Tumorigenesis In Animal Models Research Articles

Abstract 4039: Inhibition of Pak4 blocks growth of breast cancer cells

Abstract The p21-activated kinase family of proteins promotes cell survival and plays an important role in cell proliferation, cell cycle regulation and cell shape determination. There are six mammalian PAK proteins which can be subdivided into two groups by sequence homology and mode of activation- Group A Paks consisting of Pak 1, 2 and 3 and Group B Paks consisting of Pak 4, 5 and 6. There is a growing list of evidence that PAK proteins are overexpressed in many cancer types, including colon, lung, and breast cancer. PAK4 is frequently overproduced in breast cancer, including Her2 positive and triple negative breast cancers, while it is expressed at low levels in normal mammary tissue. Our preliminary evidence showed that untransformed mouse mammary epithelial cells have low levels of PAK4 that become elevated when these cells are transformed by Her2 overexpression. Furthermore, PAK4 overexpressed in mammary epithelial cells leads to oncogenic transformation and tumorigenesis in mice. We hypothesize that PAK4 plays an important role in promoting mammary tumorigenesis, and that it can serve as an effective drug target for breast cancer treatment. To test this hypothesis, we have analyzed two orally available PAK4 Allosteric Modulators (PAM; KPT-8752 and KPT-9274), which reduce the steady state PAK4 protein level in cancer cells. We observed that when we treat breast cancer cells with KPT-8752, we severely block the cell growth. KPT-8752, is effective both in Her2 positive and triple negative breast cancer cells. Our results indicate that Pak4 is an important regulator of breast cancer cell growth. Experiments studying the effects of PAMs (KPT8752 and KPT9274) on tumorigenesis in animal models of breast cancer are ongoing. Citation Format: Chetan K. Rane, William Senapedis, Erkan Baloglu, Sharon Shacham, Audrey G. Minden. Inhibition of Pak4 blocks growth of breast cancer cells. [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 4039. doi:10.1158/1538-7445.AM2015-4039

β‐Cryptoxanthin and Its Cleavage Metabolite, 3‐OH‐β‐Apo‐10′‐Carotenal, can Inhibit LPS‐induced Inflammatory Responses in Human Bronchial Epithelial Cells

We have previously demonstrated that supplementation with the xanthophyll β‐cryptoxanthin (BCX)suppresses smoke/nicotine induced‐inflammation, emphysema, and lung tumorigenesis in animal models, which is likely to be independent of its provitamin A activity. These studies raised the question as to whether the protective effects of BCX result from the intact molecule or from its metabolites, independent of vitamin A. In the present study, we examined the effects of BCX and its cleavage metabolite by β‐carotene‐9′,10′‐oxygenase, 3‐OH‐β‐apo‐10′‐carotenal (3OH‐BA10C), against lipopolysaccharide (LPS)‐induced inflammatory responses of human bronchial epithelial cell line BEAS‐2B in vitro. Results showed that pre‐treatments of either BCX or 3OH‐BA10C in BEAS‐2B cells up‐regulated sirtuin 1 (SIRT1, a NAD+‐dependent protein deacetylase) protein expression and inhibited the LPS‐induced mRNA expressions of IL‐6 and TNF‐α in a dose‐dependent manner (1 to 4 μM concentrations). While these effects were associated with reduced AKT phosphorylation, BCX, not 3‐OH‐BA10C, up‐regulated IκB‐α (inhibitor of NF‐κB) protein without affecting its phosphorylation in BEAS‐2B cells. In contrast, 3OH‐BA10C induced the expression of hemo oxygenase‐1 (HO‐1) at both mRNA and protein levels in both dose‐ and time‐dependent manners. Taken together, these data demonstrate that both BCX and 3OH‐BA10C, at comparable doses, attenuate LPS‐induced inflammatory responses via differential molecular mechanisms, indicating thatthese biological activities could be due to action of their own molecule. Supported by the NIH grant CA176256

Abstract 4416: IKBKE is a key mediator of Ras activation of NF-κB and Ras oncogenic function

Abstract Accumulating evidence indicates that the NF-κB transcription factor pathway is important for oncogenic RAS to transform cells and to drive tumorigenesis in animal models. IKBKE has been shown to activate NF-κB through both canonical and non-canonical pathways. Here we show that activating mutations of Ras significantly induce IKBKE kinase activity and that depletion of KRas results in decrease of IKBKE activity only in KRAS mutant but wild-type cells. KRas-induced NF-κB DNA-binding and transcription activity was abrogated by knockdown of IKBKE. In addition, we demonstrated significant decrease of lung tumor development in Ikbke-/-;KRasLA1 mice when compared to Ikbke+/-;KRasLA1 and Ikbke+/+;KRasLA1 animals. Furthermore, depletion of IKBKE selectively reduces cell survival and tumor growth in K-Ras mutant non-small cell lung cancer cells. These data identify IKBKE as a downstream effector of Ras which mediates RAS activation of NF-κB and Ras tumorigenic activity. Citation Format: Donghwa Kim, Jianping Guo, Sridevi Challa, Domenico Coppola, Jin Q. Cheng. IKBKE is a key mediator of Ras activation of NF-κB and Ras oncogenic function. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4416. doi:10.1158/1538-7445.AM2014-4416

Vitamin D and colon cancer.

Calcitriol, 1α, 25-dihydroxyvitamin D3 (1,25 (OH)2D3), the most active form of vitamin D, is a pleotropic hormone with a wide range of biological activities. Due to its ability to regulate calcium and phosphate metabolism, 1,25D3 plays a major role in bone health. In addition, 1,25D3 binds to the vitamin D receptor and thereby regulates the expression of a number of genes which control growth, differentiation and survival of cancer cells. In agreement, the levels of vitamin D3 appear to be an essential determinant for the development and progression of colon cancer and supplementation with vitamin D3 is effective in suppressing intestinal tumorigenesis in animal models. Vitamin D3 has been estimated to lower the incidence of colorectal cancer by 50%, which is consistent with the inverse correlation between dietary vitamin D3 intake or sunlight exposure and human colorectal cancer. Several studies confirmed that increasing vitamin D3 lowers colon cancer incidence, reduces polyp recurrence, and that sufficient levels of vitamin D3 are associated with better overall survival of colon cancer patients. Vitamin D regulates the homeostasis of intestinal epithelium by modulating the oncogenic Wnt signaling pathway and by inhibiting tumor-promoting inflammation. Both activities contribute to the ability of 1,25D3 to prevent the development and progression of colon cancer.

GSK-3α Promotes Oncogenic KRAS Function in Pancreatic Cancer via TAK1–TAB Stabilization and Regulation of Noncanonical NF-κB

Mutations in KRAS drive the oncogenic phenotype in a variety of tumors of epithelial origin. The NF-κB transcription factor pathway is important for oncogenic RAS to transform cells and to drive tumorigenesis in animal models. Recently, TGF-β-activated kinase 1 (TAK1), an upstream regulator of IκB kinase (IKK), which controls canonical NF-κB signaling, was shown to be important for chemoresistance in pancreatic cancer and for regulating KRAS-mutant colorectal cancer cell growth and survival. Here, we show that mutant KRAS upregulates glycogen synthase kinase 3α (GSK-3α), leading to its interaction with TAK1 to stabilize the TAK1-TAB complex to promote IKK activity. In addition, GSK-3α is required for promoting critical noncanonical NF-κB signaling in pancreatic cancer cells. Pharmacologic inhibition of GSK-3 suppresses growth of human pancreatic tumor explants, consistent with the loss of expression of oncogenic genes such as c-myc and TERT. These data identify GSK-3α as a key downstream effector of oncogenic KRAS via its ability to coordinately regulate distinct NF-κB signaling pathways.

Abstract 2273: Metformin promotes tumorigenesis in animal models of cancer prevention.

Abstract Metformin is a bi-guanidine employed in treating Type II diabetes. Epidemiologic studies have suggested that diabetics receiving metformin vs thialidizones or insulin have a lower incidence of cancer. In addition, metformin decreases levels of AMPK and IGF1; encouraging its use in both cancer prevention and therapy settings. Most preclinical studies with metformin have employed cell culture or xenografts. We examined its efficacy in multiple in situ animal cancer models. The preventive effect of Metformin administered by gavage or in the diet, at roughly the human equivalent dose (HED), was determined in four standard animal models: (1) methylnitrosourea (MNU)-induced ER+ mammary cancers; (2) MMTV-Neu ER− mammary cancers; (3) hydroxybutyl(butyl)nitrosamine (OH-BBN) induced urinary bladder cancers; and (4) Min mouse model of intestinal tumorigenesis. In the MNU model, Metformin (150 or 50 mg/Kg BW/day) was ineffective as a preventive dose; decreasing neither tumor multiplicity nor latency. Furthermore, both doses increased final tumor weights in treated rats. PK studies at the higher dose of Metformin (150 mg/kg BW/day) showed serum levels slightly higher than humans taking 1.5 g per day. In the MMTV-Neu model, dietary metformin (1200 PPM in diet) decreased the latency of tumor development as well as slightly, but insignificantly, increasing the final tumor multiplicity. Metformin (1200 ppm in diet) in the Min mouse model marginally increased the multiplicity of intestinal adenomas. In contrast, the NSAID naproxen (400 ppm in diet) examined simultaneously in the min mouse strongly inhibited adenoma development. Metformin (150 mg/Kg BW/day) in the OH-BBN induced model of urinary bladder cancer failed to significantly reduce bladder cancers despite relatively high levels of Metformin in the urine. In the MNU model, when rats were placed on a high fat diet to induce a pre-diabetic state, we observed roughly a 20% decrease in tumor multiplicity in the metformin treated rats (P> 0.10). In contrast, tamoxifen and Targretin (an RXR agonist) that were used as positive controls were highly effective in rats on a high fat diet. Metformin didn't decrease tumorigenesis in these standard models, but actually increased tumor formation (incidence, multiplicity, weight) in three of the four models at their HED. These results should particularly discourage any large phase clinical trials in individuals without insulin resistance. The final study certainly raises the question whether the agent might be effective in animals that are diabetic or show insulin resistance Citation Format: Clinton J. Grubbs, Margie L. Clapper, Joel M. Reid, Vernon E. Steele, Ronald A. Lubet. Metformin promotes tumorigenesis in animal models of cancer prevention. [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 2273. doi:10.1158/1538-7445.AM2013-2273

Specific Small Molecule Inhibitors of Skp2-Mediated p27 Degradation

In the ubiquitin proteasome system, the E3 ligase SCF-Skp2 and its accessory protein, Cks1, promote proliferation largely by inducing the degradation of the CDK inhibitor p27. Overexpression of Skp2 in human cancers correlates with poor prognosis, and deregulation of SCF-Skp2-Cks1 promotes tumorigenesis in animal models. We identified small molecule inhibitors specific to SCF-Skp2 activity using in silico screens targeted to the binding interface for p27. These compounds selectively inhibited Skp2-mediated p27 degradation by reducing p27 binding through key compound-receptor contacts. In cancer cells, the compounds induced p27 accumulation in a Skp2-dependent manner and promoted cell-type-specific blocks in the G1 or G2/M phases. Designing SCF-Skp2-specific inhibitors may be a novel strategy to treat cancers dependent on the Skp2-p27 axis.

Novel Processed Form of Syndecan-1 Shed from SCC-9 Cells Plays a Role in Cell Migration

The extracellular milieu is comprised in part by products of cellular secretion and cell surface shedding. The presence of such molecules of the sheddome and secretome in the context of the extracellular milieu may have important clinical implications. In cancer they have been hypothesized to play a role in tumor growth and metastasis. The objective of this study was to evaluate whether the sheddome/secretome from two cell lines could be correlated with their potential for tumor development. Two epithelial cell lines, HaCaT and SCC-9, were chosen based on their differing abilities to form tumors in animal models of tumorigenesis. These cell lines when stimulated with phorbol-ester (PMA) showed different characteristics as assessed by cell migration, adhesion and higher gelatinase activity. Proteomic analysis of the media from these treated cells identified interesting, functionally relevant differences in their sheddome/secretome. Among the shed proteins, soluble syndecan-1 was found only in media from stimulated tumorigenic cells (SCC-9) and its fragments were observed in higher amount in the stimulated tumorigenic cells than stimulated non-tumorigenic cells (HaCaT). The increase in soluble syndecan-1 was associated with a decrease in membrane-bound syndecan-1 of SCC-9 cells after PMA stimuli. To support a functional role for soluble syndecan-1 fragments we demonstrated that the synthetic syndecan-1 peptide was able to induce cell migration in both cell lines. Taken together, these results suggested that PMA stimulation alters the sheddome/secretome of the tumorigenic cell line SCC-9 and one such component, the syndecan-1 peptide identified in this study, was revealed to promote migration in these epithelial cell lines.

Activity of the leukotriene pathway in Barrett’s metaplasia and oesophageal adenocarcinoma

Leukotriene (LT) B(4) is a lipid inflammatory mediator implicated in tumorigenesis in animal models of Barrett's oesophagitis, but little is known about the cysteinyl-leukotrienes (LTC(4), LTD(4), LTE(4)), which have distinct inflammatory and tumorigenic actions in other tissues. We recently showed that the terminal enzymes for the synthesis of both LT families are highly expressed in human oesophageal adenocarcinoma (OA) tissues. This study therefore examined the capacity of Barrett's metaplasia (BM) and OA tissues to synthesise LTs in vitro. Oesophageal biopsies from patients with BM (n=14), high-grade dysplasia (n=2), OA (n=11), and squamous control tissues (n=11) were cultured with calcium ionophore A32187 (2μM) for 60min. LTB(4) and cysteinyl-leukotrienes were extracted and measured by specific enzyme immunoassays. Levels of LTB(4) and cysteinyl-leukotrienes were 8.6-fold (P<0.01) and 2.4-fold (P<0.02) higher, respectively, in OA tissues than in squamous control tissues, but levels in BM tissues (n=14) were not altered. Production of the two LT families correlated across all tissue types (r=0.62, p<0.00005). Increased synthesis of LTB(4) and cysteinyl-leukotrienes has not previously been shown in human OA tissue and our results may indicate a role of these lipids in Barrett's disease progression.

The impact of curcumin on breast cancer

Curcumin, the active ingredient of turmeric (curry spice), is believed to be associated with reducing the incidence of breast cancers in Asian countries. Anti-cancer efficacy of curcumin and analogs has been tested in pre-clinical studies in some cancer models including breast cancer. These studies reported promising results in inhibiting human cancer cell proliferation and tumorigenesis in animal models. Both in vitro and in vivo studies have shown that curcumin and its analogs target critical genes associated with angiogenesis, apoptosis, cell cycle, and metastasis. The inhibition of human breast cancer cell growth by curcumin is mediated via certain signaling cascades including the modulation of the NF-κB signaling pathway. Epidemiological and experimental data also demonstrated the efficacy of curcumin in chemoprevention and reversing chemo-resistance of tumors of certain cancers. This review summarizes the studies revealing the preventive and therapeutic effects of curcumin and its analogs with an emphasis on multi-targeted biological and molecular effects in a breast cancer model.

Abstract LB-172: MicroRNAs mediate the inhibition of tumor cell invasion by sulindac

Abstract A large body of evidence indicates that nonsteroidal anti-inflammatory drugs (NSAIDs) have strong antineoplastic properties against a broad range of cancer types in early or late stage animal models of tumorigenesis. However, their use in humans for chemoprevention is limited by toxicities resulting from cyclooxygenase (COX) inhibition and the suppression of physiologically important prostaglandins. The anticancer properties of NSAIDs are generally attributed to the suppression of tumor cell proliferation and induction of apoptosis by inhibiting cyclooxygenase (COX), although numerous studies suggest that a COX-independent mechanism may either contribute to or be fully responsible for their activity. The effect of NSAIDs on tumor cell motility and invasion has not been well studied, despite clinical studies showing that certain NSAIDs can significantly increase the survival of patients with metastatic disease. Our results show that the NSAID, sulindac sulfide (SS) can potently inhibit the motility of human breast (MDA-MB-231 and SUM1315) and colorectal (HCT116 and HT29) tumor cells by a mechanism that is distinct from its tumor cell growth and COX inhibitory activity. To study the molecular basis for this activity, we investigated the involvement of microRNA (miRNA). A total of 132 miRNAs were found to be altered in response to SS treatment including miR-10b, miR-17, miR-21, and miR-9, which have been previously implicated in tumor invasion and metastasis. We confirmed that these miRNAs can stimulate tumor cell invasion and show that SS can attenuate their invasive effects (individual and cooperative) by down-regulating their expression. Employing luciferase and chromatin immunoprecipitation (ChIP) assays, NF-κB was found to bind the promoters of all four miRNAs to regulate their expression at the transcriptional level. Results from the immunofluorescence and Western Blotting assays show that SS can inhibit the translocation of NF-κB to the nucleus by decreasing the phosphorylation of IKKβ and IκB, which leads to down-regulation of these miRNAs. Analysis of the promoter sequences of the miRNAs suppressed by SS revealed that 81 of 115 sequences contained NF-κB binding sites. Our results demonstrate that SS can inhibit tumor cell invasion by suppressing NF-κB mediated transcription of miRNAs, which illustrate the mechanistic basis of this novel anticancer property of sulindac on tumor progression and metastasis. We expect these results are capable of supporting future clinical trials of sulindac in patients with metastatic disease. 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 LB-172. doi:1538-7445.AM2012-LB-172

Cdt1 Is Differentially Targeted for Degradation by Anticancer Chemotherapeutic Drugs

BackgroundMaintenance of genome integrity is crucial for the propagation of the genetic information. Cdt1 is a major component of the pre-replicative complex, which controls once per cell cycle DNA replication. Upon DNA damage, Cdt1 is rapidly targeted for degradation. This targeting has been suggested to safeguard genomic integrity and prevent re-replication while DNA repair is in progress. Cdt1 is deregulated in tumor specimens, while its aberrant expression is linked with aneuploidy and promotes tumorigenesis in animal models. The induction of lesions in DNA is a common mechanism by which many cytotoxic anticancer agents operate, leading to cell cycle arrest and apoptosis.Methodology/Principal FindingIn the present study we examine the ability of several anticancer drugs to target Cdt1 for degradation. We show that treatment of HeLa and HepG2 cells with MMS, Cisplatin and Doxorubicin lead to rapid proteolysis of Cdt1, whereas treatment with 5-Fluorouracil and Tamoxifen leave Cdt1 expression unaffected. Etoposide affects Cdt1 stability in HepG2 cells and not in HeLa cells. RNAi experiments suggest that Cdt1 proteolysis in response to MMS depends on the presence of the sliding clamp PCNA.Conclusion/SignificanceOur data suggest that treatment of tumor cells with commonly used chemotherapeutic agents induces differential responses with respect to Cdt1 proteolysis. Information on specific cellular targets in response to distinct anticancer chemotherapeutic drugs in different cancer cell types may contribute to the optimization of the efficacy of chemotherapy.

Chemopreventive Activity of Vitamin E in Breast Cancer: A Focus on γ- and δ-Tocopherol

Vitamin E consists of eight different variants: α-, β-, γ-, and δ-tocopherols (saturated phytyl tail) and α-, β-, γ-, and δ-tocotrienols (unsaturated phytyl tail). Cancer prevention studies with vitamin E have primarily utilized the variant α-tocopherol. To no avail, a majority of these studies focused on variant α-tocopherol with inconsistent results. However, γ-tocopherol, and more recently δ-tocopherol, have shown greater ability to reduce inflammation, cell proliferation, and tumor burden. Recent results have shown that γ-enriched mixed tocopherols inhibit the development of mammary hyperplasia and tumorigenesis in animal models. In this review, we discuss the possible differences between the variant forms, molecular targets, and cancer-preventive effects of tocopherols. We recommend that a γ-enriched mixture, γ- and δ-tocopherol, but not α-tocopherol, are promising agents for breast cancer prevention and warrant further investigation.

Medications Altering Sex Hormone Balance and Risk of Advanced Liver Disease in HCV-infected Males

Purpose: Males have increased risk of advanced liver disease across disease etiologies including chronic infection with the hepatitis C virus (HCV). This had led to the hypothesis that sex hormones may play an important role in etiopathogenesis of liver disease. Several experimental studies suggest a link between sex hormone and hepatic tumorigenesis in animal models. However, little is known about the association between medications known to alter sex hormone signaling/balance, including anti-androgens or methadone which is associated with hypogondadism, and the risk of advanced HCV-related liver disease. Methods: We performed a medical record review study in 257 consecutive male veterans with serologically-confirmed chronic HCV infection seen at a VA Hepatitis C Clinic from May 1st, 2009 to December 31st, 2010. A physician-performed electronic medical record review was used to determine presence of prescriptions for methadone and anti-androgens (e.g., Finasteride) for a maximum 15 year time-period. We used the FibroSURE test to define the degree of hepatic fibrosis and inflammatory activity. Advanced fibrosis status was assigned if the FibroSURE test stage was ‘F3/4' or ‘F4', and advanced inflammation assigned if the grade was ‘A2' to ‘A3'. Logistic regression models were used to assess association between fibrosis and medication status while adjusting for age, diabetes, and ethnicity. Results: Most of these HCV-infected male veterans were White or African-American (40.1% and 54.1%, respectively), with average age of 56.3 years. Prevalence of advanced fibrosis was 30.7%, with an advanced inflammation prevalence of 24.5%. The anti-androgen Finasteride was more commonly prescribed than methadone (10.5% vs. 5.1%, respectively). There were no significant associations between Anti-Androgen use with either advanced inflammation or fibrosis. However, Methadone use was associated with a significant 4.5-fold excess risk of advanced fibrosis (10.1% advanced vs. 2.8% mild fibrosis, adjusted OR=4.51, 95% CI 1.37-14.85, p=0.013) after adjusting for age, diabetes and ethnicity. Conclusion: Methadone use is associated with excess liver fibrosis risk in HCV-infected male veterans. Given the low prevalence of methadone use in this population, replication is needed in larger samples.

Tomato Lycopene and Lung Cancer Prevention: From Experimental to Human Studies

Increasing evidence suggests that tomato lycopene may be preventive against the formation and the development of lung cancer. Experimental studies demonstrated that lycopene may inhibit the growth of several cultured lung cancer cells and prevent lung tumorigenesis in animal models through various mechanisms, including a modulation of redox status, cell cycle arrest and/or apoptosis induction, a regulation of growth factor signaling, changes in cell growth-related enzymes, an enhancement of gap junction communication and a prevention of smoke-induced inflammation. In addition, lycopene also inhibited cell invasion, angiogenesis, and metastasis. Several lycopene metabolites have been identified, raising the question as to whether the preventive effects of lycopene on cancer risk is, at least in part, due to its metabolites. Despite these promising reports, it is difficult at the moment to directly relate available experimental data to human pathophysiology. More well controlled clinical intervention trials are needed to further clarify the exact role of lycopene in the prevention of lung cancer cell growth. Such studies should take into consideration subject selection, specific markers of analysis, the levels of carotenoids being tested, metabolism and isomerization of lycopene, interaction with other bioactive food components. This article reviews data on the cancer preventive activities of lycopene, possible mechanisms involved, and the relationship between lycopene consumption and human cancer risk.

Abstract 2730: Role of Stat1 in skin tumor promotion

Abstract Inflammation is a key component of cancer development in many tissues. Emerging clinical observations support the idea of a strong association of chronic inflammation and cancer. The JAK-STAT pathway is one of the major signaling pathways involved in modulating both pro- and anti-inflammatory responses. Aberrant expression of STATs has been reported in multiple human cancers and in animal models of tumorigenesis. Previous work performed in our lab demonstrated a role for Stat1 in mediating the promotion stage of epithelial multi-stage carcinogenesis in mouse skin when chrysarobin was used as the promoting agent. To further investigate the role of Stat1 in chrysarobin-mediated skin tumor promotion, Stat1 knockout (KO) mice and wild-type controls were treated with chrysarobin and the inflammatory response was assessed. Stat1 deficiency caused a reduction in the dermal inflammatory response following a single topical application of chrysarobin. In this regard, Stat1 KO mice had reduced dermal immune cell influx following chrysarobin treatment. In particular, Stat1 KO mice exhibited reduced influx of macrophages following a single application. Other results also suggest that Stat1 may regulate various cytokine/chemokines involved in the inflammatory response following chrysarobin treatment. Mice deficient in Stat1 displayed an attenuated induction of Cox-2 mRNA and protein compared to wild-type controls following a single application of chrysarobin (200 nmol per mouse). This latter data suggest that Stat1 may be involved in the regulation of Cox-2 in keratinocytes. Collectively, these findings suggest that Stat1 may contribute to chrysarobin-mediated skin tumor promotion by regulating, in part, levels of Cox-2, PGE2 and ultimately skin inflammation. These and other ongoing studies aimed at identifying the mechanistic basis for the role of Stat1 in chrysarobin-mediated tumor promotion will be presented. 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 2730. doi:10.1158/1538-7445.AM2011-2730

The survey on use of photo-catalytic nanoparticles in Korea

Despite nanotechnology is an important and rapidly growing field of scientific and practical innovations, little is known about the potential risks of nanomaterials and nanotechnology to human health and environment. Titanium dioxide (TiO2) nanoparticle is important in consumer products because of its high stability and anticorrosion and photo-catalytic nature. It is frequently used in the cosmetics, pharmaceutical, paint, and paper industries. Recent studies, however, have shown that TiO2 nanoparticles induce cytotoxicity and genotoxicity in various lines of cultured cells as well as tumorigenesis in animal models. We do not have enough information on types and quantities of manufactured nanoparticles and the levels of exposure in Korea. To evaluate the use of photo-catalytic TiO2 nanoparticles, we have surveyed the use of photo-catalytic TiO2 nanoparticles from 94 Korean companies. The results indicate that forty-eight companies declared to use and/or produce nanoparticles. The results will be used for the basis of risk assessments and development of guidelines for the risk and safety decision framework.

Bisphosphonates in preclinical bone oncology

Bisphosphonates, especially nitrogen-containing bisphosphonates, are widely used to block bone destruction in cancer patients with bone metastasis because they are effective inhibitors of osteoclast-mediated bone resorption. In addition to their antiresorptive effects, preclinical evidence strongly suggests that nitrogen-containing bisphosphonates exert direct and indirect anticancer activities through inhibition of tumor cell functions, enhancement of the cytotoxic activity of chemotherapy agents, inhibition of tumor angiogenesis, and stimulation of antitumor immune reactions. This review examines the current evidence and provides insights into ongoing preclinical research on anticancer activities of these bisphosphonates in animal models of tumorigenesis and metastasis.

The rexinoid bexarotene represses cyclin D1 transcription by inducing the DEC2 transcriptional repressor

Bexarotene is an RXR-selective vitamin A analog that has been shown to prevent ER-negative mammary tumorigenesis in animal models. While investigating the mechanism by which bexarotene prevents ER-negative breast cancer development, we found that the expression of cyclin D1, a critical cell cycle promoter, was repressed by bexarotene in vitro and in vivo. Time course and cycloheximide experiments show that repression of cyclin D1 is a late effect and requires new protein synthesis. Previously we discovered that DEC2 (differentially expressed in chondrocytes-2), a helix-loop-helix transcription repressor, was induced by bexarotene in human mammary epithelial cells. Therefore, we hypothesized that bexarotene represses the transcription of cyclin D1 through induction of DEC2. Luciferase reporter studies demonstrated that either bexarotene treatment or forced expression of DEC2 can repress the transcription of a cyclin D1 promoter reporter by affecting the basal transcriptional activity. Results from chromatin immunoprecipitation experiments showed that bexarotene treatment causes the recruitment of DEC2 and HDAC1 (histone deacetylase 1) to the cyclin D1 promoter. Co-immunoprecipitation confirms the interaction between DEC2 and HDAC1, suggesting that the recruitment of HDAC1 to the cyclin D1 promoter is through DEC2. Trichostatin A, a HDAC inhibitor, reverses the cyclin D1 repression by bexarotene, suggesting that repression of cyclin D1 involves histone deacetylation. Knock-down of DEC2 by siRNA abolishes the cyclin D1 repression, further supporting our hypothesis. Finally, we demonstrated that overexpression of DEC2 dramatically inhibited cell proliferation and repressed the expression of cyclin D1 in human mammary epithelial cells. These results suggest that bexarotene down-regulates cyclin D1 through induction of DEC2, followed by recruitment of HDAC1 to the cyclin D1 promoter causing transcriptional repression. By elucidating the mechanism by which rexinoids inhibit cell proliferation, it will be possible to develop more effective and less toxic drugs to prevent ER-negative breast cancers.

Abstract 861: Relationships of prolactin serum levels to breast cancer risk and tumor characteristics in a population-based case-control study from Poland

Abstract Background: Prolactin is a peptide hormone that is important in growth and development of the human breast. Prolactin also induces migration, proliferation, and survival of cancer cells in vitro and mammary gland tumorigenesis in animal models. Recent studies suggest that elevated serum prolactin levels are related to increased breast cancer risk, but confirmation and extension of these results are needed. Accordingly, we analyzed associations of serum prolactin levels with breast cancer risk using data from a population-based breast cancer case-control study conducted in Poland. Methods: The Polish study included 2,386 consenting cases with pathologically confirmed breast cancer and 2,502 age and residency matched controls living in Warsaw and Lodz, Poland recruited during the years 2000 to 2003. Participation rates were 79% for cases and 69% for controls. This analysis included 773 cases and 776 controls with available serum and twofold representation of tumor in tissue microarrays. 70% of this study population was postmenopausal. Serum prolactin was measured by immunoassay at Quest Diagnostics. The overall CV for the prolactin serum assay was 99%. Detailed medical history and breast cancer risk factor information were obtained by interview. Tumor pathology data were collected via surgical pathology reports and independently reviewed in the U.S. Among controls, we assessed associations of prolactin levels with breast cancer risk factors using analysis of variance; case-control associations between breast cancer risk and prolactin levels (quartiles) were assessed by logistic regression. Results: Among premenopausal controls, nulliparity was inversely associated with prolactin levels (p=0.05), whereas among postmenopausal women, current/recent use of combined hormone replacement therapy (p&amp;lt;0.0001) and lower body mass index (BMI, p&amp;lt;0.0001) were associated with higher prolactin levels. After adjustment for these and other known breast cancer risk factors, as well as for matching factors, elevated prolactin levels were significantly associated with postmenopausal breast cancer risk (OR=1.95; 95% CI 1.37-2.78, p&amp;lt;0.0001), when comparing the highest quartile of prolactin levels to the lowest. Among premenopausal women, risk also was elevated for all levels of prolactin, but risks were not significant and did not increase in a monotonic pattern. Conclusions: Prolactin levels are significantly associated with breast cancer risk factors and risk for postmenopausal breast cancer. Our results confirm and extend prior studies focused on circulating prolactin levels and human breast cancer risk. Analyses examining associations between prolactin and tumor subclassifications based on immunological staining using tumor tissue microarrays are ongoing. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 861.