Defining the spatial distribution of extracellular adenosine revealed a myeloid-dependent immunosuppressive microenvironment in pancreatic ductal adenocarcinoma

BACKGROUND

The prognosis for patients with pancreatic ductal adenocarcinoma (PDAC) remains extremely poor. It has been suggested that the adenosine pathway contributes to the ability of PDAC to evade the immune system and hence, its resistance to immuno-oncology therapies (IOT), by generating extracellular adenosine (eAdo).

METHODS

Using genetically engineered allograft models of PDAC in syngeneic mice with defined and different immune infiltration and response to IOT and autochthonous tumors in KPC mice we investigated the impact of the adenosine pathway on the PDAC tumor microenvironment (TME). Flow cytometry and imaging mass cytometry (IMC) were used to characterize the subpopulation frequency and spatial distribution of tumor-infiltrating immune cells. Mass spectrometry imaging (MSI) was used to visualize adenosine compartmentalization in the PDAC tumors. RNA sequencing was used to evaluate the influence of the adenosine pathway on the shaping of the immune milieu and correlate our findings to published data sets in human PDAC.

RESULTS

We demonstrated high expression of adenosine pathway components in tumor-infiltrating immune cells (particularly myeloid populations) in the murine models. MSI demonstrated that extracellular adenosine distribution is heterogeneous in tumors, with high concentrations in peri-necrotic, hypoxic regions, associated with rich myeloid infiltration, demonstrated using IMC. Protumorigenic M2 macrophages express high levels of the Adora2a receptor; particularly in the IOT resistant model. Blocking the in vivo formation and function of eAdo (Adoi), using a combination of anti-CD73 antibody and an Adora2a inhibitor slowed tumor growth and reduced metastatic burden. Additionally, blocking the adenosine pathway improved the efficacy of combinations of cytotoxic agents or immunotherapy. Adoi remodeled the TME, by reducing the infiltration of M2 macrophages and regulatory T cells. RNA sequencing analysis showed that genes related to immune modulation, hypoxia and tumor stroma were downregulated following Adoi and a specific adenosine signature derived from this is associated with a poorer prognosis in patients with PDAC.

CONCLUSIONS

The formation of eAdo promotes the development of the immunosuppressive TME in PDAC, contributing to its resistance to conventional and novel therapies. Therefore, inhibition of the adenosine pathway may represent a strategy to modulate the PDAC immune milieu and improve therapy response in patients with PDAC.

Novel arginase inhibitor, AZD0011, demonstrates immune cell stimulation and anti-tumor efficacy with diverse combination partners

Anti-tumor immunity can be hampered by immunosuppressive mechanisms in the tumor microenvironment including recruitment of arginase (ARG) expressing myeloid cells which deplete L-arginine essential for optimal T cell and natural killer cell function. Hence, ARG inhibition can reverse immunosuppression enhancing anti-tumor immunity. We describe AZD0011, a novel peptidic boronic acid prodrug to deliver an orally available, highly potent, ARG inhibitor payload (AZD0011-PL). We demonstrate that AZD0011-PL is unable to permeate cells, suggesting this compound will only inhibit extracellular ARG. In vivo, AZD0011 monotherapy leads to arginine increases, immune cell activation, and tumor growth inhibition (TGI) in various syngeneic models. Anti-tumor responses increase when AZD0011 is combined with anti-PD-L1 treatment, correlating with increases in multiple tumor immune cell populations. We demonstrate a novel triple combination of AZD0011, anti-PD-L1 and anti-NKG2A, and combination benefits with type I interferon (IFN) inducers including polyI:C and radiation. Our pre-clinical data demonstrates AZD0011's ability to reverse tumor immunosuppression and enhance immune stimulation and anti-tumor responses with diverse combination partners providing potential strategies to increase immuno-oncology therapies clinically.

Pharmacokinetic/Pharmacodynamic Analysis of Savolitinib Plus Osimertinib in an EGFR-Mutation Positive, MET-Amplified Non-Small Cell Lung Cancer Model

Osimertinib is a third-generation, irreversible, oral epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), recommended as first-line treatment for patients with locally advanced/metastatic EGFR-mutation positive (EGFRm) non-small cell lung cancer (NSCLC). However, MET-amplification/overexpression is a common acquired osimertinib resistance mechanism. Savolitinib is an oral, potent, and highly selective MET-TKI; preliminary data suggest that combining osimertinib with savolitinib may overcome MET-driven resistance. A patient-derived xenograft (PDX) mouse model with EGFRm, MET-amplified NSCLC was tested with a fixed osimertinib dose (10 mg/kg, for exposures equivalent to [≈] 80 mg), combined with doses of savolitinib (0-15 mg/kg, ≈0-600 mg once-daily), both with 1-aminobenzotriazole (to better match clinical half-life). After 20 days of oral dosing, samples were taken at various timepoints to follow the time-course of drug exposure in addition to phosphorylated MET and EGFR (pMET; pEGFR) change. Population pharmacokinetics, savolitinib concentration versus percentage inhibition from baseline in pMET, and the relationship between pMET and tumor growth inhibition (TGI) were also modeled. As single agents, savolitinib (15 mg/kg) showed significant anti-tumor activity, reaching ~84% TGI and osimertinib (10 mg/kg) showed no significant anti-tumor activity (34% TGI, P>0.05 vs. vehicle). Upon combination, at a fixed dose of osimertinib, significant savolitinib dose-related anti-tumor activity was shown, ranging from 81% TGI (0.3 mg/kg) to 84% tumor regression (15 mg/kg). Pharmacokinetic-pharmacodynamic modeling showed that the maximum inhibition of both pEGFR and pMET increased with increasing savolitinib doses. Savolitinib demonstrated exposure-related combination anti-tumor activity when combined with osimertinib in the EGFRm MET-amplified NSCLC PDX model.

Quantitative Evaluation of Dendritic Nanoparticles in Mice: Biodistribution Dynamics and Downstream Tumor Efficacy Outcomes

A physiologically based pharmacokinetic model was developed to describe the tissue distribution kinetics of a dendritic nanoparticle and its conjugated active pharmaceutical ingredient (API) in plasma, liver, spleen, and tumors. Tumor growth data from MV-4-11 tumor-bearing mice were incorporated to investigate the exposure/efficacy relationship. The nanoparticle demonstrated improved antitumor activity compared to the conventional API formulation, owing to the extended released API concentrations at the site of action. Model simulations further enabled the identification of critical parameters that influence API exposure in tumors and downstream efficacy outcomes upon nanoparticle administration. The model was utilized to explore a range of dosing schedules and their effect on tumor growth kinetics, demonstrating the improved antitumor activity of nanoparticles with less frequent dosing compared to the same dose of naked APIs in conventional formulations.

Oncogenic switch and single-agent MET inhibitor sensitivity in a subset of EGFR-mutant lung cancer

[Figure: see text].

Conversion of ATP to adenosine by CD39 and CD73 in multiple myeloma can be successfully targeted together with adenosine receptor A2A blockade

Background

PD1/PDL1-directed therapies have been unsuccessful for multiple myeloma (MM), an incurable cancer of plasma cells in the bone marrow (BM). Therefore, other immune checkpoints such as extracellular adenosine and its immunosuppressive receptor should be considered. CD39 and CD73 convert extracellular ATP to adenosine, which inhibits T-cell effector functions via the adenosine receptor A2A (A2AR). We set out to investigate whether blocking the adenosine pathway could be a therapy for MM.

Methods

Expression of CD39 and CD73 on BM cells from patients and T-cell proliferation were determined by flow cytometry and adenosine production by Liquid chromatograpy-mass spectrometry (HPCL/MS). ENTPD1 (CD39) mRNA expression was determined on myeloma cells from patients enrolled in the publicly available CoMMpass study. Transplantable 5T33MM myeloma cells were used to determine the effect of inhibiting CD39, CD73 and A2AR in mice in vivo.

Results

Elevated level of adenosine was found in BM plasma of MM patients. Myeloma cells from patients expressed CD39, and high gene expression indicated reduced survival. CD73 was found on leukocytes and stromal cells in the BM. A CD39 inhibitor, POM-1, and an anti-CD73 antibody inhibited adenosine production and reduced T-cell suppression in vitro in coculture of myeloma and stromal cells. Blocking the adenosine pathway in vivo with a combination of Sodium polyoxotungstate (POM-1), anti-CD73, and the A2AR antagonist AZD4635 activated immune cells, increased interferon gamma production, and reduced the tumor load in a murine model of MM.

Conclusions

Our data suggest that the adenosine pathway can be successfully targeted in MM and blocking this pathway could be an alternative to PD1/PDL1 inhibition for MM and other hematological cancers. Inhibitors of the adenosine pathway are available. Some are in clinical trials and they could thus reach MM patients fairly rapidly.

Small molecule AZD4635 inhibitor of A2AR signaling rescues immune cell function including CD103+ dendritic cells enhancing anti-tumor immunity

Accumulation of extracellular adenosine within the microenvironment is a strategy exploited by tumors to escape detection by the immune system. Adenosine signaling through the adenosine 2A receptor (A_2AR) on immune cells elicits a range of immunosuppressive effects which promote tumor growth and limit the efficacy of immune checkpoint inhibitors. Preclinical data with A_2AR inhibitors have demonstrated tumor regressions in mouse models by rescuing T cell function; however, the mechanism and role on other immune cells has not been fully elucidated.

AZ1366: An Inhibitor of Tankyrase and the Canonical Wnt Pathway that Limits the Persistence of Non-Small Cell Lung Cancer Cells Following EGFR Inhibition

Purpose: The emergence of EGFR inhibitors such as gefitinib, erlotinib, and osimertinib has provided novel treatment opportunities in EGFR-driven non-small cell lung cancer (NSCLC). However, most patients with EGFR-driven cancers treated with these inhibitors eventually relapse. Recent efforts have identified the canonical Wnt pathway as a mechanism of protection from EGFR inhibition and that inhibiting tankyrase, a key player in this pathway, is a potential therapeutic strategy for the treatment of EGFR-driven tumors.Experimental Design: We performed a preclinical evaluation of tankyrase inhibitor AZ1366 in combination with multiple EGFR-inhibitors across NSCLC lines, characterizing its antitumor activity, impingement on canonical Wnt signaling, and effects on gene expression. We performed pharmacokinetic and pharmacodynamic profiling of AZ1366 in mice and evaluated its therapeutic activity in an orthotopic NSCLC model.Results: In combination with EGFR inhibitors, AZ1366 synergistically suppressed proliferation of multiple NSCLC lines and amplified global transcriptional changes brought about by EGFR inhibition. Its ability to work synergistically with EGFR inhibition coincided with its ability to modulate the canonical Wnt pathway. Pharmacokinetic and pharmacodynamic profiling of AZ1366-treated orthotopic tumors demonstrated clinically relevant serum drug levels and intratumoral target inhibition. Finally, coadministration of an EGFR inhibitor and AZ1366 provided better tumor control and improved survival for Wnt-responsive lung cancers in an orthotopic mouse model.Conclusions: Tankyrase inhibition is a potent route of tumor control in EGFR-dependent NSCLC with confirmed dependence on canonical Wnt signaling. These data strongly support further evaluation of tankyrase inhibition as a cotreatment strategy with EGFR inhibition in an identifiable subset of EGFR-driven NSCLC. Clin Cancer Res; 23(6); 1531-41. ©2016 AACR.

The MET Inhibitor AZD6094 (Savolitinib, HMPL-504) Induces Regression in Papillary Renal Cell Carcinoma Patient-Derived Xenograft Models

PURPOSE

Papillary renal cell carcinoma (PRCC) is the second most common cancer of the kidney and carries a poor prognosis for patients with nonlocalized disease. The HGF receptor MET plays a central role in PRCC and aberrations, either through mutation, copy number gain, or trisomy of chromosome 7 occurring in the majority of cases. The development of effective therapies in PRCC has been hampered in part by a lack of available preclinical models. We determined the pharmacodynamic and antitumor response of the selective MET inhibitor AZD6094 in two PRCC patient-derived xenograft (PDX) models.

EXPERIMENTAL DESIGN

Two PRCC PDX models were identified and MET mutation status and copy number determined. Pharmacodynamic and antitumor activity of AZD6094 was tested using a dose response up to 25 mg/kg daily, representing clinically achievable exposures, and compared with the activity of the RCC standard-of-care sunitinib (in RCC43b) or the multikinase inhibitor crizotinib (in RCC47).

RESULTS

AZD6094 treatment resulted in tumor regressions, whereas sunitinib or crizotinib resulted in unsustained growth inhibition. Pharmacodynamic analysis of tumors revealed that AZD6094 could robustly suppress pMET and the duration of target inhibition was dose related. AZD6094 inhibited multiple signaling nodes, including MAPK, PI3K, and EGFR. Finally, at doses that induced tumor regression, AZD6094 resulted in a dose- and time-dependent induction of cleaved PARP, a marker of cell death.

CONCLUSIONS

Data presented provide the first report testing therapeutics in preclinical in vivo models of PRCC and support the clinical development of AZD6094 in this indication.

Preclinical evaluation of the WEE1 inhibitor MK-1775 as single-agent anticancer therapy

Inhibition of the DNA damage checkpoint kinase WEE1 potentiates genotoxic chemotherapies by abrogating cell-cycle arrest and proper DNA repair. However, WEE1 is also essential for unperturbed cell division in the absence of extrinsic insult. Here, we investigate the anticancer potential of a WEE1 inhibitor, independent of chemotherapy, and explore a possible cellular context underlying sensitivity to WEE1 inhibition. We show that MK-1775, a potent and selective ATP-competitive inhibitor of WEE1, is cytotoxic across a broad panel of tumor cell lines and induces DNA double-strand breaks. MK-1775-induced DNA damage occurs without added chemotherapy or radiation in S-phase cells and relies on active DNA replication. At tolerated doses, MK-1775 treatment leads to xenograft tumor growth inhibition or regression. To begin addressing potential response markers for MK-1775 monotherapy, we focused on PKMYT1, a kinase functionally related to WEE1. Knockdown of PKMYT1 lowers the EC(50) of MK-1775 by five-fold but has no effect on the cell-based response to other cytotoxic drugs. In addition, knockdown of PKMYT1 increases markers of DNA damage, γH2AX and pCHK1(S345), induced by MK-1775. In a post hoc analysis of 305 cell lines treated with MK-1775, we found that expression of PKMYT1 was below average in 73% of the 33 most sensitive cell lines. Our findings provide rationale for WEE1 inhibition as a potent anticancer therapy independent of a genotoxic partner and suggest that low PKMYT1 expression could serve as an enrichment biomarker for MK-1775 sensitivity.

Mu-opioid receptor knockout mice show diminished food-anticipatory activity

We have previously suggested that during or prior to activation of anticipatory behaviour to a coming reward, mu-opioid receptors are activated. To test this hypothesis schedule induced food-anticipatory activity in mu-opioid receptor knockout mice was measured using running wheels. We hypothesized that mu-knockout mice show little food-anticipatory activity. In wildtype mice we observed that food-anticipatory activity increased proportional to reduced food intake levels during daily scheduled food access, and thus reflects the animal's physiological need for food. mu-Knockout mice do not adjust their schedule induced running wheel behaviour prior to and during feeding time in the same way as wildtype mice; rather than showing more running wheel activity before than during feeding, they showed an equal amount of activity before and during feeding. As food-anticipatory activity is dependent on the mesolimbic dopamine system and mu-opioid receptors regulate dopaminergic activity, these data suggest a change in the dopamine system's activity in mu-knockout mice. As we observed that mu-knockout mice tended to show a stronger locomotor activity response than wildtype mice to the indirect dopamine agonist d-amphetamine, it appears that the dopaminergic system per se is intact and sensitive to activation. We found no differences in the expression of pro-opiomelanocortin, a precursor of endogenous endorphin, in the arcuate nucleus between mu-knockout mice and wildtype mice during restricted feeding, showing that the mu-opioid receptor does not regulate endogenous endorphin levels. These data overall suggest a role for mu-opioid receptors in adapting reward related behaviour to the requirements of the environment.

Selective alterations in organ sizes in mice with a targeted disruption of the insulin-like growth factor binding protein-2 gene

Insulin-like growth factor binding protein 2 (IGFBP-2) is one member of the family of IGF binding proteins believed to have both endocrine functions elicited by modulating serum IGF half-life and transport as well as autocrine/paracrine functions that result from blocking or enhancing the availability of IGFs to bind cell surface receptors. To clarify the in vivo role of IGFBP-2, we have used gene targeting to introduce a null IGFBP-2 allele into the mouse genome. Animals homozygous for the altered allele are viable and fertile, contain no IGFBP-2 mRNA, and have no detectable IGFBP-2 in the adult circulation. Heterozygous and homozygous animals showed no significant differences in prenatal or postnatal body growth. Analyses of organ weights in adult males, however, revealed that spleen weight was reduced and liver weight was increased in the absence of IGFBP-2. In addition, ligand blot analyses of sera from adult IGFBP-2 null males showed that IGFBP-1, IGFBP-3, and IGFBP-4 levels were increased relative to wild-type mice. These results demonstrate that up-regulation of multiple IGFBPs accompanies the absence of IGFBP-2 and that IGFBP-2 has a critical role, either directly or indirectly, in modulating spleen and liver size.

Generation of antisera to mouse insulin-like growth factor binding proteins (IGFBP)-1 to -6: comparison of IGFBP protein and messenger ribonucleic acid localization in the mouse embryo

The insulin-like growth factor (IGF) system is an important regulator of fetal growth and differentiation. IGF bioavailability is modulated by IGF binding proteins (IGFBPs). We have generated six different antisera, directed to synthetic peptide fragments of mouse IGFBP-1 through -6. The specificity of the produced antisera was demonstrated by enzyme-linked immunosorbent assay, Western blotting, and by immunohistochemistry on sections of mouse embryos of 13.5 days post coitum. Specificity for the IGFBP-2 through -6 antisera also was confirmed immunohistochemically in liver and lung of corresponding gene deletion (knock-out) mutant mice and wild-type litter mates. Immunohistochemistry and messenger RNA (mRNA) in situ hybridization on sections of mouse embryos of 13.5 days post coitum revealed tissue-specific expression patterns for the six IGFBPs. The only site of IGFBP-1 protein and mRNA production was the liver. IGFBP-2, -4, and -5 protein and mRNA were detected in various organs and tissues. IGFBP-3 and -6 protein and mRNA levels were low. In several tissues, such as lung, liver, kidney, and tongue, more than one IGFBP (protein and mRNA) could be detected. Differences between mRNA and protein localization were extensive for IGFBP-3, -5, and -6, suggesting that these IGFBPs are secreted and transported. These results confirm the different spatial localization of the IGFBPs, on the mRNA and protein level. The overlapping mRNA and protein localization for IGFBP-2 and -4, on the other hand, may indicate that these IGFBPs also function in an auto- or paracrine manner.

Retention of supraspinal delta-like analgesia and loss of morphine tolerance in delta opioid receptor knockout mice

Gene targeting was used to delete exon 2 of mouse DOR-1, which encodes the delta opioid receptor. Essentially all 3H-[D-Pen2,D-Pen5]enkephalin (3H-DPDPE) and 3H-[D-Ala2,D-Glu4]deltorphin (3H-deltorphin-2) binding is absent from mutant mice, demonstrating that DOR-1 encodes both delta1 and delta2 receptor subtypes. Homozygous mutant mice display markedly reduced spinal delta analgesia, but peptide delta agonists retain supraspinal analgesic potency that is only partially antagonized by naltrindole. Retained DPDPE analgesia is also demonstrated upon formalin testing, while the nonpeptide delta agonist BW373U69 exhibits enhanced activity in DOR-1 mutant mice. Together, these findings suggest the existence of a second delta-like analgesic system. Finally, DOR-1 mutant mice do not develop analgesic tolerance to morphine, genetically demonstrating a central role for DOR-1 in this process.

Hypoglycaemia associated with the production of insulin-like growth factor II and insulin-like growth factor binding protein 6 by a haemangiopericytoma

Non-islet-cell tumour-induced hypoglycaemia (NICTH) is, in most cases, attributable to tumour production of insulin-like growth factor II (IGF-II). Tumour-derived IGF-II has a higher than normal molecular weight (big 'IGF-II') and an impaired ability to form the normal ternary 150 kD complex with IGF binding protein-3 (IGFBP-3) and the acid-labile subunit (ALS). Consequently, tumoral IGF-II circulates mainly in smaller binary complexes which have a higher bioavailability than the ternary complex. We had the opportunity to analyze IGFs and IGF-related factors in both pre- and post-operative blood, tumour tissue and tumour cyst fluid from a patient with a disseminated haemangiopericytoma and severe hypoglycaemia. In addition, the effect of serum and tumour cyst fluid on autophosphorylation of the insulin receptor was examined. Patient serum contained low levels of IGF-I, IGFBP-3 and ALS, while the concentrations of IGFBP-2 and IGFBP-6 were markedly elevated. The total level of circulating IGF-II was within the normal range, but Biogel P-60 gel filtration of patient serum revealed that 77% of the IGF-II was present in high molecular weight forms (normal: 10-15%), which decreased to 53% after partial removal of the tumour. Most of the IGF-II immunoreactivity in pre- and post-operative patient serum was associated with 50-60 kD complexes with only a minimal contribution (<10%) from the 150 kD complex. Tumour cyst fluid contained excessive amounts of both big IGF-II and IGFBP-6. Northern blot analysis of total mRNA isolated from the tumour demonstrated high expression of the IGF-II gene and abundant 1.1 kb IGFBP-6 transcript, while the genes encoding IGFBP-3, -4 and -5 were only weakly expressed and mRNA of IGFBP-1, -2 and IGF-I could not be detected. mRNAs for the IGF type II receptor could be easily demonstrated, whereas those for the insulin- and IGF type I receptor were hardly detectable. In contrast to patient serum tumour cyst fluid strongly stimulated the insulin receptor in vitro. The present study suggests an important role of the simultaneous production of IGF-II and IGFBP-6 in the pathophysiology of tumour-induced hypoglycaemia.

Expression of IGF system genes during T-antigen driven pituitary tumorigenesis

Expression of IGF-I, IGF-II, the Type-I IGF receptor and six IGF binding proteins were examined in three different T-ag-driven mouse tumors. Unlike the widespread expression of IGF-II in pancreatic beta-cell tumors, IGF-II was not widely expressed in the two different pituitary tumors examined indicating that a mechanism independent of focal IGF-II expression can also drive T-antigen tumorigenesis. In addition, multiple IGF binding proteins were expressed in all three tumor types. This expression, however, was generally heterogeneous with no specific changes to indicate a required role for any IGF binding protein in T-antigen tumorigenesis.

Retention of heroin and morphine-6 beta-glucuronide analgesia in a new line of mice lacking exon 1 of MOR-1

Morphine produces analgesia by activating mu opioid receptors encoded by the MOR-1 gene. Although morphine-6 beta-glucuronide (M6G), heroin and 6-acetylmorphine also are considered mu opioids, recent evidence suggests that they act through a distinct receptor mechanism. We examined this question in knockout mice containing disruptions of either the first or second coding exon of MOR-1. Mice homozygous for either MOR-1 mutation were insensitive to morphine. Heroin, 6-acetylmorphine and M6G still elicited analgesia in the exon-1 MOR-1 mutant, which also showed specific M6G binding, whereas M6G and 6-acetylmorphine were inactive in the exon-2 MOR-1 mutant. These results provide genetic evidence for a unique receptor site for M6G and heroin analgesia.

Mouse insulin-like growth factor binding protein-6: expression, purification, characterization and histochemical localization

The mitogenic and metabolic activities of insulin-like growth factors (IGF) are modulated by a family of six high affinity IGF binding proteins (IGFBPs). This study describes the expression of the mouse IGFBP-6 which is unique among IGFBPs in its preferential binding of IGF II, in insect cells using the baculovirus system. The purified, O-glycosylated IGFBP-6 was functional as shown by IGF binding and by inhibition of IGF II-stimulated DNA synthesis in human fibroblasts. Specific antibodies generated in chicken against the recombinant IGFBP-6 were used for Western blotting analysis and immunohistochemistry. Strong immunoreactivity was found in ossifying bones of the cranial base, in cell clusters of the pancreas anlage, in the trigeminal ganglion, on myoblasts, on motoneurons of the spinal cord of embryonic mice. In tissues of adult mouse, strong IGFBP-6 immunostaining was present in epidermal and peridermal layers of the skin, in meningeal layers, in long-striated skeletal muscle, and in the Langerhans' islets of the pancreas. No immunopositive staining was observed in lung and liver indicating that sites of synthesis and IGFBP action are different.

IGF, type I IGF receptor and IGF-binding protein mRNA expression in kidney and liver of potassium-depleted and normal rats infused with IGF-I

Dietary potassium (K) depletion is known to reduce body weight gain and organ growth, except for kidney which increases in weight. This renal hypertrophy is preceded by increased renal IGF-I levels. In the present study, we investigated IGF-I and -II, type I IGF receptor and IGF-binding protein (IGFBP) mRNA expression in liver and kidney of K-depleted and normal rats infused with vehicle or recombinant human IGF-I. Body weight gain was almost completely arrested in K-depleted rats without any stimulatory effect of IGF-I infusion. Both absolute and relative kidney weight (kidney weight/body weight) were significantly increased in K-depleted rats and this was further enhanced by IGF-I infusion. In contrast, relative liver weight was comparable in the different groups and unaffected by IGF-I infusion. IGF-I mRNA expression was significantly lower in kidney and liver of K-depleted animals whereas type I IGF receptor levels were unchanged. In contrast, in kidney, K depletion increased IGFBP-1 and -2 mRNA expression with no additional effect of IGF-I infusion. In liver of K-depleted animals, IGFBP-1 mRNA expression was increased whereas increased IGFBP-1 and -2 mRNA expression was observed when these animals were infused with IGF-I. These observations may point towards a differential mode of action of the IGFBPs. In kidney increased IGFBP-1 and -2 mRNA expression may enhance IGF-I bioavailability with subsequent kidney growth. In liver, with clearly detectable type I IGF receptor mRNA expression, increased IGFBP levels may protect from IGF-I-induced organ growth by decreasing IGF-I bioavailability.

Stimulation of hepatic insulin-like growth factor-binding protein-1 and -3 gene expression by octreotide in rats

It has recently been demonstrated in various clinical experiments that native somatostatin and its long-acting analogues increase circulating levels of insulin-like growth factor-binding protein-1 (IGFBP-1) within 1-2 h, independent of effects on circulating insulin or glucose levels. Using human hepatoma cells in vitro the somatostatin analogue, octreotide, has been shown to increase IGFBP-1 mRNA within 24 h indicative of a direct stimulatory effect of octreotide on IGFBP-1 synthesis. In order to ascertain whether octreotide acutely stimulates IGFBP-1 mRNA in vivo, placebo or two doses of octreotide were injected subcutaneously into three groups of rats. One hour after saline or octreotide administration, liver, kidney and serum were obtained for the measurement of IGFBPs-1 to -6 mRNA in tissue and IGFBPs and IGF-I in serum. Octreotide increased liver IGFBP-1 (562%) and IGFBP-3 (23%) mRNA expression with a concomitant rise in the circulating 30 kDa (106%) and 38-42 kDa (23%) IGFBPs. No detectable changes were seen in other liver IGFBP transcripts, other circulating IGFBPs or in any of the kidney IGFBP transcripts. Serum IGF-I increased by 37% in the animals receiving the high octreotide dose. No concomitant changes were observed in glucose or insulin levels. These data show that octreotide acutely stimulates hepatic IGFBP-1 and -3 mRNA in vivo in rats. The stimulating effect on IGFBP-3 presents a possible hitherto unknown form of regulation of IGFBP-3 whilst the effect on IGFBP-1 indicates that the stimulatory effect of octreotide on circulating IGFBP-1 described in clinical trials may be due to increased hepatic production. The present findings may be of importance in the clinical use of octreotide.

Regulation of insulin-like growth factor (IGF)-binding protein-6 and mannose 6-phosphate/IGF-II receptor expression in IGF-IL-overexpressing NIH 3T3 cells

Insulin-like growth factor II (IGF-II)-overexpressing NIH 3T3 cells were used to examine regulation of insulin-like growth factor binding protein (IGFBP) and mannose 6-phosphate (M6P)/IGF-II receptor expression. Ligand blot analysis of conditioned media indicated a predominant IGFBP of 26-28 kilodaltons the abundance of which is 3- to 10-fold higher in media of IGF-II-overexpressing cells. The IGFBP level in control cell medium was increased by incubation in the presence of IGF-II, IGF-I, and mutant IGF-II forms with reduced affinities for IGF-I or M6P/IGF-II receptors. Further proof that IGF-II regulated the IGFBP was obtained by incubation of IGF-II overexpressing cells in the presence of antisense IGF-II oligomers or anti-IGF-II antibodies, which resulted in significant reduction of the IGFBP in conditioned medium. Mouse IGFBP-6 mRNA expression was increased in IGF-II-overexpressing or IGF-II-treated control cells. The IGFBP contained O-linked carbohydrate residues and was recognized by an antiserum to rat IGFBP-6. To determine whether IGFs were influencing proteolytic degradation of IGFBPs, cell-free conditioned media were incubated at 37 C with recombinant human IGFBPs. At neutral pH proteolysis of IGFBP-5 occurred during incubation in conditioned media from control and IGF-II-overexpressing cells. Upon acidification of the medium samples, only the degradation of IGFBP-6 was prevented in IGF-II-overexpressing cell-conditioned medium.(ABSTRACT TRUNCATED AT 250 WORDS)

IGF, type I IGF receptor and IGF-binding protein mRNA expression in the developing mouse lung

The IGFs are important mitogens involved in lung growth and development. The regulation of IGF action depends not only on the expression of IGFs and IGF receptors, but also on the modulation of IGF activity by IGF-binding proteins (IGFBPs). In this study, we describe the mRNA expression of IGF-I, IGF-II, type I IGF receptor, IGFBP-2, IGFBP-4 and IGFBP-5 during mouse lung development as studied by in situ hybridization techniques. The IGF, type I IGF receptor and IGFBP-2, -4 and -5 genes were expressed in developing lung as early as embryonal day 12.5. Expression of IGFBPs-1, -3 and -6 was below detection. IGF and IGFBP-2 mRNAs were expressed both in mesenchymal and epithelial cells. Type I IGF receptor transcripts were also observed throughout the developing lung, with the exception of the epithelial cells of the bronchi after embryonal day 15. Furthermore, mRNA expression of IGFBPs-4 and -5 was noted in neighbouring cell types, and after embryonal day 15, co-expression of the type I IGF receptor and IGFBP-4 transcripts was detected. The observed expression patterns imply that the IGFBP-2, -4 and -5 genes are differentially regulated during embryonic development and suggest that each may have a discrete function. A possible role for IGFBPs-2, -4 and -5 is to participate in the regulation of cell-specific IGF responses during mouse lung development.

Expression of growth factors and receptors during specific phases in regenerating urothelium after acute injury in vivo

We investigated the spatio-temporal changes in RNA and protein expression of growth factors and their receptors by in situ hybridization and immunocytochemistry during regeneration after acute injury of mouse urothelium in vivo. These data were correlated with changes in morphology and proliferation during regeneration. Except for an enhanced muscular transforming growth factor-beta 1 (TGF-beta 1) and TGF-beta type II receptor expression, changes in expression patterns of growth factors or receptors were confined to the urothelium. Increased mucosal RNA expression of insulin-like growth factor-II (IGF-II) and particularly of type I IGF receptor, as well as fibroblast growth factor-1 (FGF-1) but not of FGF-2, coincided with re-epithelialization and urothelial proliferation. Both high levels of urothelial TGF-beta 1 RNA and protein expression were associated with re-epithelialization and differentiation. In addition, TGF beta type II receptor protein expression was similarly enhanced in the same urothelial cells. Platelet-derived growth factor-A (PDGF-A) RNA was expressed constitutively in the mucosa but decreased in the reepithelialization phase. The data are consistent with the notion that urothelial regeneration can be achieved by paracrine or autocrine acting, urothelium-derived growth factors. Since analogous growth factor RNA expression patterns in regenerating skin epidermis have been found, a more general growth factor-regulated mechanism for epithelial regeneration may be suggested.

cDNA cloning and mRNA expression of the six mouse insulin-like growth factor binding proteins

The insulin-like growth factor binding proteins (IGFBPs) comprise a family of six distinct proteins which modulate insulin-like growth factor action. We have isolated cDNAs encoding the six mouse IGFBPs (mIGFBPs). In addition, we studied the mRNA expression of the six mIGFBPs during development and in various adult tissues. Our results show that each of the six mIGFBPs is highly homologous to their human and rat counterparts, whereas only the N and C terminal ends are conserved between the six mIGFBPs. Northern blotting revealed that mIGFBP-2, -3, -4 and -5 genes are already expressed at gestational day 11.5, suggesting a role for these mIGFBPs in embryonal development. In liver, a peak of mIGFBP-1 mRNA expression was found around birth, suggesting a function for mIGFBP-1 in the newborn mouse. Finally, tissue-specific expression of the six mouse IGFBP genes was observed in adult tissues suggesting different roles or modes of actions in adult life.

Gene expression of the IGF binding proteins during post-implantation embryogenesis of the mouse; comparison with the expression of IGF-I and -II and their receptors in rodent and human

The IGF binding proteins (IGFBPs) comprise at least six distinct species which may modulate the action of IGFs. IGFs are important regulators of fetal growth and differentiation. We have studied the mRNA expression of the six IGFBPs during post-implantation embryogenesis (day 11-18) by in situ hybridization techniques. Expression of IGFBP-1 was detected in mouse conceptuses after day 12 of gestation and seemed restricted to the liver. Transcripts for IGFBP-2, -4 and -5 were detected in various tissues and were found in all stages tested. In contrast, expression of IGFBP-3 and -6 could be detected only weakly in late gestational embryos. Comparison of the expression pattern of IGFBP-2, -4 and -5, which were found widely distributed in mouse conceptuses, revealed that IGFBP-2 was expressed mainly in the ectodermal layer and also in the mesoderm derived part of the tongue (day 13.5). Transcripts for IGFBP-4 however, only were detected in the mesoderm derived tissues, whereas expression of IGFBP-5 was restricted to the ectodermal layer. A similar distribution pattern was observed in the lung. In general, expression of IGFBP-2 and -5 was detected in the same cells, whereas IGFBP-4 and -5 were expressed mainly in different cell types. In rodents as in the human there is widespread expression of the genes coding IGFs, the IGFBPs and the receptors during pre- and postimplantation embryogenesis. These data support the assumption that the IGFs play an important role during embryogenesis.

Insulin-like growth factor binding protein-2, 28 kDa and 24 kDa insulin-like growth factor binding protein levels are decreased in fluid of dominant follicles, obtained from normal and polycystic ovaries

In order to investigate potential changes in insulin-like growth factor binding proteins (IGFBPs) during human follicle maturation, we examined the IGFBP profiles in follicular fluid from follicles in different stages of maturation. Samples were obtained from ovaries of women with regular menstrual cycles and of subjects with cycle abnormalities and polycystic ovaries (diagnosed as polycystic ovary syndrome (PCOS)) and analyzed by Western ligand blotting. IGFBPs of 43 kDa, 37 kDa, 31 kDa, a doublet around 28 kDa and a minor band of 24 kDa were detected in follicle fluid of normal non-dominant (size < 10 mm) and atretic (androstenedione/estradiol ratio > 4) follicles of both regularly menstruating women and PCOS patients. The 43 and 37 kDa IGFBPs could be identified as IGFBP-3 and the 31 kDa IGFBP as IGFBP-2, whereas the 28 kDa IGFBP could not be identified as IGFBP-1, all by immunoblotting techniques. A dramatic decrease in IGFBP-2, the 28 kDa and 24 kDa IGFBPs was observed in follicular fluid of dominant follicles (size > 10 mm) of both regular menstruating individuals and one PCOS patient as compared with follicular fluid of normal non-dominant or atretic follicles. These observations indicate that the PCOS follicle may not be different from normal with respect to IGFBP profiles. Furthermore, these results suggest that at least one of these IGFBPs might be involved in human folliculogenesis.

Gene expression of the six insulin-like growth factor binding proteins in the mouse conceptus during mid- and late gestation

The insulin-like growth factor-binding proteins (IGFBPs) comprise at least six distinct species that may modulate the action of IGFs. IGFs are important regulators of fetal growth and differentiation. To define sites of IGFBP mRNA synthesis, we have used in situ hybridization techniques in mouse conceptuses of different gestational ages (11-18 days). Expression of mouse (m) IGFBP-1 was detected in mouse conceptuses after day 12 of gestation and was restricted to the liver. Transcripts for mIGFBP-2, -4, and -5 were detected in various tissues and were found in all stages tested. In contrast, expression of mIGFBP-3 and -6 could be only weakly detected in late gestational conceptuses. Comparison of the expression patterns of mIGFBP-2, -4, and -5, which were found widely distributed in mouse conceptuses, revealed that mIGFBP-2 was expressed in the mesoderm-derived part of the tongue (day 13.5), but mainly in the ectodermal layer. Transcripts for mIGFBP-4, however, were detected only in the mesodermal part, whereas expression of mIGFBP-5 was restricted to the ectodermal layer. A similar distribution pattern was observed in the lung (day 18). In general, expression of mIGFBP-2 and -5 was detected in the same cells, whereas mIGFBP-4 and -5 were expressed mainly in different cell types. These data suggest that the different mIGFBPs might play distinct roles in mouse embryonal and fetal life.

Localization of the epitope of a monoclonal antibody against human insulin-like growth factor binding protein-1, functionally interfering with insulin-like growth factor binding

In order to identify regions in insulin-like growth factor binding protein-1 involved in the binding of IGFs, we tested three monoclonal antibodies, designated MAb A, B, and C on their interference with IGF-binding. Monoclonal A interfered with the binding of IGF to IGFBP-1 as determined by immunoprecipitation whereas monoclonal B and C did not. Furthermore MAb A was found to abolish IGFBP-1 inhibition of IGF stimulation in an in vitro proliferation assay. The epitopes of all three monoclonal antibodies were found to be located within the C-terminal part of IGFBP-1. The regions surrounding residue 188-196 and 222-227 are especially important for antibody recognition. These results indicate that MAb A functionally interferes with the binding of IGF to IGFBP-1. Furthermore, we suggest that part of the epitope of MAb A is located at or sterically near the IGF binding domain of IGFBP-1.

Structural aspects of the IGFBP family

To date six IGF binding proteins (IGFBP) have been characterized. Analysis of the amino acid sequence reveals that the IGFBPs are clearly distinct but are sharing regions with strong homology. Specifically the hydrophobic cysteine rich N-terminal region and to a lesser extend the C-terminal part are preserved. The alignment of the cysteine molecules is strongly conserved across the 6 IGFBPs. The middle one-third region, where no cysteines are present (except for IGFBP-4) is most divergent. IGFBP-3 and -4 are glycosylated, whereas IGFBP-1 and -2 contain an Arg-Gly-Asp sequence near the carboxyl terminus. Determination of the number of free-SH groups of IGFBP-1 and -3 has revealed that most likely all cysteine residues are involved in disulfide bond formation. All members of the IGFBP family bind IGF-I and IGF-II with about equal affinity. Studies involving deletion mutation and site-directed mutagenesis of IGFBP-1 and -3 have suggested that the three-dimensional structure of the protein plays an important role in IGF binding. However at present it is unclear whether the IGFBPs share one or more specific IGF binding domain. The predominant function of the IGFBPs is to allocate IGF in the various body fluid compartments and tissues and to modulate IGF binding to receptors. For this purpose there exists a very sophisticated control of the routing of circulating IGF both from and to the cell. There is mounting evidence that the structure of the IGFBP proteins plays a key role in the regulation of IGF bioavailability, by modulating its molecular size, capillary membrane permeability, target tissue specificity, cell membrane adherence and IGF affinity.

Site-directed mutagenesis of the N-terminal region of IGF binding protein 1; analysis of IGF binding capability

To define domains involved in IGF binding 60 N-terminal amino acid residues of IGFBP-1 were deleted. This deletion resulted in loss of IGF binding suggesting that the N-terminus may enclose an IGF binding domain. However, most point mutations introduced in this region did not affect IGF binding. In contrast to Cys-34, only substitution of Cys-38 for a tyrosine residue abolished IGF binding. With the determination that all 18 cysteine residues are involved in disulphide bond formation our data suggest that, although not all cysteines contribute to the same extent, the ligand binding site may be spatially organized.