MDM2 RNA binding is blocked by novel monoclonal antibody h-MDM2-F4-14

Amplification of MDM2 has been described in a variety of human cancers. Prognostic studies have revealed that abnormal MDM2 expression correlates with poor prognosis. Many of the consequences of mdm2/p53 interactions have been investigated, and mdm2-p53 dependent events characterized. In contrast, understanding of mdm2-p53 independent activities is comparatively in it's infancy amongst these the ability of mdm2 to bind RNA. However, although the significance of this activity has been the subject of some speculation, the precise role and impact of this function upon cell replication or apoptosis has yet to be fully defined. These studies have been obstructed by a lack of specific reagents able to interfere with this reaction. As a prelude to further exploring the significance of mdm2 RNA binding we report the inhibition of mdm2 RNA binding activity by newly produced MDM2 monoclonal antibodies anti-h-mdm2 F4-14 and F2-2. A variety of MDM2 specific antibodies have been produced and applied in research without complete knowledge of their reactivity profiles, but in the face of the growing number of mdm2 RNA isoforms, the results of such studies can be difficult to interpret. Each of the RNA binding inhibitory antibodies produced in this study was found to be reactive with full length MDM2 protein expressed in tumor cell lysates, transfected NIH3T3 cell lysates and via eukaryotic cell free rabbit reticulocyte in vitro translation. Antibody F4-14, the most potently inhibitory antibody, reacts strongly with the full length MDM2 together with protein isoforms A, B, C and D. In contrast, antibody F2-2 reacts only with full-length MDM2 protein. The ability of h-mdm2-F4-14 and to a lesser extent F2-2 to inhibit RNA binding presents the possibility of modulating human mdm2s ability to bind RNA, compromise this function and present opportunities to investigate in more detail the biological significance of this activity.

Small-Molecule Inhibitors of the MDM2-p53 Protein−Protein Interaction Based on an Isoindolinone Scaffold

From a set of weakly potent lead compounds, using in silico screening and small library synthesis, a series of 2-alkyl-3-aryl-3-alkoxyisoindolinones has been identified as inhibitors of the MDM2-p53 interaction. Two of the most potent compounds, 2-benzyl-3-(4-chlorophenyl)-3-(3-hydroxypropoxy)-2,3-dihydroisoindol-1-one (76; IC(50) = 15.9 +/- 0.8 microM) and 3-(4-chlorophenyl)-3-(4-hydroxy-3,5-dimethoxybenzyloxy)-2-propyl-2,3-dihydroisoindol-1-one (79; IC(50) = 5.3 +/- 0.9 microM), induced p53-dependent gene transcription, in a dose-dependent manner, in the MDM2 amplified, SJSA human sarcoma cell line.

Cyclooxygenase-2 inhibition: a potential mechanism for increasing the efficacy of bacillus calmette-guerin immunotherapy for bladder cancer

PURPOSE

Intravesical bacillus Calmette-Guerin (BCG) therapy is the principal treatment for high risk, noninvasive urothelial carcinoma and carcinoma in situ of the bladder. However, up to 40% of patients fail to respond to this treatment. In this study the potential for inhibition of PGE2 production by BCG treated dendritic cells (DCs) was studied in the context of preferential polarization of the immune response toward a cancer clearing T-helper type 1 immune response.

MATERIALS AND METHODS

Murine bone marrow derived DCs were cultured with interleukin (IL)-4 and granulocyte-macrophage colony-stimulating factor. After 7 days the cells were stimulated with BCG. Cell surface expression of co-stimulatory molecules and phagocytic ability were measured by flow cytometry analysis to verify cell activation. The production of IL-10 and IL-12 was measured after DC stimulation with BCG in the presence of IL-10, prostaglandin E2(Cayman Chemical, Ann Arbor, Michigan), antiIL-10 antibody (Insight Biotechnology, Wembley, United Kingdom), NS-398 and indomethacin (Sigma, Poole, United Kingdom).

RESULTS

Prostaglandin E2 stimulated a dose dependent increase in the levels of IL-10 produced by BCG activated DCs (p <0.01). IL-10 significantly decreased IL-12 production (p <0.001), while IL-10 blockade significantly increased IL-12 levels (p <0.05). The COX-2 selective inhibitor NS-398 caused a dose dependent increase in the concentration of IL-12 produced by BCG activated DCs (p <0.01). This effect was also seen with the partially selective COX-1 inhibitor indomethacin (p <0.05).

CONCLUSIONS

The inhibition of PGE2 synthesis by COX inhibition favored the production of IL-12 by BCG activated DC. This potentially will result in the generation of a T-helper type 1, polarized T-cell response that may improve the efficacy of BCG therapy.

Isoindolinone-based inhibitors of the MDM2-p53 protein-protein interaction

A series of 2-N-alkyl-3-aryl-3-alkoxyisoindolinones has been synthesised and evaluated as inhibitors of the MDM2-p53 interaction. The most potent compound, 3-(4-chlorophenyl)-3-(4-hydroxy-3,5-dimethoxybenzyloxy)-2-propyl-2,3-dihydroisoindol-1-one (NU8231), exhibited an IC50 of 5.3 +/- 0.9 microM in an ELISA assay, and induced p53-dependent gene transcription in a dose-dependent manner, in the SJSA human sarcoma cell line.

Genomic organisation of the human MDM2 oncogene and relationship to its alternatively spliced mRNAs

The MDM2 proto-oncogene, which encodes a protein that binds to the p53 tumour suppressor, has been found amplified and overexpressed in a range of human tumours. Although the human MDM2 cDNA sequence has been reported, the genomic organisation of the human gene has not been documented. We have previously reported the detection of five alternative internally deleted MDM2 transcripts in human tumours and suggested these may represent alternatively spliced forms. Here we demonstrate two novel MDM2 transcripts with internal deletions, using RT-PCR followed by sequencing. To definitively ascribe these variant transcript forms to alternative splicing, and to explore associated mechanisms, we have determined the intron--exon organisation of the human genomic sequence. The human MDM2 gene spans approximately 33 kb and is divided into 12 exons. Exon sizes range from 50 to > or =1161 bp and intron sizes vary from 121 to approximately 7000 bp. The positions of intron--exon boundaries are compared with the deletion junctions of the multiple-sized transcripts and discussed in relation to alternative splicing mechanism.

Polarisation of a T-helper cell immune response by activation of dendritic cells with CpG-containing oligonucleotides: a potential therapeutic regime for bladder cancer immunotherapy

Intravesical bacillus Calmette–Guerin (BCG) is a treatment for transitional cell carcinoma (TCC) and carcinoma in situ (cis) of the urinary bladder, but some patients remain refractory. The mechanism of cancer clearance is not known, but T cells are thought to play a contributory role. Tissue dendritic cells (DCs) are known to initiate antigen-specific immune responses following activation of receptors, which recognise molecular patterns on the surface of microorganisms. A family of these receptors, the toll-like receptors (TLRs), are also crucial for activating DC to produce cytokines that polarise the T-cell response towards a T helper (Th)1 or Th2 phenotype. This study compared the potential of intact BCG to activate DC with that of the defined TLR4 ligand lipopolysaccharide (LPS) and the TLR9 ligand CpG-oligonucleotide. It was found that all three stimuli efficiently activated normal DC, but cells expressing a mutant TLR4 responded poorly to stimulation with LPS. Importantly, stimulation with BCG induced both IL-12 and IL-10, suggesting subsequent development of a poorly focused T-cell immune response containing both Th1 and Th2 immune function. By contrast, LPS- and CpG-oligonucleotides induced only IL-12, indicating the potential to produce a Th1 response, which is likely to clear cancer most efficiently. Given the toxicity of LPS, our data suggest that CpG-oligonucleotides may be beneficial for intravesical therapy of bladder cancer.

Outpatient total body irradiation as a component of a comprehensive outpatient transplant program

Outpatient total body irradiation (TBI) as part of a comprehensive outpatient transplant program was delivered to 142 of 167 (85%) consecutive patients receiving TBI-based conditioning therapy. Outpatients received either a single fraction of 500 cGy (110 patients) or 1200 cGy in six fractions over 3 days (32 patients). Patients were assessed daily and were administered oral ondansetron and dexamethasone for prophylaxis of nausea and vomiting as well as i.v. hydration. Accommodation during outpatient TBI-based conditioning was either the patient's home if within 30 min of the hospital, a hotel on the hospital grounds or on a closed hospital ward. None of the 142 patients required admission to the inpatient program during their TBI. There was no difference in 100-day mortality between those receiving TBI as an outpatient (9%) vs as an inpatient (16%). Of four deaths occurring within the first 14 days post transplant, none could be attributed to receiving TBI as an outpatient. Two hundred and six inpatient days were saved through the delivery of outpatient TBI. A comprehensive outpatient program, appropriate patient selection, daily hydration, the use of prophylactic 5HT3 antagonist anti-emetic therapy all contribute to the safe delivery of outpatient TBI.

Autologous blood and marrow transplantation in patients 60 years and older

Although many hematologic malignancies are more common in older patients, autologous blood and marrow transplantation (ABMT) has traditionally been restricted to patients younger than 60 years because of concerns that older patients would be either unable to provide a graft or unable to tolerate the therapy. From June 1995 to May 1998, 30 patients > or = 60 years underwent ABMT at our institution for low-grade lymphoma (4 patients), relapsed intermediate-grade lymphoma (17 patients), or multiple myeloma (9 patients). The median patient age was 62.5 years (range 60-73). Pretransplantation conditioning regimens were CBV (cyclophosphamide, BCNU [carmustine], etoposide) or BEAM (carmustine, etoposide, cytarabine, melphalan) for intermediate-grade lymphoma patients and melphalan 140 mg/m2 + etoposide 60 mg/kg + total body irradiation 500 cGy for the others. The rescue product was bone marrow (BM; 4 patients), peripheral blood stem cells (PBSC; 23 patients), or BM+PBSC (3 patients). The median number of CD34+ cells/kg infused was 3.60 x 10(6) (range 0.53-31.0), by the International Society for Hematotherapy and Graft Engineering method. The treatment-related mortality at day 100 and at 6 months was 10% and 16.7%, respectively. The median days to neutrophil > 0.5 x 10(9)/L was 11 (range 9-25) and platelets > 20 x 10(9)/L was 16 (range 6-70). Three patients died of infection (days 26, 27, and 38), and 1 died of an intracranial hemorrhage related to persistent thrombocytopenia (day 130). Bearman regimen-related toxicity was moderate, with most toxicities < or = grade 2. Seven patients developed significant gut toxicity: 4 patients with Clostridium difficile colitis and 3 patients with neutropenic enterocolitis. Depressive symptoms and signs were noted in 4 patients. Three male patients developed decreased gonadal function after transplantation. These transplantations accounted for 997 patient days, of which 266 days (27%) were in the outpatient BMT program--a smaller percentage than in patients < 60 years (56%, P = .002). Twenty patients are alive 153 to > or = 1224 days after transplantation. ABMT in patients > or = 60 years of age is feasible. Further studies addressing supportive care particular to older patients and comparisons of ABMT with traditional approaches to multiple myeloma and relapsed non-Hodgkin's lymphoma in older patients are needed. Further work to identify elderly patients most likely to benefit from this approach is also required.

Exploiting tumor-specific defects in the interferon pathway with a previously unknown oncolytic virus

Interferons are circulating factors that bind to cell surface receptors, activating a signaling cascade, ultimately leading to both an antiviral response and an induction of growth inhibitory and/or apoptotic signals in normal and tumor cells. Attempts to exploit the ability of interferons to limit the growth of tumors in patients has met with limited results because of cancer-specific mutations of gene products in the interferon pathway. Although interferon-non-responsive cancer cells may have acquired a growth/survival advantage over their normal counterparts, they may have simultaneously compromised their antiviral response. To test this, we used vesicular stomatitis virus (VSV), an enveloped, negative-sense RNA virus exquisitely sensitive to treatment with interferon. VSV rapidly replicated in and selectively killed a variety of human tumor cell lines even in the presence of doses of interferon that completely protected normal human primary cell cultures. A single intratumoral injection of VSV was effective in reducing the tumor burden of nude mice bearing subcutaneous human melanoma xenografts. Our results support the use of VSV as a replication-competent oncolytic virus and demonstrate a new strategy for the treatment of interferon non-responsive tumors.

Therapy for patients with high grade astrocytoma using intraarterial chemotherapy and radiation therapy

BACKGROUND

High grade astrocytomas account for approximately 40% of all primary brain tumors. The median survival is approximately 8-10 months for patients with glioblastoma multiforme and 36 months for patients with anaplastic astrocytoma. The results of systemic chemotherapy in the treatment of brain tumors have been reported to be less than satisfactory, mainly because of the blood-brain barrier impermeability for chemotherapeutic drugs. Intraarterial chemotherapy has been an attractive alternative with which to overcome this problem.

METHODS

Eighty-three patients with high grade astrocytoma (glioblastoma multiforme [63 patients] and anaplastic astrocytoma--[20 patients]) were treated with intraarterial (intracarotid and/or intravertebral) chemotherapy and radiation therapy between 1987 and 1997. Patients received cisplatin, 60 mg/m2, and etoposide, 40 mg/m2. Radiation therapy was delivered either after completion of the chemotherapy or concomitantly with the chemotherapy.

RESULTS

Thirty-four of 71 evaluable patients with high grade astrocytoma (48%) responded to the chemotherapy. The median survival for patients with glioblastoma multiforme who received chemotherapy prior to radiation therapy was 20 months versus 7 months for those patients who underwent concomitant chemotherapy/radiation therapy. Patients with anaplastic astrocytoma who received chemotherapy prior to radiation therapy had a median survival of 45 months compared with 12 months for patients who received concomitant chemotherapy/ radiation therapy. The toxicity profile has been reported to be mild and well tolerated.

CONCLUSIONS

Intraarterial chemotherapy for patients with glioblastoma multiforme, delivered prior to radiation therapy, appears to result in a median survival three times longer than that achieved with concomitant chemotherapy/radiation therapy. In addition, patients appear to survive substantially longer than they do after radiation therapy with the addition of systemic chemotherapy. Side effects are reported to be acceptable.

Nontargeted stable integration of recombinant adeno-associated virus into human leukemia and lymphoma cell lines as evaluated by fluorescence in situ hybridization

A number of studies on human epithelial cells of varying origin have demonstrated integration of recombinant adeno-associated virus (AAV) vectors into a variety of chromosomes compared with the site-specific integration on chromosome 19 predominantly observed for wild-type (wt) AAV. We have constructed a recombinant AAV (rAAV) vector and tested the integration into hematopoietic cells, using the human acute myeloid leukemia cell line AML5 and the human non-Hodgkin's lymphoma cell line OCI-LY18 as targets. The integration sites were visualized by fluorescence in situ hybridization (FISH). Positive signals were observed for chromosomes 1, 2, 3, 8, 14, 15, 19, and Y. The majority of cells demonstrated integration into one specific site. A minority showed simultaneous integration into more than one chromosome. The frequency of observed integrations was not uniformly distributed among chromosomes; for instance, in AML5 chromosome 2 seemed to be favored. Colony-derived AML5 clones bore unique integration patterns indicating successful transduction of clonogenic progenitor cells with high proliferative potential. The integration was stable and observed for more than 12 months after transduction. FISH has been shown to be a powerful tool for detailed analyses of rAAV integration patterns and can be used to evaluate targets and transduction conditions.

A randomized trial of granulocyte colony-stimulating factor (Neupogen) starting day 1 vs day 7 post-autologous stem cell transplantation

The purpose of the study was to evaluate the effect of delayed granulocyte colony-stimulating factor (G-CSF) use on hematopoietic recovery post-autologous peripheral blood progenitor cell (PBPC) transplantation. Patients were randomized to begin G-CSF on day +1 or day +7 post transplantation. Thirty-seven patients with lymphoma or myeloma undergoing high-dose therapy and autologous PBPC rescue were randomized to daily subcutaneous G-CSF beginning on day +1 or day +7 post-transplant. Patients < or =70 kg received 300 microg/day and >70 kg 480 microg/day. All patients were reinfused with PBPCs with a CD34+ cell count >2.0 x 10(6)/kg. Baseline characteristics of age, sex and CD34+ cell count were similar between the two arms, the median CD34+ cell count being 5.87 x 10(6)/kg in the day +1 group and 7.70 x 10(6)/kg in the day +7 group (P=0.7). The median time to reach a neutrophil count of >0.5 x 10(9)/l was 9 days in the day +1 arm and 10 days in the day +7 arm, a difference which was not statistically significant (P=0.68). Similarly, there was no difference in median days to platelet recovery >20000 x 10(9)/l, which was 10 days in the day +1 arm and 11 days in the day +7 arm (P=0.83). There was also no significant difference in the median duration of febrile neutropenia (4 vs 6 days; P=0.7), intravenous antibiotic use (7 vs 8 days; P=0.54) or median number of red blood cell transfusions (4 vs 7 units; P=0.82) between the two arms. Median length of hospital stay was 11 days post-PBPC reinfusion in both groups. The median number of G-CSF injections used was 8 in the day +1 group and 3 in the day +7 group (P < 0.0001). There is no significant difference in time to neutrophil or platelet recovery when G-CSF is initiated on day +7 compared to day +1 post-autologous PBPC transplantation. There is also no difference in number of febrile neutropenic or antibiotic days, number of red blood cell transfusions or length of hospital stay. The number of doses of G-CSF used per transplant is significantly reduced with delayed initiation, resulting in a significant reduction in drug costs. For patients with an adequately mobilized PBPC graft, the initiation of G-CSF can be delayed until day +7 post-PBPC reinfusion.

Quality of life following bone marrow transplantation: a comparison of patient reports with population norms

All surviving patients who had received an allogeneic bone marrow transplant at the Princess Margaret Hospital were asked to participate in a health-related quality of life (HQL) study using the Medical Outcomes Survey-Short Form 36 (MOS SF-36), the Satisfaction with Life Domains Scale-Bone Marrow Transplantation (SLDS-BMT) and a current symptoms checklist. The main objective was to compare the health status of BMT survivors with age-adjusted population norms. Of the 251 patients contacted, 93% returned questionnaires. The median follow-up after BMT was 40 months, ranging from 1-253 months. On average, survivors had some diminished HQL relative to the health status of the population in general. Time since transplant had a significant influence on HQL; those less than 3 years from transplant experienced considerable impairment while those who had survived beyond this point were indistinguishable from the normal population in most domains and significantly better in certain psychosocial aspects of health. Many patients still reported symptoms months after BMT; some were mildly affected while others experienced more troublesome symptoms. However, 81% of patients were satisfied with the HQL outcome that they had achieved and 94% would recommend a transplant for someone in similar circumstances.

Human hematopoiesis in SCID mice implanted with human adult cancellous bone

The persistence of hematopoietic cells from human adult cancellous bone fragments implanted subcutaneously into CB-17 scid/scid mice was studied. Recipient mice received either no pretreatment (control group) or pretreatment with 3 Gy total-body irradiation and anti-asialo GM1 sera (ASGM1; pretreated group) before implantation. Pretreated severe combined immunodeficient (SCID) mice implanted with human bone were subsequently given ASGM1 every 7 days for the duration of the experiments. At 12 weeks postimplantation, flow cytometry of cells from pretreated and control animal tissues detected human CD45+ cells in the mouse spleen (mean, 7.8% and 3.4% positive cells, pretreated and control animals, respectively), bone marrow (BM; mean, 16.5% and 4.8% positive cells, respectively), and blood (mean, 5.5% and < 2% positive cells, respectively), and in the implanted human bone (73% and 8.9% positive cells, respectively). At 12 weeks, pretreated mice had human granulocyte-macrophage colony-forming cells (GM-CFC) and burst-forming units-erythrocyte (BFU-E) in the implanted human bone in the murine BM and in some of the spleens. The spleens also had extensive infiltration of human B cells and macrophages. Mean serum levels of human IgG in pretreated animals were 14 micrograms/mL during weeks 6 to 12, compared with trace levels (< 1 microgram/mL) in control mice. Bone from patients with acute myeloblastic leukemia (AML) was also implanted in pretreated SCID mice, and retrieved at 8 weeks for analysis. Comparison of preimplantation and implanted samples showed that the original histology was maintained, and massive infiltration of human CD68+ cells was observed in the mice spleens and BM. Implantation of AML bone in SCID mice facilitates analysis of in situ AML cell interaction with stromal cells in the leukemic state, and therapies against AML can be tested in this system, especially the selective killing of AML cells in the presence of other BM cells. Furthermore, this model requires no exogenous administration of cytokines to maintain human hematopoiesis with both normal or AML bone. Because the structure and function of both normal and diseased human adult bone is maintained, this animal model should facilitate investigation of both normal human hematopoiesis and hematopoietic malignancies.