Lentivectors for Stem Cell Transduction
Authors: Theodore Friedman
Journal: Molecular Therapy (2004)

Research published the first week of October 2004 in the early online edition of the The Proceedings of the National Academy of Sciences, demonstrates that lentiviral vectors might be useful for the introduction of therapeutic genes into neural stem cells. The ability to introduce foreign genes stably into the genome of adult stem cells is a key challenge for researchers studying the process of development and those developing experimental therapeutics for acquired and genetic disease in humans. In the new study, Luigi Naldini and coworkers used in vivo marking studies to show that injection of lentiviral vectors into the subventricular zone of the adult mouse brain lead to efficient gene transfer into long-term self- renewing neural precursors. Importantly, they also showed that they could detect robust and stable expression of the green fluorescent protein (GFP) reporter gene in the neural progeny of the precursor cells throughout the subventricular zone and its rostral extension, up to the olfactory bulb. They showed that the marked precursor cells displayed selfrenewal and multipotency, both characteristics of neural stem cells. The Proceedings of the National Academy of Sciences, online, doi: 10.1073/0404180101 New research shows that stem cells taken from umbilical cord blood and given intravenously, along with a drug known to temporarily breach the brain's protective barrier, can dramatically reduce stroke size and damage. The study was published in the October 2004 issue of the journal, Stroke. In an animal model of stroke, researchers first gave the drug, mannitol, to enable passage through the blood-brain barrier, and then transfused human umbilical cord blood cells. When treated within the first hours and days, stroke size decreased by forty percent and the resulting disability was significantly reduced. “We have two potential routes of delivery, intravenously through the jugular vein or directly transplanting the cells into the brain,” says lead author, Dr. Cesario Borlongan. Initial studies comparing the two approaches showed the intravenous approach ineffective until researchers added mannitol. “Intravenous delivery poses an efficient and noninvasive cell therapy for disorders characterized by a narrow therapeutic window,” the researchers write. “A multidrug treatment for stroke may be realized via a cell-based therapy that involves routine clinical IV infusion of stem/pro- genitor cells allowing the biological release of a cocktail of trophic factors into the brain.” Although no evidence could be found of the umbilical cord blood stem cells themselves in the brain three days after the treatment, evidence of neuroprotection was clear, Dr. Borlongan says. “The critical factors we have seen elevated in this stroke animal model are the neurotrophic factors.” “When we blocked the neurotrophic factors, it blocked the positive effect,” Dr. Borlongan explains. “This is an important finding because it shows that umbilical cord blood cells do not have to become new brain cells to protect the brain,” says Dr. Paul Sanberg, a coauthor on the study. A separate article in the same issue of Stroke shows that ten times the number of stem cells or more would be needed to produce similar results if cells were given intravenously without any help crossing the blood-brain barrier. The first study used 200,000 umbilical cord blood cells and a low dose of mannitol. The second study showed a dose-response relationship with significant recovery in behavioral performance when one million or more cells were given, says Dr. Sanberg. Stem cells are difficult to harvest, so by using mannitol or similar drugs, it may be possible to treat stroke patients in the future with cells from only a few umbilical cords, adds Sanberg. Dr. Borlongan is a consultant and Dr. Sanberg is cofounder of Saneron CCEL Therapeutics, Inc., which provided the umbilical cord cells for the study. Stroke, online, dois: 10.1161/01.STR.0000141681.06735.9b and 10.1161/01.STR.0000141680.49960.d7 Phase II trials of a new antisense cancer drug will soon be underway in the wake of a successful Phase I study. In the Phase I study the drug, OGX-011, being developed by OncoGenex Technologies Inc. (Vancouver, BC) and Isis Pharmaceuticals, Inc. (Carlsbad, CA), inhibited the production of clusterin, a protein that protects cell survival. Clusterin is overproduced in many cancers, where it protects the cancer cells from apoptosis and counters the effectiveness of more standard treatment regimens. Dr. Kim Chi told the EORTC-NCI- AACR* Symposium on Molecular Targets and Cancer Therapeutics on 29 September 2004 that the Phase I trial was able to demonstrate that the target clusterin was inhibited by OGX- 011 in patients’ cancers in a dose- dependent manner. “This means that the drug is doing what it is supposed to be doing-something that we can't always say about targeted therapeutics-and we were able to identify a biologically active dose,” he said. Pre-clinical studies had shown that blocking the production of clusterin with OGX-011 impaired a cancer cell's survival and enhanced the effectiveness of standard chemotherapy, radiation and hormone therapy. Twenty- five patients with localized prostate cancer that was to be removed by surgery were given escalating doses in the Phase I trial. Two conventional prostate cancer hormone therapies, buserelin and flutamide, were given alongside OGX- 011. Post surgery analysis of the patients’ prostate cancers showed that higher doses of OGX-011 were correlated with lower clusterin levels within the cancer cells. The drug was well tolerated by patients. The Phase II studies will look at response rates from OGX-011 plus standard chemotherapy in patients with metastatic, hormone-refractory prostate, breast and lung cancer. Phase II breast and prostate studies will begin near the end of the year, and a Phase I lung cancer trial started in September. The trials will recruit around forty to fifty patients each and accrual should be complete in around six to twelve months. * EORTC (European Organisation for Research and Treatment of Cancer); NCI (National Cancer Institute); AACR (American Association for Cancer Research). When I heard of the death of Francis Crick, I was thinking about science—some recent experiments, some interesting results, and what to do next. I also happened to be listening to the radio, on which was playing the sixth symphony of Beethoven, the “Pastoral.” It is one of the more serene pieces of music ever written; not fiery, not feverishly heroic as is much of mature Beethoven, but rather a pensive and peaceful glorification of nature. Coincidentally, as I was driving to the memorial ceremony for Francis Crick at the Salk Institute last week, Beethoven was again playing, this time his “Eroica Variations,” a theme that he later used as the basis for his paean to his heroic human ideal—Napoleon—in his third symphony, the “Eroica.” In these immortal creations, Beethoven presented two different visions of the beauty and power of nature and of the spirit of humanity. He saw nature and humans as no one had seen them before, and used the magical innate eloquence and power of music as no one had done before to connect with nature, often to rail against it but more often to revel in it and to reveal to humanity a glimpse of its universal beauty and power. He saw through irrelevant distractions and expressed core human yearning in incomparable musical forms. The last movement of the “Pastoral” is one of the most sublime expressions of thanks ever uttered by humanity— thanks to God and to nature for the birds that he could hear only in his thoughts and his memory, for the trees, and for the sky. The spiritual connection between Beethoven and Francis Crick is powerful—how Beethoven would have admired and probably even have envied Francis Crick! Crick did for science what Beethoven did for music— they both illuminated human creativity in novel ways. They presented to humanity a picture of the universal beauty and principles of art and knowledge. They enabled us to understand the incomprehensible nature of life and thought. That insight could very well have been Beethoven's idea of the ultimate power and glory of humanity. One can imagine Beethoven asking Crick to explain life, to explain the bird songs that he himself could only remember and the searing or triumphal music that he could only imagine or hear in his head. One can only imagine how dazzled he would have been by Crick's unifying picture of the biology of his creativity. Crick could very well have been the kind of immortal hero that Beethoven was seeking. It is not difficult to imagine Beethoven dedicating the beauty of the pastoral symphony and the heroism of the Eroica variations to Crick, if only they had known each other. When we finally achieve a true understanding of the biology of creativity and consciousness, we and future generations will certainly owe much of it to the towering work of Francis Crick. We will remember and celebrate him and his life, as we do now in mourning his death.