The G2-phase enriched lncRNA SNHG26 is necessary for proper cell cycle progression and proliferation

Long noncoding RNAs (lncRNAs) are involved in the regulation of cell cycle, although only a few have been functionally characterized. By combining RNA sequencing and ChIP sequencing of cell cycle synchronized HaCaT cells we have previously identified lncRNAs highly enriched for cell cycle functions. Based on a cyclic expression profile and an overall high correlation to histone 3 lysine 4 trimethylation (H3K4me3) and RNA polymerase II (Pol II) signals, the lncRNA SNHG26 was identified as a top candidate. In the present study we report that downregulation of SNHG26 affects mitochondrial stress, proliferation, cell cycle phase distribution, and gene expression in cis- and in trans, and that this effect is reversed by upregulation of SNHG26. We also find that the effect on cell cycle phase distribution is cell type specific and stable over time. Results indicate an oncogenic role of SNHG26, possibly by affecting cell cycle progression through the regulation of downstream MYC-responsive genes.

The lncRNA EPB41L4A-AS1 regulates gene expression in the nucleus and exerts cell type-dependent effects on cell cycle progression

The long non-coding RNA (lncRNA) EPB41L4A-AS1 is aberrantly expressed in various cancers and has been reported to be involved in metabolic reprogramming and as a repressor of the Warburg effect. Although the biological relevance of EPB41L4A-AS1 is evident, its functional role seems to vary depending on cell type and state of disease. By combining RNA sequencing and ChIP sequencing of cell cycle synchronized HaCaT cells we previously identified EPB41L4A-AS1 to be one of 59 lncRNAs with potential cell cycle functions. Here, we demonstrate that EPB41L4A-AS1 exists as bright foci and regulates gene expression in the nucleus in both cis and trans. Specifically, we find that EPB41L4A-AS1 positively regulates its sense overlapping gene EPB41L4A and influences expression of hundreds of other genes, including genes involved in cell proliferation. Finally, we show that EPB41L4A-AS1 affects cell cycle phase distribution, though these effects vary between cell types.

Differential Effects of IGF-1R Small Molecule Tyrosine Kinase Inhibitors BMS-754807 and OSI-906 on Human Cancer Cell Lines

We have determined the effects of the IGF-1R tyrosine kinase inhibitors BMS-754807 (BMS) and OSI-906 (OSI) on cell proliferation and cell-cycle phase distribution in human colon, pancreatic carcinoma, and glioblastoma cell lines and primary cultures. IGF-1R signaling was blocked by BMS and OSI at equivalent doses, although both inhibitors exhibited differential antiproliferative effects. In all pancreatic carcinoma cell lines tested, BMS exerted a strong antiproliferative effect, whereas OSI had a minimal effect. Similar results were obtained on glioblastoma primary cultures, where HGUE-GB-15, -16 and -17 displayed resistance to OSI effects, whereas they were inhibited in their proliferation by BMS. Differential effects of BMS and OSI were also observed in colon carcinoma cell lines. Both inhibitors also showed different effects on cell cycle phase distribution, BMS induced G2/M arrest followed by cell death, while OSI induced G1 arrest with no cell death. Both inhibitors also showed different effects on other protein kinases activities. Taken together, our results are indicative that BMS mainly acts through off-target effects exerted on other protein kinases. Given that BMS exhibits a potent antiproliferative effect, we believe that this compound could be useful for the treatment of different types of tumors independently of their IGF-1R activation status.

Protein convertase subtilisin/Kexin type 9 inhibits hepatocellular carcinoma growth by interacting with GSTP1 and suppressing the JNK signaling pathway

Background PCSK9 has been found to be closely related to the occurrence and development of a variety of tumors. However, the concrete role of PCSK9 and its relationship with HCC development is largely unknown. Methods The expression levels of PCSK9 in HCC tissues and HCC cell lines were determined by quantitative real-time polymerase chain reaction (qRT-PCR), western blot and immunohistochemistry assays. The effects of PCSK9 expression on HCC biological traits were investigated by overexpressing and downregulating PCSK9 protein in vivo and in vitro. The mechanism by which PCSK9 mediates the depolymerization of the GSTP1 dimer and the phosphorylation of the JNK signaling pathway was further investigated. Results PCSK9 is downregulated in human HCC tissues. HCC cell proliferation, cell cycle phase distribution and apoptosis were inhibited by PCSK9 in vitro. PCSK9 suppresses tumor growth and metastasis of HCC in vivo. PCSK9 interacts with GSTP1 and promotes the depolymerization of the GSTP1 dimer and inactivation of the JNK signaling pathway. Furthermore, low PCSK9 protein expression in primary HCC tissues correlated with worse clinical outcomes. Conclusions PCSK9 inhibits HCC cell proliferation, cell cycle phase distribution and apoptosis by interacting with GSTP1 and suppressing the JNK signaling pathway, suggesting that PCSK9 might act as a tumor suppressor and may serve as a therapeutic target for the treatment of HCC.

Anticancer and apoptotic effects of theaflavin-3-gallate in non-small cell lung carcinoma

<p class="Abstract">The objective was to determine the antiproliferative and apoptotic effects of theaflavin-3-gallate in human non-small cell lung cancer cells (A-549) along with determining the effect on cell cycle phase distribution, cell migration and invasion. Cell viability was determined by MTT assay while as phase contrast and fluorescence microscopies were involved to study apoptotic morphologi-cal features in these cells. Flow cytometry investigated the effect of theaflavin-3-gallate on cell cycle phase distribution. Theaflavin-3-gallate treatment led to a substantial cytotoxic effect in A-549 cancer cells with IC₅₀ values of 42.1 µM and 27.9 µM at 24 and 48 hours respectively. Further, 80 and 160 µM dose of theaflavin-3-gallate induced apoptotic features including chromatin margina-tion and micronuclei presence. The population of cells in G2/M phase increased from 2.7% (control) to 6.8%, 17.2% and finally to 46.5% after treatment with 20, 80 and 160 µM concentration of theaflavin-3-gallate respectively indicating G2/M phase cell cycle arrest.</p><p> </p>