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.

Background. Immunomagnetic EpCAM based methods are used to enrich circulating tumor cells (CTCs) in metastatic breast cancer (mBC) patients. EpCAM negative CTCs may be missed. We addressed the question of the reliability of an EpCAM dependent assay to enrich CTCs. Methods. To elucidate this issue, our study has been designed to assess two different CTC enrichment technologies (i) in EpCAM positive (+) and EpCAM negative cell lines and (ii) in mBC patients in dependency on their respective EpCAM expression. These two technologies encompass one anti-EpCAM immunomagnetic enrichment technology, MACS HEA MicroBeads^® (MACS), and one EpCAM independent density centrifugation method, OncoQuick^® plus (OQ+). Furthermore, the coherence between EpCAM expression in the primary tumor tissue of mBC patients and the CTC detection rates in the corresponding patients is analyzed. Results. (i) MACS recovered significantly more EpCAM (+) than EpCAM (−) tumor cells (p < 0.001) in spiked blood samples. With OQ+ no significantly different recovery rates between EpCAM (+) and EpCAM (−) tumor cells (p = 0.796) were detected. (ii) In mBC patients MACS yielded a significantly higher (p = 0.024) detection rate of EpCAM (+) CTCs. No statistically significant difference (p = 0.070) was found concerning the EpCAM status-based detection rate of CTCs by OQ+. (iii) CTC detection rates are independent of the primary tumors’ EpCAM expression. Conclusions. EpCAM (−) CTCs can not be detected by immunomagnetic EpCAM dependent enrichment methods. EpCAM independent enrichment technologies seem to be superior to detect the entire CTC population. Evaluation of CTCs as prognostic marker should compromise EpCAM (+) and (−) subpopulations.

Purpose: To evaluate serum C-reactive protein (CRP) as prognostic variable in patients with epithelial ovarian cancer (EOC). Experimental Design: In a multicenter study, preoperative serum CRP was evaluated in 623 patients with EOC. Results were correlated with clinical data. Results: Mean (SD) preoperative serum CRP was 3.6 (4.8) mg/dL. Serum CRP was significantly associated with International Federation of Gynecologists and Obstetricians stage (P < 0.001) and postoperative residual tumor mass (P < 0.001) but not with histologic grade (P = 0.1) and type (P = 0.7), patients' age (Pearson's correlation coefficient = 0.05; P = 0.2), and serum CA 125 (Pearson's correlation coefficient = 0.02; P = 0.6). Patients with platinum-resistant EOC had significantly higher CRP serum levels compared with patients with platinum-sensitive EOC [6.0 (6.6) mg/dL versus 2.8 (3.8) mg/dL; P < 0.001]. Higher International Federation of Gynecologists and Obstetricians stage (P < 0.001), presence of postoperative residual tumor mass (P < 0.001), tumor grade (P = 0.001), serum CA 125 (P = 0.03), and serum CRP (P = 0.001) were independently associated with overall survival. Patients with serum CRP ≤1 mg/dL versus >1 mg/dL had an overall 5-year survival of 82% versus 58.5% (P < 0.001). Conclusion: Serum CRP can be seen as a novel, widely available independent prognostic variable of ovarian cancer.

We constructed a plasmid for the in vitro synthesis of a competitor RNA for use as an internal exogenous control during reverse transcriptase--PCR (RT-PCR) detection of epidermal growth factor receptor (EGFR) expression. The competitor RNA harbors a 32-base deletion compared with wild-type EGFR mRNA and generates a PCR product that is easily distinguished from the wild-type PCR product by agarose gel electrophoresis. We encountered the problem of heteroduplex formation during later stages of PCR, which could be solved by decreasing the PCR cycle number. This was accompanied by a significant loss of sensitivity. Sensitivity could be restored by using a novel and extremely sensitive DNA stain (SYBR Green I) instead of ethidium bromide.