Biomedical subjects

Alan N Houghton

Publications and source records attributed to Alan N Houghton.

At least 19 recordsLinked to original sources

PubMed2006

Phase II study of temozolomide and thalidomide in patients with metastatic melanoma in the brain: high rate of thromboembolic events (CALGB 500102).

BACKGROUND: Preliminary studies suggesting that extended-dose temozolomide with thalidomide is safe and active in patients with metastatic melanoma have led to frequent use of this oral regimen. To confirm these observations the combination was tested in a multicenter Phase II trial in patients with melanoma brain metastases. METHODS: Eligible patients had melanoma brain metastases, with or without systemic metastases. The primary endpoint was response rate in brain metastases. Patients received temozolomide at a dose of 75 mg/m2/day for 6 weeks with a 2-week rest between cycles, and thalidomide (escalated to 400 mg/day for patients age < 70 years or to 200 mg/day for patients age > or = 70 years). A 2-stage design required > or = 3 responses in the first 21 patients before enrolling 29 additional patients in the second stage. RESULTS: Sixteen eligible patients were enrolled. No objective responses were observed. The median survival was 23.9 weeks. Seven patients withdrew because of tumor progression; 7 were removed during Cycle 1 because of adverse events, including allergic reaction (1 patient), severe fatigue (1 patient), sudden death (1 patient), and thromboembolic events (pulmonary embolism in 3 patients and deep vein thrombosis in 1 patient); 2 patients withdrew when the study was suspended and subsequently closed. No associations could be established between baseline characteristics and toxicity. CONCLUSIONS: The proportion of patients with lethal or potentially life-threatening adverse events was high (0.31, 95% confidence interval, 0.11-0.59), and the absence of objective responses made it unlikely that further accrual would demonstrate the efficacy of the regimen. These observations provide little support for the use of this combination for melanoma brain metastases unless safe and effective methods to prevent thrombosis are developed.

Adult↗

PubMed2006

Adjuvanticity of plasmid DNA encoding cytokines fused to immunoglobulin Fc domains.

PURPOSE: Plasmid DNAs encoding cytokines enhance immune responses to vaccination in models of infectious diseases and cancer. We compared DNA adjuvants for their ability to enhance immunity against a poorly immunogenic self-antigen expressed by cancer. EXPERIMENTAL DESIGN: DNAs encoding cytokines that affect T cells [interleukin (IL)-2, IL-12, IL-15, IL-18, IL-21, and the chemokine CCL21] and antigen-presenting cells [granulocyte macrophage colony-stimulating factor (GM-CSF)] were compared in mouse models as adjuvants to enhance CD8+ T-cell responses and tumor immunity. A DNA vaccine against a self-antigen, gp100, expressed by melanoma was used in combination with DNA encoding cytokines and cytokines fused to the Fc domain of mouse IgG1 (Ig). RESULTS: We found that (a) cytokine DNAs generally increased CD8+ T-cell responses against gp100; (b) ligation to Fc domains further enhanced T-cell responses; (c) adjuvant effects were sensitive to timing of DNA injection; (d) the most efficacious individual adjuvants for improving tumor-free survival were IL-12/Ig, IL-15/Ig, IL-21/Ig, GM-CSF/Ig, and CCL21; and (e) combinations of IL-2/Ig+IL-12/Ig, IL-2/Ig+IL-15/Ig, IL-12/Ig+IL-15/Ig, and IL-12/Ig+IL-21/Ig were most active; and (f) increased adjuvanticity of cytokine/Ig fusion DNAs was not related to higher tissue levels or greater stability. CONCLUSIONS: These observations support the potential of cytokine DNA adjuvants for immunization against self-antigens expressed by cancer, the importance of timing, and the enhancement of immune responses by Fc domains through mechanisms unrelated to increased half-life.

Acute-Phase Reaction↗

PubMed2006

DNA immunization against tissue-restricted antigens enhances tumor immunity after allogeneic hemopoietic stem cell transplantation.

Malignant relapse remains a major problem for recipients of allogeneic hemopoietic stem cell transplantation (HSCT). We hypothesized that immunization of allogeneic HSCT recipients against tissue-restricted Ags using DNA vaccines would decrease the risk of relapse without enhancing graft-vs-host disease (GVHD). Using the mouse B16 melanoma model, we found that post-HSCT DNA immunization against a single tumor Ag induces tumor rejection that is significantly greater than HSCT alone in a T cell-depleted MHC-matched minor Ag-mismatched allogeneic HSCT model (LP --> B6). In treatment models, post-HSCT DNA immunization provides significantly greater overall survival than the vaccine alone. Donor leukocyte infusion further enhances tumor-free survival, including in treatment models. There was no GVHD in HSCT recipients treated with DNA vaccination and donor leukocyte infusion. Further analysis demonstrated that these effects are dependent on CD8+ T cells of donor origin that recognize multiple epitopes. These results demonstrate that DNA immunization against tissue-restricted Ags after allogeneic T cell-depleted HSCT can induce potent antitumor effects without causing GVHD.

Animals↗

PubMed2006

Phase II study of temozolomide plus pegylated interferon-alpha-2b for metastatic melanoma.

BACKGROUND: Temozolomide and interferon-alpha-2b (IFN-alpha-2b) are both active in melanoma. Therefore, the efficacy and safety of temozolomide in combination with pegylated IFN-alpha-2b in patients with metastatic melanoma without brain metastases was investigated. METHODS: Patients with histologically confirmed, unresectable, American Joint Committee on Cancer Stage IV melanoma were enrolled in an open-label, Phase II study. The primary endpoints were tumor response and safety. Patients received temozolomide (75 mg/m2/dayx6 weeks with a 2-week break between cycles) plus concomitant subcutaneous pegylated IFN-alpha-2b (0.5 microg/kg/wk, continuously). Treatment was continued until unacceptable toxicity or disease progression occurred. RESULTS: Thirty-five patients (median age, 55 years) with Stage IV melanoma and a median of 3 metastatic sites were enrolled and received a median of 1 cycle (i.e., 8 weeks) of therapy (range, 0-6 cycles). Eleven patients (31%) (95% confidence interval, 16% to 47%) had an objective tumor response, including 3 with clinical complete response durations of 6 months, 20 months, and 32+ months and 8 with partial responses. Three patients with a partial or mixed response were subsequently rendered free of clinically detectable disease with surgery. The median survival was 12 months with a median follow-up among survivors of 16 months. No patient developed brain metastases while receiving study treatment. Treatment was generally well tolerated. Hematologic toxicity consisted mainly of lymphopenia and leukopenia (National Cancer Institute Common Toxicity Criteria Grades 1-3); no Grade 4 hematologic toxicity was observed. CONCLUSIONS: The combination of temozolomide plus pegylated IFN-alpha-2b had antitumor activity and was well tolerated in patients with metastatic melanoma. Therefore, further study is warranted.

Adult↗

PubMed2006

Glucocorticoid-induced TNF receptor family related gene activation overcomes tolerance/ignorance to melanoma differentiation antigens and enhances antitumor immunity.

Glucocorticoid-induced TNF receptor family related protein (GITR) is present on many different cell types. Previous studies have shown that in vivo administration of an anti-GITR agonist mAb (DTA-1) inhibits regulatory T cells (Treg)-dependent suppression and enhances T cell responses. In this study, we show that administration of DTA-1 induces >85% tumor rejection in mice challenged with B16 melanoma. Rejection requires CD4+, CD8+, and NK1.1+ cells and is dependent on IFN-gamma and Fas ligand and independent of perforin. Depletion of Treg via anti-CD25 treatment does not induce B16 rejection, whereas 100% of the mice depleted of CD25+ cells and treated with DTA-1 reject tumors, indicating a predominant role of GITR on effector T cell costimulation rather than on Treg modulation. T cells isolated from DTA-1-treated mice challenged with B16 are specific against B16 and several melanoma differentiation Ags. These mice develop memory against B16, and a small proportion of them develop mild hypopigmentation. Consistent with previous studies showing that GITR stimulation increases Treg proliferation in vitro, we found in our model that GITR stimulation expanded the absolute number of FoxP3+ cells in vivo. Thus, we conclude that overall, GITR stimulation overcomes self-tolerance/ignorance and enhances T cell-mediated antitumor activity with minimal autoimmunity.

Adjuvants, Immunologic↗

PubMed2006

Agonist anti-GITR antibody enhances vaccine-induced CD8(+) T-cell responses and tumor immunity.

Immunization of mice with plasmids encoding xenogeneic orthologues of tumor differentiation antigens can break immune ignorance and tolerance to self and induce protective tumor immunity. We sought to improve on this strategy by combining xenogeneic DNA vaccination with an agonist anti-glucocorticoid-induced tumor necrosis factor receptor family-related gene (GITR) monoclonal antibody (mAb), DTA-1, which has been shown previously both to costimulate activated effector CD4(+) and CD8(+) T cells and to inhibit the suppressive activity of CD4(+)CD25(+) regulatory T cells. We found that ligation of GITR with DTA-1 just before the second, but not the first, of 3 weekly DNA immunizations enhanced primary CD8(+) T-cell responses against the melanoma differentiation antigens gp100 and tyrosinase-related protein 2/dopachrome tautomerase and increased protection from a lethal challenge with B16 melanoma. This improved tumor immunity was associated with a modest increase in focal autoimmunity, manifested as autoimmune hypopigmentation. DTA-1 administration on this schedule also led to prolonged persistence of the antigen-specific CD8(+) T cells as well as to an enhanced recall CD8(+) T-cell response to a booster vaccination given 4 weeks after the primary immunization series. Giving the anti-GITR mAb both during primary immunization and at the time of booster vaccination increased the recall response even further. Finally, this effect on vaccine-induced CD8(+) T-cell responses was partially independent of CD4(+) T cells (both helper and regulatory), consistent with a direct costimulatory effect on the effector CD8(+) cells themselves.

Animals↗

PubMed2006

Vaccination with human tyrosinase DNA induces antibody responses in dogs with advanced melanoma.

Antitumor immune responses can be elicited in preclinical mouse melanoma models using plasmid DNA vaccines encoding xenogeneic melanosomal differentiation antigens. We previously reported on a phase I clinical trial of human tyrosinase (huTyr) DNA vaccination of 9 dogs with advanced malignant melanoma (World Health Organization stages II-IV), in which we demonstrated the safety of the treatment and the prolongation of the expected survival time (ST) of subjects as compared to historical, stage-matched controls. As a secondary goal of the same study, we report here on the induction of tyrosinase-specific antibody responses in three of the nine dogs vaccinated with huTyr DNA. The antibodies in two of the three responders cross-react with syngeneic canine tyrosinase, demonstrating the ability of this vaccine to overcome host immune tolerance and/or ignorance to or of "self" antigens. Most interestingly, the onset of antibody induction in these three dogs coincides with observed clinical responses and may suggest a means to account for their long-term tumor control and survival.

Amino Acid Sequence↗

PubMed2006

Optimization of a self antigen for presentation of multiple epitopes in cancer immunity.

T cells recognizing self antigens expressed by cancer cells are prevalent in the immune repertoire. However, activation of these autoreactive T cells is limited by weak signals that are incapable of fully priming naive T cells, creating a state of tolerance or ignorance. Even if T cell activation occurs, immunity can be further restricted by a dominant response directed at only a single epitope. Enhanced antigen presentation of multiple epitopes was investigated as a strategy to overcome these barriers. Specific point mutations that create altered peptide ligands were introduced into the gene encoding a nonimmunogenic tissue self antigen expressed by melanoma, tyrosinase-related protein-1 (Tyrp1). Deficient asparagine-linked glycosylation, which was caused by additional mutations, produced altered protein trafficking and fate that increased antigen processing. Immunization of mice with mutated Tyrp1 DNA elicited cross-reactive CD8(+) T cell responses against multiple nonmutated epitopes of syngeneic Tyrp1 and against melanoma cells. These multi-specific anti-Tyrp1 CD8(+) T cell responses led to rejection of poorly immunogenic melanoma and prolonged survival when immunization was started after tumor challenge. These studies demonstrate how rationally designed DNA vaccines directed against self antigens for enhanced antigen processing and presentation reveal novel self epitopes and elicit multi-specific T cell responses to nonimmunogenic, nonmutated self antigens, enhancing immunity against cancer self antigens.

Animals↗

PubMed2006

Langerhans-type dendritic cells genetically modified to express full-length antigen optimally stimulate CTLs in a CD4-dependent manner.

Oncoretroviral vectors encoding either full-length Ag or a corresponding immunodominant peptide were expressed in Langerhans-type dendritic cells (LCs) differentiated from CD34(+) progenitors. We used human CMV as a model Ag restricted by HLA-A*0201 to define parameters for eventual expression of cancer Ags by LCs for active immunization against tumors. Stimulation by CMVpp65(495-503)-pulsed LCs, CMVpp65(495-503)-transduced LCs, and full-length CMVpp65-transduced LCs respectively increased tetramer-reactive T cells with an effector memory phenotype by 10 +/- 11, 34 +/- 21, and 51 +/- 24-fold (p < 0.05) from CMV-seropositive donors. CMV-specific CD8(+) CTLs achieved respective frequencies of 231 +/- 102, 583 +/- 219, and 714 +/- 281 spot-forming cells per 10(5) input cells (p < 0.01) in ELISPOT assays for IFN-gamma secretion. LCs expressing full-length Ag stimulated greater lytic activity than either peptide-transduced or peptide-pulsed LCs (p < 0.05), all in the absence of exogenous cytokines. pp65-transduced LCs presenting class I and II MHC-restricted epitopes expanded IFN-gamma-secreting CD4(+) T cells, whereas pp65(495-503)-transduced LCs did not. CD4(+) T cell numbers even declined after stimulation by pp65(495-503) peptide-pulsed LCs. CD4(+) T cell depletion confirmed their contribution to the more robust CTL responses. LCs, transduced with a retroviral vector encoding full-length Ag, stimulate potent CTLs directed against multiple epitopes in a CD4(+) Th cell-dependent manner.

Antigens, CD34↗

PubMed2006

Autoimmunity and tumor immunity induced by immune responses to mutations in self.

Little is known about the consequences of immune recognition of mutated gene products, despite their potential relevance to autoimmunity and tumor immunity. To identify mutations that induce immunity, here we have developed a systematic approach in which combinatorial DNA libraries encoding large numbers of random mutations in two syngeneic tyrosinase-related proteins are used to immunize black mice. We show that the libraries of mutated DNA induce autoimmune hypopigmentation and tumor immunity through cross-recognition of nonmutated gene products. Truncations are present in all immunogenic clones and are sufficient to elicit immunity to self, triggering recognition of normally silent epitopes. Immunity is further enhanced by specific amino acid substitutions that promote T helper cell responses. Thus, presentation of a vast repertoire of antigen variants to the immune system can enhance the generation of adaptive immune responses to self.

Amino Acid Sequence↗

PubMed2006

Estimates of stage-specific survival are altered by changes in the 2002 American Joint Committee on Cancer staging system for melanoma.

BACKGROUND: The objectives of the current study were to examine how the estimated stage-specific survival is altered in the 2002 American Joint Committee on Cancer (AJCC) melanoma staging system compared with the 1997 AJCC staging system and to contrast the predictive accuracy of the 2 staging systems. METHODS: There were 5847 consecutive melanoma patients who presented to Memorial Sloan-Kettering Cancer Center from 1996 to 2004 and who were entered prospectively into a data base. These patients were staged according to both the 1997 and 2002 AJCC staging criteria. Overall survival estimates were determined using the Kaplan-Meier method. The overall predictive accuracy of the two staging systems was compared using concordance estimation. RESULTS: In total, 1035 patients were shifted to a lower stage in the 2002 staging system, whereas only 15 patients were upstaged. The number of patients with Stage I melanoma increased by 697 under the 2002 system (n = 2166 patients) compared with the 1997 system (n = 1463 patients). Because of the changes in 2002, the estimated 5-year overall survival for patients with Stage II melanoma decreased considerably, from 79% (1997) to 64% (2002). With the initiation of subgroups in 2002, it became apparent that patients with Stage III melanoma were very heterogeneous in terms of their survival probabilities (5-yr overall survival ranged from 70% in patients with Stage IIIA disease to 24% in patients with Stage IIIC disease). Furthermore, in the 2002 system, there was substantial prognostic overlap between Stage II and Stage III. Despite the increased complexity of the 2002 system, the 2 staging systems had similar concordance estimates: 58% for the 1997 staging system compared with 58% (ignoring the subgroups) and 59% (with subgroups) for the 2002 system. CONCLUSIONS: Estimates of stage-specific survival were altered substantially by the changes made in the 2002 AJCC staging system for melanoma, particularly for Stage II. Stage subgroups that were added in the 2002 system resulted in a large diversity of risk within Stage III. This must be taken into account to stratify patients properly for clinical trials. The increased complexity of the 2002 system did not improve its predictive ability over the simpler 1997 system, highlighting the importance of developing individualized risk-prediction models.

Databases, Factual↗

PubMed2006

Unraveling the complex relationship between cancer immunity and autoimmunity: lessons from melanoma and vitiligo.

A relationship between melanoma and vitiligo, a skin disorder characterized by the loss of melanocytes, has been postulated for many decades. In some cases, vitiligo is almost certainly a manifestation of autoimmune-mediated destruction of melanocytes. Melanocytes and melanoma cells share melanocyte differentiation antigens. Based on a number of observations, de novo vitiligo developing in patients with melanoma has been regarded as a sign of good prognosis. The immune system tolerates or ignores differentiation antigens because these antigens are self-derived. Therefore, immune tolerance or ignorance must be overcome to prime naive T and B cells to induce cancer immunity and autoimmunity against melanocyte differentiation antigens. Mouse models of concurrent melanoma and autoimmune vitiligo have revealed strategies to overcome immune ignorance or tolerance to melanocyte differentiation antigens: immunization with self-antigens as altered self (e.g., orthologues or mutated versions), expression in viral vectors, passive immunization with antibodies or T cells, incorporating potent adjuvants into active immunization, and blockade or removal of a downregulatory mechanism. Extensive investigations into the mechanisms that lead to tumor immunity and autoimmunity elicited by certain differentiation antigens have further revealed a variety of distinct cellular and molecular requirements, which are redundant and alternative.

Animals↗

PubMed2006

Melanoma.

Explore the source record for details and available documents.

Algorithms↗

PubMed2005

Comparison of two cancer vaccines targeting tyrosinase: plasmid DNA and recombinant alphavirus replicon particles.

PURPOSE: Immunization of mice with xenogeneic DNA encoding human tyrosinase-related proteins 1 and 2 breaks tolerance to these self-antigens and leads to tumor rejection. Viral vectors used alone or in heterologous DNA prime/viral boost combinations have shown improved responses to certain infectious diseases. The purpose of this study was to compare viral and plasmid DNA in combination vaccination strategies in the context of a tumor antigen. EXPERIMENTAL DESIGN: Using tyrosinase as a prototypical differentiation antigen, we determined the optimal regimen for immunization with plasmid DNA. Then, using propagation-incompetent alphavirus vectors (virus-like replicon particles, VRP) encoding tyrosinase, we tested different combinations of priming with DNA or VRP followed by boosting with VRP. We subsequently followed antibody production, T-cell response, and tumor rejection. RESULTS: T-cell responses to newly identified mouse tyrosinase epitopes were generated in mice immunized with plasmid DNA encoding human (xenogeneic) tyrosinase. In contrast, when VRP encoding either mouse or human tyrosinase were used as single agents, antibody and T-cell responses and a significant delay in tumor growth in vivo were observed. Similarly, a heterologous vaccine regimen using DNA prime and VRP boost showed a markedly stronger response than DNA vaccination alone. CONCLUSIONS: Alphavirus replicon particle vectors encoding the melanoma antigen tyrosinase (self or xenogeneic) induce immune responses and tumor protection when administered either alone or in the heterologous DNA prime/VRP boost approaches that are superior to the use of plasmid DNA alone.

Alphavirus↗

PubMed2005

Induction of autoantibodies to syngeneic prostate-specific membrane antigen by xenogeneic vaccination.

Prostate-specific membrane antigen (PSMA) is a prototypical differentiation antigen expressed on normal and neoplastic prostate epithelial cells, and on the neovasculature of many solid tumors. Monoclonal antibodies specific for PSMA are in development as therapeutic agents. Methodologies to actively immunize against PSMA may be limited by immunologic ignorance and/or tolerance that restrict the response to self-antigens. Our studies have previously shown that xenogeneic immunization with DNA vaccines encoding melanosomal differentiation antigens induces immunity in a mouse melanoma model. Here we apply this approach to PSMA to establish proof of principle in a mouse model. Immunization with xenogeneic human PSMA protein or DNA induced antibodies to both human and mouse PSMA in mice. Monoclonal antibodies specific for mouse PSMA were generated to analyze antibody isotypes and specificity for native and denatured PSMA at the clonal level. Most antibodies recognized denatured PSMA, but C57BL/6 mice immunized with xenogeneic PSMA DNA followed by a final boost with xenogeneic PSMA protein yielded autoantibodies that reacted with native folded mouse PSMA. Monoclonal antibodies were used to confirm the expression of PSMA protein in normal mouse kidney. These results establish the basis for clinical trials to test PSMA DNA vaccines in patients with solid tumors that either express PSMA directly or that depend on normal endothelial cells expressing PSMA for their continued growth.

Animals↗

PubMed2005

Antiviral T cell responses: phalanx or multipronged attack?

Around 700 BCE, a new military formation called the phalanx was established in ancient Greece: a tight column of heavy infantry carrying long spears, or pikes, used in a single prong of attack. Later, in the battle of Marathon described by Herodotus, the Greeks learned the advantages of multipronged attacks, a strategy still used in modern warfare. Is the immune system similar in its approach to combatting pathogens or tumors?

Antigens, CD↗

PubMed2005

Temozolomide plus thalidomide in patients with brain metastases from melanoma: a phase II study.

BACKGROUND: Temozolomide plus thalidomide is a promising oral combination regimen for the treatment of metastatic melanoma. The current Phase II study examined the efficacy and safety of this combination in chemotherapy-naive patients with brain metastases. METHODS: Patients with histologically confirmed metastatic melanoma and measurable brain metastases received temozolomide (75 mg/m2 per day for 6 weeks with a 2-week break between cycles) plus concomitant thalidomide (200 mg/day escalating to 400 mg/day for patients < 70 years or 100 mg/day escalating to 250 mg/day for patients > or = 70 years). The primary end point was tumor response in the brain assessed every 8 weeks. RESULTS: Twenty-six patients with a median age of 60 years were treated. All patients had progressive brain metastases: 16 were symptomatic and 25 had extensive extracranial metastases. Eight patients had received whole-brain radiotherapy, 4 had received stereotactic radiotherapy, and 8 had received craniotomy with resection of hemorrhagic lesions. Fifteen patients completed > or = 1 cycle (median, 1 cycle; range, 0-4 cycles), and 11 discontinued treatment before completing 1 cycle (7 for intracranial hemorrhage, 2 for pulmonary embolism, 1 for deep vein thrombosis, and 1 for Grade 3 rash). Of 15 patients assessable for response, 3 had a complete or partial response (12% intent to treat) and 7 had minor response or stable disease in the brain. However, 5 of these 10 patients had disease progression at extracranial sites. The median survival period was 5 months for all 26 patients and 6 months for the 15 assessable patients. CONCLUSIONS: Temozolomide plus thalidomide was an active oral regimen for patients with brain metastases from malignant melanoma.

Adult↗

PubMed2005

Antigens recognized by autologous antibodies of patients with soft tissue sarcoma.

Serological analysis of recombinant cDNA libraries (SEREX) uses high titer IgGs to identify antigens expressed by autologous cancers. In order to identify tumor antigens in soft tissue sarcoma (STS), sera from four patients with malignant fibrous histiocytoma (MFH), gastrointestinal stromal tumor (GIST), pleomorphic liposarcoma, and dedifferentiated liposarcoma were screened against cDNA libraries derived from autologous tumor. We identified 18 antigens encoded by 15 different genes, including DLG7, which is located on chromosome 14q22, a locus previously found to be altered in STS, and the proto-oncogene JUN. Ten of fourteen antigens (71%) do not react with sera from healthy donors, suggesting that antibody recognition takes place during cancer progression. Using oligonucleotide microarray technology, most genes were variably expressed across a panel of 16 benign specimens and 41 STSs of different histologies. DLG7, however, showed restricted expression in testes and cancer, similarly to known germ cell cancer-testis antigens (or germ cell antigens, GCAs). Thus, the current study identified several antigens, including molecules implicated in tumorigenesis that were recognized by high titer IgGs in STS patients. Further studies of these selected novel STS antigens are warranted to identify and characterize potential antigen targets expressed by STS.

Antibodies, Neoplasm↗