Accepted 6 December 2012 Published online 6 March 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI /hed.23241

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1 CASE REPORT Jonathan Irish, MD, FRCSC, Section Editor Novel tandem germline RET proto-oncogene mutations in a patient with multiple endocrine neoplasia type 2B: Report of a case and a literature review of tandem RET mutations with in silico analysis Kanako Tanase Nakao, MD, 1 Takeshi Usui, MD, PhD, 2 * Mayumi Ikeda, MD, 1 Yusuke Mori, MD, 3 Tetsuro Yamamoto, MD, 4 Sachiko Tsukamoto Kawashima, MD, 1 Kazutaka Nanba, MD, 1 Akiko Yuno, MD, 1,5 Tamiko Tamanaha, MD, 1 Tetsuya Tagami, MD, PhD, 1 Mitsuhide Naruse, MD, PhD, 2 Ryo Asato, MD, PhD, 3 Akira Shimatsu, MD, PhD 2 1 Department of Endocrinology and Metabolism, National Hospital Organization, Kyoto Medical Center, Kyoto, Japan, 2 Clinical Research Institute, National Hospital Organization, Kyoto Medical Center, Kyoto, Japan, 3 Department of Head and Neck Surgery, National Hospital Organization, Kyoto Medical Center, Kyoto, Japan, 4 Department of Surgical Pathology, National Hospital Organization, Kyoto Medical Center, Kyoto, Japan, 5 Department of Endocrinology and Metabolism, Kin-i-kyo Chuo Hospital, Sapporo, Japan. Accepted 6 December 2012 Published online 6 March 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI /hed ABSTRACT: Background. Multiple endocrine neoplasia type 2B (MEN2B) is the rarest and most aggressive form of MEN2. MEN2B cases usually carry either an M918T or A883T mutation of the RET, but to date, there are 3 atypical MEN2B caused by tandem mutations. Methods and Results. A 32-year-old woman with no family history of medullary thyroid carcinoma (MTC) presented with a neck tumor and multiple mucosal nodules. She was diagnosed with MEN2B. Genetic analyses of RET revealed that she had 2 mutations, Q781R and V804M. Subclone and genetic analyses revealed that Q781R was on the paternal allele and V804M was a de novo. In silico analysis of the tandem mutations showed a high prediction score. Conclusions. We describe a novel combination of tandem RET mutations (Q781R/V804M) in a MEN2B-like patient. In silico analysis showed a high prediction score, which was compatible with the clinical phenotype in the present case. VC 2013 Wiley Periodicals, Inc. Head Neck 35: E363 E368, 2013 KEY WORDS: RET, MEN2B, tandem mutation, de novo, in silico *Corresponding author: T. Usui, Clinical Research Institute, National Hospital Organization, Kyoto Medical Center, Mukaihata-cho Fukakusa, Fushimi-ku, Kyoto , Japan. tusui@kuhp.kyoto-u.ac.jp Contract grant sponsor: This work is part of the Ministry of Education, Culture, Sports, Science, and Technology KAKENHI and a grant from the Smoking Research Foundation. INTRODUCTION Multiple endocrine neoplasia type 2 (MEN2) is an autosomal dominant inherited neoplasia syndrome caused by activating mutations in the RET proto-oncogene. 1,2 MEN2 is classified into 3 subtypes: MEN2A, MEN2B, and familial medullary thyroid carcinoma (FMTC). MEN2A, which accounts for 90% to 95% of MEN2 cases, is characterized by the development of medullary thyroid carcinoma (MTC) in more than 90% of RET mutation carriers; depending on the mutation, pheochromocytoma, and primary hyperparathyroidism also develop in 0% to 50% and 0% to 20%, respectively, of individuals with MEN2A. 3 FMTC is a clinical variant of MEN2A in which MTC is the only manifestation. 4 In contrast, MEN2B accounts for 5% to 10% of MEN2 cases 3 and is characterized by MTC (100% of cases), pheochromocytoma (up to 50% of cases), and specific phenotypic features such as mucosal neuromas of the lips, tongue, and conjunctiva ( mucosal neuromas ), enlarged lips, medullated corneal-nerve fibers, ganglioneuromatosis of the gastrointestinal tract, and an asthenic Marfanoid body habitus. 4 More than 95% of patients with MEN2B carry an M918T mutation of RET, and 2% to 3% of patients harbor an A883F mutation. The frequency of de novo gene mutations is approximately 50% in patients with MEN2B, much higher than the 2% to 9% in MEN2A cases and this, rather than tumor behavior, is considered to be a reason for the delayed diagnosis and higher mortality of patients with MEN2B. 4 Although a single mutation of RET, such as M918T or A883T, is enough to cause MEN2 in the majority of cases, double mutations of RET have been reported to cause MEN2 in a limited number of cases Herein, we describe a patient with MEN2B who carries a novel combination of double RET germline mutations, V804M and Q781R, on the same allele. To date, 5 other MEN2 cases with RET 804-associated double mutations have been reported. 5 9 To understand the significance of the tandem mutation, we review such cases and perform in silico analysis using the Align-Grantham Variation-Grantham Deviation (Align-GVGD) web-based program, which is proposed to be a valid alternative to in vitro analysis for determining the transforming ability of the rare mutated RET gene. 14 CASE REPORT A 32-year-old woman presented with a right anterior neck mass. She had bumpy lips and multiple nodules on HEAD & NECK DOI /HED DECEMBER 2013 E363

2 NAKAO ET AL. FIGURE 1. (A) Bumpy lips (indicated by the arrow). Nodules (indicated by arrowheads) on the tongue (A) and buccal mucosa (B). Buccal nodule showing irregularly hypertrophied nerves scattered throughout the submucosa in a disorganized arrangement (C). Individual nerve fascicle containing nerve fibers and their accompanying S-100 protein positive Schwann cells (D), and surrounded by epithelial membrane antigenpositive perineurium (E). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] her lips, tongue, buccal mucosa (Figure 1A, B), and conjunctiva since childhood. She had no apparent Marfanoid body habitus (arm span to height ratio was 0.92). There was no family history of endocrine disease, including thyroid tumor. Her serum calcitonin level was 6080 pg/ml (normal range, pg/ml), and her carcinoembryonic antigen level was 435 ng/ml (normal range, 5 ng/ml). Thyroid ultrasonography and neck CT showed a mm thyroid mass with adjacent lymph node swelling (Figure 2A, B). Fine-needle aspiration cytology of the thyroid mass and cervical lymph nodes was compatible with MTC (Figure 2C). Serum levels of calcium, intact parathyroid hormone, catecholamines, and metanephrines in the urine were all within the normal range. She had normal blood pressure and imaging studies did not indicate pheochromocytoma (data not shown). Histopathologic examination of the buccal mucosa nodules showed vaguely nodular aggregates of hypertrophied nerve bundles in the submucosa, compatible with mucosal neuroma (Figure 1C E). Based on these findings, she was diagnosed with MEN2B. A total thyroidectomy was performed with a central and right modified neck dissection. Histopathologic examination of the resected specimen confirmed a diagnosis of MTC with lymph node metastasis (Figure 2D F). No distant metastasis was found, and her TNM staging was confirmed to be T2N1bM0. After the patient provided informed consent, the proband s genomic DNA was extracted from the peripheral blood and screened for mutations in exons 10, 11, and 13 to 16 of the RET gene by polymerase chain reaction (PCR)-direct sequencing analysis, as described previously. 15 Subclone analysis was performed as follows. PCR was performed using primers S13 and S The PCR product E364 HEAD & NECK DOI /HED DECEMBER 2013

3 NOVEL RET TANDEM MUTATIONS WITH IN SILICO ANALYSIS FIGURE 2. Imaging study of the neck showed a mm low echoic thyroid mass in ultrasonography (A), and heterogeneous enhanced mass in the right thyroid lobe in CT (B), with adjacent lymph node swelling. Fine-needle aspiration cytology of the thyroid mass and the cervical lymph node showed loosely cohesive clusters of polygonal and spindle cells, which were positive for calcitonin (C). The yellow-whitish tumor was located in the right lobe of the resected specimen (D), and the microscopic findings showed polygonal, round, and spindle-shaped cells in a tubular formation (E; hematoxylin-eosin stain), which were positively stained for calcitonin (F). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] was subcloned into pcr2.1-topo R using a TOPO R TA cloning kit (Invitrogen, Carlsbad, CA). After transforming the product into DH5a-competent cells, several ampicillin-resistant clones were picked up and subsequently sequenced. 16 An in silico analysis was performed to predict the transforming activity of the mutated genes, using the Align- GVGD web-based program ( iarc.fr). 17,18 This is an extension of the Grantham Difference, which is popular for measuring biochemical distances between pairs of amino acids. 19 Based on multiple sequence alignments, the program calculates 2 scores for each amino acid residue substitution, GD and Grantham Variation (GV). Grantham Deviation (GD) is a measure of the biochemical difference between the mutant and the observed variation at that position according to the multiple sequence alignments. GV is a measure of the amount of observed biochemical variation in a particular position in the alignment. Accordingly, the GV and GD scores predict the degree of structural difference between the mutated and wild-type protein. The degree of this difference is expressed as a numerical prediction score ranging from 0 (no difference) to 65 (maximum difference). The assumption is that the higher the score, the more powerful the transforming activity. 17 We detected 2 heterozygous missense mutations: Q781R in exon 13 and V804M in exon 14, by PCR direct sequencing (Figure 3A). Subcloning analysis of the PCR product covering exons 13 and 14 of the proband s RET gene revealed that both mutations were present on the same clone (Figure 3B, 3C). The genotype of her parents and brother was also examined under their informed consent. A Q781R mutation was found in her father (64 years old) and brother (31 years old), but the V804M mutation was not detected in either of them, suggesting that V804M was a de novo mutation in the proband HEAD & NECK DOI /HED DECEMBER 2013 E365

4 NAKAO ET AL. FIGURE 3. Polymerase chain reaction (PCR)-direct sequencing analysis of RET in the proband s peripheral blood (A). A single nucleic acid substitution was observed at codon 781 (Q781R CAG>CGG) and codon 804 (V804M GTG>ATG). Subclone analysis of the PCR product of the proband s RET gene covering exons 13 and 14. One of the clones showed the wild-type genotype on both codons 781 and 804 (B). The other clone showed mutant sequences on both codons 781 and 804 (C). Summary of the genotypes of the family members (D). The arrow indicates the proband in the present study. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] (Figure 3D). Her father s and brother s neck ultrasonography showed no abnormalities and their basal serum calcitonin levels were within the normal range (data not shown). Neither of them had hypertension. In silico analysis was applied for the double mutation Q781R/V804M found in the present case, in addition to single Q781R and V804M mutations. The prediction scores of Q781R and V804M were 35 and 15, respectively, whereas the prediction score for tandem Q781R/ V804M scores was 65, higher than that for each single mutation (Table 1). The results of in silico analysis of 5 previously reported RET 804-associated tandem mutations are summarized in Table 1. DISCUSSION Recent guidelines for the management of MTC recommend RET gene analysis to exclude MEN2 and related diseases. 20 As approximately 50% of MEN2B patients carry a de novo mutation, screening for RET mutations for MTC is extremely important in patients with no apparent family history of thyroid disease, as in the present case. Although most MEN2B cases are due to the M918T mutation, and some are due to the A883F missense mutation of RET, tandem RET mutations of codons 805, 7 806, 5 and in cis configuration with the V804M mutation are reported to cause MEN2B without either the M918T or A883F mutation. To the best of our knowledge, this is the first reported case of a combination of RET missense double mutations, V804M and Q781R, in a patient with MEN2B. There are no reports of MEN2 with single germline mutations of codon 805, 806, or 904 alone. Miyauchi et al 5 first described a case of MEN2B with a tandem mutation (Y806C/V804M). They demonstrated that the patient s Y806C mutation was inherited from her father and the V804M mutation was de novo on the paternal allele. The mutation carriers (proband s father and brother) of Y806C showed no signs of MTC, suggesting that the single Y806C mutation was not pathogenic or at least very indolent. In addition, V778I is considered to be a variant that potentially affects the phenotype through an additional effect in the presence of V804M. 21,22 Similarly, a patient with a single Q781R mutation, reported in a family with FMTC, was 71 years of age and a small MTC was accidentally found in her thyroid gland, which was removed due to a E366 HEAD & NECK DOI /HED DECEMBER 2013

5 NOVEL RET TANDEM MUTATIONS WITH IN SILICO ANALYSIS TABLE 1. In silico analysis of the mutations Q781R, V804M, and 804 associated tandem mutations with Align-Grantham Variation-Grantham Deviation and their phenotypes. Amino acid substitution GV GD Align-GVGD score Phenotype Reference Q781R FMTC (22) V804M FMTC or MEN2A (23) V804M* / Y806C MEN2B (5) V804M / S904C MEN2B (6) V804M / E805K MEN2B (7) V804M / V778I FMTC (8) V804M / R844L FMTC (9) V804M* / Q781R MEN2B Present case Abbreviations: GV, Grantham Variation; GD, Grantham Deviation; Align-GVGD, Align-Grantham Variation-Grantham Deviation; FMTC, familial medullary thyroid carcinoma; MEN2A, multiple endocrine neoplasia type 2B. GV is a measure of the amount of observed biochemical variation. GD is a measure of the biochemical difference between the mutant and the observed variation at that position. Align-GVGD score: the degree of structural difference between the mutated and wild-type protein is expressed as a score ranging from 0 (no difference) to 65 (maximum difference). * De novo mutations. hyperfunctioning autonomous nodule, suggesting its slow growing nature. 23 Furthermore, 2 family members (the proband s father and brother) who carried this mutation had not developed MTC. On the other hand, a single V804M mutation was reported in several families with FMTC or MEN2A, 24 but not MEN2B. Although the precise mechanism is yet to be clarified, the aggressive nature of MEN2B compared to MEN2A or FMTC suggests that the double mutations can cause phenotype modifications, probably by increasing the transforming activities. In vitro, the transforming activity of RET with the V804M/Y806C double mutation is approximately 8- fold to 13-fold higher than that of RET with a single V804M or Y806C mutation and two-thirds that of a single M918T mutation. 25 In silico analysis predicts that the V804M/E805K mutation is more severely deleterious in combination than in isolation, and RET 804 is suggested to constitute a critical gatekeeper residue that when mutated in combination with RET 805 induces a conformational change and makes the kinase constitutively active 7 as in the M918T mutation-associated MEN2B cases. We performed in silico analysis of the tandem mutations, which is proposed to be a valid alternative to in vitro analysis for determining the transforming ability of mutated genes. 14 The Align-GVGD program was previously applied to 6 rare RET mutations, revealing a positive correlation between the in silico score and in vitro focus forming units. 14 The prediction score for tandem Q781R/V804M was 65, higher than that for each single mutation (35 for Q781R and 15 for V804M). We evaluated in silico analysis for the 5 previously reported double mutation cases (Table 1). All 4 cases (including our case) with a prediction score of 65 had the MEN2B phenotype. The 2 cases with lower prediction scores of 25 showed the FMTC phenotype (Table 1). Cosci et al 14 reported that although in silico results did not completely correlate with the in vitro assay results, the aggressiveness of RET mutations can be predicted by in silico analysis. Although the Align-GVGD program was originally designed to address protein loss of function and not gain of function, the analysis of the 6 double mutation cases, including V804M, provided us a better understanding of the individual clinical phenotypes; a higher prediction score suggests MEN2B and a lower prediction score suggests FMTC. In conclusion, we identified a novel combination of tandem RET mutations in a patient with MEN2B. In silico analysis using the Align-GVGD program demonstrated that the double mutation in the present case leads to a higher prediction score, supporting the aggressive nature of MTC. Acknowledgements The authors thank Ms. Matsuda for technical assistance in the polymerase chain reaction and sequencing. REFERENCES 1. Mulligan LM, Kwok JB, Healey CS, et al. Germ-line mutations of the RET proto-oncogene in multiple endocrine neoplasia type 2A. Nature 1993;363: Hofstra RM, Landsvater RM, Ceccherini I, et al. 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