Germline ESR2 mutation predisposes to medullary thyroid carcinoma and causes up-regulation of RET expression.

Familial medullary thyroid cancer (MTC) and its precursor, C cell hyperplasia (CCH), is associated with germline RET mutations causing multiple endocrine neoplasia type 2. However, some rare families with apparent MTC/CCH predisposition do not have a detectable RET mutation. To identify novel MTC/CCH predisposition genes we undertook exome resequencing studies in a family with apparent predisposition to MTC/CCH and no identifiable RET mutation. We identified a novel ESR2 frameshift mutation, c.948delT, which segregated with histological diagnosis following thyroid surgery in family members and demonstrated loss of ESR2-encoded ERß expression in the MTC tumour. ERα and ERß form heterodimers binding DNA at specific oestrogen-responsive elements (EREs) to regulate gene transcription. ERß represses ERα-mediated activation of the ERE and the RET promoter contains three EREs. In vitro, we showed that ESR2 c.948delT results in unopposed ERα mediated increased cellular proliferation, activation of the ERE and increased RET expression. In vivo, immunostaining of CCH and MTC using an anti-RET antibody demonstrated increased RET expression. Together these findings identify germline ESR2 mutation as a novel cause of familial MTC/CCH and provide important insights into a novel mechanism causing increased RET expression in tumourigenesis.

A clinical and genetic analysis of multiple primary cancer referrals to genetics services.

Multiple primary malignant tumours (MPMT) are frequently taken as an indicator of potential inherited cancer susceptibility and occur at appreciable frequency both among unselected cancer patients and, particularly, among referrals to cancer genetics services. However, there is a paucity of information on the clinical genetic evaluation of cohorts of MPMT patients representing a variety of tumour types. We ascertained a referral-based series of MPMT cases and describe the patterns of tumours observed. Service-based molecular genetic testing had demonstrated a pathogenic germline variant in an inherited cancer gene in fewer than one in four unselected referrals. To assess for evidence of thus far unidentified variants in those who tested negative, comparisons were made with those who tested positive. This revealed considerable overlap between the two groups with respect to clinical characteristics indicative of an inherited cancer syndrome. We therefore proceeded to test a subset of unexplained MPMT cases (n=62) for pathogenic germline variants in TP53 and PTEN but none were detected. Individuals with MPMT may receive negative genetic test results for a number of reasons, which are discussed. Many of these may be addressed by the increasing application of next generation sequencing techniques such as inherited cancer gene panels.