Pancreatic ductal adenocarcinoma (PDA) has the worst prognosis of all malignancies, and current therapeutic options do not target cancer stem cells (CSCs), which may be the reason for the extreme aggressiveness. The dietary agents sulforaphane and quercetin enriched e.g., in broccoli, and the main and best studied green tea catechin EGCG hold promise as anti-CSC agents in PDA. We examined the efficacy of additional catechins and the combination of these bioactive agents to stem cell features and miRNA signaling. Two established and one primary PDA cell line and non-malignant pancreatic ductal cells were used. Whereas each agent strongly inhibited colony formation, the catechins ECG and CG were more effective than EGCG. A mixture of green tea catechins (GTCs) significantly inhibited viability, migration, expression of MMP-2 and -9, ALDH1 activity, colony and spheroid formation and induced apoptosis, but the combination of GTCs with sulforaphane or quercetin was superior. Following treatment with bioactive agents, the expression of miR-let7-a was specifically induced in cancer cells but not in normal cells and it was associated with K-ras inhibition. These data demonstrate that sulforaphane, quercetin and GTC complement each other in inhibition of PDA progression by induction of miR-let7-a and inhibition of K-ras.

Ferroportin (FPN) exports iron from duodenal enterocytes, macrophages, and hepatocytes to maintain systemic iron homeostasis. In addition, FPN is expressed in various cancer cells. Here, we show that in lung cancer, FPN expression is regulated by miR-20a. Within the FPN-3′-untranslated region (3′UTR), we identify and experimentally validate three evolutionarily conserved target sites for the microRNA (miRNA) members of the miR-17 seed family, including miR-20a. Our analysis of RNA sequencing data from patients with lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) revealed that FPN messenger RNA (mRNA) levels are significantly decreased in tumor compared to matched healthy tissue, while miR-20a levels are increased. A significant negative correlation of miR-20a and FPN expression was observed. Functional studies further demonstrate that FPN is post-transcriptionally regulated by miR-20a in non-small cell lung cancer (NSCLC) cells and that overexpression or knockdown of miR-20a or FPN affects NSCLC proliferation and colony formation. Taken together, our data suggest that increased expression of miR-20 in lung cancer may decrease iron export, leading to intracellular iron retention, which, in turn, favors cell proliferation.Key messagesmiR-20a controls expression of the iron exporter ferroportin (FPN) by binding to highly conserved target sites in its 3′UTR.Expression of miR-20a is inversely correlated to FPN in lung cancer.Low FPN expression stimulates proliferation and colony formation of non-small cell lung cancer (NSCLC) cells, possibly by increasing iron availability for cancer cell proliferation.Electronic supplementary materialThe online version of this article (doi:10.1007/s00109-015-1362-3) contains supplementary material, which is available to authorized users.

RNA-binding proteins (RBPs) are key regulators of posttranscriptional processes such as RNA maturation, localization, turnover and translation. Despite their dysregulation in various diseases including cancer, the landscape of RBP expression in human cancer has not been well elucidated. Here, we built a comprehensive expression landscape of 1504 RBPs across 16 human cancer types, which revealed that RBPs are predominantly upregulated in tumours and this phenomenon is affected by the tumour immune subtypes and microenvironment. Across different cancer types, 109 RBPs are consistently upregulated while 41 RBPs are consistently downregulated. These up-regulated and down-regulated RBPs show distinct molecular characteristics and prognostic effects, whereas their dysregulation is mediated by distinct cis/trans-regulatory mechanisms. Finally, we validated one candidate PABPC1L that might promote colon tumorigenesis by regulating mRNA splicing. In summary, we built a comprehensive expression landscape of RBPs across different cancer types and identified consistently dysregulated RBPs which could be novel targets for developing broad-spectrum anticancer agents. ARTICLE HISTORY

Reactive oxygen species (ROS) are highly reactive oxygen-containing chemical species formed as a by-product of normal aerobic respiration and also from a number of other cellular enzymatic reactions. ROS function as key mediators of cellular signaling pathways involved in proliferation, survival, apoptosis, and immune response. However, elevated and sustained ROS production promotes tumor initiation by inducing DNA damage or mutation and activates oncogenic signaling pathways to promote cancer progression. Recent studies have shown that ROS can facilitate carcinogenesis by controlling microRNA (miRNA) expression through regulating miRNA biogenesis, transcription, and epigenetic modifications. Likewise, miRNAs have been shown to control cellular ROS homeostasis by regulating the expression of proteins involved in ROS production and elimination. In this review, we summarized the significance of ROS in cancer initiation, progression, and the regulatory crosstalk between ROS and miRNAs in cancer.