Andrea M. H. Towlerton

Epigenetic modulation to enable antigen-specific T-cell therapy of colorectal cancer

Development of specific immunotherapy for colorectal cancer (CRC) will require identification of antigens selectively or exclusively expressed on CRC cells and strategies to induce and enhance immune responses against these antigenic targets. Cancer-testis (C-T) antigens are proving to be excellent targets for immunotherapy of solid tumors such as melanoma, but their clinical utility for treatment of CRC has to date been limited by their infrequent expression in CRC cells. Here we report that the hypomethylating agent 5-aza-2′-deoxycytidine (DAC) induces expression of NY-ESO-1 and other C-T genes in CRC cells both in vitro and in vivo in a dose-dependent manner but has negligible effects on the expression of C-T genes in normal nontransformed cells such as fibroblasts. The induction by DAC of NY-ESO-1 expression in CRC cells persists over 100 days after DAC exposure and is associated with increased levels of NY-ESO-1 protein. CRC cells exposed to DAC at concentrations that can be readily achieved in vivo are rendered susceptible to major histocompatibility complex-restricted recognition by CD8+ NY-ESO-1-specific T cells. We also demonstrate that retroviral transduction of polyclonal peripheral blood T cells from a metastatic CRC patient with the T-cell receptor &agr;-chain and &bgr;-chain genes encoding a human leukocyte antigen-A2-restricted, NY-ESO-1157-165-specific T-cell receptor can be used to generate both CD8+ and CD4+ NY-ESO-1157-165-specific T cells that selectively recognize DAC-treated CRC but not nontransformed cells. Collectively, these results suggest that the combination of epigenetic modulation and adoptive transfer of genetically engineered T lymphocytes may enable specific immunotherapy for CRC.

Immune escape from NY-ESO-1-specific T-cell therapy via loss of heterozygosity in the MHC.

Adoptive immunotherapy of tumors with T cells specific for the cancer-testis antigen NY-ESO-1 has shown great promise in preclinical models and in early stage clinical trials. Tumor persistence or recurrence after NY-ESO-1-specific therapy occurs, however, and the mechanisms of recurrence remain poorly defined. In a murine xenograft model of NY-ESO-1+ multiple myeloma, we observed tumor recurrence after adoptive transfer of CD8+ T cells genetically redirected to the prototypic NY-ESO-1157-165 peptide presented by HLA-A*02:01. Analysis of the myeloma cells that had escaped from T-cell control revealed intact expression of NY-ESO-1 and B2M, but selective, complete loss of HLA-A*02:01 expression from the cell surface. Loss of heterozygosity (LOH) in the major histocompatibility complex (MHC) involving the HLA-A locus was identified in the tumor cells, and further analysis revealed selective loss of the allele encoding HLA-A*02:01. Although LOH involving the MHC has not been described in myeloma patients with persistent or recurrent disease after immune therapies such as allogeneic hematopoietic cell transplantation (HCT), it has been described in patients with acute myelogenous leukemia who relapsed after allogeneic HCT. These results suggest that MHC loss should be evaluated in patients with myeloma and other cancers who relapse after adoptive NY-ESO-1-specific T-cell therapy.

Phenotypic and Transcriptional Fidelity of Patient-Derived Colon Cancer Xenografts in Immune-Deficient Mice

Xenografts of human colorectal cancer (CRC) in immune-deficient mice have great potential for accelerating the study of tumor biology and therapy. We evaluated xenografts established in NOD/scid/IL2Rγ-null mice from the primary or metastatic tumors of 27 patients with CRC to estimate their capacity for expanding tumor cells for in vitro studies and to assess how faithfully they recapitulated the transcriptional profile of their parental tumors. RNA-seq analysis of parental human CRC tumors and their derivative xenografts demonstrated that reproducible transcriptional changes characterize the human tumor to murine xenograft transition. In most but not all cases, the human stroma, vasculature, and hematopoietic elements were systematically replaced by murine analogues while the carcinoma component persisted. Once established as xenografts, human CRC cells that could be propagated by serial transplantation remained transcriptionally stable. Three histologically atypical xenografts, established from patients with peritoneal metastases, contained abundant human stromal elements and blood vessels in addition to human tumor cells. The transcriptomes of these mixed tumor/stromal xenografts did not closely resemble those of their parental tumors, and attempts to propagate such xenografts by serial transplantation were unsuccessful. Stable expression of numerous genes previously identified as high priority targets for immunotherapy was observed in most xenograft lineages. Aberrant expression in CRC cells of human genes that are normally only expressed in hematopoietic cells was also observed. Our results suggest that human CRC cells expanded in murine xenografts have great utility for studies of tumor immunobiology and targeted therapies such as immunotherapy but also identify potential limitations.

High-throughput sequencing of the B-cell receptor in African Burkitt lymphoma reveals clues to pathogenesis

Burkitt lymphoma (BL), the most common pediatric cancer in sub-Saharan Africa, is a malignancy of antigen-experienced B lymphocytes. High-throughput sequencing (HTS) of the immunoglobulin heavy (IGH) and light chain (IGK/IGL) loci was performed on genomic DNA from 51 primary BL tumors: 19 from Uganda and 32 from Ghana. Reverse transcription polymerase chain reaction analysis and tumor RNA sequencing (RNAseq) was performed on the Ugandan tumors to confirm and extend the findings from the HTS of tumor DNA. Clonal IGH and IGK/IGL rearrangements were identified in 41 and 46 tumors, respectively. Evidence for rearrangement of the second IGH allele was observed in only 6 of 41 tumor samples with a clonal IGH rearrangement, suggesting that the normal process of biallelic IGHD to IGHJ diversity-joining (DJ) rearrangement is often disrupted in BL progenitor cells. Most tumors, including those with a sole dominant, nonexpressed DJ rearrangement, contained many IGH and IGK/IGL sequences that differed from the dominant rearrangement by < 10 nucleotides, suggesting that the target of ongoing mutagenesis of these loci in BL tumor cells is not limited to expressed alleles. IGHV usage in both BL tumor cohorts revealed enrichment for IGHV genes that are infrequently used in memory B cells from healthy subjects. Analysis of publicly available DNA sequencing and RNAseq data revealed that these same IGHV genes were overrepresented in dominant tumor-associated IGH rearrangements in several independent BL tumor cohorts. These data suggest that BL derives from an abnormal B-cell progenitor and that aberrant mutational processes are active on the immunoglobulin loci in BL cells.

A Multi-center Phase I Trial of Ipilimumab in Patients with Myelodysplastic Syndromes following Hypomethylating Agent Failure

Purpose: After failure of hypomethylating agents (HMA), patients with myelodysplastic syndromes (MDS) have dismal survival and no approved treatment options. Patients and Methods: We conducted a phase 1b investigator-initiated trial of ipilimumab in patients with higher risk MDS who have failed HMAs. Patients received monotherapy at two dose levels (DL; 3 and 10 mg/kg) with an induction followed by a maintenance phase. Toxicities and responses were evaluated with CTCAE.4 and IWG-2006 criteria, respectively. We also performed immunologic assays and T-cell receptor sequencing on serial samples. Results: Twenty-nine patients from 7 centers were enrolled. In the initial DL1 (3 mg), 3 of 6 patients experienced grade 2–4 immune-related adverse events (IRAE) that were reversible with drug discontinuation and/or systemic steroids. In DL2, 4 of 5 patients experienced grade 2 or higher IRAE; thus, DL1 (3 mg/kg) was expanded with no grade 2–4 IRAEs reported in 18 additional patients. Best responses included marrow complete response (mCR) in one patient (3.4%). Prolonged stable disease (PSD) for ≥46 weeks occurred in 7 patients (24% of entire cohort and 29% of those treated with 3 mg/kg dose), including 3 patients with more than a year of SD. Five patients underwent allografting without excessive toxicity. Median survival for the group was 294 days (95% CI, 240–671+). Patients who achieved PSD or mCR had significantly higher frequency of T cells expressing ICOS (inducible T-cell co-stimulator). Conclusions: Our findings suggest that ipilimumab dosed at 3 mg/kg in patients with MDS after HMA failure is safe but has limited efficacy as a monotherapy. Increased frequency of ICOS-expressing T cells might predict clinical benefit. Clin Cancer Res; 24(15); 3519–27. ©2018 AACR.

T-Cell Receptor Sequencing of Kaposi Sarcoma Tumors to Identify Candidate Tumor-Reactive T Cells

Abstract 60Background:Development of Kaposi sarcoma (KS) is strongly associated with immune dysfunction in the context of HIV infection, but little is known about T-lymphocyte responses against KS tumor cells or human herpesvirus-8, the viral cause of KS. Increasing evidence suggests that treatment response in KS is attributable in part to an antitumor immune response that is mediated by tumor-infiltrating lymphocytes (TIL). The aim of this work was to identify TIL characteristics that are associated with tumor regression in patients with KS who were treated with antiretroviral therapy and chemotherapy as well as to identify a molecular signature of response.Methods:High-throughput sequencing of the T-cell receptor β chain (TRB) was used to define the repertoire of T cells that infiltrate up to two pretreatment and two post-treatment KS tumors and matched normal skin obtained from HIV-infected adults with KS who received care at the Uganda Cancer Institute. We compared TRB repertoire in serially collected...

High-throughput sequencing reveals novel features of immunoglobulin gene rearrangements in Burkitt lymphoma

TO THE EDITOR: We thank Ralf Kuppers for his interest in our article[1][1] and for his thoughtful commentary.[2][2] We address each of the points he raises below. First, Kuppers claims that, in contrast to what has been demonstrated in mice,[3][3] not all normal human B-cell progenitors undergo