Martin van Hagen

Somatostatin Receptor Subtypes in Human Thymoma and Inhibition of Cell Proliferation by Octreotide in Vitro

Somatostatin (SS) and SS receptor (SSR) subtypes, code-named sst1-5, are heterogeneously expressed in the normal human thymus. This suggests their involvement in controlling the immune and/or neuroendocrine functions in this organ. Moreover, recently a high in vivo uptake of [111In-DTPA-D-Phe1]octreotide has been reported in patients bearing thymoma. The present study characterizes in vivo and in vitro, functional SS-binding sites in a human thymoma. A high uptake of [111In-DTPA-D-Phe1]octreotide was observed in the chest of a patient with myasthenia gravis due to a cortical thymoma. Specific binding of [125I-Tyr11] SS-14 was found on a membrane preparation of the surgically removed thymoma. Scatchard analysis showed high affinity binding sites (Kd, 47.5 +/- 2.5 pmol/L) with low maximum binding capacity (23.5 +/- 2.5 fmol/mg membrane protein). RT-PCR analysis showed the presence of sst1, sst2A, and a predominant sst3 messenger RNA (mRNA) expression in the tumor tissue. Primary cultured tumor cells expressed sst3 mRNA only. In contrast to the normal thymus, SS mRNA was not expressed. By immunohistochemistry, the tumor cells highly expressed sst3 receptors, weakly expressed sst1 receptors, and showed no immunostaining for sst2A receptors. sst2A immunoreactivity was found in the stromal compartment of the tumor, particularly on the endothelium of small intratumoral blood vessels. In primary cultured tumor cells, both SS and octreotide (10 nmol/L) significantly inhibited [3H]thymidine incorporation by 40.6% and 43.2%, respectively. The following conclusions were reached. 1) As this tumor displayed a high immunoreactivity for sst3 and the cultured tumor cells expressed the sst3 mRNA only, this SSR may be the subtype involved in the inhibition of epithelial tumor cell proliferation by octreotide in vitro. 2) A loss of endogenous SS production in this thymoma might be implicated in the uncontrolled cell growth. 3) In this case, the sst3 may play a role in determining the uptake of [111In-DTPA-D-Phe1]octreotide by in vivo SS receptor scintigraphy.

Radiolabeled RGD-DTPA-Tyr3-Octreotate for Receptor-Targeted Radionuclide Therapy

The aim of this study was to develop and investigate a radiopeptide for the treatment of cancers which overexpress cell surface somatostatin receptors. The new radiopharmaceutical is composed of a somatostatin receptor-targeting peptide, a chelator (DTPA) to enable radiolabeling, and an apoptosis-inducing RGD (arginine-glycine-aspartate) peptide moiety. The receptor-targeting peptide portion of the molecule, Tyr3-octreotate, is specific for the somatostatin subtype-2 cell surface receptor (sst2), which is overexpressed on many tumor cells. Because of the rapid endocytosis of the somatostatin receptor, the entire molecule can thus be internalized, allowing the RGD portion to activate intracellular caspases, which in turn promotes apoptosis. In this paper, we present the synthesis and the in vitro and in vivo tumor binding and internalization characteristics of this hybrid peptide. In vitro internalization into sst2-positive tumor cells of the radiolabeled hybrid peptide appeared to be a rapid process and could be blocked by an excess of unlabeled octreotide, indicating an sst2-specific process. Tumor uptake in vivo in rats of radiolabeled RGD-DTPA-Tyr3-octreotate was in agreein vitro data and similar to that of radiolabeled DOTA-Tyr3-octreotate. The combined molecule is expected to significantly enhance the therapeutic efficacy of the somatostatin-based agent.

Somatostatin Analogues for Receptor Targeted Photodynamic Therapy

Photodynamic therapy (PDT) is an established treatment modality, used mainly for anticancer therapy that relies on the interaction of photosensitizer, light and oxygen. For the treatment of pathologies in certain anatomical sites, improved targeting of the photosensitizer is necessary to prevent damage to healthy tissue. We report on a novel dual approach of targeted PDT (vascular and cellular targeting) utilizing the expression of neuropeptide somatostatin receptor (sst2) on tumor and neovascular-endothelial cells. We synthesized two conjugates containing the somatostatin analogue [Tyr3]-octreotate and Chlorin e6 (Ce6): Ce6-K3-[Tyr3]-octreotate (1) and Ce6-[Tyr3]-octreotate-K3-[Tyr3]-octreotate (2). Investigation of the uptake and photodynamic activity of conjugates in-vitro in human erythroleukemic K562 cells showed that conjugation of [Tyr3]-octreotate with Ce6 in conjugate 1 enhances uptake (by a factor 2) in cells over-expressing sst2 compared to wild-type cells. Co-treatment with excess free Octreotide abrogated the phototoxicity of conjugate 1 indicative of a specific sst2-mediated effect. In contrast conjugate 2 showed no receptor-mediated effect due to its high hydrophobicity. When compared with un-conjugated Ce6, the PDT activity of conjugate 1 was lower. However, it showed higher photostability which may compensate for its lower phototoxicity. Intra-vital fluorescence pharmacokinetic studies of conjugate 1 in rat skin-fold observation chambers transplanted with sst2 + AR42J acinar pancreas tumors showed significantly different uptake profiles compared to free Ce6. Co-treatment with free Octreotide significantly reduced conjugate uptake in tumor tissue (by a factor 4) as well as in the chamber neo-vasculature. These results show that conjugate 1 might have potential as an in-vivo sst2 targeting photosensitizer conjugate.

In vivo and in vitro detection of dopamine d2 receptors in uveal melanomas.

Scintigraphy with radiolabeled benzamides was used in melanoma patients. Studies with a newer benzamide called 123I-epidepride, a high-affinity D2 receptor (D2R) antagonist, showed high sensitivity in D2R-positive pituitary adenomas. We evaluated the presence of D2R in patients with uveal melanomas in vivo with 123I-epidepride, and in vitro in melanomas, using immunohistochemistry (IHC) and 125I-epidepride autoradiography. We studied the in vivo tumor-to-background (TB) ratios in six patients with posterior uveal melanoma (one previously enucleated). IHC was performed in 3 of 6 tumors after enucleation and in another 20 uveal melanomas, 7 metastatic lymph nodes from skin melanoma, and 2 normal specimens. 125I-epidepride autoradiography was performed in 10 uveal melanomas (3 of which were studied in vivo), 7 metastases, and 2 normal samples. Radioligand uptake was present in the affected eye of 5 patients with uveal melanoma (TB = 3.1-6.1) and absent in the operated one (TB = 1). Eight uveal tumors were positive at IHC (35%), 14 weakly positive (61%), and 1 negative (4%). Two metastases were positive (29%), 2 weakly positive (29%), and 3 negative (42%). Two uveal tumors were positive at autoradiography (20%), 7 had nonspecific binding (70%), and 1 was negative (10%). One metastasis was positive (14%), while 6 were negative (86%). 123I-epidepride scintigraphy in uveal melanomas seems promising for sensitivity and image quality. D2R was demonstrated in a significant proportion of the melanomas, although 123I-epidepride uptake might also be nonspecific and unrelated to D2R binding. Although further studies on larger series are needed, 123I-epidepride could represent a future tool to study the expression of D2R in other classes of neuroendocrine tumors.

Strategies for B-cell receptor repertoire analysis in primary immunodeficiencies: from severe combined immunodeficiency to common variable immunodeficiency

The antigen receptor repertoires of B- and T-cells form the basis of the adaptive immune response. The repertoires should be sufficiently diverse to recognize all possible pathogens. However, careful selection is needed to prevent responses to self or harmless antigens. Limited antigen receptor repertoire diversity leads to immunodeficiency, whereas unselected or misdirected repertoires can result in autoimmunity. The antigen receptor repertoire harbors information about abnormalities in many immunological disorders. Recent developments in next generation sequencing allow the analysis of the antigen receptor repertoire in much greater detail than ever before. Analyzing the antigen receptor repertoire in patients with mutations in genes responsible for the generation of the antigen receptor repertoire will give new insights into repertoire formation and selection. In this perspective, we describe strategies and considerations for analysis of the naive and antigen-selected B-cell repertoires in primary immunodeficiency patients with a focus on severe combined immunodeficiency and common variable immunodeficiency.

IgG4-related disease as an emerging cause of scleritis

Doppler imaging (Heidelberg retinal flowmeter (HRF)). Intraocular pressure (IOP) was assessed using Goldmann applanation tonometry, and blood pressure (systolic and diastolic: SBP, DBP) was assessed using an automated ambulatory sphygmomanometer after a fiveminute rest immediately prior to IOP assessment. Hypertensive and nonhypertensive OAG groups were based upon self-reported hypertensive status, and all first comers were welcomed to total a recruitment goal of 42. We found significant differences in the relationships (Person,multivariate ttests) between BP, IOP, OPP, and RBF between hypertensive and non-hypertensive patients with OAG (Table 1). In hypertensive patients, there was a significant negative association between IOP and RBF, while non-hypertensive patients demonstrated a weak positive relationship. In hypertensive patients, SBP and IOP had a significant positive correlation, while non-hypertensive patients demonstrated a weak negative association. Hypertensive patients demonstrated a weak association between SBP and OPP, while non-hypertensive patients demonstrated a significant positive association. The differences in relationships of all comparisons between groups were found to be at or within statistical significance. Our pilot data suggest that hypertension may have an effect on the relationships between BP, IOP, OPP, and RBF in patients with OAG. Previous studies have shown that patients with hypertension have alterations in retrobulbar blood flow velocities (Widjaya et al. 2015), and systemic alterations in blood flow have been shown to correlate with glaucoma progression (Tielsch et al. 1995). While the exact mechanism by which hypertension affects glaucoma is unknown at this time, we hypothesize that hypertension may induce changes in vascular biomechanics, thus disrupting blood flow to retinal ganglion cells and ONH structures. In our study, we found that in hypertensive patients, increased SBP was associated with increased IOP,whichwasassociatedwith decreased RBF. These associations were not present in non-hypertensive patients. Our data suggests that hypertensionmay impact the normal relationships of IOP and ocular haemodynamics, possibly providing a vascular autoregulatory mechanism of contribution to OAG pathology. An important limitation of our study was that ocular and systemic hypertensive medications in our patient populations could potentially have an affect on retinal blood flow, although no statistically significant differences between groups was present in terms of ocular hypertensive therapies. Longitudinal studies specifically designed to evaluate the impact of hypertension in glaucoma, including alterations in ocular blood flow, may be important considerations of future research.

Prevalence of atopic diseases in patients with sarcoidosis.

It remains unclear whether atopy is associated with the occurrence of sarcoidosis or affects its severity. The purpose of this study was to compare the lifetime prevalence of atopic eczema, asthma, and hay fever in sarcoidosis patients with controls and to assess whether atopy influences the severity of sarcoidosis. The prevalence of atopic disorders assessed with a validated postal questionnaire in sarcoidosis patients with pulmonary, uveitis, and cutaneous sarcoidosis was compared with that of their domestic partners in a case-control study. The serological parameters, the pulmonary function tests, and the high-resolution computed tomography (HRCT) scans of atopic and nonatopic sarcoidosis patients were compared in a nested cohort. Multivariate logistic regression models were used to calculate the odds ratios (ORs) and the 95% confidence intervals (CIs). Two hundred twenty-five sarcoidosis patients and 177 controls were included. The prevalences of atopic eczema, asthma, and hay fever were comparable between patients and controls (12.4% versus 12.4%, 5.3% versus 5.6%, and 16.9% versus 15.8%, respectively). After adjusting for gender and ethnicity, those with sarcoidosis and a history of atopic eczema were significantly less likely to have uveitis (OR, 0.30; 95% CI, 0.13-0.71). Within the sarcoidosis cohort, the distributions of serological markers, the lung function tests, and the HRCT scans were similar between atopic and nonatopic patients. Atopy is not associated with the occurrence of sarcoidosis, but atopic eczema may decrease the likelihood of eye involvement.

Hyper IgE in the Allergy Clinic- when is it Primary Immunodeficiency?

The 2017 International Union of Immunological Societies (IUIS) classification recognizes 3 hyper‐IgE syndromes (HIES), including the prototypic Jobs syndrome (autosomal dominant STAT3‐loss of function) and autosomal recessive PGM3 and SPINK5 syndromes. Early diagnosis of PID can direct life‐saving or transformational interventions; however, it remains challenging owing to the rarity of these conditions. This can result in diagnostic delay and worsen prognosis. Within increasing access to “clinical‐exome” testing, clinicians need to be aware of the implication and rationale for genetic testing, including the benefits and limitations of current therapies. Extreme elevation of serum IgE has been associated with a growing number of PID syndromes including the novel CARD11 and ZNF341 deficiencies. Variable elevations in IgE are associated with defects in innate, humoral, cellular and combined immunodeficiency syndromes. Barrier compromise can closely phenocopy these conditions. The aim of this article was to update readers on recent developments at this important interface between allergy and immunodeficiency, highlighting key clinical scenarios which should draw attention to possible immunodeficiency associated with extreme elevation of IgE, and outline initial laboratory assessment and management.