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.

Dysregulation of apoptosis may support tumorigenesis by allowing cells to live beyond their normally intended life span. The various receptors for tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) are located on chromosome 8p21.2, a region frequently deleted in ovarian cancer. Lack of expression of TRAIL receptor 1 (death receptor 4, DR4) correlates with resistance to TRAIL-induced apoptosis in ovarian cancer cells. Reconstitution of DR4 in the TRAIL-resistant A2780 ovarian cancer cell line was investigated with the demethylating agent 5-aza-2′-deoxycytidine and transient gene transfer. Regulation of other genes in the TRAIL pathway by 5-aza-2′-deoxycytidine was assessed in DNA GeneChip experiments. Primary ovarian cancers were analyzed by methylation-specific PCR and immunohistochemical analysis of a tissue microarray. Regulation of DR4 expression by demethylation or transient transfection is of functional relevance for TRAIL resistance in an ovarian cancer cell line. Hypermethylation of the DR4 promoter could be found in 10 of 36 (27.7%) DNAs isolated from ovarian cancer tissue. In an independent set of 68 ovarian cancer cases, a complete loss or down-regulation of DR4 protein expression was observed 10.3% and 8.8% patients, respectively. A significant (P = 0.019) majority of these patients was below 50 years of age. Our findings show a functional relevance of the level of DR4 expression in ovarian cancer and suggest a substantial contribution of DR4 hypermethylation and consequent loss of DR4 expression to ovarian cancer pathogenesis, particularly in premenopausal patients.

Summary: N₂ fixation is an O₂‐sensitive process and some filamentous diazotrophic cyanobacteria that grow performing oxygenic photosynthesis confine their N₂ fixation machinery to heterocysts, specialized cells that maintain a reducing environment adequate for N₂ fixation. Respiration is thought to contribute to the diazotrophic metabolism of heterocysts and the genome of the heterocyst‐forming cyanobacterium Anabaena sp. PCC 7120 bears three gene clusters putatively encoding cytochrome c oxidases. Transcript analysis of these cox gene clusters through RNA/DNA hybridization identified two cox operons, cox2 and cox3, that are induced after nitrogen step‐down in an NtcA‐ and HetR‐dependent manner and appear to be expressed specifically in heterocysts. In contrast, cox1 was expressed only in vegetative cells. Expression of cox2 and cox3 occurred at an intermediate stage (about 9 h) during the process of heterocyst development following nitrogen step‐down. Inactivation of genes in the two inducible cox operons, but not separately in either of them, strongly reduced nitrogenase activity and prevented diazotrophic growth in aerobic conditions. These results show that the nitrogen‐regulated cytochrome c oxidase‐type respiratory terminal oxidases Cox2 and Cox3 are essential for heterocyst function in Anabaena sp. PCC 7120.

Tumor cachexia is an important prognostic parameter in epithelial ovarian cancer (EOC). Tumor cachexia is characterized by metabolic and inflammatory disturbances. These conditions might be reflected by body composition measurements (BCMs) ascertained by pre-operative computed tomography (CT). Thus, we aimed to identify the prognostically most relevant BCMs assessed by pre-operative CT in EOC patients. We evaluated muscle BCMs and well established markers of nutritional and inflammatory status, as well as clinical-pathological parameters in 140 consecutive patients with EOC. Furthermore, a multiplexed inflammatory marker panel of 25 cytokines was used to determine the relationship of BCMs with inflammatory markers and patient’s outcome. All relevant parameters were evaluated in uni- and multivariate survival analysis. Muscle attenuation (MA)—a well established BCM parameter—is an independent prognostic factor for survival in multivariate analysis (HR 2.25; p = 0.028). Low MA—reflecting a state of cachexia—is also associated with residual tumor after cytoreductive surgery (p = 0.046) and with an unfavorable performance status (p = 0.015). Moreover, MA is associated with Eotaxin and IL-10 out of the 25 cytokine multiplex marker panel in multivariate linear regression analysis (p = 0.021 and p = 0.047, respectively). MA—ascertained by routine pre-operative CT—is an independent prognostic parameter in EOC patients. Low MA is associated with the inflammatory, as well as the nutritional component of cachexia. Therefore, the clinical value of pre-operative CT could be enhanced by the assessment of MA.

BACKGROUND: Loss of heterozygosity on chromosomal band 8p22 is a common event in several epithelial tumors including ovarian carcinoma. So far, no clear evidence for a tumor suppressor gene (TSG) in this region has been found.METHODS: On the basis of publicly available expression data in ovarian tissues, the authors selected the eight most noteworthy genes from 8p22 (DLC1, N33, ZDHHC2, FLJ32642, PDGFRL, MTSG1, PCM1, and EFA6R) for a detailed expression analysis in 58 primary ovarian carcinoma tissues and in 38 ovarian cancer cell lines by using quantitative real‐time reverse transcriptase‐polymerase chain reaction (qRT‐PCR). Expression data were correlated to various clinicopathologic characteristics and survival.RESULTS: Two genes showed a significantly (P< 0.05) lower expression in grade 3 tumors compared with tumors of lower grade (N33) or compared with normal controls and tumors with lower grade (EFA6R). Expression of N33 and EFA6R seems to have an impact on survival, in particular when the combined expression of both genes was used as predictive factor (P< 0.003). In addition, N33 and EFA6R showed a complete loss of expression in several ovarian cancer cell lines. Three genes (FLJ32642, MTSG1, and PCM1) had a significantly (P< 0.001, P< 0.004, and P< 0.001) lower expression in primary ovarian carcinoma compared with controls (ovarian tissues and cysts).CONCLUSIONS: Two to five new potential tumor suppressor or antagonizing gene candidates (N33 and EFA6R with impact on survival, and potentially FLJ32642, MTSG1, and PCM1) for ovarian carcinoma, were identified from the chromosomal band 8p22 and are promising candidates for further functional analysis in ovarian carcinoma. Cancer 2005. © 2005 American Cancer Society.