Translational development of active immunotherapy for hematologic malignancies

Phase I trial of TGF-beta 2 antisense GM-CSF gene-modified autologous tumor cell (TAG) vaccine

PURPOSE

On the basis of the hypothesis that the combined expression of immunostimulatory granulocyte macrophage colony stimulating factor (GM-CSF) and antitumor suppressor TGF-β2 antisense (AS) transgenes can break tolerance and stimulate immune responses to cancer-associated antigens, we constructed an expression plasmid [the tumor-associated glycoprotein (TAG) plasmid] that coexpresses GM-CSF and TGF-β2 AS nucleotide sequences and which was incorporated into an autologous whole-cell vaccine.

EXPERIMENTAL DESIGN

Patients undergoing resection were enrolled. Freshly harvested autologous tumor cells were mechanically and enzymatically disaggregated, then electroporated with the TAG vector. The resulting vaccine was irradiated, then aliquoted and cryopreserved until the time of injection. Patients received a minimum of 5 to a maximum of 12 monthly intradermal injections. Immune function was monitored at baseline and at months 3 and 6.

RESULTS

Vaccine manufacturing efficiency was 84% (32/38). Twenty-three patients received at least 1 vaccination. There were no grade 3 or 4 toxicities, and grade 1 and 2 events were local in nature. Seventeen of 21 patients had stable disease (SD) at month 2 or later as their best response, and 1 patient with stage IVa malignant melanoma achieved a complete response (CR) following 11 vaccinations and remains without evidence of disease 2 years following initiation of therapy. Six of 13 patients displayed a positive enzyme-linked immunospot (ELISPOT) response to autologous TAG vaccine at week 12 including 3 patients with prolonged SD or CR. The 3 other patients survived through week 24, as compared with none of the 7 ELISPOT-negative patients.

CONCLUSIONS

On the basis of safety and clinical and immunologic results, further evaluation of bifunctional vaccines is warranted.

Thymic stromal lymphopoietin plays an adjuvant role in BCG-mediated CD8(+) cytotoxic T cell responses through dendritic cell activation

Although Bacillus Calmette-Guérin (BCG) has historically emerged as a potent adjuvant in cancer immunization through dendritic cell (DC) activation, the efficacy of its antitumor effect has been limited. Therefore, the strategy of adjuvant therapy using BCG needs to be improved by adding enhancers. Here we found that thymic stromal lymphopoietin (TSLP) acts as an enhancer for the BCG-mediated antitumor effect. While BCG-stimulated DCs induced CD8(+) T cell production of IFN-gamma without strong cell expansion, TSLP-stimulated DCs induced robust CD8(+) T cell expansion without high quantities of IFN-gamma production. Notably, DCs stimulated with both BCG and TSLP induced robust expansion of CD8(+) T cells that produced a large amount of IFN-gamma with a potent cytolytic activity related to granzyme B expression. Our data suggest that TSLP is a good adjuvant to enhance the BCG-mediated cytotoxic T cell effect through DC activation, and provide a functional basis for a novel strategy for antitumor immune-based therapy.

In Situ Conversion of Melanoma Lesions into Autologous Vaccine by Intratumoral Injections of α-gal Glycolipids

Autologous melanoma associated antigens (MAA) on murine melanoma cells can elicit a protective anti-tumor immune response following a variety of vaccine strategies. Most require effective uptake by antigen presenting cells (APC). APC transport and process internalized MAA for activation of anti-tumor T cells. One potential problem with clinical melanoma vaccines against autologous tumors may be that often tumor cells do not express surface markers that label them for uptake by APC. Effective uptake of melanoma cells by APC might be achieved by exploiting the natural anti-Gal antibody which constitutes ~1% of immunoglobulins in humans. This approach has been developed in a syngeneic mouse model using mice capable of producing anti-Gal. Anti-Gal binds specifically to α-gal epitopes (Galα1-3Galβ1-4GlcNAc-R). Injection of glycolipids carrying α-gal epitopes (α-gal glycolipids) into melanoma lesions results in glycolipid insertion into melanoma cell membranes, expression of α-gal epitopes on the tumor cells and binding of anti-Gal to these epitopes. Interaction between the Fc portions of bound anti-Gal and Fcγ receptors on APC induces effective uptake of tumor cells by APC. The resulting anti-MAA immune response can be potent enough to destroy distant micrometastases. A clinical trial is now open testing effects of intratumoral α-gal glycolipid injections in melanoma patients.

Gene immunotherapy for non-small cell lung cancer

Historically, limited results have been observed with immunity in non-small cell lung cancer (NSCLC). In the last 5 years, however, several immune-stimulating products have demonstrated enhancement of tumor antigen recognition through activation of dendritic cell-involved processes. Moreover, clinical benefit has been demonstrated in subsets of patients, justifying ongoing phase III investigation. Results of key gene immunotherapies being tested in NSCLC are reviewed. Preliminary results in advanced NSCLC suggest evidence of well-tolerated immune activation with suggested evidence of clinical benefit with respect to survival and response.

Distribution patterns of dendritic cells and T cells in diffuse large B-cell lymphomas correlate with prognoses

PURPOSE

Diffuse large B-cell lymphoma (DLBCL), the most common subtype of non-Hodgkin's lymphomas, accounts for 30% to 40% of all lymphoma cases. However, long-term survival by current chemotherapy was achieved in only 40% of patients, warranting the development of novel therapeutic strategies including T-cell immunotherapy. However, the level of baseline immune activation in DLBCL is unclear.

EXPERIMENTAL DESIGN

The density and distribution of dendritic cells and T cells in 48 cases of primary DLBCL was evaluated by immunohistochemistry.

RESULTS

Increased numbers of intratumoral CD1a+ dendritic cells and increased S100+ cells and CD45RO+ T cells around the edges of the tumors were seen in 10 of 48 (21%), 9 of 48 (19%), and 10 of 48 (21%) cases and these were correlated with a favorable prognosis (P = 0.015; P = 0.070, and P = 0.017, respectively), along with increased granzyme B+ T cells in tumor beds (P = 0.013). Increased peritumoral T cells were correlated with tumor expression of HLA-DR (r = 0.446; P = 0.002). Extranodal lymphomas showed fewer tumor-associated CD45RO+ T cells (r = -0.407; P = 0.001) and less conspicuous dendritic cell infiltrates.

CONCLUSIONS

In DLBCL, the presence of baseline antitumor immune response is associated with favorable clinical outcome, and thus adjuvant T-cell immunotherapy may further boost treatment responses.

New approaches for monitoring CTL activity in clinical trials

We have developed a modification of the ELISPOT assay that measures Granzyme B (GrB) release from cytotoxic T lymphocytes (CTLs). The GrB ELISPOT assay is a superior alternative to the 51Cr-release assay since it is significantly more sensitive and provides an estimation of cytotoxic effector cell frequency. Additionally, unlike the IFN-gamma ELISPOT assay, the GrB ELISPOT directly measures the release of a cytolytic protein. We report that the GrB ELISPOT can be utilized to measure ex vivo antigen-specific cytotoxicity of peripheral blood mononuclear cells (PBMCs) from cancer patients vaccinated with a peptide-based cancer vaccine. We compare the reactivity of patients' PBMCs in the GrB ELISPOT, with reactivity in the tetramer, IFN-gamma ELISPOT and chromium (51Cr)-release assays. Differences in immune response over all assays tested were found between patients, and four response patterns were observed. Reactivity in the GrB ELISPOT was more closely associated with cytotoxicity in the 51Cr-release assay than the tetramer or IFN-gamma ELISPOT assays. We also optimized the GrB ELISPOT assay to directly measure immune responses against autologous primary tumor cells in vaccinated cancer patients. A perforin ELISPOT assay was also adapted to evaluate peptide-stimulated reactivity of PMBCs from vaccinated melanoma patients. Modifications of the ELISPOT assay described in this chapter allow a more comprehensive evaluation of low-frequency tumor-specific CTLs and their specific effector functions and can provide a valuable insight into immune responses in cancer vaccine trials.

Lung cancer immunotherapy

Recent insights into anti-tumor immunotherapy have led to a wave of clinical trials involving immunotherapy for lung cancer. Vaccines have evolved from nonspecific immune stimulants, like Bacillus Calmette-Guerin (BCG), to much more specific and potent strategies, some of which generate active immune responses against tumor-associated antigens. Understanding the mechanisms of anti-tumor immunity and identifying target antigens will likely improve these therapeutic strategies and provide them with a niche in the future of lung cancer therapy.

Cancer vaccines entering Phase III clinical trials

The last 10 years have seen a growth in the number of tumour antigens identified from immune responses raised in patients. The discovery that tumours can be recognised by the immune system stimulated a great deal of work characterising the molecular mechanisms underlying immune recognition. This in turn has led to an impressive array of immunological approaches to the generation of cancer vaccines; these range from molecularly defined T cell epitopes, antibody-based vaccines, cytokine therapies, immune modulators and DNA vaccines, to whole cell vaccines and, more recently, combinations of these methods. Many of these approaches have entered Phase I/II trials and have shown interesting clinical results. Moreover, they have extended our knowledge of the immune system and our understanding of the mechanisms required to design a successful cancer vaccine. This review outlines some of the approaches that have led to some of these vaccines entering Phase III clinical trials, discusses their modes of action and reports on their current status in trial.

Fibromodulin as a novel tumor-associated antigen (TAA) in chronic lymphocytic leukemia (CLL), which allows expansion of specific CD8+ autologous T lymphocytes

Fibromodulin (FMOD) was shown to be highly overexpressed in chronic lymphocytic leukemia (CLL) cells compared with normal B lymphocytes by gene expression profiling. Therefore FMOD might serve as potential tumor-associated antigen (TAA) in CLL, enabling expansion of FMOD-specific T cells. In CLL samples derived from 16 different patients, high expression of FMOD by real-time reverse transcriptase–polymerase chain reaction (RT-PCR) was detectable in contrast to normal B lymphocytes. We used unpulsed native CLL cells and CD40 ligand (CD40L)–stimulated CLL cells as antigen-presenting cells (APCs) to expand autologous T cells from 13 patients. The number of T cells during 4 weeks of in vitro culture increased 2- to 3.5-fold and the number of T cells recognizing FMOD peptides bound to HLA-A2 dimers increased 10-fold. The expanded T cells also were able to secrete interferon-γ (IFN-γ) upon recognition of the antigen demonstrated by IFN-γ ELISPOT assays. T cells not only recognized HLA-A2–binding FMOD peptides presented by transporter-associated with antigen-processing (TAP)–deficient T2 cells, but also FMOD overexpressing autologous CLL cells in an HLA-A2–restricted manner. In summary, FMOD was shown for the first time to be naturally processed and presented as TAA in primary CLL cells, enabling the expansion of autologous tumor-specific T cells.

Modified ELISPOT

The use of the IFN-γ ELISPOT assay to evaluate cellular immune responses has gained increasing popularity, especially as a surrogate measure for CTL responses. We developed and validated some modifications of the IFN-γ ELISPOT assay to optimize immunological monitoring of various cancer vaccine trials. Taking into consideration that the main mechanism of cell-mediated cytotoxicity is the release of cytolytic granules that contain, among others, cytolytic protein Granzyme B (GrB), we developed the GrB ELISPOT assay. Extensive studies demonstrated that the GrB ELISPOT assay is specific, accurately measures the rapid release of GrB, is more sensitive than the 51Cr-release assay, and that it may be successfully applied to measuring CTL precursory frequency in PBMC from cancer patients. Assuming that immunological assays that demonstrate recognition of native tumor cells (tumor-specific) may be more clinically relevant than assays that demonstrate recognition of tumor protein or peptide (antigen-specific), we developed and validated the Autologous Tumor IFN-γ ELISPOT assay using PBMC from idiotype vaccinated lymphoma patients as effectors and autologous B cell lymphoma tumor cells as targets. The precursor frequency of tumor-reactive T cells was significantly higher in the postvaccine PBMC, compared with prevaccine samples in all patients tested. Furthermore, the specificity of these T cells was established by the lack of reactivity against autologous normal B cells. These results demonstrate the feasibility of evaluating tumor-specific T cell responses when autologous, primary tumor cells are available as targets. Modifications of ELISPOT assay described in this chapter allow more comprehensive assessment of low frequency tumor-specific CTL and their specific effector functions and can provide valuable insight with regards to immune responses in cancer vaccine trials.

New chemotherapeutic strategies in colorectal cancer

Since colorectal cancer is the second most prevalent cancer worldwide, its treatment remains a major challenge for researchers, gastroenterologists and oncologists. Despite curative resections, half of all patients diagnosed with colorectal cancer die because of their underlying disease. Integral chemotherapeutic components of standard regimens are 5-fluorouracil (5-FU), its modulation by folinic acid and irinotecan or oxaliplatin. All these drugs sequentially given have results in terms of median overall survival of more than 20 months in the palliative treatment of advanced colorectal cancer. Oral fluoropyrimidines, currently under clinical investigation, are likely to substitute continuous 5-FU. Inhibitors of growth factor receptors or their signaling may further prolong disease-free and overall survival rates. Preliminary evidence exists that improved adjuvant and neoadjuvant chemotherapy strategies may further improve the prognosis, mainly because more patients are able to go for primary or secondary surgery with curative intent.

A modified human ELISPOT assay to detect specific responses to primary tumor cell targets

Background

The desired outcome of cancer vaccination is to induce a potent T cell response which can specifically recognize and eliminate autologous tumor cells in vivo. Accordingly, immunological assays that demonstrate recognition of native tumor cells (tumor-specific) may be more clinically relevant than assays that demonstrate recognition of tumor protein or peptide (antigen-specific).

Methods

Towards this goal, we adapted the IFN-γ ELISPOT assay to measure immune responses against autologous primary tumor cells in vaccinated cancer patients. As a model system to develop the assay, we utilized peripheral blood mononuclear cells (PBMC) directly isolated from follicular lymphoma patients vaccinated with tumor-derived idiotype protein.

Results

After optimizing several variables, we demonstrated that the modified IFN-γ ELISPOT assay could be used to reliably and reproducibly determine the tumor-reactive T cell frequency in the PBMC of these patients. The precursor frequency of tumor-reactive T cells was significantly higher in the postvaccine PBMC, compared with prevaccine samples in all patients tested. Furthermore, the specificity of these T cells was established by the lack of reactivity against autologous normal B cells.

Conclusions

These results demonstrate the feasibility of quantitating tumor-specific T cell responses when autologous, primary tumor cells are available as targets.