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Biomedical subjects

Patrick Hwu

Publications and source records attributed to Patrick Hwu.

36 records · Page 2Linked to original sources
PubMed2003

Cancer regression and autoimmunity induced by cytotoxic T lymphocyte-associated antigen 4 blockade in patients with metastatic melanoma.

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a critical immunoregulatory molecule (expressed on activated T cells and a subset of regulatory T cells) capable of down-regulating T cell activation. Blockade of CTLA-4 has been shown in animal models to improve the effectiveness of cancer immunotherapy. We thus treated 14 patients with metastatic melanoma by using serial i.v. administration of a fully human anti-CTLA-4 antibody (MDX-010) in conjunction with s.c. vaccination with two modified HLA-A*0201-restricted peptides from the gp100 melanoma-associated antigen, gp100:209-217(210M) and gp100:280-288(288V). This blockade of CTLA-4 induced grade III/IV autoimmune manifestations in six patients (43%), including dermatitis, enterocolitis, hepatitis, and hypophysitis, and mediated objective cancer regression in three patients (21%; two complete and one partial responses). This study establishes CTLA-4 as an important molecule regulating tolerance to "self" antigens in humans and suggests a role for CTLA-4 blockade in breaking tolerance to human cancer antigens for cancer immunotherapy.

Adult↗
PubMed2003

CD40-stimulated B lymphocytes pulsed with tumor antigens are effective antigen-presenting cells that can generate specific T cells.

Although they are considered as antigen-presenting cells, the role of antigen-unspecific B lymphocytes in antigen presentation and T-lymphocyte stimulation remains controversial. In this paper, we tested the capacity of normal human peripheral activated B cells to stimulate T cells using melanoma antigens or melanoma cell lysates. B lymphocytes activated through CD40 ligation and then pulsed with tumor antigens efficiently processed and presented MHC class II-restricted peptides to specific CD4(+) T-cell clones. This suggests that CD40-activated B cells have the functional and molecular competence to present MHC class II epitopes when pulsed with exogenous antigens, thereby making them a relevant source of antigen-presenting cells to generate T cells. To test this hypothesis, CD40-activated B cells were pulsed with a lysate prepared from melanoma cells and used to stimulate peripheral autologous T cells. Interestingly, T cells specific to melanoma antigens were generated. Additional analysis of these T-cell clones revealed that they recognized MHC class II-restricted epitopes from tyrosinase, a known melanoma tumor antigen. The efficient antigen presentation by antigen-unspecific activated B cells was correlated with a down-regulation in the expression of HLA-DO, a B cell-specific protein known to interfere with HLA-DM function. Because HLA-DM is important in MHC class II peptide loading, the observed decrease in HLA-DO may partially explain the enhanced antigen presentation after B-cell activation. Results globally suggest that when they are properly activated, antigen-unspecific B-lymphocytes can present exogenous antigens by MHC class II molecules and stimulate peripheral antigen-specific T cells. Antigen presentation by activated B cells could be exploited for immunotherapy by allowing the in vitro generation of T cells specific against antigens expressed by tumors or viruses.

Antigen Presentation↗
PubMed2003

Inability to immunize patients with metastatic melanoma using plasmid DNA encoding the gp100 melanoma-melanocyte antigen.

Immunization with plasmid DNA represents a theoretically attractive method for increasing T cell responses against cancer antigens. We administered plasmid DNA encoding the gp100 melanoma-melanocyte differentiation antigen to 22 patients with metastatic melanoma and evaluated immunologic and clinical responses. Patients were randomized to receive plasmid DNA either intradermally (n = 10) or intramuscularly (n = 12). One patient (4.5%) exhibited a partial response of several subcentimeter cutaneous nodules. All other patients had progressive disease. Of 13 patients with cells available before and after immunization, no patient exhibited evidence of the development of anti-gp100 cell responses using in vitro boost assays. The same assays were capable of demonstrating immunologic precursors after immunization with fowl poxvirus encoding gp100 or with gp100 peptides. We were thus unable to demonstrate significant clinical or immunologic responses to plasmid DNA encoding the "self" nonmutated gp100 tumor antigen.

Adult↗
PubMed2002

Dual-specific T cells combine proliferation and antitumor activity.

An effective immune response against cancer requires the activation and expansion of specific T cells. Tumor antigens, however, are generally poor immunogens. To achieve expansion of tumor-reactive T cells in vivo, we used a strategy of generating dual-specific T cells that could respond to a powerful immunogen while also possessing tumor reactivity. We generated dual-specific T cells by genetic modification of alloreactive T cells with a chimeric receptor recognizing folate-binding protein, an ovarian cancer-associated antigen. Mouse dual-specific T cells responded in vitro to both allogeneic antigen and tumor cells expressing folate-binding protein, and expanded in number in vivo in response to immunization with allogeneic cells. Most importantly, the combination of dual-specific T cells and immunization had an antitumor effect in vivo. We also generated human dual-specific T cells and characterized the dual-specific nature of individual clones. Assigning the tasks of expansion and tumor reactivity to different receptors within the same lymphocyte may help to overcome the problem of poor immunogenicity of tumor antigens.

Adenocarcinoma↗
PubMed2002

Redirecting migration of T cells to chemokine secreted from tumors by genetic modification with CXCR2.

T-cell-based immunotherapies provide a promising means of cancer treatment although durable antitumor responses are infrequent. A potential reason for these shortcomings may lie in the observed lack of trafficking of specific T cells to tumor. Our increasing knowledge of the process of trafficking involving adhesion molecules and chemokines affords us the opportunity to intervene and correct deficiencies in this process. Chemokines can be expressed by a range of tumors and may serve as suitable targets for directing specific T cells toward tumor. We initially sought to identify which chemokines were produced by a range of human tumor cell lines, and which chemokines and chemokine receptors were expressed by cultured T cells. We identified two chemokines: Growth-Regulated Oncogene-alpha (Gro-alpha; CXCL1) and Regulated on Activation Normal T Cell-Expressed and Secreted (RANTES; CCL5), to be secreted by several human tumor cell lines. Expression was also detected in fine-needle aspirates of melanoma from patients. In addition, we determined the expression of several chemokine receptors on cultured human T cells including CCR1, CCR2, CCR4, CCR5, CXCR3, and CXCR4. Cultured, activated human T cells expressed the chemokines lymphotactin (XCL1), RANTES, macrophage inflammatory protein-1 alpha (MIP-1 alpha; CCL3) and MIP-1 beta (CCL4), but no appreciable Gro-alpha. In a strategy to direct T cells toward chemokines expressed by tumors we chose Gro-alpha as the target chemokine because it was produced by tumor and not by T cells themselves. However, T cells did not express the receptor for Gro-alpha, CXCR2, and therefore, T cells were transduced with a retroviral vector encoding CXCR2. Calcium ion mobilization, an important first step in chemokine receptor signaling, was subsequently demonstrated in transduced T cells in response to Gro-alpha. In addition, Gro-alpha was chemotactic for T cells expressing CXCR2 in vitro toward both recombinant protein and tumor-derived chemokine. Interestingly we demonstrate, for the first time, that Gro-alpha was able to induce interferon-gamma (IFN-gamma) secretion from transduced T cells, thereby extending our knowledge of other potential functions of CXCR2. This study demonstrates the feasibility of redirecting the migration properties of T cells toward chemokines secreted by tumors.

Calcium↗
PubMed2002

Cancer regression and autoimmunity in patients after clonal repopulation with antitumor lymphocytes.

We report here the adoptive transfer, to patients with metastatic melanoma, of highly selected tumor-reactive T cells directed against overexpressed self-derived differentiation antigens after a nonmyeloablative conditioning regimen. This approach resulted in the persistent clonal repopulation of T cells in those cancer patients, with the transferred cells proliferating in vivo, displaying functional activity, and trafficking to tumor sites. This led to regression of the patients' metastatic melanoma as well as to the onset of autoimmune melanocyte destruction. This approach presents new possibilities for the treatment of patients with cancer as well as patients with human immunodeficiency virus-related acquired immunodeficiency syndrome and other infectious diseases.

Adolescent↗
PubMed2002

Expression of a "self-"antigen by human tumor cells enhances tumor antigen-specific CD4(+) T-cell function.

CD4(+) T cells can recognize "self" tumor antigens, but the impact of tumor cell expression of self-antigens on CD4(+) T-cell function in humans is unknown. Here, we identify a new epitope (ISPNSVFSQWRVVCDSLEDYD) derived from tyrosinase-related protein-1 (TRP-1) using a predictive algorithm and mice transgenic for a chimeric HLA-DRB1*0401 molecule. We then compared the functions of TRP-1-epitope-specific, CD4(+) T-cell responses in normal healthy individuals to those found in patients with metastatic malignant melanoma. Surprisingly, we found that tumor-bearing patients had significantly higher levels of TRP-1-specific, CD4(+) T-cell function than healthy volunteers as measured ex vivo. Thus, the net effect of "self" antigen expression by tumor cells was the enhancement of tumor antigen-specific CD4(+) T-cell function, rather than immunosuppression. These findings indicate that antigens expressed by malignant melanoma cells can partially activate CD4(+) T lymphocytes.

Amino Acid Sequence↗
PubMed2002

CD40 ligand and lipopolysaccharide enhance the in vitro generation of melanoma-reactive T-cells.

Cancer vaccine trials require sensitive assays for evaluating T-cell responses in immunized patients. In addition, these methods are used for identifying novel tumor-associated antigens (TAA). Therefore, our aim was to improve the methods for evaluating patients receiving the cancer vaccines by enhancing the in vitro detection of tumor-specific T cells from the peripheral blood. We have developed an efficient and reproducible method for detecting tumor-specific T cells by optimizing the activation of antigen presenting cells (APC) in peripheral blood mononuclear cells (PBMC) of metastatic melanoma patients with soluble trimeric CD40-ligand (CD40L) or lipopolysaccharide (LPS). This method significantly improved the generation of Melan-A/MART-1:27-35 and Melan-A/MART-1:26-35(27L) peptide/tumor-specific cells as well as lower frequency tyrosinase:368-376(370D) specific T cells from the PBMC of melanoma patients. T-cell enhancement from activated PBMC cultures was found to be reproducible within individual patients and was observed after the addition of either CD40L or LPS to PBMC cultures. Additionally, PBMC activation improved the detection of tumor-specific precursors from melanoma patients previously immunized with peptides derived from Melan-A/MART-1, tyrosinase and gp100. Collectively, these findings describe a novel approach for evaluating patients receiving the cancer vaccines and may provide a useful method for the characterization of novel tumor-associated antigens.

Antigen Presentation↗
PubMed2002

Phase I study of the intravenous administration of attenuated Salmonella typhimurium to patients with metastatic melanoma.

PURPOSE: A strain of Salmonella typhimurium (VNP20009), attenuated by chromosomal deletion of the purI and msbB genes, was found to target to tumor and inhibit tumor growth in mice. These findings led to the present phase I study of the intravenous infusion of VNP20009 to patients with metastatic cancer. PATIENTS AND METHODS: In cohorts consisting of three to six patients, 24 patients with metastatic melanoma and one patient with metastatic renal cell carcinoma received 30-minute intravenous bolus infusions containing 10(6) to 10(9) cfu/m(2) of VNP20009. Patients were evaluated for dose-related toxicities, selective replication within tumors, and antitumor effects. RESULTS: The maximum-tolerated dose was 3 x 10(8) cfu/m(2). Dose-limiting toxicity was observed in patients receiving 1 x 10(9) cfu/m(2), which included thrombocytopenia, anemia, persistent bacteremia, hyperbilirubinemia, diarrhea, vomiting, nausea, elevated alkaline phosphatase, and hypophosphatemia. VNP20009 induced a dose-related increase in the circulation of proinflammatory cytokines, such as interleukin (IL)-1beta, tumor necrosis factor alpha, IL-6, and IL-12. Focal tumor colonization was observed in two patients receiving 1 x 10(9) cfu/m(2) and in one patient receiving 3 x 10(8) cfu/m(2). None of the patients experienced objective tumor regression, including those patients with colonized tumors. CONCLUSION: The VNP20009 strain of Salmonella typhimurium can be safely administered to patients, and at the highest tolerated dose, some tumor colonization was observed. No antitumor effects were seen, and additional studies are required to reduce dose-related toxicity and improve tumor localization.

Adult↗
PubMed2002

MHC class I and class II presentation of tumor antigen in retrovirally and adenovirally transduced dendritic cells.

The unique antigen-presenting capabilities of dendritic cells (DCs) make them an attractive means with which to initiate an antitumor immune response. Using DCs transduced with tumor antigens for immunotherapy has several theoretical advantages over peptide-pulsed DCs including the possibility that transduced DCs are capable of presenting epitopes on both class I and class II MHC molecules. To test this theory, we inserted the human tumor antigen gp100 into mouse DCs transgenic for HLA-DRbeta1*0401 using either adenoviral vector or a VSV-G pseudotyped retroviral vector. DCs transduced with tumor antigen were able to be recognized by both a murine CD8(+) T-cell clone and a murine CD4(+) T-cell line in a cytokine release assay, thereby demonstrating presentation of both MHC class I and class II gp100 epitopes. This study describes the simultaneous presentation of a tumor-associated antigen to both CD4(+) and CD8(+) T cells and lends support to the use of gene-modified DCs as a means to initiate both CD4(+) and CD8(+) antitumor responses.

Animals↗
PubMed2002

Induction of CD4(+) T cell-dependent antitumor immunity by TAT-mediated tumor antigen delivery into dendritic cells.

Dendritic cell-based (DC-based) immunotherapy represents a promising approach to the prevention and treatment of many diseases, including cancer, but current strategies have met with only limited success in clinical and preclinical studies. Previous studies have demonstrated that a TAT peptide derived from the HIV TAT protein has the ability to transduce peptides or proteins into various cells. Here, we describe the use of TAT-mediated delivery of T cell peptides into DCs to prolong antigen presentation and enhance T cell responses. While immunization of mice with DCs pulsed with an antigenic peptide derived from the human TRP2 protein generated partial protective immunity against B16 tumor, immunization with DCs loaded with a TAT-TRP2 peptide resulted in complete protective immunity, as well as significant inhibition of lung metastases in a 3-day tumor model. Although both DC/TRP2 and DC/TAT-TRP2 immunization increased the number of TRP2-specific CD8(+) T cells detected by K(b)/TRP2 tetramers, T cell activity elicited by DC/TAT-TRP2 was three- to tenfold higher than that induced by DC/TRP2. Furthermore, both CD4(+) and CD8(+) T cells were required for antitumor immunity demonstrated by experiments with antibody depletion of subsets of T cells, as well as with various knockout mice. These results suggest that a TAT-mediated antigen delivery system may have important clinical applications for cancer therapy.

Animals↗
PubMedDate not supplied

The immunotherapy of patients with ovarian cancer.

Ovarian cancer is a leading cause of cancer mortality. Chemotherapy is effective in reducing tumor burden in a majority of patients, however, only approximately 20% of advanced disease patients will ultimately survive tumor free, and further treatment options are needed. Continuing advances in immunology make immunotherapy a promising area for future research. The design of immunotherapy strategies for ovarian cancer requires an understanding of the immune microenvironment of the peritoneal cavity, which is frequently involved with ovarian cancer metastases and is the site of its most devastating effects. Immunotherapy approaches for ovarian cancer include locoregional and systemic cytokine therapies, prophylactic and therapeutic vaccines, and adoptive immunotherapy strategies. This review will summarize previous clinical trials as well as future directions for research. Further progress in T-cell specific immune responses will require the identification of specific ovarian cancer antigens that are processed and presented on the surface of tumor cells in the context of specific HLA molecules. In addition, a more detailed understanding of functional relations between the peritoneal microenvironment and the metastatic process is required.

Female↗
PubMedDate not supplied

Immunization of patients with metastatic melanoma using both class I- and class II-restricted peptides from melanoma-associated antigens.

Cancer vaccines targeting CD8+ T cells have been successful in eliciting immunologic responses but disappointing in inducing clinical responses. Strong evidence supports the importance of CD4+ T cells in "helping" cytotoxic CD8+ cells in antitumor immunity. We report here on two consecutive clinical trials evaluating the impact of immunization with both human leukocyte antigen class I- and class II-restricted peptides from the gp100 melanoma antigen. In Protocol 1, 22 patients with metastatic melanoma were immunized with two modified class I A*0201-restricted peptides, gp100:209-217(210M) and MART-1:26-35(27L). In Protocol 2, 19 patients received the same class I-restricted peptides in combination with a class II DRB1*0401-restricted peptide, gp100:44-59. As assessed by in vitro sensitization assays using peripheral blood mononuclear cells (PBMC) against the native gp100:209-217 peptide, 95% of patients in Protocol 1 were successfully immunized after two vaccinations in contrast to 50% of patients in Protocol 2 (P(2) < 0.005). Furthermore, the degree of sensitization was significantly lower in patients in Protocol 2 (P = 0.01). Clinically, one patient in Protocol 2 had an objective response, and none did in Protocol 1. Thus, the addition of the class II-restricted peptide gp100:44-59 did not improve clinical response but might have diminished the immunologic response of circulating PBMC to the class I-restricted peptide gp100:209-217. The reasons for this decreased immune reactivity are unclear but may involve increased CD4+CD25+ regulatory T-cell activity, increased apoptosis of activated CD8+ T cells, or the trafficking of sensitized CD8+ reactive cells out of the peripheral blood. Moreover, the sequential, nonrandomized nature of patient enrollment for the two trials may account for the differences in immunologic response.

Adult↗
PubMedDate not supplied

Cell transfer therapy for cancer: lessons from sequential treatments of a patient with metastatic melanoma.

The development of effective autologous cell transfer therapies for the treatment of patients with cancer has been difficult, in part because the cells used to treat each patient are different, as are the patient's tumor and immune status. Much can thus be learned by sequential treatments of the same patient with the same cells, making single modifications in the treatments to determine which factors are critical. The authors have treated a single patient with five sequential administrations of the same cells with minor modifications in the mode of administration and the immune status of the patient. The treatment of this patient strongly suggested that 1) the highly avid recognition of tumor antigens in vitro by a transferred lymphocyte population does not necessarily predict in vivo antitumor activity; 2) the administration of highly avid antitumor autologous lymphocyte populations can be far more active in mediating tumor regression in vivo when administered after nonmyeloablative chemotherapy than when administered without this prior chemotherapy; 3) intra-arterial administration of highly avid antitumor autologous lymphocytes into the blood supply of the tumor can be more effective in mediating tumor regression than the intravenous administration of these same tumor infiltrating lymphocytes; 4) one mechanism of tumor escape from immunotherapy is loss of class I MHC antigen expression by the tumor due to mutation of the beta-2 microglobulin gene.

Adult↗
PubMedDate not supplied

Presentation of tumor antigens by dendritic cells genetically modified with viral and nonviral vectors.

Genetic modification of dendritic cells (DCs) with recombinant vectors encoding tumor antigens may aid in developing new immunotherapeutic treatments for patients with cancer. Here, we characterized antigen presentation by human DCs genetically modified with plasmid cDNAs, RNAs, adenoviruses, or retroviruses, encoding the melanoma antigen gp100 or the tumor-testis antigen NY-ESO-1. Monocyte-derived DCs were electroporated with cDNAs or RNAs, or transduced with adenoviruses. CD34+ hematopoietic stem cell-derived DCs were used for retroviral transduction. Genetically modified DCs were coincubated with CD8+ and CD4+ T cells that recognized major histocompatibility complex class I- and class II-restricted epitopes from gp100 and NY-ESO-1, and specific recognition was evaluated by interferongamma secretion. Cytokine release by both CD8+ and CD4+ T cells was consistently higher in response to DCs modified with adenoviruses than cDNAs or RNAs, and maturation of DCs after genetic modification did not consistently alter patterns of recognition. Also, retrovirally transduced DCs encoding gp100 were well recognized by both CD8+ and CD4+ T cells. These data suggest that DCs transduced with viral vectors may be more efficient than DCs transfected with cDNAs or RNAs for the induction of tumor reactive CD8+ and CD4+ T cells in vitro and in human vaccination trials.

Adenoviridae↗
PubMedDate not supplied

A phase I study of nonmyeloablative chemotherapy and adoptive transfer of autologous tumor antigen-specific T lymphocytes in patients with metastatic melanoma.

This report describes a phase I clinical trial using nonmyeloablative, lympho-depleting chemotherapy in combination with adoptive immunotherapy in patients with metastatic melanoma. The chemotherapy-conditioning schedule that induced transient lymphopenia consisted of cyclophosphamide (30 or 60 mg/kg per day for 2 days) followed by fludarabine (25 mg/m(2) per day for 5 days). Immunotherapy for all patients consisted of in vitro expanded, tumor-reactive, autologous T-cell clones selected for high avidity recognition of melanoma antigens. Cohorts of three to six patients each received either no interleukin (IL)-2, low-dose IL-2 (72,000 IU/kg intravenously three times a day to a maximum of 15 doses), or high-dose IL-2 (720,000 IU/kg intravenously three times a day for a maximum of 12 doses). The toxicities associated with this treatment were transient and included neutropenia and thrombocytopenia that resolved in all patients. High dose intravenous IL-2 was better tolerated by patients after chemotherapy than during previous immunotherapy cycles without chemotherapy. No patient exhibited an objective clinical response to treatment, although five patients demonstrated mixed responses or transient shrinkage of metastatic deposits. This study established a nonmyeloablative-conditioning regimen that could be safely administered in conjunction with adoptive T-cell transfer and IL-2 in patients with metastatic melanoma.

Adolescent↗
PubMedDate not supplied

Mobilization of dendritic cell precursors in patients with cancer by flt3 ligand allows the generation of higher yields of cultured dendritic cells.

Flt3 ligand (Flt3L) stimulates the proliferation and differentiation of hematopoietic cells. Subcutaneous Flt3L administration has been shown to effectively manage some murine cancers and in humans, to lead to an increase in peripheral blood monocyte and dendritic cell (DC) counts. In the current study, we determined the effects of Flt3L therapy on patients with melanoma and renal cancer, and in particular, if Flt3L could be used either by enhancing the immunization of patients with melanoma to tumor antigen peptides in vivo, or by mobilizing DC precursors to allow the production of larger numbers of cultured DC. Flt3 ligand administration resulted in a 19-fold increase in DC counts in the peripheral blood of patients. The DC generated in vivo appeared only partially activated, expressing increased levels of CD86, CD33, and major histocompatibility complex class II, but no or low levels of CD80 and CD83. This partial activation may account for the lack of enhanced immune responses to melanoma antigens and absence of clinical responses in the patients even in combination with antigen immunization. Flt3 ligand administration did result, however, in a 7-fold increased yield of monocytes per liter of blood from leukapheresed patients. Dendritic cells were as readily generated from monocytes collected before and after Flt3L therapy, and they stimulated allogeneic T-cell proliferation in a mixed leukocyte reaction to a similar magnitude. Thus, the use of Flt3L may be an important method to mobilize DC precursors to allow patient therapy with larger numbers of cultured DC.

Cells, Cultured↗