Gene Therapy Articles

Gene Therapy Raises Hopes...But Only Time Will Tell

Dr. Joseph A. Treat
Department of Medicine
University of Pennsylvania
(215) 662-7711

For more than five years, scientists have been trying to use gene therapy on cancer. More than 100 laboratories in 13 countries have been involved in research to find so-called "suicide genes" that would attack invading cancer cells while leaving healthy cells alone. Such is the theory behind research now being conducted at the University of Pennsylvania and involving our fellow member, Donald Hardy, the victim of mesothelioma.

Researchers at the University's Medical Center have infected cancer cells in Brother Hardy's chest with a virus or "vector," bioengineered to carry a killer gene. It is hoped that the vector has carried the gene into cancer cells making them vulnerable to an antiviral drug known as "ganciclovir", administered several days later.

In theory, the procedure is designed to fool the drug into thinking that the cancer is a viral infection and thus the drug would attack only the cancer cells, leaving healthy cells alone.

The procedure began with the insertion of a tube into Brother Hardy's chest cavity. Thoracic Surgeon Dr. Larry Kaiser then placed a syringe into the chest tube.

The syringe had been filled with "suicide genes" that were pushed into the chest cavity through the tube. Hardy, who remained conscious during the procedure, was asked to roll back and forth on the operating table so the vector would slosh up against the cancer cells.

The suicide genes make cells sensitive to the ganciclovir drug, so that when the cells containing the gene are exposed to the drug, they are killed.

The genes, in this case are herpes simplex thymidine kinase genes, which are delivered to cancer cells via a crippled common-cold virus called an adenovirus.

"Mr. Hardy has tolerated the gene therapy very well. He is our first patient in a clinical trial that is designed to prove only the safety of this particular form of gene therapy -- which has already been shown to be safe and effective in animal models."
- Dr. Steven Albelda, principal investigator for the study

Although all cells exposed to the virus take up the genes, only those cells that are rapidly dividing - such as tumor cells - are damaged by the ganciclovir. Thus, the theory is that tumor cells, not normal cells, are destroyed when the drug is given.

By way of review, the treatment is a four-step process:

In mesothelioma, the cancer attacks the fragile membranes on the surface of the lung and the opposing chest wall. These membranes form the pleural cavity. To kill the cancer, researchers first insert a tube through the patient's chest wall into the cavity and inject the adenovirus. The injected adenovirus carries a gene that forces the pleural cells to make the enzyme thymidine kinase (TK).

The patient is then injected with the antiviral drug ganciclovir. The drug kills only those cells making TK, thus knocking out the cancer.

Tense hours followed Brother Hardy's procedure. His temperature and heart rate increased, suggesting that perhaps the injection of killer cells had been too high. However, vital signs returned to normal and four days later biopsies were taken to determine the effectiveness of the treatment. Unfortunately, the results were inconclusive.

However, today Brother Hardy remains a picture of health - active and robust. And to some degree, he already has beaten the odds. Having been diagnosed with mesothelioma more than two years ago, he has outlived the usual prognosis for average life expectancy of no more than 18 months.

And, more importantly, there have been no signs of new tumors since his treatment. Monthly outpatient visits to the Medical Center allow doctors to continually monitor his condition and for now, so far so good.

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Intrapleural administration of interleukin-2 for the treatment of patients with malignant pleural mesothelioma: a Phase II study

Cancer 1998 Nov 15;83(10):2099-104
Astoul P, Picat-Joossen D, Viallat JR, Boutin C
Department of Pulmonology, Hopital de la Conception, Marseille, France.

BACKGROUND:The prognosis associated with malignant pleural mesothelioma (MPM) is poor in spite of surgery, radiotherapy, photodynamic therapy, or chemotherapy. Therefore, new therapeutic strategies, including intrapleural immunotherapy, are being investigated. Several clinical studies have demonstrated objective antitumoral responses to intrapleural interleukin-2 (IL-2) administration in the treatment of malignant pleurisy. The maximum tolerated dose, 24 x 10(6) IU/m2/day for 5 days, was determined in a Phase I study. Based on these results, a Phase II study was conducted, in which intrapleural IL-2 (21 x 10(6) IU/m2/day for 5 days) was given to patients with MPM. METHODS: Patients with histologically documented MPM were evaluated for response 36 days after treatment by computed tomography scan and thoracoscopy with biopsies. Toxicity was recorded and graded according to World Health Organization criteria. Survival was calculated from the start of treatment to death according to the Kaplan-Meier method, and the survival of responders and nonresponders was compared using the log rank test. RESULTS: Twenty-two patients entered this study. Of the 22 cases of MPM, 19 were epithelial, 2 were mixed, and 1 was fibrosarcomatous. Three patients had Stage IA disease, 1 had Stage IB, 16 had Stage II, 1 had Stage III, and 1 had Stage IV (Butchart classification). All patients received their planned treatment. No dose reduction or interruption occurred. There were 11 partial responses and 1 complete response. Stable disease occurred in 3 patients and disease progression in 7 patients. The overall median survival time was 18 months; the median survival time of responders differed significantly from that of nonresponders (28 months vs. 8 months, P less than 0.01). The 24- and 36-month survival rates for responders were 58% and 41%, respectively. CONCLUSIONS: These results confirm that intrapleural administration of IL-2 is well tolerated and has antitumor activity in patients with MPM. The authors recommend a dose of 21 x 10(6) IU/m2/day for 5 days. However, determination of the schedule of IL-2 and its superiority to conventional treatment in a Phase III study has yet to be accomplished.

PMID: 9827714, UI: 99043416

The Treatment of Malignant Pleural Mesothelioma With Gene Modified Cancer Cells: A Phase-I Study

Louisiana State University Medical Center and Stanley S. Scott Cancer Center
Paul Schwarzenberger, M.D. (Principal Investigator)
Jay Kolls, M.D.; Scott Freeman, M.D.; Lynn Harrison, M.D.

Abstract

Malignant mesothelioma is a tumor of the pleura for which there is no satisfactory treatment. It is almost universally fatal, regardless of the stage of the tumor at the time of diagnosis. Current treatment modalities include surgery, chemotherapy, and radiation therapy, although in some series none of these modalities is superior to no treatment at all. Because of the dismal prognosis for patients with malignant mesothelioma, a new mode of treatment is desperately needed. A promising area of research into the treatment of various malignancies is gene therapy.

Recent studies have demonstrated the utility of exposing tumor cells to cells transduced to express the Herpes simplex virus gene for thymidine kinase (HSV-TK). By virtue of their expression of HSV-TK, the transduced cells are rendered susceptible to the antiviral drug, ganciclovir (GCV). Nearby tumor cells are killed by a so-called bystander effect. In this protocol we propose a Phase I trial to study the safety and determine the maximal tolerated dose of an HSV-TK-transduced ovarian cancer cell line (PA1-STK cells) infused into the pleural cavities of patients with malignant pleural mesothelioma, followed by systemic administration of ganciclovir. The hope is that administration of ganciclovir will result in killing of the transduced ovarian cancer cells as well as the nearby malignant mesothelioma cells. This is a standard dose-escalation protocol.

For More Information about the Study, call the LSU GCRC at (504) 585-4017.

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PHASE I CLINICAL GENE THERAPY TRIAL, LOUISIANA STATE UNIVERSITY MEDICAL CENTER

Malignant mesothelioma is a tumor for which there is currently no satisfactory treatment. Mesothelioma is an almost universally fatal disease, regardless of the stage of the tumor at the time of diagnosis. Current treatment modalities include surgery, chemotherapy and radiation therapy, although in some circumstances none of these modalities is superior to no treatment at all. A promising area of research in the treatment of various malignancies is gene therapy. Recent studies have demonstrated the utility of exposing tumor cells to cells transduced to express the Herpes simplex virus gene for thymidine kinase (HSV-TK). By virtue of their expression of HSV-TK, the transduced cells are rendered susceptible to the antiviral drug ganciclovir. Nearby untransduced cells are killed by a so-called bystander effect. A Phase I clinical gene therapy trial for mesothelioma is underway at the Louisiana State University Medical Center of New Orleans. The purpose is to study the safety and to determine the maximal tolerated dose of an HSV-TK-transduced ovarian cancer cell line that is infused into the pleural cavities of patients. This infusion is followed by systemic administration of ganciclovir. The hope is that administration of ganciclovir will result in killing of both the transduced ovarian cancer cells as well as the nearby malignant cells. "Gene therapy for malignant mesothelioma: a novel approach for an incurable cancer with increased incidence in Louisiana", Schwarzenberger, et al., Journal of the Louisiana State Medical Society, 150(4):168-74, April 1998.

PROMISING GENE THERAPY IN TREATMENT OF MALIGNANT MESOTHELIOMA

Modified, nonneurovirulent herpes simplex viruses (HSVs) have shown promise in treatment of brain tumors. However, HSV-1 can infect and cause disintegration of a wide variety of cell types. HSV-1716, a mutant of the virus lacking both copies of the gene coding ICP-34.5, can effectively treat a localized intraperitoneal malignancy. Human malignant mesothelioma cells supported the growth of HSV-1716 and efficiently disintegrated in vitro. Intraperitoneal injection of HSV-1716 into animals with established tumor nodules reduced tumor burden and significantly prolonged survival in an animal model of non-central nervous system-localized human malignancy, without dissemination or persistence, after intraperitoneal injection into mice bearing human tumors. These findings suggest that this virus may be efficacious and safe for use in localized human malignancies of non-neural origin such as malignant mesothelioma. "Use of a 'replication-restricted' herpes virus to treat experimental human malignant mesothelioma", Kucharczyk, et al.., Cancer Research, 57(3):466-71, February 1, 1997.Modified, nonneurovirulent herpes simplex viruses (HSVs) have shown promise in treatment of brain tumors. However, HSV-1 can infect and cause disintegration of a wide variety of cell types. HSV-1716, a mutant of the virus lacking both copies of the gene coding ICP-34.5, can effectively treat a localized intraperitoneal malignancy. Human malignant mesothelioma cells supported the growth of HSV-1716 and efficiently disintegrated in vitro. Intraperitoneal injection of HSV-1716 into animals with established tumor nodules reduced tumor burden and significantly prolonged survival in an animal model of non-central nervous system-localized human malignancy, without dissemination or persistence, after intraperitoneal injection into mice bearing human tumors. These findings suggest that this virus may be efficacious and safe for use in localized human malignancies of non-neural origin such as malignant mesothelioma. "Use of a 'replication-restricted' herpes virus to treat experimental human malignant mesothelioma", Kucharczyk, et al.., Cancer Research, 57(3):466-71, February 1, 1997.

POTENTIAL "SUICIDE" GENE THERAPY FOR MALIGNANT MESOTHELIOMA

Replication -defective adenovirus vectors were generated in which the gene of interest lacZ, luciferase or herpes simplex virus thymidine kinase (HSV-tk) is driven by the adenovirus major late promoter (MLP) or the human cytomegalovirus immediate-early gene promoter/enhancer (CMV). In vitro experiments with rat and human mesothelioma cell lines revealed that the CMV promoter was stronger than the MLP promoter regarding levels of expression of the luciferase reporter gene and ganciclovir (GCV) killing efficiency after tk gene transfer. Following administration of lacZ recombinant adenovirus into the pleural cavity of rats with established mesothelioma, a widespread distribution of infectious virus particles through the thorax contents was demonstrated. However, a relatively small proportion of tumor cells were transduced. Nevertheless, a strong growth inhibition was observed following treatment with recombinant tk adenovirus and GCV. In a survival study, animals were treated with recombinant tk adenovirus and a 14 days course of GCV. This treatment prolonged symptom-free survival time from 19 days in the controls to 33 days in the treated group. These responses can be best explained by assuming continued tk expression in or around the tumor tissue during GCV treatment. These results confirm and extend earlier findings with the same model and demonstrate the potential of the herpes simplex virus thymidine kinase suicide gene therapy as a local treatment for malignant mesothelioma. "Gene therapy of experimental malignant mesothelioma using adenovirus vectors encoding the HSV-tk gene", Esandi, et al.,Gene Therapy, 5(4):280-7, April, 1997.

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New approaches for mesothelioma: biologics, vaccines, gene therapy, and other novel agents.[Related Titles]

Semin Oncol 2002 Feb;29(1):82-96 (ISSN: 0093-7754)
Nowak AK; Lake RA; Kindler HL; Robinson BW [Related Authors]
University Department of Medicine, University of Western Australia, Verdun St Nedlands, Australia.

Although malignant mesothelioma is not a classically immunogenic cancer, there is abundant evidence for immune recognition. The relative ease of obtaining tumor tissue makes mesothelioma ideal for studying surrogate biomarkers such as lymphocytic infiltration or expression of transduced genes. There is evidence that malignant mesothelioma patients as well as asbestos-exposed persons without mesothelioma have impaired immune responsiveness. Substantial progress has been made in animal models using several biological and immunological techniques, but clinical application has been problematic. Systems studied have included lysis by interleukin-2 (IL-2)-activated lymphokine-activated killer (LAK) cells, tumor necrosis factor-alpha (TNF-alpha), a p16-expressing adenovirus vector, suicide gene therapy using the herpes simplex virus-tyrosine kinase (HSV-tk) followed by ganciclovir, and immunomodulatory gene therapy with IL-2, IL-4, interferon-gamma (IFN-gamma), IFN-alpha, TNF-alpha, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-6, and IL-1beta transfected into tumors. Vaccinia virus has been studied as a vector for cytokine gene transfer. Suicide gene therapy has been combined with a tumor vaccine. The University of Western Australia is initiating a pilot study of autologous vaccination in malignant mesothelioma. Novel agents under study include the angiogenesis inhibitors SU5416, bevacizumab, and thalidomide. ZD1839, an orally administered, highly selective inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase, is being tested in a phase II trial. Since platelet-derived growth factor (PDGF) is thought to be an autocrine growth factor for mesothelioma STI-571 (Gleevec; Novartis, Basel, Switzerland), a highly selective inhibitor of the PDGF receptor tyrosine kinase, is being tested in a phase II trial. The development of more active cytotoxic combinations in this disease should facilitate further studies of chemoimmunotherapy. It seems likely that no single treatment modality will be effective by itself. [Copyright 2002 by W.B. Saunders Company.].