Generation of peptide-specific cytotoxic T lymphocytes using allogeneic dendritic cells capable of lysing human pancreatic cancer cells

Role of immune cells in pancreatic cancer from bench to clinical application: An updated review

BACKGROUND

Pancreatic cancer (PC) remains difficult to treat, despite the recent advances in various anticancer therapies. Immuno-inflammatory response is considered to be a major risk factor for the development of PC in addition to a combination of genetic background and environmental factors. Although patients with PC exhibit evidence of systemic immune dysfunction, the PC microenvironment is replete with immune cells.

METHODS

We searched PubMed for all relevant English language articles published up to March 2016. They included clinical trials, experimental studies, observational studies, and reviews. Trials enrolled at Clinical trial.gov were also searched.

RESULTS

PC induces an immunosuppressive microenvironment, and intratumoral activation of immunity in PC is attenuated by inhibitory signals that limit immune effector function. Multiple types of immune responses can promote an immunosuppressive microenvironment; key regulators of the host tumor immune response are dendritic cells, natural killer cells, macrophages, myeloid derived suppressor cells, and T cells. The function of these immune cells in PC is also influenced by chemotherapeutic agents and the components in tumor microenvironment such as pancreatic stellate cells. Immunotherapy of PC employs monoclonal antibodies/effector cells generated in vitro or vaccination to stimulate antitumor response. Immune therapy in PC has failed to improve overall survival; however, combination therapies comprising immune checkpoint inhibitors and vaccines have been attempted to increase the response.

CONCLUSION

A number of studies have begun to elucidate the roles of immune cell subtypes and their capacity to function or dysfunction in the tumor microenvironment of PC. It will not be long before immune therapy for PC becomes a clinical reality.

Results of the first phase 1 clinical trial of the HER-2/neu peptide (GP2) vaccine in disease-free breast cancer patients: United States Military Cancer Institute Clinical Trials Group Study I-04

BACKGROUND

HER-2/neu, overexpressed in breast cancer, is a source of immunogenic peptides that include GP2 and E75. Phase 2 testing of E75 as an adjuvant vaccine has suggested a clinical benefit. GP2, derived from the transmembrane portion of HER-2/neu, has differing binding characteristics and may be more immunogenic than E75. Results of the first phase 1 trial of GP2 peptide vaccine are presented.

METHODS

Disease-free, lymph node-negative, human leukocyte antigen (HLA)-A2(+) breast cancer patients were enrolled. This dose escalation trial included 4 groups to determine safety and optimal GP2 peptide/granulocyte-macrophage colony-stimulating factor (GM-CSF) dose. Toxicities were monitored. Immunologic response was assessed ex vivo via the HLA-A2:immunoglobulin dimer assay to detect GP2-specific CD8(+) T cells (and E75-specific CD8(+) T cells to assess epitope spreading) and in vivo via delayed type hypersensitivity (DTH) reaction (medians/ranges).

RESULTS

Eighteen patients were enrolled. All toxicities were grade < or =2. Eight (88.9%) of 9 patients in the first 3 dose groups required GM-CSF dose reductions for local reactions > or =100 mm or grade > or =2 systemic toxicity. GM-CSF dose was reduced to 125 microg for the final dose group. All patients responded immunologically ex vivo (GP2-specific CD8(+) T cells from prevaccination to maximum, 0.4% [0.0%-2.0%] to 1.1% [0.4%-3.6%], P < .001) and in vivo (GP2 pre- to postvaccination DTH, 0 mm [0.0-19.5 mm] to 27.5 mm [0.0-114.5 mm, P < .001). E75-specific CD8(+) T cells also increased in response to GP2 from prevaccination to maximum (0.8% [0.0%-2.41%] to 1.6% [0.86%-3.72%], P < .001).

CONCLUSIONS

The GP2 peptide vaccine appears safe and well tolerated with minimal local/systemic toxicity. GP2 elicited HER-2/neu-specific immune responses, including epitope spreading, in high-risk, lymph node-negative breast cancer patients. These findings support further investigation of the GP2 vaccine for the prevention of breast cancer recurrence.

Selected allogeneic dendritic cells markedly enhance human tumour antigen-specific T cell response in vitro

BACKGROUND

Alloreaction is known to accumulate several theoretical advantages that can improve dendritic cell (DC)-based anti-infective or antitumour strategies. Allogeneic DC have already been tested in experimental and clinical studies, but their efficacy compared with their autologous counterparts was rarely investigated and conclusions diverge.

OBJECTIVE

This study compared antigen-specific T cell responses following priming with autologous versus allogeneic DC and examined the possibility of screening these responses in order to select allogeneic DC that lead to a great amplification.

RESULTS

Allogeneic DC obtained from donors matched with the single HLA-A2 allele were efficient in generating in vitro peptide-specific T cell responses. When randomly chosen, allogeneic DC generated a broad range of antigen-specific T cell responses in comparison with autologous DC. When screened and selected, allogeneic DC markedly enhanced peptide-specific T cell priming and allowed a more efficient boosting of resulting T cells. These selected allogeneic DC provided a favourable cytokinic and cellular environment that can help concurrent antigen-specific responses.

CONCLUSION

Ex vivo selected allogeneic DC provide adjuvant effects that lead to amplification of concomitant antigen-specific T cell responses.

Current immunotherapeutic strategies in pancreatic cancer

The immune systems of patients with newly diagnosed pancreatic cancers are functional, with T-cell responses capable of responding to tumor antigen presentation. Pancreatic tumors have been demonstrated to express tumor antigens as mutated, altered, underglycosylated and/or inappropriately overexpressed proteins. Considering these two facts, it should be possible for patients' bodies to recognize their tumors as foreign and to reject them. A number of clinical trials have been initiated to exploit this immune activation to eradicate or stabilize tumor growth. Immunotherapeutic trials include the specific testing of a variety of tumor vaccines, of cytokines as adjuvants or directed cytotoxicity, and of monoclonal antibodies to target specific molecules. This article reviews evidence for immune-cell activation and function in patients with pancreatic cancer, and evidence that pancreatic tumor cells express tumor antigens, or mutated (or altered) proteins. Nevertheless, tumors survive immune attacks by producing products that help them to circumvent effector T cells. The article thus examines complications of immune evasion by cancer cells, as well as the challenges of trying to exploit the immune system in solid tumors where tumor cell products can turn off invading immune T cells set to kill them. Finally, the article discusses the choices of a variety of clinical trials using immune modulation for patients with pancreatic cancer.

Dendritic cell biology, dysfunction and immunotherapy in gastrointestinal cancers

Gastrointestinal (GI) cancers make up a significant proportion of newly diagnosed malignant disease. The five-year survival for these GI cancers is poor. Anti-cancer host defences are thought to play a role in these cancers, albeit they are suboptimal. Novel immunotherapies are being introduced to treat such patients. This review describes basic cell biology of dendritic cells, as they are thoughtto play a key role in generating effective anti-tumour responses. Dendritic cell dysfunction in patients with various cancers is documented and immunotherapy using dendritic cells in a range of GI cancers is described and discussed

Evaluation of the HER2/neu-derived peptide GP2 for use in a peptide-based breast cancer vaccine trial

BACKGROUND

E75 and GP2 are human leukocyte antigen (HLA)-A2-restricted immunogenic peptides derived from the HER2/neu protein. In a E75 peptide-based vaccine trial, preexisting immunity and epitope spreading to GP2 was detected. The purpose of this study was to further investigate GP2 for potential use in vaccination strategies. Importantly, a naturally occurring polymorphism (I-->V at position 2, 2VGP2) associated with increased breast cancer risk was addressed.

METHODS

Prevaccination peripheral blood samples (PBMC) from HLA-A2 breast cancer patients and CD8+ T cells from HLA-A2 healthy donors were stimulated with autologous dendritic cells (DC) pulsed with GP2 and tested in standard cytotoxicity assays with HER2/neu+ tumor cells or GP2- or 2VGP2-loaded T2 targets. Additional cytotoxicity experiments used effectors stimulated with DC pulsed with E75, GP2, or the combination of E75+GP2.

RESULTS

GP2-stimulated prevaccination PBMC from 28 patients demonstrated killing of MCF-7, SKOV3-A2, and the HLA-A2- control target SKOV3 of 28.8+/-3.7% (P<.01), 29.5+/-4.0% (P<.01), and 16.9+/-2.7%, respectively. When compared with E75, GP2-stimulated CD8+ T cells lysed HER2/neu+ targets at 43.8+/-5.2% versus 44.2+/-5.7% for E75 (P=.87). When combined, an additive effect was noted with 58.6+/-5.4% lysis (P=.05). GP2-stimulated CD8+ T cells specifically recognized both GP2-loaded (19.6+/-5.7%) and 2VGP2-loaded T2 targets (17.7+/-5.2%).

CONCLUSIONS

GP2 is a clinically relevant HER2/neu-derived peptide with immunogenicity comparable to that of E75. Importantly, GP2-specific effectors recognize 2VGP2-expressing targets; therefore, a GP2 vaccine should be effective in patients carrying this polymorphism. GP2 may be most beneficial used in a multiepitope vaccine.

Dendritic cells incubated with irradiated tumor cells effectively stimulate T lymphocyte activation and induce enhanced expression of CD69, CD25 as well as production of IFNγ and IL4

Understanding of immunological processes at the molecular level in the cancer-bearing organism is the prerequisite for development of specific tumor vaccines. Most of these vaccines are aimed at enhancing the immunogenicity of the antigens presented by the tumor cells. Since dendritic cells (DC) are potent antigen presenting cells (APC) in the organism, they are considered as a powerful tool to deliver the signals essential for the activation of immune system. In an attempt to clarify the functional importance of DC in the process of anti-tumor vaccination, we characterized the effect of DC activated with a classical tumor vaccine (mixture of irradiated B16F1 tumor cells and MVE-2) on the activation of T lymphocytes. The T lymphocyte activation was assessed by determination of expression of CD25, CD69, and intracellular IFNgamma and IL4 production. Activated DC significantly increased the proportion of CD25+ and CD69+ cells as well as IFNgamma+ and IL4+ cells among CD3+ T lymphocytes. On the other hand, the direct effect of the tumor vaccine on T lymphocytes was just an increment in the proportion of IL4+ T lymphocytes. With the results of in vivo experiments, the phagocytic cells (including DC) were proved to be essential for establishing an active protection against tumor cells (tumor development), but more importantly, also for formation of the memory cell pool. These data indicate that DC loaded with tumor antigens are required for effective stimulation of T lymphocytes, and that the phagocytic cells (including DC) are essential for the anti-tumor immunity triggered by this kind of vaccine.

Gene therapy for pancreatic cancer

Gene transfer technology has the potential to revolutionize cancer treatment. Developments in molecular biology, genetics, genomics, stem cell technology, virology, bioengineering, and immunology are accelerating the pace of innovation and movement from the laboratory bench to the clinical arena. Pancreatic adenocarcinoma, with its particularly poor prognosis and lack of effective traditional therapy for most patients, is an area where gene transfer and immunotherapy have a maximal opportunity to demonstrate efficacy. In this review, we have discussed current preclinical and clinical investigation of gene transfer technology for pancreatic cancer. We have emphasized that the many strategies under investigation for cancer gene therapy can be classified into two major categories. The first category of therapies rely on the transduction of cells other than tumor cells, or the limited transduction of tumor tissue. These therapies, which do not require efficient gene transfer, generally lead to systemic biological effects (e.g., systemic antitumor immunity, inhibition of tumor angiogenesis, etc) and therefore the effects of limited gene transfer are biologically "amplified." The second category of gene transfer strategies requires the delivery of therapeutic genetic material to all or most tumor cells. While these elegant approaches are based on state-of-the-art advances in our understanding of the molecular biology of cancer, they suffer from the current inadequacies of gene transfer technology. At least in the short term, it is very likely that success in pancreatic cancer gene therapy will involve therapies that require only the limited transduction of cells. The time-worn surgical maxim, "Do what's easy first," certainly applies here.

Cytotoxic T lymphocyte mediated recognition of human pancreatic cancer cells

T lymphocytes play an important role in tumor rejection and their response to human malignant melanoma has been well documented. In contrast, the existence of cytotoxic T lymphocytes (CTL) to pancreatic cancer remains unclear. Tumor-associated lymphocytes (TAL) and peripheral blood monocytes (PBMC) were isolated from pancreatic cancer patients. Tumor-specific CTL were generated from TAL and PBMC using solid-phase anti-CD3, low-dose IL-2 (50 IU/ml) and repetitive autologous tumor stimulation. The specificity of CTL was tested in standard cytotoxicity assays using autologous tumor cells, autologous fibroblasts when available, several allogeneic pancreatic tumor cells and the NK-sensitive cell line K562. Anti-HLA-Class I MAb, W6/32, was used to demonstrate that tumor-specific CTL were HLA-Class I restricted. HLA-molecules of human pancreatic cancer cells were washed out using acid elution. Eight consecutive, histologically confirmed pancreatic cancer specimen as well as peripheral blood mononuclear cells were analyzed. CTL were capable of lysing autologous tumor cells significantly after 3 stimulations with autologous tumor cells. T cell mediated recognition was HLA-Class I restricted as shown by incubation with MAb anti-HLA-Class I. In case of HLA-A2 positivity, incubation of tumor cells in cytotoxicity assays resulted in significant inhibition. Autologous fibroblasts or K562 cells were lysed significantly less. HLA-Class I molecule elution resulted in significantly lower recognition of these cells by CTL. These results show for the first time in a larger series the possibility of generating CTL in human pancreatic cancer. The identification of new tumor associated antigens or tumor antigens will be crucial for establishing new treatment strategies.

Generation in vitro of B-cell chronic lymphocytic leukaemia-proliferative and specific HLA class-II-restricted cytotoxic T-cell responses using autologous dendritic cells pulsed with tumour cell lysate

Immunotherapy using dendritic cells has shown encouraging results in both haematological and non-haematological malignancies. In this study, monocyte-derived dendritic cells from patients with B-CLL were cultured for 6 days in the presence of IL-4 and GM-CSF. Autologous B-CLL T-cells were cultured alone or with B-CLL lysate-pulsed and unpulsed autologous dendritic cells. IFN-gamma secretion was assessed using ELISA. Cytotoxicity was assessed, after 21 days in culture and re-stimulation, using flow cytometry with and without blockade by anti-HLA class I, anti-HLA class II, anti-CD4, anti-CD8 and anti-TCRalphabeta monoclonal antibodies. B-CLL T cells stimulated with B-CLL lysate-pulsed autologous dendritic cells showed a significant (P = 0.0004) increase in IFN-gamma secretion and a significant (P = 0.0008) increase in specific cytotoxicity to autologous B-cell targets, but none to autologous T cell or B cell targets from healthy individuals. B-CLL T cells cultured with (non-B-CLL) B-cell lysate-pulsed B-CLL dendritic cells showed no significant response. Pulsing dendritic cells from healthy volunteers with an autologous (non-B-CLL) B-cell lysate did not stimulate proliferation, cytokine production or cytotoxicity by autologous T cells. Pulsing B-CLL dendritic cells with allogeneic B-CLL lysates and culturing with autologous T-cells elicited cytotoxicity against autologous B-CLL targets in some cases, but not in others. Cytotoxicity was significantly reduced by blocking with anti-HLA class II (P = 0.001), anti-TCRalphabeta (P = 0.03) and anti-CD4 (P = 0.046) antibodies. Phenotyping of the responding T-cell population demonstrated the majority to be CD4 positive. Our data demonstrate that HLA class II-restricted proliferative and cytotoxic T-cell responses to B-CLL can be generated using autologous dendritic cells pulsed with tumour cell lysate.

In vitro immunization of patient T cells with autologous bone marrow antigen presenting cells pulsed with tumor lysates

Presentation of cell-associated antigen to T cells is a critical event in the initiation of an anti-tumor immune response but it appears to often be deficient or limiting. Here we report an experimental system for stimulation of human T lymphocytes using autologous antigen presenting cells (APCs) and autologous tumor cells. Two types of APCs were prepared from human bone marrow: MC and DC. MC were produced by using GM-CSF and SCF. DC were obtained with the same cytokines plus IL-4. DC and MC were generated in parallel from the same patients and their phenotypes and capacities to prime T lymphocytes were analyzed and compared. MC were CD14+, CD1a-, CD33+ and HLA-DR+. Two populations of DC were defined: immature DC were uniformly CD1a-; mature DC expressed CD1a, CD80, CD86, HLA-DR, CD54 and CD58 but lacked surface CD14. Stimulation of autologous T lymphocytes was studied by measuring their proliferation and cytotoxic function. In more than 80% of our experiments the proliferation of autologous T lymphocytes cocultured with APC pulsed or not with tumor cell lysates was higher than that of T cells cultured alone. DC were more effective than MC in stimulating proliferation of lymphocytes. The capacity of a patient's autologous bone marrow-derived APC to stimulate T cells when exposed to autologous tumor cell lysates suggest that such antigen-exposed APC may be useful in specific anti-tumor immunotherapy protocols.

Dendritic cells: development, function and potential use for cancer immunotherapy

Dendritic cells (DC) are potent antigen presenting cells that are essential for the initiation of primary immune responses. They richly express MHC, costimulatory and adhesion molecules necessary for the stimulation of naive T cell populations. Dendritic cells are located at sites of antigen capture where they demonstrate phagocytic capacity and subsequently migrate to lymphatic areas for antigen presentation. Their phenotypic and functional characteristics are intimately linked to their stage of maturation. The hematopoietic development of dendritic cells is distinct and may follow several precursor pathways some closely linked to monocytes. Generation of large numbers of cells for potential clinical use has recently been accomplished through the in vitro culturing of progenitors with cytokines. The use of dendritic cell vaccines for cancer immunotherapy has emerged as an exciting new focus of investigation. Various strategies have been adopted to introduce tumor antigens into dendritic cells so that they may be more effectively presented to T cells in the context of costimulation. Animal models demonstrate that dendritic cell tumor vaccines reverse T-cell anergy and result in subsequent tumor rejection. Incorporating the expanding knowledge of dendritic cell biology into vaccine design is essential for the generation of effective immunotherapy for cancer patients.