Yifang Liu

Priming of protective T cell responses against virus-induced tumors in mice with human immune system components

Many pathogens that cause human disease infect only humans. To identify the mechanisms of immune protection against these pathogens and also to evaluate promising vaccine candidates, a small animal model would be desirable. We demonstrate that primary T cell responses in mice with reconstituted human immune system components control infection with the oncogenic and persistent Epstein-Barr virus (EBV). These cytotoxic and interferon-γ–producing T cell responses were human leukocyte antigen (HLA) restricted and specific for EBV-derived peptides. In HLA-A2 transgenic animals and similar to human EBV carriers, T cell responses against lytic EBV antigens dominated over recognition of latent EBV antigens. T cell depletion resulted in elevated viral loads and emergence of EBV-associated lymphoproliferative disease. Both loss of CD4+ and CD8+ T cells abolished immune control. Therefore, this mouse model recapitulates features of symptomatic primary EBV infection and generates T cell–mediated immune control that resists oncogenic transformation.

Decreased differentiation of erythroid cells exacerbates ineffective erythropoiesis in β-thalassemia

In beta-thalassemia, the mechanism driving ineffective erythropoiesis (IE) is insufficiently understood. We analyzed mice affected by beta-thalassemia and observed, unexpectedly, a relatively small increase in apoptosis of their erythroid cells compared with healthy mice. Therefore, we sought to determine whether IE could also be characterized by limited erythroid cell differentiation. In thalassemic mice, we observed that a greater than normal percentage of erythroid cells was in S-phase, exhibiting an erythroblast-like morphology. Thalassemic cells were associated with expression of cell cycle-promoting genes such as EpoR, Jak2, Cyclin-A, Cdk2, and Ki-67 and the antiapoptotic protein Bcl-X(L). The cells also differentiated less than normal erythroid ones in vitro. To investigate whether Jak2 could be responsible for the limited cell differentiation, we administered a Jak2 inhibitor, TG101209, to healthy and thalassemic mice. Exposure to TG101209 dramatically decreased the spleen size but also affected anemia. Although our data do not exclude a role for apoptosis in IE, we propose that expansion of the erythroid pool followed by limited cell differentiation exacerbates IE in thalassemia. In addition, these results suggest that use of Jak2 inhibitors has the potential to profoundly change the management of this disorder.

Flow sorting and exome sequencing reveal the oncogenome of primary Hodgkin and Reed-Sternberg cells

Classical Hodgkin lymphoma (cHL) is characterized by sparsely distributed Hodgkin and Reed-Sternberg (HRS) cells amid reactive host background, complicating the acquisition of neoplastic DNA without extensive background contamination. We overcame this limitation by using flow-sorted HRS and intratumor T cells and optimized low-input exome sequencing of 10 patient samples to reveal alterations in genes involved in antigen presentation, chromosome integrity, transcriptional regulation, and ubiquitination. β-2-microglobulin (B2M) is the most commonly altered gene in HRS cells, with 7 of 10 cases having inactivating mutations that lead to loss of major histocompatibility complex class I (MHC-I) expression. Enforced wild-type B2M expression in a cHL cell line restored MHC-I expression. In an extended cohort of 145 patients, the absence of B2M protein in the HRS cells was associated with lower stage of disease, younger age at diagnosis, and better overall and progression-free survival. B2M-deficient cases encompassed most of the nodular sclerosis subtype cases and only a minority of mixed cellularity cases, suggesting that B2M deficiency determines the tumor microenvironment and may define a major subset of cHL that has more uniform clinical and morphologic features. In addition, we report previously unknown genetic alterations that may render selected patients sensitive to specific targeted therapies.

KSHV LANA inhibits TGF-beta signaling through epigenetic silencing of the TGF-beta type II receptor.

Signaling through the transforming growth factor-beta (TGF-beta) pathway results in growth inhibition and induction of apoptosis in various cell types. We show that this pathway is blocked in Kaposi sarcoma herpesvirus (KSHV)-infected primary effusion lymphoma through down-regulation of the TGF-beta type II receptor (TbetaRII) by epigenetic mechanisms. Our data also suggest that KSHV infection may result in lower expression of TbetaRII in Kaposi sarcoma and multicentric Castleman disease. KSHV-encoded LANA associates with the promoter of TbetaRII and leads to its methylation and to the deacetylation of proximal histones. Reestablishment of signaling through this pathway reduces viability of these cells, inferring that KSHV-mediated blockage of TGF-beta signaling plays a role in the establishment and progression of KSHV-associated neoplasia. These data suggest a mechanism whereby KSHV evades both the antiproliferative effects of TGF-beta signaling by silencing TbetaRII gene expression and immune recognition by suppressing TGF-beta-responsive immune cells through the elevated secretion of TGF-beta1.

Inherited human OX40 deficiency underlying classic Kaposi sarcoma of childhood

Human OX40 is necessary for robust CD4+ T cell memory and confers selective protective immunity against HHV-8 infection in endothelial cells.

Immunophenotypic analysis of the Kaposi sarcoma herpesvirus (KSHV; HHV-8)-infected B cells in HIV+ multicentric Castleman disease (MCD)

Aims:  Kaposi sarcoma herpesvirus (KSHV) is aetiologically related to Kaposi sarcoma, classical and extracavitary primary effusion lymphoma (PEL; EC‐PEL) and multicentric Castleman disease (MCD), entities preferentially occurring in HIV‐infected individuals. Characterization of HIV‐associated PELs/EC‐PELs suggests that the KSHV‐infected malignant cells originate from a pre‐terminal stage of B‐cell differentiation. However, only limited phenotypic studies have been performed on HIV+ MCD, including for PR domain containing 1 with zinc finger domain/B lymphocyte‐induced maturation protein 1 (PRDM1/BLIMP1), a key regulator of terminal B‐cell differentiation. The aim was to characterize KSHV‐infected cells in 17 cases of HIV+ MCD.

Accurately Assessing HER-2/neu Status in Needle Core Biopsies of Breast Cancer Patients in the Era of Neoadjuvant Therapy: Emerging Questions and Considerations Addressed

BackgroundEmerging data show that patients with operable, HER-2/neu overexpressed/amplified breast carcinomas have significantly better responses (more frequently obtaining pathologic complete response and greater percent disease-free survival) when treated with trastuzumab (Herceptin) simultaneously with neoadjuvant chemotherapy than with chemotherapy alone. With the increasing use of neoadjuvant therapies, clinicians require information on biomarkers including HER-2/neu status at the time of needle core biopsy. Concordance rates between fluorescence in situ hybridization (FISH)-determined HER-2/neu status on needle core biopsies and on subsequent excisional biopsies of the same tumor have not been well studied. Moreover, the practice of automatically performing (“reflexing”) 2+ immunohistochemical (IHC) staining needle core biopsies for FISH analysis on the same sample needs to be validated. In this study, we set out to (1) determine the accuracy of HER-2/neu status as determined by FISH on needle core biopsy material compared with FISH on the subsequent excisional biopsy of the same tumor with special consideration of IHC 2+staining cases and (2) determine the constancy of HER-2/neu status in pre-neoadjuvant and post-neoadjuvant chemotherapy-treated tumor in the form of needle core biopsy and excisional biopsy samples, respectively. Design100 patients whose needle core biopsies and subsequent excisional biopsy samples were pathologically evaluated at our institution were studied. For each patient, unstained sections from both specimens were prepared and used for IHC or FISH. IHC was carried out using the HercepTest kit (DAKO, Carpinteria, CA). Parallel unstained slides were used to carry out FISH (dual probe, Vysis). Statistical analyses were carried out on the resulting data generated after interpretation. ResultsThe concordance rate between FISH results determined on the needle core biopsy and subsequent excisional biopsy of the same tumor was 86% (κ=0.56, P=2×10−8). If equivocal FISH cases (≥1.8 to ≤2.2 amplification ratio) in a needle core biopsy or excisional biopsy specimen or both, were excluded, the concordance rate increased to 95% (κ coefficient=0.86, P=2×10−15). Fourteen of 100 (14%) cases showed 2+ IHC staining in the needle core biopsy specimen with good concordance of FISH-determined HER-2/neu status between the needle core biopsy and excisional biopsy specimens (79% agreement and κ=0.512, P=0.05). Nine, 3, and 2 cases of the 14 cases were amplified, equivocal, and negative on the excisional biopsy specimens, respectively. Of the 15 patients who received neoadjuvant chemotherapy, 93% and 87% had no change in HER-2/neu status as determined by IHC or FISH, respectively, in the excisional biopsy specimen when compared with that determined on the prior core biopsy sample. ConclusionsExcellent overall concordance was achieved between FISH-determined HER-2/neu status on the needle core biopsy and that determined on the subsequent excisional biopsy of the same tumor. These results suggest that intratumoral heterogeneity of HER-2/neu assessed by FISH is not a significant confounding factor when analyzing smaller sized samples. Furthermore, 79% of 2+IHC staining needle core biopsy cases showed concordant FISH results in the needle core biopsy and subsequent excisional biopsy specimens. Our results show good concordance, however, larger cohorts need to be studied to verify this finding. HER-2/neu status remains unchanged in the majority of cases when comparing pre-neoadjuvant and post-neoadjuvant chemotherapy-treated specimens.

Epigenetic Down-Regulation of the Tumor Suppressor Gene PRDM1/Blimp-1 in Diffuse Large B Cell Lymphomas: A Potential Role of the MicroRNA Let-7

PRDM1/Blimp-1, a master regulator for B cell terminal differentiation, is a putative tumor suppressor in diffuse large B cell lymphomas (DLBCL). Inactivating mutations of PRDM1 have been previously identified in a subset of nongerminal center B cell-like (GCB) DLBCL. We investigated the presence of alternative mechanisms of down-regulating PRDM1 in a cohort of 25 primary DLBCL and six DLBCL cell lines. While some DLBCL, predominantly the GCB-type, showed low levels of both PRDM1alpha mRNA and protein, presumably as a result of direct transcription repression, discordant expressions between the two were identified in a subset of DLBCL without PRDM1 mutations, the primarily non-GCB type, consistent with translational down-regulation. This subset of DLBCL exhibits relatively high PRDM1alpha mRNA levels but low levels of PRDM1. Data obtained from expression analysis, luciferase reporter assays, and transfection experiments support a role of targeting of PRDM1 by microRNA let-7 family in mediating this down-regulation. Let-7, in particular let-7b, is overexpressed in DLBCL relative to normal GCB cells, suggesting that it is deregulated. Thus, abnormal epigenetic down-regulation of PRDM1 by let-7 and other microRNAs may represent an alternative mechanism of reducing normal PRDM1 function in a subset of DLBCL with relatively high PRDM1alpha mRNA expression and unmutated PRDM1. These findings provide further evidence for an important role of impairment of terminal B cell differentiation in DLBCL pathogenesis.

MYB-NFIB gene fusion in adenoid cystic carcinoma of the breast with special focus paid to the solid variant with basaloid features

Adenoid cystic carcinomas (ACCs) from various anatomical sites harbor a translocation t(6;9)(q22-23;p23-24), resulting in MYB-NFIB gene fusion. This gene fusion is not well studied in mammary ACCs, and there are no studies examining this abnormality in solid variant of ACC with basaloid features (SBACC), a high-grade variant thought to behave more aggressively than ACCs with conventional histologic growth. Our aim was to investigate the frequency of MYB-NFIB gene fusion in mammary ACCs with a focus paid to SBACC. MYB rearrangement and MYB-NFIB fusion were assessed by fluorescence in situ hybridization and reverse-transcription polymerase chain reaction, respectively. Histologic features and the presence of MYB rearrangement were correlated with clinical outcome. MYB rearrangement was present in 7 (22.6%) of 31 mammary ACCs (5/15 [33.3%] ACCs with conventional growth; 2/16 [12.5%] SBACCs). One patient with conventional ACC developed distant metastasis, and no patients had axillary lymph node involvement by ACC (mean follow-up, 34 months; range, 12-84 months). Two patients with SBACC had axillary lymph node involvement at initial surgery, and 2 additional patients experienced disease recurrence (1 local, 1 distant; mean follow-up, 50 months; range, 9-192 months). MYB-NFIB fusion status did not correlate with clinical outcome in studied patients. We confirm that MYB-NFIB gene fusion is observed in mammary ACCs and that a subset lacks this abnormality. This study is the first to confirm the presence of MYB rearrangement in SBACC. Additional validation with long-term follow-up is needed to determine the relationship, if any, between MYB-NFIB gene fusion and clinical outcome.

Tissue-Specific Cadherin CDH17 Is a Useful Marker of Gastrointestinal Adenocarcinomas With Higher Sensitivity Than CDX2

Cadherin 17 (CDH17) is a cell adhesion molecule expressed in intestinal epithelium and transcriptionally regulated by CDX2. We compared the usefulness of CDH17 as an immunohistochemical intestinal marker to that of CDX2 in gastrointestinal and extragastrointestinal carcinomas and nonneoplastic tissues. Nonneoplastic intestinal and pancreatic duct epithelia were CDH17-positive. Most esophageal (79%), gastric (86%), and colonic (99%) adenocarcinomas were CDH17-positive/CDX2-positive, whereas 1% of colonic, 18% of esophageal, and 10% of gastric adenocarcinomas were CDH17-negative/CDX2-negative. Rare colonic, esophageal, and gastric adenocarcinomas were CDH17-positive/CDX2-negative (1%, 3%, and 4%, respectively), and none were CDH17-negative/CDX2-positive. Diffuse CDH17 was also observed in all metastatic colon carcinomas, 20% of which were only focally CDX2-positive. Of intestinal low-grade neuroendocrine tumors, 74% coexpressed CDX2 and CDH17. CDH17 was also positive in 12% of pancreatic and 24% of bronchial neuroendocrine tumors, all of which were CDX2-negative. Pancreatic adenocarcinomas and cholangiocarcinomas were more frequently CDH17-positive than CDX2-positive (50% vs 27%, 53% vs 27%). One (2%) hepatocellular carcinoma was CDH17-positive/CDX2-negative. Nine percent of non-small cell lung cancers and 7% of endometrial carcinomas were CDH17-positive, whereas 3% of lung, 5% of endometrial, 3% of ovarian, and 2% of breast carcinomas were CDX2-positive. Thus, CDH17 is slightly more sensitive than CDX2 when detecting gastrointestinal adenocarcinomas.