Implementation of a gene therapy education initiative by the ASGCT and Muhimbili University of Health and Allied Sciences

There has been rapid growth in gene therapy development with an expanding list of approved clinical products. Several therapies are particularly relevant to patients in low- and middle-income countries. Moreover, investing in research and manufacturing presents an opportunity for economic development. To increase awareness of gene therapy, the American Society of Gene and Cell Therapy partnered with the Muhimbili University of Health and Allied Sciences, Tanzania, to create a certificate-bearing course. The goal was to provide faculty teaching in graduate and medical schools with the tools needed to add gene therapy to the university curriculum. The first virtual course was held in October of 2022, and 45 individuals from 9 countries in Africa completed the training. The content was new to approximately two-thirds of participants, with the remaining third indicating that the course increased their knowledge base. The program was well received and will be adapted for other under-resourced regions.

Ablation of the endoplasmic reticulum stress kinase PERK induces paraptosis and type I interferon to promote anti-tumor T cell responses

Activation of unfolded protein responses (UPRs) in cancer cells undergoing endoplasmic reticulum (ER) stress promotes survival. However, how UPR in tumor cells impacts anti-tumor immune responses remains poorly described. Here, we investigate the role of the UPR mediator pancreatic ER kinase (PKR)-like ER kinase (PERK) in cancer cells in the modulation of anti-tumor immunity. Deletion of PERK in cancer cells or pharmacological inhibition of PERK in melanoma-bearing mice incites robust activation of anti-tumor T cell immunity and attenuates tumor growth. PERK elimination in ER-stressed malignant cells triggers SEC61β-induced paraptosis, thereby promoting immunogenic cell death (ICD) and systemic anti-tumor responses. ICD induction in PERK-ablated tumors stimulates type I interferon production in dendritic cells (DCs), which primes CCR2-dependent tumor trafficking of common-monocytic precursors and their intra-tumor commitment into monocytic-lineage inflammatory Ly6C+CD103+ DCs. These findings identify how tumor cell-derived PERK promotes immune evasion and highlight the potential of PERK-targeting therapies in cancer immunotherapy.

WHSC1/NSD2 regulates immune infiltration in prostate cancer

BACKGROUND

Immunotherapy in prostate cancer (PCa) lags behind the progresses obtained in other cancer types partially because of its limited immune infiltration. Tumor-resident immune cells have been detected in the prostate, but the regulatory mechanisms that govern tumor infiltration are still poorly understood. To address this gap, we investigated the role of Wolf-Hirschhorn syndrome candidate 1 (WHSC1), a histone methyltransferase enzyme that targets dimethyl and trimethyl H3K36. WHSC1 is known to promote malignant growth and progression in multiple tumors, but its role in the interface between PCa and immune system is unknown.

METHODS

RNA Sequencing (RNASeq) data from patients with PCa from The Cancer Genome Atlas (TCGA) were collected and divided into top/bottom 30% based on the expression of WHSC1 and disease-free survival was calculated. Publicly available chromatin immunoprecipitation (ChIPSeq) data were obtained from Cistrome and integrated with the available RNASeq data. RNASeq, ATACSeq and methylomic were analyzed using R Bioconductor packages comparing C42 cells with or without stable knockdown on WHSC1. Flow cytometry was used to measure Major Histocompatibility complex (MHC) levels, MHC-bound ovalbumin and tumor infiltration. C57B6 and NOD scid gamma (NSG) mice were subcutaneously grafted with TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) C2 cells and treated with MCTP39 (10 mg/kg); tumor size was monitored over time and curves were compared using permutation analyses. All analyses used a significance threshold of 0.05.

RESULTS

Leveraging TCGA data, we demonstrated that elevated WHSC1 levels positively correlate with the presence of an immunosuppressive microenvironment. We validated those results in vitro, demonstrating that genetic and pharmacological inhibition of WHSC1 restores antigen presentation. This occurs via an elegant epigenetic regulation of gene expression at the chromatin and DNA methylation levels. In vivo studies in immunocompetent mice also show an increased frequency of CD8⁺ T cells in tumors from mice treated with WHSC1 inhibitor, supporting the hypothesis that the antitumor effect following WHSC1 inhibition requires a fully functional immune system.

CONCLUSIONS

This study demonstrates a novel role for WHSC1 in defining immune infiltration in PCa, with significant future implications for the use of immunotherapies in prostate malignancies.

Synthesis, Tumor Specificity, and Photosensitizing Efficacy of Erlotinib-Conjugated Chlorins and Bacteriochlorins: Identification of a Highly Effective Candidate for Photodynamic Therapy of Cancer

Erlotinib was covalently linked to 3-(1'-hexyloxy)ethyl-3-devinylpyropheophorbide-a (HPPH) and structurally related chlorins and bacteriochlorins at different positions of the tetrapyrrole ring. The functional consequence of each modification was determined by quantifying the uptake and subcellular deposition of the erlotinib conjugates, cellular response to therapeutic light treatment in tissue cultures, and in eliminating of corresponding tumors grown as a xenograft in SCID mice. The experimental human cancer models the established cell lines UMUC3 (bladder), FaDu (hypopharynx), and primary cultures of head and neck tumor cells. The effectiveness of the compounds was compared to that of HPPH. Furthermore, specific functional contribution of the carboxylic acid side group at position 17² and the chiral methyl group at 3(1') to the overall activity of the chimeric compounds was assessed. Among the conjugates investigated, the PS 10 was identified as the most effective candidate for achieving tumor cell-specific accumulation and yielding improved long-term tumor control.

Abstract B36: TGFβ blockade and epigenetic modulation for cancer treatment: Efficient breast cancer targeted therapy with TCR-T cell transfer

Introduction: The cancer testis (CT) antigens, such as NY-ESO1, are considered ideal targets for immunotherapy as they are highly immunogenic and their restricted expression malignancies and not normal tissue except testis. However, the expression of CT antigen is downregulated in many tumor types, including breast cancer due to DNA methylation. DNA methylation is a common epigenetic mechanism to regulate gene expression and phenotype and maintain DNA integrity and stability. DNA methylation inhibition can induce NY-ESO1 expression on tumor cells and sensitize them to NY-ESO1 specific T cells. NY-ESO1 targeted T cell receptors (TCR) have been successfully used to engineer T cells for adoptive T cell therapy (ACT). We hypothesize that incorporating a dominant-negative TGFβ receptor II (dnTGFβRII) into the NY-ESO-1 TCR construct to transduce T cells combined with epigenetic modulator treatment may improve T cell effector function in immunosuppressive tumor microenvironment.

Methods: Seven different human breast cancer cell lines were treated with epigenetic modulators at different doses and analyzed by flow cytometry to check the increase in expression of NY-ESO1 antigen and HLA-A2.1. Eight-weeks or older NSG mice were inoculated with HLA-A2.1+, NY-ESO negative at baseline breast cancer cells subcutaneously. PBMCs from healthy donors were transduced with a HLA-A2.1 NY-ESO1 TCR with/without dnTGFβRII two day after activation with OKT3 antibody plus IL-2. The transduction efficiency was confirmed by flow cytometry prior to ACT. Equal numbers of TCR+ cells were injected 10 days after tumor inoculation. Mice were then monitored for tumor growth till endpoint. The spleens and tumors were collected for further analysis of immunophenotype and function.

Results: The expression of NY-ESO1 was inducible with epigenetic modulation in the majority of breast cancer cell-lines tested (5/7). More than 60% of Vβ+ (marker for surface expression of specific TCR) cells were observed after retroviral transduction to PBMCs. The transduced NY-ESO1 TCR/dnTGFβRII cells with epigenetic modulator were successfully able to infiltrate into tumor microenvironment in higher numbers and control cancer growth of inoculated tumor significantly (p<0.01) in comparison to control tumor and control NY-ESO1 TCR only groups. The tumor infiltrated lymphocytes (TILs) from NY-ESO1 TCR/dnTGFβRII with treatment showed that regulatory T cells and cytotoxic T cells were significantly lower and higher, respectively.

Conclusions: Epigenetic modification enhances the cytotoxicity of TCR engineered T cells with dnTGFβRII. Our results demonstrate the feasibility of combined epigenetic modulation and TCR-T treatment for breast cancer patients.

Citation Format: Satoko Matsueda, Kunle Odunsi, Richard C. Koya. TGFβ blockade and epigenetic modulation for cancer treatment: Efficient breast cancer targeted therapy with TCR-T cell transfer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B36.

Efficient identification of neoantigen-specific T-cell responses in advanced human ovarian cancer

Background

Efficient identification of neoantigen-specific T-cell responses in epithelial ovarian cancer (EOC) remains a challenge. Existing investigations of spontaneous T-cell response to tumor neoepitope in EOC have taken the approach of comprehensive screening all neoantigen candidates, with a validation rate of 0.5–2%.

Methods

Whole-exome and transcriptome sequencing analysis of treatment-naive EOC patients were performed to identify neoantigen candidates, and the immunogenicity of prioritized neoantigens was evaluated by analyzing spontaneous neoantigen-specfic CD4⁺ and CD8⁺ T-cell responses in the tumor and/or peripheral blood. The biological relevance of neoantigen-specific T-cell lines and clones were analyzed by evaluating the capacity of autologous ovarian tumor recognition. Genetic transfer of T-cell receptor (TCR) from these neoantigen-specific T-cell clones into peripheral blood T-cells was conducted to generate neoepitope-specific T-cells. The molecular signature associated with positive neoantigen T-cell responses was investigated, and the impacts of expression level and lymphocyte source on neoantigen identification were explored.

Results

Using a small subset of prioritized neoantigen candidates, we were able to detect spontaneous CD4⁺ and/or CD8⁺ T-cell responses against neoepitopes from autologous lymphocytes in half of treatment-naïve EOC patients, with a significantly improved validation rate of 19%. Tumors from patients exhibiting neoantigen-specific T-cell responses exhibited a signature of upregulated antigen processing and presentation machinery, which was also associated with favorable patient survival in the TCGA ovarian cohort. T-cells specific against two mutated cancer-associated genes, NUP214 and JAK1, recognized autologous tumors. Gene-engineering with TCR from these neoantigen-specific T-cell clones conferred neoantigen-reactivity to peripheral T-cells.

Conclusions

Our study demonstrated the feasibility of efficiently identifying both CD4⁺ and CD8⁺ neoantigen-specific T-cells in EOC. Autologous lymphocytes genetically engineered with tumor antigen-specific TCR can be used to generate cells for use in the personalized adoptive T-cell transfer immunotherapy.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0629-6) contains supplementary material, which is available to authorized users.

Mature neutrophils suppress T cell immunity in ovarian cancer microenvironment

Epithelial ovarian cancer (EOC) often presents with metastases and ascites. Granulocytic myeloid-derived suppressor cells are an immature population that impairs antitumor immunity. Since suppressive granulocytes in the ascites of patients with newly diagnosed EOC were morphologically mature, we hypothesized that PMN were rendered suppressive in the tumor microenvironment (TME). Circulating PMN from patients were not suppressive but acquired a suppressor phenotype (defined as ≥1 log10 reduction of anti-CD3/CD28-stimulated T cell proliferation) after ascites supernatant exposure. Ascites supernatants (20 of 31 supernatants) recapitulated the suppressor phenotype in PMN from healthy donors. T cell proliferation was restored with ascites removal and restimulation. PMN suppressors also inhibited T cell activation and cytokine production. PMN suppressors completely suppressed proliferation in naive, central memory, and effector memory T cells and in engineered tumor antigen-specific cytotoxic T lymphocytes, while antigen-specific cell lysis was unaffected. Inhibition of complement C3 activation and PMN effector functions, including CR3 signaling, protein synthesis, and vesicular trafficking, abrogated the PMN suppressor phenotype. Moreover, malignant effusions from patients with various metastatic cancers also induced the C3-dependent PMN suppressor phenotype. These results point to PMN impairing T cell expansion and activation in the TME and the potential for complement inhibition to abrogate this barrier to antitumor immunity.

Measurement and Quantitative Characterization of Whole-Body Pharmacokinetics of Exogenously Administered T Cells in Mice

Here we have investigated whole-body pharmacokinetics (PK) of exogenously administered T cells in a mouse model of melanoma and have developed a physiologically based pharmacokinetic (PBPK) model to quantitatively characterize the data. T cells were isolated from the spleen of tumor-bearing mice, activated, and labeled with chromium-51 to facilitate the quantification. Labeled T cells were injected in the tumor-bearing mice, and PK was measured in 19 different tissues. It was found that T cells disappear from the blood rapidly after administration and accumulate in the tissues to various extents. Spleen, liver, lung, kidney, bone, and lymph nodes accounted for more than 90% of T cells in the body. The distribution of T cells in solid tumors was found to be very low, hovering below 1%ID/g (percent of injected dose per gram of tissue) during the entire study. However, this observation may differ for targeted TCR-T and CAR-T cells. Observed PK profiles also suggest that T-cell-based therapies may be more successful in treating cancers of the lymphatic system and bone marrow metastases compared to solid tumors. A PBPK model was developed to characterize the whole-body PK of T cells, which incorporated key processes such as extravasation, elimination, and recirculation of T cells via lymph flow. Retention factors were incorporated into the spleen, liver, and kidney compartment to adequately capture the PK profiles. The model was able to characterize observed PK profiles reasonably well, and parameters were estimated with good confidence. The PK data and PBPK model presented here provide unprecedented insight into the biodistribution of exogenously administered T cells.

A rare population of tumor antigen-specific CD4+CD8+ double-positive αβ T lymphocytes uniquely provide CD8-independent TCR genes for engineering therapeutic T cells

Background

High-affinity tumor antigen-specific T-cell receptor (TCR) gene is required to engineer potent T cells for therapeutic treatment of cancer patients. However, discovery of suitable therapeutic TCR genes is hampered by the fact that naturally occurring tumor antigen-specific TCRs are generally of low-affinity, and artificial modification of TCRs can mediate cross-reactivity to other antigens expressed in normal tissues. Here, we discovered a naturally occurring T-cell clone which expressed high-affinity HLA-A*02:01 (A*02)-restricted TCR against NY-ESO-1 from a patient who had NY-ESO-1-expressing ovarian tumor.

Methods

A*02-restricted NY-ESO-1-specific T-cell clones were established from peripheral blood of patients who had NY-ESO-1-expressing ovarian tumors. TCR α and β chain genes were retrovirally transduced into polyclonally activated T cells. Phenotype and function of the parental and TCR-transduced T cells were analyzed by flow cytometry, ELISA and cytotoxicity assay. In vivo therapeutic efficacy was investigated in a xenograft model using NOD/SCID/IL-2Rγ-deficient (NSG) mice.

Results

A rare population of NY-ESO-1-specific T cells, which we named 19305DP, expressed cell surface CD4, CD8α, and CD8β but not CD56 and recognized A*02⁺NY-ESO-1⁺ cancer cell lines in a CD4- and CD8-independent manner. 19305DP showed a gene expression profile that is consistent with a mixed profile of CD4⁺ and CD8⁺ single-positive T cells. Both CD4⁺ and CD8⁺ T cells that were retrovirally transduced with 19305DP-derived TCR gene (19305DP-TCR) showed strong reactivity against A*02⁺NY-ESO-1⁺ cancer cells, whereas TCR genes from the conventional A*02-restricted NY-ESO-1-specific CD8⁺ single-positive T-cell clones functioned only in CD8⁺ T cells. Both 19305DP-TCR gene-engineered CD4⁺ and CD8⁺ T cells eliminated A*02⁺NY-ESO-1⁺ tumor xenografts in NSG mice. Finally, based on reactivity against a series of alanine-substituted peptides and a panel of normal human tissue-derived primary cells, 19305DP-TCR was predicted to have no cross-reactivity against any human non-NY-ESO-1 proteins.

Conclusion

Together, our results indicate that the naturally occurring 19305DP-TCR derived from CD4⁺CD8⁺ double-positive αβ T cells, is a promising therapeutic TCR gene for effective and safe adoptive T-cell therapy in A*02⁺ patients with NY-ESO-1-expressing tumor.

Electronic supplementary material

The online version of this article (10.1186/s40425-018-0467-y) contains supplementary material, which is available to authorized users.

Rapid Construction of Antitumor T-cell Receptor Vectors from Frozen Tumors for Engineered T-cell Therapy

T cells genetically engineered with tumor antigen-specific T-cell receptor (TCR) genes have demonstrated therapeutic potential in patients with solid tumors. In order to achieve broader application, an efficient method to identify TCR genes for an array of tumor antigens and HLA restriction elements is required. Here, we have developed a method to construct a TCR-expression library from specimens, including frozen tumor biopsies, that contain antigen-specific T cells. TCR-expressing cassettes were constructed and cloned in a retroviral plasmid vector within 24 hours by unbiased PCR amplification of TCR α and β chain variable regions assembled with TCR constant regions. The method was validated by constructing TCR-expressing vectors from tumor antigen-specific T-cell clones and functionally assessing TCR gene-transduced T cells. We applied this method to frozen ovarian tumor specimens that were infiltrated by tumor antigen-specific T cells. The tumor-derived TCR libraries were expressed in peripheral T cells from healthy volunteers and screened for tumor antigen-specific TCR pairs with the use of an MHC/peptide tetramer reagent. Tumor antigen-specific TCR-expressing transgenes were recovered from isolated tetramer-positive T cells. Peripheral T cells that were engineered with library-derived TCR gene showed potent therapeutic antitumor effect in a tumor xenograft model. Our method can efficiently and rapidly provide tumor-specific TCR-expressing viral vectors for the manufacture of therapeutic and personalized antitumor T-cell products. Cancer Immunol Res; 6(5); 594-604. ©2018 AACR.

Abstract LB-186: Sustained efficacy of immunotherapy for solid tumors with novel dual CD4/CD8 T cell receptor engineered synergistic combination of hematopoietic stem cells and T cells

The goal of our studies is to generate durable anti-cancer T cell responses to improve the outcome of patients with solid tumors. Re-engineering patient’s mature immune cells and administering billions of these cells have shown to be promising but unfortunately, the anti-tumor effect is largely short-lived. In an effort to generate tumor-associated antigen (TAA) specific T cells we have identified NYESO-1 as the prototypic TAA for cancer immunotherapy. We have recently discovered a novel and distinct subset of human CD4+ Th1 cells that directly recognize NYESO-1 naturally presented by MHC II on cancer cells. In contrast to conventional CD4 T cells, these tumor-recognizing (TR) CD4 T cells also potently provide help to CD8 T cells in an antigen-presenting cell (APC) independent fashion. Our central hypothesis is that CD4TCR engineered human hematopoietic stem/progenitor cells (hHSC) will lead to durable in vivo supply of fully active TR-CD4 cells with anti-tumor activity, and provide sustained help to co-injected CD8TCR transduced effector T cells (which will serve to immediately "debulk" the tumor), leading to long-lasting tumor rejection. Results: We successfully accomplished molecular cloning, construction and generation of lentiviral viral vectors with two unique NYESO-1 (TR)CD4TCRs (MHC II restricted HLA DR1 and DP4), as well as, another novel CD8 (MHC I HLA A2.1) TCR for NYESO-1. Transduction efficiency of hHSC was high with transgene expression levels of 40-51% (0.5-1 vector copies/cell); and 65-92% tetramer+ for mature T cells. We confirmed specific functional activity of all TCRs by co-incubating transduced T cells with various tumor targets (SKMEL-37, MZ19, or aAPC: K562/DR1/DP4/A2.1 +/- cognate peptides) by ELISA and intracellular staining for IFNg. For this project we generated new transgenic mouse models based on a highly immunodeficient NSG background with expression of human MHC II DP4 and DR1 in order to study hHSC differentiation/function in vivo and to test anti-human cancer activity with our adoptive cell transfer (ACT) platform. Utilizing these transgenic mice, we injected CD34+ hHSC transduced with (TR)CD4 TCR and after 2 to 3 months we confirmed generation of engineered TCR expressing human T cells by FACS-based immunophenotyping through blood sampling. We then moved forward to test anti-tumor efficacy in vivo with s.q. injection of human melanoma (MZ19) or human ovarian carcinoma (A2780/A2/NY) cells in mice injected with (TR)CD4 TCR transduced or non-transduced-control hHSC. We injected a low dose (5x10^5 cells) of NYESO-1 HLA A2.1 CD8TCR-transduced hPBMC and followed tumor growth. Remarkable tumor control was obtained (p<0.05) in the mouse group that received (TR)CD4 TCR transduced hHSC (tumor size=28mm^2; SE+/-11) versus mice that received untransduced hHSC (152.7mm^2; SE+/-24) or control untreated (no hHSC, no CD8 T cell ACT) (196mm^2; SE+/-40) assessed at day 32 after tumor (A2780/A2/NY) injection. Conclusion: Here we demonstrate for the first time that a combined ACT approach of (TR)CD4 TCR transduced hHSC with CD8 TCR transduced PBMC leads to a synergistic and efficient in vivo control of tumor burden. These results provide basis to pursue a Phase I/IIa clinical trial based on our novel adoptive cell immunotherapy platform to benefit patients with advanced solid tumors.

Citation Format: Richard C. Koya, Thinle Chodon, Junko Matsuzaki, Takemasa Tsuji, Satoko Matsueda, Kunle Odunsi. Sustained efficacy of immunotherapy for solid tumors with novel dual CD4/CD8 T cell receptor engineered synergistic combination of hematopoietic stem cells and T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-186. doi:10.1158/1538-7445.AM2017-LB-186

Improved antitumor activity of immunotherapy with BRAF and MEK inhibitors in BRAF(V600E) melanoma

Combining immunotherapy and BRAF targeted therapy may result in improved antitumor activity with the high response rates of targeted therapy and the durability of responses with immunotherapy. However, the first clinical trial testing the combination of the BRAF inhibitor vemurafenib and the CTLA4 antibody ipilimumab was terminated early because of substantial liver toxicities. MEK [MAPK (mitogen-activated protein kinase) kinase] inhibitors can potentiate the MAPK inhibition in BRAF mutant cells while potentially alleviating the unwanted paradoxical MAPK activation in BRAF wild-type cells that lead to side effects when using BRAF inhibitors alone. However, there is the concern of MEK inhibitors being detrimental to T cell functionality. Using a mouse model of syngeneic BRAF(V600E)-driven melanoma, SM1, we tested whether addition of the MEK inhibitor trametinib would enhance the antitumor activity of combined immunotherapy with the BRAF inhibitor dabrafenib. Combination of dabrafenib and trametinib with pmel-1 adoptive cell transfer (ACT) showed complete tumor regression, increased T cell infiltration into tumors, and improved in vivo cytotoxicity. Single-agent dabrafenib increased tumor-associated macrophages and T regulatory cells (Tregs) in tumors, which decreased with the addition of trametinib. The triple combination therapy resulted in increased melanosomal antigen and major histocompatibility complex (MHC) expression and global immune-related gene up-regulation. Given the up-regulation of PD-L1 seen with dabrafenib and/or trametinib combined with antigen-specific ACT, we tested the combination of dabrafenib, trametinib, and anti-PD1 therapy in SM1 tumors, and observed superior antitumor effect. Our findings support the testing of triple combination therapy of BRAF and MEK inhibitors with immunotherapy in patients with BRAF(V600E) mutant metastatic melanoma.

Inhibition of colony stimulating factor-1 receptor improves antitumor efficacy of BRAF inhibition

Background

Malignant melanoma is an aggressive tumor type that often develops drug resistance to targeted therapeutics. The production of colony stimulating factor 1 (CSF-1) in tumors recruits myeloid cells such as M2-polarized macrophages and myeloid derived suppressor cells (MDSC), leading to an immune suppressive tumor milieu.

Methods

We used the syngeneic mouse model of BRAF^V600E-driven melanoma SM1, which secretes CSF-1, to evaluate the ability of the CSF-1 receptor (CSF-1R) inhibitor PLX3397 to improve the antitumor efficacy of the oncogenic BRAF inhibitor vemurafenib.

Results

Combined BRAF and CSF-1R inhibition resulted in superior antitumor responses compared with either therapy alone. In mice receiving PLX3397 treatment, a dramatic reduction of tumor-infiltrating myeloid cells (TIM) was observed. In this model, we could not detect a direct effect of TIMs or pro-survival cytokines produced by TIMs that could confer resistance to PLX4032 (vemurafenib). However, the macrophage inhibitory effects of PLX3397 treatment in combination with the paradoxical activation of wild type BRAF-expressing immune cells mediated by PLX4032 resulted in more tumor-infiltrating lymphocytes (TIL). Depletion of CD8+ T-cells abrogated the antitumor response to the combination therapy. Furthermore, TILs isolated from SM1 tumors treated with PLX3397 and PLX4032 displayed higher immune potentiating activity.

Conclusions

The combination of BRAF-targeted therapy with CSF-1R blockade resulted in increased CD8 T-cell responses in the SM1 melanoma model, supporting the ongoing evaluation of this therapeutic combination in patients with BRAF^V600 mutant metastatic melanoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1377-8) contains supplementary material, which is available to authorized users.

Improved antitumor activity of immunotherapy with BRAF and MEK inhibitors in BRAF(V600E) melanoma

Combining immunotherapy and BRAF targeted therapy may result in improved antitumor activity with the high response rates of targeted therapy and the durability of responses with immunotherapy. However, the first clinical trial testing the combination of the BRAF inhibitor vemurafenib and the CTLA4 antibody ipilimumab was terminated early because of substantial liver toxicities. MEK [MAPK (mitogen-activated protein kinase) kinase] inhibitors can potentiate the MAPK inhibition in BRAF mutant cells while potentially alleviating the unwanted paradoxical MAPK activation in BRAF wild-type cells that lead to side effects when using BRAF inhibitors alone. However, there is the concern of MEK inhibitors being detrimental to T cell functionality. Using a mouse model of syngeneic BRAF(V600E)-driven melanoma, SM1, we tested whether addition of the MEK inhibitor trametinib would enhance the antitumor activity of combined immunotherapy with the BRAF inhibitor dabrafenib. Combination of dabrafenib and trametinib with pmel-1 adoptive cell transfer (ACT) showed complete tumor regression, increased T cell infiltration into tumors, and improved in vivo cytotoxicity. Single-agent dabrafenib increased tumor-associated macrophages and T regulatory cells (Tregs) in tumors, which decreased with the addition of trametinib. The triple combination therapy resulted in increased melanosomal antigen and major histocompatibility complex (MHC) expression and global immune-related gene up-regulation. Given the up-regulation of PD-L1 seen with dabrafenib and/or trametinib combined with antigen-specific ACT, we tested the combination of dabrafenib, trametinib, and anti-PD1 therapy in SM1 tumors, and observed superior antitumor effect. Our findings support the testing of triple combination therapy of BRAF and MEK inhibitors with immunotherapy in patients with BRAF(V600E) mutant metastatic melanoma.

Tunable-combinatorial mechanisms of acquired resistance limit the efficacy of BRAF/MEK cotargeting but result in melanoma drug addiction

Combined BRAF- and MEK-targeted therapy improves upon BRAF inhibitor (BRAFi) therapy but is still beset by acquired resistance. We show that melanomas acquire resistance to combined BRAF and MEK inhibition by augmenting or combining mechanisms of single-agent BRAFi resistance. These double-drug resistance-associated genetic configurations significantly altered molecular interactions underlying MAPK pathway reactivation. (V600E)BRAF, expressed at supraphysiological levels because of (V600E)BRAF ultra-amplification, dimerized with and activated CRAF. In addition, MEK mutants enhanced interaction with overexpressed (V600E)BRAF via a regulatory interface at R662 of (V600E)BRAF. Importantly, melanoma cell lines selected for resistance to BRAFi+MEKi, but not those to BRAFi alone, displayed robust drug addiction, providing a potentially exploitable therapeutic opportunity.

Abstract 5015: TCR usage analysis in blood reveals different mechanisms of action of CTLA-4 and PD-1 blockade in patients

Immune-checkpoint blockade therapies are providing long-lasting responses in a subset of patients with malignant metastatic melanoma. In an effort to better understand the underlying mechanism, the T-cell population in peripheral blood mononuclear cells (PBMCs) was characterized. The complementarity determining region 3 (CDR3) of the rearranged T cell receptor variable ß chain genes (TCR Vß) was sequenced. This was performed using gDNA extracted from the PBMCs of twenty-one patients that were treated with antibody to Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4) (tremelimumab) and seven patients that were treated with antibody to the Programmed Death-1 (PD-1) blockade (MK-3475) at baseline and at day 30-60 post first treatment. Four healthy donors were also sequenced as controls. Control PBMCs displayed random distribution with three patients showing a decrease and one showing an increase in the number of unique productive sequences (UPS) from baseline to the time after first cycle. In PBMCs from patients receiving the CTLA-4 antibody, two out of 21 samples showed a decrease in total number of UPS, while 19 out of 21samples experienced an increase. In PBMCs from patients receiving PD-1 antibody, the reponse was more similar to healthy donors as 5 out of 7 (71%) displayed a decrease and 2 out 7 (29%) an increase in total UPS from the pre to post timepoint. There was an increase in the absolute lymphocyte count (ALC) after CTLA-4 blockade therapy (p=0.03), but not in the samples from patients treated with PD-1 antibody (p=0.53). A direct correlation between ALC increase and increase in UPS for CTLA-4 blockade was ruled out (p=0.1 Spearman Correlation). When analyzing according to clinical response status, all responders to CTLA-4 blockade (4 out of 19) experienced an increase in the number of circulating clones. However, samples from clinical responders to PD-1 blockade showed an increase (2 out of 5) or decrease (1 out of 2) in the circulating pool. Considering the concerning toxicity profile for CTLA-4-blockade versus the mild toxicity for PD-1 antibodies, this data supports a model where CTLA-4 blockade induces a non-specific systemic expansion of T cells, while PD-1 blockade may have more specific effects directly in the tumor.

Citation Format: Lidia Robert, Christina L. Harview, Ryan Emerson, Stephen Mok, Blanca Homet, Begonya Comin-Anduix, Richard C. Koya, Harlan Robins, Paul C. Tumeh, Antoni Ribas. TCR usage analysis in blood reveals different mechanisms of action of CTLA-4 and PD-1 blockade in patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5015. doi:10.1158/1538-7445.AM2014-5015

HSV-sr39TK positron emission tomography and suicide gene elimination of human hematopoietic stem cells and their progeny in humanized mice

Engineering immunity against cancer by the adoptive transfer of hematopoietic stem cells (HSC) modified to express antigen-specific T-cell receptors (TCR) or chimeric antigen receptors generates a continual supply of effector T cells, potentially providing superior anticancer efficacy compared with the infusion of terminally differentiated T cells. Here, we demonstrate the in vivo generation of functional effector T cells from CD34-enriched human peripheral blood stem cells modified with a lentiviral vector designed for clinical use encoding a TCR recognizing the cancer/testes antigen NY-ESO-1, coexpressing the PET/suicide gene sr39TK. Ex vivo analysis of T cells showed antigen- and HLA-restricted effector function against melanoma. Robust engraftment of gene-modified human cells was demonstrated with PET reporter imaging in hematopoietic niches such as femurs, humeri, vertebrae, and the thymus. Safety was demonstrated by the in vivo ablation of PET signal, NY-ESO-1-TCR-bearing cells, and integrated lentiviral vector genomes upon treatment with ganciclovir, but not with vehicle control. Our study provides support for the efficacy and safety of gene-modified HSCs as a therapeutic modality for engineered cancer immunotherapy. Cancer Res; 74(18); 5173-83. ©2014 AACR.

Distinct immunological mechanisms of CTLA-4 and PD-1 blockade revealed by analyzing TCR usage in blood lymphocytes

Targeting immune inhibitory receptors has brought excitement, innovation and hope to cancer patients. Our recent work revealed the immunological effects of blocking the CTLA4 and PD-1 immune checkpoints on T cell receptor usage among peripheral blood cells, and further uncovers how the expansion of the T cell repertoire matches the immunotoxicity profile of the therapy.

Adoptive transfer of MART-1 T-cell receptor transgenic lymphocytes and dendritic cell vaccination in patients with metastatic melanoma

PURPOSE

It has been demonstrated that large numbers of tumor-specific T cells for adoptive cell transfer (ACT) can be manufactured by retroviral genetic engineering of autologous peripheral blood lymphocytes and expanding them over several weeks. In mouse models, this therapy is optimized when administered with dendritic cell (DC) vaccination. We developed a short 1-week manufacture protocol to determine the feasibility, safety, and antitumor efficacy of this double cell therapy.

EXPERIMENTAL DESIGN

A clinical trial (NCT00910650) adoptively transferring MART-1 T-cell receptor (TCR) transgenic lymphocytes together with MART-1 peptide-pulsed DC vaccination in HLA-A2.1 patients with metastatic melanoma. Autologous TCR transgenic cells were manufactured in 6 to 7 days using retroviral vector gene transfer, and reinfused with (n = 10) or without (n = 3) prior cryopreservation.

RESULTS

A total of 14 patients with metastatic melanoma were enrolled and 9 of 13 treated patients (69%) showed evidence of tumor regression. Peripheral blood reconstitution with MART-1-specific T cells peaked within 2 weeks of ACT, indicating rapid in vivo expansion. Administration of freshly manufactured TCR transgenic T cells resulted in a higher persistence of MART-1-specific T cells in the blood as compared with cryopreserved. Evidence that DC vaccination could cause further in vivo expansion was only observed with ACT using noncryopreserved T cells.

CONCLUSION

Double cell therapy with ACT of TCR-engineered T cells with a very short ex vivo manipulation and DC vaccines is feasible and results in antitumor activity, but improvements are needed to maintain tumor responses.

CTLA4 blockade broadens the peripheral T-cell receptor repertoire

PURPOSE

To evaluate the immunomodulatory effects of cytotoxic T-lymphocyte-associated protein 4 (CTLA4) blockade with tremelimumab in peripheral blood mononuclear cells (PBMC).

EXPERIMENTAL DESIGN

We used next-generation sequencing to study the complementarity-determining region 3 (CDR3) from the rearranged T-cell receptor (TCR) variable beta (V-beta) in PBMCs of 21 patients, at baseline and 30 to 60 days after receiving tremelimumab.

RESULTS

After receiving tremelimumab, there was a median of 30% increase in unique productive sequences of TCR V-beta CDR3 in 19 out of 21 patients, and a median decrease of 30% in only 2 out of 21 patients. These changes were significant for richness (P = 0.01) and for Shannon index diversity (P = 0.04). In comparison, serially collected PBMCs from four healthy donors did not show a significant change in TCR V-beta CDR3 diversity over 1 year. There was a significant difference in the total unique productive TCR V-beta CDR3 sequences between patients experiencing toxicity with tremelimumab compared with patients without toxicity (P = 0.05). No relevant differences were noted between clinical responders and nonresponders.

CONCLUSIONS

CTLA4 blockade with tremelimumab diversifies the peripheral T-cell pool, representing a pharmacodynamic effect of how this class of antibodies modulates the human immune system.

Exposure to a histone deacetylase inhibitor has detrimental effects on human lymphocyte viability and function

Histone deacetylase inhibitors (HDACi) have been reported to increase tumor antigen expression, and have been successfully tested as adjuvants for melanoma immunotherapy in mouse models. In this work, we tested the effects of a pan-HDACi on human lymphocytes and melanoma cell lines. Effects of the pan-HDACi panobinostat (LBH589) on cell viability, cell cycle, apoptosis, and DNA damage were determined in peripheral blood mononuclear cells (PBMC) from 2 healthy donors, 13 patients with metastatic melanoma, 2 bone marrow samples from patients with different malignances, and 12 human melanoma cell lines. Intracellular signaling in lymphocytes, with or without cytokine stimulation, was analyzed by phospho-flow cytometry in one of each type. The IC50 in PBMCs was <20 nmol/L compared with >600 nmol/L in melanoma cell lines; >40% apoptotic cell death in PBMCs versus <10% in melanoma cell lines was seen at the same concentration. Phospho-histone variant H2A.X (pH2A.X) increased 2-fold in healthy donor PBMCs at 1 nmol/L, whereas the same effect in the melanoma cell line M229 required 10 nmol/L. pH2A.X was inhibited slightly in the PBMCs of 3 patients with metastatic melanoma at 1 nmol/L and in the melanoma cell line M370 at 10 nmol/L. Panobinostat inhibited phospho-STAT1/3/5/6, -p38, -ERK, -p53, -cyclin D3, and -histone H3 in flow cytometry-gated healthy donor B and T cells, whereas it induced up to 6-fold activation in patients with metastatic melanoma and bone marrow samples. In human lymphocytes, panobinostat alters key lymphocyte activation signaling pathways and is cytotoxic at concentrations much lower than those required for melanoma antitumor activity, resulting in an adverse therapeutic window.

Inhibition of CSF-1 receptor improves the antitumor efficacy of adoptive cell transfer immunotherapy

Colony stimulating factor 1 (CSF-1) recruits tumor-infiltrating myeloid cells (TIM) that suppress tumor immunity, including M2 macrophages and myeloid-derived suppressor cells (MDSC). The CSF-1 receptor (CSF-1R) is a tyrosine kinase that is targetable by small molecule inhibitors such as PLX3397. In this study, we used a syngeneic mouse model of BRAF(V600E)-driven melanoma to evaluate the ability of PLX3397 to improve the efficacy of adoptive cell therapy (ACT). In this model, we found that combined treatment produced superior antitumor responses compared with single treatments. In mice receiving the combined treatment, a dramatic reduction of TIMs and a skewing of MHCII(low) to MHCII(hi) macrophages were observed. Furthermore, mice receiving the combined treatment exhibited an increase in tumor-infiltrating lymphocytes (TIL) and T cells, as revealed by real-time imaging in vivo. In support of these observations, TILs from these mice released higher levels of IFN-γ. In conclusion, CSF-1R blockade with PLX3397 improved the efficacy of ACT immunotherapy by inhibiting the intratumoral accumulation of immunosuppressive macrophages.

A novel AKT1 mutant amplifies an adaptive melanoma response to BRAF inhibition

BRAF inhibitor (BRAFi) therapy leads to remarkable anti melanoma responses, but the initial tumor shrinkage is commonly incomplete, providing a nidus for subsequent disease progression. Adaptive signaling may underlie early BRAFi resistance and influence the selection pattern for genetic variants, causing late, acquired resistance. We show here that BRAFi (or BRAFi + MEKi) therapy in patients frequently led to rebound phosphorylated AKT (p-AKT) levels in their melanomas early on-treatment. In cell lines, BRAFi treatment led to rebound levels of receptor tyrosine kinases (RTK; including PDGFRβ), phosphatidyl (3,4,5)-triphosphate (PIP3), pleckstrin homology domain recruitment, and p-AKT. PTEN expression limited this BRAFi-elicited PI3K-AKT signaling, which could be rescued by the introduction of a mutant AKT1 (Q79K) known to confer acquired BRAFi resistance. Functionally, AKT1(Q79K) conferred BRAFi resistance via amplification of BRAFi-elicited PI3K-AKT signaling. In addition, mitogen-activated protein kinase pathway inhibition enhanced clonogenic growth dependency on PI3K or AKT. Thus, adaptive or genetic upregulation of AKT critically participates in melanoma survival during BRAFi therapy.

Acquired resistance and clonal evolution in melanoma during BRAF inhibitor therapy

BRAF inhibitors elicit rapid antitumor responses in the majority of patients with BRAF(V600)-mutant melanoma, but acquired drug resistance is almost universal. We sought to identify the core resistance pathways and the extent of tumor heterogeneity during disease progression. We show that mitogen-activated protein kinase reactivation mechanisms were detected among 70% of disease-progressive tissues, with RAS mutations, mutant BRAF amplification, and alternative splicing being most common. We also detected PI3K-PTEN-AKT-upregulating genetic alterations among 22% of progressive melanomas. Distinct molecular lesions in both core drug escape pathways were commonly detected concurrently in the same tumor or among multiple tumors from the same patient. Beyond harboring extensively heterogeneous resistance mechanisms, melanoma regrowth emerging from BRAF inhibitor selection displayed branched evolution marked by altered mutational spectra/signatures and increased fitness. Thus, melanoma genomic heterogeneity contributes significantly to BRAF inhibitor treatment failure, implying upfront, cotargeting of two core pathways as an essential strategy for durable responses.

Natural killer T cells in advanced melanoma patients treated with tremelimumab

A significant barrier to effective immune clearance of cancer is loss of antitumor cytotoxic T cell activity. Antibodies to block pro-apoptotic/downmodulatory signals to T cells are currently being tested. Because invariant natural killer T cells (iNKT) can regulate the balance of Th1/Th2 cellular immune responses, we characterized the frequencies of circulating iNKT cell subsets in 21 patients with melanoma who received the anti-CTLA4 monoclonal antibody tremelimumab alone and 8 patients who received the antibody in combination with MART-1_26–35 peptide-pulsed dendritic cells (MART-1/DC). Blood T cell phenotypes and functionality were characterized by flow cytometry before and after treatment. iNKT cells exhibited the central memory phenotype and showed polyfunctional cytokine production. In the combination treatment group, high frequencies of pro-inflammatory Th1 iNKT CD8⁺ cells correlated with positive clinical responses. These results indicate that iNKT cells play a critical role in regulating effective antitumor T cell activity.

Abstract 3969: Blocking colony stimulating factor 1 receptor (CSF1R) improves anti-tumor effects of adoptive T cell transfer therapy

Tumors can escape immune responses by creating an inflammatory milieu that supports and recruits tumor-infiltrating myeloid cells (TIMs) with immune suppressive functions, such as myeloid derived suppressor cells (MDSC) and M2-polarized macrophages. Therapies that block recruitment of suppressor TIMs have the potential to enhance adoptive cell transfer (ACT) of T cell based-immunotherapies.

We originally established a BRAFV600E mutant murine melanoma cell line (SM1) for which ACT of melanoma-targeted T cells induced anti-tumor responses, but not complete eradication in vivo. By gene expression profiling and single-nucleotide polymorphism (SNP) arrays, we found that, out of 108 cytokines produced by SM1, colony stimulating factor 1 (CSF1) was highly expressed. CSF1 induces proliferation of immune suppressors Gr-1(+) CD11b(+) MDSC and F4/80(+) CD11b(+) macrophages. In order to block the recruitment of TIMs, we tested a potent CSF1R inhibitor, PLX3397. Cultured primary murine T cells exposed to PLX3397 with a broad range of concentrations (0.1 to 50 μM) showed no evidence of cytotoxicity by MTS assay. We then tested the combination of PLX3397 and ACT in vivo using two models. In the first one, SM1 cells stably expressing the chicken ovalbumin (OVA) antigen were implanted in C57BL/6 mice. Daily oral gavage with PLX3397 (50mg/kg) combined with ACT of OVA-specific TCR transgenic cells (OT-1) demonstrated superior effects of the combined treatment (tumor size on day 14_vehicle: 1611.2±22.5 mm2, PLX3397: 1028.0±24.0 mm2, OT-1: 1112.5±35.7 mm2, combined PLX3397+OT-1: 347.3±15.5 mm2, p&lt;0.001). We have observed a dramatic reduction of the number of macrophages in the tumor tissue (vehicle: 10.3±1.6%, PLX3397: 1.35±0.5%, OT-1: 12.0±0.6%, combined: 2.33±0.3%, p&lt;0.001) and a skewing of type M2 to type M1 macrophages. In vivo real-time T cell tracking by luciferase bioluminescence imaging demonstrated an increased number of tumor infiltrating lymphocytes (TILs) in the combined therapy group (photon counts/pixel on day 5 post ACT: OT-1: 4424.5±412, combined: 9176±1780, p&lt;0.001). The second in vivo model was based on pmel-1 transgenic T cells, which targeted the endogenous melanoma antigen (gp100) expressed by SM1. The combined treatment of PLX3397 and ACT of pmel-1 also resulted in significant tumor shrinkage, reduction of M2 macrophages, and increased number of TILs. TILs were also collected and analyzed for function by intracellular staining of IFNγ. TILs from the combined treatment group released significantly higher levels of IFNγ (ACT: 48.2±8.7%, combined: 78.8±3.5%, p&lt;0.001).

In conclusion, our data derived from two independent in vivo models demonstrated dramatic potentiation of anti-tumor effects with the combination of CSF1R blockade and ACT immunotherapy, supporting the rationale for further testing in patients with metastatic melanoma.

Citation Format: Stephen Mok, Christopher Tsui, Jingying Xu, Begonya Comin-Anduix, Thinle Chodon, Antoni Ribas, Richard C. Koya. Blocking colony stimulating factor 1 receptor (CSF1R) improves anti-tumor effects of adoptive T cell transfer therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3969. doi:10.1158/1538-7445.AM2013-3969

Multifunctional T-cell analyses to study response and progression in adoptive cell transfer immunotherapy

Adoptive cell transfer (ACT) of genetically engineered T cells expressing cancer-specific T-cell receptors (TCR) is a promising cancer treatment. Here, we investigate the in vivo functional activity and dynamics of the transferred cells by analyzing samples from 3 representative patients with melanoma enrolled in a clinical trial of ACT with TCR transgenic T cells targeted against the melanosomal antigen MART-1. The analyses included evaluating 19 secreted proteins from individual cells from phenotypically defined T-cell subpopulations, as well as the enumeration of T cells with TCR antigen specificity for 36 melanoma antigens. These analyses revealed the coordinated functional dynamics of the adoptively transferred, as well as endogenous, T cells, and the importance of highly functional T cells in dominating the antitumor immune response. This study highlights the need to develop approaches to maintaining antitumor T-cell functionality with the aim of increasing the long-term efficacy of TCR-engineered ACT immunotherapy.

SIGNIFICANCE

A longitudinal functional study of adoptively transferred TCR–engineered lymphocytes yielded revealing snapshots for understanding the changes of antitumor responses over time in ACT immunotherapy of patients with advanced melanoma.

Host immunity contributes to the anti-melanoma activity of BRAF inhibitors

The BRAF mutant, BRAF(V600E), is expressed in nearly half of melanomas, and oral BRAF inhibitors induce substantial tumor regression in patients with BRAF(V600E) metastatic melanoma. The inhibitors are believed to work primarily by inhibiting BRAF(V600E)-induced oncogenic MAPK signaling; however, some patients treated with BRAF inhibitors exhibit increased tumor immune infiltration, suggesting that a combination of BRAF inhibitors and immunotherapy may be beneficial. We used two relatively resistant variants of Braf(V600E)-driven mouse melanoma (SM1 and SM1WT1) and melanoma-prone mice to determine the role of host immunity in type I BRAF inhibitor PLX4720 antitumor activity. We found that PLX4720 treatment downregulated tumor Ccl2 gene expression and decreased tumor CCL2 expression in both Braf(V600E) mouse melanoma transplants and in de novo melanomas in a manner that was coincident with reduced tumor growth. While PLX4720 did not directly increase tumor immunogenicity, analysis of SM1 tumor-infiltrating leukocytes in PLX4720-treated mice demonstrated a robust increase in CD8(+) T/FoxP3(+)CD4(+) T cell ratio and NK cells. Combination therapy with PLX4720 and anti-CCL2 or agonistic anti-CD137 antibodies demonstrated significant antitumor activity in mouse transplant and de novo tumorigenesis models. These data elucidate a role for host CCR2 in the mechanism of action of type I BRAF inhibitors and support the therapeutic potential of combining BRAF inhibitors with immunotherapy.

T cell receptor (TCR)-transgenic CD8 lymphocytes rendered insensitive to transforming growth factor beta (TGFβ) signaling mediate superior tumor regression in an animal model of adoptive cell therapy

Tumor antigen-reactive T cells must enter into an immunosuppressive tumor microenvironment, continue to produce cytokine and deliver apoptotic death signals to affect tumor regression. Many tumors produce transforming growth factor beta (TGFβ), which inhibits T cell activation, proliferation and cytotoxicity. In a murine model of adoptive cell therapy, we demonstrate that transgenic Pmel-1 CD8 T cells, rendered insensitive to TGFβ by transduction with a TGFβ dominant negative receptor II (DN), were more effective in mediating regression of established B16 melanoma. Smaller numbers of DN Pmel-1 T cells effectively mediated tumor regression and retained the ability to produce interferon-γ in the tumor microenvironment. These results support efforts to incorporate this DN receptor in clinical trials of adoptive cell therapy for cancer.

BRAF inhibitor vemurafenib improves the antitumor activity of adoptive cell immunotherapy

Combining immunotherapy with targeted therapy blocking oncogenic BRAFV600 may result in improved treatments for advanced melanoma. In this study, we developed a BRAFV600E-driven murine model of melanoma, SM1, which is syngeneic to fully immunocompetent mice. SM1 cells exposed to the BRAF inhibitor vemurafenib (PLX4032) showed partial in vitro and in vivo sensitivity resulting from the inhibition of MAPK pathway signaling. Combined treatment of vemurafenib plus adoptive cell transfer therapy with lymphocytes genetically modified with a T-cell receptor (TCR) recognizing chicken ovalbumin (OVA) expressed by SM1-OVA tumors or pmel-1 TCR transgenic lymphocytes recognizing gp100 endogenously expressed by SM1 resulted in superior antitumor responses compared with either therapy alone. T-cell analysis showed that vemurafenib did not significantly alter the expansion, distribution, or tumor accumulation of the adoptively transferred cells. However, vemurafenib paradoxically increased mitogen-activated protein kinase (MAPK) signaling, in vivo cytotoxic activity, and intratumoral cytokine secretion by adoptively transferred cells. Taken together, our findings, derived from 2 independent models combining BRAF-targeted therapy with immunotherapy, support the testing of this therapeutic combination in patients with BRAFV600 mutant metastatic melanoma.

Safety and efficacy of dendritic cell immunotherapy with ad-GMCAIX in an immunocompetent preclinical tumor model of renal cell carcinoma

e13045

Background: We have previously reported the successful ex vivo generation of hCAIX-specific cytotoxic T lymphocytes (CTLs) by adenoviral (Ad) transduction of the GMCAIX fusion protein in dendritic cells (DC). We then produced GMP-grade material (NIH-RAID program, NSC 740833). Now we test, for the first time, the in vivo anti-tumor activity of DC-Ad-GMCAIX against renal cell carcinoma (RCC) in a unique immunocompetent mouse tumor model. Methods: Tumor growth inhibition and specificity were studied in BALB/c mice s.c. transplanted with either syngeneic RENCA cells transduced with hCAIX (URCAIX) or with non-hCAIX-expressing RENCA cells (RENCA). In a tumor prevention model, cohorts of mice were first immunized s.c. twice with DC-Ad-GMCAIX, DC-Ad-null, or no DCs, followed by tumor challenge with s.c. transplantation of URCAIX or RENCA cells. In an intervention model, tumors were first established and then immunotherapy was employed. Tumor volume and body weight were regularly assessed. Partial necropsy, immunohistochemistry of harvested tumors, and complete blood count were performed at termination of each study. Results: In the prevention model, URCAIX tumor growth was specifically and significantly inhibited for 15 days (p<0.0001). At termination, median growth inhibition reached 79% (113 vs. 531 mm3) and half of the mice remained tumor-free. In the intervention model, DC-Ad-GMCAIX-treated mice showed specific and significant growth inhibition of URCAIX tumors for 8 days (p<0.0018) with a median growth inhibition reaching 60% (487 vs. 1,205 mm3). The threshold of 15% weight loss was delayed in the therapeutic groups of both models (p<0.0167). No treatment-related weight loss or organ toxicity was observed. hCAIX staining was absent or minimally present in URCAIX-tumors that evaded DC-Ad-GMCAIX therapy. Conclusions: DC-Ad-GMCAIX therapy in a novel immunocompetent mouse model demonstrated, for the first time, both tumor prevention and growth inhibition of established RCC tumors without evidence of systemic toxicity. These studies form the basis for first-in-human clinical trial in patients with advanced RCC.

Antitumor effects of the investigational selective MEK inhibitor TAK733 against cutaneous and uveal melanoma cell lines

BACKGROUND

TAK733 is a novel allosteric, non-ATP-binding, inhibitor of the BRAF substrates MEK-1/2.

METHODS

The growth inhibitory effects of TAK733 were assessed in a panel of 27 cutaneous and five uveal melanoma cell lines genotyped for driver oncogenic mutations. Flow cytometry, Western blots and metabolic tracer uptake assays were used to characterize the changes induced by exposure to TAK733.

RESULTS

Fourteen cutaneous melanoma cell lines with different driver mutations were sensitive to the antiproliferative effects of TAK733, with a higher proportion of BRAFV600E mutant cell lines being highly sensitive with IC50s below 1 nM. The five uveal melanoma cell lines had GNAQ or GNA11 mutations and were either moderately or highly sensitive to TAK733. The tested cell lines wild type for NRAS, BRAF, GNAQ and GNA11 driver mutations were moderately to highly resistant to TAK733. TAK733 led to a decrease in pERK and G1 arrest in most of these melanoma cell lines regardless of their origin, driver oncogenic mutations and in vitro sensitivity to TAK733. MEK inhibition resulted in increase in pMEK more prominently in NRASQ61L mutant and GNAQ mutant cell lines than in BRAFV600E mutant cell lines. Uptake of the metabolic tracers FDG and FLT was inhibited by TAK733 in a manner that closely paralleled the in vitro sensitivity assays.

CONCLUSIONS

The MEK inhibitor TAK733 has antitumor properties in melanoma cell lines with different oncogenic mutations and these effects could be detectable by differential metabolic tracer uptake.

Abstract 3510: Paradoxical MAPK activation and beneficial effects of vemurafenib on T-cell phenotype resulting in improved functionality in vivo

Adoptive T cell transfer (ACT) based immunotherapy for melanoma can induce remarkable and highly durable tumor responses, which may last many years. Vemurafenib (Vmf) is a potent inhibitor of BRAF mutated at V600E with response rates of up to 80% in patients with metastatic melanoma. However, drug resistance develops in most of patients leading to response durations of only several months. We previously showed that the combined approach of BRAF inhibition with adoptive cell immunotherapy leads to an improved outcome in vivo. Here we show that Vmf also directly and independently affects T lymphocytes, resulting in favorable anti-tumoral phenotypic changes. We had created a transplantable murine melanoma cell-line driven by V600E BRAF oncogene (SM1) derived from a spontaneously arising melanoma in transgenic mice harboring the V600E BRAF mutation under the control of tyrosinase promoter. SM1 cells stably expressing the ovalbumin (OVA) model antigen were implanted in C57BL6 mice. Daily i.p. Vmf combined with ACT of OVA-specific TCR transgenic cells generated by retroviral transduction demonstrated superior tumor control of the combined treatment in comparison to each treatment alone. We also confirmed better outcomes with this combination in the pmel-1 model, which is based on the ACT of TCR transgenic cells against the endogenously expressed and relevant melanoma antigen, gp100. We then cultured primary T cells in the presence of Vmf with a broad range of concentration (0.1 to up to 100 uM). There was no evidence of cytotoxicity, but interestingly, T cells differentiated into a phenotype resembling T central memory (CM) cells (CD44+, CD62L+) in a dose dependent manner as assessed by flow-cytometry. CM T cells were shown to induce superior anti-tumoral responses in comparison to ACT of Effector T cells in murine models. As expected for CM T cells, further analysis of 24 h collection supernatants from in vitro cognate peptide stimulated T cells showed dose-dependent lower interferon-gamma secretion with Vmf as analyzed by ELISA. Pmel-1 T cells were then analyzed by Immunoblotting for phosphorylation status (activation) of protein kinases at 1, 5, 15, 30 min and at 24h after Vmf treatment (concentrations from 1 to 15 uM). Vmf induced increased levels of pERK and pMEK. Co-immunoprecipitation studies and kinase assays further demonstrated a role of C-Raf in this paradoxical activation of the MAPK pathway in T cells induced by Vmf. Furthermore, in vivo studies in C57BL6 mice treated with Vmf daily or vehicle control for 3 weeks demonstrated skewing of CD3+ cells towards a phenotype resembling central memory T cells (CD44+, CD62L+, LY-6C+). Taken all our data together, we provide further support for the rationale of combining BRAF targeted therapy and adoptive T cell immunotherapy and the testing of such combinations in patients with V600E BRAF mutant metastatic melanoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3510. doi:1538-7445.AM2012-3510

Abstract 1563: In vivo safety and efficacy of a novel dendritic cell based Ad-GMCAIX vaccine with activity against renal cell carcinoma

Carbonic anhydrase IX (CAIX) expression is constitutively up-regulated in clear cell renal cell carcinoma (ccRCC) due to loss of the VHL gene. Its up-regulation in ccRCC and low expression levels in normal tissues led us to develop an immunotherapeutic approach targeting the CAIX tumor antigen. We previously reported the successful generation and ex vivo priming of CAIX-specific, MHC restricted cytotoxic T lymphocytes (CTLs) by adenoviral (Ad) transduction of the GM-CAIX fusion protein in dendritic cells (DCs). Our current study tests, for the first time, the in vivo anti-tumor activity of DC-Ad-GMCAIX in preventing and intervening in the growth of RCC in immunocompetent mouse models. Tumor growth was studied in BALB/c mice transplanted s.c. with either the syngeneic CAIX-expressing RCC cell line RENCA-CAIX (PRCAIX) or the non-CAIX-expressing parental RENCA line. In the preventative model, cohorts of mice were s.c. immunized twice 6 days apart with either DC-Ad-GMCAIX, DC-Ad-null, or no DC transplantation, followed by s.c. challenge with PRCAIX or RENCA lines 12 days later. In the interventional model, tumors were first established and then immunotherapy was employed. At the end of each study, tumors were harvested, and partial necropsy, immunohistochemistry, and complete blood count were performed. DC-Ad-GMCAIX expressed in vivo the hCAIX protein that primed CTLs to specifically target hCAIX expressed by the PRCAIX line. In the preventative model, PRCAIX tumor growth was specifically and significantly inhibited by DC-Ad-GMCAIX for 15 days (all p&lt;0.0001), reaching 79% median growth inhibition at termination (113 vs. 531 mm3). In the therapeutic cohort, time to 15% weight loss was significantly delayed (log-rank test p&lt;0.001). Half of the mice in the treatment cohort did not develop tumors. The results were confirmed by a repeated study (inhibition for 15 days; all p&lt;0.0001; 7/8 mice without tumor). In the interventional model, DC-Ad-GMCAIX-vaccinated mice demonstrated a specific and significant growth inhibition of PRCAIX-tumors for 8 days, with 60% median growth inhibition at termination (all p&lt;0.0018; 487 vs. 1,205 mm3). In the therapeutic cohort, time to 15% weight loss was significantly delayed (log-rank test p&lt;0.0167). No vaccine-related weight loss or organ toxicity was observed. hCAIX staining was absent or only minimally present in PRCAIX-tumors that grew despite therapy with DC-Ad-GMCAIX, compared to strong staining in the negative control groups. In conclusion, DC-Ad-GMCAIX therapy is capable of in vivo generation of CAIX specific CTLs in immunocompetent mice, leading to a significant inhibition of RCC tumor growth without systemic toxicity. Additional studies are being done to analyze the immune response, and the differential global gene and miRNA expression of tumor cells resistant to CAIX-based therapy. NCI RAID Initiative NSC 740833. § co-corresponding.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1563. doi:1538-7445.AM2012-1563

Abstract 836: Insulin-like growth factor-I receptor (IGF-IR) dowregulation in cisplatin-resistant human ovarian cancer cells

Introduction: Ovarian cancer is the most lethal of the gynecological malignancies and the 5th leading cause of cancer related deaths amongst women in the US. It is a chemotherapy-sensitive disease, and about 85% of patients respond to first line treatment with platinum-based chemotherapeutic agents. However, 15% of all patients present with primary platinum-resistant disease, and those with recurrent ovarian cancer develop resistance. Resistance to platinum-based drugs is a major obstacle in ovarian cancer treatment, and mechanisms of platinum resistance are not well understood. Insulin-like growth factor-1 receptor (IGF-1R) signaling has not only been implicated in ovarian cancer development, but has also been suggested to mediate platinum-resistance. The IGF-1R has been proposed as a potential molecular target for ovarian cancer, and clinical trials evaluating the use of small molecule kinase inhibitors or humanized monoclonal antibodies against the IGF-1R are currently under way. This study examines the role of IGF-1R in cisplatin resistance in human ovarian carcinoma. Experimental Procedures: Differential gene expression in two pairs of cisplatin-resistant cell lines (SKOV3-CisR and OVCAR-CisR) and their syngeneic cisplatin-sensitive counterpart (SKOV3 and OVCAR5, respectively) was analyzed using the Affymetrix GeneChip Human Genome U133 Plus 2.0 Array. IGF-1R mRNA transcripts and protein levels were verified via qRT-PCR and immunoblotting, respectively. Protein expression levels of IGF-1Rα and IGF-1Rα (immunoblotting) were correlated with cisplatin IC50 (XTT cell viability) in a panel of 12 ovarian cancer cell lines. IGF-1R was overexpressed (stable transfection) in SKOV3-CisR cells and the effect on cisplatin sensitivity evaluated. The effect of short-term cisplatin treatment on IGF-1Rα and IGF-1Rα protein levels was studied in SKOV3 and OVCAR5 cells. Results: Cisplatin-resistant SKOV3-CisR and OVCAR5-CisR cells exhibited 2-3 fold lower levels of IGF-1R mRNA transcripts compared to cisplatin-sensitive SKOV3 and OVCAR5 cells in the DNA microarray and via qRT-PCR. Correspondingly, decreased levels of IGF-1Rα and IGF-1Rα protein were found in immunoblot analyses. IGF-1Rα (r = −0.6118; p = 0.0345) and IGF-1Rα (r = −0.5839; p = 0.0462) protein levels and cisplatin IC50were negatively correlated. IGF-1R overexpression in SKOV3-CisR cells sensitized the cells to cisplatin, from 5 μg/ml (SKOV3-CisR) to 10-12 μg/ml (SKOV3-CisR-IGF-1R). Cisplatin induced a decrease in IGF-1Rα and IGF-1Rα levels after 24 and 48 hours treatment. Conclusions: Cisplatin treatment of ovarian cancer cells results in IGF-1R downregulation, which in turn decreases cisplatin sensitivity. Our results have important implications in the design of IGF-1R targeting strategies in clinical trials for ovarian cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 836. doi:1538-7445.AM2012-836

Abstract 4713: Detrimental effects of a histone deacetylase inhibitor on human lymphocytes

Background:Histone deacetylase inhibitors (HDACi) have been shown to increase cancer-testing and melanomasomal tumor antigen expression, which may allow their use as adjuvants to immunotherapy for melanoma. For this use, a key question is to test the effects of HDACi on lymphocytes compared to melanoma cells. Methods: We tested the effects on cell viability, cell cycle, apoptosis and DNA damage of the pan-HDACi LBH589 on peripheral blood mononuclear cells (PBMC) from a healthy donor (HD), four patients with metastatic melanoma (MM), two previously established human melanoma cell lines (M229 and M370), and two bone marrow samples of patients with multiple myeloma previously treated with GM-CSF. In addition, phospho-flow cytometry was used to study the effects of the HDACi on intracellular signalling in lymphocytes with or without pulsing with IL2 (400IU) or IFNα (10,000). For some experiments, HD PBMC were genetically modified to express the T cell receptor (TCR) for the melanoma antigen MART-1 using retroviral transduction for testing in in vitro cytotoxicity assays. Results. In replicate experiments the 50% inhibition concentration (IC50) of LBH589 for PBMC was low (&lt; 20 nM) in comparison to the melanoma cells (&gt; 600 nM). LBH589 induced &gt; 20% (10 nM) and &gt; 40% (1-10 mM) apoptotic cell death demonstrated by double presence of a sub-G0/G1 peak and cleaved poly (ADP-ribose) polymerase (PARP) in PBMC samples, while it was &lt; 10% in melanoma cell lines at these same concentrations. In a DNA damage assay, there was around 2-fold increase in the phosphorylation of the histone variant H2A.X in HD PBMC at 1 nM, while it required 10 nM for the similar effect in the melanoma cell line M229. However, the phosphorylation of H2A.X in PBMCs of three patients with MM (1 nM LBH589) was slightly inhibited. The pH2A.X of the other cell line and one of the MM patients was a 1.5- fold increase. The maximal effects on signaling pathways were seen after 30 minutes of treatment. LBH589 slightly inhibited phosphorylation of STATs 1, 3, 5 and 6 and MAPK proteins (p38, ERK), p53, cyclin D3 and histone H3 in flow gated B and T cells from the HD. On the contrary, the same phosphoproteins were activated up to six times higher in the MM patient samples and in a bone marrow sample. Conclusions. The HDACi LBH589 induced cytotoxic effects at nanomolar concentrations on human lymphocytes and altered key signaling pathways involved in lymphocyte activation. These effects are at lower concentrations than the antitumor activity in melanoma in vitro, resulting in an adverse therapeutic window. Therefore, LBH589 should be used with caution if intended to sensitize melanoma to immunotherapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4713. doi:1538-7445.AM2012-4713

Preexisting MEK1 exon 3 mutations in V600E/KBRAF melanomas do not confer resistance to BRAF inhibitors

BRAF inhibitors (BRAFi) induce antitumor responses in nearly 60% of patients with advanced V600E/KBRAF melanomas. Somatic activating MEK1 mutations are thought to be rare in melanomas, but their potential concurrence with V600E/KBRAF may be selected for by BRAFi. We sequenced MEK1/2 exon 3 in melanomas at baseline and upon disease progression. Of 31 baseline V600E/KBRAF melanomas, 5 (16%) carried concurrent somatic BRAF/MEK1 activating mutations. Three of 5 patients with BRAF/MEK1 double-mutant baseline melanomas showed objective tumor responses, consistent with the overall 60% frequency. No MEK1 mutation was found in disease progression melanomas, except when it was already identified at baseline. MEK1-mutant expression in V600E/KBRAF melanoma cell lines resulted in no significant alterations in p-ERK1/2 levels or growth-inhibitory sensitivities to BRAFi, MEK1/2 inhibitor (MEKi), or their combination. Thus, activating MEK1 exon 3 mutations identified herein and concurrent with V600E/KBRAF do not cause BRAFi resistance in melanoma.

SIGNIFICANCE

As BRAF inhibitors gain widespread use for treatment of advanced melanoma, biomarkers for drug sensitivity or resistance are urgently needed. We identify here concurrent activating mutations in BRAF and MEK1 in melanomas and show that the presence of a downstream mutation in MEK1 does not necessarily make BRAF–mutant melanomas resistant to BRAF inhibitors.

RAS mutations in cutaneous squamous-cell carcinomas in patients treated with BRAF inhibitors

BACKGROUND

Cutaneous squamous-cell carcinomas and keratoacanthomas are common findings in patients treated with BRAF inhibitors.

METHODS

We performed a molecular analysis to identify oncogenic mutations (HRAS, KRAS, NRAS, CDKN2A, and TP53) in the lesions from patients treated with the BRAF inhibitor vemurafenib. An analysis of an independent validation set and functional studies with BRAF inhibitors in the presence of the prevalent RAS mutation was also performed.

RESULTS

Among 21 tumor samples, 13 had RAS mutations (12 in HRAS). In a validation set of 14 samples, 8 had RAS mutations (4 in HRAS). Thus, 60% (21 of 35) of the specimens harbored RAS mutations, the most prevalent being HRAS Q61L. Increased proliferation of HRAS Q61L-mutant cell lines exposed to vemurafenib was associated with mitogen-activated protein kinase (MAPK)-pathway signaling and activation of ERK-mediated transcription. In a mouse model of HRAS Q61L-mediated skin carcinogenesis, the vemurafenib analogue PLX4720 was not an initiator or a promoter of carcinogenesis but accelerated growth of the lesions harboring HRAS mutations, and this growth was blocked by concomitant treatment with a MEK inhibitor.

CONCLUSIONS

Mutations in RAS, particularly HRAS, are frequent in cutaneous squamous-cell carcinomas and keratoacanthomas that develop in patients treated with vemurafenib. The molecular mechanism is consistent with the paradoxical activation of MAPK signaling and leads to accelerated growth of these lesions. (Funded by Hoffmann-La Roche and others; ClinicalTrials.gov numbers, NCT00405587, NCT00949702, NCT01001299, and NCT01006980.).

Decitabine immunosensitizes human gliomas to NY-ESO-1 specific T lymphocyte targeting through the Fas/Fas ligand pathway

Background

The lack of effective treatments for gliomas makes them a significant health problem and highlights the need for the development of novel and innovative treatment approaches. Immunotherapy is an appealing strategy because of the potential ability for immune cells to traffic to and destroy infiltrating tumor cells. However, the absence of well-characterized, highly immunogenic tumor-rejection antigens (TRA) in gliomas has limited the implementation of targeted immune-based therapies.

Methods

We hypothesized that treatment with the demethylating agent, decitabine, would upregulate the expression of TRA on tumor cells, thereby facilitating enhanced surveillance by TRA-specific T cells.

Results and Discussion

Treatment of human glioma cells with decitabine increased the expression of NY-ESO-1 and other well characterized cancer testes antigens. The upregulation of NY-ESO-1 made these tumors susceptible to NY-ESO-1-specific T-cell recognition and lysis. Interestingly, decitabine treatment of T98 glioma cells also sensitized them to Fas-dependent apoptosis with an agonistic antibody, while a Fas blocking antibody could largely prevent the enhanced functional recognition by NY-ESO-1 specific T cells. Thus, decitabine treatment transformed a non-immunogenic glioma cell into an immunogenic target that was efficiently recognized by NY-ESO-1--specific T cells.

Conclusions

Such data supports the hypothesis that agents which alter epigenetic cellular processes may "immunosensitize" tumor cells to tumor-specific T cell-mediated lysis.

Abstract A65: Improved immunological responses against melanoma in vivo with T lymphocyte adoptive cell therapy coupled with targeted inhibition of mutated and activated BRAF

Vemurafenib blocks activated BRAF with V600E driver mutation and induces unprecedented high response rates in patients with metastatic melanoma. However, most patients have response durations limited to only several months. Conversely, immunotherapy based on adoptive transfer of T cells has induced low frequency, but highly durable tumor responses. We previously reported (Clin Cancer Res. 16(24), 2010) that T lymphocytes exposed to high concentrations of vemurafenib had preserved viability and function, providing a compelling rationale for a combined targeted drug/immunotherapy approach.

We first established an implantable murine melanoma cell line driven by the V600E BRAF oncogene (SM1) from a spontaneously arising melanoma in transgenic mice harboring the V600E BRAF mutation under the control of tyrosinase promoter. SM1 cells exposed to vemurafenib had partial in vitro sensitivity (IC50 of 14 uM) resulting from inhibition of MAPK pathway signaling (as demonstrated by Immunoblotting), while murine lymphocytes were spared. In vitro assays indicated that SM1 cells undergo apoptosis and cell cycle arrest at G1 phase in the presence of vemurafenib. Mice implanted with SM1 tumors responded significantly with daily i.p. injection of vemurafenib, confirming its efficacy in vivo. We then tested the combination of vemurafenib and immunotherapy in vivo using two models of adoptive cell transfer (ACT) therapy. OT-1 T cell receptor-expressing lymphocytes targeting ovalbumin (OVA) present in SM1-OVA tumors or pmel-1 lymphocytes targeting the melanoma-associated-antigen gp100 (endogenously expressed by SM1) combined with daily i.p. injections of vemurafenib resulted in superior antitumor responses compared to either therapy alone. We then quantified the adoptively transferred T cells in spleen and tumor biopsies by tissue immunostaining. There were no significant differences in numbers of T cells infiltrating the tumors with or without vemurafenib. Further analysis with two different molecular imaging-based in vivo T cell tracking (1-Luciferin bioluminescence and 2-Positron Emission Tomography with dFAC tracer) confirmed that vemurafenib did not significantly alter the expansion, distribution or tumor accumulation of the adoptively transferred T cells. Also, vemurafenib did not alter SM1 antigen presentation as demonstrated by lack of significant differences in gp100 expression and MHC-I levels in SM1, as well as, in vivo cytotoxic activity of adoptively transferred cells against their cognate antigen. We then performed immunophenotypic analysis of transferred T cells. Vemurafenib skewed these cells towards a phenotype resembling central memory T cells, a favorable characteristic for superior and prolonged tumor control. Further functional analysis of tumor infiltrating lymphocytes indicated increased interferon-gamma secretion as assayed by intracellular staining and FACS.

In conclusion, our data derived from two independent models combining BRAF targeted therapy and immunotherapy indicated favorable changes in T cell function/immunophenotype and support the testing of such combination in patients with BRAFV600 mutant metastatic melanoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr A65.

A clinical microchip for evaluation of single immune cells reveals high functional heterogeneity in phenotypically similar T cells

Cellular immunity has an inherent high level of functional heterogeneity. Capturing the full spectrum of these functions requires analysis of large numbers of effector molecules from single cells. We report a microfluidic platform designed for highly multiplexed (more than ten proteins), reliable, sample-efficient (∼1 × 10(4) cells) and quantitative measurements of secreted proteins from single cells. We validated the platform by assessment of multiple inflammatory cytokines from lipopolysaccharide (LPS)-stimulated human macrophages and comparison to standard immunotechnologies. We applied the platform toward the ex vivo quantification of T cell polyfunctional diversity via the simultaneous measurement of a dozen effector molecules secreted from tumor antigen-specific cytotoxic T lymphocytes (CTLs) that were actively responding to tumor and compared against a cohort of healthy donor controls. We observed profound, yet focused, functional heterogeneity in active tumor antigen-specific CTLs, with the major functional phenotypes quantitatively identified. The platform represents a new and informative tool for immune monitoring and clinical assessment.

CTLA4 blockade induces frequent tumor infiltration by activated lymphocytes regardless of clinical responses in humans

BACKGROUND

CTLA4 blocking monoclonal antibodies provide durable clinical benefit in a subset of patients with advanced melanoma mediated by intratumoral lymphocytic infiltrates. A key question is defining whether the intratumoral infiltration (ITI) is a differentiating factor between patients with and without tumor responses.

METHODS

Paired baseline and postdosing tumor biopsy specimens were prospectively collected from 19 patients with metastatic melanoma, including 3 patients with an objective tumor response, receiving the anti-CTLA4 antibody tremelimumab within a clinical trial with primary endpoint of quantitating CD8(+) cytotoxic T-lymphocyte (CTL) infiltration in tumors. Samples were analyzed for cell density by automated imaging capture and further characterized for functional lymphocyte properties by assessing the cell activation markers HLA-DR and CD45RO, the cell proliferation marker Ki67, and the regulatory T-cell marker FOXP3.

RESULTS

There was a highly significant increase in ITI by CD8(+) cells in biopsy samples taken after tremelimumab treatment. This included increases between 1-fold and 100-fold changes in 14 of 18 evaluable cases regardless of clinical tumor response or progression. There was no difference between the absolute number, location, or cell density of infiltrating cells between clinical responders and patients with nonresponding lesions that showed acquired intratumoral infiltrates. There were similar levels of expression of T-cell activation markers (CD45RO, HLA-DR) in both groups and no difference in markers for cell replication (Ki67) or the suppressor cell marker FOXP3.

CONCLUSION

CTLA4 blockade induces frequent increases in ITI by T cells despite which only a minority of patients have objective tumor responses.