Microemulsion-made gadolinium carbonate hollow nanospheres showing magnetothermal heating and drug release.

Gadolinium carbonate (Gd2(CO3)3) hollow nanospheres and their suitability for drug transport and magnetothermally-induced drug release are presented. The hollow nanospheres are prepared via a microemulsion-based synthesis using tris(tetramethylcyclopentadienyl)gadolinium(iii) and CO2 as the starting materials. Size, structure and composition of the as-prepared Gd2(CO3)3 hollow nanospheres are comprehensively validated by several independent analytical methods (HRTEM, HAADF-STEM, DLS, EDXS, XRD, FT-IR, DTA-TG). Accordingly, they exhibit an outer diameter of 26 ± 4 nm, an inner cavity of 7 ± 2 nm, and a wall thickness of 9 ± 3 nm. As a conceptual study, the nanocontainer-functionality of the Gd2(CO3)3 hollow nanospheres is validated upon filling with the anti-cancerogenic agent doxorubicin (DOX), which is straightforward via the microemulsion (ME) strategy. The resulting DOX@Gd2(CO3)3 nanocontainers provide the option of multimodal imaging including optical and magnetic resonance imaging (OI, MRI) as well as magnetothermal heating and drug release. As a proof-of-concept, we could already prove the intrinsic DOX-based fluorescence, a low systemic toxicity according to in vitro studies as well as the magnetothermal effect and a magnetothermally-induced DOX release. In particular, the latter is new for Gd-containing nanoparticles and highly promising in view of theranostic nanocontainers and synergistic physical and chemical tumor treatment.

p21Waf1/Cip1 deficiency causes multiple mitotic defects in tumor cells.

As a multifaceted molecule, p21 plays multiple critical roles in cell cycle regulation, differentiation, apoptosis, DNA repair, senescence, aging and stem cell reprogramming. The important roles of p21 in the interphase of the cell cycle have been intensively investigated. The function of p21 in mitosis has been proposed but not systematically studied. We show here that p21 is abundant in mitosis and binds to and inhibits the activity of Cdk1/cyclin B1. Deficiency of p21 prolongs the duration of mitosis by extending metaphase, anaphase and cytokinesis. The activity of Aurora B is reduced and the localization of Aurora B on the central spindle is disturbed in anaphase cells without p21. Moreover, HCT116 p21-/-, HeLa and Saos-2 cells depleted of p21 encounter problems in chromosome segregation and cytokinesis. Gently inhibiting the mitotic Cdk1 or add-back of p21 rescues segregation defect in HCT116 p21-/- cells. Our data demonstrate that p21 is important for a fine-tuned control of the Cdk1 activity in mitosis, and its proper function facilitates a smooth mitotic progression. Given that p21 is downregulated in the majority of tumors, either by the loss of tumor suppressors like p53 or by hyperactive oncogenes such as c-myc, this finding also sheds new light on the molecular mechanisms by which p21 functions as a tumor suppressor.

Restoration of the tumor suppressor p53 by downregulating cyclin B1 in human papillomavirus 16/18-infected cancer cells.

Abrogation of functional p53 is responsible for malignant cell transformation and the maintenance of malignant state of human papillomavirus-infected cancer cells. Thus, restoration of p53 has been regarded as an important strategy for molecular intervention combating papillomavirus-associated malignancies. We show here that depleting cyclin B1 stabilizes and reactivates p53 in papillomavirus-infected cervical cancer cell lines HeLa and CaSki. HeLa cells depleted of cyclin B1 exhibit mitotic defects in spindle formation and chromosome alignment. Downregulation of cyclin B1 increases p14 alternative reading frame of p16, the positive regulator of p53, and decreases phosphorylation of Ser315 in p53. Whereas RO-3306, a selective inhibitor of cyclin-dependent kinase 1 (Cdk1), suppresses this phosphorylation at Ser315 of p53, ZM447439, targeting Aurora A/B kinases, shows no effect. Further analyses in HeLa cells and HCT116 p53(-/-) cells suggest that the Ser315 phosphorylation by Cdk1 regulates negatively the protein stability and the function of p53. Moreover, increased p53 in HeLa cells is functional by showing its increased downstream effectors p21, mouse double minute 2 and Bax. Restoration of p53 and silencing cyclin B1 render cervical carcinoma cells more susceptible to DNA damage agent camptothecin. Taken together, targeting cyclin B1 might be an attractive strategy for preventing and treating papillomavirus-associated cancer by reactivating p53 and by reducing the Cdk1 activity.

MCAK is present at centromeres, midspindle and chiasmata and involved in silencing of the spindle assembly checkpoint in mammalian oocytes.

Mitotic centromere-associated kinesin (MCAK) is an ATP-dependent microtubule (MT) depolymerase regulated by Aurora kinase (AURK) phosphorylation and implicated in resolution of improper MT attachments in mitosis. Distribution of MCAK was studied in oocyte maturation by anti-MCAK antibody, anti-tubulin antibody, anti-AURKB antibody and anti-centromere antibody (ACA) and by the expression of MCAK-enhanced green fluorescent protein fusion protein in maturing mouse oocytes. Function was assessed by knockdown of MCAK and Mad2, by inhibiting AURK or the proteasome, by live imaging with polarization microscope and by chromosomal analysis. The results show that MCAK is transiently recruited to the nucleus and transits to spindle poles, ACA-positive domains and chiasmata at prometaphase I. At metaphase I and II, it is present at centrosomes and centromeres next to AURKB and checkpoint proteins Mad2 and BubR1. It is retained at centromeres at telophase I and also at the midbody. Knockdown of MCAK causes a delay in chromosome congression but does not prevent bipolar spindle assembly. MCAK knockdown also induces a meiosis I arrest, which is overcome by knockdown of Mad2 resulting in chiasma resolution, chromosome separation, formation of aberrant meiosis II spindles and increased hypoploidy. In conclusion, MCAK appears to possess a unique distribution and function in oocyte maturation. It is required for meiotic progression from meiosis I to meiosis II associated with silencing of the spindle assembly checkpoint. Alterations in abundance and activity of MCAK, as implicated in aged oocytes, may therefore contribute to the loss of control of cell cycle and chromosome behaviour, thus increasing risk for errors in chromosome segregation and aneuploidy.