Anti-ESR1 monoclonal antibody, clone FS60

Background Endocrine therapy (ET) is the mainstay of treatment for hormone receptor-positive human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer; however, adaptive mechanisms emerge in about 25-30% of cases through alterations in the estrogen receptor ligand-binding domain, with a consequent ligand-independent estrogen receptor activity. Epigenetic-mediated events are less known and potentially involved in alternative mechanisms of resistance. The aim of this study was to test the feasibility ofestrogen receptor 1(ESR1) epigenetic characterization through liquid biopsy and to show its potential longitudinal application for an early ET sensitivity assessment. Methods A cohort of 49 women with hormone receptor-positive HER2-negative MBC was prospectively enrolled and characterized through circulating tumor DNA using methylation-specific droplet digital PCR (MS-ddPCR) before treatment start (BL) and after 3 months concomitantly with computed tomography (CT) scan restaging (EV1).ESR1epigenetic status was defined by assessing the methylation of its main promoters (promA and promB). The most established cell-free tumor DNA (ctDNA) factors associated with ET resistance [ESR1and phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) mutations] were assessed through next-generation sequencing. Associations were tested through Mann-WhitneyUtest, matched pairs variations through Wilcoxon signed rank test, and survival was analyzed by log-rank test. Results The ET backbone was mainly based on aromatase inhibitors (AIs) (70.83%) in association with CDK4/6 inhibitors (93.75%). Significantly lower promA levels at baseline were observed in patients with liver metastases (P= 0.0212) and in patients withESR1mutations (P= 0.0091). No significant impact on PFS was observed for promA (P= 0.3777) and promB (P= 0.7455) dichotomized at the median while a >= 2-fold increase in promB or in either promA or promB at EV1 resulted in a significantly worse prognosis (respectivelyP= 0.0189,P= 0.0294). A significant increase at EV1 was observed for promB among patients withPIK3CAmutation (P= 0.0173). A trend was observed for promB inESR1wild-type patients and for promA in theESR1mutant subgroup. Conclusion The study proofed the concept of an epigenetic characterization strategy based on ctDNA and is capable of being integrated in the current clinical workflow to give useful insights on treatment sensitivity.

Background: Non-functioning pituitary adenomas (NFPAs) are common pituitary tumors, and surgery is generally the only treatment option. Few attempts have been made to explore target molecules for the development of NFPA pharmacological treatments. Method: We quantitatively assessed the expression profiles of estrogen receptor (ER) transcripts and proteins in NFPA samples, using reverse transcription-digital polymerase chain reaction (RT-dPCR) and immunohistochemistry, and further investigated the correlations between the expression levels of ER and those of downstream responsive genes. All patients had undergone surgery at the same high-volume hospital. A total of 20 patients with NFPAs were included. All patients were new-onset, and none were diagnosed with intratumoral hemorrhages or cysts. Results: NFPA samples exhibited a bimodal ESR1 expression pattern and were categorized into significantly different high- and low-ESR1 expression level groups (P < 0.05). In contrast, expression levels of ESR1 variants and ESR2 could barely be detected. Similar results were obtained through the immunohistochemical staining of NFPAs, using well-validated antibodies against ERs. The expression levels of ESR1 positively correlated with those of GREB1, an estrogen-responsive gene [correlation coefficient (r) = 0.623, P = 0.003]. Conclusions: ESR1 expression levels in NFPAs exhibited a bimodal pattern and were positively correlated with GREB1 expression levels. The accurate assessment of ER expression levels may further advance future NFPA-related research.