Purpose: Mutations in the ligand-binding domain (LBD) of estrogen receptor a (ER) confer constitutive transcriptional activity and resistance to endocrine therapies in patients with breast cancer. Accumulating clinical data suggest adverse outcome for patients harboring tumors expressing these mutations. We aimed to elucidate mechanisms conferring this aggressive phenotype.Experimental Design: Cells constitutively expressing physiologic levels of ER-harboring activating LBD mutations were generated and characterized for viability, invasiveness, and tumor formation in vivo. Gene expression profile was studied using microarray and RNAseq technologies. Metabolic properties of the cells were assessed using global metabolite screen and direct measurement of metabolic activity.Results: Cells expressing mutated ER showed increased proliferation, migration, and in vivo tumorigenicity compared with cells expressing the wild-type ER (WT-ER), even in the presence of estrogen. Expression of the mutated ER was associated with upregulation of genes involved in invasion and metastases, as well as elevation of genes associated with tumor cell metabolism. Indeed, a metabolic examination revealed four distinct metabolic profiles: WT-ER-expressing cells either untreated or estrogen treated and mutated ER-expressing cells either untreated or estrogen treated. Pathway analyses indicated elevated tricarboxylic acid cycle activity of 537S-ERexpressing cells. Thus, while WT-ER cells were mostly glucosedependent, 537S-ER were not addicted to glucose and were able to utilize glutamine as an alternative carbon source.Conclusions: Taken together, these data indicate estrogenindependent rewiring of breast cancer cell metabolism by LBD-activating mutations. These unique metabolic activities may serve as a potential vulnerability and aid in the development of novel treatment strategies to overcome endocrine resistance.

Objective To evaluate the precision and utility of fine‐needle aspiration (FNA) in differentiating between benign and malignant parotid tumours, and the implications of FNA results on management and outcomes. Design Retrospective case series. Setting Tertiary medical centre. Participants All adults who underwent preoperative FNA, followed by postoperative histological examination, between 1986 and 2014. Main outcome measures Differences in clinical management and outcomes of patients with parotid masses in light of FNA results. Results We analysed 505 samples from 485 patients. According to histopathological results, preoperative FNA successfully identified benign tumours in 89% of the cases (362/405) and only 59% of malignant tumours (59/100). Overall sensitivity and specificity of FNA in distinguishing between different subtypes of benign lesions were 80% and 99%, respectively, whereas positive predictive value (PPV) and negative predictive value (NPV) were 85% and 98%. Moreover, malignant lesions subtyping had high false‐positive and false‐negative rates with sensitivity, specificity, PPV and NPV of 44%, 100%, 75% and 99%, respectively. Additionally, when FNA falsely classified malignant tumours as benign, surgeries were inappropriately delayed and the durations of surgeries and hospitalisations were shorter, compared to true malignant FNA results. Interestingly, survival was not affected in falsely benign lesions that were mostly low‐grade, conversely non‐diagnostic FNA for malignant tumours resulted in decreased survival. Conclusions Our findings highlight the limitations of FNA as a decision‐making tool in preoperative evaluation of parotid masses. Clinicians should take into account that FNA is inaccurate for identifying specific subtypes of malignant lesions, which may eventually delay treatment and influence outcome.

Background Estrogen receptor α (ESR1) plays a critical role in promoting growth of various cancers. Yet, its role in the development of pancreatic cancer is not well-defined. A less studied region of ESR1 is the hinge region, connecting the ligand binding and DNA domains. rs142712646 is a rare SNP in ESR1, which leads to a substitution of arginine to cysteine at amino acid 269 (R269C). The mutation is positioned in the hinge region of ESR1, hence may affect the receptor structure and function. We aimed to characterize the activity of R269C-ESR1 and study its role in the development of pancreatic cancer. Methods Transcriptional activity was evaluated by E2-response element (ERE) and AP1 –luciferase reporter assays and qRT-PCR. Proliferation and migration were assessed using MTT and wound healing assays. Gene-expression analysis was performed using RNAseq. Results We examined the presence of this SNP in various malignancies, using the entire database of FoundationOne and noted enrichment of it in a subset of pancreatic non-ductal adenocarcinoma (n = 2800) compared to pancreatic ductal adenocarcinoma (PDAC) as well as other tumor types (0.53% vs 0.29%, p = 0.02). Studies in breast and pancreatic cancer cells indicated cell type-dependent activity of ESR1 harboring R269C. Thus, expression of R269C-ESR1 enhanced proliferation and migration of PANC-1 and COLO-357 pancreatic cancer cells but not of MCF-7 breast cancer cells. Moreover, R269C-ESR1 enhanced E2-response elements (ERE) and AP1-dependent transcriptional activity and increased mRNA levels of ERE and AP1-regulated genes in pancreatic cancer cell lines, but had a modest effect on MCF-7 breast cancer cells. Accordingly, whole transcriptome analysis indicated alterations of genes associated with tumorigenicity in pancreatic cancer cells and upregulation of genes associated with cell metabolism and hormone biosynthesis in breast cancer cells. Conclusions Our study shed new light on the role of the hinge region in regulating transcriptional activity of the ER and indicates cell-type specific activity, namely increased activity in pancreatic cancer cells but reduced activity in breast cancer cells. While rare, the presence of rs142712646 may serve as a novel genetic risk factor, and a possible target for therapy in a subset of non-ductal pancreatic cancers.