Histone deacetylase (HDAC) 6 is a subtype of the HDAC family; it deacetylates a-tubulin and increases cell motility. Here, we investigate the impact of an alteration of HDAC6 expression in estrogen receptor a (ER)-positive breast cancer MCF-7 cells, as we identified that HDAC6 is a novel estrogen-regulated gene. MCF-7 treated with estradiol showed increased expression of HDAC6 mRNA and protein and a four-fold increase in cell motility in a migration assay. Cell motility was increased to the same degree by stably transfecting the HDAC6 expression vector into MCF-7 cells. In both cases, the cells changed in appearance from their original round shape to an axon-extended shape, like a neuronal cell. This HDAC6 accumulation caused the deacetylation of a-tubulin. Either the selective estrogen receptor modulator tamoxifen (TAM) or the pure antiestrogen ICI 182,780 prevented estradiol-induced HDAC6 accumulation and deacetylation of a-tubulin, leading to reduced cell motility. Tubacin, an inhibitory molecule that binds to the tubulin deacetylation domain of HDAC6, also prevented estradiol-stimulated cell migration. Finally, we evaluated HDAC6 protein expression in 139 consecutively archived human breast cancer tissues by immunohistochemical staining. The prognostic analyses for these patients revealed no significant differences based on HDAC6 expression. However, subset analysis of ERpositive patients who received adjuvant treatment with TAM (n ¼ 67) showed a statistically significant difference in relapse-free survival and overall survival in favor of the HDAC6-positive group (Po0.02 and Po0.05, respectively). HDAC6 expression was an independent prognostic indicator by multivariate analysis (odds ratio ¼ 2.82, P ¼ 0.047). These results indicate the biological significance of HDAC6 regulation via estrogen signaling.

Ever since the estrogen receptor (ER) beta was discovered in 1996, we have been trying to determine its value as a prognostic and/or predictive factor in breast cancer and its potential as a novel target for pharmacological intervention. Recent progress in cellular experiments has shown that ERbeta works as counter partner of ERalpha through inhibition of the transactivating function of ERalpha by heterodimerization, distinct regulation on several specific promoters by ERalpha or ERbeta, and ERbeta-specific regulated genes which are probably related to its anti-proliferative properties. Accumulated data from protein studies in breast cancer tissues indicate that positive expression of ERbeta appears to correlate with a favorable prognosis. Although the number of studies is small, a positive response to tamoxifen treatment is observed in both ERalpha- and ERbeta-positive populations. The significance of ERbeta2/cx, a splicing variant of ERbeta, remains controversial and needs to be analyzed in further studies. We postulate that a combined evaluation of ERbetacx with progesterone receptor may help the stratification of ERalpha-positive breast cancer. Epidemiological studies of hormone replacement therapy and isoflavone (genistein) consumption indicate the possible contribution of ERbeta-specific signaling in breast cancer prevention. A selective estrogen receptor modulator, which works as an antagonist of ERalpha and an agonist of ERbeta, may be a promising chemo-preventive treatment.

Purpose: Removal of fucose residues from the oligosaccharides of human antibody is a powerful approach to enhance antibody-dependent cellular cytotoxicity (ADCC), a potential important antitumor mechanism of therapeutic antibodies. To provide clinically relevant evidence of this mechanism, we investigated ADCC of a fucose-negative version of trastuzumab [anti^human epidermal growth factor receptor 2 (HER2) humanized antibody] using peripheral blood mononuclear cells (PBMC) from breast cancer patients as effector cells. Experimental Design: Thirty volunteers, including 20 breast cancer patients and 10 normal healthy control donors, were recruited randomly, and aliquots of peripheral blood were collected. ADCC of commercial trastuzumab (fucosylated) and its fucose-negative version were measured using PBMCs drawn from the volunteers as effector cells and two breast cancer cell lines with different HER2 expression levels as target cells. Relationships between cytotoxicity and characteristics of the patients, such as content of natural killer cells in PBMCs, type of therapy, FCGR3A genotypes, etc. were also analyzed. Results: ADCC was significantly enhanced with the fucose-negative antibody compared with the fucose-positive antibody using PBMCs from either normal donors or breast cancer patients. Enhancement of ADCC was observed irrespective of the various clinical backgrounds of the patients, even in the chemotherapy cohort that presented with a reduced number of natural killer cells and weaker ADCC. Conclusions: This preliminary study suggests that the use of fucose-negative antibodies may improve the therapeutic effects of anti-HER2 therapy for patients independent of clinical backgrounds.

Although it has been assumed that synchronized firing of gonadotropin-releasing hormone (GnRH) neurons is necessary for pulsatile GnRH secretion, there is no clear evidence for this. In the present study we simultaneously recorded spontaneous action potentials from multiple cells. Immortalized GnRH neurons (GT1-7 cells) were cultured on a multi-electrode dish (MED) and action potentials recorded by an extracellular recording method. One to two weeks after the beginning of culture, spontaneous action potentials appeared, exhibiting bursts composed of 5–10 action potentials. Burst activity was intermittent and periodic with mean burst intervals of 13.3 s. Furthermore, burst activity was recorded almost simultaneously from several micro-electrodes, suggesting that electrical activities of GT1-7 cells were synchronized with each other. Periodic bursts were completely and reversibly blocked by 1–5 µM tetrodotoxin, indicating that voltage-dependent Na⁺ channels are involved in their generation. γ-Aminobutyric acid (GABA) given at a 10-µM concentration shortened inter-burst intervals, whereas 10 µM bicuculline lengthened them. Finally, the gap junctional blockers n-octyl alcohol (1 mM) and carbenoxolone (100 µM) reversibly blocked periodic burst activity. The present study provides direct evidence that the electrical activity of GT1-7 cells exhibits synchronous and periodic bursts composed of action potentials. In addition, endogenous GABA is involved in GT1-7 cells in determining burst frequency. Although the precise mechanism of synchronized burst activities needs to be clarified, gap junctional communications among GT1-7 cells are at least partially involved.

Estrogens play an important role in the pathobiology of breast cancer. In postmenopausal women, peripheral synthesis of estrogens from adrenal/ovarian androgens, dehydroepiandrosterone (DHEA) or androstenedione (Adione), by estrogen-metabolizing enzymes is important. Besides estrone (E1) and estradiol (E2), androgen metabolites, such as androstene-3b, 17b-diol (Aenediol) or 5a-androstane-3b, 17b-diol (Aanediol), are known to have estrogenic functions, although they have been studied much less in breast cancer. To precisely elucidate steroid metabolism in breast cancer patients and to identify the pathobiological role of estrogenic androgen metabolites, concentrations of DHEA, Adione, Aenediol, Aanediol, E1, and E2 in pairs of serum and tumor tissue from patients with primary breast cancer were measured by liquid chromatography-tandem mass spectrometry. Cell proliferation assays using Aenediol were performed for four breast cancer cell lines. Serous E2 concentration was extremely low in postmenopausal women; however, a marked increase in tumor tissue was observed in hormone receptor-positive cases. E1 concentration, in contrast, was sustained at a higher level, even in postmenopausal serum, and did not increase in tumor tissue irrespective of the hormone receptor status. Dehydroepiandrosterone was most abundant in all samples, and exhibited a similar pattern as Adione and Aenediol. 5a-Androstane-3b, 17b-diol was undetectable in most samples. Androstene-3b, 17b-diol proliferated estrogen receptor-apositive breast cancer cells in the absence of E2. The intratumoral increase of E2, but not E1, in hormone receptor-positive postmenopausal breast cancer tissue, as well as the proliferative role of Aenediol, was elucidated. (Cancer Sci 2011; 102: 1848-1854 E strogen plays an important role in the pathobiology of breast cancer.(1,2) In postmenopausal women, in whom ovarian function has decreased, the peripheral metabolism of estrogens via estrogen-metabolizing enzymes is important (Fig. 1). (3,4) Peripheral aromatase converts circulating androgens, such as dehydroepiandrosterone (DHEA) and androstenedione (Adione), from the adrenal gland or ovary into estrogens. Steroid sulfatase (STS) hydrolyzes biologically-inactive sulfates of sex steroids, both estrogens and androgens, producing active steroids. 17b-Hydroxysteroid deydrogenase (HSD)-1 converts estrone (E1) into estradiol (E2), the most potent estrogen. In breast cancer tissue, aromatase, (3-7) STS, (8)(9)(10) and HSD-1 (11) have been reported to be abundant. An increase of E2 concentration in cancerous tissue, compared with the serum in postmenopausal women, has been explained by those enzymes localized in the tumor tissue.(4) Estrone sulfotransferase and HSD-2 play opposite roles to STS and HSD-1, respectively (Fig. 1). Aromatase inhibitors (AI) have been standardized for the treatment of postmenopausal patients with hormone receptor-positive breast cancers, (12) in the expectation of decreasing estrogens. Inhibitors of STS (13) or HSD-1 (14,15) have been also devel...