Mina Takahashi

Bone morphogenetic protein 6 (BMP6) and BMP7 inhibit estrogen-induced proliferation of breast cancer cells by suppressing p38 mitogen-activated protein kinase activation

Estrogen is involved in the development and progression of breast cancer. Here, we investigated the effects of bone morphogenetic proteins (BMPs) on breast cancer cell proliferation caused by estrogen using human breast cancer MCF-7 cells. MCF-7 cells express estrogen receptors (ESR1 and ESR2), BMP receptors, and SMAD signaling molecules. Estradiol and membrane-impermeable estradiol stimulated MCF-7 cell proliferation. Estradiol also reduced mRNA levels of ESR1, aromatase, and steroid sulfatase. Treatment with BMPs and activin had no effects on MCF-7 cell proliferation. However, BMP2, BMP4, BMP6, BMP7, and activin suppressed estradiol-induced cell mitosis, with the effects of BMP6, BMP7, and activin being more prominent than those of BMP2 and BMP4. Activin decreased ESR1 mRNA expression, while BMP6 and BMP7 impaired steroid sulfatase expression in MCF-7 cells. Interestingly, SMAD1,5,8 activation elicited by BMP6 and BMP7, but not by BMP2 and BMP4, was preserved even under the exposure of a high concentration of estradiol. The difference of BMP responsiveness was likely due to the differential modulation of BMP receptor expression induced by estradiol. In this regard, estradiol decreased the expression levels of BMPR1A, BMPR1B, ACVR2A, and ACVR2B but did not affect ACVR1 and BMPRII, leading to the sustained effects of BMP6 and BMP7 in estrogen-treated MCF-7 cells. Estradiol rapidly activated MAPK phosphorylation including extracellular signal-regulated kinase 1/2, p38, and stress-activated protein kinase/c-Jun NH2-terminal kinase pathways and BMP6, BMP7, and activin preferentially inhibited estradiol-induced p38 phosphorylation. SB203580, a selective p38 MAPK inhibitor effectively suppressed estradiol-induced cell mitosis, suggesting that p38 MAPK plays a key role in estrogen-sensitive breast cancer cell proliferation. Thus, a novel interrelationship between estrogen and the breast cancer BMP system was uncovered, in which inhibitory effects of BMP6 and BMP7 on p38 signaling and steroid sulfatase expression were functionally involved in the suppression of estrogen-induced mitosis of breast cancer cells.

p38-Mitogen-Activated Protein Kinase Stimulated Steroidogenesis in Granulosa Cell-Oocyte Cocultures: Role of Bone Morphogenetic Proteins 2 and 4

Roles of the p38-MAPK pathway in steroidogenesis were investigated using coculture of rat granulosa cells with oocytes. Activin and FSH readily phosphorylated p38 in granulosa cells. Activin effect on p38 phosphorylation was abolished by a selective activin receptor-like kinase-4, -5, and -7 inhibitor, SB431542. SB431542 decreased FSH-induced estradiol but had no effect on progesterone production with a marginal cAMP reduction, suggesting that endogenous activin is primarily involved in estradiol synthesis. FSH-induced p38 activation was not affected either by SB431542 or follistatin, suggesting that FSH activates p38 not through the endogenous activin. Bone morphogenetic protein (BMP)-2 and BMP-4 also enhanced FSH-induced p38 phosphorylation, which was augmented by oocyte action. A specific p38 inhibitor, SB203580, decreased FSH-induced estradiol production. However, FSH-induced cAMP accumulation was not changed by SB203580, suggesting that p38 activation is linked to estradiol synthesis independently of cAMP. BMP-2 and BMP-4 inhibited FSH- and forskolin (FSK)-induced progesterone and cAMP synthesis regardless of oocyte action. BMP-2, BMP-4, and activin increased FSH-induced estradiol production, which was enhanced in the presence of oocytes. In contrast to activin that enhanced FSK-induced estradiol, BMP-2 and BMP-4 had no effects on FSK-induced estradiol production, suggesting that BMP-2 and BMP-4 directly activate FSH-receptor signaling. Given that activin increased, but BMP-2 and BMP-4 decreased, FSH-induced cAMP, the effects of BMP-2 and BMP-4 on estradiol enhancement appeared to be diverged from the cAMP-protein kinase A pathway. Thus, BMP-2 and BMP-4 differentially regulate steroidogenesis by stimulating FSH-induced p38 and suppressing cAMP. The former is involved in estradiol production and enhanced by oocyte action, whereas the latter leads to reduction of progesterone synthesis.

Clinical experience with nanoparticle albumin-bound paclitaxel, a novel taxane anticancer agent, and management of adverse events in females with breast cancer.

Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) is currently approved in Japan for treatment of breast cancer. However, apart from phase I clinical trials, data regarding Japanese patients are scant. In the present study, the efficacy and safety of nab-paclitaxel therapy were retrospectively analyzed in 22 patients with advanced or metastatic breast cancer who were treated at the National Hospital Organization Shikoku Cancer Center between November 2010 and June 2012. The nab-paclitaxel was administered once every three weeks. The median age of the patients was 59 years. The tumors were estrogen-receptor positive and/or progesterone-receptor positive in 63.6% patients. None of the patients had HER2-positive breast cancer. The median number of treatment cycles was six (range, two to 12). Six patients exhibited a partial response; the response rate was 27.3% and the clinical benefit rate was 31.8%. The response rate and clinical benefit rate were higher in patients who received nab-paclitaxel as first- or second-line treatment. The median time to treatment failure was 127 days (range, 27–257). Major adverse events were peripheral neuropathy (59%; Grade 3, 9%), myalgia (59%), rash (45%), and nausea and vomiting (50%). The results suggest that nab-paclitaxel is a well-tolerated and clinically useful anticancer preparation.

The efficacy and feasibility of dose-dense sequential chemotherapy for Japanese patients with breast cancer

BackgroundPerioperative dose-dense chemotherapy (DDCT) with granulocyte-colony stimulating factor (G-CSF) prophylaxis is a standard treatment for patients with high-risk breast cancer. The approval of this approach in Japan led to the widespread adoption of DDCT, despite limited efficacy and safety data among Japanese patients. We evaluated the efficacy and safety of neoadjuvant DDCT for Japanese patients with breast cancer.MethodsThis prospective, multicenter, phase II study evaluated 52 women with operable human epidermal growth factor receptor 2-negative breast cancer and axillary lymph node metastasis. Neoadjuvant DDCT (adriamycin plus cyclophosphamide or epirubicin plus cyclophosphamide followed by paclitaxel) was administrated every 2 weeks with G-CSF support. The study endpoints were the rates of pathological complete response (pCR), febrile neutropenia, treatment completion, toxicities, and the relative dose intensity (RDI).ResultsThe pCR rate was 21.9% (9/41) and the triple-negative (TN) subtype was significantly associated with a high pCR rate (triple-negative: 53.3% vs. luminal A: 7.7% and luminal B: 0%; p = 0.003). The treatment completion rate was 80.8% (42/52) and the average RDI was 98.9%. Most adverse events were manageable and tolerable. Six patients (11.5%) developed febrile neutropenia. Grade 3–4 adverse events were slightly more common among older patients (57%) with a low protocol completion rate (≥ 65 years: 42.9% vs. <65 years: 86.7%, p = 0.0062).ConclusionThe pCR rate for DDCT was similar to that of standard chemotherapy, although it was remarkably effective for the TN subtype. DDCT may be feasible for Japanese patients with breast cancer although caution is needed for older patients.