Editorial Board Focus – February 2007

Abstract

From our panel of expert Editorial Board members, an update on the developments and activities ongoing in thier laboratories and institutions, as well as recommendations of other groups whose work is of considerable interest to the readers of EOBT.

1. Angus Dalgleish

Research interests and projects of Angus Dalgleish (St George’s Hospital Medical School, UK) are listed below:

•	Dendritic cell vaccines; basic research and clinical trials. Focus on TLR signaling and maturation optimisation. Funded by the Cancer Vaccine Institute and the Fischer Familiy Trust. Clinical trial with John Anderson UCL/UCL co-funded with CRUK.
•	The role of the new class of small molecules, the IMiDs (immunomodulatory drugs), on the immune response to tumors and the role of T regulatory cells. Investigating the potential for combination with standard chemotherapy based on their proven antiangiogenic activity. Funded by the Celgene corporation.
•	The clinical development of a novel vaccine for prostate cancer with Onyvax Ltd.
•	The optimisation of antiprostate cancer therapy using differentiation and apoptopic agent combinations. Funded by the Ralph Bates Pancreatic Cancer Research Fund.
•	Pathogenesis of AIDS, identification of disease inducing epitopes and the development of a therapeutic vaccine for use with interupted HAART therapy. Similar approach being used for Flu viruses. Both being funded by the MRC Norway and Bionor.
•	The role of chronic inflammation and cancer, and the case for anti-inflammatories, antiangiogenics and nonspecific immune stimulation. Funded by the Cancer Vaccine Institute and Celgene.

2. Dwaine Emerich

From Dwaine Emerich (LCT BioPharma, USA) – Our research programs are directed towards developing xenogeneic cell-based transplant modalities to treat diseases characterized by cellular dysfunction. We are approaching this by encapsulating porcine cells within alginate microcapsules. The microcapsules permit cell viability post-transplantation while limiting access of the host immune system to the encapsulated cells. To date we have developed encapsulation materials that have controllable degradation profiles and can be extremely stable for long periods of time when implanted into sites as divergent as the brain, subcutaneous space and peritoneum. Our primary clinical targets include Huntington’s disease (HD) and diabetes. In the first case, we have recently demonstrated that intracerebral implants of encapsulated porcine choroid plexus epithelial cells are potently neuroprotective in vitro and in vivo in models of HD and other CNS diseases. At present, we are also exploring the use of choroid plexus transplants in various diseases, including ALS, stroke and hearing loss. These data have implications for using choroidal epithelial cells therapeutically, but also point to underappreciated roles of the choroid plexus in ageing, CNS diseases and in the maintenance of the normal secretory milieu of the brain. In the second case, we and our colleagues in New Zealand (LCT Diatranz) have recently received regulatory approval to manufacture transplantable encapsulated procine islets under GMP conditions.

3. Mark Glassy

From Mark Glassy (Rajko Medenica Research Foundation, USA) – Our overall research program is to fundamentally understand the natural human immune response to cancer cell antigens. We have used a two-part approach to these studies. First, we utilize the microenvironment of regional draining lymph nodes of cancer patients as a window of opportunity for our studies. Regional draining lymph nodes are removed from cancer patients, and the antibody-secreting B lymphocytes are isolated and characterized. Our second approach is to characterize tumor-infiltrating B lymphocytes in cancer tissues and clarify their importance in cancer immunophysiology. Based on these two approaches, we have been able to identify unique tumor antigens that may be clinically useful. To test the hypothesis that naturally derived human anticancer antibodies may be useful in the disease management of cancer patients, we are currently in the process of mass-producing a panel of these antibodies for clinical trials. Finally, based on our studies, the natural human immune response is not monoclonal, but rather oligoclonal, meaning that a few antibodies are generated by the patient for immunosurveillance of the cancer. Therefore, a cocktail of a few antibodies should be used to more closely mimic the natural human immune response. At present, we are exploring the use of antibody cocktails as a method of immunotherapy in cancer patients. For further reading see [101,102].

4. Robert J Kreitman

From Robert J Kreitman (National Cancer Institute, National Institutes of Health, USA) – Our research program includes the preclinical and clinical development of recombinant immunotoxins for the treatment of patients with hematologic malignancies. These agents are proteins containing an Fv fragment genetically fused to truncated Pseudomonas exotoxin. They intoxicate cells by binding to the surface of target cells and internalizing. Inside the cell, a fragment of the toxin translocates to the cytosol, where one toxin fragment is sufficient for cell death. Laboratory-designed recombinant immunotoxins that are in clinical testing at present include LMB-2 targeting CD25, and BL22 targeting CD22. We have tested these agents in Phase I and II trials at the NIH. These agents have been remarkably effective in hairy cell leukaemia (HCL) and efficacy is observed in some other hematologic malignancies. Trials are open at present for LMB-2 in chronic lymphocytic leukemia (CLL), HCL, cutaneous T cell lymphoma and Hodgkin’s disease, and for BL22 in HCL, CLL and non-Hodgkin’s lymphoma (NHL). A mutated form of BL22, called HA22 (CAT-8015), binds with higher affinity than BL22 to CD22, is much more cytotoxic toward CLL, and will begin Phase I clinical testing in CLL, HCL and NHL. Patient samples are studied in the laboratory to better predict and understand recombinant toxin efficacy and unwanted toxicity, to better understand the role of T and B cells in hairy cell leukemia patients, to study novel and established tumor markers in patients to better quantitate overall tumor burden, and to develop new assays of minimal residual disease.

5. Vladimir Mironov

‘Are adult stem cells totipotent?’ from Vladimir Mironov (Medical University of South Carolina, SC, USA). Group members: Richard P Visconti and Roger R Markwald.

Regenerative medicine is one of the most promising directions in the biomedical field [1]. Autologous adult stem cells are the most logical choice for cell therapy, but, until now, the general belief was that they are only multipotent and are difficult to propagate in vitro. Conversely, the politically, ethically and economically controversial human embryonic stem cell is considered to be totipotent from a biological point of view. The multipotentiality of adult stem cells is usually studied in vitro or by transplantation in vivo. The overall research program of our group is to fundamentally understand the role of adult stem cells in heart valve and myocardial regeneration. Using clonal EGFP⁺ (enhanced green fluorescent protein-expressing) adult hematopoietic stem cells to create chimeric mice, we demonstrated that circulating bone marrow-derived adult stem cells can be recruited both to the heart valves and the infarcted myocardium. Importantly, they express collagen type I and thus can contribute to maintenance of the biomechanical properties of both heart valves and myocardial tissue [2-4]. However, in his recently published new textbook Regenerative Medicine and Biology, D Stocum [5,103] wrote that the best way to examine the multipotentiality of stem cells is by implanting labeled adult stem cells into the embryonic blastula and then tracing their fate in the developing organism. Professor B Nadal-Ginard from the New York Medical College (Valhalla, NY, USA) presented exciting data at a conference in Japan [6], which unequivocally demonstrated that adult cardiac stem cells implanted into embryonic blastulae contribute to tissues of endodermal, mesodermal and ectodermal origin. This means that resident cardiac stem cells can generate practically any tissue. If it is true, this is the first direct evidence of adult stem cell totipotentiality. By logical extension, totipotent adult stem cells could exist in practically any organ and tissue of the human organism. Thus, new approaches in regenerative medicine should not simply focus on cell therapy or cell transplantation, but rather on organospecific mobilization of adult stem cells. Furthermore, if adult stem cells are truly totipotent, the generally assumed ‘inferiority’ of adult stem cells is no longer an issue.

6. Michael Morse

The Molecular Therapeutics Program at Duke University Medical Center (Principal Investigators: Michael Morse MD, Timothy Clay PhD, Gayathri Devi PhD and H Kim Lyerly MD) has been studying tumor–host interactions through the lens of the immune response to cancer with the goal of translating laboratory observations into early phase human clinical trials of various immunotherapy strategies. Our research in the last year has focused on:

•	Prime–boost strategies to overcome tolerance against tumor antigens. We have studied combinations of poxvirus, adenovirus and alphavirus modified to express tumor antigens, such as HER2, carcinoembryonic antigen (CEA) and WT1, in animal models of malignancies, and we will be initiating Phase I clinical trials of combinations of these vectors.
•	Modulating regulatory T cell (Treg) downregulation of the immune response. We have confirmed observations that Tregs modulate the activation of tumor antigen-specific immune responses following immunization in tumor-bearing animals. We have translated this into a clinical trial in which we are administering denileukin diftitox to deplete Tregs prior to immunization with a dendritic cell vaccine targeting CEA.
•	Studying the role of ex vivo generated antigen-specific lymphocytes as adoptive therapy for viral infections and malignancies. At present, we are performing a Phase I clinical trial of the adoptive transfer of cytomegalovirus (CMV)-specific T cells to treat CMV infections in patients with hematologic malignancies undergoing stem cell transplantation.
•	Modifying the tumor and its microenvironment to enhance the efficacy of tumor antigen-specific T cells. We are studying the role of modulators of antigen expression, such as interferon-γ, and the role of antitumor therapies, such as antivascular endothelial growth factor antibodies, in modifying tumors to increase their susceptibility to immune-mediated destruction.
•	Developing new antigenic targets, especially those expressed by tumor stem cells.
•	Studying the genomic signature of the immune response to tumors and following anticancer immunotherapy.
•	Identifying the mediators of resistance to anticancer immunotherapy, such as anti-HER2 antibodies.

7. Daniele Santini

‘Antiangiogenic effects of bisphosphonates: new clinical evidences’ from Daniele Santini (University Campus Biomedico, Italy). Group members: Bruno Vincenzi, Sara Galluzzo, Maria Elisabetta Fratto, Laura Rocci, Federica Uzzalli, Fabrizio Battistoni and Giordano Dicuonzo; Group Chief: Giuseppe Tonini.

Bisphosphonates are analogs of endogenous pyrophosphates in which a carbon atom replaces the central oxygen atom, and they are potent inhibitors of bone resorption; therefore, they are widely used for treating or preventing malignant hypercalcemia, tumoral osteolysis, Paget’s disease and osteoporosis. Recent data suggest that bisphosphonates may also have antitumor effects [7]. Finally, recent evidence suggests that part of the antitumor activity of bisphosphonates may be attributed to an antiangiogenic effect. On the basis of these preclinical data, our research group have designed many studies to investigate the potential antiangiogenic role of bisphosphonates in patients with solid tumors. First, our group has evaluated the effect of a single infusion of pamidronate on circulating levels of vascular endothelial growth factor (VEGF), IFN-γ, IL-6 and IL-8 in 25 cancer patients with bone metastasis [8]. Our study has clearly demonstrated a statistically significant decrease, compared with basal values, in VEGF levels after 1, 2 and 7 days from pamidronate infusion. This study represented the first demonstration in humans of a potential antiangiogenic effect of bisphosphonates. On the basis of these data, we designed a second study to investigate the potential antiangiogenic role of zoledronic acid in patients with malignancies [9]. Thirty patients with advanced solid cancer and bone metastates received 4 mg of intravenous zoledronic acid in a period of 15 min before any anticancer chemotherapy administration. Our study has clearly demonstrated a statistically significant decrease, compared with basal values, in VEGF levels at 1, 2, 7 and 21 days after zoledronic acid infusion. Compared with the effects of pamidronate on serum VEGF levels, zoledronic acid clearly demonstrated to induce a longer-lasting decrease of this angiogenic cytokine. Moreover, we have investigated whether VEGF modifications observed after the first intravenous zoledronic acid administration can be correlated to skeletal survival in breast cancer patients [10]. Forty-two breast cancer patients with bone metastasis were treated with a single infusion of 4 mg zoledronic acid before any anticancer chemotherapy administration. Analysing survival, patients with VEGF reduction presented a longer time for first skeletal-related event, a longer time to bone progression and to performance status worsening. Finally, we designed another study to investigate the antiangiogenic role of zoledronic acid when administered with a ‘metronomic’ schedule (in small doses on a frequent schedule) in patients with metastatic bone disease (ongoing trial). The 26 patients enrolled received 1 mg of zoledronic acid over a period of 15 min every week, then, after day 28, they received 4 mg of zoledronic acid every 28 days. Blood was collected before infusion beginning and at 7, 14, 21, 28, 56 and 84 days after the first infusion. Our preliminary results have confirmed that zoledronic acid is able to induce a significant early decrease of VEGF levels. These are the first reports in literature about a potential antiangiogenic role of bisphosphonates in humans. Other experimental trials should be designed to assess the real clinical impact in anticancer therapy of antiangiogenic properties of bisphosphonates. The results of such studies will provide important insights into the optimal integration of bisphosponates with standard chemotherapy and with antiangiogenic drugs in the relevant patient populations.