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Background A subgroup of patients with HER2-positive metastatic gastric and gastroesophageal junction cancers shows long-term response under trastuzumab maintenance monotherapy. Obviously, HER2 status alone is not able to identify these patients. We performed this study to identify potential new prognostic biomarkers for this long-term responding patient group. Patients and methods Tumor samples of 19 patients with HER2-positive metastatic gastric and gastroesophageal junction cancer who underwent trastuzumab treatment were retrospectively collected from multiple centers. Patients were divided into long-term responding (n=7) or short-term responding group (n=12) according to progression-free survival (PFS≥12 months vs. PFS

GEP-NETs are heterogeneous tumors originating from the pancreas (panNET) or the intestinal tract. Only a few patients with NETs are amenable to curative tumor resection, and for most patients, only palliative treatments to successfully control the disease or manage symptoms remain, such as with synthetic somatostatin (SST) analogs (SSAs), such as octreotide (OCT) or lanreotide (LAN). However, even cells expressing low levels of SST receptors (SSTRs) may exhibit significant responses to OCT, which suggests the possibility that SSAs signal through alternative mechanisms, e.g., transforming growth factor (TGF)-β. This signaling mode has been demonstrated in the established panNET line BON but not yet in other permanent (i.e., QGP) or primary (i.e., NT-3) panNET-derived cells. Here, we performed qPCR, immunoblot analyses, and cell counting assays to assess the effects of SST, OCT, LAN, and TGF-β1 on neuroendocrine marker expression and cell proliferation in NT-3, QGP, and BON cells. SST and SSAs were found to regulate a set of neuroendocrine genes in all three cell lines, with the effects of SST, mainly LAN, often differing from those of OCT. However, unlike NT-3 cells, BON cells failed to respond to OCT with growth arrest but paradoxically exhibited a growth-stimulatory effect after treatment with LAN. As previously shown for BON, NT-3 cells responded to TGF-β1 treatment with induction of expression of SST and SSTR2/5. Of note, the ability of NT-3 cells to respond to TGF-β1 with upregulation of the established TGF-β target gene SERPINE1 depended on cellular adherence to a collagen-coated matrix. Moreover, when applied to NT-3 cells for an extended period, i.e., 14 days, TGF-β1 induced growth suppression as shown earlier for BON cells. Finally, next-generation sequencing-based identification of microRNAs (miRNAs) in BON and NT-3 revealed that SST and OCT impact positively or negatively on the regulation of specific miRNAs. Our results suggest that primary panNET cells, such as NT-3, respond similarly as BON cells to SST, SSA, and TGF-β treatment and thus provide circumstantial evidence that crosstalk of SST and TGF-β signaling is not confined to BON cells but is a general feature of panNETs.

Liver metastases are the most common site of metastatic spread in colorectal cancer. Current treatment approaches involve effective systemic therapies in combination with surgical and/or interventional strategies. Multimodal strategies greatly improved clinical outcomes of patients with metastatic colorectal cancer over the last decades. Identification of predictive and prognostic biomarkers helped to comprehensively refine individual targeted treatment approaches and resulted in median overall survival rates of 30 months or longer. Current guidelines, thus, recommend treatment selection according to patients’ performance status, tumor localization and stage as well as the tumor’s molecular and genetic status. Here, we outline the latest developments in molecular decision-making for patients with upfront resectable, potentially or initially unresectable and non/never-resectable colorectal cancer liver metastases.

Since 2010, Trastuzumab combined with chemotherapy is the standard treatment for patients with HER2 (ERBB2) positive advanced or metastatic gastric and gastroesophageal junction cancer (GGEJ). While few patients show long-term response to the treatment, most suffer from rapid disease progression. Several studies revealed that genomic alterations, gene expression changes and altered HER2 signaling activity contribute to impaired therapy response. However, the underlying mechanism remains unclear. The aim of this research project is to analyze differences between patients with long and short progression-free survival by utilizing combined genetic, histologic, clinical and gene expression data. We collected a retrospective German patient cohort (n=20) including patients with HER2 positive advanced GGEJ who received Trastuzumab combined with chemotherapy. Using archival samples that were obtained prior to Trastuzumab treatment, we created a dataset including clinical information, histologic assessment, immunostaining, target amplicon sequencing (TAS; 409 gene panel) and human transcriptome data using the Affymetrix platform. To analyze the TAS sequencing data, we generated an automated analysis pipeline, which detects single nucleotide variants (SNV) and copy number alterations (CNA). Information about genomic alteration will be correlated with pathway and gene set enrichment analysis (GSEA) from the Affymetrix data. Furthermore, the data will be supported by investigating the functional status of HER2 in patient samples via electron microscopy. The results of this study could give insights on how genetic and transcriptomic alterations are connected to long-term Trastuzumab therapy response in HER2 positive GGEJ patients. This could potentially support therapy decision in personalized medicine. Citation Format: Isabel Porth, Philip Weidner, Sylvie Lorenzen, Wilko Weichert, Thorsten Oliver Götze, Sven Perner, Kim Luley, Daniela Hirsch, Ralf-Dieter Hofheinz, Diana B. Peckys, Zahra Mostajeran, Niels de Jonge, Timo Gaiser. Long-term response to Trastuzumab in patients with advanced gastric or gastroesophageal adenocarcinoma - A retrospective study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4018.