Patient-derived xenografts effectively capture responses to oncology therapy in a heterogeneous cohort of patients with solid tumors

Background

While patient-derived xenografts (PDXs) offer a powerful modality for translational cancer research, a precise evaluation of how accurately patient responses correlate with matching PDXs in a large, heterogeneous population is needed for assessing the utility of this platform for preclinical drug-testing and personalized patient cancer treatment.

Patients and methods

Tumors obtained from surgical or biopsy procedures from 237 cancer patients with a variety of solid tumors were implanted into immunodeficient mice and whole-exome sequencing was carried out. For 92 patients, responses to anticancer therapies were compared with that of their corresponding PDX models.

Results

We compared whole-exome sequencing of 237 PDX models with equivalent information in The Cancer Genome Atlas database, demonstrating that tumorgrafts faithfully conserve genetic patterns of the primary tumors. We next screened PDXs established for 92 patients with various solid cancers against the same 129 treatments that were administered clinically and correlated patient outcomes with the responses in corresponding models. Our analysis demonstrates that PDXs accurately replicate patients' clinical outcomes, even as patients undergo several additional cycles of therapy over time, indicating the capacity of these models to correctly guide an oncologist to treatments that are most likely to be of clinical benefit.

Conclusions

Integration of PDX models as a preclinical platform for assessment of drug efficacy may allow a higher success-rate in critical end points of clinical benefit.

Trabectedin phase II clinical trials: Pooled analysis of safety in patients with solid tumors

e13510

Background: Trabectedin is an originally marine-derived antineoplastic agent. Its unique antitumor properties, attributed to specific binding to the small groove of DNA, have been demonstrated activity against soft-tissue sarcoma (STS), ovarian, breast and prostate cancer. Trabectedin treatment has been authorized by EMEA for STS after failure of standard treatment and shows efficacy in relapsed ovarian cancer in a phase III study. This retrospective report on safety includes single-agent trabectedin phase II studies in patients (pts) with solid tumors. Methods: A total of 1,132 pts were treated with trabectedin in 19 international trials (Feb’99 - Apr’08). Three schedules were analyzed: 24-hour infusion every 3 weeks (wk) (570 pts), 3-h every 3 wk (258 pts), and 3-h for 3 out of 4 wk (304 pts). Safety analyses included pts who received at least part of 1 infusion. MedDRA and NCI-CTC v1.0/2.0 were used to code and grade treatment-emergent adverse events (AEs). Results: Median pt age was 54 years with ECOG 0–1 (>99%). Diagnosis included sarcoma (56%), ovary (26%) and breast (7%) cancer, for which 90% of pts had received chemotherapy, 37.5% radiotherapy, and 96.0% surgery. Trabectedin lasted for a median of 3 cy (9.4 wks) and 28% of pts received ≥ 6 cycles, with a median dose intensity of 0.4 (0.1–0.6) mg/m2/wk. The overall rate of discontinuations due to toxicity was 10.3%, similar between all three dose schedules. Most common trabectedin-related AEs (≥ 20% of pts) were nausea, fatigue and vomiting. Most common lab abnormalities were reversible myelosuppression, mainly neutropenia (37% grade3–4) though G-CSF was given to less than 10% of pts; and transient transaminase increases (grade3–4: ALT, 45%; AST, 30%). Of note, only 3.7% and 5.7% of pts had alopecia or mucositis/stomatitis, respectively. Fifteen drug-related deaths (1.3%) occurred. Conclusions: Single-agent trabectedin was reasonably well tolerated, with low rates of drug-related discontinuations and deaths. Sustained clinical benefit in the absence of relevant cumulative toxicities allows its administration to patients for prolonged periods of time.

[Table: see text]

A SARC global collaborative phase II trial of R1507, a recombinant human monoclonal antibody to the insulin-like growth factor-1 receptor (IGF1R) in patients with recurrent or refractory sarcomas

10503

Background: The IGF1 system has been implicated in sarcoma development and inhibition of IGF1R function has been shown to induce clinical responses in select sarcomas. Methods: Objectives included response rate (RR) and progression-free survival (PFS) to R1507 in patients with recurrent or refractory Ewing's (ES, 2 cohorts- primary refractory vs. others) osteo (OS), synovial (SS), rhabdomyosarcoma (RMS), and other sarcomas. Eligibility included recurrent/refractory measurable disease, age ≥ 12 yrs, life expectancy ≥ 6 weeks, Karnofsky PS ≥ 70, adequate renal, hepatic and bone marrow function. R1507 was administered i.v. at 9 mg/kg over one hour weekly. Response was assessed by WHO criteria every 6 wks X 4 and every 12 wks thereafter. A two-stage design (Green and Dahlberg) was used. The endpoint for the primary refractory ES cohort was PFS at week 18 (planned n=65). RR was the primary endpoint for the remaining cohorts (planned n=240). Results: From 12/07–12/08, 203 eligible patients from 29 centers across the US, Europe and Australia were enrolled. Age ranged from 12–85 yrs (median=27 yrs) and 126 were male. Verified histologic subtypes were ES (n=71), OS (n=43), RMS (n=28), SS (n=25), and others (n=25). 15 severe adverse events were reported in 9 patients, the most common being fatigue (n=2), thrombocytopenia (n=2), dehydration (n=2), and hyperglycemia (n=2). Clinically significant activity has been observed in ES, RMS and OS with several dramatic responses seen in ES and RMS. Independent radiologic review is currently ongoing and updated data will be presented. Conclusions: The rapid accrual amongst many centers in diverse geographical locations demonstrates the feasibility of collaborative research in sarcomas. R1507 is well tolerated and a promising new agent for the treatment of various sarcomas. SARC and Roche are collaborating in additional clinical trials to better define the role of R1507 in the treatment of selected sarcomas.

[Table: see text]

Phase 1 dose-escalation study of 17-allylamino-17-demethoxygeldanamycin (17AAG) in combination with irinotecan in patients with solid tumors

3533

Background: 17AAG is an inhibitor of the molecular chaperone Hsp90. Pre-clinical studies from our laboratory showed that treatment of cancer cells with 17AAG caused depletion of two critical checkpoint kinases, Chk1 and Wee1, resulting in abrogation of the G2/M checkpoint triggered by topoisomerase I poison, and selective induction of apoptosis in p53-defective cells. Methods: We initiated a phase 1 study of irinotecan (CPT) and 17AAG to determine the maximally tolerated doses (MTD) and tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of the combination. During the dose-escalating phase, patients (Pts) received CPT over 30 min followed by 17AAG over 2 hrs once weekly for two weeks in a 21-day cycle. At the MTD, Pts underwent post-treatment tumor biopsy for PD biomarker analysis after CPT only during week 1 and after the combination during week 2. Results: 22 Pts (median age 53; range 32–73; median KPS 80) with a wide spectrum of solid tumor types were enrolled. Four Pts developed dose-limiting toxicity in cohort 4 (100 mg/m2 CPT and 375 mg/m2 17AAG) including nausea, vomiting, diarrhea, and pulmonary embolism. The PKs of 17AAG and its metabolite 17AG were not affected by the co-administration of CPT. Although no CR/PR’s by RECIST criteria have been seen, minor responses were observed in CPT-naive Pts with pancreas (2), breast (1), and high grade neuroendocrine tumor (1). Pts are currently enrolled to the MTD expanded cohort for further assessment of tolerability and PD analysis. So far, paired tumor biopsies have been successfully obtained in 8/8 Pts and samples will be analyzed for p53 status, Hsp90 client protein depletion, G2/M checkpoint abrogation, and apoptosis. Conclusions: The combination of 17AAG and CPT can be given to Pts with acceptable toxicity. The recommended phase II dose of the combination is 100 mg/m2 CPT and 300 mg/m2 17AAG. (Supported by ASCO CDA and NCI K08 awards)

No significant financial relationships to disclose.

Analysis of toxicity in a phase II study of sorafenib in soft tissue sarcoma (STS)

10061

Background: Sorafenib (BAY 43–9006) is an oral multi-targeted kinase inhibitor. Sorafenib causes dermatologic toxicity and hypertension, although the mechanisms are poorly understood. We observed significant toxicity requiring dose reductions in our phase II study of sorafenib in STS. Methods: 120 patients (40 M, 80 F; median age, 55 years) were treated between 10/05 and 12/06; accrual continues. All patients initially received sorafenib 400 mg BID. 118/120 registered patients were evaluable for toxicity. Clinical and laboratory variables were analyzed for association with dose reduction, using Kruskal-Wallis rank sum test for continuous variables and Fisher exact test for categorical variables. Variables significant at the p=0.05 level were further analyzed with a multivariate logistic regression model for their effects on dose reduction. Results: 53% of patients (63/118) required dose reductions, 53/63 for grade 2 or greater skin toxicity. Most common grade 3–4 drug-related toxicities included lymphopenia (14%), rash (12%), and hand-foot skin reaction (10%). Sex, height, weight, BSA and serum creatinine (Cr) were significantly associated with dose reduction by univariate analysis. Adjusting for sex and/or low serum Cr, BSA was not significantly associated with dose reduction. Sex and low serum Cr were borderline statistically significant predictors of dose reductions when both variables were included in a multivariate model. Only female sex remained a significant predictor when eliminating one outlier with BSA 2.83 (p=0.04). Conclusions: Female gender appears associated with skin toxicity, requiring dose reductions. Based on this multivariate analysis, a starting dose of 400 mg oral daily in women may limit side effects. Correlation with trough serum sorafenib levels is pending. This study is funded in part by NCI Grant P01-CA47179.

No significant financial relationships to disclose.

A putative tumor suppressor role for Wnt-signaling in sarcomagenesis

9507

Background: We sought to elucidate the relationship between the human adult mesenchymal stem cell (hMSC), Wnt signaling and sarcomagenesis. Methods: In vitro hMSC differentiation, microarray gene expression analysis, distance correlation analysis, and standard molecular biology techniques were used to explore the role of Wnt in controlling the differentiation of both hMSCs and high grade undifferentiated sarcoma (HGUS; MFH, malignant fibrous histiocytoma), a common form of adult soft tissue sarcoma. Results: We determined that 1) hMSCs appear to be the progenitor cells of HGUS/MFH; 2) Dickkopf-1 (Dkk1), a specific inhibitor of Wnt signaling, is overexpressed in MFH as compared to other sarcoma subtypes and is involved in the proliferation of hMSCs; 3) in hMSCs, Dkk1 levels decline and nuclear β-catenin accumulates as hMSCs reach confluence, a prerequisite for initiation of in vitro differentiation, while in an MFH cell line Dkk1 levels do not decline and there is no nuclear β-catenin accumulation; 3) MFH cells appear to be primed for differentiation and express early markers of mesenchymal differentiation, then undergo apoptosis, if nuclear β-catenin is manipulated to enter the nucleus; 4) Wnt2 signals via the canonical β-catenin pathway and is responsible for “commitment” of hMSC and an MFH cell line to various differentiation pathways, while Wnt5a signals via the non-canonical JNK pathway in preventing apoptosis upon appropriate commitment toward differentiation. Conclusions: We identified the contribution of canonical and non-canonical Wnt signaling in the differentiation of hMSCs and showed that enhancing signaling via these pathways could be exploited as a potential target for therapy for high grade undifferentiated sarcomas. These data implicate Wnt-signaling as a mechanism of tumor suppression in early sarcomagenesis.

No significant financial relationships to disclose.

Sarcoma

ASCO 2001 was a banner year for innovative systemic therapy for sarcomas. Imatinib mesylate (STI571, Gleevec) shows clear activity not only in chronic myelogenous leukemia, for which the drug received Food and Drug Administration approval, but also in gastrointestinal stromal tumors as well, by virtue of imatinib mesylate binding to the abl, kit, and platelet-derived growth factor receptor tyrosine kinases. Ecteinascidin-743 (ET-743) demonstrates activity against a fraction of other soft-tissue sarcomas. Gemcitabine-based regimens show at least some activity against a subset of soft-tissue sarcomas. Given the lack of new agents for sarcoma therapy since the development of ifosfamide, these studies give hope that the term "effective systemic therapy for sarcoma" might become a reality.

A mutation in a case of early onset narcolepsy and a generalized absence of hypocretin peptides in human narcoleptic brains

We explored the role of hypocretins in human narcolepsy through histopathology of six narcolepsy brains and mutation screening of Hcrt, Hcrtr1 and Hcrtr2 in 74 patients of various human leukocyte antigen and family history status. One Hcrt mutation, impairing peptide trafficking and processing, was found in a single case with early onset narcolepsy. In situ hybridization of the perifornical area and peptide radioimmunoassays indicated global loss of hypocretins, without gliosis or signs of inflammation in all human cases examined. Although hypocretin loci do not contribute significantly to genetic predisposition, most cases of human narcolepsy are associated with a deficient hypocretin system.

How a multidisciplinary team improved a process to attain positive patient outcome

A case study approach will be used to demonstrate the effectiveness of a continuous quality improvement team designed to explore the process of preoperative medical record completeness. The goal of this team was to improve essential chart components (e.g., electrocardiography, history and physical examination) required 48 hours before the date of surgery in an effort to facilitate optimum patient management and timely flow of patients to the operating room. When the 48-hour compliance rule is followed, the nurse reviewer has sufficient time to review all patient data and notify attending physicians or designees of any abnormalities. In essence, improving component compliance provides better quality care because patients are able to be assessed before surgery with enough time to solve any problems.

GOOSECOID inhibits erythrocyte differentiation by competing with Rb for PU.1 binding in murine cells

Misexpression of the dorsal mesodermal patterning factor goosecoid on the ventral side of amphibian embryos results in inhibition of blood formation in early embryogenesis. To investigate the mechanism of this inhibition, we ectopically expressed goosecoid in erythroleukemia cells. While erythroid differentiation of these cells can be induced by activin, goosecoid expressing cells were unresponsive to activin. We demonstrate an in vitro interaction between the oncogene PU.1, an ets family transcription factor thought to play a role in erythropoiesis, and the goosecoid protein (GSC). Interaction with PU.1 was specific as GSC did not bind to the ets family members, Fli-1 or Ets-2. The ability of goosecoid expressing erythroleukemia cells to differentiate in response to activin was rescued by coexpression of the GSC-binding N-terminal portion of PU.1. The N-terminal portion of PU.1 was co-immunoprecipitated with anti-GSC antibodies as well. The N-terminal domain of PU.1 is the region recognized by the retinoblastoma protein (Rb), a tumor suppressor gene presumably involved in erythroid differentiation. We show that GSC competitively inhibits binding of Rb to PU.1. Our data suggest that the suppression of blood formation by GSC could, at least in part, be mediated by binding to PU.1.

Expression profile of the copper homeostasis gene, rAtox1, in the rat brain

In humans the regulation of cellular copper homeostasis is essential for proper organ development and function. A novel cytosolic protein, named Atox 1, was recently identified in yeast that functions in shuttling intracellular mononuclear copper [Cu(I)] to copper-requiring proteins. Atox 1 and its human homolog, hAtox1, are members of an emerging family of proteins termed copper chaperones that are involved in the maintenance of copper homeostasis. Northern blot analysis demonstrates that Atox 1 is widely expressed at varying levels in a variety of rat tissues including brain. Using in situ hybridization histochemistry, we characterized the expression profile for the rat homolog of Atox1 (rAtox1) in the normal adult rat brain. There is widespread expression within the brain that appears to be primarily neuronal. The highest levels of Atox1 message consists of distinct neuronal subtypes that are also characterized by their high levels of metals like copper, iron, and zinc, which include the pyramidal neurons of the cerebral cortex and hippocampus in addition to the neurons of the locus coeruleus. The high levels of a metal chaperone like Atox1 in subsets of neurons that also sequester metals suggests that Atox1 may be important in maintaining the functionality of metal requiring enzymes. A detailed analysis of the restricted expression profile for a novel copper chaperone, rAtox1, is described in the adult rat CNS. Further analysis shows that Atoxl expression is associated with neuronal populations that sequester copper.

Characterization of fractalkine in rat brain cells: migratory and activation signals for CX3CR-1-expressing microglia

Molecular analyses of the chemokine fractalkine and its receptor CX3C-R1 in the rat brain have revealed a striking polarization: fractalkine is expressed constitutively in neurons and is up-regulated by TNF-alpha and IL-1beta in astrocytes. Expression of its specific receptor, CX3C-R1, is restricted to astrocytes and microglia. We have analyzed the functional correlates of this expression and demonstrate that fractalkine induces microglial cell migration and activation. However, the activity of this chemokine on astrocytes may also be highly relevant in inducing astrocyte-microglia cell interactions through cytokine/mediator release leading to microglial activation.

Chemokines and chemokine receptors in the CNS: a possible role in neuroinflammation and patterning

Chemokines constitute a growing family of structurally and functionally related small (8-10 kDa) proteins associated with inflammatory-cell recruitment in host defence. In addition to their well-established role in the immune system, recent data suggest their involvement in the maintenance of CNS homeostasis, in neuronal patterning during ontogeny and as potential mediators of neuroinflammation, playing an essential role in leukocyte infiltration into the brain. Chemokines and their G protein-coupled receptors are constitutively expressed at low-to-negligible levels in various cell types in the brain. Their expression is rapidly induced by various neuroinflammatory stimuli, implicating them in various neurological disorders such as trauma, stroke and Alzheimer's disease, in tumour induction and in neuroimmune diseases such as multiple sclerosis or acquired immunodeficiency syndrome (AIDS). Here, F. Mennicken, R. Maki, E. B. De Souza and R. Quirion briefly summarize recent exciting findings in the field.

Selective chemokine mRNA accumulation in the rat spinal cord after contusion injury

Following traumatic injury to the spinal cord, hematogenous inflammatory cells including neutrophils, monocytes, and lymphocytes infiltrate the lesion in a distinct temporal sequence. To examine potential mechanisms for their recruitment, we measured chemokine mRNAs in the contused rat spinal cord, using specific and sensitive reverse transcriptase polymerase chain reaction (RT-PCR) dot-blot hybridization assays. The neutrophil chemoattractant GRO-alpha was 30-fold higher than control values at 6 hr postinjury and decayed rapidly thereafter. LIX, a highly related alpha-chemokine, also was elevated early postinjury. Monocyte chemoattractant peptide (MCP)-1 and MCP-5 mRNAs, potent chemoattractants for monocytes, were significantly elevated at the lesion epicenter at 12 and 24 hr postinjury and declined thereafter. Interferon-gamma-inducible protein, 10 kDa (IP-10), chemoattractant towards activated T-lymphocytes, was significantly elevated at 6 and 12 hr postinjury. The dendritic cell chemoattractant MIP-3alpha also was increased, perhaps contributing to the development of T-cell autoreactivity to neural components after spinal cord injury (SCI) in rats. Other beta-chemokines, including MIP-1alpha and RANTES (regulated on expression normal T-cell expressed and secreted), were minimally affected by SCI. Expression of chemokines, therefore, directly precedes the influx of target neutrophils, monocytes, and T-cells into the spinal cord postinjury, as noted previously. Thus, selective chemokine expression may be integral to inflammatory processes within the injured spinal cord as a mechanism of recruitment for circulating leukocytes.

Use of RDA analysis of knockout mice to identify myeloid genes regulated in vivo by PU.1 and C/EBPalpha

PU.1 and C/EBPalpha are transcription factors essential for normal myeloid development. Loss-of-function mutation of PU.1 leads to an absolute block in monocyte/macrophage development and abnormal granulocytic development while that of C/EBPalpha causes a selective block in neutrophilic differentiation. In order to understand these phenotypes, we studied the role of PU.1 and C/EBPalpha in the regulation of myeloid target genes in vivo . Northern blot analysis revealed that mRNAs encoding receptors for M-CSF, G-CSF and GM-CSF, were expressed at low levels in PU.1(-/-) fetal liver compared with wild type. To identify additional myeloid genes regulated by PU.1 and C/EBPalpha, we performed representational difference analysis (RDA), a PCR-based subtractive hybridization using fetal livers from wild type and PU.1 or C/EBPalpha knockout mice. By introducing a new modification of RDA, that of tissue-specific gene suppression, we could selectively identify a set of differentially expressed genes specific to myeloid cells. Differentially expressed genes included both primary and secondary granule protein genes. In addition, eight novel genes were identified that were upregulated in expression during myeloid differentiation. These methods provide a general strategy for elucidating the genes affected in murine knockout models.

[Evaluation of a synthetic peptide based species specific EIA kit for detection of antibodies to Chlamydia trachomatis with clinical specimens]

We have evaluated a new kit, PEPTIDE Chlamydia (Meiji Milk Products Co., Ltd, Tokyo), for detecting species specific antibodies to Chlamydia trachomatis with synthetic peptide as an antigen. Serum samples from women with C. trachomatis cervicitis (n = 45), healthy pregnant women (n = 100), and children suffering from C. pneumoniae lower respiratory tract infection (n = 9) were used. We have measured the serum IgG or IgA antibodies to C. trachomatis of those sera with PEPTIDE, Sero IPALIZA Chlamydia (Savyon Diagnostics, Israel), and HITAZYME Chlamydia (Hitachi Chemical Co., Ltd, Hitachi). Serum samples with discrepant results were further analyzed by a microimmunofluorescence test and immunoblotting (western blotting). IgG and IgA serum positive rate to C. trachomatis of sera from women with C. trachomatis cervicitis were similar in three kits, that is, 91% and 80% in PEPTIDE, 89% and 82% in Sero IPALIZA, and 84% and 76% in HITAZYME, respectively. IgG and IgA serum positive rate to C. trachomatis of sera from healthy pregnant women were 18% and 9% in PEPTIDE, 12% and 15% in Sero IPALIZA, and 15% and 13% in HITAZYME, respectively. Serum antibodies to C. trachomatis in serum samples from children with C. pneumoniae infection were all negative in PEPTIDE, but falsely positive in several cases in Sero IPALIZA or HITAZYME. In sera with discrepant results, PEPTIDE gave more identical results with a micro-IF test and immunoblotting analysis than Sero IPALIZA or HITAZYME. These results indicate that PEPTIDE is an useful kit to detect more species specific antibodies to Chlamydia trachomatis than former kits.

Osteopetrosis in mice lacking haematopoietic transcription factor PU.1

Osteoclasts are multinucleated cells and the principal resorptive cells of bone. Although osteoclasts are of myeloid origin, the role of haematopoietic transcription factors in osteoclastogenesis has not been explored. Here we show that messenger RNA for the myeloid- and B-cell-specific transcription factor PU.1 progressively increases as marrow macrophages assume the osteoclast phenotype in vitro. The association between PU.1 and osteoclast differentiation was confirmed by demonstrating that PU.1 expression increased with the induction of osteoclastogenesis by either 1,25-dihydroxyvitamin D3 or dexamethasone. Consistent with the participation of PU.1 in osteoclastogenesis, we found that the development of both osteoclasts and macrophages is arrested in PU.1-deficient mice. Reflecting the absence of osteoclasts, PU.1-/- mice exhibit the classic hallmarks of osteopetrosis, a family of sclerotic bone diseases. These animals were rescued by marrow transplantation, with complete restoration of osteoclast and macrophage differentiation, verifying that the PU.1 lesion is intrinsic to haematopoietic cells. The absence of both osteoclasts and macrophages in PU.1-mutant animals suggests that the transcription factor regulates the initial stages of myeloid differentiation, and that its absence represents the earliest developmental osteopetrotic mutant yet described.

Expression cloning of cDNA by phage display selection

Expression cloning of a mouse kappa chain fragment has been achieved from a cDNA library by display of expressed proteins on filamentous phage and affinity selection for binding to anti-mouse Fab antibodies. Expressed proteins were anchored to the phage coat by a synthetic, anti-parallel leucine zipper, which had been selected from a semi-randomized zipper library for the ability to connect a test protein to phage. From a library of 4 x 10(6) transformants, two separate clones displaying different size cDNA inserts were recovered after four selection rounds. These results further demonstrate the utility of phage display for cDNA expression cloning.

Rat homolog of mouse interleukin-1 receptor accessory protein: cloning, localization and modulation studies

A protein which facilitates the binding between interleukin-1 (IL-1) and the type I IL-1 receptor (designated as interleukin-1 receptor accessory protein, IL-1RAcP) has recently been cloned in mouse cells. In the present study, a rat homolog of the mouse IL-1RAcP was isolated from a rat superior cervical ganglion library. The deduced 570 amino acid sequences between rat and mouse IL-1RAcP have > 95% sequence identity to each other with similar predicted signal peptide sequence (20 amino acids), extracellular domain (339 amino acids), a single transmembrane domain (24 amino acids) and a long intracellular domain (187 amino acids). The rat IL-1RAcP has approximately 25% sequence identity to the rat type I IL-1 receptor and a predicted extracellular domain with three immunoglobulin-like loops. RNase protection assays demonstrated that rat IL-1RAcP is expressed in both brain and peripheral tissues with the highest densities present in liver and brain areas such as hypothalamus, cerebral cortex, hippocampus and cerebellum; significantly lower densities were present in lung and in immune tissues such as thymus and spleen. The presence of IL-1RAcP in brain was confirmed by in situ hybridization histochemical studies with a discrete localization present in the dentate gyrus of the hippocampus. The IL-1RAcp was down-regulated in parallel with the type I IL-1 receptor in the liver following endotoxin treatment in rats. These data demonstrating the presence and modulation of a rat homolog of a mouse IL-1RAcP, which is highly expressed in brain and peripheral tissues containing type I rat IL-1 receptor, further suggest the importance of the interaction between the two proteins in rat in modulating the actions of IL-1. On the other hand, the presence of the IL-1RAcP in brain areas which show an absence of type I IL-1 receptors suggests additional functions for this protein in the rat.

TOR: a new orphan receptor expressed in the thymus that can modulate retinoid and thyroid hormone signals

Vitamin A and other fat-soluble hormones and vitamins have important roles as modulators of essential biological processes such as homeostasis, development, differentiation, and oncogenesis and also as regulators of the immune system. The active form of vitamin A, retinoic acid, as well as vitamin D3 and thyroid hormones exert their actions by binding to specific nuclear receptors that represent one subfamily of the steroid/thyroid hormone receptor superfamily. To identify new members of the retinoid/thyroid hormone receptor subfamily that could play a role in the immune system, a screening of a T cell cDNA library was performed using a retinoid X receptor probe. A clone was isolated encoding a novel nuclear receptor expressed mainly in the thymus and T cell lines. This new receptor, TOR (thymus orphan receptor), is most closely related in both its DNA-binding domain and ligand-binding domain, 90% and 53%, respectively, to ROR alpha/RZR alpha and clusters with these two receptors and RZR beta in a phylogenetic tree, when both the DNA-binding domain and the ligand-binding domain sequences of nuclear receptors are compared. Thus, TOR is part of a subgroup of receptors, one of which has recently been reported to be activated by melatonin. TOR binds specifically to a direct repeat of the half-site sequence 5'-AGGTCA-3' with a four- or five-nucleotide spacer, DNA sequences that also serve as binding sites for thyroid hormone (TR), and retinoic acid receptors (RAR). In transient transfection experiments TOR does not activate a reporter gene carrying these sequences in the absence or the presence of any known nuclear receptor ligands. TOR, however, is able to repress TR and RAR activity on DR-4-TREs or DR-5-RAREs, respectively. Therefore, our data suggest that TOR, similar to COUP-TF, can negatively regulate retinoic acid and thyroid hormone signals. However, the response elements recognized by TOR and COUP-TF differ as do the expression patterns of these receptors. Thus, one important role of TOR could be to modulate retinoid and thyroid hormone signals in the thymus.

Frequency-dependent depression of excitatory synaptic transmission is independent of activation of MCPG-sensitive presynaptic metabotropic glutamate receptors in cultured hippocampal neurons

1. A paired-pulse paradigm, and a high-frequency train followed by a test pulse, were used to investigate the possible role of presynaptic metabotropic glutamate receptors (mGluRs) in frequency-dependent modulation of the amplitude of excitatory post-synaptic currents (EPSCs). Paired whole cell patch-clamp recordings from monosynaptically connected hippocampal neurons maintained in very low-density cultures were performed, using the mGluR antagonist (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG, 500 microM) and the mGluR agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid [(1S,3R)-ACPD, 100 microM]. 2. Paired-pulse depression (PPD) was observed in all the excitatory pairs recorded. The average PPD ratio (amplitude of the 2nd EPSC divided by the amplitude of the 1st EPSC) was 0.80 +/- 0.1 (SD) (n = 8). Application of the mGluR antagonist MCPG had no effect on the amplitude of the EPSCs and did not affect the ratio of the two EPSCs (PPD ratio 0.79 +/- 0.2). 3. The amplitudes of 10 successive EPSCs stimulated at a high frequency (20 Hz) decremented on average in both 4 mM extracellular Ca2+ (n = 5) and in 1 mM extracellular Ca2+ (n = 6). In all pairs tested, posttetanic depression (PTD) was observed (PTD ratio 0.7 +/- 0.2). Bath application of MCPG (500 microM) did not affect the amplitudes of the EPSCs during the train; MCPG also did not affect PTD. 4. The mGluR agonist (1S,3R)-ACPD depressed the amplitudes of the EPSCs in both the paired-pulse (1st EPSC, 35 +/- 9%; 2nd EPSC, 36 +/- 10%) and posttetanic pulse (1 and 4 mM extracellular Ca2+) paradigms. The amount of depression observed, both PPD and PTD, remained unaffected by application of (1S,3R)-ACPD. Coapplication of the antagonist MCPG (500 microM) blocked the effects of (1S,3R)-ACPD (100 microM). 5. We conclude that frequency-dependent depression of EPSC amplitudes occurs independent of endogenous activation of MCPG-sensitive mGluRs in cultured hippocampal neurons. Moreover, we demonstrate that exogenous activation of mGluRs by the agonist (1S,3R)-ACPD can produce additional EPSC depression above that already present due to frequency-dependent mechanisms.

The glutamate uptake inhibitor L-trans-pyrrolidine-2,4-dicarboxylate depresses excitatory synaptic transmission via a presynaptic mechanism in cultured hippocampal neurons

Sodium-dependent high-affinity uptake of glutamate is thought to play a major role in the maintenance of very low extracellular concentrations of excitatory amino acids (EAA), and may modulate the actions of released transmitter at G-protein-coupled receptors and extrasynaptic receptors that are activated over a longer distance and time course. We have examined the effects of the recently developed uptake inhibitor L-trans-pyrrolidine-2,4-dicarboxylate (L-trans-PDC) on monosynaptically evoked excitatory postsynaptic currents (EPSCs) in very-low-density cultures of hippocampal neurons. L-Trans-PDC produced a decreased amplitude of both the non-NMDA and NMDA receptor-mediated components of monosynaptically evoked EPSCs. Examination of miniature EPSCs (mEPSCs) indicated that changes in the sensitivity of postsynaptic non-NMDA receptors did not underline the decrease in evoked EPSC amplitudes. The metabotropic receptor agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) also depressed both components of the EPSC. The competitive metabotropic receptor antagonist (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG) blocked the depression of EPSC amplitude induced by 1S,3R-ACPD and also blocked the effects of L-trans-PDC. Finally, low concentrations of L-glutamate (2 microM) mimicked the effects of L-trans-PDC on EPSC amplitude. From these results we conclude that the application of L-trans-PDC to cultured hippocampal neurons results in the activation of presynaptic metabotropic receptors, leading to a decrease in synaptic transmission. We propose that this effect is due to an increase in ambient glutamate concentrations following inhibition of glutamate uptake, resulting in presynaptic inhibition of excitatory synaptic transmission.

Oncogene activation of human keratin 18 transcription via the Ras signal transduction pathway

Keratin 8 (K8) and keratin 18 (K18) are intermediate filament proteins normally expressed in simple epithelial tissues and persistently expressed in a wide variety of carcinomas. Ectopic expression of K8 and K18 occurs in some epidermal and murine skin carcinomas induced by chemical carcinogenesis or oncogenic ras expression. We show here that K18 is a direct target of the Ras signal transduction pathway, by demonstrating that activated Ha-Ras, as well as activated Src, Lck, or Raf, stimulates the transcription of K18. This activation is mediated by an enhancer element containing essential and closely spaced Ets and AP-1 transcription factor binding sites. Oncogene activation of K18 transcription provides a molecular explanation for the persistent and sometimes unexpected expression of K18 in such a wide variety of tumors.

Hematopoietic lineage- and stage-restricted expression of the ETS oncogene family member PU.1

The ETS oncogene family member PU.1 is a transcriptional activator that is dysregulated by Friend erythroleukemia virus insertion. Northern analysis found that PU.1 is highly expressed in cells of myeloid and B-lymphoid origin, but not expressed at all in a number of nonhematopoietic tissues. Interferon-gamma and retinoic acid downregulated PU.1 expression in marrow macrophages. In situ immunohistochemistry found that PU.1 is expressed only in early granulocytic and erythroid cells and megakaryocytes, but not in mature erythroid cells, mature granulocytes, endothelial cells, or osteocytes. Thus, its expression pattern makes PU.1 a candidate for a genetic determinant of lineage commitment and stage progression in blood cell development. It also lends insight into how PU.1 might play a role in Friend virus erythroleukemia.

Regulation of lymphoid-specific immunoglobulin mu heavy chain gene enhancer by ETS-domain proteins

The enhancer for the immunoglobulin mu heavy chain gene (IgH) activates a heterologous gene at the pre-B cell stage of B lymphocyte differentiation. A lymphoid-specific element, microB, is necessary for enhancer function in pre-B cells. A microB binding protein is encoded by the PU.1/Spi-1 proto-oncogene. Another sequence element, microA, was identified in the mu enhancer that binds the product of the ets-1 proto-oncogene. The microA motif was required for microB-dependent enhancer activity, which suggests that a minimal B cell-specific enhancer is composed of both the PU.1 and Ets-1 binding sites. Co-expression of both PU.1 and Ets-1 in nonlymphoid cells trans-activated reporter plasmids that contained the minimal mu enhancer. These results implicate two members of the Ets family in the activation of IgH gene expression.

Quantitative analysis of cytokine gene expression in rheumatoid arthritis

Previous studies of the cytokine profile of rheumatoid arthritis (RA) have been primarily limited to the assessment of the levels of these mediators in synovial fluid (SF) or synovial tissues (ST) by biologic or immunologic assays. We have studied cytokine gene expression in RA by in situ hybridization of SF cells, enzymatically dispersed ST cells, and frozen sections of ST. RA ST cells (n = 7) were studied and a high percentage of cells hybridized to the following anti-sense probes: IL-6 = 19 +/- 3.3%; IL-1 beta = 9.9 +/- 1.7%; TNF-alpha = 5.8 +/- 1.4%; granulocyte-macrophage-CSF = 2.2 +/- 0.8%; transforming growth factor-beta 1 = 1.3 +/- 0.2% (p less than 0.05 for each compared to sense probes). Similar results were found using osteoarthritis ST cells, although the percentage of cells expressing the IL-6 gene (7.1 +/- 2.5%) was significantly less in osteoarthritis compared to RA. RA ST cells did not significantly bind the IFN-gamma probe (0.2 +/- 0.1% positive), although they were capable of expressing the IFN-gamma gene if stimulated with PHA. The OKM1+ population of ST cells (i.e., macrophage lineage cells) was greatly enriched for IL-1 beta and TNF-alpha, whereas the OKM1- population (lymphocytes, fibroblasts, and type B synoviocytes) was enriched for IL-6. The vast majority of cells expressing the IL-6 gene were non-T cells. Furthermore, hybridization to RA ST frozen sections localized IL-6 mRNA to the synovial lining layer, which is comprised of type A and type B synoviocytes. In contrast to the high level of cytokine gene expression observed in ST, SF cells did not hybridize significantly to any of the cytokine probes. If stimulated with LPS or PHA, SF cells expressed IL-1 beta or IFN-gamma genes, respectively.

Quantitative analysis of cytokine gene expression in rheumatoid arthritis

Previous studies of the cytokine profile of rheumatoid arthritis (RA) have been primarily limited to the assessment of the levels of these mediators in synovial fluid (SF) or synovial tissues (ST) by biologic or immunologic assays. We have studied cytokine gene expression in RA by in situ hybridization of SF cells, enzymatically dispersed ST cells, and frozen sections of ST. RA ST cells (n = 7) were studied and a high percentage of cells hybridized to the following anti-sense probes: IL-6 = 19 +/- 3.3%; IL-1 beta = 9.9 +/- 1.7%; TNF-alpha = 5.8 +/- 1.4%; granulocyte-macrophage-CSF = 2.2 +/- 0.8%; transforming growth factor-beta 1 = 1.3 +/- 0.2% (p less than 0.05 for each compared to sense probes). Similar results were found using osteoarthritis ST cells, although the percentage of cells expressing the IL-6 gene (7.1 +/- 2.5%) was significantly less in osteoarthritis compared to RA. RA ST cells did not significantly bind the IFN-gamma probe (0.2 +/- 0.1% positive), although they were capable of expressing the IFN-gamma gene if stimulated with PHA. The OKM1+ population of ST cells (i.e., macrophage lineage cells) was greatly enriched for IL-1 beta and TNF-alpha, whereas the OKM1- population (lymphocytes, fibroblasts, and type B synoviocytes) was enriched for IL-6. The vast majority of cells expressing the IL-6 gene were non-T cells. Furthermore, hybridization to RA ST frozen sections localized IL-6 mRNA to the synovial lining layer, which is comprised of type A and type B synoviocytes. In contrast to the high level of cytokine gene expression observed in ST, SF cells did not hybridize significantly to any of the cytokine probes. If stimulated with LPS or PHA, SF cells expressed IL-1 beta or IFN-gamma genes, respectively.

Evidence for multiple major histocompatibility class II X-box binding proteins

The X box is a loosely conserved DNA sequence that is located upstream of all major histocompatibility class II genes and is one of the cis-acting regulatory elements. Despite the similarity between all X-box sequences, each promoter-proximal X box in the mouse appears to bind a separate nuclear factor.

Inhibition of MHC class II-restricted T cell response by Lyt-2 alloantigen

T cell hybridomas were established by fusing a CD8+ V beta 8.1+ CTL clone and a CD4+ V beta 8.1+ helper T lymphocyte (HTL) clone to the thymoma cell line BW5147. In contrast to the HTL x BW hybridomas, which retain the same antigen specificity as the original T cell clone, the CTL x BW hybridomas lost the class I MHC-restricted antigen response but acquired a new specificity to Mlsa antigen. Mlsa reactivity of CTL x BW hybridomas was shown to be mediated by the CTL TCR as assayed by inhibition using an anticlonotypic antibody to the CTL clone. Since hybridomas established with BW5147 lose CD8 expression, we have introduced the CD8 molecule into CTL x BW5147 hybridomas by gene transfection. The CD8+ V beta 8.1+ hybridoma was no longer capable of reacting to Mlsa antigen but exhibited the same antigen specificity as the parental CTL clone. Furthermore, the presence of the transfected CD8 molecule in the HTL x BW hybridomas was found to be inhibitory to class II MHC-restricted antigen reactivity. These results demonstrate that, besides its role in increasing the overall avidity of T cell-class I MHC/antigen interaction, the CD8 molecule inhibits T cell-class II MHC gene product/antigen interaction. This negative effect of the CD8 molecule on a class II MHC-restricted response may account for the failure of CD8+ T cells using either V beta 8.1 or V beta 6, which impart reactivity to the Mlsa antigen on CD4+ T cells, to respond to the Mlsa antigen.

Altered I-A protein-mediated transmembrane signaling in B cells that express truncated I-Ak protein

Recent evidence suggests that the major histocompatibility complex class II molecules of B lymphocytes function as signal-transducing receptors during the generation of T lymphocyte-dependent humoral immune responses. By analogy with other receptors, we postulate that perturbation of the class II molecules is coupled to the generation of intracellular second messengers through interactions involving the transmembrane and/or cytoplasmic domains of the class II molecules. We report a series of experiments that assess which amino acids of the class II molecule I-Ak are required for coupling it to the signal-transduction pathway. We prepared a series of B-lymphocyte transfectants that express I-Ak molecules with COOH-terminal truncations of either the Ak alpha or Ak beta chain or both. The ability of each transfected class II molecule to transduce a signal after being bound by monoclonal antibody was found by monitoring the translocation of protein kinase C from the cytosol to the "nuclear compartment" of the transfected B lymphocyte. Results indicate that the Ak beta chain plays the dominant role in signal transduction and that the 6 cytoplasmic amino acids of Ak beta chain most proximal to the inner plasma membrane are of greatest importance in coupling I-Ak molecules to the molecules of the signaling cascade.

Picture memory: recognizing added and deleted details

When people are presented simple and complex pictures and then tested in a same-changed recognition test with a simple or complex form of each, d' is greater for the simple than the complex picture (Pezdek & Chen, 1982). The results of three experiments confirm the robustness of this "asymmetric confusability effect" and test a model of the processes underlying this effect. According to the model, pictures are schematically encoded such that the memory representation of both simple and complex pictures is similar to the simple form of each. In Experiment 1, a sentence was presented that described the central schema in the picture prior to subjects' viewing each picture. This manipulation exaggerated the asymmetric confusability effect; schematic processing thus underlies the effect. Results of Experiment 2 refute the hypothesis that the effect results from subjects erroneously anticipating a recall test rather than a recognition test. Furthermore, although some of the nonschematic elaborative information in complex pictures is stored in memory, it is difficult to retrieve to verify that something is missing when complex presentation pictures are changed to simple test pictures (Experiment 3). Thus, although people are able to distinguish large sets of old pictures from new distractor pictures, their ability to detect missing elaborative visual details is more limited.

Comparative sequence analysis of cDNA clones encoding I-A molecules of the CH12 B cell lymphoma: nucleotide differences do not account for their "defective" function in B cell stimulation

The CH12 B cell lymphoma can be stimulated to secrete antibody by helper T cells that interact with I-EK but not I-AK molecules expressed on its membrane. Both molecules present antigen to the appropriate T cells. We have analyzed the mRNA by Northern blot analysis and obtained partial sequences of cDNA clones encoding A alpha and A beta of the I-A molecule to determine if deletions or mutations in the cytoplasmic or transmembrane domains account for the "defect" in triggering following interaction with I-A restricted helper T cells. The results provide no evidence for structural alterations in either A alpha or A beta which could account for these observations. The implications of these findings on the role of class II molecules in B cell activation is discussed.

The role of DNA rearrangement and alternative RNA processing in the expression of immunoglobulin delta genes

We have established the exon-intron structure of the gene coding for the constant (C) region of the mouse immunoglobulin delta heavy chain, using DNA clones isolated from BALB/c embryos and the delta mRNA extracted from two delta-producing hybridomas, B1-8. delta 1 and GCL2.8. At least three types of C delta gene structures are identified. A 2.7 kb delta mRNA reveals six exons. This delta mRNA may code for a membrane-bound delta chain. A second delta mRNA of 1.8 kb shares the first (5' side relative to direction of transcription) three exons with the 2.7 kb delta mRNA and in addition contains a fourth exon unique to this mRNA species. This delta mRNA most likely codes for a secreted delta chain. A third delta mRNA, also of 1.8 kb, shares the first four exons and a part of the fifth exon with the 2.7 kb mRNA. Its function, if any, remains unclear. We investigated the question of how a lymphocyte can produce the mu and delta heavy chains simultaneously, using the hybridoma GCL 2.8, which makes both IgM and IgD. Results of Southern gel blot analysis and gene cloning experiments indicate that this cell utilizes the same rearranged VH gene for the synthesis of the mu and delta chains, and yet maintains the embryonic configuration for the C mu and C delta genes and for the intervening region. Based on these results, we conclude that the VH sequence is spliced alternatively to the C mu or C delta sequence during processing of the primary RNA transcript. An alternative mechanism for the expression of the delta gene is found in hybridoma B1-8. delta 1, which actively secretes delta chains and synthesizes no mu chain. This mechanism involves deletion of the C mu gene, which brings the complete VH gene closer to the C delta gene.