Aur-A Stabilization in Cancer

Background. The serine/threonine kinase Aurora-A (Aur-A) is a proto-oncoprotein overexpressed in a wide range of human cancers. Overexpression of Aur-A is thought to be caused by gene amplification or mRNA overexpression. However, recent evidence revealed that the discrepancies between amplification of Aur-A and overexpression rates of Aur-A mRNA were observed in breast cancer, gastric cancer, hepatocellular carcinoma, and ovarian cancer. We found that aggressive head and neck cancers exhibited overexpression and stabilization of Aur-A protein without gene amplification or mRNA overexpression. Here we tested the hypothesis that aberration of the protein destruction system induces accumulation and consequently overexpression of Aur-A in cancer. Principal Findings. Aur-A protein was ubiquitinylated by APCCdh1 and consequently degraded when cells exited mitosis, and phosphorylation of Aur-A on Ser51 was observed during mitosis. Phosphorylation of Aur-A on Ser51 inhibited its APCCdh1-mediated ubiquitylation and consequent degradation. Interestingly, constitutive phosphorylation on Ser51 was observed in head and neck cancer cells with protein overexpression and stabilization. Indeed, phosphorylation on Ser51 was observed in head and neck cancer tissues with Aur-A protein overexpression. Moreover, an Aur-A Ser51 phospho-mimetic mutant displayed stabilization of protein during cell cycle progression and enhanced ability to cell transformation. Conclusions/Significance. Broadly, this study identifies a new mode of Aur-A overexpression in cancer through phosphorylation-dependent inhibition of its proteolysis in addition to gene amplification and mRNA overexpression. We suggest that the inhibition of Aur-A phosphorylation can represent a novel way to decrease Aur-A levels in cancer therapy

Periostin promotes invasion and anchorage-independent growth in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is one of the most common types of human cancer. Typically HNSCC cells show persistent invasion that frequently leads to local recurrence and distant lymphatic metastasis. However, molecular mechanisms associated with invasion and metastasis of HNSCC remain poorly understood. Here we identified Periostin as an invasion promoting factor in HNSCC by comparing the gene expression profiles between parent HNSCC cells and a highly invasive clone. Indeed, Periostin overexpression promoted the invasion and anchorage independent growth both in vitro and in vivo in HNSCC cells. Moreover, Periostin overexpressing cells spontaneously metastasized to cervical lymph nodes and to the lung through their aggressive invasiveness in an orthotopic mouse model of HNSCC. Interestingly, Periostin was highly expressed in HNSCCs in comparison with normal tissues, and the level of Periostin expression was well correlated with the invasiveness of HNSCC cases. In summary, these findings suggest that Periostin plays an important role for invasion and anchorage independent growth in the metastatic process of HNSCC

A KDM6 inhibitor potently induces ATF4 and its target gene expression through HRI activation and by UTX inhibition

UTX/KDM6A encodes a major histone H3 lysine 27 (H3K27) demethylase, and is frequently mutated in various types of human cancers. Although UTX appears to play a crucial role in oncogenesis, the mechanisms involved are still largely unknown. Here we show that a specific pharmacological inhibitor of H3K27 demethylases, GSK-J4, induces the expression of transcription activating factor 4 (ATF4) protein as well as the ATF4 target genes (e.g. PCK2, CHOP, REDD1, CHAC1 and TRIB3). ATF4 induction by GSK-J4 was due to neither transcriptional nor post-translational regulation. In support of this view, the ATF4 induction was almost exclusively dependent on the heme-regulated eIF2α kinase (HRI) in mouse embryonic fibroblasts (MEFs). Gene expression profiles with UTX disruption by CRISPR-Cas9 editing and the following stable re-expression of UTX showed that UTX specifically suppresses the expression of the ATF4 target genes, suggesting that UTX inhibition is at least partially responsible for the ATF4 induction. Apoptosis induction by GSK-J4 was partially and cell-type specifically correlated with the activation of ATF4-CHOP. These findings highlight that the anti-cancer drug candidate GSK-J4 strongly induces ATF4 and its target genes via HRI activation and raise a possibility that UTX might modulate cancer formation by regulating the HRI-ATF4 axis

Constitutive Phosphorylation of Aurora-A on Ser51 Induces Its Stabilization and Consequent Overexpression in Cancer

The serine/threonine kinase Aurora-A (Aur-A) is a proto-oncoprotein overexpressed in a wide range of human cancers. Overexpression of Aur-A is thought to be caused by gene amplification or mRNA overexpression. However, recent evidence revealed that the discrepancies between amplification of Aur-A and overexpression rates of Aur-A mRNA were observed in breast cancer, gastric cancer, hepatocellular carcinoma, and ovarian cancer. We found that aggressive head and neck cancers exhibited overexpression and stabilization of Aur-A protein without gene amplification or mRNA overexpression. Here we tested the hypothesis that aberration of the protein destruction system induces accumulation and consequently overexpression of Aur-A in cancer.Aur-A protein was ubiquitinylated by APC(Cdh1) and consequently degraded when cells exited mitosis, and phosphorylation of Aur-A on Ser51 was observed during mitosis. Phosphorylation of Aur-A on Ser51 inhibited its APC(Cdh1)-mediated ubiquitylation and consequent degradation. Interestingly, constitutive phosphorylation on Ser51 was observed in head and neck cancer cells with protein overexpression and stabilization. Indeed, phosphorylation on Ser51 was observed in head and neck cancer tissues with Aur-A protein overexpression. Moreover, an Aur-A Ser51 phospho-mimetic mutant displayed stabilization of protein during cell cycle progression and enhanced ability to cell transformation.Broadly, this study identifies a new mode of Aur-A overexpression in cancer through phosphorylation-dependent inhibition of its proteolysis in addition to gene amplification and mRNA overexpression. We suggest that the inhibition of Aur-A phosphorylation can represent a novel way to decrease Aur-A levels in cancer therapy

Effect of Ewald sphere curvature on the GISAXS analysis of capped Germanium nanodot samples in the soft X-ray region

Buried Interface Sciences with X-rays and Neutrons 2010 25–27 July 2010, NagoyaUse of soft X-rays (SX) for assessing three dimensional structures in thin films by grazing-incidence small-angle X-ray scattering (GI-SAXS) has been discussed with an example of Ge nanodot structures grown on (001) Si substrates and capped with Si. GISAXS patterns obtained by the measurements were compared with model calculations, and several characteristic differences between GISAXS in the SX and that in hard X-rays have been discussed. It was concluded that although the curvature of the Ewald sphere slightly affects the two-dimensional GISAXS profiles, a two dimensional detector can be still used at the photon energy of about 2 keV. On the other hand, such effect may become dominant when the size of the nanostructure becomes smaller and the photon energy decreases

Near-surface relaxation structure of annealed block copolymer film on Si substrates examined by grazing-incidence small-angle scattering utilizing soft X-rays

Two-dimensional grazing-incidence small-angle X-ray scattering (GISAXS) measurements of SEBS8 block copolymer films deposited on Si(001) substrates have been performed to demonstrate depth-sensitive GISAXS utilizing soft X-rays of 1.77 keV. Remarkable elongation of the Bragg spots in the qz direction, corresponding to microphase separation, was observed for an angle of incidence close to the critical angle. The elongation was explained in terms of the penetration depth, which limits the effective size in the direction perpendicular to the sample surface. Lattice distortion near the surface was confirmed

Contrast matching of an Si substrate with polymer films by anomalous dispersion at the Si

Anomalous dispersion at the Si K absorption edge has been used to control the reflection from the interface between a film and an Si substrate, which otherwise complicates the nanostructure analysis of such a film, particularly for the soft-matter case, in grazing-incidence small-angle scattering. Such a reflectionless condition has been chosen for a triblock copolymer thin film, and two-dimensional grazing-incidence small-angle scattering patterns were obtained without the effect of the reflection. The present approach is useful for analysing nanostructures without introducing complicated corrections arising from the reflection

Anomalous Grazing Incidence Small-Angle Scattering of Capped Ge Nanodots at the Si K Absorption Edge

Grazing incidence small-angle scattering (GISAXS) of capped Ge nanodots in the soft X-ray (SX) region using an anomalous dispersion effect at the Si K absorption edge has been analyzed and compared with results obtained using hard X-rays. The GISAXS profiles obtained at about 1.8 keV were found to give the same structure information for the nanodots as obtained from conventional GISAXS in the hard X-ray region. These could be explained by distorted wave Born approximation simulations. Enhancement of the contrast by anomalous dispersion was confirmed