Karin Müller-Decker

Cancer cells, immune cells, and stromal cells within the tumor microenvironment (TME) collaboratively influence disease progression and therapeutic responses. The nutrient-limited conditions of the TME, particularly the scarcity of glucose, amino acids, and lipids, challenge cancer cell survival ^1–4 . However, the metabolic constraints faced by immune and stromal cells in comparison to cancer cells, and how these limitations affect therapeutic outcomes, remain poorly understood. Here, we introduce Dual Ribosome Profiling (DualRP), a method that allows for simultaneous analysis of translation and identification of ribosome stalling, revealing amino acid shortages in different cell types within tumors. Using DualRP, we uncover that interactions between cancer cells and fibroblasts trigger an inflammatory response, mitigating amino acid limitations during glucose starvation. In immunocompetent mouse models, we observe that immune checkpoint blockade therapy induces serine and glycine restrictions specifically in T cells, but not in cancer cells. We further demonstrate that these amino acids are essential for optimal T cell function both in vitro and in vivo , highlighting their critical role in effective immunotherapy. Our findings show that therapeutic interventions create distinct metabolic demands across different tumor cell types, with nutrient availability significantly influencing the success of immunotherapy. DualRP’s ability to explore cell type-specific metabolic vulnerabilities offers a promising tool for advancing our understanding of tumor biology and improving therapeutic strategies.

Human induced pluripotent stem cells (hiPSC) harbor the potential to differentiate into diverse cardiac cell types. Previous experimental efforts were primarily directed at the generation of hiPSC-derived cells with ventricular cardiomyocyte characteristics. Aiming at a straightforward approach for pacemaker cell modeling and replacement, we sought to selectively differentiate cells with nodal-type properties. hiPSC were differentiated into spontaneously beating clusters by co-culturing with visceral endoderm-like cells in a serum-free medium. Subsequent culturing in a specified fetal bovine serum (FBS)-enriched cell medium produced a pacemaker-type phenotype that was studied in detail using quantitative real-time polymerase chain reaction (qRT-PCR), immunocytochemistry, and patch-clamp electrophysiology. Further investigations comprised pharmacological stimulations and co-culturing with neonatal cardiomyocytes. hiPSC co-cultured in a serum-free medium with the visceral endoderm-like cell line END-2 produced spontaneously beating clusters after 10–12 days of culture. The pacemaker-specific genes HCN4, TBX3, and TBX18 were abundantly expressed at this early developmental stage, while levels of sarcomeric gene products remained low. We observed that working-type cardiomyogenic differentiation can be suppressed by transfer of early clusters into a FBS-enriched cell medium immediately after beating onset. After 6 weeks under these conditions, sinoatrial node (SAN) hallmark genes remained at high levels, while working-type myocardial transcripts (NKX2.5, TBX5) were low. Clusters were characterized by regular activity and robust beating rates (70–90 beats/min) and were triggered by spontaneous Ca2+ transients recapitulating calcium clock properties of genuine pacemaker cells. They were responsive to adrenergic/cholinergic stimulation and able to pace neonatal rat ventricular myocytes in co-culture experiments. Action potential (AP) measurements of cells individualized from clusters exhibited nodal-type (63.4%) and atrial-type (36.6%) AP morphologies, while ventricular AP configurations were not observed. We provide a novel culture media-based, transgene-free approach for targeted generation of hiPSC-derived pacemaker-type cells that grow in clusters and offer the potential for disease modeling, drug testing, and individualized cell-based replacement therapy of the SAN.

The devastating diseases of human cancer are mimicked in basic and translational cancer research by a steadily increasing number of tumor models, a situation requiring a platform with standardized reports to share model data. Models in Translational Oncology (MiTO) database was developed as a unique Web platform aiming for a comprehensive overview of preclinical models covering genetically engineered organisms, models of transplantation, chemical/physical induction, or spontaneous development, reviewed here. MiTO serves data entry for metastasis profiles and interventions. Moreover, cell lines and animal lines including tool strains can be recorded. Hyperlinks for connection with other databases and file uploads as supplementary information are supported. Several communication tools are offered to facilitate exchange of information. Notably, intellectual property can be protected prior to publication by inventor-defined accessibility of any given model. Data recall is via a highly configurable keyword search. Genome editing is expected to result in changes of the spectrum of model organisms, a reason to open MiTO for species-independent data. Registered users may deposit own model fact sheets (FS). MiTO experts check them for plausibility. Independently, manually curated FS are provided to principle investigators for revision and publication. Importantly, noneditable versions of reviewed FS can be cited in peer-reviewed journals. Cancer Res; 77(10); 2557–63. ©2017 AACR.

Mutational activation of K-Ras is an initiating event of pancreatic ductal adenocarcinomas (PDAC) that may develop either from pancreatic intraepithelial neoplasia (PanIN) or intraductal papillary mucinous neoplasms (IPMN). Cyclooxygenase-2 (COX-2)-derived prostaglandin E₂ (PGE₂) is causally related to pancreatic carcinogenesis. Here, we deciphered the impact of COX-2, a key modulator of inflammation, in concert with active mutant K-Ras^G12D on tumor burden and gene expression signature using compound mutant mouse lines. Concomitant activation of COX-2 and K-Ras^G12D accelerated the progression of pancreatic intraepithelial lesions predominantly with a cystic papillary phenotype resembling human IPMN. Transcriptomes derived from laser capture microdissected preneoplastic lesions of single and compound mutants revealed a signature that was significantly enriched in Notch1 signaling components. In vitro, Notch1 signaling was COX-2-dependent. In line with these findings, human IPMN stratified into intestinal, gastric and pancreatobillary types displayed Notch1 immunosignals with high prevalence, especially in the gastric lesions. In conclusion, a yet unknown link between activated Ras, protumorigenic COX-2 and Notch1 in IPMN onset was unraveled.

Introduction: Breast cancer stem cells are suspected to be responsible for tumour recurrence, metastasis formation as well as chemoresistance. Consequently, great efforts have been made to understand the molecular mechanisms underlying cancer stem cell maintenance. In order to study these rare cells in-vitro, they are typically enriched via mammosphere culture. Here we developed a mammosphere-based negative selection shRNAi screening system suitable to analyse the involvement of thousands of genes in the survival of cells with cancer stem cell properties. Methods: We describe a sub-population expressing the stem-like marker CD44⁺/CD24^-/low in SUM149 that were enriched in mammospheres. To identify genes functionally involved in the maintenance of the sub-population with cancer stem cell properties, we targeted over 5000 genes by RNAi and tested their ability to grow as mammospheres. The identified candidate ATG4A was validated in mammosphere and soft agar colony formation assays. Further, we evaluated the influence of ATG4A expression on the sub-population expressing the stem-like marker CD44⁺/CD24^low. Next, the tumorigenic potential of SUM149 after up- or down-regulation of ATG4A was examined by xenograft experiments. Results: Using this method, Jak-STAT as well as cytokine signalling were identified to be involved in mammosphere formation. Furthermore, the autophagy regulator ATG4A was found to be essential for the maintenance of a sub-population with cancer stem cell properties and to regulate breast cancer cell tumourigenicity in vivo. Conclusion: In summary, we present a high-throughput screening system to identify genes involved in cancer stem cell maintenance and demonstrate its utility by means of ATG4A.

Cyclooxygenase (COX)-derived prostaglandins (PGs) exhibit manifold functions in acute and chronic skin inflammation induced by a number of physical (ultraviolet (UV) light, wounding) and chemical (12-O-tetradecanoylphorbol 13-acetate (TPA), arachidonic acid) noxious stimuli. Depending on the challenge and the context, constitutively expressed COX-1 or the transiently induced COX-2 isoform are of relevance. Moreover, squamous cell carcinoma (SCC) of skin is a prominent example of epithelial neoplasia that consistently overexpresses COX-2 in the parenchyme and the mesenchyme of premalignant and malignant lesions, while COX-1 expression remains unaltered. Pharmacological, clinical, and experimental animal studies as well as a few epidemiological studies document the importance of PG signaling in non-melanoma skin cancer including SCC and basal cell carcinoma (BCC) in humans and mice. Increased levels of PGE₂ and PGF_2α in premalignant and/or malignant epithelial skin cancers are due to the constitutive upregulation of enzymes involved in PG biosynthesis, such as COX-2, and downregulation of the tumor suppressor gene 15-hydroxy-prostaglandin dehydrogenase (15-PGDH), which is involved in the inactivation of PG, thus counteracting the activities of COX. Most remarkably, genetic studies show that mice which are deficient in COX-2 or COX-1 are protected from the development of SCC when applying the multi-stage chemical carcinogenesis protocol. Conversely, the forced overexpression of COX-2 in the proliferative basal compartment of the stratified skin epidermis results in spontaneous hyperplasia and dysplasia in transgenic mice and furthermore a sensitization for cancer development by conferring an auto-promoted skin phenotype. In multi-stage carcinogenesis, it also becomes clear that aberrant COX-2 overexpression and activity are causally involved in tumor promotion and tumor progression rather than initiation. In contrast, using as inducer of carcinogenesis the complete carcinogen UV B light, depletion of COX-2 but not of COX-1 makes mouse skin resistant for SCC, indicating that here, only COX-2 is essential. Depending on the type of challenge, COX-2-dependent signaling contributes to the pre-invasive growth of the skin epidermis by a delayed onset of terminal differentiation, or stimulation of hyperproliferation and survival. With respect to BCC, the genetic ablation of COX-2 but also of COX-1 leads to a strongly reduced tumor burden in the skin of Patched (Ptch)1^+/− mice, which due to the deletion of a Ptch1 allele, spontaneously develop BCC resembling human familial basal cell nevus syndrome and sporadic BCC. Nonsteroidal anti-inflammatory drugs and the COX-2-selective inhibitors (COXibs) exhibit impressive efficacy inhibiting tumor burden in various mouse models of SCC and BCC. Most importantly, in humans the interruption of COX-2 signaling is an effective strategy to treat and chemo-prevent non-melanoma skin cancer in individuals who are at high risk for the disease. However, any potential beneficial effect of this medicine has to be balanced against the adverse effects that are known to be associated with these drugs in a subset of patients.

Cyclooxygenases (COX) 1 and 2 are the key enzymes of prostaglandin biosynthesis. Like in many tissues, in adult skin COX-1 is a constitutive ‘housekeeping’ enzyme, while COX-2 is induced transiently in stress situations such as tissue damage and regeneration. In human skin carcinomas and corresponding early-stage cancer lesions, permanent COX-2 expression and activation is a consistent feature. Knockout and various transgenic approaches and pharmacologic studies show strong evidence for a cause-and-effect relationship between the aberrant COX-2 activation and tumor formation. In skin epidermis, keratin 5 promoter-driven overexpression of COX-2 caused hyperplasia and dysplasia, and sensitized skin for carcinogenesis. Therefore, this model offers the unique possibility of identifying COX-2-dependent and prostaglandin-mediated molecular pathways leading to the formation and malignant progression of early-stage cancer lesions.

Zusammenfassung: Cyclooxygenasen (COX)‐1 und COX‐2 sind die Schrittmacherenzyme in der Prostaglandinbiosynthese und repräsentieren die molekularen Targets für nicht‐steroidale Entzündungshemmer. In gesunden Geweben von Erwachsenen wird in der Regel COX‐1, nicht jedoch COX‐2 exprimiert. Nach Schnittverletzung der Haut oder Auslösung einer akuten irritativen Kontaktdermatitis wird COX‐2 transient in der Epidermis gebildet. Insbesondere die Entwicklung von UV‐induziertem Erythem und Ödem aber auch von Hauttumoren werden maßgeblich durch die Aktivität von COX‐2 beeinflußt. Plattenepithelkarzinome und aktinische Keratosen der Haut gelten als ein prominentes Beispiel von epithelialen Tumoren, für die eine permanente Überexpression der COX‐2 im Tumorparenchym, im entzündlichen Tumorinfiltrat und in Tumorgefäßen ein hervorstechendes Merkmal ist. Mehrstufenkarzinogeneseversuchen in der Maushaut und Experimenten mit transgenen Mäusen zufolge besteht ein kausaler Zusammenhang zwischen aberranter COX‐2‐Expression und Aktivität im Epithel und der Tumorpromotion und ‐progression. Die transgene Überexpression der COX‐2 verursacht nämlich einen autopromovierten Hautphänotyp, d. h. das Enzym sensibilisiert das Gewebe drastisch für die Entwicklung von Plattenepithelkarzinomen. Umgekehrt führt die genetische Ausschaltung der COX‐2, aber auch der COX‐1, in der Maushaut zu einer reduzierten Tumorlast. Die Störung der terminalen Differenzierung der Epidermis scheint ein Hauptmechanismus zu sein, wie COX‐2 zur epidermalen Tumorbildung beiträgt. Aufgrund dieser Erkenntnisse werden COX‐2‐selektive Inhibitoren als vielversprechende Substanzen zur Prävention und Therapie von Hautkrebs eingestuft.