SKOV3 Tumor Research Articles

In Vivo Dual-Modality Terahertz/Magnetic Resonance Imaging Using Superparamagnetic Iron Oxide Nanoparticles as a Dual Contrast Agent

Molecular imaging is one of the most promising tools for diagnosis of cancer. We assessed whether commercially available superparamagnetic iron oxide nanoparticles (SPIO; Feridex <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> ) could be utilized as a dual modality contrast agent for terahertz (THz) imaging as well as magnetic resonance (MR) imaging. Feridex particles were transfected into SKOV3 cancer cells, at concentrations of 0, 0.35, 0.70, and 1.38 mM, and the magnetic and optical properties of the particles were examined by MR and THz reflection imaging. Mice were inoculated with Feridex-labeled SKOV3 cells, and in vivo MR and THz images were taken 1, 3, 7, and 14 days after inoculation. THz images and T2*-weighted MR images of Feridex-labeled SKOV3 tumors showed similar patterns; the signal intensities of both image sets increased with Feridex concentration. The signal intensity of in vivo MR and THz images from mice decreased over time. H&E and Prussian blue staining results correlated with imaging data. Dual-modality molecular MR and THz imaging of Feridex-labeled cells may be used to identify cancer cells both in vivo and in vitro. Such a noninvasive multimodal imaging method may be valuable in future cellular and molecular studies.

Blocking Epidermal Growth Factor Receptor Activation by 3,3′-Diindolylmethane Suppresses Ovarian Tumor Growth In Vitro and In Vivo

Genetic alterations, including the overexpression of epidermal growth factor receptor (EGFR) (in approximately 70% of ovarian tumors), play a crucial role in the signal transduction pathways that regulate key cellular functions, such as cell survival and proliferation, and are responsible for compromising traditional chemotherapy. 3,3'-Diindolylmethane (DIM) is an indole compound present in Brassica vegetables. In our previous studies, we demonstrated that BR-DIM, a formulated version of DIM, suppressed the growth of ovarian cancer cells by causing cell cycle arrest and apoptosis. In the present study, we delineated the mechanism by which DIM suppressed the growth of SKOV-3, OVCAR-3, and TOV-21G human ovarian cancer cells. DIM treatment caused significant down-regulation of the constitutive EGFR protein level as well as phosphorylation of EGFR at Tyr1068, Tyr992, Tyr845, and Tyr1173 in various ovarian cancer cells. To determine whether DIM suppressed the activation of EGFR by activating phosphorylation, cells were treated with epidermal growth factor. Epidermal growth factor treatment significantly blocked the DIM-mediated inhibition of EGFR activation and apoptosis in both SKOV-3 and OVCAR-3 cells. In addition, DIM treatment drastically reduced the phosphorylation of mitogen-activated protein kinase kinase (MEK) and extracellular signal-regulated kinase (ERK), which are downstream to EGFR, without affecting their protein levels. DIM treatment also inhibited the kinase activity of ERK, as observed by the down-regulation of phospho-E twenty-six like transcription factor 1 (p-ELK1) in all three ovarian cancer cell lines. DIM significantly suppressed the growth of ovarian tumors in vivo. Tumor growth suppressive effects of DIM in SKOV-3 tumor xenografts were associated with reduced phosphorylation of EGFR, MEK, and ERK. These results indicate that DIM induces apoptosis in ovarian cancer cells by inhibiting the EGFR-ERK pathway in vitro and in vivo.

An injectable depot system for sustained intraperitoneal chemotherapy of ovarian cancer results in favorable drug distribution at the whole body, peritoneal and intratumoral levels

The current study characterizes the impact of docetaxel (DTX) distribution on efficacy following sustained intraperitoneal (IP) chemotherapy in murine models of ovarian cancer. A polymer-lipid biodegradable depot (PoLigel) was used to deliver DTX in a sustained manner over 21-days following IP administration. Distribution and efficacy studies were carried out in SCID mice bearing SKOV3 IP solid tumors or C57BL/6 mice with ID8 IP ascites fluid. In addition, a subcutaneous (SC) SKOV3 model was used to determine whether systemic drug levels that result from IP administration of the PoLigel influence antitumor efficacy. Immunostained IP and SC SKOV3 tumor sections were used to study cell death, intratumoral drug distribution and tumor penetration. Sustained concentrations of DTX were observed in plasma, tissue, tumor and ascites over the entire study period. Drug accumulation was several fold greater in tumors and ascites when compared to plasma levels. Sustained chemotherapy resulted in significant reduction in tumor burden and ascites volume. IP tumors showed greater cell death compared to the SC tumors as seen by higher TUNEL and caspase-3 expression. At the intratumoral level, DTX distributed more towards the core of IP tumors compared to the SC tumors. Tumor penetration of drug from nearest blood vessel was 1.5 fold greater in the IP tumors than the SC tumors. Overall, favorable drug distribution at the whole-body, peritoneal and intratumoral levels in combination with local and systemic sustained drug exposure contribute to the high efficacy observed. These results encourage the clinical use of IP sustained chemotherapy for ovarian cancer.

Glucocorticoid Regulation of SLIT/ROBO Tumour Suppressor Genes in the Ovarian Surface Epithelium and Ovarian Cancer Cells

The three SLIT ligands and their four ROBO receptors have fundamental roles in mammalian development by promoting apoptosis and repulsing aberrant cell migration. SLITs and ROBOs have emerged as candidate tumour suppressor genes whose expression is inhibited in a variety of epithelial tumours. We demonstrated that their expression could be negatively regulated by cortisol in normal ovarian luteal cells. We hypothesised that after ovulation the locally produced cortisol would inhibit SLIT/ROBO expression in the ovarian surface epithelium (OSE) to facilitate its repair and that this regulatory pathway was still present, and could be manipulated, in ovarian epithelial cancer cells. Here we examined the expression and regulation of the SLIT/ROBO pathway in OSE, ovarian cancer epithelial cells and ovarian tumour cell lines. Basal SLIT2, SLIT3, ROBO1, ROBO2 and ROBO4 expression was lower in primary cultures of ovarian cancer epithelial cells when compared to normal OSE (P<0.05) and in poorly differentiated SKOV-3 cells compared to the more differentiated PEO-14 cells (P<0.05). Cortisol reduced the expression of certain SLITs and ROBOs in normal OSE and PEO-14 cells (P<0.05). Furthermore blocking SLIT/ROBO activity reduced apoptosis in both PEO-14 and SKOV-3 tumour cells (P<0.05). Interestingly SLIT/ROBO expression could be increased by reducing the expression of the glucocorticoid receptor using siRNA (P<0.05). Overall our findings indicate that in the post-ovulatory phase one role of cortisol may be to temporarily inhibit SLIT/ROBO expression to facilitate regeneration of the OSE. Therefore this pathway may be a target to develop strategies to manipulate the SLIT/ROBO system in ovarian cancer.

Abstract C136: Exploring the functional contribution of STAT3 activity in tumor and tumor-associated stromal cells with species-selective generation 2.5 antisense oligonucleotides in preclinical cancer models.

Abstract The transcription factor STAT3 is a point of convergence for multiple signaling pathways and is activated in both tumor and non-tumor stromal cells in the tumor microenvironment. STAT3 activation mediates the expression of genes involved in many aspect of tumorigenesis. Thus, STAT3 has been hotly pursued as a target for cancer. Although inhibitors of STAT3 upstream signaling pathways have shown anti-tumor activity in preclinical animal models, the relative contributions of STAT3 in tumor cells versus tumor-associated stromal cells to the observed antitumor effects remains unclear. To address this question we have developed potent next generation (Generation 2.5) antisense oligonucleotides (ASOs) that are selective for either mouse or human STAT3 and we haveassessed their specificity, potency, and antitumor activities in several preclinical cancer models. The safety of targeting STAT3 with ASOs was first confirmed in both rodents and non-human primates. STAT3 ASOs were very well tolerated at doses that resulted in complete abrogation of STAT3 expression in the liver of treated animals, Next, we evaluated the relative contribution of STAT3 in tumor cells and tumor-associated stromal cells in a human ovarian cancer xenograft model (SKOV3), using both mouse and human specific STAT3 ASOs. Mouse and human STAT3 ASOs selectively reduced their respective target STAT3 mRNA levels in SKOV3 tumors. However, when we evaluated the level of IL-6, a key cytokine in ovarian cancer and known to be regulated by STAT3, it was significantly reduced only by the inhibition of the STAT3 in the tumor associated-stromal cells (mouse STAT3). Moreover, the antitumor activity of the mouse STAT3 was superior to that observed with inhibition of STAT3 in the tumor cells themselves, suggesting that the tumor promoting effects of STAT3 in this model is mediated through STAT3 activation in tumor-associated stromal cells. To evaluate the effects of STAT3 inhibition in a mouse model of cancer we employed the APCmin model in which mice develop intestinal neoplasia at a young age. Treatment of APCmin mice with mouse STAT3 ASOs led to a &amp;gt;90% inhibition of STAT3 mRNA levels in both the small intestine and colon. In addition, STAT3 ASO treatment resulted in a significant decrease in the number of polyps in the intestine. Finally, we evaluated the effects of human-specific STAT3 ASO in NSCLC s.c. xenograft models using either PC9 or primary human tumor explants. Human STAT3 ASO treatment resulted in &amp;gt;50% inhibition in STAT3 mRNA levels in the tumor cells and resulted in significant tumor growth inhibition (∼50% and 90% &amp;gt;, respectively), suggesting that relative contributions of mouse stromal cells to tumor growth may vary in different tumor types. Taken together, these results demonstrate that STAT3 ASO can selectively downregulate STAT3 in both tumor and stromal compartments, affect anti-tumor activity in vivo and that stromal derived STAT3 activity is important contributor to tumor growth and survival. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C136.

Abstract A7: The heparan sulfate mimetic PG545 as a monotherapy or in combination with the standard-of-care agents paclitaxel or carboplatin inhibits solid tumor progression in two murine models of ovarian cancer.

Abstract PG545 is a fully synthetic heparan sulfate (HS) mimetic currently being assessed by subcutaneous administration in Phase I clinical trials for advanced cancer patients. PG545 inhibits the enzymatic activity of heparanase, angiogenesis, solid tumor growth and spontaneous metastases in different tumor types. As a role for tumor angiogenesis emerged in the development of ovarian cancer, the number the clinical investigations using avascular therapies have increased in recent years. Moreover, given the fact that ovarian cancers can metastasize by multiple routes, the dual antiangiogenic and antimetastatic activity of PG545 may offer a promising approach to treat ovarian cancer patients. Standard treatment with PG545 involved a loading and maintenance dosing regimen of 20 mg/kg followed by weekly injections of 10 mg/kg as previously reported. In these studies the antitumor effect of weekly dosing with PG545, both as a monotherapy and in combination with standard-of-care agents, was investigated. In the first study, mice bearing A2780 tumors were treated with PG545 alone, paclitaxel alone (15 mg/kg, qw) or in combination of both compounds. Treatment with PG545 reduced tumor growth (TGI = 42%) compared to vehicle control and was more effective than paclitaxel alone (TGI = 11%). In combination, PG545 and paclitaxel significantly reduced tumor volume (TGI = 61%) compared to vehicle control. In a second model, mice bearing SKOV3 tumors received PG545, carboplatin (60 mg/kg) or in combination. Treatment with PG545 significantly inhibited tumor growth (TGI = 40%) compared to vehicle control, almost equivalent to the effect of carboplatin monotherapy (TGI = 41%). The combination regimen further impacted tumor growth, showing a significant effect by day 19 of treatment (TGI = 71% versus the vehicle control and the monotherapy groups). In conclusion, PG545 demonstrates antitumor activity as a monotherapy in ovarian cancer models which can be substantially enhanced using combination regimens with current standard-of-care agents such as paclitaxel and carboplatin. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A7.

A cathepsin-cleavage site between the adenovirus capsid protein IX and a tumor-targeting ligand improves targeted transduction

Human adenoviruses have a great potential as anticancer agents. One strategy to improve their tumor-cell specificity and anti-tumor efficacy is to include tumor-specific targeting ligands in the viral capsid. This can be achieved by fusion of polypeptide-targeting ligands with the minor capsid protein IX. Previous research suggested that protein IX-mediated targeting is limited by inefficient release of protein IX-fused ligands from their cognate receptors in the endosome. This thwarts endosomal escape of the virus particles. Here we describe that the targeted transduction of tumor cells is augmented by a cathepsin-cleavage site between the protein IX anchor and the HER2/neu-binding ZH Affibody molecule as ligand. The cathepsin-cleavage site did not interfere with virus production and incorporation of the Affibody molecules in the virus capsid. Virus particles harboring the cleavable protein IX-ligand fusion in their capsid transduced the HER2/neu-positive SKOV-3 ovarian carcinoma cells with increased efficiency in monolayer cultures, three-dimensional spheroid cultures and in SKOV-3 tumors grown on the chorioallantoic membrane of embryonated chicken eggs. These data show that inclusion of a cathepsin-cleavage sequence between protein IX and a high-affinity targeting ligand enhances targeted transduction. This modification further augments the applicability of protein IX as an anchor for coupling tumor-targeting ligands.

In vivo targeting of HER2-positive tumor using 2-helix affibody molecules.

Molecular imaging of human epidermal growth factor receptor type 2 (HER2) expression has drawn significant attention because of the unique role of the HER2 gene in diagnosis, therapy and prognosis of human breast cancer. In our previous research, a novel cyclic 2-helix small protein, MUT-DS, was discovered as an anti-HER2 Affibody analog with high affinity through rational protein design and engineering. MUT-DS was then evaluated for positron emission tomography (PET) of HER2-positive tumor by labeling with two radionuclides, 68Ga and 18F, with relatively short half-life (t1/2<2 h). In order to fully study the in vivo behavior of 2-helix small protein and demonstrate that it could be a robust platform for labeling with a variety of radionuclides for different applications, in this study, MUT-DS was further radiolabeled with 64Cu or 111In and evaluated for in vivo targeting of HER2-positive tumor in mice. Design 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) conjugated MUT-DS (DOTA-MUT-DS) was chemically synthesized using solid phase peptide synthesizer and I2 oxidation. DOTA-MUT-DS was then radiolabeled with 64Cu or 111In to prepare the HER2 imaging probe (64Cu/111In-DOTA-MUT-DS). Both biodistribution and microPET imaging of the probe were evaluated in nude mice bearing subcutaneous HER2-positive SKOV3 tumors. DOTA-MUT-DS could be successfully synthesized and radiolabeled with 64Cu or 111In. Biodistribution study showed that tumor uptake value of 64Cu or 111In-labeled DOTA-MUT-DS was 4.66±0.38 or 2.17±0.15%ID/g, respectively, in nude mice bearing SKOV3 xenografts (n=3) at 1 h post-injection (p.i.). Tumor-to-blood and tumor-to-muscle ratios for 64Cu-DOTA-MUT-DS were attained to be 3.05 and 3.48 at 1 h p.i., respectively, while for 111In-DOTA-MUT-DS, they were 2.04 and 3.19, respectively. Co-injection of the cold Affibody molecule ZHER2:342 with 64Cu-DOTA-MUT-DS specifically reduced the SKOV3 tumor uptake of the probe by 48%. 111In-DOTA-MUT-DS displayed lower liver uptake at all the time points investigated and higher tumor to blood ratios at 4 and 20 h p.i., when compared with 64Cu-DOTA-MUT-DS. This study demonstrates that the 2-helix protein based probes, 64Cu/111In DOTA-MUT-DS, are promising molecular probes for imaging HER2-positive tumor. Two-helix small protein scaffold holds great promise as a novel and robust platform for imaging and therapy applications.

A vaccine approach for breast cancer immunotherapy by targeting HER2/neu antigen to B cells via CD19 molecule.

287 Background: Trastuzumab has been proven to be effective in the immunotherapy for Her-2/neu-positive breast cancer. However, this adoptively transferred therapeutic Ab must be continuously given to the patient with huge financial cost. Thus, it would be desirable if tumor vaccines could elicit long-lasting trastuzumab-like Ab. Methods: Constructing fusion protein of anti-mouse CD19 single chain variable fragment (anti-CD19-scFv) with human Her-2/neu extracellular domain P3-4 (P3-4) by extracting total RNA from Rat anti-mouse CD19 hybridoma (1D3) and first strand cDNA was synthesized accordingly. VH and VL were amplified using designed primers. Single chain Fv (VL-VH) was then synthesized by overlapping PCR. Then constructs were sequenced and cloned into pET-20b(+) vectors. Fragments P3-4 of extracellular domains of human Her-2/neu was cloned from pcDNA3.1-Her2 and then cloned into pET-20b(+)-scFv. Series of constructs were expressed and purified according to standard protocol and verified by Western Blot. Results: Both in vitro and in vivo studies demonstrated that fusion proteins anti-CD19-scFv and anti-CD19-scFv-P3-4 but not P3-4 could specifically bind to B cells with high affinity. Mice immunized with anti-CD19-scFv-P3-4 secreted higher titers of IgG and IgM than those from controls (p&lt;0.05). Studies also demonstrated that sera from anti-CD19-scFv-P3-4 but not anti-CD19-scFv or P3-4 immunized mice stained with Her-2/neu expressing SKOV-3 tumor cells. These Abs also competitively inhibited trastuzumab-mediated Ag binding, suggesting that trastuzumab-like Ab responses were elicited. WT mice immunized with anti-CD19-scFv-P3-4 fusion protein then challenged with D2/F2-Her-2 mammary tumor cells showed significantly reduced tumor burden compared to those immunized with control fusion proteins (p&lt;0.05) and had enhanced median overall survival to 45 days versus 34 days in WT mice immunized with either anti-CD19-scFv or P3-4. Conclusions: Targeting of Her-2/neu antigens to B cells stimulates Th-dependent humoral immune responses with anti tumor effect in mouse model. These findings provide a novel avenue for successful development of breast cancer vaccination strategy and help to fight for cancer.

A comparison of 111In- or 64Cu-DOTA-trastuzumab Fab fragments for imaging subcutaneous HER2-positive tumor xenografts in athymic mice using microSPECT/CT or microPET/CT

BackgroundOur objective was to compare 111In- or 64Cu-DOTA-trastuzumab Fab fragments for imaging small or large s.c. tumor xenografts in athymic mice that display a wide range of human epidermal growth factor receptor-2 (HER2) expression using microSPECT/CT or microPET/CT.MethodsTrastuzumab Fab were labeled with 111In or 64Cu by conjugation to 1,4,7,10-tetraazacyclododecane N, N', N'', N'''-tetraacetic acid (DOTA). The purity of 111In- and 64Cu-DOTA-trastuzumab Fab was measured by SDS-PAGE and HPLC. HER2 binding affinity was determined in saturation radioligand binding assays using SKBR-3 cells (1.3 × 106 HER2/cell). MicroSPECT/CT and microPET/CT were performed in athymic mice bearing s.c. BT-20 and MDA-MB-231 xenografts with low (0.5 to 1.6 × 105 receptors/cell), MDA-MB-361 tumors with intermediate (5.1 × 105 receptors/cell) or SKOV-3 xenografts with high HER2 expression (1.2 × 106 receptors/cell) at 24 h p.i. of 70 MBq (10 μg) of 111In-DOTA-trastuzumab Fab or 22 MBq (10 μg) of 64Cu-DOTA-trastuzumab Fab or irrelevant 111In- or 64Cu-DOTA-rituximab Fab. Tumor and normal tissue uptake were quantified in biodistribution studies.Results111In- and 64Cu-DOTA-trastuzumab were > 98% radiochemically pure and bound HER2 with high affinity (Kd = 20.4 ± 2.5 nM and 40.8 ± 3.5 nM, respectively). MDA-MB-361 and SKOV-3 tumors were most clearly imaged using 111In- and 64Cu-DOTA-trastuzumab Fab. Significantly higher tumor/blood (T/B) ratios were found for 111In-DOTA-trastuzumab Fab than 111In-DOTA-rituximab Fab for BT-20, MDA-MB-231 and MDA-MB-361 xenografts, and there was a direct association between T/B ratios and HER2 expression. In contrast, tumor uptake of 64Cu-DOTA-trastuzumab Fab was significantly higher than 64Cu-DOTA-rituximab Fab in MDA-MB-361 tumors but no direct association with HER2 expression was found. Both 111In- and 64Cu-DOTA-trastuzumab Fab imaged small (5 to 10 mm) or larger (10 to 15 mm) MDA-MB-361 tumors. Higher blood, liver, and spleen radioactivity were observed for 64Cu-DOTA-trastuzumab Fab than 111In-DOTA-trastuzumab Fab.ConclusionsWe conclude that 111In-DOTA-trastuzumab Fab was more specific than 64Cu-DOTA-trastuzumab Fab for imaging HER2-positive tumors, especially those with low receptor density. This was due to higher levels of circulating radioactivity for 64Cu-DOTA-trastuzumab Fab which disrupted the relationship between HER2 density and T/B ratios. Use of alternative chelators that more stably bind 64Cu may improve the association between T/B ratios and HER2 density for 64Cu-labeled trastuzumab Fab.

Biodegradable polymer − cisplatin(IV) conjugate as a pro-drug of cisplatin(II)

A Pt(IV) complex was covalently conjugated to a new biodegradable amphiphilic tri-block copolymer, MPEG-b-PCL-b-PLL, which contains pendant amino groups, to form a polymeric pro-drug of cisplatin(II), MPEG-b-PCL-b-PLL/Pt(IV). The conjugate was assembled into nano-micelles. The Pt(IV) complex, the polymer carrier and the conjugate were characterized systematically. In vitro release experiments showed that drug release from the polymer-Pt(IV) micelles follows an acid responsive and oxidation-reduction sensitive kinetics. HPLC-ICP-MS analysis revealed that cisplatin(II) can be released from the conjugate under an acidic plus a reductive condition which is available inside a cancerous cell. In vitro MTT assay demonstrated that the polymer-Pt(IV) micelles display higher cytotoxicity against SKOV-3 tumor cells than both cisplatin(II) and Pt(IV) complex. This enhanced cytotoxicity is attributed to effective internalization of the micelles by the cells via endocytosis mechanism, which was observed by fluorescence imaging and by direct determination of the platinum uptake by the cells. This polymer-Pt(IV) conjugate is a promising polymeric pro-drug of cisplatin in micellar form. It can protect the Pt(IV) complex against blood clearance. It can enter cancerous cells via endocytosis mechanism and then cisplatin(II) can be released. Therefore, this polymeric pro-drug of cisplatin is expected to find clinical applications in the future.

A novel 18F-labeled two-helix scaffold protein for PET imaging of HER2-positive tumor

Two-helix scaffold proteins (~ 5 kDa) against human epidermal growth factor receptor type 2 (HER2) have been discovered in our previous work. In this research we aimed to develop an (18)F-labeled two-helix scaffold protein for positron emission tomography (PET) imaging of HER2-positive tumors. An aminooxy-functionalized two-helix peptide (AO-MUT-DS) with high HER2 binding affinity was synthesized through conventional solid phase peptide synthesis. The purified linear peptide was cyclized by I(2) oxidation to form a disulfide bridge. The cyclic peptide was then conjugated with a radiofluorination synthon, 4-(18)F-fluorobenzyl aldehyde ((18)F-FBA), through the aminooxy functional group at the peptide N terminus (30% yield, non-decay corrected). The binding affinities of the peptides were analyzed by Biacore analysis. Cell uptake assay of the resulting PET probe, (18)F-FBO-MUT-DS, was performed at 37°C. (18)F-FBO-MUT-DS with high specific activity (20-32 MBq/nmol, 88-140 μCi/μg, end of synthesis) was injected into mice xenograft model bearing SKOV3 tumor. MicroPET and biodistribution and metabolic stability studies were then conducted. Cell uptake assays showed high and specific cell uptake (~12% applied activity at 1 h) by incubation of (18)F-FBO-MUT-DS with HER2 high-expressing SKOV3 ovarian cancer cells. The affinities (K(D)) of AO-MUT-DS and FBO-MUT-DS as tested by Biacore analysis were 2 and 1 nM, respectively. In vivo small animal PET demonstrated fast tumor targeting, high tumor accumulation, and good tumor to normal tissue contrast of (18)F-FBO-MUT-DS. Biodistribution studies further revealed that the probe had excellent tumor uptake (6.9%ID/g at 1 h post-injection) and was cleared through both liver and kidneys. Co-injection of the probe with 500 μg of HER2 Affibody protein reduced the tumor uptake (6.9 vs 1.8%ID/g, p < 0.05). F-FBO-MUT-DS displays excellent HER2 targeting ability and tumor PET imaging quality. The two-helix scaffold proteins are suitable for development of (18)F-based PET probes.

Trastuzumab and Pertuzumab Produce Changes in Morphology and Estrogen Receptor Signaling in Ovarian Cancer Xenografts Revealing New Treatment Strategies

The aim of this study was to investigate the antitumor effects of HER2-directed combination therapy in ovarian cancer xenograft models to evaluate their potential. The combinations of trastuzumab and pertuzumab, and trastuzumab and aromatase inhibitor therapy were investigated. The effects of trastuzumab, pertuzumab, and letrozole on growth response, apoptosis, morphology, and gene and protein expression were evaluated in the SKOV3 ovarian cancer cell line xenograft and a panel of five human ovarian xenografts derived directly from clinical specimens. The combination of HER2-directed antibodies showed enhanced antitumor activity compared with single antibody therapy in the SKOV3 xenograft model. Apoptosis, morphology, and estrogen-regulated gene expression were modulated by these antibodies in both spatial and temporal manners. A panel of ovarian cancer xenografts showed differential growth responses to the combination of trastuzumab and pertuzumab. High HER2 expression and increasing HER3 protein expression on treatment were associated with growth response. In trastuzumab-treated SKOV3 tumors, there was a change in tumor morphology, with a reduction in frequency of estrogen receptor alpha (ERα)-negative clear cell areas. Trastuzumab, but not pertuzumab, increased expression of ERα in SKOV3 xenografts when analyzed by quantitative immunofluorescence. ERα and downstream signaling targets were modulated by trastuzumab alone and in combination. Trastuzumab enhanced the responsiveness of SKOV3 xenografts to letrozole when given in combination. These data suggest that trastuzumab in combination with pertuzumab could be an effective approach in high HER2-expressing ovarian cancers and could also enhance sensitivity to endocrine therapy in ERα-positive ovarian cancer.

The Development of Peptide-Based Tools for the Analysis of Angiogenesis

Limitations to the application of molecularly targeted cancer therapies are the inability to accurately match patient with effective treatment and the absence of a prompt readout of posttreatment response. Noninvasive agents that rapidly report vascular endothelial growth factor (VEGF) levels using positron emission tomography (PET) have the potential to enhance anti-angiogenesis therapies. Using phage display, two distinct classes of peptides were identified that bind to VEGF with nanomolar affinity and high selectivity. Co-crystal structures of these different peptide classes demonstrate that both bind to the receptor-binding region of VEGF. (18)F-radiolabelling of these peptides facilitated the acquisition of PET images of tumor VEGF levels in a HM7 xenograph model. The images obtained from one 59-residue probe, (18)F-Z-3B, 2hr postinjection are comparable to those obtained with anti-VEGF antibody B20 72hr postinjection. Furthermore, VEGF levels in growing SKOV3 tumors were followed using (18)F-Z-3B as a PET probe with VEGF levels increasing with tumor size.

The effect of sulfonate leaving groups on the hypoxia-selective toxicity of nitro analogs of the duocarmycins

A series of 3-substituted (5-nitro-2,3-dihydro-1H-benzo[e]indol-1-yl)methyl sulfonate (nitroCBI) prodrugs containing sulfonate leaving groups undergo hypoxia-selective metabolism to form potent DNA minor groove alkylating agents. They were evaluated (along with chloride leaving group analogs for comparison) for their cytotoxicity against cultures of SKOV3 and HT29 human tumor cell lines under both aerobic and hypoxic conditions. Sulfonates with neutral side chains (e.g., 5,6,7-trimethoxyindole; TMI) show consistently higher hypoxic cytotoxicity ratios (HCRs) (34–246) than the corresponding chloro analogs (2.8–3.1) in SKOV3 cells, but these trends do not hold for compounds with cationic or polar neutral side chains.

Targeting HER2/neu antigen to B cells via CD19 molecule: A vaccine approach for breast cancer immunotherapy.

e13074 Background: Herceptin has been proven to be effective in the immunotherapy for Her-2/neu+ breast cancer. However, this adoptively transferred therapeutic Ab must be continuously given to the patient with huge financial cost. Thus, it would be desirable if tumor vaccines could elicit long-lasting Herceptin-like Ab. Methods: Constructing fusion protein of anti-mouse CD19 single chain variable fragment (anti-CD19-scFv) with human Her-2/neu extracellular domain P3-4 (P3-4) by extracting total RNA from Rat anti-mouse CD19 hybridoma (1D3) and first strand cDNA was synthesized accordingly. VH and VL were amplified using designed primers. Single chain Fv (VL-VH) was then synthesized by overlapping PCR. Then constructs were sequenced and cloned into pET-20b(+) vectors. Fragments P3-4 of extracellular domains of human Her-2/neu was cloned from pcDNA3.1-Her2 and then cloned into pET-20b(+)-scFv. Series of constructs were expressed and purified according to standard protocol and verified by Western Blot. Results: Both in vitro and in vivo studies demonstrated that fusion proteins anti-CD19-scFv and anti-CD19-scFv-P3-4 but not P3-4 could specifically bind to B cells with high affinity. Mice immunized with anti-CD19-scFv-P3-4 secreted higher titers of IgG and IgM than those from controls (p<0.05). Studies also demonstrated that sera from anti-CD19-scFv-P3-4 but not anti-CD19-scFv or P3-4 immunized mice stained with Her-2/neu expressing SKOV-3 tumor cells. These Abs also competitively inhibited Herceptin-mediated Ag binding, suggesting that Herceptin-like Ab responses were elicited. WT mice immunized with anti-CD19-scFv-P3-4 fusion protein then challenged with D2/F2-Her-2 mammary tumor cells showed significantly reduced tumor burden compared to those immunized with control fusion proteins (p<0.05) and had enhanced median overall survival to 45 days versus 34 days in WT mice immunized with either anti-CD19-scFv or P3-4. Conclusions: Targeting of Her-2/neu antigens to B cells stimulates Th-dependent humoral immune responses with anti tumor effect in mouse model. These findings provide a novel avenue for successful development of breast cancer vaccination strategy and help to fight for cancer.

Abstract 679: NDC-1308 nanoparticles inhibit tumor growth by novel mechanisms controlling cancer cell proliferation

Abstract It has previously been demonstrated that treatment of tumor cells with an estrogen receptor beta (ER-β) agonist can lead to cessation of cell division and cell death. We recently reported the discovery of NDC-1308, a member of our estradiol-related family of ER-β agonists, which is cytotoxic to a broad range of human tumor cell lines (EC50 is 5-20 uM). Although NDC-1308 has similar binding affinity for ER-α and ER-β (70-100 nM), functional studies show that it activates ER-β about 5-fold more compared to ER-α. To understand the mechanism of cytotoxicity, A549 (lung), SKOV-3 (ovary), and Panc-1 (pancreatic) human tumor cell lines were treated with NDC-1308 and gene expression changes evaluated by microarray. In all cell lines, NDC-1308 caused a significant down-regulation of key genes critical for chromosome replication, along with the up-regulation of at least two nucleases, granzyme K (GzmK) and apoptosis enhancing nuclease (AEN). There was also a significant up-regulation of pro-apoptotic pathway genes including BBC3 and GDF15 and an up-regulation of a death receptor pathway gene TNFRSF10B (DR5). These results suggest that ER-β activation by NDC-1308 may be useful to trigger DNA damage, cell cycle arrest and ultimately the death of cancer cells. However, PK studies in rodents showed that NDC-1308 has a short half-life, thereby lowering its potential efficacy as a cancer therapeutic. In order to optimize the blood circulation time and to enhance the accumulation of NDC-1308 in tumors, the drug was formulated into several different types of nanoparticles (50-100 nm), including an amorphous drug particle, a lipid-containing particle and a micelle-based particle. Whole body imaging studies showed that NDC-1308 nanoparticles conjugated with AlexaFluor 750 could localize to human tumors such as colon adenocarcinomas, renal cell carcinomas and lung adenocarcinomas in nude mice (N=4 per tumor type). To determine the efficacy of NDC-1308 as an anti-cancer therapy, nude mice bearing A549 human tumors (N=12 per group) were dosed every other day with NDC-1308 nanoparticles (up to 24 mg/kg of the active drug) via tail vein injection. During treatment, this led to a significant, dose-dependent reduction in tumor size in drug treated animals versus untreated controls. We conclude that intravenous administration of NDC-1308 nanoparticles can inhibit the rate of human tumor growth in a mouse model of cancer. Our future development plans include large animal safety and toxicity studies, followed by IND submission and Phase 1 clinical trials. 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 679. doi:10.1158/1538-7445.AM2011-679

Abstract 1759: Design optimization and characterization of novel herceptin-based immunotoxins for cancer therapy. Enhanced antitumor activity in vitro and in vivo

Abstract The human epidermal growth factor receptor (Her) family plays an important role in cell survival and proliferation, and is implicated in oncogenesis. Overexpression of Her2/neu is associated with aggressive disease and poor prognosis. Herceptin, the only anti-Her2/neu, humanized monoclonal antibody approved by FDA for therapy of mammary carcinoma is currently and successfully prescribed for treatment of Her2/neu positive cancer. However, in 40-60% of all patients with Her2/neu-overexpressing tumors, Herceptin has little or no effect. The goal of this study was to demonstrate the construction and characterization of various Herceptin-based immunotoxins, loaded with a highly cytotoxic recombinant gelonin (rGel) molecule. Utilizing a humanized anti-Her2/neu scFv (4D5), we generated 2 orientation constructs: 4D5/rGel and rGel/4D5. We also generated a conventional chemical conjugate with full-length Herceptin (Herceptin/rGel conjugate), and we generated a unique fusion of anti-Her2/neu IgG containing 2 rGel molecules (Aglyco-Herceptin/rGel). This is the first report of the preparation of active full-length antibody-toxin construct from E.coli. In vitro studies showed that all immunotoxins retained the affinity and specificity of the original antibody, as well as the biological activity of rGel toxin. Against the Her2/neu overexpressing cancer cell lines, all immunotoxins demonstrated specific cytotoxic effects, even against Herceptin-resistant breast cancer cells. Against ovarian (SKOV3) cells, the Herceptin/rGel conjugate, Aglyco-Herceptin/rGel and rGel/4D5 fusion constructs demonstrated the best in vitro efficacy (IC50 of 0.28nM, 12.19nM and 1.57nM for each construct respectively vs 70.86 nM for 4D5/rGel). rGel/4D5 outperformed 4D5/rGel demonstrating improved internalization efficiency and increased intracellular delivery of rGel. All the immunotoxins displayed similar minimal exposure times to target cells for optimal cytotoxic activity. All constructs demonstrated a distinct cell-killing efficiency time course. Functional stability studies of the constructs showed that all remained biologically active after incubation in human plasma. Efficacy studies of the various constructs against SKOV3 tumor xenografts are ongoing and will be reported. Based on our in vitro results, the bivalent full-length antibody-toxin immunotoxins were superior to the corresponding recombinant monovalent constructs. Among monovalent constructs, the rGel/4D5 fusion was superior in vitro overall to 4D5/rGel. Different orientations of antibody and toxin can promote optimal cell internalization and toxicity of the immunotoxin, and may be valuable considerations for further construct optimization. Research conducted, in part, by the Clayton Foundation for Research. 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 1759. doi:10.1158/1538-7445.AM2011-1759

MUC16 (CA125) regulates epithelial ovarian cancer cell growth, tumorigenesis and metastasis

Objectives MUC16 (CA125) protein is a high molecular weight mucin overexpressed in the majority of epithelial ovarian cancers (EOC) but not in the epithelium of normal ovaries suggesting that it might play a role in EOC pathogenesis. Here, we explored the phenotypic consequences of MUC16 knockdown and expression of its C-terminal domain with the aim of establishing a role for MUC16 in tumorigenesis. Methods MUC16 was down-regulated by stably expressing an anti-MUC16 endoplasmic reticulum-targeted single-chain antibody which prevented MUC16 cell surface localization in NIH:OVCAR3 cells. In addition, we generated epitope tagged, N-terminal region-deleted MUC16 constructs with (MUC16TMU) and without (MUC16CTD) cytoplasmic tail deletions and stably expressed them in SKOV3 cells. Results Although MUC16 knockdown did not affect the cell growth rate, knockdown cells reached a stationary growth phase after 4 days whereas control cells continued to grow for up to 7 days. Colony formation assays in soft agar demonstrated that MUC16 knockdown cells had > 8-fold reduction in their ability to form colonies. Importantly, MUC16 knockdown completely prevents the formation of subcutaneous tumors in nude mice. Conversely, we show that ectopic expression of the MUC16CTD enhances SKOV3 tumor cell growth, colony formation in soft agar and enhances tumor growth and metastases in SCID mice. In addition, MUC16CTD expression increases cell motility, invasiveness, and metastatic property. Deletion of the cytoplasmic tail from the MUC16CTD completely abolished its ability to enhance tumor cell growth, cell motility and invasiveness. Furthermore, the increased invasive properties of MUC16CTD-expressing cells correlated with decreased expression of E-cadherin and increased expression of N-cadherin and vimentin. Conclusion These findings provide the first evidence for a critical role of MUC16 in tumor cell growth, tumorigenesis and metastases.

Molecular Design and Optimization of 99mTc-Labeled Recombinant Affibody Molecules Improves Their Biodistribution and Imaging Properties

Affibody molecules are a recently developed class of targeting proteins based on a nonimmunoglobulin scaffold. The small size (7 kDa) and subnanomolar affinity of Affibody molecules enables high-contrast imaging of tumor-associated molecular targets, particularly human epidermal growth factor receptor type 2 (HER2). (99m)Tc as a label offers advantages in clinical practice, and earlier studies demonstrated that (99m)Tc-labeled recombinant Affibody molecules with a C-terminal cysteine could be used for HER2 imaging. However, the renal retention of radioactivity exceeded tumor uptake, which might complicate imaging of metastases in the lumbar region. The aim of this study was to develop an agent with low renal uptake and preserved tumor targeting. A series of recombinant derivatives of the HER2-binding Z(HER2)(:342) Affibody molecule with a C-terminal chelating sequence, -GXXC (X denoting glycine, serine, lysine, or glutamate), was designed. The constructs were labeled with (99m)Tc and evaluated in vitro and in vivo. All variants were stably labeled with (99m)Tc, with preserved capacity to bind specifically to HER2-expressing cells in vitro and in vivo. The composition of the chelating sequence had a clear influence on the cellular processing and biodistribution properties of the Affibody molecules. The best variant, (99m)Tc-Z(HER2)(:V2), with the C-terminal chelating sequence -GGGC, provided the lowest radioactivity retention in all normal organs and tissues including the kidneys. (99m)Tc-Z(HER2)(:V2) displayed high uptake of radioactivity in HER2-expressing xenografts, 22.6 ± 4.0 and 7.7 ± 1.5 percentage injected activity per gram of tissue at 4 h after injection in SKOV-3 (high HER2 expression) and DU-145 (low HER2 expression) tumors, respectively. In both models, the tumor uptake exceeded the renal uptake. These results demonstrate that the biodistribution properties of recombinant (99m)Tc-labeled Affibody molecules can be optimized by modification of the C-terminal cysteine-containing chelating sequence. (99m)Tc-Z(HER2)(:V2) is a promising candidate for further development as a diagnostic radiopharmaceutical for imaging of HER2-expressing tumors. These results may be useful for the development of imaging agents based on other Affibody molecules and, hopefully, other scaffolds.