Interactions between dendritic cells and cytokine-induced killer cells lead to an activation of both populations

Dendritic cells (DCs) are major antigen-presenting cells. They are capable of capturing and processing tumor antigens, expressing lymphocyte costimulatory molecules, and secreting cytokines to initiate immune responses. Here, the authors tested the effect of cytokine-induced killer (CIK) cells, a population that includes CD3+CD56+ cells (natural killer T cells), with regard to their capacity to immunomodulate DCs. Cytokine-induced killer cells were cocultured with autologous DCs generated from peripheral blood mononuclear cells. Expression of markers typical for both populations was measured using flow cytometry, and secretion of interleukin (IL)-12 was determined using enzyme-linked immunosorbent assays. Cytotoxicity assays were performed to investigate the role of IL-12 and the importance of cell-cell interactions. Considering this, receptors for IL-12 and CD40 were blocked and cocultures were performed with cell culture inserts. Coculture of CIK cells led to a significant increase of DC-specific, costimulatory, and antigen-presenting molecules in DC cultures. In addition, coculture resulted in a dramatically increase of IL-12 secretion by DCs and to a significant increase in cytotoxic activity of CIK cells toward carcinoma cells. Blockage of IL-12 uptake decreased the cytolytic activity of CIK cells. Cytokine secretion was shown to be important for activation of CIK cells, and also cellular interactions between DCs and effector cells caused a higher cytolytic capacity. Interactions between DCs and CIK cells caused changes in the surface molecule expression of both populations, led to an increase of IL-12 secretion, and rendered an improved cytotoxic activity. The natural killer T cell subpopulation seems to be responsible for this effect. Therefore, coculture of DCs with CIK cells may have a major impact on immunotherapeutic protocols for patients with cancer.

Enhanced lytic activity of cytokine-induced killer cells against multiple myeloma cells after co-culture with idiotype-pulsed dendritic cells

BACKGROUND AND OBJECTIVES

There are numerous reports of in vitro and in vivo usage of dendritic cells (DC) pulsed with idiotype, the tumor-specific antigen of multiple myeloma (MM), for immunotherapy of MM. Data suggest that not only T-cells, but also the innate immune system reacts against MM. Here, we examined the cytotoxic activity of cytokine-induced killer (CIK) cells against myeloma cells. This heterogeneous effector population consists of T-, NK- and NKT-cells.

DESIGN AND METHODS

CIK cells generated from buffy coats or blood from patients with MM were co-cultured with autologous idiotype-pulsed DC. The cytotoxic activity was investigated in lactate dehydrogenase release assays against cell lines or autologous CD138 positive cells from bone marrow.

RESULTS

CIK cells were able to lyse MM cells at low effector to target ratios. This effect was significantly enhanced by co-culturing with specifically pulsed DC (83.8% lysis at an effector to target ratio of 16:1). Using an interferon-g secreting MACS separation assay, the cytotoxic activity of CIK cells was enhanced to maximal lysis at the lower effector to target ratio of 5:1. High cytotoxic activity was also shown in a completely autologous setting against enriched CD138+ cells from a patient with MM (54.4% lysis at an effector to target ratio of 6:1). Interestingly, there was no cytotoxic activity against the CD138- fraction of the bone-marrow.

INTERPRETATION AND CONCLUSIONS

Using a heterogeneous population of effector cells, we were able to activate the innate and the adoptive immune-system against myeloma cells. CIK cells showed high lytic activity against MM cells, which could be enhanced by co-culturing with antigen-specific pulsed DC.

Clostridium difficile infection in patients with neutropenia

Clostridium difficile is the most important cause of nosocomial infectious diarrhea. The importance of C. difficile-associated diarrhea (CDAD) has been poorly investigated in patients with neutropenia who have hematologic malignancies. A retrospective chart review of all patients treated in the leukemia ward of a university medical center during 1991-2000 determined that 875 courses of myelosuppressive chemotherapy were administered. CDAD occurred in 7.0% of all cycles. In 8.2% of the patients, severe enterocolitis developed. Two patients died while they had diarrhea. However, in no patient was C. difficile infection clinically considered to be the primary cause of death. The response rate to oral metronidazole was 90.9%. These data indicate that C. difficile infection is not rare and should be suspected whenever a hospitalized patient with neutropenia develops diarrhea. Oral metronidazole can be recommended as initial drug of choice for treatment of patients with neutropenia who have hematologic malignancies and CDAD.

A novel minimal-size vector (MIDGE) improves transgene expression in colon carcinoma cells and avoids transfection of undesired DNA

Viral and plasmid vectors may cause unwanted immunological side effects resulting from the expression of nontherapeutic genes contained in their sequence. Furthermore, replication-defective viral vectors carry the potential risk of recombination with wild-type viruses or activation of oncogenes. A new vector type for minimalistic, immunologically defined gene expression (MIDGE) may overcome these problems. MIDGE is a minimal-size gene transfer unit containing the expression cassette, including promoter, gene, and RNA-stabilizing sequence, flanked by two short hairpin oligonucleotide sequences. The resulting vector is a small, linear, covalently closed, dumbbell-shaped molecule. DNA not encoding the desired gene is reduced to a minimum. Here, we transfected colon carcinoma cell lines using cationic lipid, cationic polymer, and electroporation with several MIDGE vectors and corresponding plasmids containing transgenes encoding enhanced green fluorescent protein (eGFP) and human interleukin-2 (hIL-2). Transfection efficiency as measured qualitatively and quantitatively with eGFP was found to be comparable for both vector types. However, hIL-2 secretion and eGFP expression were approximately two- to fourfold higher in most cells transfected with these transgenes using MIDGE vectors compared to the plasmid control. This report demonstrates the advantages of this new vector type and its prospects for ex vivo gene therapy studies.

Effects of adenoviral wild-type p53 gene transfer in p53-mutated lymphoma cells

The present study assessed the role of adenoviral vector-mediated wild-type p53 gene transfer in B lymphoma cells. Deficiency of p53-mediated cell death is common in human cancer contributing to both tumorigenesis and chemoresistance. Lymphoma cells are being considered as suitable targets for gene therapy protocols. Recently, we reported an adenoviral protocol leading to highly efficient gene transfer to B lymphoma cells. All lymphoma cell lines (n=5) tested here showed mutations in the p53 gene locus. The aim of this work was to transduce lymphoma cells with the wild-type p53 gene. Using this protocol, 88% of Raji, 75% of Daudi, and 45% of OCI-Ly8-LAM53 cells were transfected with the reporter gene green fluorescent protein at a multiplicity of infection of 200. The expression of green fluorescent protein in CA46 and BL41 cells was 27% and 42%, respectively. At this multiplicity of infection, growth characteristics of lymphoma cell lines were not changed significantly. In contrast, cells transduced with wild-type p53 gene showed an inhibition of proliferation as well as an increase in apoptosis. Cell loss by apoptosis after p53 gene transfer was up to 40% as compared to transduction with an irrelevant vector. In addition, we determined the effects of DNA damage produced by the DNA topoisomerase II inhibitor etoposide on wild-type p53 transfected lymphoma cells. In Ad-p53-transfected Raji cells, treatment with the drug resulted in a marked increase of cell loss in comparison to Ad-beta-Gal-transfected cells (45% vs. 77%). Interestingly, performing cytotoxicity studies, we could show an increased sensitivity of Raji and Daudi cells against immunological effector cells. In conclusion, transduction of wild-type p53 into lymphoma cells expressing mutated p53 was efficient and led to inhibition of proliferation and increase in apoptotic rate in some cell lines dependent on p53 mutation. This protocol should have an impact on the use of lymphoma cells in cancer gene therapy protocols.

Transfection of dendritic cells (DCs) with the CIITA gene: increase in immunostimulatory activity of DCs

Dendritic cells (DCs) are the major antigen-presenting cells. They are able to present tumor antigens to immunologic effector cells. MHC class II molecules on DC surfaces play an important role in priming effector cells against tumor cells and their antigens. The transactivator CIITA (MHC class II transactivator) is a non-DNA-binding transactivator, which regulates the expression of MHC class II, HLA-DM, and invariant chain and behaves as a master controller of constitutive and inducible MHC class II gene activation. Here, we transfected DCs with the CIITA gene using a novel transfection technique. The vector system consisted of a plasmid bound to an adenovirus via poly-L-lysine, which is covalently bound to a UV-irradiated adenovirus. After transfection, expression of MHC class II on DCs increased from 27% to 75% on day 2 after transfection. Transfected DCs were co-cultured with immunologic effector cells. Cytotoxicity of effector cells against tumor cells increased after co-culture with transfected DCs to 63% compared to 15% with effector cells co-cultured with irrelevantly transfected DCs (P=.037). This effect was dependent on the timing and period of co-culture. In conclusion, transfection of DCs led to an increase in antitumoral immunostimulatory capacity of DCs. We can further conclude that DCs could be efficiently transfected with the CIITA gene. Transfection of DCs led to an increase in antitumoral immunostimulatory capacity of DCs and may have a major impact on immunotherapeutic protocols for patients with cancer.

Resistance of pancreatic carcinoma cells is reversed by coculturing NK-like T cells with dendritic cells pulsed with tumor-derived RNA and CA 19-9

Immunization with defined tumor antigens is limited to the small number of cancers in which specific tumor antigens have been defined but insufficient tumor material is available to produce an antitumor vaccine. In this study, we investigated whether pulsing dendritic cells (DC) using a liposomal transfer technique with a pancreatic tumor cell line-derived RNA can effectively activate NK-like T cells and tumor immunity. Pulsed DC were cocultured with NK-like T cells, i.e., CD3+CD56+ cells, as immunologic effector cells. Target cells resistant to NK-like T-cell-mediated lysis were used. Total tumor-derived RNA transfected into DC was found to completely reverse tumor cell resistance. Total tumor RNA transfection (30 microg) was found to be superior to poly(A)(+) RNA transfection (5 microg) in inducing NK-like T lymphocytes. Interestingly, additional pulsing of DC with the CA 19-9 peptide in a CA 19-9-positive cell line further increased the sensitivity of pancreas carcinoma cells to NK-like T cells. Treatment of tumor RNA with RNase completely blocked the effect of RNA-transfected DC on NK-like T cells, suggesting that intact tumor-derived RNA is needed for reversal of tumor cell resistance. In conclusion, coculture of NK-like T cells with DC transfected with pancreatic tumor cell line-derived RNA reverses pancreatic tumor cell resistance by directly triggering NK-like T lymphocytes.

Increase in the immunostimulatory effect of dendritic cells by pulsing with serum derived from pancreatic and colorectal cancer patients

Both we and others have observed a relative resistance of solid tumor cells to immunological effector cells in vitro, which may be one reason for the clinical phenomenon of resistance of patients with pancreatic carcinoma or other solid tumors to immunological therapeutic approaches. Dendritic cells (DC) are professional antigen-presenting cells which can process and present tumor-associated antigens such as CA 19-9. Here we tested DC pulsed with serum containing CA 19-9 for their capacity to stimulate immunological effector cells against pancreatic carcinoma cells. Coculture of immunological effector cells with DC led to a significant increase in cytotoxic activity as measured by a lactic dehydrogenase release assay. Most interestingly, cytotoxic activity against tumor cells was further increased using DC pulsed with patient-derived CA 19-9 containing serum. Similar results have been obtained using either autologous or allogeneic serum from patients with pancreas carcinoma. The effect of serum on the cytotoxicity of effector cells increased in a dose-dependent manner. Interestingly, heat inactivation led to a significant loss of immunostimulatory capacity of the serum. Cytotoxicity was partially inhibited by using an antibody directed against CA 19-9 on the surface of the target cells. Best results were obtained when adding CA 19-9 protein to CA 19-9 containing serum for pulsing of DC. In conclusion, DC pulsed with CA 19-9 containing serum increased the cytotoxic activity of immunological effector cells against pancreatic cancer cells. DC pulsed with CA 19-9 containing serum with or without additional exogenous CA 19-9 protein may have an impact on immunotherapeutic protocols for patients with CA 19-9 secreting tumors.