In vitro stimulation of ovarian tumour-associated lymphocytes with a peptide derived from HER2/neu induces cytotoxicity against autologous tumour

Natural Compounds with Potential to Modulate Cancer Therapies and Self-Reactive Immune Cells

Cancer-related deaths are approaching 10 million each year. Survival statistics for some cancers, such as ovarian cancer, have remained unchanged for decades, with women diagnosed at stage III or IV having over 80% chance of a lethal cancer recurrence after standard first-line treatment (reductive surgery and chemotherapy). New treatments and adjunct therapies are needed. In ovarian cancer, as in other cancers, the immune response, particularly cytotoxic (CD8⁺) T cells are correlated with a decreased risk of recurrence. As well as completely new antigen targets resulting from DNA mutations (neo-antigens), these T cells recognize cancer-associated overexpressed, re-expressed or modified self-proteins. However, there is concern that activation of self-reactive responses may also promote off-target pathology. This review considers the complex interplay between cancer-reactive and self-reactive immune cells and discusses the potential uses for various leading immunomodulatory compounds, derived from plant-based sources, as a cancer therapy option or to modulate potential autoimmune pathology. Along with reviewing well-studied compounds such as curcumin (from turmeric), epigallocatechin gallate (EGCG, from green tea) and resveratrol (from grapes and certain berries), it is proposed that compounds from novel sources, for example, native Australian plants, will provide a useful source for the fine modulation of cancer immunity in patients.

The impact of T-cell immunity on ovarian cancer outcomes

Ovarian cancer remains a challenging disease for which improved treatments are urgently needed. Most patients present with advanced disease that is highly responsive to surgery combined with platinum- and taxane-based chemotherapy, with a state of minimal residual disease being achieved in many cases. However, chemotherapy-resistant recurrent tumors typically appear within 1-5 years and are ultimately fatal. Recently, several groups have shown that ovarian tumors are often infiltrated by activated T cells at the time of diagnosis, and patients with dense infiltrates of CD3+CD8+ T cells experience unexpectedly favorable progression-free and overall survival. Other cell types in the immune infiltrate oppose anti-tumor immunity, including CD4+CD25+FoxP3+ regulatory T cells, CD8+ regulatory T cells, macrophages, and dendritic cells. The composition of immune infiltrates is shaped by the expression of cytokines, chemokines, antigens, major histocompatibility complex molecules, and costimulatory molecules. The relationship between these various immunological factors is reviewed here with a strong emphasis on outcomes data so as to create a knowledge base that is well grounded in clinical reality. With improved understanding of the functional properties of natural CD8+ T-cell responses to ovarian cancer, there is great potential to improve clinical outcomes by amplifying host immunity.

Tumor-infiltrating T cells correlate with NY-ESO-1-specific autoantibodies in ovarian cancer

Background

Tumor-infiltrating CD8+ T cells are correlated with prolonged progression-free and overall survival in epithelial ovarian cancer (EOC). A significant fraction of EOC patients mount autoantibody responses to various tumor antigens, however the relationship between autoantibodies and tumor-infiltrating T cells has not been investigated in EOC or any other human cancer. We hypothesized that autoantibody and T cell responses may be correlated in EOC and directed toward the same antigens.

Methodology and Principal Findings

We obtained matched serum and tumor tissue from 35 patients with high-grade serous ovarian cancer. Serum samples were assessed by ELISA for autoantibodies to the common tumor antigen NY-ESO-1. Tumor tissue was examined by immunohistochemistry for expression of NY-ESO-1, various T cell markers (CD3, CD4, CD8, CD25, FoxP3, TIA-1 and Granzyme B) and other immunological markers (CD20, MHC class I and MHC class II). Lymphocytic infiltrates varied widely among tumors and included cells positive for CD3, CD8, TIA-1, CD25, FoxP3 and CD4. Twenty-six percent (9/35) of patients demonstrated serum IgG autoantibodies to NY-ESO-1, which were positively correlated with expression of NY-ESO-1 antigen by tumor cells (r = 0.57, p = 0.0004). Autoantibodies to NY-ESO-1 were associated with increased tumor-infiltrating CD8+, CD4+ and FoxP3+ cells. In an individual HLA-A2+ patient with autoantibodies to NY-ESO-1, CD8+ T cells isolated from solid tumor and ascites were reactive to NY-ESO-1 by IFN-γ ELISPOT and MHC class I pentamer staining.

Conclusion and Significance

We demonstrate that tumor-specific autoantibodies and tumor-infiltrating T cells are correlated in human cancer and can be directed against the same target antigen. This implies that autoantibodies may collaborate with tumor-infiltrating T cells to influence clinical outcomes in EOC. Furthermore, serological screening methods may prove useful for identifying clinically relevant T cell antigens for immunotherapy.

Definition of an Immunogenic Region Within the Ovarian Tumor Antigen Stratum Corneum Chymotryptic Enzyme

PURPOSE

The serine protease stratum corneum chymotryptic enzyme (SCCE) is overexpressed by ovarian tumor cells, but is not expressed by normal tissues, suggesting that SCCE may be an attractive target for immunotherapy. In this study, we tested the hypothesis that dendritic cells loaded with SCCE peptides will induce ovarian tumor antigen-specific CD8+ CTL responses and antigen-specific CD4+ helper T cell responses.

EXPERIMENTAL DESIGN

Computer algorithms were used to identify candidate HLA-A2.1-restricted CD8+ CTL epitopes and HLA-DR-binding CD4+ helper T cell epitopes within SCCE. CD8+ CTL stimulated with peptide-loaded dendritic cells were tested against targets expressing endogenous SCCE, including HLA-A2.1-matched ovarian tumor cells. Dendritic cells were also loaded with an extended SCCE peptide, SCCE 110-139, which encompassed a defined CD8+ CTL epitope and multiple candidate CD4+ T helper cell epitopes.

RESULTS

CD8+ CTL specific for SCCE 123-131 lysed autologous macrophages infected with an SCCE-expressing recombinant adenovirus, and also lysed HLA-A2.1-matched, SCCE-expressing ovarian tumor cells. Dendritic cells loaded with SCCE 5-13 peptide stimulated an HLA-A2.1-restricted CD8+ CTL response, but with a reduced level of lysis against ovarian tumor cells. Dendritic cells loaded with SCCE 110-139 induced antigen-specific CD4+ T cell and CD8+ T cell responses. Although SCCE 110-139-loaded dendritic cells processed and presented the 123-131 epitope, the dominant CD8+ CTL response was directed against alternative epitopes within SCCE 110-139.

CONCLUSIONS

The 110-139 region of SCCE incorporates multiple CD8+ CTL and CD4+ helper T cell epitopes, and represents an attractive target antigen for immunotherapy of ovarian cancer.

Development of a CTL vaccine for Her-2/neu using peptide-microspheres and adjuvants

With the ultimate goal of developing a therapeutic cancer vaccine, we encapsulated the Her-2/neu peptide p369-377 in poly(lactide-co-glycolide) microspheres. This formulation was found to effectively elicit CD8+ cytotoxic T cell (CTL) responses in an HLA-A*0201 transgenic mouse model. In contrast, immunization with either peptide alone or peptide formulated in incomplete Freund's adjuvant (IFA) failed to elicit such CTL responses. Responses induced by the peptide-microsphere formulation were found to peak at approximately 6 weeks post-immunization, and were enhanced by delivering increased doses of peptide and with repeated administrations over time. Co-administration of the peptide-microspheres with adjuvants, including granulocyte-macrophage colony stimulating factor, MPL adjuvant and select synthetic Toll-Like Receptor 4 ligands, the aminoalkyl glucosaminide-4 phosphates, significantly augmented CTL responses. These studies provide important guidance for the design of human clinical trials of microsphere vaccines in terms of optimal peptide-microsphere formulation, vaccination regimen, vaccine dose, and adjuvant selection.

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

BACKGROUND

Dendritic cells (DCs) are potent antigen presenting cells (APCs), able to efficiently induce primary T cell-mediated responses to foreign antigens. In earlier studies we were able to identify a histocompatibility antigen (HLA)-A 2-restricted nine amino acid peptide (GP2, peptide 654-662) from the transmembrane portion of the protooncogene HER2/neu as a tumor-associated antigen (TAA) in human pancreatic cancer.

METHODS

Peripheral blood mononuclear cells (PBMCs) of HLA-A2+ and HLA-A2 healthy volunteers were isolated. PBMCs were grown with initial anti-CD3, low-dose interleukin-2 (IL-2), and peptide-pulsed DC stimulation. T-cell lines were analyzed in functional studies.

RESULTS

After 4 weeks, T-cell cultures were more than 50% CD8+. All peptide-pulsed T cells significantly lysed APC pulsed with the immunizing antigen in an HLA-A2 restricted fashion. Furthermore, HLA-A2+,HER2/neu+ human pancreatic cancer cells were lysed significantly higher than HLA-A2 HER2/neu+ pancreatic cancer cells. Transfection of an HLA-A2 pancreatic cancer cell line with the HLA-A2 gene resulted in a significantly higher lysis of the transfected cell line compared to the wild type. In HLA-A2+ pancreatic cancer targets, specific lysis was HLA-A2 restricted.

CONCLUSION

The ability to use DCs for presentation of either tumor or peptide antigen in an HLA-restricted fashion to stimulate T-cell proliferation, as well as cytotoxicity, demonstrates the potential of this technology for future development of a pancreatic cancer vaccine.

The HER2/neu-derived peptide p654-662 is a tumor-associated antigen in human pancreatic cancer recognized by cytotoxic T lymphocytes

The protooncogene HER2/neu encodes a 185-kDa transmembrane protein with extensive homology to the epidermal growth factor receptor. It is overexpressed in several human cancers of epithelial origin, such as pancreatic cancer. Previously, we demonstrated that cytotoxic T lymphocytes (CTL) derived from breast, ovarian, and non-small cell lung cancer recognized a peptide derived from HER2/neu. To evaluate whether this HLA-A2-binding peptide is a tumor-associated antigen (TAA) in pancreatic cancer, the ability of HER2/neu-reactive CTL to lyse human pancreatic carcinoma cells was tested. CTL were generated from tumor-associated T lymphocytes from HLA-A2+ HER2/neu+ breast and ovarian cancer patients. All CTL recognized autologous and allogeneic HER2/ neu+ tumor cells in an HLA-A2-restricted fashion. Furthermore, all CTL recognized p654-662 (GP2) derived from HER2/neu. These CTL also recognized HER2/neu+ pancreatic cancer cells in an HLA-A2-restricted fashion. HER2/neu+ HLA-A2- pancreatic cancer were not or only poorly lysed. Repeated stimulation of HLA-A2+ PBL from pancreatic cancer patients using the HER2/neu-derived peptide resulted in specific recognition of this peptide and, more importantly, HER2/neu+ pancreatic tumors in an HLA-A2-restricted fashion. Autologous HLA-A2+ fibroblasts or HLA-A2+ malignant melanoma cells were not recognized. HLA-A2- peptide-stimulated T lymphocytes showed no significant cytotoxicity. These results demonstrate that this HER2/neu-derived peptide is a shared TAA among several adenocarcinomas including pancreatic carcinoma, suggesting a common mechanism of recognition of these human tumors by T lymphocytes. The identification of the HER2/neu-derived peptide GP2 as a TAA in pancreatic cancer provides an opportunity for the design of novel immunotherapy and vaccine strategies.

Simultaneous production of T helper-1-like cytokines and cytolytic activity by tumor-specific T cells in ovarian and breast cancer

Cytotoxic T-cell (CTL) cultures were generated from five ovarian cancer patients (OvCTL) and from three breast cancer patients (BrCTL). All CTL lines were T-cell receptor (TcR) alphabeta+ and predominantly CD8+ (73 +/- 13%). These CTL lines preferentially recognized autologous tumor cells in an HLA class I-restricted, and in part HLA-A2-restricted, manner. In addition, the CTL lines recognized allogeneic HLA-A2+ ovarian and breast tumor cells. Specific recognition was determined by T-cell-mediated cytotoxicity as well as cytokine release. Coculture of irradiated autologous tumor cells with OvCTL induced secretion of IFN-gamma, GM-CSF and TNF-alpha, but not IL-4, indicating a T helper-1-type response. Similar results were obtained when OvCTL and BrCTL were stimulated with histologically matched HLA-A2+ tumor cells. Also, BrCTL stimulated with HLA-A2+ but not HLA-A2- ovarian tumor cells produced significant levels of GM-CSF and TNF-alpha. Finally, the Her2/neu peptide p654-662, earlier identified as a tumor antigen in both ovarian and breast cancer, induced cytotoxicity as well as the specific release of IFN-gamma and TNF-alpha but not IL-4 by OvCTL and BrCTL. Thus, tumor-specific recognition by CTL was verified by cytotoxicity and cytokine release. The secretion of Th1-like cytokines as opposed to Th2-like cytokines suggest that therapeutically OvCTL and BrCTL could potentially enhance the endogenous immune response to tumor.

Improved in vivo efficacy of tumor-infiltrating lymphocytes after restimulation with irradiated tumor cells in vitro

BACKGROUND

We investigated different culture conditions for tumor-infiltrating lymphocytes (TILs) with regard to proliferation, phenotypic changes, in vitro cytotoxicity, and in vivo therapeutic efficacy.

METHODS

After enzymatic digestion of the murine fibrosarcoma, MCA-105, TIL cultures were initiated as pure lymphocyte (groups 1 and 2) or mixed lymphocyte/tumor suspensions (groups 3 and 4). Group I TILs were grown in culture medium containing 100 IU/ml recombinant interleukin-2 (rIL-2). Group 2 TILs were stimulated with solid-phase anti-CD3 monoclonal antibody (mAb) for 48 h and cultured in rIL-2 (100 IU/ml)-containing medium. Group 3, which consisted initially of a surplus of tumor cells, received the same treatment as group 2. Group 4 was also activated with anti-CD3 mAb and rIL-2 but was additionally restimulated weekly with irradiated tumor cells (TILs to tumor, 20:1).

RESULTS

Groups 1 and 2 showed up to twofold higher increases in TIL numbers compared with groups 3 and 4 by the end of culture week 5. Although the original lymphocyte/tumor cell suspension consisted of 12.0 +/- 3.8% CD4+ T cells and 5.3 +/- 3.3% CD8+ T cells, all four TIL cultures showed approximately 80% CD8+ TILs and no CD4+ TILs by the end of culture week 4. In vitro cytotoxicity did not correlate with in vivo efficacy of the examined TIL cultures. By using the MCA-105 pulmonary metastases model in C57BL/6 mice, only suboptimal doses of TILs (2 x 10(6)) from group 4, which had been restimulated weekly with irradiated tumor, showed significant tumor eradication compared with all other treatment groups (p < 0.01).

CONCLUSIONS

We conclude that in vitro tumor restimulation of TILs improves in vivo efficacy, most likely through the education of tumor-reactive T cells.

The role of CD4+ tumor-infiltrating lymphocytes in human solid tumors

Many, if not all, solid tumors are characterized by a T cell infiltrate, usually consisting of CD4+ and CD8+ T cells. Characterization of both subsets of tumor-infiltrating lymphocytes (TIL) have shown that each population can be divided into tumor-specific and tumor-nonspecific T cells. A small proportion of tumor-specific CD4+ TIL can directly lyse tumor cells in an HLA class I- or II-restricted fashion. The majority of tumor-specific CD4+ TIL, however, recognize tumor antigens presented on HLA class II molecules by antigen-presenting cells (APC). At the same time, APC in the tumor environment express elevated levels of heat shock antigen (Hsp) 70 (and perhaps other antigens) that can be specifically recognized by tumor-nonspecific CD4+ TIL when presented by HLA class II. Functionally, CD4+ T cells can be distinguished into Th0 (production of IL-2, IL-4, and IFN-gamma), Th1 (IL-2 and IFN-gamma), and Th2 (IL-4). In addition, stressed CD4+ TIL have the ability to produce the growth factors heparin binding epidermal growth factor and basic fibroblast growth factor that support tumor growth. Since the efficacy of an antitumor immune response is codetermined by the net effect of stimulatory and inhibitory cytokines, a detailed understanding of the developmental pathways of CD4+ TIL subsets and their interactions is critical for the design of clinical protocols.