Richard Eric Davis

Persistent antigen at vaccination sites induces tumor-specific CD8+ T cell sequestration, dysfunction and deletion

To understand why cancer vaccine–induced T cells often do not eradicate tumors, we studied immune responses in mice vaccinated with gp100 melanoma peptide in incomplete Freunds adjuvant (peptide/IFA), which is commonly used in clinical cancer vaccine trials. Peptide/IFA vaccination primed tumor-specific CD8+ T cells, which accumulated not in tumors but rather at the persisting, antigen-rich vaccination site. Once there, primed T cells became dysfunctional and underwent antigen-driven, interferon-γ (IFN-γ)- and Fas ligand (FasL)-mediated apoptosis, resulting in hyporesponsiveness to subsequent vaccination. Provision of CD40-specific antibody, Toll-like receptor 7 (TLR7) agonist and interleukin-2 (IL-2) reduced T cell apoptosis but did not prevent vaccination-site sequestration. A nonpersisting vaccine formulation shifted T cell localization toward tumors, inducing superior antitumor activity while reducing systemic T cell dysfunction and promoting memory formation. These data show that persisting vaccine depots can induce specific T cell sequestration, dysfunction and deletion at vaccination sites; short-lived formulations may overcome these limitations and result in greater therapeutic efficacy of peptide-based cancer vaccines.

ONCOGENIC BRAF(V600E) PROMOTES STROMAL CELL-MEDIATED IMMUNOSUPPRESSION VIA INDUCTION OF INTERLEUKIN-1 IN MELANOMA

Purpose: In this study, we assessed the specific role of BRAF(V600E) signaling in modulating the expression of immune regulatory genes in melanoma, in addition to analyzing downstream induction of immune suppression by primary human melanoma tumor-associated fibroblasts (TAF). Experimental Design: Primary human melanocytes and melanoma cell lines were transduced to express WT or V600E forms of BRAF, followed by gene expression analysis. The BRAF(V600E) inhibitor vemurafenib was used to confirm targets in BRAF(V600E)-positive melanoma cell lines and in tumors from melanoma patients undergoing inhibitor treatment. TAF lines generated from melanoma patient biopsies were tested for their ability to inhibit the function of tumor antigen-specific T cells, before and following treatment with BRAF(V600E)-upregulated immune modulators. Transcriptional analysis of treated TAFs was conducted to identify potential mediators of T-cell suppression. Results: Expression of BRAF(V600E) induced transcription of interleukin 1 alpha (IL-1α) and IL-1β in melanocytes and melanoma cell lines. Further, vemurafenib reduced the expression of IL-1 protein in melanoma cell lines and most notably in human tumor biopsies from 11 of 12 melanoma patients undergoing inhibitor treatment. Treatment of melanoma-patient–derived TAFs with IL-1α/β significantly enhanced their ability to suppress the proliferation and function of melanoma-specific cytotoxic T cells, and this inhibition was partially attributable to upregulation by IL-1 of COX-2 and the PD-1 ligands PD-L1 and PD-L2 in TAFs. Conclusions: This study reveals a novel mechanism of immune suppression sensitive to BRAF(V600E) inhibition, and indicates that clinical blockade of IL-1 may benefit patients with BRAF wild-type tumors and potentially synergize with immunotherapeutic interventions. Clin Cancer Res; 18(19); 5329–40. ©2012 AACR.

Double hit lymphoma: The MD Anderson Cancer Center clinical experience

We report our experience with 129 cases of double hit lymphoma (DHL), defined as B‐cell lymphoma with translocations and/or extra signals involving MYC plus BCL2 and/or BCL6. All cases were reviewed for histopathological classification. Median age was 62 years (range, 18–85), 84% of patients had advanced‐stage disease, and 87% had an International Prognostic Index score ≥2. Fourteen patients (11%) had a history of low‐grade follicular lymphoma. MYC translocation was present in 81%, and extra signals of MYC in 25% of patients. IGH‐BCL2 translocation was present in 84% and extra signals of BCL2 in 12% of patients. Two‐year event‐free survival (EFS) rates in all patients and patients who received R‐CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone), R‐EPOCH (rituximab, etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin), and R‐HyperCVAD/MA (rituximab, hyperfractionated cyclophosphamide, vincristine, doxorubicin, dexamethasone, alternating with cytarabine plus methotrexate) were 33%, 25%, 67% and 32%, respectively. In patients achieving complete response with initial therapy (n = 71), 2‐year EFS rates in patients who did (n = 23) or did not (n = 48) receive frontline stem cell transplantation were 68% and 53%, respectively (P = 0·155). The cumulative incidence of central nervous system involvement was 13% at 3 years. Multivariate analysis identified performance status ≥2 and bone marrow involvement as independent adverse prognostic factors for EFS and OS. Further research is needed to identify predictive and/or targetable biological markers and novel therapeutic approaches for DHL patients.

Reciprocal leukemia-stroma VCAM-1/VLA-4-dependent activation of NF-κB mediates chemoresistance

Leukemia cells are protected from chemotherapy-induced apoptosis by their interactions with bone marrow mesenchymal stromal cells (BM-MSCs). Yet the underlying mechanisms associated with this protective effect remain unclear. Genome-wide gene expression profiling of BM-MSCs revealed that coculture with leukemia cells upregulated the transcription of genes associated with nuclear factor (NF)-κB signaling. Moreover, primary BM-MSCs from leukemia patients expressed NF-κB target genes at higher levels than their normal BM-MSC counterparts. The blockade of NF-κB activation via chemical agents or the overexpression of the mutant form of inhibitor κB-α (IκBα) in BM-MSCs markedly reduced the stromal-mediated drug resistance in leukemia cells in vitro and in vivo. In particular, our unique in vivo model of human leukemia BM microenvironment illustrated a direct link between NF-κB activation and stromal-associated chemoprotection. Mechanistic in vitro studies revealed that the interaction between vascular cell adhesion molecule 1 (VCAM-1) and very late antigen-4 (VLA-4) played an integral role in the activation of NF-κB in the stromal and tumor cell compartments. Together, these results suggest that reciprocal NF-κB activation in BM-MSCs and leukemia cells is essential for promoting chemoresistance in the transformed cells, and targeting NF-κB or VLA-4/VCAM-1 signaling could be a clinically relevant mechanism to overcome stroma-mediated chemoresistance in BM-resident leukemia cells.

Protein arginine methyltransferase 5 is essential for growth of lung cancer cells.

PRMT5 (protein arginine methyltransferase 5) is an enzyme that catalyses transfer of methyl groups from S-adenosyl methionine to the arginine residues of histones or non-histone proteins and is involved in a variety of cellular processes. Although it is highly expressed in some tumours, its direct role in cancer growth has not been fully investigated. In the present study, in human lung tissue samples we found that PRMT5 was highly expressed in lung cancer cells, whereas its expression was not detectable in benign lung tissues. Silencing PRMT5 expression strongly inhibited proliferation of lung adenocarcinoma A549 cells in tissue culture, and silencing PRMT5 expression in A549 cells also abolished growth of lung A549 xenografts in mice. In vitro and in vivo studies showed that the cell growth arrest induced by loss of PRMT5 expression was partially attributable to down-regulation of fibroblast growth factor receptor signalling. These results suggest that PRMT5 and its methyltransferase activity is essential for proliferation of lung cancer cells and may serve as a novel target for the treatment of lung cancer.

Connective tissue growth factor regulates adipocyte differentiation of mesenchymal stromal cells and facilitates leukemia bone marrow engraftment

Mesenchymal stromal cells (MSCs) are a major component of the leukemia bone marrow (BM) microenvironment. Connective tissue growth factor (CTGF) is highly expressed in MSCs, but its role in the BM stroma is unknown. Therefore, we knocked down (KD) CTGF expression in human BM-derived MSCs by CTGF short hairpin RNA. CTGF KD MSCs exhibited fivefold lower proliferation compared with control MSCs and had markedly fewer S-phase cells. CTGF KD MSCs differentiated into adipocytes at a sixfold higher rate than controls in vitro and in vivo. To study the effect of CTGF on engraftment of leukemia cells into BM, an in vivo model of humanized extramedullary BM (EXM-BM) was developed in NOD/SCID/IL-2rg(null) mice. Transplanted Nalm-6 or Molm-13 human leukemia cells engrafted at a threefold higher rate in adipocyte-rich CTGF KD MSC-derived EXM-BM than in control EXM-BM. Leptin was found to be highly expressed in CTGF KD EXM-BM and in BM samples of patients with acute myeloid and acute lymphoblastic leukemia, whereas it was not expressed in normal controls. Given the established role of the leptin receptor in leukemia cells, the data suggest an important role of CTGF in MSC differentiation into adipocytes and of leptin in homing and progression of leukemia.

Effect of Long-term Storage in TRIzol on Microarray-Based Gene Expression Profiling

Background: Although TRIzol is widely used for preservation and isolation of RNA, there is suspicion that prolonged sample storage in TRIzol may affect array-based gene expression profiling (GEP) through premature termination during reverse transcription. Methods: GEP on Illumina arrays compared paired aliquots (cryopreserved or stored in TRIzol) of primary samples of multiple myeloma (MM) and acute myeloid leukemia (AML). Data were analyzed at the “probe level” (a single consensus value) or “bead level” (multiple measurements provided by individual beads). Results: TRIzol storage does not affect standard probe-level comparisons between sample groups: different preservation methods did not generate differentially expressed probes (DEP) within MM or AML sample groups, or substantially affect the many DEPs distinguishing between these groups. Differences were found by gene set enrichment analysis, but these were dismissible because of instability with permutation of sample labels, unbalanced restriction to TRIzol aliquots, inconsistency between MM and AML groups, and lack of biological plausibility. Bead-level comparisons found many DEPs within sample pairs, but most (73%) were <2-fold changed. There was no consistent evidence that TRIzol causes premature reverse transcription termination. Instead, a subset of DEPs were systematically due to increased signals in TRIzol-preserved samples from probes near the 5′ end of transcripts, suggesting better mRNA preservation with TRIzol. Conclusions: TRIzol preserves RNA quality well, without a deleterious effect on GEP. Samples stored frozen with and without TRIzol may be compared by GEP with only minor concern for systematic artifacts. Impact: The standard practice of prolonged sample storage in TRIzol is suitable for GEP. Cancer Epidemiol Biomarkers Prev; 19(10); 2445–52. ©2010 AACR.

Nonstereotyped Lymphoma B Cell Receptors Recognize Vimentin as a Shared Autoantigen

Ag activation of the BCR may play a role in the pathogenesis of human follicular lymphoma (FL) and other B cell malignancies. However, the nature of the Ag(s) recognized by tumor BCRs has not been well studied. In this study, we used unbiased approaches to demonstrate that 42 (19.35%) of 217 tested FL Igs recognized vimentin as a shared autoantigen. The epitope was localized to the N-terminal region of vimentin for all vimentin-reactive tumor Igs. We confirmed specific binding to vimentin by using recombinant vimentin and by performing competitive inhibition studies. Furthermore, using indirect immunofluorescence staining, we showed that the vimentin-reactive tumor Igs colocalized with an anti-vimentin mAb in HEp-2 cells. The reactivity to N-terminal vimentin of IgG FL Igs was significantly higher than that of IgM FL Igs (30.4 versus 10%; p = 0.0022). However, vimentin-reactive FL Igs did not share CDR3 motifs and were not homologous. Vimentin was expressed in the T cell–rich regions of FL, suggesting that vimentin is available for binding with tumor BCRs within the tumor microenvironment. Vimentin was also frequently recognized by mantle cell lymphoma and multiple myeloma Igs. Our results demonstrate that vimentin is a shared autoantigen recognized by nonstereotyped FL BCRs and by the Igs of mantle cell lymphoma and multiple myeloma and suggest that vimentin may play a role in the pathogenesis of multiple B cell malignancies. These findings may lead to a better understanding of the biology and natural history of FL and other B cell malignancies.

The p44/wdr77-dependent cellular proliferation process during lung development is reactivated in lung cancer

During lung development, cells proliferate for a defined length of time before they begin to differentiate. Factors that control this proliferative process and how this growth process is related to lung cancer are currently unknown. Here, we found that the WD40-containing protein (p44/wdr77) was expressed in growing epithelial cells at the early stages of lung development. In contrast, p44/wdr77 expression was diminished in fully differentiated epithelial cells in the adult lung. Loss of p44/wdr77 gene expression led to cell growth arrest and differentiation. Re-expression of p44/wdr77 caused terminally differentiated cells to re-enter the cell cycle. Our findings suggest that p44/wdr77 is essential and sufficient for proliferation of lung epithelial cells. P44/Wdr77 was re-expressed in lung cancer, and silencing p44/wdr77 expression strongly inhibited growth of lung adenocarcinoma cells in tissue culture and abolished growth of lung adenocarcinoma tumor xenografts in mice. The growth arrest induced by loss of p44/wdr77 expression was partially through the p21–Rb signaling. Our results suggest that p44/wdr77 controls cellular proliferation during lung development, and this growth process is reactivated during lung tumorigenesis.

Pre-BCR signaling in precursor B-cell acute lymphoblastic leukemia regulates PI3K/AKT, FOXO1 and MYC, and can be targeted by SYK inhibition

Precursor-B-cell receptor (pre-BCR) signaling and spleen tyrosine kinase (SYK) recently were introduced as therapeutic targets for patients with B-cell acute lymphoblastic leukemia (B-ALL), but the importance of this pathway in B-ALL subsets and mechanism of downstream signaling have not fully been elucidated. Here, we provide new detailed insight into the mechanism of pre-BCR signaling in B-ALL. We compared the effects of pharmacological and genetic disruption of pre-BCR signaling in vitro and in mouse models for B-ALL, demonstrating exquisite dependency of pre-BCR+ B-ALL, but not other B-ALL subsets, on this signaling pathway. We demonstrate that SYK, PI3K/AKT, FOXO1 and MYC are important downstream mediators of pre-BCR signaling in B-ALL. Furthermore, we define a characteristic immune phenotype and gene expression signature of pre-BCR+ ALL to distinguish them from other B-ALL subsets. These data provide comprehensive new insight into pre-BCR signaling in B-ALL and corroborate pre-BCR signaling and SYK as promising new therapeutic targets in pre-BCR+ B-ALL.