Cell Cycle Inhibitory Proteins P21 Research Articles

P53, p21, and cyclin d1 protein expression patterns in patients with breast cancer.

Background and Aim:The mutation in the wild-type tumor suppressor gene p53 is the most common genetic change in human tumors. In addition, the normal function of p21, which is both antiproliferative and an inhibitor of the cell cycle, is disrupted in some types of cancer. Meanwhile, cyclin D1 is a member of the cyclin protein family that is involved in regulating cell cycle progression. This study aimed to assess the expressions of the cell cycle inhibitory proteins p21, cyclin D1, and tumor suppressor gene p53, as well as their influence on the expressed histopathological changes in breast cancer tissues.Materials and Methods:Overall, 40 breast tissue specimens were investigated in this study, 30 of which were cancerous, while 10 were healthy tissues. p53, p21, and cyclin D1 expression patterns were detected using an immunohistochemistry (IHC) system.Results:The IHC reactions for p53 were positively observed in 27/30 (90%) cancerous tissues, compared with 2/10 (20%) normal breast tissues. For p21, reactions were observed in 28/30 (93.33%) cancerous tissues and 3/10 (30%) control tissues. For cyclin D1, reactions were observed in 25/30 (83.33%) cancerous tissues and 1/10 (10%) control tissues. The differences between the breast cancer tissues and the control tissues were statistically highly significant (p<0.01).Conclusion:The high expression rates of p21, cyclin D1, and p53 in malignant breast cancer cells with little or no regulatory role might imply mutational events in these proteins operating in concert with a variety of other genetic mutations in these tissues, which may play a molecular role in the development and/or progression of breast carcinogenesis.

Esculetin induces cell cycle arrest and apoptosis in human colon cancer LoVo cells.

We investigated the anti-cancer effects of ESC in human colon cancer LoVo cells. Cell counting assay results showed that ESC inhibited the proliferation of LoVo cells. Cell cycle arrest results showed that cell cycle was arrested during the G0/G1 phase in the ESC-treated LoVo cells. Western blot results showed that the cell cycle inhibitory proteins p53, p27, and p21 were increased, and cyclin D1, the cell cycle progressive protein, was decreased. Sp1 is a transcription factor regulating cell proliferation, was decreased in the ESC-treated LoVo cells. Annexin V/propidium iodide staining results showed that ESC induces apoptosis in LoVo cells. Western blot results showed that Bax, cleaved caspase -3, -7, -9, and poly(ADP-ribose) polymerase, which are proapoptotic proteins, were increased and the antiapoptotic protein Bcl-2 was decreased. Taken together, ESC induced apoptosis and has an anti-cancer effect in LoVo cells.

EGR1 is essential for deoxynivalenol-induced G2/M cell cycle arrest in HepG2 cells via the ATF3ΔZip2a/2b-EGR1-p21 pathway

Deoxynivalenol (DON) is a type B trichothecene mycotoxin that exerts multiple toxic effects on plants, animals and humans. Several reports have shown that DON leads to G2/M cell cycle arrest. However, its molecular mechanism is still unclear. In this study, we showed that DON induced strong G2/M cell cycle arrest in HepG2 cells, and the cell cycle-inhibitory protein p21 was highly upregulated by DON. Further analysis showed that the cell cycle regulating gene EGR1 was highly induced by DON and that EGR1 knockdown abolished the upregulation of p21 and G2/M cell cycle arrest. Furthermore, we showed that the induction of EGR1 was regulated by the stress-responsive transcription factor ATF3. ATF3ΔZip2a/2b, which is a DNA binding domain truncated isoform of ATF3, was upregulated by DON. ATF3 knockdown weakened the expression induction of EGR1 and G2/M cell cycle arrest by DON. Moreover, the upregulation of ATF3ΔZip2a/2 highly depended on the enhanced presence of histones H3K9ac and H3K27ac. H3K9ac and H3K27ac were enriched at the promoter region of ATF3 following the DON treatment, and the knocking down of the genes responsible for H3K9ac and H3K27ac abolished the upregulation of ATF3 by DON. In summary, we found that DON induced G2/M cell cycle arrest by sequentially inducing the expression of ATF3ΔZip2a/2b, EGR1 and p21, and EGR1 played an essential role in this process, which is a novel molecular mechanism of cell cycle arrest by DON and is important for understanding its toxicology.

Antifibrosis Effect of Novel Oridonin Analog CYD0618 Via Suppression of the NF-κB Pathway

BackgroundLiver fibrosis is characterized as excessive deposition of the extracellular matrix proteins, primarily by activated hepatic stellate cells (HSCs). NF-κB has been reported as one of the major mediators of HSC activation. Previously, our team reported that oridonin exhibited antihepatic fibrogenetic activity in vitro. In this study, we examined the effects of its novel derivative CYD0618 on HSC viability, apoptosis, and NF-κB signaling. MethodsCell proliferation of activated human and rat HSC lines LX-2 and HSC-T6 was measured using Alamar Blue Assay. Apoptosis was measured by a Cell Death Detection ELISA kit. Cellular proteins were determined by Western blots and immunofluorescence. ResultsCYD0618 significantly inhibited LX-2 and HSC-T6 cell proliferation in a dose-dependent manner. CYD0618 induced cell apoptosis in both cell lines. CYD0618 treatment increased cell cycle inhibitory protein p21, p27, and induced apoptosis marker cleaved poly (ADP-ribose) polymerase, while suppressing the expression of Collagen type 1. CYD0618 blocked lipopolysaccharide (LPS)-induced NF-κB p65 nuclear translocation and DNA binding activity and prevented LPS-induced NF-κB inhibitory protein IκBα phosphorylation and degradation. LPS-stimulated NF-κB downstream target cytokines IL-6 and MCP-1 were attenuated by CYD0618. Endogenous and LPS-stimulated NF-κB p65 S536 phosphorylation was inhibited by CYD0618 treatment. ConclusionsThe potent antihepatic fibrogenetic effect of CYD0618 may be mediated via suppression of the NF-κB pathway.

Abstract 2794: A novel bis-aspirinyl selenazolidine compound AS-10 as potential colon cancer therapeutic

Abstract Despite rigorous screening and aggressive surgical and chemotherapeutic treatments, colorectal cancer (CRC) remains the third leading cause of cancer-related deaths in women and the second leading cause in men in the United States. It is expected to cause about 50,260 deaths during 2017 (American Cancer Society). The 5-year survival rate for patients with colorectal cancer (CRC) is 64%, although for patients who present with distant metastases at diagnosis the 5 year survival is only 12%. Therefore, there is an urgent need to develop effective therapeutic strategies that will enhance the survival and improve quality of life of CRC patients. Non-steroidal anti-inflammatory drugs (NSAIDs), particularly aspirin, have recently been shown to be effective in reducing colon cancer incidences and are proposed to be effective CRC chemopreventive agents. Through extensive structure activity relationship (SAR) studies based on designing selenium-NSAID hybrid small molecules, we have identified a small drug-like molecule, AS-10, which contains two aspirinyl groups flanked to a selenazolidine ring. AS-10 effectively inhibited the viability of CRC cells (HT29, RKO, and HCT116) with an EC50 in the range of 1 to 2.5 µM. Interestingly, AS-10 showed more selectivity towards killing cancer cells than normal mouse embryonic fibroblasts (MEFs) and was &amp;gt;50 times more potent than current standard of care, 5-FU, for in killing CRC cells. Cell cycle studies revealed AS-10 treated CRC cells to have G1 and G2/M phase cell cycle arrest. Further, increasing protein expression of cell cycle inhibitory protein p21 confirmed our cell cycle findings in AS-10 treated CRC cells. Since these CRC cell lines are p53 mutant cells, it was noteworthy to see p53 independent expression of p21. Moreover, we explored the possibility of apoptosis in these cell cycle arrested cells and found that AS-10 treatment increased casapse 3/7 activity, and cells positive for phosphatidylserine on the outer cell membrane surface indicative of apoptosis. In silico evaluation shows that AS-10 with cLogP 2.2 and MW 473 fits perfectly into the requirements of Lipinski's Rule-of-Five, formulated to determine the drug-likeness of a small molecule. In addition, in nude mice, AS-10 exhibited a high maximum tolerated dose (MTD) (~80 mg/kg, IP, three times per week). Furthermore, AS-10 (45 mg/kg, IP, three times per week) effectively inhibited tumor growth by ~70% in a nude mouse colon cancer xenograft model without any apparent systemic toxicity. Overall, AS-10 appears to be a promising small molecule worthy of further development as a therapeutic for CRC patients. Citation Format: Deepkamal N. Karelia, Manoj Pandey, Daniel Plano, Shantu Amin, Arun K. Sharma. A novel bis-aspirinyl selenazolidine compound AS-10 as potential colon cancer therapeutic [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2794.

Cell-cycle arrest in mature adipocytes impairs BAT development but not WAT browning, and reduces adaptive thermogenesis in mice

We previously reported brown adipocytes can proliferate even after differentiation. To test the involvement of mature adipocyte proliferation in cell number control in fat tissue, we generated transgenic (Tg) mice over-expressing cell-cycle inhibitory protein p27 specifically in adipocytes, using the aP2 promoter. While there was no apparent difference in white adipose tissue (WAT) between wild-type (WT) and Tg mice, the amount of brown adipose tissue (BAT) was much smaller in Tg mice. Although BAT showed a normal cellular morphology, Tg mice had lower content of uncoupling protein 1 (UCP1) as a whole, and attenuated cold exposure- or β3-adrenergic receptor (AR) agonist-induced thermogenesis, with a decrease in the number of mature brown adipocytes expressing proliferation markers. An agonist for the β3-AR failed to increase the number of proliferating brown adipocytes, UCP1 content in BAT, and oxygen consumption in Tg mice, although the induction and the function of beige adipocytes in inguinal WAT from Tg mice were similar to WT mice. These results show that brown adipocyte proliferation significantly contributes to BAT development and adaptive thermogenesis in mice, but not to induction of beige adipocytes.

Abstract 3081: Novel cucurbitacin analogue Cuc D exhibits potent anti-cancer activity in cervical cancer

Abstract Background: Cervical cancer is one of the leading cause of mortality among women in US. Naturally occurring dietary compounds have gained increasing attention for their anticancer effects. Cucurbitacins, tetracyclic triterpenoid compound, belong to a family of Cucurbitaceae have shown promising anti-cancer activity. Herein, we investigated the potential anti-cancer effects of a novel analogue of cucurbitacin D (Cuc D) against cervical cancer in in vitro and in a xenograft mouse model. Methods: In our study, we used human cervical cancer cells (CaSki and SiHa). Cells were treated with Cuc D (0.05 to 1μM) for 48 and 72 hrs. MTS and colony formation assays were performed to investigate the effects of Cuc D on cell viability and proliferation. Western Blot analysis was performed to investigate the effects of Cuc D on cell proliferation and apoptotic markers. To determine the therapeutic effects of Cuc D, we used female athymic nude mice and injected CaSki cells (4 × 106) into the cervix to develop orthotopic xenograft tumors. Cuc D (1 mg/kg body weight) was administered through intratumoral injection four weeks post-tumor cell injection. Tumor volume in these mice were recorded bi-weekly. Results: Cuc D inhibited cell viability of cervical cancer cells in a dose-dependent manner. IC50 of Cuc D was observed 400 nM and 250 nM in Caski and SiHa cells, respectively. Cuc D treatment effectively inhibited growth of cervical cancer cells which was determined by decreased cell proliferation and colony formation assays. Cuc D treatment induced apoptosis in cervical cancer cells as measured by enhanced Annexin V staining. Western blot result also illustrated cleavage in PARP protein in Cuc D treated cells which further confirms apoptosis induction. Cuc D treatment also inhibited PI3K and c-Myc protein levels and phosphorylation of STAT3 and Rb proteins. In addition, Cuc D treatment induced the cell cycle inhibitory proteins (p21 and p27) and PTEN and the expression of a tumor suppressor microRNA, miR-145, as determined by qRT-PCR. In an orthotopic tumor xenograft mouse model, Cuc D treatment effectively inhibited tumor growth as compared to vehicle control treated mice. Conclusion: Taken together, our results demonstrate potent anti-cancer efficacy of Cuc D in cervical cancer cells via modulation of key onco/tumor suppressor proteins. Thus, Cuc D could be a useful therapeutic agent for cervical cancer treatment. Citation Format: Mohammed Sikander, Bilal Bin Hafeez, Fathi T. Halaweish, Murali M. Yallapu, Meena Jaggi, Subhash C. Chauhan. Novel cucurbitacin analogue Cuc D exhibits potent anti-cancer activity in cervical cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3081.

Progesterone receptor activation is required for folic acid-induced anti-proliferation in colorectal cancer cell lines

Previously, we demonstrated that folic acid (FA) could inhibit proliferation of colorectal cancer cell lines through activating the folate receptor (FR)α/cSrc/ERK1/2/NFκB/p53 pathway and anti-COLO-205 tumor growth in vivo. Since we recently also demonstrated that female sex hormones could affect the FA's action in regulating endothelial cell proliferation and migration, the aim of this study was to investigate the effect of progesterone (P4) on the FA-induced anti-proliferation in colorectal cancer cells. Treatment with FA significantly reduced the proliferation of the P4 receptor (PR)-positive colon cancer cell lines, COLO-205, HT-29 and LoVo, but did not significantly affect the proliferation of the PR-negative colon cancer cell lines, HCT116 and DLD-1. Pre-treatment with Org 31710, a PR specific antagonist, abolished the FA-induced proliferation inhibition and activation in the signaling pathway involved in regulating proliferation inhibition in these PR positive colorectal cancer cell lines. The involvement of PR in the FA-induced activation of cSrc and up-regulations in cell cycle inhibitory proteins (p21, p27 and p53) was confirmed by knock-down of PR expression using the siRNA technique. Importantly, we show direct protein interaction between FR and PR in COLO-205. Moreover, treatment with FA induced PR activation in COLO-205. Taken together, these data suggest that FA induced proliferation inhibition in colon cancer cells through activation of PR. This finding might explain some of the controversies of FA's effects on cancer growth and provide valuable reference for clinical applications of FA in treating colorectal cancer.

Cryptic sequence features within the disordered protein p27Kip1 regulate cell cycle signaling

Peptide motifs embedded within intrinsically disordered regions (IDRs) of proteins are often the sites of posttranslational modifications that control cell-signaling pathways. How do IDR sequences modulate the functionalities of motifs? We answer this question using the polyampholytic C-terminal IDR of the cell cycle inhibitory protein p27(Kip1) (p27). Phosphorylation of Thr-187 (T187) within the p27 IDR controls entry into S phase of the cell division cycle. Additionally, the conformational properties of polyampholytic sequences are predicted to be influenced by the linear patterning of oppositely charged residues. Therefore, we designed sequence variants of the p27 IDR to alter charge patterning outside the primary substrate motif containing T187. Computer simulations and biophysical measurements confirm predictions regarding the impact of charge patterning on the global dimensions of IDRs. Through functional studies, we uncover cryptic sequence features within the p27 IDR that influence the efficiency of T187 phosphorylation. Specifically, we find a positive correlation between T187 phosphorylation efficiency and the weighted net charge per residue of an auxiliary motif. We also find that accumulation of positive charges within the auxiliary motif can diminish the efficiency of T187 phosphorylation because this increases the likelihood of long-range intra-IDR interactions that involve both the primary and auxiliary motifs and inhibit their contributions to function. Importantly, our findings suggest that the cryptic sequence features of the WT p27 IDR negatively regulate T187 phosphorylation signaling. Our approaches provide a generalizable strategy for uncovering the influence of sequence contexts on the functionalities of primary motifs in other IDRs.

Suppressive Effects of Novel Oridonin Derivative CYD0625 on Activated Hepatic Stellate Cells

The natural compound oridonin has been proven to possess anti‐neoplastic and anti‐inflammatory properties. Previously, we described that oridonin caused apoptosis, inhibition of cell proliferation and down‐regulation of extracellular matrix proteins (ECM) in activated hepatic stellate cells (HSC). In this study, we investigated the potentially more potent derivative CYD0625 in vitro.MethodsCell proliferation was measured by Alamar Blue assay. Cell apoptosis was detected by staining with Yo‐Pro‐1 and propidium iodide. Immunoblot and immunofluorescence staining were performed for cellular protein expression.ResultsTreatment of CYD0625 significantly inhibited LX‐2 cells proliferation in a dose‐ and time‐dependent manner with ~20–fold greater potency than oridonin. Similar results were observed in HSC‐T6 cells, whereas 1 μM of CYD0625 treatment had no effect on the human hepatocyte cell line C3A. CYD0625 induced LX‐2 cells apoptosis and S‐phase cell cycle arrest, and it was associated with activation of cell cycle inhibitory proteins p21, p16. The myofibroblast marker protein α‐smooth muscle actin and major ECM proteins collagen type I and fibronectin were markedly down‐regulated by CYD0625. Interestingly, treatment of HSC with CYD0625 at a low dosage (0.1 μM), significantly suppressed collagen type I expression in LX‐2 cells. Furthermore, pre‐treatment with CYD0625 blocked PDGF‐BB‐induced collagen type I and fibronectin expression in LX‐2 cells. imageConclusionIn comparison with oridonin, its novel derivative CYD0625 could be a more potent and safer hepatic anti‐fibrosis agent.

Thymoquinone induces apoptosis in human colon cancer HCT116 cells through inactivation of STAT3 by blocking JAK2- and Src‑mediated phosphorylation of EGF receptor tyrosine kinase.

Thymoquinone (TQ), a compound isolated from black seed oil (Nigella sativa), has been reported to possess anti-inflammatory and anticancer activities. However, the molecular mechanisms underlying the anticancer effects of TQ remain poorly understood. In the present study, we found that TQ significantly reduced the viability of human colon cancer HCT116 cells in a concentration- and time-dependent manner. Treatment of cells with TQ induced apoptosis, which was associated with the upregulation of Bax and inhibition of Bcl-2 and Bcl-xl expression. TQ also activated caspase-9,-7, and -3, and induced the cleavage of poly-(ADP-ribose) polymerase (PARP). Pretreatment with a pan-caspase inhibitor, z-VAD-fmk, abrogated TQ-induced apoptosis by blocking the cleavage of caspase-3 and PARP. Treatment of cells with TQ also diminished the constitutive phosphorylation, nuclear localization and the reporter gene activity of signal transducer and activator of transcription-3 (STAT3). TQ attenuated the expression of STAT3 target gene products, such as survivin, c-Myc, and cyclin-D1, -D2, and enhanced the expression of cell cycle inhibitory proteins p27 and p21. Treatment with TQ attenuated the phosphorylation of upstream kinases, such as Janus-activated kinase-2 (JAK2), Src kinase and epidermal growth factor receptor (EGFR) tyrosine kinase. Pharmacological inhibition of JAK2 and Src blunted tyrosine phosphorylation of EGFR and STAT3, while treatment with an EGFR tyrosine kinase inhibitor gefitinib inhibited phosphorylation of STAT3 without affecting that of JAK2 and Src in HCT116 cells. Collectively, our study revealed that TQ induced apoptosis in HCT116 cells by blocking STAT3 signaling via inhibition of JAK2- and Src-mediated phosphorylation of EGFR tyrosine kinase.

Hypoxia Induces Drug Resistance In Multiple Myeloma

IntroductionMultiple Myeloma (MM) is a plasma cell malignancy, characterized by plasma cell accumulation in the bone marrow (BM) and overproduction of immunoglobulin. The interaction of MM cells with the BM microenvironment was shown to play an important role in the drug resistance in MM. Hypoxia was shown to develop in the BM niche during progression of MM and to play a major role in the dissemination of MM cells to the new BM niches. In this study, we tested the effect of hypoxia on the proliferation, cells cycle, apoptosis and induction of drug resistance in MM cells. MethodsMM cell lines were exposed to normoxia (21% O2) or hypoxia (1% O2) and the effect of hypoxia on cell survival (by MTT assay), apoptosis (by annexin-PI staining and analysis with flow cytometry) and cell cycle (by cell fixation and permeabilization, RNA degradation and DNA staining with PI, and analysis with flow cytometry) was tested. Moreover, the effect of hypoxia on the expression of PI3K pathway-associated proteins (p-PI3K, p-AKT and p-mTOR), cell cycle proteins (cyclin-D, cyclin-E, p-Rb and p27) and apoptosis proteins (cleaved PARP, caspase-3, Bcl-2, Bcl-Xl and Mcl-1) were studied. We tested the effect of hypoxia on the sensitivity of MM cells to different therapeutic agents using MTT assay after the MM cells were treated with increasing concentrations of bortezomib, carfilzomib and melphalan. Finally, we examined the effect of a HIF inhibitor on the sensitivity of MM cells to therapy. ResultsHypoxia decreased the proliferation of MM cells and reduced phosphorylation of p-PI3K, p-AKT and p-mTOR. Similarly, MM cells exhibited G1 cell cycle arrest, decreased expression of cell cycle-associated proteins including cyclin-D3, cyclin-E, p-Rb, and increase in cell cycle inhibitory protein p27. However, hypoxia did not alter the apoptosis of MM cells, where neither apoptosis was detected in MM cells due to hypoxia using annexin-PI staining, nor pro-apoptosis proteins were activated due to hypoxia as shown by the unchanged levels of cleaved PARP, caspase-3, Bcl-2, Bcl-Xl, and Mcl-1 proteins.Moreover, we found that hypoxic cells displayed less sensitivity to bortezomib and carfilzomib, but it did not induce any change in melphalan activity. Treatment with carfilzomib or bortezomib (5nM for 48hrs) showed decreased survival of about 50% of normoxic cells, while no effect of the drugs was observed on survival in hypoxia. The same trends where observed in higher and lower concentrations of the drugs. Moreover, we found that treatment with a HIF inhibitor could partially rescue the sensitivity of MM cells to bortezomib and carfilzomib. ConclusionsWe report that hypoxia decreases the proliferation and cell cycle of MM cells without signs of apoptosis, and that hypoxia induces drug resistance to bortezomib and carfilzomib, an effect which was partially reversed by a HIF inhibitor. This data suggests the hypoxia signaling as a therapeutic target for sensitization of MM cells to therapy, and suggests the use of HIF inhibitors in combination with other drugs as a novel therapeutic strategy for treatment of MM. Disclosures:Ghobrial:Onyx: Advisoryboard Other; BMS: Advisory board, Advisory board Other, Research Funding; Noxxon: Research Funding; Sanofi: Research Funding.

Benzopyran derivative CDRI-85/287 induces G2-M arrest in estrogen receptor-positive breast cancer cells via modulation of estrogen receptors α- and β-mediated signaling, in parallel to EGFR signaling and suppresses the growth of tumor xenograft

In an endeavor to develop novel and improved selective estrogen receptor modulators as anti-breast cancer agents, the benzopyran compounds have been synthesized and identified which act as potent anti-estrogen at uterine level. The present study evaluates the anti-tumor activity of 2-[piperidinoethoxyphenyl]-3-phenyl-2H-benzo(b)pyran (CDRI-85/287) and explores the mechanism of action with a view to describe its potential to inhibit proliferation in ER-positive breast cancer cells MCF-7 and T47D. The compound decreased the expression of ERα while increased the expression of ERβ thereby altering ERα/ERβ ratio in both cell lines. Although the compound showed low binding affinity to ERs, it acted as ERα antagonist and ERβ agonist in decreasing ERE- or AP-1-mediated transcriptional activation in these cells. Transactivation studies in ERα/β-transfected MDA-MB231 cells suggested that at cyclin D1 promoter, compound antagonized the action of ERα-mediated E2 response while acted as estrogen agonist via ERβ. Further, the compound led to decreased expression of ERα-dependent proliferation markers and ERβ-dependent cell cycle progression markers. The expression of cell cycle inhibitory protein p21 was increased leading to G2/M phase arrest. In parallel, compound also interfered with EGFR activation, caused inhibition of PI-3-K/Akt pathway and subsequent induction of apoptosis via intrinsic pathway. A significant reduction in tumor mass and volume was observed in 85/287-treated mice bearing MCF-7 xenograft. We conclude that compound 85/287 exhibits significant anti-tumor activity via modulation of genomic as well as non-genomic mechanisms involved in cellular growth and arrested the cells in G2 phase in both MCF-7 and T47D breast cancer cells. Study suggests that CDRI-85/287 may have therapeutic potential in ER-positive breast cancer.

GSK3β/β-catenin signaling is correlated with the differentiation of glioma cells induced by wogonin

Malignant gliomas are the most common and most aggressive primary brain tumor, and for which differentiation therapy has emerged as a promising candidate strategy. In this study, we used in vitro and in vivo assays to examine the differentiation effects of wogonin, a major active constituent of Scutellaria baicalensis, on glioma C6 and U251 cells. We found that wogonin can suppress cell proliferation and induce G0/G1 arrest under a concentration-dependent manner. Wogonin also triggered significant reduction in the G1 cell-cycle regulatory proteins cyclin D1, cyclin-dependent kinase 2 and 4 along with overexpression of cell-cycle inhibitory proteins p27. Immunofluorescence and western blot analysis indicated that wogonin increased the expression of lineage-specific differentiation marker glial fibrillary acidic protein (GFAP). In mechanisms, we verified that wogonin significantly diminished the phosphorylated level of protein kinase B (AKT), and maintenance of low β-catenin expression level was dependent on glycogen synthase kinase 3β (GSK3β) activation at Ser9. Blocking GSK3β/β-catenin pathway was required for wogonin-induced proliferation inhibition and terminal differentiation by using canonical activator lithium chloride (LiCl) and inhibitor dickkopf-1 (Dkk1). Moreover, intravenous administration of wogonin delayed the growth of C6 glioma in the intracranial tumor model. These findings provide the evidence and mechanistic support for wogonin-based differentiation therapies for malignant glioblastoma. Furthermore, inhibition of GSK3β/β-catenin pathway may be a key and requisite factor in glioma differentiation.

Abstract 5425: Epidermal respiratory uncoupling blocks skin carcinogenesis by inhibiting Akt.

Abstract Metabolic reprogramming, characterized by increased glycolysis and decreased oxygen consumption, is now considered a hallmark of malignancy. Mitochondrial uncoupling proteins oppose this phenotype by driving futile mitochondrial respiration that is uncoupled from ATP synthesis, and mice expressing a keratin 5 - uncoupling protein 3 (K5-UCP3) transgene in the epidermis are completely protected from the formation of chemically induced skin carcinomas. We crossed these mice with Tg.AC mice that express a cutaneous oncogenic v-Ha-Ras transgene, bypassing tumor initiation. Bi-transgenic Tg.AC/K5-UCP3 mice were still remarkably resistant to 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumorigenesis, indicating that UCP3 likely inhibits tumor promotion. Accordingly, K5-UCP3 mice exhibited striking resistance to epidermal proliferation induced by TPA as measured using a bromodeoxyuridine (BrdU) based labeling assay. In agreement with these data, K5-UCP3 epidermis failed to show activation of Akt (Ser473 &amp; Thr308 phosphorylation) and phosphorylation of downstream signaling molecules in response to TPA treatment. This effect corresponded to decreased expression of cyclins D1 and A, and increased expression of the cell cycle inhibitory proteins p21 and p27. Decreased Akt activation was also observed in vitro in response to epidermal growth factor (EGF) treatment of serum starved, isolated K5-UCP3 primary keratinocytes. To test the notion that the lack of Akt signaling was responsible for the lack of TPA induced proliferation and tumorigenesis, we bred bi-transgenic K5-UCP3/K5-Akt mice, and found that over-expression of wild type Akt recovered proliferation following TPA treatment. Future experiments will elucidate the mechanism underlying UCP3-induced inhibition of Akt activation and signaling. Citation Format: Sara M. Nowinski, Joyce E. Rundhaug, Okkyung Rho, Cory U. Lago, Susan M. Fischer, John DiGiovanni, Edward M. Mills. Epidermal respiratory uncoupling blocks skin carcinogenesis by inhibiting Akt. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5425. doi:10.1158/1538-7445.AM2013-5425

Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone), isolated from Plumbago zeylanica, inhibits ultraviolet radiation-induced development of squamous cell carcinomas

Plumbagin (PL) (5-hydroxy-2-methyl-1,4-napthoquinone), a medicinal plant-derived naphthoquinone, was isolated from the roots of the Plumbago zeylanica L. (also known as Chitrak). The roots of P. zeylanica L. have been used in Indian medicine for >2500 years as an anti-atherogenic, cardiotonic, hepatoprotective and neuroprotective agent. We present here that topical application of non-toxic doses (100-500 nmol) of PL to skin elicits dose-dependent inhibition of ultraviolet radiation (UVR)-induced development of squamous cell carcinomas (SCC). In this experiment, FVB/N mice were exposed to UVR (2 kJ/m(2)) three times weekly from a bank of six Kodacel-filtered FS40 sunlamps (∼ 60% UVB and 40% UVA). Carcinoma incidence in mice treated with vehicle, 100, 200 or 500 nmol PL, at 44 weeks post-UVR, were 86, 80 (P = 0.67), 53 (P = 0.12) and 7% (P = 0.0075), respectively. Both vehicle and PL-treated mice gained weight and did not exhibit any signs of toxicity during the entire period of the experiment. Molecular mechanisms associated with inhibition of UVR-induced development of SCC involved induction of apoptosis and inhibition of cell proliferation. Specific findings are that PL treatment (i) inhibited UVR-induced DNA binding of activating protein-1, nuclear factor-kappaB, Stat3 transcription factors and Stat3-regulated molecules (cdc25A and Survivin); (ii) inhibited protein levels of pERK1/2, PI3K85, pAKTSer473, Bcl(2), BclxL, proliferating cell nuclear antigen and cell cycle inhibitory proteins p27 and p21 and (iii) increased UVR-induced Fas-associated death domain expression, poly (ADP-ribose) polymerase protein cleavage and Bax/Bcl(2) ratio. Taken together, our findings suggest that PL may be a novel agent for the prevention of skin cancer.

Inhibitory effects of cocoa tea (Camellia ptilophylla) in human hepatocellular carcinoma HepG2 in vitro and in vivo through apoptosis

Cocoa tea (Camellia ptilophylla), a naturally decaffeinated tea commonly consumed as a healthy beverage in southern China, has been recently found to be a potential candidate for the treatment of different diseases, including obesity and cancers. The present study aimed to evaluate the anti-liver cancer activities of green cocoa tea infusion (GCTI) in vitro and in vivo using human hepatocarcinoma cell line HepG2 cells and nude mice xenograft model. The apoptotic activities of GCTI were assessed using flow cytometry, Western blotting and immunohistochemical analysis. Our results showed that GCTI significantly inhibited the proliferation of HepG2 cells in a dose-dependent manner (IC50 values=292 μg/ml at 72 h). GCTI induced HepG2 cells to undergo apoptosis, which was demonstrated by cell cycle analysis and annexin-V and propidium iodide staining. The caspase cascade was activated as shown by significant proteolytic cleavage of caspase-3 and PARP in GCTI-treated cells in a dose- and time-dependent manner. In addition, GCTI increased the expression of cell cycle inhibitory proteins (p21, p27 and p53) and the Bax-to-Bcl-2 ratio to induce apoptosis. The antiproliferative effect of GCTI was confirmed in HepG2 xenograft nude mice. The tumor growth was effectively inhibited by GCTI in a dose-dependent manner as indicated by the decrease in tumor volume and tumor weight after 4 weeks of treatment. Administration of GCTI increased terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and caspase-3-positive cells in the tumor section. In conclusion, these results revealed that GCTI may be a potential and promising agent of natural resource to treat liver cancer.

Accelerated apoptosis contributes to aging-related hyperinflammation in endotoxemia

Sepsis is associated with an increase in circulating levels of bacterial endotoxin. Sepsis is a particularly serious problem in the geriatric population due to the associated high mortality rate. However, it remains unknown whether this phenomenon is related to an increase in apoptosis in splenic cells. To investigate this issue, male Fischer-344 rats (young, 3 months old; aged, 24 months old) were subjected to endotoxemia by injection of LPS. Splenic samples were collected 4 h thereafter. Apoptosis was determined by cleaved caspase-3 levels and TUNEL staining. The levels of proinflammatory mediators, TNF-alpha, IL-6 and high mobility group box-1 (HMGB-1), were also measured. Our results showed that, while splenic cell apoptosis increased in the young and aged rats with endotoxemia, the aged animals had much higher levels of apoptotic cell death. The elevated expression of cell cycle inhibitory protein P21 was also observed in the aged animals after treatment with LPS. Moreover, endotoxemia significantly increased TNF-alpha, IL-6 and HMGB-1. The accelerated apoptosis in the aged animals was correlated with significantly higher levels of TNF-alpha, IL-6 and HMGB-1. It is suggested that this accelerated rate of apoptosis contributes to age-related hyperinflammation in endotoxemia. To investigate the factors involving accelerated apoptosis in aged animals, we analyzed the Fas/Fas ligand (Fas-L) pathway. Our results showed that Fas and Fas-L gene expression was markedly higher in the spleen in the aged animals after LPS. Similarly, cleaved caspase-8 expression, a downstream element of Fas and Fas-L, was also significantly higher in the aged rats after LPS. Fas-L neutralizing antibodies markedly decreased apoptosis and proinflammatory cytokines in the aged animals after endotoxemia. Thus, there is substantial evidence that the Fas/Fas-L pathway may play an important role in LPS-induced accelerated apoptosis and hyperinflammation in aged animals.

Antiproliferative effect of salvianolic acid A on rat hepatic stellate cells

Suppression of activation or proliferation, or induction of apoptosis in hepatic stellate cells (HSCs) have been proposed as therapeutic strategies against liver fibrosis. Salvia miltiorrhiza has been reported to exert antifibrotic effects in rats with hepatic fibrosis, but its mechanisms of action remain to be clarified. We have investigated the effects of salvianolic acid A (Sal A), an active principle from S. miltiorrhiza, on the proliferation-related biomarkers in a cell line of rat HSCs (HSC-T6) stimulated with platelet-derived growth factor-BB homodimer (PDGF-BB). DNA synthesis (bromodeoxyuridine (BrdU) incorporation), cell cycle related proteins and apoptosis markers were determined to evaluate the inhibitory effects of Sal A. The results showed that Sal A (1-10 microM) concentration-dependently attenuated PDGF-BB-stimulated proliferation (BrdU incorporation) in HSC-T6 cells. Sal A at 10 microM induced cell apoptosis in PDGF-BB-incubated HSCs, together with a reduction of Bcl-2 protein expression, induction of cell cycle inhibitory proteins p21 and p27, and down-regulation of cyclins D1 and E, suppression of Akt phosphorylation, reduction in PDGF receptor phosphorylation, and an increase in caspase-3 activity. Sal A exerted no direct cytotoxicity on primary hepatocytes and HSC-T6 cells under experimental concentrations. Our results suggested that Sal A inhibited PDGF-BB-activated HSC proliferation, partially through apoptosis induction.

Abstract A64: Mechanistic insights into the misregulation of p27 in HER2-positive breast cancers

Abstract Although it is often stated that low amounts of the cell cycle inhibitory protein p27 are predictive of a poor outcome in breast cancers, this is an oversimplifcation of the data. Typically, tumor cells exhibit decreased expression of p27 in the nucleus, while preserving or even increasing the pool of p27 in the cytoplasm. Whereas nuclear p27 is tumor suppressive by inhibiting cell proliferation, newer evidence suggests that cytoplasmic p27 has an oncogenic action: it interacts with the GTPase RhoA to promote cellular migration and motility. Thus, cytoplasmic p27 may be an indicator of tumor cell invasiveness and metastatic potential. Understanding the mechanism of p27 mislocalization in breast cancers may offer insight into pathways of oncogenic transformation, and provide new markers for predicting clinical responses to specific therapies. Toward this goal, we developed antibodies that reliably detect cytoplasmic p27, and also identified a subset of breast cancers positive for the growth factor receptor HER2 that exhibited increased amounts of cytoplasmic p27. In parallel experiments we discovered an E3 ubiquitin ligase, Trim62 that regulates p27 stability, and found that it is overexpressed in HER2+ breast cancers. siRNA knock down of Trim62 in HER2+ breast cancer cell lines not only induced cell cycle arrest but also caused p27 to relocate entirely to the nucleus. We compared knock down of Trim62 to that of the well-characterized p27 regulator, the F box protein Skp2. Unlike Trim62, Skp2 inhibition had no detectable effect on p27 in these cells. As pharmacological inhibition of HER2 has also been shown to increase nuclear p27 protein levels, we investigated the role of Trim62 in modulating the response of breast cancer cells to anti-HER2 therapeutics. Like Trim62 siRNA, the HER2/EGFR inhibitor, Lapatinib increased p27 amounts, and this increase in p27 was located exclusively in the nucleus. Furthermore, we showed that knockdown of Trim62 increased cellular sensitivity to Lapatinib. Overexpression of Trim62 had the opposite effect. Collectively, our results suggest Trim62 underlies the misregulation of p27 in HER2+ breast cancer cell lines. By modulating p27 expression and cellular localization, Trim62 may mediate the antiproliferative effect of HER2 antagonists in breast cancer cells. Moreover, Trim62 could be a potential biomarker to predict biological response of breast cancer cells to anti-HER2 therapeutics such as Lapatinib. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A64.