Suicide gene therapy for human uterine adenocarcinoma cells using herpes simplex virus thymidine kinase

Towards fibroid gene therapy: adenovirus-mediated delivery of herpes simplex virus 1 thymidine kinase gene/ganciclovir shrinks uterine leiomyoma in the Eker rat model

BACKGROUND/AIMS

The objective of this study was to assess in vivo gene therapy of uterine leiomyomas in the Eker rat model using adenovirus (Ad)-mediated delivery of herpes simplex virus 1 thymidine kinase gene (HSV1TK) followed by ganciclovir (GCV) treatment.

METHODS

We randomized 27 female Eker rats with MRI-confirmed uterine leiomyomas to a single treatment with direct intra-tumor injection of Ad-HSV1TK/GCV, Ad-LacZ/GCV, or medium alone. Samples were collected from tumors, other body organs, and blood at 10, 20, and 30 days after treatment to assess the safety and efficacy of the treatment.

RESULTS

Ad-HSV1TK/GCV treatment significantly decreased uterine fibroid volume by 75 +/- 16, 58.7 +/- 6.3, and 67.5 +/- 27.5%, of the pretreatment volume at days 10, 20, and 30, respectively. Ad-HSV1TK/GCV increased caspase-3 activity, Bax expression, and TUNEL apoptosis marker, and it decreased cyclin D1, PCNA, Bcl2, and PARP protein expressions. Ad transfection induced local CD4+ and CD8+ infiltration and serum anti-Ad antibodies. Additionally, Ad transfection was tumor-localized and safe to non-target tissues.

CONCLUSION

These studies demonstrate a marked efficiency and high safety for the Ad-HSV1TK/GCV therapeutic approach in the context of Eker rat uterine leiomyomas and provide essential preclinical data for the development of Ad-HSV1TK/GCV gene therapy for uterine fibroids.

Herpes simplex virus-thymidine kinase-based suicide gene therapy as a "molecular switch off" for nerve growth factor production in vitro

Tissue-engineered constructs offer a new hope to patients suffering from functional impairment after nerve injury. An effort has been made to focus on delivery, regulation, and "molecular shutoff" of nerve growth factor (NGF) in tissue-engineered constructs. We have previously demonstrated that human embryonic kidney (HEK-293) cells can be genetically modified to secrete NGF at varying time points upon up regulation with Ponasterone A (PonA) both in vitro and in vivo. In the present study, HEK-293 cells that stably and inducibly produce NGF were further stably transfected with herpes simplex virus-thymidine kinase gene as a suicide gene (hNGF-EcR-293-TK) in order to shut off the NGF secretion and kill the cells upon treatment with ganciclovir (GCV). These cells following induction with PonA secreted NGF levels of 6659.2 +/- 489.4 pg/mL at day 10 postbooster dose at day 5, which was significantly higher than the control noninduced cells. The NGF secreted by these cells was bioactive as determined by a rat adrenal pheochromocytoma (PC-12) cell bioassay. Treatment of these cells with GCV significantly reduced the NGF levels to 645.3 +/- 16.2 pg/mL at day 10 and live cell numbers dropped to 7.95 x 10(3) +/- 278 compared to 2.73 x 10(5) +/- 6.1 x 10(4). GCV-treated cell media when transferred to the PC-12 cell bioassay demonstrated less than 10% cells differentiating into neurite-like extensions. We conclude that hNGF-EcR-293-TK cells can inducibly secrete bioactive NGF when treated with the inducing agent and can also be killed upon treatment with GCV. This double-gene transfection for gene expression and molecular shutoff mechanism will be a useful tool in tissue-engineered nerve constructs.

Gonadotropin-releasing hormone receptor–targeted gene therapy of gynecologic cancers

The majority of ovarian, endometrial, and breast cancers express gonadotropin-releasing hormone (GnRH) receptors. Apart from reproductive organs (ovaries, fallopian tubes, and uterus) that are normally removed during surgical therapy of ovarian or endometrial cancer, pituitary gonadotrophs also express GnRH receptors. The signal transduction pathway in tumor cells is basically different from the classic GnRH receptor signal transduction, which is known to operate in the pituitary gonadotrophs and can therefore be considered tumor specific. Other organs and hematopoetic stem cells do not express GnRH receptors. We have recently shown specific activation of nucleus factor κB in ovarian, endometrial, and breast cancers after treatment with GnRH agonists. Based on this tumor-specific signaling pathway and the distribution pattern of GnRH receptors, we have developed and successfully tested a gene therapy concept by using a GnRH analogue as an inducer for the transcription of a therapeutic gene in cell culture and in nude mice.

Gene therapy and reproductive medicine

OBJECTIVE

To review the literature on the principles of gene therapy and its potential application in reproductive medicine.

DESIGN

Literature review.

SETTING

Gene therapy involves transfer of genetic material to target cells using a delivery system, or vector. Attention has primarily focused on viral vectors. Significant problems remain to be overcome including low efficacy of gene transfer, the transient expression of some vectors, safety issues with modified adenoviruses and retroviruses, and ethical concerns. If these issues can be resolved, gene therapy will be applicable to an increasing spectrum of single and multiple gene disorders, as the Human Genome Project data are analyzed, and the genetic component of human disease becomes better understood. Gynecologic gene therapy has advanced to human clinical trials for ovarian carcinoma, and shows potential for the treatment of uterine leiomyomata. Obstetric applications of gene therapy, including fetal gene therapy, remain more distant goals.

CONCLUSION(S)

Concerns about the safety of human gene therapy research are being actively addressed, and remarkable progress in improving DNA transfer has been made. The first treatment success for a genetic disease (severe combined immunodeficiency disease) has been achieved, and ongoing research efforts will eventually yield clinical applications in many spheres of reproductive medicine.

Specific inhibition of estrogen receptor alpha function by antisense oligodeoxyribonucleotides

We have tested the effect of a range of antisense oligodeoxyribonucleotides (ODN) directed against the human estrogen receptor alpha (ERalpha) on ERalpha protein expression and function. Antisense ERalpha ODN transfected into the ERalpha-positive human breast carcinoma cell line MCF7-K2 showed variable responses dependent on the oligo used. The most active antisense ODN (oligo 7) decreased the levels of ERa protein by 61% as measured by Western blot analysis. Exogenous 17beta-estradiol (17beta-E2), but not 17alpha-E2, augmented this effect, with a threshold effect at 10(-8) M 17beta-E2. The inhibitory effect of antisense ERa oligo 7 was confirmed by measurement of functional ERalpha protein. 3H-17beta-E2 binding to MCF7 cell extracts was inhibited to approximately 40% of control values in the presence of oligo 7. Antisense-transfected MCF7-K2 cell cultures produced a further 30% binding reduction in the presence of exogenous 17beta-E2. An inhibitory effect on 17beta-E2-dependent cell function was confirmed by the demonstration that ERalpha oligo 7-transfected MCF7-K2 cells failed to exhibit 17beta-E2-stimulated cell proliferation. Exogenous 17beta-E2 enhanced the inhibitory effect of the antisense ODN by increasing ODN transfection efficiency but without ERalpha catabolism via the proteosomal pathway, suggesting an effect of 17beta-E2 on the plasma membrane and the existence of different ERalpha degradation pathways in the MCF7-K2 cell subclone. As 17beta-E2 had no effect on ERalpha protein degradation, we conclude that the observed reduction of ERalpha protein levels is due solely to the presence of the antisense ERalpha ODN. Antisense ERalpha ODN molecules, therefore, may form the basis of effective therapies against ERalpha-dependent malignancies.

Ganciclovir and penciclovir, but not acyclovir, induce apoptosis in herpes simplex virus thymidine kinase-transformed baby hamster kidney cells

The efficacies of ganciclovir (GCV), penciclovir (PCV) and acyclovir (ACV) in inducing cell death in the herpes simplex virus thymidine kinase (HSVTK) system were compared. HSVTK-transformed baby hamster kidney cells treated with GCV, PCV or ACV were monitored for growth by viable count, and for death by TUNEL assay, propidium iodide staining, detection of phosphatidyl serine translocation and detection of DNA laddering. All compounds delayed growth or reduced viability of HSVTK-transformed cells. Drug treatment reduced levels of cyclin B1 message (which normally peaks in G2/M-phase of the cell cycle) and induced a four- to fivefold upregulation of GADD45 message. Treatment with GCV or PCV induced rapid accumulation of cells in S-phase and apoptotic death. Treatment with ACV, however, was associated with sustained S-phase arrest. GCV (and to a lesser extent PCV) increased phosphatidyl serine translocation, induced positive TUNEL results with alterations in cell morphology, caused marked propidium iodide staining and induced DNA laddering. By contrast, up to 7 days' exposure to ACV did not induce DNA laddering, with very little TUNEL staining. ACV treatment had little effect on phosphatidyl serine translocation and propidium iodide staining was markedly reduced compared with treatment with the other compounds. Thus, by all criteria, GCV was the most potent inducer of cell death. The current theories regarding apoptosis or necrosis as the preferred form of cell death in prodrug gene therapy are considered and the suitability of PCV or ACV as potential alternatives to GCV in the HSVTK system is discussed.

Gene therapy for endometrial carcinoma with the herpes simplex thymidine kinase gene

We investigated whether retrovirus-mediated transfer of the herpes simplex thymidine kinase gene into a human endometrial carcinoma (EC4) cell line can sensitize these cells to the prodrug ganciclovir (GCV) and thereby provide a therapeutic option for this cancer. A retrovirus encoding for the herpes simplex virus tip-1 (HSV) thymidine kinase (tk) gene was generated in which expression of tk is under control of the myeloproliferative sarcoma virus (MPSV) promoter/enhancer. We used human mutated dihydrofolate reductase (DHFR) cDNA as a selectable marker. Expression of tk was confirmed by Northern blot analysis and reverse transcription polymerase chain reaction. We demonstrated that the combination of retrovirally mediated tk gene transfer and GCV treatment effectively inhibits proliferation and causes death of EC4 cells in vitro. A bystander killing effect was observed when 90% of uninfected tumor cells were mixed with only 10% of HSVtk-infected cells. We suggest that a gene therapy approach to endometrial carcinoma can be established using retroviral transfer of HSVtk to tumor cells and subsequent administration of GCV.

Newcastle disease virus (NDV): brief history of its oncolytic strains

BACKGROUND

While genetically engineered viruses are now being tested for the virus therapy of human cancers, some naturally occurring viruses display unmatched oncolytic activity. Newcastle disease virus (NDV) excels as an oncolytic agent.

OBJECTIVES

As its virulence versus attenuation can be explained on molecular biological bases, it may be possible to develop or select highly oncolytic strains of NDV without adverse toxicity.

STUDY DESIGN

Questions are posed as to the mechanisms of viral oncolysis, the appropriateness of tests to predict oncolytic activity of a given NDV strain and the best modes of administration for oncolytic effects. Answers are provided based on specific data or on considerations drawn from experience (the authors use NDV oncolysates to immunize against melanoma and kidney carcinoma) or from analogous clinical situations (therapeutic use of mumps or measles viruses).

RESULTS AND CONCLUSIONS

NDV oncolysates probably suit better for immunotherapy (providing also active tumor-specific immunization) than massive repeated inoculations of NDV strains, especially when the NDV strain used is not proven to be oncolytic by appropriate pre-clinical tests.