Abstract 414: Identifying selective vulnerabilities in colorectal cancer molecular subtypes using in vivo functional genomic screens

Colorectal cancer (CRC) is a leading cause of cancer-related morbidity and mortality with significantly heterogeneous features and drug responses. Recently, the international Colorectal Cancer Subtyping Consortium identified four robust consensus molecular subtypes of CRC (CMS1-4) using large-scale gene expression data. These findings may enable us to identify molecularly homogenous subsets of CRC patients and accelerate effective drug development strategies. To identify potential therapeutic targets and novel selective vulnerabilities in CRC molecular subtypes, we developed an in vivo loss-of-function genomic screen using CRC patient-derived xenografts (PDXs) for each molecular subtype. Our PDX-derived CRC models underwent comprehensive integrated molecular characterization of mRNA profiles, DNA mutations, and histochemical profiles upon confirmed serial retransplantation to determine whether characteristics of the subtypes are recapitulated in vivo. Because the original CMS classification algorithm was trained and validated using Affymetrix data, profiling the PDX-derived cell lines using this technology provided the most robust analysis of the CMS subtypes. In vivo pooled short hairpin RNA (shRNA) screens rely on specific elimination of individual shRNAs in a cell population and require that the infected tumor cell population is adequately endowed with engraftment capacity when implanted into recipient mice. Therefore, we determined the transduction efficiency of the PDX models, the frequency of tumor-initiating cells, and the maximum library complexity allowed by each model. To identify targets that represent selective vulnerabilities in specific CRC molecular subtypes, we screened each model in vivo with an shRNA library targeting about 200 genes specifically belonging to U.S. Food and Drug Administration-approved targeted therapies (FDAome; 10 shRNAs/gene ). We leveraged redundant shRNA activity analysis to evaluate “hits” (or top-scoring genes) emerging from our screening. We further applied ranking-based analytics in combination with integromic approaches (use of computational packages to unravel relationships between -omics) to inform on selective CMS specific top-scoring genes. One of the benefits of using an FDAome library is the direct correspondence of target genes with clinically available drugs. We therefore tested these drugs for validation in fully annotated PDXs. These efforts, in association with systematic profiling of the CMS subtypes at the patient level through adaptation of NanoString technology, may enable us to stratify CRC patients who will benefit from selective U.S. Food and Drug Administration-approved drugs and to rapidly design successful preclinical and clinical trials in CRC patients.

Citation Format: Akira Inoue, Bahar Salimian Rizi, Alessandro Carugo, Sahil Seth, Christopher Bristow, Giannicola Genovese, Andrea Viale, David G. Menter, Scott Kopetz, Giulio F. Draetta. Identifying selective vulnerabilities in colorectal cancer molecular subtypes using in vivo functional genomic screens [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 414. doi:10.1158/1538-7445.AM2017-414

Abstract 4742: APC WT /RAS WT /BRAF WT tumors represent an under recognized poor prognostic group of right sided colorectal cancer

Background: Side of primary tumor has prognostic and predictive significance in metastatic colorectal cancer (mCRC). RAS/BRAF wild type (WT) left (L) sided tumors have improved outcomes with anti-EGFR therapy while right (R) sided tumors do worse. We aimed to identify mutations (MTS) in RAS/BRAF WT patients (pts) which may explain the differing response.

Methods: Using a 46 gene panel, we compared MT frequencies by side in 1880 mCRC pts. Overall survival (OS) was summarized with Kaplan-Meier curves, the log rank test, and Cox models. Microsatellite unstable pts were excluded from univariate OS analysis.

Results: RAS mutant (MT) pts were more likely to be APC MT (OR 1.64, P<0.0001) than RAS WT pts. Presence of APC MTS was associated with improved OS in WT RAS/BRAF (HR 0.58, P=0.0003) and MT RAS/BRAF pts (HR 0.69, P=0.0004). Multivariate analysis confirmed APC MTS were associated with improved OS (HR 0.67, P=0.001) after controlling for RAS/BRAF, side, and MSI.

Given the association of tumor location and OS, we stratified pts by side and compared APC MT/WT pts. Improved OS with APC MTS was independent of side (L-HR 0.70, P=0.0011; R-HR 0.62, P=0.0012), but pts with R APC WT tumors stood out as an extreme risk group with the worst OS of all L/R and APC MT/WT combinations even in RAS/BRAF WT pts (P<0.0001). This group of R sided RAS/BRAF/APC WT pts represents a novel poor prognostic group and its baseline characteristics are summarized below.

When stratifying APC MT by genomic location, only MTS in the mutation cluster region (n=686) that contains axin and β-catenin binding sites remained prognostic in multivariate models (HR 0.63, P<0.0001), while other APC MTS (n=163) were no longer significant (HR 0.82, P=0.27).

Conclusion: APC WT R sided pts represents a group with poor prognosis regardless of RAS/BRAF MT status. Given the difference in CTNNB1 MT rate and importance of MTS in axin/ β-catenin binding sites, WNT signaling differences between L and R sided tumors may be important to explore further.

Baseline Characteristics of Patients with APC/RAS/BRAF Wild Type Right Sided TumorsBaseline CharacteristicRight Sided APC/RAS/BRAF WT (N=88, 15.2%)Other Right Sided Tumors (N=492, 84.8%)P-ValueMedian Age (IQR)56 (47-61)56 (48-64)0.23GenderFemale46 (52.3%)241 (49.0%)0.56Male42 (47.7%)251 (51.0%)MSI-H8 (10.5%)25 (6.5%)0.22HistologyAdenocarcinoma50 (56.8%)366 (74.4%)0.0018Mucinous / Signet38 (43.2%)123 (25.0%)Other03 (0.6%)Average # of Mutations Per Patient (+/- SD)1.38+/- 2.013.10 +/- 1.79<0.0001Synchronous Metastasis76 (86.4%)401 (81.5%)0.36TP53 MT47 (53.4%)275 (55.9%)0.67PIK3CA MT6 (6.8%)111 (22.6%)0.001CTNNB1 MT7 (8.0%)11 (2.2%)0.004

Citation Format: Jonathan M. Loree, Krittiya K. Korphaisarn, Michael Lam, Van K. Morris, Kanwal P. Raghav, Michael J. Overman, Cathy Eng, Arvind Dasari, Bryan K. Kee, David Fogelman, Robert A. Wolff, Kenna Shaw, Russell Broaddus, Mark J. Routbort, Rajyalakshmi Luthra, Dipen M. Maru, David G. Menter, Funda Meric-Bernstam, Scott Kopetz. APCWT/RASWT/BRAFWT tumors represent an under recognized poor prognostic group of right sided colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4742. doi:10.1158/1538-7445.AM2017-4742

Platelet "first responders" in wound response, cancer, and metastasis

Platelets serve as "first responders" during normal wounding and homeostasis. Arising from bone marrow stem cell lineage megakaryocytes, anucleate platelets can influence inflammation and immune regulation. Biophysically, platelets are optimized due to size and discoid morphology to distribute near vessel walls, monitor vascular integrity, and initiate quick responses to vascular lesions. Adhesion receptors linked to a highly reactive filopodia-generating cytoskeleton maximizes their vascular surface contact allowing rapid response capabilities. Functionally, platelets normally initiate rapid clotting, vasoconstriction, inflammation, and wound biology that leads to sterilization, tissue repair, and resolution. Platelets also are among the first to sense, phagocytize, decorate, or react to pathogens in the circulation. These platelet first responder properties are commandeered during chronic inflammation, cancer progression, and metastasis. Leaky or inflammatory reaction blood vessel genesis during carcinogenesis provides opportunities for platelet invasion into tumors. Cancer is thought of as a non-healing or chronic wound that can be actively aided by platelet mitogenic properties to stimulate tumor growth. This growth ultimately outstrips circulatory support leads to angiogenesis and intravasation of tumor cells into the blood stream. Circulating tumor cells reengage additional platelets, which facilitates tumor cell adhesion, arrest and extravasation, and metastasis. This process, along with the hypercoagulable states associated with malignancy, is amplified by IL6 production in tumors that stimulate liver thrombopoietin production and elevates circulating platelet numbers by thrombopoiesis in the bone marrow. These complex interactions and the "first responder" role of platelets during diverse physiologic stresses provide a useful therapeutic target that deserves further exploration.

Modeling of Patient-Derived Xenografts in Colorectal Cancer

Developing realistic preclinical models using clinical samples that mirror complex tumor biology and behavior are vital to advancing cancer research. While cell line cultures have been helpful in generating preclinical data, the genetic divergence between these and corresponding primary tumors has limited clinical translation. Conversely, patient-derived xenografts (PDX) in colorectal cancer are highly representative of the genetic and phenotypic heterogeneity in the original tumor. Coupled with high-throughput analyses and bioinformatics, these PDXs represent robust preclinical tools for biomarkers, therapeutic target, and drug discovery. Successful PDX engraftment is hypothesized to be related to a series of anecdotal variables namely, tissue source, cancer stage, tumor grade, acquisition strategy, time to implantation, exposure to prior systemic therapy, and genomic heterogeneity of tumors. Although these factors at large can influence practices and patterns related to xenotransplantation, their relative significance in determining the success of establishing PDXs is uncertain. Accordingly, we systematically examined the predictive ability of these factors in establishing PDXs using 90 colorectal cancer patient specimens that were subcutaneously implanted into immunodeficient mice. Fifty (56%) PDXs were successfully established. Multivariate analyses showed tissue acquisition strategy [surgery 72.0% (95% confidence interval (CI): 58.2-82.6) vs. biopsy 35% (95% CI: 22.1%-50.6%)] to be the key determinant for successful PDX engraftment. These findings contrast with current empiricism in generating PDXs and can serve to simplify or liberalize PDX modeling protocols. Better understanding the relative impact of these factors on efficiency of PDX formation will allow for pervasive integration of these models in care of colorectal cancer patients. Mol Cancer Ther; 16(7); 1435-42. ©2017 AACR.

Endothelial cell malignancies: new insights from the laboratory and clinic

Endothelial cell malignancies are rare in the Western world and range from intermediate grade hemangioendothelioma to Kaposi sarcoma to aggressive high-grade angiosarcoma that metastasize early and have a high rate of mortality. These malignancies are associated with dysregulation of normal endothelial cell signaling pathways, including the vascular endothelial growth factor, angiopoietin, and Notch pathways. Discoveries over the past two decades related to mechanisms of angiogenesis have led to the development of many drugs that intuitively would be promising therapeutic candidates for these endothelial-derived tumors. However, clinical efficacy of such drugs has been limited. New insights into the mechanisms that lead to dysregulated angiogenesis such as mutation or amplification in known angiogenesis related genes, viral infection, and chromosomal translocations have improved our understanding of the pathogenesis of endothelial malignancies and how they evade anti-angiogenesis drugs. In this review, we describe the major molecular alterations in endothelial cell malignancies and consider emerging opportunities for improving therapeutic efficacy against these rare but deadly tumors.

Dual Inhibition of EGFR and c-Src by Cetuximab and Dasatinib Combined with FOLFOX Chemotherapy in Patients with Metastatic Colorectal Cancer

Purpose: Aberrant activation of the intracellular tyrosine kinase Src has been implicated as a mechanism of acquired chemotherapy resistance in metastatic colorectal cancer (mCRC). Here, the oral tyrosine kinase Src inhibitor, dasatinib, was investigated in combination with FOLFOX and cetuximab.Experimental Design: We performed a phase IB/II study of 77 patients with previously treated mCRC. Primary objectives were to determine the maximum tolerated dose, dose-limiting toxicities (DLT), pharmacodynamics, and efficacy. Using a 3 + 3 design, patients received FOLFOX6 with cetuximab and escalating doses of dasatinib (100, 150, 200 mg daily), followed by a 12-patient expansion cohort at 150 mg. Phase II studies evaluated FOLFOX plus dasatinib 100 mg in KRAS c12/13^mut patients or in combination with cetuximab if KRAS c12/13^WT FAK and paxillin were utilized as surrogate blood biomarkers of Src inhibition, and paired biopsies of liver metastases were obtained in patients in the expansion cohort.Results: In phase IB, the DLTs were grade 3/4 fatigue (20%) and neutropenia (23%). In phase II, grade 3/4 fatigue (23%) and pleural effusions (11%) were present. Response rates were 20% (6 of 30) in the phase IB escalation and expansion cohort and 13% (3 of 24) and 0% (0 of 23) in the KRAS c12/13^WT and mutant cohorts of phase II, respectively. Median progression-free survival was 4.6, 2.3, and 2.3 months, respectively. There was no evidence of Src inhibition based on surrogate blood biomarkers or paired tumor biopsies.Conclusions: The combination of dasatinib plus FOLFOX with or without cetuximab showed only modest clinical activity in refractory colorectal cancer. This appears to be primarily due to a failure to fully inhibit Src at the achievable doses of dasatinib. The combination of dasatinib plus FOLFOX with or without cetuximab did not show meaningful clinical activity in refractory colorectal cancer due to failure to fully inhibit Src. Clin Cancer Res; 23(15); 4146-54. ©2017 AACR.

Developing hyperpolarized silicon particles for in vivo MRI targeting of ovarian cancer

Silicon-based nanoparticles are ideally suited for use as biomedical imaging agents due to their biocompatibility, biodegradability, and simple surface chemistry that facilitates drug loading and targeting. A method of hyperpolarizing silicon particles using dynamic nuclear polarization, which increases magnetic resonance imaging signals by several orders-of-magnitude through enhanced nuclear spin alignment, has recently been developed to allow silicon particles to function as contrast agents for in vivo magnetic resonance imaging. The enhanced spin polarization of silicon lasts significantly longer than other hyperpolarized agents (tens of minutes, whereas [Formula: see text] for other species at room temperature), allowing a wide range of potential applications. We report our recent characterizations of hyperpolarized silicon particles, with the ultimate goal of targeted, noninvasive, and nonradioactive molecular imaging of various cancer systems. A variety of particle sizes (20 nm to [Formula: see text]) were found to have hyperpolarized relaxation times ranging from [Formula: see text] to 50 min. The addition of various functional groups to the particle surface had no effect on the hyperpolarization buildup or decay rates and allowed in vivo imaging over long time scales. Additional in vivo studies examined a variety of particle administration routes in mice, including intraperitoneal injection, rectal enema, and oral gavage.

Abstract 2285: Microsomal PGE2 synthase-1 regulates melanoma cell survival and associates with melanoma disease progression

COX-2 and its product PGE2 enhance carcinogenesis and tumor progression, which has been previously reported in melanoma. As most COX inhibitors cause much toxicity, the downstream microsomal PGE2 synthase-1 (mPGES1) is a consideration for targeting. Human melanoma TMAs were employed for testing mPGES1 protein staining intensity and percentage levels and both increased with clinical stage; employing a different Stage III TMA, mPGES1 intensity (not percentage) associated with reduced patient survival. Our results further show that iNOS was also highly expressed in melanoma tissues with high mPGES1 levels, and iNOS-mediated NO promoted mPGES1 expression and PGE2 production. An mPGES1specific inhibitor (CAY10526) as well as siRNA attenuated cell survival and increased apoptosis. CAY10526 significantly suppressed tumor growth and increased apoptosis in melanoma xenografts. Our findings support the value of a prognostic and predictive role for mPGES1, and suggest targeting this molecule in the PGE2 pathway as another avenue toward improving melanoma therapy.

Citation Format: Sun-Hee Kim, Yuuri Hashimoto, Sung-Nam Cho, Jason Roszik, Denái R. Milton, Fulya Dal, Sangwon F. Kim, David G. Menter, Peiying Yang, Suhendan Ekmekcioglu, Elizabeth A. Grimm. Microsomal PGE2 synthase-1 regulates melanoma cell survival and associates with melanoma disease progression. [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 2285.

Microsomal PGE2 synthase-1 regulates melanoma cell survival and associates with melanoma disease progression

COX-2 and its product PGE2 enhance carcinogenesis and tumor progression, which has been previously reported in melanoma. As most COX inhibitors cause much toxicity, the downstream microsomal PGE2 synthase-1 (mPGES1) is a consideration for targeting. Human melanoma TMAs were employed for testing mPGES1 protein staining intensity and percentage levels, and both increased with clinical stage; employing a different Stage III TMA, mPGES1 intensity (not percentage) associated with reduced patient survival. Our results further show that iNOS was also highly expressed in melanoma tissues with high mPGES1 levels, and iNOS-mediated NO promoted mPGES1 expression and PGE2 production. An mPGES1-specific inhibitor (CAY10526) as well as siRNA attenuated cell survival and increased apoptosis. CAY10526 significantly suppressed tumor growth and increased apoptosis in melanoma xenografts. Our findings support the value of a prognostic and predictive role for mPGES1, and suggest targeting this molecule in the PGE2 pathway as another avenue toward improving melanoma therapy.

Mechanisms of nonsteroidal anti-inflammatory drugs in cancer prevention

Various clinical and epidemiologic studies show that nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin and cyclooxygenase inhibitors (COXIBs) help prevent cancer. Since eicosanoid metabolism is the main inhibitory targets of these drugs the resulting molecular and biological impact is generally accepted. As our knowledge base and technology progress we are learning that additional targets may be involved. This review attempts to summarize these new developments in the field.

Real-Time MRI-Guided Catheter Tracking Using Hyperpolarized Silicon Particles

Visualizing the movement of angiocatheters during endovascular interventions is typically accomplished using x-ray fluoroscopy. There are many potential advantages to developing magnetic resonance imaging-based approaches that will allow three-dimensional imaging of the tissue/vasculature interface while monitoring other physiologically-relevant criteria, without exposing the patient or clinician team to ionizing radiation. Here we introduce a proof-of-concept development of a magnetic resonance imaging-guided catheter tracking method that utilizes hyperpolarized silicon particles. The increased signal of the silicon particles is generated via low-temperature, solid-state dynamic nuclear polarization, and the particles retain their enhanced signal for ≥ 40 minutes--allowing imaging experiments over extended time durations. The particles are affixed to the tip of standard medical-grade catheters and are used to track passage under set distal and temporal points in phantoms and live mouse models. With continued development, this method has the potential to supplement x-ray fluoroscopy and other MRI-guided catheter tracking methods as a zero-background, positive contrast agent that does not require ionizing radiation.

Abstract 4763: Correlation of CpG island methylation with clinical and pathologic characteristics in metastatic colorectal cancer patients

Background: Colorectal cancer morbidity and mortality rates vary by race and ethnicity. The combined contribution of genetics and environment to response to chemotherapy, progression-free and overall survival in colorectal cancer patients is unclear, but CpG island hypermethylation (CIMP), a discrete molecular subtype of colorectal cancer, is associated with inflammation and environmental exposures. Hence our main objective is to assess correlation between various modifiable risk factors and CIMP status among metastatic colorectal cancer patients.

Methods: We characterized CIMP methylation (MINT1, MINT2, MINT31, p14, p16, and MLH1) in 229 metastatic colorectal cancer patients using PCR amplification of bisulfite treated DNA followed by pyrosequencing. The number of methylated probes were averaged to obtain the% methylation with CIMP-High (CIMP-H) being defined as ≥40% of probes methylated. Associations of demographic and clinical characteristics, including BMI, diabetes, obesity, physical activity, smoking and drinking status, as well as presence or absence of other molecular alterations (BRAF, KRAS, NRAS, PIK3CA and PTEN loss) with overall survival were assessed in multivariable-adjusted Cox proportional hazards models.

Results:

When treating methylation as a continuous variable, patients with BRAF mutation had higher methylation as compared to participants with BRAF wildtype (40.6% vs 20.5%, p = 0.001). White, non-Hispanic (WNH) patients had greater degree of tumor methylation (24.8%) as compared to other racial categories (p = 0.02). When classified as a categorical variable, moderate to vigorous physical activity was associated with higher rate of having any methylated probes, as compared to sedentary patients (p = 0.02). CIMP status was not associated with OS in these patients in multivariable-adjusted Cox models. However when stratified by CIMP status. When stratified by CIMP status; among patients with 0-40% methylation, KRAS mutation was associated with poor OS(HR = 3.19, p = 0.006) and diabetes was protective (HR = .14, p = 0.025). Among patients with high methylation(41-100%) methylation, obesity was associated with poor OS (HR = 5.20, p = 0.038) and former smoking was associated with poor OS(HR = 2.92, p = 0.05). When stratified by KRAS mutation status, among patients with KRAS wildtype, obesity was associated with poor OS(HR = 2.86, p = 0.019) and among patients with KRAS mutation, diabetes was protective (HR = 0.18, p = 0.033)

Conclusion and Impact:

CpG island methylator phenotype was associated with unique clinicopathologic characteristics. Methylation, as assessed by the 6-gene CIMP panel, was not associated with worse outcomes after correcting for the KRAS mutations, a well-established genetic marker of poor prognosis. Hypermethylation did appear to modulate outcomes in obese patients with hypermethylated tumors.

Citation Format: Shailesh M. Advani, Michael Sangmin Lee, Michael James Overman, David Fogelman, Bryan K. Kee, Shanequa D. Manuel, Jennifer Davis, Van Karlyle Morris, Callisia Nathelee Clarke, Carrie R. Daniel, David G. Menter, Stanley R. Hamilton, Dipen Maheshbhai Maru, Scott Kopetz. Correlation of CpG island methylation with clinical and pathologic characteristics in metastatic colorectal cancer patients. [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 4763. doi:10.1158/1538-7445.AM2015-4763

Cytokine profile and prognostic significance of high neutrophil-lymphocyte ratio in colorectal cancer

Background:

High circulating neutrophil-lymphocyte ratio (NLR) appears to be prognostic in metastatic colorectal cancer (mCRC). We investigated the relationship of NLR with circulating cytokines and molecular alterations.

Methods:

We performed retrospective analyses on multiple cohorts of CRC patients (metastatic untreated (n=166), refractory metastatic (n=161), hepatectomy (n=198), stage 2/3 (n=274), and molecularly screened (n=342)). High NLR (ratio of absolute neutrophil-to-lymphocyte counts in peripheral blood) was defined as NLR>5. Plasma cytokines were evaluated using multiplex-bead assays. Kaplan–Meier estimates, non-parametric correlation analysis, and hierarchical cluster analyses were used.

Results:

High NLR was associated with poor prognosis in mCRC (hazard ratio (HR) 1.73; 95% confidence interval (CI):1.03–2.89; P=0.039) independent of known prognostic factors and molecular alterations (KRAS/NRAS/BRAF/PIK3CA/CIMP). High NLR correlated with increased expression of interleukin 6 (IL-6), IL-8, IL-2Rα, hepatocyte growth factor, macrophage-colony stimulating factor, and vascular epidermal growth factor in exploratory (n=39) and validation (n=166) cohorts. Fourteen additional cytokines correlated with high NLR in the validation cohort. All 20 cytokines fell into three major clusters: inflammatory cytokines, angiogenic cytokines, and epidermal growth factor ligands. In mCRC, composite stratification based on NLR-cytokine score provided enhanced prognostic information (HR 2.09; 95% CI: 1.59–2.76; P<0.001) over and above NLR.

Conclusions:

High NLR is an independent poor prognostic marker in CRC and correlates with a distinct cytokine profile related to key biological processes involved in carcinogenesis. A composite NLR-cytokine stratification has enhanced prognostic value in mCRC.

Convergence of nanotechnology and cancer prevention: are we there yet?

Nanotechnology is emerging as a promising modality for cancer treatment; however, in the realm of cancer prevention, its full utility has yet to be determined. Here, we discuss the potential of integrating nanotechnology in cancer prevention to augment early diagnosis, precision targeting, and controlled release of chemopreventive agents, reduced toxicity, risk/response assessment, and personalized point-of-care monitoring. Cancer is a multistep, progressive disease; the functional and acquired characteristics of the early precancer phenotype are intrinsically different from those of a more advanced anaplastic or invasive malignancy. Therefore, applying nanotechnology to precancers is likely to be far more challenging than applying it to established disease. Frank cancers are more readily identifiable through imaging and biomarker and histopathologic assessment than their precancerous precursors. In addition, prevention subjects routinely have more rigorous intervention criteria than therapy subjects. Any nanopreventive agent developed to prevent sporadic cancers found in the general population must exhibit a very low risk of serious side effects. In contrast, a greater risk of side effects might be more acceptable in subjects at high risk for cancer. Using nanotechnology to prevent cancer is an aspirational goal, but clearly identifying the intermediate objectives and potential barriers is an essential first step in this exciting journey.

Platelets and cancer: a casual or causal relationship: revisited

Human platelets arise as subcellular fragments of megakaryocytes in bone marrow. The physiologic demand, presence of disease such as cancer, or drug effects can regulate the production circulating platelets. Platelet biology is essential to hemostasis, vascular integrity, angiogenesis, inflammation, innate immunity, wound healing, and cancer biology. The most critical biological platelet response is serving as "First Responders" during the wounding process. The exposure of extracellular matrix proteins and intracellular components occurs after wounding. Numerous platelet receptors recognize matrix proteins that trigger platelet activation, adhesion, aggregation, and stabilization. Once activated, platelets change shape and degranulate to release growth factors and bioactive lipids into the blood stream. This cyclic process recruits and aggregates platelets along with thrombogenesis. This process facilitates wound closure or can recognize circulating pathologic bodies. Cancer cell entry into the blood stream triggers platelet-mediated recognition and is amplified by cell surface receptors, cellular products, extracellular factors, and immune cells. In some cases, these interactions suppress immune recognition and elimination of cancer cells or promote arrest at the endothelium, or entrapment in the microvasculature, and survival. This supports survival and spread of cancer cells and the establishment of secondary lesions to serve as important targets for prevention and therapy.

Prostaglandin E2 regulates pancreatic stellate cell activity via the EP4 receptor

OBJECTIVES

Pancreatic stellate cells are source of dense fibrotic stroma, a constant pathological feature of chronic pancreatitis and pancreatic adenocarcinoma. We observed correlation between levels of cyclooxygenase 2 (COX-2) and its product prostaglandin E2 (PGE2) and the extent of pancreatic fibrosis. The aims of this study were to delineate the effects of PGE2 on immortalized human pancreatic stellate cells (HPSCs) and to identify the receptor involved.

METHODS

Immunohistochemistry, reverse transcription-polymerase chain reaction and quantitative reverse transcription-polymerase chain reaction were used to assess COX-2, extracellular matrix, and matrix metalloproteinase gene expression. Eicosanoid profile was determined by liquid chromatography-tandem mass spectrometry. Human pancreatic stellate cell proliferation was assessed by MTS assay, migration by Boyden chamber assay, and invasion using an invasion chamber. Transient silencing was obtained by small interfering RNA.

RESULTS

Human pancreatic stellate cells express COX-2 and synthesize PGE2. Prostaglandin E2 stimulated HPSC proliferation, migration, and invasion and stimulated expression of both extracellular matrix and matrix metalloproteinase genes. Human pancreatic stellate cells expressed all 4 EP receptors. Only blocking the EP4 receptor resulted in abrogation of PGE2-mediated HPSC activation. Specificity of EP4 for the effects of PGE2 on stellate cells was confirmed using specific antagonists.

CONCLUSIONS

Our data indicate that PGE2 regulates pancreatic stellate cell profibrotic activities via EP4 receptor, thus suggesting EP4 receptor as useful therapeutic target for pancreatic cancer to reduce desmoplasia.

Computerized analysis of tumor cell interactions with extracellular matrix proteins, peptides, and endothelial cells under laminar flow

Arrest and formation of stable adhesive interactions between circulating cells and the endothelium or exposed subendothelial matrix are important processes in many biological situations. We have developed a highly sensitive hydrodynamic assay that utilizes a parallel-plate flow chamber, video microscopy, and digital image processing to separate and measure the primary arrest and adhesion stabilization of flowing cells. Our data indicate that primary cell contact triggers secondary adhesion stabilization, and the secondary events are likely to be critical to metastasis formation. To study the relationship between tumor cell adhesion stabilization and organ-specific blood-borne metastasis, we investigated the adhesion stabilization of metastatic murine RAW117 large-cell lymphoma cells to the extracellular matrix proteins fibronectin and vitronectin, several Arg-Gly-Asp (RGD) containing peptides, and microvascular endothelial cells from the liver or lung. The highly liver metastatic RAW117-H10 subline showed the fastest stabilization to fibronectin, vitronectin, and RGD peptides. Poorly metastatic RAW117-P cells had stabilization times 3-10 times longer than for RAW117-H10 cells, while the lung- and liver-metastatic RAW117-L17 subline failed to stabilize at all. The adhesion stabilization of the RAW117-H10 cells to the extracellular matrix proteins and RGD peptides was inhibited by anti-beta(3) integrin monoclonal antibodies and RGD peptides. In contrast, the RAW117-L17 subline had the shortest stabilization time to unstimulated microvascular endothelial cells of the lung and hepatic sinusoids, followed by RAW117-H10 cells and RAW117-P cells. Monoclonal antibodies against the beta(3) integrin subunit and RGD peptides did not inhibit adhesion stabilization of RAW117-H10 cells to endothelial cells, suggesting that different metastatic variants of large-cell lymphoma cells use differing mechanisms to adhere to organ-specific endothelial cells.

Abstract 3251: Linking prostaglandin E2 signaling, lipid rafts, and DNA protein kinase

Colorectal cancer (CRC) is the second-leading cause of death from cancer in the USA. Chronic inflammation in the gastrointestinal tract is a significant risk factor for developing CRC. Generally, CRC involves the upregulation of inflammation-induced cyclooxygenase-2 (COX-2) that is blocked by non-steroidal anti-inflammatory drugs (NSAIDS). Among the downstream prostaglandin synthases that produce bioactive prostaglandins (PGs), prostaglandin E2 (PGE2) synthase products are proinflammatory. After export from cells, PGE2 can bind to G-protein coupled PG cell surface receptors EP2/4 and activate adenylate cyclase and elevate cAMP. In turn, cAMP activates downstream effectors such as protein kinase A (PKA) and/or exchange protein directly activated by cAMP (EPAC). We studied effects of PGE2 on PKA activation in CRC cells and their relationship to lipid raft function. After isolating lipid rafts from PGE2 stimulated cells we performed shotgun proteomics. Among the lipid raft proteins identified were DNA-protein kinase (DNA-PK), and heterodimer complex proteins Ku70 and Ku80, which we verified by immunoprecipitation and immunofluorescence. Of these lipid raft proteins, Ku80 contained a PKA consensus phosphorylation sites and phosphorylation increased after stimulation of CRC cells by PGE2. Typically found in the nucleus, Ku70, Ku80 and DNA-PK complexes bind to DNA double-strand breaks and initiate non-homologous end joining DNA repair. These data are the first to demonstrate the Ku70, Ku80 and DNA-PK complexes in a new non-nuclear action, which involves lipid rafts and the DNA repair complex. Furthermore, PGE2 stimulated LS174T CRC cells exhibit an increase in non-nuclear pDNA-PK (S2056). Additionally, treatment of a number of colon cancer cell lines with the selective DNA-PK inhibitor Nu7026 significantly decreased cell viability in the absence of any overt DNA damaging stimuli, suggesting that non-nuclear, and in particular, lipid raft localized DNA-PK complex may play an important role in cell growth. Finally, treatment with both PGE2 and Nu7026 causes a profound change in cell morphology involving numerous spindle-like processes. These data suggest there are important downstream effects of proinflammatory PGE2 on CRC cells that influence lipid raft associated Ku70, Ku80 and DNA-PK complexes as well as cell proliferation. Support: T. Boone Pickens Distinguished Chair for Early Prevention of Cancer to E.T.H., R37 DK47297, NCI P01 CA77839, CPRIT-RP100960, Ellen F. Knisely Distinguished Chair in Colon Cancer Research, The National Colorectal Cancer Research Alliance to R.N.D. and 5U54CA151668-02 to D.G.M.

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 3251. doi:1538-7445.AM2012-3251

Differential effects of pravastatin and simvastatin on the growth of tumor cells from different organ sites

3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) inhibitors, commonly known as statins, may possess cancer preventive and therapeutic properties. Statins are effective suppressors of cholesterol synthesis with a well-established risk-benefit ratio in cardiovascular disease prevention. Mechanistically, targeting HMGCR activity primarily influences cholesterol biosynthesis and prenylation of signaling proteins. Pravastatin is a hydrophilic statin that is selectively taken up by a sodium-independent organic anion transporter protein-1B1 (OATP1B1) exclusively expressed in liver. Simvastatin is a hydrophobic statin that enters cells by other mechanisms. Poorly-differentiated and well-differentiated cancer cell lines were selected from various tissues and examined for their response to these two statins. Simvastatin inhibited the growth of most tumor cell lines more effectively than pravastatin in a dose dependent manner. Poorly-differentiated cancer cells were generally more responsive to simvastatin than well-differentiated cancer cells, and the levels of HMGCR expression did not consistently correlate with response to statin treatment. Pravastatin had a significant effect on normal hepatocytes due to facilitated uptake and a lesser effect on prostate PC3 and colon Caco-2 cancer cells since the OATP1B1 mRNA and protein were only found in the normal liver and hepatocytes. The inhibition of cell growth was accompanied by distinct alterations in mitochondrial networks and dramatic changes in cellular morphology related to cofilin regulation and loss of p-caveolin. Both statins, hydrophilic pravastatin and hypdrophobic simvastatin caused redistribution of OATP1B1 and HMGCR to perinuclear sites. In conclusion, the specific chemical properties of different classes of statins dictate mechanistic properties which may be relevant when evaluating biological responses to statins.

Nuclear orphan receptor NR4A2 modulates fatty acid oxidation pathways in colorectal cancer

Although cancer cells have traditionally been thought to rely on the glycolytic pathway to generate ATP, recent studies suggest that cancer cells can shift to the fatty acid oxidation pathway as an alternative energy source. All of the factors that induce and regulate this adaptive shift in metabolism are not known. Cyclooxygenase-2-derived prostaglandin E(2) (PGE(2)) is produced at high levels in colon cancer, and multiple lines of evidence from human-, animal-, and cell line-based studies indicate that PGE(2) plays a pro-oncogenic role in colorectal cancer progression. We have shown previously that exposure of colon cancer cells to PGE(2) promotes cell survival, in part by inducing the expression of the nuclear orphan receptor NR4A2. Here, we report that PGE(2)-induced NR4A2 increased fatty acid oxidation by inducing the expression of multiple proteins in the fatty acid oxidation pathway. NR4A2 was found to bind directly to Nur77-binding response elements located within the regulatory region of these genes. Nur77-binding response element binding also resulted in the recruitment of transcriptional coactivators and induction of gene expression. Collectively, our findings suggest that NR4A2 plays a key role as a transcriptional integration point between the eicosanoid and fatty acid metabolic pathways. Thus, PGE(2) is a potential regulator of the adaptive shift to energy utilization via fatty acid oxidation that has been observed in several types of cancer.

γ-Tocotrienol induces growth arrest through a novel pathway with TGFβ2 in prostate cancer

Regions along the Mediterranean and in southern Asia have lower prostate cancer incidence compared to the rest of the world. It has been hypothesized that one of the potential contributing factors for this low incidence includes a higher intake of tocotrienols. Here we examine the potential of γ-tocotrienol (GT3) to reduce prostate cancer proliferation and focus on elucidating pathways by which GT3 could exert a growth-inhibitory effect on prostate cancer cells. We find that the γ and δ isoforms of tocotrienol are more effective at inhibiting the growth of prostate cancer cell lines (PC-3 and LNCaP) compared with the γ and δ forms of tocopherol. Knockout of PPAR-γ and GT3 treatment show inhibition of prostate cancer cell growth, through a partially PPAR-γ-dependent mechanism. GT3 treatment increases the levels of the 15-lipoxygenase-2 enzyme, which is responsible for the conversion of arachidonic acid to the PPAR-γ-activating ligand 15-S-hydroxyeicosatrienoic acid. In addition, the latent precursor and the mature forms of TGFβ2 are down-regulated after treatment with GT3, with concomitant disruptions in TGFβ receptor I, SMAD-2, p38, and NF-κB signaling.

Abstract 4612: Cell-type dependent responses to selenium and knockdown of SBP2

Selenium is a trace element essential for human health. Evidence from previous epidemiologic studies and clinical trials suggested that selenium is associated with prostate cancer prevention, but its failure in the Selenium and Vitamin E Cancer Prevention Trial (SELECT) to reduce prostate cancer incidence diminished its promise. The question of whether some patients could benefit from selenium supplementation while others might not demands a clearer understanding of selenium's mechanisms of action. One of the ways in which selenium acts as a chemopreventive agent is through incorporation into selenoproteins, which are antioxidant enzymes required to maintain redox homeostasis; however, selenoproteins’ large number and redundant functions make analyzing their effects on cellular functions difficult. Therefore, we recently targeted selenocysteine insertion sequence-binding protein 2 (SBP2), required for selenoprotein synthesis; knocked down SBP2 expression in different cell lines; and examined the effect on cell survival, cell cycle, and cell survival pathways. We found that knocking down SBP2 resulted in apoptosis in NIH/3T3 and HEK-293 cells, especially in the presence of H2O2. Interestingly abrogation of SBP2 function affected the level of p21 protein in a cell type-specific manner. Additionally, sodium selenite or seleno-methionine treatment led to distinct changes in p21 and p53 protein status in HEK-293, LNCaP, and DU145 cells. Molecular effects induced by knocking down SBP2 were cell-type dependent. Further studies involving a combinational approach are expected to contribute to understanding how selenium and selenoproteins mediate chemopreventive effects in prostate cancer.

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 4612. doi:10.1158/1538-7445.AM2011-4612

Tumor Cell - Substrate Stabilization Mediated by Integrins

Metastasis formation is dependent on the arrest and stabilization of adhesive interactions to prevent detachment from secondary sites. Primary receptor-ligand interactions are not sufficient to maintain prolonged adhesive contacts without secondary events that lead to stabilization. Tumor cell arrest and stabilization were studied under physiologically relevant shear conditions. We used a parallel-plate flow chamber with surfaces coated with human plasma fibronectin or vitronectin. Our previous work suggested that stabilization of cells to immobilized proteins is in part attributed to transglutaminase covalently cross-linking cytoskeletal-integrin-fibronectin multiprotein complexes via lysine-glutamine linkages. To study the role of integrins in mediating arrest and initiating stabilization we used a human melanoma line (70w) and polyclonal antibodies that inhibit the function of the fibronectin (α5β1) and vitronectin (αvβ3/β5) integrin receptors. To confirm the role of integrins in initiating stabilization we used CHO (Chinese hamster ovary) cells selected for low levels of α5β1integrin expression and integrin transfected CHO cells selected for α5βloverexpression. The level of fibronectin receptor surface expression was inversely related to the adhesion stabilization lag time. These studies confirmed that integrins are essential for mediating arrest and initiating stabilization. They also confirm that secondary events are necessary for complete stabilization to occur. Finally, it is important to note that the arrest and stabilization methods we have developed are capable of detecting biologic effects at far greater sensitivity than static adhesion assays. Some examples of pharmacologic agents or biomaterials effects that can be detected using stabilization assays include: 1) very low drug doses, 2) very low levels of peptide, carbohydrate, and antibody inhibitors, 3) slight modification of endogenous protein expression by antisense oligonucleotides or transfected genetic expression constructs.

Human enhancer of filamentation 1 Is a mediator of hypoxia-inducible factor-1alpha-mediated migration in colorectal carcinoma cells

Human enhancer of filamentation 1 (HEF1; also known as NEDD9 or Cas-L) is a scaffolding protein that is implicated in regulating diverse cellular processes, such as cellular attachment, motility, cell cycle progression, apoptosis, and inflammation. Here, we identify HEF1 as a novel hypoxia-inducible factor-1alpha (HIF-1alpha)-regulated gene and reveal that HEF1 mediates hypoxia-induced migration of colorectal carcinoma cells. HEF1 is highly expressed in cultured colorectal carcinoma cells exposed to hypoxia and in the hypoxic areas of human colorectal cancer (CRC) specimens. Moreover, our data show that HIF-1alpha mediates the effects of hypoxia on induction of HEF1 expression via binding to a hypoxia-responsive element of the HEF1 promoter. Importantly, the induction of HEF1 expression significantly enhances hypoxia-stimulated HIF-1alpha transcriptional activity by modulating the interaction between HIF-1alpha and its transcriptional cofactor p300. Inhibition of HEF1 expression also reduced the levels of hypoxia-inducible genes, including those that regulate cell motility. Cell migration was reduced dramatically following knockdown of HEF1 expression under hypoxic conditions. Thus, this positive feedback loop may contribute to adaptive responses of carcinoma cells encountering hypoxia during cancer progression.