Patricia Ohana

c-di-GMP-binding protein, a new factor regulating cellulose synthesis in Acetobacter xylinum.

A protein which specifically binds cyclic diguanylic acid (c‐di‐GMP), the reversible allosteric activator of the membrane‐bound cellulose synthase system of Acetobacter xylinum, has been identified in membrane preparations of this organism. c‐di‐GMP binding is of high affinity (K D 20 nM), saturable and reversible. The equilibrium of the reaction is markedly and specifically shifted towards the binding direction by K+. The c‐di‐GMP binding protein, structurally associated with the cellulose synthase, appears to play a major role in modulating the intracellular concentration of free c‐di‐GMP and thus may constitute an essential factor in regulating cellulose synthesis in vivo.

The oncofetal H19 RNA connection: Hypoxia, p53 and cancer

Expression of the imprinted H19 gene is remarkably elevated in a large number of human cancers. Recently, we reported that H19 RNA is up-regulated in hypoxic stress and furthermore, it possesses oncogenic properties. However, the underlying mechanism(s) of these phenomena remain(s) unknown. Here we demonstrate a tight correlation between H19 RNA elevation by hypoxia and the status of the p53 tumor suppressor. Wild type p53 (p53(wt)) prevents the induction of H19 upon hypoxia, and upon its reconstitution in p53(null) cells. The last case is accompanied by a decrease in cell viability. The p53 effect is nuclear and seems independent of its tetramerization. Furthermore, using knockdown and over-expression approaches we identified HIF1-alpha as a critical factor that is responsible for H19 induction upon hypoxia. Knocking down HIF1-alpha abolishes H19 RNA induction, while its over-expression significantly enhances the H19 elevation in p53(null) hypoxic cells. In p53(wt) hypoxic cells simultaneous suppression of p53 and over-expression of HIF1-alpha are needed to induce H19 significantly, while each treatment separately resulting in a mild induction, indicating that the molecular mechanism of p53 suppression effect on H19 may at least in part involve interfering with HIF1-alpha activity. In vivo a significant increase in H19 expression occurred in tumors derived from p53(null) cells but not in p53(wt) cells. Taken together, our results indicate that a functional link exists between p53, HIF1-alpha and H19 that determines H19 elevation in hypoxic cancer cells. We suggest that this linkage plays a role in tumor development.

Possible physiological role of H19 RNA

The product of the imprinted oncofetal H19 gene is an untranslated RNA of unknown function. With the human cDNA Atlas microarray, we detected differentially expressed genes modulated by the presence of H19 RNA. Many of the genes that are upregulated by H19 RNA are known to contribute to the invasive, migratory, and angiogenic capacities of cells. Moreover, we provided experimental data indicating that whereas H19 RNA did not have any growth advantage for the cells when cultured in 10% fetal calf serum, it did confer an advantage when cells were cultured in serum‐poor medium. This observation can be explained in part by the inability of the H19‐expressing cells to induce the cyclin‐dependent kinase inhibitor p57kip2 in response to serum stress. Our results favor the possible role of the H19 gene in promoting cancer progression, angiogenesis, and metastasis.

Phase I/II Marker Lesion Study of Intravesical BC-819 DNA Plasmid in H19 Over Expressing Superficial Bladder Cancer Refractory to Bacillus Calmette-Guerin

PURPOSE We studied the safety and preliminary efficacy (marker tumor ablation) of 5 doses of BC-819 given as 6 intravesical infusions in patients with superficial bladder cancer in whom intravesical therapy with bacillus Calmette-Guerin had failed. BC-819 is a DNA plasmid that contains H19 gene regulatory sequences that drive the expression of an intracellular toxin. MATERIALS AND METHODS A total of 18 patients in 4 groups of 3 and 1 group of 6 received escalating doses of BC-819 intravesically during 7 weeks. Patients had low grade superficial bladder cancer, which expressed H19. The effect on a marker tumor was examined 12 weeks after starting treatment. The escalating doses were 2, 4, 6, 12 and 20 mg plasmid per intravesical treatment. Responders continued to receive BC-819 once monthly every month for 1 year. RESULTS No dose limiting toxicity was observed. The most frequent adverse events were mild to moderate bladder discomfort, dysuria, micturition urgency, urinary tract infection, diarrhea, hypertension and asthenia. Intravesical administration of BC-819 resulted in complete ablation of the marker tumor without any new tumors in 4 of the 18 patients for a 22% overall complete response rate. Eight of the 18 patients (44%) had complete marker tumor ablation or a 50% reduction of the marker lesion. Nine patients received monthly maintenance, of whom 4 and 1 were disease-free at 35 and 49 weeks, respectively. CONCLUSIONS Intravesical BC-819 causes tumor ablation following intravesical administration at doses that were well tolerated. It is worthy of continued clinical investigation.

Development of targeted therapy for ovarian cancer mediated by a plasmid expressing diphtheria toxin under the control of H19 regulatory sequences.

BackgroundOvarian cancer ascites fluid (OCAF), contains malignant cells, is usually present in women with an advanced stage disease and currently has no effective therapy. Hence, we developed a new therapy strategy to target the expression of diphtheria toxin gene under the control of H19 regulatory sequences in ovarian tumor cells. H19 RNA is present at high levels in human cancer tissues (including ovarian cancer), while existing at a nearly undetectable level in the surrounding normal tissue.MethodsH19 gene expression was tested in cells from OCAF by the in-situ hybridization technique (ISH) using an H19 RNA probe. The therapeutic potential of the toxin vector DTA-H19 was tested in ovarian carcinoma cell lines and in a heterotopic animal model for ovarian cancer.ResultsH19 RNA was detected in 90% of patients with OCAF as determined by ISH. Intratumoral injection of DTA-H19 into ectopically developed tumors caused 40% inhibition of tumor growth.ConclusionThese observations may be the first step towards a major breakthrough in the treatment of human OCAF, while the effect in solid tumors required further investigation. It should enable us to identify likely non-responders in advance, and to treat patients who are resistant to all known therapies, thereby avoiding treatment failure.

H19 expression in hepatic metastases from a range of human carcinomas

Aims: To investigate the expression of the imprinted oncofetal H19 gene in hepatic metastases derived from a range of human carcinomas and assess its prognostic value with the view of developing a DNA based treatment for such metastases. Methods: Non-radioactive in situ hybridisation for H19 RNA was performed on paraffin wax embedded sections of liver biopsies or partial hepatectomy specimens, taken from 80 patients with hepatic metastases derived from carcinomas from several medical centres in Israel. The degree of expression was graded qualitatively according to the number of cells expressing H19 and the intensity of staining. The medical files were searched for demographic data and survival times before and after diagnosis of hepatic metastases. Results: H19 expression was found in the hepatic metastases of 64 of 80 patients. High expression (higher staining grades) of H19 in the metastases was found in 43 of 80 patients. However, H19 expression status in the hepatic metastases did not correlate with either the length of time to development of metastasis or overall survival. Conclusions: H19 is highly expressed in more than half of hepatic metastases derived from a range of carcinomas. Thus, these metastases may be suitable candidates for H19 DNA based treatment. Further studies are needed to determine whether H19 expression has prognostic value in metastatic liver disease using larger numbers of specific subtypes of primary carcinomas.

The Increasing Complexity of the Oncofetal H19 Gene Locus: Functional Dissection and Therapeutic Intervention

The field of the long non-coding RNA (lncRNA) is advancing rapidly. Currently, it is one of the most popular fields in the biological and medical sciences. It is becoming increasingly obvious that the majority of the human transcriptome has little or no-protein coding capacity. Historically, H19 was the first imprinted non-coding RNA (ncRNA) transcript identified, and the H19/IGF2 locus has served as a paradigm for the study of genomic imprinting since its discovery. In recent years, we have extensively investigated the expression of the H19 gene in a number of human cancers and explored the role of H19 RNA in tumor development. Here, we discuss recently published data from our group and others that provide further support for a central role of H19 RNA in the process of tumorigenesis. Furthermore, we focus on major transcriptional modulators of the H19 gene and discuss them in the context of the tumor-promoting activity of the H19 RNA. Based on the pivotal role of the H19 gene in human cancers, we have developed a DNA-based therapeutic approach for the treatment of cancers that have upregulated levels of H19 expression. This approach uses a diphtheria toxin A (DTA) protein expressed under the regulation of the H19 promoter to treat tumors with significant expression of H19 RNA. In this review, we discuss the treatment of four cancer indications in human subjects using this approach, which is currently under development. This represents perhaps one of the very few examples of an existing DNA-based therapy centered on an lncRNA system. Apart from cancer, H19 expression has been reported also in other conditions, syndromes and diseases, where deregulated imprinting at the H19 locus was obvious in some cases and will be summarized below. Moreover, the H19 locus proved to be much more complicated than initially thought. It houses a genomic sequence that can transcribe, yielding various transcriptional outputs, both in sense and antisense directions. The major transcriptional outputs of the H19 locus are presented here.

Use of H19 regulatory sequences for targeted gene therapy in cancer.

We present a tumor gene therapy approach based on the use of regulatory sequences of the H19 gene that are differentially expressed between normal and cancer cells. We constructed expression vectors carrying the gene for the A fragment of diphtheria toxin (DT‐A) or herpes simplex virus thymidine kinase (HSV‐tk), under the control of a 814 bp 5′‐flanking region of the H19 gene. The cell killing activity of these constructs was in accordance with the relative activity of the H19 regulatory sequences in the transfected cells. We evaluated the therapeutic potential of the gene expression constructs driven by H19 regulatory sequences in an animal model of bladder cancer induced by subcutaneous injection of syngeneic bladder tumor cell lines. Intratumoral injection of these constructs caused a significant suppression of subcutaneous tumor growth, with no obvious toxicity toward the host.

Regulatory sequences of H19 and IGF2 genes in DNA-based therapy of colorectal rat liver metastases

Malignant tumors of the liver are among the most common causes of cancer‐related death throughout the world. Current therapeutic approaches fail to control the disease in most cases. This study seeks to explore the potential utility of transcriptional regulatory sequences of the H19 and insulin growth factor 2 (IGF2) genes for directing tumor‐selective expression of a toxin gene (A fragment of diphtheria toxin), delivered by non‐viral vectors.

Inhibition of tumor growth by DT-A expressed under the control of IGF2 P3 and P4 promoter sequences.

The human IGF2 P3 and P4 promoters are highly active in a variety of human cancers. We here present an approach for patient oriented therapy of TCC bladder carcinoma by driving the diphtheria toxin A-chain (DT-A) expression under the control of the IGF2 P3 and P4 promoter regulatory sequences. High levels of IGF2 mRNA expression from P3, P4 or both promoters were detected in 18 TCC samples (n = 29) by ISH or RT-PCR. Normal bladder samples (n = 4) showed no expression from either promoter. The activity and specificity of the IGF2 P3 and P4 regulatory sequences were established in human carcinoma cell lines by means of luciferase reporter gene assay. These sequences were used to design DT-A expressing, therapeutic vectors (P3-DT-A and P4-DT-A). The activity of both was determined in cell lines (in vitro) and the activity of P3-DT-A was determined in a heterotopic animal model (in vivo). The treated cell lines highly responded to the treatment in a dose-response manner, and the growth rate of the developed tumors in vivo was highly inhibited (70%) after intratumoraly injection with P3-DT-A compared to non-treated tumors (P < 0.0002) or tumors treated by luciferase gene expressing LucP3 vector (P < 0.002).