Antiproliferative Response Research Articles

Type I Interferons Induce Apoptosis by Balancing cFLIP and Caspase-8 Independent of Death Ligands

Interferons induce a pleiotropy of responses through binding the same cell surface receptor. Here we investigated the molecular mechanism driving interferon-induced apoptosis. Using a nonbiased small interfering RNA (siRNA) screen, we show that silencing genes whose products are directly engaged in the initiation of interferon signaling completely abrogate the interferon antiproliferative response. Apoptosis-related genes such as the caspase-8, cFLIP, and DR5 genes specifically interfere with interferon-induced apoptosis, which we found to be independent of the activity of death ligands. The one gene for which silencing resulted in the strongest proapoptotic effect upon interferon signaling is the cFLIP gene, where silencing shortened the time of initiation of apoptosis from days to hours and increased dramatically the population of apoptotic cells. Thus, cFLIP serves as a regulator for interferon-induced apoptosis. A shift over time in the balance between cFLIP and caspase-8 results in downstream caspase activation and apoptosis. While gamma interferon (IFN-γ) also causes caspase-8 upregulation, we suggest that it follows a different path to apoptosis.

ANP-NPRA Signaling Pathway - A Potential Therapeutic Target for the Treatment of Malignancy

It was well established that the atrial natriuretic peptide (ANP)/natriuretic peptide receptor-A (NPRA) signaling pathway controls natriuretic, diuretic, vasorelaxant, and anti-proliferative responses in the regulation of the human cardiovascular system by previous studies. Yet in recent years, more and more evidence has shown that the ANP/NPRA signaling pathway plays an important role in human cancer. For example, NPRA is abundantly expressed on tumorigenic mouse and human prostate cancer (PCa) cells, but not in nontumorigenic prostate epithelial cells and down-regulation of NPRA-induced apoptosis in PCa cells. Dexamethasone can increase the expression of ANP markedly, and that is the reason why dexamethasone is the cornerstone in the treatment of multiple myeloma. NPRA deficiency can substantially protect C57BL/6 mice from lung, skin, and ovarian cancers. These results strongly suggest ANP and NPRA may play an anti-cancer and carcinogenesis role, respectively, and this signaling pathway could be a more potent target for cancer therapy. In light of these new insights, this review will summarize the structures, functions, and their regulation by cell signaling, and their different impacts on tumors.

P53 and regulation of tumor metabolism

The tumor suppressor p53 plays a pre-eminent role in protecting against cancer, through its ability to sense various stresses and in turn invoke anti-proliferative and repair responses. Emerging evidence suggest that p53 is both a central sentinel for metabolic stresses and a master regulator of metabolic fluxes. This newly identified function of p53, along with the ability of p53 to induce senescence, appears to be crucial for the prevention of oncogenic transformation. A better understanding of the reciprocal regulation of p53 and metabolism, as well as p53-mediated connection between metabolism and senescence, may lead to the identification of valuable targets for tumor therapy.

Abstract P6-04-29: Vitamin D induces expression of estrogen receptor and restores endocrine therapy response in estrogen receptor-negative breast cancer

Abstract Background: Approximately 30% of all breast tumors do not express estrogen receptor (ER) and patients with these tumors present poor prognosis and respond poorly to hormone therapy. Calcitriol through its vitamin D receptor (VDR) exerts antiproliferative, apoptotic and pro-differentiating effects in cancer. Calcitriols effects upon ER expression in breast cancer cells is controversial. Therefore, in order to clarify this issue, the aim of the present study was to determine if calcitriol induces ERα expression in ERα-negative breast cancer cells and could restore antiestrogen responses. The evaluation of calcitriol effects was performed in terms of proliferation and regulation of the following genes: Cyclin D1, involved in cell cycle, and Ether-à-go-go 1 (Eag1), related to cell proliferation and tumor progression. Methods: Cultured cells derived from ERα-negative breast tumors and an established ERα-negative breast cancer cell line (SUM 229) were used in this study. These cells were treated with calcitriol and reverse transcription-PCR or western blotting analyses were performed to assess ERα expression. Growth assays with XTT were used to evaluate the antiproliferative response to the antiestrogens fulvestran and tamoxifen. Gene expression analysis for Cyclin D1 and Eag1 was evaluated by real time PCR in cells treated simultaneously with calcitriol plus estradiol or fulvestran. Results: The treatment with calcitriol in ER-negative breast cancer cells resulted in the induction of ERα. This effect was specifically mediated through the vitamin D3 receptor (VDR), since the VDR antagonist TEI-9647 effectively inhibited the ability of calcitriol to stimulate ERα gene expression. Consequently, the induction of ERα by calcitriol restores the response to antiestrogens in breast cancer cells by inhibiting cell proliferation. Co-treatment of calcitriol and antiestrogens down-regulated Cyclin D1 and Eag1 gene expression. Conclusion: Calcitriol induced the expression of ERα and restored antiestrogenic responses in ERα-negative breast cancer cells. Moreover, fulvestran down regulated mRNA expression of Cyclin D1 and Eag1 when ERα-negative cells were pre-treated with calcitriol. These results suggest that the combined treatment with calcitriol and antiestrogens could be a new therapeutic strategy for ERα-negative breast cancer patients. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-04-29.

Abstract PD07-07: Prediction of antiproliferative response to lapatinib by HER3 in an exploratory analysis of HER2-non-amplified (HER2−) breast cancer in the MAPLE presurgical study (CRUK E/06/039)

Abstract Aim: To identify pretreatment biomarker predictors of Ki67 response to lapatinib in women with HER2− primary breast cancer. Background: Lapatinib is an EGFR/HER2 inhibitor. Its clinical use is restricted to HER2 overexpressing disease. The MAPLE (Molecular Antiproliferative Predictors of Lapatinib's Effects) presurgical window of opportunity study of lapatinib vs placebo was conducted in women with HER2-amplified (HER2+) or HER2− primary disease. Ki67 (primary end-point) was reduced by a geomean 46% (95%CI 23–63%, p = 0.002) and 27% (95%CI 8–42%, p = 0.008) in HER2+ and HER2− disease, respectively (Leary et al, AACR 2012). We have now assessed whether predictive biomarkers of the antiproliferative response in HER2− disease could be identified. Methods: 121 primary breast cancer patients were randomized (3:1) to 14 days of 1500mg/d lapatinib or placebo before surgery. Biopsies were taken before treatment and at surgery. Ki67 responders were defined as having a >/=50% reduction in Ki67 compared to baseline (Ellis, P et al, Breast Cancer Res Treat 1998, 48, 107). ER, PgR, HER2, EGFR, pAKT, pERK1/2 (nuclear and cytoplasmic), stathmin and apoptosis (TUNEL) were assessed by IHC (+FISH for HER2[all cases]) and scored visually by continuous methods. HER2, HER3, epiregulin (epir), amphiregulin (amphir) and neuregulin (neur) were assessed by qrtPCR. Results: Three of the 121 patients were excluded because of inadequate biopsy material. Ninety-one of the remaining 118 patients received lapatinib: 7/19 (37%) HER2+ cases and 10/72 (14%) HER2− cases were Ki67 responders. Thus while the proportion of Ki67 responders was higher for HER2+ disease there was a similar or higher absolute number of responders with HER2− disease. All of the following relates to patients with HER2− disease. None of the pretreatment levels of ER, PgR, pAKT, pERK1/2, EGFR, epir, amphir or neur were associated with Ki67 response (p > 0.20). However, HER3 (p = 0.01) and HER2 (p = 0.06) mRNA levels were associated with greater Ki67 response. There was a tendency for Ki67 response to be greater with lower baseline Ki67 (p = 0.07). Multivariate analysis showed only HER3 mRNA levels to be independently significant. HER2 and HER3 mRNA levels were highly correlated (rho = 0.67, p < 0.001), a relationship confirmed in 2 other datasets (Wang et al, Breast Cancer Res, 2011, 13, R92; Dunbier et al, submitted). All Ki67 responders were above the median for both HER3 and HER2 expression. Conclusions: Lapatinib is antiproliferative in a subgroup of HER2− tumours. This exploratory analysis indicates that they are characterized by high HER3 expression. The possible importance of high HER2:HER3 heterodimers in predicting this response is supported by the relationship between HER2 and HER3 expression. Further exploration of lapatinib is merited in HER2− cases with high HER3 expression. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD07-07.

Brucine induces the apoptosis of U266 multiple myeloma cells by phosphorylation of c-Jun

The aim of this study was to investigate the mechanism of the apoptotic effect of brucine on human multiple myeloma (MM) cells. U266 cells (5x104) were plated in the presence or absence of brucine (0, 0.05, 0.1, 0.2 and 0.4 mg/ml) in 96‑well culture plates for 24‑72 h. The anti-proliferative response to brucine was assessed by MTT assay. Analysis of the cell cycle of U266 cells treated with or without brucine was performed using flow cytometry. The expression change of c-Jun following treatment with brucine or brucine plus the c-Jun N-terminal kinase (JNK)-specific inhibitor SP600125 was detected using RT-PCR. Brucine appeared to have an effect on apoptosis in a dose- and time‑dependent manner. Cell cycle analysis using flow cytometry revealed the accumulation of cells at the sub-G0/G1 phase. The apoptotic rates were 4.137, 10.55, 12.31, 27.67 and 29.67% (0, 0.05, 0.1, 0.2, 0.4 mg/ml brucine, respectively; P<0.01). The gray scale values were 0.7961 ± 0.007 and 0.4683 ± 0.003 (mRNA expression of c-Jun of U266 cells with or without SP600125, respectively). Concentrations of ≤ 0.4 mg/ml brucine induced apoptosis in U266 cells. Thus, brucine‑induced apoptosis in U266 cells occurs via the JNK signaling pathway and phosphorylation of c-Jun.

Estrogen receptor β agonists affect growth and gene expression of human breast cancer cell lines

Expression of estrogen receptor β (ERβ) has been described to reduce growth of cancer cell lines derived from hormone-dependent tumors, like breast cancer. In this study we tested to what extent two ERβ agonists, androgen derivative 3β-Adiol and flavonoid Liquiritigenin, would affect growth and gene expression of different ERβ-positive human breast cancer cell lines. Under standard cell culture conditions, we observed 3β-Adiol to inhibit growth of MCF-7 cells in a dose-dependent manner, whereas growth of BT-474 and MCF-10A cells was suppressed by the maximum concentration (100nM) only. When treated in serum-free medium, all cell lines except of MDA-MB-231 were responsive to 1nM 3β-Adiol, and ZR75-1 cells exhibited a dose-dependent antiproliferative response. Providing putative mechanisms underlying the observed growth-inhibitory effect, expression of Ki-67 or cyclins A2 and B1 was downregulated after 3β-Adiol treatment in all responsive lines. In contrast, treatment with lower doses of Liquiritigenin did not affect growth. In MCF-7 cells, the highest dose of this flavonoid exerted proliferative effects accompanied by increased expression of cyclin B1, PR and PS2, indicating unspecific activation of ERα. In conclusion, the ERβ agonists tested exerted distinct concentration-dependent and cell line-specific effects on growth and gene expression. The observed inhibitory effects of 3β-Adiol on breast cancer cell growth encourage further studies on the potential of this and other ERβ agonists as targeted drugs for breast cancer therapy.

Sildenafil Potentiates Bone Morphogenetic Protein Signaling in Pulmonary Arterial Smooth Muscle Cells and in Experimental Pulmonary Hypertension

Mutations in the bone morphogenetic protein type II receptor (BMPR-II) are responsible for the majority of cases of heritable pulmonary arterial hypertension (PAH), and BMPR-II deficiency contributes to idiopathic and experimental forms of PAH. Sildenafil, a potent type-5 nucleotide-dependent phosphodiesterase inhibitor, is an established treatment for PAH, but whether sildenafil affects bone morphogenetic protein (BMP) signaling in the pulmonary circulation remains unknown. Studies were undertaken in human pulmonary arterial smooth muscle cells (PASMCs) and in vivo in the monocrotaline rat model of PAH. In PASMCs, sildenafil enhanced BMP4-induced phosphorylation of Smad1/5, Smad nuclear localization, and Inhibitor of DNA binding protein 1 gene and protein expression. This effect was mimicked by 8-bromo-cyclic GMP. Pharmacological inhibition or small interfering RNA knockdown of cyclic GMP-dependent protein kinase I inhibited the effect of sildenafil on BMP signaling. In functional studies, we observed that sildenafil potentiated the antiproliferative effects of BMP4 on PASMC proliferation. Furthermore, sildenafil restored the antiproliferative response to BMP4 in PASMCs harboring mutations in BMPR-II. In the monocrotaline rat model of PAH, which is characterized by BMPR-II deficiency, sildenafil prevented the development of pulmonary hypertension and vascular remodeling, and partly restored Smad1/5 phosphorylation and Inhibitor of DNA binding protein 1 gene expression in vivo in monocrotaline exposed rat lungs. Sildenafil enhances canonical BMP signaling via cyclic GMP and cyclic GMP-dependent protein kinase I in vitro and in vivo, and partly restores deficient BMP signaling in BMPR-II mutant PASMCs. Our findings demonstrate a novel mechanism of action of sildenafil in the treatment of PAH and suggest that targeting BMP signaling may be beneficial in this disease.

Therapeutic potential of targeting ceramide/glucosylceramide pathway in cancer

Sphingolipids including ceramides and its derivatives such as ceramide-1-phosphate, glucosylceramide (GlcCer), and sphingosine-1-phosphate are essential structural components of cell membranes. They now recognized as novel bioeffector molecules which control various aspects of cell growth, proliferation, apoptosis, and drug resistance. Ceramide, the central molecule of sphingolipid metabolism, generally mediates anti-proliferative responses such as inhibition of cell growth, induction of apoptosis, and/or modulation of senescence. There are two major classes of sphingolipids. One of them is glycosphingolipids which are synthesized from the hydrophobic molecule, ceramide. GlcCer, generated by glucosylceramide synthase (GCS) that transfers the glucose from UDP-glucose to ceramide, is an important glycosphingolipid metabolic intermediate. GCS regulates the balance between apoptotic ceramide and antiapoptotic GlcCer. Downregulation or inhibition of GCS results in increased apoptosis and decreased drug resistance. The mechanism underlying the drug resistance which develops with increased glucosylceramide expression is associated with P-glycoprotein. In various types of cancers, overexpression of GCS has been observed which renders GCS a good target for the treatment of cancer. This review summarizes our current knowledge on the structure and functions of glucosylceramide synthase and glucosylceramide and on the roles of glucosylceramide synthase in cancer therapy and drug resistance.

TGF-β – an excellent servant but a bad master

The transforming growth factor (TGF-β) family of growth factors controls an immense number of cellular responses and figures prominently in development and homeostasis of most human tissues. Work over the past decades has revealed significant insight into the TGF-β signal transduction network, such as activation of serine/threonine receptors through ligand binding, activation of SMAD proteins through phosphorylation, regulation of target genes expression in association with DNA-binding partners and regulation of SMAD activity and degradation. Disruption of the TGF-β pathway has been implicated in many human diseases, including solid and hematopoietic tumors. As a potent inhibitor of cell proliferation, TGF-β acts as a tumor suppressor; however in tumor cells, TGF-β looses anti-proliferative response and become an oncogenic factor. This article reviews current understanding of TGF-β signaling and different mechanisms that lead to its impairment in various solid tumors and hematological malignancies.

P111 USP18 establishes the transcriptional and anti-proliferative interferon alpha/beta differential

Introduction Type I interferons (IFNs) are pathogen-induced immunoregulatory cytokines that exert antiviral and anti-proliferative activities through binding to a common cell surface receptor. Among the 17 human IFN subtypes, IFN β binds the IFNAR1/IFNAR2 receptor chains with particularly high affinity and is especially potent in select bioactivities (e.g. anti-proliferative and pro-apoptotic) when compared to IFN α2. However, no molecular basis has been ascribed to this differential action, since the two ligands are equipotent in immediate early signaling events. Methods Using standard immunoassays we monitored Stat phosphorylation and interferon stimulated gene (ISG) protein accumulation in response to prolonged treatment with IFN α2 or IFN β, while monitoring ISG mRNA levels by qPCR and proliferation by crystal violet staining. RNA interference was used to assess the role of USP18 in establishing differential Stat signaling, ISG mRNA and protein production, and anti-proliferative responses in response to the two type-I interferon subtypes. Results Here we report that IFN β induces Stat phosphorylation and transcriptional activation of ISGs, including two genes with pro-apoptotic functions, for a considerably longer time frame than IFN α2. We show that the diversification of α2/β responses progressively builds up at the receptor level as a result of accumulating USP18, itself an ISG, which exerts its negative feeback action by taking advantage of the weakness of IFN α2 binding to the receptor. Conclusion This represents a novel type of signaling regulation that diversifies the biological potential of IFNs α and β.

Transcriptional consequences of aneuploidy

Aneuploidy, or an aberrant karyotype, results in developmental disabilities and has been implicated in tumorigenesis. However, the causes of aneuploidy-induced phenotypes and the consequences of aneuploidy on cell physiology remain poorly understood. We have performed a metaanalysis on gene expression data from aneuploid cells in diverse organisms, including yeast, plants, mice, and humans. We found highly related gene expression patterns that are conserved between species: genes that were involved in the response to stress were consistently upregulated, and genes associated with the cell cycle and cell proliferation were downregulated in aneuploid cells. Within species, different aneuploidies induced similar changes in gene expression, independent of the specific chromosomal aberrations. Taken together, our results demonstrate that aneuploidies of different chromosomes and in different organisms impact similar cellular pathways and cause a stereotypical antiproliferative response that must be overcome before transformation.

The atypical E2F family member E2F7 couples the p53 and RB pathways during cellular senescence

Oncogene-induced senescence is an anti-proliferative stress response program that acts as a fail-safe mechanism to limit oncogenic transformation and is regulated by the retinoblastoma protein (RB) and p53 tumor suppressor pathways. We identify the atypical E2F family member E2F7 as the only E2F transcription factor potently up-regulated during oncogene-induced senescence, a setting where it acts in response to p53 as a direct transcriptional target. Once induced, E2F7 binds and represses a series of E2F target genes and cooperates with RB to efficiently promote cell cycle arrest and limit oncogenic transformation. Disruption of RB triggers a further increase in E2F7, which induces a second cell cycle checkpoint that prevents unconstrained cell division despite aberrant DNA replication. Mechanistically, E2F7 compensates for the loss of RB in repressing mitotic E2F target genes. Together, our results identify a causal role for E2F7 in cellular senescence and uncover a novel link between the RB and p53 pathways.

A peroxisome proliferator-activated receptor ligand MCC-555 imparts anti-proliferative response in pancreatic cancer cells by PPARgamma-independent up-regulation of KLF4

MCC-555 is a novel PPARα/γ dual ligand of the thiazolidinedione class and was recently developed as an anti-diabetic drug with unique properties. MCC-555 also has anti-proliferative activity through growth inhibition and apoptosis induction in several cancer cell types. Our group has shown that MCC-555 targets several proteins in colorectal tumorigenesis including nonsteroidal anti-inflammatory drug (NSAID)-activated gene (NAG-1) which plays an important role in chemoprevention responsible for chemopreventive compounds. NAG-1 is a member of the TGF-β superfamily and is involved in tumor progression and development; however, NAG-1's roles in pancreatic cancer have not been studied. In this report, we found that MCC-555 alters not only NAG-1 expression, but also p21 and cyclin D1 expression. NAG-1 and p21 expression was not blocked by PPARγ-specific antagonist GW9662, suggesting that MCC-555-induced NAG-1 and p21 expression is independent of PPARγ activation. However, decreasing cyclin D1 by MCC-555 seems to be affected by PPARγ activation. Further, we found that the GC box located in the NAG-1 promoter play an important role in NAG-1 transactivation by MCC-555. Subsequently, we screened several transcription factors that may bind to the GC box region in the NAG-1 promoter and found that KLF4 potentially binds to this region. Expression of KLF4 precedes NAG-1 and p21 expression in the presence of MCC-555, whereas blocking KLF4 expression using specific KLF4 siRNA showed that both NAG-1 and p21 expression by MCC-555 was blocked. In conclusion, MCC-555's actions on anti-proliferation involve both PPARγ-dependent and -independent pathways, thereby enhancing anti-tumorigenesis in pancreatic cancer cells.

Jacaranone Induces Apoptosis in Melanoma Cells via ROS-Mediated Downregulation of Akt and p38 MAPK Activation and Displays Antitumor Activity In Vivo

BackgroundMalignant melanoma is a deadly type of metastatic skin cancer with increased incidence over the past 30 years. Despite the advanced knowledge on the biology, immunobiology and molecular genetics of melanoma, the alternatives of treatment are limited with poor prognosis. On clinical trials, natural products and among them redox-active quinones have been tested in the attempt to control the growth of cancer cells. Recently, we isolated jacaranone from Pentacalia desiderabilis, a benzoquinone derivative that showed a broad antitumor activity and protective anti-melanoma effect in a syngeneic model. The purified substance is active at micromolar concentrations, is not hemolytic, and is not toxic in naïve mice.Methodology/Principal FindingsThe jacaranone antitumor activity was shown against several human cancer cell lines in vitro. Moreover, the induction of apoptosis in murine melanoma cells and jacaranone antitumor activity in vivo, in a melanoma experimental model, were also shown. Jacaranone renders antiproliferative and proapoptotic responses in tumor cells, by acting on Akt and p38 MAPK signaling pathways through generation of reactive oxygen species (ROS). The free radical scavenger N-acetyl-cysteine (NAC) was able to completely suppress cell death induced by jacaranone as it blocked Akt downregulation, p38 MAPK activation as well as upregulation of proapoptotic Bax. Notably, treatment of melanoma growing subcutaneously in mice with jacaranone significantly extended the mean survival times in a dose-dependent manner.Conclusions/SignificanceThe results provide evidence for the mechanisms of action of jacaranone and emphasize the potential use of this quinone for the treatment of melanoma.

Preclinical and clinical studies of estrogen deprivation support the PDGF/Abl pathway as a novel therapeutic target for overcoming endocrine resistance in breast cancer

IntroductionThe majority of breast tumors at primary diagnosis are estrogen receptor positive (ER+). Estrogen (E) mediates its effects by binding to the ER. Therapies targeting the estrogenic stimulation of tumor growth reduce mortality from ER+ breast cancer. However, resistance remains a major clinical problem.MethodsTo identify molecular mechanisms associated with resistance to E-deprivation, we assessed the temporal changes in global gene expression during adaptation to long-term culture of MCF7 human breast cancer cells in the absence of estradiol (E2), long term estrogen deprived (LTED), that leads to recovery of proliferative status and models resistance to an aromatase inhibitor (AI). The expression levels of proteins were determined by western blotting. Proliferation assays were carried out using the dual platelet derived growth factor receptor (PDGFR)/Abelson tyrosine kinase (Abl) inhibitor nilotinib. Luciferase reporter assays were used to determine effects on ER-mediated transactivation. Changes in recruitment of cofactors to the gene regulated by estrogen in breast cancer 1 (GREB1) promoter were determined by chromatin immunoprecipitation (ChIP). Gene expression data were derived from 81 postmenopausal women with ER+ BC pre-treatment and at two-weeks post-treatment with single agent anastrozole in a neoadjuvant trial.ResultsThe PDGF/Abl canonical pathway was significantly elevated as early as one week post E-deprivation (P = 1.94 E-04) and this became the top adaptive pathway at the point of proliferative recovery (P = 1.15 E-07). Both PDGFRβ and Abl protein levels were elevated in the LTED cells compared to wild type (wt)-MCF7 cells. The PDGF/Abl tyrosine kinase inhibitor nilotinib, suppressed proliferation in LTED cells in the presence or absence of E. Nilotinib also suppressed ER-mediated transcription by destabilizing the ER and reducing recruitment of amplified in breast cancer-1 (AIB1) and the CREB binding protein (CBP) to the promoter of the E-responsive gene GREB1. High PDGFRβ in primary ER+ breast cancer of 81 patients prior to neoadjuvant treatment with an AI was associated with poorer antiproliferative response. Additionally PDGFRβ expression increased after two weeks of AI therapy (1.25 fold, P = 0.003).ConclusionsThese preclinical and clinical data indicate that the PDGF/Abl signaling pathway merits clinical evaluation as a therapeutic target with endocrine therapy in ER+ breast cancer.

Retraction Note: Role of senescence and mitotic catastrophe in cancer therapy

Senescence and mitotic catastrophe (MC) are two distinct crucial non-apoptotic mechanisms, often triggered in cancer cells and tissues in response to anti-cancer drugs. Chemotherapeuticals and myriad other factors induce cell eradication via these routes. While senescence drives the cells to a state of quiescence, MC drives the cells towards death during the course of mitosis. The senescent phenotype distinguishes tumor cells that survived drug exposure but lost the ability to form colonies from those that recover and proliferate after treatment. Although senescent cells do not proliferate, they are metabolically active and may secrete proteins with potential tumor-promoting activities. The other anti-proliferative response of tumor cells is MC that is a form of cell death that results from abnormal mitosis and leads to the formation of interphase cells with multiple micronuclei. Different classes of cytotoxic agents induce MC, but the pathways of abnormal mitosis differ depending on the nature of the inducer and the status of cell-cycle checkpoints. In this review, we compare the two pathways and mention that they are activated to curb the growth of tumors. Altogether, we have highlighted the possibilities of the use of senescence targeting drugs, mitotic kinases and anti-mitotic agents in fabricating novel strategies in cancer control.

Expansion of a subset of CD14highCD16negCCR2low/neg monocytes functionally similar to myeloid-derived suppressor cells during SIV and HIV infection

Monocytes have been categorized in three main subpopulations based on CD14 and CD16 surface expression. Classical monocytes express the CD14(++)CD16(-)CCR2(+) phenotype and migrate to inflammatory sites by quickly responding to CCL2 signaling. Here, we identified and characterized the expansion of a novel monocyte subset during HIV and SIV infection, which were undistinguishable from classical monocytes, based on CD14 and CD16 expression, but expressed significantly lower surface CCR2. Transcriptome analysis of sorted cells demonstrated that the CCR2(low/neg) cells are a distinct subpopulation and express lower levels of inflammatory cytokines and activation markers than their CCR2(high) counterparts. They exhibited impaired phagocytosis and greatly diminished chemotaxis in response to CCL2 and CCL7. In addition, these monocytes are refractory to SIV infection and suppress CD8(+) T cell proliferation in vitro. These cells express higher levels of STAT3 and NOS2, suggesting a phenotype similar to monocytic myeloid-derived cells, which suppress expansion of CD8(+) T cells in vivo. They may reflect an antiproliferative response against the extreme immune activation observed during HIV and SIV infections. In addition, they may suppress antiviral responses and thus, have a role in AIDS pathogenesis. Antiretroviral therapy in infected macaque and human subjects caused this population to decline, suggesting that this atypical phenotype is linked to viral replication.

Possible aryl hydrocarbon receptor-independent pathway of 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced antiproliferative response in human breast cancer cells

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a ligand with high affinity for the aryl hydrocarbon receptor (AhR). It suppresses 17β-estradiol (E2)-induced cell proliferation in human breast cancer cells. Although it has been theorized that the AhR is involved in TCDD-induced antiestrogenic activity and antiproliferation in human breast cancer cells, some evidence suggests that these activities of chlorinated aromatic compounds also occur by AhR-independent pathways. Here, we investigated the possibility of TCDD-induced antiproliferative responses in human breast cancer cells through AhR-independent pathways. Compared with that in vehicle-treated controls, DNA synthesis was significantly suppressed in MCF-7 cells and ZR75-1 cells treated with TCDD at a very low concentration (0.01nM), whereas that in human ovarian carcinoma OVCAR3 cells, human cervical carcinoma HeLa cells and human choriocarcinoma JEG-3 cells was unaffected, even by exposure to 10nM TCDD. The suppression induced by TCDD was not associated with the estrogen receptor α-signaling pathway. Another AhR agonist, 3,3′,4,4′,5-pentachlorobiphenyl, had no effect on DNA synthesis in MCF-7 cells at concentrations high enough to induce the transactivation function of the AhR. Furthermore, in MCF-7 cells, knockdown of the AhR by RNA interference had no effect on TCDD-induced antiproliferation. These findings suggest that the principal pathways of TCDD-induced antiproliferation in breast cancer cells are not AhR dependent.

Abstract 3729: Resveratrol enhances the anti-proliferative response of zinc by increasing zinc-transporter protein ZIP1 in prostate cancer cells: A novel combinatorial approach for prostate cancer management

Abstract Prostate Cancer (PCa) is one of the most prevalent cancers in males across the globe. In the United States alone, 240,890 new PCa cases and 33,720 related deaths are predicted for the year 2011. Studies suggest that the essential trace element zinc is extremely important in prostate cell functions and survival. Prostate tissue can accumulate zinc at up to ten-fold higher concentration than other organs. However, the cancerous prostatic cells lose the ability to accumulate zinc and lower levels of prostatic zinc have been associated with PCa development and progression. Based on several studies, it has been suggested that lower expression of zinc transporter protein ZIP1 is associated with this neoplastic transformation and restoration of adequate zinc levels in premalignant/malignant prostate cells can abort prostate malignancy. In addition, zinc has been shown to function as an anti-proliferative agent against PCa. However, because of low ZIP1 in cancerous cells, active transport of zinc into the cells is compromised. Thus, zinc supplementation is not effective since very high concentrations of zinc are needed to achieve enough zinc inside cancerous cells. Therefore new means to enhance the bioaccumulation of sufficient zinc in the prostate tissue could be useful towards PCa management. In this study, we tested the hypothesis that grape antioxidant resveratrol will enhance zinc bioaccumulation via increasing ZIP1 in prostate, to impart a superior anti-proliferative response against PCa cells. Our data demonstrated that ZIP1 protein was markedly downregulated in human PCa tissue as compared to normal prostate tissue. Employing androgen-responsive 22Rα1 and LNCaP as well as androgen-unresponsive DU145 cell lines, we observed that a combination of resveratrol and zinc resulted in a remarkable increase in ZIP1 mRNA and protein expression in PCa cells. Further, a combination of resveratrol and zinc was found to impart a superior anti-proliferative response (inhibition of cell growth/viability and induction of apoptosis) in PCa cells, compared to either of the agent alone. Furthermore, we also found that resveratrol-zinc combination resulted in an increase in the levels of metallothioneins (MT1A, MT1X, MT2A and MT3), which play critical role in regulation of intracellular zinc levels. Taken together, our data indicate that resveratrol enhances the cellular transport of zinc via enhancing ZIP1 transporter protein and a combination of resveratrol and zinc may be a useful approach for PCa management. However, further in vivo studies are needed in appropriate animal model(s) with relevance to human disease to determine the clinical benefits of resveratrol and zinc combination against PCa. 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 3729. doi:1538-7445.AM2012-3729