Despite a strong rationale for why cancer cells are susceptible to redox-targeting drugs, such drugs often face tumor resistance or dose-limiting toxicity in preclinical and clinical studies. An ...important reason is the lack of specific biomarkers to better select susceptible cancer entities and stratify patients. Using a large panel of lung cancer cell lines, we identified a set of “antioxidant-capacity” biomarkers (ACB), which were tightly repressed, partly by STAT3 and STAT5A/B in sensitive cells, rendering them susceptible to multiple redox-targeting and ferroptosis-inducing drugs. Contrary to expectation, constitutively low ACB expression was not associated with an increased steady state level of reactive oxygen species (ROS) but a high level of nitric oxide, which is required to sustain high replication rates. Using ACBs, we identified cancer entities with a high percentage of patients with favorable ACB expression pattern, making it likely that more responders to ROS-inducing drugs could be stratified for clinical trials.
RNAi is widely applied to inhibit expression of specific genes, but it is limited by variable efficiency and specificity of empirically designed siRNA or shRNA constructs. This complicates studies ...targeting individual genes and significantly impairs large-scale screens using genome-wide knockdown libraries. Here, we show that ectopic expression of the RISC slicer Argonaute-2 (Ago2, eIF2C2) dramatically enhances RNAi specifically for mRNA targets with perfectly matched binding sites. This effect depends on its endonuclease activity and is uncoupled from its regulation of microRNA expression. To model the application of Ago2 coexpression with shRNA knockdown, we targeted the EGF receptor (EGFR) in lung cancer cells exhibiting oncogene addiction to EGFR. Whereas multiple empirically designed shRNA constructs exhibited highly divergent efficiencies in mediating EGFR knockdown and cell killing, coexpression of Ago2 resulted in uniform and highly specific target gene suppression and apoptosis in EGFR-dependent cells. Codelivery of Ago2 with shRNA constructs or siRNA duplexes thus provides a strategy to enhance the efficacy and the specificity of RNAi in experimental and potentially therapeutic settings.
Lung cancer continues to be the leading cause of cancer-related deaths worldwide, with little improvement in patient survival rates in the past decade. Long non-coding RNAs (lncRNAs) are gaining ...importance as possible biomarkers with prognostic potential. By large-scale data mining, we identified
as a lncRNA which was significantly downregulated in lung cancer. Low expression of
was associated with recurrence and poor patient survival in lung adenocarcinoma. Moreover, the gene pair of
and its neighbor
were significantly co-regulated.
as well as
negatively correlated with markers for epithelial-to-mesenchymal transition (EMT) and were suppressed by the EMT inducer TGFβ. Hierarchical clustering of gene expression data from lung cancer cell lines could further verify the association of high
/
expression to an epithelial gene signature. Furthermore, higher expression of the
/
locus was associated with lung cancer cell lines with lower migratory capacity. All these data establish
and
as an epithelial-specific marker pair, downregulated during EMT and lung cancer progression, and associated with lower cell migration potential in lung cancer cells.
Transcriptional termination is an important yet incompletely understood aspect of gene expression. Proudfoot, Jopling and colleagues now identify a new Microprocessor-mediated mechanism of ...transcriptional termination, which acts specifically on long noncoding transcripts that serve as microRNA precursors.
Despite decades of skin research, regulation of proliferation and homeostasis in human epidermis is still insufficiently understood. To address the role of mitoses in tissue regulation, we utilized ...human long-term skin equivalents and systematically assessed mitoses during early epidermal development and long-term epidermal regeneration. We now demonstrate four different orientations: (1) horizontal, i.e., parallel to the basement membrane (BM) and suggestive of symmetric divisions; (2) oblique with an angle of 45°-70°; or (3) perpendicular, suggestive of asymmetric division. In addition, we demonstrate a fourth substantial fraction of suprabasal mitoses, many of which are committed to differentiation (Keratin K10-positive). As verified also for normal human skin, this spatial mitotic organization is part of the regulatory program of human epidermal tissue homeostasis. As a potential marker for asymmetric division, we investigated for Numb and found that it was evenly spread in almost all undifferentiated keratinocytes, but indeed asymmetrically distributed in some mitoses and particularly frequent under differentiation-repressing low-calcium conditions. Numb deletion (stable knockdown by CRISPR/Cas9), however, did not affect proliferation, neither in a three-day follow up study by life cell imaging nor during a 14-day culture period, suggesting that Numb is not essential for the general control of keratinocyte division.
Distant metastasis is the predominant cause of death in early-stage non-small cell lung cancer (NSCLC). Currently, it is impossible to predict the occurrence of metastasis at early stages and thereby ...separate patients who could be cured by surgical resection alone from patients who would benefit from additional chemotherapy. In this study, we applied a comparative microarray approach to identify gene expression differences between early-stage NSCLC patients whose cancer ultimately did or did not metastasize during the course of their disease. Transcriptional profiling of 82 microarrays from two patient groups revealed differential expression of several gene families including known predictors of metastasis (e.g., matrix metalloproteinases). In addition, we found S100P, S100A2, trypsinogen C (TRY6), and trypsinogen IVb (PRSS3) to be overexpressed in tumors that metastasized during the course of the disease. In a third group of 42 patients, we confirmed the induction of S100 proteins and trypsinogens in metastasizing tumors and its significant correlation with survival by real-time quantitative reverse transcription-PCR. Overexpression of S100A2, S100P, or PRSS3 in NSCLC cell cultures led to increased transendothelial migration, corroborating the role of S100A2, S100P, and PRSS3 in the metastatic process. Taken together, we provide evidence that expression of S100 proteins and trypsinogens is associated with metastasis and predicts survival in early stages of NSCLC. For the first time, this implicates a role of S100 proteins and trypsinogens in the metastatic process of early-stage NSCLC.
Drosha is a key enzyme in microRNA biogenesis, generating the precursor miRNA (pre-miRNA) by excising the stem-loop embedded in the primary transcripts (pri-miRNA). The specificity for the pri-miRNAs ...and determination of the cleavage site are provided by its binding partner DGCR8, which is necessary for efficient processing. The crucial Drosha domains for pri-miRNA cleavage are the middle part, the two enzymatic RNase III domains (RIIID), and the dsRNA binding domain (dsRBD) in the C-terminus. Here, we identify alternatively spliced transcripts in human melanoma and NT2 cell lines, encoding C-terminally truncated Drosha proteins lacking part of the RIIIDb and the entire dsRBD. Proteins generated from these alternative splice variants fail to bind to DGCR8 but still interact with Ewing sarcoma protein (EWS). In vitro as well as in vivo , the Drosha splice variants are deficient in pri-miRNA processing. However, the aberrant transcripts in melanoma cells do not consistently reduce mature miRNA levels compared with melanoma cell lines lacking those splice variants, possibly owing to their limited abundance. Our findings show that alternative processing-deficient Drosha splice variants exist in melanoma cells. In elevated amounts, these alternatively spliced transcripts could provide one potential mechanism accounting for the deregulation of miRNAs in cancer cells. On the basis of our results, the search for alternative inactive splice variants might be fruitful in different tumor entities to unravel the molecular basis of the previously observed decreased microRNA processing efficiency in cancer.
In mammals, females have two X chromosomes, whereas males have only one. To ensure that the expression of genes from the X chromosome is equal between the two sexes, one X chromosome, dubbed Xi, is ...inactivated in all female cells except eggs. X-chromosome inactivation (XCI) involves the long non-coding RNA (lncRNA) Xist, but only a few proteins that directly bind to Xist have been identified1,2. The development of two techniques for isolating RNA-bound proteins (one described on page 232 of this issue3 and one published in Cell4) now sheds light on more Xist-interacting proteins that have a role in XCI.
Although the number of documented noncoding RNAs (ncRNAs) is rapidly increasing, knowledge of their molecular function is lagging behind. The identification of specific RNA motifs that mediate ...transcript stability, interactions and localization may aid in the prediction of these features in new transcripts and may have potential implications for ncRNA function. Here, we review RNA motifs, focusing on four recent studies identifying nuclear-retention motifs, and discuss the limited specificity of short-RNA motifs and the resulting challenge for effective functional prediction. Future approaches may succeed by integrating combinatorial and cooperative effects of additional partially sequence-based properties.
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