A Postnatal Pax7+ Progenitor Gives Rise to Pituitary Adenomas

Pituitary adenomas are classified into functioning and nonfunctioning (silent) tumors on the basis of hormone secretion. However, the mechanism of tumorigenesis and the cell of origin for pituitary adenoma subtypes remain to be elucidated. Employing a tamoxifen-inducible mouse model, we demonstrate that a novel postnatal Pax7+ progenitor cell population in the pituitary gland gives rise to silent corticotroph macro-adenomas when the retinoblastoma tumor suppressor is conditionally deleted. While Pax transcriptional factors are critical for embryonic patterning as well as postnatal stem cell renewal for many organs, we have discovered that Pax7 marks a restricted cell population in the postnatal pituitary intermediate lobe. This Pax7+ early progenitor cell population is overlapping but ontologically downstream of the Nestin+ pituitary stem cell population, yet upstream of another newly discovered Myf6+ late progenitor cell population. Interestingly, the Pax7+ progenitor cell population is evolutionarily conserved in primates and humans, and Pax7 expression is maintained not only in murine tumors but also in human functioning and silent corticotropinomas. Taken together, our results strongly suggest that human silent corticotroph adenomas may in fact arise from a Pax7 lineage of the intermediate lobe, a region of the human pituitary bearing closer scientific interest as a reservoir of pituitary progenitor cells

A monoclonal antibody-GDNF fusion protein is not neuroprotective and is associated with proliferative pancreatic lesions in parkinsonian monkeys.

Glial cell line derived neurotrophic factor (GDNF) is a neurotrophic factor that has neuroprotective effects in animal models of Parkinson's disease (PD) and has been proposed as a PD therapy. GDNF does not cross the blood brain barrier (BBB), and requires direct intracerebral delivery to be effective. Trojan horse technology, in which GDNF is coupled to a monoclonal antibody (mAb) against the human insulin receptor (HIR), has been proposed to allow GDNF BBB transport (ArmaGen Technologies Inc.). In this study we tested the feasibility of HIRMAb-GDNF to induce neuroprotection in parkinsonian monkeys, as well as its tolerability and safety. Adult rhesus macaques were assessed throughout the study with a clinical rating scale, a computerized fine motor skills task and general health evaluations. Following baseline measurements, the animals received a unilateral intracarotid artery MPTP injection. Seven days later the animals were evaluated, matched according to disability and blindly assigned to receive twice a week i.v. treatments (vehicle, 1 or 5 mg/kg HIRmAb-GDNF) for a period of three months. HIRmAb-GDNF did not improve parkinsonian motor symptoms and induced a dose-dependent hypersensitivity reaction. Quantification of dopaminergic striatal optical density and stereological nigral cell counts did not demonstrate differences between treatment groups. Focal pancreatic acinar to ductular metaplasia (ADM) was noted in four of seven animals treated with 1 mg/kg HIRmAb-GDNF; two of four with ADM also had focal pancreatic intraepithelial neoplasia 1B (PanIN-1B) lesions. Minimal to mild, focal to multifocal, nonsuppurative myocarditis was noted in all animals in the 5 mg/kg treatment group. Our results demonstrate that HIRmAb-GDNF dosing in a monkey model of PD is not an effective neuroprotective strategy and may present serious health risks that should be considered when planning future use of the IR antibody as a carrier, or of any systemic treatment of a GDNF-containing molecule

GDNF fusion protein dosing induced response lesions in the liver and the skin, associated with anaphylactic responses.

<p>(A to C) Microphotographs of the liver (A) and the skin (B and C) of a monkey (rh2134) treated with 5 mg/kg HIRmAb-GDNF (H&E staining). Scale bar: 100 µm (A and B); 50 µm (C). (A) Liver shows mild multifocal lymphocytic hepatitis with necrosis of individual hepatocytes. (B) Dermis shows subdermal hemorrhage (a) saponification of tissue adipocytes, and mild lymphocytic dermatitis. (b). (C) Dermis shows mild lymphocytic perivascular and periadnexal dermatitis.</p

VMAT2 expression is not affected by HIRmAb-GDNF treatment.

<p>(A to F) Coronal images of the striatum at the level of the anterior commissure (A, C, and E) and of the substantia nigra at the level of the red nucleus (B, D, and F) stained with the dopaminergic marker VMAT2 of monkeys treated with vehicle (A and B), 1 mg/kg (C and D), or 5 mg/kg (E and F) HIRmAb-GDNF. Scale bar: 2.5 mm (A, C, and E); 1 mm (B, D, and F); 110 µm (insets b, d, and f). (G) VMAT2 optical density (OD) in the caudate and putamen nucleus. (H) Stereological cell counts of VMAT2-positive neuron cells in the substantia nigra.</p

GDNF fusion protein dosing was associated with myocarditis.

<p>(A to D) Microphotographs of the heart of monkeys treated with vehicle (A and C) or 5 mg/kg HIRmAb-GDNF (B and D) (H&E staining). The HIRmAb-GDNF-treated animal [rh2134 (B)] shows a moderate multifocal degeneration with interstitial fibrosis (*) and individual myocardiocyte hypertrophy (arrow). Higher-magnification images in (C) and (D) correspond to boxed areas in (A) and (B). Note the presence of lymphocytes, plasma cells, and rare eosinophils in (D). Scale bar: 100 µm (A and B); 25 µm (C and D).</p

GDNF was not intracerebrally detected by immunohistochemistry or ELISA methods.

<p>(A to C) Coronal images of GDNF immunostained striatal sections of vehicle (A), 1 mg/kg (B), and 5 mg/kg (C) HIRmAb-GDNF treatments. *Inset in (A) corresponds to a positive control tissue stained in parallel from a monkey that received intracerebral injections of human neuroprogenitor cells expressing GDNF. Scale bar: 1 mm. (D and E) ELISA determination of GDNF levels in the brain (D) and in the pancreas (E).</p

HIRmAb-GDNF does not induce improve parkinsonian signs and is associated with type I hypersensitivity reaction.

<p>(A) Clinical rating score. (B) Fine motor skills task. (C) Hypersensitivity response over time, by treatment group. (D) Optical density (OD) of HIRmAb-GDNF antibody levels in serum.</p

Tyrosine Hydroxylase (TH) expression is not affected by HIRmAb-GDNF.

<p>(A to F) Coronal images of the TH immunostained striatum at the level of the anterior commissure (A, C, and E) and of the substantia nigra at the level of the red nucleus (B, D, and F) of monkeys treated with vehicle (A and B), 1 mg/kg (C and D), or 5 mg/kg (E and F) HIRmAb-GDNF. Scale bar: 2.5 mm (A, C, and E); 1 mm (B, D, and F); 110 µm (insets b, d, and f). (G) Average TH optical density (OD) in the caudate and putamen nucleus. (H) Stereological cell counts of TH-positive neuron cells in the substantia nigra (SN).</p

Number of animals used per treatment group in the efficacy and safety experiments.

<p>Number of animals used per treatment group in the efficacy and safety experiments.</p