Triumphs and challenges in exploiting poly(ADP-ribose) polymerase inhibition to combat triple-negative breast cancer

Poly(ADP-ribose) polymerase 1 (PARP1) regulates a myriad of DNA repair mechanisms to preserve genomic integrity following DNA damage. PARP inhibitors (PARPi) confer synthetic lethality in malignancies with a deficiency in the homologous recombination (HR) pathway. Patients with triple-negative breast cancer (TNBC) fail to respond to most targeted therapies because their tumors lack expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Certain patients with TNBC harbor mutations in HR mediators such as breast cancer susceptibility gene 1 (BRCA1) and breast cancer susceptibility gene 2 (BRCA2), enabling them to respond to PARPi. PARPi exploits the synthetic lethality of BRCA-mutant cells. However, de novo and acquired PARPi resistance frequently ensue. In this review, we discuss the roles of PARP in mediating DNA repair processes in breast epithelial cells, mechanisms of PARPi resistance in TNBC, and recent advances in the development of agents designed to overcome PARPi resistance in TNBC.

Dibenzyl trisulfide induces caspase-independent death and lysosomal membrane permeabilization of triple-negative breast cancer cells

The Petiveria alliacea L. (P. alliacea) plant is traditionally used in folklore medicine throughout tropical regions of the world to treat arthritis, asthma, and cancer. Dibenzyl trisulfide (DTS) is one of the active ingredients within the P. alliacea plant. Triple-negative breast cancer (TNBC) is associated with a poor prognosis, particularly among women of West African ancestry, due in part to limited effective therapy. Though potent anticancer actions of DTS have been reported in a TNBC cell line, the mechanism of DTS-mediated cytotoxicity and cell death remains ill-defined. In the current study, we show that DTS exhibits cytotoxicity in a panel of triple-negative breast cancer (TNBC) cells derived from patients of European and West African ancestry. We found that DTS inhibits proliferation and migration of CRL-2335 cells derived from a patient of West African ancestry. DTS induces the expression of pro-apoptotic genes BAK1, GADD45a, and LTA in CRL2335 cells though it primarily promotes caspase-independent CRL-2335 cell death. DTS also promotes destabilization of the lysosomal membrane resulting in cathepsin B release in CRL-2335 cells. Finally, Kaplan-Meier survival curves reveal that higher expression of BAK1 and LTA in tumors from patients with TNBC is associated with longer relapse-free survival. Collectively, our data suggest that DTS confers promising antitumor efficacy in TNBC, in part, via lysosomal-mediated, caspase-independent cell death to warrant furthering its development as an anticancer agent.

Aminoflavone upregulates putative tumor suppressor miR-125b-2-3p to inhibit luminal A breast cancer stem cell-like properties

Metastatic breast cancer is incurable and often due to breast cancer stem cell (CSC)-mediated self-renewal. We previously determined that the aryl hydrocarbon receptor (AhR) agonist aminoflavone (AF) inhibits the expression of the CSC biomarker α6-integrin (ITGA6) to disrupt the formation of luminal (hormone receptor-positive) mammospheres (3D breast cancer spheroids). In this study, we performed miRNA-sequencing analysis of luminal A MCF-7 mammospheres treated with AF to gain further insight into the mechanism of AF-mediated anti-cancer and anti-breast CSC activity. AF significantly induced the expression of >70 microRNAs (miRNAs) including miR125b-2–3p, a predicted stemness gene regulator. AF-mediated miR125b-2–3p induction was validated in MCF-7 mammospheres and cells. miR125b-2–3p levels were low in breast cancer tissues irrespective of subtype compared to normal breast tissues. While miR125b-2–3p levels were low in MCF-7 cells, they were much lower in AHR¹⁰⁰ cells (MCF-7 cells made unresponsive to AhR agonists). The miR125b-2–3p mimic decreased, while the antagomiR125b-2–3p increased the expression of stemness genes ITGA6 and SOX2 in MCF-7 cells. In MCF-7 mammospheres, the miR125b-2–3p mimic decreased only ITGA6 expression although the antagomiR125b-2–3p increased ITGA6, SOX2 and MYC expression. AntagomiR125b-2–3p reversed AF-mediated suppression of ITGA6. The miR125b-2–3p mimic decreased proliferation, migration, and mammosphere formation while the antagomiR125b-2–3p increased proliferation and mammosphere formation in MCF-7 cells. The miR125b-2–3p mimic also inhibited proliferation, mammosphere formation, and migration in AHR100 cells. AF induced AhR- and miR125b2-3p-dependent anti-proliferation, anti-migration, and mammosphere disruption in MCF-7 cells. Our findings suggest that miR125b-2–3p is a tumor suppressor and AF upregulates miR125b-2–3p to disrupt mammospheres via mechanisms that rely at least partially on AhR in luminal A breast cancer cells.

Abstract PO-110: Plant isolate dibenzyl trisulfide induces caspase-independent death in triple negative breast cancer cells derived from patients of West African descent

Patients with triple negative breast cancer (TNBC) possess tumors that lack estrogen receptor, progesterone receptor, and human epidermal growth receptor expression. While these patients traditionally receive chemotherapy to combat this aggressive breast cancer subtype, others use natural remedies. Dibenzyl trisulfide (DTS) is derived from Petiveria alliacea, a perennial shrub that grows in tropical regions of the world. Many TNBC patients residing in the tropics are of West African descent. Therefore, we evaluated the anticancer actions of DTS in TNBC cells, including those derived from patients of West African descent. We found that DTS inhibited TNBC cell viability, migration and proliferation in a dose-dependent manner. Interestingly, DTS blocked the propensity of pro-carcinogen benzo-A-pyrene to induce proliferation of immortalized breast epithelial cells. Moreover, we found that DTS induced early apoptosis in TNBC cells, which was only partially attenuated following pretreatment with pan-caspase inhibitor zVAD-fmk. Though DTS induced pro-apoptotic gene and protein expression along with PARP cleavage, it failed to produce appreciable caspase 3 cleavage and promote significant apoptotic body formation. This suggests that this plant isolate induces caspase-independent and non-apoptotic death of TNBC cells. Furthermore, DTS promoted lysosomal membrane destabilization and cathepsin B release in TNBC cells. Taken together, DTS exhibits promising chemotherapeutic and chemopreventive ability by inducing non-apoptotic TNBC cell death and thwarting TNBC progression, supporting its evaluation in clinical trials as an agent to combat TNBC among patients of West African descent.

Citation Format: Jonathan Wooten, Shaniece Wooten, Cristina Araújo, Joyce Aja, Nicole Mavingire, Rupika Delgoda, Eileen Brantley. Plant isolate dibenzyl trisulfide induces caspase-independent death in triple negative breast cancer cells derived from patients of West African descent [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-110.

Cancer stem cells: Culprits in endocrine resistance and racial disparities in breast cancer outcomes

Breast cancer stem cells (BCSCs) promote endocrine therapy (ET) resistance, also known as endocrine resistance in hormone receptor (HR) positive breast cancer. Endocrine resistance occurs via mechanisms that are not yet fully understood. In vitro, in vivo and clinical data suggest that signaling cascades such as Notch, hypoxia inducible factor (HIF), and integrin/Akt promote BCSC-mediated endocrine resistance. Once HR positive breast cancer patients relapse on ET, targeted therapy agents such as cyclin dependent kinase inhibitors are frequently implemented, though secondary resistance remains a threat. Here, we discuss Notch, HIF, and integrin/Akt pathway regulation of BCSC activity and potential strategies to target these pathways to counteract endocrine resistance. We also discuss a plausible link between elevated BCSC-regulatory gene levels and reduced survival observed among African American women with basal-like breast cancer which lacks HR expression. Should future studies reveal a similar link for patients with luminal breast cancer, then the use of agents that impede BCSC activity could prove highly effective in improving clinical outcomes among African American breast cancer patients.

Abstract 6553: Plant power: Plant isolate dibenzyl trisulfide induces death of triple-negative breast cancer cells derived from an African American patient

Triple negative breast cancer (TNBC), characterized by tumors that lack estrogen receptor, progesterone receptor, and human epidermal growth receptor expression, represents one of the most aggressive subtypes of breast cancer. TNBC carries a poor prognosis due, in part, to a lack of clinically available targeted therapy. Novel therapeutic strategies to combat TNBC primarily involve the use of synthetic small molecules. However, the World Health Organization reports that there is increased use of natural remedies and traditional medicine to treat diseases. Our lab has investigated the chemotherapeutic and chemopreventive effects of a variety of plant isolates. Dibenzyl trisulfide (DTS) is derived from Petiveria alliacea, a perennial shrub that grows in tropical regions of the world. Previous investigations surrounding DTS are limited to anticancer actions in European American breast cancer cells. The purpose of this study was to evaluate the anticancer actions of DTS in CRL-2335 cells which are derived from an African American patient with TNBC. We found that DTS inhibited TNBC cell migration and proliferation using wound healing and colony forming assays. Furthermore, we found DTS induced apoptotic body formation and nuclear fragmentation using relief contrast and fluorescence microscopy respectively. Moreover, using the Annexin V/PI assay we found that DTS induced early apoptosis, which was partially attenuated in cells pretreated with pan-caspase inhibitor zVAD-fmk. Finally, quantitative polymerase chain reaction analyses revealed that DTS induced the expression of pro-apoptotic genes BAK1, LTA and GADD45A. Our data suggest that DTS effectively induces caspase-independent death of TNBC cells derived from an African American patient and represents a promising agent to treat more refractory forms of breast cancer.

Citation Format: Jonathan Wooten, Cristina Araújo, Shaniece Wauchope, Joyce Aja, Nicole Mavingire, Rupika Delgoda, Eileen Brantley. Plant power: Plant isolate dibenzyl trisulfide induces death of triple-negative breast cancer cells derived from an African American patient [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6553.

Abstract 1304: Aryl hydrocarbon receptor ligands 5F 203 and 3,3'-Diindolylmethane disrupt mammospheres derived from MCF-7 cells and induce tumor suppressor miR125b-2 expression

While anti-estrogen tamoxifen (Tam) effectively treats many patients with estrogen receptor positive (ER+) tumors, up to 40% experience relapse following resistance. Breast cancer stem cells (CSCs) within tumors greatly contribute to tamoxifen resistance (TamR) and exhibit unique molecular signatures that drive metastasis and promote relapse. Tumor suppressor miRNAs aid in suppressing breast cancer progression. We have previously shown that aryl hydrocarbon receptor (AhR)-ligand Aminoflavone disrupts the formation of spheres and inhibits the expression of putative stemness marker α6-integrin and α6-integrin-src-Akt signaling. We hypothesize that two AhR ligands, 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203) and 3,3'-Diindolylmethane (DIM), exhibit anticancer properties in MCF-7 breast cancer cells by targeting the CSC population in an AhR-dependent fashion. We found that DIM and 5F 203 disrupted mammospheres derived from MCF-7 cells but demonstrated a reduced capacity to do so in mammospheres derived from AHR100 cells (MCF-7 variants that are AhR-unresponsive). Wound healing and colony forming assays respectively revealed that 5F 203 and DIM also decreased cell migration and cell proliferation in MCF-7 cells and to a much lesser extent in AhR100 cells. 5F 203 and DIM induced miR125b-2 expression and suppressed the expression of stemness-regulating genes such as α6-integrin, a predicted miR125b-2 target. The reduction in stemness-gene expression in MCF-7 cells was attenuated following pretreatment with AhR antagonist CH223191. These data suggest that AhR ligands such as DIM and 5F 203 confer their anticancer actions including those against breast CSCs in an AhR-dependent manner. Our data is expected to provide a rationale for the development of anticancer AhR ligands designed to combat ER+ breast cancer and decrease the risk of relapse.

Citation Format: Eileen Brantley, Nicole Mavingire, Jonathan Wooten, Petreena Campbell. Aryl hydrocarbon receptor ligands 5F 203 and 3,3'-Diindolylmethane disrupt mammospheres derived from MCF-7 cells and induce tumor suppressor miR125b-2 expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1304.

Glaucarubulone glucoside from Castela macrophylla suppresses MCF-7 breast cancer cell growth and attenuates benzo[a]pyrene-mediated CYP1A gene induction

Quassinoids often exhibit antioxidant and antiproliferative activity. Emerging evidence suggests that these natural metabolites also display chemopreventive actions. In this study, we investigated the potential for the quassinoid glaucarubulone glucoside (Gg), isolated from the endemic Jamaican plant Castela macrophylla (Simaroubaceae), to display potent cytotoxicity and inhibit human cytochrome P450s (CYPs), particularly CYP1A enzymes, known to convert polyaromatic hydrocarbons into carcinogenic metabolites. Gg reduced the viability of MCF-7 breast adenocarcinoma cells (IC₅₀ = 121 nm) to a greater extent than standard of care anticancer agents 5-fluorouracil, tamoxifen (IC₅₀ >10 μm) and the tamoxifen metabolite 4-hydroxytamoxifen (IC₅₀ = 2.6 μm), yet was not cytotoxic to non-tumorigenic MCF-10A breast epithelial cells. Additionally, Gg induced MCF-7 breast cancer cell death. Gg blocked increases in reactive oxygen species in MCF-10A cells mediated by the polyaromatic hydrocarbon benzo[a]pyrene (B[a]P) metabolite B[a]P 1,6-quinone, yet downregulated the expression of genes that promote antioxidant activity in MCF-7 cells. This implies that Gg exhibits antioxidant and cytoprotective actions in non-tumorigenic breast epithelial cells and pro-oxidant, cytotoxic actions in breast cancer cells. Furthermore, Gg inhibited the activities of human CYP1A according to non-competitive kinetics and attenuated the ability of B[a]P to induce CYP1A gene expression in MCF-7 cells. These data indicate that Gg selectively suppresses MCF-7 breast cancer cell growth without impacting non-tumorigenic breast epithelial cells and blocks B[a]P-mediated CYP1A induction. Taken together, our data provide a rationale for further investigations of Gg and similar plant isolates as potential agents to treat and prevent breast cancer. Copyright © 2017 John Wiley & Sons, Ltd.

Accelerating the culture change!

Exide Electronics, a major supplier of uninterruptible power system equipment, embarked on a journey of changing a culture to improve quality, enhance customer responsiveness, and reduce costs. This case study examines the evolution of change over a period of seven years, with particular emphasis on the most recent years, 1992 through 1995. The article focuses on the Raleigh plant operations and describes how each succeeding year built on the successes and fixed the shortcomings of the prior years to accelerate the culture change, including corrective action and continuous improvement processes, organizational structures, expectations, goals, achievements, and pitfalls. The real challenge to changing the culture was structuring a dynamic approach to accelerate change! The presentation also examines how the evolutionary process itself can be created and accelerated through ongoing communication, regular feedback of progress and goals, constant evaluation and direction of the process, and measuring and paying for performance.

Clinical manifestations of transdermal scopolamine addiction

Transdermal scopolamine patches have been extensively prescribed for nonspecific dizziness and vestibular disorders. Patient response may be favorable and side effects are generally limited to xerostomia and blurred vision. However, subtle dependency and outright addiction may develop. Tapered reduction and drug elimination will suffice to eliminate the dependency. However, hospitalization may be necessary to treat severe cases of physiological chemical dependency. Long-term use of transdermal scopolamine patches carries a risk of chemical dependency. Prescribing physicians should review and heed the manufacturer's recommended use.

Treatment of vacutainers for use in the analysis of volatile organic compounds in human blood at the low parts-per-trillion level

Vacutainers that are routinely used for blood collection contain significant amounts of volatile organic compounds (VOCs). These VOCs interfere with the low parts-per-trillion analysis of VOCs in whole blood either by causing false positives or by masking the presence of VOCs because of high background levels. Benzene, bromoform, ethylbenzene, m/p-xylene, o-xylene, styrene, and various hydrocarbons are the most significant sources of VOC contamination present in the vacutainers. A method of removing VOCs from 10-mL gray-top vacutainers is presented. This method uses a combination of heat and vacuum to reduce the VOCs to levels compatible with low parts-per-trillion analysis of VOCs in whole blood.

Production and oxidation of indole by Haemophilus influenzae

During growth in high concentrations of iron nitrate, H. influenzae produces compounds reactive in biochemical assays for hydroxamates. Mixing experiments established that nitrate was responsible for inducing these compounds. Analysis by 1H and 13C NMR and high resolution mass spectrometry identified the active species as 2,2-bis(3'-indolyl)indoxyl. Bacterial production of the latter compound has been previously observed only in Pseudomonas aureofaciens. A mutant defective in the production of 2,2-bis(3'-indolyl)indoxyl was constructed by marker insertion. The formation of indole and 2,2-bis (3'-indolyl)indoxyl was quantitated by reverse-phase high pressure liquid chromatography during growth in high concentrations of nitrate. The mutant produced high concentrations of indole, but only minimal amounts of 2,2-bis(3'-indolyl)indoxyl, and also proved to be defective in nitrate reduction. These data suggest that indole may function as an electron donor for nitrate reductase in H. influenzae.