After taking hair or skin cells from patients with Fanconi anemia, the investigators corrected the defective gene in the patients' cells using gene therapy techniques pioneered in Verma's laboratory. They then successfully reprogrammed the repaired cells into induced pluripotent stem (iPS) cells using a combination of transcription factors, OCT4, SOX2, KLF4 and cMYC. The resulting FA-iPS cells were indistinguishable from human embryonic stem cells and iPS cells generated from healthy donors.

Since bone marrow failure as a result of the progressive decline in the numbers of functional hematopoietic stem cells is the most prominent feature of Fanconi anemia, the researchers then tested whether patient-specific iPS cells could be used as a source for transplantable hematopoietic stem cells. They found that FA-iPS cells readily differentiated into hematopoietic progenitor cells primed to differentiate into healthy blood cells.

"We haven't cured a human being, but we have cured a cell," Belmonte explains. "In theory we could transplant it into a human and cure the disease."

Although hurdles still loom before that theory can become practice-in particular, preventing the reprogrammed cells from inducing tumors-in coming months Belmonte and Verma will be exploring ways to overcome that and other obstacles. In April 2009, they received a $6.6 million from the California Institute Regenerative Medicine (CIRM) to pursue research aimed at translating basic science into clinical cures.

"If we can demonstrate that a combined iPS-gene therapy approach works in humans, then there is no limit to what we can do," says Verma.

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