CREB1 activation promotes human papillomavirus oncogene expression and cervical cancer cell transformation.

Human papillomaviruses (HPVs) infect the oral and anogenital mucosa and can cause cancer. The high-risk (HR)-HPV oncoproteins, E6 and E7, hijack cellular factors to promote cell proliferation, delay differentiation and induce genomic instability, thus predisposing infected cells to malignant transformation. cAMP response element (CRE)-binding protein 1 (CREB1) is a master transcription factor that can function as a proto-oncogene, the abnormal activity of which is associated with multiple cancers. However, little is known about the interplay between HPV and CREB1 activity in cervical cancer or the productive HPV lifecycle. We show that CREB is activated in productively infected primary keratinocytes and that CREB1 expression and phosphorylation is associated with the progression of HPV+ cervical disease. The depletion of CREB1 or inhibition of CREB1 activity results in decreased cell proliferation and reduced expression of markers of epithelial to mesenchymal transition, coupled with reduced migration in HPV+ cervical cancer cell lines. CREB1 expression is negatively regulated by the tumor suppressor microRNA, miR-203a, and CREB1 phosphorylation is controlled through the MAPK/MSK pathway. Crucially, CREB1 directly binds the viral promoter to upregulate transcription of the E6/E7 oncogenes, establishing a positive feedback loop between the HPV oncoproteins and CREB1. Our findings demonstrate the oncogenic function of CREB1 in HPV+ cervical cancer and its relationship with the HPV oncogenes.

MicroRNA-18a targeting of the STK4/MST1 tumour suppressor is necessary for transformation in HPV positive cervical cancer.

Human papillomaviruses (HPV) are a major cause of malignancy worldwide. They are the aetiological agents of almost all cervical cancers as well as a sub-set of other anogenital and head and neck cancers. Hijacking of host cellular pathways is essential for virus pathogenesis; however, a major challenge remains to identify key host targets and to define their contribution to HPV-driven malignancy. The Hippo pathway regulates epithelial homeostasis by down-regulating the function of the transcription factor YAP. Increased YAP expression has been observed in cervical cancer but the mechanisms driving this increase remain unclear. We found significant down-regulation of the master Hippo regulatory kinase STK4 (also termed MST1) in cervical disease samples and cervical cancer cell lines compared with healthy controls. Re-introduction of STK4 inhibited the proliferation of HPV positive cervical cells and this corresponded with decreased YAP nuclear localization and decreased YAP-dependent gene expression. The HPV E6 and E7 oncoproteins maintained low STK4 expression in cervical cancer cells by upregulating the oncomiR miR-18a, which directly targeted the STK4 mRNA 3'UTR. Interestingly, miR-18a knockdown increased STK4 expression and activated the Hippo pathway, significantly reducing cervical cancer cell proliferation. Our results identify STK4 as a key cervical cancer tumour suppressor, which is targeted via miR-18a in HPV positive tumours. Our study indicates that activation of the Hippo pathway may offer a therapeutically beneficial option for cervical cancer treatment.

Factors affecting sorption behaviors of tetracycline to soils: Importance of soil organic carbon, pH and Cd contamination.

The abuse of tetracycline arises the risk of antibiotic resistance genes and has been paid much attention. To understand the potential bioavailability of tetracycline (TC) in soil environments, this study explored the behaviors of TC adsorbing to six types of soils sampled from different regions of China. Moreover, the solution pH and existence of Cd2+ effect on TC sorption to soils were investigated to understand the influential factors affecting TC sorption. The results showed that the soil properties and sorption capacity of TC varied significantly with different soils. The sorption capacity of TC to soils might be largely affected by cation exchange capacity (CEC) and soil organic carbon (SOC), while the sorption rate, interaction strength and equilibrium sorption binding might be affected by soil pH, pHPZC, soil inorganic carbon (SIC) and H content. The result of solution pH effect suggested that the predominant sorption mechanism for acid soils might be hydrophobic interactions between soils and H2TC0, and the cation exchange was possibly proposed as the primary mechanism for TC sorption to alkaline soils. Furthermore, the presence of Cd2+ might increase TC sorption to acid soil, while reduce TC sorption to alkaline soil. It is expected that this study may provide important information for predicting the potential fate of TC (or similar antibiotics) in different soils, and thus helping to assess the bioavailability of TC in soils.

Screening of anti-cancer agent using zebrafish: comparison with the MTT assay.

The MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide) assay is a classical method for screening cytotoxic anti-cancer agents. Candidate drugs from the MTT assay need in vivo models to test their efficiency and to assess the absorption, distribution, metabolism, excretion, and toxicity of the drugs. An in vivo screening model could increase the rate of development of anti-cancer drugs. Here, we used zebrafish to screen a library of 502 natural compounds and compared the results with those from an MTT assay of the MCF7 breast cancer cell line. We identified 59 toxic compounds in the zebrafish screen, 21 of which were also identified by the MTT assay, and 28 of which were already known for their anti-cancer and apoptosis-inducing effects. These compounds induced apoptosis and activated the p53 pathway in zebrafish within 3h treatment. Our results indicate that zebrafish is a simple, reliable and highly efficient in vivo tool for cancer drug screening, and could complement the MTT assay.

Argonaute Utilization for miRNA Silencing Is Determined by Phosphorylation-Dependent Recruitment of LIM-Domain-Containing Proteins.

As core components of the microRNA-induced silencing complex (miRISC), Argonaute (AGO) proteins interact with TNRC6 proteins, recruiting other effectors of translational repression/mRNA destabilization. Here, we show that LIMD1 coordinates the assembly of an AGO-TNRC6 containing miRISC complex by binding both proteins simultaneously at distinct interfaces. Phosphorylation of AGO2 at Ser 387 by Akt3 induces LIMD1 binding, which in turn enables AGO2 to interact with TNRC6A and downstream effector DDX6. Conservation of this serine in AGO1 and 4 indicates this mechanism may be a fundamental requirement for AGO function and miRISC assembly. Upon CRISPR-Cas9-mediated knockout of LIMD1, AGO2 miRNA-silencing function is lost and miRNA silencing becomes dependent on a complex formed by AGO3 and the LIMD1 family member WTIP. The switch to AGO3 utilization occurs due to the presence of a glutamic acid residue (E390) on the interaction interface, which allows AGO3 to bind to LIMD1, AJUBA, and WTIP irrespective of Akt signaling.