The Pharmacogenomics Journal (2008) 8, 357–363 & 2008 Nature Publishing Group All rights reserved 1470-269X/08 $30.00 www.nature.com/tpj ORIGINAL ARTICLE Dopamine D2 receptor gene polymorphisms and response to cabergoline therapy in patients with prolactin-secreting pituitary adenomas M Filopanti1, AM Barbieri1, Dopamine-agonist cabergoline (CB) reduces prolactin (PRL) secretion and 1 2 3 tumor size in 80% of patients with prolactin-secreting adenomas (PRL-omas) AR Angioni ,AColao , V Gasco , by binding type 2 dopamine receptor (DRD2). The mechanisms responsible 3 4 4 S Grottoli , A Peri , S Baglioni , for resistance to CB remain largely unknown. To assess the association of MF Fustini5, F Pigliaru6, DRD2 with sensitivity to CB, TaqI-A1/A2, TaqI-B1/B2, HphI-G/T and NcoI-C/T PD Monte7, G Borretta8, genotypes were determined in a cross-sectional retrospective study, B Ambrosi9, ML Jaffrain-Rea10, including 203 patients with PRL-oma. DRD2 alleles frequencies did not differ 11 12 between patients and 212 healthy subjects. Conversely, NcoI-T allele M Gasperi , S Brogioni , frequency was higher in resistant rather than responsive patients, considering S Cannavo` 13, G Mantovani1, both PRL normalization (56.6 vs 45.3%, P ¼ 0.038) and tumor shrinkage P Beck-Peccoz1, A Lania1 and (70.4 vs 41.4%, P ¼ 0.006). Finally, [TaqIA1À/TaqIB1À/HphITÀ/NcoITÀ] A Spada1 haplotype was found in 34.5% of patients normalizing PRL with p3 mg/ week of CB vs 11.3% of resistants (P ¼ 0.021). In conclusion, resistance to CB 1Department of Medical Sciences, University of Milan, was associated with DRD2 NcoI-T þ allele, consistent with evidence Endocrine and Diabetes Unit Fondazione Ospedale suggesting that this variant may lead to reduction and instability of DRD2 Maggiore IRCCS, Milan, Italy; 2Department of mRNA or protein. Molecular and Clinical Endocrinology and Oncology, The Pharmacogenomics Journal (2008) 8, 357–363; doi:10.1038/tpj.2008.1; Federico II University of Naples, Naples, Italy; 3Division of Endocrinology and Metabolism, published online 11 March 2008 Department of Internal Medicine, University of Turin, Turin, Italy; 4Endocrine Unit, Department of Clinical Keywords: prolactinomas; cabergoline; polymorphisms; DRD2 Physiopathology, Center for Research, Transfer and High Education DENOThe, University of Florence, Florence, Italy; 5Endocrinology Unit, Department of Medicine, Ospedale Bellaria, Bologna, Italy; 6Endocrinology, Department of Medical Sciences ‘M. Aresu’, University of Cagliari, Cagliari, Italy; 7Unit of Endocrinology, Galliera Hospital, Genoa, Italy; Introduction 8Endocrinology Unit, Santa Croce Hospital, Cuneo, Italy; 9Endocrinology Unit, Department of Medical Prolactin-secreting pituitary adenomas (PRL-omas) are rare and well-differen- and Surgical Sciences, University of Milan, IRCCS 10 tiated tumors constituted by lactotroph cells with an estimated incidence of 6–10 Policlinico San Donato, Milan, Italy; Department of 1 Experimental Medicine, University of L’Aquila and cases per million per year. The first-choice treatment of patients with PRL-omas Neuromed IRCCS, Pozzilli, Italy; 11Chair of is the dopamine agonist cabergoline (CB), a lysergic acid amide derivative, which Endocrinology, University of Molise, Campobasso, is a potent type 2 dopamine receptor (DRD2) agonist and causes less side effects 12 Italy; Department of Endocrinology, University of and a better pharmacological profile than other dopamine agonists. Resistance to Pisa, Pisa, Italy and 13Department of Medicine and Pharmacology, University of Messina, Messina, Italy CB, defined as failure to normalize PRL levels and/or to reduce tumor size, is reported in 10–15% of patients with PRL-omas.2 Reduction of dopaminergic Correspondence: binding sites, decreased expression of DRD2 mRNA and a relative decrease in Gai Professor A Spada, University of Milan, expression have been described in resistant PRL-omas, as well as reduced levels of Department of Medical Sciences, Endocrine the short receptor isoform.3–5 Finally, no mutations in the DRD2 gene have been and Diabetes Unit, Pad. Granelli, Via Francesco 6 Sforza 35, Milan 20122, Italy; so far described in PRL-omas resistant to medical treatment. E-mail: [email protected] Multiple alternative splicing, including that occurring in exon 6 and generating the two major long and short isoforms, have been described for the Received 18 July 2007; revised 12 December 7,8 2007; accepted 20 December 2007; published DRD2. Moreover, there are several single nucleotide polymorphisms of the online 11 March 2008 DRD2 gene that have mostly synonymous changes. Due to the critical role of DRD2 polymorphisms and response to cabergoline in PRL-omas M Filopanti et al 358 dopaminergic activity in the central nervous system, several heterozygotes, forming TaqIA1þ , TaqIB1þ , HphITþ and studies examined the association between common poly- NcoITþ groups, respectively. morphisms of the DRD2 gene and behavioral traits, No association between DRD2 polymorphisms and sex, psychiatric and neurological diseases, such as schizophrenia, age at diagnosis and PRL levels was observed in patients with alcoholism, smoking, opioids and polysubstance abuse, and PRL-oma (Table 2). PRL Z-scores did not significantly differ susceptibility to migraine.9–14 Accordingly, in vivo evidence between genotypes (TaqIA1À 275.4±440.0 vs A1 þ supporting the potential functional significance of DRD2 550.0±280.5, P ¼ 0.187; TaqIB1À 550.3±486.7 vs B1 þ variants has been accumulating. In particular, previous 267.4±442.3, P ¼ 0.176; HphITÀ 529.5±292.2 vs studies reported the association of DRD2 TaqIA,TaqIB TÀ 1171.7±1235.4, P ¼ 0.262; NcoITÀ 506.5±432.3 vs and NcoI polymorphisms with modifications in D2 receptor T þ 1328.0±753.6, P ¼ 0.592). Conversely, patients with binding and expression in human central nervous system, microadenoma showed a strong linkage disequilibrium particularly in the striatum.15–18 between TaqIA1À and HphITÀ polymorphisms (D0 ¼ 1.0, The aim of this study was to assess the possible association r2 ¼ 0.879), which was not present in patients with macro- between four common DRD2 gene polymorphisms (that is, adenoma. TaqI A1/A2, TaqI B1/B2, HphI G/T and NcoI C/T) and the efficacy of CB treatment in patients with PRL-oma. Genotype analysis in patients with PRL-omas and sensitivity to CB Results treatment When considering patients who achieved PRL normaliza- Clinical data tion and tumor-size reduction under CB treatment (from 0.5 Two hundred and three patients with PRL-omas (98 male to 3 mg/week), no association between DRD2 polymorph- and 105 female, mean age at diagnosis 36.6±15.0 years) isms and the effective CB dosage was observed. Similarly, no were enrolled in this retrospective cross-sectional study. As it association between TaqIA,TaqI B and HphI polymorphisms is known that the size of the tumor is one of the major and resistance to CB in terms of PRL and tumor size was determinants of PRL levels, the study included a similar found (Table 3). By contrast, the prevalence of NcoI number of patients with either micro- or macro-PRL-oma genotype was different in patients resistant to CB treatment (adenoma size o10 mm or X10 mm, respectively) consecu- in comparison with those who were responsive. In fact, NcoI tively seen by the different centers. Subsequently, about half T þ allele was identified in 56.6% (12/22) of patients (50.3%) of the patients had a macroadenoma. All patients resistant to CB and 45.3% (84/181) of those normalizing at had a clinical and hormonal reevaluation every 3–4 months CB p3 mg/week (Fisher’s exact test, P ¼ 0.038) (Table 3). In and magnetic resonance imaging every 6–9 months. During the group of patients with NcoI T allele, TT homozygotes follow-up (range: 18–38 months), the mean lowest dosage of were 36% in responsive subjects vs 50% in resistants and TC CB required for PRL normalization and reduction of the heterozygotes were 9 vs 4%, respectively. tumor size was 1.40±1.13 mg/week, 45.3% patients requir- This association was also found, considering the tumor ing o1 mg/week. Twenty-two (10.8%) patients failed to shrinkage in response to CB, as NcoITþ variant was present normalize PRL levels with CB at the dosage of 43 mg/week in 70.4% of patients (12/17) who did not reach a 430% after 3–4 months follow-up and were considered resistant. In tumor-size reduction at CB p3 mg/week vs 41.4% (77/186) this subset, 54.6% of patients were males, 68.2% had a in the responsive group (Fisher’s exact test, P ¼ 0.006) (Table macroadenoma and the median PRL was 452 ng/ml (inter- 3). In the set of NcoI T allele carriers, TT homozygotes were quartile range 257–12 230). Seventeen (8.4%) patients did 35% in responsive patients vs 65% in resistants, and TC not reduce tumor size at CB 43 mg/week. A discrepancy heterozygotes were 7 vs 6%, respectively. between hormonal and tumor size responses was observed A multivariate logistic regression analysis has been carried in five patients with macroadenoma (three males and two out using backward method, considering failure to normal- females) in whom 43 mg/week of CB induced a tumor-size ize PRL levels with CB at the dosage of 43 mg/week as reduction from 60 to 75% without normalizing PRL levels. dependent variable and with the following predictors: TaqI The increase of CB dosage to 4, 4.5, 5 and 9 mg/week in 17, A þ , TaqIBþ , Hph T þ, NcoITþ, PRL levels, presence of 2, 2 and 1 patient, respectively, did not overcome the macroadenoma and age at diagnosis. Only NcoITþ resistance in terms of PRL normalization and tumor-size genotype was a significant predictor of the unsuccessful reduction in any patient. normalization of PRL by CB therapy (odds ratio 5.181, 95% confidence interval 1.369–19.1645, P ¼ 0.015).