Preemptive Antifungal Therapy for Febrile Neutropenic Hematological Malignancy Patients in China

Background

The aim of this study was to evaluate the efficiency, adverse effects, and pharmacoeconomic impact of empirical and preemptive antifungal therapy for febrile neutropenic hematological malignancy patients in China.

Material/Methods

Patients with febrile neutropenia during hematological malignancy were randomly divided into an empirical group and a preemptive group. The preemptive antifungal treatment was initiated if patient status was confirmed by clinical manifestation, imaging diagnosis, 1-3-β-D glucan(G) testing, and galactomannan (GM) test. The treatment was ended 2 weeks later if the patient was recovered from neutropenia. Voriconazole was used as the first-line medicine. All patients received intravenous administration of voriconazole every 12 h, with an initiating dose of 400 mg, then the dose was reduced to 200 mg.

Results

The overall survival rate was 97.1% and 94.6% in the empirical group and preemptive group, respectively, with no significant difference observed (χ²=1.051, P=0.305). However, the occurrence rate of invasive fungal disease (IFD) in the preemptive group was 9.2% vs. 2.2% in the empirical group. Moreover, the mortality rate due to IFD was 0.7% and 2.3% for the empirical group and preemptive group, respectively. The average duration and cost of preemptive antifungal therapy were 13.8±4.7 days and 8379.00±2253.00 RMB, respectively, which were lower than for empirical therapy. However, no significant differences were observed for incidence of adverse effects and hospital stay between the 2 groups.

Conclusions

Preemptive antifungal therapy for patients with febrile neutropenic hematological malignancy demonstrated a similar survival rate as with empirical therapy but is economically favorable in a Chinese population.

The Plasma microRNA miR-1914* and -1915 Suppresses Chemoresistant in Colorectal Cancer Patients by Down-regulating NFIX

OBJECTIVE

We investigated mechanisms of colorectal cancer (CRC) chemoresistance to first-line chemotherapy (capecitabine plus oxaliplatin (XELOX)) and identified two putative chemoresistant microRNAs, miR-1914* and -1915, that are downregulated in plasma samples from patients with chemoresistant CRC.

METHODS

A number of plasma samples from CRC patients were analyzed for the levels of miR-1914* and - 1915. Effects of stable and transient expression of 2 microRNAs in human chemoresistant CRC cell lines were analyzed. Tumor formation and chemoresistance in HCT116/5-Fu/OXA that did or did not express 2 microRNAs were analyzed in mice. Nuclear factor I/X (NFIX) was predicted to target the gene of 2 miRNAs and verified in vivo and in vitro.

RESULTS

Plasma levels of miR-1914* and -1915 in chemoresistant CRC patients were different than levels in responders, and associated with clinical response. Overexpression of miR-1914* and -1915 in chemoresistant CRC cells reduced resistance to 5-FU and Oxaliplatin in vitro. The microRNAs suppressed chemoresistance in CRC tumors in mice by affecting cell growth, invasion, apoptosis and tumor suppressor function. miR-1914* and -1915 interacted with the 3'-untranslated region of NFIX and reduced NFIX its level in chemoresistant CRC cells. Overexpression of NFIX did not inhibit chemoresistant CRC cell motility and chemoresistant proteins when miR-1914* and -1915 were transfected.

CONCLUSION

Plasma miR-1914* and -1915 interact with NFIX RNA and reduce its level in chemoresistant CRC cells to first-line chemotherapy. Up-regulation of miR-1914* and -1915 decreased the chemoresistance abilities of chemoresistant CRC cells. The plasma miR-1914* and -1915 may play a role in colorectal cancer therapy and diagnosis.

Guttiferone K impedes cell cycle re-entry of quiescent prostate cancer cells via stabilization of FBXW7 and subsequent c-MYC degradation

Cell cycle re-entry by quiescent cancer cells is an important mechanism for cancer progression. While high levels of c-MYC expression are sufficient for cell cycle re-entry, the modality to block c-MYC expression, and subsequent cell cycle re-entry, is limited. Using reversible quiescence rendered by serum withdrawal or contact inhibition in PTEN(null)/p53(WT) (LNCaP) or PTEN(null)/p53(mut) (PC-3) prostate cancer cells, we have identified a compound that is able to impede cell cycle re-entry through c-MYC. Guttiferone K (GUTK) blocked resumption of DNA synthesis and preserved the cell cycle phase characteristics of quiescent cells after release from the quiescence. In vehicle-treated cells, there was a rapid increase in c-MYC protein levels upon release from the quiescence. However, this increase was inhibited in the presence of GUTK with an associated acceleration in c-MYC protein degradation. The inhibitory effect of GUTK on cell cycle re-entry was significantly reduced in cells overexpressing c-MYC. The protein level of FBXW7, a subunit of E3 ubiquitin ligase responsible for degradation of c-MYC, was reduced upon the release from the quiescence. In contrast, GUTK stabilized FBXW7 protein levels during release from the quiescence. The critical role of FBXW7 was confirmed using siRNA knockdown, which impaired the inhibitory effect of GUTK on c-MYC protein levels and cell cycle re-entry. Administration of GUTK, either in vitro prior to transplantation or in vivo, suppressed the growth of quiescent prostate cancer cell xenografts. Furthermore, elevation of FBXW7 protein levels and reduction of c-MYC protein levels were found in the xenografts of GUTK-treated compared with vehicle-treated mice. Hence, we have identified a compound that is capable of impeding cell cycle re-entry by quiescent PTEN(null)/p53(WT) and PTEN(null)/p53(mut) prostate cancer cells likely by promoting c-MYC protein degradation through stabilization of FBXW7. Its usage as a clinical modality to prevent prostate cancer progression should be further evaluated.

Texas Native Plants Yield Compounds with Cytotoxic Activities against Prostate Cancer Cells

There remains a critical need for more effective therapies for the treatment of late-stage and metastatic prostate cancers. Three Texas native plants yielded three new and three known compounds with antiproliferative and cytotoxic activities against prostate cancer cells with IC50 values in the range of 1.7-35.0 μM. A new sesquiterpene named espadalide (1), isolated from Gochnatia hypoleuca, had low micromolar potency and was highly effective in clonogenic assays. Two known bioactive germacranolides (2 and 3) were additionally isolated from G. hypoleuca. Dalea frutescens yielded two new isoprenylated chalcones, named sanjuanolide (4) and sanjoseolide (5), and the known sesquiterpenediol verbesindiol (6) was isolated from Verbesina virginica. Mechanistic studies showed that 1-4 caused G2/M accumulation and the formation of abnormal mitotic spindles. Tubulin polymerization assays revealed that 4 increased the initial rate of tubulin polymerization, but did not change total tubulin polymer levels, and 1-3 had no effects on tubulin polymerization. Despite its cytotoxic activity, compound 6 did not initiate changes in cell cycle distribution and has a mechanism of action different from the other compounds. This study demonstrates that new compounds with significant biological activities germane to unmet oncological needs can be isolated from Texas native plants.

Identification of Compounds with Efficacy against Malaria Parasites from Common North American Plants

Some of the most valuable antimalarial compounds, including quinine and artemisinin, originated from plants. While these drugs have served important roles over many years for the treatment of malaria, drug resistance has become a widespread problem. Therefore, a critical need exists to identify new compounds that have efficacy against drug-resistant malaria strains. In the current study, extracts prepared from plants readily obtained from local sources were screened for activity against Plasmodium falciparum. Bioassay-guided fractionation was used to identify 18 compounds from five plant species. These compounds included eight lupane triterpenes (1-8), four kaempferol 3-O-rhamnosides (10-13), four kaempferol 3-O-glucosides (14-17), and the known compounds amentoflavone and knipholone. These compounds were tested for their efficacy against multi-drug-resistant malaria parasites and counterscreened against HeLa cells to measure their antimalarial selectivity. Most notably, one of the new lupane triterpenes (3) isolated from the supercritical extract of Buxus sempervirens, the common boxwood, showed activity against both drug-sensitive and -resistant malaria strains at a concentration that was 75-fold more selective for the drug-resistant malaria parasites as compared to HeLa cells. This study demonstrates that new antimalarial compounds with efficacy against drug-resistant strains can be identified from native and introduced plant species in the United States, which traditionally have received scant investigation compared to more heavily explored tropical and semitropical botanical resources from around the world.

Abstract P5-03-04: Identification of compounds from natural sources with selective activity against triple-negative breast cancer molecular subtypes

Triple negative breast cancers (TNBCs) lack expression of the estrogen and progesterone receptors (ER/PR) and do not have amplified HER2. While targeted therapies for ER+/PR+ and HER2-amplified breast cancers have greatly improved patient survival, there are no targeted therapies for TNBCs and no effective therapies to treat metastatic disease. There is a need to identify new therapeutic agents and molecular targets for treating TNBCs, but efforts have been limited by a lack of understanding of the subtypes of these heterogeneous diseases. However, gene expression profiling of TNBC patients recently identified 6 molecular subtypes of TNBC and representative cell lines, providing the first opportunity to identify subtype-specific leads for TNBC.

We performed high-content screening to evaluate novel libraries of extracts from Texas plants and diverse fungal cultures for antiproliferative and/or cytotoxic activity in a panel of cell lines modeling five different TNBC molecular subtypes. The aim was to identify extracts with selective activity in a single cell line. We hypothesized that extracts found to have selective activity in one of these cell lines may target a protein or cellular process critical to the growth of that subtype. We identified 11 extracts with selective activity against cell lines representing four different TNBC molecular subtypes. From a fungal culture we identified a new compound called maximiscin, which was found to have selective cytotoxic efficacy against the MDA-MB-468 cell line of the basal-like 1 subtype. From a plant extract we isolated deguelin, which had selective activity in the MDA-MB-453 cell line, a model of the luminal androgen receptor (LAR) subtype.

The molecular mechanisms of action of each compound were investigated in cell line models. Initial cell cycle studies using flow cytometry showed that maximiscin caused an accumulation of cells in G1 after 18h of treatment. Protein microarray studies indicated that maximiscin increased levels of phospho-p53, which was consistent with the observed G1 accumulation. Based on these findings, we hypothesized that maximiscin induces DNA damage and investigated the effects of maximiscin on the phosphorylation of several DNA damage response proteins. Maximiscin increased phosphorylation of Chk1, Chk2, p53 and H2A.X as soon as 2h after treatment, indicating an accumulation of DNA damage.

Previous studies have shown that LAR TNBC cells are particularly sensitive to PI3K inhibitors in vitro compared to other TNBC subtypes. The effects of deguelin on PI3K-Akt-mTORC1 signaling were evaluated in both MDA-MB-453 and MDA-MB-231 cells. Phosphorylation of both ribosomal protein S6 and 4E-BP1 were dramatically reduced in MDA-MB-453 cells 2h after deguelin treatment. Interestingly this was not observed in MDA-MB-231 cells, suggesting inhibition of mTORC1 signaling may be involved in the selective activity of deguelin in MDA-MB-453 cells. Preliminary studies suggest deguelin may also decrease androgen receptor abundance in MDA-MB-453 cells, indicating multiple molecular mechanisms may be involved in its selective effects. These results demonstrate that compounds with selective activity against TNBC subtypes can be identified from nature.

Citation Format: Robles AJ, Du L, Cai S, Risinger AL, Cichewicz RH, Mooberry SL. Identification of compounds from natural sources with selective activity against triple-negative breast cancer molecular subtypes. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-03-04.

Abstract P4-07-02: Targeted therapies for TNBC: Exploiting vulnerabilities that arise from DNA damage repair pathway dependencies

We examined the synergistic effects of DNA damage, Chk1 inhibition and poly(ADP-ribose) polymerase (PARP) inhibition in TNBC. This combinatorial targeting allows us to exploit vulnerabilities in two pathways that are often deregulated in TNBCs: DNA damage checkpoint defects due to TP53 deficiency and DNA repair defects due to alterations in homologous recombination repair (HRR). TP53 maintains genome integrity by inhibiting cells that are experiencing genotoxic stress from progressing through the cell cycle, or by inducing apoptosis or senescence. In response to DNA damage, p53 activates gene expression to arrest cells in the G1 phase of the cell cycle and to reinforce the S- and G2-checkpoints. Thus, p53-deficient cells lack a G1 checkpoint and are impaired in their ability to sustain S- and G2-checkpoints. This makes p53-deficient tumors particularly sensitive to agents that abrogate these checkpoints. Because Chk1 inhibitors abrogate both S- and G2-checkpoints, combining Chk1 inhibitors with agents that induce genotoxic stress provides a rational therapeutic strategy for killing p53-deficient TNBC.

Loss of HRR increases dependence of cells on a class of enzymes called PARPs, and Chk1 has also been shown to be important for efficient HRR. Thus, by interfering with HRR, Chk1 inhibitors are predicted to sensitize TNBC cells to PARP inhibitors. We tested the hypotheses that by impairing HRR, Chk1 inhibitors will sensitize TNBCs to PARP inhibition, and that therapies that combine Chk1 inhibitors with PARP inhibitors will be effective at killing TNBCs because they will simultaneously induce checkpoint bypass and block DNA repair. We generated a set of isogenic TNBC cell lines that are p53-proficient (p53WT) or p53-deficient (p53KD), and evaluated their sensitivity to Chk1 inhibitors (LY2606368) and DNA damaging agents (cisplatin). Loss of p53 conferred a dramatic increase in sensitivity to treatment with cisplatin + LY2606368. Surprisingly, inhibition of PARP1 (BMN673) did not increase sensitivity to Chk1 inhibitor ± cisplatin. To determine why Chk1 inhibition did not sensitize cells to PARP inhibition, we evaluated the effect of Chk1 inhibition on the ability of cells to recruit HRR proteins to sites of DNA damage. In line with CHK1 regulating HRR, Chk1 inhibition was associated with an inability of Rad51 to localize to sites of DNA double strand breaks. Interestingly, we also found that upstream of Rad51, there was a significant alteration in the formation of phopho-RPA2 foci in cells treated with the Chk1 inhibitor. On-going studies are evaluating whether there are changes in the kinetics of formation and/or resolution of Rad51 and phospho-RPA2 foci in response to Chk1 inhibition.

Citation Format: Redwood AB, Cai S, Piwnica-Worms H. Targeted therapies for TNBC: Exploiting vulnerabilities that arise from DNA damage repair pathway dependencies. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-07-02.

Abstract P5-04-18: Extracts derived from fungi and plants demonstrate specificity for subtyptes of triple negative breast cancer

New effective therapies are needed for patients with triple negative breast cancers (TNBC). The identification by Lehmann and Bauer1 of distinct subtypes of TNBC and representative cell lines that are driven by different defects and signaling pathways provided the opportunity, for the first time, to screen for selective activities against these subtypes of TNBC. Using this knowledge, we initiated a screen of diverse natural product extract libraries with the goal of identifying extracts selective for subtypes of TNBC. The compounds with this selective activity will then be purified using bioassay-guided fractionation. Drugs derived from plants and fungi have provided some of the most important pharmaceuticals used today, including numerous anticancer agents.2 Natural products occupy a biologically validated chemical space that does not overlap with compounds found in most synthetic chemical libraries.3 Additionally, there are differences in chemical space between plant and fungal-derived compounds4 and different compound classes are expected to be isolated from these two sources. A total of 1,953 extracts of fungi collected from diverse environments, including Great Lakes sediments and 2,200 plant extracts from tropical environments have been screened for selective cytotoxic activities against cell lines representing 5 subtypes of TNBC. These subtypes are the basal-like 1 and 2 (BL1, BL2), mesenchymal (M), mesenchymal stem-like (MSL) and luminal androgen receptor (LAR). The initial screening using one concentration, 2 µg/ml for fungal extracts and 20 µg/ml for plant extracts, identified many extracts with selective activity against the TNBC subtypes. Detailed dose response curves were then generated with these extracts in each of the TNBC cell lines. A total of 4 fungal extracts and 7 plant extracts with selective cytotoxic activities were identified with selectivity up to 100-fold for 3 of the extracts. Bioassay-guided fractionation is ongoing to identify the active constituents. These results demonstrate that natural product extracts can yield selective actions against TNBC subtypes. We expect that these plant and fungal extracts will yield compounds that target molecular drivers specific to the TNBC subtypes. It is our expectation that compounds with selective, targeted activities will continue to be isolated from these extract collections.

1. Lehman BD and Bauer JA et al. J Clin Invest: 121, 2750-2767, 2011.

2. Newman DJ and Cragg GM. J Nat Prod: 75, 311-335, 2012.

3. Feher M and Schmidt JM. J Chem Inf Comput Sci: 43, 218-227, 2003.

4. El-Elimat, T et al. ACS Med Chem Lett: 3, 645-649, 2012.

Citation Format: Shaffer CV, Cai S, Perez A, Risinger AL, Du L, O'Keefe BR, Cichewicz RH, Mooberry SL. Extracts derived from fungi and plants demonstrate specificity for subtyptes of triple negative breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-04-18.

Abstract P3-06-04: Investigating clonal dynamics in triple negative breast cancer chemoresistance

Approximately 50% of triple-negative breast cancer (TNBC) patients have extensive residual disease following neoadjuvant chemotherapy (NAC). These patients have a four-fold increase in mortality risk and an increased risk of distant metastases within three years (1). Understanding the molecular basis of resistance to NAC is expected to provide opportunities to better treat patients in the primary setting. Extensive intratumoral subclonal heterogeneity has been well documented in primary, treatment-naïve TNBC (2). Subclonal populations harboring distinct molecular profiles may confound targeted therapy strategies, yet the functional impact of subclonal heterogeneity in TNBC resistance to therapy is unknown. We are implementing DNA barcoding to quantitatively track changes in subclonal architecture pre- and post-treatment in patient-derived xenograft (PDX) models of TNBC in order to design novel combination therapies. Such barcoding strategies have been used to monitor clonal dynamics in breast cancer PDXs with great sensitivity (3).

We have established an orthotopic PDX from a treatment-naïve TNBC patient (PIM1, procured from a patient later found to have chemoresistant disease). In order to model chemoresistance, we treated PIM1 with Adriamycin and cyclophosphamide (AC), standard of care NAC for TNBC patients, which resulted in partial response but left residual disease. To characterize subclonal dynamics in response to NAC, we transduced freshly isolated PIM1 cells with a lentiviral library expressing 25 million unique DNA barcodes (Cellecta) using conditions to ensure each transduced cell contained a single unique barcode. Transduced cells were selected with puromycin, then orthotopically implanted into immuno-compromised mice. High-throughput barcode sequencing revealed reproducible maintenance of greater than 60,000 unique barcodes in PDX tumors. Comparison of barcode distribution in tumors treated with vehicle or NAC will reveal whether NAC selects for a subpopulation of cells during the development of resistance. Future directions will include whole-exome and RNA sequencing to characterize genomic changes associated with alterations in barcode distribution in response to NAC treatment. Our ultimate goal is to identify novel combination therapies to eliminate subclones that contribute to chemoresistance in primary TNBC.

References

1. Cortazar P, et al. (Pathological complete response and long-term clinical benefit in breast cancer: the CTNeoBC pooled analysis. The Lancet 384(9938):164-172.

2. Shah SP, et al. (2012) The clonal and mutational evolution spectrum of primary triple-negative breast cancers. Nature 486(7403):395-399.

3. Nguyen LV, et al. (2014) DNA barcoding reveals diverse growth kinetics of human breast tumour subclones in serially passaged xenografts. Nat Commun 5.

Citation Format: Echeverria GV, Seth S, Moulder S, Symmans W, Chang J, Cai S, Heffernan T, Piwnica-Worms H. Investigating clonal dynamics in triple negative breast cancer chemoresistance. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-06-04.

Cytotoxicity, genotoxicity and antibacterial effectiveness of a bioceramic endodontic sealer

AIM

To compare the characteristics of bioceramic endodontic sealer Endosequence BC sealer with those of AH Plus sealer.

METHODOLOGY

Cytotoxicity and genotoxicity were analysed on human gingival fibroblasts submitted to cell culture medium conditioned by sealers using the MTT reduction assay and micronucleus formation test (MNT), respectively. Cells grown on fresh medium served as controls. Cell viabilities were measured at 1, 3, 5 and 7 days. The antibacterial activity was analysed on an Enterococcus faecalis strain (ATCC 29212) using both on agar diffusion test (ADT) and a direct contact test (DCT). The inhibition zones in ADT were measured after 48 h and the colony-forming units counting in the DCT after 1, 24, 72 and 168 h. Data were compared by anova and Tukey's test and MNT by Fisher's exact test (P < 0.05).

RESULTS

Cultures submitted to Endosequence BC sealer had a significantly higher number of viable cells (P < 0.01) and less micronucleus formation (P < 0.05) than AH Plus sealer. Endosequence BC sealer exhibited significantly smaller inhibition zones (6.00 ± 0.03 mm) than AH Plus sealer (10.31 ± 0.21 mm) (P < 0.05). Moreover, Endosequence BC sealer had significantly smaller antibacterial activity than AH Plus sealer up to 1 h of direct contact (P < 0.05). On other exposure times, both materials had similar antibacterial effectiveness (P > 0.05).

CONCLUSIONS

Bioceramic-based sealer had less cytotoxicity and genotoxicity and similar antibacterial effect against E. faecalis in comparison with AH Plus sealer.

The prognostic value of pSTAT3 in gastric cancer: a meta-analysis

INTRODUCTION

The prognostic value of pSTAT3 in gastric cancer has been assessed for years while the results remain controversial and heterogeneous. Therefore, we conducted this meta-analysis to determine the prognostic effect of pSTAT3 in gastric cancer patients.

METHODS

We searched PubMed, Embase and Web of Science and eight studies comprising 1314 gastric cancer patients were included in our meta-analysis. Hazard ratios (HRs) with 95 % confidence interval (95 % CI) were extracted to perform meta-analysis on the overall survival. Subgroup analysis according to study location, publication year, number of patients and quality score of studies were also investigated.

RESULTS

Our results revealed that pSTAT3-positive patients had a significant increase in mortality risk as compared to pSTAT3-negative patients in the random-effects model (combined HR 1.87, 95 % CI 1.28-2.74). However, our result showed no statistically significant association between pSTAT3 and clinicopathological characteristics (TMN stage, lymph node metastasis, grade of differentiation, Lauren classification and distant metastasis) of gastric cancer.

CONCLUSION

In conclusion, our meta-analysis suggests that positive expression of pSTAT3 is associated with poor prognosis in gastric cancer patients.

Abstract 5545: Deguelin selectively inhibits proliferation of luminal androgen receptor (LAR) triple-negative breast cancer cells

Triple negative breast cancers (TNBCs) lack expression of the estrogen and progesterone receptors (ER/PR) and HER2 amplification. These aggressive malignancies have higher mortality rates than other breast cancer subtypes. While targeted therapies for ER+/PR+ and HER2-amplified breast cancers have greatly improved survival for these patients, there are no approved targeted therapies for TNBCs. Development of targeted therapies for TNBC will likely provide a similar survival benefit over traditional cytotoxic therapy. The identification of molecular targets for TNBC has been limited without a better understanding of the subtypes of these heterogeneous diseases. Gene expression profiling recently identified 6 defined subtypes of TNBC and representative cell lines, providing the first opportunity to identify subtype-specific leads for TNBC. In this study, we used high-content phenotypic screening to evaluate novel libraries of plant and fungal extracts for antiproliferative and cytotoxic activity in a panel of cell lines modeling the different TNBC subtypes. The aim was to identify extracts with selective activity in a single cell line with the hypothesis that the selectivity resulted from a target relevant specifically to that subtype. A plant extract selectively inhibited proliferation of MDA-MB-453 cells, which represent the luminal androgen receptor (LAR) subtype. Bioassay-guided fractionation identified deguelin, which showed potent and highly selective activity in MDA-MB-453 cells compared to all the other TNBC cell lines, with 240 to 1000-fold higher potency. Further studies investigated the molecular mechanisms of action of degeulin in MDA-MB-453 cells. Based on the sensitivity of LAR TNBCs to both antiandrogens and Hsp90 inhibitors, as well as prior studies demonstrating Hsp90 inhibition by deguelin, we hypothesized that deguelin's mechanism in MDA-MB-453 cells involves Hsp90 inhibition, resulting in AR destabilization and reduced proliferation. Immunoblotting of deguelin-treated MDA-MB-453 whole-cell lysates indicated that deguelin reduced cellular levels of AR, which are noticeable 8 h after treatment. Immunofluorescence microscopy studies also suggested reduced nuclear localization of AR 18 h after treatment. Previous studies showed that LAR TNBC cells are highly sensitive to PI3K inhibitors compared to other TNBC subtypes, and thus the effects of deguelin on PI3K-Akt signaling were evaluated in MDA-MB-453 cells. Immunoblotting indicated that deguelin reduced the relative phosphorylation of Akt at T308, but had no effect on phosphorylation of S473, suggesting inhibition of PI3K but not mTORC2. Ongoing studies are aimed at better characterizing the mechanisms of deguelin in MDA-MB-453 cells with the goal of identifying targets to develop better therapies for LAR TNBC patients.

Citation Format: Andrew J. Robles, Shengxin Cai, Robert H. Cichewicz, Susan L. Mooberry. Deguelin selectively inhibits proliferation of luminal androgen receptor (LAR) triple-negative breast cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5545. doi:10.1158/1538-7445.AM2015-5545

Polyketide glycosides from Bionectria ochroleuca inhibit Candida albicans biofilm formation

One of the challenges presented by Candida infections is that many of the isolates encountered in the clinic produce biofilms, which can decrease these pathogens' susceptibilities to standard-of-care antibiotic therapies. Inhibitors of fungal biofilm formation offer a potential solution to counteracting some of the problems associated with Candida infections. A screening campaign utilizing samples from our fungal extract library revealed that a Bionectria ochroleuca isolate cultured on Cheerios breakfast cereal produced metabolites that blocked the in vitro formation of Candida albicans biofilms. A scale-up culture of the fungus was undertaken using mycobags (also known as mushroom bags or spawn bags), which afforded four known [TMC-151s C-F (1-4)] and three new [bionectriols B-D (5-7)] polyketide glycosides. All seven metabolites exhibited potent biofilm inhibition against C. albicans SC5314, as well as exerted synergistic antifungal activities in combination with amphotericin B. In this report, we describe the structure determination of the new metabolites, as well as compare the secondary metabolome profiles of fungi grown in flasks and mycobags. These studies demonstrate that mycobags offer a useful alternative to flask-based cultures for the preparative production of fungal secondary metabolites.

Bioactive sulfur-containing sulochrin dimers and other metabolites from an Alternaria sp. isolate from a Hawaiian soil sample

Polluxochrin (1) and dioschrin (2), two new dimers of sulochrin linked by thioether bonds, were purified from an Alternaria sp. isolate obtained from a Hawaiian soil sample. The structures of the two metabolites were established by NMR, mass spectrometry data, and X-ray analysis. Metabolite 1 was determined to be susceptible to intramolecular cyclization under aqueous conditions, resulting in the generation of 2 as well as another dimeric compound, castochrin (3). An additional nine new metabolites were also obtained, including four new pyrenochaetic acid derivatives (8-11), one new asterric acid analogue (13), and four new secalonic acid analogues (14-17). Bioassay analysis of these compounds revealed 1-3 displayed antimicrobial and weak cytotoxic activities.

Scoring Functions Based on Second Level Score for k-SAT with Long Clauses

It is widely acknowledged that stochastic local search (SLS) algorithms can efficiently find models for satisfiable instances of the satisfiability (SAT) problem, especially for random k-SAT instances. However, compared to random 3-SAT instances where SLS algorithms have shown great success, random k-SAT instances with long clauses remain very difficult. Recently, the notion of second level score, denoted as "score_2", was proposed for improving SLS algorithms on long-clause SAT instances, and was first used in the powerful CCASat solver as a tie breaker. In this paper, we propose three new scoring functions based on score_2. Despite their simplicity, these functions are very effective for solving random k-SAT with long clauses. The first function combines score and score_2, and the second one additionally integrates the diversification property "age". These two functions are used in developing a new SLS algorithm called CScoreSAT. Experimental results on large random 5-SAT and 7-SAT instances near phase transition show that CScoreSAT significantly outperforms previous SLS solvers. However, CScoreSAT cannot rival its competitors on random k-SAT instances at phase transition. We improve CScoreSAT for such instances by another scoring function which combines score_2 with age. The resulting algorithm HScoreSAT exhibits state-of-the-art performance on random k-SAT (k>3) instances at phase transition. We also study the computation of score_2, including its implementation and computational complexity.