Use of αv Integrin Linked to Green Fluorescent Protein in Osteosarcoma Cells and Confocal Microscopy to Image Molecular Dynamics During Lung Metastasis in Nude Mice

BACKGROUND

We report here imaging of the behavior of αv integrin linked to green fluorescent protein (GFP) in human osteosarcoma cells colonizing the lung of nude mice.

MATERIALS AND METHODS

143B osteosarcoma cells expressing αv integrin-GFP were generated by transfection of an αv integrin-GFP fusion-gene vector pCMV-AC- ITGAV-GFP. In order to generate experimental lung metastases, 143B osteosarcoma cells (1×10(6)), stably expressing αv integrin-GFP, were injected intravenously via the tail vein. The osteosarcoma cells were transplanted orthotopically in the tibia of nude mice in order to generate spontaneous metastases. Lungs were harvested and imaged by confocal microscopy within 1 hour.

RESULTS

In the experimental lung-metastasis model, extravasating and deformed osteosarcoma cells expressing αv integrin-GFP were observed. Pseudopodia of the osteosarcoma cells contained small puncta of αv integrin-GFP. In early-stage spontaneous lung metastasis, tumor emboli were observed in pulmonary vessels. At high magnification, small αv integrin-GFP puncta were observed in the tumor embolus. In late-stage spontaneous metastasis, tumor emboli were also observed in pulmonary vessels. Invading cancer cells with strong expression of αv integrin-GFP were observed at the margin of the tumor emboli.

CONCLUSION

The results of this study demonstrate that molecular dynamics of αv integrin-GFP can be imaged in lung metastasis, which will allow further understanding of the role of αv integrin in this process. The results also suggest a general concept for imaging molecular behavior in vivo.

In Vivo Isolation of a Highly-aggressive Variant of Triple-negative Human Breast Cancer MDA-MB-231 Using Serial Orthotopic Transplantation

AIM

We describe the development of a highly-invasive, triple-negative breast cancer (TNBC) variant using serial orthotopic implantation of MDA-MB-231 human breast cancer in nude mice.

MATERIALS AND METHODS

MDA-MB-231 cells expressing red fluorescent protein (RFP) (1×10(7) cells/site) were initially injected subcutaneously in the flank of nude mice. After the subcutaneous tumors grew, they were harvested and cut into small pieces for orthotopic implantation in the right lower mammary gland. After the orthotopic tumors grew, they were resected and cut into small pieces and orthotopically re-implanted into the mammary gland of nude mice. The tumors grew and metastasized to lymph nodes. The lymph node metastases were harvested and cut into small pieces and orthotopically re-implanted into the mammary gland of nude mice. After the orthotopic tumors grew, the tumor was removed leaving residual cancer cells, which grew and metastasized to lymph nodes. The lymph node metastases were harvested, cut into pieces and orthotopically re-implanted into the mammary gland of nude mice for two cycles and then isolated.

RESULTS

The isolated variant is highly invasive in the mammary gland and metastasized to lymph nodes in 10 of 12 mice compared to 2 of 12 of the parental cell line.

CONCLUSION

The availability of a highly invasive variant of TNBC targeting lymph nodes will be very useful for drug discovery of TNBC, a recalcitrant cancer and for mechanistic studies of its aggressiveness.

Efficacy of the Combination of a PARP Inhibitor and UVC on Cancer Cells as Imaged by Focus Formation by the DNA Repair-related Protein 53BP1 Linked to Green Fluorescent Protein

BACKGROUND

The ability to image DNA repair in cancer cells after irradiation, as well as its inhibition by potential therapeutic agents, is important for the further development of effective cancer therapy. 53BP1 is a DNA repair protein that is overexpressed and forms foci when double-stranded DNA breaks occur in DNA.

MATERIALS AND METHODS

The re-localization of green fluorescent protein (GFP) fused to the chromatin-binding domain of 53BP1 to form foci was imaged after UVC irradiation of breast and pancreatic cancer cells expressing 53BP1-GFP using confocal microscopy.

RESULTS

During live-cell imaging, 53BP1-GFP focus formation was observed within 10 minutes after UVC irradiation. Most 53BP1 foci resolved by 100 minutes. To block UVC-induced double-strand break repair in cancer cells, poly(ADP-ribose) polymerase (PARP) was targeted with ABT-888 (veliparib). PARP inhibition markedly enhanced UVC-irradiation-induced persistence of 53BP1-foci, even beyond 100 minutes after UVC irradiation, and reduced proliferation of breast and pancreatic cancer cells.

CONCLUSION

Confocal microscopy of 53BP1-GFP is a powerful method for imaging UVC-induced DNA damage and repair, as well as inhibition of repair.

Centrality Dependence of the Charged-Particle Multiplicity Density at Midrapidity in Pb-Pb Collisions at sqrt[s_{NN}]=5.02 TeV

The pseudorapidity density of charged particles, dN_{ch}/dη, at midrapidity in Pb-Pb collisions has been measured at a center-of-mass energy per nucleon pair of sqrt[s_{NN}]=5.02  TeV. For the 5% most central collisions, we measure a value of 1943±54. The rise in dN_{ch}/dη as a function of sqrt[s_{NN}] is steeper than that observed in proton-proton collisions and follows the trend established by measurements at lower energy. The increase of dN_{ch}/dη as a function of the average number of participant nucleons, ⟨N_{part}⟩, calculated in a Glauber model, is compared with the previous measurement at sqrt[s_{NN}]=2.76  TeV. A constant factor of about 1.2 describes the increase in dN_{ch}/dη from sqrt[s_{NN}]=2.76 to 5.02 TeV for all centrality classes, within the measured range of 0%-80% centrality. The results are also compared to models based on different mechanisms for particle production in nuclear collisions.

Measurement of an Excess in the Yield of J/ψ at Very Low p_{T} in Pb-Pb Collisions at sqrt[s]_{NN}=2.76 TeV

We report on the first measurement of an excess in the yield of J/ψ at very low transverse momentum (p_{T}<0.3  GeV/c) in peripheral hadronic Pb-Pb collisions at sqrt[s_{NN}]=2.76  TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor of J/ψ in the rapidity range 2.5<y<4 reaches about 7 (2) in the p_{T} range 0-0.3  GeV/c in the 70%-90% (50%-70%) centrality class. The J/ψ production cross section associated with the observed excess is obtained under the hypothesis that coherent photoproduction of J/ψ is the underlying physics mechanism. If confirmed, the observation of J/ψ coherent photoproduction in Pb-Pb collisions at impact parameters smaller than twice the nuclear radius opens new theoretical and experimental challenges and opportunities. In particular, coherent photoproduction accompanying hadronic collisions may provide insight into the dynamics of photoproduction and nuclear reactions, as well as become a novel probe of the quark-gluon plasma.

Use of αv Integrin Linked to GFP to Image Molecular Dynamics in Trafficking Cancer-Cell Emboli

Human osteosarcoma cells with an α_v integrin green fluorescent protein (GFP) fusion gene were previously established and imaged in vitro and in vivo. In the present study, we imaged the interaction of α_v integrin-GFP in osteosarcoma cells and collagen fibers in vascular-trafficking osteosarcoma emboli in nude mice. Human 143B osteosarcoma cells, expressing α_v integrin-GFP, were injected by a vascular route in an abdominal skin flap in nude mice. Osteosarcoma cells were fluorescently imaged in the epigastric cranialis vein in the abdominal skin flap by confocal microscopy. Collagen fibers were imaged in reflectance mode. At early stages of tumor embolus-formation, cancer cells adhered firmly to each other, diffusely expressing α_v integrin-GFP. Two weeks after injection, collagen fiber scaffolds were visualized at the margins of tumor emboli or within them. Four weeks after injection, cancer cells invading from emboli were strongly expressing α_v integrin-GFP, and were aligned along collagen fibers. The results suggest α_v integrin and collagen fiber scaffolds are important for tumor embolus formation, which are potential seeds of metastasis. J. Cell. Biochem. 118: 26-30, 2017. © 2016 Wiley Periodicals, Inc.

Centrality dependence of charged jet production in p-Pb collisions at [Formula: see text] = 5.02 TeV

Measurements of charged jet production as a function of centrality are presented for  p-Pb  collisions recorded at [Formula: see text] TeV with the ALICE detector. Centrality classes are determined via the energy deposit in neutron calorimeters at zero degree, close to the beam direction, to minimise dynamical biases of the selection. The corresponding number of participants or binary nucleon-nucleon collisions is determined based on the particle production in the Pb-going rapidity region. Jets have been reconstructed in the central rapidity region from charged particles with the anti-[Formula: see text] algorithm for resolution parameters [Formula: see text] and [Formula: see text] in the transverse momentum range 20 to 120 GeV/c. The reconstructed jet momentum and yields have been corrected for detector effects and underlying-event background. In the five centrality bins considered, the charged jet production in  p-Pb   collisions is consistent with the production expected from binary scaling from pp collisions. The ratio of jet yields reconstructed with the two different resolution parameters is also independent of the centrality selection, demonstrating the absence of major modifications of the radial jet structure in the reported centrality classes.

Tumor-specific cell-cycle decoy by Salmonella typhimurium A1-R combined with tumor-selective cell-cycle trap by methioninase overcome tumor intrinsic chemoresistance as visualized by FUCCI imaging

We previously reported real-time monitoring of cell cycle dynamics of cancer cells throughout a live tumor intravitally using a fluorescence ubiquitination cell cycle indicator (FUCCI). Approximately 90% of cancer cells in the center and 80% of total cells of an established tumor are in G0/G1 phase. Longitudinal real-time FUCCI imaging demonstrated that cytotoxic agents killed only proliferating cancer cells at the surface and, in contrast, and had little effect on the quiescent cancer cells. Resistant quiescent cancer cells restarted cycling after the cessation of chemotherapy. Thus cytotoxic chemotherapy which targets cells in S/G2/M, is mostly ineffective on solid tumors, but causes toxic side effects on tissues with high fractions of cycling cells, such as hair follicles, bone marrow and the intestinal lining. We have termed this phenomenon tumor intrinsic chemoresistance (TIC). We previously demonstrated that tumor-targeting Salmonella typhimurium A1-R (S. typhimurium A1-R) decoyed quiescent cancer cells in tumors to cycle from G0/G1 to S/G2/M demonstrated by FUCCI imaging. We have also previously shown that when cancer cells were treated with recombinant methioninase (rMETase), the cancer cells were selectively trapped in S/G2, shown by cell sorting as well as by FUCCI. In the present study, we show that sequential treatment of FUCCI-expressing stomach cancer MKN45 in vivo with S. typhimurium A1-R to decoy quiescent cancer cells to cycle, with subsequent rMETase to selectively trap the decoyed cancer cells in S/G2 phase, followed by cisplatinum (CDDP) or paclitaxel (PTX) chemotherapy to kill the decoyed and trapped cancer cells completely prevented or regressed tumor growth. These results demonstrate the effectiveness of the praradigm of "decoy, trap and shoot" chemotherapy.

Eradication of osteosarcoma by fluorescence-guided surgery with tumor labeling by a killer-reporter adenovirus

In a previous study, we developed fluorescence-guided surgery (FGS) for osteosarcoma using an orthotopic model with 143B human osteosarcoma cells expressing red fluorescent protein (RFP) implanted into the intramedullary cavity of the tibia in nude mice. The FGS-treated mice had a significantly higher disease-free survival (DFS) rate than the bright-light surgery (BLS). However, although FGS significantly reduced the recurrence of the primary tumor, it did not reduce lung metastasis. In the present study, we utilized the OBP-401 telomerase-dependent killer-reporter adenovirus, carrying green fluorescent protein (GFP), to label human osteosarcoma in situ in orthotopic mouse models. OBP-401-illuminated human osteosarcoma cell lines, 143B and MNNG/HOS cells in vitro and in vivo. OBP-401 tumor illumination enabled effective FGS of the 143B-derived orthotopic mouse model of human osteosarcoma model as well as FGS eradication of residual cancer cells after BLS. OBP-401-assisted FGS significantly inhibited local recurrence and lung metastasis after surgery, thereby prolonging DFS and overall survival (OS), achieving a very important improvement of therapeutic outcomes over our previously reported FGS study. These therapeutic benefits of FGS were demonstrated using a clinically-viable methodology of direct labeling of human osteosarcoma in situ with the OBP-401 killer-reporter adenovirus in contrast with previous reports, which used genetically engineered labeled cells or antibody-based fluorescent labels for FGS. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:836-844, 2016.

Production of K[Formula: see text](892)[Formula: see text] and [Formula: see text](1020) in p-Pb collisions at [Formula: see text] = 5.02 TeV

The production of K[Formula: see text](892)[Formula: see text] and [Formula: see text](1020) mesons has been measured in p-Pb collisions at [Formula: see text][Formula: see text] 5.02 TeV. K[Formula: see text] and [Formula: see text] are reconstructed via their decay into charged hadrons with the ALICE detector in the rapidity range [Formula: see text]. The transverse momentum spectra, measured as a function of the multiplicity, have a p[Formula: see text] range from 0 to 15 GeV/c for K[Formula: see text] and from 0.3 to 21 GeV/c for [Formula: see text]. Integrated yields, mean transverse momenta and particle ratios are reported and compared with results in pp collisions at [Formula: see text][Formula: see text] 7 TeV and Pb-Pb collisions at [Formula: see text][Formula: see text] 2.76 TeV. In Pb-Pb and p-Pb collisions, K[Formula: see text] and [Formula: see text] probe the hadronic phase of the system and contribute to the study of particle formation mechanisms by comparison with other identified hadrons. For this purpose, the mean transverse momenta and the differential proton-to-[Formula: see text] ratio are discussed as a function of the multiplicity of the event. The short-lived K[Formula: see text] is measured to investigate re-scattering effects, believed to be related to the size of the system and to the lifetime of the hadronic phase.

Heterogeneous cell-cycle behavior in response to UVB irradiation by a population of single cancer cells visualized by time-lapse FUCCI imaging

The present study analyzed the heterogeneous cell-cycle dependence and fate of single cancer cells in a population treated with UVB using a fluorescence ubiquitination-based cell-cycle (FUCCI) imaging system. HeLa cells expressing FUCCI were irradiated by 100 or 200 J/m(2) UVB. Modulation of the cell-cycle and apoptosis were observed by time-lapse confocal microscopy imaging every 30 min for 72 h. Correlation between cell survival and factors including cell-cycle phase at the time of the irradiation of UVB, mitosis and the G1/S transition were analyzed using the Kaplan-Meier method along with the log rank test. Time-lapse FUCCI imaging of HeLa cells demonstrated that UVB irradiation induced cell-cycle arrest in S/G2/M phase in the majority of the cells. The cells irradiated by 100 or 200 J/m(2) UVB during G0/G1 phase had a higher survival rate than the cells irradiated during S/G2/M phase. A minority of cells could escape S/G2/M arrest and undergo mitosis which significantly correlated with decreased survival of the cells. In contrast, G1/S transition significantly correlated with increased survival of the cells after UVB irradiation. UVB at 200 J/m(2) resulted in a greater number of apoptotic cells.

Real-Time In Vivo Confocal Fluorescence Imaging of Prostate Cancer Bone-Marrow Micrometastasis Development at the Cellular Level in Nude Mice

In the present report, we demonstrate in vivo fluorescence imaging of bone-marrow micrometastasis of prostate cancer at the cellular level in nude mice. PC-3 human prostate cancer cells labeled with green fluorescent protein (GFP) or red fluorescent protein (RFP) were injected into the left ventricle or intratibial bone marrow of nude mice. PC-3-GFP, as well as selected high metastatic variants of PC-3-GFP, PC-3-GFP-BM6 or PC-3-RFP were visualized by real-time fluorescence imaging, to traffic and grow in the bone marrow. Formation of bone marrow micrometastasis could be imaged at the single-cell level in live mice, using confocal microscopy. The ability to track bone marrow micrometastasis in real time at the cellular level provides a visual target for evaluating new therapeutics for this recalcitrant disease. J. Cell. Biochem. 117: 2533-2537, 2016. © 2016 Wiley Periodicals, Inc.

Inclusive quarkonium production at forward rapidity in pp collisions at [Formula: see text]TeV

We report on the inclusive production cross sections of [Formula: see text], [Formula: see text], [Formula: see text](1S), [Formula: see text](2S) and [Formula: see text](3S), measured at forward rapidity with the ALICE detector in [Formula: see text] collisions at a center-of-mass energy [Formula: see text] TeV. The analysis is based on data collected at the LHC and corresponds to an integrated luminosity of 1.23 pb[Formula: see text]. Quarkonia are reconstructed in the dimuon-decay channel. The differential production cross sections are measured as a function of the transverse momentum [Formula: see text] and rapidity y, over the [Formula: see text] ranges [Formula: see text] GeV/c for [Formula: see text], [Formula: see text] GeV/c for all other resonances, and for [Formula: see text]. The cross sections, integrated over [Formula: see text] and y, and assuming unpolarized quarkonia, are [Formula: see text] [Formula: see text]b, [Formula: see text] [Formula: see text]b, [Formula: see text] nb, [Formula: see text] nb and [Formula: see text] nb, where the first uncertainty is statistical and the second one is systematic. These values agree, within at most [Formula: see text], with measurements performed by the LHCb collaboration in the same rapidity range.

Anisotropic Flow of Charged Particles in Pb-Pb Collisions at √[s{NN}]=5.02 TeV

We report the first results of elliptic (v_{2}), triangular (v_{3}), and quadrangular (v_{4}) flow of charged particles in Pb-Pb collisions at a center-of-mass energy per nucleon pair of sqrt[s_{NN}]=5.02  TeV with the ALICE detector at the CERN Large Hadron Collider. The measurements are performed in the central pseudorapidity region |η|<0.8 and for the transverse momentum range 0.2<p_{T}<5  GeV/c. The anisotropic flow is measured using two-particle correlations with a pseudorapidity gap greater than one unit and with the multiparticle cumulant method. Compared to results from Pb-Pb collisions at sqrt[s_{NN}]=2.76  TeV, the anisotropic flow coefficients v_{2}, v_{3}, and v_{4} are found to increase by (3.0±0.6)%, (4.3±1.4)%, and (10.2±3.8)%, respectively, in the centrality range 0%-50%. This increase can be attributed mostly to an increase of the average transverse momentum between the two energies. The measurements are found to be compatible with hydrodynamic model calculations. This comparison provides a unique opportunity to test the validity of the hydrodynamic picture and the power to further discriminate between various possibilities for the temperature dependence of shear viscosity to entropy density ratio of the produced matter in heavy-ion collisions at the highest energies.

Real-time fluorescence imaging of the DNA damage repair response during mitosis

The response to DNA damage during mitosis was visualized using real-time fluorescence imaging of focus formation by the DNA-damage repair (DDR) response protein 53BP1 linked to green fluorescent protein (GFP) (53BP1-GFP) in the MiaPaCa-2(Tet-On) pancreatic cancer cell line. To observe 53BP1-GFP foci during mitosis, MiaPaCa-2(Tet-On) 53BP1-GFP cells were imaged every 30 min by confocal microscopy. Time-lapse imaging demonstrated that 11.4 ± 2.1% of the mitotic MiaPaCa-2(Tet-On) 53BP1-GFP cells had increased focus formation over time. Non-mitotic cells did not have an increase in 53BP1-GFP focus formation over time. Some of the mitotic MiaPaCa-2(Tet-On) 53BP1-GFP cells with focus formation became apoptotic. The results of the present report suggest that DNA strand breaks occur during mitosis and undergo repair, which may cause some of the mitotic cells to enter apoptosis in a phenomenon possibly related to mitotic catastrophe.

Intraperitoneal administration of tumor-targeting Salmonella typhimurium A1-R inhibits disseminated human ovarian cancer and extends survival in nude mice

Peritoneal disseminated cancer is highly treatment resistant. We here report the efficacy of intraperitoneal (i.p.) administration of tumor-targeting Salmonella typhimurium A1-R in a nude mouse model of disseminated human ovarian cancer. The mouse model was established by intraperitoneal injection of the human ovarian cancer cell line SKOV3-GFP. Seven days after implantation, mice were treated with S. typhimurium A1-R via intravenous (i.v.) or i.p. administration at the same dose, 5×10⁷ CFU, once per week. Both i.v. and i.p. treatments effected prolonged survival compared with the untreated control group (P=0.025 and P<0.001, respectively). However, i.p. treatment was less toxic than i.v. treatment. Tumor-specific targeting of S. typhimurium A1-R was confirmed with bacterial culture from tumors and various organs and tumor or organ colony formation after i.v. or i.p. injection. Selective tumor targeting was most effective with i.p. administration. The results of the present study show S. typhimurium A1-R has promising clinical potential for disseminated ovarian cancer, especially via i.p. administration.

Multiplicity and transverse momentum evolution of charge-dependent correlations in pp, p-Pb, and Pb-Pb collisions at the LHC

We report on two-particle charge-dependent correlations in pp, p-Pb, and Pb-Pb collisions as a function of the pseudorapidity and azimuthal angle difference, [Formula: see text] and [Formula: see text] respectively. These correlations are studied using the balance function that probes the charge creation time and the development of collectivity in the produced system. The dependence of the balance function on the event multiplicity as well as on the trigger and associated particle transverse momentum ([Formula: see text]) in pp, p-Pb, and Pb-Pb collisions at [Formula: see text] 7, 5.02, and 2.76 TeV, respectively, are presented. In the low transverse momentum region, for [Formula: see text] GeV/c, the balance function becomes narrower in both [Formula: see text] and [Formula: see text] directions in all three systems for events with higher multiplicity. The experimental findings favor models that either incorporate some collective behavior (e.g. AMPT) or different mechanisms that lead to effects that resemble collective behavior (e.g. PYTHIA8 with color reconnection). For higher values of transverse momenta the balance function becomes even narrower but exhibits no multiplicity dependence, indicating that the observed narrowing with increasing multiplicity at low [Formula: see text] is a feature of bulk particle production.

Improved Resection and Outcome of Colon-Cancer Liver Metastasis with Fluorescence-Guided Surgery Using In Situ GFP Labeling with a Telomerase-Dependent Adenovirus in an Orthotopic Mouse Model

Fluorescence-guided surgery (FGS) of cancer is an area of intense development. In the present report, we demonstrate that the telomerase-dependent green fluorescent protein (GFP)-containing adenovirus OBP-401 could label colon-cancer liver metastasis in situ in an orthotopic mouse model enabling successful FGS. OBP-401-GFP-labeled liver metastasis resulted in complete resection with FGS, in contrast, conventional bright-light surgery (BLS) did not result in complete resection of the metastasis. OBP-401-FGS reduced the recurrence rate and prolonged over-all survival compared with BLS. In conclusion, adenovirus OBP-401 is a powerful tool to label liver metastasis in situ with GFP which enables its complete resection, not possible with conventional BLS.

Traditional Chinese medicine herbal mixture LQ arrests FUCCI-expressing HeLa cells in G₀/G₁ phase in 2D plastic, 2.5D Matrigel, and 3D Gelfoam culture visualized with FUCCI imaging

We used the fluorescence ubiquitination-based cell cycle indicator (FUCCI) to monitor cell cycle arrest after treatment of FUCCI-expressing HeLa cells (FUCCI-HeLa) with a traditional Chinese medicine (TCM) herbal mixture LQ, previously shown to have anti-tumor and anti-metastatic activity in mouse models. Paclitaxel was used as the positive control. In 2D monolayer culture, the untreated control had approximately 45% of the cells in S/G₂/M phase. In contrast, the LQ-treated cells (9 mg/ml) were mostly in the G₀/G₁ (>90%) after 72 hours. After treatment with paclitaxel (0.01 μm), for 72 hours, 95% of the cells were in S/G₂/M. In 2.5D Matrigel^® culture, the colonies in the untreated control group had 40% of the cells in S/G₂/M. LQ arrested the cells in G₀/G₁ after 72 hours. Paclitaxel arrested almost all the cells in S/G₂/M after 72 hours. In 3D Gelfoam^® culture, the untreated control culture had approximately 45% of cells in G₂/M. In contrast, the LQ-treated cells were mostly in G₀/G₁ phase (>80%) after 72 hours treatment. Paclitaxel resulted in 90% of the cells arrested in S/G₂/M after 72 hours. The present report suggests the non-toxic LQ has potential to maintain cancers in a quiescent state for long periods of time.

Salmonella typhimurium A1-R and Cell-Cycle Decoy Therapy of Cancer

Cancer cells in G0/G1 are resistant to cytotoxic chemotherapy agents which kill only cycling cancer cells. Salmonella typhimurium A1-R (S. typhimurium A1-R) decoyed cancer cells in monolayer culture and in tumor spheres to cycle from G0/G1 to S/G2/M, as demonstrated by fluorescence ubiquitination-based cell cycle indicator (FUCCI) imaging. S. typhimurium A1-R targeted FUCCI-expressing subcutaneous tumors, and tumors growing on the liver, growing in nude mice and also decoyed quiescent cancer cells, which were the majority of the cells in the tumors, to cycle from G0/G1 to S/G2/M. The S. typhimurium A1-R-decoyed cancer cells became sensitive to cytotoxic agents.

Cancer cells mimic in vivo spatial-temporal cell-cycle phase distribution and chemosensitivity in 3-dimensional Gelfoam® histoculture but not 2-dimensional culture as visualized with real-time FUCCI imaging

The phase of the cell cycle can determine whether a cancer cell can respond to a given drug. We previously reported monitoring of real-time cell cycle dynamics of cancer cells throughout a live tumor, intravitally in live mice, using a fluorescence ubiquitination-based cell-cycle indicator (FUCCI). Approximately 90% of cancer cells in the center and 80% of total cells of an established tumor are in G0/G1 phase. 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 cessation of chemotherapy. These results suggested why most drugs currently in clinical use, which target cancer cells in S/G2/M, are mostly ineffective on solid tumors. In the present report, we used FUCCI imaging and Gelfoam® collagen-sponge-gel histoculture, to demonstrate in real time, that the cell-cycle phase distribution of cancer cells in Gelfoam® and in vivo tumors is highly similar, whereby only the surface cells proliferate and interior cells are quiescent in G0/G1. This is in contrast to 2D culture where most cancer cells cycle. Similarly, the cancer cells responded similarly to toxic chemotherapy in Gelfoam® culture as in vivo, and very differently than cancer cells in 2D culture which were much more chemosensitive. Gelfoam® culture of FUCCI-expressing cancer cells offers the opportunity to image the cell cycle of cancer cells continuously and to screen for novel effective therapies to target quiescent cells, which are the majority in a tumor and which would have a strong probability to be effective in vivo.

Cell-cycle fate-monitoring distinguishes individual chemosensitive and chemoresistant cancer cells in drug-treated heterogeneous populations demonstrated by real-time FUCCI imaging

Essentially every population of cancer cells within a tumor is heterogeneous, especially with regard to chemosensitivity and resistance. In the present study, we utilized the fluorescence ubiquitination-based cell cycle indicator (FUCCI) imaging system to investigate the correlation between cell-cycle behavior and apoptosis after treatment of cancer cells with chemotherapeutic drugs. HeLa cells expressing FUCCI were treated with doxorubicin (DOX) (5 μM) or cisplatinum (CDDP) (5 μM) for 3 h. Cell-cycle progression and apoptosis were monitored by time-lapse FUCCI imaging for 72 h. Time-lapse FUCCI imaging demonstrated that both DOX and CDDP could induce cell cycle arrest in S/G2/M in almost all the cells, but a subpopulation of the cells could escape the block and undergo mitosis. The subpopulation which went through mitosis subsequently underwent apoptosis, while the cells arrested in S/G2/M survived. The present results demonstrate that chemoresistant cells can be readily identified in a heterogeneous population of cancer cells by S/G2/M arrest, which can serve in future studies as a visible target for novel agents that kill cell-cycle-arrested cells.