Radiation and anti-PD-L1 synergize by stimulating a stem-like T cell population in the tumor-draining lymph node

Radiotherapy (RT) and anti-PD-L1 synergize to enhance local and distant (abscopal) tumor control. However, clinical results in humans have been variable. With the goal of improving clinical outcomes, we investigated the underlying synergistic mechanism focusing on a CD8+ PD-1+ Tcf-1+ stem-like T cell subset in the tumor-draining lymph node (TdLN). Using murine melanoma models, we found that RT + anti-PD-L1 induces a novel differentiation program in the TdLN stem-like population which leads to their expansion and differentiation into effector cells within the tumor. Our data indicate that optimal synergy between RT + anti-PD-L1 is dependent on the TdLN stem-like T cell population as either blockade of TdLN egress or specific stem-like T cell depletion reduced tumor control. Together, these data demonstrate a multistep stimulation of stem-like T cells following combination therapy which is initiated in the TdLN and completed in the tumor.

Novel MED15::ATF1 fusion in a pediatric melanoma with spitzoid features and aggressive presentation

Childhood melanoma is a rare and biologically heterogeneous pediatric malignancy. The differential diagnosis of pediatric melanoma is usually broad, including a wide variety of spindle cell or epithelioid neoplasms. Different molecular alterations affecting the MAPK and PI3K/AKT/mTOR pathways, tumor suppressor genes, and telomerase reactivation have been implicated in melanoma tumorigenesis and progression. Here, we report a novel MED15::ATF1 fusion in a pediatric melanoma with spitzoid features and an aggressive clinical course.

Genomic and global gene expression profiling in pediatric and young adult acute leukemia with PICALM::MLLT10 Fusion

PICALM

MLLT10 fusion is a rare but recurrent genetic driver in acute leukemias. To better understand the genomic landscape of PICALM::MLLT10 (PM) positive acute leukemia, we performed genomic profiling and gene expression profiling in twenty PM-positive patients, including AML (n = 10), T-ALL/LLy (n = 8), Mixed-phenotype acute leukemia (MPAL), T/B (n = 1) and acute undifferentiated leukemia (AUL) (n = 1). Besides confirming the known activation of HOXA, differential gene expression analysis compared to hematopoietic stem cells demonstrated the enrichment of genes associated with cell proliferation-related pathways and relatively high expression of XPO1 in PM-AML and PM-T-ALL/LLy. Our study also suggested PHF6 disruption as a key cooperating event in PICALM::MLLT10-positive leukemias. In addition, we demonstrated differences in gene expression profiles as well as remarkably different spectra of co-occurring mutations between PM-AML and PM-T-ALL/LLy. Alterations affecting TP53 and NF1, hallmarks of PM-AML, are strongly associated with disease progression and relapse, whereas EZH2 alterations are highly enriched in PM-T-ALL/LLy. This comprehensive genomic and transcriptomic profiling provides insights into the pathogenesis and development of PICALM::MLLT10 positive acute leukemia.

Immune niches in brain metastases contain TCF1+ stem-like T cells, are associated with disease control and are modulated by preoperative SRS

The CD8+ T-cell response is prognostic for survival outcomes in several tumor types. However, whether this extends to tumors in the brain, an organ with barriers to T cell entry, remains unclear. Here, we analyzed immune infiltration in 67 brain metastasis (BrM) and found high frequencies of PD1+ TCF1+ stem-like CD8+ T-cells and TCF1- effector-like cells. Importantly, the stem-like cells aggregate with antigen presenting cells in immune niches, and niches were prognostic for local disease control. Standard of care for BrM is resection followed by stereotactic radiosurgery (SRS), so to determine SRS's impact on the BrM immune response, we examined 76 BrM treated with pre-operative SRS (pSRS). pSRS acutely reduced CD8+ T cells at 3 days. However, CD8+ T cells rebounded by day 6, driven by increased frequency of effector-like cells. This suggests that the immune response in BrM can be regenerated rapidly, likely by the local TCF1+ stem-like population.

Targeting vasoactive intestinal peptide-mediated signaling enhances response to immune checkpoint therapy in pancreatic ductal adenocarcinoma

A paucity of effector T cells within tumors renders pancreatic ductal adenocarcinoma (PDAC) resistant to immune checkpoint therapies. While several under-development approaches target immune-suppressive cells in the tumor microenvironment, there is less focus on improving T cell function. Here we show that inhibiting vasoactive intestinal peptide receptor (VIP-R) signaling enhances anti-tumor immunity in murine PDAC models. In silico data mining and immunohistochemistry analysis of primary tumors indicate overexpression of the neuropeptide vasoactive intestinal peptide (VIP) in human PDAC tumors. Elevated VIP levels are also present in PDAC patient plasma and supernatants of cultured PDAC cells. Furthermore, T cells up-regulate VIP receptors after activation, identifying the VIP signaling pathway as a potential target to enhance T cell function. In mouse PDAC models, VIP-R antagonist peptides synergize with anti-PD-1 antibody treatment in improving T cell recruitment into the tumors, activation of tumor-antigen-specific T cells, and inhibition of T cell exhaustion. In contrast to the limited single-agent activity of anti-PD1 antibodies or VIP-R antagonist peptides, combining both therapies eliminate tumors in up to 40% of animals. Furthermore, tumor-free mice resist tumor re-challenge, indicating anti-cancer immunological memory generation. VIP-R signaling thus represents a tumor-protective immune-modulatory pathway that is targetable in PDAC.

A CTNNB1-altered medulloblastoma shows the immunophenotypic, DNA methylation, and transcriptomic profiles of SHH-activated, and not WNT-activated, medulloblastoma

Recent advancement in molecular characterisation has identified four principal molecular groups of medulloblastoma (MB), namely WNT, SHH, group 3, and group 4, and each has its characteristic clinical features, predilection for specific anatomic sites, signature genetic alterations, and distinct DNA methylome profiles [1]. Immunophenotypically, MB can be divided into WNT, SHH, and non-WNT/non-SHH groups by their expression of YAP1 and GAB1-WNT MB expresses YAP1, in addition to its characteristic nuclear b-catenin positivity, and SHH MB expresses both. In contrast, non-WNT/non-SHH MB is negative for both [2]. Thus far, CTNNB1 mutations have been considered pathognomonic of WNT MB. Furthermore, it has been shown that CTNNB1 mutations dominantly drive the WNT-activated phenotype in MB, even in the presence of alterations in the SHH pathway [3, 4].

Risk Perception and Knowledge, Attitudes, and Practices Against COVID-19 in a Hypertensive Population From a Semi-Urban City of Ecuador

Background: In an elderly population with hypertension, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is associated with a higher incidence of mortality and a protracted course of clinical symptoms. Objective: To assess the perceived risk of infection and complications due to COVID-19 in people with hypertension living in a semi-urban city of Ecuador. Methods: A cross-sectional telephone survey of adult outpatients with a previous diagnosis of hypertension in the semi-urban community of Conocoto in Quito, Ecuador was conducted from August to December 2020. Results: A total of 260 adult outpatients, aged 34-97 years, completed telephone surveys. Of total, 71.5% (n = 186) of respondents were women and 28.5% (n = 74) of respondents were men. Overall, 18.1% believe that their risk of infection is "very high," 55.4% believe that their risk of infection is "high," 21.5% believe that their risk of infection is "low," and 5% believe that their risk of infection is "very low." The perceived risk of complications, if infected by COVID-19, revealed that 21.9% believe that their risk of complication is "very high," 65.0% believe that their risk of complication is "high," 10.4% believe that their risk of complication is "low," and 2.7% believe that their risk of complication is "very low." Conclusion: Patients with hypertension are aware of the risks posed by COVID-19 infection and its impact on their health. However, the health system must educate the population on health practices and behaviors to avoid COVID-19 infection until the majority of the population of Ecuador can be vaccinated.

Abstract PO-072: Inhibiting vasoactive intestinal peptide receptor signaling elicits T cell dependent anti-tumor response of pancreatic ductal adenocarcinoma to immune checkpoint therapy

Pancreatic ductal adenocarcinoma (PDAC) is unresponsive to immune checkpoint therapy largely due to a paucity of T cells within the tumor microenvironment (TME) and abundant immunosuppressive signaling pathways. In this study we show that human PDAC tumors over-express vasoactive intestinal peptide (VIP), an immunosuppressive neuropeptide that suppresses T cell effector properties and promotes the generation of regulatory T cells (Tregs). Therefore, we treated tumor-bearing mice with VIP receptor peptide antagonists and measured T cell homing, activation, and anti-tumor responses in preclinical murine models of PDAC. Pharmacological inhibition of VIP receptor (VIP-R) signaling using daily subcutaneous injections of peptide antagonists had no discernable toxicity in healthy and tumor-bearing mice. Treatment with VIP-R antagonists in combination with anti-PD-1 checkpoint blockade significantly decreased tumor burden, and improved survival in subcutaneous and orthotopic murine PDAC models. Combination therapy significantly enhanced T cell activation and proliferation and decreased frequencies of Tregs within the TME. Anti-tumor responses were T cell dependent, as the combination therapy failed to improve survival in CD4 or CD8 deficient mice using knock-out strains and antibody depletion. Furthermore, combination therapy significantly increased frequencies of tumor specific T cells (measured with a tetramer reagent) and provided protective immunity against tumor rechallenge. Combination therapy led to significant increases in the infiltration of adoptively transferred GFP+ T cells into PDAC tumors and decreased CXCR4 expression levels on T cells. Encouragingly, peptide-based VIP-R antagonists enhanced the in vitro activation of human T cells isolated from peripheral blood of PDAC patients. Human T cells cultured with VIP-R antagonists had increased proliferation, activation, and decreased proportions of T regs and exhausted T cells co-expressing PD-1, Tim-3 and Lag-3. Taken together, our findings show that VIP is a targetable mechanism of immune escape in PDAC. Inhibiting VIP receptor signaling improves T cell effector properties and synergistically improves anti-tumor responses to checkpoint inhibitors in mouse PDAC models. Additionally, as the VIP sequence is identical between human and mice, and since VIP-R antagonists have similar effects on human and murine T cells in culture, clinical translation is highly feasible.

Citation Format: Sruthi Ravindranathan, Passang Tenzin, Jian Ming Li, Rohan Dhamsania, Michael Ware, Mohammad Zaidi, Shuhua Wang, Jingru Zhu, Maria Cardenas, Yuan Liu, Gaurav Joshi, Sanjeev Gumber, Brian Robinson, Anish Sen-Majumdar, Shanmuganathan Chandrakasan, Haydn Kissick, Alan Frey, Susan Thomas, Bassel El-Rayes, Gregory Lesinski, Edmund K. Waller. Inhibiting vasoactive intestinal peptide receptor signaling elicits T cell dependent anti-tumor response of pancreatic ductal adenocarcinoma to immune checkpoint therapy [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-072.

640 Stem-like CD4 T cells in cancer

Background

CD4 T cells can differentiate into multiple effector subsets that can mediate variable functions. In this work we aim to understand how CD4 T cells differentiate in response to tumor antigens and their respective function in the anti-tumor response.

Methods

Tumor tissue was collected from patients undergoing surgery at Emory University Hospital. Activated PD1+ CD45RA- tumor infiltrating CD4 T cells were sent for 10X single cell RNA-seq. Tumor samples were also processed for flow cytometry and ex vivo functional analyses. For in vivo studies, prostate cancer mouse model expressing the LCMV glycoprotein (TRAMPC1-GP) was used, as well as LCMV Armstrong infection.

Results

To characterize the heterogeneity of CD4 T cells infiltrating kidney tumors, we performed single cell RNAseq. We found three distinct activated (PD1+ CD45RA-) CD4 T cell populations. Two effector clusters consisting of Th1-like (EOMES+) and Treg (FOXP3+) cells, and a third cluster expressing TCF1, and genes associated with stemness and survival that did not fit defined CD4 effector lineages. We further confirmed these data by flow cytometry and found the same tumor infiltrating CD4 subsets in 100 kidney cancer patients. When placed in culture under different polarization conditions, tumor TCF1+ CD4 T cells proliferated and differentiated into the Th1-like and Treg effector populations found in the tumor, in addition to other effector lineages (Th1, Tfh) given the appropriate conditions, while the Th1-like and Treg cells underwent no proliferation or phenotype changes. These data suggests that the TCF1+ CD4s act as activated unpolarized precursors to the effector subsets in the tumor. To further test this hypothesis in vivo, we adoptively transferred tumor specific (SMARTA) CD4 T cells into mice followed by TRAMPC1-GP tumor inoculation. Transferred SMARTAs activated and first acquired a TCF1+ phenotype in the TDLN prior to predominantly differentiating into Tregs in the tumor. Given their plasticity in vitro, we asked whether TCF1+ SMARTAs primed in tumors were destined to differentiate into Tregs. To test this, we transferred 4-week activated TCF1+ SMARTAs from TDLNs of TRAMPC1-GP mice into naïve mice that were immediately infected with LCMV Armstrong. We found that the transferred SMARTAs differentiated into Th1 and Tfh cells in response to the virus, similar to the endogenous virus specific CD4 T cells.

Conclusions

Overall, this work shows that CD4 T cells remain in an activated phenotype in the tumor with the capacity to differentiate into non-suppressive effector lineages given the appropriate conditions that may benefit the anti-tumor response.

929 Dissecting intratumoral immune organization: defining the comparative cellular composition of tertiary lymphoid structures T-cell supportive antigen presenting niches in renal tumors

Background

Tumor infiltrating T-cells have a prognostic benefit in many tumor types,1–8 and we recently sought to determine whether the level of T-cell infiltration into renal tumors predicts clinical outcomes. In our recent publication,9 we showed that patients with high of CD8 T-cell infiltration have improved progression free survival (PFS). Further, we found that this T-cell response is supported by TCF1+ stem-like CD8 T-cells, which reside within dense regions of closely clustered antigen presenting cells within the tumor. Interestingly, aggregations of immune cells have also been described in other tumor types and termed ‘tertiary lymphoid structures’ (TLS), which are typically defined as B-cell-dominant aggregates, containing high endothelial venules and reactive germinal centers.10–12 Together, these findings raise several important questions, which we explore here—(1) what additional cell types comprise these niches?9 and (2) how are these niches similar to or different from TLS?

Methods

Tumor tissue was collected from patients with renal tumors undergoing surgery at Emory University Hospital. Intraoperative tumor samples were analyzed by flow cytometry, RNA sequencing, immunofluorescence, and immunohistochemistry. Immunofluorescence data was analyzed using our custom quantitative analysis pipelines, which allows for delineation of cell type and location, cell-cell distance, and density of cellular aggregation.

Results

The proportion of CD8 T-cells infiltration human renal tumors varied widely, consistent with our previous reports.9 TCF1+ stem-like CD8 T-cells were identifiable by both flow cytometry and immunofluorescence and resided in dense antigen presenting niches. Quantitative immunofluorescence revealed the location of aSMA+ fibroblasts within tumor tissue, in relation to antigen presenting niches, and in tumors with many infiltrating T-cells. Pathologist scored hematoxylin and eosin-stained slides were delineated TLS+ or TLS-. Quantitative immunofluorescence imaging analysis revealed the detailed composition of tumor infiltrating immune cell populations and the contrasting cellular organization in TLS as compared to in antigen presenting niches.

Conclusions

As we have shown CD8 T-cell infiltration to predict PFS in renal tumors and that antigen presenting niches containing stem-like cells maintain the anti-tumor T-cell response,9 it is critical to understand the additional cell types present in these niches and to understand how these niches relate to previously described phenomena of immune organization, such as TLS.10–12 This mechanistic understanding of the anti-tumor immune response represents an opportunity to inform development of enhanced prognostic tools and innovative therapeutic possibilities.

References

Azimi F, et al. Tumor-infiltrating lymphocyte grade is an independent predictor of sentinel lymph node status and survival in patients with cutaneous melanoma. J Clin Oncol 2012;30(21):2678–83. Epub 2012/06/20. doi: 10.1200/jco.2011.37.8539. PubMed PMID: 22711850.

Galon J, et al. Type, density, and location of immune cells within human colorectal tumors predict clinical outcome. Science 2006;313(5795):1960–4. Epub 2006/09/30. doi: 10.1126/science.1129139. PubMed PMID: 17008531.

Mlecnik B, et al. Integrative analyses of colorectal cancer show immunoscore is a stronger predictor of patient survival than microsatellite instability. Immunity 2016;44(3):698–711. Epub 2016/03/18. doi: 10.1016/j.immuni.2016.02.025. PubMed PMID: 26982367.

Mlecnik B, et al. Histopathologic-based prognostic factors of colorectal cancers are associated with the state of the local immune reaction. J Clin Oncol 2011;29(6):610–8. Epub 2011/01/20. doi: 10.1200/JCO.2010.30.5425. PubMed PMID: 21245428.

Pagès F, et al. Immune infiltration in human tumors: a prognostic factor that should not be ignored. Oncogene 2009;29:1093. doi: 10.1038/onc.2009.416.

Peranzoni E, et al. Macrophages impede CD8 T cells from reaching tumor cells and limit the efficacy of anti-PD-1 treatment. Proceedings of the National Academy of Sciences of the United States of America 2018;115(17):E4041–E50. Epub 2018/04/11. doi: 10.1073/pnas.1720948115. PubMed PMID: 29632196.

Savas P, et al. Single-cell profiling of breast cancer T cells reveals a tissue-resident memory subset associated with improved prognosis. Nat Med 2018;24(7):986–93. Epub 2018/06/27. doi: 10.1038/s41591-018-0078-7. PubMed PMID: 29942092.

Tosolini M, et al. Clinical impact of different classes of infiltrating T cytotoxic and helper cells (Th1, th2, treg, th17) in patients with colorectal cancer. Cancer Res 2011;71(4):1263–71. Epub 2011/02/10. doi: 10.1158/0008-5472.Can-10-2907. PubMed PMID: 21303976.

Jansen CS, et al. An intra-tumoral niche maintains and differentiates stem-like CD8 T cells. Nature 2019;576(7787):465–70. doi: 10.1038/s41586-019-1836-5.

Dieu-Nosjean MC, et al. Tertiary lymphoid structures in cancer and beyond. Trends Immunol 2014;35(11):571–80. Epub 2014/12/03. doi: 10.1016/j.it.2014.09.006. PubMed PMID: 25443495.

Goc J, et al. Characteristics of tertiary lymphoid structures in primary cancers. Oncoimmunology 2013;2(12):e26836. Epub 2014/02/06. doi: 10.4161/onci.26836. PubMed PMID: 24498556; PMCID: PMC3912008.

Sautes-Fridman C, et al. Tertiary lymphoid structures in the era of cancer immunotherapy. Nature reviews Cancer 2019;19(6):307–25. Epub 2019/05/17. doi: 10.1038/s41568-019-0144-6. PubMed PMID: 31092904.

Ethics Approval

Samples are collected under an approved IRB protocol (The Urological Satellite Specimen Bank at Emory University, IRB00055316). All patients provided informed consent.

Consent

Samples are collected under an approved IRB protocol (The Urological Satellite Specimen Bank at Emory University, IRB00055316). All patients provided informed consent.

658 CD8 T cell activation in cancer is comprised of two distinct phases

Background

CD8 T cell are a crucial part of the immune response to tumors, with CD8 infiltration predicting disease progression in numerous cancer types. Recently two subsets of CD8 T cells that respond to tumors have been described, a stem-like (TCF1+) CD8 T cell that can give rise to a more cytotoxic terminally differentiated (TD) (TCF1-Tim3+) CD8 T cell. In this study we aimed to understand the origin of stem-like TCF1+ CD8 T cells within tumors.

Methods

Human patient TDLN and tumor samples from kidney and prostate cancer were processed after resection and used for flow cytometry, RNA-seq, TCR-seq and whole genome DNA methylation analysis. We also used a prostate cancer mouse model that expresses the LCMV GP protein (TRAMPC1-LCMV-GP) to track tumor-specific CD8 T cells in both TDLNs and tumors.

Results

We studied human prostate and kidney cancer tumor-draining lymph nodes (TDLN) and found that CD8 T cells are activated but fail to acquire an effector phenotype within the TDLN. Instead, they share functional, transcriptional, and epigenetic traits with stem-like cells in the tumor. We also found that activated CD8 T cells from TDLNs shared TCR overlap with both CD8 subsets within tumors. This suggests that these activated cells are a precursor to the stem-like CD8 T cells in tumors. To further test this hypothesis, we used our TRAMPC1-LCMV-GP tumor model to study tumor-specific CD8 T cell activation. We found that CD8 T cells are activated in TDLNs but fail to acquire an effector program. These cells then establish the stem-like CD8s within tumor where they require additional co-stimulation from antigen presenting cells to differentiate into TCF1- TD CD8 T cells. This is strikingly different from canonical CD8 T cell activation to acute viruses, where the effector program is acquired immediately. We also showed that human stem-like CD8 T cells require co-stimulation and TCR stimulation to divide and differentiate into terminally differentiated CD8s in-vitro, and DCs from autologous tumors can also induce this differentiation.

Conclusions

Overall this work shows a model of CD8 T cell activation in response to tumors that has two distinct phases. The first occurs in the TDLN where CD8 T cells are initially activated, the second occurs in the tumor where CD8 T cells acquire an effector function after additional co-stimulation. This model of T cell differentiation adds to our understanding of basic CD8 T cell biology and has important implications to improve our current immunotherapies.

Novel Anaplastic Thyroid Cancer PDXs and Cell Lines: Expanding Preclinical Models of Genetic Diversity

CONTEXT

Anaplastic thyroid cancer (ATC) is a rare, aggressive, and deadly disease. Robust preclinical thyroid cancer models are needed to adequately develop and study novel therapeutic agents. Patient-derived xenograft (PDX) models may resemble patient tumors by recapitulating key genetic alterations and gene expression patterns, making them excellent preclinical models for drug response evaluation.

OBJECTIVE

We developed distinct ATC PDX models concurrently with cell lines and characterized them in vitro and in vivo.

METHODS

Fresh thyroid tumor from patients with a preoperative diagnosis of ATC was surgically collected and divided for concurrent cell line and PDX model development. Cell lines were created by generating single cells through enzymatic digestion. PDX models were developed following direct subcutaneous implantation of fresh tumor on the flank of immune compromised/athymic mice.

RESULTS

Six ATC PDX models and 4 cell lines were developed with distinct genetic profiles. Mutational characterization showed one BRAF/TP53/CDKN2A, one BRAF/CDKN2A, one BRAF/TP53, one TP53 only, one TERT-promoter/HRAS, and one TERT-promoter/KRAS/TP53/NF2/NFE2L2 mutated phenotype. Hematoxylin-eosin staining comparing the PDX models to the original patient surgical specimens show remarkable resemblance, while immunohistochemistry stains for important biomarkers were in full concordance (cytokeratin, TTF-1, PAX8, BRAF). Short tandem repeats DNA fingerprinting analysis of all PDX models and cell lines showed strong concordance with the original tumor. PDX successful establishment rate was 32%.

CONCLUSION

We have developed and characterized 6 novel ATC PDX models with 4 matching cell lines. Each PDX model harbors a distinct genetic profile, making them excellent tools for preclinical therapeutic trials.

A High-throughput Approach to Identify Effective Systemic Agents for the Treatment of Anaplastic Thyroid Carcinoma

BACKGROUND

Despite the use of aggressive multimodality treatment, most anaplastic thyroid carcinoma (ATC) patients die within a year of diagnosis. Although the combination of BRAF and MEK inhibitors has recently been approved for use in BRAF-mutated ATC, they remain effective in a minority of patients who are likely to develop drug resistance. There remains a critical clinical need for effective systemic agents for ATC with a reasonable toxicity profile to allow for rapid translational development.

MATERIAL AND METHODS

Twelve human thyroid cancer cell lines with comprehensive genomic characterization were used in a high-throughput screening (HTS) of 257 compounds to select agents with maximal growth inhibition. Cell proliferation, colony formation, orthotopic thyroid models, and patient-derived xenograft (PDX) models were used to validate the selected agents.

RESULTS

Seventeen compounds were effective, and docetaxel, LBH-589, and pralatrexate were selected for additional in vitro and in vivo analysis as they have been previously approved by the US Food and Drug Administration for other cancers. Significant tumor growth inhibition (TGI) was detected in all tested models treated with LBH-589; pralatrexate demonstrated significant TGI in the orthotopic papillary thyroid carcinoma model and 2 PDX models; and docetaxel demonstrated significant TGI only in the context of mutant TP53.

CONCLUSIONS

HTS identified classes of systemic agents that demonstrate preferential effectiveness against aggressive thyroid cancers, particularly those with mutant TP53. Preclinical validation in both orthotopic and PDX models, which are accurate in vivo models mimicking tumor microenvironment, may support initiation of early-phase clinical trials in non-BRAF mutated or refractory to BRAF/MEK inhibition ATC.

Sequencing of a central nervous system tumor demonstrates cancer transmission in an organ transplant

This study uses DNA sequencing to trace a donor organ transplant–mediated cancer transmission and illustrates how precise molecular pathology profiles might reduce future risk for transplant recipients.

Four organ transplant recipients from an organ donor diagnosed with anaplastic pleomorphic xanthoastrocytoma developed fatal malignancies for which the origin could not be confirmed by standard methods. We identified the somatic mutational profiles of the neoplasms using next-generation sequencing technologies and tracked the relationship between the different samples. The data were consistent with the presence of an aggressive clonal entity in the donor and the subsequent proliferation of descendent tumors in each recipient. Deleterious mutations in BRAF, PIK3CA, SDHC, DDR2, and FANCD2, and a chromosomal deletion spanning the CDKN2A/B genes, were shared between the recipients’ lesions. In addition to demonstrating that DNA sequencing tracked a donor/recipient cancer transmission, this study established that the genetic profile of a donor tumor and its potential aggressive phenotype could have been determined before transplantation was considered. As the genetic correlates of tumor invasion and metastases become better known, adding genetic profiling by DNA sequencing to the data considered for transplant safety should be considered.

CD8 T cell differentiation in cancer is comprised of two distinct phases

A crucial part of the immune response to tumors are CD8 T cells, with CD8 infiltration predicting disease progression in many cancers. Recent work has shown two subsets of CD8 T cells that respond to tumors, one a stem-like CD8 T cell (TCF1+) that can give rise to a more cytotoxic terminally differentiated cell (TCF1−). To understand the CD8 T cell response to tumors it is important to study how tumor-specific CD8 T cells activate and differentiate. To study this we have made a prostate cancer model which expresses the LCMV glycoprotein (GP) and acts as a tumor-specific antigen. This model allows us to transfer LCMV GP specific P14 CD8 T cells into TRAMPC1-GP bearing mice to study how tumor-specific CD8 T cells activate. These studies have shown that tumor-specific CD8 T cells are activated in tumor draining lymph nodes (TDLN), where they retain an activated undifferentiated phenotype, upregulating CD44, PD1, while maintaining TCF1. These tumor-specific CD8 T cells only differentiate (TCF1−) once they have migrated into the tumor. This model can also be seen in human prostate cancer, with CD8 T cells in TDLNs retaining an activated undifferentiated phenotype (PD1+CD45RA-TCF1+). To determine if these cells are related to the CD8s within the tumor we have shown TCR overlap between the activated CD8s T cells in human prostate TDLNs and the CD8 T cell subsets within the tumor. These data suggest a two-step differentiation process for tumor-specific CD8 T cells where they are activated in TDLNs and differentiate further only in the tumor. This model of two distinct phases of CD8 T cell differentiation adds to the basic understanding of the immune response to cancer.

Integrated Analysis of TP53 Gene and Pathway Alterations in The Cancer Genome Atlas

The TP53 tumor suppressor gene is frequently mutated in human cancers. An analysis of five data platforms in 10,225 patient samples from 32 cancers reported by The Cancer Genome Atlas (TCGA) enables comprehensive assessment of p53 pathway involvement in these cancers. More than 91% of TP53-mutant cancers exhibit second allele loss by mutation, chromosomal deletion, or copy-neutral loss of heterozygosity. TP53 mutations are associated with enhanced chromosomal instability, including increased amplification of oncogenes and deep deletion of tumor suppressor genes. Tumors with TP53 mutations differ from their non-mutated counterparts in RNA, miRNA, and protein expression patterns, with mutant TP53 tumors displaying enhanced expression of cell cycle progression genes and proteins. A mutant TP53 RNA expression signature shows significant correlation with reduced survival in 11 cancer types. Thus, TP53 mutation has profound effects on tumor cell genomic structure, expression, and clinical outlook.

Computational discovery of non-mutational tumor-restricted antigens reveals evidence of immunoediting in head and neck squamous cell carcinoma

6564

Background: We previously identified 107 expression-based tumor antigens (EbTAgs) defined as genes with negligible expression in healthy tissue and overexpression in cancer. EbTAgs present novel targets for the adaptive anti-tumor immune response and exhibit evidence of immunoediting in highly immune infiltrated oral cavity tumors. To detail the landscape of EbTAgs in head and neck squamous cell carcinoma (HNSC) and further elucidate EbTAg immunoediting, we compared the expression EbTAgs in the context of tumor immune infiltration among four HNSCC subtypes: oral cavity (OC), HPV+ oropharyngeal (HPV+OP), HPV- oropharyngeal (HPV-OP), and laryngeal/hypopharyngeal (LH). Methods: Upper quartile FPKM gene expression values of all protein coding genes were calculated for all HNSC samples using RNAseq data from The Cancer Genome Atlas (TCGA). TCGA HNSC tumors were divided into subtypes and analyzed for EbTAg expression. Individual tumor sample immune infiltrate was determined using unsupervised clustering of 14 immune cell signature ssGSEA scores for the HNSC dataset as a whole and for each subtype. Results: LH tumors expressed significantly more EbTAgs than other subtypes (p=0.0014), specifically HPV+OP (p=0.0008, Tukey’s test). Immune clustering analysis showed that LH tumors were significantly more likely to be in the low than the high immune cluster whereas the reverse was true for HPV+OP tumors (p<0.0001). Hypothesizing that EbTAg expression was a function of tumor immune infiltration rather than HNSC subtype, we compared EbTAg expression between tumors in low and high immune clusters of the entire HNSC dataset as well as of each HNSC subtype. Significantly more EbTAgs were expressed in low immune tumors compared to high immune tumors of the HNSC dataset (p<0.0001). Similarly, significantly more EbTAgs were expressed in low immune tumors compared to high immune tumors of the OC, OP-all tumors, and HPV+OP datasets (p=0.0003, p<0.0001, p=0.0006) with a trend of more EbTAgs in the immune low versus high tumors in the HPV-OP and LH datasets (p=0.12, p=0.095). Conclusions: EbTAg expression in TCGA HNSC samples correlates with tumor immune infiltration resulting in lower expression under greater immunological pressure. These results reinforce the hypothesis that EbTAgs undergo immunoediting and are immunologically relevant. Exploration of EbTAgs as antigenic targets of modular vaccines or adoptive T-cell therapy as well as biomarkers of immune checkpoint inhibition therapy response is warranted.

Tumor-specific CD8 T cell activation in draining lymph nodes supports the anti-tumor CD8 T cell response

CD8 T cells are a critical part of the immune response to tumors, with CD8 T cell infiltration predicting disease progression in many types of cancer. Recent work in CD8 T cell immunology described how CD8 T cells respond to chronic diseases, finding two subsets of CD8 T cells within tumors. One is a stem-like CD8 T cell and the other is a terminally differentiated CD8 T cell with cytotoxic capabilities. Determining how tumor-specific CD8 T cells activate and differentiate is critical to understanding why some tumors are highly infiltrated. To study how tumor-specific CD8 T cells are activated, I have made a prostate cancer model that expresses the viral LCMV glycoprotein (GP) which acts as a tumor-specific antigen. We have used this model to study tumor-specific CD8 T cell activation by adoptively transferring LCMV GP specific TCR transgenic P14 CD8 T cells into TRAMPC1-LCMV-GP bearing mice. We have found when tumor-specific CD8 T cells are activated in the tumor-draining lymph node they acquire an undifferentiated but activated program, upregulating CD44, PD1 but retaining high TCF1 and CD62L expression. These undifferentiated activated CD8 T cells do not acquire a typical effector program that is seen in an acute viral infection such as LCMV Armstrong, yet they are able to migrate to the tumor to establish the anti-tumor response. In conclusion, tumor-specific CD8 T cells do not acquire an effector program after activation and instead gain an undifferentiated activated phenotype. These data suggest that tumor-specific CD8 T cells are activated in the TDLN and differentiate to become the stem-like CD8 T cells within the tumor, establishing the anti-tumor CD8 response.

An intra-tumoral niche maintains and differentiates stem-like CD8 T cells

Tumour-infiltrating lymphocytes are associated with a survival benefit in several tumour types and with the response to immunotherapy^1-8. However, the reason some tumours have high CD8 T cell infiltration while others do not remains unclear. Here we investigate the requirements for maintaining a CD8 T cell response against human cancer. We find that CD8 T cells within tumours consist of distinct populations of terminally differentiated and stem-like cells. On proliferation, stem-like CD8 T cells give rise to more terminally differentiated, effector-molecule-expressing daughter cells. For many T cells to infiltrate the tumour, it is critical that this effector differentiation process occur. In addition, we show that these stem-like T cells reside in dense antigen-presenting-cell niches within the tumour, and that tumours that fail to form these structures are not extensively infiltrated by T cells. Patients with progressive disease lack these immune niches, suggesting that niche breakdown may be a key mechanism of immune escape.

Abstract 567: Comparative mining of normal and tumor tissue RNAseq gene expression datasets to define expression-based neo-antigens

Background: Mutational neo-antigens (MuNeoAgs) are attractive targets for cancer vaccines because they are unique to tumors. However, limited epitope potential of point mutations, inherent difficulties predicting immunogenicity, and lack of shared mutations across patient tumors has hindered vaccine development. Alternatively, we elected to identify non-mutated, expression-based tumor-specific neo-antigens (EbNeoAgs) defined by their overexpression in tumors and negligible expression in healthy tissue. EbNeoAgs have a low probability of cross-reactivity, while allowing epitope creation across the entire protein. Additionally, they should be present in a higher proportion of patients and could be used to make modular off-the-shelf vaccines.

Methods: RNAseq data from the NIH Genotype-Tissue Expression (GTEx) and The Cancer Genome Atlas (TCGA) projects, previously harmonized with a common calling/ mapping algorithm and available from the University of California Santa Cruz TOIL RNAseq recompute project, were used to calculate upper quartile FPKM gene expression values for all samples based on protein coding RNAs. RNAseq data from 27 normal tissue types (excluding testis) from GTEx and TCGA normal tissue was analyzed to identify genes with negligible expression across all healthy tissue. Genes with negligible expression were then analyzed to determine if they were elevated (i.e. expressed at intermediate or higher levels) in samples across 32 different cancer types (excluding testicular tumors). Thresholds for intermediate expression were calculated individually for each tumor type based upon the median FPKM expression values for all protein coding genes with 95% confidence intervals.

Results: 1296 genes were expressed below threshold in all healthy tissues, and 107 of these genes were elevated in 5% or more of samples in at least one cancer. 40/107 EbNeoAgs (37%) are known Cancer Testis Antigens (CTAs), with the remaining 67 representing potentially novel EbNeoAgs. If the threshold for elevated expression is lowered to just 1% of samples for at least one cancer, 58 of the known 276 CTAs are detected. The remaining CTAs are overexpressed in at least one healthy tissue or were not elevated in cancer. In melanoma (cancer with the most EbNeoAgs), 53 (52.0%), 69 (67.6%), and 88 (86.3%) samples expressed at least 5, 3, or 1 EbNeoAg respectively. Comparatively, in lung adenocarcinoma, 81 (15.8%), 97 (18.9%), and 228 (44.4%) samples expressed at least 5, 3, or 1 EbNeoAg respectively.

Conclusion: We leveraged publicly available tumor and normal RNAseq datasets to comprehensively identify EbNeoAgs in an unbiased fashion across 32 tumor types. Many of the EbNeoAgs were known CTAs, but a significant number of EbNeoAgs were novel. Approximately half the cancers exhibited EbNeoAg expression in a large proportion of patients making them broad targets for cancer vaccine development.

Citation Format: Jan O. Kemnade, Maria Cardenas, David Wheeler, Andrew G. Sikora, Mitchell J. Frederick. Comparative mining of normal and tumor tissue RNAseq gene expression datasets to define expression-based neo-antigens [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 567.

Very low or undetectable intact parathyroid hormone levels in patients with surgically verified parathyroid adenomas

OBJECTIVES

To report and explore potential reasons for undetectable or low-normal serum intact PTH levels in patients with surgically verified primary hyperparathyroidism with parathyroid adenomas, review the relevant literature, and offer suggestions for management of such patients occasionally encountered in clinical practice. For future research, to help understand mechanisms underlying 'undetectable' or inappropriately low serum intact PTH levels.

METHODS

Serum intact PTH levels were measured pre- and postoperatively by immunochemiluminescent assay (ICMA) and the results were confirmed by at least two repeated measurements on different occasions in each patient.

PATIENTS

We encountered two unusual patients with primary hyperparathyroidism who had suggestive biochemical and/or clinical features of primary hyperparathyroidism. However, serum intact PTH levels were either very low or undetectable in the context of hypercalcaemia, with no other obvious cause. A (99m)Tc sestamibi scan showed increased uptake in one of the parathyroid glands, suggesting a single adenoma in each case that was confirmed at surgery.

RESULTS

In the first patient, from India, mean +/- SD serum calcium was 2.6 +/- 0.32 mmol/l (reference range 2.12-2.74 mmol/l) with intact PTH of 0.11 pmol/l (reference range 1.1-7.59 pmol/l). In the second patient, from the USA, mean +/- SD serum calcium and intact PTH were 2.9 +/- 0.07 mmol/l (reference range 2.17-2.51 mmol/l) and 1.35 pmol/l (reference range 1.1-7.59 pmol/l), respectively. Following curative parathyroidectomy, serum calcium levels normalized in both patients. By contrast, serum intact PTH levels, which were either suppressed or very low before surgery, rose into the low-normal reference range in all patients.

CONCLUSIONS

When the clinical suspicion is high, the diagnosis of primary hyperparathyroidism should be pursued despite suppressed or low-normal serum intact PTH levels after carefully excluding other causes of hypercalcaemia. Further research on various intact PTH molecular species secreted by parathyroid adenomas or post-translational changes in the intact PTH molecule that might interfere with in vitro measurements should be undertaken to understand the precise reason(s) for such anomalous findings.

Systemic high blood pressure and inner ear dysfunction: a preliminary study

OBJECTIVE

To assess the association between inner ear dysfunction and retinal vascular changes related to systemic arterial hypertension.

DESIGN

A comparative, cross-sectional and observational study.

SETTING

Primary care.

MAIN OUTCOMES MEASURES

Hearing and vestibular symptoms evaluated by a standardized questionnaire; cochlear function evaluated by audiometry and distortion product otoacoustic emissions; vestibular function evaluated by oculomotor and bithermal caloric tests and vascular retinal compromise evaluated by ophthalmoscopy (according to the modified Scheie classification).

RESULTS

Forty-two subjects participated in the study, 21 with and 21 without arterial hypertension, age and sex matched; with no history of diabetes mellitus and with normal glucose levels and normal blood lipids. Although patients with hypertension reported vertigo more frequently than control subjects, conventional oculomotor and bithermal caloric tests showed no difference between the two groups. Patients with hypertension showed deterioration of hearing thresholds at 8 kHz and, compared with normotensive subjects, a higher frequency of abnormal otoacoustic emissions (P = 0.01). According to Scheie classification, 43% (95% CI: 33-53%) of the patients showed second degree retinal vascular compromise and 24% (95% CI: 15-33%) of them showed first degree compromise. The degree of the vascular retinal compromise was significantly correlated with the hearing thresholds at 8 kHz (Spearman's correlation coefficient 0.45, P = 0.002) and it was also consistent with the absence of otoacoustic emissions at frequencies between 4 and 8 kHz.

CONCLUSION

The results of this preliminary study suggest that patients with systemic arterial hypertension may have cochlear dysfunction associated with the vascular disease because of hypertension, which could be silent and without clear evidence of vestibular dysfunction.

Surface complexation of DNA with insoluble monolayers. Influence of divalent counterions

DNA interacts with insoluble monolayers made of cationic amphiphiles as well as with monolayers of zwitterionic lipids in the presence of divalent ions. Binding to dioctadecyldimethylammonium bromide (DODAB) or distearoyl-sn-glycero-3-phosphocholine (DSPC) monolayers in the presence of calcium is accompanied by monolayer expansion. For the positively charged DODAB monolayer, this causes a decrease of surface potential, while an increase is observed for the DSPC monolayers. Binding to dipalmitoyl-sn-glycero-3-phosphocholine preserves most of the liquid expanded-liquid condensed coexistence region. The liquid condensed domains adopt an elongated morphology in the presence of DNA, especially in the presence of calcium. The interaction of DNA with phospholipid monolayers is ion specific: the presence of calcium leads to a stronger interaction than magnesium and barium. These results were confirmed by bulk complexation studies.

Comparative study of cerebral blood flow between postural tachycardia and neurocardiogenic syncope, during head-up tilt test

We assessed the cerebral blood flow velocity response to head-up tilt test in patients with typical neurocardiogenic syncope compared with patients showing postural tachycardia. Fifty patients (21 men) with history of orthostatic intolerance, younger than 50 years (mean 27 +/- 10), participated in the study. Transcranial Doppler sonography of the middle cerebral artery, heart rate and brachial blood pressure were recorded during a head-up tilt test. According to the outcome of the test, patients were categorized in two groups: neurocardiogenic syncope (29 patients) and postural tachycardia (21 patients). The clinical history of the two groups was similar. During baseline in the supine position, no differences in haemodynamic parameters were observed. From the first min of tilt, the heart rate was higher in patients with postural tachycardia than in patients with neurocardiogenic syncope. Although, during tilt, the absolute values of the cerebral blood flow parameters were similar in the two groups, throughout tilt, continuous observation of the Doppler recording in patients with postural tachycardia showed intermittent fluctuation of the blood flow velocity, with an oscillatory pattern, which were not observed in the recordings in patients with neurocardiogenic syncope. Comparison of patients with neurocardiogenic syncope, and those with postural tachycardia also showed larger variations of the pulsatility index (P < 0.05) in the postural tachycardia group. These findings support the possibility that abnormalities within the central nervous system play a pivotal role in the pathogenesis of postural tachycardia.

Tilt testing in neurocardiogenic syncope: isosorbide versus isoproterenol

OBJECTIVE

To compare the diagnostic value of pharmacological stimulation with sublingual isosorbide dinitrate and intravenous isoproterenol during tilt testing in patients with neurocardiogenic syncope and with a negative tilt test without pharmacological provocation.

METHODS AND RESULTS

One hundred and twenty patients with a history of neurocardiogenic syncope (aged 15 to 77 years) and 50 healthy volunteers (aged 25 to 70 years) were prospectively submitted to head-up tilt (HUT). Those who did not develop syncope or presyncope during passive HUT for 30 minutes underwent repeated HUT with isoproterenol infusion at 4 microg/min (ISOP HUT), for 10 minutes, and, subsequently, were tilted after sublingual administration of 5 mg of isosorbide dinitrate (ISDN HUT) for another 12 minutes. ISDN HUT was always performed after ISOP HUT. Sensitivity and specificity of passive HUT were 41% (95% C.I. 32.9% to 51.0%) and 100%, respectively. Sensitivity of ISOP HUT was 51.4% (95% C.I. 39.2% to 63.6%) and specificity 70% (95% C.I. 55.4% to 82.1%) and for ISDN HUT were 70% (95% C.I. 57.9% to 80.4%) and 88% (95% C.I. 75.7% to 95.5%), respectively. The accuracy of ISDN HUT was significantly higher than the accuracy of ISOP HUT 77.5% (95% C.I. 68.9% to 84.6%). There were fewer side effects during ISDN HUT.

CONCLUSION

Sublingual isosorbide dinitrate is at least as sensitive as isoproterenol to assess patients with suspected neurocardiogenic syncope and with a negative tilt test without provocation. The low rate of side effects and the higher accuracy of ISDN HUT, along with the simplicity of this challenge compared to ISOP HUT, suggest that sublingual isosorbide dinitrate should be preferred as a provocative agent to evaluate neurocardiogenic syncope after a negative passive tilt test.

Selective protein kinase inhibitors block head-specific differentiation in hydra

Several studies have suggested that morphogenesis and patterning in hydra are regulated through pathways involving protein kinase C (PKC). Nevertheless, the complete signal system for regeneration in hydra is still not completely understood. Using inhibitors of different signalling pathways we are dissecting this system. We found that sphingosine (2 microM), staurosporine (0.1 microM), PP1/AGL1872 (1 microM) and H7 (25 microM) were able to inhibit head but not foot regeneration. The inhibition was reversible. When the inhibitor was replaced with hydra medium the animals continue their regeneration in a normal way. The exception was PP1/AGL1872, in this case the animals regenerated only one or two tentacles. These results imply that head and foot regeneration are independent processes and they are not directly related as has been proposed. Sphingosine and PP1/AGL1872 inhibit the transcription of ks1, an early regeneration gene, at 24 and 48 h of treatment. Sphingosine 2 microM arrested the cells on the G1 phase of the cell cycle, but 1 microM of PP1/AGL1872 did not. The regeneration was not affected if the animals were exposed to inhibitors of human growth factor receptors. We propose that head regeneration in hydra may be regulated at least by two pathways, one going through PKC and the other through Src. The first pathway could be related to cellular proliferation and the second one to cellular differentiation.

[Validity of a job stressors measurement scale in nursing staff: the nursing stress scale]

BACKGROUND

The aim of this work was to determine the reliability and construct validity of a scale intended to measure job stressors to which hospital nursing staff may be exposed.

SUBJECTS AND METHODS

The nursing stress scale contains 34 stressors. The scale's trans-cultural adaptation was carried out by means of the translation-back translation method. Validation was conducted on a random sample of 201 health professionals in a public hospital in Valencia. The reliability of the scale was assessed after its readministration on a sub-sample of 30 nursing professionals, with a 15 day interval. The construct validity was obtained through the correlation of the scale with another two scales: The 28 item version of Goldberg's General Health Questionnaire and 7 dimensions of the Health questionnaire SF-36.

RESULTS

The scale in Spanish language contains 34 items after eliminating the first item from the original scale (N1: computer failure) and including a new item (E1: Frequent job interruptions). The distribution of scores obtained in the initial administration of the scale and fifteen days later do not differ statistically. The Cronbach's alfa coefficient is 0.92 for the total scale and in each of the sub-scales ranges between 0. 83 and 0.49. The correlation between the scale and the GHQ-28 items questionnaire is 0.34. For each one of the seven dimensions of the SF-36 questionnaire the correlations range between -0.21 and -0.31.

CONCLUSION

The nursing stress scale is a useful instrument for measuring possible stressors in this collective. It has high internal consistency and construct validity, as does the original American version, however reliability is moderate.

An encyclopedia of mouse genes

The laboratory mouse is the premier model system for studies of mammalian development due to the powerful classical genetic analysis possible (see also the Jackson Laboratory web site, http://www.jax.org/) and the ever-expanding collection of molecular tools. To enhance the utility of the mouse system, we initiated a program to generate a large database of expressed sequence tags (ESTs) that can provide rapid access to genes. Of particular significance was the possibility that cDNA libraries could be prepared from very early stages of development, a situation unrealized in human EST projects. We report here the development of a comprehensive database of ESTs for the mouse. The project, initiated in March 1996, has focused on 5' end sequences from directionally cloned, oligo-dT primed cDNA libraries. As of 23 October 1998, 352,040 sequences had been generated, annotated and deposited in dbEST, where they comprised 93% of the total ESTs available for mouse. EST data are versatile and have been applied to gene identification, comparative sequence analysis, comparative gene mapping and candidate disease gene identification, genome sequence annotation, microarray development and the development of gene-based map resources.

Relationship between the site of a myocardial infarction and signal-averaged electrocardiogram indices

We evaluated the relationship between the site of a myocardial infarction (MI) and signal-averaged electrocardiogram (SAECG) indices in both time-domain (TDA) and spectral turbulence (STA) analyses, and their implications in the prediction of infarct-related artery (IRA) patency, in 114 survivors of a first MI. They were divided into two groups based on MI location (57 anterior and 57 inferior). Patients with bundle branch block were not included. Fifty patients had been treated with thrombolytic therapy (TT). The STA was done in both XYZ-leads and in vector magnitude. Forty patients had an abnormal SAECG in TDA and 37 in STA, but only 22 (19%) in both (71% of agreement, kappa=0.35). Fifty-four patients (47%) had an occluded IRA. The best predictors from multivariate analysis of having an occluded IRA in the inferior MI group were: an abnormal Y-lead in STA (odds ratio 4.9; P=0.005); an abnormal RMS40 in TDA (odds ratio, 4.8; P=0.02); absence of TT (odds ratio, 9.15; P=0.001). Conversely, in the anterior MI group they were: an abnormal SAECG in TDA (odds ratio 6.83; P=0.005); absence of TT (odds ratio, 4.3; P=0.02). The multivariate receiver operator characteristic curves clearly showed the effect of MI location on the SAECG indices. This study suggests that the myocardial infarction site is an important factor for the variability and poor concordance between TDA and STA. Such differences may alter the predictive accuracy of SAECG. TDA and STA should be complementary methods, and the exploration in each orthogonal lead appears to be better than in vector magnitude.

All cyclophilins and FK506 binding proteins are, individually and collectively, dispensable for viability in Saccharomyces cerevisiae

The cyclophilins and FK506 binding proteins (FKBPs) bind to cyclosporin A, FK506, and rapamycin and mediate their immunosuppressive and toxic effects, but the physiological functions of these proteins are largely unknown. Cyclophilins and FKBPs are ubiquitous and highly conserved enzymes that catalyze peptidyl-prolyl isomerization, a rate-limiting step during in vitro protein folding. We have addressed their functions by a genetic approach in the yeast Saccharomyces cerevisiae. Five cyclophilins and three FKBPs previously were identified in yeast. We identified four additional enzymes: Cpr6 and Cpr7, which are homologs of mammalian cyclophilin 40 that have also recently been independently isolated by others, Cpr8, a homolog of the secretory pathway cyclophilin Cpr4, and Fpr4, a homolog of the nucleolar FKBP, Fpr3. None of the eight cyclophilins or four FKBPs were essential. Surprisingly, yeast mutants lacking all 12 immunophilins were viable, and the phenotype of the dodecuplet mutant resulted from simple addition of the subtle phenotypes of each individual mutation. We conclude that cyclophilins and FKBPs do not play an essential general role in protein folding and find little evidence of functional overlap between the different enzymes. We propose that each cyclophilin and FKBP instead regulates a restricted number of unique partner proteins that remain to be identified.

Effect of exercise-induced hyperventilation on airway resistance and cycling endurance

The purpose of the present study was to investigate the effect of exercise induced hyperventilation and hypocapnia on airway resistance (Raw), and to try to answer the question whether a reduction of Raw is a mechanism contributing to the increase of endurance time associated with a reduction of exercise induced hyperventilation as for example has been observed after respiratory training. Eight healthy volunteers of both sexes participated in the study. Cycling endurance tests (CET) at 223 (SD 47) W, i.e. at 74 (SD 5)% of the subject's peak exercise intensity, breathing endurance tests and body plethysmograph measurements of pre- and postexercise Raw were carried out before and after a 4-week period of respiratory training. In one of the two CET before the respiratory training CO2 was added to the inspired air to keep its end-tidal concentration at 5.4% to avoid hyperventilatory hypocapnia (CO2-test); the other test was the control. The pre-exercise values of specific expiratory Raw were 8.1 (SD 2.8), 6.8 (SD 2.6) and 8.0 (SD 2.1) cm H2O.s and the postexercise values were 8.5 (SD 2.6), 7.4 (SD 1.9) and 8.0 (SD 2.7) cm H2O.s for control CET, CO2-CET and CET after respiratory training, respectively, all differences between these tests being nonsignificant. The respiratory training significantly increased the respiratory endurance time during breathing of 70% of maximal voluntary ventilation from 5.8 (SD 2.9) min to 26.7 (SD 12.5) min. Mean values of the cycling endurance time (tcend) were 22.7 (SD 6.5) min in the control, 19.4 (SD 5.4) min in the CO2-test and 18.4 (SD 6.0) min after respiratory training. Mean values of ventilation (VE) during the last 3 min of CET were 123 (SD 35.8) l.min-1 in the control, 133.5 (SD 35.1) l.min-1 in the CO2-test and 130.9 (SD 29.1) l.min-1 after respiratory training. In fact, six subjects ventilated more and cycled for a shorter time, whereas two subjects ventilated less and cycled for a longer time after the respiratory training than in the control CET. In general, the subjects cycled longer the lower the VE, if all three CET are compared. It is concluded that Raw measured immediately after exercise is independent of exercise-induced hyperventilation and hypocapnia and is probably not involved in limiting tcend, and that tcend at a given exercise intensity is shorter when VE is higher, no matter whether the higher VE occurs before or after respiratory training or after CO2 inhalation.

Chloroquine stabilization of phospholipid membranes against diacylglycerol-induced perturbation

The effects of 1-stearoyl,2-sn-arachidonoylglycerol (SAG) and the antimalarial drug chloroquine on lipid bilayer structure were studied by 2H-NMR spectroscopy. Model lipid systems were established with compositions similar to those of normal human erythrocytes, malaria-infected erythrocytes, or malaria parasite membranes. The 2H-NMR spectra of the membranes formed from the lipids extracted from normal human erythrocytes were similar to those obtained using the corresponding lipid mixtures. The order parameters of the model "infected" and model "parasite" membranes were reduced markedly relative to that of normal erythrocytes. Addition of SAG induced formation of non-bilayer lipid phases in all lipid systems. Only a small decrease in the order parameters of the acyl side chains of the phosphatidylserine, but not of the phosphatidylcholine component of the lipid membranes, was observed upon the addition of chloroquine. A dramatic effect was observed upon the addition of chloroquine to the SAG-containing membranes: this antimalarial almost totally abolished the formation of SAG-induced non-bilayer lipid phases. Since SAG, endogenously formed in erythrocyte membranes, is a potent activator of phospholipase A2, this membrane-stabilizing action of chloroquine may partially account for the phospholipase A2-inhibiting properties of this drug, and, consequently, for both its therapeutic and toxic modes of action.