Apoptosis Of Breast Tumor Cells Research Articles

Targeted intracellular delivery of BH3 mimetic peptide inhibits BCL-2 activity and prevents breast cancer development

<p class="MsoNormal" style="margin-top: 12pt; text-align: justify;"><span lang="EN-US" style="font-family: Cambria, serif; font-size: 14pt;">Breast cancer, as a malignant tumor with easy metastasis and poor prognosis, threatens the health of women around the world. Increasing studies have shown that the Bcl-2 family of apoptosis-related proteins is often expressed abnormally in breast cancer. The Bcl-2 homology 3 (BH3) mimetic peptide can bind and neutralize Bcl-2, preventing its binding to the apoptosis "effector" proteins Bak and Bax, thereby promoting the apoptosis process. However, there is a lack of effective intracellular delivery system for BH3 to exert its biological activity. Therefore, this study utilized an activatable supercharged polypeptide (ASCP) tumor-targeted delivery platform based on pH and protease response to achieve the targeted release of BH3 at the tumor site. Ultimately, intracellular delivery of BH3 was achieved and induced apoptosis of breast tumor cells, preventing the development of breast cancer.</span></p>

Orbygnia martiana: Immunomodulation, oxidative stress and induction of apoptosis in breast tumor cells

Studies have demonstrated the ability of Orbygnia martiana to alter apoptosis and necrosis in tumor cells, but the results are still controversial. Thus, this study aimed to evaluate the effects of Orbygnia martiana under the mechanisms of oxidative stress in coculture between human peripheral blood mononuclear cells and breast tumor cells and its association with cell death mechanisms.

Effect of Preventive Acupunture Combined with CMNS6-1 Electroacupuncture Instrument on Promoting Apoptosis of 7,12-Dimethylbenzene (a) Anthracene-Induced Breast Cancer Model Rats

The purpose of this study was to evaluate the effect of preventive acupuncture combined with CMNS6-1 electroacupuncture on 7,12-dimethylbenzanthracene induced mammary tumors in Sprague-Dawley rats and to explore the effect of preventive acupuncture on mammary tumors from the perspective of apoptosis. 48 w old female Sprague-Dawley rats were randomly divided into control (10), model (10), tamoxifen (10) and preventive acupuncture (10) groups. The model group, tamoxifen group and preventive acupuncture group were administered once intragastrically with 100 mg/kg body weight of 7,12-dimethylbenzanthracene to induce spontaneous breast cancer. On d 1 after modeling, acupuncture plus electrical stimulation was administered to the preventive acupuncture group. Density wave was selected for electrical stimulation with a frequency of 2 Hz/100 Hz and an intensity of 1 mA and three acupoints, "Zu San Li", "San Yin Jiao" and "Tan Zhong", were stimulated for 20 min per treatment, once every other day, three times a week for 16 w. Tamoxifen (3 mg/kg body weight, intragastrically, every day) was started the day after 7,12-dimethylbenzanthracene administration and continued for 16 w, as positive control treatment. Apoptosis of breast tumor tissue cells was detected by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, and expression of caspase-3 and B-cell lymphoma-2 was assessed by immunohistochemistry. During the experiment, no tumors were detected in rats from the control+sham group, all the rats in the 7,12-dimethylbenzanthracene+sham group developed tumors and the cumulative incidence of tumors was 100 %, meanwhile the cumulative incidence of tumors in the 7,12-dimethylbenzanthracene+preventive acupuncture group and the 7,12-dimethylbenzanthracene+tamox group were 60 % and 50 %, respectively. Terminal deoxynucleotidyl transferase dUTP nick-end labeling assay showed that preventive acupuncture could significantly promote apoptosis in breast tumor cells in 7,12-dimethylbenzanthracene induced rat, while increased the expression levels of pro-apoptotic proteins such as caspase-3 and B-cell lymphoma-2 associated X. The expression level of antiapoptotic protein B-cell lymphoma-2 was down-regulated and the ratio of B-cell lymphoma-2/B-cell lymphoma-2 associated X was increased. Preventive acupuncture therapy combined with CMNS6-1 electroacupuncture instrument inhibited 7,12-dimethylbenzanthracene-induced mammary tumorigenesis in rats and the mechanism may be related to the regulation of apoptosis-related protein expression and promotion of tumor cell apoptosis.

SH3BGRL confers innate drug resistance in breast cancer by stabilizing HER2 activation on cell membrane

BackgroundHER2-positive breast cancer is usually associated to the more aggressive progression and the worse prognosis, but the mechanism underlying the innate resistance to HER2-targeted therapy remains elusive. The scaffold protein SH3-domain-binding glutamic acid-rich protein-like protein (SH3BGRL) is indicated as a tumor suppressor in some cancers, but it is highly expressed in breast cancers. Here we characterized the tumorigenic function of SH3BGRL in HER2-expressing breast cancer cells and the subsequent effect in HER2-targeted therapies.MethodsThe interaction of SH3BGRL to HER2 were characterized with various truncated SH3BGRL mutants by immunoprecipitation and molecule docking simulation. The physiological roles of SH3BGRL interacting with HER2 in tumor progression and therapy implication were characterized by gain and loss of function approaches in vitro and in vivo. Immunohistochemistry was used for detections of SH3BGRL and p-HER2 (Y1196) expressions in xenografted tumors and human breast cancer tissues. Clinical relevance of SH3BGRL expression with HER2 was validated with both breast patient sample and the public data analyses.ResultsOur results demonstrated that SH3BGRL directly binds with HER2 on cell membrane via its motifs α1, α2 helixes and β3 sheet, which postpones HER2 internalization upon EGF stimulation. Consequently, the association between SH3BGRL and HER2 contributed to the prolonged HER2 phosphorylation at specific tyrosine sites, especially at Y1196, and their downstream signaling activation. The relevance between SH3BGRL expression and p-HER2 (Y1196) phosphorylation was validated in both xenografted tumors and the breast cancer patient tissues. Mechanistically, SH3BGRL promoted breast tumor cell proliferation and survival, while reduced the cell sensitivity to anti-tumor drugs, especially to the HER2-targeted drugs. In contrast, Silencing SH3BGRL or inhibiting its downstream signals efficiently induced apoptosis of breast tumor cells with HER2 and SH3BGRL doubly positive expression. Database analysis also highlighted that SH3BGRL is a poor prognostic marker, especially for HER2-positive breast cancers.ConclusionsOur results disclose SH3BGRL as a novel posttranslational modulator of HER2 hyperactivation, which can lead to the intrinsic resistance to HER2-targeted therapy. SH3BGRL would be a pivotal therapy target and a diagnostic marker to HER2-positve patients. Thus, targeting SH3BGRL or the downstream signaling could relieve the innate resistance to some HER2-tageted therapies for both HER2 and SH3BGRL-postive breast cancers.

Atorvastatin Inhibits Breast Cancer Cells by Downregulating PTEN/AKT Pathway via Promoting Ras Homolog Family Member B (RhoB).

Background Breast cancer (BC) is one of the most common malignant tumors in women around the world. Atorvastatin (ATO) was found to be associated with a decreased risk of recurrence and mortality in cancer. But the exact mechanism of its carcinostatic effects is unclear. The expression level of Ras homolog family member B (RhoB) in breast cancer cells was found to be upregulated after being treated with ATO. Thus, we conjecture that altered expression of RhoB induced by ATO may be decisive for the migration and progression of breast cancer. Methods The effects of ATO on breast tumor cells in vivo and in vitro were detected by clone formation assay, CCK-8 assay, flow cytometry, wound healing, transwell assays, tumor xenograft model, and immunohistochemistry. Distribution of RhoB in different breast cancer tissues and its influence on prognosis were analyzed using the data from TCGA or GEO databases. The relationship between RhoB and PTEN/AKT pathway was detected by Western blotting and RT-qPCR. Results ATO inhibits proliferation, invasion, EMT, and PTEN/AKT pathway and promotes apoptosis in breast tumor cells. In addition, ATO inhibits the volume and weight of breast tumor in tumor-bearing mice and upregulated RhoB in tumor tissues. The expression of RhoB in mRNA and protein level was upregulated in statin-treated breast cancer cells and downregulated in cancer tissues. Low expression of RhoB links with poor prognosis in patients with breast cancer (HR = 0.74[0.66–0.83], p =7e−8, log-rank test). Further research found that RhoB inhibits the proliferation, invasion, EMT, and PTEN/AKT signal pathway in breast tumor cells. Conclusions The exact mechanism of ATO's carcinostatic effects in breast cancer is related to downregulating PTEN/AKT pathway via promoting RhoB. Our study also demonstrates the potential applicability of RhoB as a therapeutic target for breast cancer.

Abstract P2-01-05: Targeting of casein kinase 1δ inhibits triple negative breast cancer metastasis

Abstract Metastasis is responsible for most breast cancer mortalities and 30% of the patients with breast cancer will develop metastases. Despite the establishment of efficient targeted therapies for breast cancer, there is no cure for metastatic disease. Our research team have developed a potent, highly selective, small molecule inhibitor of casein kinase-1 delta (CK1δ), a serine/threonine kinase. We have demonstrated that our lead molecule (SR-3029) provokes tumor specific cell death and tumor regression in pre-clinical orthotopic xenograft models of triple negative breast cancer (TNBC) including, basal-like patient derived (PDX) breast cancer models. Herein, we demonstrate that targeting CK1δ inhibits tumor cell invasion in cell based studies and markedly reduces both the number and size of metastasis lesions spreading from the breast to the lung in vivo. We show that invasion impairment is due to the inhibition of key effectors of the epithelial-mesenchymal transition. We have developed Lumifluor patient-derived xenograft models and assessed the effect of our inhibitors at various stages during the process of metastases. We have identified CK1δ as an efficacious therapeutic target with dual potential for triggering apoptosis of breast tumor cells and impairing metastatic spread from the primary tumor. Citation Format: Bayle S, Lafitte M, Quereda V, Roush WR, Duckett DR. Targeting of casein kinase 1δ inhibits triple negative breast cancer metastasis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-01-05.

Eriocalyxin B, a novel autophagy inducer, exerts anti-tumor activity through the suppression of Akt/mTOR/p70S6K signaling pathway in breast cancer

Eriocalyxin B (EriB), a natural ent-kaurane diterpenoid presented in the plant Isodon eriocalyx var. laxiflora, has been reported to diminish angiogenesis-dependent breast tumor growth. In the present study, the effects of EriB on human breast cancer and its underlying mechanisms were further investigated. The in vitro anti-breast cancer activity of EriB was determined using MCF-7 and MDA-MB-231 cell lines. MDA-MB-231 xenograft model of human breast cancer was also established to explore the anti-tumor effect in vivo.We found that EriB was able to induce apoptosis accompanied by the activation of autophagy, which was evidenced by the increased accumulation of autophagosomes, acidic vesicular organelles formation, the microtubule-associated protein 1A/1B-light chain 3B-II (LC3B-II) conversion from LC3B-I and p62 degradation. Meanwhile, EriB treatment time-dependently decreased the phosphorylation of Akt, mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase (p70S6K), leading to the inhibition of Akt/mTOR/p70S6K signaling pathway. Moreover, the blockage of autophagy obviously sensitized EriB-induced cell death, which suggested the cytoprotective function of autophagy in both MCF-7 and MDA-MB-231 cells. Interestingly, the autophagic features and apoptosis induction were prevented by reactive oxygen species (ROS) scavenger N-acetyl-l-cysteine, indicating that ROS played an essential role in the mediation of EriB-induced cell death. Furthermore, in MDA-MB-231 xenograft model, EriB displayed a significant anti-tumor effect via the activation of autophagy and apoptosis in breast tumor cells. Taken together, our findings firstly demonstrated that EriB suppressed breast cancer cells growth both in vitro and in vivo, and thus could be developed as a promising anti-breast tumor agent.

The kinesin Eg5 inhibitor K858 induces apoptosis but also survivin-related chemoresistance in breast cancer cells.

Inhibitors of kinesin spindle protein Eg5 are characterized by pronounced antitumor activity. Our group has recently synthesized and screened a library of 1,3,4-thiadiazoline analogues with the pharmacophoric structure of K858, an Eg5 inhibitor. We herein report the effects of K858 on four different breast cancer cell lines: MCF7 (luminal A), BT474 (luminal B), SKBR3 (HER2 like) and MDA-MB231 (basal like). We demonstrated that K858 displayed anti-proliferative activity on every analyzed breast cancer cell line by inducing apoptosis. However, at the same time, we showed that K858 up-regulated survivin, an anti-apoptotic molecule. We then performed a negative regulation of survivin expression, with the utilization of wortmannin, an AKT inhibitor, and obtained a significant increase of K858-dependent apoptosis. These data demonstrate that K858 is a potent inhibitor of replication and induces apoptosis in breast tumor cells, independently from the tumor phenotype. This anti-proliferative response of tumor cells to K858 can be limited by the contemporaneous over-expression of survivin; consequently, the reduction of survivin levels, obtained with AKT inhibitors, can sensitize tumor cells to K858-induced apoptosis.

MCPIP1 Selectively Destabilizes Transcripts Associated with an Antiapoptotic Gene Expression Program in Breast Cancer Cells That Can Elicit Complete Tumor Regression.

The ability of cancer cells to evade apoptosis is dictated by a shift in the balance between proapoptotic and antiapoptotic gene expression programs. Monocyte chemotactic protein-induced protein 1 (MCPIP1) is a zinc-finger RNA binding protein with important roles in mediating inflammatory responses. Overexpression of MCPIP1 in different cancer cell types has been implicated in eliciting an antitumor response, but a direct role of MCPIP1 in apoptosis has not been established. In this study, we demonstrate that MCPIP1 functions as a potent tumor suppressor that induces apoptosis of breast tumor cells by selectively enhancing mRNA decay of antiapoptotic gene transcripts, including Bcl2L1, Bcl2A1, RelB, Birc3, and Bcl3. Mechanistically, MCPIP1 physically interacted with a stem-loop structure in the 3' untranslated region of these transcripts through its PIN domain, causing mRNA destabilization. Furthermore, we found that MCPIP1 expression was repressed in breast tumor cells, and overexpression of MCPIP1 induced apoptosis, whereas its depletion enhanced cancer cell proliferation. Moreover, MCPIP1 induction in vivo resulted in complete regression of established tumors and a significant reduction in metastatic disease. Notably, low MCPIP1 expression in tumor samples from breast cancer patients was strongly associated with poor survival over 13 years of follow-up. Collectively, our results highlight that MCPIP1 is a new tumor suppressor in breast cancer that induces cell death by tipping the balance in favor of proapoptotic gene expression.

Abstract LB-042: MCPIP1 suppresses breast tumor progression by targeting anti-apoptosis pathway

Abstract The ability to evade apoptosis is a hallmark of cancer and also plays a significant role in cancer resistance to conventional therapy. While recent progress has broadened our understanding of the apoptosis-evasion mechanisms by cancer cells, how apoptosis resistance develops in cancer cells through posttranscriptional mechanisms, especially by the newly discovered RNA-binding protein monocyte chemotactic protein induced protein 1 (MCPIP1), remains unknown. Here, we report that MCPIP1 expression is impaired in breast tumors and breast tumor cell lines, with the severest impairment in highly metastatic tumors. Ectopic expression of MCPIP1 causes apoptosis of breast tumor cells through selectively suppression of anti-apoptotic gene transcripts, including Bcl2L1, Bcl2A1, RelB, Birc3 and Bcl3. This suppression is medicated through a physical interaction between the PIN domain of MCPIP1 and the 3′UTRs of anti-apoptotic transcripts, resulting in mRNA degradation and tumor cell apoptosis. In difference from the RNA-binding protein tristetraprolin which binds to the ARE in the 3′UTR of target genes for mRNA decay, MCPIP1 specially recognizes a stem-loop structure in the 3′UTR of anti-apoptotic genes for binding and mRNA decay. Furthermore, induction of MCPIP not only ameliorates breast tumor formation but also completely shrinks the established tumors within six days. Lung metastasis is also significantly reduced by MCPIP1 induction. The tumor suppressive effect of MCPIP1 acts through activation of apoptosis. Importantly, by analysis of the excised breast tumors of 251 patients, we found that low MCPIP1 levels in tumors are strongly associated with poor survival of patients over 13 years of follow up. Taken together, we demonstrate that MCPIP1 is a novel potent tumor suppressor which induces tumor apoptosis through tipping the balance between pro-apoptotic and anti-apoptotic genes via selectively targeting the mRNAs of anti-apoptotic genes for degradation. MCPIP1 can serve as a new therapeutic target for treatment of breast cancer and other cancers as well. Citation Format: Jianguo Liu, Wenbao Lu, Huan Ning, Hui Peng, Qinghong Wang, Rong Hou. MCPIP1 suppresses breast tumor progression by targeting anti-apoptosis pathway. [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 LB-042. doi:10.1158/1538-7445.AM2015-LB-042

Chemopreventive Activity of Ferulago angulate against Breast Tumor in Rats and the Apoptotic Effect of Polycerasoidin in MCF7 Cells: A Bioassay-Guided Approach.

Ferulago angulata leaf hexane extract (FALHE) was found to be a potent inducer of MCF7 cell apoptosis. The aims of the present study were to investigate the in vivo chemopreventive effect of FALHE in rats, to identify the contributing anticancer compound in FALHE and to determine its potential mechanism of action against MCF7 cells. Thirty rats harboring LA7-induced breast tumors were divided into five groups: tumor control, low-dose FALHE, high-dose FALHE, treatment control (tamoxifen) and normal control. Breast tissues were then subjected to histopathological and immunohistochemical analyses. A bioassay-guided investigation on FALHE was performed to identify the cytotoxic compound and its mechanism of action through flow cytometry, real-time qPCR and western blotting analyses. An in vivo study showed that FALHE suppressed the expression of the tumor markers PCNA and Ki67. The tumor size was reduced from 2031 ± 281 mm3 to 432 ± 201 mm3 after FALHE treatment. FALHE administration induced apoptosis in breast tumor cells, and this was confirmed by high expression levels of Bax, p53 and caspase 3. Cell cycle arrest was suggested by the expression of p21 and p27. The in vitro experimental results resulted in the isolation of polycerasoidin as a bioactive ingredient of FALHE with an IC50 value of 3.16 ± 0.31 μg/ml against MCF7 cells. Polycerasoidin induced mitochondrial-dependent apoptosis in breast cancer cells via caspase activation and changes in the mRNA and protein expression of Bax and Bcl-2. In addition, flow cytometric analysis demonstrated that the treated MCF7 cells were arrested at the G1 phase, and this was associated with the up-regulation of p21 and p27 at both the mRNA and protein levels. The results of the present study reinforce further investigations scrutinizing the promising potential of the F. angulata chemical constituents as breast cancer chemopreventive agents.

Abstract P1-08-08: Reduction of HER2-associated lipogenic phenotype by docosahexaenoic acid (DHA) induces apoptosis in breast tumor cells harboring HER2 overexpression

Abstract The lipogenic phenotype is associated with oncogenic transformation and malignancy in the cancer setting. Our hypothesis is that the oncogenic nature of lipogenesis depends on the expression of HER2 oncogene, and its modulation by docosahexaenoic acid-DHA, might induce apoptosis in breast tumor cells with HER2 overexpression. To evaluate if the lipogenic phenotype might be induced by HER2 overexpression, we used a oncogenic transformation cell model in which, cells were engineered to overexpress HER-2 receptor (HB4aC5.2), but are identical to their parental strain (HB4a) in all other aspects, permitting an specific analysis of enhanced HER-2 effects. Toward this end the lipogenesis profiling was characterized, evaluating several molecular features, including synthesis (FASN), uptake(CD36), transport(FABP4) and storage(DGAT) of FA by RT-PCR and lipogenic regulatory pathways (mTOR, DEPTOR, SREBP1 and PPARγ) in both cells. Lipogenic contribution to lipid rafts formation, which is necessary to HER2 receptor location and activation in the cell membrane, was evaluated by gas chromatography and confocal microscopy. The influence of HER2 overexpression and lipogenic phenotype on proteins activated by HER-2 (AKT, ERK1/2 and FASN) was analyzed by western blot. Next, HB4a and HB4aC5.2 cells were treated, alone or in combination, with DHA, Trastuzumab (anti-HER2), and GW9662 (PPARγ inhibitor) for 72h, and the above experiments were repeated. Cell death was analyzed by flow cytometry and confocal microscopy. Results: In HB4aC5.2 cells, the oncogenic transformation by HER2 overexpression was associated with a lipogenic phenotype, which contributed to increase of lipid rafts formation, activation of survival and proliferation signals, as compared to HB4a normal cells (p<0.001). It is believed that PPARγ is the main regulator of cell lipogenesis. However, our data have shown that mTOR/SREBP pathway, exclusively mTORC1, was decreased concomitantly to increase of DEPTOR gene expression and AKT activation, in HB4aC5.2 cells. Also, the treatment with GW9662 did not change the expression of lipogenic genes, suggesting that lipogenesis seems independent of PPARγ activation, and that HER-2 overexpressing cells may use alternative mechanisms to maintain the lipogenic phenotype. DEPTOR is overexpressed in white adipose tissue and is associated with regulation of lipogenesis. Moreover, DEPTOR overexpression suppresses S6K1 but, by relieving feedback inhibition from mTORC1 to PI3K signaling, activates Akt. In HB4aC5.2 cells, only the DHA treatment decreased the lipogenic phenotype, DEPTOR expression, disrupted lipid raft, inhibited HER-2 signaling, and induced apoptosis (p<0.001). In addition the combined treatment using DHA and Trastuzumab increased cell death. Conclusion: We show that lipogenic phenotype was associated with HER-2 in breast cancer, can be induced early in the oncogenic transformation, and it seems important to promote survival and proliferation. Otherwise, Its modulation by DHA increased death in tumor cells, suggesting this kind of FA may represent a useful tool for controlling the HER2-positive breast cancer. Citation Format: Graziela R Ravacci, Maria M Brentani, William Festuccia, Tharcisio Tortelli, Angela F Waitzberg, Dan L Waitzberg. Reduction of HER2-associated lipogenic phenotype by docosahexaenoic acid (DHA) induces apoptosis in breast tumor cells harboring HER2 overexpression [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-08-08.

PP082-MON: HER2-Associated Lipogenic Phenotype Modulation by Docosahexaenoic Acid (DHA) Induces Apoptosis in Breast Tumor Cells Harboring HER2 Overexpression

PP082-MON: HER2-Associated Lipogenic Phenotype Modulation by Docosahexaenoic Acid (DHA) Induces Apoptosis in Breast Tumor Cells Harboring HER2 Overexpression

Local Anesthetics Induce Apoptosis in Human Breast Tumor Cells

Previous studies have shown that local anesthetics may induce apoptosis in some cell types. In this study, we investigated the apoptotic effects of local anesthetics in human breast tumor cells. Human breast cancer (MCF-7) and mammary epithelial (MCF-10A) cell lines were treated with lidocaine and/or bupivacaine. Cell viability, DNA fragmentation, and annexin V immunofluorescence staining were assessed. The effects on apoptosis-related protein expression were investigated by Western blot analysis. The findings were extended to studies in an in vivo xenograft model. Treatment of breast tumor cells with lidocaine and bupivacaine resulted in inhibition of cell viability via induction of apoptosis. The effects were more prominent in MCF-7 cells than in MCF-10A cells. Treatment with local anesthetics induced caspase 7, 8, 9, and poly ADP-ribose polymerase cleavage. The cleavage of caspase 7 and poly ADP-ribose polymerase induced by local anesthetics were effectively blocked by caspase inhibitors. Furthermore, treatment of MCF-7 xenografts with local anesthetics resulted in higher expression of cleaved caspase 7 and an increase in terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining. Lidocaine and bupivacaine induce apoptosis of breast tumor cells at clinically relevant concentrations. Our results reveal previously unrecognized beneficial actions of local anesthetics and call for further studies to assess the oncologic advantages of their use during breast cancer surgery.

Abstract 570: Breast cancer chemopreventive activity of a novel amide derivative of sulindac involves inhibition of PDE5, activation of PKG, and attenuation of Wnt/β-catenin signaling

Abstract The nonsteroidal anti-inflammatory drugs (NSAIDs) and cyclooxygenase-2 (COX2) inhibitors demonstrate promising chemopreventive activity against a number of cancer types, including breast cancer. Unfortunately, potentially fatal toxicities associated with COX inhibition have precluded the development of these drugs for such indications. However, some studies suggest that their anticancer activity may be due to COX-independent mechanisms, suggesting the ability to target such mechanisms for the development of potentially safer and more effective chemopreventive agents. Here we describe a novel amide derivative of the NSAID sulindac sulfide (SS), termed sulindac sulfide amide (SSA). SSA lacked the ability to inhibit either COX1 or COX2 but demonstrated as much as a twenty-fold increase in potency to inhibit growth and induce apoptosis of breast tumor cells compared to SS. Moreover, SSA was selective for tumor cells, having no measurable effect on apoptosis of nontumorigenic mammary epithelial cells. As we have shown previously with SS, SSA inhibited the cGMP specific phosphodiesterase 5 (PDE5) enzyme. This resulted in accumulation of intracellular cGMP and activation of cGMP-dependent protein kinase (PKG) at concentrations comparable to those that induced breast tumor cell apoptosis. Mirroring the effects on PKG, SSA also resulted in decreased Wnt/β-catenin signaling, including decreased expression of the Tcf/Lef controlled proteins, cyclin D1 and survivin. Furthermore, SSA caused a 50% reduction in the incidence and a 30% reduction in the multiplicity of mammary tumors using the MNU model of mammary carcinogenesis. Interestingly, mammary tumors induced by MNU displayed high levels of PDE5 expression. These findings further demonstrate the COX-independent nature of the anticancer activity of certain NSAIDs, provide additional evidence that PDE5 may serve as an effective target for breast cancer chemoprevention, and reveal the utility of chemically modifying the NSAIDs to remove COX inhibitory activity while enhancing anticancer activity in order to produce safer and more effective chemopreventive agents. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 570. doi:1538-7445.AM2012-570

Inhibition of PDE5 by Sulindac Sulfide Selectively Induces Apoptosis and Attenuates Oncogenic Wnt/β-Catenin–Mediated Transcription in Human Breast Tumor Cells

Nonsteroidal anti-inflammatory drugs (NSAID) such as sulindac sulfide (SS) display promising antineoplastic properties, but toxicities resulting from COX inhibition limit their clinical use. Although COX inhibition is responsible for the anti-inflammatory activity of SS, recent studies suggest that phosphodiesterase (PDE) 5 inhibition and activation of cyclic guanosine monophosphate (cGMP) signaling are closely associated with its ability to induce apoptosis of tumor cells. However, the underlying mechanisms responsible for apoptosis induction, factors that influence sensitivity of tumor cells to SS, and the importance of PDE5 for breast tumor cell growth have not been established. Here we show that SS can induce apoptosis of breast tumor cells, which predominantly rely on PDE5 for cGMP hydrolysis but not normal mammary epithelial cells, which rely on PDE isozymes other than PDE5 for cGMP hydrolysis. Inhibition of PDE5 and activation of protein kinase G (PKG) by SS was associated with increased β-catenin phosphorylation, decreased β-catenin mRNA and protein levels, reduced β-catenin nuclear localization, decreased T-cell factor/lymphoid enhancer factor (Tcf/Lef) promoter activity, and decreased expression of Wnt/β-catenin-regulated proteins. Suppression of PDE5 with siRNA or known PDE5 inhibitors was sufficient to selectively induce apoptosis and attenuate β-catenin-mediated transcription in breast tumor cells with minimal effects on normal mammary epithelial cells. These findings provide evidence that SS induces apoptosis of breast tumor cells through a mechanism involving inhibition of PDE5 and attenuation of oncogenic Wnt/β-catenin-mediated transcription. We conclude that PDE5 represents a novel molecular target for the discovery of safer and more efficacious drugs for breast cancer chemoprevention.

Abstract 1853: PDE5 suppression selectively induces apoptosis of human breast tumor cells and attenuates Wnt/β-catenin mediated transcription

Abstract Nonsteroidal anti-inflammatory drugs (NSAIDs) such as sulindac sulfide (SS) display promising antineoplastic properties in experimental models, but toxicities from cyclooxygenase (COX) inhibition limit their clinical use for cancer chemoprevention. While COX inhibition is responsible for the anti-inflammatory activity of SS, recent studies suggest that phosphodiesterase (PDE) 5 inhibition and activation of cGMP signaling are closely associated with its ability to induce apoptosis of tumor cells. However, the underlying mechanisms responsible for apoptosis induction and factors that influence sensitivity to SS have not been well studied. Here we show that SS can induce apoptosis of breast tumor cells that express PDE5, but not normal mammary epithelial cells, which do not express PDE5. Inhibition of PDE5 and subsequent activation of PKG by SS was associated with increased β-catenin phosphorylation, decreased β-catenin mRNA and protein levels, reduced β-catenin nuclear localization, decreased Tcf/Lef promoter activity, and decreased expression of Wnt/β-catenin regulated proteins such as survivin. Suppression of PDE5 by siRNA or known PDE5 inhibitors was sufficient to selectively induce apoptosis and attenuate β-catenin mediated transcription in breast tumor cells with no effect on normal mammary epithelial cells. These findings provide evidence that PDE5 expression can influence the sensitivity of human breast tumor cells to SS and that cGMP can inhibit Wnt/β-catenin signaling and suppress the transcription of key apoptosis regulatory proteins. We conclude that PDE5 represents a novel molecular target for the discovery of safer and more efficacious drugs for the prevention and treatment of breast cancer. Funding provided by NIH/NCI grants CA131378 and CA148817. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1853. doi:10.1158/1538-7445.AM2011-1853

Abstract 3833: Molecular mechanisms by which BAY 80-6946 induces apoptosis in breast tumor cells as single agent or in combination

Abstract PI3K/PTEN/AKT pathway has been found frequently activated and mutated in human breast cancer, which contributes to the development and progression of breast cancer as well as drug resistance. As genetic alteration of PIK3CA and PTEN as well as PI3K pathway activation are observed in almost all breast cancer categories, it is important to define the strategy for the development of PI3K inhibitors in breast cancer. BAY 80-6946 is a highly potent and selective pan-class I PI3K inhibitor in PhI clinical development. Molecular profiling of BAY 80-6946 in 24 breast tumor cell lines indicated that tumor cells with either PIK3CA mutation and/or HER2 expression were extremely sensitive to BAY 80-6946 with an average IC50 value of 17 (n=7) and 19 nM (n=8), respectively. In contrast wild type PIK3CA and HER2- breast tumor cells (n=12) were relatively insensitive or resistant to BAY 80-6946 with an average IC50 value of 773 nM. With regard to apoptosis induction, BAY 80-6946 demonstrated superior activity against other PI3K pathway inhibitors tested in PIK3CA mutant breast tumor cells. We found that the expression of Bcl-2, but not Mcl-1 nor survivin determined the sensitivity to apoptosis. Tumor cells that lack Bcl-2 expression immediately underwent apoptosis after exposure to BAY 80-6946. On the other hand, cells expressing high level of Bcl-2 such as T47D (PIK3CAmut) were resistant to the apoptosis induced by BAY 80-6946, despite a potent anti-proliferative activity of BAY 80-6946 (single-digit nM IC50). Combining BAY 80-6946 with ABT737 sensitized T47D cells to apoptosis, further supporting our hypothesis. On the other hand, PTEN-null, EGFRhigh and Bcl2 negative MDA-MB-468 tumor cells, are resistant to apoptosis induction by BAY 80-6946. Using shRNA and inhibitor against mTOR (TORC1 or TORC2), we identified an mTOR-dependent, PI3K-independent phosphorylation of AKT at S473, which might cause tumor cells resistance to the PI3K inhibition by BAY 80-6946. Rictor knockdown or combination with rapamycin can sensitize MDA-MB-468 to BAY 80-6946 with the respect to inhibition of proliferation and induction of apoptosis. Interestingly, the dual PI3K/mTOR inhibitor BEZ-235 could not induce apoptosis in MDA-MB-468, suggesting that the ratio of PI3K vs mTOR inhibition might be important in apoptosis induction. In conclusion, BAY 80-6946 was extremely effective to induce apoptosis in breast cancer cells expressing Her2 and/or PIK3CA mutation in the absence of Bcl-2. BAY 80-6946 in combination with anti-Bcl agents or mTOR inhibitors might be the promising approach to achieve tumor responses in Bcl-2 positive tumors or EGFR expressing/PTEN-null breast tumors, respectively. These findings provide a rationale to develop personalized therapies for the treatment of molecular subtypes of breast cancer.

Protein kinase Cδ and caspase-3 modulate TRAIL-induced apoptosis in breast tumor cells

This report describes that protein kinase C delta (PKCδ) overexpression prevents TRAIL-induced apoptosis in breast tumor cells; however, the regulatory mechanism(s) involved in this phenomenon is(are) incompletely understood. In this study, we have shown that TRAIL-induced apoptosis was significantly inhibited in PKCδ overexpressing MCF-7 (MCF7/PKCδ) cells. Our data reveal that PKCδ inhibits caspase-8 activation, a first step in TRAIL-induced apoptosis, thus preventing TRAIL-induced apoptosis. Inhibition of PKCδ using rottlerin or PKCδ siRNA reverses the inhibitory effect of PKCδ on caspase-8 activation leading to TRAIL-induced apoptosis. To determine if caspase-3-induced PKCδ cleavage reverses its inhibition on caspase-8, we developed stable cell lines that either expresses wild-type PKCδ (MCF-7/cas-3/PKCδ) or caspase-3 cleavage-resistant PKCδ mutant (MCF-7/cas-3/PKCδ mut) utilizing MCF-7 cells expressing caspase-3. Cells that overexpress caspase-3 cleavage-resistant PKCδ mutant (MCF-7/cas-3/PKCδmut) significantly inhibited TRAIL-induced apoptosis when compared to wild-type PKCδ (MCF-7/cas-3/PKCδ) expressing cells. In MCF-7/cas-3/PKCδmut cells, TRAIL-induced caspase-8 activation was blocked leading to inhibition of apoptosis when compared to wild-type PKCδ (MCF-7/cas-3/PKCδ) expressing cells. Together, these results strongly suggest that overexpression of PKCδ inhibits caspase-8 activation leading to inhibition of TRAIL-induced apoptosis and its inhibition by rottlerin, siRNA, or cleavage by caspase-3 sensitizes cells to TRAIL-induced apoptosis. Clinically, PKCδ overexpressing tumors can be treated with a combination of PKCδ inhibitor(s) and TRAIL as a new treatment strategy.

Reactivation of epigenetically silenced HER4/ERBB4 results in apoptosis of breast tumor cells

Experimental and clinical data support a growth inhibitory role for HER4 in breast cancer. Clinically HER4 expression is extinguished during breast tumorigenesis supporting a tumor suppressor function for HER4, however, a molecular mechanism to explain the selective loss of HER4 expression has remained elusive. Epigenetic mechanisms, for example, aberrant gene promoter hypermethylation, have been shown to ablate tumor suppressor gene expression in breast carcinomas. We identified a CpG island within the HER4 promoter and show by pyrosequencing of bisulfite-treated DNA an inverse correlation between HER4 expression and the extent of promoter methylation. Treatment of the HER4-negative BT20 cell line with the DNA demethylating agent 5-aza-2′-deoxycytidine (DAC)-enhanced HER4 expression, confirming a role for DNA methylation in suppressed HER4 expression. DAC treatment to reactive HER4 expression in combination with the HER4 ligand heregulin-β1 (HRG) resulted in apoptosis of BT20 cells providing a novel therapeutic strategy for triple-negative tumors. The BT20 cells were rescued from apoptosis when preincubated with HER4 small interfering RNA, thereby confirming a role for HER4 in DAC/HRG-induced apoptosis. We verified HER4 promoter methylation in primary breast carcinomas and detected a significant increase in HER4 promoter methylation in HER4-negative breast tumors (P<0.001). Furthermore, increased levels of HER4 promoter methylation were significantly associated with worse patient prognosis (P=0.0234). Taken together, our data support a tumor suppressor function for HER4, which is epigenetically suppressed in breast tumors through promoter hypermethylation.