Circular RNAs are a recently (re-)discovered abundant RNA species with presumed function as miRNA sponges, thus part of the competing endogenous RNA network. We analysed the expression of circular and linear RNAs and proliferation in matched normal colon mucosa and tumour tissues. We predicted >1,800 circular RNAs and proved the existence of five randomly chosen examples using RT-qPCR. Interestingly, the ratio of circular to linear RNA isoforms was always lower in tumour compared to normal colon samples and even lower in colorectal cancer cell lines. Furthermore, this ratio correlated negatively with the proliferation index. The correlation of global circular RNA abundance (the circRNA index) and proliferation was validated in a non-cancerous proliferative disease, idiopathic pulmonary fibrosis, ovarian cancer cells compared to cultured normal ovarian epithelial cells, and 13 normal human tissues. We are the first to report a global reduction of circular RNA abundance in colorectal cancer cell lines and cancer compared to normal tissues and discovered a negative correlation of global circular RNA abundance and proliferation. This negative correlation seems to be a general principle in human tissues as validated with three different settings. Finally, we present a simple model how circular RNAs could accumulate in non-proliferating cells.

In this study we aimed to analyze the biological mechanisms underlying apparently different modes of peritoneal tumor spread in serous ovarian cancer: miliary (widespread, millet-like lesions) versus non-miliary (bigger, exophytically growing implants). Tumor tissues and ascites from 23 chemotherapy naive patients were analyzed by RNA-sequencing and flow cytometry. On the basis of differential gene expression between miliary and non-miliary, gene signatures were developed. A calculated tumor spread factor revealed a significant independent negative impact of miliary spread on overall survival (HR 3.77; CI95 1.14–12.39; p = 0.029) in an independent cohort of 165 serous ovarian cancer patients. Comparing previously published epithelial-mesenchymal transition (EMT) gene signatures, non-miliary spread correlated significantly with a reduced epithelial status. We conclude that serous ovarian cancer is a heterogeneous disease with distinct modes of peritoneal tumor spread, differing not only in clinical appearance, but also in molecular characteristics and outcome.. EMT, peritoneal inflammation status, and therapeutic options are discussed.SignificanceMore than half of serous epithelial ovarian cancer patients present with a newly described type of intraperitoneal tumor spread, associated with differences in the inflammation status, activated oncogenic pathways, lack of EMT, and thus reduced overall survival. Both, the diminished immune reaction and the enhanced epithelial and malignant characteristics of the tumor cells open new avenues for therapeutic options and strategies, like Catumaxomab, already in clinical use.

Cancer metabolism is characterized by alterations including aerobic glycolysis, oxidative phosphorylation, and need of fuels and building blocks. Targeted metabolomics of preoperative and follow-up sera, ascites, and tumor tissues, RNA sequencing of isolated tumor cells, local and systemic chemokine, and local immune cell infiltration data from up to 65 high-grade serous ovarian cancer patients and 62 healthy controls were correlated to overall survival and integrated in a Systems Medicine manner. Forty-three mainly (poly)unsaturated glycerophospholipids and four essential amino acids (citrulline) were significantly reduced in patients with short compared with long survival and healthy controls. The glycerophospholipid fingerprint is identical to the fingerprint from isolated (very) low-density lipoproteins (vLDL), indicating that the source of glycerophospholipids consumed by tumors is (v)LDL. A glycerophospholipid-score (HR, 0.46; = 0.007) and a 100-gene signature (HR, 0.65; = 0.004) confirmed the independent impact on survival in training ( = 65) and validation ( = 165) cohorts. High concentrations of LDLs and glycerophospholipids were independently predictors for favorable survival. Patients with low glycerophospholipids presented with more systemic inflammation (C-reactive protein and fibrinogen negatively and albumin positively correlated) but less adaptive immune cell tumor infiltration (lower tumor and immune cell PD-L1 expression), less oxygenic respiration and increased triglyceride biosynthesis in tumor cells, and lower histone expressions, correlating with higher numbers of expressed genes and more transcriptional noise, a putative neo-pluripotent tumor cell phenotype. Low serum phospholipids and essential amino acids are correlated with worse outcome in ovarian cancer, accompanied by a specific tumor cell phenotype. .