[Neoadjuvant Epirubicin-Cyclophosphamide Therapy followed by Nab-Paclitaxel in Patients with Operable Breast Cancer-A Single-Center Phase â ¡ Trial].

Clinical studies have confirmed that nab-paclitaxel(nab-PTX)therapy is effective and safe in patients with metastatic breast cancer. Neoadjuvant chemotherapy(NAC) with nab-PTX has resulted in a pathological complete response (pCR) rate of 29% in all cases and 58% in HER2-positive cases. However, these data were obtained from an overseas study, and the effectiveness and safety of NAC with nab-PTX remain unclear in Japan. Thus, the present study was conducted to investigate these aspects. In patients with T1-3, N0-2, M0 breast cancer, 4 cycles of 260 mg/m2 nab-PTX were administered every 3 weeks after 4 cycles of EC therapy(100 mg/m2 of epirubicin and 600 mg/m2 of cyclophosphamide)as NAC. In HER2- positive patients, trastuzumab was used in combination with nab-PTX. Overall, 14 patients were registered between October 2014 and October 2018. One patient who had requested for another drug after providing informed consent was excluded, and the remaining 13 patients were analyzed. The primary endpoint was pCR rate. The median age of the subjects was 57 years, and the median tumor diameter was 35 mm. There were 7 cases of Stage Ⅱ disease and 6 cases of Stage Ⅲ disease. As for tumor subtype, there were 7 cases of Luminal-type, 2 cases of Luminal- HER2-type, 4 cases of HER2-type, and no triple negative-type tumors(the cut-off values for estrogen receptor [ER] and progesterone receptor were both 1%). The objective response rate to NAC was 77%(10/13 cases), and no PD was observed. The pCR rate was 54%(7/13 cases): 2 patients had Luminal-type tumors, 1 had a Luminal-HER2-type tumor, and 4 had HER2-type tumors. Predictive factors for pCR were ER negativity and HER2 positivity. Common adverse events of chemotherapy were hair loss, pain, malaise, anemia, dysgeusia, constipation, itchiness, and numbness, but their severity was modest, and they were manageable. This study suggests the efficacy and safety of nab-PTX after EC therapy in Japanese patients with operable breast cancer.

Resistance to cyclin-dependent kinase (CDK) 4/6 inhibitors confers cross-resistance to other CDK inhibitors but not to chemotherapeutic agents in breast cancer cells.

BACKGROUND: Combined endocrine therapy with a cyclin-dependent kinase (CDK) 4/6 inhibitor has been indicated to improve not only progression-free survival, but also overall survival in patients with hormone receptor (HR)-positive, HER2-negative advanced breast cancer. However, resistance to this combination therapy inevitably develops. How to manage this resistant breast cancer is one of the most important clinical issues. To investigate the mechanisms of action responsible for resistance, we developed breast cancer cells resistant to CDK4/6 inhibitors, and analyzed their biological characteristics and sensitivity to different anticancer agents. METHODS: HR-positive, HER2-negative MCF-7 and KPL-1 breast cancer cells were cultivated in palbociclib (PAL) or abemaciclib (ABE)-added culture medium for over 5 months, and we successfully developed PAL- or ABE-resistant cells. The effects of PAL or ABE on the cell growth, basal RB expression, RB phosphorylation, cell cycle and cell senescence were compared between resistant and parental cells. Effects of the other CDK4/6 inhibitor, different chemotherapeutic agents and estrogen on the cell growth were also examined. The expression levels of cyclin D1, CDK2, CDK4, CDK6, cyclin E1 and estrogen receptor (ER)-ɑ were measured using RT-PCR. RESULTS: Long-term exposure to up to 200 nM PAL or ABE resulted in the development of PAL- or ABE-resistant MCF-7 or KPL-1 breast cancer cells. Basal expression levels of RB in both resistant cells were down-regulated. Inhibitory effects of either PAL or ABE on RB phosphorylation were reduced in both resistant cells. Accordingly, G1-S cell cycle retardation and cell senescence induced by either inhibitor were also attenuated in both resistant cells. Both resistant cells were cross-resistant to the other CDK4/6 inhibitor but almost as equally sensitive to different chemotherapeutic agents (5-fluorouracil, gemcitabine, paclitaxel, docetaxel, doxorubicin and eribulin) as the parental cells. The mRNA expression level of CDK6 significantly increased in the resistant MCF-7 cells and that of Rb1 significantly decreased in the resistant KPL-1 cells. Although both resistant cells were less sensitive to estrogen than the parental cells, the expression levels of ER-ɑ did not significantly change in either. CONCLUSIONS: Our study suggests that acquired resistance to PAL or ABE confers cross-resistance to the other CDK4/6 inhibitor but not to chemotherapeutic agents in HR-positive, HER2-negative breast cancer cells. Down-regulation of basal RB expression and normalized RB phosphorylation reduced by CDK4/6 inhibitors may be responsible for the attenuated anti-cell growth effects of the inhibitors.

Anti-cell growth and anti-cancer stem cell activity of the CDK4/6 inhibitor palbociclib in breast cancer cells.

BACKGROUND: A cyclin-dependent kinase (CDK) 4/6 inhibitor, palbociclib, has been used to treat patients with estrogen receptor (ER)-positive (+) and human epidermal growth factor receptor (HER) 2-negative (-) advanced breast cancer. To investigate the mechanisms underlying the antitumor activity of palbociclib, we conducted a preclinical study on the anti-cell growth and anti-cancer stem cell (CSC) activity of palbociclib in breast cancer cells. METHODS: The effects of palbociclib on Rb phosphorylation, cell growth, cell cycle progression, apoptosis, cell senescence and the proportion of CSCs were investigated in five human breast cancer cell lines of different subtypes. To investigate the mechanisms of the anti-CSC activity of palbociclib, small-interfering RNAs for CDK4 and/or CDK6 were used. Palbociclib dose-dependently reduced Rb phosphorylation and cell growth in association with G1-S cell cycle blockade and the induction of cell senescence, but without increased apoptosis, in all breast cancer cell lines. RESULTS: The anti-cell growth activity of palbociclib widely differed among the cell lines. Palbociclib also dose-dependently reduced the CSC proportion measured by three different assays in four of five cell lines. The inhibition of CDK4 expression, but not CDK6 expression, reduced the increased proportion of putative CSCs induced by estradiol in ER (+)/HER2 (-) cell lines. CONCLUSIONS: These results suggest that palbociclib exhibits significant anti-cell growth and anti-CSC activity in not only ER (+) breast cancer cell lines but also ER (-) cell lines. CDK4 inhibition induced by palbociclib may be responsible for its anti-CSC activity.

Comprehensive immunohistochemical analyses on expression levels of hedgehog signaling molecules in breast cancers.

BACKGROUND: The hedgehog (Hh) signaling pathway plays important roles in cell proliferation, malignant progression, invasion and metastasis, and the expansion of cancer stem cells (CSCs). Comprehensive immunohistochemical (IHC) analyses have not yet been conducted on the expression levels of Hh signaling molecules in breast cancer tissues. METHODS: A total of 204 patients with invasive breast cancer treated in our institute were study subjects. IHC analyses on the expression levels of the Hh signaling molecules, sonic Hh (SHH), PTCH1, GLI1, GLI2, and GLI3 and the CSC-related factor, SOX2, were investigated. RESULTS: Positive correlations were observed among all of the Hh signaling molecules tested. SOX2 expression correlated with the expression levels of all Hh signaling molecules. SHH expression positively correlated with tumor size, the Ki-67 labeling index, histological grade, estrogen receptor negativity, progesterone receptor negativity, and HER2 positivity. GLI1 expression positively correlated with the histological grade. GLI2 expression positively correlated with the histological grade, Ki-67 labeling index, and HER2 positivity. Univariate analyses revealed that a younger age, larger tumor size, positive lymph node metastasis, higher histological grade, positive lymphatic invasion, and higher Ki-67 labeling index were related to poor relapse-free survival (RFS). The positivity of all Hh signaling molecules and SOX2 did not correlate with poor RFS. A multivariate analysis revealed that positive lymphatic invasion and a younger age were independent worse prognostic factors for RFS. CONCLUSIONS: This comprehensive analysis demonstrated for the first time that SHH, GLI1, and GLI2 expression levels positively correlated with the malignant phenotypes of tumor cells.