Cynthia S. Snyder

MOZ-TIF2-induced acute myeloid leukemia requires the MOZ nucleosome binding motif and TIF2-mediated recruitment of CBP.

The MOZ-TIF2 fusion is associated with acute myeloid leukemia (AML) with inv(8)(p11q13). MOZ is a MYST family histone acetyltransferase (HAT), whereas TIF2 is a nuclear receptor coactivator that associates with CREB binding protein (CBP). Here we demonstrate that MOZ-TIF2 has transforming properties in vitro and causes AML in a murine bone marrow transplant assay. The C2HC nucleosome recognition motif of MOZ is essential for transformation, whereas MOZ HAT activity is dispensable. However, MOZ-TIF2 interaction with CBP through the TIF2 CBP interaction domain (CID) is essential for transformation. These results indicate that nucleosomal targeting by MOZ and recruitment of CBP by TIF2 are critical requirements for MOZ-TIF2 transformation and indicate that MOZ gain of function contributes to leukemogenesis.

Fluorescence-Guided Surgery Allows for More Complete Resection of Pancreatic Cancer, Resulting in Longer Disease-Free Survival Compared with Standard Surgery in Orthotopic Mouse Models

BACKGROUND Negative surgical margins are vital to achieve cure and prolong survival in patients with pancreatic cancer. We inquired if fluorescence-guided surgery (FGS) could improve surgical outcomes and reduce recurrence rates in orthotopic mouse models of human pancreatic cancer. STUDY DESIGN A randomized active-control preclinical trial comparing bright light surgery (BLS) to FGS was used. Orthotopic mouse models of human pancreatic cancer were established using the BxPC-3 pancreatic cancer cell line expressing red fluorescent protein (RFP). Two weeks after orthotopic implantation, tumors were resected with BLS or FGS. Pre- and postoperative images were obtained with the OV-100 Small Animal Imaging System to assess completeness of surgical resection in real time. Postoperatively, noninvasive whole body imaging was done to assess recurrence and follow tumor progression. Six weeks postoperatively, mice were sacrificed to evaluate primary pancreatic and metastatic tumor burden at autopsy. RESULTS A more complete resection of pancreatic cancer was achieved using FGS compared with BLS: 98.9% vs 77.1%, p = 0.005. The majority of mice undergoing BLS (63.2%) had evidence of gross disease with no complete resections; 20% of mice undergoing FGS had complete resection and an additional 75% had only minimal residual disease (p = 0.0001). The mean postoperative tumor burden was significantly less with FGS compared with BLS: 0.08 ± 0.06 mm(2) vs 2.64 ± 0.63 mm(2), p = 0.001. The primary tumor burden at termination was significantly less with FGS compared with BLS: 19.3 ± 5.3 mm(2) vs 6.2 ± 3.6 mm(2), p = 0.048. FGS resulted in significantly longer disease-free survival than BLS (p = 0.02, hazard ratio = 0.39, 95% CI 0.17, 0.88). CONCLUSIONS Surgical outcomes were improved in pancreatic cancer using fluorescence-guidance. This novel approach has significant potential to improve surgical treatment of cancer.

Knockdown of the β1 integrin subunit reduces primary tumor growth and inhibits pancreatic cancer metastasis

To address the role of β1 integrins in pancreatic cancer progression, we stably knocked down β1 integrin subunit expression in human FG‐RFP pancreatic cancer cells using lentiviral‐based RNA interference. We then examined the effects of β1 integrin subunit knockdown on pancreatic cancer cell adhesion, migration and proliferation on tumor microenvironment‐specific extracellular matrix proteins in vitro and on tumor progression in vivo using a clinically relevant fluorescent orthotopic mouse model of pancreatic cancer. Knockdown of the β1 integrin subunit inhibited cell adhesion, migration and proliferation on types I and IV collagen, fibronectin and laminin in vitro. In vivo, knockdown of the β1 integrin subunit reduced primary tumor growth by 50% and completely inhibited spontaneously occurring metastasis. These observations indicate a critical role for the β1 integrin subunit in pancreatic cancer progression and metastasis in particular. Our results suggest the β1 integrin subunit as a therapeutic target for the treatment of pancreatic cancer, especially in the adjuvant setting to prevent metastasis of this highly aggressive cancer.

Fluorescence-guided surgery of human colon cancer increases complete resection resulting in cures in an orthotopic nude mouse model

BACKGROUND We inquired if fluorescence-guided surgery (FGS) could improve surgical outcomes in fluorescent orthotopic nude mouse models of human colon cancer. METHODS We established fluorescent orthotopic mouse models of human colon cancer expressing a fluorescent protein. Tumors were resected under bright light surgery (BLS) or FGS. Pre- and post-operative images with the OV-100 Small Animal Imaging System (Olympus Corp, Tokyo Japan) were obtained to assess the extent of surgical resection. RESULTS All mice with primary tumor that had undergone FGS had complete resection compared with 58% of mice in the BLS group (P = 0.001). FGS resulted in decreased recurrence compared with BLS (33% versus 62%, P = 0.049) and lengthened disease-free median survival from 9 to >36 wk. The median overall survival increased from 16 wk in the BLS group to 31 weeks in the FGS group. FGS resulted in a cure in 67% of mice (alive without evidence of tumor at >6 mo after surgery) compared with only 37% of mice that underwent BLS (P = 0.049). CONCLUSIONS Surgical outcomes in orthotopic nude mouse models of human colon cancer were significantly improved with FGS. The present study can be translated to the clinic by various effective methods of fluorescently labeling tumors.

An LED light source and novel fluorophore combinations improve fluorescence laparoscopic detection of metastatic pancreatic cancer in orthotopic mouse models.

BACKGROUND The aim of this study was to improve fluorescence laparoscopy of pancreatic cancer in an orthotopic mouse model with the use of a light-emitting diode (LED) light source and optimal fluorophore combinations. STUDY DESIGN Human pancreatic cancer models were established with fluorescent FG-RFP, MiaPaca2-GFP, BxPC-3-RFP, and BxPC-3 cancer cells implanted in 6-week-old female athymic mice. Two weeks postimplantation, diagnostic laparoscopy was performed with a Stryker L9000 LED light source or a Stryker X8000 xenon light source 24 hours after tail-vein injection of CEA antibodies conjugated with Alexa 488 or Alexa 555. Cancer lesions were detected and localized under each light mode. Intravital images were also obtained with the OV-100 Olympus and Maestro CRI Small Animal Imaging Systems, serving as a positive control. Tumors were collected for histologic analysis. RESULTS Fluorescence laparoscopy with a 495-nm emission filter and an LED light source enabled real-time visualization of the fluorescence-labeled tumor deposits in the peritoneal cavity. The simultaneous use of different fluorophores (Alexa 488 and Alexa 555), conjugated to antibodies, brightened the fluorescence signal, enhancing detection of submillimeter lesions without compromising background illumination. Adjustments to the LED light source permitted simultaneous detection of tumor lesions of different fluorescent colors and surrounding structures with minimal autofluorescence. CONCLUSIONS Using an LED light source with adjustments to the red, blue, and green wavelengths, it is possible to simultaneously identify tumor metastases expressing fluorescent proteins of different wavelengths, which greatly enhanced the signal without compromising background illumination. Development of this fluorescence laparoscopy technology for clinical use can improve staging and resection of pancreatic cancer.

Tumor-specific fluorescence antibody imaging enables accurate staging laparoscopy in an orthotopic model of pancreatic cancer.

BACKGROUND/AIMS Laparoscopy is important in staging pancreatic cancer, but false negatives remain problematic. Making tumors fluorescent has the potential to improve the accuracy of staging laparoscopy. METHODOLOGY Orthotopic and carcinomatosis models of pancreatic cancer were established with BxPC-3 human pancreatic cancer cells in nude mice. Alexa488-antiCEA conjugates were injected via tail vein 24 hours prior to laparoscopy. Mice were examined under bright field laparoscopic (BL) and fluorescence laparoscopic (FL) modes. Outcomes measured included time to identification of primary tumor for the orthotopic model and number of metastases identified within 2 minutes for the carcinomatosis model. RESULTS FL enabled more rapid and accurate identification and localization of primary tumors and metastases than BL. Using BL took statistically significantly longer time than FL (p<0.0001, fold change and 95% CI for BL vs. FL: 8.12 (4.54,14.52)). More metastatic lesions were detected and localized under FL compared to BL and with greater accuracy, with sensitivities of 96% vs. 40%, respectively, when compared to control. FL was sensitive enough to detect metastatic lesions <1mm. CONCLUSIONS The use of fluorescence laparoscopy with tumors labeled with fluorophore-conjugated anti-CEA antibody permits rapid detection and accurate localization of primary and metastatic pancreatic cancer in an orthotopic model. The results of the present report demonstrate the future clinical potential of fluorescence laparoscopy.

Development of the Transgenic Cyan Fluorescent Protein (CFP)-Expressing Nude Mouse for ''Technicolor'' Cancer Imaging

A major goal for in vivo biology is to develop models which can express multiple colors of fluorescent proteins in order to image many processes simultaneously in real time. Towards this goal, the cyan fluorescent protein (CFP) nude mouse was developed by crossing non‐transgenic nude mice with the transgenic CK/ECFP mouse in which the β‐actin promoter drives expression of CFP in almost all tissues. In crosses between nu/nu CFP male mice and nu/+ CFP female mice, approximately 50% of the embryos fluoresced blue. In the CFP nude mice, the pancreas and reproductive organs displayed the strongest fluorescent signals of all internal organs which vary in intensity. Orthotopic implantation of XPA‐1 human pancreatic cancer cells expressing red fluorescent protein (RFP); or green fluorescent protein (GFP) in the nucleus and RFP in the cytoplasm, was performed in female nude CFP mice. Color‐coded fluorescence imaging of these human pancreatic cancer cells implanted into the bright blue fluorescent pancreas of the CFP nude mouse afforded novel insight into the interaction of the pancreatic tumor and the normal pancreas, in particular the strong desmoplastic reaction of the tumor. The naturally enhanced blue fluorescence of the pancreas in the CFP mouse serves as an ideal background for color‐coded imaging of the interaction of implanted cancer cells and the host. The CFP nude mouse will provide unique understanding of the critical interplay between the cancer cells and their microenvironment. J. Cell. Biochem. 107: 328–334, 2009.

Complementarity of ultrasound and fluorescence imaging in an orthotopic mouse model of pancreatic cancer

BackgroundPancreatic cancer is a devastating disease characterized by dismal 5-year survival rates and limited treatment options. In an effort to provide useful models for preclinical evaluation of new experimental therapeutics, we and others have developed orthotopic mouse models of pancreatic cancer. The utility of these models for pre-clinical testing is dependent upon quantitative, noninvasive methods for monitoring in vivo tumor progression in real time. Toward this goal, we performed whole-body fluorescence imaging and ultrasound imaging to evaluate and to compare these noninvasive imaging modalities for assessing tumor burden and tumor progression in an orthotopic mouse model of pancreatic cancer.MethodsThe human pancreatic cancer cell line XPA-1, engineered for stable, high-level expression of red fluorescent protein (RFP), was implanted into the pancreas of nude mice using orthotopic implantation. The tumors were allowed to grow over a period of one to several weeks during which time the mice were imaged using both fluorescence imaging and ultrasound imaging to measure tumor burden and to monitor tumor growth.ResultsWhole-body fluorescence imaging and ultrasound imaging both allowed for the visualization and measurement of orthotopic pancreatic tumor implants in vivo. The imaging sessions were well-tolerated by the mice and yielded data which correlated well in the quantitative assessment of tumor burden. Whole-body fluorescence and two-dimensional ultrasound imaging showed a strong correlation for measurement of tumor size over a range of tumor sizes (R2 = 0.6627, P = 0.003 for an exposure time of 67 msec and R2 = 0.6553, P = 0.003 for an exposure time of 120 msec).ConclusionOur findings suggest a complementary role for fluorescence imaging and ultrasound imaging in assessing tumor burden and tumor progression in orthotopic mouse models of human cancer.

Normal hematopoiesis after conditional targeting of RXRα in murine hematopoietic stem/progenitor cells

Because of the retinoic acid receptor‐α (RARα) gene’s involvement in acute promyelocytic leukemia, the important role of RARs in hematopoiesis is now well established. However, relatively few studies of hematopoiesis have focused on the role of the retinoid X receptors (RXRs), the obligate heterodimeric partners of the RARs. We sought to establish whether conditional targeting of RXRα in early hematopoietic progenitors, ideally to the level of the hematopoietic stem cell (HSC), would compromise hematopoiesis. For hematopoietic targeting of RXRα, we characterized IFN‐inducible MxCre mice for use in studying the role of RXRα in hematopoiesis. We established that MxCre executes recombination of loxP‐flanked RXRα in hematopoietic progenitors immunophenotypically enriched for HSC, leading to widespread and sustained targeting of RXRα in hematopoietic cells. However, we found no evidence of hematologic compromise in mice lacking RXRα, suggesting that RXRα is dispensable for normal murine hematopoiesis. Nonetheless, RXRα null bone marrow cells cultured in methylcellulose form colonies more efficiently than bone marrow cells obtained from control mice. This result suggests that although RXRα is not required for murine hematopoiesis, there may be hematopoietic signaling pathways that respond selectively to RXRα or settings in which combined expression of RXR (α, β, and γ) is limiting.

Submillimeter-Resolution Fluorescence Laparoscopy of Pancreatic Cancer in a Carcinomatosis Mouse Model Visualizes Metastases Not Seen with Standard Laparoscopy

BACKGROUND Staging laparoscopy can visualize peritoneal and liver metastases in pancreatic cancer otherwise undetectable by preoperative imaging. However, false-negative rates may be as high as 18%-26%. The aim of the present study was to improve detection of metastatic pancreatic cancer with the use of fluorescence laparoscopy (FL) in a nude-mouse model with the tumors expressing green fluorescent protein (GFP). METHODS The carcinomatosis mouse model of human pancreatic cancer was established by intraperitoneal injections of green fluorescent protein-expressing MiaPaca-2 human pancreatic cancer cells into 6-week-old female athymic mice. Two weeks later, mice underwent diagnostic laparoscopy. Laparoscopy was performed first under standard brightfield lighting, followed by fluorescent lighting. The number of metastatic foci identified within the four quadrants of the peritoneal cavity was recorded. After laparoscopy, the animals were sacrificed, opened, and imaged with the OV-100 Small Animal Imaging system as a positive control to identify metastasis. Tumors were collected and processed for histologic review. RESULTS FL enabled visualization of pancreatic cancer metastatic foci not visualized with standard brightfield laparoscopy (BL). Under FL, in 1 representative mouse, 26 separate micrometastatic lesions were identified. In contrast, only very large tumors were seen using BL. Use of the OV-100 images, as positive controls, confirmed the presence of tumor foci. FL thus allowed identification and exact localization of submillimeter tumor foci. Such small-sized tumor foci were not distinguished from surrounding tissue under BL. All malignant lesions were histologically confirmed. CONCLUSIONS The use of FL enables the identification of tumor foci that cannot be seen with standard laparoscopy. The technology described in this report has important potential for the clinical development of FL.