimental drug's toxicity. But the applications also will be indispensable as ways to watch how a disease progresses from the moment of inception until it matures into a deadly killer.

Beyond the technical challenges are the hot political issues.

Because scientists destroy days-old embryos to extract stem cells, powerful social conservatives, including the Roman Catholic Church and many other Christians, oppose the research as immoral. What's more, a growing number of liberal groups, such as women's rights organizations and biotechnology foes oppose the work as dehumanizing.

Because President Bush has strictly limited the amount of federal funding for the work, scientists are left to rely on support from a few philanthropic groups and one corporate backer: Geron Corp., the money-losing Menlo Park, Calif., biotechnology company that has poured $100 million into human embryonic stem cell research since 1996 - about twice the amount the U.S. government has committed.

Geron is by far the largest company in the field, and it lost about $80 million last year. Other stem cell companies are struggling to stay afloat.

Advanced Cell Technology, a Worcester, Mass., firm has run into big financial problems. It also can't obtain a steady supply of women's eggs, a necessity and a giant ethical minefield.

The egg supply has become a crucial sticking point for cloning supporters, which include California's new $3 billion stem cell agency - the California Institute for Regenerative Medicine.

Agency President Zach Hall and other scientists say that cloning human embryos to harvest stem cells will be an indispensable way to make tailor-made drugs and develop powerful research tools.

However, the institute has had its share of problems, bogged down in political fighting with state legislators over its management practices. The agency also faces a lawsuit claiming there is an overall lack of legislative oversight of its expenditures.

Still, Zon said the field is growing dramatically despite all its problems. Attendance is expected to be double what it was at the society's first conference two years ago.

The field was energized earlier this month when a South Korean research team announced they had successfully harvested stem cells from cloned embryos, a huge step toward creating tailor-made drugs for the sick.

Dr. Edward Holmes, dean of the University of California, San Diego Medical Center and a member of the board that oversees California's stem cell agency, called the Koreans' work "phenomenal," noting that it proved personalized medicine is closer than many previously thought.

"The potential seems so much more real than it did just a couple of months ago," Holmes said.

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