PD-L1 quantification across tumor types using the reverse phase protein microarray: implications for precision medicine

BACKGROUND

Anti-programmed cell death protein 1 and programmed cell death ligand 1 (PD-L1) agents are broadly used in first-line and second-line treatment across different tumor types. While immunohistochemistry-based assays are routinely used to assess PD-L1 expression, their clinical utility remains controversial due to the partial predictive value and lack of standardized cut-offs across antibody clones. Using a high throughput immunoassay, the reverse phase protein microarray (RPPA), coupled with a fluorescence-based detection system, this study compared the performance of six anti-PD-L1 antibody clones on 666 tumor samples.

METHODS

PD-L1 expression was measured using five antibody clones (22C3, 28-8, CAL10, E1L3N and SP142) and the therapeutic antibody atezolizumab on 222 lung, 71 ovarian, 52 prostate and 267 breast cancers, and 54 metastatic lesions. To capture clinically relevant variables, our cohort included frozen and formalin-fixed paraffin-embedded samples, surgical specimens and core needle biopsies. Pure tumor epithelia were isolated using laser capture microdissection from 602 samples. Correlation coefficients were calculated to assess concordance between antibody clones. For two independent cohorts of patients with lung cancer treated with nivolumab, RPPA-based PD-L1 measurements were examined along with response to treatment.

RESULTS

Median-center PD-L1 dynamic ranged from 0.01 to 39.37 across antibody clones. Correlation coefficients between the six antibody clones were heterogeneous (range: -0.48 to 0.95) and below 0.50 in 61% of the comparisons. In nivolumab-treated patients, RPPA-based measurement identified a subgroup of tumors, where low PD-L1 expression equated to lack of response.

CONCLUSIONS

Continuous RPPA-based measurements capture a broad dynamic range of PD-L1 expression in human specimens and heterogeneous concordance levels between antibody clones. This high throughput immunoassay can potentially identify subgroups of tumors in which low expression of PD-L1 equates to lack of response to treatment.

Nitrosative Redox Homeostasis and Antioxidant Response Defense in Disused Vastus lateralis Muscle in Long-Term Bedrest (Toulouse Cocktail Study)

Increased oxidative stress by reactive oxygen species (ROS) and reactive nitrogen species (RNS) is a major determinant of disuse-induced muscle atrophy. Muscle biopsies (thigh vastus lateralis, VL) obtained from healthy male subjects enrolled in the Toulouse Cocktail bedrest (BR) study were used to assess efficacy of an antioxidant cocktail (polyphenols, omega-3, vitamin E, and selenium) to counteract the increased redox homeostasis and enhance the antioxidant defense response by using label-free LC–MS/MS and NITRO-DIGE (nitrosated proteins), qPCR, and laser confocal microscopy. Label-free LC–MS/MS indicated that treatment prevented the redox homeostasis dysregulation and promoted structural remodeling (TPM3, MYH7, MYBPC, MYH1, MYL1, HRC, and LUM), increment of RyR1, myogenesis (CSRP3), and skeletal muscle development (MUSTN1, LMNA, AHNAK). These changes were absent in the Placebo group. Glycolysis, tricarboxylic acid cycle (TCA), oxidative phosphorylation, fatty acid beta-oxidation, and mitochondrial transmembrane transport were normalized in treated subjects. Proteins involved in protein folding were also normalized, whereas protein entailed in ion homeostasis decreased. NITRO-DIGE analysis showed significant protein nitrosylation changes for CAT, CA3, SDHA, and VDAC2 in Treatment vs. Placebo. Similarly, the nuclear factor erythroid 2-related factor 2 (Nrf-2) antioxidant response element (Nrf-2 ARE) signaling pathway showed an enhanced response in the Treatment group. Increased nitrosative redox homeostasis and decreased antioxidant defense response were found in post-BR control (Placebo, n = 10) vs. the antioxidant cocktail treated group (Treatment, n = 10). Taken together, increased nitrosative redox homeostasis and muscle deterioration during BR-driven physical inactivity were prevented, whereas decreased antioxidant nitrosative stress defense response was attenuated by Treatment suggesting positive effects of the nutritional intervention protocol in bedrest.

Reactive Jumps Preserve Skeletal Muscle Structure, Phenotype, and Myofiber Oxidative Capacity in Bed Rest

Identification of countermeasures able to prevent disuse-induced muscle wasting is crucial to increase performance of crew members during space flight as well as ameliorate patient’s clinical outcome after long immobilization periods. We report on the outcome of short but high-impact reactive jumps (JUMP) as countermeasure during 60 days of 6° head-down tilt (HDT) bed rest on myofiber size, type composition, capillarization, and oxidative capacity in tissue biopsies (pre/post/recovery) from the knee extensor vastus lateralis (VL) and deep calf soleus (SOL) muscle of 22 healthy male participants (Reactive jumps in a sledge, RSL-study 2015–2016, DLR:envihab, Cologne). Bed rest induced a slow-to-fast myofiber shift (type I –>II) with an increased prevalence of hybrid fibers in SOL after bed rest without jumps (control, CTRL, p = 0.016). In SOL, JUMP countermeasure in bed rest prevented both fast and slow myofiber cross-sectional area (CSA) decrements (p = 0.005) in CTRL group. In VL, bed rest only induced capillary rarefaction, as reflected by the decrease in local capillary-to-fiber ratio (LCFR) for both type II (pre vs. post/R + 10, p = 0.028/0.028) and type I myofibers (pre vs. R + 10, p = 0.012), which was not seen in the JUMP group. VO_2maxFiber (pL × mm^–1 × min^–1) calculated from succinate dehydrogenase (SDH)-stained cryosections (OD_{660 nm}) showed no significant differences between groups. High-impact jump training in bed rest did not prevent disuse-induced myofiber atrophy in VL, mitigated phenotype transition (type I – >II) in SOL, and attenuated capillary rarefaction in the prime knee extensor VL however with little impact on oxidative capacity changes.

Reflection of neuroblastoma intratumor heterogeneity in the new OHC-NB1 disease model

Accurate modeling of intratumor heterogeneity presents a bottleneck against drug testing. Flexibility in a preclinical platform is also desirable to support assessment of different endpoints. We established the model system, OHC-NB1, from a bone marrow metastasis from a patient diagnosed with MYCN-amplified neuroblastoma and performed whole-exome sequencing on the source metastasis and the different models and passages during model development (monolayer cell line, 3D spheroid culture and subcutaneous xenograft tumors propagated in mice). OHC-NB1 harbors a MYCN amplification in double minutes, 1p deletion, 17q gain and diploid karyotype, which persisted in all models. A total of 80-540 single-nucleotide variants (SNVs) was detected in each sample, and comparisons between the source metastasis and models identified 34 of 80 somatic SNVs to be propagated in the models. Clonal reconstruction using the combined copy number and SNV data revealed marked clonal heterogeneity in the originating metastasis, with four clones being reflected in the model systems. The set of OHC-NB1 models represents 43% of somatic SNVs and 23% of the cellularity in the originating metastasis with varying clonal compositions, indicating that heterogeneity is partially preserved in our model system.

Abstract 469: Patient-derived sarcoma models: First results from the SARQMA study

Objective: The development of new targeted therapeutics has allowed an essential improvement in carcinoma treatment. For sarcomas, however, the main approach is still the combination of surgery, chemotherapy and radiation, which is due to their high heterogeneity, with more than 70 histopathological subtypes, and the limited knowledge of the molecular drivers of tumor development and progression. Here we show that patient-derived 3D (PD3D) cell culture models allow for an in vitro system to systematically test compounds and combos in a semi-automated way, generating a pre-clinical dataset that in combination with clinical data, genomic and proteomics profiles may help to better understand the biology and ultimately identify more potent treatment regimens.

Methods: Fresh surgical specimen underwent several steps of dissociation. Cell aggregates were then seeded into 24w plates in matrix-like scaffolds and grown until >100μm. Organoids were then harvested, transferred to 384w plates and treated with a set of compounds that resemble standard-of-care treatments and novel compounds. Finally, viability was calculated. In parallel, protein extracts were used for DigiWest, a multiplexed protein profiling assay allowing to interrogate up to 800 (phospho)-proteins.

Results: Of 49 cases with a biopsy, 23 had too little material available. Of these 23 samples, 5 were reported as sarcoma tissue afterwards, while 5 of the taken 26 samples were not sarcomas according to the final histopathology. Of all sarcomas, 90% (19/21) were taken from tumors localized at the extremities, the rest was located at the trunk. 52% (11/21) were growing in short term cell culture at least to passage 1 (p1), 28% (6/21) were growing for long term analyses. Two of those six were myxoid liposarcomas, two were undifferentiated pleomorphic sarcomas or classified as not otherwise specified (UPS/NOS), one was a myxoid liposarcoma and one a biphasic synovial sarcoma. Here we show that it is feasible to generate organoids from sarcoma tissues for extensive characterization in order to better understand their biology and mechanisms of treatment. High-throughput drug screening allows for an profiling of pharmacokinetic properties of individual sarcomas. Using the same material for additional (phospho)-proteomics provides multiple layers of understanding.

Conclusion: At present, the structure of clinical trials is not amenable to N of 1 studies, so applying the information garnered from this platform, particularly combination therapy drug screens, remains a significant hurdle. The major limitation to the establishment of organoid cultures was insufficient amounts of fresh tissue with viable tumor cells. Increasing the tumor tissue available for organoid production would lead to a greater success rate. Nevertheless, by their recapitulation of the donor tissue architecture, they provide an interesting and important tool to study the huge variety of soft-tissue tumors.

Citation Format: Manuela Gaebler, Alessandra Silvestri, Peter Reichardt, Eva Wardelmann, Guido Gambara, Johannes Haybaeck, Philipp Stroebel, Maya Niethard, Gerrit Erdmann, Christian R. Regenbrecht. Patient-derived sarcoma models: First results from the SARQMA study [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 469.

Abstract 5013: Rapid generation of phenomic and functional profiles of patient-derived 3D cell culture models for identification of treatment vulnerabilities of breast cancer: Early results of the EFRE-PoP project

Targeted treatment for breast cancer subsets currently relies on the occurrence of estrogen, progesterone and Her2/neu receptors. For triple negative breast cancer (TNBC) there is no identified targeted therapy. The mutational landscape for breast cancer subsets has been characterized, but drug development has been limited due to the lack of appropriate preclinical models. Development of patient-derived xenograft models (PDX) has been difficult with take rates of below 30%.To establish a series of patient-derived 3D (PD3D) cell culture models as a versatile resource for ex vivo drug sensitivity screens as well as secondary establishment of PDX. We obtained breast cancer specimens either by biopsy or surgical resection. Upon arrival tumor tissue was minced and enzymatically digested. After subsequent filtering, respective tissue size fractions were seeded as Matrix-droplets into 24-well plates and incubated under standard conditions. Growth of PD3Ds was monitored daily by microscopy. PD3Ds were splitted when their diameter reached appropriate size. Organoids were than fixed and embedded. FFPE sections of donor-tissues and derived PD3D models were than used for IHC and inspected by a pathologist. In parallel, mutational profiling of snap-frozen tumor tissue and cell cultures was performed. All models were subjected to a semi-automated multi-drug response assay in a 384-well format to assess individual compound sensitivities.We established a scalable workflow for culturing and screening of PD3D cell cultures from limited quantities of breast cancer tissue from true-cut and vacuum biopsies as well as surgical specimen. Tissue fragments of ca. 3mm in diameter were sufficient to successfully establish PD3D cell cultures at a high yield. The time needed to expand PD3D cell cultures to obtain a sufficient amount of cells for subsequent molecular analyses varies from 2-6 weeks depending on amount and quality of samples as well as grade and stage of the donor tumor tissue. At the time, we can report a rate of culture establishment rate of 75% (11 models from 15 patient samples) for various clinical relevant subgroups, including TNBC, HR+, Her 2 pos. BC and one DCIS sample. The immunohistology and mutational profiles of these samples are currently being confirmed. The established workflow for culturing PD3D cell cultures offers high yield rates within a potentially clinically relevant time-frame for HTP cytotoxicity screenings. We are encouraged that this method is suitable for various molecular subtypes of breast cancer. Once adequately validated in co-clinical trials, PD3D models would make for an intriguing tool in supporting clinical decision-making for individual patients. Particularly patients with breast cancer refractory to standard of care compounds could benefit from this approach.

Citation Format: Verena I. Kiver, Guido Gambara, Olga Gorea, Jens-Uwe Blohmer, Philipp Jurmeister, Carsten Denkert, Alessandra Silvestri, Caroline M. Schweiger, Maxine Silvestrov, Ulrich Keilholz, Christian R. Regenbrecht. Rapid generation of phenomic and functional profiles of patient-derived 3D cell culture models for identification of treatment vulnerabilities of breast cancer: Early results of the EFRE-PoP project [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5013.

Abstract 4099: Novel patient-derived 3D (PD3D) cell models and matched patient-derived xenografts (PDX) from peritoneal metastasis of colorectal cancer for drug testing and biomarker analysis

For patients with colorectal cancer (CRC) peritoneal metastases (PM) represent a terminal tumor stage with limited therapeutic options. To increase therapeutic efficacy and overall survival, availability of appropriate patient-derived 3D cell culture (PD3D) and patient-derived xenografts (PDX) models of PM could help improving the predictability of drug response for a specific tumor, but also foster the identification of novel biomarkers and therapeutic targets for CRC-PM patients. In this context, we generated the first scaffold-based PD3D and matching PDX models of CRC-PM as platform to test for chemotherapy response and to identify novel biomarkers.

For model establishment, surgical specimens were processed either for PD3D cell culture or transplanted subcutaneously (s.c.) onto immunocompromized NOD scid gamma (NSG) mice. For 3D cell culture models, tissue was dissected, digested and filtered before embedding into a scaffold matrix. For PDX models engrafted tumors were transferred to NMRI nu/nu mice for further passaging. They were characterized by histopathology, immunohistochemistry and gene expression analyses using real-time RT-PCR. Chemosensitivity of both sibling models was evaluated on a panel of conventional chemotherapeutic and of targeted drugs.

The same panel of drugs was used in 15 matched PD3D/PDX models and revealed individual response patterns both in PD3D and PDX. Most interestingly, different drug response pattern was observed in models derived from tumor tissue of the omentum vs. tissue from the peritoneum of the same patient.

Our results demonstrate, that matched models maintain basic characteristics such as the morphology of the patient tumor in early passages, reflect heterogeneous response rates, and can be used as preclinical platform for translational studies of potential clinical use.

Citation Format: Christian RA Regenbrecht, Guido Gambara, Eva Pachmayr, Alessandra Silvestri, Mathias Dahlmann, Bernadette Brzezicha, Britta Buettner, Beate Rau, Ulrich Keilholz, Urike Stein, Wolfgang Walther. Novel patient-derived 3D (PD3D) cell models and matched patient-derived xenografts (PDX) from peritoneal metastasis of colorectal cancer for drug testing and biomarker analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4099.

From Chemotherapy to Combined Targeted Therapeutics: In Vitro and in Vivo Models to Decipher Intra-tumor Heterogeneity

Recent advances in next-generation sequencing and other omics technologies capable to map cell fate provide increasing evidence on the crucial role of intra-tumor heterogeneity (ITH) for cancer progression. The different facets of ITH, from genomic to microenvironmental heterogeneity and the hierarchical cellular architecture originating from the cancer stem cell compartment, contribute to the range of tumor phenotypes. Decoding these complex data resulting from the analysis of tumor tissue complexity poses a challenge for developing novel therapeutic strategies that can counteract tumor evolution and cellular plasticity. To achieve this aim, the development of in vitro and in vivo cancer models that resemble the complexity of ITH is crucial in understanding the interplay of cells and their (micro)environment and, consequently, in testing the efficacy of new targeted treatments and novel strategies of tailoring combinations of treatments to the individual composition of the tumor. This challenging approach may be an important cornerstone in overcoming the development of pharmaco-resistances during multiple lines of treatment. In this paper, we report the latest advances in patient-derived 3D (PD3D) cell cultures and patient-derived tumor xenografts (PDX) as in vitro and in vivo models that can retain the genetic and phenotypic heterogeneity of the tumor tissue.

Ned-19 inhibition of parasite growth and multiplication suggests a role for NAADP mediated signalling in the asexual development of Plasmodium falciparum

Background

Although malaria is a preventable and curable human disease, millions of people risk to be infected by the Plasmodium parasites and to develop this illness. Therefore, there is an urgent need to identify new anti-malarial drugs. Ca²⁺ signalling regulates different processes in the life cycle of Plasmodium falciparum, representing a suitable target for the development of new drugs.

Results

This study investigated for the first time the effect of a highly specific inhibitor of nicotinic acid adenine dinucleotide phosphate (NAADP)-induced Ca²⁺ release (Ned-19) on P. falciparum, revealing the inhibitory effect of this compound on the blood stage development of this parasite. Ned-19 inhibits both the transition of the parasite from the early to the late trophozoite stage and the ability of the late trophozoite to develop to the multinucleated schizont stage. In addition, Ned-19 affects spontaneous intracellular Ca²⁺ oscillations in ring and trophozoite stage parasites, suggesting that the observed inhibitory effects may be associated to regulation of intracellular Ca²⁺ levels.

Conclusions

This study highlights the inhibitory effect of Ned-19 on progression of the asexual life cycle of P. falciparum. The observation that Ned-19 inhibits spontaneous Ca²⁺ oscillations suggests a potential role of NAADP in regulating Ca²⁺ signalling of P. falciparum.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-2013-7) contains supplementary material, which is available to authorized users.

Kinase-driven metabolic signalling as a predictor of response to carboplatin-paclitaxel adjuvant treatment in advanced ovarian cancers

BACKGROUND

The biological mechanisms underlying early- and advanced-stage epithelial ovarian cancers (EOCs) are still poorly understood. This study explored kinase-driven metabolic signalling in early and advanced EOCs, and its role in tumour progression and response to carboplatin-paclitaxel treatment.

METHODS

Tumour epithelia were isolated from two independent sets of primary EOC (n=72 and 30 for the discovery and the validation sets, respectively) via laser capture microdissection. Reverse phase protein microarrays were used to broadly profile the kinase-driven metabolic signalling of EOC with particular emphasis on the LBK1-AMPK and AKT-mTOR axes. Signalling activation was compared between early and advanced lesions, and carboplatin-paclitaxel-sensitive and -resistant tumours.

RESULTS

Advanced EOCs were characterised by a heterogeneous kinase-driven metabolic signature and decreased phosphorylation of the AMPK-AKT-mTOR axis compared to early EOC (P<0.05 for AMPKα T172, AMPKα1 S485, AMPKβ1 S108, AKT S473 and T308, mTOR S2448, p70S6 S371, 4EBP1 S65, GSK-3 α/β S21/9, FOXO1 T24/FOXO3 T32, and FOXO1 S256). Advanced tumours with low relative activation of the metabolic signature and increased FOXO1 T24/FOXO3 T32 phosphorylation (P=0.041) were associated with carboplatin-paclitaxel resistance.

CONCLUSIONS

If validated in a larger cohort of patients, the decreased AMPK-AKT-mTOR activation and phosphorylation of FOXO1 T24/FOXO3 T32 may help identify carboplatin-paclitaxel-resistant EOC patients.

Abstract 5656: Quantitative measurement of PDL1 expression across tumor types using laser capture microdissection and reverse phase protein microarray

Background: The efficacy of immunotherapy, including therapeutic strategies capable of modulating innate/adaptive immune resistance, varies greatly across tumor types. As the number of available immunotherapies accelerates, the study of predictive markers by IHC (e.g. PDL1 expression) is under intense investigation. However, staining protocol inconsistency, variation across scoring systems, and subjective interpretation of the immunostaining have produced conflicting results thus far. This work explored the role of Laser Capture Microdissection (LCM) coupled with Reverse Phase Protein Microarray (RPPA) as an alternative high throughput, quantitative, operator independent platform for measuring PDL1 expression across tumor types.

Material and Methods: Pure epithelial cells were isolated via LCM from 178 samples including: 72 ovarian cancers (OC), 57 lung adenocarcinomas (LC), 30 metastatic breast cancers (MBC), and 19 pancreatic cancers (PC). PDL1 expression was measured on a continuous scale using quantitative RPPA based analysis. Each tumor type was processed and arrayed independently. Experimental samples and reference standards used for inter-assay normalization were printed in triplicates.

Results: PDL1 expression varied greatly across tumor types. LC were characterized by the greatest intra-tumor fold dynamic range (&gt; 35-fold), followed by OC (&lt; 13-fold), MBC (&lt; 4-fold), and PC (&lt; 2-fold). PDL1 expression of 46/57 (80.7%) LC, 17/30 (56.7%) MBC, 6/19 (31.5%) PC, and 20/72 (27.8%) OC was greater than the population median of all tumors combined. Within the LC samples with PDL1 expression equal to the top quartile of the population, 10 (71.4%) were KRAS mutant lesions and 4 (28.6%) were WT tumors. Finally, amongst LC and PC harboring a KRAS mutation, PC showed an overall lower expression of PDL1 with only 2/19 (10.5%) cases been above the population median and none within the top quartile of the population.

Conclusions: The LCM-RPPA workflow has the unique ability to capture immune checkpoint expression on a continuous quantitative scale as well as capture its broad dynamic range. Because RPPA is unconstrained by antigen retrieval issues as well as subjectivity of IHC interpretation, this approach may generate more accurate cut-point of therapeutic response prediction. Overall the dynamic range of PDL1 was broader in LC compared to other solid tumors, and LC had a much higher proportion of patients with tumors expressing high levels of PDL1. These quantitative differences may explain therapeutic efficacy of PDL1 inhibition across tumor types. Such speculative hypothesis should be further validated in prospective clinical trials. Finally, these preliminary data suggest that organ specific microenvironments more than specific driving mutations (e.g. KRAS) may strongly influence PDL1 expression in malignant lesions.

Citation Format: Elisa Baldelli, Valerie Calvert, K. Alex Hodge, Maria Isabella Sereni, Guido Gambara, Eric B. Haura, Lucio Crino', Bryant Dunetz, Sergio Pecorelli, David J. Perry, Stephen P. Anthony, Nicholas Robert, Donald W. Northfelt, Mohammad Jahanzeb, Emanuel F. Petricoin, Mariaelena Pierobon. Quantitative measurement of PDL1 expression across tumor types using laser capture microdissection and reverse phase protein microarray [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5656. doi:10.1158/1538-7445.AM2017-5656

Microgravity-Induced Transcriptome Adaptation in Mouse Paraspinal longissimus dorsi Muscle Highlights Insulin Resistance-Linked Genes

Microgravity as well as chronic muscle disuse are two causes of low back pain originated at least in part from paraspinal muscle deconditioning. At present no study investigated the complexity of the molecular changes in human or mouse paraspinal muscles exposed to microgravity. The aim of this study was to evaluate longissimus dorsi adaptation to microgravity at both morphological and global gene expression level. C57BL/N6 male mice were flown aboard the BION-M1 biosatellite for 30 days (BF) or housed in a replicate flight habitat on ground (BG). Myofiber cross sectional area and myosin heavy chain subtype patterns were respectively not or slightly altered in longissimus dorsi of BF mice. Global gene expression analysis identified 89 transcripts differentially regulated in longissimus dorsi of BF vs. BG mice. Microgravity-induced gene expression changes of lipocalin 2 (Lcn2), sestrin 1(Sesn1), phosphatidylinositol 3-kinase, regulatory subunit polypeptide 1 (p85 alpha) (Pik3r1), v-maf musculoaponeurotic fibrosarcoma oncogene family protein B (Mafb), protein kinase C delta (Prkcd), Muscle Atrophy F-box (MAFbx/Atrogin-1/Fbxo32), and Muscle RING Finger 1 (MuRF-1) were further validated by real time qPCR analysis. In conclusion, our study highlighted the regulation of transcripts mainly linked to insulin sensitivity and metabolism in longissimus dorsi following 30 days of microgravity exposure. The apparent absence of robust signs of back muscle atrophy in space-flown mice, despite the overexpression of Atrogin-1 and MuRF-1, opens new questions on the possible role of microgravity-sensitive genes in the regulation of peripheral insulin resistance following unloading and its consequences on paraspinal skeletal muscle physiology.

Enrichment of PI3K-AKT-mTOR Pathway Activation in Hepatic Metastases from Breast Cancer

Purpose: Little is known about the molecular signatures associated with specific metastatic sites in breast cancer. Using comprehensive multi-omic molecular profiling, we assessed whether alterations or activation of the PI3K-AKT-mTOR pathway is associated with specific sites of breast cancer metastasis.Experimental Design: Next-generation sequencing-based whole-exome sequencing was coupled with reverse-phase protein microarray (RPPA) functional signaling network analysis to explore the PI3K-AKT-mTOR axis in 32 pretreated breast cancer metastases. RPPA-based signaling data were further validated in an independent cohort of 154 metastatic lesions from breast cancer and 101 unmatched primary breast tumors. The proportion of cases with PI3K-AKT-mTOR genomic alterations or signaling network activation were compared between hepatic and nonhepatic lesions.Results:PIK3CA mutation and activation of AKT (S473) and p70S6K (T389) were detected more frequently among liver metastases than nonhepatic lesions (P < 0.01, P = 0.056, and P = 0.053, respectively). However, PIK3CA mutations alone were insufficient in predicting protein activation (P = 0.32 and P = 0.19 for activated AKT and p70S6K, respectively). RPPA analysis of an independent cohort of 154 tumors confirmed the relationship between pathway activation and hepatic metastasis [AKT (S473), mTOR (S2448), and 4EBP1 (S65); P < 0.01, P = 0.02, and P = 0.01, respectively]. Similar results were also seen between liver metastases and primary breast tumors [AKT (S473) P < 0.01, mTOR (S2448) P < 0.01, 4EBP1 (S65) P = 0.01]. This signature was lost when primary tumors were compared with all metastatic sites combined.Conclusions: Breast cancer patients with liver metastasis may represent a molecularly homogenized cohort with increased incidence of PIK3CA mutations and activation of the PI3K-AKT-mTOR signaling network. Clin Cancer Res; 23(16); 4919-28. ©2017 AACR.

Gene Expression Profiling in Slow-Type Calf Soleus Muscle of 30 Days Space-Flown Mice

Microgravity exposure as well as chronic disuse are two main causes of skeletal muscle atrophy in animals and humans. The antigravity calf soleus is a reference postural muscle to investigate the mechanism of disuse-induced maladaptation and plasticity of human and rodent (rats or mice) skeletal musculature. Here, we report microgravity-induced global gene expression changes in space-flown mouse skeletal muscle and the identification of yet unknown disuse susceptible transcripts found in soleus (a mainly slow phenotype) but not in extensor digitorum longus (a mainly fast phenotype dorsiflexor as functional counterpart to soleus). Adult C57Bl/N6 male mice (n = 5) flew aboard a biosatellite for 30 days on orbit (BION-M1 mission, 2013), a sex and age-matched cohort were housed in standard vivarium cages (n = 5), or in a replicate flight habitat as ground control (n = 5). Next to disuse atrophy signs (reduced size and myofiber phenotype I to II type shift) as much as 680 differentially expressed genes were found in the space-flown soleus, and only 72 in extensor digitorum longus (only 24 genes in common) compared to ground controls. Altered expression of gene transcripts matched key biological processes (contractile machinery, calcium homeostasis, muscle development, cell metabolism, inflammatory and oxidative stress response). Some transcripts (Fzd9, Casq2, Kcnma1, Ppara, Myf6) were further validated by quantitative real-time PCR (qRT-PCR). Besides previous reports on other leg muscle types we put forth for the first time a complete set of microgravity susceptible gene transcripts in soleus of mice as promising new biomarkers or targets for optimization of physical countermeasures and rehabilitation protocols to overcome disuse atrophy conditions in different clinical settings, rehabilitation and spaceflight.

Functional characterization of epithelial ovarian cancer histotypes by drug target based protein signaling activation mapping: implications for personalized cancer therapy

Epithelial ovarian carcinoma (EOC) is a deadly disease, with a 5-year survival of 30%. The aim of the study was to perform broad-scale protein signaling activation mapping to evaluate if EOC can be redefined based on activated protein signaling network architecture rather than histology. Tumor cells were isolated using laser capture microdissection (LCM) from 72 EOCs. Tumors were classified as serous (n = 38), endometrioid (n = 13), mixed (n = 8), clear cell (CCC; n = 7), and others (n = 6). LCM tumor cells were lysed and subjected to reverse-phase protein microarray to measure the expression/activation level of 117 protein drug targets. Unsupervised hierarchical clustering analysis was utilized to explore the overall signaling network. ANOVA was used to detect significant differences among the groups (p < 0.05). Regardless of histology, unsupervised analysis revealed five pathway-driven clusters. When the EOC histotypes were compared by ANOVA, only CCC showed a distinct signaling network, with activation of EGFR, Syk, HER2/ErbB2, and SHP2 (p = 0.0007, p = 0.0021, p < 0.0001, and p = 0.0410, respectively). The histological classification of EOC fails to adequately describe the underpinning protein signaling network. Nevertheless, CCC presents unique signaling characteristics compared to the other histotypes. EOC may need to be characterized by functional signaling activation mapping rather than pure histology.

TLR3 engagement induces IRF-3-dependent apoptosis in androgen-sensitive prostate cancer cells and inhibits tumour growth in vivo

Toll-like receptors (TLRs) are a family of highly conserved transmembrane proteins expressed in epithelial and immune cells that recognize pathogen associated molecular patterns. Besides their role in immune response against infections, numerous studies have shown an important role of different TLRs in cancer, indicating these receptors as potential targets for cancer therapy. We previously demonstrated that the activation of TLR3 by the synthetic double-stranded RNA analogue poly I:C induces apoptosis of androgen-sensitive prostate cancer (PCa) LNCaP cells and, much less efficiently, of the more aggressive PC3 cell line. Therefore, in this study we selected LNCaP cells to investigate the mechanism of TLR3-mediated apoptosis and the in vivo efficacy of poly I:C-based therapy. We show that interferon regulatory factor-3 (IRF-3) signalling plays an essential role in TLR3-mediated apoptosis in LNCaP cells through the activation of the intrinsic and extrinsic apoptotic pathways. Interestingly, hardly any apoptosis was induced by poly I:C in normal prostate epithelial cells RWPE-1. We also demonstrate for the first time the direct anticancer effect of poly I:C as a single therapeutic agent in a well-established human androgen-sensitive PCa xenograft model, by showing that tumour growth is highly impaired in poly I:C-treated immunodeficient mice. Immunohistochemical analysis of PCa xenografts highlights the antitumour role of poly I:C in vivo both on cancer cells and, indirectly, on endothelial cells. Notably, we show the presence of TLR3 and IRF-3 in both human normal and PCa clinical samples, potentially envisaging poly I:C-based therapy for PCa.

VEGF-induced neoangiogenesis is mediated by NAADP and two-pore channel-2-dependent Ca2+ signaling

Vascular endothelial growth factor (VEGF) and its receptors VEGFR1/VEGFR2 play major roles in controlling angiogenesis, including vascularization of solid tumors. Here we describe a specific Ca(2+) signaling pathway linked to the VEGFR2 receptor subtype, controlling the critical angiogenic responses of endothelial cells (ECs) to VEGF. Key steps of this pathway are the involvement of the potent Ca(2+) mobilizing messenger, nicotinic acid adenine-dinucleotide phosphate (NAADP), and the specific engagement of the two-pore channel TPC2 subtype on acidic intracellular Ca(2+) stores, resulting in Ca(2+) release and angiogenic responses. Targeting this intracellular pathway pharmacologically using the NAADP antagonist Ned-19 or genetically using Tpcn2(-/-) mice was found to inhibit angiogenic responses to VEGF in vitro and in vivo. In human umbilical vein endothelial cells (HUVECs) Ned-19 abolished VEGF-induced Ca(2+) release, impairing phosphorylation of ERK1/2, Akt, eNOS, JNK, cell proliferation, cell migration, and capillary-like tube formation. Interestingly, Tpcn2 shRNA treatment abolished VEGF-induced Ca(2+) release and capillary-like tube formation. Importantly, in vivo VEGF-induced vessel formation in matrigel plugs in mice was abolished by Ned-19 and, most notably, failed to occur in Tpcn2(-/-) mice, but was unaffected in Tpcn1(-/-) animals. These results demonstrate that a VEGFR2/NAADP/TPC2/Ca(2+) signaling pathway is critical for VEGF-induced angiogenesis in vitro and in vivo. Given that VEGF can elicit both pro- and antiangiogenic responses depending upon the balance of signal transduction pathways activated, targeting specific VEGFR2 downstream signaling pathways could modify this balance, potentially leading to more finely tailored therapeutic strategies.

Protein network mapping of platinum-resistant and poor-survival ovarian cancer

5560

Background: Epithelial ovarian carcinoma (EOC) is the fifth leading cause of tumor related death in the female population, with only 30% of patients alive at 5 years after diagnosis. Platinum resistance is a major cause of treatment failure. The aim of the study was to perform broad-scale drug target activation mapping of EOC to identify new druggable targets for personalized therapy. Methods: 72 ovarian primary lesions collected from chemo-naïve EOC patients were analyzed. Highly enriched tumor epithelial cells were isolated by laser capture microdissection, lysed and subjected to reverse phase protein microarray analysis for multiplexed protein pathway activation mapping. The activation/phosphorylation level of 156 key signaling proteins was analysed. Based on the disease-free interval to platinum therapy, 61 stage II-IV patients were segregated into platinum-resistant (<6 months), platinum-sensitive (6-12 months), and platinum-supersensitive disease (>12 months). One-way analysis of variance was used to detect significant differences among the three groups in the drug target activation profile. Results: Expression of the drug target PDGF Receptor β and activation of ErbB2/HER2 (Y1248) were significantly higher in patients with resistant disease compared to sensitive groups (respectively, p 0.0033 and p 0.0134), while the expression of Estrogen receptor α was greater in the supersensitive group (p 0.0295). Moreover, overall survival analysis including all stages revealed that the expression level of Cox2 is significantly higher in patients with shorter survival (HR: 2.48, p 0.0179). Conclusions: Functional drug target activation mapping revealed the unique signaling architecture of platinum-resistant EOC. If confirmed in independent study sets, these results suggest that the utilization of drugs targeting PDGF Receptor β and ErbB2/HER2 could be evaluated in platinum resistant EOC and/or in combination with platinum therapy in order to overcome acquired resistance. Finally, this study indicates that Cox2 may play an important role in aggressive EOC, and that the addition of Cox-inhibitors to standard of care could be rationally evaluated as a novel therapeutic regimen for ovarian cancer.

Toll-like receptors in prostate infection and cancer between bench and bedside

Toll-Like receptors (TLRs) are a family of evolutionary conserved transmembrane proteins that recognize highly conserved molecules in pathogens. TLR-expressing cells represent the first line of defence sensing pathogen invasion, triggering innate immune responses and subsequently priming antigen-specific adaptive immunity. In vitro and in vivo studies on experimental cancer models have shown both anti- and pro-tumoural activity of different TLRs in prostate cancer, indicating these receptors as potential targets for cancer therapy. In this review, we highlight the intriguing duplicity of TLR stimulation by pathogens: their protective role in cases of acute infections, and conversely their negative role in favouring hyperplasia and/or cancer onset, in cases of chronic infections. This review focuses on the role of TLRs in the pathophysiology of prostate infection and cancer by exploring the biological bases of the strict relation between TLRs and prostate cancer. In particular, we highlight the debated question of how reliable mutations or deregulated expression of TLRs are as novel diagnostic or prognostic tools for prostate cancer. So far, the anticancer activity of numerous TLR ligands has been evaluated in clinical trials only in organs other than the prostate. Here we review recent clinical trials based on the most promising TLR agonists in oncology, envisaging a potential application also in prostate cancer therapy.

A novel biomarker harvesting nanotechnology identifies Bak as a candidate melanoma biomarker in serum

BACKGROUND

Melanoma represents only 4% of all skin cancers, but nearly 80% of skin cancer deaths. This manuscript applies several new measurement technologies with the purpose of elucidating molecular signatures of melanoma aggressiveness.

PURPOSE

We sought to determine whether low-abundant serum proteins related to apoptotic pathways could be measured and correlated with defined melanoma subtypes. Hydrogel core shell nanoparticles, a new technology capable of selectively entrapping low molecular weight proteins and protecting them from enzymatic degradation, were used to capture candidate serum biomarkers. Biomarker levels were correlated with confocal microscopy, thereby representing a combination of new technologies for in vivo histologic documentation.

RESULTS

Among a panel of analyzed serum proteins, Bak was differentially expressed between nevi and melanomas. Melanomas with higher Bak serum levels exhibited more pronounced junctional activity on confocal imaging, whereas lesions with 'sparse' dermal nests had weak Bak expression.

CONCLUSIONS

Our study links serum proteome analysis with confocal microscopic clinical in vivo histologic classification of melanomas. Bak has not been previously measured in serum. Bak differential expression among melanoma subtypes confirms the importance of the apoptotic pathway as a contributor to melanoma aggressiveness.

A novel biomarker harvesting nanotechnology identifies Bak as a candidate melanoma biomarker in serum

BACKGROUND

Melanoma represents only 4% of all skin cancers, but nearly 80% of skin cancer deaths. This manuscript applies several new measurement technologies with the purpose of elucidating molecular signatures of melanoma aggressiveness.

PURPOSE

We sought to determine whether low-abundant serum proteins related to apoptotic pathways could be measured and correlated with defined melanoma subtypes. Hydrogel core shell nanoparticles, a new technology capable of selectively entrapping low molecular weight proteins and protecting them from enzymatic degradation, were used to capture candidate serum biomarkers. Biomarker levels were correlated with confocal microscopy, thereby representing a combination of new technologies for in vivo histologic documentation.

RESULTS

Among a panel of analyzed serum proteins, Bak was differentially expressed between nevi and melanomas. Melanomas with higher Bak serum levels exhibited more pronounced junctional activity on confocal imaging, whereas lesions with 'sparse' dermal nests had weak Bak expression.

CONCLUSIONS

Our study links serum proteome analysis with confocal microscopic clinical in vivo histologic classification of melanomas. Bak has not been previously measured in serum. Bak differential expression among melanoma subtypes confirms the importance of the apoptotic pathway as a contributor to melanoma aggressiveness.

Tumorigenic and metastatic activity of human thyroid cancer stem cells

Thyroid carcinoma is the most common endocrine malignancy and the first cause of death among endocrine cancers. We show that the tumorigenic capacity in thyroid cancer is confined in a small subpopulation of stem-like cells with high aldehyde dehydrogenase (ALDH(high)) activity and unlimited replication potential. ALDH(high) cells can be expanded indefinitely in vitro as tumor spheres, which retain the tumorigenic potential upon delivery in immunocompromised mice. Orthotopic injection of minute numbers of thyroid cancer stem cells recapitulates the behavior of the parental tumor, including the aggressive metastatic features of undifferentiated thyroid carcinomas, which are sustained by constitutive activation of cMet and Akt in thyroid cancer stem cells. The identification of tumorigenic and metastagenic thyroid cancer cells may provide unprecedented preclinical tools for development and preclinical validation of novel targeted therapies.

Nanoparticle technology: amplifying the effective sensitivity of biomarker detection to create a urine test for hGH

Several clinical-grade immunoassays exist for the specific measurement of hGH or its isoforms in blood but there is an urgent need to apply these same reliable assays to the measurement of hGH in urine as a preferred 'non-invasive' biofluid. Unfortunately, conventional hGH immunoassays cannot attain the sensitivity required to detect the low concentrations of hGH in urine. The lowest limit of sensitivity for existing hGH immunoassays is >50 pg/mL, while the estimated concentration of urinary hGH is about 1 pg/m-50 times lower than the sensitivity threshold. We have created novel N-isopropylacrylamide (NIPAm)-based hydrogel nanoparticles functionalized with an affinity bait. When introduced into an analyte-containing solution, the nanoparticles can perform, in one step, (1) complete harvesting of all solution phase target analytes, (2) full protection of the captured analyte from degradation and (3) sequestration of the analyte, effectively increasing the analyte concentration up to a hundredfold. N-isopropylacrylamide nanoparticles functionalized with Cibacron Blue F3GA bait have been applied to raise the concentration of urinary hGH into the linear range of clinical grade immunoassays. This technology now provides an opportunity to evaluate the concentration of hGH in urine with high precision and accuracy.

Investigation of the ovarian and prostate cancer peptidome for candidate early detection markers using a novel nanoparticle biomarker capture technology

Current efforts to identify protein biomarkers of disease use mainly mass spectrometry (MS) to analyze tissue and blood specimens. The low-molecular-weight "peptidome" is an attractive information archive because of the facile nature by which the low-molecular-weight information freely crosses the endothelial cell barrier of the vasculature, which provides opportunity to measure disease microenvironment-associated protein analytes secreted or shed into the extracellular interstitium and from there into the circulation. However, identifying useful protein biomarkers (peptidomic or not) which could be useful to detect early detection/monitoring of disease, toxicity, doping, or drug abuse has been severely hampered because even the most sophisticated, high-resolution MS technologies have lower sensitivities than those of the immunoassays technologies now routinely used in clinical practice. Identification of novel low abundance biomarkers that are indicative of early-stage events that likely exist in the sub-nanogram per milliliter concentration range of known markers, such as prostate-specific antigen, cannot be readily detected by current MS technologies. We have developed a new nanoparticle technology that can, in one step, capture, concentrate, and separate the peptidome from high-abundance blood proteins. Herein, we describe an initial pilot study whereby the peptidome content of ovarian and prostate cancer patients is investigated with this method. Differentially abundant candidate peptidome biomarkers that appear to be specific for early-stage ovarian and prostate cancer have been identified and reveal the potential utility for this new methodology.

Abstract 4585: Verification of prostate cancer biomarker candidates by nanoparticle-capture MRM

Prostate adenocarcinoma (PCa) is highly diffuse between older men, and biomarkers that allow discrimination of cancerous pathologies from benign diseases, identification of clinical aggressive cancer with high specificity and monitor cancer progression are required. Recently we applied a new workflow for the discovery of candidate biomarkers based on hydrogel nanoparticle capture of LMW serum borne analytes. Comparing serum from pre and post prostatectomy patients we identified 112 candidates biomarkers. Our novel nanoparticle technology provides a rapid and near 100% efficient means to capture and greatly amplify the resting concentration of LMW protein analytes. Since most of these markers do not have well performing specific antibodies commercially available, we utilized MRM to verify their differential expression as first identified by Orbitrap-MS/MS.

Hydrogel nanoparticle serum pre-processing was used for both Orbitrap-LTQ based discovery and MRM verification such that the same analyte fractionation workflow was used but different downstream mass spectrometry. MRM was performed on a Thermo Quantum triple quadrupole-MS using the nanoparticle trapped analyte archive as the input for analysis. The following biomarker candidates were selected for MRM verification: Apolipoprotein E, Diacylglycerol kinase alpha, complement 1 subcomponent q B chain precursor, complement component 1 q subcomponent gamma polypeptide, serpin peptidase inhibitor, vitronectin precursor, angiotensinogen preproprotein, H4 histone family member J, fibronectin 1 isoform 2, orosomucoid 1 precursor, alpha-2-HS-glycoprotein, annexin I.

Several prostate candidate biomarkers were verified by Nanoparticle capture-MRM, thus providing data supporting the use and continued improvement of this novel biomarker discovery system for the identification of protein biomarker panels for early disease detection and therapeutic monitoring.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4585.

Abstract 4584: Verification of ovarian cancer biomarker candidates by nanoparticle-capture MRM

Background: Detection of early stage ovarian cancer offers the best opportunity to reduce mortality. In the attempt to improve Ovarian Cancer prognosis there is a sheer need for new sensitive and specific early detection biomarkers.

We have recently proposed a new workflow to overcome the limitations that characterize serum protein biomarker discovery. A new class of hydrogel (NIPAm) nanoparticle, with the incorporation of an affinity bait (AAC), had been developed and tested, showing to successfully separate from albumin, harvest, concentrate, and protect from degradation low abundance and LMW potential protein biomarkers, amenable for downstream mass spectrometry (LTQ-Orbitrap) analysis. Applying such workflow to a set of 40 serum samples from ovarian cancer patients and benign controls a list of 163 differentially expressed peptides was generated.

Our novel nanoparticle technology provides a rapid and near 100% efficient means to capture and greatly amplfy the resting concentration of LMW protein analytes. Since most of these markers do not have well performing specific antibodies commercially available, in this work we utilized MRM to verify, in an independent study set of 20 cancer samples and 24 benign controls, their differential expression as first identified by Orbitrap-MS/MS.

Method: NIPAm/AAC type of core-shell hydrogel nanoparticle was used for both orbitrap-LTQ based discovery and MRM verification such that the same analyte fractionation workflow was used but different downstream mass spectrometry. MRM was performed on a Thermo Quantum triple quadropole-MS using the nanoparticle trapped analyte archive as the input for analysis. On the basis of their biological significance and following manual verification of the raw LTQ-Orbitrap analysis data, a list of 35 biomarker candidates was selected for MRM verification. Among which i.e.: gelsolin isoform b, integrin α 2b preproprotein, apolipoprotein B precursor, fibronectin 1 isoform 2 preproprotein, LPS-binding protein precursor, ceruloplasmin, α-1apolipoprotein L1 isoform a precursor, leucine-rich α-2-glycoprotein 1, apolipoprotein C-IV, thrombospondin 1 precursor, pro-platelet basic protein precursor, serum amyloid A4, apolipoprotein H precursor, gelsolin isoform b, UNC-112 related protein 2 long form, H4 histone familymember J, cadherin 1, apolipoprotein AV, H2A histone family, member D, apolipoprotein C-III precursor, heterogeneous nuclear ribonucleoprotein AB isoform a, ras suppressor protein 1 isoform 2, cofilin 1 (non-muscle), a disintegrin & metalloproteinase domain 7, transgelin 2, S100-A7, mucin 16.

Conclusions: Several ovary candidate biomarkers were verified by Nanoparticle capture-MRM, thus providing data supporting the use and continued improvement of this novel biomarker discovery system for the identification of protein biomarker panels for early disease detection and therapeutic monitoring.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4584.

Explant-derived human dental pulp stem cells enhance differentiation and proliferation potentials

Numerous stem cell niches are present in the different tissues and organs of the adult human body. Among these tissues, dental pulp, entrapped within the ‘sealed niche’ of the pulp chamber, is an extremely rich site for collecting stem cells. In this study, we demonstrate that the isolation of human dental pulp stem cells by the explants culture method (hD-DPSCs) allows the recovery of a population of dental mesenchymal stem cells that exhibit an elevated proliferation potential. Moreover, we highlight that hD-DPSCs are not only capable of differentiating into osteoblasts and chondrocytes but are also able to switch their genetic programme when co-cultured with murine myoblasts. High levels of MyoD expression were detected, indicating that muscle-specific genes in dental pulp cells can be turned on through myogenic fusion, confirming thus their multipotency. A perivascular niche may be the potential source of hD-DPSCs, as suggested by the consistent Ca²⁺ release from these cells in response to endothelin-1 (ET-1) treatment, which is also able to significantly increase cell proliferation. Moreover, response to ET-1 has been found to be superior in hD-DPSCs than in DPSCs, probably due to the isolation method that promotes release of stem/progenitor cells from perivascular structures. The ability to isolate, expand and direct the differentiation of hD-DPSCs into several lineages, mainly towards myogenesis, offers an opportunity for the study of events associated with cell commitment and differentiation. Therefore, hD-DPSCs display enhanced differentiation abilities when compared to DPSCs, and this might be of relevance for their use in therapy.

NAADP-induced Ca(2+ signaling in response to endothelin is via the receptor subtype B and requires the integrity of lipid rafts/caveolae

We have investigated the role of NAADP-mediated Ca(2+) mobilization in endothelin (ET) signaling via endothelin receptor subtype A (ETA) and endothelin receptor subtype B (ETB) in rat peritubular smooth muscle cells. Microinjection and extracellular application of NAADP were both able to elicit Ca(2+) release which was blocked by inhibitory concentrations of NAADP, by impairing Ca(2+) uptake in acidic stores with bafilomycin, and by thapsigargin. Ca(2+) release in response to selective ETB stimulation was abolished by inhibition of NAADP signaling through the same strategies, while these treatments only partially impaired ETA-dependent Ca(2+) signaling, showing that transduction of the ETB signal is dependent on NAADP. In addition, we show that lipid rafts/caveolae contain ETA, ETB, and NAADP/cADPR generating enzyme CD38 and that stimulation of ETB receptors results in increased CD38 activity; interestingly, ETB- (but not ETA-) mediated Ca(2+) responses were antagonized by disruption of lipid rafts/caveolae with methyl-beta-cyclodextrin. These data demonstrate a primary role of NAADP in ETB-mediated Ca(2+) signaling and strongly suggest a novel role of lipid rafts/caveolae in triggering ET-induced NAADP signaling.

Association of Dystrobrevin and Regulatory Subunit of Protein Kinase A: A New Role for Dystrobrevin as a Scaffold for Signaling Proteins

The dystrophin-related and -associated protein dystrobrevin is a component of the dystrophin-associated protein complex, which directly links the cytoskeleton to the extracellular matrix. It is now thought that this complex also serves as a dynamic scaffold for signaling proteins, and dystrobrevin may play a role in this context. Since dystrobrevin involvement in signaling pathways seems to be dependent on its interaction with other proteins, we sought new insights and performed a two-hybrid screen of a mouse brain cDNA library using beta-dystrobrevin, the isoform expressed in non-muscle tissues, as bait. Among the positive clones characterized after the screen, one encodes the regulatory subunit RIalpha of the cAMP-dependent protein kinase A (PKA). We confirmed the interaction by in vitro and in vivo association assays, and mapped the binding site of beta-dystrobrevin on RIalpha to the amino-terminal region encompassing the dimerization/docking domain of PKA regulatory subunit. We also found that the domain of interaction for RIalpha is contained in the amino-terminal region of beta-dystrobrevin. We obtained evidence that beta-dystrobrevin also interacts directly with RIIbeta, and that not only beta-dystrobrevin but also alpha-dystrobrevin interacts with PKA regulatory subunits. We show that both alpha and beta-dystrobrevin are specific phosphorylation substrates for PKA and that protein phosphatase 2A (PP2A) is associated with dystrobrevins. Our results suggest a new role for dystrobrevin as a scaffold protein that may play a role in different cellular processes involving PKA signaling.

Endothelin induces functional hypertrophy of peritubular smooth muscle cells

When chronically stimulated with agonists of contraction, smooth muscle cells (SMCs) undergo cell hypertrophy, a process defined as increase in size and potentiation of the contractile phenotype in the absence of proliferation. Hypertrophic response has long been associated to a number of pathologies of the cardiovascular and respiratory systems. We have investigated the phenotypic and functional response of SMCs to long-term treatment with endothelin. Our model was primary cultures of peritubular smooth muscle cells (PSMC) a testicular cell type target of locally produced endothelin and characterized by an unusual phenotypic stability when cultured in simple medium in complete absence of serum. We report the following responses of PSMC to 4-day exposure to ET-1: (i) increased protein synthesis without induction of cell proliferation; (ii) increase in cell size (evaluated by means of flow cytometry) and increased expression of SM-alpha-actin, desmin, caldesmon and calponin, markers of the contractile phenotype. In experiments of selective stimulation of either ETA or ETB receptor subtypes, both proved to be involved in inducing the observed hypertrophic responses. The hypertrophic cells exhibit the ultrastructural features of differentiated SMCs and are capable of calcium mediated contractile response when acutely stimulated with ET-1 specifically through ETA and/or ETB receptors, as evaluated by calcium imaging and scanning electron microscopy. These observations demonstrate that engagement of ET receptors is capable of inducing potentiation of the contractile phenotype and functional hypertrophy of PSMC.

β-Dystrobrevin interacts directly with kinesin heavy chain in brain

β-Dystrobrevin, a member of the dystrobrevin protein family, is a dystrophin-related and -associated protein restricted to non-muscle tissues and is highly expressed in kidney, liver and brain. Dystrobrevins are now thought to play an important role in intracellular signal transduction, in addition to providing a membrane scaffold in muscle, but the precise role of β-dystrobrevin has not yet been determined. To study β-dystrobrevin's function in brain, we used the yeast two-hybrid approach to look for interacting proteins. Four overlapping clones were identified that encoded Kif5A, a neuronal member of the Kif5 family of proteins that consists of the heavy chains of conventional kinesin. A direct interaction of β-dystrobrevin with Kif5A was confirmed by in vitro and in vivo association assays. Co-immunoprecipitation with a monoclonal kinesin heavy chain antibody precipitated both α- and β-dystrobrevin, indicating that this interaction is not restricted to the β-dystrobrevin isoform. The site for Kif5A binding to β-dystrobrevin was localized in a carboxyl-terminal region that seems to be important in heavy chain-mediated kinesin interactions and is highly homologous in all three Kif5 isoforms, Kif5A, Kif5B and Kif5C. Pull-down and immunofluorescence experiments also showed a direct interaction between β-dystrobrevin and Kif5B. Our findings suggest a novel function for dystrobrevin as a motor protein receptor that might play a major role in the transport of components of the dystrophin-associated protein complex to specific sites in the cell.