RxPG News : Progeria

Farnesyl Transferase Inhibitors in Hutchinson-Gilford progeria syndrome

Wed, 28 Sep 2005 13:19:38 PST

( from http://www.rxpgnews.com ) The new Hopkins research, and similar results from other labs, shows that a class of drugs known as farnesyl transferase inhibitors, or FTIs, can reverse an abnormality in laboratory-grown cells engineered to mimic cells from progeria patients. In the laboratory, however, treating these engineered cells with an FTI already in clinical trials in cancer patients restored the cells to a normal appearance, the researchers report Sept. 26 in the advance online section of the Proceedings of the National Academy of Sciences. The drug blocks the first step in processing the faulty protein that causes the syndrome.

"We've been hopeful that our two decades of research on how proteins are processed and modified in cells might ultimately help people with certain forms of cancer," says Susan Michaelis, Ph.D., professor of cell biology at Johns Hopkins' Institute for Basic Biomedical Sciences.

"But for progeria, we and others only recently learned that it involves the one of the modified proteins we've been studying, a nuclear protein called lamin A. As a basic scientist, it is really exciting to have leapfrogged from studying a fundamental process to finding evidence that an existing drug might be useful in treating a devastating disease in children," she says.

Michaelis emphasizes that no one knows whether making the cells' nuclei look normal will be enough to reverse the disease process or slow it down. The class of drugs they tested prevents the first step in cells' processing of certain critical proteins in yeast and mammals. For more than 20 years, Michaelis has been studying this complex process.

The process starts with a fully assembled protein, then adds a fatty appendage called farnesyl very close to the protein's end, and then a tiny modification called a methyl group to a nearby building block. In yeast, the protein that gets the full treatment helps the single-celled organisms reproduce -- and the useful protein is the smaller part with all the fancy modifications. In cells' processing of lamin A in mammals, however, the plain, big chunk is the active part, and it's critical for the proper function and organization of cells' nuclei.

In children with progeria, however, a genetic mutation causes a piece of the original lamin A protein to be deleted, a discovery made by National Institutes of Health researchers and reported in 2003. "The normal mammalian protein, lamin A, doesn't have all those modifications; the modified part is thrown away," says Michaelis. So Michaelis and postdoctoral fellow Monica Mallampalli, Ph.D., set out to test that idea. Mallampalli genetically engineered a human cell line (HeLa) to have either of two mutations in the gene for lamin A. One mutation halted the process at the very beginning, by preventing addition of the fatty farnesyl appendage. The other affected the end of the process by preventing cleavage of the otherwise normal, fully modified protein.

"Neither has the correct lamin A protein, but only one has a modified protein hanging around," says Michaelis. "We found that only the cells with the farnesyl-modified protein had the problems seen in cells with the HGPS mutation."
Mallampalli also altered the version of the gene that produces the abnormal, persistently modified, disease-causing protein, called progerin, to uncover the effect of preventing the addition of farnesyl. Sure enough, even though the cells still didn't have normal lamin A, their nuclei looked normal when the faulty protein couldn't get modified.

"We were thrilled that, as our genetic studies predicted, the experimental drug did the trick," says Michaelis. "Because FTIs are already in advanced clinical trials with cancer patients and seem to be quite well-tolerated, it's hopeful that they could be tested in patients with progeria fairly quickly."

FTIs prevent addition of farnesyl to all proteins that have a particular molecular tag. In cancer, the key target among these proteins is one called Ras, which is activated by the same farnesyl-triggered process as lamin A and which promotes cancerous growth when there's too much of it.

Anti-cancer drugs might work in aging disease

Tue, 30 Aug 2005 19:44:38 PST

( from http://www.rxpgnews.com ) Working together, scientists at the National Institutes of Health and the University of North Carolina at Chapel Hill have developed a promising new strategy for treating a form of progeria. That rare but deadly and heartbreaking genetic disease causes children to age remarkably fast and die almost always before they complete their teens.

The average lifespan of victims, who eventually resemble very old bald people or, some might say, Hollywood's conception of space aliens, is 12 years.

Along with their staffs and students, Dr. Francis S. Collins, director of the National Human Genome Research Institute, has collaborated with Drs. Channing J. Der and Adrienne D. Cox of the UNC School of Medicine in laboratory studies.

They have shown that certain anti-cancer drugs known as FTIs can block some of the complex biochemical processes that result in progeria's symptoms. The collaboration came about because the UNC scientists have been working on the drugs for more than a decade, and Collins' group has been actively investigating progeria of childhood, which also is known as Hutchinson-Gilford syndrome.

The potential treatment has not been used with patients yet but had a strong positive effect on progeria patients' cells, they said.

Respectively, Cox and Der are associate professor of radiation oncology and pharmacology and professor of pharmacology and members of UNC's Lineberger Comprehensive Cancer Center. Collins, a UNC medical graduate, attracted widespread attention in 1989 as the discoverer of the defective gene that causes cystic fibrosis, another fatal illness that afflicts children.

A report on the research appears in the Sept. 6 issue of the Proceedings of the National Academy of Sciences. Other authors of the report include M.D.-Ph.D. student Brian C. Capell of Collins' NIH laboratory; NIH staff members Drs. Michael R. Erdos, Renee Varga and Leslie B. Gordon (also medical director of the Progeria Research Foundation); doctoral student James P. Madigan of Cox's laboratory; Dr. James Fiordalisi, assistant professor of radiation oncology at UNC; and Dr. Karen N. Conneely of the University of Michigan School of Public Health.

"Fortunately, progeria is very rare, and only about one child in four million comes down with it," Der said. "It was first identified in the early 1900s. Since then only 100 or so cases have been found. Still, it is quite devastating for those children who have it and their families."

He and Cox concentrate on FTIs, or farnesyltransferase inhibitors, which block the action of the enzyme farnsyltransferase. Currently, several chemical variations are undergoing clinical trials with cancer patients.

"There's a lot of interest in FTIs now because they target an enzyme that's required for a protein called RAS to cause cancer," Der said. "The idea that these FTIs also might be useful in treating progeria came up because it turns out that the gene that is mutated in that rare illness also requires this enzyme for generating an active protein known as lamin A."

In progeria patients, he said, the process that results in the normal, mature form of lamin A doesn't work correctly because of the genetic mutation, so a damaged form of lamin A is made instead. Researchers reasoned that the anti-cancer drugs might block the enzyme and hence interfere with the mutated lamin A gene's haywire actions.

"In the paper, we describe experiments showing that the mutant form of lamin A was indeed sensitive to these drugs," Der said. "The second thing we found was that some of the aberrant biology that this mutant protein causes can be stopped when we treat the cells with the inhibitors."

Because the drugs already are undergoing clinical trials and much is known about their action and safety, scientists have a significant head start in getting the possible treatment to patients, Cox said.

"We are very excited about the possibility that a drug class whose actions we have been working so hard to understand in cancer might soon be useful for this devastating 'orphan disease,'" she said. "Progeria is clearly an illness that would otherwise get no attention from pharmaceutical companies due to the tiny numbers of children afflicted."

The next step will be to test the enzyme inhibitors in mouse models of the disease which already have been made, Cox said. If those experiments succeed, then scientists could start clinical trials with patients.

Lamin research project provides clues about premature aging

Tue, 30 Aug 2005 19:41:38 PST

( from http://www.rxpgnews.com ) A step towards understanding cell mutations that cause a variety of human diseases, particularly in children -- including that which brings about premature aging and early death -- has been taken by researchers at the Hebrew University of Jerusalem Silberman Institute of Life Sciences and the John Hopkins University School of Medicine.

The scientists have focused their research on a study of induced mutations in the nuclear envelope of cells from the tiny C. elegans worm. Their aim is to thus provide clues towards a better understanding of mutations in proteins of the envelope of the cell nucleus in humans.

Such mutations, particularly in lamin (nuclear envelope) proteins A and C, cause many different diseases, including Hutchison Gilford progeria syndrome. Children with this disease develop premature aging and die usually before the age of 13. Other diseases brought about by these mutations include a form of muscular dystrophy, cardiomyopathy (a weakening of the heart muscle), and various other forms of irregular or retarded growth in childhood.

A report on the lamin research project was published in a recent issue of the Proceedings of the National Academy of Sciences in the U.S. The project was carried out primarily by Ayelet Margalit, a doctoral student in genetics at the Hebrew University, working under the supervision of Prof. Yosef Gruenbaum, and in cooperation with Prof. Katherine L. Wilson and Dr. Miriam Segura-Totten of Johns Hopkins University.

Experimenting with removal of the worm's lamin protein or its interacting protein partners emerin, MAN1 or BAF, the researchers have described "down-the-line" consequences, including the disruption of various proteins necessary for normal cell reproduction. Even though the C. elegans worm has only one lamin protein and few proteins that interact with it, the processes that occur there are similar to what happens in humans and provide clues to the laminopathic diseases affecting people..

The results seen from these lamin complex disruptions are a halted process of cell division, resulting in a static "bridge" structure between cells that should have separated, plus damage to the gonad cell structure. In both cases, the ability of the organism to grow and to reproduce is severely impaired.

The researchers hope that through further laboratory experimentation with the worm they will be able to better understand the functions of lamin-based complexes, and why mutations in these proteins cause a variety of different laminopathic diseases, such as progeria and muscular dystrophy in humans.

Drug prevents cell abnormality leading to progeria

Tue, 30 Aug 2005 19:38:38 PST

( from http://www.rxpgnews.com ) BACKGROUND: One in 4 million children are born with progeria, a genetic disease marked by accelerated aging and early cardiovascular disease. The children suffer from dwarfism, baldness, wrinkles, hardened arteries and osteoporosis. Most die from heart disease before age 15.

The rare disorder stems from a mutation in a gene that produces an abnormal cellular protein, which attaches itself to structures in the cell's nucleus. The accumulated protein deforms the nucleus, sparking miscommunications with other cells and leading to the genetic disease.

FINDINGS: UCLA scientists studied cells isolated from people with progeria and cultured the cells with a drug that blocked the mutant protein from attaching to the cells' nuclei. The drug significantly reduced the number of human cells with misshapen nuclei. The UCLA team earlier used the same approach to improve the shape of abnormal nuclei from mice genetically engineered to develop progeria.

IMPACT: The findings offer new clues into how progeria develops and could lead to new drugs to treat the disease and its related disorders, including osteoporosis and hardening of the arteries. UCLA's next step will be to test whether returning the shape of the nuclei to normal stops development of progeria in mice.

Farnesyltransferase inhibitors (FTIs) might be useful in Hutchinson-Gilford Progeria Syndrome

Tue, 30 Aug 2005 19:32:38 PST

( from http://www.rxpgnews.com ) In a surprising development, a research team led by the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health (NIH), has found that a class of experimental anti-cancer drugs also shows promise in laboratory studies for treating a fatal genetic disorder that causes premature aging.

In a study published Monday in the online edition of the Proceedings of the National Academy of Sciences (PNAS), Brian Capell and his colleagues at NHGRI reported that drugs known as farnesyltransferase inhibitors (FTIs), which are currently being tested in people with myeloid leukemia, neurofibromatosis and other conditions, might also provide a potential therapy for children suffering from Hutchinson-Gilford Progeria Syndrome, commonly referred to as progeria. A related study from Stephen Young, M.D., and colleagues at the University of California at Los Angeles is being published in the same issue of PNAS.

There are currently no treatments for progeria, which is a genetic disorder estimated to affect one child in 4 million. When they are born, children with progeria appear normal. But, as they grow older, they experience growth retardation and show dramatically accelerated symptoms of aging -- namely hair loss, skin wrinkling and fat loss. Accelerated cardiovascular disease also ensues, typically causing death from heart attack or stroke at about the age of 12.

"Our findings show that FTIs, originally developed for cancer, are capable of reversing the dramatic nuclear structure abnormalities that are the hallmark of cells from children with progeria. This is a stunning surprise, rather like finding out that the key to your house also works in the ignition of your car," said NHGRI Director Francis S. Collins, M.D., Ph.D., who is the study's senior author.

The new work involved using FTIs to treat skin cells taken from progeria patients and grown in laboratory conditions. If upcoming studies in a mouse model validate the results of the cell experiments and translate into improvements in the animals' conditions, a clinical trial of FTIs in children with progeria may begin as early as next spring, researchers said.

Dr. Collins and his colleagues discovered in April 2003 that mutations in the lamin A (LMNA) gene cause progeria, spurring renewed interest among researchers to study this rare syndrome. Among those were Capell, a New York University medical student participating in the Howard Hughes Medical Institute/NIH (HHMI/NIH) Research Scholars Program. In July 2004, he joined Dr. Collins' lab and immediately set his sights on understanding the molecular basis of progeria.

"What really interested me in this research in the first place were the potential links to aging and atherosclerotic disease," said Capell. Indeed, understanding progeria at the molecular level may illuminate the general processes involved in normal human aging.

The LMNA gene codes for a protein called lamin A, which constitutes a major component of the scaffold-like network of proteins just inside the cell's nuclear membrane, called the lamina. The gene mutation implicated in progeria causes a section of 50 amino acids within the lamin A protein to be deleted, resulting in a mutated protein that is called progerin. This protein fails to integrate properly into the lamina, thereby disrupting the nuclear scaffolding and causing gross disfigurement of the nucleus. Cells with progerin have a nucleus with a characteristic "blebbed," or lobular, shape.

To find its way to the lamina, lamin A carries two tags, rather like ZIP codes, that help to direct the protein's travels. One tag at the end of lamin A instructs another protein to modify it through a process called farnesylation. Farnesylation tethers lamin A to the inner nuclear membrane. Once there, a second tag within the protein signals an enzyme to cleave off the terminal portion of the protein, including the farnesyl group, freeing lamin A to integrate properly into the nuclear lamina.

Because progerin carries the farnesylation tag but lacks the second cleavage tag, Capell speculated that progerin was becoming permanently stuck to the inner nuclear membrane. There, he suspected, it enmeshed other scaffolding proteins, preventing their proper integration into the lamina. If progerin's tendency to stick to the inner nuclear membrane is indeed the culprit in nuclear blebbing and the root of the progeria defect, Capell and his colleagues reasoned that they could prevent these defects by blocking farnesylation of progerin.

The researchers' hunch proved correct. When they changed one amino acid within progerin's farnesylation tag to prevent the addition of a farnesyl group and tested the effect in cells grown in the laboratory, progerin did not anchor itself to the inner nuclear membrane and instead clumped within the nucleus. Moreover, they observed no nuclear blebbing.

The researchers then tried treating the cells carrying progerin with FTIs, which are drugs originally developed to inhibit certain cancer-causing proteins that require farnesylation for function. FTIs are now being tested in phase III clinical trials of patients with myeloid leukemia. So far, clinical trials using FTIs have found little toxicity, even when the drug treatment significantly raises levels of unfarnesylated proteins.

After FTI treatment, the progerin-carrying cells showed no blebbing. More importantly, researchers saw the same effect when they used FTIs to treat cells grown from skin biopsies of progeria patients: Cell blebbing decreased to near normal levels.