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Simple Summary Spitzoid melanoma is a rare tumor type and so far preclinical models for translational research have also been also lacking. We established a cell line from a metastatic spitzoid melanoma that is, according to our knowledge, the first cell model from this tumor type. The cells carried a novel activating mutation in the region of the MEK1 protein that influences the sensitivity of the mutant protein to MEK inhibitors. We tested the cells’ sensitivity to clinically used and newly developed MEK inhibitors in both in vitro and in vivo models. The clinically approved MEK inhibitor strongly reduced both in vitro and in vivo tumor growth and might be an effective therapy for tumors with this kind of MEK mutation. Abstract Spitzoid melanoma is a rare malignancy with histological characteristics similar to Spitz nevus. It has a diverse genetic background and in adults, a similarly grim clinical outcome as conventional malignant melanoma. We established a spitzoid melanoma cell line (PF130) from the pleural effusion sample of a 37-year-old male patient. We found that the cell line carries a rare MEK1 mutation (pGlu102_Lys104delinsGln) that belongs to the RAF- and phosphorylation-independent subgroup of MEK1 alternations supposedly insensitive to allosteric MEK inhibitors. The in vivo tumorigenicity was tested in three different models by injecting the cells subcutaneously, intravenously or into the thoracic cavity of SCID mice. In the intrapleural model, macroscopic tumors formed in the chest cavity after two months, while subcutaneously and intravenously delivered cells showed limited growth. In vitro, trametinib—but not selumentinib—and the ATP-competitive MEK inhibitor MAP855 strongly decreased the viability of the cells and induced cell death. In vivo, trametinib but not MAP855 significantly reduced tumor growth in the intrapleural model. To the best of our knowledge, this is the first patient-derived melanoma model with RAF- and phosphorylation-independent MEK mutation and we demonstrated its sensitivity to trametinib.

OA Förderung 2021 Objective: Uterine carcinosarcoma (UCS) is a rare but highly aggressive malignancy with biphasic growth pattern. This morphology can be attributed to epithelial-mesenchymal transition (EMT) that often associates with tumor invasion and metastasis. Accordingly, we analyzed a novel patient-derived preclinical model to explore whether EMT is a potential target in UCS. Methods: A novel UCS cell line (PF338) was established from the malignant pleural effusion of a 59-year-old patient at time of disease progression. Immunohistochemistry was performed in primary and metastatic tumor lesions. Oncogenic mutations were identified by next-generation sequencing. Viability assays and cell cycle analyses were used to test in vitro sensitivity to different standard and novel treatments. E-cadherin, beta-catenin and pSMAD2 expressions were measured by immunoblot. Results: Whereas immunohistochemistry of the metastatic tumor showed a predominantly sarcomatous vimentin positive tumor that has lost E-cadherin expression, PF338 cells demonstrated biphasic growth and carried mutations in KRAS, PIK3CA, PTEN and ARID1A. PF338 tumor cells were resistant to MEK- and TGF-beta signaling-inhibition but sensitive to PIK3CA- and PARP-inhibition and first-line chemotherapeutics. Strikingly, histone deacetylase (HDAC) inhibition markedly reduced cell viability by inducing a dose-dependent G0/1 arrest and led to mesenchymal-epithelial transition as evidenced by morphological change and increased E-cadherin and beta-catenin expression. Conclusions: Our data suggest that HDAC inhibition is effective in a novel UCS cell line by interfering with both viability and differentiation. These findings emphasize the dynamic manner of EMT/MET and epigenetics and the importance of molecular profiling to pave the way for novel therapies in UCS.

The PIKTAM study evaluated the efficacy and safety of the PI3K inhibitor buparlisib in combination with tamoxifen in hormone receptor‐positive (HR+), HER2‐negative advanced breast cancer patients after failure of prior endocrine therapy. In this open‐label, single‐arm phase II trial, 25 patients were enrolled in 11 sites in Germany. Patients were stratified according to PIK3CA mutation status (tissue and cfDNA from serum samples) and/or loss of PTEN expression. Patients received buparlisib (100 mg) and tamoxifen (20 mg) once daily on a continuous schedule (28‐day cycle) until progression or unacceptable toxicity. Primary endpoint was overall 6‐month progression‐free survival (PFS) rate. Key secondary endpoints included the 6‐month PFS rate in subpopulations, PFS, overall survival, overall response rate (ORR), disease control rate (DCR), and safety. Overall, the 6‐month PFS rate was 33.3% (n/N = 7/21, one‐sided 95% CI 16.8‐100) and median PFS was 6.1 (CI 2.6‐10.6) months. The ORR and DCR were 12.5% and 44%. The PIK3CA‐mutated subgroup consistently showed the highest 6‐month PFS rate (62.5%, n/N = 5/8), median PFS (8.7 months), ORR (40%), and DCR (80%). No new safety signals emerged. Most common adverse events were gastrointestinal disorders (56%), psychiatric/mood disorders (48%), skin rash/hypersensitivity (44%), cardiovascular (40%), and hepatic (32%) events. The trial was prematurely terminated due to the substantially altered risk‐benefit profile of buparlisib. Nevertheless, PIK3CA mutations emerged as a clinically feasible and useful biomarker for combined PI3K inhibition and endocrine therapy in patients with HR+ breast cancer. Further biomarker‐stratified studies with isoform‐specific PI3K inhibitors are warranted. EudraCT No: 2014‐000599‐24., This phase II study evaluated the efficacy and safety of buparlisib plus tamoxifen in pretreated patients with advanced HR+/HER2− breast cancer, stratified for PIK3CA mutations and/or loss of PTEN expression in tumor tissue and circulating blood DNA. A signal for higher buparlisib/tamoxifen activity in patients with PIK3CA‐mutated tumors was obtained. Our findings support the value of somatic PIK3CA mutations as predictive biomarker for PI3K‐targeting therapies combined with antihormonal treatment in metastatic HR+ breast cancer.

Fabian Mairinger,1 Agnes Bankfalvi,1 Kurt Werner Schmid,1 Elena Mairinger,2 Pawel Mach,3 Robert FH Walter,2 Sabrina Borchert,1 Sabine Kasimir-Bauer,3 Rainer Kimmig,3 Paul Buderath3 1Institute for Pathology, University Hospital Essen, Essen, Germany; 2Ruhrlandklinik, West German Lung Centre, University Hospital Essen, University of Duisburg-Essen, Essen, Germany; 3Department of Gynecology and Obstetrics, University Hospital Essen, Essen, GermanyCorrespondence: Paul BuderathDepartment of Gynecology and Obstetrics, University Hospital Essen, Hufelandstraße 55, Essen 45122, GermanyTel +49 201 723 2442Email paul.buderath@uk-essen.dePurpose: Response to platinum-based therapy is a major prognostic factor in high-grade serous ovarian cancer (HGSOC). While the exact mechanisms of platinum-resistance remain unclear, evidence is accumulating for a connection between the organism’s immune-response and response to platinum. However, predictive tools are missing. This study was performed to examine the putative role of the genetic tumor immune-microenvironment in mediating differential chemotherapy response in HGSOC patients.Patients and methods: Expression profiling of 770 immune-related genes was performed in tumor tissues from 23 HGSOC cases. Tumors were screened for prognostic and predictive biomarkers using the NanoString nCounter platform for digital gene expression analysis with the appurtenant PanCancer Immune Profiling panel. As validation cohort, gene expression data (RNA Seq) of 303 patients with epithelial ovarian carcinoma (EOC) were retrieved from the The Cancer Genome Atlas (TCGA) database. Different scoring-systems were computed for prediction of risk-of-resistance to cisplatin, disease-free survival (DFS) and overall survival (OS).Results: Validated on the TCGA-dataset, the developed scores identified 11 significantly differentially expressed genes (p