First step results from a phase II study of a dendritic cell vaccine in glioblastoma patients (CombiG-vax).

Background: Glioblastoma (GBM) is a poor prognosis grade 4 glioma. After surgical resection, the standard therapy consists of concurrent radiotherapy (RT) and temozolomide (TMZ) followed by TMZ alone. Our previous data on melanoma patients showed that Dendritic Cell vaccination (DCvax) could increase the amount of intratumoral-activated cytotoxic T lymphocytes. Methods: This is a single-arm, monocentric, phase II trial in two steps according to Simon's design. The trial aims to evaluate progression-free survival (PFS) at three months and the safety of a DCvax integrated with standard therapy in resected GBM patients. DCvax administration begins after completion of RT-CTwith weekly administrations for 4 weeks, then is alternated monthly with TMZ cycles. The primary endpoints are PFS at three months and safety. One of the secondary objectives is to evaluate the immune response both in vitro and in vivo (DTH skin test). Results: By December 2022, the first pre-planned step of the study was concluded with the enrollment, treatment and follow up of 9 evaluable patients. Two patients had progressed within three months after leukapheresis, but none had experienced DCvax-related G3-4 toxicities Five patients experienced a positive DTH test towards KLH and one of these also towards autologous tumor homogenate. The median PFS from leukapheresis was 11.3 months and 12.2 months from surgery. Conclusions: This combination therapy is well-tolerated, and the two endpoints required for the first step have been achieved. Therefore, the study will proceed to enroll the remaining 19 patients. (Eudract number: 2020-003755-15 https://www.clinicaltrialsregister.eu/ctr-search/trial/2020-003755-15/IT).

Dendritic cell vaccines as cancer treatment: focus on 13 years of manufacturing and quality control experience in advanced therapy medicinal products.

BACKGROUND AIMS: Dendritic cells (DCs) are professional antigen-presenting cells of the mammalian immune system. Ex vivo differentiated DCs represent a unique Advanced Therapy Medicinal Product (ATMP), used in several clinical trials as personalized cancer immunotherapy. The therapy's reliability depends on its capacity to produce high-quality mature DCs (mDCs) in compliance with Good Manufacturing Practices. AIMS: From March 2010 to December 2023, 103 patients were enrolled in multiple clinical trials at the Immuno-Gene Therapy Factory at IRCCS Istituto Romagnolo per lo Studio dei Tumori (IRST) "Dino Amadori". Six hundred forty-two doses were produced, and the manufacturing process was implemented to optimize production. Our study is a retrospective analysis focusing on the quality control results. METHODS: We retrospectively analyzed the results of the quality control tests carried out on each produced batch, evaluating viability, purity and phenotype of mDCs and their quality in terms of microbiological safety. The data obtained are given with median and interquartile range. RESULTS: The batches were found to be microbiologically safe in terms of sterility, mycoplasma, and endotoxins. An increase in DC maturation markers was found. The release criteria checks showed a high percentage of viability and purity was maintained during the production process. CONCLUSIONS: Our findings have confirmed that the measures implemented have ensured the safety of the products and have contributed to the establishing a robust "Pharmaceutical Quality System." This has enabled many safe mDCs to be produced for clinical trials.

In vitro CAR-T cell killing: validation of the potency assay.

For advanced therapy medicinal products, the development and validation of potency assays are required, in accordance with international guidelines, to characterise the product and obtain reliable and consistent data. Our purpose was to validate the killing assay for the evaluation of autologous anti-CD19 chimeric antigen receptor (CAR) T potency. We used CD4 + and CD8 + lymphocytes or anti-CD19 CAR-T cells as effector cells and REH (CD19 +) or MOLM-13 (CD19 -) cell lines as target cells. After co-culturing target and effector cells (1:1 ratio) for 24 h, samples were labelled with 7-AAD, anti-CD3 and anti-CD19 antibodies and the frequency of CD19 + dead cells was evaluated by flow cytometry. In order to verify the CAR-T specificity for the CD19 + target, the co-culture between CAR-T and REH or MOLM-13 at different effector-to-target ratios was scheduled. Moreover, not transduced CD4 + and CD8 + lymphocytes were tested in comparison with CAR-T from the same donor to demonstrate the assay specificity. Linearity and accuracy were evaluated, and established acceptance criteria were compiled for both parameters (r2 ≥ 0.97 for linearity and average relative error ≤ 10% for accuracy). Furthermore, the method was considered robust when performed between 23 and 25 h of co-culture, and the intra-assay, inter-assay and inter-day precision was obtained. Finally, in order to verify the inter-analyst precision, the test was executed by three different operators and the intra-class correlation coefficient was > 0.4 in both cases. In conclusion, we consider this CAR-T potency assay as validated and usable in all steps of product development and quality control.

The Renewal of Cancer Immunotherapy.

Cancer immunotherapy embraces many current, promising therapeutic approaches to eradicate tumors by activating host antitumor activity [...].

Stability Program in Dendritic Cell Vaccines: A "Real-World" Experience in the Immuno-Gene Therapy Factory of Romagna Cancer Center.

Advanced therapy medical products (ATMPs) are rapidly growing as innovative medicines for the treatment of several diseases. Hence, the role of quality analytical tests to ensure consistent product safety and quality has become highly relevant. Several clinical trials involving dendritic cell (DC)-based vaccines for cancer treatment are ongoing at our institute. The DC-based vaccine is prepared via CD14+ monocyte differentiation. A fresh dose of 10 million DCs is administered to the patient, while the remaining DCs are aliquoted, frozen, and stored in nitrogen vapor for subsequent treatment doses. To evaluate the maintenance of quality parameters and to establish a shelf life of frozen vaccine aliquots, a stability program was developed. Several parameters of the DC final product at 0, 6, 12, 18, and 24 months were evaluated. Our results reveal that after 24 months of storage in nitrogen vapor, the cell viability is in a range between 82% and 99%, the expression of maturation markers remains inside the criteria for batch release, the sterility tests are compliant, and the cell costimulatory capacity unchanged. Thus, the data collected demonstrate that freezing and thawing do not perturb the DC vaccine product maintaining over time its functional and quality characteristics.

Radiotherapy and High-Dose Interleukin-2: Clinical and Immunological Results of a Proof of Principle Study in Metastatic Melanoma and Renal Cell Carcinoma.

High-dose interleukin-2 (HD IL-2) has curative potential in metastatic melanoma (MM) and renal cell carcinoma (RCC). Radiotherapy (RT) kills cancer cells and induces immunomodulatory effects. Prospective trials exploring clinical and immunological properties of combined RT/HD IL-2 are still needed. We designed a phase II, single-arm clinical trial for patients with MM and RCC. The treatment schedule consisted of 3 daily doses of 6-12 Gy of RT to 1-5 non-index metastatic fields, before IL-2 at the first and third treatment cycle. HD IL-2 was administered by continuous infusion for 72 hours and repeated every 3 weeks for up to 4 cycles, thereafter every 4 weeks for a maximum of 2 cycles. The primary endpoint was the immunological efficacy of the combined RT/HD IL-2 treatment (assessed by IFN-γ ELISPOT). Nineteen out of 22 patients were evaluable for immunological and clinical response. Partial response occurred in 3 (15.7%) patients and stable disease was observed in 7 (36.8%). The disease control rate was 52.6% after a median follow up of 39.2 months. According to Common Terminology Criteria for Adverse Events 4.0 (CTCAE 4.0), the majority of toxicities were grade 1-2. Immunological responses were frequent and detected in 16 (84.2%) patients. Increased levels of IL-8 and IL-10 in melanoma, circulating effector memory CD4+ and intratumoral CD8+ T cells in both tumor types were detected after therapy. Overall the treatment was well tolerated and immunologically active. Immunomonitoring and correlative data on tumor and peripheral blood cell subsets suggest that this combination treatment could be a promising strategy for patients progressing after standard treatments.

Potency Assessment of Dendritic Cell Anticancer Vaccine: Validation of the Co-Flow DC Assay.

For many years, oncological clinical trials have taken advantage of dendritic cells (DC) for the design of DC-based cellular therapies. This has required the design of suitable quality control assays to evaluate the potency of these products. The purpose of our work was to develop and validate a novel bioassay that uses flow cytometry as a read-out measurement. In this method, CD3+ cells are labeled with a fluorescent dye and the DC costimulatory activity is measured by the degree of T cell proliferation caused by the DC-T cell interaction. The validation of the method was achieved by the evaluation of essential analytical parameters defined by international guidelines. Our results demonstrated that the method could be considered specific, selective, and robust. The comparison between measured values and estimated true values confirmed a high level of accuracy and a lack of systematic error. Repeated experiments have shown the reproducibility of the assay and the proportionality between the potency and the DC amount has proven its linearity. Our results suggest that the method is compliant with the guidelines and could be adopted as a quality control assay or batch-release testing within GMP facilities.

Dendritic Cell Vaccination in Metastatic Melanoma Turns "Non-T Cell Inflamed" Into "T-Cell Inflamed" Tumors.

Dendritic cell (DC)-based vaccination effectively induces anti-tumor immunity, although in the majority of cases this does not translate into a durable clinical response. However, DC vaccination is characterized by a robust safety profile, making this treatment a potential candidate for effective combination cancer immunotherapy. To explore this possibility, understanding changes occurring in the tumor microenvironment (TME) upon DC vaccination is required. In this line, quantitative and qualitative changes in tumor-infiltrating T lymphocytes (TILs) induced by vaccination with autologous tumor lysate/homogenate loaded DCs were investigated in a series of 16 patients with metastatic melanoma. Immunohistochemistry for CD4, CD8, Foxp3, Granzyme B (GZMB), PDL1, and HLA class I was performed in tumor biopsies collected before and after DC vaccination. The density of each marker was quantified by automated digital pathology analysis on whole slide images. Co-expression of markers defining functional phenotypes, i.e., Foxp3+ regulatory CD4+ T cells (Treg) and GZMB+ cytotoxic CD8+ T cells, was assessed with sequential immunohistochemistry. A significant increase of CD8+ TILs was found in post-vaccine biopsies of patients who were not previously treated with immune-modulating cytokines or Ipilimumab. Interestingly, along with a maintained tumoral HLA class I expression, after DC vaccination we observed a significant increase of PDL1+ tumor cells, which significantly correlated with intratumoral CD8+ T cell density. This observation might explain the lack of a significant concurrent cytotoxic reactivation of CD8+ T cell, as measured by the numbers of GZMB+ T cells. Altogether these findings indicate that DC vaccination exerts an important role in sustaining or de novo inducing a T cell inflamed TME. However, the strength of the intratumoral T cell activation detected in post-DC therapy lesions is lessened by an occurring phenomenon of adaptive immune resistance, yet the concomitant PDL1 up-regulation. Overall, this study sheds light on DC immunotherapy-induced TME changes, lending the rationale for the design of smarter immune-combination therapies.

Complementary vaccination protocol with dendritic cells pulsed with autologous tumour lysate in patients with resected stage III or IV melanoma: protocol for a phase II randomised trial (ACDC Adjuvant Trial).

INTRODUCTION: Surgery is one of the treatments of choice for patients with a single metastasis from melanoma but is rarely curative. Such patients could potentially benefit from consolidation immunotherapy. Vaccination with dendritic cells (DCs) loaded with tumour antigens elicits a tumour-specific immune response. In our experience, patients who developed delayed type hypersensitivity (DTH) after DC vaccination showed a median overall survival (OS) of 22.9 monthsvs4.8 months for DTH-negative cases. A phase II randomised trial showed an advantage OS of a DC vaccine over a tumour cell-based vaccine (2-year OS 72% vs31%, respectively). Given that there is no standard therapy after surgical resection of single metastases, we planned a study to compare vaccination with DCs pulsed with autologous tumour lysate versus follow-up. METHODS AND ANALYSIS: This is a randomised phase II trial in patients with resected stage III/IV melanoma. Assuming a median relapse-free survival (RFS) of 7.0 months for the standard group and 11.7 months for the experimental arm (HR 0.60), with a two-sided tailed alpha of 0.10, 60 patients per arm must be recruited. An interim futility analysis will be performed at 18 months. The DC vaccine, produced in accordance with Good Manufacturing Practice guidelines, consists of autologous DCs loaded with autologous tumour lysate and injected intradermally near lymph nodes. Vaccine doses will be administered every 4 weeks for six vaccinations and will be followed by 3 million unit /day of interleukin-2 for 5 days. Tumour restaging, blood sampling for immunological biomarkers and DTH testing will be performed every 12 weeks. ETHICS AND DISSEMINATION: The protocol, informed consent and accompanying material given to patients were submitted by the investigator to the Ethics Committee for review. The local Ethics Committee and the Italian Medicines Agency approved the protocol (EudraCT code no.2014-005123-27). Results will be published in a peer-reviewed international scientific journal. TRIAL REGISTRATION NUMBER: 2014-005123-27.

Skewing effect of sulprostone on dendritic cell maturation compared with dinoprostone.

BACKGROUND: Dendritic cells (DCs) are the most efficient antigen-presenting cells and act at the center of the immune system owing to their ability to control both immune tolerance and immunity. In cancer immunotherapy, DCs play a key role in the regulation of the immune response against tumors and can be generated ex vivo with different cytokine cocktails. METHODS: We evaluated the feasibility of dinoprostone (PGE2) replacement with the molecular analog sulprostone, in our good manufacturing practice (GMP) protocol for the generation of DC-based cancer vaccine. We characterized the phenotype and the function of DCs matured in the presence of sulprostone as a potential substitute of dinoprostone in the pro-inflammatory maturation cocktail consisting of tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1ß) and IL-6. RESULTS: We found that sulprostone invariably reduces the recovery, but does not significantly modify the viability and the purity of DCs. The presence of sulprostone in the maturation cocktail increases the adhesion of single cells and of clusters of DCs to the flask, making them more similar to their immature counterpart in terms of adhesion and spreading proprieties. Moreover, we observed that sulprostone impairs the expression of co-stimulatory molecules and the spontaneous as well as the directed migration capacity of DCs. DISCUSSION: These findings underscore that the synthetic analog sulprostone strongly reduces the functional quality of DCs, thus cannot replace dinoprostone in the maturation cocktail of monocyte-derived DCs.

Dendritic cell vaccination for metastatic melanoma: a 14-year monoinstitutional experience.

Although immunomodulating antibodies are highly effective in metastatic melanoma, their toxicity, related to the activation of T lymphocytes, can be severe. Anticancer vaccines promote a fairly specific response and are very well tolerated, but their effectiveness has yet to be demonstrated. We have been treating patients with advanced melanoma with an autologous dendritic cell vaccine since 2001; to better characterize the safety and efficacy of our product, we designed a retrospective study on all of our patients treated with the vaccine to date. We retrospectively reviewed both case report forms of patients included in clinical trials and medical records of those treated within a compassionate use program. Response was assessed according to the Response Evaluation Criteria In Solid Tumors criteria and toxicity has been graded according to CTCAE 4.0. Although the response rate has been rather low, the median overall survival of 11.4 months and the 1-year survival rate of 46.9% are encouraging, especially considering the fact that data were obtained in a heavily pretreated population and only about one quarter of the patients had received ipilimumab and/or BRAF inhibitors. Multivariate analysis confirmed that the development of an immune response was significantly correlated with a better prognosis (hazard ratio 0.54; P=0.019). The adverse events observed were generally mild and self-limiting. Our analysis confirms the excellent tolerability of our vaccine, making it a potential candidate for combination therapies. As efficacy seems largely restricted to immunoresponsive patients, future strategies should aim to increase the number of these patients.

Vaccination with autologous dendritic cells loaded with autologous tumor lysate or homogenate combined with immunomodulating radiotherapy and/or preleukapheresis IFN-α in patients with metastatic melanoma: a randomised "proof-of-principle" phase II study.

BACKGROUND: Vaccination with dendritic cells (DC) loaded with tumor antigens elicits tumor-specific immune responses capable of killing cancer cells without inducing meaningful side-effects. Patients with advanced melanoma enrolled onto our phase II clinical studies have been treated with autologous DC loaded with autologous tumor lysate/homogenate matured with a cytokine cocktail, showing a clinical benefit (PR + SD) in 55.5% of evaluable cases to date. The beneficial effects of the vaccine were mainly restricted to patients who developed vaccine-specific immune response after treatment. However, immunological responses were only induced in about two-thirds of patients, and treatments aimed at improving immunological responsiveness to the vaccine are needed. METHODS/DESIGN: This is a phase II, "proof-of-principle", randomized, open-label trial of vaccination with autologous DC loaded with tumor lysate or homogenate in metastatic melanoma patients combined with immunomodulating RT and/or preleukapheresis IFN-α. All patients will receive four bi-weekly doses of the vaccine during the induction phase and monthly doses thereafter for up to a maximum of 14 vaccinations or until confirmed progression. Patients will be randomized to receive:(1.) three daily doses of 8 Gy up to 12 Gy radiotherapy delivered to one non-index metastatic field between vaccine doses 1 and 2 and, optionally, between doses 7 and 8, using IMRT-IMAT techniques;(2.) daily 3 MU subcutaneous IFN-α for 7 days before leukapheresis;(3.) both 1 and 2;(4.) neither 1 nor 2.At least six patients eligible for treatment will be enrolled per arm. Daily 3 MU IL-2 will be administered subcutaneously for 5 days starting from the second day after each vaccine dose. Serial DTH testing and blood sampling to evaluate treatment-induced immune response will be performed. Objective response will be evaluated according to immune-related response criteria (irRC). DISCUSSION: Based upon the emerging role of radiotherapy as an immunologic modifier, we designed a randomized phase II trial adding radiotherapy and/or preleukapheresis IFN-α to our DC vaccine in metastatic melanoma patients. Our aim was to find the best combination of complementary interventions to enhance anti-tumor response induced by DC vaccination, which could ultimately lead to better survival and milder toxicity.

Low-dose temozolomide before dendritic-cell vaccination reduces (specifically) CD4+CD25++Foxp3+ regulatory T-cells in advanced melanoma patients.

BACKGROUND: In cancer immunotherapy, dendritic cells (DCs) play a fundamental role in the dialog between innate and adaptive immune response, but several immunosuppressive mechanisms remain to be overcome. For example, a high number of CD4+CD25++Foxp3+ regulatory T-cells (Foxp3+Tregs) have been observed in the peripheral blood and tumor microenvironment of cancer patients. On the basis of this, we conducted a study on DC-based vaccination in advanced melanoma, adding low-dose temozolomide to obtain lymphodepletion. METHODS: Twenty-one patients were entered onto our vaccination protocol using autologous DCs pulsed with autologous tumor lysate and keyhole limpet hemocyanin. Patients received low-dose temozolomide before vaccination and 5 days of low-dose interleukin-2 (IL-2) after vaccination. Circulating Foxp3+Tregs were evaluated before and after temozolomide, and after IL-2. RESULTS: Among the 17 evaluable patients we observed 1 partial response (PR), 6 stable disease (SD) and 10 progressive disease (PD). The disease control rate (PR+SD = DCR) was 41% and median overall survival was 10 months. Temozolomide reduced circulating Foxp3+Treg cells in all patients. A statistically significant reduction of 60% was observed in Foxp3+Tregs after the first cycle, whereas the absolute lymphocyte count decreased by only 14%. Conversely, IL-2 increased Foxp3+Treg cell count by 75.4%. Of note the effect of this cytokine, albeit not statistically significant, on the DCR subgroup led to a further 33.8% reduction in Foxp3+Treg cells. CONCLUSIONS: Our results suggest that the combined immunological therapy, at least as far as the DCR subgroup is concerned, effectively reduced the number of Foxp3+Treg cells, which exerted a blunting effect on the growth-stimulating effect of IL-2. However, this regimen, with its current modality, would not seem to be capable of improving clinical outcome.

Dendritic cell-based vaccine in advanced melanoma: update of clinical outcome.

Dendritic cells (DCs) are unique specialized antigen-presenting cells capable of priming naive T cells and inducing antigen-specific cytotoxic T lymphocytes. This study presents an update of clinical results from a DC-based phase I-II clinical vaccine trial in stage IV melanoma. From 2003 to 2010, 27 patients with metastatic melanoma were treated with mature DCs pulsed with autologous tumor lysate and keyhole limpet hemocyanin and with subcutaneous low-dose interleukin-2. Delayed-type hypersensitivity (DTH) tests for in-vivo immunomonitoring were performed at baseline and every four vaccinations thereafter. Two complete, two mixed and six partial responses, and five stable diseases were observed (overall response, 37.0%; clinical benefit, 55.5%). All 15 responders showed DTH positivity. A median overall survival of 22.9 months [95% confidence interval (CI): 13.4-61.3] for DTH-positive patients (19) and 4.8 months (95% CI: 3.9-11.9) for DTH-negative patients (8; log rank=7.26; P=0.007) was observed. The overall median overall survival was 16 months (95% CI: 9-33). Our results would seem to highlight a relationship between positive-DTH test and an improved survival.

Unexpected high response rate to traditional therapy after dendritic cell-based vaccine in advanced melanoma: update of clinical outcome and subgroup analysis.

We reviewed the clinical results of a dendritic cell-based phase II clinical vaccine trial in stage IV melanoma and analyzed a patient subgroup treated with standard therapies after stopping vaccination. From 2003 to 2009, 24 metastatic melanoma patients were treated with mature dendritic cells pulsed with autologous tumor lysate and keyhole limpet hemocyanin and low-dose interleukin-2. Overall response (OR) to vaccination was 37.5% with a clinical benefit of 54.1%. All 14 responders showed delayed type hypersensitivity positivity. Median overall survival (OS) was 15 months (95% CI, 8-33). Eleven patients underwent other treatments (3 surgery, 2 biotherapy, 2 radiotherapy, 2 chemotherapy, and 4 biochemotherapy) after stopping vaccination. Of these, 2 patients had a complete response and 5 a partial response, with an OR of 63.6%. Median OS was 34 months (range 16-61). Our results suggest that therapeutic DC vaccination could favor clinical response in patients after more than one line of therapy.

FRET microscopy autologous tumor lysate processing in mature dendritic cell vaccine therapy.

BACKGROUND: Antigen processing by dendritic cells (DC) exposed to specific stimuli has been well characterized in biological studies. Nonetheless, the question of whether autologous whole tumor lysates (as used in clinical trials) are similarly processed by these cells has not yet been resolved. METHODS: In this study, we examined the transfer of peptides from whole tumor lysates to major histocompatibility complex class II molecules (MHC II) in mature dendritic cells (mDC) from a patient with advanced melanoma. Tumor antigenic peptides-MHC II proximity was revealed by Förster Resonance Energy Transfer (FRET) measurements, which effectively extends the application of fluorescence microscopy to the molecular level (<100A). Tumor lysates were labelled with Alexa-488, as the donor, and mDC MHC II HLA-DR molecules were labelled with Alexa-546-conjugated IgG, as the acceptor. RESULTS: We detected significant energy transfer between donor and acceptor-labelled antibodies against HLA-DR at the membrane surface of mDC. FRET data indicated that fluorescent peptide-loaded MHC II molecules start to accumulate on mDC membranes at 16 hr from the maturation stimulus, steeply increasing at 22 hr with sustained higher FRET detected up to 46 hr. CONCLUSIONS: The results obtained imply that the patient mDC correctly processed the tumor specific antigens and their display on the mDC surface may be effective for several days. These observations support the rationale for immunogenic efficacy of autologous tumor lysates.

Tumor endothelial marker 8 expression levels in dendritic cell-based cancer vaccines are related to clinical outcome.

Previous studies have shown that tumor endothelial markers (TEMs 1-9) are up modulated in immunosuppressive, pro-angiogenic dendritic cells (DCs) found in tumor microenvironments. We recently reported that monocyte-derived DCs used for vaccination trials may accumulate high levels of TEM8 gene transcripts. Here, we investigate whether TEM8 expression in DC preparations represents a specific tumor-associated change of potential clinical relevance. TEM8 expression at the mRNA and protein level was evaluated by quantitative real-time RT-PCR and cytofluorimetric analysis in human clinical grade DCs utilized for the therapeutic vaccination of 17 advanced cancer patients (13 melanoma and 4 renal cell carcinoma). The analyses revealed that DCs from patients markedly differ in their ability to up-modulate TEM8. Indeed, mDCs from eight non-progressing patients [median overall survival (OS) = 32 months, all positive to the delayed-type hypersensitivity test (DTH)], had similar TEM8 mRNA expression levels [mDCs vs. immature iDCs; mean fold increase (mfi) = 1.97] to those found in healthy donors (mfi = 2.7). Conversely, mDCs from nine progressing patients (OS < 5 months, all but one with negative DTH) showed an increase in TEM8 mRNA levels (mfi = 12.88, p = 0.0018). The present observations suggest that TEM8 expression levels in DC-based therapeutic vaccines would allow the selection of a subgroup of patients who are most likely to benefit from therapeutic vaccination.

Human embryo immune escape mechanisms rediscovered by the tumor.

Towards the end of the 1990s, the two opposing theories on immunosurveillance and immunostimulation were extensively studied by researchers in an attempt to understand the complex mechanisms that regulate the relation between tumors and the host's immune system. Both theories probably have elements that would help us to comprehend how the host can induce anti-tumor clinical responses through stimulation of the immune system and which could also give us a deeper insight into the mechanisms of tumor immunosuppression. The model that most resembles the behavior of tumor cells in terms of growth, infiltration and suppression of the immune system of the environment in which they live is undoubtedly that of the embryonic cell. The fetus behaves like an allogenic transplant within the mother's body, using every means it has to escape from and defend itself against the mother's immune system. The majority of these mechanisms are the same as those found in tumor cells: antigenic loss, lack of expression of classic HLA-I molecules, production of immunosuppressive cytokines, induction of lack of expression of co-stimulatory molecules in antigen presenting cells, and induction of apoptosis in infiltrating lymphocytes, with activation of a type Th2 regulatory lymphocyte response. A careful and comparative study of key mechanisms capable of triggering tolerance or cytotoxicity in both embryonic and tumor cells could prove immensely valuable in designing new strategies for anti-tumor immunotherapy.

Improved overall survival in dendritic cell vaccination-induced immunoreactive subgroup of advanced melanoma patients.

BACKGROUND: We present our experience of therapeutic vaccination using dendritic cells (DC) pulsed with autologous tumor antigens in patients with advanced melanoma. METHODS: Twenty-one pretreated advanced melanoma patients were vaccinated with autologous DC pulsed with 100 microg/ml of autologous-tumor-lysate (ATL) or -homogenate (ATH) and 50 microg/ml of keyhole limpet hemocyanin (KLH). The first 8 patients were treated subcutaneously or intradermally with immature-DC (iDC) (range 4.5-82 x 10(6)) and the remaining 13 intradermally with in vitro matured DC (mDC) (range 1.2-26 x 10(6)). Subcutaneous interleukin-2 (3 x 10(6) IU) was administered from days 3 to 7 of each treatment cycle. RESULTS: Three of the 8 iDC patients obtained stabilizations (SD), each of 6 months' duration. The 13 mDC patients showed 1 complete response (8 months), 1 partial response (3 months), 2 mixed responses (6 and 12 months) and 3 SD (9, 7+, and 3+ months). Overall responses (OR) were observed in 4/21 (19%) patients, or 4/13 (30.7%) considering mDC treatment only. 10/21 (47.6%) patients showed non progressive disease (NPD), with 7/13 (53.8%) cases of NPD for mDC-treated patients. No major toxicities were observed. The positive delayed-type hypersensitivity (DTH) test to ATL/ATH and/or KLH correlated with increased overall survival (OS). Median OS was 24 months (range 3-45) for the 10 DTH-positive (1 iDC and 9 mDC) and 5 months (range 3-14) for the 11 DTH-negative patients (P < 0.001). The in vitro evaluation of gamma IFN-secreting T-cells in 10 patients showed good correlation with both DTH (75%) and clinical outcome (70%). CONCLUSION: Vaccination using DC pulsed with ATL/ATH and KLH in advanced melanoma patients is well tolerated and can induce a clinical response, especially when mDC are used. Successful immunization, verified by positive DTH, leads to longer survival.

Evaluation of in vivo labelled dendritic cell migration in cancer patients.

BACKGROUND: Dendritic Cell (DC) vaccination is a very promising therapeutic strategy in cancer patients. The immunizing ability of DC is critically influenced by their migration activity to lymphatic tissues, where they have the task of priming naïve T-cells. In the present study in vivo DC migration was investigated within the context of a clinical trial of antitumor vaccination. In particular, we compared the migration activity of mature Dendritic Cells (mDC) with that of immature Dendritic Cells (iDC) and also assessed intradermal versus subcutaneous administration. METHODS: DC were labelled with 99mTc-HMPAO or 111In-Oxine, and the presence of labelled DC in regional lymph nodes was evaluated at pre-set times up to a maximum of 72 h after inoculation. Determinations were carried out in 8 patients (7 melanoma and 1 renal cell carcinoma). RESULTS: It was verified that intradermal administration resulted in about a threefold higher migration to lymph nodes than subcutaneous administration, while mDC showed, on average, a six-to eightfold higher migration than iDC. The first DC were detected in lymph nodes 20-60 min after inoculation and the maximum concentration was reached after 48-72 h. CONCLUSIONS: These data obtained in vivo provide preliminary basic information on DC with respect to their antitumor immunization activity. Further research is needed to optimize the therapeutic potential of vaccination with DC.