Down-regulation of E-cadherin enhances prostate cancer chemoresistance via Notch signaling

Abstract Background The chemoresistance of prostate cancer (PCa) is invariably associated with the aggressiveness and metastasis of this disease. New emerging evidence indicates that the epithelial-to-mesenchymal transition (EMT) may play pivotal roles in the development of chemoresistance and metastasis. As a hallmark of EMT, E-cadherin is suggested to be a key marker in the development of chemoresistance. However, the molecular mechanisms underlying PCa chemoresistance remain unclear. The current study aimed to explore the association between EMT and chemoresistance in PCa as well as whether changing the expression of E-cadherin would affect PCa chemoresistance. Methods Parental PC3 and DU145 cells and their chemoresistant PC3-TxR and DU145-TxR cells were analyzed. PC3-TxR and DU145-TxR cells were transfected with E-cadherin-expressing lentivirus to overexpress E-cadherin; PC3 and DU145 cells were transfected with small interfering RNA to silence E-cadherin. Changes of EMT phenotype-related markers and signaling pathways were assessed by Western blotting and quantitative real-time polymerase chain reaction. Tumor cell migration, invasion, and colony formation were then evaluated by wound healing, transwell, and colony formation assays, respectively. The drug sensitivity was evaluated using MTS assay. Results Chemoresistant PC3-TxR and DU145-TxR cells exhibited an invasive and metastatic phenotype that associated with EMT, including the down-regulation of E-cadherin and up-regulation of Vimentin, Snail, and N-cadherin, comparing with that of parental PC3 and DU145 cells. When E-cadherin was overexpressed in PC3-TxR and DU145-TxR cells, the expression of Vimentin and Claudin-1 was down-regulated, and tumor cell migration and invasion were inhibited. In particular, the sensitivity to paclitaxel was reactivated in E-cadherin-overexpressing PC3-TxR and DU145-TxR cells. When E-cadherin expression was silenced in parental PC3 and DU145 cells, the expression of Vimentin and Snail was up-regulated, and, particularly, the sensitivity to paclitaxel was decreased. Interestingly, Notch-1 expression was up-regulated in PC3-TxR and DU145-TxR cells, whereas the E-cadherin expression was down-regulated in these cells comparing with their parental cells. The use of γ-secretase inhibitor, a Notch signaling pathway inhibitor, significantly increased the sensitivity of chemoresistant cells to paclitaxel. Conclusion The down-regulation of E-cadherin enhances PCa chemoresistance via Notch signaling, and inhibiting the Notch signaling pathway may reverse PCa chemoresistance.https://deepblue.lib.umich.edu/bitstream/2027.42/136217/1/40880_2017_Article_203.pd

Control capacity and bimodality in target control

Controlling large networks is a fundamental problem and a great challenge in network science. Typically, full control is not necessary and infeasible. In many cases, only a preselected subset of nodes is required to be controlled, which is the target control problem. Each node does not participate in controlling the target set with equal probability, prompting us to quantify their contributions for target control. Here we develop a random sampling method to estimate the likelihood of each node participating as a driver node in target control configurations and demonstrate the unbiasedness of sampling. Each node is assigned with a role of critical, intermittent or redundant as it appears in all, some and none of the minimum driver node sets accordingly. We apply the method to Erdős-Rényi (ER) and scale-free (SF) networks and find that the fractions of critical and intermittent nodes increase as the scale of the target set increases. Furthermore, when the size of target node is fixed in SF networks, the fraction of redundant nodes may show a bimodal behavior as the networks become denser, leading to two control modes: centralized control and distributed control. The findings help understand the dynamics of control and offer tools for target control in complex systems

Emerging roles of circular RNAs in gastric cancer metastasis and drug resistance

Abstract Gastric cancer (GC) is an aggressive malignancy with a high mortality rate and poor prognosis, primarily caused by metastatic lesions. Improved understanding of GC metastasis at the molecular level yields meaningful insights into potential biomarkers and therapeutic targets. Covalently closed circular RNAs (circRNAs) have emerged as crucial regulators in diverse human cancers including GC. Furthermore, accumulating evidence has demonstrated that circRNAs exhibit the dysregulated patterns in GC and have emerged as crucial regulators in GC invasion and metastasis. However, systematic knowledge regarding the involvement of circRNAs in metastatic GC remains obscure. In this review, we outline the functional circRNAs related to GC metastasis and drug resistance and discuss their underlying mechanisms, providing a comprehensive delineation of circRNA functions on metastatic GC and shedding new light on future therapeutic interventions for GC metastases

Table_1_The MYC Paralog-PARP1 Axis as a Potential Therapeutic Target in MYC Paralog-Activated Small Cell Lung Cancer.docx

Poly (ADP-ribose) polymerase 1 (PARP1) is highly expressed in small cell lung cancer (SCLC) and has emerged as an attractive target for treatment of SCLC. However, the clinical significance of PARP1 expression in SCLC remains elusive. In this study, we showed that high PARP1 expression was associated with better overall survival (OS), and was positively correlated with the expression of MYC paralogs in patients with SCLC. We demonstrated that PARP1 was transcriptionally regulated by MYC paralogs. Integrative analysis of multiple RNA-seq data sets indicated that DNA damage response (DDR) genes involved in the replication stress response (RSR) and homologous recombination (HR) repair pathways were highly enriched in MYC paralog-addicted SCLC cell models and in human SCLC specimens. Targeting the MYC paralog-PARP1 axis with concomitant BET and PARP inhibition resulted in synergistic effects in MYC paralog-activated SCLC. Our study identified a critical PARP1 regulatory pathway, and provided evidence for a rational combination treatment strategy for MYC paralog-activated SCLC.</p

Structural basis of the novel S. pneumoniae virulence factor, GHIP, a glycosyl hydrolase 25 participating in host-cell invasion.

Pathogenic bacteria produce a wide variety of virulence factors that are considered to be potential antibiotic targets. In this study, we report the crystal structure of a novel S. pneumoniae virulence factor, GHIP, which is a streptococcus-specific glycosyl hydrolase. This novel structure exhibits an α/β-barrel fold that slightly differs from other characterized hydrolases. The GHIP active site, located at the negatively charged groove in the barrel, is very similar to the active site in known peptidoglycan hydrolases. Functionally, GHIP exhibited weak enzymatic activity to hydrolyze the PNP-(GlcNAc)5 peptidoglycan by the general acid/base catalytic mechanism. Animal experiments demonstrated a marked attenuation of S. pneumoniae-mediated virulence in mice infected by ΔGHIP-deficient strains, suggesting that GHIP functions as a novel S. pneumoniae virulence factor. Furthermore, GHIP participates in allowing S. pneumoniae to colonize the nasopharynx and invade host epithelial cells. Taken together, these findings suggest that GHIP can potentially serve as an antibiotic target to effectively treat streptococcus-mediated infection

Adherence and invasion of the <i>ΔGHIP</i> mutant into host cells <i>in vitro</i>.

<p>(A) & (B) <i>S. pneumoniae</i> type R6 and their isogenic R6Δ<i>GHIP</i> mutants were examined for adherence to A549 and CNE2 cells, respectively. (C) & (D) <i>S. pneumoniae</i> type R6 and their isogenic R6Δ<i>GHIP</i> were examined for invasion into A549 and CNE2 cells, respectively. Infection experiments were conducted for 4 h at 37°C. Wild-type <i>S. pneumoniae</i> and GHIP-deficient mutants were generated to be devoid of pneumolysin in order to avoid destruction of the monolayer in the <i>in vitro</i> infection system. Scoring the number of adherent and invasive bacteria indicate that adhesion and invasion are substantially reduced for GHIP-deficient <i>S. pneumoniae</i>. Results are presented as the mean ± standard deviation for at least three independent experiments. Asterisks and triangles denote values significantly different from wild-type by Student’s <i>t</i>-test (**, P<0.01; ▴, P<0.05).</p

The glycosyl hydrolase activity of <i>S. pneumoniae</i> GHIP.

<p>(A) <i>S. pneumoniae</i> GHIP (green) superimposed on its homolog from <i>Bacillus anthracis</i>, PlyB (cyan) (PDB code 2NW0). The magenta arrow points toward the major difference, where the N-terminal regions form a helix (α1) which is absent in PlyB. The sticks represent the four key acidic residues to their enzyme activities, inculding Asp56, Asp154, Glu156, and Asp245 of GHIP and Asp6, Asp90, Asp92, and Asp171 of PlyB. (B) The enlarged image of the four key residues at the active site. Close up view of <i>S. pneumoniae</i> GHIP showing overlay of key acidic residues: Asp56, Asp154, Glu156, and Asp245 of GHIP and Asp6, Asp90, Asp92, and Asp171 of PlyB, which exhibit similar locations and orientations. (C) The month of TIM barrel in <i>S. pneumoniae</i> GHIP is active site which contains 14 residues in sticks, including Asp56, Ser58, Ser84, Tyr121, Tyr123, Glu154, Glu156, Asp157, Tyr185, Tyr209, Asp212, Ser233, Asp243 and Asp245. The GHIP structure is shown in the context of a transparent (gray) surface. (D) The enlarged image of the 14 residues at the active site and the background is the electrostatic potential surface of <i>S. pneumoniae</i> GHIP. Saturated red indicates Φ<−10 kiloteslas/e, and saturated blue indicates Φ>10 kiloteslas/e, T = 20°C. (E) & (F) The temperature and pH activity analyses of <i>S. pneumoniae</i> GHIP. Peptidoglycan hydrolase activity was measured at various pH (4.0 to 8.0) and temperatures (25 to 45°C) ranges as described in the Materials and Methods. (G) Hydrolase activity of <i>S. pneumoniae</i> GHIP on PNP-(GlcNAc)₅. Lane 1 represents the positive control using HEWL (egg white lysozyme); lane 2 is native GHIP; lanes 3–6 are active-site mutants D56A, D154A, E156A, and D245A, respectively. Asterisks denote values significantly different from the wild-type strain by Student’s <i>t</i>-test (*, P<0.05; **, P<0.01).</p

Animal and colonization experiments testing <i>S. pneumoniae</i> GHIP function.

<p>(A) & (B) The effect of the <i>GHIP</i> deletion mutation on virulence. Groups of 18 BALB/c mice were intranasally or intraperitoneally challenged with 1.0 × 10⁸ and 1.0 × 10³ CFU, respectively, of D39 or the isogenic <i>ΔGHIP</i> mutant. Each datum point represents one mouse. Solid line, wild-type D39; dotted line, <i>ΔGHIP</i> mutant. Asterisks denote values significantly different from wild-type by Student’s <i>t-</i>test (*, P<0.05). (C) The effect of the <i>GHIP</i> deletion mutation on bacteria recovered from nasopharynxes, lungs, and blood samples of BALB/c mice after intranasal challenge. BALB/c mice were intranasally challenged with either wild-type D39 or the <i>ΔGHIP</i> mutant at 1.0 × 10⁸CFU/mouse. At 12, 24, and 36 h post-infection, six mice from each group were scarified, and the number of recovered bacteria was determined by plating on blood agar. Results are expressed as log₁₀ CFUs per gram tissue and represent individually recorded values for each mouse. Horizontal bars represent geometric means. Asterisks denote values significantly different from wild-type by Student’s <i>t-</i>test (*, P<0.05).</p