Mosquera, Juan Miguel

Several reports describing a rare primary liver tumor with histologic features reminiscent of follicular thyroid neoplasms have been published under a variety of descriptive terms including thyroid-like, solid tubulocystic, and cholangioblastic cholangiocarcinoma. Although these tumors are considered to represent histologic variants, they lack classic features of cholangiocarcinoma and have unique characteristics, namely immunoreactivity for inhibin and NIPBL::NACC1 fusions. The purpose of this study is to present clinicopathologic and molecular data for a large series of these tumors to better understand their pathogenesis. We identified 11 hepatic tumors with these features. Immunohistochemical and NACC1 and NIPBL fluorescence in situ hybridization assays were performed on all cases. Four cases had available material for whole-genome sequencing (WGS) analysis. Most patients were adult women (mean age: 42 y) who presented with abdominal pain and large hepatic masses (mean size: 14 cm). Ten patients had no known liver disease. Of the patients with follow-up information, 3/9 (33%) pursued aggressive behavior. All tumors were composed of bland cuboidal cells with follicular and solid/trabecular growth patterns in various combinations, were immunoreactive for inhibin, showed albumin mRNA by in situ hybridization, and harbored the NIPBL::NACC1 fusion by fluorescence in situ hybridization. WGS corroborated the presence of the fusion in all 4 tested cases, high tumor mutational burden in 2 cases, and over 30 structural variants per case in 3 sequenced tumors. The cases lacked mutations typical of conventional intrahepatic cholangiocarcinoma. In this report, we describe the largest series of primary inhibin–positive hepatic neoplasms harboring a NIPBL::NACC1 fusion and the first WGS analysis of these tumors. We propose to name this neoplasm NIPBL:NACC1 fusion hepatic carcinoma.

GLI1 encodes a transcription factor that targets cell cycle regulators affecting stem cell proliferation. GLI1 gene fusions were initially described in pericytomas with a t[7;12] translocation and more recently in gastric plexiform fibromyxomas and gastroblastomas. This study describes the clinicopathologic, immunohistochemical, and molecular features of three intestinal-based neoplasms harboring GLI1 gene fusions. We studied three unique mesenchymal small bowel tumors. Paraffin embedded tumor tissues from these cases and 62 additional tumor samples that included a plexiform fibromyxoma were sequenced using a targeted RNAseq method to detect fusion events. The study patients included two women and one man who were 52, 80, and 22 years of age at the time of diagnosis. The tumors involved the submucosa and muscularis propria of the duodenum, jejunum, and ileum. All 3 tumors contained a proliferation of monotonous oval or spindle cells with scattered, somewhat dilated vessels. Two cases showed epithelioid structures such as glands, tubules, or nests. Immunohistochemical analysis revealed cytokeratin expression in the epithelioid components of both tumors displaying these features, and variable numbers of mesenchymal cells. Diffuse CD56 positivity was seen in the mesenchymal component of 2 tumors and desmin and smooth muscle actin staining in the other tumor. Immunostains for S-100 protein, DOG-1, and CD117 were negative in all cases. GLI1 fusions with different partner genes were detected in all tumors, and in the plexiform fibromyxoma, used as a control. Validation by fluorescence in situ hybridization was performed. None of the tumors have recurred or metastasize after surgery. We describe novel GLI1 fusions in 3 mesenchymal neoplasms of the small intestine, including 2 with biphenotypic features. Thus far, all cases have pursued indolent clinical courses. We propose the term “ GLI1 -rearranged enteric tumor” to encompass this group of unique neoplasms of the small intestine that harbor GLI1 gene fusions and expand the spectrum of gastrointestinal neoplasms with these alterations.

Abstract Expression of DLL3 was examined in additional tumor types, as it was found to be highly expressed in tumor-initiating cells (TIC) in small cell lung cancer (SCLC), where a DLL3-targeted antibody drug conjugate (ADC), rovalpituzumab tesirine (Rova-T; SC16LD6.5; Saunders et al. 2015 Sci Transl Med 7:302ra136)) exerted clinically meaningful anti-tumor effects in a phase I trial (Spigel et al. 2016 Lancet Oncology; In Press). DLL3 expression was profiled by qRT-PCR, ELISA and immunohistochemistry in multiple tumor types. Patient-derived xenografts (PDX) from melanoma and ovarian small cell carcinoma were established and used for efficacy studies to determine the ability of Rova-T to impact tumor growth and TIC frequency. DLL3 expression was seen in metastatic melanoma (55%), low grade gliomas (90%), glioblastoma (70%), medullary thyroid cancer (65%), carcinoids (33%), dispersed neuroendocrine tumors in the pancreas (9%), bladder (57%) and prostate (24%), testicular cancer (90%), and lung adenocarcinomas with neuroendocrine features (80%). Unlike SCLC, where DLL3 does not predict clinical outcome on standard therapies, DLL3 expression negatively correlates with overall survival in melanoma and small cell bladder cancer. In mice bearing DLL3 positive melanoma PDX, treatment with a single dose of Rova-T resulted in effective and durable responses (>100 days), which correlated with a significant impact on TIC frequency. Similarly, in mice bearing DLL3-positive ovarian small cell PDX, a single dose of Rova-T resulted in effective and durable responses (>100 days). Our results show that DLL3 is expressed in many neuroendocrine tumors (lung, ovarian, prostate, bladder, etc), metastatic melanoma, medullary thyroid cancer, low-grade gliomas and glioblastoma. Given pre-clinical results showing efficacy of Rova-T in melanoma and ovarian small cell carcinoma, as well as encouraging clinical data with Rova-T in patients with recurrent/refractory SCLC, clinical evaluation of Rova-T in DLL3-positive melanoma, glioblastoma, medullary thyroid cancer and other high-grade neuroendocrine carcinomas is warranted. A “basket” trial enrolling patients with DLL3-positive solid tumors is now recruiting patients (NCT02709889). Citation Format: Laura R. Saunders, Samuel A. Williams, Sheila Bheddah, Kumiko Isse, Sarah Fong, Marybeth A. Pysz, Himisha Beltran, Loredana Puca, Verena Sailer, Juan M. Mosquera, Yu Yin, Jiaoti Huang, Andrew J. Armstrong, Jorge Garcia, Cristina Magi-Galluzzi, Vadim Koshkin, Petros Grivas, Farhad Kosari, John Cheville, Justin C. Moser, Thomas J. Flotte, Thorvardur Halfdanarson, Aaron Mansfield, Konstantinos N. Leventakos, Julian R. Molina, Douglas W. Ball, Barry D. Nelkin, Jill E. Shea, Courtney L. Scaife, Scott J. Dylla. Expression of DLL3 in metastatic melanoma, glioblastoma and high-grade extrapulmonary neuroendocrine carcinomas as potential indications for rovalpituzumab tesirine (Rova-T; SC16LD6.5), a delta-like protein 3 (DLL3)-targeted antibody drug conjugate (ADC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3093. doi:10.1158/1538-7445.AM2017-3093