CHIP is a U-box-type ubiquitin ligase that induces ubiquitylation and degradation of its substrates, which include several oncogenic proteins. The relationship between CHIP and tumour progression, however, has not been elucidated. Here, we show that CHIP suppresses tumour progression in human breast cancer by inhibiting oncogenic pathways. CHIP levels were negatively correlated with the malignancy of human breast tumour tissues. In a nude mouse xenograft model, tumour growth and metastasis were significantly inhibited by CHIP expression. In contrast, knockdown of CHIP (shCHIP) in breast cancer cells resulted in rapid tumour growth and metastastic phenotypes in mice. In cell-based experiments, anchorage-independent growth and invasiveness of shCHIP cells was significantly elevated due to increased expression of Bcl2, Akt1, Smad and Twist. Proteomic analysis identified the transcriptional co-activator SRC-3 (refs 13, 14, 15, 16, 17, 18, 19) as a direct target for ubiquitylation and degradation by CHIP. Knocking down SRC-3 in shCHIP cells reduced the expression of Smad and Twist, and suppressed tumour metastasis in vivo. Conversely, SRC-3 co-expression prevented CHIP-induced suppression of metastasis formation. These observations demonstrate that CHIP inhibits anchorage-independent cell growth and metastatic potential by degrading oncogenic proteins including SRC-3.

We investigated the thermal conductivity of 200-nm-thick amorphous indium–gallium–zinc-oxide (a-IGZO) films. Films with a chemical composition of In:Ga:Zn= 1:1:0.6 were prepared by dc magnetron sputtering using an IGZO ceramic target and an Ar–O2 sputtering gas. The carrier density of the films was systematically controlled from 1014 to >1019 cm-3 by varying the O2 flow ratio. Their Hall mobility was slightly higher than 10 cm2·V-1·s-1. Those films were sandwiched between 100-nm-thick Mo layers; their thermal diffusivity, measured by a pulsed light heating thermoreflectance technique, was ∼5.4×10-7 m2·s-1 and was almost independent of the carrier density. The average thermal conductivity was 1.4 W·m-1·K-1.

The estrogen pathway plays an important role in the etiology of human endometrial carcinoma (EC). We examined whether estrogen biosynthesis in the tumor microenvironment promotes endometrial cancer. To examine the contribution of stromal cells to estrogen signaling in EC, we used reporter cells stably transfected with the estrogen response element (ERE) fused to the destabilized green fluorescent protein (GFP) gene. In this system, the endometrial cancer stromal cells from several patients activated the ERE of cancer cells to a variable extent. The GFP expression level increased when testosterone, a substrate for aromatase, was added. The effect was variably inhibited by aromatase inhibitors (AIs), although the response to AIs varied among patients. These results suggest that GFP expression is driven by estrogen synthesized by aromatase in the endometrial cancer stromal cells. In a second experiment, we constructed an adenovirus reporter vector containing the same construct as the reporter cells described above, and visualized endogenous ERE activity in primary culture cancer cells from 15 EC specimens. The GFP expression levels varied among the cases, and in most primary tissues, ERE activities were strongly inhibited by a pure anti-estrogen, fulvestrant. Interestingly, a minority of primary tissues in endometrial cancer showed ERE activity independent of the estrogen-ER pathway. These results suggest that AI may have some therapeutic value in EC; however, the hormonal microenvironment must be assessed prior to initiating therapy.

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Neoadjuvant chemotherapy (NAC) has become the standard treatment for advanced breast cancer. Several prognostic markers, including estrogen receptor-α (ERα), are used to predict the response to NAC. However, the molecular significance of ERα expression in the efficacy of chemotherapy is not yet fully understood. To examine this issue, we first evaluated ERα transcriptional activity in breast cancer cells derived from pre-NAC specimens using estrogen response element-green fluorescent protein (ERE-GFP) as a reporter gene, and found that, in the cases for which ERα activities determined by GFP expression were not detected or low, pCR (pathological complete response) could be achieved even though ERα protein was expressed. Next, we examined the effects of alterations in ERα expression levels on sensitivity to paclitaxel, a key drug in NAC, by stable expression of ERα in ER-negative SKBR3 cells and by siRNA-mediated down-regulation of ERα in ER-positive MCF-7 cells, and showed that ERα expression and sensitivity to paclitaxel showed an inverse correlation. We also established paclitaxel-resistant MCF-7 cell clones and found that they have higher estrogen-induced ER activity than parent cells. Paclitaxel is a microtubule-stabilizing agent, while HDAC6 (histone deacetylase 6), which we previously identified as an estrogen-regulated gene, enhances cell motility by destabilizing microtubules via deacetylation of α-tubulin. Finally, we demonstrate herein that ERα knockdown in MCF-7 cells prevents deacetylation of α-tubulin, thereby increasing sensitivity to paclitaxel. Taken together, these results suggest that ERα expression directly regulates sensitivity to paclitaxel in NAC for breast cancer via the effect on microtubule stability.