Tag Archives: gene therapy

Gene Therapy Helps Restore Sight For Some

The degenerative eye disease choroideremia affects about one in 50,000 Americans. It is a progressive form of blindness in which parts of the eye called the choroid and the retinal pigment epithelium, along with the retina, gradually decay. Ordinarily the epithelium provides materials and protection for the choroid and the retina, while the choroid lines the eye and helps get nourishment to the retina. When these layers start to break down, they can no longer support optical function and vision loss results. The disease runs in families, but the rate and degree of loss varies from person to person. The degeneration is irreversible, and there is currently no treatment that can stop its progress.

Now, however, researchers say a new approach using gene therapy may hold the key to not just stopping the degradation of the eye layers, but restoring sight already lost. Patients are injected with a clean copy of the gene that is damaged in people with the disease. This is intended to supplant the damaged gene and stop the destruction of cells in the eye. The treatment has only been tested in half a dozen patients, but all of them report success. In fact, one of the two patients in the study who had the most advanced choroideremia, with the most profound vision loss, was able to read four lines further down an eye chart six months after treatment, and night vision, in which the loss generally starts, improved in all six subjects.

Researchers warn, however, that these are only preliminary results, and it remains to be seen how well the treatment will work in the long term. In particular, scientists suspect that the treatment slows degeneration, but does not stop it entirely. Even if that is the case, however, the added years of functioning vision are a benefit to patients. Furthermore, the scientists note that the success of this genetic therapy for choroideremia suggests both other avenues to pursue in efforts to battle the disease—which has not proven treatable until this study—and ways to use gene therapy or similar approaches to treat other eye diseases, which may have similar pathologies, be likewise genetically linked, or both.

Gene Therapy For Down Syndrome

When women have children late in life, there is an increased risk that those children will have a condition that results in stunted growth, significant cognitive deficits, a flat face with a protruding tongue, and often short fingers and poor muscle tone. Down syndrome occurs in one in 35 babies born to women over 45, as compared to one in 400 babies born to women under 35; having a baby with Down syndrome is itself a risk factor, raising the chances of subsequent children also having the condition.

The most common form of Down syndrome is called trisomy 21 because it is caused by an extra 21st chromosome, three rather than the usual two. The other, vastly rarer, forms can also be traced to excess 21st-chromosome material, either present in some cells but not others (called mosaic Down syndrome) or attached to other chromosomes (called translocation Down syndrome). The translocation type accounts for about one in 25 cases of the condition and is the only type that can be inherited.

The extra chromosomal material, scientists now believe, appears to affect stem cell regulation. The primary culprit appears to be a gene on the chromosome called Usp16; an extra copy of the gene means more stem cells are used in development. While that one gene is almost certainly not solely responsible for all the symptoms of the condition, treatments that dial it back causes neural cells that typically grow slowly in Down patients to instead grow in the usual way.

This suggests a possible direction for research into genetic-based treatments for Down syndrome. The study that identified the role of Usp16 included tests in human cells, so there is some insight into how it works in people. Current treatments for Down syndrome are focused on early intervention and team care to address the symptoms and possible complications—specialists in developmental pediatrics, cardiology, speech therapy, neurology, and all the other areas the condition touches—but gene therapy may in the future prevent the condition from showing symptoms in the first place.

Treating Sickle Cell At The Source

More and more, pharmaceutical and medical researchers are finding ways to treat sickle-cell anemia. A genetic condition affecting 90,000 Americans, sickle-cell anemia is found primarily in people of African descent. The red blood cells of people with sickle-cell anemia are rigid and misshapen, impeding circulation. In addition, the red blood cells are fragile, needing to be replenished after less than three weeks, as opposed to the usual lifespan of up to four months. Due to these factors, sickle-cell patients are prone to infection, and experience pain in the chest and joints.

Singer T-Boz was diagnosed with sickle-cell anemia as a child.

Singer T-Boz was diagnosed with sickle-cell anemia as a child.

Because sickle-cell is caused by a genetic problem with the red blood cells, it is a lifelong disease, with effects starting in infancy, and causing slowed growth and delayed puberty as well as symptoms in adulthood. It has been considered incurable, but a woman in Chicago who was treated with a stem cell transplant showed no symptoms of the disease—and her red blood cells were found to be normal after the transplant, meaning the procedure completely eliminated the patient’s disease. The woman is one of the first people to be successfully cured by this technique, which requires a healthy donor who is genetically a sibling of the patient. The stem cells gradually take over the task of making red blood cells from the patient’s own cells, and makes normal red blood cells.

For patients who are not eligible for the stem cell procedure, there are other options. Some researchers are exploring the possibility of gene therapy that repairs the red-blood-cell-making mechanism in the patient’s own cells. Rather than relying on donor bone marrow to manufacture healthy cells, the flaw that causes the patient to produce sickled cells is repaired. This technique is only in preliminary stages, but clinical trials are expected to begin in 2014.

Already in trials are two medications that may help alleviate the symptoms of sickle-cell disease. The drug regadenoson is currently used to diagnose heart disease. It has anti-inflammatory properties, and researchers are hoping that it is can improve blood flow in sickle-cell patients. The other medication being tested, referred to as SelG1, prevents blood cells from sticking together and keeps blood vessels from becoming blocked.

Getting Under Your Skin

Skin cancer patients and others may soon benefit from a non-invasive form of gene therapy. A topical treatment uses nanotechnology to deliver gene-regulation technology exactly where it’s needed.

Topical gene therapy has been in use since the 1990s, but the advance made by a Northwestern University research team is to mate it with nanotechnology to overcome some of the difficulties in using it for skin can​cer treatment. The skin, as the protector of the body, is highly resistant to letting substances through.

The team, led by dermatologist Amy S. Paller and chemist Chad Mirkin, uses specially constructed nucleic acids called small interfering RNA. The siRNA clusters around gold nanoparticles consisting of only a few atoms to form spheres about 1,000 times smaller than the diameter of a human hair. The RNA is highly programmable, meaning it is relatively easy to manufacture to target a specific gene.

In the study, siRNA was engineered to bind to natural proteins the skin does let through. When it gets inside it identifies cancer cells with epidermal growth factor receptor. The nanomedication then switches the cancer cells off, leaving healthy cells alone.

“This allows us to treat a skin problem precisely where it is manifesting—on the skin,” Dr. Paller said in a release. “We can target our therapy to the drivers of disease, at a level so minute that it can distinguish mutant genes from normal genes. Risks are minimized, and side effects have not been seen to date in our human skin and mouse models.”

In addition to the common skin cancers melanoma and squamous cell carcinoma, this technique is being looked at for use in fighting psoriasis, diabetic wound healing and the rare genetic disorder epidermolytic ichthyosis, a skin disease for which no treatment is known. Future research may look at using it for wrinkles and other signs of aging.

“Many of the ways we treat disease are based on old methods and materials. Nanotechnology offers the ability to very rapidly create new structures with properties that are very different from conventional forms of matter,” Mirkin said.

Mirkin developed the technology used more than 15 years ago. While it has widespread diagnostic applications, only recently was its ability to penetrate skin realized, along with the possibility of using that ability to improve delivery of treatments.

Switching Off Breast Cancer

There’s some good news for women—and men—at risk for breast cancer. New advances in the understanding of how tumors develop is providing an unprecedented understanding of what triggers normal cells to become cancerous. This means that it may be possible for doctors to see signs of breast cancer earlier than ever, possibly before cancer even develops.

Researchers say that biochemical signaling pathways in the body can be triggered by inflammation to transform healthy breast tissue into cancer cells. This triggering leads to a self-sustaining chain reaction, where even once the initial inflammation dies down, the signals continue to travel along the pathway. These signals inhibit the action of tumor-suppressing RNA.

The implications of this discovery are being looked into. Doctors speculate that targeted treatments can be used to block the signals and reactivate the tumor suppressant.

Another treatment option being investigated is gene therapy, the introduction of tumor-suppressing genetic material into the patient. The idea is to induce the body to cut off the tumor cells’ blood and oxygen supply. this will cause the tumor to whither away rather than grow and metastasize.

Other teams of researcher are studying the possibility of vaccinations. Patients at high risk—such as women over 50, people with a family history of breast cancer, and women who experienced menarche before age 12 or menopause after age 55—may soon be able to get a vaccine to avoid the disease.