Thirupandiyur S. Udayakumar

The E2F1/Rb and p53/MDM2 pathways in DNA repair and apoptosis: understanding the crosstalk to develop novel strategies for prostate cancer radiotherapy.

Both the p53- and E2F1-signaling pathways are defective in almost all types of tumors, suggesting very important roles for their signaling networks in regulating the process of tumorigenesis and therapy response. Studies on Radiation Therapy Oncology Group tissue samples have identified aberrant expression of p53, MDM2 (an E3 ubiquitin ligase that targets p53 for proteosomal degradation), and p16 (an upstream regulator of retinoblastoma and hence E2F1 in prostate cancer); abnormal expression of these biomarkers has been associated with clinical outcome after radiotherapy ± androgen deprivation therapy. Although the proapoptotic properties of p53 are well documented, a relatively new aspect of p53 function as an active mediator of prosurvival signaling pathways is now emerging. E2F1 is a transcription factor that possesses both proapoptotic and prosurvival properties. Thus, the role of E2F1 in the process of tumorigenesis versus apoptosis is a contested issue that needs to be resolved. Furthermore, the role of E2F1 in DNA repair is being increasingly recognized. Thus, novel approaches to curb the prosurvival and DNA repair capability of E2F1 while promoting apoptotic function are of interest. In this review, we discuss the challenges involved in targeting the p53/E2F1 pathways and the crosstalk networks, and further propose potential therapeutic strategies for prostate cancer management.

Interaction of HIF-1α and Notch3 Is Required for the Expression of Carbonic Anhydrase 9 in Breast Carcinoma Cells

Expression of carbonic anhydrase 9 (CA9) is associated with poor prognosis and increased tumor aggressiveness and does not always correlate with HIF-1α expression. Presently, we analyzed the regulation of CA9 expression during hypoxia by HIF-1α, Notch3, and the von Hippel-Lindau (VHL) in breast carcinoma cells. Both HIF-1α and Notch3 were absolutely required for the expression of CA9 mRNA, protein, and reporter. Reciprocal co-immunoprecipitation of HIF-1α, Notch3 intracellular domain (NICD3), and pVHL demonstrated their association. The presence of common consensus prolyl hydroxylation and pVHL binding motifs (L(XY)LAP);LLPLAP(2191) suggested an oxygen-dependent regulation for NICD3. However, unlike the HIF-1α protein, NICD3 protein levels were not modulated with hypoxia or hypoxia-mimetic agents. Surprisingly, mutations of the common prolyl hydroxylation and pVHL binding domain lead to the loss of CA9 mRNA, protein, and reporter activity. Chromatin immunoprecipitation assay demonstrated the association of NICD3, HIF-1α, and pVHL at the CA9 promoter. Further, the NICD3 mutant defective in prolyl hydroxylation and subsequent pVHL binding caused a reduction in cell proliferation of breast carcinoma cells. We show here for the first time that the interaction of HIF-1α with NICD3 is important for the regulation of CA9 expression. These findings suggest that although CA9 is a hypoxia-responsive gene, its expression is modulated by the interaction of HIF-1α, Notch3, and VHL proteins. Targeting the expression of CA9 by targeting upstream regulators could be useful in cancer/stem cell therapy.

Adenovirus E2F1 Overexpression Sensitizes LNCaP and PC3 Prostate Tumor Cells to Radiation In Vivo

PURPOSE We previously showed that E2F1 overexpression radiosensitizes prostate cancer cells in vitro. Here, we demonstrate the radiosensitization efficacy of adenovirus (Ad)-E2F1 infection in growing (orthotopic) LNCaP and (subcutaneous) PC3 nude mice xenograft tumors. METHODS AND MATERIALS Ad-E2F1 was injected intratumorally in LNCaP (3 × 10(8) plaque-forming units [PFU]) and PC3 (5 × 10(8) PFU) tumors treated with or without radiation. LNCaP tumor volumes (TV) were measured by magnetic resonance imaging, caliper were used to measure PC3 tumors, and serum prostate-specific antigen (PSA) levels were determined by enzyme-linked immunosorbent assay. Apoptosis was measured by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling, and key proteins involved in cell death signaling were analyzed by Western blotting. RESULTS Intracellular overexpression of Ad-E2F1 had a significant effect on the regression of TV and reduction of PSA levels relative to that of adenoviral luciferase (Ad-Luc)-infected control. The in vivo regressing effect of Ad-E2F1 on LNCaP tumor growth was significant (PSA, 34 ng/ml; TV, 142 mm(3)) compared to that of Ad-Luc control (PSA, 59 ng/ml; TV, 218 mm(3); p <0.05). This effect was significantly enhanced by radiation therapy (compare: Ad-E2F1+RT/PSA, 16 ng/ml, and TV, 55 mm(3) to Ad-Luc+RT/PSA, 42 ng/ml, and TV, 174 mm(3), respectively; p <0.05). For PC3 tumors, the greatest effect was observed with Ad-E2F1 infection alone; there was little or no effect when radiotherapy (RT) was combined. However, addition of RT enhanced the level of in situ apoptosis in PC3 tumors. Molecularly, addition of Ad-E2F1 in a combination treatment abrogated radiation-induced BCL-2 protein expression and was associated with an increase in activated BAX, and together they caused a potent radiosensitizing effect, irrespective of p53 and androgen receptor functional status. CONCLUSIONS We show here for the first time that ectopic overexpression of E2F1 in vivo, using an adenoviral vector, significantly inhibits orthotopic p53 wild-type LNCaP tumors and subcutaneous p53-null PC3 tumors in nude mice. Furthermore, we demonstrate that E2F1 strongly sensitizes LNCaP tumors to RT. These findings suggest that E2F1 overexpression can sensitize prostate tumor cells in vivo, independent of p53 or androgen receptor status.

Liposomes: Clinical Applications and Potential for Image-Guided Drug Delivery

Liposomes have been extensively studied and are used in the treatment of several diseases. Liposomes improve the therapeutic efficacy by enhancing drug absorption while avoiding or minimizing rapid degradation and side effects, prolonging the biological half-life and reducing toxicity. The unique feature of liposomes is that they are biocompatible and biodegradable lipids, and are inert and non-immunogenic. Liposomes can compartmentalize and solubilize both hydrophilic and hydrophobic materials. All these properties of liposomes and their flexibility for surface modification to add targeting moieties make liposomes more attractive candidates for use as drug delivery vehicles. There are many novel liposomal formulations that are in various stages of development, to enhance therapeutic effectiveness of new and established drugs that are in preclinical and clinical trials. Recent developments in multimodality imaging to better diagnose disease and monitor treatments embarked on using liposomes as diagnostic tool. Conjugating liposomes with different labeling probes enables precise localization of these liposomal formulations using various modalities such as PET, SPECT, and MRI. In this review, we will briefly review the clinical applications of liposomal formulation and their potential imaging properties.

Optical molecular imaging‐guided radiation therapy part 2: Integrated x‐ray and fluorescence molecular tomography

Purpose Differentiating tumor from its surrounding soft tissues is challenging for x‐ray computed tomography (CT). Fluorescence molecular tomography (FMT) can directly localize the internal tumors targeted with specific fluorescent probes. A FMT system was developed and integrated onto a CT‐guided irradiator to improve tumor localization for image‐guided radiation. Methods The FMT system was aligned orthogonal to the cone‐beam CT onboard our previously developed image‐guided small animal arc radiation treatment system (iSMAART). Through rigorous physical registration, the onboard CT provides accurate surface contour which is used to generate three‐dimensional mesh for FMT reconstruction. During FMT experiments, a point laser source perpendicular to the rotating axis was used to excite the internal fluorophores. The normalized optical images from multiple projection angles were adopted for tomographic reconstruction. To investigate the accuracy of the FMT in locating the tumor and recovering its volume, in vivo experiments were conducted on two breast cancer models: MDA‐MB‐231 cancer xenograft on nude mice and 4T1 cancer xenograft on white mice. Both cancer cell lines overexpress the epidermal growth factor receptor (EGFR). A novel fluorescent poly(lactic‐co‐glycolic) acid (PLGA) nanoparticle conjugated with anti‐EGFR was intravenously injected to specifically target the breast cancer cells. Another ex vivo experiment on a mouse bearing a surgically implanted Indocyanine Green‐containing glass tube was conducted, to additionally validate the precision of FMT‐guided radiation therapy. Results The FMT can accurately localize the single‐nodule breast tumors actively targeted with fluorescent nanoparticles with localization error < 0.5 mm calculated between the centers of mass of tumors in FMT and CT. The reconstructed tumor volume in FMT was significantly correlated with that in the iodinated contrast‐enhanced CT (R2 = 0.94, P < 0.001). The FMT was able to guide focal radiation delivery with submillimeter accuracy. Conclusion Using the tumor‐targeting fluorescent probes, the iSMAART with onboard FMT system can accurately differentiate tumors from their surrounding soft tissue, guide precise focal radiation delivery, and potentially assess tumor response in cancer research.

Optical molecular imaging‐guided radiation therapy part 1: Integrated x‐ray and bioluminescence tomography

Purpose X‐ray CT faces challenges in differentiating tumors from surrounding healthy tissues. A bioluminescence tomography (BLT) system which can directly reconstruct the internal luminescent tumors, was developed and integrated with CT system to accurately guide radiation dose delivery. Methods The BLT system, employing a lens‐coupled CCD camera, was physically registered with an onboard cone beam CT system in an image‐guided small animal arc radiation treatment system (iSMAART). The onboard CT provides animal anatomy and accurate surface contour used to construct the three‐dimensional mesh for the BLT reconstruction. Bioluminescence projections were captured from multiple angles, once every 90° rotation. The BLT reconstruction was performed on an orthotopic prostate tumor model to evaluate its robustness and accuracy in locating and delineating bioluminescent tumors. The location and volume of the tumor identified from iodinated contrast CT was used to validate the BLT performance. Phantom experiment was also conducted to confirm the precision of BLT‐guided radiation. Results The BLT was able to accurately locate the bioluminescent tumors with < 0.5 mm error. The tumor volume in BLT was significantly correlated with that in the iodinated contrast CT (R2 = 0.81, P < 0.001). Phantom experiments further validated that BLT can be used to guide radiation with submillimeter accuracy. Conclusion Together with CT, BLT can provide precision radiation guidance and robust tumor volume assessment in small animal cancer research.

Edelfosine Promotes Apoptosis in Androgen Deprived Prostate Tumors by Increasing ATF3 and Inhibiting Androgen Receptor Activity

Edelfosine is a synthetic alkyl-lysophospholipid that possesses significant antitumor activity in several human tumor models. Here, we investigated the effects of edelfosine combined with androgen deprivation (AD) in LNCaP and VCaP human prostate cancer cells. This treatment regimen greatly decreased cell proliferation compared with single agent or AD alone, resulting in higher levels of apoptosis in LNCaP compared with VCaP cells. Edelfosine caused a dose-dependent decrease in AKT activity, but did not affect the expression of total AKT in either cell line. Furthermore, edelfosine treatment inhibited the expression of androgen receptor (AR) and was associated with an increase in activating transcription factor 3 (ATF3) expression levels, a stress response gene and a negative regulator of AR transactivation. ATF3 binds to AR after edelfosine + AD and represses the transcriptional activation of AR as demonstrated by PSA promoter studies. Knockdown of ATF3 using siRNA-ATF3 reversed the inhibition of PSA promoter activity, suggesting that the growth inhibition effect of edelfosine was ATF3 dependent. Moreover, expression of AR variant 7 (ARv7) and TMPRSS2-ERG fusion gene were greatly inhibited after combined treatment with AD and edelfosine in VCaP cells. In vivo experiments using an orthotopic LNCaP model confirmed the antitumor effects of edelfosine + AD over the individual treatments. A significant decrease in tumor volume and PSA levels was observed when edelfosine and AD were combined, compared with edelfosine alone. Edelfosine shows promise in combination with AD for the treatment of prostate cancer patients. Mol Cancer Ther; 15(6); 1353–63. ©2016 AACR.

Plasmonic optical imaging of gold nanorods localization in small animals

Gold nanoparticles (GNP) have been intensively investigated for applications in cancer imaging and therapy. Most imaging studies focused on microscopic imaging. Their potential as optical imaging probes for whole body small animal imaging has rarely been explored. Taking advantage of their surface plasmon resonance (SPR) properties, we aim to develop a noninvasive diffuse optical imaging method to map the distribution of a special type of GNP, gold nanorods (GNR), in small animals. We developed an integrated dual-modality imaging system capable of both x-ray computed tomography (XCT) and diffuse optical tomography (DOT). XCT provides the animal anatomy and contour required for DOT; DOT maps the distribution of GNR in the animal. This SPR enhanced optical imaging (SPROI) technique was investigated using simulation, phantom and mouse experiments. The distribution of GNR at various concentrations (0.1–100 nM, or 3.5 ug/g–3.5 mg/g) was successfully reconstructed from centimeter-scaled volumes. SPROI detected GNR at 18 μg/g concentration in the mouse breast tumor, and is 3 orders more sensitive than x-ray imaging. This study demonstrated the high sensitivity of SPROI in mapping GNR distributions in small animals. It does not require additional imaging tags other than GNR themselves. SPROI can be used to detect tumors targeted by GNR via passive targeting based on enhanced permeability and retention or via active targeting using biologically conjugated ligands.

TH-EF-207A-07: An Integrated X-Ray/bioluminescence Tomography System for Radiation Guidance and Tumor Evaluation

PURPOSE CT is not able to differentiate tumors from surrounding soft tissue. This study is to develop a bioluminescence tomography (BLT) system that is integrated onto our previously developed CT guided small animal arc radiation treatment system (iSMAART) to guide radiation, monitor tumor growth and evaluate therapeutic response. METHODS The BLT system employs a CCD camera coupled with a high speed lens, and is aligned orthogonally to the x-ray beam central axis. The two imaging modalities, CT and BLT, are physically registered through geometrical calibration. The CT anatomy provides an accurate contour of animal surface which is used to construct 3D mesh for BLT reconstruction. Bioluminescence projections are captured from multiple angles, once every 45 degree rotation. The diffusion equation based on analytical Kirchhoff approximation is adopted to model the photon propagation in tissues. A discrete cosine transform based reweighted L1-norm regularization (DCT-re-L1) algorithm is used for BLT reconstruction. Experiments are conducted on a mouse orthotopic prostate tumor model (n=12) to evaluate the BLT performance, in terms of its robustness and accuracy in locating and quantifying the bioluminescent tumor cells. Iodinated contrast agent was injected intravenously to delineate the tumor in CT. The tumor location and volume obtained from CT also serve as a benchmark against BLT. RESULTS With our cutting edge reconstruction algorithm, BLT is able to accurately reconstruct the orthotopic prostate tumors. The tumor center of mass in BLT is within 0.5 mm radial distance of that in CT. The tumor volume in BLT is significantly correlated with that in CT (R2 = 0.81). CONCLUSION The BLT can differentiate, localize and quantify tumors. Together with CT, BLT will provide precision radiation guidance and reliable treatment assessment in preclinical cancer research.

Abstract 1467: The miR-23b/-27b cluster decreases metastasis of aggressive prostate cancer

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Metastasis is responsible for the vast majority of prostate cancer deaths. As such, it is essential to understand the mechanisms driving prostate cancer to this lethal stage. Deregulation of microRNAs is increasingly implicated in the progression and metastasis of prostate and other cancers. MiR-23b and miR-27b, two members of the same miR cluster (miR-23b/-27b), are down-regulated in human metastatic, castration resistant prostate cancer (CRPC) as compared to primary tumors and benign tissue. However, the role of the miR-23b/-27b cluster is not fully understood, particularly in metastatic disease. Interpretation of existing data is complicated by the analysis of the individual effects of miR-23b and miR-27b even though these miRs are co-transcribed and coordinately expressed. The primary goal of our study is to determine the effects of miR-23b/-27b on metastatic processes in vitro and in vivo. Ectopic expression of miR-23b/-27b in two aggressive prostate cancer cell lines decreases migration, invasion and anchorage-independent growth. Conversely, inhibition of miR-23b/-27b using specific antagomirs in relatively indolent prostate cancer cells promotes increased invasion and migration. E-cadherin protein and mRNA levels were inversely related to miR-23b/-27b levels. In contrast, manipulation of miR-23b/-27b levels had no effect on prostate cancer cell proliferation in any of the tested cell lines. These findings suggest that miR-23b/-27b is specifically linked to metastasis suppression. The Rho GTPase, Rac1, is hyperactive in CRPC cell lines and patient samples. Since Rac1 promotes invasion and migration, we investigated the effects of miR-23b/-27b expression and inhibition on Rac1 activity. Ectopic expression of miR-23b/-27b in aggressive prostate cancer cell lines significantly attenuates active Rac1 while having no effect on total Rac1 levels. Conversely, inhibition of miR-23b/-27b in less aggressive prostate cancer cells increased Rac1 activity but not Rac1 levels. We further examined the effects of miR-23b/-27b on prostate cancer metastasis in vivo. Metastatic prostate cancer cells expressing luciferase and miR-23b/-27b or a scrambled control, were injected into the ventral prostates of nude mice. Orthotopic tumor formation and metastases were assessed by bioluminescence imaging. Metastatic tumor burden was greatly decreased in the tumors derived from miR-23b/-27b expressing cells. Taken together, these data demonstrate that expression of miR-23b/-27b exerts metastasis-suppressing effects in vitro and in vivo. The miR-23b/-27b cluster may be a useful biomarker of poor prognosis in addition to having therapeutic potential in advanced, metastatic prostate cancer. Citation Format: Meghan A. Rice, Reema Ishteiwy, Thirupandiyur Udayakumar, Derek Dykxhoorn, Kerry L. Burnstein. The miR-23b/-27b cluster decreases metastasis of aggressive prostate cancer. [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 1467. doi:10.1158/1538-7445.AM2014-1467