Functional Phosphodiesterase 11 A Mutations May Modify the Risk of Familial and Bilateral Testicular Germ Cell Tumors

Inactivating germline mutations in phosphodiesterase 11A (PDE11A) have been implicated in adrenal tumor susceptibility. PDE11A is highly expressed in endocrine steroidogenic tissues, especially the testis, and mice with inactivated Pde11a exhibit male infertility, a known testicular germ cell tumor (TGCT) risk factor. We sequenced the PDE11A gene-coding region in 95 patients with TGCT from 64 unrelated kindreds. We identified 8 nonsynonymous substitutions in 20 patients from 15 families: four (R52T, F258Y, G291R, and V820M) were newly recognized, three (R804H, R867G, and M878V) were functional variants previously implicated in adrenal tumor predisposition, and one (Y727C) was a known polymorphism. We compared the frequency of these variants in our patients to unrelated controls that had been screened and found negative for any endocrine diseases: only the two previously reported variants, R804H and R867G, known to be frequent in general population, were detected in these controls. The frequency of all PDE11A -gene variants (combined) was significantly higher among patients with TGCT (P = 0.0002), present in 19% of the families of our cohort. Most variants were detected in the general population, but functional studies showed that all these mutations reduced PDE activity, and that PDE11A protein expression was decreased (or absent) in TGCT samples from carriers. This is the first demonstration of the involvement of a PDE gene in TGCT, although the cyclic AMP signaling pathway has been investigated extensively in reproductive organ function and their diseases. In conclusion, we report that PDE11A-inactivating sequence variants may modify the risk of familial and bilateral TGCT. [Cancer Res 2009;69(13):5301–6] Introduction The molecular causes of testicular germ cell tumor (TGCT), the most common malignancy in Caucasian men ages 15 to 45 years, remain elusive (1, 2). A genetic basis for TGCT is supported by familial clustering, younger-than-usual age at diagnosis, and an increased risk of bilateral disease (3, 4). Thus, a positive family history is an accepted and major risk factor, with an estimated relative risk of 8 to 10 for brothers of patients with TGCT, significantly greater than the 2to 3-fold increase in familial risk observed in most adult solid tumors (5–7). Two consortium-based linkage analyses have identified genomic regions of modest statistical interest, but the data provide no definitive evidence of a single, rare, highpenetrance susceptibility gene (8–11). A consensus is emerging that familial susceptibility to TGCT may be best explained by the combined interaction of multiple, more common, low-penetrance genes. We recently described adrenocortical tumors in patients who carry germline inactivating mutations of isoform 4 of PDE11A (PDE11A4), an essential regulator of cyclic AMP (cAMP) signaling in adrenal and other steroidogenic tissues (12, 13). Several lines of evidence suggested that PDE11A might be a candidate gene for TGCT: (a) we have observed high expression of the PDE11A4 isoform in human testes; testicular tissue was also the only tissue to express all four known isoforms of PDE11A (12); (b) nongerm cell testicular tumors have been linked to genetic aberrations of the cAMP signaling pathway, including somatic activating mutations of the G-stimulatory subunit of the G-protein (GNAS1) in Leydig cell hyperplasia and tumors and in McCune-Albright syndrome, and germline inactivating PRKAR1A mutations that are responsible for large cell calcifying Sertoli cell tumors in the context of Carney complex (14, 15); and (c) male-limited infertility has been reported in the Pde11a / mouse, and is a known risk factor for TGCTs in humans (16–18). We analyzed the PDE11A coding sequence in patients with familial and bilateral TGCT and various groups of control individuals. We then assessed the functional effects of the identified variants in vitro , evaluated their segregation with the TGCT phenotype in families, and studied PDE11A protein expression in TGCTs. Our data suggest that germline PDE11A mutations may modify the risk of familial and bilateral TGCTs. Materials and Methods The PDE11A gene was analyzed in 95 patients with TGCT from 64 families enrolled in National Cancer Institute Clinical Genetics Branch Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). A. Horvath and L. Korde have contributed equally to this work and are thus sharing the first authorship. Requests for reprints: Anelia Horvath, Program on Developmental Endocrinology and Genetics (PDEGEN), Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, 10 Center Drive, CRC, Room 1-3330, Bethesda, MD 20892. Phone: 301-402-1998; Fax: 301-402-0574; E-mail: horvatha@mail.nih.gov. I2009 American Association for Cancer Research. doi:10.1158/0008-5472.CAN-09-0884 www.aacrjournals.org 5301 Cancer Res 2009; 69: (13). July 1, 2009 Priority Report Published Online First on June 23, 2009 as 10.1158/0008-5472.CAN-09-0884 Research. on May 1, 2017. © 2009 American Association for Cancer cancerres.aacrjournals.org Downloaded from Published OnlineFirst June 23, 2009; DOI: 10.1158/0008-5472.CAN-09-0884