Treatment Of Metastatic Solid Tumors Research Articles

Abstract 6593: Rejuvenation of tumor-infiltrating lymphocytes (TIL): A novel strategy to revitalize TIL antitumor function for cell therapy

Abstract TIL therapy is a promising approach for the treatment of metastatic solid tumors, but its efficacy is limited by T-cell exhaustion and terminal differentiation. In addition, recent studies have underscored the adverse effects of aging on T cells. Reprogramming T cells into induced pluripotent stem cells (iPSC) and differentiating them back to the T-cell lineage has proven to be complex and time-consuming. In particular for TIL applications, de novo T cell production via iPSCs requires each TCR in the final product to be derived from an independently established iPSC clone. To overcome these barriers, we developed a novel technology called Rejuvenation, which bypasses the need for reprogramming of T cells into iPSCs. Rejuvenated TIL products retain their TCR diversity while offering several significant advantages, including reduced T-cell epigenetic age, improved expansion capacity, stem cell-like phenotype, and enhanced secretion of cytokines upon activation by target antigens. In this study, we used TIL derived from patients with melanoma and NSCLC. Rejuvenated TIL were generated by the transient expression of transcription factors in a process called ‘Partial Reprogramming’ and returned back to a T-cell lineage phenotype by a process called ‘Redirection’. Partially reprogrammed TIL showed an altered morphology resembling adherent stromal cells and down-regulated conventional T-cell markers including CD3, CD4, and CD8. Redirected T cells reacquired a conventional CD4/CD8 phenotype including morphology, surface markers and function, and demonstrated decreased epigenetic age (>7 years younger, N=3). We also observed a higher proliferative capacity, improved metabolic state, and increased expression of biomarkers associated with T-cell stemness, including CCR7 and CD62L, when compared with untreated TIL. Rejuvenated TIL demonstrated improved cytokine secretion, including IFNγ, TNFα and IL-2 in functional assays. Immune repertoire analysis revealed a significant polyclonal population of putative tumor-reactive TCRs. In vivo functionality was also evaluated using a xenograft model of engineered A375 melanoma cell line that agonizes T-cells in hIL2-NOG mice. Adoptive transfer of rejuvenated TIL resulted in significantly improved suppression of tumor growth and prolonged survival compared with TIL expanded by conventional methods. These results were also confirmed in other surrogate models, including rejuvenated PBMC, TCR and CAR T cells, demonstrating the broad applicability of Rejuvenation technology. Our results indicate TIL Rejuvenation enhances the functionality and antitumor characteristics of T cells, while preserving a broad TCR repertoire. This technology holds substantial promise and may pave the way for the development of the first rejuvenated autologous polyclonal TIL therapy for treatment of advanced solid tumors. Citation Format: Raul Vizcardo, Yin Huang, Jessica Fioravanti, Takuya Maeda, Naritaka Tamaoki, Yasuhiro Yamazaki, Burak Kutlu, Kriti Bahl, Biao Wang, Zheng Zhong, Shobha Potluri, Nicholas P. Restifo, Gary Lee. Rejuvenation of tumor-infiltrating lymphocytes (TIL): A novel strategy to revitalize TIL antitumor function for cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6593.

MHC class III lymphocyte antigens 6 as endogenous immunotoxins: Unlocking immunotherapy in proficient mismatch repair colorectal cancer.

A majority of cancers, including colorectal cancer (CRC) with intact DNA mismatch repair, exhibit a paralyzed antitumor immune response and resistance to immune checkpoint inhibitors. Members of MHC class III lymphocyte antigen 6G (LY6G) encode glycosylphosphatidylinositol (GPI) proteins anchored to the membrane. Snake venom neurotoxins and LY6G proteins share a three-finger (3F) folding domain. LY6 proteins such as LY6G6D are gaining a reputation as excellent tumor-associated antigens that can potently inhibit anti-tumor immunity in cancers with proficient mismatch repair. Thus, we called MHC class III LY6G endogenous immunotoxins. Since the discovery of LY6G6D as a tumor-associated antigen, T-cell engagers (TcEs) have been developed to simultaneously bind LY6G6D on cancer cells and CD3 on T cells, improving the treatment of metastatic solid tumors that are resistant to ICIs. We present a current understanding of how alterations in MHC class III genes inhibit antitumor immunity, and how these understandings can be turned into effective treatments for patients who are refractory to standard immunotherapy. This article is categorized under: Cancer > Genetics/Genomics/Epigenetics Cancer > Molecular and Cellular Physiology.

Discovery of VIP236, an αvβ3-Targeted Small-Molecule-Drug Conjugate with Neutrophil Elastase-Mediated Activation of 7-Ethyl Camptothecin Payload for Treatment of Solid Tumors.

The emerging field of small-molecule-drug conjugates (SMDCs) using small-molecule biomarker-targeted compounds for tumor homing may provide new perspectives for targeted delivery. Here, for the first time, we disclose the structure and the synthesis of VIP236, an SMDC designed for the treatment of metastatic solid tumors by targeting αvβ3 integrins and extracellular cleavage of the 7-ethyl camptothecin payload by neutrophil elastase in the tumor microenvironment. Imaging studies in the Lewis lung mouse model using an elastase cleavable quenched substrate showed pronounced elastase activity in the tumor. Pharmacokinetics studies of VIP236 in tumor-bearing mice demonstrated high stability of the SMDC in plasma and high tumor accumulation of the cleaved payload. Studies in bile-duct-cannulated rats showed that biliary excretion of the unmodified conjugate is the primary route of elimination. Treatment- and time-dependent phosphorylation of H2AX, a marker of DNA damage downstream of topoisomerase 1 inhibition, verified the on-target activity of the payload cleaved from VIP236 in vivo. Treatment with VIP236 resulted in long-lasting tumor regression in subcutaneous patient-derived xenograft (PDX) models from patients with non-small-cell lung, colon, and renal cancer as well as in two orthotopic metastatic triple-negative breast cancer PDX models. In these models, a significant reduction of brain and lung metastases also was observed.

Abstract CT170: Initial safety and feasibility results from a first-in-human clinical trial evaluating a novel magnetic hyperthermia approach for the treatment of metastatic solid tumors

Abstract A novel approach for cancer therapy was developed, comprising of magnetic multicore iron oxide nanoparticles (SaNPs) and alternating magnetic field (AMF) application. SaNPs are administered IV to the patient and accumulate in tumors through the enhanced permeability and retention (EPR) effect. The patient then undergoes regional AMF application (300kHz) that is converted to thermal energy, inducing sub-ablative hyperthermic cancer cell death. Based on extensive pre-clinical testing, treatment was proven safe and biocompatible in animal models without any associated toxicities. Efficacy studies in a murine metastatic cancer model, demonstrated the ability to reduce the number and size of metastatic lesions. Methods: A First-in-Human open label dose escalation study was designed to evaluate the feasibility and safety of treatment in patients (n=18) with advanced metastatic solid tumors. A secondary objective was to evaluate initial efficacy signs. Eligibility criteria included patients with a life expectancy of at least 30 days with measurable disease according to RECIST 1.1. The patients underwent toxicity analysis and MRI scans without contrast media before (baseline), after treatment, and at the end of the follow-up period of 1 month. Vital signs were monitored before, during, and after treatment. Measurements included ECG, oral and body surface temperatures, blood pressure, heart rate, and oxygen saturation. Results: 3 patients were enrolled in the first cohort that received a single SaNP injection of 10% (first dose level) without AMF. No systemic toxicity was observed. 7 patients were then enrolled and SaNP was administered at the same dose followed by AMF irradiation (first dose level of 40%) of the torso area, conducted for two intervals of 5 min. each. SaNP administration procedures were successful in all cases whereas, 3 patients succeeded to complete the full treatment in accordance to the study protocol. During AMF exposure, the patients were covered with a cooling blanket and temperatures were monitored using fiber-optic sensors. There were no significant temperature deviations beside one patient, where a rise in oral temperature was noted due to the presence of dental implants which heated up. In all patients there were no significant differences in any of the vital signs post-injection nor before or after AMF except for one patient, for whom increased heart rate was observed during irradiation, returning to baseline thereafter. No treatment-related abnormal clinical pathology or urinalysis results were identified. Some fluctuations were observed, attributed to the disease stage. Although tumor response was not expected at the first dose levels, MRI and CT results for one patient showed a reduction in a breast tumor and in another patient, stable disease was reported. Conclusion: SaNP administration either alone or followed by AMF application was not associated with any significant adverse reactions, and no clinical or humoral toxicity was observed at initial doses of 10% SaNP and 40% AMF. Citation Format: Sarah Kraus, Cheri Tal, Boaz Shalev, Moshe Eltanani, Pazit Rukenstein, Shir Arbib, Michal Eck, Raz Khandadash, Shaul Atar, Arnoldo Cyjon, Ofer Shalev. Initial safety and feasibility results from a first-in-human clinical trial evaluating a novel magnetic hyperthermia approach for the treatment of metastatic solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT170.

Use of CRISPR-based screens to identify mechanisms of chemotherapy resistance.

Despite the development of new classes of targeted anti-cancer drugs, the curative treatment of metastatic solid tumors remains out of reach owing to the development of resistance to current chemotherapeutics. Although many mechanisms of drug resistance have been described, there is still a general lack of understanding of the many means by which cancer cells elude otherwise effective chemotherapy. The traditional strategy of isolating resistant clones in vitro, defining their mechanism of resistance, and testing to see whether these mechanisms play a role in clinical drug resistance is time-consuming and in many cases falls short of providing clinically relevant information. In this review, we summarize the use of CRISPR technology, including the promise and pitfalls, to generate libraries of cancer cells carrying sgRNAs that define novel mechanisms of resistance. The existing strategies using CRISPR knockout, activation, and inhibition screens, and combinations of these approaches are described. In addition, specialized approaches to identify more than one gene that may be contributing to resistance, as occurs in synthetic lethality, are described. Although these CRISPR-based approaches to cataloguing drug resistance genes in cancer cells are just beginning to be utilized, appropriately used they promise to accelerate understanding of drug resistance in cancer.

1285P Risk of immune-related adverse events associated with adjuvant antiPD-1/PDL-1 in solid tumors

Immune checkpoint inhibitors targeting PD-1/PD-L1 (IO) have deeply transformed the landscape of treatment of metastatic solid tumors and are likely to shape the adjuvant setting. Balance between safety and efficacy should be considered, especially potential serious adverse events. The aim of this systematic review was to determine the risk of developing serious immune related adverse events (irAEs) in patients treated with IO in the adjuvant setting. We performed a systematic review of the evidence available in Pubmed of all randomized phase II-III clinical trials comparing IO versus placebo or observation in the adjuvant setting published up to March 2022. Protocol was registered in PROSPERO. Odds ratio (OR) of adverse events for all grade and high-grade were calculated. Seven studies involving 5425 patients were included (2876 patients in the IO arm and 2549 in the observation/placebo control group). 19% of patients receiving IO reported an irAE compared to 8,7% in the control arm, and 1 out of 7 patients had a high-grade irAE with IO compared to 1 out of 14 patients in the control arm. The OR in the IO group vs placebo/observation was 3,20 (95% CI, 2,41 – 4,26) in all-grade irAEs; 3,49 (95% CI, 1,82 – 6,69) in high-grade (grade 3-4) irAEs; and 4,17 (95% CI, 1,47 – 11,89) in serious AEs. There was not a statistically significant difference between the incidence of deaths due to irAEs, with an OR 3,66 (95% CI, 0,60 – 22,32). Our study showed that the risk of developing irAEs is a more than three times higher risk of developing an immune-related adverse event in the group of adjuvant antiPD-1/PDL-1 compared to observation/placebo, with no differences in the incidence of deaths. This analysis provides a comprehensive overview of ICI-associated AEs in the adjuvant setting, and these findings may help and guide clinicians in management and decision-making of patients with indication of adjuvant treatment.

CAR T-cell Integration of Multiple Input Signals Allows for Precise Targeting of Cancer.

Chimeric antigen receptor (CAR)-mediated adoptive T-cell therapy has achieved unprecedented success in the treatment of relapsed and refractory hematologic malignancies. However, this success may be more difficult to recapitulate in the treatment of metastatic solid tumors, where the lack of costimulatory signals and cytokine support as well as the strongly inhibitory microenvironment pose a substantial challenge to unleashing the antitumor potential of CAR T cells. Furthermore, nearly all described target antigens are expressed on normal tissue. In this issue of Cancer Discovery, Sukumaran and colleagues address these challenges by engineering T cells to recognize a specific expression pattern unique to the tumor site using independent chimeric molecules that cooperatively deliver a fully functional T-cell response selectively in the tumor microenvironment. Cancer Discov; 8(8); 918-20. ©2018 AACRSee related article by Sukumaran et al., p. 972.

Surgical treatment of pulmonary metastases in pediatric solid tumors

Most children who succumb to solid malignancies do so because of the burden of metastatic disease or due to complications associated with the therapy administered to treat metastatic disease. Approximately one-quarter of children with solid tumors will present with metastatic disease, and an additional 20% ultimately develop metastatic disease, most commonly in the lung. The role of surgery in the treatment of metastatic solid tumors, given its disseminated nature, is not intuitive, yet there are circumstances in which surgical resection of metastatic disease can potentially be curative. However, the utility of surgery is very much dependent on histology, and generally is most appropriate for those malignancies with histologies that are refractory to other adjuvant therapies.

NEDD9 Depletion Destabilizes Aurora A Kinase and Heightens the Efficacy of Aurora A Inhibitors: Implications for Treatment of Metastatic Solid Tumors

Aurora A kinase (AURKA) is overexpressed in 96% of human cancers and is considered an independent marker of poor prognosis. While the majority of tumors have elevated levels of AURKA protein, few have AURKA gene amplification, implying that posttranscriptional mechanisms regulating AURKA protein levels are significant. Here, we show that NEDD9, a known activator of AURKA, is directly involved in AURKA stability. Analysis of a comprehensive breast cancer tissue microarray revealed a tight correlation between the expression of both proteins, significantly corresponding with increased prognostic value. A decrease in AURKA, concomitant with increased ubiquitination and proteasome-dependent degradation, occurs due to depletion or knockout of NEDD9. Reexpression of wild-type NEDD9 was sufficient to rescue the observed phenomenon. Binding of NEDD9 to AURKA is critical for AURKA stabilization, as mutation of S296E was sufficient to disrupt binding and led to reduced AURKA protein levels. NEDD9 confers AURKA stability by limiting the binding of the cdh1-substrate recognition subunit of APC/C ubiquitin ligase to AURKA. Depletion of NEDD9 in tumor cells increases sensitivity to AURKA inhibitors. Combination therapy with NEDD9 short hairpin RNAs and AURKA inhibitors impairs tumor growth and distant metastasis in mice harboring xenografts of breast tumors. Collectively, our findings provide rationale for the use of AURKA inhibitors in treatment of metastatic tumors and predict the sensitivity of the patients to AURKA inhibitors based on NEDD9 expression.

In Vitro Generation of Mature T Lymphocytes From Human Ips Cells and Genetic Analysis of TCR Gene Rearrangements

Abstract 2984T lymphocytes play central roles in cellular immunity, exerting their proliferative and effector activities when they recognize antigens via T-cell receptors (TCRs) in HLA-restricted and antigen-specific manner. Adoptive cell transfer therapy (ACT), the administration of ex vivo-activated and -expanded autologous tumor-reactive T lymphocytes, is currently one of the effective methods for immunotherapy, especially for treatment of metastatic solid tumors including melanoma. However, the successful applications of this method are currently limited for tumor therapies. To broaden the range of the application of ACT, we endeavored to develop easier method to obtain cells that carry antigen-specific TCR genes. For the purpose, generation of induced pluripotent stem (iPS) cells from an antigen-reactive single T lymphocyte is attractive and rewarding way. iPS cells have a capacity for unlimited self-renewal while maintaining pluripotency. These features may enable us to induce an unlimited number of T lymphocytes, especially high proliferative naïve / central memory-type T lymphocytes, showing reactivity to specific antigens. If they retain properties of naïve T lymphocytes, they may proliferate for a longer period and achieve better therapeutic effects than their peripheral blood counterparts expanded in vitro.Peripheral T lymphocytes were isolated from healthy volunteers. Then reprogramming factors (OCT4, SOX2, KLF4, and c-MYC) were transduced into fresh or frozen / thawed T lymphocytes. T lymphocyte-derived iPS-like colonies were observed within 3 weeks and they were isolated and clonally expanded. They exhibited standard ES-like morphology, cell surface marker expression, alkaline phosphatase activity, as well as differentiation potential into various tissues related to all three germ layers. Human TCRs are encoded in four genes (TCRA, TCRB, TCRG, TCRD), which should be genetically assembled in an irreversible manner during T-lymphocyte development. This feature allowed us to retrospectively confirm that the iPS cells were generated from T lymphocyte. The TCR gene rearrangements encoded in an iPS colony were clonal for all iPS lines, indicating that each iPS colony was derived from a single T lymphocyte. Sequence analyses of TCR genes revealed whether the rearrangements were productive, and the productivity might promise the conservation of TCR genes rearrangement during the reprogramming process.Next, we tried to re-differentiate T lymphocyte derived-iPS (T-iPS) cells into T cells by co-culturing them with murine stromal cell layers (OP9 and OP9-DL1). T-cell differentiation was evidenced by the expression of T-cell markers, such as CD5, CD7, CD27, CD4, CD8, TCR α β and CD3. We obtained 33.5 ± 17.9% CD4+ CD8+ double positive (DP) cells, 6.51 ± 5.40% CD4+ CD8− single positive (SP) cells and 3.80 ± 1.28% CD4− CD8+ SP cells. They could be activated via TCR stimulation, and produce cytokines as functionally matured T lymphocytes do. The re-differentiation efficiency of T-iPS cells was higher than those of other pluripotent stem cells, such as embryonic stem (ES) cells, fibroblasts derived-iPS cells, or cord blood derived-iPS cells. Transcribed TCR mRNA sequences in re-differentiated T cells were analyzed, and they were revealed to be identical to that engraved in the pre-differentiated T-iPS cells genome in CD4+ CD8+ DP phase. However, fully matured CD4+ CD8− or CD4− CD8+ SP phase cells had several TCRA gene rearrangement patterns distinct from the original T-iPS cell’s. On the other hand, TCRB gene maintained identity with the original. The variance of the sequences, especially antigen-recognition site sequences, indicated that the antigen-specificity in the original T lymphocyte might be converted during DP to SP transition process in vitro.These data indicate that functionally matured T cells were generated by re-differentiating T-iPS cells in vitro, and that re-assemble of TCRA genes could take place during SP T cell maturation process. In order to fulfill the T-iPS-mediated immunotherapy, we need to overcome the obstacle of further TCRA gene rearrangements. We think the solution lies in refinement of the re-differentiation method for controlling the expression of RAG1 and RAG2 recombinases or for inhibiting their activities. Disclosures:No relevant conflicts of interest to declare.

Disruption of the AKT pathway inhibits metastasis in an orthotopic model of head and neck squamous cell carcinoma

MK-2206 is an orally active, allosteric inhibitor of AKT, a component of the phosphatidylinositol-3 kinase (PI3K) pathway. The PI3K-AKT pathway is a downstream signaling pathway that has recently been found to play an important role in head and neck squamous cell carcinoma (HNSCC). The objective of this study is to examine the role AKT inhibition may play in treatment of HNSCC. In vivo and in vitro study. Cell migration after 24-hour treatment with subtherapeutic doses of MK-2206 was assessed using an enzyme-linked immunosorbent assay in four HNSCC cell lines: CAL27, FaDu, SCC-1, and SCC-5. In vitro effect of MK-2206 on cell migration was assessed by making linear scratches in culture plates after cell lines were grown to confluency. Images were taken at 8, 16, and 24 hours. In vivo analysis was performed on nude mice with human SCC1-orthotopic tongue tumors. After tumors were allowed to grow for 7 days, mice were treated with oral dosing of 120 mg/kg of MK-2206 every other day for 2 weeks. Tumor size was assessed after each treatment using a pair of digital calipers. At the end of the treatment period, mice were sacrificed and cervical lymph nodes were assessed for metastasis using fluorescent imaging of tumor cell markers. Subtherapeutic doses of MK-2206 were sufficient to significantly reduce cell migration in FaDu, SCC-1, and SCC-5 cell lines (P < .001) but not in Cal27 (P = .09). In vitro scratch test results in SCC-1 cells yielded significant reduction in cell movement at 8, 16, and 14 hours (P < .001). In vivo orthotopic model yielded significant reduction in primary tumor size (P = .04) and reduction in positive cervical lymph nodes (P = .01) between treatment and control mice. In addition we found 100% survival of MK-2206 treated mice after 2 weeks of treatment compared with 70% survival in our control group (P = .03). Treatment with MK-2206 is sufficient to inhibit HNSCC chemotaxis and migration in vitro. In an orthotopic model, treatment with MK-2206 reduces primary tumor size and cervical metastasis while improving survival. MK-2206 currently is being used in phase II clinical trials for combination treatment of metastatic solid tumors and may be useful for treating HNSCC as well.

Monitoring long-term treatment with pegylated liposomal doxorubicin: how important is intensive cardiac follow-up?

Pegylated liposomal doxorubicin (PLD; Doxil or Caelyx) has been shown to be as effective as conventional doxorubicin, and to have a significantly better cardiac safety profile. The aim of this study was to assess the safety of delivering doses exceeding 700 mg/m of PLD to patients with solid tumors. A review of the medical records of 149 patients with a variety of solid tumors treated with PLD was performed. The findings in 12 patients who had reached or exceeded cumulative doses of 700 mg/m (median=1.071 mg/m, range 712-1856 mg/m) were reviewed. Changes in left ventricular ejection fraction (LVEF), and in clinical cardiac status were analyzed. The median age of the patients was 53.9 years and the median follow-up from the start of PLD treatment was 44.6 months. None of the 12 patients had clinical congestive heart failure secondary to cardiomyopathy. Seven of the 12 patients underwent further assessment of LVEF by echocardiography or multiple gated acquisition scan, which revealed a stable or improved ejection fraction.PLD is cardiac safe for long-term treatment of metastatic solid tumors. Its maximal cumulative dose remains undefined. Frequent determinations of LVEF, as routinely done for other anthracyclines, do not appear to have any clinical value in patient follow-up. In metastatic patients with no evidence of cardiac risk factors, it may be sufficient to measure LVEF at baseline.

Research Highlights

Research Highlights

Targeted therapy for incurable solid cancers: A meta-analysis.

e19617 Background: Despite the growing number of trials incorporating targeted chemotherapy in the treatment of metastatic solid tumors, their overall impact on treatment is unknown. Methods: An electronic bibliographic search of MEDLINE, EMBase, and the Cochrane Central Register of Controlled Trials, was performed to identify recently published English-language RCTs on the treatment of end-stage solid cancers with monoclonal antibodies or small molecules compared to conventional chemotherapy. Two reviewers independently assessed all papers for eligibility. Abstracted data included tumor type, phase of trial, methods for the intervention's incorporation into treatment regimen, progression free survival, and overall survival. Results: Of the 5,846 papers identified on the original search, 65 were included in the final analysis. Targeted chemotherapy has led to an increase in median progression free survival of 0.81 months (95% CI, 0.29-1.29, i∧2=79%), and median survival of 0.87 months (95% CI, 0.29- 1.29, i∧2=53%). However, using standardized mean differences and grouping trials by positive or equivocal effect virtually eliminates heterogeneity, with effect sizes of 0.3 (95% CI, 0.25-0.34, i∧2=33%) and 0.21 (95% CI, 0.16-0.26, i∧2=0%) for progression-free survival and median survival, respectively. Conclusions: Targeted chemotherapy has a significant positive effect on survival in specific cancers. However, determining the prognostic mutations that are required to render equivocal treatments effective will probably lead to similar gains only for smaller numbers of patients. It is unclear whether such a significant investment is worthwhile. No significant financial relationships to disclose.

Partly MHC Matched Allogeneic Tumor Specific T Cells Mediate Tumor Regression without Inducing GVHD in Immunosuppressed Host.

Adoptive cell transfer (ACT) immunotherapy following lymphodepleting conditioning is a promising strategy for the treatment of metastatic solid tumors, however the difficulties in generating autologous tumor specific lymphocytes for every patient has significantly limited its applications. Allogeneic partly matched tumor specific T cells could be used for patients in whom autologous cells are not available, however their rapid rejection by the host restricts this approach. When CD8+ pmel-1 T cells from B6-BALB-C F1 (b/d) were transferred into B16 tumor-bearing B6 mice (b/b) or into a different F1 (b/k), these tumor-specific T cells were rapidly rejected, and had no impact on the tumor regression. Here we show that following myeloablative conditioning, the adoptive transfer of allogeneic, major histocompatibility mismatched tumor-specific T lymphocytes resulted in the regression of large vascularized tumors. The ability of adoptively transferred allogeneic T cells to mediate tumor regression was directly proportional to the dose of irradiation given prior T cell transfer which also correlated with the in vivo survival of the transferred cells. At the highest irradiation dose used (i.e. 11 Gy) allogeneic T cells could survive for as long as 4 weeks and their efficacy was comparable to syngeneic tumor-reactive T cells. In addition we found that the risk of inducing a graft versus host (GVH) reaction was minor when the specificity of transferred TCR is confined. In fact co-transfer of transgenic cells and small amounts of open repertoire T cells (2*10e4) able to react with the host did not result in any measurable toxicity whereas co transfer of greater quantities (2*10e5 or more) could cause fatal GVHD effect. Interestingly GVH reaction was associated with an improved tumor treatment, though this effect was transient as most of the animals succumbed to GVHD. Here we demonstrate that allogeneic T cells might represent an important tool in cancer immunotherapy allowing treatment of patients for whom it is not possible to obtain autologous cells. Furthermore the possible synergy between tumor specific allogeneic T cells and GVH effect could be exploited in bone marrow transplant protocols.

Minor histocompatibility antigens: allo target molecules for tumor-specific immunotherapy.

Minor histocompatibility antigens have to be considered as key molecules in the stem cell-based immunotherapy of malignancies. Allogeneic stem cell transplantation (SCT) is a well-established and effective therapy for advanced hematologic malignancies. The apparent powerful graft-versus-leukemia effect of SCT led clinicians to apply SCT for the treatment of metastatic solid tumors. The SCT-based graft-versus-tumor reaction in the allogeneic human leukocyte antigen-matched SCT setting is mediated by allo-immune effectorcells directed against tumor-related target antigens. The target molecules involved in the allo-immune graft-versus-tumor reaction are tumor-specific antigens, tumor-associated antigens, and tissue- and cell-specific minor histocompatibility antigens. The power of the minor histocompatibility antigens in the human leukocyte antigen-identical, stem cell-based immunotherapy for malignancies is their "allo-ness." As opposed to tumor-associated self antigens, the complexes of MHC and allo-target peptide are likely to be more immunogeneic than the major histocompatibility complex and self-target peptide complexes. Moreover, minor histocompatibility allo-antigens are not subject to self tolerance. Earlier minor histocompatibility antigens were seen as alien entities, disturbing the success of the so ideally matched organ and SCT donor-recipient combinations. To date, minor histocompatibility antigens can be set in the favorable light of useful tools for immunotherapy for cancer. The first clinical application of the hematopoietic minor histocompatibility antigens HA-1 and HA-2 is currently being explored in a stem cell-based setting for hematologic malignancies. Because HA-1 is also expressed on carcinoma cells, a stem cell-based vaccination trial for patients with metastatic breast or renal cancer is about to start as well. The immunotherapeutic potential of minor histocompatibility antigens demands serious searches for new minor histocompatibility antigens and analyses of their phenotype frequency, tissue distribution, and functional membrane expression. The minor histocompatibility antigens meeting the prerequisites for specific immunotherapy for malignancies, such as membrane expression and tissue and/or cell specificity, may offer the curative tools for stem cell-based immunotherapy for various hematologic and nonhematologic malignancies.

Active specific immunotherapy as an adjunct to the treatment of metastatic solid tumors: present and future prospects.

Surgery remains the most effective therapy for the majority of solid tumors, offering the best possibility of cure or palliation in most circumstances. Further improvements in surgical techniques are unlikely to produce vastly improved cure rates because anatomically defined limits have already been reached for the excision of most tumors (1). Adjuvant chemotherapy and radiation therapy play relatively minor roles in the treatment of cancer because tumors develop resistance to the therapy or because dosages are limited by toxicity considerations (2). Thus, new strategies for the treatment of metastatic solid tumors are desperately needed (3).