Purpose Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer. Eribulin was approved for the treatment of metastatic breast cancer through the EMBRACE trial, and a subgroup analysis in this clinical trial indicated the efficacy of eribulin in patients with TNBC. However, the prognosis of patients with TNBC is still poor due to various molecular characteristics. Therefore, there is an urgent need for a more effective treatment for the management of TNBC. Methods We investigated the synergistic effect of a novel histone deacetylase (HDAC) inhibitor, OBP-801, and eribulin in TNBC cell lines because OBP-801 has been known to enhance the anti-tumor activities of other chemotherapeutic agents. The cell growth was analyzed, and the flow cytometry analysis was conducted to evaluate the effects on cell cycle and the induction of apoptosis. The mechanism underlying the enhancement of inhibition of TNBC cell growth was investigated through Western blot analyses. Results The combination treatment of OBP-801 with eribulin showed the synergistic inhibition of the growth in TNBC cells, involved with the enhancement of apoptosis. We, for the first time, found that eribulin upregulated survivin and also that OBP-801 could remarkably suppress the upregulation of survivin by eribulin. Moreover, this combination potently suppressed Bcl-xL and the MAPK pathway compared with either agent alone. Conclusion We found that the combination of OBP-801 and eribulin synergistically inhibited the growth with apoptosis in TNBC cells, suggesting that this combination might be a promising novel strategy for treating TNBC patients.

AbstrAct:The membrane-anchored matrix metalloproteinase-regulator RECK is often downregulated in various types of cancers; the levels of residual RECK in resected tumors often correlate with better prognosis. Forced expression of RECK in cancer cells suppresses tumor angiogenesis, invasion, and metastasis in xenograft models. RECK is therefore a promising marker for benignancy and a potential effector in cancer therapy. We established a cell line containing two transgene systems: (1) the secreted alkaline phosphatase (SEAP) gene fused to Reck promoter and (2) the HRAS 12V oncogene driven by the Tet-off promoter system. This cell line exhibits transformed phenotype in regular medium and flat morphology with increased SEAP activity in the presence of doxycycline, allowing the assessment of RECK-inducing activity of chemicals in the contexts of both transformed and untransformed cells. Our pilot experiments with 880 known bioactive compounds detected 34 compounds that activate RECK promoter; among these, 10 were authentic anticancer drugs. Four selected compounds up-regulated endogenous RECK protein in several human cancer cell lines. The top-ranking compound, disulfiram, strongly suppressed spontaneous lung-metastasis of human fibrosarcoma cells in nude mice. Our data demonstrate the value of this screen in discovering effective cancer therapeutics.

The tumor suppressor protein RECK has been implicated in the regulation of matrix metalloproteinases (MMPs), NOTCH-signaling and WNT7-signaling. It remains unclear, however, how broad the spectrum of RECK targets extends. To find novel RECK binding partners, we took the unbiased approach of yeast two-hybrid screening. This approach detected ADAMTS10 as a RECK-interactor. ADAMTS10 has been characterized as a metalloproteinase involved in fibrillin-rich microfibril biogenesis, and its mutations have been implicated in the connective tissue disorder Weill-Marchesani syndrome. Experiments in vitro using recombinant proteins expressed in mammalian cells indicated that RECK indeed binds ADAMTS10 directly, that RECK protects ADAMTS10 from fragmentation following chemical activation and that ADAMTS10 interferes with the activity of RECK to inhibit MT1-MMP. In cultured cells, RECK increases the amount of ADAMTS10 associated with the cells. Hence, the present study has uncovered novel interactions between two molecules of known clinical importance, RECK and ADAMTS10..

Squamous cell lung carcinoma (SQCLC) is an aggressive type of lung cancer. In contrast with the marked advances that have been achieved in the treatment of lung adenocarcinoma, there are currently no effective targeted therapies for SQCLC, for with cytotoxic drugs are still the main treatment strategy. Therefore, the present study aimed to develop novel combination therapies for SQCLC. The results demonstrated that a combined treatment with the potent histone deacetylase (HDAC) inhibitor OBP-801 and the third-generation anthracycline amrubicin synergistically inhibited the viability of SQCLC cell lines by inducing apoptosis signal-regulating kinase 1 (ASK1)-dependent, as well as JNK-and p38 mitogen-activated protein kinase (MAPK)-independent apoptosis. OBP-801 treatment strongly induced the protein expression levels of thioredoxin-interacting protein (TXNIP), and amrubicin treatment increased the levels of intracellular reactive oxygen species (ROS), which suggested that this combination oxidized and dissociated thioredoxin 2 (Trx2) from mitochondrial ASK1 and activated ASK1. Moreover, mouse xenograft experiments using human H520 SQCLC cells revealed that the co-treatment potently suppressed tumor growth in vivo. These results suggested that a combined treatment with OBP-801 and amrubicin may have potential as a therapeutic strategy for SQCLC.

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