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Dopamine and Somatostatin Analogues Resistance of Pituitary Tumors: Focus on Cytoskeleton Involvement.

ABSTRACT: Pituitary tumors, that origin from excessive proliferation of a specific subtype of pituitary cell, are mostly benign tumors, but may cause significant morbidity in affected patients, including visual and neurologic manifestations from mass-effect, or endocrine syndromes caused by hormone hypersecretion. Dopamine (DA) receptor DRD2 and somatostatin (SS) receptors (SSTRs) represent the main targets of pharmacological treatment of pituitary tumors since they mediate inhibitory effects on both hormone secretion and cell proliferation, and their expression is retained by most of these tumors. Although long-acting DA and SS analogs are currently used in the treatment of prolactin (PRL)- and growth hormone (GH)-secreting pituitary tumors, respectively, clinical practice indicates a great variability in the frequency and entity of favorable responses. The molecular basis of the pharmacological resistance are still poorly understood, and several potential molecular mechanisms have been proposed, including defective expression or genetic alterations of DRD2 and SSTRs, or an impaired signal transduction. Recently, a role for cytoskeleton protein filamin A (FLNA) in DRD2 and SSTRs receptors expression and signaling in PRL- and GH-secreting tumors, respectively, has been demonstrated, first revealing a link between FLNA expression and responsiveness of pituitary tumors to pharmacological therapy. This review provides an overview of the known molecular events involved in SS and DA resistance, focusing on the role played by FLNA.

SUBMITTER: Peverelli E

PROVIDER: S-EPMC4686608 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Dopamine and Somatostatin Analogues Resistance of Pituitary Tumors: Focus on Cytoskeleton Involvement.

Peverelli Erika E Treppiedi Donatella D Giardino Elena E Vitali Eleonora E Lania Andrea G AG Mantovani Giovanna G

Frontiers in endocrinology 20151222

Pituitary tumors, that origin from excessive proliferation of a specific subtype of pituitary cell, are mostly benign tumors, but may cause significant morbidity in affected patients, including visual and neurologic manifestations from mass-effect, or endocrine syndromes caused by hormone hypersecretion. Dopamine (DA) receptor DRD2 and somatostatin (SS) receptors (SSTRs) represent the main targets of pharmacological treatment of pituitary tumors since they mediate inhibitory effects on both horm ...[more]

PMID: 26733942

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Project description:BackgroundGrowth hormone-secreting pituitary adenomas (somatotroph adenoma) predominantly express somatostatin receptors (SSTRs) subtypes 2 and 5. Higher SSTR2 expression on somatotroph adenomas results in a better response to somatostatin analogues (SSAs), which preferentially bind, but also downregulate, SSTR2. The effect of the combined treatment with SSAs and the GH receptor antagonist pegvisomant (PEGV) on SSTR expression in somatotroph adenomas is currently unknown.Aim of the studyTo assess SSTR2 and SSTR5 expression in three groups of somatotroph adenomas: drug-naive, treated with long-acting (LA) SSA monotherapy, or LA-SSA/PEGV combination therapy before surgery. Additionally, we evaluated the required PEGV dose to achieve insulin-like growth factor I (IGF-I) normalization in relation to the SSTR expression.Materials and methodsAt our Pituitary Center Rotterdam, we selected acromegalic patients who underwent transsphenoidal neurosurgery. All patients were eventually treated with LA-SSA/PEGV combination therapy during their medical history. SSTR2 and SSTR5 expression in somatotroph adenoma tissues was determined using immunohistochemistry.ResultsOut of 39 somatotroph adenoma tissue samples, 23 were drug-naive, 9 received pretreatment with LA-SSA and 7 LA-SSA/PEGV combined treatment. SSTR2 expression was significantly higher in treatment-naive compared to combined treatment somatotroph adenomas (p = 0.048), while SSTR5 expression did not differ. Noteworthy, SSTR2 expression in naive somatotroph adenoma tissues was inversely correlated with the required PEGV dose to achieve IGF-I normalization during postsurgical medical treatment (? = -0.538, p = 0.024).ConclusionIn our specific cohort, the SSTR2 expression was lower in patients pretreated with LA-SSA/PEGV compared to the drug-naive acromegalic patients. Additionally, the SSTR2 expression in treatment-naive somatotroph adenoma tissues was inversely correlated with the required PEGV dose to achieve IGF-I normalization.

Project description:In recent decades, the incidence of neuroendocrine tumors (NETs) has steadily increased. Due to the slow-growing nature of these tumors and the lack of early symptoms, most cases are diagnosed at advanced stages, when curative treatment options are no longer available. Prognosis and survival of patients with NETs are determined by the location of the primary lesion, biochemical functional status, differentiation, initial staging, and response to treatment. Somatostatin analogue (SSA) therapy has been a mainstay of antisecretory therapy in functioning neuroendocrine tumors, which cause various clinical symptoms depending on hormonal hypersecretion. Beyond symptomatic management, recent research demonstrates that SSAs exert antiproliferative effects and inhibit tumor growth via the somatostatin receptor 2 (SSTR2). Both the PROMID (placebo-controlled, prospective, randomized study in patients with metastatic neuroendocrine midgut tumors) and the CLARINET (controlled study of lanreotide antiproliferative response in neuroendocrine tumors) trial showed a statistically significant prolongation of time to progression/progression-free survival (TTP/PFS) upon SSA treatment, compared to placebo. Moreover, the combination of SSA with peptide receptor radionuclide therapy (PRRT) in small intestinal NETs has proven efficacy in the phase 3 neuroendocrine tumours therapy (NETTER 1) trial. PRRT is currently being tested for enteropancreatic NETs versus everolimus in the COMPETE trial, and the potential of SSTR-antagonists in PRRT is now being evaluated in early phase I/II clinical trials. This review provides a synopsis on the pharmacological development of SSAs and their use as antisecretory drugs. Moreover, this review highlights the clinical evidence of SSAs in monotherapy, and in combination with other treatment modalities, as applied to the antiproliferative management of neuroendocrine tumors with special attention to recent high-quality phase III trials.

Project description:PurposeEvaluate patients' and nurses' experiences, including injection problem frequency, with the somatostatin analogues (SSAs) lanreotide autogel® (Somatuline® autogel®, deep subcutaneous) and octreotide long-acting release (LAR) (Sandostatin® LAR®, intramuscular) when treating gastroenteropancreatic neuroendocrine tumors (GEP-NETs).MethodsAn observational, cross-sectional study across 2 NET centers in Sweden. Questionnaires based on participants' most recent injection experience were sent to patients with GEP-NETs treated with octreotide or lanreotide, and to nurses administering these treatments. Nurses were identified via patients completing their questionnaires. Resource use was sourced from Swedish prescription registry records. The planned sample size was 200, based on an estimated proportion of 0.50 and ±7% precision.Results119/156 patients (n=53, lanreotide; n=66, octreotide) and 43/53 nurses (n=22, lanreotide; n=21, octreotide) completed questionnaires. Despite smaller recruitment than planned, the endpoint precision was ±9% with 119 participants, and still considered reasonable. More octreotide-treated patients reported problems (18% vs none; P=0.001) and experienced moderate-to-high anxiety pre-injection (11% vs 2%). Patients had similar physical HRQoL scores overall (Short Form-12 mean composite scores: physical: 39.4 vs 37.6; mental: 50.7 vs 49.6). The mean number of lanreotide and octreotide doses dispensed per year were 11.1 and 12.6, respectively (P<0.05). In the lanreotide group, 28% self-injected, while 29% were not aware they could self-inject. In the octreotide group, 3% self-injected and 73% were unaware of the availability of an SSA for self-injection. Most patients (61%) felt well-informed about their disease and treatment. Nurses were generally experienced and felt confident and well-informed about giving SSA injections; however, only 12% felt well-informed about the disease and treatment.ConclusionThose treated with lanreotide reported fewer injection problems and experienced less pre-injection anxiety than those treated with octreotide. SSA choice did not appear to affect patients' HRQoL. Some patients treated with octreotide were unaware of an SSA with the flexibility of self-injection.

Dataset Information

Dopamine and Somatostatin Analogues Resistance of Pituitary Tumors: Focus on Cytoskeleton Involvement.

Publications

Dopamine and Somatostatin Analogues Resistance of Pituitary Tumors: Focus on Cytoskeleton Involvement.

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