Anti-Myeloma Effects of Panobinostat in Combination with Duvelisib

Introduction: Panobinostat (Secura Bio) is a non-selective histone deacetylase inhibitor (HDACi) that has shown anti-tumor activity in preclinical studies in both solid and hematological malignancies. Duvelisib (Secura Bio) is an FDA-approved oral drug and a potent small molecule inhibitor of the delta (δ) and gamma (γ) isoforms of phosphoinositide-3 kinase (PI3K) with potential immunomodulating and antineoplastic activities. There is no data regarding in combination of an HDACi with duvelisib for multiple myeloma (MM) treatment. We evaluated the anti-myeloma effects of the panobinostat in combination with duvelisib. Methods: The human MM cell lines U266, RPMI 8226 and MM1s were obtained from ATCC. Primary MM tumor cells were isolated from MM patients' bone marrow (BM) aspirates and mononuclear cells (MCs) were isolated. The cells were seeded at 10 5 cells/well in 96-well plates and incubated for 24 h in the presence of vehicle, panobinostat or duvelisib alone, or the two drugs together for 48 h. Cell viability was quantified using the MTS cell proliferation assay. For the apoptosis assay, U266, RPMI 8226, MM1s, or primary MM tumor cells were cultured at 1 x 10 6 cells per well for 48 hours at 37°C in 5% CO2 with or without the addition of panobinostat or duvelisib. Next, the cells were washed twice with PBS, re-suspended in binding buffer, and stained with FITC-conjugated annexin V and fluorescent dye propidium iodide (PrI) following annexin V assay standard protocol (BioVision, USA). For each drug treatment, 1 x 10 5 gated events were recorded. Results and Discussion: The MTS cell proliferation assay showed that panobinostat alone inhibited cell proliferation of the MM cell lines U266 and MM1s but not RPMI8226. Panobinostat alone induced concentration-dependent inhibition of BMMCs. Panobinostat (20nM) in combination with duvelisib markedly increased inhibition of primary MM cell proliferation. Panobinostat alone induced MM cell apoptosis in all three MM cell lines. Panobinostat in combination with duvelisib enhanced MM cell apoptosis in MM1s but not U266 and RPMI 8226 cells. We further examined apoptosis of primary MM cell treated with panobinostat alone and in combination with duvelisib. The results showed panobinostat alone induced primary MM cell apoptosis and in combination with duvelisib markedly increased the induction of apoptosis. This study illustrates that the combination of panobinostat and duvelisib shows potent anti-MM effects in vitro and we are currently evaluating the anti-MM effects of this combination in vivo using our human MM xenograft models. *The study was partially funded by Secura Bio, Inc Disclosures No relevant conflicts of interest to declare.

Analysis of Estrogenic Activity in Maryland Coastal Bays Using the MCF-7 Cell Proliferation Assay

Contaminants of Emerging Concern (CECs) with estrogenic or estrogenic-like activity have been increasingly detected in aquatic environments and have been an issue of global concern due to their potential negative effects on wildlife and human health. This study used the MCF-7 cell proliferation assay (E-Screen) to assess the estrogenic activity profiles in Maryland Coastal Bays (MCBs), a eutrophic system of estuaries impacted by human activities. Estrogenic activity was observed in all study sites tested. Water samples from MCBs increased MCF-7 cell proliferation above the negative control from 2.1-fold at site 8, located in Sinepuxent Bay close to the Ocean City Inlet, to 6.3-fold at site 6, located in Newport Bay. The proliferative effects of the sediment samples over the negative control ranged from 1.9-fold at the Assateague Island National Seashore site to 7.7-fold at the Public Landing site. Moreover, elevated cell proliferation (p < 0.05) was observed when cells were co-exposed with 17ß-Estradiol (E2), while reduction in cell proliferation was observed when cells were co-exposed with the antagonist ICI 182, 780 suggesting that cell proliferative effects were primarily mediated by the estrogen receptor (ER). These results suggest the occurrence of some estrogenic or hormonal-like compounds in the MCBs and are consistent with our previous findings based on vitellogenin analyses.

Antioxidant-Rich Extracts of Terminalia ferdinandiana Interfere with Estimation of Cell Viability

The impact of plant extracts and phytochemicals on in vitro cell viability is usually assessed by employing cell viability assays dependent upon the activity of dehydrogenase enzymes. The CellTiter 96® AQueous One Solution Cell Proliferation Assay (CellTiter) was used to measure cell viability in response to antioxidant-rich extracts of Terminalia ferdinandiana fruits. Conflicting results were obtained from this assay whereby higher concentrations of extracts significantly increased cell viability compared to lower concentrations. Intrinsic reductive potential was observed in a cell-free system when extracts were added directly to the CellTiter assay reagent. To confirm this effect in a similar cell proliferation assay, we employed the CellTiter-Blue® Cell Viability Assay and again observed increased viability with increased concentrations of the extracts and direct reduction of the assay reagent by the extracts in cell-free systems. In the search for a cell proliferation assay that would not be directly affected by the plant extracts, we identified the CyQUANT® NF Cell Proliferation Assay that is based on the estimation of DNA content in viable cells. Cell viability decreased with increasing concentrations of the extracts. Accordingly, the results of the present study indicated that cell viability assays reliant upon dehydrogenase activity may lead to false positive results when testing antioxidant-rich plant extracts with intrinsic reductive potential, and alternative cell viability assays should be used to measure the cell viability.

Targeting the androgen receptor as a novel therapeutic strategy for high-grade gliomas by suppressing glioma cancer stem cells.

e13504 Background: Glioblastoma (GBM) is the most aggressive and most common type of primary brain malignancies with median overall survival being only 20.9 months. The incidence of GBM is 50% greater in men than in women, and GBM transplanted into animals grow at a slower rate in females compared with males. Gender difference in GBM indicates that sex hormones such as androgen receptor (AR) may be involved in the tumorigenesis of GBM. A newer generation of AR antagonist, Enzalutamide, is available for prostate cancer treatment in clinic and can pass the blood-brain barrier, thus a good candidate for GBM treatment. Methods: Cell proliferation assay, cell cycle analysis, and cell apoptosis assay were performed on different GBM cell lines after Enzalutamide treatment. After treating GBM cells with or without Enzalutamide in mono-layer cell culturing or tumor spheres, cancer stem cell sub-population (CD133+ cells) in different groups was compared using flow cytometry. After enriching GBM cancer stem cells by sorting CD133+ U87MG cells out, cell proliferation assay was performed on CD133+ U87MG cells. Western blotting was performed comparing marker gene expression levels including CD133 and c-Myc with total protein isolated from GBM cells treated with Enzalutamide at different time points. A syngeneic orthotopic GBM mouse model was used for in vivo study. The size of tumors in the brain was monitored weekly with and without Enzalutamide treatment by in vivo imaging system for the luciferase activities. Results: Enzalutamide inhibited the proliferation of GBM cells both in vitro and in vivo. Enzalutamide induced apoptosis of GBM cells as well as arrested the cell cycle at G2/M phase in a cell cycle that has a potential of radio-sensitizing effect. Enzalutamide decreased the cancer stem cells population both in cultured mono-layer cells and in tumor spheres. Enzalutamide inhibited the proliferation of CD133+ U87MG cells after four days’ treatment. c-Myc is a proto-oncogene and required for maintenance of GBM cancer stem cells. Both CD133 and c-Myc expression levels decreased in GBM cell lines after Enzalutamide treatment in a time-dependent manner. Conclusions: Enzalutamide targets cancer stem cells and inhibits the proliferation of GBM.