Protein Levels Of PARP Research Articles

Vitamin D enhances omega-3 polyunsaturated fatty acids-induced apoptosis in breast cancer cells.

Breast cancer is a leading type of cancer in women and generally classified into three subtypes of ER+ /PR+ , HER2+ and triple negative. Both omega-3 polyunsaturated fatty acids and vitamin D3 play positive role in the reduction of breast cancer incidence. However, whether combination of omega-3 polyunsaturated fatty acids and vitamin D3 has stronger protective effect on breast carcinogenesis still remains unknown. In this study, we show that the combination of ω-3 free fatty acids (ω-3 FFAs) and 1α, 25-dihydroxy-vitamin D3 (VD3 ) dramatically enhances cell apoptosis among three subtypes of breast cancer cell lines. Bcl-2 and total PARP protein levels are decreased in combined treatment MCF-7 and SK-BR-3 cells. Caspase signals play a vital role in cell apoptosis induced by combination. Moreover, Raf-MAPK signaling pathway is involved in the apoptosis induction by combination of ω-3 FFAs+VD3 . These results demonstrate that the induction of cell apoptosis by combined treatment is dependent on different signaling pathways in three subtypes of breast cancer cell lines.

Abstract 471: HER2 regulates PARP-1 expression by suppressing the let-7a microRNA in HER2+ breast cancer

Abstract Background: HER2+ breast cancers are sensitive to PARP inhibition and express elevated levels of the PARP-1 protein. However, the mode of regulation of PARP-1 expression by HER2 is not well understood. MicroRNAs are small non-coding RNAs that function in RNA silencing and post-transcriptional regulation of gene expression. In this study, we investigate whether PARP1 expression in human breast cancer cells is regulated by HER2 regulation of microRNAs. Methods: Human HER2+ breast cancer cell lines BT-474 and SKBR3 were used in this study. MDA-MB-231 (non-HER2 expressing breast cancer cells) stably transfected with a HER2 wild-type plasmid (231 HER2) or the vector control (231 NEO) were also utilized. To identify candidate microRNAs regulated by HER2 overexpression, we performed the nCounter miRNA Expression Assay. MicroRNA and mRNA expression were validated via qRT-PCR analysis in breast cancer cell lines or patient primary tumors. Cells were also transfected with a HER2 siRNA, a let-7a mimic, and an inhibitor of let-7a as well as their respective controls. Western blot analysis and firefly luciferase assays were used to determine whether the 3’UTR of PARP1 was being directly targeted by the let-7a microRNA. Results: HER2 did not regulate PARP-1 at the mRNA level but increased PARP-1 protein in HER2+ breast cancer cells. Specifically, ectopic HER2 overexpression correlated with increased PARP-1 protein levels in the 231 HER2 cell line. Conversely, silencing HER2 reduced PARP-1 protein levels in the BT-474 and SKBR3 cell lines. NanoString nCounter analysis revealed that the HER2+ breast cancer cell lines expressed low levels of the let-7a microRNA. Further, let-7a expression was upregulated after HER2 knockdown in the two native HER2+ breast cancer cell lines. The let-7a mimic also reduced both PARP1 protein expression and luciferase activity in the 231 HER2 and BT-474 cell lines, whereas the let-7a inhibitor reversed these effects in the 231 NEO cell line. Importantly, human HER2+ breast tumors expressed higher levels of PARP-1 and lower levels of let-7a; whereas, the HER2- breast tumors expressed lower levels of PARP-1 and higher levels of let-7a. Further, overexpression of the let-7a mimic reduced cell proliferation in HER2+ breast cancer cells. Conclusions: These results suggest that let-7a regulates PARP-1 expression in HER2+ breast tumors. Let-7a may also be a potential therapeutic target and predictive biomarker of PARPi sensitivity in HER2+ breast cancer patients. Citation Format: Eddy Shih-Hsin Yang, Monicka Wielgos, Rajani Rajbhandari, Shi Wei, Susan Nozell. HER2 regulates PARP-1 expression by suppressing the let-7a microRNA in HER2+ breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 471. doi:10.1158/1538-7445.AM2017-471

Abstract 5863: Identifying the radiosensitizing effects of PARP inhibitor in ovarian cancer

Abstract Ovarian cancer is the seventh-most common cancer with a high mortality rate among women. Radiation therapy (RT) is used in ovarian cancer for local relapse, but doses are limited due to concern for small bowel obstruction in patients who have had multiple surgeries and chemotherapeutic regimens. Therefore, it’s an ideal setting to improve the therapeutic window by combining RT and a radiosensitizer. Poly (ADP-ribose) polymerase-1 (PARP-1) is involved in the recognition of DNA damage and the facilitation of DNA repair by recognizing DNA single-strand breaks (SSB). Inhibition of PARP1, especially in tumors driven by BRCA1 or 2 mutations, has been shown to potentiate the DNA-damaging effects of radiation in vitro and in vivo and to increase tumor vasculature perfusion and oxygenation. Approximately half of ovarian cancers have germline or somatic BRCA gene mutation, epigenetic silencing or other mutations that affect homologous recombination (HR) competency resulting in DNA repair defects, making this tumor particularly susceptible to the radiation-sensitizing effects of PARP inhibitors. Here, we investigated the therapeutic effects of the PARP inhibitor olaparib in preclinical models of ovarian cancer. Basic BRCA1 and PARP1 protein and mRNA levels were characterized in a panel of ovarian cancer cell lines. The radiosensitizing effects of olaparib were tested on both HR-proficient and HR-deficient ovarian cancer cells by evaluating the colony formation, DNA damage, apoptosis, and PARP1 activity. Survival benefit of olaparib was also examined in xenograft models of ovarian cancer. Our results demonstrate that combination of olaparib with IR decreased colony formation, inhibited DNA damage (γH2AX) repair, and induced more apoptosis compared to olaparib or IR alone. In addition, HR-deficient cells were more sensitive to IR than HR-proficient cells in the presence of olaparib. Furthermore, olaparib inhibited PARP1 activity in vivo, significantly decreased tumor growth and increased overall survival when combined with IR in mice bearing subcutaneous xenografts of HR-deficient OVCAR8 cells while producing a relative modest effect on overall survival of mice bearing xenografts of HR-proficient SKOV3 cells. These results provide a preclinical rationale for improved treatment modalities using olaparib as an effective radiosensitizer in ovarian cancer, particularly in tumors with HR-deficiencies. Citation Format: Yue Bi, Ioannis Verginadis, Souvik Dey, linlang Guo, Lilie Lin, Yanfang Zheng, Constantinos Koumenis. Identifying the radiosensitizing effects of PARP inhibitor in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5863. doi:10.1158/1538-7445.AM2017-5863

PARP-1 serves as a novel molecular marker for hepatocellular carcinoma in a Southern Chinese Zhuang population.

PARP-1 (poly(ADP-ribose) polymerase-1) plays an important role in tumorigenesis. Since its effects on different populations are varied, this study investigated the impact of PARP-1 on primary hepatocellular carcinoma in a Southern Chinese Zhuang population. We assessed the global PARP-1 messenger RNA expression in patients with hepatocellular carcinoma using The Cancer Genome Atlas dataset. Increased PARP-1 expression, related to alpha-fetoprotein level, was observed. The area under the receiver operating characteristic curve value was 0.833. Kaplan-Meier survival curves indicated that higher PARP-1 expression was not correlated with poorer overall survival and recurrence-free survival. In a Zhuang population, PARP-1 messenger RNA and protein levels were increased in the hepatocellular carcinoma tissue and its adjacent liver tissues as assessed by quantitative polymerase chain reaction, immunohistochemistry, and western blotting. Higher PARP-1 level was associated with a higher tumor stage (p < 0.05), without correlation with age, gender, smoking, drinking, tumor size, serum alpha-fetoprotein level, hepatitis B virus infection, metastasis, and invasion (p > 0.05). Further analysis suggested that H2AX, a PARP-1 protein interaction partner, was coordinated with PARP-1 in hepatocellular carcinoma tumorigenesis. Overall, some new characteristics of PARP-1 expression were noted in the Zhuang population. PARP-1 is a novel promising diagnostic marker for hepatocellular carcinoma in the Southern Chinese Zhuang population.

Evaluation of in vitro cytotoxicity, biocompatibility, and changes in the expression of apoptosis regulatory proteins induced by cerium oxide nanocrystals

Cerium oxide nanocrystals (CeO2-NCs) exhibit superoxide dismutase and catalase mimetic activities. Based on these catalytic activities, CeO2-NCs have been suggested to have the potential to treat various diseases. The crystalline size of these materials is an important factor that influences the performance of CeO2-NCs. Previous reports have shown that several metal-based nanocrystals, including CeO2-NCs, can induce cytotoxicity in cancer cells. However, the underlying mechanisms have remained unclear. To characterize the anticancer activities of CeO2-NCs, several assays related to the mechanism of cytotoxicity and induction of apoptosis has been performed. Here, we have carried out a systematic study to characterize CeO2-NCs phase purity (X-ray diffraction), morphology (electron microscopy), and optical features (optical absorption, Raman scattering, and photoluminescence) to better establish their potential as anticancer drugs. Our study revealed anticancer effects of CeO2-NCs in HT29 and SW620 colorectal cancer cell lines with half-maximal inhibitory concentration (IC50) values of 2.26 and 121.18 μg ml–1, respectively. Reductions in cell viability indicated the cytotoxic potential of CeO2-NCs in HT29 cells based on inverted and florescence microscopy assessments. The mechanism of cytotoxicity confirmed by estimating possible changes in the expression levels of Bcl2, BclxL, Bax, PARP, cytochrome c, and β-actin (control) proteins in HT29 cells. Down-regulation of Bcl2 and BclxL and up-regulation of Bax, PARP, and cytochrome c proteins suggested the significant involvement of CeO2-NCs exposure in the induction of apoptosis. Furthermore, biocompatibility assay showed minimum effect of CeO2-NCs on human red blood cells.

Autophagy (A) inhibition to enhance combined immunotherapy (I) and anti-EGFR treatment (E) in colorectal cancer (CRC).

e14554 Background: Resistance to E impairs survival of metastatic CRC (mCRC) patients. The aim of this study is to assess the preclinical activity of triple inhibition of E, I and A in CRC. Methods: RKO and Colo-205 cell lines were treated with E [cetuximab (C) / panitamumab (P)] and/or I [pembrolizumab (PE) or nivolumab (NI) with/without ipilimumab (IPI)] and/or autophagy inhibitor 3-Methyladenine (3-MA). Phosphorylated EGFR (pEGFR), p62 (SQSTM1), MAP1LC3 (LC3B) and PARP protein levels were detected by Western blotting. Cell viability was determined by MTT Assay. Tumor volumes were determined from 3D cell culture on Corning Matrigel Matrix as well as the apoptotic cell death. Results: E+I combination compared to E alone decreased pEGFR and increased A activation through p62 downregulation and LC3II activation. Similar results were shown for cell viability/apoptosis. Cells were also treated with C or P combined with I plus 3-MA. Triple inhibition suppresses EGFR and blocks A. Compared to E+I, triple inhibition reduced more cell growth/viability. Caspase-3 activity was increased as well as proportion of apoptotic cells (Table). Conclusions: Τhese results indicate that the combinatorial inhibition of A, E and I represents a promising treatment strategy in mCRC that needs further testing. [Table: see text]

A murine preclinical syngeneic transplantation model for breast cancer precision medicine.

We previously demonstrated that altered activity of lysophosphatidic acid in murine mammary glands promotes tumorigenesis. We have now established and characterized a heterogeneous collection of mouse-derived syngeneic transplants (MDSTs) as preclinical platforms for the assessment of personalized pharmacological therapies. Detailed molecular and phenotypic analyses revealed that MDSTs are the most heterogeneous group of genetically engineered mouse models (GEMMs) of breast cancer yet observed. Response of MDSTs to trametinib, a mitogen-activated protein kinase (MAPK) kinase inhibitor, correlated with RAS/MAPK signaling activity, as expected from studies in xenografts and clinical trials providing validation of the utility of the model. Sensitivity of MDSTs to talazoparib, a poly(adenosine 5'-diphosphate-ribose) polymerase (PARP) inhibitor, was predicted by PARP1 protein levels and by a new PARP sensitivity predictor (PSP) score developed from integrated analysis of drug sensitivity data of human cell lines. PSP score-based classification of The Cancer Genome Atlas breast cancer suggested that a subset of patients with limited therapeutic options would be expected to benefit from PARP-targeted drugs. These results indicate that MDSTs are useful models for studies of targeted therapies, and propose novel potential biomarkers for identification of breast cancer patients likely to benefit from personalized pharmacological treatments.

Let-7 Status Is Crucial for PARP1 Expression in HER2-Overexpressing Breast Tumors

HER2+ breast tumors have been shown to express elevated levels of PARP1 protein. Yet, the mechanism by which PARP1 is upregulated in HER2+ breast cancer is unknown. Here, knockdown of HER2 (ERBB2) in HER2+ breast cancer cells resulted in a reduction in PARP1 protein. Conversely, ectopic overexpression of HER2 in a non-HER2-overexpressing cell line resulted in increased PARP1 protein levels. Alterations in HER2 expression had no significant effect on PARP1 transcript levels. Instead, HER2 mRNA status was inversely correlated with let-7a miRNA levels in breast cancer cells. Ectopic expression of let-7a miRNA resulted in downregulation of PARP1 protein, whereas expression of the let-7a anti-miRNA increased PARP1 protein. Furthermore, luciferase assays demonstrate that let-7a regulates PARP1 via its 3'UTR. Importantly, let-7a was significantly lower in human HER2+ breast tumors compared with HER2- breast tumors and inversely correlated with PARP1 protein levels. Finally, HER2+ breast cancer cells exhibited similar cytotoxicity to ectopic let-7a expression as the PARP inhibitor veliparib (ABT-888). Collectively, these results reveal that increased PARP1 expression in HER2+ breast cancers is regulated by the let-7a miRNA, and that let-7a is a potential strategy to suppress PARP1 activity.Implications: This study reports the novel findings that HER2 increases PARP1 protein via suppression of the let-7a miRNA, which regulates the PARP1 3'-UTR. Moreover, HER2 status correlates with high PARP1 and low let-7a in breast cancer clinical specimens. Mol Cancer Res; 15(3); 340-7. ©2016 AACR.

Abstract B11: HER2 regulates PARP-1 expression via the let-7a microRNA in HER2+ breast cancer

Abstract Background: HER2+ breast cancers are sensitive to PARP inhibition and express elevated levels of the PARP-1 protein. However, the mode of regulation of PARP-1 expression by HER2 is not well understood. In this study, we report that the let-7a microRNA is regulating PARP-1 expression at the post-transcriptional level in HER2+ breast cancer cells. Methods: Human HER2+ breast cancer cell lines BT-474 and SKBR3 were used in this study. MDA-MB-231 (non-HER2 expressing breast cancer cells) were also stably transfected with a HER2 wild-type plasmid (231 HER2) or the vector control (231 NEO). Further, to identify candidate microRNAs regulated by HER2 overexpression we used the nCounter miRNA Expression Assay. MicroRNA and mRNA expression were validated via qRT-PCR analysis in breast cancer cell lines or patient primary tumors. Cells were also transfected with a HER2 siRNA, a let-7a mimic, and an inhibitor of let-7a as well as their respective controls. Western blot analysis and firefly luciferase assays were used to determine whether the 3'UTR of PARP1 was being directly targeted by the let-7a microRNA. Results: HER2 did not regulate PARP-1 at the mRNA level but increased PARP-1 protein in HER2+ breast cancer cells. Specifically, ectopic HER2 overexpression correlated with increased PARP-1 protein levels in the 231 HER2 cell line. Conversely, silencing HER2 reduced PARP-1 protein levels in the BT-474 and SKBR3 cell lines. NanoString nCounter analysis revealed that the HER2+ breast cancer cell lines expressed low levels of the let-7a microRNA. Further, let-7a expression was upregulated after HER2 knockdown in the two native HER2+ breast cancer cell lines. The let-7a mimic also reduced both PARP1 protein expression and luciferase activity in the 231 HER2 and BT-474 cell lines, whereas the let-7a inhibitor reversed these effects in the 231 NEO cell line. Importantly, HER2+ breast tumors expressed higher levels of PARP-1 and lower levels of let-7a; whereas, the HER2- breast tumors expressed lower levels of PARP-1 and higher levels of let-7a. Conclusions: These results suggest that let-7a regulates PARP-1 expression in HER2+ breast tumors. Let-7a may also be a potential therapeutic target and predictive biomarker of PARPi sensitivity in HER2+ breast cancer patients. Citation Format: Monicka Wielgos, Rajani Rajbhandari, Susan Nozell, Shi Wei, Eddy S. Yang. HER2 regulates PARP-1 expression via the let-7a microRNA in HER2+ breast cancer. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr B11.

Echinacoside Alleviates UVB Irradiation-Mediated Skin Damage via Inhibition of Oxidative Stress, DNA Damage, and Apoptosis.

Ultraviolet B (UVB) irradiation has been known to cause skin damage, which is associated with oxidative stress, DNA damage, and apoptosis. Echinacoside is a phenylethanoid glycoside isolated from Herba Cistanches, which exhibits strong antioxidant activity. In this study, we evaluate the photoprotective effect of echinacoside on UVB-induced skin damage and explore the potential molecular mechanism. BALB/c mice and HaCaT cells were treated with echinacoside before UVB exposure. Histopathological examination was used to evaluate the skin damage. Cell viability, lactate dehydrogenase (LDH) levels, antioxidant enzyme activities, reactive oxygen species (ROS) generation, DNA damage, and apoptosis were measured as well. Western blot was used to measure the expression of related proteins. The results revealed that pretreatment of echinacoside ameliorated the skin injury; attenuated oxidative stress, DNA damage, and apoptosis caused by UVB exposure; and normalized the protein levels of ATR, p53, PIAS3, hnRNP K, PARP, and XPA. To summarize, echinacoside is beneficial in the prevention of UVB-induced DNA damage and apoptosis of the skin in vivo and in vitro.

Abstract A35: Olaparib causes premature loss of cohesion in cancer cells

Abstract Although it has been decades since PARP inhibitors were initially discovered and various clinical trials have been performed, their mode of action in killing tumor cells subsequent to PARP inhibition is still not fully understood. We have recently identified poly(ADP-ribosyl)ation (PARylation) as a new post-translational modification of the cohesin complex, a key player in chromosome segregation during mitosis. We investigated the effect of PARP inhibition on mitosis in a panel of cells of cancer (cervical, breast, ovarian) and normal tissue origin. We treated cancerous and non-cancerous cell lines labelled with chromatin markers with a selected set of PARP inhibitors and imaged them with fluorescence live microscopy. Out of 5 tested inhibitors, a well-known and clinically relevant PARP inhibitor olaparib, induced strongest perturbations in mitotic progression. Olaparib induced a delay in entering anaphase, problems aligning chromosomes at the metaphase plate and premature loss of cohesion (cohesion fatigue) after a prolonged metaphase arrest. Cohesion fatigue, leading to cell death, was observed in cancer cell lines exhibiting S-phase stalling or G2/M arrest with increased protein levels of PARP1. Olaparib is known to entrap PARP1 at replication forks and thereby perturb replication fork movement. While its addition before the onset of mitosis did not result in mitotic defects, addition of olaparib only in S-phase was sufficient to cause mitotic phenotypes. Our results indicate that PARP inhibition by olaparib in S phase has downstream effects on mitotic progression. PARP1 RNAi in addition to olaparib treatment rescues the cohesion fatigue phenotype, suggesting that entrapment of PARP1 at the replication fork upon its inhibition is the main cause of cohesion fatigue. Cohesion fatigue was observed only in highly aneuploid cancer cells that are described to have an increased rate of chromosome mis-segregation. In conclusion, higher susceptibility of aneuploid cancer to cohesion fatigue and cell death upon olaparib treatment relative to normal cells would support its use as anti-mitotic chemotherapy. Citation Format: Eva Kukolj, Tanja Kaufmann, Amalie E. Dick, Robert Zeillinger, Daniel W. Gerlich, Dea Slade. Olaparib causes premature loss of cohesion in cancer cells. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr A35.

Neurohormetic responses of quercetin and rutin in a cell line over-expressing the amyloid precursor protein (APPswe cells)

BackgroundPlant secondary metabolites may induce adaptive cellular stress-responses in a variety of cells including neurons at the sub-toxic doses ingested by humans. Such ‘neurohormesis’ phenomenon, activated by flavonoids such as quercetin or rutin, may involve cell responses driven by modulation of signaling pathways which are responsible for its neuroprotective effects. PurposeWe attempt to explore the molecular mechanisms involved in the neurohormetic responses to quercetin and rutin exposure, in a SH-SY5Y cell line which stably overexpresses the amyloid precursor protein (APP) Swedish mutation, based on a biphasic concentration-response relationship for cell viability. MethodsWe examined the impact of both natural compounds, at concentrations in its hormetic range on the following cell parameters: chymotrypsin-like activity of the proteasome system; PARP-1 protein levels and expression and caspase activation; APP processing; and the main endogenous antioxidant enzymes. ResultsProteasome activities following quercetin or rutin treatment were significantly augmented in comparison with non-treated cells. Activity of caspase-3 was significantly attenuated by treatment with quercetin or rutin. Modest increased levels of PARP-1 protein and mRNA transcripts were observed in relation to the mild increase of proteasome activity. Significant reductions of the full-length APP and sAPP protein and APP mRNA levels were related to significant enhancements of α-secretase ADAM-10 protein and mRNA transcripts and significant increases of BACE processing in cells exposed to rutin. Furthermore, quercetin or rutin treatment displayed an overall increase of the four antioxidant enzymes. ConclusionsThe upregulation of the proteasome activity observed upon quercetin or rutin treatment could be afforded by a mild increased of PARP-1. Consequently, targeting the proteasome by quercetin or rutin to enhance its activity in a mild manner could avoid caspase activation. Moreover, it is likely that APP processing of cells upon rutin treatment is mostly driven by the non-amyloidogenic pathway leading to a putative reduction of βA production. Overall induction of endogenous antioxidant enzymes under quercetin or rutin treatments of APPswe cells might modulate its proteasome activity. We might conclude that quercetin and rutin might exert a neurohormetic cell response affecting various signaling pathways and molecular networks associated with modulation of proteasome function.

Manumycin A induces apoptosis in malignant pleural mesothelioma through regulation of Sp1 and activation of the mitochondria-related apoptotic pathway.

ManumycinA (ManuA) is a natural product isolated from Streptomyces parvulus and has been reported to have anti-carcinogenic and anti-biotic properties. However, neither its molecular mechanism nor its molecular targets are well understood. Thus, the aim of the present study was to explore the possibility that ManuA has cancer preventive and chemotherapeutic effects on malignant pleural mesothelioma (MPM) through regulation of Sp1 and induction of mitochondrial cell death pathway. ManuA inhibited the cell viability of MSTO-211H and H28 cells in a concentration‑dependent manner as determined by MTS assay. IC50 values were calculated as 8.3 and 4.3µM in the MSTO-311H and H28 cells following 48h incubation, respectively. ManuA induced a significant increase in apoptotic indices as shown by DAPI staining, AnnexinV assay, multi-caspase activity and mitochondrial membrane potential assay. The downregulation of Sp1 mRNA and protein expression by ManuA led to apoptosis by suppressing Sp1-regulated proteins (cyclinD1, Mcl-1 and survivin). ManuA decreased the protein levels of BID, Bcl-xL and PARP while it increased Bax levels. ManuA caused depolarization of the mitochondrial membrane with induction of CHOP, DR4 and DR5. Our results demonstrated that ManuA exerted anticancer effects by inducing apoptosis via inhibition of the Sp1-related signaling pathway in human MPM.

Chemotherapy reduces PARP1 in cancers of the ovary: implications for future clinical trials involving PARP inhibitors.

BackgroundPARP inhibitors have shown promising clinical results in cancer patients carrying BRCA1/2 mutations. Their clinical efficacy could logically be influenced by PARP1 protein levels in patient tumors.MethodsWe screened three cohorts of patients with ovarian cancer, totaling 313 samples, and evaluated PARP1 protein expression by immunohistochemistry with further validation by western blotting.ResultsWe observed that up to 60 % of tumors showed little PARP1 protein expression. In serous ovarian tumors, comparing intratumoral PARP1 expression between chemo-naïve and post-chemotherapy patients revealed a decrease in intratumoral PARP1 following chemotherapy in all three cohorts (immunohistochemistry: p < 0.001, n = 239; western blot: p = 0.012, n = 74). The findings were further confirmed in a selection of matched samples from the same patients before and after chemotherapy.ConclusionOur data suggest that patients should be screened for PARP1 expression prior to therapy with PARP inhibitors. Further, the observed reduction of intratumoral PARP1 post-chemotherapy suggests that treating chemo-naïve patients with PARP inhibitors prior to the administration of chemotherapy, or concurrently, might increase the responsiveness to PARP1 inhibition. Thus, a change in the timing of PARP inhibitor administration may be warranted for future clinical trials.Electronic supplementary materialThe online version of this article (doi:10.1186/s12916-015-0454-9) contains supplementary material, which is available to authorized users.

PARP1 and phospho-p65 protein expression is increased in human HER2-positive breast cancers.

Previous studies have shown that basal breast cancers, which may have an inherent "BRCAness" phenotype and sensitivity to inhibitors of poly (ADP-Ribose) polymerase (PARP), express elevated levels of PARP1. Our lab recently reported that HER2+ breast cancers also exhibit sensitivity to PARP inhibitors (PARPi) by attenuating the NF-κB pathway. In this study, we assessed PARP1 and phospho-p65, a marker of activated NF-κB levels in human breast cancer tissues. PARP1 and PARP2 copy number, mRNA, and protein expression was assessed by interrogating the PAM-50 defined breast cancer patient set from the TCGA using cBioPortal. PARP1 and phospho-p65 immunohistochemistry and correlation to clinical parameters was conducted using 307 primary breast cancer specimens (132 basal, 82 luminal, 93 HER2+) through univariate and multivariate analyses. In the PAM50 breast cancer data set, PARP1 and 2 expression was altered in 24/58 (41 %) HER2+, 32/81 (40 %) basal, and 75/324 (23 %) luminal A/B breast cancer patients. This correlated with a statistically significant increase in PARP1 protein levels in HER2+ and basal but not luminal breast cancers (p = 0.003, p = 0.027, p = 0.289, respectively). No change in PARP2 protein level was observed. Interestingly, using breast cancer specimens from 307 patients, HER2 positivity correlated with elevated PARP1 expression (p < 0.0001) and was three times more likely than HER2 negative breast cancers to exhibit high PARP1 levels. No significant differences were noted between race, ER status, or PR status for PARP1 expression. Additionally, we found a significant correlation between HER2 status and phospho-p65 expression (p < 0.0001). Lastly, a direct correlation between PARP1 and phospho-p65 (p < 0.0001) was noted. These results indicate a potential connection between HER2, PARP1, and phospho-p65. Furthermore, these data suggest that the PARPi sensitivity we previously observed in HER2+ breast cancer cells may be due to elevated PARP1 expression.

Bortezomib inhibits gastric carcinoma HGC-27 cells through the phospho-Jun N-terminal kinase (p-JNK) pathway in vitro

The study is designed to explore the anticancer mechanism of Bortezomib. The effects of Bortezomib on the proliferation of human gastric cancer cells HGC-27 and expression levels of the phospho-Jun N-terminal kinase (p-JNK) pathway-related proteins in vitro were investigated. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay revealed that the Bortezomib significantly decreased the viability of HGC-27 cells and induced apoptosis. Western blot showed that the Bortezomib strongly increased the levels of p-JNK, caspase-3, PARP, and bax proteins while it increased the level of bcl-2. However, SP600125 can significantly decrease antitumour effects of Bortezomib in HGC-27 cells. It can be concluded that Bortezomib has significant inhibitory effects on the growth of HGC-27 cells. The effect may be achieved partly via upregulating JNK pathway and its down-stream apoptosis-related proteins. Therefore, Bortezomib may be beneficial in gastric carcinoma treatment.

Equol inhibits proliferation of human gastric carcinoma cells via modulating Akt pathway.

To investigate the anti-tumor effects of equol in gastric cancer cells and the underlying molecular mechanisms. MGC-803 cells were employed for in vitro experiments in this study. Cells were treated with control (vehicle, 0.1% DMSO) or equol under specified dose titration or time courses. Cell viability was examined by MTS assay, and the levels of Ki67 were determined by qPCR and immunofluorescent assay. Changes in cell cycle distribution and apoptosis rate were detected by flow cytometry. The mRNA expression of cyclin E1 and P21(WAF1) was determined by qPCR. The protein levels of cell cycle regulators, PARP and Caspase-3 cleavage, and the phosphorylation of Akt were examined by Western blot. In addition, to characterize the role of elevated Akt activation in the anti-tumor effect exerted by equol, Ly294002, a PI3K/AKT pathway inhibitor, was used to pretreat MGC-803 cells. Equol (5, 10, 20, 40, or 80 μmol/L) inhibited viability of MGC-803 cells in a dose- and time-dependent manner after treatment for 24, 36, or 48 h (P < 0.05 for all). Equol also decreased the mRNA (P < 0.05 for 12 and 24 h treatment) and protein levels of Ki67. Equol treatment significantly induced G0/G1 cell cycle arrest (P < 0.05), with the percentages of G0/G1 cells of 32.23% ± 3.62%, 36.31% ± 0.24%, 45.58% ± 2.29%, and 65.10% ± 2.04% for equol (0, 10, 20, or 30 μmol/L) treatment, respectively, accompanied by a significant decrease of CDK2/4 (P < 0.05 for 24 and 48 h treatment) and Cyclin D1/Cyclin E1 (P < 0.05), and an increased level of P21(WAF1) (P < 0.05). A marked increase of apoptosis was observed, with the percentages of apoptotic cells of 5.01% ± 0.91%, 14.57% ± 0.99%, 37.40% ± 0.58%, and 38.46% ± 2.01% for equol (0, 5, 10, or 20 μmol/L) treatment, respectively, accompanied by increased levels of cleaved PARP and caspase-3. In addition, we found that equol treatment increased P-Akt (Ser473 and Thr308) at 12 and 24 h compared to vehicle-treated control; longer treatment for 48 h decreased P-Akt (Ser473 and Thr308). P-Akt at Thr450, however, was decreased by equol treatment at all time points examined (P < 0.05 for all). Moreover, Akt inhibition by Ly294002 could not prevent but led to enhanced G0/G1 arrest and apoptosis. Equol inhibits MGC-803 cells proliferation by induction of G0/G1 arrest and apoptosis. Its anti-cancer effects are likely mediated by dephosphorylation of Akt at Thr450.

MMSET Regulates IRF4, a Transcription Factor Critical for the Survival of T(4;14) Myeloma Myeloma Cells, and Its Silence Potentiates the Effect of Antimyeloma Agents

Multiple myeloma (MM) is a genetically complex disease that is becoming more common in today’s ageing population. Approximately 50% of MM harbour recurrent translocations involving the immunoglobulin heavy chain (IgH) locus on chromosome 14q32. The translocation t(4;14)(p16;q32) is one of the most common translocation in MM and is associated with very poor prognosis. The multiple myeloma SET domain (MMSET), involved in the fusion to the IgH locus in t(4;14) MM, is universally overexpressed and has been suggested to play an important role in tumorigenicity in t(4;14) MM. In order to identify downstream functional targets of MMSET, we knocked down MMSET expression with shRNAs in KMS11, a t(4;14) MM cell line, and identified differentially expressed genes by gene expression microarray analysis. The results identified 321 down-regulated and 375 up-regulated genes upon MMSET knockdown. Of interest, the knockdown reduced the transcription levels of the transcription factor IRF4 (interferon regulatory factor 4), which has been shown recently to be required for myeloma cell survival. Quantitative PCR (QPCR) analysis confirmed the transcription levels of IRF4 were reduced upon MMSET knockdown in t(4;14) MM cells (KMS11, KMS18, KMS28BM). Western-blots analysis indicated MMSET knockdown reduced protein levels of IRF4, c-Myc and PARP, and IRF4 knockdown could also reduce protein levels of c-Myc and PARP. Flow cytometric analysis indicated silencing of MMSET or IRF4 could induce apoptosis in t(4;14) MM cells. QPCR and Western-blot analysis revealed that ectopic expression of MMSET could increase IRF4 expression in KMS11 cells. Using chromatin immunoprecipitation (ChIP), both MMSET and NFκB can bind to the promoter region of IRF4, and the binding region of MMSET is located 1 kb upstream of that of NFκB. Furthermore, endogenous NFκB p65 could be coprecipitated by anti-MMSET antibody, indicating the association of MMSET and NFκB. These data suggest that MMSET may be a coactivator for NFkB in the regulation of IRF4 expression. Luciferase reporter assays in KMS11 cells showed the activity of IRF4 promoters were decreased significantly upon MMSET knockdown, suggesting MMSET is an important functional element for IRF4 promoter. Cell proliferation assays and apoptosis analysis showed that silencing of MMSET could sensitize t(4;14) MM cells to Bortezomib and Melphalan killing. In myeloma xenograft, combined MMSET silencing with Melphalan or Bortezomib resulted in significantly greater inhibition of t(4;14) MM tumorigeness than treatments with either drugs alone. Importantly, we found both of Melphalan and Bortezomib could also reduce protein levels of MMSET and IRF4. QPCR analysis indicated that they inhibited MMSET and IRF4 expression through transcription control. These results might partly explain the additive mechanism of combination of MMSET knockdown and Melphalan or Bortezomib. Overall, our data indicated MMSET is involved in the regulatory network of IRF4 that is critical for t(4:14) MM cell survival, and its silence potentiates the effect of antimyeloma agents in vitro and in vivo. DisclosuresNo relevant conflicts of interest to declare.

PARP-2 depletion results in lower radiation cell survival but cell line-specific differences in poly(ADP-ribose) levels.

Poly(ADP-ribose) polymerase-2 (PARP-2) activity contributes to a cells' poly(ADP-ribosyl)ating potential and like PARP-1, has been implicated in several DNA repair pathways including base excision repair and DNA single strand break repair. Here the consequences of its stable depletion in HeLa, U20S, and AS3WT2 cells were examined. All three PARP-2 depleted models showed increased sensitivity to the cell killing effects on ionizing radiation as reported in PARP-2 depleted mouse embryonic fibroblasts providing further evidence for a role in DNA strand break repair. The PARP-2 depleted HeLa cells also showed both higher constitutive and DNA damage-induced levels of polymers of ADP-ribose (PAR) associated with unchanged PARP-1 protein levels, but higher PARP activity and a concomitant lower PARG protein levels and activity. These changes were accompanied by a reduced maximal recruitment of PARP-1, XRCC1, PCNA, and PARG to DNA damage sites. This PAR-associated phenotype could be reversed in HeLa cells on re-expression of PARP-2 and was not seen in U20S and AS3WT2 cells. These results highlight the complexity of the relationship between different members of the PARP family on PAR metabolism and suggest that cell model dependent phenotypes associated with the absence of PARP-2 exist within a common background of radiation sensitivity.

2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucoside protects human umbilical vein endothelial cells against lysophosphatidylcholine-induced apoptosis by upregulating superoxide dismutase and glutathione peroxidase.

2,3,5,4'-Tetrahydroxystilbene-2-O-β-d-glucoside (TSG) has been shown to protect human umbilical vein endothelial cells (HUVECs) from lysophosphatidylcholine (LPC)-induced injury; however, the underlying molecular mechanism remains to be determined. The aim of this study was to investigate the protective mechanism of TSG against LPC-induced injury in HUVECs. We established a stable LPC-induced cell model by treating HUVECs with various concentrations of LPC and found 10.0 µg/mL of LPC to be optimal for inducing HUVECs injury. The effects of TSG on LPC-induced cell injury were assessed by cell counting kit-8, apoptosis assay, transmission electron microscope, and measurement of malondialdehyde (MDA), the antioxidant enzymes superoxide dismutase (SOD), reactive oxygen species (ROS), glutathione peroxidase, and mitochondrial membrane potential. The mRNA and protein levels of caspase-3, Bax, Bcl-2, PARP-1, and cytochrome C were assayed by real-time reverse transcriptase-polymerase chain reaction and immunoblotting, respectively. TSG pretreatment was able to prevent LPC-induced HUVECs injury and restore cell viability in a concentration-dependent manner. LPC treated cells showed typical apoptotic morphological changes including cytoplasmic vacuolation, swollen mitochondria, and characteristic biochemical hallmarks of apoptosis including loss of mitochondrial membrane potential, activation of caspase-3, decrease of Bcl-2, increase of PARP-1, upregulation of Bax, and release of cytochrome C, all of which were apparently inhibited by TSG pretreatment. Treatment of HUVECs with LPC led to decrease of SOD and glutathione peroxidase in addition to rapid increase of MDA and ROS levels. Pretreatment with TSG restored SOD and glutathione peroxidase levels to that of normal levels, and significantly decreased ROS and MDA levels. Our data indicate that TSG inhibits apoptosis of HUVECs mediated by LPC through blocking the mitochondrial apoptotic pathway and suggest that the mechanisms underlying the protective effects of TSG are related to the activation of SOD and glutathione peroxidase, the clearance of intracellular ROS, and reduction of lipid peroxidation.