Poor prognosis of retroperitoneal mixed extragonadal germ cell tumors in an HIV-infected man with severe immunosuppression and bilateral cryptorchidism: a case report.

BACKGROUND: Nonseminomatous germ cell tumors (NSGCTs) represent one of the main groups of germ cell tumors (GCTs), and they have a more invasive course than seminomatous GCTs. Human immunodeficiency virus (HIV) positivity is considered to be a risk factor for testicular seminoma patients, but reports about HIV-infected individuals with NSGCTs are rare. CASE PRESENTATION: We report a case of a retroperitoneal mixed extragonadal germ cell tumor in an HIV-infected man who has been diagnosed with bilateral cryptorchidism since birth. A 30-year-old man presented with a large heterogeneously mixed echo mass located in the right lower abdomen according to an abdominal ultrasound; he was HIV-positive and had a low CD4 count of 70 cells/ml in the followed test, which suggested severe immunosuppression, and ultrasound-guided biopsy histology revealed a malignant yolk sac tumor of the testis. First, the patient received combination antiretroviral therapy; then, to relieve his symptoms, an exploratory laparotomy and retroperitoneal neoplasm resection under general anesthesia were performed for subsequent treatment. The postoperative histopathological examination indicated that the patient exhibited malignant mixed GCTs of the undescended testis that were composed predominantly of yolk sac tumors with foci of embryonal cell carcinoma and seminoma; It is a rare type in various GCTs, especially in HIV-infected patients. After the operation, the patient underwent computed tomography follow-up scans at 1 week and 2 weeks, and the results showed that the size of the right inguinal mass gradually increased, which suggested a poor outcome. To limit the growth of the tumors, right inguinal mass resection under local anesthesia was performed 17 days after the initial operation, and pathological examination revealed mixed GCT metastasis. Subsequently, the patient received salvage chemotherapy with a regimen of cisplatin, etoposide, and ifosfamide. Unfortunately, the patient died 1 week after the first cycle of chemotherapy because of severe immunosuppression, a low platelet count and cancer cachexia. CONCLUSIONS: Because of severe immunosuppression, the treatment of advanced extragonadal NSGCTs in an HIV-infected patient resulted in a poor prognosis. This outcome should be considered in further research, and appropriate management for achieving long-term survival needs to be established.

The HERV-K accessory protein Np9 controls viability and migration of teratocarcinoma cells.

Human endogenous retroviruses are remnants of ancient germline infections that make up approximately 8% of the modern human genome. The HERV-K (HML-2) family is one of the most recent entrants into the human germline, these viruses appear to be transcriptionally active, and HERV-K viral like particles (VLPs) are found in cell lines from a number of human malignancies. HERV-K VLPs were first found to be produced in teratocarcinoma cell lines, and since then teratocarcinoma has been thought of as the classical model for HERV-Ks, with the NCCIT teratocarcinoma cell line particularly known to produce VLPs. Treatment for teratocarcinoma has progressed since its discovery, with improved prognosis for patients. Since the introduction of platinum based therapy, first year survival has greatly improved even with disseminated disease; however, it is estimated that 20% to 30% of patients present with metastatic germ cell tumor relapse following initial treatments. Also, the toxicity associated with the use of chemotherapeutic agents used to treat germ cell tumors is still a major concern. In this study, we show that the depletion of the HERV-K accessory protein Np9 increases the sensitivity of NCCIT teratocarcinoma cells to bleomycin and cisplatin. While decreasing the expression of Np9 had only a modest effect on the baseline viability of the cells, the reduced expression of Np9 increased the sensitivity of the teratocarcinoma cells to environmental (serum starvation) and chemical (chemotherapeutic) stresses. Np9 is also essential to the migration of NCCIT teratocarcinoma cells: in a wound closure assay, reduced expression of Np9 resulted in cells migrating into the wound at a slower rate, whereas reintroduction of Np9 resulted in NCCIT cells migrating back into the wound in a manner similar to the control. These findings support the implication that the HERV-K accessory protein Np9 has oncogenic potential.

Acquired cancer resistance to combination immunotherapy from transcriptional loss of class I HLA.

Understanding mechanisms of late/acquired cancer immunotherapy resistance is critical to improve outcomes; cellular immunotherapy trials offer a means to probe complex tumor-immune interfaces through defined T cell/antigen interactions. We treated two patients with metastatic Merkel cell carcinoma with autologous Merkel cell polyomavirus specific CD8+ T cells and immune-checkpoint inhibitors. In both cases, dramatic remissions were associated with dense infiltration of activated CD8+s into the regressing tumors. However, late relapses developed at 22 and 18 months, respectively. Here we report single cell RNA sequencing identified dynamic transcriptional suppression of the specific HLA genes presenting the targeted viral epitope in the resistant tumor as a consequence of intense CD8-mediated immunologic pressure; this is distinguished from genetic HLA-loss by its reversibility with drugs. Transcriptional suppression of Class I loci may underlie resistance to other immunotherapies, including checkpoint inhibitors, and have implications for the design of improved immunotherapy treatments.

DNA hypomethylation and aberrant expression of the human endogenous retrovirus ERVWE1/syncytin-1 in seminomas.

BACKGROUND: Syncytin-1 and 2, human fusogenic glycoproteins encoded by the env genes of the endogenous retroviral loci ERVWE1 and ERVFRDE1, respectively, contribute to the differentiation of multinucleated syncytiotrophoblast in chorionic villi. In non-trophoblastic cells, however, the expression of syncytins has to be suppressed to avoid potential pathogenic effects. Previously, we have shown that the transcriptional suppression of ERVWE1 promoter is controlled epigenetically by DNA methylation and chromatin modifications. In this study, we describe the aberrant expression of syncytin-1 in biopsies of testicular germ cell tumors. RESULTS: We found efficient expression and splicing of syncytin-1 in seminomas and mixed germ cell tumors with seminoma component. Although another fusogenic gene, syncytin-2 was also derepressed in seminomas, its expression was significantly lower than that of syncytin-1. Neither the transcription factor GCM1 nor the increased copy number of ERVWE1 were sufficient for this aberrant expression of syncytin-1 in seminomas. In accordance with our recent finding of the highly increased expression of TET1 dioxygenase in most seminomas, the ERVWE1 promoter was significantly hypomethylated in comparison with the matched controls. In contrast, 5-hydroxymethylcytosine levels were not detectable at the ERVWE1 promoter. We further describe that another endogenous retroviral element adjacent to ERVWE1 remains transcriptionally suppressed and two additional HERV-W family members are only slightly upregulated in seminomas. CONCLUSIONS: We conclude that DNA demethylation of the ERVWE1 promoter in seminomas is a prerequisite for syncytin-1 derepression. We propose the spliced syncytin-1 expression as a marker of seminoma and suggest that aberrant expression of endogenous retroviruses might be a correlate of the hypomethylated genome of seminomas.

Acute kidney injury and inflammatory immune reconstitution syndrome in mixed genotype (A/E) hepatitis B virus co-infection in HIV-associated lymphoma.

We report a first case of HIV-associated lymphoma (HAL) presenting with acute kidney injury (AKI) and inflammatory immune reconstitution syndrome (IRIS). A 39-year-old male, treated with nonsteroidal anti-inflammatory drugs (NSAIDs) for one month prior to admission, developed AKI, left testicular tumor, and recurrent swelling of the right parotid gland. A resected testicular tumor exhibited features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma. Renal biopsy showed hydro-degeneration of renal tubules, interstitial inflammatory cells, and a small number of lymphoma cells in the sub-capsule, compatible with acute interstitial nephritis. His renal dysfunction rapidly recovered following chemotherapy and combination antiretroviral therapy (cART). He developed pneumonia concomitantly with a decrease in HIV-RNA level and an increase in CD4+ cells after the first cycle of chemotherapy, which spontaneously resolved after the second cycle of chemotherapy without additional anti-infection drugs; thus, his pneumonia fulfilled the diagnostic criteria for IRIS. We suggest that IRIS may frequently develop during chemotherapy for HAL, but may be overlooked. He was coinfected with hepatitis B virus (HBV), which genotypes known as is associated with liver-related mortality and response to antiviral therapy; recently, an intimate interplay between HIV and HBV in the onset of lymphoma has been reported. Therefore, we addressed the HBV genotype in the patient. The analysis revealed that he exhibited a mixed genotype (A/E) not native to Japan and primarily found in Europe and North America or West Africa. These findings suggest that universal vaccination for juveniles against HBV is warranted in Japan.

Microscopic diffuse large B-cell lymphoma (DLBCL) occurring in pseudocysts: do these tumors belong to the category of DLBCL associated with chronic inflammation?

We report 2 cases of localized, microscopic diffuse large B-cell lymphoma (DLBCL) that were detected incidentally within pseudocysts. In case 1, the neoplasm was identified within a 26-cm, 860-g adrenal gland pseudocyst. In case 2, the neoplasm was detected within a 9-cm, 90-g paratesticular pseudocyst. In both cases, the neoplastic cells were large, had a nongerminal center B-cell immunophenotype, and were positive for Epstein-Barr virus (EBV)-encoded RNA detected by in situ hybridization. The most appropriate classification of these tumors using current World Health Organization classification is uncertain. The best fit seems to be DLBCL associated with chronic inflammation (DLBCL-CI), defined as DLBCL arising in the context of long-standing chronic inflammation and associated with EBV infection, with the prototype for this category being pyothorax-associated lymphoma. This term has been used by others in the literature for tumors similar to the cases reported here. However, in the 2 cases we report chronic inflammation was not a prominent feature, and the inflammatory cells that were present showed little relationship to the lymphoma cells. The findings in these cases have led us to question the role of chronic inflammation in pathogenesis. Perhaps the closed space of the pseudocyst, by preventing a cytolytic response to EBV-infected cells, results in local immunodeficiency that may be most important for pathogenesis. We also have concerns about using the term DLBCL-CI for these tumors. Perhaps the cases we report and the few other similar cases reported previously deserve their own category in a future version of the World Health Organization classification.

Custom human endogenous retroviruses dedicated microarray identifies self-induced HERV-W family elements reactivated in testicular cancer upon methylation control.

Endogenous retroviruses (ERVs) are an inherited part of the eukaryotic genomes, and represent approximately 400,000 loci in the human genome. Human endogenous retroviruses (HERVs) can be divided into distinct families, composed of phylogenetically related but structurally heterogeneous elements. The majority of HERVs are silent in most physiological contexts, whereas a significant expression is observed in pathological contexts, such as cancers. Owing to their repetitive nature, few of the active HERV elements have been accurately identified. In addition, there are no criteria defining the active promoters among HERV long-terminal repeats (LTRs). Hence, it is difficult to understand the HERV (de)regulation mechanisms and their implication on the physiopathology of the host. We developed a microarray to specifically detect the LTR-containing transcripts from the HERV-H, HERV-E, HERV-W and HERV-K(HML-2) families. HERV transcriptome was analyzed in the placenta and seven normal/tumoral match-pair samples. We identified six HERV-W loci overexpressed in testicular cancer, including a usually placenta-restricted transcript of ERVWE1. For each locus, specific overexpression was confirmed by quantitative RT-PCR, and comparison of the activity of U3 versus U5 regions suggested a U3-promoted transcription coupled with 5'R initiation. The analysis of DNA from tumoral versus normal tissue revealed that hypomethylation of U3 promoters in tumors is a prerequisite for their activation.

Maternal Epstein-Barr virus and cytomegalovirus infections and risk of testicular cancer in the offspring: a nested case-control study.

During recent decades the incidence of testicular cancer (TC) has increased rapidly around the world. Associated exogenous etiological factors might therefore be identifiable. We performed a case-control study nested within Finnish, Swedish and Icelandic maternity cohorts exploiting early pregnancy serum samples to evaluate the role of congenital or neonatal infections with Epstein-Barr virus (EBV) and cytomegalovirus (CMV) as risk factors of TC in the offspring. For each case-index mother pair, three or four matched control-control mother pairs were identified using national population registries. First trimester sera were retrieved from the index mothers of 66 TC cases and 258 matched control mothers, and were tested for antibodies to EBV and CMV. High level of maternal EBV IgG antibodies was associated with significantly increased risk of TC in the offspring (odds ratio (OR), 2.50; 95% confidence interval (CI), 1.15, 5.40), especially with risk of non-seminoma TC (OR, 2.73; 950% CI, 1.25, 5.99) and non-seminoma TC diagnosed under 8 years of age (OR, 2.72; 95% CI, 1.05, 7.04). In contrast, offspring of CMV IgG-seropositive mothers had a decreased risk of TC diagnosed under 8 years of age (OR, 0.35; 95% CI, 0.14, 0.89). Our results suggest that EBV and CMV infections may be associated with TC.

Testicular persistence of Parvovirus B19: evidence for preferential infection of germ cell tumors.

Human Parvovirus B19 has previously been implicated in the pathogenesis of testicular germ cell tumors, but this could not have been confirmed. This study was designed to investigate the testicular persistence of Parvovirus B19 and possible associations with germ cell tumors. Paraffin-embedded or fresh tissues from 36 germ cell tumors, 20 germ cell aplasias, 26 normal testicular tissues, 20 liver tissues, and 20 spleen tissues were evaluated by two different molecular assays: a nested PCR for Parvovirus B19 capsid genes and a commercial quantitative real-time PCR. Positive results were further confirmed by another commercial real-time PCR assay. Viral DNA was detected in 3 of 36 (8.3%) germ cell tumors, but not in other groups. Viral loads observed in all positive samples were less than 20 IU/reaction, suggesting very low levels of viral replication or latency. These results either directly or indirectly imply the involvement of Parvovirus B19 with testicular germ cell tumors. Viral persistence in normal testis, germ cell aplasia tissues, or hepatic/splenic tissues was not observed in this study.

Histopathologic and molecular aspects of CD56+ natural killer/ T-cell lymphoma of the testis.

Primary nasal-type natural killer/T-cell lymphoma of the testis is a rare malignancy. Although dissemination to the testis from other sites occurs somewhat more frequently than a primary presentation, even secondary testicular involvement is uncommon. In this article, the authors report on the comprehensive histopathologic, immunohistochemical, and molecular analysis of a case of primary testicular nasal-type natural killer/T-cell lymphoma, and review the features of 16 previously reported patients. The investigation carried out in this study indicates that the testicular nasal-type natural killer/T-cell lymphomas occur at a younger age than their B-cell counterparts, express cytoplasmic CD3 and surface CD56, and consistently show an infection by Epstein-Barr virus. These tumors have variable expression of T-cell antigens other than cytoplasmic CD3 and may show monoclonal rearrangement of T-cell receptor genes. Testicular natural killer/T-cell lymphomas of nasal type invariably follow an aggressive clinical course.

At least 50% of human-specific HERV-K (HML-2) long terminal repeats serve in vivo as active promoters for host nonrepetitive DNA transcription.

We report the first genome-wide comparison of in vivo promoter activities of a group of human-specific endogenous retroviruses in healthy and cancerous germ line tissues. To this end, we employed a recently developed technique termed genomic repeat expression monitoring. We found that at least 50% of human-specific long terminal repeats (LTRs) possessed promoter activity, and many of them were up- or downregulated in a seminoma. Individual LTRs were expressed at markedly different levels, ranging from approximately 0.001 to approximately 3% of the housekeeping beta-actin gene transcript level. We demonstrated that the main factors affecting the LTR promoter activity were the LTR type (5'-proviral, 3' proviral, or solitary) and position with regard to genes. The averaged promoter strengths of solitary and 3'-proviral LTRs were almost identical in both tissues, whereas 5'-proviral LTRs displayed two- to fivefold higher promoter activities. The relative content of promoter-active LTRs in gene-rich regions was significantly higher than that in gene-poor loci. This content was maximal in those regions where LTRs "overlapped" readthrough transcripts. Although many promoter-active LTRs were mapped near known genes, no clear-cut correlation was observed between transcriptional activities of genes and neighboring LTRs. Our data also suggest a selective suppression of transcription for LTRs located in gene introns.

HIV and plasmablastic lymphoma manifesting in sinus, testicles, and bones: a further expansion of the disease spectrum.

Patients with HIV infection are at increased risk for B-cell neoplasms and plasma cell dyscrasias. Both B cell and plasma cell tumors tend to be intermediate or high grade and are frequently associated with Epstein-Barr virus. Patients with HIV infection are also at higher risk of acquiring plasmablastic lymphoma. Until this time, only sinus, oral gastrointestinal, and lung manifestation have been noted. In this report we describe a 41-year-old male with HIV infection who developed multiple pleomorphic, extramedullary plasmablastic lymphomas associated with Epstein-Barr virus. We review the clinical and immunological features of his malignancy and thereby expand the spectrum of disease to include additional sites (bones, testicles) not previously reported.

NK and NK-like T-cell lymphoma in extranasal sites: a comparative clinicopathological study according to site and EBV status.

AIMS: To analyse the clinicopathological findings of extranasal CD56+ cytotoxic T- or NK-cell lymphomas in different organs and to compare Epstein-Barr virus (EBV)+ and EBV- lymphoma of non-blastoid cytomorphology. METHODS AND RESULTS: Fifty-one cases of cCD3+ T-cell intracellular antigen (TIA-1)+ CD56+ lymphomas of extranodal/extranasal origin were included in the study. The primary sites of the CD56+ tumours were soft tissue (n = 10), the gastrointestinal (GI) tract (n = 13), the skin (n = 15), upper aerodigestive tract excluding nasal and nasopharyngeal regions (n = 11), the testis (n = 1), and parotid gland (n = 1). TCR gene rearrangement was detected in seven of 47 cases examined (16%). EBV was positive in 39 of 51 cases (76%). The positive rate of EBV was higher in tumours of soft tissue (80%), GI tract (92%), and skin (80%), and lowest in the upper aerodigestive tract excluding the nasal and nasopharyngeal region (50%). Tumours of the soft tissue and the upper aerodigestive tract tended to present with localized disease (P = 0.002). The 2-year survival rate was lowest for tumours of the GI tract (P = 0.0256). EBV- TCR- lymphoma showed less necrosis (P = 0.0133) and a better 2-year survival rate (P = 0.0066) than EBV+ TCR- lymphoma. Patients with EBV+ TCR+ lymphomas tended to present with localized disease, more often than EBV+ TCR- lymphoma (P = 0.0186). Significant prognostic factors in all CD56+ lymphomas were the site (P = 0.0256), EBV status (P = 0.0026), necrosis with or without perforation (P = 0.0338) and the presence of pleomorphic large tumour cells (P = 0.0428). Cox's regression analysis adjusting for other pathological parameters showed EBV status to be the only independent prognostic factor (P = 0.018). CONCLUSIONS: Extranodal CD56+ EBV- lymphoma at extranasal sites is a clinically less aggressive malignancy and displays less necrosis than CD56+ EBV+ lymphoma. Because CD56+ EBV+ TCR+ lymphomas show similar pathological and clinical findings to CD56+ EBV+ TCR- lymphomas, nasal-type NK/T-cell lymphomas at extranasal sites should be diagnosed as such on the basis of EBV+, cytotoxic T or NK phenotype irrespective of the genotype determined by molecular study.

Outcome of patients with HIV-related germ cell tumours: a case-control study.

Testicular germ cell tumour (GCT) is not an AIDS-defining illness despite an increased incidence in men with HIV infection. We performed a matched case-control study comparing outcomes in HIV-positive men and the general population with GCT, using three age and stage matched controls for each case. There was no difference in the 5-year GCT-free survival between cases and controls. However, overall survival was significantly decreased in the cases (log rank P=0.03). HIV was responsible for 70% of this mortality. The relapse-free survival for stage I patients treated with orchidectomy and surveillance was not affected by HIV status (log rank P=0.68). There was no difference in disease free survival in patients with metastatic disease (log rank P=0.78). The overall survival has not improved since the introduction of highly active antiretroviral therapy (log rank P=0.4). Thus, HIV-related GCT is not more aggressive than GCT in the general population.

Sertoli cell tumor associated with polyomavirus infection in a Gouldian finch (Erythrura gouldiae).

A 3-yr-old male Gouldian finch (Erythrura gouldiae) died after 2 wk of lethargy, emaciation, feather loss, and abdominal distension. The bird was housed in an aviary for breeding, but it had shown loss of fertility in the previous breeding season. Necropsy revealed a gross, firm, and yellow mass involving the left testis. Histologically, the mass was a mixed form, intratubular and diffuse, Sertoli cell tumor. Some neoplastic cells had intranuclear inclusion bodies that immunoelectron microscopy proved to be polyomavirus particle aggregates. There were no viral inclusions in other tissues. The possible role of infection in the pathogenesis of the tumor is discussed.

No association between human parvovirus B19 and testicular germ cell cancer.

The incidence of testicular germ cell cancer, which is the most common cancer among young male adults, is increasing. The aetiology remains unknown, although a virus has been proposed. A previous study has shown a high prevalence of human parvovirus B19 (B19) DNA in the testes of patients with testicular germ cell tumours (85%) and suggested that B19 may play a role in tumour development. To address this question of causality, seroreactivity to B19 was studied among cases (n=80) and controls (n=241) using serum samples drawn before the onset of disease, in addition to an elucidation of the frequency of virus DNA in a retrospectively collected 2-year testicular carcinoma series. No association was found between B19 seropositivity and the risk of testicular cancer (odds ratio=1.03; 95% confidence interval=0.60-1.77) nor was there any dose-response relation (P for trend=0.53). This study did, however, confirm the observation that B19 DNA can be detected in testicular carcinoma tissue, as 4 of 24 cases were found to be positive, while no B19 DNA could be detected in the control cases. It is speculated that this finding may be due to susceptibility of the carcinoma cells to B19 virus owing to high-level expression of the viral receptor glycosphingolipid (Gb4) and possible other putative cellular factors resulting in a localized persistence initiated after the development of cancer.

Selective Differential Display of RNAs containing interspersed repeats: analysis of changes in the transcription of HERV-K LTRs in germ cell tumors.

A technique for the Selective Differential Display of RNAs containing Interspersed Repeats (SDDIR) has been elaborated. SDDIR involves two main steps: (1) selective amplification by RT-PCR of a subset of the total cellular RNA containing a certain type of repetitive element, and (2) side-by-side display of the amplicons derived from the tissues under comparison by means of gel electrophoresis in parallel lanes. The technique was used to compare the expression of transcripts containing LTR (Long Terminal Repeat) sequences derived from human endogenous retrovirus K (HERV-K) in testicular germ cell tumors and in corresponding normal tissue. SDDIR enabled us to obtain an overview of LTRs represented in the total transcribed fraction and to reveal differences in transcription patterns of the LTRs in normal and tumor tissues. An unexpectedly large number of LTRs was found to be transcribed, and the levels of many of the transcripts differed between normal and tumor tissues.

Clinical aspects and management of Hodgkin's disease and other tumours in HIV-infected individuals.

As the AIDS epidemic advances, the spectrum of malignancies encountered is expanding. Several non-AIDS defining cancers, i.e. Hodgkin's disease (HD), anal and testicular cancer, are increasing in incidence in HIV-infected patients. The widespread use of highly active antiretroviral therapy (HAART) in industrialised countries has resulted in substantial improvement in the survival of HIV-infected patients. It is likely that in the future, cancers associated with long-term mild immune suppression will occur at an increased rate in long-term survivors of HIV infection. The natural history of the majority of non-AIDS defining tumours differs from that of the general population. Unusual aspects of tumour localisation, growth behaviour and therapeutical responses distinguish tumours in patients with HIV infection from those without. This paper reviews the most relevant data on the epidemiology, pathology, clinical features and treatment of the most frequently reported non-AIDS defining tumours, i.e. HD, lung, testicular and skin cancers.

Gonadal tumors of mice double transgenic for inhibin-alpha promoter-driven simian virus 40 T-antigen and herpes simplex virus thymidine kinase are sensitive to ganciclovir treatment.

We have previously produced transgenic (TG) mice expressing the mouse inhibin alpha-subunit promoter/Simian virus 40 T-antigen (Inhalpha/Tag) fusion gene. The mice develop gonadal somatic cell tumors at the age of 5-7 months; the ovarian tumors originate from granulosa cells, and those of the testes from Leydig cells. In the present study another TG mouse line was produced, expressing under the same inh-alpha promoter the herpes simplex virus thymidine kinase gene (Inhalpha/TK). Crossbreeding of the two TG mouse lines resulted in double TG mice (Inhalpha/TK-Inhalpha/Tag), which also developed gonadal tumors. The single (Inhalpha/Tag) and double TG (Inhalpha/TK-Inhalpha/Tag) mice, both bearing gonadal tumors, were treated at the age of 5.5-6.5 months with ganciclovir (GCV, 150 mg/kg body weight twice daily i.p.) for 14 days, or with aciclovir (ACV, 300-400 mg/kg body weight per day perorally) for 2 months. During GCV treatment, the total gonadal volume including the tumor, decreased in double TG mice by an average of 40% (P<0.05), while in single TG mice, there was a concomitant increase of 60% in gonadal size (P<0.05). GCV was also found to increase apoptosis in gonads of the double TG mice. Peroral treatment with ACV was less effective, it did not reduce significantly the gonadal volume. We also analyzed the in vitro efficacy of ACV and GCV treatments in transiently HSV-TK-transfected KK-1 murine granulosa tumor cells, originating from a single-positive Inhalpha/Tag mouse. GCV proved to be more effective and more specific than ACV in action. These results prove the principle that targeted expression of the HSV-TK gene in gonadal somatic cell tumors is potentially useful for tumor ablation by antiherpes treatment. The findings provide a lead for further development of somatic gene therapy for gonadal tumors.