Abstract B116: Immunovirotherapy in combination with immune checkpoint inhibitors for treating glioblastoma

Glioblastoma, the most common primary brain tumor in adults, is invariably fatal despite all current therapies, with a median survival of about 15 months. Glioblastoma contains cancer stem cells or tumor-initiating cells, a subpopulation of cancer cells that are thought to be important in tumor initiation, progression, heterogeneity, recurrence and resistance to therapy, and thus likely critical targets for therapy. We used a mouse syngeneic glioblastoma stem cell (GSC) tumor model with 005 GSCs, isolated from activated H-Ras and Akt induced, Tp53+/- gliomas in C57Bl/6 mice, which recapitulates the hallmarks of human glioblastoma. Immunovirotherapy takes advantage of the natural inflammatory responses to virus infection and oncolytic virus-induced cancer cell death to drive antitumor immunity. Oncolytic herpes simplex viruses (oHSVs) are genetically-engineered to selectively replicate in cancer cells without harming normal tissue. In this study, we test G47∆-mIL12, an oHSV expressing murine IL-12, a critical cytokine involved in adaptive and innate immune responses as well as anti-angiogenesis.

Immune checkpoints, such as co-inhibitory molecules like CTLA-4 and PD-1 with its ligand PD-L1 play a critical role in regulating immune responses and suppressing antitumor immune effector cells. PD-1 and CTLA-4 are expressed predominantly on T-cells, while PD-L1 is also expressed on endothelial and tumor cells. Blocking antibodies to these molecules have been shown to be very effective at reversing tumor-induced immunosuppression. Therefore, we hypothesized that an IL-12 expressing oHSV, which induces antitumor immune responses, should synergize with checkpoint inhibitor antibodies in inhibiting glioblastoma growth.

Mouse 005 GSCs are highly tumorigenic and relatively non-immunogenic, lacking MHC1 expression, with PD-L1 only expressed on a minority of 005 GSCs in vitro. Both MHC1 and PD-L1 can be induced by IFN-γ. Mice with established orthotopic 005 GSC-derived tumors were treated with a single intratumoral injection of G47∆-mIL12 followed by systemic administration of anti-mPD-1, anti-mPD-L1, anti-mCTLA-4, or isotype control antibodies. Single treatments significantly, but modestly, improved survival compared to mock treatment. The combination of G47∆-mIL12 with either of the three checkpoint inhibitors further extended survival. However, the combination of G47∆-mIL12 with 2 checkpoint inhibitors is able to ‘cure’ mice of 005 brain tumors and protect them from tumor rechallenge. This is associated with a large increase in M1-like macrophages and T effector cells and decrease in T regulatory cells. In this representative glioblastoma stem cell model, the combination of oHSV, local IL12 expression, and 2 systemic checkpoint inhibitors was necessary to eliminate established tumors.

Citation Format: Dipongkor Saha, Robert Martuza, Samuel Rabkin. Immunovirotherapy in combination with immune checkpoint inhibitors for treating glioblastoma [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B116.

Abstract 3195: STAT3 inhibition using shRNA inhibits GBM proliferation, cell migration, anchorage-independent growth of mouse, rat, and human stem-like cells in vitro; and it induces long term survival and anti-GBM immunity in vivo

The purpose of this study was to elucidate the role of Signal Transducers and Activators of Transcription 3 (STAT3) signaling on the tumor microenvironment in the most commonly occurring and aggressive primary brain tumor, Glioblastoma Multiforme (GBM), including preclinical testing of inhibition of STAT3 expression in vivo in syngeneic and patient derived xenograft (PDX) models of GBM. GBM is genetically heterogeneous, but always overexpresses genes that are vital to cell cycle regulation, cell growth and proliferation, cell invasion, and angiogenesis. STAT proteins are transcription factors associated with gene regulation and expression signatures that are implicated in several survival pathways that enable human GBMs to grow in the brain parenchyma. In addition, STAT3 has been identified as a central mechanism in tumor-induced immunosuppression in GBM and other cancers. We studied the effects of STAT3 inhibition via shRNA down-regulation in vivo and in vitro using patient derived primary glioma cells (HF2303 & MGG8) in conjunction with other glioma lines from humans, mice, and rats (U251, GL26, and CNS-1, respectively). In this study, we found that GBM cells harboring down-regulated STAT3 signaling exhibit delayed proliferation, increased apoptosis, and anchorage independence. In vivo, STAT3 inhibition resulted in increased survival rates when tumor cells were treated with the STAT3 shRNA both pre- and post-GBM implantation (syngeneic GBM model). Our data demonstrate that STAT3 has a profound influence on the GBM microenvironment, which prevents the host from clearing the tumor. Down-regulating this signaling pathway using gene therapeutic strategies allows for infiltration of immune cells, decreased invasion, and a decrease in GBM cells’ proliferation that leads to the tumor elimination in ∼83% of the animals, this was associated with the development of an effective anti-tumor immunity that prevents tumor recurrence. Given the phenotype of STAT3 inhibition in in vitro assays and its success in in vivo GBM models, inhibition of STAT3 expression using shRNA and gene therapy technologies constitutes an attractive strategy for preclinical development as a potent therapeutic target for GBM.

Citation Format: Nathan T. VanderVeen, Nicholas Raja, Elizabeth Yi, James Curtin, Peter Chockley, Hikmat Assi, Jonathan Savakus, Tom Mikkelsen, Samuel Rabkin, Pedro R. Lowenstein, Maria G. Castro. STAT3 inhibition using shRNA inhibits GBM proliferation, cell migration, anchorage-independent growth of mouse, rat, and human stem-like cells in vitro; and it induces long term survival and anti-GBM immunity in vivo. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3195. doi:10.1158/1538-7445.AM2015-3195

Abstract 4227: PARP inhibitors sensitize glioblastoma stem cells to oncolytic herpes simplex virus therapy

Glioblastoma (GBM) is an invariably fatal brain tumor in adults and remains a great challenge for preclinical and clinical research. PARP inhibitors (PARPi) have been used alone or in combination with genotoxic agents for the treatment of cancers with homologous recombination (HR) repair deficiencies. Oncolytic herpes simplex viruses (oHSVs) are genetically-engineered to selectively replicate in cancer cells, and previous studies have shown that oHSV infection of glioblastoma stem cells (GSC) induces DNA damage and compromises HR DNA repair. Therefore, we hypothesized that PARPi and oHSV would synergistically kill GSCs through inducing lethal DNA damage.

Here, we show that PARPi consistently inhibited PARylation in a panel of patient-derived GSC lines. Surprisingly, half of GSCs (4 of 8) were sensitive to PARPi killing, with the other half being resistant. When combined with 2 different oHSVs, MG18L and G47Δ, PARPi olaparib and oHSV synergistically killed olaparib-sensitive GSCs in vitro. Moreover, olaparib sensitized PARPi-resistant GSCs to the cytotoxic effects of MG18L or G47Δ, leading to increased DNA damage and cell death. While monotherapy with systemic olaparib or intratumoral injection of MG18L increased survival in an orthotopic xenograft model generated with olaparib-sensitive GSCs, combination treatment greatly extended survival over either monotherapy alone, with concomitant induction of robust DNA damage and apoptosis in the tumors. Furthermore, in an orthotopic model with olaparib-resistant GSCs, in which olaparib monotherapy was not effective, combinatorial therapy of olaparib and MG18L was significantly more efficacious than MG18L alone in prolonging lifespan. Our studies demonstrate that PARPi have anti-GSC activity in about half of GBMs tested, and combining PARPi with oHSV targets DNA damage responses and induces a synthetic lethal effect in vitro and in vivo against both PARPi-sensitive and -resistant GSCs. This report describes a new therapeutic strategy for GBM and supports investigations of this combination in the clinic.

Citation Format: Jianfang Ning, Hiroaki Wakimoto, Robert Martuza, Samuel Rabkin. PARP inhibitors sensitize glioblastoma stem cells to oncolytic herpes simplex virus therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4227. doi:10.1158/1538-7445.AM2015-4227

Abstract 5389: Oncolytic herpes simplex virus expressing interleukin-12 for treating glioma stem cells

Glioblastoma multiforme (GBM) is an aggressive adult brain tumor that despite surgery, radiation and chemotherapy, inevitably recurs. This tumor recurrence is thought to be due to a subpopulation of cells with stem cell-like properties called glioma stem cells (GSCs), and specific targeting of these GSCs might improve GBM treatment. Oncolytic herpes simplex virus (oHSV) vectors are genetically engineered to selectively replicate in, and kill cancer cells, without harming normal tissue, and have been shown to be safe in glioma clinical trials. Our group has shown that oHSV G47delta (G47D) can kill human GSCs, yet its efficacy in vivo was insufficient. Moreover, it is not well understood if GSCs can be targeted effectively by an anti-tumor immune response, partly due to the lack of immune-competent mouse models of GSCs. In this study, we hypothesize that arming G47D with interleukin-12 (IL-12), a critical cytokine involved in adaptive and innate immune responses as well as anti-angiogenesis, will be more effective at targeting GSCs, and tested this using a new syngeneic mouse model of GSCs.

We characterized mouse 005 GSCs (obtained from I. Verma, UCSD) which constitutively express H-Ras and are p53-/+. They exhibit stem cells markers such as nestin and CD133, could be differentiated into neuronal and glial phenotype, and could form tumors in C57BL/6 mice with characteristic GBM necrosis, giant cells and CD31-positive vasculature. These 005 mGSCs expressed MHC/NK ligand markers, but lacked significant expression of co-stimulatory signaling molecules for T cells as observed by flow cytometry. In vitro, treatment of 005 GSCs with increasing concentrations of G47D-Empty (−E; without transgene) or G47D-IL12 resulted in increase in cytotoxicity with similar EC50 values (MOI∼0.1 at 4 days). G47D-IL12 also replicated well in 005 mGSCs leading to a significant release of IL-12 as measured by ELISA. Intracranial tumors established by implanting 005 mGSC in C57BL/6 mice were then treated with two intratumoral injections of either G47D-E or G47D-IL12 oHSV. This resulted in a significant inhibition in tumor growth with extension of survival with G47D-E (median survival 40.5 days; p< 0.03) and G47D-IL12 (median survival 56 days; p< 0.0001) compared with control saline-injected mice with a median survival of 37 days. Importantly, there was a significant increase in survival of mice treated with G47D-IL12 (p< 0.0003) when compared with G47D-E. This increase in survival, potentially due to increased immune response and/or decrease in angiogenesis, is currently under investigation.

This is the first demonstration that GSC can be effectively targeted with oHSV-IL12 in a syngeneic GSC mouse model, showing its marked efficacy over G47D-E. This may be a promising strategy to eradicate glioma cell populations through direct oncolysis combined with enhancing anti-tumor immunity as well as altering the tumor vasculature microenvironment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5389. doi:10.1158/1538-7445.AM2011-5389

Abstract P2-18-01: Treatment of Human Breast Tumors by Oncolytic Herpes Simplex Virus

Background: Breast cancer is the most common cancer for women in the world, although current therapies have improve the outcome, the breast cancer deaths are still the second highest among cancers in women. Metastasis to the lung frequently results in severe complications, and currently, there are no curative treatment options available for patients with metastetic breast cancer. Oncolytic viral therapy is a new strategy for treating cancers. Replication-competent herpes simplex virus (HSV) can infect, replicate and kill tumor cells by a direct cytopathic effect and then spread within the tumor cells. In this study, the cytotoxicity of HSV vectors, G47Δ were examined on different human breast cancer cell lines, immortalized human breast cell lines, and primary culture normal human breast cells. Pulmonary metastasis model of breast cancer was constructed and the treatment effect of G47D was evaluated. Methods: Human BC cell lines SK-BR-3, MDA-MB-453, and MCF-7, immortalized breast cells MCF-10A and 76N-tert, and cultured primary normal breast cells HMEC1 and HMEC2 were cultured in vitro and infected with G47Δ at different multiplicities of infection (MOIs). The viability of infected cells was measured. G47Δ-infected cells were identified using X-gal histochemistry for LacZ expression. A pulmonary metastatic BC model was established with Balb-c nude mice by tail vein injection of MDA-MB-435 cells. Treatment was initiated 21 days after injection of tumor cells, with the virus group treated twice weekly with four total i.v. administrations of G47Δ (2*107pfu/100ul) and on day 60 mice were sacrificed and tumor nodules on the surface of the lung counted after Indian ink staining.

Results: G47Δ was highly cytotoxic to BC cells and 76N-tert in vitro at very low MOI (0.01). For all of these cell lines, more than 85% and 95% cells were killed at MOI=0.01 and MOI=0.1 respectively on the fifth day after infection. However, both HMEC1 and HMEC2 cells were viable even 5 days after infection. A slight effect was found with MCF-10A, of which only 7% and 24.5% were killed at MOI=0.01 and MOI=0.1 respectively on day 5. In the pulmonary metastatic model, the average number of surface lung tumor nodules in the G47Δ group was one, but ten in the control group. X-gal staining illustrated viral replication and spread in the tumor cells in vitro and in vivo.

Conclusions: Recently constructed oncolytic HSV vector G47Δ was effective at killing human breast cancer cells and immortalized breast cells, but didn't infect the normal breast cells. The i.v. administrations of G47Δ could effectively cure metastatic breast cancer. Our studies demonstrated that as a novel therapeutic agents, G47Δ was safe and exhibited superior antitumor effects, thereby making it appropriate for human clinical trials. It is worth noting that G47Δ was effective for lung metastatic breast cancer, which could assure the long survival rate of patients with advance breast cancer. The efficiency of G47Δ warrants consideration of clinical application.

(Key words) breast cancer; cancer therapy; herpes simplex virus; oncolytic virus; gene therapy;

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-18-01.

Treatment of Implantable NF2 Schwannoma Tumor Models with Oncolytic Herpes Simplex Virus G47Δ

Schwannomas are benign tumors composed of dedifferentiated Schwann cells that form along peripheral nerves causing nerve compression often associated with pain and loss of function. Current surgical therapy involves total or subtotal surgical removal of the tumor, which may cause permanent nerve damage. In the present study, we explore an alternate means of therapy in which schwannomas are injected with a replication-conditional herpes simplex virus (HSV) vector to shrink the tumor through cell lysis during virus propagation. The oncolytic vector used, G47Delta, has deletions in HSV genes, which allow it to replicate selectively in dividing cells, sparing neurons. Two schwannoma cell lines were used to generate subcutaneous tumors in nude mice: HEI193, an immortalized human line previously established from an NF2 patient and NF2S-1, a newly generated spontaneous mouse line. Subcutaneous HEI193 tumors grew about ten times as fast as NF2S-1 tumors, and both regressed substantially following injection of G47Delta. Complete regression of HEI193 tumors was achieved in most animals, whereas all NF2S-1 tumors resumed growth within 2 weeks after vector injection. These studies provide a new schwannoma model for testing therapeutic strategies and demonstrate that oncolytic HSV vectors can be successfully used to shrink growing schwannomas.

Effect of chemotherapy-induced DNA repair on oncolytic herpes simplex viral replication

BACKGROUND

Gliomas treated with the alkylating agent temozolomide have incomplete responses in part because of tumoral repair of chemotherapy-induced DNA damage. Data from phase I trials suggest that G207, an oncolytic herpes simplex virus (HSV) with mutated ribonucleotide reductase (RR) and gamma34.5 genes, is safe but needs greater viral oncolysis to be effective. We hypothesized that temozolomide and G207 treatment limitations could be jointly addressed using temozolomide-induced tumor-protective DNA repair pathways to enhance viral replication.

METHODS

Human glioblastoma cells (U87, T98, and U373) and U87 cells transfected with the gene for the DNA repair enzyme O6-methylguanine DNA methyltransferase (MGMT) were treated with G207 and/or temozolomide. Drug interactions, expression of the growth arrest DNA damage 34 (GADD34) and RR transcripts before and after their knockdown with short interfering RNAs, DNA strand breaks, and apoptosis were measured using Chou-Talalay analysis, real-time reverse transcription-polymerase chain reaction, the comet assay, and flow cytometry, respectively. Survival of mice (groups of ten) with intracranial U87 xenograft tumors treated with temozolomide and/or G207 was analyzed using Kaplan-Meier analysis.

RESULTS

Temozolomide exhibited strong synergy with G207 in both MGMT-negative and the MGMT inhibitor O6-benzylguanine-treated MGMT-expressing gliomas (Chou-Talalay combination indices = 0.005 to 0.39) and induced GADD34 expression primarily in nonapoptotic MGMT-negative U87 glioma cells (fold difference = 16, 95% confidence interval [CI] = 12.6 to 20.4, compared with untreated cells). MGMT-expressing T98 and U87/MGMT cells treated with temozolomide plus O6-benzylguanine had higher RR expression than untreated cells (fold difference =14.9, 95% CI = 10.1 to 22.0 [T98]; 9.9, 95% CI = 7.0 to 13.8 [U87/MGMT]). GADD34 and RR knockdown increased temozolomide-induced DNA damage and inhibited the synergy of G207 and temozolomide in U87 and O6-benzylguanine-treated U87/MGMT cells. Mice bearing intracranial U87 tumors survived longer after combination therapy (100% survival at 90 days) than after single-agent therapy (median survival = 46 and 48 days with G207 and temozolomide treatment, respectively).

CONCLUSIONS

Temozolomide-induced DNA repair pathways vary with MGMT expression and enhance HSV-mediated oncolysis in glioma cells. These findings unveil the potential of HSV to target cells surviving temozolomide treatment.

Treatment of Schwannomas with an Oncolytic Recombinant Herpes Simplex Virus in Murine Models of Neurofibromatosis Type 2

Gene therapy for schwannomas was evaluated in two mouse models of neurofibromatosis type 2 (NF2): (1) a transgenic model in which mice express a dominant mutant form of merlin and spontaneously develop schwannomas, and (2) a xenograft model in which human schwannoma tissue is implanted subcutaneously into immune- compromised mice. In both models, schwannoma volumes were monitored by magnetic resonance imaging (MRI) and showed strong gadolinium enhancement typical of these tumors in humans. Both types of tumor were positive for the Schwann cell marker S100, and highly infectable with herpes simplex virus (HSV) vectors. Schwannomas were injected with an oncolytic HSV-1 recombinant virus vector, G47Delta, which has deletions in genes for ribonucleotide reductase (ICP6), gamma34.5, and ICP47. In the NF2 transgenic model, schwannomas were reduced by more than half their original size by 10 days after infection. In the case of subcutaneous schwannoma xenografts, reduction in size after infection occurred more slowly, with a mean reduction of onethird by 42 days after treatment. Schwannomas injected with control vehicles continued to grow slowly over time in both schwannoma models. These studies demonstrate the ability of an oncolytic recombinant HSV vector to reduce the volume of schwannoma tumors in NF2 tumor models in mice and extend the possible therapeutic applications of oncolytic vectors for benign tumors to reduce mass while minimizing nerve damage.

Viral vectors as therapeutic agents for glioblastoma

Established treatments such as surgery, radiation and chemotherapy have not altered the median survival of glioblastoma, the most common malignant brain tumor. Since these failures reflect the highly invasive nature of glioblastoma, as well as the fact that few cells are actively replicating at any given point in time, therapies need to act in areas of the brain distant from the site of tumor origin and for long after their introduction. Over the past decade, laboratory studies and early clinical trials have raised hope that these therapeutic requirements may be fulfilled by gene therapy using non-replicating transgene-bearing viruses, oncolytic viruses or migratory stem cells to deliver tumoricidal transgenes. The principles behind these approaches and their initial results are reviewed.

The 2000 Canadian recommendations for the management of hypertension: part two--diagnosis and assessment of people with high blood pressure

OBJECTIVE

To provide updated, evidence-based recommendations for the diagnosis and assessment of high blood pressure in adults.

OPTIONS

For people with high blood pressure, the assignment of a diagnosis of hypertension depends on the appropriate measurement of blood pressure, the level of the blood pressure elevation, the duration of follow-up and the presence of concomitant vascular risk factors, target organ damage and established atherosclerotic diseases. For people diagnosed with hypertension, defining the overall risk of adverse cardiovascular outcomes requires laboratory testing, a search for target organ damage and an assessment of the modifiable causes of hypertension. Out-of-clinic blood pressure assessment and echocardiography are options for selected patients.

OUTCOMES

People at increased risk of adverse cardiovascular outcomes and were identified and quantified.

EVIDENCE

Medline searches were conducted from the period of the last revision of the Canadian recommendations for the management of hypertension (May 1998 to October 2000). Reference lists were scanned, experts were polled, and the personal files of the subgroup members and authors were used to identify other studies. All relevant articles were reviewed and appraised, using prespecified levels of evidence, by content experts and methodological experts.

VALUES

A high value was placed on the identification of people at increased risk of cardiovascular morbidity and mortality.

BENEFITS, HARMS AND COSTS

The identification of people at higher risk of cardiovascular disease will permit counselling for lifestyle manoeuvres and the introduction of antihypertensive drugs to reduce blood pressure for patients with sustained hypertension. In certain settings, and for specific classes of drugs, blood pressure lowering has been associated with reduced cardiovascular morbidity and/or mortality.

RECOMMENDATIONS

The present document contains detailed recommendations pertaining to aspects of the diagnosis and assessment of patients with hypertension, including the accurate measurement of blood pressure, criteria for the diagnosis of hypertension and recommendations for follow-up, routine and optional laboratory testing, assessment for renovascular hypertension, home and ambulatory blood pressure monitoring, and the role of echocardiography in hypertension.

VALIDATION

All recommendations were graded according to strength of the evidence and voted on by the Canadian Hypertension Recommendations Working Group. Only the recommendations achieving high levels of consensus are reported here. These guidelines will be updated annually.

ENDORSEMENT

These recommendations are endorsed by the Canadian Hypertension Society, The Canadian Coalition for High Blood Pressure Prevention and Control, The College of Family Physicians of Canada, The Heart and Stroke Foundation of Canada, The Adult Disease Division and Bureau of Cardio-Respiratory Diseases and Diabetes at the Centre for Chronic Disease Prevention and Control of Health Canada.

The 2000 Canadian recommendations for the management of hypertension: Part one--therapy

OBJECTIVE

To provide updated, evidence-based recommendations for the therapy of hypertension in adults.

OPTIONS

For patients with hypertension, there are a number of lifestyle manoeuvres and antihypertensive agents that may control blood pressure. Randomized trials evaluating first- line therapy with thiazides, beta-adrenergic antagonists, angiotensin-converting enzyme inhibitors, calcium channel blockers, alpha-blockers, centrally acting agents or angiotensin II receptor antagonists were reviewed.

OUTCOMES

The health outcomes considered were changes in blood pressure, cardiovascular morbidity, and cardiovascular and/or all-cause mortality rates. Economic outcomes were not considered due to insufficient evidence.

EVIDENCE

Medline searches were conducted from the period of the last revision of the Canadian Recommendations for the Management of Hypertension (May 1998 to October 2000). Reference lists were scanned, experts were polled, and the personal files of the subgroup members and authors were used to identify other studies. All relevant articles were reviewed and appraised, using prespecified levels of evidence, by content experts and methodological experts.

VALUES

A high value was placed on the avoidance of cardiovascular morbidity and mortality.

BENEFITS, HARMS, AND COSTS

Various lifestyle manoeuvres and antihypertensive agents reduce the blood pressure of patients with sustained hypertension. In certain settings, and for specific classes of drugs, blood pressure lowering has been associated with reduced cardiovascular morbidity and/or mortality.

RECOMMENDATIONS

The present document contains detailed recommendations pertaining to all aspects of the therapy of patients with hypertension, including lifestyle modifications proven to lower blood pressure, treatment thresholds, target blood pressures, choice of agents in various settings and strategies to enhance adherence. Lower thresholds for blood pressure treatment are advocated for people with other cardiovascular risk factors or established hypertensive target organ damage. Implicit in the recommendations for therapy is the principle that treatment should be individualized for each patient and the choice of agent should be dictated by coexistent conditions. For the treatment of uncomplicated essential hypertension, thiazides, beta-adrenergic antagonists, angiotensin-converting enzyme inhibitors or calcium channel blockers may be appropriate, depending on individual circumstances.

VALIDATION

All recommendations were graded according to strength of the evidence and voted on by the Canadian Hypertension Recommendations Working Group. Only those recommendations achieving high levels of consensus are reported here. These guidelines will be updated annually.

Effect of prior exposure to herpes simplex virus 1 on viral vector-mediated tumor therapy in immunocompetent mice

Replication-competent, attenuated mutants of herpes simplex virus type 1 (HSV-1) have been shown to be efficacious for tumor therapy. However, these studies did not address the consequences of prior exposure to HSV, as will be the case with many patients likely to receive this therapy. Two strains of mice, A/J and BALB/c, were infected with wild-type HSV-1 by intraperitoneal injection and the immune response was determined by plaque reduction assay for neutralizing antibody and ELISA for IgG and IgM. Syngeneic tumors, N18 neuroblastoma and CT26 colon carcinoma, were implanted subcutaneously in HSV-1 seropositive and naive A/J and BALB/c mice, respectively. Established tumors were subsequently treated intratumorally with a multi-mutated HSV-1, G207. G207 inhibited tumor growth to a similar extent whether the mice were seropositive or not. We next examined the effect of multiple intratumoral inoculations of a 10-fold lower dose of G207 on tumor growth. In the multiple treatment group (biweekly for 3 weeks), 75% of tumors were cured, whereas no cures were seen in the single treatment group. We conclude that HSV seropositivity should not deleteriously affect the efficacy of G207 tumor therapy, and multiple inoculations of virus should be considered for clinical evaluation.

DNA polymorphisms in and around the Apo-A1-CIII genes and genetic hyperlipidemias

We have studied the frequency of DNA polymorphisms in and around the apolipoprotein A-1 (Apo-A1) and apolipoprotein CIII (Apo-CIII) gene loci in 53 persons of Caucasian descent with genetic hyperlipidemias. Three restriction-fragment-length polymorphisms (RFLPs) have previously been located 5' and 3' to the Apo-A1 gene and in the Apo-CIII gene and were detected after digestion with XmnI, PstI, and SstI, respectively, and hybridization with a 2.2-kb fragment of the Apo-A1 gene. These RFLPs are in linkage equilibrium. The rare variant sites for XmnI (X2) and SstI (S2) were more frequent in familial combined hyperlipidemia (FCH) than in controls and persons with other genetic hyperlipidemias. When considered as a haplotype, this difference was significant (P less than .03). The findings in this study suggest that the previously reported association between S2 and hypertriglyceridemia may be accounted for, in part, by inclusion of numerous patients with FCH. Our data provide further evidence that these RFLPs around and within the Apo-A1/Apo-CIII genes do not participate in unmasking clinical expression in persons with familial dysbetalipoproteinemia.

Relationship between weight change and the reduction or cessation of cigarette smoking

To determine the relationship between body weight and reduction or cessation of cigarette smoking, body weight and height as well as serum thiocyanate concentration were measured in 107 persons before and after participation in smoking-cessation programs. Body weight increased in only 67.3 percent of cases, but increases in body weight were associated with the greater reduction in cigarette consumption while the absence of weight gain was associated with a small reduction in cigarette consumption. Body weight increases after participation in the program were significantly (P less than 0.05) greater in men than in women despite the absence of a significant difference in the reduction of cigarette consumption between men and women. Analysis of variance failed to show a significant deviation from linearity in the significant relationship between reduction in tobacco consumption and increase in body weight. A number of variables assessed at entry into the study, such as age, age at starting smoking, cigarette consumption, initial body weight or anxiety level (Manifest Anxiety Scale) did not correlate with the change in weight in men or women. These data suggest that the most important determinant of weight gain is the amount of reduction in cigarette consumption and that there are important sex differences in response of body weight to reduction of tobacco consumption.

The role of DNA polymerase in base substitution mutagenesis on non-instructional templates

In vitro DNA synthesis on phi X174 or M13 templates with non-instructional lesions such as UV dimers or AP (apurinic/apyrimidinic) sites terminates one base before the site of the lesion when synthesis is catalyzed by T4 DNA polymerase or E. coli polymerase I. E. Coli polymerase I also produces termination bands at the site of AP lesions. Substitution of Mn2+ for Mg2+ and increasing the concentration of dNTP's results in elongation of the newly synthesized strand opposite the site of the lesion and beyond. Purine deoxynucleoside triphosphates are utilized for insertion opposite lesions to a greater extent than are pyrimidine deoxynucleoside triphosphates. Deoxy ATP is used almost exclusively for elongation opposite AP sites with pol I-Klenow fragment in the presence of Mg2+. We suppose that these results illustrate the previously observed greater affinity of polymerases under template-free conditions for purine nucleotides. We also suppose that the results can be used to account for mutagenic base selection on noninstructional DNA templates. If purines are preferentially selected by polymerases, then treatments which inactivate pyrimidines will lead to an excess of transitions whereas inactivation of purines will produce more transversions. Data in the literature support this hypothesis.

Herpes simplex virus DNA polymerase, thymidine kinase and deoxyribonuclease activities in cells infected with wild type, ultraviolet-irradiated and defective virus

The DNA polymerase, thymidine kinase and deoxyribonuclease activities were studied in cells infected with wild type (wt), ultraviolet (UV)-irradiated and defective herpes simplex virus type 1. All three enzymatic activities were expressed in cells infected with wt virus. In cells infected with UV-irradiated virus, the thymidine kinase and deoxyribonuclease activities were inhibited and the DNA polymerase activity was markedly suppressed. In cells producing defective virus, there was thymidine kinase activity, but the viral deoxyribonuclease activity was considerably reduced. The DNA polymerase activity was fully expressed in cells producing defective virus at passage level 5, but at passage level 6, the activity of the viral DNA polymerase declined.

Defective herpes simplex virus DNA: circular and circular-linear molecules resembling rolling circles

The formation of defective herpes simplex virus (HSV) in BSC-1 cells and the synthesis of defective virus DNA was studied. The fourth consecutive passage of undiluted virus yielded defective DNA that was 0.008 g/ml more dense than wild type (w.t.) virus DNA. The amount of defective DNA increased at passage 6 concomitantly with the decrease in infectious virus progeny. The synthesis of defective DNA was always accompanied by w.t. virus DNA synthesis. Defective DNA from both infected nuclei and defective virions had a mol. wt. of 100 X 10(6) and was linear as determined by electron microscopy. Electron microscopy of defective virus DNA at passage 6 revealed circular molecules varying in size in addition to linear DNA molecules with the length of intact virion DNA. The circular DNA molecules had contour lengths of 10, 5, 2.5 and less than 2.5 micron. The smallest circular DNA molecules had a contour length of 0.3 micron, possibly one virus gene. In addition, circular-linear DNA molecules were observed in which both the circular and the linear components varied in length. Most of these DNA molecules had circular components of either 2.5 or 5.0 micron, and linear components varying in length from less than 1 to 50 micron. Based on the present study, it is proposed that the S component of w.t. virus DNA is fragmented into small circular molecules that serve as templates for DNA synthesis, possibly by the rolling circle mechanism.