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The potent ability of CRISPR/Cas9 system to inhibit the expression of targeted gene is being exploited as a new class of therapeutics for a variety of diseases. However, the efficient and safe delivery of CRISPR/Cas9 into specific cell populations is still the principal challenge in the clinical development of CRISPR/Cas9 therapeutics. In this study, a flexible aptamer-liposome-CRISPR/Cas9 chimera was designed to combine efficient delivery and increased flexibility. Our chimera incorporated an RNA aptamer that specifically binds prostate cancer cells expressing the prostate-specific membrane antigen as a ligand. Cationic liposomes were linked to aptamers by the post-insertion method and were used to deliver therapeutic CRISPR/Cas9 that target the survival gene, polo-like kinase 1, in tumor cells. We demonstrate that the aptamer-liposome-CRISPR/Cas9 chimeras had a significant cell-type binding specificity and a remarkable gene silencing effect in vitro. Furthermore, silencing promoted a conspicuous regression of prostate cancer in vivo. Importantly, the approach described here provides a universal means of cell type-specific CRISPR/Cas9 delivery, which is a critical goal for the widespread therapeutic applicability of CRISPR/Cas9 or other nucleic acid drugs.

Polo-like kinase PLK1 is a cell cycle protein that plays multiple roles in promoting cell cycle progression. Among the many roles, the most prominent role of PLK1 is to regulate the mitotic spindle formation checkpoint at the M-phase. Recently we reported the expression of SLAMF3 in Hepatocytes and show that it is down regulated in tumor cells of hepatocellular carcinoma (HCC). We also show that the forced high expression level of SLAMF3 in HCC cells controls proliferation by inhibiting the MAPK ERK/JNK and the mTOR pathways. In the present study, we provide evidence that the inhibitory effect of SLAMF3 on HCC proliferation occurs through Retinoblastoma (RB) factor and PLK1-dependent pathway. In addition to the inhibition of MAPK ERK/JNK and the mTOR pathways, expression of SLAMF3 in HCC retains RB factor in its hypophosphorylated active form, which in turn inactivates E2F transcription factor, thereby repressing the expression and activation of PLK1. A clear inverse correlation was also observed between SLAMF3 and PLK expression in patients with HCC. In conclusion, the results presented here suggest that the tumor suppressor potential of SLAMF3 occurs through activation of RB that represses PLK1. We propose that the induction of a high expression level of SLAMF3 in cancerous cells could control cellular mitosis and block tumor progression.

Regulation of the cell cycle is complex but critical for proper development, reproduction and stress resistance. To survive unfavourable environmental conditions, the crustacean Artemia produces diapause embryos whose metabolism is maintained at extremely low levels. In the present study, the expression profiles of miRNAs during Artemia diapause entry and termination were characterized using high-throughput sequencing. A total of 13 unclassified miRNAs and 370 miRNAs belonging to 87 families were identified; among them, 107 were differentially expressed during diapause entry and termination. We focused on the roles of two of these miRNAs, miR-100 and miR-34, in regulating cell cycle progression; during the various stages of diapause entry, these miRNAs displayed opposing patterns of expression. A functional analysis revealed that miR-100 and miR-34 regulate the cell cycle during diapause entry by targeting polo-like kinase 1 (PLK1), leading to activation of the mitogen-activated protein kinase kinase-extracellular signal-regulated kinase-ribosomal S6 kinase 2 (MEK-ERK-RSK2) pathway and cyclin K, leading to suppression of RNA polymerase II (RNAP II) activity respectively. The findings presented in the present study provide insights into the functions of miR-100 and miR-34 and suggest that the expression profiles of miRNAs in Artemia can be used to characterize their functions in cell cycle regulation., (© 2015 Authors; published by Portland Press Limited.)

MYC levels are tightly regulated in cells, and deregulation is associated with many cancers. In this report, we describe the existence of a MYC-protein kinase A (PKA)-polo-like kinase 1 (PLK1) signaling loop in cells. We report that sequential MYC phosphorylation by PKA and PLK1 protects MYC from proteasome-mediated degradation. Interestingly, short term pan-PKA inhibition diminishes MYC level, whereas prolonged PKA catalytic subunit α (PKACα) knockdown, but not PKA catalytic subunit β (PKACβ) knockdown, increases MYC. We show that the short term effect of pan-PKA inhibition on MYC is post-translational and the PKACα-specific long term effect on MYC is transcriptional. These data also reveal distinct functional roles among PKA catalytic isoforms in MYC regulation. We attribute this effect to differential phosphorylation selectivity among PKA catalytic subunits, which we demonstrate for multiple substrates. Further, we also show that MYC up-regulates PKACβ, transcriptionally forming a proximate positive feedback loop. These results establish PKA as a regulator of MYC and highlight the distinct biological roles of the different PKA catalytic subunits.