Spatial-temporal FUCCI imaging of each cell in a tumor demonstrates locational dependence of cell cycle dynamics and chemoresponsiveness

The phase of the cell cycle can determine whether a cancer cell can respond to a given drug. We report here on the results of monitoring of real-time cell cycle dynamics of cancer cells throughout a live tumor intravitally using a fluorescence ubiquitination cell cycle indicator (FUCCI) before, during, and after chemotherapy. In nascent tumors in nude mice, approximately 30% of the cells in the center of the tumor are in G₀/G₁ and 70% in S/G₂/M. In contrast, approximately 90% of cancer cells in the center and 80% of total cells of an established tumor are in G₀/G₁ phase. Similarly, approximately 75% of cancer cells far from (> 100 µm) tumor blood vessels of an established tumor are in G₀/G₁. Longitudinal real-time imaging demonstrated that cytotoxic agents killed only proliferating cancer cells at the surface and, in contrast, had little effect on quiescent cancer cells, which are the vast majority of an established tumor. Moreover, resistant quiescent cancer cells restarted cycling after the cessation of chemotherapy. Our results suggest why most drugs currently in clinical use, which target cancer cells in S/G₂/M, are mostly ineffective on solid tumors. The results also suggest that drugs that target quiescent cancer cells are urgently needed.

Imaging UVC-induced DNA damage response in models of minimal cancer

We have previously demonstrated that the ultraviolet (UV) light is effective against a variety of cancer cells in vivo as well as in vitro. In the present report, we imaged the DNA damage repair response of minimal cancer after UVC irradiation. DNA-damage repair response to UV irradiation was imaged on tumors growing in 3D culture and in superficial tumors grown in vivo. UV-induced DNA damage repair was imaged with GFP fused to the DNA damage response (DDR)-related chromatin-binding protein 53BP1 in MiaPaCa-2 human pancreatic cancer cells. Three-dimensional Gelfoam® histocultures and confocal imaging enabled 53BP1-GFP nuclear foci to be observed within 1 h after UVC irradiation, indicating the onset of DNA damage repair response. A clonogenic assay showed that UVC inhibited MiaPaCa-2 cell proliferation in a dose-dependent manner, while UVA and UVB showed little effect on cell proliferation. Induction of UV-induced 53BP1-GFP focus formation was limited up to a depth of 40 µm in 3D-culture of MiaPaCa-2 cells. The MiaPaCa-2 cells irradiated by UVC light in a skin-flap mouse model had a significant decrease of tumor growth compared to untreated controls. Our results also demonstrate that 53BP1-GFP is an imageable marker of UV-induced DNA damage repair response of minimal cancer and that UVC is a useful tool for the treatment of residual cancer since UVC can kill superficial cancer cells without damage to deep tissue.

Successful fluorescence-guided surgery on human colon cancer patient-derived orthotopic xenograft mouse models using a fluorophore-conjugated anti-CEA antibody and a portable imaging system

BACKGROUND

Fluorescence-guided surgery (FGS) can enable successful cancer surgery where bright-light surgery often cannot. There are three important issues for FGS going forward toward the clinic: (a) proper tumor labeling, (b) a simple portable imaging system for the operating room, and (c) patient-like mouse models in which to develop the technology. The present report addresses all three.

MATERIALS AND METHODS

Patient colon tumors were initially established subcutaneously in nonobese diabetic (NOD)/severe combined immune deficiency (SCID) mice immediately after surgery. The tumors were then harvested from NOD/SCID mice and passed orthotopically in nude mice to make patient-derived orthotopic xenograft (PDOX) models. Eight weeks after orthotopic implantation, a monoclonal anti-carcinoembryonic antigen (CEA) antibody conjugated with AlexaFluor 488 (Molecular Probes Inc., Eugene, OR) was delivered to the PDOX models as a single intravenous dose 24 hours before laparotomy. A hand-held portable fluorescence imaging device was used.

RESULTS

The primary tumor was clearly visible at laparotomy with the portable fluorescence imaging system. Frozen section microscopy of the resected specimen demonstrated that the anti-CEA antibody selectively labeled cancer cells in the colon cancer PDOX. The tumor was completely resected under fluorescence navigation. Histologic evaluation of the resected specimen demonstrated that cancer cells were not present in the margins, indicating successful tumor resection. The FGS animals remained tumor free for over 6 months.

CONCLUSIONS

The results of the present report indicate that FGS using a fluorophore-conjugated anti-CEA antibody and portable imaging system improves efficacy of resection for CEA-positive colorectal cancer. These data provide the basis for clinical trials.

Invading cancer cells are predominantly in G0/G1 resulting in chemoresistance demonstrated by real-time FUCCI imaging

Invasive cancer cells are a critical target in order to prevent metastasis. In the present report, we demonstrate real-time visualization of cell cycle kinetics of invading cancer cells in 3-dimensional (3D) Gelfoam® histoculture, which is in vivo-like. A fluorescence ubiquitination cell cycle indicator (FUCCI) whereby G0/G1 cells express a red fluorescent protein and S/G2/M cells express a green fluorescent protein was used to determine the cell cycle position of invading and non-invading cells. With FUCCI 3D confocal imaging, we observed that cancer cells in G0/G1 phase in Gelfoam® histoculture migrated more rapidly and further than cancer cells in S/G2/M phases. Cancer cells ceased migrating when they entered S/G2/M phases and restarted migrating after cell division when the cells re-entered G0/G1. Migrating cancer cells also were resistant to cytotoxic chemotherapy, since they were preponderantly in G0/G1, where cytotoxic chemotherapy is not effective. The results of the present report suggest that novel therapy targeting G0/G1 cancer cells should be developed to prevent metastasis.

Hand-held high-resolution fluorescence imaging system for fluorescence-guided surgery of patient and cell-line pancreatic tumors growing orthotopically in nude mice

BACKGROUND

In this study, we investigated the advantages of fluorescence-guided surgery (FGS) in mice of a portable hand-sized imaging system compared with a large fluorescence imaging system or a long-working-distance fluorescence microscope.

METHODS

Mouse models of human pancreatic cancer for FGS included the following: (1) MiaPaCa-2-expressing green fluorescent protein, (2) BxPC3 labeled with Alexa Fluor 488-conjucated anti-carcinoembryonic antigen (CEA) antibody, and (3) patient-derived orthotopic xenograft (PDOX) labeled with Alexa Fluor 488-conjugated anti-carbohydrate antigen 19-9 antibody.

RESULTS

Each device could clearly detect the primary MiaPaCa-2-green fluorescent protein tumor and any residual tumor after FGS. In the BxPC3 model labeled with Alexa Fluor 488-conjugated anti-CEA, each device could detect the primary tumor, but the MVX10 could not clearly detect the residual tumor remaining after FGS whereas the other devices could. In the PDOX model labeled with Alexa Fluor 488-conjugated anti-carbohydrate antigen 19-9, only the portable hand-held device could distinguish the residual tumor from the background, and complete resection of the residual tumor was achieved under fluorescence navigation.

CONCLUSIONS

The results described in the present report suggest that the hand-held mobile imaging system can be applied to the clinic for FGS because of its convenient size and high sensitivity which should help make FGS widely used.

Abstract B13: Salmonella typhimurium A1-R targets human pancreatic cancer patient-derived orthotopic xenograft (PDOX) in nude mice

The aim of this study is to determine the efficacy of tumor-targeting Salmonella typhimurium A1-R (A1-R) on pancreatic cancer patient-derived orthotopic xenografts (PDOX) in nude mice compared to standard chemotherapy. The pancreatic cancer PDOX was orthotopically implanted in transgenic nude red fluorescent protein (RFP) mice in order that the PDOX acquire RFP-expressing stroma for the purposes of imaging the tumor in non-colored nude mice in order to non-invasively image tumor growth and drug response. The nude mice were treated with A1-R or standard chemotherapy including gemcitabine (GEM). Histopathological response to treatment was defined according to Evans's criteria. A1-R treatment significantly reduced tumor weight as well as tumor fluorescence area compared to untreated control (p=0.011), with comparable efficacy to GEM, CDDP and 5-FU. A1-R had the highest efficacy compared to any of the chemotherapy drugs tested based on Evan's histological response criteria. Salmonella typhimurium A1-R was effective on a human pancreatic PDOX and is a promising therapy for this disease in the clinic.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B13.

Citation Format: Yukihiko Hiroshima, Ming Zhao, Ali Maawy, Yong Zhang, Matthew H.G. Katz, Jason B. Fleming, Fuminari Uehara, Shinji Miwa, Shuya Yano, Masashi Momiyama, Atsushi Suetsugu, Takashi Chishima, Kuniya Tanaka, Michael Bouvet, Itaru Endo, Robert M. Hoffman. Salmonella typhimurium A1-R targets human pancreatic cancer patient-derived orthotopic xenograft (PDOX) in nude mice. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B13.

Comparison of efficacy of Salmonella typhimurium A1-R and chemotherapy on stem-like and non-stem human pancreatic cancer cells

The XPA1 human pancreatic cancer cell line is dimorphic, with spindle stem-like cells and round non-stem cells. We report here the in vitro IC 50 values of stem-like and non-stem XPA1 human pancreatic cells cells for: (1) 5-fluorouracil (5-FU), (2) cisplatinum (CDDP), (3) gemcitabine (GEM), and (4) tumor-targeting Salmonella typhimurium A1-R (A1-R). IC 50 values of stem-like XPA1 cells were significantly higher than those of non-stem XPA1 cells for 5-FU (P = 0.007) and CDDP (P = 0.012). In contrast, there was no difference between the efficacy of A1-R on stem-like and non-stem XPA1 cells. In vivo, 5-FU and A1-R significantly reduced the tumor weight of non-stem XPA1 cells (5-FU; P = 0.028; A1-R; P = 0.011). In contrast, only A1-R significantly reduced tumor weight of stem-like XPA1 cells (P = 0.012). The combination A1-R with 5-FU improved the antitumor efficacy compared with 5-FU monotherapy on the stem-like cells (P = 0.004). The results of the present report indicate A1-R is a promising therapy for chemo-resistant pancreatic cancer stem-like cells.

Color-coded imaging of spontaneous vessel anastomosis in vivo

Vessel anastomosis is important in tumor angiogenesis as well as for vascularization therapy for ischemia and other diseases. We report here the development of a color-coded imaging model that can visualize the anastomosis between blood vessels of red fluorescent protein (RFP)-expressing vessels in vascularized Gelfoam® previously transplanted into RFP transgenic mice and then re-transplanted into nestin-driven green fluorescent protein (ND-GFP) mice where nascent blood vessels express GFP. Gelfoam® was initially transplanted subcutaneously in the flank of transgenic RFP nude mice. Skin flaps were made at 14 days after transplantation of Gelfoam® to allow observation of vascularization of the Gelfoam® using confocal fluorescence imaging. The implanted Gelfoam® became highly vascularized with RFP vessels. Fourteen days after transplantation into RFP transgenic nude mice, the Gelfoam® was removed and re-transplanted into the subcutis on the flank of ND-GFP transgenic nude mice in which nascent blood vessels express GFP. Skin flaps were made and anastomosis between the GFP-expressing nascent blood vessels of ND-GFP transgenic nude mice and RFP blood vessels in the Gelfoam® was imaged 14 and 21 days after re-transplantation. The results presented in this report indicate a possible mechanism for tumor angiogenesis and suggest a new paradigm of therapeutic revascularization of ischemic organs requiring new blood vessels and in other diseases.

Nestin-Expressing Stem Cells Promote Nerve Growth in Long-Term 3-Dimensional Gelfoam®-Supported Histoculture

We have previously reported that hair follicles contain multipotent stem cells which express nestin. The nestin-expressing cells form the hair follicle sensory nerve. In vitro, the nestin-expressing hair follicle cells can differentiate into neurons, Schwann cells, and other cell types. In the present study, the sciatic nerve was excised from transgenic mice in which the nestin promoter drives green fluorescent protein (ND-GFP mice). The ND-GFP cells of the sciatic nerve were also found to be multipotent as the ND-GFP cells in the hair follicle. When the ND-GFP cells in the mouse sciatic nerve cultured on Gelfoam® and were imaged by confocal microscopy, they were observed forming fibers extending the nerve. The fibers consisted of ND-GFP-expressing spindle cells, which co-expressed the neuron marker β-III tubulin, the immature Schwann-cell marker p75^NTR and TrkB which is associated with neurons. The fibers also contain nestin-negative spherical cells expressing GFAP, a Schwann-cell marker. The β-III tubulin-positive fibers had growth cones on their tips expressing F-actin, indicating they are growing axons. When the sciatic nerve from mice ubiquitously expressing red fluorescent protein (RFP) was co-cultured on Gelfoam® with the sciatic nerve from ND-GFP transgenic mice, the interaction of nerves was observed. Proliferating nestin-expressing cells in the injured sciatic nerve were also observed in vivo. Nestin-expressing cells were also observed in posterior nerves but not in the spinal cord itself, when placed in 3-D Gelfoam® culture. The results of the present report suggest a critical function of nestin-expressing cells in peripheral nerve growth and regeneration.

Effect of salmonella typhimurium A1-R on quiescent cancer cells that do not respond to standard chemotherapy

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Background: Quiescent cancer cells are a major impediment to treating solid cancer with chemotherapy, since in most tumors the majority of the cells are quiescent. Methods: The cell-cycle phase of each human MKN45 gastric cancer cell was imaged using a fluorescence ubiquitination cell cycle indicator (FUCCI). With FUCCI, quiescent cancer cells express mKusabira-Orange fluorescent protein (red) and proliferating cells express mAzami-Green fluorescent protein (green). FUCCI-labeled cancer cells in tumor spheres and subcutaneous tumor in nude mice were treated with Salmonella typhimurium A1-R. Results: Time-lapse confocal imaging showed that cancer cells in tumor spheres in serum-free culture become and remained quiescent. S. typhimurium A1-R infected and killed quiescent cancer cells in tumor spheres. In contrast, cytotoxic agents did not kill the quiescent cancer cells in the tumor spheres. S. typhimurium A1-R targeting of FUCCI-expressing subcutaneous tumors growing in nude mice resulted in the killing of quiescent cancer cells resistant to cytotoxic agents. Conclusions: S. typhimurium A1-R can kill quiescent cancer cells which suggests a new therapeutic paradigm potentially more effective than current therapeutics which are ineffective against quiescent cancer cells.

Effect of dormant cancer cells on angiogenesis after resisting chemotherapy

e13577

Background: Dormant cancer cells are a significant problem in clinical cancer as they are usually chemoresistant and can give rise to recurrence years after treatment. Methods: Dormant cancer cells were identified with a fluorescence ubiquitination cell cycle indicator (FUCCI) and confocal microscopy. FUCCI-expressing xenografts were established from MKN45 gastric cancer cells. Results: Within 7 days after implantation in nude mice, FUCCI-expressing tumors contained a mixture of cancer cells in G0/G1 and S/G2/M phases. Cancer cells in G0/G1 phase survived and become dormant after treatment with cytotoxic agents. As the tumors grew, proliferating cells were only found at the surface. Chemotherapy killed only the proliferating cancer cells at the surface and had little effect on the majority of dormant cancer cells in the tumor center. Furthermore, we investigated tumor chemoresistance using nestin-driven green fluorescent protein (GFP) transgenic mice that have GFP-expressing nascent tumor vessels. Chemotherapy-treated tumors had much more and deeper tumor vessels than control tumors. Conclusions: These results suggest that dormant cancer cells may protect themselves by inducing angiogenesis.

Abstract 585: Salmonella typhimurium A1-R targets quiescent cancer cells

Quiescent cancer cells are resistant to cytotoxic agents which target only proliferating cancer cells. The cell-cycle phase of each cancer cell in real time was imaged using a fluorescence ubiquitination cell cycle indicator (FUCCI). With FUCCI, quiescent cancer cells express mKusabira-Orange fluorescent protein (red) and proliferating cells express mAzami-Green fluorescent protein (green). FUCCI-labeled cancer cells in monolayer culture and tumor spheres were treated with Salmonella typhimurium A1-R. Time-lapse confocal imaging showed that A1-R encircled and invaded quiescent cancer cells in monolayer culture, thereby eliminating them. Cancer cells in tumor spheres in serum-free culture become and remain quiescent. A1-R infected and killed quiescent cancer cells in tumor spheres. In contrast, cytotoxic agents did not kill quiescent cancer cells in tumor spheres. A1-R infection of FUCCI-expressing subcutaneous tumors growing in nude mice resulted in killing quiescent cancer cells resistant to cytotoxic agents. This study demonstrates that A1-R can kill quiescent cancer cells and suggests a new therapeutic paradigm potentially more effective than current therapeutics which are ineffective against quiescent cancer cells.

Citation Format: Shuya Yano, Yong Zhang, Fuminari Uehara, Yukihiko Hiroshima, Shinji Miwa, Robert M. Hoffman, Ming Zhao. Salmonella typhimurium A1-R targets quiescent cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 585. doi:10.1158/1538-7445.AM2013-585

Abstract 1756: Intravital imaging of cancer cell cycle in the bone marrow

The cell cycle of cancer cells in the bone marrow was imaged using a fluorescence ubiquitination cell cycle indicator (FUCCI). With FUCCI, quiescent cancer cells express mKusabira-Orange fluorescent protein (red) and proliferating cells express mAzami-Green fluorescent protein (green). FUCCI-expressing cancer cells were injected into the bone marrow of tibia of mice. At the early stage after injection (7 days), approximately 90% of the cells were in G0/G1. In contrast, at late stage after injection (28 days more), in the endosteal lesion, approximately 80% of the cancer cells were in S/G2/M phases and in the central zone, approximately 75% of cancer cells were in G0/G1. Thus, cancer-cell location and time in the bone marrow determines cell cycle position and possibly dormancy. Thus, quiescent (dormant) cancer cells in the bone marrow need to be targeted as well as proliferating cancer cells, which is a significant current challenge.

Citation Format: Shuya Yano, Shinji Miwa, Yasunori Tome, Fuminari Uehara, Michelle Digman, Enrico Gratton, Robert M. Hoffman. Intravital imaging of cancer cell cycle in the bone marrow. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1756. doi:10.1158/1538-7445.AM2013-1756

Abstract 1754: Dormant cancer cells are resistant to conventional therapies and induce tumor vessels after chemotherapy

Dormant cancer cells were visualized with a fluorescence ubiquitination cell cycle indicator (FUCCI). FUCCI-expressing xenografts were established from MKN45 gastric cancer cells. Within 7 days after inoculation, FUCCI-expressing nascent tumors contained a mixture of cancer cells in G0/G1 phase and in S/G2/M phases. Nascent tumors treated with cyto-toxic agents showed that cancer cells in G0/G1 phase can survive and become dormant. As tumors grew, the proliferating area was only at the surface and the dormant area predominated. Chemotherapy killed only the minority population of proliferating cancer cells at the surface and had little effect on the majority of dormant cancer cells in the tumor center. Furthermore, we investigated tumor chemoresistance using nestin-driven GFP transgenic mice that have GFP-expressing nascent tumor vessels. Chemotherapy-treated tumors had much more and deeper tumor vessels than control tumors, suggesting that dormant cancer cells may protect themselves by inducing tumor vessels. This report suggests that dormant cancer cells play a large role in drug resistance.

Citation Format: Shuya Yano, Sumiyuki Mii, Yasunori Tome, Yukihiko Hiroshima, Fuminari Uehara, Shinji Miwa, Toshiyoshi Fujiwara, Robert M. Hoffman. Dormant cancer cells are resistant to conventional therapies and induce tumor vessels after chemotherapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1754. doi:10.1158/1538-7445.AM2013-1754

Abstract 1755: Invasive cancer cells are mostly in the G0/G1 phase of the cell cycle

Invasive cancer cells are a critical target for chemotherapy. However, the cell cycle phase of invasive cancer cells is poorly understood. Cancer cells were cultured in 3D Gelfoam® culture where they have in vivo-like cell cycle kinetics. Cancer cell-cycle kinetics were visualized using a fluorescence ubiquitination cell cycle indicator (FUCCI), whereby quiescent cancer cells express mKusabira-Orange fluorescent protein (red) and proliferating cells express mAzami-Green fluorescent protein (green). Real-time imaging demonstrated that cancer cells in the G0/G1 phase are invasive and disseminate in Gelfoam histoculture. Moreover, in vivo, FUCCI-expressing cancer cells were in G0/G1 phase when they metastasized to the liver. Disseminated cancer cells in the peritoneal cavity were also in G0/G1 phase. Most drugs currently in use target cells in S/G2/M are therefore may not be able to target invasive cancer cells. Color-coded cell-cycle imaging of cancer cell invasion should provide a novel platform for the rapid screening of candidate therapeutic agents against quiescent, invasive cancer cells.

Citation Format: Shuya Yano, Sumiyuki Mii, Yasunori Tome, Yukihiko Hiroshima, Fuminari Uehara, Shinji Miwa, Toshiyoshi Fujiwara, Robert M. Hoffman. Invasive cancer cells are mostly in the G0/G1 phase of the cell cycle. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1755. doi:10.1158/1538-7445.AM2013-1755

Single cell time-lapse imaging of focus formation by the DNA damage-response protein 53BP1 after UVC irradiation of human pancreatic cancer cells

We have previously demonstrated that ultraviolet (UV) light treatment is effective against various types of cancer cells expressing fluorescent proteins. In order to further understand the efficacy of UV treatment of cancer cells, we determined the kinetics of focus formation by imaging of a DNA damage-response (DDR) protein after UVC irradiation of human pancreatic cancer cells. A fusion protein consisting of the DDR protein 53BP1 and green fluorescent protein (GFP) (GFP-53BP1) was used as a live-cell imaging marker for cellular response after UVC irradiation. GFP-53BP1 foci were observed after UVC irradiation of MiaPaCa-2 human pancreatic cancer cells. During live-cell imaging, GFP-53BP1 foci were observed in the cells within 15 min after UVC irradiation, and some of the foci remained stable for at least three hours. GFP-53BP1 focus formation was observed in the pancreatic-cancer cells irradiated by 25-200 J/m(2) UVC. Our results indicate that an early response to DNA damage caused by UVC irradiation can be visualized by increased GFP-53BP1 focus formation by pancreatic cancer cells.

A color-coded imaging model of the interaction of αv integrin-GFP expressed in osteosarcoma cells and RFP expressing blood vessels in Gelfoam® vascularized in vivo

The integrin family of proteins has been shown to be involved in the malignant behavior of cells. We report here development of a color-coded imaging model that can visualize the interaction between αv integrin linked to green fluorescent protein (GFP) in osteosarcoma cells and blood vessels in Gelfoam® vascularized after implantation in red fluorescent protein (RFP) transgenic nude mice. Human 143B osteosarcoma cells expressing αv integrin-GFP were generated by transfection with an αv integrin-GFP vector. Gelfoam® (5×5 mm) was transplanted subcutaneously in transgenic RFP nude mice. The implanted Gelfoam® became highly vascularized with RFP vessels within 14 days. Skin flaps were made at days 7, 14, 21, 28 after transplantation of Gelfoam® for observing vascularization of the Gelfoam® using fluorescence imaging. Gelfoam® is a useful tool to observe angiogenesis in vivo. 143B cells (5 × 10(5)) expressing αv integrin-GFP were injected into the Gelfoam® seven days after transplantation of Gelfoam®. Seven days after cancer-cell injection, cancer cells and blood vessels were observed in the Gelfoam® by color-coded confocal microscopy via the skin flap. The 143B cells expressing αv integrin-GFP proliferated into the Gelfoam®, which contained RFP-expressing blood vessels. Strong expression of αv integrin-GFP in 143B cells was observed near RFP vessels in the Gelfoam®. The observation of the behavior of αv integrin-GFP and blood vessels will allow further understanding of the role of αv integrin in cancer cells.

Abstract A92: Killing quiescent cancer cells in vitro and in vivo with tumor targeting Salmonella typhimurium A1-R

Quiescent cancer cells are resistant to cytotoxic agents which target only proliferating cancer cells. Cancer cells were imaged to indicate the cell-cycle phase of each cancer cell in real time in solid tumors growing in vivo as well for cancer cells as in vitro using a fluorescence ubiquitination cell cycle indicator (FUCCI). With FUCCI, quiescent cancer cells express mKusabira-Orange fluorescent protein (red) and proliferating cells express mAzami-Green fluorescent protein (green). FUCCI-labeled cancer cells in monolayer culture and tumor spheres were treated with Salmonella typhimurium A1-R. Time-lapse confocal imaging showed that A1-R encircled and invaded quiescent cancer cells in monlayer culture, thereby eliminating them. Cancer cells in tumor spheres in serum-free culture become and remain quiescent. A1-R infected and killed quiescent cancer cells in tumor spheres. In contrast, cytotoxic agents did not kill quiescent cancer cells in tumor spheres. A1-R infection of FUCCI-expressing subcutaneous tumors growing in nude mice resulted in killing quiescent cancer cells resistant to cytotoxic agents. This study demonstrates that A1-R can kill quiescent cancer cells and suggest a new therapeutic paradigm potentially more effective than current therapy of cancer.

Citation Format: Shuya Yano, Yong Zhang, Fuminari Uehara, Yukihiko Hiroshima, Shinji Miwa, Robert M. Hoffman, Ming Zhao. Killing quiescent cancer cells in vitro and in vivo with tumor targeting Salmonella typhimurium A1-R. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A92.

Photoreceptor cell differentiation in retinoblastoma demonstrated by a new immunohistochemical marker mucin-like glycoprotein associated with photoreceptor cells (MLGAPC)

AIMS

For further understanding of specific differentiation in retinoblastoma, we studied the expression of newly detected mucin-like glycoprotein associated with photoreceptor cells (MLGAPC), which is specific for photoreceptor cells of retina and analogous to interphotoreceptor matrix proteoglycan-1 (IMPG1).

METHODS AND RESULTS

Surgically enucleated retinoblastomas (n=21; undifferentiated type, n=15, differentiated type, n=6) were immunohistochemically studied with a polyclonal antibody against MLGAPC, and 17/21 cases (81%) showed positive staining of tumour cells. We classified various staining patterns and structures into four groups: type 1 showing a granular intracellular scattered staining pattern with round small cells; type 2 showing a reticular staining pattern between spindle-shaped tumour cells; type 3 showing radiating staining from the centre of Homer-Wright rosettes; type 4 showing ring-shaped, radiating and granular staining associated with Flexner-Wintersteiner rosettes. Eleven of 15 undifferentiated retinoblastomas (73%) showed type 1 or 2, and all the six differentiated cases showed type 3 or 4. Image analysis of immunostaining revealed an increase in MLGAPC-positive area from 0.48% in undifferentiated cases to 1.60% in differentiated cases, and a negative correlation was shown between mitotic frequency and MLGAPC-positive area.

CONCLUSIONS

This study proved MLGAPC as a valuable marker of retinoblastoma, and that photoreceptor differentiation takes place even in 'undifferentiated' retinoblastoma.

Isolation and characterization of galectins in the mammalian retina

PURPOSE

Previous studies have suggested that galectins may be involved in retinal adhesion and photoreceptor cell survival. To elucidate the underlying mechanisms, the authors isolated retinal galectins, determined their types and distributions, and investigated the validity of the hypothesis, using rat models.

METHODS

An antibody was prepared against a bovine retinal lectin that was isolated by use of a lactose-agarose column. cDNA of the lectin was isolated by screening of a bovine retinal cDNA library, using the antibody, and then was sequenced. The cDNAs of rat retinal galectins were also isolated by means of polymerase chain reaction and used to produce an antibody against recombinant galectin-3. Using the described antibodies, the authors examined the distributions of galectins in bovine and rat retinas, morphologic changes of rat retinas induced by the antibodies, and distributional changes of galectins in constant-light-exposed rat retinas.

RESULTS

The cDNAs of bovine galectin-1, rat galectin-1, and rat galectin-3 were isolated. Galectin-1 was found in various regions, including the retinal pigment epithelium, outer limiting membrane, and outer plexiform layer in bovine and rat retinas. Galectin-3 was increasingly detected in the cytoplasm of Müller cells after constant light exposure after an increase in its transcript. Retinal detachment and vacuolation of the outer plexiform layer were induced in rat eyes by intravitreous injection of the anti-galectin-1 antibody.

CONCLUSIONS

Galectin-1 may be involved in adhesion of the photoreceptor and outer plexiform layers by interacting with glycoconjugates with beta-galactoside residues in the interphotoreceptor matrix and synaptic cleft matrix. Galectin-3 may increase in Müller cells of a degenerative rat retina, probably through endogenous anti-apoptosis.

Ultrastructural changes associated with accumulation of inclusion bodies in rat retinal pigment epithelium

PURPOSE

To determine the structural changes in the retinal pigment epithelium (RPE) and neighboring structures induced by intravitreal injection of a lysosomal protease inhibitor.

METHODS

Eleven-week-old Sprague-Dawley rats were injected with 5 microliter of a lysosomal protease inhibitor, E-64 (2.22 microM), intravitreally once and killed at 24 hours, 48 hours, or 7 days later. Others received two or three injections at 48-hour intervals or three daily injections, and killed at 1, 4, and 7 days after the last injection. Eyes were enucleated and retinal tissues were processed for light and electron microscopy.

RESULTS

A single injection of E-64 caused only a transient accumulation of phagosome-like and phagolysosome-like inclusion bodies in the RPE. By contrast, repeated injection caused progressive accumulation of these inclusions followed by altered RPE cell conformation, and changes in organelles such as loss of smooth endoplasmic reticulum (SER). This was accompanied by shortening and loss of photoreceptor outer segments without prior dysmorphic changes, alteration of choroidal capillaries, and invasion of Bruch's membrane by fibroblasts and pericytes. Intravitreal injection of vehicle as control induced no structural changes.

CONCLUSIONS

E-64 treatment induced structural changes in the outer retina. The causal relationship between accumulation of inclusions in RPE and changes in other subcellular organelles and neighboring cells systems is not clear. However, there are possible explanations: physical disturbance of organelles, particularly SER by inclusions; cellular damage by consequent upon accumulation of A2-E; or, shortage of recycled material due to reduced degradation of phagosomes.

Isolation and characterization of mucinlike glycoprotein associated with photoreceptor cells

PURPOSE

Although previous lectin-histochemical studies have shown that O-linked glycoproteins are distributed in cone pedicles and rod spherules, as well as in photoreceptors, including associated interphotoreceptor matrices (IPM), attention has been directed only to those in the IPM. In this study, cloning of the O-linked glycoproteins not only in the IPM but also in the region including the cone pedicles and rod spherules was attempted.

METHODS

The cDNA for the core protein of the O-linked glycoprotein in the bovine retina was isolated by screening a bovine retinal cDNA library using a polyclonal antibody against the jacalin (a lectin specific for O-linked sugar residues)-binding glycoproteins (JBGPs) in the whole bovine retina. The expression of the JPGP core protein in the retina was examined by means of in situ hybridization histochemistry and immunohistochemistry.

RESULTS

The cDNA was isolated and found to encode an entire core protein [predicted molecular mass (Mr): 101 kDa; rich in Ser and Thr; mucin-like] for the JBGPs with Mr of 120 and 135 kDa. The mRNA was expressed in both cone and rod photoreceptor cells. This protein was distributed in the cone pedicles and rod spherules as well as the photoreceptor layer.

CONCLUSIONS

Mucinlike glycoproteins with Mr of 120 and 135 kDa may be synthesized in the cone and rod photoreceptor cells, respectively, and distributed not only in the photoreceptor layer (probably including the IPM) but also in the cone pedicles and rod spherules.