RESUMEN
INTRODUCTION: It has been reported in some series that gsp+ somatotropinomas are more sensitive to somatostatin analogues (SA) and dopamine's actions which may be related to their somatostatin receptor (SSTR) and dopamine receptor (DR) profile. No previous studies have been undertaken to evaluate the SSTR and DR profile related with the gsp status in somatotropinomas. OBJECTIVES: To determine if (1) gsp status is correlated with response to octreotide LAR (LAR) and tumor expression patterns of SSTR1-5 and DR1-5 and (2) cAMP level can directly modulate SSTR and DR mRNA levels. METHODS: Response to SA was evaluated by GH and IGF-I percent reduction after 3 and 6 months of treatment with LAR. Conventional PCR and sequencing were used to identify gsp+ tumors. Quantitative real-time PCR was used to determine SSTR and DR tumor expression. Primary pituitary cell cultures of primates were used to study whether SSTR and DR expression is regulated by forskolin. RESULTS: The response to LAR did not significantly differ between patients with gsp+ and gsp- tumors; however, gsp+ tumors expressed higher levels of SSTR1, SSTR2, DR2 and a lower level of SSTR3. Forskolin increased SSTR1, SSTR2, DR1 and DR2 expression in cell cultures. CONCLUSION: Elevated SSTR1, SSTR2, and DR2 tumor expression may help improve responsiveness to SA and DA therapy; however, this study may not have been appropriately powered to observe significant effects in the clinical response. Elevated cAMP levels could be directly responsible for the upregulation in SSTR1, SSTR2 and DR2 mRNA levels observed in gsp+ patients.
Asunto(s)
Adenoma/tratamiento farmacológico , Adenoma/metabolismo , Subunidades alfa de la Proteína de Unión al GTP Gs/metabolismo , Octreótido/farmacología , Neoplasias Hipofisarias/tratamiento farmacológico , Neoplasias Hipofisarias/metabolismo , Receptores Dopaminérgicos/biosíntesis , Receptores de Somatostatina/biosíntesis , Adenoma/sangre , Adolescente , Adulto , Animales , Biomarcadores Farmacológicos/sangre , Técnicas de Cultivo de Célula , Cromograninas , Colforsina/farmacología , Preparaciones de Acción Retardada , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Masculino , Persona de Mediana Edad , Octreótido/administración & dosificación , Papio anubis , Hipófisis/efectos de los fármacos , Hipófisis/metabolismo , Neoplasias Hipofisarias/sangreRESUMEN
CONTEXT: Dopamine receptor (DR) and somatostatin receptor subtype expression in pituitary adenomas may predict the response to postsurgical therapies. OBJECTIVES: Our objectives were to assess and compare the mRNA levels of DR1-5 and somatostatin receptors 1-5 in normal pituitaries (NPs), nonfunctioning pituitary adenomas (NFPAs), and somatotropinomas. In addition, we determined whether the level of DR expression correlates with the in vivo response to octreotide-LAR in acromegalic patients. DESIGN AND PATIENTS: Eight NPs, 30 NFPAs, and 39 somatotropinomas were analyzed for receptor mRNA levels by real-time RT-PCR. The DR2 short variant was estimated as the DR2 long/DR2 total (DR2T). The relationship between DR expression and the postsurgical response to octreotide-LAR was assessed in 19 of the acromegalic patients. RESULTS: DR3 was not detected. The relationship between expression levels of DR subtypes in NPs and somatotropinomas was DR2T>>>DR4>>DR5>DR1, whereas in NFPAs, DR2T>>>DR4>>DR1>DR5. The DR2 short variant was the predominant DR2 variant in the majority of samples. In acromegalics treated with octreotide-LAR, DR1 was negatively correlated with percent GH reduction (3 months: r = -0.67, P = 0.002; and 6 months: r = -0.58, P = 0.009), and DR5 was positively correlated with percent IGF-I reduction (3 months: r = 0.55, P = 0.01; and 6 months: r = 0.47, P = 0.04). CONCLUSIONS: DR2 is the predominant DR subtype in NPs, NFPAs, and somatotropinomas. The fact that DR1, DR4, and DR5 are also expressed in many adenomas tested suggests that these receptors might also play a role in the therapeutic impact of postsurgical medical therapies in patients with NFPA and acromegaly. This was supported by the finding that the in vivo response to octreotide-LAR was negatively associated with DR1 and positively associated with DR5.
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Acromegalia/tratamiento farmacológico , Adenoma/genética , Adenoma Hipofisario Secretor de Hormona del Crecimiento/genética , Octreótido/uso terapéutico , Hipófisis/metabolismo , Neoplasias Hipofisarias/genética , Receptores Dopaminérgicos/genética , Receptores de Somatostatina/genética , Acromegalia/etiología , Acromegalia/genética , Acromegalia/metabolismo , Adenoma/metabolismo , Preparaciones de Acción Retardada/administración & dosificación , Perfilación de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Adenoma Hipofisario Secretor de Hormona del Crecimiento/complicaciones , Adenoma Hipofisario Secretor de Hormona del Crecimiento/metabolismo , Humanos , Octreótido/administración & dosificación , Neoplasias Hipofisarias/complicaciones , Neoplasias Hipofisarias/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , ARN Mensajero/análisis , Receptores Dopaminérgicos/metabolismo , Receptores de Somatostatina/metabolismo , Receptores de Somatostatina/fisiologíaRESUMEN
OBJECTIVE: To determine whether the somatostatin receptor subtype (SSTR) expression profile correlates with hormonal and tumor volume responses to postsurgical octreotide long acting repeatable (OCT LAR) treatment. DESIGN AND METHODS: Quantitative real-time RT-PCR was used to evaluate the absolute mRNA copy numbers for all five SSTR subtypes in 22 somatotropinomas. Response to OCT LAR was studied by hormone levels (GH and IGF-I) and tumor volume (sella turcica magnetic resonance imaging). RESULTS: SSTR5 was present at the highest level followed by SSTR2, SSTR3, SSTR1, and SSTR4 (2327 (1046-5555), 2098 (194-23 954), 97 (0-460), 14 (0-29 480), and 0 (0-652) copies respectively). Positive correlations were found between SSTR2 levels and the percentage decrease of GH and IGF-I after 3 (r=0.49, P<0.027 and r=0.49, P<0.029 respectively) and 6 (r=0.59, P<0.006 and r=0.58, P<0.008 respectively) months of OCT LAR. A negative correlation was found between SSTR5 mRNA levels and the percentage decrease of GH after 3 months of OCT LAR (r=-0.52, P=0.016, n=21). A higher SSTR2/SSTR5 ratio was observed among patients who obtained hormonal control with OCT LAR, when compared with those uncontrolled (2.4 (0.7-10) vs 0.3 (0.1-7.7), P=0.001). A ROC curve analysis showed a SSTR2/SSTR5 ratio of 1.3 as the best predictor of disease control, with a sensitivity of 88% and a specificity of 92% - area under curve, 0.9. A positive correlation was also found between SSTR2 mRNA levels and the percentage decrease in tumor volume after 6 months of OCT LAR (r=0.79, P=0.002, n=12). CONCLUSIONS: Somatostatin receptor subtype 2 mRNA expression levels in somatotropinomas correlate positively with in vivo hormonal and tumor volume responses to OCT LAR.
Asunto(s)
Adenoma/tratamiento farmacológico , Adenoma/patología , Antineoplásicos Hormonales/uso terapéutico , Octreótido/uso terapéutico , Neoplasias Hipofisarias/tratamiento farmacológico , Neoplasias Hipofisarias/patología , Receptores de Somatostatina/genética , Acromegalia/tratamiento farmacológico , Acromegalia/fisiopatología , Adenoma/metabolismo , Adulto , Femenino , Hormona del Crecimiento/metabolismo , Humanos , Imagen por Resonancia Magnética , Masculino , Proteínas de la Membrana/genética , Persona de Mediana Edad , Neoplasias Hipofisarias/metabolismo , Valor Predictivo de las Pruebas , ARN Mensajero/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Resultado del TratamientoRESUMEN
OBJECTIVE: It is believed that the variable effectiveness of somatostatin analogs in post-surgical management of somatotropinomas and non-functioning pituitary adenomas (NFPA) may be due in part to variable expression of somatostatin receptor isoforms (SSTR1-5), within and between pituitary tumor types. DESIGN AND METHODS: Quantitative real-time RT-PCR was used to compare absolute mRNA copy numbers for all five SSTR isoforms in 23 somatotropinomas and 19 NFPA. RESULTS: Somatostatin receptor subtype 5 mRNA was present at the highest level in somatotropinomas, followed by SSTR2>SSTR3>>SSTR1>>>SSTR4. In contrast, SSTR3 mRNA was present at the highest level in NFPA, followed by SSTR2, while SSTR1, SSTR4, and SSTR5 transcripts were only detectable in select tumors. Among somatotropinomas, a positive correlation was found between SSTR2 mRNA levels and the percent decrease of GH (%GH) after 3 and 6 months of therapy with octreotide long acting repeatable (LAR) (r=0.51 and r=0.66; P=0.05 and P=0.008). Also the percent decrease of IGF-I (%IGF-I) after 3 months of octreotide LAR was negatively correlated with SSTR5 and %IGF-I after 6 months of octreotide LAR was positively correlated with SSTR2. CONCLUSIONS: The present report is a large series examining SSTR mRNA levels in somatotropinomas and NFPA. These initial findings suggest that detailed knowledge of the SSTR mRNA expression profile in somatotropinomas can help to predict the hormonal response to therapy with LAR. Also, it appears that SSTR3 in NFPA may be a potential target for SSTR3 preferential or universal ligands such as pasireotide.