DNA-methylation patterns imply a common cellular origin of virus- and UV-associated Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a neuroendocrine tumor either induced by integration of the Merkel cell polyomavirus into the cell genome or by accumulation of UV-light-associated mutations (VP-MCC and UV-MCC). Whether VP- and UV-MCC have the same or different cellular origins is unclear; with mesenchymal or epidermal origins discussed. DNA-methylation patterns have a proven utility in determining cellular origins of cancers. Therefore, we used this approach to uncover evidence regarding the cell of origin of classical VP- and UV-MCC cell lines, i.e., cell lines with a neuroendocrine growth pattern (n = 9 and n = 4, respectively). Surprisingly, we observed high global similarities in the DNA-methylation of UV- and VP-MCC cell lines. CpGs of lower methylation in VP-MCC cell lines were associated with neuroendocrine marker genes such as SOX2 and INSM1, or linked to binding sites of EZH2 and SUZ12 of the polycomb repressive complex 2, i.e., genes with an impact on carcinogenesis and differentiation of neuroendocrine cancers. Thus, the observed differences appear to be rooted in viral compared to mutation-driven carcinogenesis rather than distinct cells of origin. To test this hypothesis, we used principal component analysis, to compare DNA-methylation data from different epithelial and non-epithelial neuroendocrine cancers and established a scoring model for epithelial and neuroendocrine characteristics. Subsequently, we applied this scoring model to the DNA-methylation data of the VP- and UV-MCC cell lines, revealing that both clearly scored as epithelial cancers. In summary, our comprehensive analysis of DNA-methylation suggests a common epithelial origin of UV- and VP-MCC cell lines.

Gastric Neuroendocrine Tumor Mimicking Gastrointestinal Stromal Tumor: A Case Report

Gastric neuroendocrine tumors (NETs) are rare lesions that arise from enterochromaffin-like cells of the gastric mucosa. Gastric NETs are classified into 3 types of NETs and poorly differentiated neuroendocrine cancers. Most gastric NETs usually present as hemispherical, yellowish, polypoid lesions with a central depression and often as subepithelial tumors (SETs) because they are confined within the submucosal layer. Here, we report a case of gastric NET presenting as SET mimicking a gastrointestinal stromal tumor (GIST). Endoscopy revealed a 2.3-cm-sized SET with intact surface mucosa, and endoscopic ultrasonography showed a homogeneous hypoechoic lesion with a well-circumscribed margin. Typical features of gastric NET, such as yellowish mucosal changes or central ulceration, were not observed. GIST was suspected, and a laparoscopic wedge resection was performed. The final diagnosis was gastric NET with grade 2 differentiation.

Reciprocal Induction of MDM2 and MYCN in Neural and Neuroendocrine Cancers

MYC family oncoproteins MYC, MYCN, and MYCL are deregulated in diverse cancers and via diverse mechanisms. Recent studies established a novel form of MYCN regulation in MYCN-overexpressing retinoblastoma and neuroblastoma cells in which the MDM2 oncoprotein promotes MYCN translation and MYCN-dependent proliferation via a p53-independent mechanism. However, it is unclear if MDM2 also promotes expression of other MYC family members and has similar effects in other cancers. Conversely, MYCN has been shown to induce MDM2 expression in neuroblastoma cells, yet it is unclear if MYC shares this ability, if MYC family proteins upregulate MDM2 in other malignancies, and if this regulation occurs during tumorigenesis as well as in cancer cell lines. Here, we report that intrinsically high MDM2 expression is required for high-level expression of MYCN, but not for expression of MYC, in retinoblastoma, neuroblastoma, small cell lung cancer, and medulloblastoma cells. Conversely, ectopic overexpression of MYC as well as MYCN induced high-level MDM2 expression and gave rise to rapidly proliferating and MDM2-dependent cone-precursor-derived masses in a cultured retinoblastoma genesis model. These findings reveal a highly specific collaboration between the MDM2 and MYCN oncoproteins and demonstrate the origin of their oncogenic positive feedback circuit within a normal neuronal tissue.

Randomized phase II trial of topotecan plus M6620 (VX-970) versus topotecan alone in patients with relapsed small-cell neuroendocrine cancers including small cell lung cancer.

TPS3653 Background: Ataxia telangiectasia and Rad3-related (ATR) is an essential kinase that senses stressed replication forks and orchestrates the multifaceted replication stress response. Cancer cells under replication stress are particularly susceptible to ATR inhibition. Small-cell neuroendocrine cancers (SCNCs) are highly aggressive and arise in multiple tissues, most commonly lung (SCLC). We hypothesized that SCNCs are under replication stress and that exacerbating this stress could selectively kill SCNC by replicative damage. Based on promising data from a single-arm study, this study seeks to evaluate the improvement of progression free survival (PFS) by adding M6620 to topotecan in patients with SCNC. Methods: This study is an investigator-initiated, multicenter, open-label randomized phase 2 clinical trial. Key inclusion criterion are patients at age ≥18 with SCNCs that had relapsed after at least one prior chemotherapy, ECOG PS ≤ 2, and adequate organ function. Patents with asymptomatic brain metastasis, irrespective sensitivity with prior platinum-based chemotherapy, and previously treated with immune checkpoint inhibitors are eligible. The primary cohort consists of 54 patients with SCLC randomized 2:1 to receive either topotecan in combination with M6620 or topotecan alone. Topotecan is administered 1.25 mg/m2 intravenously over 30 minutes every 23 hours on day 1 through 5, pegfilgrastim 6 mg subcutaneously on day 6 and M6620 is administered at 210 mg/m2 intravenously over 60 minutes on day 2 and day 5 if the patient is randomized to the combination arm, in 21-day cycles. Patients randomized to the topotecan alone arm can cross-over to the combination arm at disease progression. An exploratory cohort will enroll 20 patients with SCNC. Primary endpoint is PFS improvement with the combination compared with topotecan alone. Secondary endpoints are ORR and overall survival. To evaluate the genomic features associated with clinical outcomes and to gain insight into the underlying mechanisms of ATR inhibitor response, we require mandatory biopsy before starting treatment. Clinical trial information: NCT03896503 .

Young-onset pancreas cancer (PC) in patients less than or equal to 50 years old at Memorial Sloan Kettering (MSK): Descriptors, genomics, and outcomes.

774 Background: For individuals ≤ 50 years old, cancer incidence is increasing, particularly gastrointestinal and obesity related cancers (Sung, Lancet Public Health 2019). Limited details are known about young onset PC. Herein, we report the epidemiologic, pathologic, and molecular characteristics of PC in patients (pts) ≤ 50 years. Methods: MSK institutional database was queried for medical and treatment history, genomics, and outcomes in pts ≤ 50 years old diagnosed with PC between January 2008 and July 2018. Neuroendocrine cancers were excluded. Overall survival (OS) from date of PC diagnosis was estimated using Kaplan-Meier methods. Results: N = 450 pts ≤ 50 years old with a diagnosis of PC were identified. Ninety-six percent had adenocarcinoma, and 4% had acinar cell carcinoma/other histologies. Table summarizes demographics. Median OS was 16 months in the entire cohort and 11.3 months in stage IV disease. For N = 236 pts diagnosed after 2014, 119 (50%) underwent successful somatic testing with at least one alteration identified, and 21/119 tumors were RAS wild-type with identification of several actionable alterations (NRG1 fusions (n=2), NTRK fusions (n=2), IDH1 R132C (n=1), and microsatellite unstable tumors (n=1) ). N = 114 pts had germline testing (routine after 2015), and 33/114 (29%) had pathologic germline alterations, including BRCA1/2 (n=18), CHEK2 (n=3), PALB2 (n=3), ATM (n=2), MLH1 (n=1), and MSH3 (n=1). Conclusions: Pathogenic germline alterations are present in a substantial percentage of pts with young onset PC, and actionable somatic alterations were seen frequently in the subgroup of young onset PC RAS-wild type tumors. These observations underpin the need for germline and somatic profiling in PC. [Table: see text]

Angiogenesis and de novo Arteriogenesis

Arteriogenesis supply oxygen and nutrients in tumor microenvironment (TME), which may play an important role in tumor growth and metastasis. Current anti-angiogenetic targeted treatments have not shown substantial clinical benefits and they are poorly tolerated, and even lead to more malignant relapse. The heterogeneity of tumor-associated endothelial cells (TAECs) and tumor vasculature may be important and should be appreciated in therapeutic targeting the TME. In this regard, the de novo arteriogenesis within the TME may be associated with tumor progression, stemness of cancer stem-like cells (CSCs) and therapeutic resistance and relapse. Targeting tumor arteriogenesis may thus be a potential novel therapeutic target. Specifically, targeting the FoxO1-CD36-Notch pathway could show the clinical potential by acting on arteriolar niche and CSCs at the same time in a variety of cancers including neuroendocrine cancers, breast cancers, lung cancers and malignant melanoma.