Safety, tolerability and pharmacokinetics of TAS-108, a novel anti-oestrogen, in healthy post-menopausal Japanese women: a phase I single oral dose study

Randomized phase II study of three doses of oral TAS-108 in postmenopausal patients with metastatic breast cancer

This randomized phase II study was intended to identify the optimal dose of TAS-108, a novel steroidal antiestrogen, for the treatment of breast cancer in postmenopausal Japanese women. The potential clinical effects of TAS-108 on the uterus, bone, serum lipids, and hormones were also investigated. Postmenopausal women with hormone receptor-positive metastatic breast cancer who had previously received one or two endocrine therapies were randomly assigned to one of the three possible dose levels of TAS-108 (40, 80 or 120 mg/day). Oral TAS-108 was given daily, and the efficacy and safety of the three doses were evaluated. A total of 97 patients (33, 32, and 32 in the 40-, 80-, and 120-mg groups, respectively) were treated with TAS-108. The clinical benefit rate was 30.3% for the 40-mg, 25.0% for the 80-mg, and 25.0% for the 120-mg group. The 40-mg group achieved the prespecified target threshold. TAS-108 at all dose levels was well tolerated and appeared to have no harmful effects in terms of the variables examined in this study. We conclude that the optimal dose of TAS-108 among the three doses is 40 mg, once daily, for further studies. JAPIC Clinical Trials Information number: Japic CTI - 121754.

Inhibitory effects of ERβ on proliferation, invasion, and tumor formation of MCF-7 breast cancer cells--prognostication for the use of ERβ-selective therapy

CONTEXT

Estrogen is well-known as an important factor in the physiological functions and pathological processes of breast. Estrogen receptor β (ERβ) is expressed in the majority of breast cancers at lower levels compared with the normal breast tissue.

OBJECTIVE

The effect of ERβ on the characteristics of breast tumor cells and its prognostication for the use of ERβ-selective therapy were investigated here for the first time.

MATERIALS AND METHODS

ERβ was overexpressed in ERα positive MCF-7 breast cancer cells by gene transfection. The proliferation, motility, and xenografts growth of MCF-7 cells were investigated by MTT assays, wound-healing assay and animal study.

RESULTS

Results demonstrated that ERβ-GFP localized in both the cytoplasm and the nucleus in the presence of 17β-estradiol (E2), with stronger fluorescence-signal intensity in the nucleus, 2.8-times higher than that in the cytoplasm. The ERβ overexpressed MCF-7 cells resulted in a 38.7% decreased growth rate and motility in vitro. Furthermore, ERβ overexpression enhanced the antiproliferative effects of phytoestrogen, antiestrogen, and histone deacetylase inhibitor. Exogenous ERβ expression reduced tumor volume by 99% at 27 days postadministration, indicated that overexpression of ERβ led to retardation of tumor formation and growth in immunodeficient mice.

DISCUSSION AND CONCLUSION

This study provided a relatively new evidence to support that ERβ is an important modulator of proliferation and motility of breast cancer cells, and implied for the first time a possibility for the use of novel ERβ-selective therapies in breast cancer treatment.

SR16388: a steroidal antiangiogenic agent with potent inhibitory effect on tumor growth in vivo

Angiogenesis is one of the major processes controlling growth and metastasis of tumors. Angiogenesis inhibitors have been targeted for the treatment of various cancers for more than 2 decades. We have developed a novel class of steroidal compounds aimed at blocking the angiogenic process in cancerous tissues. Our lead compound, SR16388, is a potent antiangiogenic agent with binding affinity to estrogen receptor-α (ER-α) and -β (ER-β) at the nanomolar range. This compound inhibited the proliferation of human microvascular endothelial cells (HMVEC) and various types of human cancer cells in vitro. SR16388 inhibited embryonic angiogenesis as measured in the chick chorioallantoic membrane (CAM) assay. The blood vessel density in the CAM was greatly reduced after the embryos were treated with 3 μg/CAM of SR16388 for 24 h. SR16388 at a dose of 2 μM prevented tube formation in Matrigel after HMVEC cells were treated for 8 h. In a modified Boyden chamber assay, SR16388 inhibited the migration of HMVECs by 80% at 500 nM. Using a novel in vivo Fibrin Z-chamber model, we demonstrated that SR16388 at a single daily oral dose of 3 mg/kg for 12 days significantly inhibited the granulation tissue (GT) thickness and the microvessel density of the GT as compared to control. More importantly, SR16388 down-regulated the pro-angiogenic transcription factors, hypoxia inducible factor 1α (HIF-1α) and signal transducer and activator of transcription 3 (STAT3) in non-small cell lung cancer (NSCLC) cells. Together, these effects of SR16388 can lead to the reduction of vascularization and tumor growth in vivo.

A novel steroidal inhibitor of estrogen-related receptor alpha (ERR alpha)

The orphan nuclear receptor estrogen-related receptor alpha (ERRalpha) has been implicated in the development of various human malignancies, including breast, prostate, ovary, and colon cancer. ERRalpha, bound to a co-activator protein (e.g., peroxisome proliferator receptor gamma co-activator-1alpha, PGC-1alpha), regulates cellular energy metabolism by activating transcription of genes involved in various metabolic processes, such as mitochondrial genesis, oxidative phosphorylation, and fatty acid oxidation. Accumulating evidence suggests that ERRalpha is a novel target for solid tumor therapy, conceivably through effects on the regulation of tumor cell energy metabolism associated with energy stress within solid tumor microenvironments. This report describes a novel steroidal antiestrogen (SR16388) that binds selectively to ERRalpha, but not to ERRbeta or ERRgamma, as determined using a time-resolved fluorescence resonance energy transfer assay. SR16388 potently inhibits ERRalpha's transcriptional activity in reporter gene assays, and prevents endogenous PGC-1alpha and ERRalpha from being recruited to the promoters or enhancers of target genes. Representative in vivo results show that SR16388 inhibited the growth of human prostate tumor xenografts in nude mice as a single agent at 30mg/kg given once daily and 100mg/kg given once weekly. In a combination study, SR16388 (10mg/kg, once daily) and paclitaxel (7.5mg/kg, twice weekly) inhibited the growth of prostate tumor xenografts in nude mice by 61% compared to untreated xenograft tumors. SR16388 also inhibited the proliferation of diverse human tumor cell lines after a 24-h exposure to the compound. SR16388 thus has utility both as an experimental antitumor agent and as a chemical probe of ERRalpha biology.