Exosc9 Initiates SUMO-Dependent lncRNA TERRA Degradation to Impact Telomeric Integrity in Endocrine Therapy Insensitive Hormone Receptor-Positive Breast Cancer.

Long, noncoding RNAs (lncRNAs) are indispensable for normal cell physiology and, consequently, are tightly regulated in human cells. Yet, unlike mRNA, substantially less is known about the mechanisms for lncRNA degradation. It is important to delineate the regulatory control of lncRNA degradation, particularly for lncRNA telomeric repeat-containing RNA (TERRA), as the TERRA-telomere R-loops dictate cell cycle progression and genomic stability. We now report that the exosome complex component Exosc9 degrades lncRNA TERRA in human mammary epithelial cells. Heterochromatin protein 1 alpha (HP1α) recruits Exosc9 to the telomeres; specifically, the SUMO-modified form of HP1α supports interaction with Exosc9 and, as previously reported, lncRNA TERRA. The telomeric enrichment of Exosc9 is cell cycle-dependent and consistent with the loss of telomeric TERRA in the S/G2 phase. Elevated Exosc9 is frequently observed and drives the growth of endocrine therapy-resistant (ET-R) HR+ breast cancer (BCa) cells. Specifically, the knockdown of Exosc9 inversely impacts telomeric R-loops and the integrity of the chromosome ends of ET-R cells. Consistently, Exosc9 levels dictate DNA damage and the sensitivity of ET-R BCa cells to PARP inhibitors. In this regard, Exosc9 may serve as a promising biomarker for predicting the response to PARP inhibitors as a targeted monotherapy for ET-R HR+ BCa.

Constitutively active androgen receptor supports the metastatic phenotype of endocrine-resistant hormone receptor-positive breast cancer.

BACKGROUND: Hormone receptor positive (HR+) breast cancer (BCa) is the most frequently diagnosed subtype. Acquired and intrinsic resistance to conventional endocrine therapy (ET) commonly occurs and prompts incurable metastatic disease. Hence, ET-resistant (ET-R) HR+ BCa presents a therapeutic challenge. Previous studies show elevated androgen receptor (AR) that supports resistance to ET tamoxifen and correlates with HR+ BCa metastasis. Yet surprisingly, studies with AR-blocker enzalutamide (Enz) in ET-R HR+ BCa present conflicting results. We now report that a constitutively active, unique from canonical Enz-targeted, AR accumulates in endocrine resistant HR+ BCa cells. METHODS: AR protein profiles in acquired and intrinsic ET-R HR + -BCa were defined with cell-free modification tests, in-house in-vivo SUMOylation assays, and PLA imaging. Genomic activity of native AR and modified-AR mimetic was tested with reporter assays and limited transcriptome analysis. Spheroid growth and migration studies were used to evaluate inhibitory actions of Enz and combinatorial therapy. RESULTS: Sustained higher molecular weight SUMO-modified AR (SUMO-AR) persists in acquired and intrinsic ET-R BCa cell lines. Concurrently, SUMO isoforms and global SUMO-modified proteome also accumulates in the same cell lines. We identified AR as a novel substrate for the SUMO-E3 ligase HSPB1/Hsp27. Independent of ligand, SUMO-AR is resilient to ubiquitin-mediated proteasomal degradation, enriched in the nucleus, readily chromatin-bound, and transcriptionally active. Constitutive SUMO-AR initiates a gene-expression profile that favors epithelial-mesenchymal transition. Enz combined with a SUMO inhibitor attenuates migration and metastatic phenotype of ET-R HR+ BCa. CONCLUSION: Targeting both unmodified and SUMO-modified AR prevents the metastatic progression of HR+ BCa with ET-R. Video abstract.

Novel SUMO-Protease SENP7S Regulates ß-catenin Signaling and Mammary Epithelial Cell Transformation.

SUMO post-translational modification of proteins or SUMOylation ensures normal cell function. Disruption of SUMO dynamics prompts various pathophysiological conditions, including cancer. The burden of deSUMOylating the large SUMO-proteome rests on 6 full-length mammalian SUMO-proteases or SENP. While multiple SENP isoforms exist, the function of these isoforms remains undefined. We now delineate the biological role of a novel SENP7 isoform SENP7S in mammary epithelial cells. SENP7S is the predominant SENP transcript in human mammary epithelia but is significantly reduced in precancerous ductal carcinoma in situ and all breast cancer subtypes. Like other SENP family members, SENP7S has SUMO isopeptidase activity but unlike full-length SENP7L, SENP7S is localized in the cytosol. In vivo, SUMOylated ß-catenin and Axin1 are both SENP7S-substrates. With knockdown of SENP7S in mammary epithelial cells, Axin1-ß-catenin interaction is lost and ß-catenin escapes ubiquitylation-dependent proteasomal degradation. SUMOylated ß-catenin accumulates at the chromatin and activates multiple oncogenes. Hence, non-tumorigenic MCF10-2A cells with reduced SENP7S exhibit greater cell proliferation and anchorage-dependent growth. SENP7S depletion directly potentiates tumorigenic properties of MCF10-2A cells with induction of anchorage-independent growth and self-renewal in 3D-spheroid conditions. Collectively, the results identify SENP7S as a novel mediator of ß-catenin signaling and normal mammary epithelial cell physiology.

Assessment of genotoxicity of pyrethrin in cultured human lymphocytes.

Pyrethrin is an insecticide that is obtained from the Chrysanthemum flower (Pyrethrum). In this study, we examined the genotoxic effects of pyrethrin on cultured human lymphocytes using sister chromatid exchanges (SCEs) and 8-hydroxy deoxyguanosine (8-OHdG) assays. Cultures were treated with different concentrations of pyrethrin (25, 50, and 100 µg/mL), which was dissolved in in dimethyl sulfoxide (DMSO). The results showed that treatment of cultured lymphocytes with pyrethrin at 50 µg/mL and 100 µg/mL induced significant elevation in SCEs (p < 0.05). In addition, the 100 µg/mL concentration significantly affected both mitotic and proliferative indices (p < 0.05). Finally, pyrethrin induced significant elevation in the oxidative stress marker 8-OHdG in a dose-dependent manner (p < 0.001). In conclusion, the results suggest that pyrethrin is genotoxic as measured by two independent assays on genetic toxicity.

Evaluation of the effect of angiotensin converting enzyme inhibitors and angiotensin receptors blockers on aspirin antiplatelet effect.

OBJECTIVE: Cardiovascular disease (CVD) is one of the major burdens on societies and healthcare systems. Antiplatelet aspirin is used to prevent the occurrence or reoccurrence of cardiovascular events. However, studies have shown that a good portion of patients still suffer from cardiovascular events in spite of using aspirin (also called aspirin nonresponders). On the other hand, angiotensin-converting enzyme inhibitors (ACEIs) as well as angiotensin-receptor blockers (ARBs) are widely used in patients with different spectrums of cardiovascular diseases. In this study, the possible interactive effect of ACEIs and ARBs on aspirin response was evaluated in vitro. METHODS: A multiplate analyzer was used to assay the possible interactions between ACEIs and ARBs drugs on antiplatelet effect of aspirin using blood obtained from 6 healthy volunteers. Means of area under the aggregation curves (AUCs) of the blood samples treated with 10 µg/mL aspirin were calculated before and after exposure to captopril, lisinopril, candesartan, or losartan. RESULTS: Results showed potential antithrombotic effect of ACEIs and ARBs only at high concentrations (3.3 µg/mL).The antiplatelet effect of aspirin 10 µg/mL was significantly enhanced by the addition of captopril or lisinopril at high dose (3.3 µg/mL), candesartan at all tested doses (0.03 µg/mL, 0.33 µg/mL, 3.3 µg/mL), and losartan at doses of 0.33 µg/mL and 3.3 µg/m. CONCLUSION: Treatment with ACEIs (captopril and lisinopril) and ARBs (candesartan and losartan) improved the antiplatelet response to aspirin. Further studies are needed to confirm this action and potentially apply it to clinical practice.

Exposure of pregnant women to waterpipe and cigarette smoke.

INTRODUCTION: Throughout the Eastern Mediterranean region, tobacco is used primarily in 2 forms: cigarette smoking and waterpipe smoking. Despite the fact that tobacco use is considered as a global public health threat, waterpipe smoking is reported to be growing in popularity, particularly among women. The objectives of this study are to determine the prevalence and patterns of cigarette, waterpipe, and passive smoking among pregnant women in Jordan, and to assess their perception of harmful effects of cigarette and waterpipe smoking. METHODS: A total of 500 pregnant women were randomly recruited from maternity clinics in North and Middle of Jordan and surveyed regarding exposure to waterpipe tobacco and cigarette smoking. RESULTS: The results showed that 7.9% of women were current cigarette smokers and 8.7% were current waterpipe smokers. About 82.4% of all women reported that they are exposed to cigarette smoke and 32.8% reported that they are exposed to waterpipe smoke. The most common place where women are exposed to cigarette and waterpipe smoke was their house (50.4% and 48.7%, respectively) followed by public places (31.4% and 21.4%, respectively). In addition, the husband was the main source for exposure to cigarette and waterpipe smoke (48.5% and 42.7%, respectively). Approximately, 74% of women believed that cigarette smoking is addictive, whereas only 55.1% reported that waterpipe smoking leads to addiction. CONCLUSIONS: Exposure of pregnant women to tobacco smoke is a public health problem in Jordan that requires immediate action.