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Posts Tagged ‘gene therapy’

VCU Massey Cancer researchers find gene therapy that kills pancreatic cancer cells

Josh: Normally, I would say it’s probably not the best idea to give gene therapy to cancer patients as a treatment. The reason being that current gene therapy delivery systems have the tendency to cause cancer. However, in this case, which such low survival rates, I think any treatment is worth trying.

Researchers at the Virginia Commonwealth University Massey Cancer Center and the VCU Institute of Molecular Medicine have published findings that implicate a new chemoprevention gene therapy (CGT) for preventing and treating pancreatic cancer, one of the most lethal and treatment-resistant forms of cancer.

In the July issue of Molecular Cancer Therapeutics, the researchers showed that combining a dietary agent with a gene-delivered cytokine effectively eliminates human pancreatic cancer cells in mice displaying sensitivity to these highly aggressive and lethal cancer cells.

Cytokines are a category of proteins that are secreted into the circulation and can affect cancer cells at distant sites in the body, including metatases. The cytokine used in this study was melanoma differentiation associated gene-7/interleukin-24, known as mda-7/IL-24. … Continue Reading »

New paradigm for cell-specific gene delivery

Researchers from Northwestern University and Texas A & M University have discovered a new way to limit gene transfer and expression to specific tissues in animals. In studies to determine how plasmids enter the nuclei of non-dividing cells, the group previously identified a region of a smooth muscle cell-specific promoter that was able to mediate nuclear targeting of any plasmid carrying this sequence uniquely in cultured smooth muscle cells but in no other cell type. In their current study to appear in the July 08 issue of Experimental Biology and Medicine, the team, led by Drs. David Dean and Jennifer Young from the Department of Medicine at Northwestern University, in collaboration with Warren Zimmer from Texas A & M University, now demonstrate that such restriction of nuclear entry using this specific DNA sequence can be used in blood vessels of living animals to direct gene transfer and expression specifically to smooth muscle cells. They have also developed a novel gene delivery approach for the vasculature that uses an electric field to transiently permeabilize the plasma membrane of cells to allow entry of DNA. Thus, this work establishes the control of nuclear entry of gene therapy vectors as a novel approach to target genes and gene expression to desired cell types in the body.

Vascular smooth muscle proliferative diseases, including atherosclerosis and restenosis, are among the leading causes of morbidity and mortality in the US. Gene therapy may represent an important alternative for the treatment and prevention of these proliferative diseases of the vasculature. It can be highly cell-specific, mimic or restore normal in vivo function, and can be permanent or transient depending on vector design. Currently, a number of gene delivery systems for use on the arterial wall are being studied, but as yet their low efficiency in gene transfer and lack of cell-specific targeting and expression are major limitations. According to Dr. David Dean, “The benefit of our newly described approach is that it can target specific cell types. One of the most commonly envisioned treatments for these proliferative disorders is to deliver genes that kill or inhibit the dividing smooth muscle cells, but we need to target only these muscle cells and not any other cell in the vessel wall and this approach will enable us to do just that”. The goal of the team is to design more effective gene therapy vectors for use in the vasculature by understanding the molecular mechanisms by which DNA and DNA-protein complexes are actively transported into the nucleus. Dr. Warren Zimmer states “these results set the stage for our future use of this technology to deliver therapeutic genes to lessen the severity of restenosis which is the most common issue following angioplasty and placement of stents”. Dr. Dean continues, “Now that we have demonstrated proof of principle for this approach we can look for DNA sequences that act in other tissues and develop cell-specific treatments for any number of organs”. Dr. Steven R. Goodman, Editor-in-Chief of Experimental Biology and Medicine, stated “The exciting studies reported here are the first to demonstrate that non-viral gene delivery can be made cell-specific by controlling the nuclear entry of plasmid DNA, and as such, establishes a new paradigm for cell-selective gene delivery. Drs. Dean, Young, and Zimmer are to be congratulated on this ground-breaking study”.

Source: Society for Experimental Biology and Medicine

Jennifer L. Young, Warren E. Zimmer, and David A. Dean. Smooth Muscle-Specific Gene Delivery in the Vasculature Based on Restriction of DNA Nuclear Import. Experimental Biology and Medicine 2008 233: 840-848.

Josh says:

Gene therapy will finally become a reality once we can have a safe, specific delivery system. Specificity can sometimes be achieved with certain viruses as vectors, but this has the tendency to sometimes cause cancer. I’m not sure if this method has the same risks with cancer development, but I would guess if it did, the liklihood is significantly reduced.

Gene therapy involving antibiotics may help patients with Usher syndrome

A new approach to treating vision loss caused by Type 1 Usher syndrome (USH1), the most common condition affecting both sight and hearing, will be unveiled by a scientist at the annual conference of the European Society of Human Genetics tomorrow (Tuesday 3 June). Ms Annie Rebibo Sabbah, from the Genetics Department of the Rappaport Faculty of Medicine, Technion, Haifa, Israel, will tell the conference that preliminary results using a class of drugs called aminoglycosides, commonly used as antibiotics, had had promising effects in vitro and in cell culture.

Usher syndrome is a recessively- inherited disease; in order to have it, the child must receive a mutated form of the Usher gene from each parent. Approximately 3 to 6 percent of all children who are deaf and another 3 to 6 percent of children who are hard-of-hearing have it. In developed countries, about four babies in every 100,000 births have Usher syndrome. Children born with USH1 begin to develop visual problems in early childhood, and these develop quickly into an eye disorder called retinitis pigmentosa, which leads to complete blindness. … Continue Reading »

The good news in our DNA: Defects you can fix with vitamins and minerals

As the cost of sequencing a single human genome drops rapidly, with one company predicting a price of $100 per person in five years, soon the only reason not to look at your “personal genome” will be fear of what bad news lies in your genes.

University of California, Berkeley, scientists, however, have found a welcome reason to delve into your genetic heritage: to find the slight genetic flaws that can be fixed with remedies as simple as vitamin or mineral supplements.

“I’m looking for the good news in the human genome,” said Jasper Rine, UC Berkeley professor of molecular and cell biology.

“Headlines for the last 20 years have really been about the triumph of biomedical research in finding disease genes, which is biologically interesting, genetically important and frightening to people who get this information,” Rine said. “I became obsessed with trying to decide if there is some other class of information that will make people want to look at their genome sequence.”

What Rine and colleagues found and report this week in the online early edition of the journal Proceedings of the National Academy of Sciences (PNAS) is that there are many genetic differences that make people’s enzymes less efficient than normal, and that simple supplementation with vitamins can often restore some of these deficient enzymes to full working order.

First author Nicholas Marini, a UC Berkeley research scientist, noted that physicians prescribe vitamins to “cure” many rare and potentially fatal metabolic defects caused by mutations in critical enzymes. But those affected by these metabolic diseases are people with two bad copies, or alleles, of an essential enzyme. Many others may be walking around with only one bad gene, or two copies of slightly defective genes, throwing their enzyme levels off slightly and causing subtle effects that also could be eliminated with vitamin supplements.

“Our studies have convinced us that there is a lot of variation in the population in these enzymes, and a lot of it affects function, and a lot of it is responsive to vitamins,” Marini said. “I wouldn’t be surprised if everybody is going to require a different optimal dose of vitamins based on their genetic makeup, based upon the kind of variance they are harboring in vitamin-dependent enzymes.”

Though this initial study tested the function of human gene variants by transplanting them into yeast cells, where the function of the variants can be accurately assessed, Rine and Marini are confident the results will hold up in humans. Their research, partially supported by the Defense Advanced Research Projects Agency (DARPA) and the U.S. Army, may enable them to employ U.S. soldiers to test the theory that vitamin supplementation can tune up defective enzymes.

“Our soldiers, like top athletes, operate under extreme conditions that may well be limited by their physiology,” Rine said. “We’re now working with the defense department to identify variants of enzymes that are remediable, and ultimately hope to identify troops that have these variants and test whether performance can be enhanced by appropriate supplementation.”

In the PNAS paper, Rine, Marini and their colleagues report on their initial analysis of variants of a human enzyme called methylenetetrahydrofolate reductase, or MTHFR. The enzyme, which requires the B vitamin folate to work properly, plays a key role in synthesizing molecules that go into the nucleotide building blocks of DNA. Some cancer drugs, such as methotrexate, target MTHFR to shut down DNA synthesis and prevent tumor growth.

Using DNA samples from 564 individuals of many races and ethnicities, colleagues at Applied Biosystems of Foster City, Calif., sequenced for each person the two alleles that code for the MTHFR enzyme. Consistent with earlier studies, they found three common variants of the enzyme, but also 11 uncommon variants, each of the latter accounting for less than one percent of the sample.

They then synthesized the gene for each variant of the enzyme, and Marini, Rine and their UC Berkeley colleagues inserted these genes into separate yeast cells in order to judge the activity of each variant. Yeast use many of the same enzymes and cofactor vitamins and minerals as humans and are an excellent model for human metabolism, Rine said.

The researchers found that four different mutations affected the functioning of the human enzyme in yeast. One of these mutations is well known: Nearly 30 percent of the population has one copy, and nine percent has two copies.

The researchers were able to supplement the diet of the cultured yeast with folate, however, and restore full functionality to the most common variant, and to all but one of the less common variants.

Since this experiment, the researchers have found 30 other variants of the MTHFR enzyme and tested about 15 of them, “and more than half interfere with the function of the enzyme, producing a hundred-fold range of enzyme activity. The majority of these can be either partially or completely restored to normal activity by adding more folate. And that is a surprise,” Rine said.

Most scientists think that harmful mutations are disfavored by evolution, but Rine pointed out that this applies only to mutations that affect reproductive fitness. Mutations that affect our health in later years are not efficiently removed by evolution and may remain in our genome forever.

The health effects of tuning up this enzyme in humans are unclear, he said, but folate is already known to protect against birth defects and seems to protect against heart disease and cancer. At least one defect in the MTHFR enzyme produces elevated levels in the blood of the metabolite homocysteine, which is linked to an increased risk of heart disease and stroke, conditions that typically affect people in their post-reproductive years.

“In those people, supplementation of folate in the diet can reduce levels of that metabolite and reduce disease risk,” Marini said.

Marini and Rine estimate that the average person has five rare mutant enzymes, and perhaps other not-so-rare variants, that could be improved with vitamin or mineral supplements.

“There are over 600 human enzymes that use vitamins or minerals as cofactors, and this study reports just what we found by studying one of them,” Rine said. “What this means is that, even if the odds of an individual having a defect in one gene is low, with 600 genes, we are all likely to have some mutations that limit one or more of our enzymes.”

The subtle effects of variation in enzyme activity may well account for conflicting results of some clinical trials, including the confusing data on the effect of vitamin supplements, he noted. In the future, the enzyme profile of research subjects will have to be taken into account in analyzing the outcome of clinical trials.

If one considers not just vitamin-dependent enzymes but all the 30,000 human proteins in the genome, “every individual would harbor approximately 250 deleterious substitutions considering only the low-frequency variants. These numbers suggest that the aggregate incidence of low-frequency variants could have a significant physiological impact,” the researchers wrote in their paper.

All the more reason to poke around in one’s genome, Rine said.

“If you don’t give people a reason to become interested in their genome and to become comfortable with their personal genomic information, then the benefits of much of the biomedical research, which is indexed to particular genetic states, won’t be embraced in a time frame that most people can benefit from,” Rine said. “So, my motivation is partly scientific, partly an education project and, in some ways, a partly political project.”

Marini and Rine credit Bruce Ames, a UC Berkeley professor emeritus of molecular and cell biology now on the research staff at Children’s Hospital Oakland Research Institute, with the research that motivated them to look at enzyme variation. Ames found in the 1970s that many bacteria that could not produce a specific amino acid could do so if given more vitamin B6, and in recent years he has continued exploring the link between micronutrients and health.

“Looked at in one way, Bruce found that you can cure a genetic disease in bacteria by treating it with vitamins,” Rine said. Because the human genome contains about 6 billion DNA base pairs, each one subject to mutation, there could be between 3 and 6 million DNA sequence differences between any two people. Given those numbers, he reasoned that, as in bacteria, “there should be people who are genetically different in terms of the amount of vitamin needed for optimal performance of their enzymes.”

This touches on what Rine considers one of the key biomedical questions today. “Now that we have the complete genome sequences of all the common model organisms, including humans, it’s obvious that the defining challenge of biology in the 21st century is not what the genes are, but what the variation in the genes does,” he said.

Rine, Marini and their colleagues are continuing to study variation in the human MTHFR gene as well as other folate utilizing enzymes, particularly with respect to how defects in these enzymes may lead to birth defects. Rine also is taking advantage of the 1,500 students in his Biology 1A lab course to investigate variants of a second vitamin B6-dependent enzyme, cystathionine beta-synthase.

He also is investigating how enzyme cofactors like vitamins and minerals fix defective enzymes. He suspects that supplements work by acting as chaperones to stabilize the proper folding of the enzyme, which is critical to its catalytic activity. “That is a new principle that may be applicable to drug design,” Rine said.

Source: University of California – Berkeley

Nicholas J. Marini, Jennifer Gin, Janet Ziegle, Kathryn Hunkapiller Keho, David Ginzinger, Dennis A. Gilbert, and Jasper Rine. The prevalence of folate-remedial MTHFR enzyme variants in humans. PNAS published June 3, 2008, 10.1073/pnas.0802813105

Josh says:

The chaperone idea that’s mentioned at the end is intriguing. However, doctors have been treating these types of genetic deficiencies for a while. Most of them are in the pentose phosphate pathway, with the most common being glucose-6-phosphate dehydrogenase (G6PD). A “byproduct” of the pentose phosphate pathway is NADPH, which is also used as a cofactor by methylenetetrahydrofolate reductase (MTHFR).

Certainly, there are little mutations in some of our enzymes that will affect their efficiency. I’m not sure how much it will help to target these minor ones, though it definitely won’t hurt. In the meantime, I’m going to continue to just take my daily multi-vitamin.

Note: for biochemistry, wikipedia is a surprisingly thorough resource. It doesn’t have as much when it comes to specific proteins for developmental biology or some aspects of molecular biology, but the biochemistry is exceptional.

Gene therapy slows progression of fatal neurodegenerative disease in children

Gene therapy to replace the faulty CLN2 gene, which causes a neurodegenerative disease that is fatal by age 8-12 years, was able to slow significantly the rate of neurologic decline in treated children, according to a paper published online ahead of print in the May 2008 issue (Vol. 19 No. 5) of Human Gene Therapy, a peer-reviewed journal published by Mary Ann Liebert, Inc. The paper is available free online at www.liebertpub.com/hum

Late Infantile Neuronal Ceroid Lipofuscinosis (LINCL) is an autosomal recessive genetic disorder that causes degeneration of the central nervous system. It is a form of Batten disease, a group of lysosomal storage disease in which a lipofuscin-like material is not broken down and accumulates in neurons, causing cognitive impairment, visual failure, seizures, and progressive deterioration of motor function. … Continue Reading »

Gene therapy improves vision in patients with congenital retinal disease

In a clinical trial at The Children’s Hospital of Philadelphia, researchers from The University of Pennsylvania have used gene therapy to safely restore vision in three young adults with a rare form of congenital blindness. Although the patients have not achieved normal eyesight, the preliminary results set the stage for further studies of an innovative treatment for this and possibly other retinal diseases.

An international team led by The University of Pennsylvania, The Children’s Hospital of Philadelphia, the Second University of Naples and the Telethon Institute of Genetics and Medicine (both in Italy), and several other American institutions reported their findings today in an online article in the New England Journal of Medicine. … Continue Reading »

Clearer day for gene therapy: New vector carries big genes linked to inherited blindness

Some clinicians and researchers hope that individuals with inherited diseases (such as cystic fibrosis and recessive Stargardt disease, which causes progressive loss of sight) might one day be cured by providing them with a corrected version of their disease-causing faulty gene, i.e., by gene therapy. In gene therapy, the curative gene is packaged in an agent known as a vector, which carries the gene into cells where it is required. One of the most common vectors is derived from a virus, adeno-associated virus (AAV). However, for some diseases, such as recessive Stargardt disease, one barrier to successful gene therapy is that AAV is not able to accommodate the large size of the curative gene. New data, generated by Alberto Auricchio and colleagues, at the Telethon Institute of Genetics and Medicine, Italy, has revealed that vectors derived from a specific form of AAV known as AAV5 can accommodate large genes, including that missing in a mouse model of recessive Stargardt disease. … Continue Reading »

“Vaccine” for leukemia

Biology News reports that a research team at the Moores Cancer Center at University of California, San Diego (UCSD) have gotten a leukemia patient’s immune system to start attacking their leukemia cancer cells. To do this, the researchers modified cancer cells to make them more recognizable by the immune system. These immunity-recognizable cancer cells were then injected back into the patient so that their body could begin producing antibodies.

Basically: a vaccine for leukemia.

This works because the antibodies that are produced target a transmembrane receptor called ROR1, which is involved in the Wnt pathway. Normally our bodies destroy all immune cells that make antibodies that recognize self, which is anything that is naturally present in the body. However, this particular part of the Wnt pathway is only present early on in development, so all the ROR1 receptors are gone before the immune system develops.