SRRM4-mediated REST to REST4 dysregulation promotes tumor growth and neural adaptation in breast cancer leading to brain metastasis

BACKGROUND

Effective control of brain metastasis remains an urgent clinical need due a limited understanding of the mechanisms driving it. Although the gain of neuro-adaptive attributes in breast-to-brain metastases (BBMs) has been described, the mechanisms that govern this neural acclimation and the resulting brain metastasis competency are poorly understood. Herein, we define the role of neural-specific splicing factor Serine/Arginine Repetitive Matrix Protein 4 (SRRM4) in regulating microenvironmental adaptation and brain metastasis colonization in breast cancer cells.

METHODS

Utilizing pure neuronal cultures and brain-naive and patient-derived BM tumor cells, along with in vivo tumor modeling, we surveyed the early induction of mediators of neural acclimation in tumor cells.

RESULTS

When SRRM4 is overexpressed in systemic breast cancer cells, there is enhanced BBM leading to poorer overall survival in vivo. Concomitantly, SRRM4 knockdown expression does not provide any advantage in central nervous system metastasis. In addition, reducing SRRM4 expression in breast cancer cells slows down proliferation and increases resistance to chemotherapy. Conversely, when SRRM4/REST4 levels are elevated, tumor cell growth is maintained even in nutrient-deprived conditions. In neuronal coculture, decreasing SRRM4 expression in breast cancer cells impairs their ability to adapt to the brain microenvironment, while increasing SRRM4/RE-1 Silencing Transcription Factor (REST4) levels leads to greater expression of neurotransmitter and synaptic signaling mediators and a significant colonization advantage.

CONCLUSIONS

Collectively, our findings identify SRRM4 as a regulator of brain metastasis colonization, and a potential therapeutic target in breast cancer.

Breast-to-brain metastasis is exacerbated with chemotherapy through blood-cerebrospinal fluid barrier and induces Alzheimer's-like pathology

Control of breast-to-brain metastasis remains an urgent unmet clinical need. While chemotherapies are essential in reducing systemic tumor burden, they have been shown to promote non-brain metastatic invasiveness and drug-driven neurocognitive deficits through the formation of neurofibrillary tangles (NFT), independently. Now, in this study, we investigated the effect of chemotherapy on brain metastatic progression and promoting tumor-mediated NFT. Results show chemotherapies increase brain-barrier permeability and facilitate enhanced tumor infiltration, particularly through the blood-cerebrospinal fluid barrier (BCSFB). This is attributed to increased expression of matrix metalloproteinase 9 (MMP9) which, in turn, mediates loss of Claudin-6 within the choroid plexus cells of the BCSFB. Importantly, increased MMP9 activity in the choroid epithelium following chemotherapy results in cleavage and release of Tau from breast cancer cells. This cleaved Tau forms tumor-derived NFT that further destabilize the BCSFB. Our results underline for the first time the importance of the BCSFB as a vulnerable point of entry for brain-seeking tumor cells post-chemotherapy and indicate that tumor cells themselves contribute to Alzheimer's-like tauopathy.

BSCI-12 BREAST TO BRAIN METASTASIS IS EXACERBATED WITH CHEMOTHERAPY THROUGH BLOOD-CEREBRAL SPINAL FLUID-BARRIER AND INDUCES ALZHEIMER’S-LIKE PATHOLOGY

Control of breast to brain metastasis remains an urgent unmet clinical need. While chemotherapies are essential in reducing systemic tumor burden, they have also shown to promote non-brain metastatic invasiveness and drug-driven neurocognitive deficits through formation of neurofibrillary tangles (NFT) independently. Now, in this study we investigated the effect of chemotherapy on brain metastatic progression and promoting tumor-mediated NFT. Results show chemotherapies promote increased brain-barrier permeability and facilitate enhanced tumor infiltration, particularly through the blood-cerebrospinal fluid-barrier (BCSFB). This is attributed to increased expression of matrix metalloproteinase 9 (MMP9) which, in turn, mediates loss of Claudin-6 within the choroid plexus cells of the BCSFB. Importantly, increased MMP9 activity in the choroid epithelium following chemotherapy results in cleavage of Tau released from breast cancer cells. This cleaved Tau forms tumor-derived NFT that further destabilize the BCSFB. Our results underline for the first time the importance of the BCSFB as a vulnerable point of entry for brain-seeking tumor cells post-chemotherapy and indicate that tumor cells themselves contribute to Alzheimer’s-like tauopathy.

Cortisol promotes breast-to-brain metastasis through the blood-cerebrospinal fluid barrier

BACKGROUND

Elevated basal cortisol levels are present in women with primary and metastatic breast cancer. Although cortisol's potential role in breast-to-brain metastasis has yet to be sufficiently studied, prior evidence indicates that it functions as a double-edged sword-cortisol induces breast cancer metastasis in vivo, but strengthens the blood-brain-barrier (BBB) to protect the brain from microbes and peripheral immune cells.

AIMS

In this study, we provide a novel examination on whether cortisol's role in tumor invasiveness eclipses its supporting role in strengthening the CNS barriers. We expanded our study to include the blood-cerebrospinal fluid barrier (BCSFB), an underexamined site of tumor entry.

METHODS AND RESULTS

Utilizing in vitro BBB and BCSFB models to measure barrier strength in the presence of hydrocortisone (HC). We established that lung tumor cells migrate through both CNS barriers equally while breast tumors cells preferentially migrate through the BCSFB. Furthermore, HC treatment increased breast-to-brain metastases (BBM) but not primary breast tumor migratory capacity. When examining the transmigration of breast cancer cells across the BCSFB, we demonstrate that HC induces increased traversal of BBM but not primary breast cancer. We provide evidence that HC increases tightness of the BCSFB akin to the BBB by upregulating claudin-5, a tight junction protein formerly acknowledged as exclusive to the BBB.

CONCLUSION

Our findings indicate, for the first time that increased cortisol levels facilitate breast-to-brain metastasis through the BCSFB-a vulnerable point of entry which has been typically overlooked in brain metastasis. Our study suggests cortisol plays a pro-metastatic role in breast-to-brain metastasis and thus caution is needed when using glucocorticoids to treat breast cancer patients.

Neuronal exposure induces neurotransmitter signaling and synaptic mediators in tumors early in brain metastasis

BACKGROUND

Brain metastases (BM) are responsible for neurological decline and poor overall survival. Although the pro-metastatic roles of glial cells, and the acquisition of neuronal attributes in established BM tumors have been described, there are no studies that investigate the initial interplay between neurons and brain-seeking tumor cells. The aim of this study was to characterize early tumor-neuron interactions and the induced CNS-adaptive changes in tumor cells prior to macro-colonization.

METHODS

Utilizing pure neuronal cultures and brain-naïve and patient-derived BM tumor cells, we surveyed the early induction of mediators of neurotransmitter (NT) and synaptic signaling in breast and lung tumor cells. Reliance on microenvironmental GABA in breast-to-brain metastatic cells (BBMs) was assessed in vitro and in vivo.

RESULTS

Co-culture with neurons induces early expression of classical NT receptor genes (HTR4, GRIA2, GRIN2B, GRM4, GRM8, DRD1) and neuronal synaptic mediators (CNR1, EGR2, ARC, NGFR, NRXN1) in breast and lung cancer cells. NT-dependent classification of tumor cells within the neuronal niche shows breast cancer cells become GABAergic responsive brain metastases (GRBMs) and transition from relying on autocrine GABA, to paracrine GABA from adjacent neurons; while autocrine Dopaminergic breast and lung tumor cells persist. In vivo studies confirm reliance on paracrine GABA is an early CNS-acclimation strategy in breast cancer. Moreover, neuronal contact induces early resurgence in Reelin expression in tumor cells through epigenetic activation, facilitating CNS adaptation.

CONCLUSION

Tumor-neuron interactions allow for CNS-adaptation early in the course of brain metastasis.

Classical density functional theory and the phase-field crystal method using a rational function to describe the two-body direct correlation function

We introduce a new approach to represent a two-body direct correlation function (DCF) in order to alleviate the computational demand of classical density functional theory (CDFT) and enhance the predictive capability of the phase-field crystal (PFC) method. The approach utilizes a rational function fit (RFF) to approximate the two-body DCF in Fourier space. We use the RFF to show that short-wavelength contributions of the two-body DCF play an important role in determining the thermodynamic properties of materials. We further show that using the RFF to empirically parametrize the two-body DCF allows us to obtain the thermodynamic properties of solids and liquids that agree with the results of CDFT simulations with the full two-body DCF without incurring significant computational costs. In addition, the RFF can also be used to improve the representation of the two-body DCF in the PFC method. Last, the RFF allows for a real-space reformulation of the CDFT and PFC method, which enables descriptions of nonperiodic systems and the use of nonuniform and adaptive grids.

Dasatinib (D) in patients with accelerated phase chronic myeloid leukemia (AP-CML) who are resistant or intolerant to imatinib: Results of the CA180005 ’START-A’ study

6526

Background: Dasatinib (D) (BMS-354825) is an oral multi-targeted kinase inhibitor with preliminary evidence of efficacy in a previously reported phase I study. START A is an open-label study of dasatinib in AP-CML pts who were imatinib resistant (IM-R) or imatinib intolerant (IM-I). Methods: A total of 192 pts were enrolled between December 2004 and Jun 2005 in 39 centers worldwide. Dasatinib was given orally at 70 mg twice daily (BID). Dose escalations to 100 mg BID were allowed for poor initial response and reductions to 50 or 40 mg BID for persistent toxicity. Evaluations were weekly blood counts and monthly bone marrow evaluation including cytogenetics. The primary endpoint was major confirmed (maintained at least 4 weeks) hematologic response (MaHR) in IM-R pts. Results: The first 107 pts (99 IM-R, 8 IM-I) with at least 6 months of follow-up are currently reported; there were 55 males/52 females; median age 57 years (range 23–86); median time from diagnosis of CML 90.9 months. Prior therapy included IM>600 mg/day in 63 (59%) pts, interferon in 80 (75%) pts. Major cytogenetic response (MCyR) to prior IM was seen in 34 (32%) pts. 56 pts had Bcr-Abl kinase domain mutations. Median duration of therapy was 5.5 months. MaHR was documented in 63 (59%) pts (95% CI: 49–68) with complete hematologic response in 35 (33%) and no evidence of leukemia in 28 (26%). In IM-R pts, the MaHR rate was 59%. MCyR was documented in 33 (32%) pts (95% CI: 22.9–41.6); complete in 23 (22%), partial in 10 (10%). MaHR were seen in pts with Bcr-Abl mutations and in pts who never responded to IM. Molecular response analysis is ongoing. There were 15 disease progressions including one loss of MaHR. Myelosuppression was significant with grade 3–4 thrombocytopenia and neutropenia in 79% and 69% of pts, respectively. Non-hematologic toxicities were generally mild to moderate. The most frequent were diarrhea (46%), peripheral edema (27%), pleural effusion (16%), rash (8%), and GI hemorrhage (7%). Conclusions: Dasatinib was very effective in IM-R pts with AP-CML with high rates of durable MaHR and MCyR. Data on all 192 pts will be presented at the meeting.

[Table: see text]

Non-invasive imaging of a transgenic mouse model using a prostate-specific two-step transcriptional amplification strategy

Non-invasive assessment of transgenic animals using bioluminescence imaging offers a rapid means of evaluating disease progression in animal models of disease. One of the challenges in the field is to develop models with robust expression to image repetitively live intact animals through solid tissues. The prostate-specific antigen (PSA) promoter is an attractive model for studying gene regulation due to its hormonal response and tissue-specificity permitting us to measure signaling events that occur within the native tissues. The use of the GAL4-VP16 activator offers a powerful means to augment gene expression levels driven by a weak promoter. We have used a two-step transcriptional amplification (TSTA) system to develop a transgenic mouse model to investigate the tissue-specificity and developmental regulation of firefly luciferase (fl) gene expression in living mice using bioluminescence imaging. We employed an enhanced prostate-specific promoter to drive the yeast transcriptional activator, GAL4-VP16 (effector). The reporter construct carries five Gal4 binding sites upstream of the fl gene. We generated a transgenic mouse model using a single vector carrying the effector and reporter constructs. The transgenic mice show prostate-specific expression as early as three weeks of age. The bioluminescence signal in the prostate is significantly higher than in other organs. We also demonstrate that blocking androgen availability can downregulate the fl expression in the prostate. The transgenic mice display normal physical characteristics and developmental behavior, indicating that the high level of GAL4 driven expression is well tolerated. These findings suggest that the GAL4-VP16 transactivator can be used to amplify reporter gene expression from a relatively weak promoter in a transgenic mouse model. The transgenic TSTA model in conjunction with other transgenic cancer models should also help to detect and track malignancies. The strategies developed will be useful for transgenic research in general by allowing for amplified tissue specific gene expression.

Optical imaging of transferrin targeted PEI/DNA complexes in living subjects

Noninvasive optical bioluminescence imaging systems are important tools for evaluating gene expression in vivo for study of individual and temporal variation in a living animal. In this report, we demonstrate that expression of the firefly luciferase reporter gene (fl) delivered by transferrin (Tf) targeted polyethylenimine (PEI) complexes with, or without, poly(ethylene glycol) (PEG) modifications can be imaged in living A/J mice bearing N2A tumors using a cooled charged coupled device (CCD) camera. Tf-PEI-PEG, Tf-PEI, and PEI (positive control) complexes were tail-vein injected and mice were imaged at 5, 24, 48, and 72 h after complex injection. After imaging, the organs were analyzed ex vivo for firefly luciferase protein (FL) activity. The Tf and PEG modified formulations show significantly (P<0.05) higher FL activity in vivo and ex vivo at the tumor as compared to other organs, including the lungs (a site of high expression with PEI, the positive control). Furthermore, the in vivo bioluminescent signal correlated well (R(2)=0.83) with ex vivo FL activity. These data support that noninvasive imaging of fl reporter expression can be used to monitor the specificity of Tf-PEI and Tf-PEI-PEG polyplex targeting of N2A tumors in A/J mice.

Ex vivo cell labeling with 64Cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) for imaging cell trafficking in mice with positron-emission tomography

We have used copper-64-pyruvaldehyde-bis(N4-methylthiosemicarbazone) (64Cu-PTSM) to radiolabel cells ex vivo for in vivo positron-emission tomography (PET) imaging studies of cell trafficking in mice and for eventual application in patients. 2-[18F]-Fluoro-2-deoxy-d-glucose (FDG) cell labeling also was evaluated for comparison. 64Cu-PTSM uptake by C6 rat glioma (C6) cells increased for 180 min and then stabilized. The labeling efficiency was directly proportional to 64Cu-PTSM concentration and influenced negatively by serum. Label uptake per cell was greater with 64Cu-PTSM than with FDG. However, both 64Cu-PTSM- and FDG-labeled cells showed efflux of cell activity into supernatant. The 64Cu-PTSM labeling procedure did not interfere significantly with C6 cell viability and proliferation rate. MicroPET images of living mice indicate that tail-vein-injected labeled C6 cells traffic to the lungs and liver. In addition, transient splenic accumulation of radioactivity was clearly detectable in a mouse scanned at 3.33 h postinfusion of 64Cu-PTSM-labeled lymphocytes. In contrast, the liver was the principal organ of tracer localization after tail-vein administration of 64Cu-PTSM alone. These results indicate that in vivo imaging of cell trafficking is possible with 64Cu-PTSM-labeled cells. Given the longer t(1/2) of 64Cu (12.7 h) relative to 18F (110 min), longer cell-tracking periods (up to 24-36 h) should be possible now with PET.

Noninvasive quantitative imaging of protein-protein interactions in living subjects

We are developing methods to image molecular and cellular events in living subjects. In this study, we validate imaging of protein-protein interactions in living mice by using bioluminescent optical imaging. We use the well studied yeast two-hybrid system adapted for mammalian cells and modify it to be inducible. We employ the NF-kappaB promoter to drive expression of two fusion proteins (VP16-MyoD and GAL4-ID). We modulate the NF-kappaB promoter through tumor necrosis factor alpha. Firefly luciferase reporter gene expression is driven by the interaction of MyoD and ID through a transcriptional activation strategy. We demonstrate the ability to detect this induced protein-protein interaction in cell culture and image this induced interaction in living mice by using transiently transfected cells. The current approach will be a valuable and potentially generalizable tool to noninvasively and quantitatively image protein-protein interactions in living subjects. The approaches validated should have important implications for the study of protein-protein interactions in cells maintained in their natural in vivo environment as well as for the in vivo evaluation of new pharmaceuticals targeted to modulate protein-protein interactions.

Two-step transcriptional amplification as a method for imaging reporter gene expression using weak promoters

We are developing assays to image tissue-specific reporter gene expression in living mice by using optical methods and positron emission tomography. Approaches for imaging reporter gene expression depend on robust levels of mRNA and reporter protein. Attempts to image reporter gene expression driven by weak promoters are often hampered by the poor transcriptional activity of such promoters. Most tissue-specific promoters are weak relative to stronger but constitutively expressing viral promoters. In this study, we have validated methods to enhance the transcriptional activity of the prostate-specific antigen promoter for imaging by using a two-step transcriptional amplification (TSTA) system. We used the TSTA system to amplify expression of firefly luciferase (fl) and mutant herpes simplex virus type 1 thymidine kinase (HSV1-sr39tk) in a prostate cancer cell line (LNCaP). We demonstrate approximately 50-fold (fl) and approximately 12-fold (HSV1-sr39tk) enhancement by using the two-step approach. The TSTA system is observed to retain tissue selectivity. A cooled charge-coupled device optical imaging system was used to visualize the amplified fl expression in living mice implanted with LNCaP cells transfected ex vivo. These imaging experiments reveal a approximately 5-fold gain in imaging signal by using the TSTA system over the one-step system. The TSTA approach will be a valuable and generalizable tool to amplify and noninvasively image reporter gene expression in living animals by using tissue-specific promoters. The approaches validated should have important implications for study of gene therapy vectors, cell trafficking, transgenic models, as well as studying development of eukaryotic organisms.

Noninvasive optical imaging of firefly luciferase reporter gene expression in skeletal muscles of living mice

The ability to monitor reporter gene expression noninvasively offers significant advantages over current techniques such as postmortem tissue staining or enzyme activity assays. Here we demonstrate a novel method of repetitively tracking in vivo gene expression of firefly luciferase (FL) in skeletal muscles of mice using a cooled charged coupled device (CCD) camera. We first show that the cooled CCD camera provides consistent and reproducible results within +/-8% standard deviation from mean values, and a detection sensitivity (range tested: 1 x 10(4) - 1 x 10(9) plaque form-ing units (pfu)) of 1 x 10(6) pfu of E1-deleted adenovirus expressing FL driven by a cytomegalovirus promoter (Ad-CMV-FL). The duration and magnitude of adenoviral mediated (1 x 10(9) pfu) FL gene expression were then followed over time. FL gene expression in immunocompetent Swiss Webster mice peaks within the first 48 hours, falls by 98% after 20 days, and persists for >150 days. In contrast, FL activity in nude mice remains elevated for >110 days. Finally, transduced Swiss Webster and nude mice were sacrificed to show that the in vivo CCD signals correlate well with in vitro luciferase enzyme assays (r(2)=0.91 and 0.96, respectively). Our findings demonstrate the ability of the cooled CCD camera to sensitively and noninvasively track the location, magnitude, and persistence of FL gene expression. Monitoring of gene therapy studies in small animals may be aided considerably with further extensions of this technique.

Monitoring gene therapy with reporter gene imaging

Rapid advances in imaging technologies and gene transfer strategies offer a great opportunity to optimize clinical trials of human gene therapy. Reporter genes are emerging as very powerful tools to monitor the delivery, magnitude, and time variation of therapeutic gene transfer in vivo. Several reporter genes, such as the herpes simplex virus type 1 thymidine kinase, the dopamine type 2 receptor, and the somatostatin receptor type 2, are currently being successfully used with gamma camera, single photon emission computed tomography, and positron emission tomography imaging. These reporter genes can be coupled with a therapeutic gene of interest to indirectly monitor the expression of the therapeutic gene. Finally, applications of the reporter gene technology to other areas, such as cell trafficking studies and transgenic animal models, are now possible.

Human pharmacokinetic and dosimetry studies of [(18)F]FHBG: a reporter probe for imaging herpes simplex virus type-1 thymidine kinase reporter gene expression

9-[4-[(18)F]fluoro-3-(hydroxymethyl)butyl]guanine ([(18)F]FHBG) has been used as a reporter probe to image expression of herpes simplex virus type-1 thymidine kinase (HSV1-tk) reporter gene in living animals. Our aim was to study the kinetics, biodistribution, stability, dosimetry, and safety of [(18)F]FHBG in healthy human volunteers, preparatory to imaging patients undergoing HSV1-tk gene therapy.

METHODS

[(18)F]FHBG was synthesized with a specific activity of 37,000--444,000 GBq/mmol and a radiochemical purity > 99%. Ten healthy volunteers consented to participate in the study. A transmission scan was obtained before bolus injection of 70.3--229.4 MBq [(18)F]FHBG into a hand vein, followed by dynamic PET imaging with 4 consecutive emission scans. Warmed hand-vein blood was withdrawn at various times after injection for blood time--activity measurements. Electrocardiography, blood pressure, and blood and urine pharmacologic parameters were measured before and after injection of the [(18)F]FHBG tracer (n = 5). The stability of [(18)F]FHBG in the urine was analyzed. Attenuation-corrected images were reconstructed using the ordered-subsets expectation maximization algorithm. Image region-of-interest time-activity data were used with the MIRD program to estimate absorbed radiation dosages.

RESULTS

[(18)F]FHBG had rapid blood clearance; only 8.42% +/- 4.76% (mean +/- SD) of the peak blood activity remained at approximately 30 min. The average ratio of plasma activity to whole-blood activity during the study was 0.91 +/- 0.04. Penetration of [(18)F]FHBG across the blood-brain barrier was not observed. The primary routes of clearance were renal and hepatobiliary. High activities were observed in the bladder, gut, liver, and kidneys, but <0.0002% of the injected dose per gram was observed in other tissues. In the urine, 83% of activity 180 min after injection was stable [(18)F]FHBG. Blood and urine pharmacologic parameters did not change significantly after injection of the [(18)F]FHBG tracer. The bladder absorbed the highest radiation dose.

CONCLUSION

[(18)F]FHBG has the desirable in vivo characteristics of stability, rapid blood clearance, low background signal, biosafety, and acceptable radiation dosimetry in humans. This study forms the foundation for using [(18)F]FHBG in applications to monitor HSV1-tk reporter gene expression.

8-[18F]Fluoropenciclovir: an improved reporter probe for imaging HSV1-tk reporter gene expression in vivo using PET

We have synthesized and evaluated 8-[18F]fluoropenciclovir (FPCV) and compared it with 8-[18F]fluoroganciclovir (FGCV) for monitoring the expression of herpes simplex virus type 1 thymidine kinase (HSV1 -tk) reporter gene in cell culture and in vivo.

METHODS

C6 rat glioma cells stably transfected with HSV1-tk (C6-stb-tk+) and control C6 cells were evaluated for their ability to accumulate FGCV versus FPCV. For in vivo studies, 15 mice were injected by tail vein with increasing levels of an adenoviral vector carrying HSV1-tk. Forty-eight hours later the mice were injected with FPCV and killed 3 h later. The percentage injected dose per gram (%ID/g) liver was then determined. Two additional mice were studied by microPET and autoradiography using FPCV to image adenoviral-mediated hepatic HSV1-tk reporter gene expression. A tumor-bearing mouse (C6 control and C6-stb-tk+) was imaged with FDG, FGCV, and FPCV. Two mice carrying tumors expressing two different reporter genes, HSV1-tk and dopamine type 2 receptor (D2R), were also imaged by microPET using FPCV (day 1) and 3-(2'-[18F]fluoroethyl)spiperone (FESP) (day 2).

RESULTS

FPCV shows a significantly greater accumulation in C6-stb-tk+ cells than does FGCV (P < 0.05). Over identical ranges of adenoviral administration, mouse liver shows a higher %ID/g liver for FPCV (0%-9%) compared with our previously reported results with FGCV (0%-3%). In C6 control and C6-stb-tk+ tumor-bearing mice, FPCV has a greater accumulation than does FGCV for equal levels of HSV1-tk gene expression. In mice carrying tumors expressing either HSV1-tk or D2R reporter genes, there is a corresponding retention of FPCV and FESP, respectively.

CONCLUSION

These results indicate that FPCV is a better reporter probe than is FGCV for imaging lower levels of HSV1 -tk gene expression in vivo. The results also reveal the ability to monitor the expression of two distinct reporter genes in the same animal using reporter probes specific for each gene.

Seeing is believing: non-invasive, quantitative and repetitive imaging of reporter gene expression in living animals, using positron emission tomography

The ability to monitor reporter gene expression in living animals and in patients will permit longitudinal examinations both of somatically transferred DNA in experimental animals and patients and of transgenic constructs expressed in experimental animals. If investigators can non-invasively monitor the organ and tissue specificity, the magnitude and the duration of gene expression from somatically transferred DNA and from transgenes, conceptually new experimental paradigms will be possible. If clinicians can non-invasively monitor the location, extent and duration of somatically transferred genes, they will be better able to determine the correlations between expression of therapeutic genes and clinical outcomes. We have developed two reporter gene systems for in vivo reporter gene imaging in which the protein products of the reporter genes sequester positron-emitting reporter probes. The "PET reporter gene" dependent sequestration of the "PET reporter probes" is subsequently measured in living animals by Positron Emission Tomography (PET). We describe here the principles of PET reporter gene/PET reporter probe in vivo imaging, the development of two imaging systems, and the validation of their ability to non-invasively, quantitatively and repetitively image reporter gene expression in murine viral gene transfer and transgenic models.

A mutant herpes simplex virus type 1 thymidine kinase reporter gene shows improved sensitivity for imaging reporter gene expression with positron emission tomography

We are developing assays for noninvasive, quantitative imaging of reporter genes with positron emission tomography (PET), for application both in animal models and in human gene therapy. We report here a method to improve the detection of lower levels of PET reporter gene expression by utilizing a mutant herpes simplex virus type 1 thymidine kinase (HSV1-sr39tk) as a PET reporter gene. The HSV1-sr39tk mutant was identified from a library of site-directed mutants. Accumulation (net uptake) of the radioactively labeled substrates [8-(3)H]penciclovir ([8-(3)H]PCV), and 8-[(18)F]fluoropenciclovir (FPCV) in C6 rat glioma cells expressing HSV1-sr39tk is increased by a factor of approximately 2.0 when compared with C6 cells expressing wild-type HSV1-tk. The increased imaging sensitivity of HSV1-sr39tk when FPCV is used is also demonstrated in vivo both with tumor cells stably transfected with either HSV1-tk or HSV1-sr39tk, and after hepatic delivery of HSV1-tk or HSV1-sr39tk by using adenoviral vectors. The use of HSV1-sr39tk as a PET reporter gene and FPCV as a PET reporter probe results in significantly enhanced sensitivity for imaging reporter gene expression in vivo.

Imaging adenoviral-directed reporter gene expression in living animals with positron emission tomography

We are developing quantitative assays to repeatedly and noninvasively image expression of reporter genes in living animals, using positron emission tomography (PET). We synthesized positron-emitting 8-[18F]fluoroganciclovir (FGCV) and demonstrated that this compound is a substrate for the herpes simplex virus 1 thymidine kinase enzyme (HSV1-TK). Using positron-emitting FGCV as a PET reporter probe, we imaged adenovirus-directed hepatic expression of the HSV1-tk reporter gene in living mice. There is a significant positive correlation between the percent injected dose of FGCV retained per gram of liver and the levels of hepatic HSV1-tk reporter gene expression (r2 > 0.80). Over a similar range of HSV1-tk expression in vivo, the percent injected dose retained per gram of liver was 0-23% for ganciclovir and 0-3% for FGCV. Repeated, noninvasive, and quantitative imaging of PET reporter gene expression should be a valuable tool for studies of human gene therapy, of organ/cell transplantation, and of both environmental and behavioral modulation of gene expression in transgenic mice.

Imaging of adenoviral-directed herpes simplex virus type 1 thymidine kinase reporter gene expression in mice with radiolabeled ganciclovir

We are developing procedures to repeatedly and noninvasively image the expression of transplanted reporter genes in living animals and in patients, using PET. We have investigated the use of the Herpes Simplex Virus type 1 thymidine kinase gene (HSV1-tk) as a reporter gene and [8-14C]-ganciclovir as a reporter probe. HSV1-tk, when expressed, leads to phosphorylation of [8-14C]-ganciclovir. As a result, specific accumulation of phosphorylated [8-14C]-ganciclovir should occur almost exclusively in tissues expressing the HSV1-tk gene.

METHODS

An adenoviral vector was constructed carrying the HSV1-tk gene along with a control vector. C6 rat glioma cells were infected with either viral vector and uptake of [8-3H]-ganciclovir was determined. In addition, 12 mice were injected with varying levels of either viral vector. Adenovirus administration in mice leads primarily to liver infection. Forty-eight hours later the mice were injected with [8-14C]-ganciclovir, and 1 hr later the mice were sacrificed and biodistribution studies performed. Digital whole-body autoradiography also was performed on separate animals. HSV1-tk expression was assayed, using both normalized HSV1-tk mRNA levels and relative HSV1-TK enzyme levels, in both the cell culture and murine studies.

RESULTS

Cell culture, murine tissue biodistribution and murine in vivo digital whole-body autoradiography all demonstrate the feasibility of HSV1-tk as a reporter gene and [8-14C]-ganciclovir as an imaging reporter probe. A good correlation (r2 = 0.86) between the [8-14C]-ganciclovir percent injected dose per gram tissue from HSV1-tk positive tissues and HSV1-TK enzyme levels in vivo was found. An initial study in mice with [8-18F]-fluoroganciclovir and microPET imaging supports further investigation of [8-18F]-fluoroganciclovir as a PET reporter probe for imaging HSV1-tk gene expression.

CONCLUSION

These results demonstrate the feasibility of using [8-14C]-ganciclovir as a reporter probe for the HSV1-tk reporter gene, using an in vivo adenoviral mediated gene delivery system in a murine model. The results form the foundation for further investigation of [8-18F]-fluoroganciclovir for noninvasive and repeated imaging of gene expression with PET.

Induction of a beta-phaseolin promoter by exogenous abscisic acid in tobacco: developmental regulation and modulation by external sucrose and Ca2+ ions

Phaseolin genes are induced by unidentified factors at the onset of seed maturation in embryos of both Phaseolus and tobacco. We show that in tobacco, expression of a beta-phaseolin promoter-GUS (PHSbeta-uidA) mRNA and the corresponding GUS activity, could be induced by abscisic acid (ABA). The effect paralleled an increase in the amount of endogenous 12S globulin (Glb12S) mRNA. In contrast, ABA repressed the expression of isocitrate lyase (ll9) mRNA. The responses of PHSbeta-uidA and Glb12S to ABA declined markedly between 11 and 13 DAF, indicating that they are developmentally regulated. We also show evidence that the ABA response of PHSbeta-uidA can be modulated by the external concentrations of sucrose and Ca2+ ion. These compounds inhibited the response if added to the medium separately, in the concentration ranges of 80-200 mM for sucrose and 0.76-20 mM for CaCl2. However, the presence of both sucrose and CaCl2 restored the ABA response to 20-40% of the maximum value measured in sucrose- and CaCl2-free media. These results suggest that ABA induction of beta-phaseolin gene expression is modulated by developmental signals and by the external supply of sucrose and calcium to the embryos.

Allelic variation in the mouse Tap-1 and Tap-2 transporter genes

The TAP1 and TAP2 proteins form a heterodimer that transports short peptides from the cytosol into the endoplasmic reticulum lumen. Extensive allelic polymorphism of the rat TAP transporter has been shown to affect the repertoire of peptides presented by MHC class I molecules. Structural polymorphism in the human TAP genes is much more limited and has not been observed to have functional consequences. We have examined the polymorphism in mouse TAP1 and TAP2 in inbred mice. While the number of polymorphic positions in these molecules is more similar to that in human than to that in the rat, all strains examined have a structurally unique TAP transporter, suggesting the possibility of functional polymorphism. Furthermore, allelic variations in the mouse transporter are predominantly located in or adjacent to membrane-spanning domains, although no significant bias in the ratio of nonsynonymous to synonymous substitutions is observed. We also report that mouse TAP1 begins 172 amino acids upstream of the previously published start site and report the genomic organization of mouse Tap-1 and Tap-2.

Allelic variation in the mouse Tap-1 and Tap-2 transporter genes

The TAP1 and TAP2 proteins form a heterodimer that transports short peptides from the cytosol into the endoplasmic reticulum lumen. Extensive allelic polymorphism of the rat TAP transporter has been shown to affect the repertoire of peptides presented by MHC class I molecules. Structural polymorphism in the human TAP genes is much more limited and has not been observed to have functional consequences. We have examined the polymorphism in mouse TAP1 and TAP2 in inbred mice. While the number of polymorphic positions in these molecules is more similar to that in human than to that in the rat, all strains examined have a structurally unique TAP transporter, suggesting the possibility of functional polymorphism. Furthermore, allelic variations in the mouse transporter are predominantly located in or adjacent to membrane-spanning domains, although no significant bias in the ratio of nonsynonymous to synonymous substitutions is observed. We also report that mouse TAP1 begins 172 amino acids upstream of the previously published start site and report the genomic organization of mouse Tap-1 and Tap-2.

Human C1q induces eosinophil migration

Eosinophils (Eo) play a significant role in allergic inflammation and the host's immunity to parasitic infections. Although the presence of C1q-binding cell surface molecule(s) (C1q-R) on Eo had been previously implicated by the ability of C1q to augment IgG-dependent, Eo-mediated killing of schistosomula, little is known about the structure or the function of this receptor. The present studies were therefore undertaken to immunochemically demonstrate and to examine the biology of Eo C1q-R. Eo were purified to homogeneity (>90%) and viability (>98%) from hypereosinophilic donors by Percoll density gradient. Western blot analysis using antibodies to cC1q-R and gC1q-R showed distinct bands corresponding to cC1q-R (60 kDa) and gC1q-R (33 kDa) when immunoblotted with their respective antibodies. The Eo C1q-R was tested for its ability to induce chemokinesis and/or chemotaxis as assessed by the modified Boyden microchamber assay utilizing 5-micrometer-pore polycarbonate membranes and using C1q, cC1q, or gC1q (10 micrograms/ml) as agonists. The known chemotactic factors C5a and RANTES (10(-8)M) were used as positive controls. The results showed that at this concentration, cC1q was most efficient in its ability to induce Eo migration (20 +/- SEM 12, n = 4) followed by C1q (107 +/- SEM 7, n=7) and gC1q (77 +/- SEM 10, n = 10). When checkerboard analysis was performed, the data indicated that the observed phenomenon was likely to be due largely to chemokinesis. As expected, C5a (145 +/- SEM 15, n = 7) and RANTES (145 +/- SEM 43, n = 7) were both chemotactic. Furthermore, incubation of Eo with 50 micrograms of either C1q, gC1q, or cC1q (1 hr, 37 degrees C) did not cause release of eosinophil cationic protein as measured by RIA, nor did it enhance the expression of CD11b or CD29 as assessed by FACS analysis. The data presented in this paper show that Eo express both cC1q-R and gC1q-R and may participate in Eo function by providing a primary signal for locomotion.

Accelerated hybridization of oligonucleotides to duplex DNA

We report two strategies for accelerating the hybridization of oligonucleotides to DNA. We demonstrate that oligodeoxyribonucleotides and peptide nucleic acid oligomers hybridize to inverted repeats within duplex DNA by D-loop formation. Oligonucleotides and duplex template form an active complex, which can be recognized by T7 DNA polymerase to prime polymerization. Quantitation of polymerization products allowed the rate of hybridization to be estimated, and peptide nucleic acid oligomers and oligonucleotide-protein adducts anneal with association constants 500- and 12,000-fold greater, respectively, than the analogous unmodified oligonucleotides. Together, these results indicate that sequences within duplex DNA can be targeted by Watson-Crick base pairing and that chemical modifications can dramatically enhance the rate of strand association. These findings should facilitate targeting of oligomers for priming DNA polymerization, the detection of diagnostic sequences, and the disruption of gene expression. The observed acceleration of hybridization may offer a new perspective on the ability of RecA or other proteins to accelerate strand invasion.

Cytohistomorphology of prostatic lesions--by FNAC & scrape methods

A pilot study of transrectal fine needle aspiration biopsy was conducted in 44 patients, above the age of 50 years, who presented with features of obstructive uropathy during a one year period between August 1990 and April 1991. Histopathological study was carried out in 23 out of 44 patients, who underwent total prostatectomy or transurethral resection following the aspiration biopsy procedure. In 21 patients FNAB by the transrectal route could not be obtained because of technical difficulties; therefore intraoperative scrape cytology was studied prior to histopathology, of the fresh prostatic specimen. A good cytohistopathological correlation was obtained by both methods; an accuracy of 95.6% and 95.2% with FNAC and scrape respectively. A wide range of benign and malignant lesions were studied.

Neurologic manifestations in children with North American Lyme disease

To delineate the spectrum of neurologic manifestations and the relative frequencies of different syndromes associated with North American Lyme disease, we describe 96 children referred for neurologic problems in the setting of Borrelia burgdorferi infection. The most frequent neurologic symptom was headache, and the most common sign was facial palsy. Less common manifestations were sleep disturbance, and papilledema associated with increased intracranial pressure. Signs and symptoms of peripheral nervous system involvement were infrequent. The most common clinical syndromes were mild encephalopathy, lymphocytic meningitis, and cranial neuropathy (facial nerve palsy). In contrast with adult patients with neurologic Lyme disease, meningoradiculitis (Bannwarth's syndrome) and peripheral neuropathy syndromes were rare. However, a "pseudotumor cerebri-like" syndrome seems to be unique to North American pediatric Lyme disease.

Reactive arthropathy and autoimmunity in non-HIV-associated immunodeficiency

The spectrum of arthropathy in non-HIV immune deficiency states includes arthritis due to prevalent infectious pathogens and autoimmunity that may in some instances be triggered by microorganisms. Joint symptoms may be clinical manifestations of disease, or they may develop later during therapy for immunodeficiency. Pathogenesis can be related to occult infection, loss of mucosal barrier function, defective clearance of immune complexes, or aberrant immune responses. Proper treatment includes an appreciation of likely pathogens, an understanding of the nature of immunologic deficits, and rigorous exclusion of immune dysfunction that may be secondary to treatment.

Digital system for P-wave detection and synchronization of the artificial heart

This paper describes the implementation of a microcomputer based P-wave synchronization system for the artificial heart. This system provides for synchronization of the cardiac prosthesis pump with P-wave signals from electrodes implanted in the remnant of the natural atrium. The device carries out the functions of P-wave detection and determines the duration of systole based upon a moving average of the time intervals between successive pulses. The system has been tested both on a mock circulatory system and in vivo on calves. The purpose of the paper is to provide details of the circuitry and algorithms used.