3D-conformal very-high energy electron therapy as candidate modality for FLASH-RT: A treatment planning study for glioblastoma and lung cancer

BACKGROUND

Pre-clinical ultra-high dose rate (UHDR) electron irradiations on time scales of 100 ms have demonstrated a remarkable sparing of brain and lung tissues while retaining tumor efficacy when compared to conventional dose rate irradiations. While clinically-used gantries and intensity modulation techniques are too slow to match such time scales, novel very-high energy electron (VHEE, 50-250 MeV) radiotherapy (RT) devices using 3D-conformed broad VHEE beams are designed to deliver UHDR treatments that fulfill these timing requirements.

PURPOSE

To assess the dosimetric plan quality obtained using VHEE-based 3D-conformal RT (3D-CRT) for treatments of glioblastoma and lung cancer patients and compare the resulting treatment plans to those delivered by standard-of-care intensity modulated photon RT (IMRT) techniques.

METHODS

Seven glioblastoma patients and seven lung cancer patients were planned with VHEE-based 3D-CRT using 3 to 16 coplanar beams with equidistant angular spacing and energies of 100 and 200 MeV using a forward planning approach. Dose distributions, dose-volume histograms, coverage (V95% ) and homogeneity (HI98% ) for the planning target volume (PTV), as well as near-maximum doses (D2% ) and mean doses (Dmean ) for organs-at-risk (OAR) were evaluated and compared to clinical IMRT plans.

RESULTS

Mean differences of V95% and HI98% of all VHEE plans were within 2% or better of the IMRT reference plans. Glioblastoma plan dose metrics obtained with VHEE configurations of 200 MeV and 3-16 beams were either not significantly different or were significantly improved compared to the clinical IMRT reference plans. All OAR plan dose metrics evaluated for VHEE plans created using 5 beams of 100 MeV were either not significantly different or within 3% on average, except for Dmean for the body, Dmean for the brain, D2% for the brain stem, and D2% for the chiasm, which were significantly increased by 1, 2, 6, and 8 Gy, respectively (however below clinical constraints). Similarly, the dose metrics for lung cancer patients were also either not significantly different or were significantly improved compared to the reference plans for VHEE configurations with 200 MeV and 5 to 16 beams with the exception of D2% and Dmean to the spinal canal (however below clinical constraints). For the lung cancer cases, the VHEE configurations using 100 MeV or only 3 beams resulted in significantly worse dose metrics for some OAR. Differences in dose metrics were, however, strongly patient-specific and similar for some patient cases.

CONCLUSIONS

VHEE-based 3D-CRT may deliver conformal treatments to simple, mostly convex target shapes in the brain and the thorax with a limited number of critical adjacent OAR using a limited number of beams (as low as 3 to 7). Using such treatment techniques, a dosimetric plan quality comparable to that of standard-of-care IMRT can be achieved. Hence, from a treatment planning perspective, 3D-conformal UHDR VHEE treatments delivered on time scales of 100 ms represent a promising candidate technique for the clinical transfer of the FLASH effect.

Improving interinstitutional and intertechnology consistency of pulmonary SBRT by dose prescription to the mean internal target volume dose

Purpose

Dose, fractionation, normalization and the dose profile inside the target volume vary substantially in pulmonary stereotactic body radiotherapy (SBRT) between different institutions and SBRT technologies. Published planning studies have shown large variations of the mean dose in planning target volume (PTV) and gross tumor volume (GTV) or internal target volume (ITV) when dose prescription is performed to the PTV covering isodose. This planning study investigated whether dose prescription to the mean dose of the ITV improves consistency in pulmonary SBRT dose distributions.

Materials and methods

This was a multi-institutional planning study by the German Society of Radiation Oncology (DEGRO) working group Radiosurgery and Stereotactic Radiotherapy. CT images and structures of ITV, PTV and all relevant organs at risk (OAR) for two patients with early stage non-small cell lung cancer (NSCLC) were distributed to all participating institutions. Each institute created a treatment plan with the technique commonly used in the institute for lung SBRT. The specified dose fractionation was 3 × 21.5 Gy normalized to the mean ITV dose. Additional dose objectives for target volumes and OAR were provided.

Results

In all, 52 plans from 25 institutions were included in this analysis: 8 robotic radiosurgery (RRS), 34 intensity-modulated (MOD), and 10 3D-conformal (3D) radiation therapy plans. The distribution of the mean dose in the PTV did not differ significantly between the two patients (median 56.9 Gy vs 56.6 Gy). There was only a small difference between the techniques, with RRS having the lowest mean PTV dose with a median of 55.9 Gy followed by MOD plans with 56.7 Gy and 3D plans with 57.4 Gy having the highest. For the different organs at risk no significant difference between the techniques could be found.

Conclusions

This planning study pointed out that multiparameter dose prescription including normalization on the mean ITV dose in combination with detailed objectives for the PTV and ITV achieve consistent dose distributions for peripheral lung tumors in combination with an ITV concept between different delivery techniques and across institutions.

Supplementary Information

The online version of this article (10.1007/s00066-021-01799-w) contains supplementary material, which is available to authorized users.

A new method to visualize and to spare the ureters during SBRT for oligo metastatic patients

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Ureteral injury following abdominal irradiation may have serious consequences.

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Urography CT scan is a simple procedure to spare ureters during SBRT.

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Using a urography CT scan can significantly reduce the dose to the ureters.

This article describes a ureter-sparing procedure used to treat lymph node metastases with SBRT. We delivered 35 Gy in 5 fractions of 7 Gy to patients with lesions located less than 7 mm from the ureters using a urography CT scan for planification. Two dosimetry plans were created, one using a CT scan urography-based contour and the other using the native phase. PTV coverage were not statistically different but this technique was able to significantly reduce median delivered Dmax to the ureters. These preliminary results demonstrate the feasibility of locating the ureters in a planning CT scan to protect them.

NUCLEAR DATA UNCERTAINTY QUANTIFICATION FOR THE DECAY HEAT OF PWR MOX FUELS USING DATA ASSIMILATION OF ELEMENTARY FISSION BURSTS

Currently there is no integral experimental data for code validation regarding the decay heat of MOX fuels, excepted fission burst experiments (for fission products contributions at short cooling times) or post-irradiated experiments on nuclide inventories (restricted number of nuclide of interest for decay heat). The uncertainty quantification mainly relies on uncertainty propagation of nuclear data covariances. In the recent years, the transposition method, based on the data assimilation theory, was used in order to transpose the experiment-to-calculation discrepancies at a given set of parameters (cooling time, fuel burnup) to another set of parameters. As an example, this method was used on the CLAB experiments and the experiment-to-calculation discrepancies at 13 years were transposed to an UOX fuel between 5 and 27 years and for burnups from 10 to 50 GWd/t. The purpose of this paper is to study to what extent the transposition method could be used for MOX fuels. In particular, the Dickens fission burst experiment of 239Pu was considered for MOX fuels at short cooling times (< 1h30) and low burnup (< 10 GWd/t). The impact of fission yields (FY) correlations was also discussed. As a conclusion, the efficiency of the transposition process is limited by the experimental uncertainties larger than nuclear data uncertainties, and by the fact that fission burst experiments would only be representative to the FY contribution of the decay heat uncertainty of an irradiated reactor fuel. Nevertheless, this method strengthens the decay heat uncertainties at very short cooling times, previously based only on nuclear data covariance propagation through computation.

Curative management of a cardiac metastasis from lung cancer revealed by an electrical storm

Although cardiac metastases (CM) are more common than primary cardiac malignant tumors, they remain a rare localization of metastatic cancer. Until recently, CM were surgically treated as a palliative approach because of a lack of ablative solutions even for oligometastatic patients. Technological advances in radiation therapy (RT) in thoracic oncology have led to high precision delivery that enlarged the indications for stereotactic body radiotherapy (SBRT). To date, there are limited reports of cardiac SBRT for CM. Herein, we report a cardiac SBRT performed in curative intent for a lung cancer patient metastatic to the heart.

Integral data assimilation of the MERCI-1 experiment for the nuclear data associated with the PWR decay heat computation

Nuclear decay heat is a crucial issue for PWR in-core safety after reactor shutdown and back-end cycle. It is a dimensioning parameter for safety injection systems (SIS) to avoid a dewatering of the reactor core. The decay heat uncertainty needs to be controlled over the largest range of applications. The assimilation of the MERCI-1 experiment was studied to provide feedbacks on nuclear data. This experiment consisted in the measurement of the decay heat of a PWR UOX fuel sample irradiated in the OSIRIS reactor, for cooling times between 45 minutes and 42 days. More specifically, the consideration of several experimental values of MERCI-1 at different cooling times was tested. This raised issues about correlations to consider between different measurements. Besides, the impact of considering correlations between independent fission yields in covariance matrices on the decay heat uncertainty calculation and on the feedbacks on nuclear data is discussed.

50-Gy Stereotactic Body Radiation Therapy to the Dominant Intraprostatic Nodule: Results From a Phase 1a/b Trial

PURPOSE

Although localized prostate cancer (PCa) is multifocal, the dominant intraprostatic nodule (DIN) is responsible for disease progression after radiation therapy. PCa expresses antigens that could be recognized by the immune system. We therefore hypothesized that stereotactic dose escalation to the DIN is safe, may increase local control, and may initiate tumor-specific immune responses.

PATIENTS AND METHODS

Patients with localized PCa were treated with stereotactic extreme hypofractionated doses of 36.25 Gy in 5 fractions to the whole prostate while simultaneously escalating doses to the magnetic resonance image-visible DIN (45 Gy, 47.5 Gy, and 50 Gy in 5 fractions). The phase 1a part was designed to determine the recommended phase 1b dose in a "3 + 3" cohort-based, dose-escalation design. The primary endpoint was dose-limiting toxicities defined as ≥grade 3 gastrointestinal (GI) or genitourinary (GU) toxicity (or both) by National Cancer Institute Common Terminology Criteria for Adverse Events (version 4) up to 90 days after the first radiation fraction. The secondary endpoints were prostate-specific antigen kinetics, quality of life (QoL), and blood immunologic responses.

RESULTS

Nine patients were treated in phase 1a. No dose-limiting toxicities were observed at either level, and therefore the maximum tolerated dose was not reached. Further characterization of tolerability, efficacy, and immunologic outcomes was conducted in the subsequent 11 patients irradiated at the highest dose level (50 Gy) in the phase 1b expansion cohort. Toxicity was 45% and 25% for grades 1 and 2 GU, and 20% and 5% for grades 1 and 2 GI, respectively. No grade 3 or worse toxicity was reported. The average (±standard error of the mean) of the QoL assessments at baseline and at 3-month posttreatment were 0.8 (±0.8) and 3.5 (±1.5) for the bowel (mean difference, 2.7; 95% confidence interval, 0.1-5), and 6.4 (±0.8) and 7.27 (±0.9) for the International Prostate Symptom Score (mean difference, 0.87; 95% confidence interval, 0.3-1.9), respectively. A subset of patients developed antigen-specific immune responses against prostate-specific membrane antigen (n = 2), prostatic acid phosphatase (n = 1), prostate stem cell antigen (n = 4), and prostate-specific antigen (n = 2).

CONCLUSIONS

Irradiation of the whole prostate with 36.25 Gy in 5 fractions and dose escalation to 50 Gy to the DIN was tolerable and determined as the recommended phase 1b dose. This treatment has promising antitumor activity, which will be confirmed by the ongoing phase 2 part. Preliminary QoL analysis showed minimal impact in GU, GI, and sexual domains. Stereotactic irradiation induced antigen-specific immune responses in a subset of patients.

IMRT credentialing for prospective trials using institutional virtual phantoms: results of a joint European Organization for the Research and Treatment of Cancer and Radiological Physics Center project

Background and purpose

Intensity-modulated radiotherapy (IMRT) credentialing for a EORTC study was performed using an anthropomorphic head phantom from the Radiological Physics Center (RPC; RPC_PH). Institutions were retrospectively requested to irradiate their institutional phantom (INST_PH) using the same treatment plan in the framework of a Virtual Phantom Project (VPP) for IMRT credentialing.

Materials and methods

CT data set of the institutional phantom and measured 2D dose matrices were requested from centers and sent to a dedicated secure EORTC uploader. Data from the RPC_PH and INST_PH were thereafter centrally analyzed and inter-compared by the QA team using commercially available software (RIT; ver.5.2; Colorado Springs, USA).

Results

Eighteen institutions participated to the VPP. The measurements of 6 (33%) institutions could not be analyzed centrally. All other centers passed both the VPP and the RPC ±7%/4 mm credentialing criteria. At the 5%/5 mm gamma criteria (90% of pixels passing), 11(92%) as compared to 12 (100%) centers pass the credentialing process with RPC_PH and INST_PH (p = 0.29), respectively. The corresponding pass rate for the 3%/3 mm gamma criteria (90% of pixels passing) was 2 (17%) and 9 (75%; p = 0.01), respectively.

Conclusions

IMRT dosimetry gamma evaluations in a single plane for a H&N prospective trial using the INST_PH measurements showed agreement at the gamma index criteria of ±5%/5 mm (90% of pixels passing) for a small number of VPP measurements. Using more stringent, criteria, the RPC_PH and INST_PH comparison showed disagreement. More data is warranted and urgently required within the framework of prospective studies.

Percutaneous penetration and distribution of VX using in vitro pig or human excised skin validation of demeton-S-methyl as adequate simulant for VX skin permeation investigations

The organophosphorus (OP) chemical warfare V agent O-ethyl-S-[2(di-isopropylamino)ethyl] methyl phosphonothioate (VX), is a highly toxic compound which mainly penetrates the body via percutaneous pathways. Hence, the following prerequisite: to ascertain compound absorption and percutaneous profile distribution with a view to further assessing the efficacy of topical skin protectants. We first selected the most appropriate receptor fluid to carry out in vitro VX absorption experiments, namely: Hanks's Balanced Salt Solution (HBSS). After a 24-h topical exposure time lapse, we measured altogether the percentage of applied dose unabsorbed and absorbed, penetration rate, lag time, permeability coefficient (K(p)), and dose of VXeq present in skin. To such an end, we used full-thickness and split-thickness pig-ear or human abdominal skin membranes. Further, we scrutinised the potential use of two specific molecules as suitable surrogates for VX percutaneous penetration analyses: thus, we compared the present VX toxicokinetic parameters to earlier findings from our research unit, with respect to OP insecticides demethon-S-methyl (DSM) and paraoxon (POX). Within the framework of our study, we wish to highlight the following evidence: (a) pig-ear skin proves a relevant model to predict in vitro human abdominal skin, taking into account a 2-fold higher skin permeability to VXeq; (b) both full or split-thickness skin membranes may be used indiscriminately to gauge penetration rate and absorbed dose; (c) DSM applied on full-thickness pig-ear skin is the most relevant model to mimic the in vitro VX absorption through full-thickness skin model.

In vitro percutaneous penetration of organophosphorus compounds using full-thickness and split-thickness pig and human skin

Organophosphorus compounds (OPs), such as pesticides and chemical warfare agents like sarin (GB), soman (GD) and VX, are highly toxic compounds. The OP vapours and their liquid forms are readily absorbed through the skin, therefore, protecting the skin of people who are potentially exposed to these agents is crucial. The development of effective countermeasures relies on a better knowledge of the percutaneous penetration of such molecules. The purpose of this present study is to determine the in vitro percutaneous penetration parameters of two pesticides DSM and DFP, as potential simulants of V and G agents, respectively, using four in vitro systems: full-thickness and split-thickness human abdominal and pig-ear skin membranes mounted on static diffusion cells. Based on the toxicokinetic parameters of the percutaneous penetration of DSM and DFP, we demonstrated that (a) pig-ear skin is a relevant model to predict the in vitro human skin permeability taking into account a 2-fold difference between these two species (b) both full and split-thickness skin membranes could be used indiscriminately, (c) DSM and DFP would be appropriate surrogates for V and G agents to perform skin permeation studies.

Remarkable impact of intermode couplings on multimode vibronic dynamics: the photoelectron spectrum of CH3F

Electronic and nuclear motions on intersecting potential energy surfaces are often intricately mixed and the spectrum can become very complex. Here we choose the strongly coupled Jahn-Teller system CH3F+ as a prototype example, and establish the importance of intermode coupling terms on multimode vibronic dynamics. The theoretical approach consists of a full second-order diabatic vibronic Hamiltonian, constructed from high-quality electronic structure calculations. Our results compare amazingly well with the experimental data. This highlights the success of the present theoretical approach in explaining the complex structure of vibronic spectra, ubiquitous in molecular systems.

A recombinant rubella virus E1 glycoprotein as a rubella vaccine candidate

A recombinant rubella virus E1 (rE1) glycoprotein was produced and some of its chemical and immunological features were characterized. Two animal models were then used to establish that the rE1 glycoprotein and rubella virus particles shared antigenic and immunogenic properties. In the first one, sera from rE1 glycoprotein-immunized BALB/c mice neutralized in vitro rubella virus infection. In the second model, severe combined immune deficient (SCID) mice implanted with tonsil fragments from rubella immune donors and immunized with rE1 glycoprotein produced human anti-rubella virus antibodies. Altogether, these results showed that immunization with rE1 glycoprotein elicited neutralizing anti-rubella virus antibodies. This study thus indicated that the rE1 glycoprotein could constitute a non-replicating rubella vaccine.

Endogenous Angiotensin II Induces Atherosclerotic Plaque Vulnerability and Elicits a Th1 Response in ApoE −/− Mice

Rupture of vulnerable plaques is the main cause of acute cardiovascular events. However, mechanisms responsible for transforming a stable into a vulnerable plaque remain elusive. Angiotensin II, a key regulator of blood pressure homeostasis, has a potential role in atherosclerosis. To study the contribution of angiotensin II in plaque vulnerability, we generated hypertensive hypercholesterolemic ApoE-/- mice with either normal or endogenously increased angiotensin II production (renovascular hypertension models). Hypertensive high angiotensin II ApoE-/- mice developed unstable plaques, whereas in hypertensive normal angiotensin II ApoE-/- mice plaques showed a stable phenotype. Vulnerable plaques from high angiotensin II ApoE-/- mice had thinner fibrous cap (P<0.01), larger lipid core (P<0.01), and increased macrophage content (P<0.01) than even more hypertensive but normal angiotensin II ApoE-/- mice. Moreover, in mice with high angiotensin II, a skewed T helper type 1-like phenotype was observed. Splenocytes from high angiotensin II ApoE-/- mice produced significantly higher amounts of interferon (IFN)-gamma than those from ApoE-/- mice with normal angiotensin II; secretion of IL4 and IL10 was not different. In addition, we provide evidence for a direct stimulating effect of angiotensin II on lymphocyte IFN-gamma production. These findings suggest a new mechanism in plaque vulnerability demonstrating that angiotensin II, within the context of hypertension and hypercholesterolemia, independently from its hemodynamic effect behaves as a local modulator promoting the induction of vulnerable plaques probably via a T helper switch.

Fate and functions of human adult lymphoid cells in immunodeficient mice

Laboratory models enabling to study in vivo human leukocyte functions have been developed. Most of the models consist of human immunocytes transferred to mice homozygous for the scid mutation. Mice with additional immunodeficient-prone genetic background or with immunodeficiency-induced conditioning have also been used. Human grafts mainly consisted of human immune cells in suspension injected intraperitoneally, or in pieces of human organs containing immunocytes implanted subcutaneously. Cells in suspension could be easily manipulated in vitro before transfer to the animal, but disseminated within the mouse body. In opposition, human cells mostly remained within implantation areas of animals given human organ pieces. This favorizes cell interactions and helps for cell recovery after their in vivo passage. Moreover, the diversity of antibodies in animals transplanted with human lymphoid organ pieces appeared broader than that of mice transferred with lymphocytes in suspension. Spontaneous recall antibody and autoantibody productions have been generally observed in animals transferred with cells from donors with such antibodies. In vivo boosting of recall antibody by antigen has been most successful, but such a manipulation inconstantly boosted autoantibodies. Primary human T and B cell responses were difficult to obtain in xenochimeric animals, and success has been generally obtained by optimizing human immune response parameters, such as antigen presentation.

The mechanism for water exchange in [UO(2)(H(2)O)(5)](2+) and [UO(2)(oxalate)(2)(H(2)O)](2-), as studied by quantum chemical methods

The mechanisms for the exchange of water between [UO(2)(H(2)O)(5)](2+), [UO(2)(oxalate)(2)(H(2)O)](2)(-)(,) and water solvent along dissociative (D), associative (A) and interchange (I) pathways have been investigated with quantum chemical methods. The choice of exchange mechanism is based on the computed activation energy and the geometry of the identified transition states and intermediates. These quantities were calculated both in the gas phase and with a polarizable continuum model for the solvent. There is a significant and predictable difference between the activation energy of the gas phase and solvent models: the energy barrier for the D-mechanism increases in the solvent as compared to the gas phase, while it decreases for the A- and I-mechanisms. The calculated activation energy, Delta U(++), for the water exchange in [UO(2)(H(2)O)(5)](2+) is 74, 19, and 21 kJ/mol, respectively, for the D-, A-, and I-mechanisms in the solvent, as compared to the experimental value Delta H(++) = 26 +/- 1 kJ/mol. This indicates that the D-mechanism for this system can be ruled out. The energy barrier between the intermediates and the transition states is small, indicating a lifetime for the intermediate approximately 10(-10) s, making it very difficult to distinguish between the A- and I-mechanisms experimentally. There is no direct experimental information on the rate and mechanism of water exchange in [UO(2)(oxalate)(2)(H(2)O)](2-) containing two bidentate oxalate ions. The activation energy and the geometry of transition states and intermediates along the D-, A-, and I-pathways were calculated both in the gas phase and in a water solvent model, using a single-point MP2 calculation with the gas phase geometry. The activation energy, Delta U(++), in the solvent for the D-, A-, and I-mechanisms is 56, 12, and 53 kJ/mol, respectively. This indicates that the water exchange follows an associative reaction mechanism. The geometry of the A- and I-transition states for both [UO(2)(H(2)O)(5)](2+) and [UO(2)(oxalate)(2)(H(2)O)](2-) indicates that the entering/leaving water molecules are located outside the plane formed by the spectator ligands.

The mechanism for water exchange in [UO(2)(H(2)O)(5)](2+) and [UO(2)(oxalate)(2)(H(2)O)](2-), as studied by quantum chemical methods

The mechanisms for the exchange of water between [UO(2)(H(2)O)(5)](2+), [UO(2)(oxalate)(2)(H(2)O)](2)(-)(,) and water solvent along dissociative (D), associative (A) and interchange (I) pathways have been investigated with quantum chemical methods. The choice of exchange mechanism is based on the computed activation energy and the geometry of the identified transition states and intermediates. These quantities were calculated both in the gas phase and with a polarizable continuum model for the solvent. There is a significant and predictable difference between the activation energy of the gas phase and solvent models: the energy barrier for the D-mechanism increases in the solvent as compared to the gas phase, while it decreases for the A- and I-mechanisms. The calculated activation energy, Delta U(++), for the water exchange in [UO(2)(H(2)O)(5)](2+) is 74, 19, and 21 kJ/mol, respectively, for the D-, A-, and I-mechanisms in the solvent, as compared to the experimental value Delta H(++) = 26 +/- 1 kJ/mol. This indicates that the D-mechanism for this system can be ruled out. The energy barrier between the intermediates and the transition states is small, indicating a lifetime for the intermediate approximately 10(-10) s, making it very difficult to distinguish between the A- and I-mechanisms experimentally. There is no direct experimental information on the rate and mechanism of water exchange in [UO(2)(oxalate)(2)(H(2)O)](2-) containing two bidentate oxalate ions. The activation energy and the geometry of transition states and intermediates along the D-, A-, and I-pathways were calculated both in the gas phase and in a water solvent model, using a single-point MP2 calculation with the gas phase geometry. The activation energy, Delta U(++), in the solvent for the D-, A-, and I-mechanisms is 56, 12, and 53 kJ/mol, respectively. This indicates that the water exchange follows an associative reaction mechanism. The geometry of the A- and I-transition states for both [UO(2)(H(2)O)(5)](2+) and [UO(2)(oxalate)(2)(H(2)O)](2-) indicates that the entering/leaving water molecules are located outside the plane formed by the spectator ligands.

Human peripheral blood leukocyte engraftment into SCID mice: critical role of CD4(+) T cells

We examined the influence of donor T lymphocytes on human peripheral blood leukocytes (PBL) engraftment into severe combined immune deficient (SCID) mice. Mice were injected with unfractionated or subset-depleted human PBL, and treated at various times with OKT3, a cytotoxic monoclonal antibody against human CD3(+) T lymphocytes. PBL engraftment, high levels of human Ig, and high incidence of lymphoproliferative disease (lpd) were found in mice transplanted with unfractionated PBL and CD8- or CD14-depleted PBL, and in mice treated with OKT3 at distance from PBL transfer. Animals xenografted with CD3- or CD4-depleted PBL, or treated at transplantation time with OKT3, had very low levels of human Ig and did not develop lpd. PBL engraftment was minimal or absent in these animals, as determined by immunohistochemistry, dot-blot, and RT-PCR analyses. These results demonstrate that the presence of donor CD4(+) T lymphocytes at transplantation time is necessary for observing human PBL engraftment into SCID mice, an essential condition for human Ig production and lpd development.

Solvent effects on uranium(VI) fluoride and hydroxide complexes studied by EXAFS and quantum chemistry

The structures of the complexes UO(2)F(n)(H(2)O)(5-n)(2-n), n = 3-5, have been studied by EXAFS. All have pentagonal bipyramid geometry with U-F of and U-H(2)O distances equal to 2.26 and 2.48 A, respectively. On the other hand the complex UO(2)(OH)(4)(2-) has a square bipyramid geometry both in the solid state and in solution. The structures of hydroxide and fluoride complexes have also been investigated with wave function based and DFT methods in order to explore the possible reasons for the observed structural differences. These studies include models that describe the solvent by using a discrete second coordination sphere, a model with a spherical, or shape-adapted cavity in a conductor-like polarizable continuum medium (CPCM), or a combination of the two. Solvent effects were shown to give the main contribution to the observed structure variations between the uranium(VI) tetrahydroxide and the tetrafluoride complexes. Without a solvent model both UO(2)(OH)(4)(H(2)O)(2-) and UO(2)F(4)(H(2)O)(2-) have the same square bipyramid geometry, with the water molecule located at a distance of more than 4 A from uranium and with a charge distribution that is very near identical in the two complexes. Of the models tested, only the CPCM ones are able to describe the experimentally observed square and pentagonal bipyramid geometry in the tetrahydroxide and tetrafluoride complexes. The geometry and the relative energy of different isomers of UO(2)F(3)(H(2)O)(2-) are very similar, indicating that they are present in comparable amounts in solution. All calculated bond distances are in good agreement with the experimental observations, provided that a proper model of the solvent is used.

Corticosteroid-dependent sodium transport in a novel immortalized mouse collecting duct principal cell line

The final control of sodium balance takes place in the cortical collecting duct (CCD) of the nephron, where corticosteroid hormones regulate sodium reabsorption by acting through mineralocorticoid (MR) and/or glucocorticoid (GR) receptors. A clone of principal CCD cells (mpkCCDc14) has been established that is derived from a transgenic mouse (SV40 large T antigen under the control of the SV40 enhancer/L-type pyruvate kinase promoter). Cells grown on filters form polarized monolayers with high electrical transepithelial resistance (R(T) approximately 4700 ohm x cm2) and potential difference (P(D) approximately -50 mV) and have an amiloride-sensitive electrogenic sodium transport, as assessed by the short-circuit current method (Isc approximately 11 microA/cm2). Reverse transcription-PCR experiments using rat MR primers, [3H]aldosterone, and [3H]dexamethasone binding and competition studies indicated that the mpkCCDc14 cells exhibit specific MR and GR. Aldosterone increased Isc in a dose- (10(-10) to 10(-6) M) and time-dependent (2 to 72 h) manner, whereas corticosterone only transiently increased Isc (2 to 6 h). Consistent with the expression of 11beta-hydroxysteroid dehydrogenase type 2, which metabolizes glucocorticoids to inactive 11-dehydroderivates, carbenoxolone potentiated the corticosterone-stimulated Isc. Aldosterone (5x10(-7) M)-induced Isc (fourfold) was associated with a three- to fivefold increase in alpha-ENaC mRNA (but not in those for beta- or gamma-ENaC) and three- to 10-fold increases in alpha-ENaC protein synthesis. In conclusion, this new immortalized mammalian CCD clonal cell line has retained a high level of epithelial differentiation and sodium transport stimulated by aldosterone and therefore represents a useful mammalian cell system for identifying the genes controlled by aldosterone.

Regulation of cdc2 gene expression by the upstream stimulatory factors (USFs)

cdc2 gene expression is under the control of multiple factors. Although E2F/DP proteins have been reported to play a central role, they cannot account for all aspects of the fine modulation of cdc2 gene expression during cell cycle and embryonic development. To characterize the transcription factors that control cdc2 gene expression during nerve cell differentiation in avians, we have previously cloned the quail cdc2 gene promoter region. We had identified an octamer (CAGGTGGC) containing an E-box, which has important activity in regulating cdc2 transcription. Using in vivo genomic footprinting experiments, we show here that this motif, currently named IG, is the target of binding proteins at different stages of neuroretina development, confirming its importance as a regulatory response element for cdc2 gene expression. A subset of Helix-Loop-Helix family of transcription factors, known as Upstream Stimulatory Factors (USFs) specifically bind to this sequence as dimers. Moreover, our results indicate that USFs transactivate the promoter of cdc2 via the IG motif. These data may help to better understand the mechanisms that control cell division in differentiating nerve cells.

Epithelial sodium channel regulatory proteins identified by functional expression cloning

We describe here our current strategy for identifying and cloning proteins involved in the regulation of the epithelial sodium channel (ENaC). We have set up a complementation functional assay in the Xenopus laevis oocyte expression system. Using this assay, we have been able to identify a channel-activating protease (CAP-1) that can increase ENaC activity threefold. We propose a novel extracellular signal transduction pathway controlling ionic channels of the ENaC gene family that include genes involved in mechanotransduction (degenerins), in peptide-gated channels involved in neurotransmission (FaNaCh), in proton-gated channels involved in pH sensing (ASIC) or pain sensation (DRASIC).

Protease modulation of the activity of the epithelial sodium channel expressed in Xenopus oocytes

We have investigated the effect of extracellular proteases on the amiloride-sensitive Na+ current (INa) in Xenopus oocytes expressing the three subunits alpha, beta, and gamma of the rat or Xenopus epithelial Na+ channel (ENaC). Low concentrations of trypsin (2 microg/ml) induced a large increase of INa within a few minutes, an effect that was fully prevented by soybean trypsin inhibitor, but not by amiloride. A similar effect was observed with chymotrypsin, but not with kallikrein. The trypsin-induced increase of INa was observed with Xenopus and rat ENaC, and was very large (approximately 20-fold) with the channel obtained by coexpression of the alpha subunit of Xenopus ENaC with the beta and gamma subunits of rat ENaC. The effect of trypsin was selective for ENaC, as shown by the absence of effect on the current due to expression of the K+ channel ROMK2. The effect of trypsin was not prevented by intracellular injection of EGTA nor by pretreatment with GTP-gammaS, suggesting that this effect was not mediated by G proteins. Measurement of the channel protein expression at the oocyte surface by antibody binding to a FLAG epitope showed that the effect of trypsin was not accompanied by an increase in the channel protein density, indicating that proteolysis modified the activity of the channel present at the oocyte surface rather than the cell surface expression. At the single channel level, in the cell-attached mode, more active channels were observed in the patch when trypsin was present in the pipette, while no change in channel activity could be detected when trypsin was added to the bath solution around the patch pipette. We conclude that extracellular proteases are able to increase the open probability of the epithelial sodium channel by an effect that does not occur through activation of a G protein-coupled receptor, but rather through proteolysis of a protein that is either a constitutive part of the channel itself or closely associated with it.

An epithelial serine protease activates the amiloride-sensitive sodium channel

Sodium balance, and ultimately blood pressure and extracellular fluid volume, is maintained by precise regulation of the activity of the epithelial sodium channel (ENaC). In a Xenopus kidney epithelial cell line (A6), exposure of the apical membrane to the protease inhibitor aprotinin reduces transepithelial sodium transport. Sodium-channel activity can be restored by subsequent exposure to the nonspecific protease trypsin. Using A6 cells and a functional complementation assay to detect increases in ENaC activity, we have cloned a 329-residue protein belonging to the serine protease family. We show that coexpression of this protein with ENaC in Xenopus oocytes increases the activity of the sodium channel by two- to threefold. This channel-activating protease (CAP1) is expressed in kidney, gut, lung, skin and ovary. Sequence analysis predicts that CAP1 is a secreted and/or glycosylphosphatidylinositol-anchored protein: ENaC activity would thus be regulated by the activity of a protease expressed at the surface of the same cell. This previously undiscovered mechanism for autocrine regulation may apply to other ion channels, in particular to members of the ENaC family that are present in neurons and epithelial cells.

Activity and inducibility of drug-metabolizing enzymes in immortalized hepatocyte-like cells (mhPKT) derived from a L-PK/Tag1 transgenic mouse

This report describes the establishment and characterization of the mhPKT cell line derived from the liver of a transgenic mouse harboring the simian virus (SV40) large T and small t antigens placed under the control of the 5' regulatory sequence of the rat L-type pyruvate kinase (L-PK) gene. mhPKT cells had a prolonged life span, expressed the SV40-encoded nuclear large T antigen when grown in glucose-enriched medium, and induced tumors when injected subcutaneously into athymic (nu-nu) mice. Growth on petri dishes or filters yielded multiple layers of cuboid cells, with numerous spaces between adjacent cells that were closed by junctional complexes. These bile canaliculi-like structures exhibited numerous microvilli in which villin, an actin-binding brush-border protein, colocalized with actin. These bile canaliculi-like structures appeared to be functional as they accumulated fluorescein. mhPKT cells conserved the expression of the liver-specific transcription factors HNF1, HNF3, HNF4, and DBP together with substantial levels of L-PK and albumin but not alpha-fetoprotein mRNA transcripts. mhPKT cells mainly metabolized testosterone into androstenedione and 6beta-hydroxytestosterone, as in vivo. 3-Methylcholanthrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) markedly increased ethoxyresorufin-O-deethylase activity and the related cytochrome P450 (CYP) 1A1/2 protein, whereas alpha-naphtoflavone antagonized the TCDD-elicited induction. Phenobarbital slightly increased the CYP2B-mediated activities of pentoxyresorufin-O-depentylase, 2beta- and 16beta-testosterone hydroxylase. mhPKT cells also had substantial sulfotransferase, UDP-glucuronyltransferase, and glutathione S-transferase activities. This model may serve as a tool for long-term in vitro studies of xenobiotic metabolism, potent CYP inducers, and hepatocyte damage due to drugs and other factors.

Overproduction of a truncated hepatocyte nuclear factor 3 protein inhibits expression of liver-specific genes in hepatoma cells

Transcription of hepatocyte-specific genes requires the interaction of their regulatory regions with several nuclear factors. Among them is the hepatocyte nuclear factor 3 (HNF3) family, composed of the HNF3 alpha, HNF3 beta, and HNF3 gamma proteins, which are expressed in the liver and have very similar fork head DNA binding domains. The regulatory regions of numerous hepatocyte-specific genes contain HNF3 binding sites. We examined the role of HNF3 proteins in the liver-specific phenotype by turning off the HNF3 activity in well-differentiated mhAT3F hepatoma cells. Cells were stably transfected with a vector allowing the synthesis of an HNF3 beta fragment consisting of the fork head DNA binding domain without the transactivating amino- and carboxy-terminal domains. The truncated protein was located in the nuclei of cultured hepatoma cells and competed with endogenous HNF3 proteins for binding to cognate DNA sites. Overproduction of this truncated protein, lacking any transactivating activity, induced a dramatic decrease in the expression of liver-specific genes, including those for albumin, transthyretin, transferrin, phosphoenolpyruvate carboxykinase, and aldolase B, whereas the expression of the L-type pyruvate kinase gene, containing no HNF3 binding sites, was unaltered. Neither were the concentrations of various liver-specific transcription factors (HNF3, HNF1, HNF4, and C/EBP alpha) affected. In partial revertants, with a lower ratio of truncated to full-length endogenous HNF3 proteins, previously extinguished genes were re-expressed. Thus, the transactivating domains of HNF3 proteins are needed for the proper expression of a set of liver-specific genes but not for expression of the genes encoding transcription factors found in differentiated hepatocytes.

Transcription factors and aldolase B gene expression in microdissected renal proximal tubules and derived cell lines

Renal expression of the aldolase B isoenzyme and transcription factors previously shown to regulate the aldolase B gene promoter in the liver were analyzed in whole kidney, microdissected tubules, and the two PKSV-PCT and PKSV-PR proximal tubule cell lines derived from transgenic mice. Aldolase B gene expression appeared restricted to the proximal tubule, the site where HNF1 alpha, HNF1 beta, C/EBP alpha, and DBP transcripts were also abundant. Compared to the liver, another organ synthesizing aldolase B, proximal tubules from the kidney were characterized by the absence of HNF3 and the presence of higher ratio of HNF1 beta/HNF1 alpha transcripts. The same features were conserved in both PKSV-PCT and PKSV-PR proximal tubule cell lines. Transactivation experiments in PKSV-PCT cultured cells showed that HNF1 alpha, C/EBP alpha, and DBP behave as transactivators of the 190-bp aldolase B gene promoter, and that HNF1 beta had a low transactivating efficiency. HNF1 beta, as well as HNF3, antagonized the HNF1 alpha-dependent transactivation of the aldolase B promoter. The fact that both HNF1 beta and HNF3 factors play similar negative roles by competitively binding close to or on the HNF1 site could suggest that, in proximal tubule renal cells, HNF1 beta has the same attenuator effect on the aldolase B gene promoter as HNF3 in hepatocytes. Thus, these results indicate that such models of established renal tubule cell lines, which have conserved the same features of parental cells, represent valuable tools for studies of the regulation of genes expressed in proximal tubules of the kidney.

Glucose-dependent regulation of the L-pyruvate kinase gene in a hepatoma cell line is independent of insulin and cyclic AMP

Hepatocyte-like mhAT3F cells have been derived from the hepatoma of a transgenic mouse expressing the SV40 large T antigen under the control of the antithrombin III gene regulatory region (Antoine, B., Levrat, F., Vallet, V., Berbar, T., Cartier, N., Dubois, N., Briand, P., and Kahn, A. (1992) Gene expression in hepatocyte-like lines established by targeted carcinogenesis in transgenic mice. Exp. Cell. Res. 200, 175-185; F. Levrat et al., unpublished results). In these cells, the L-PK gene is transcriptionally activated by glucose, as it is in vivo and in cultured hepatocytes. However, in contrast to the L-PK gene regulation in the liver and isolated hepatocytes, the glucose responsiveness does not require insulin and is not blocked by cyclic AMP. In mhAT3F cells, the insensitivity to insulin might be due to the replacement of insulin-dependent glucokinase by insulin-independent hexokinases able to phosphorylate glucose in the absence of the hormone. The glucose-dependent activation of the L-PK gene is delayed, requires ongoing protein synthesis, and is mediated by the same glucose response element as in vivo and in isolated hepatocytes. These results suggest that the glucose-dependent signaling pathway responsible for the transcriptional activation of glycolytic and lipogenic genes requires glucose phosphorylation, a phenomenon that is insulin-dependent in the liver but insulin-independent in cultured hepatoma cells. Nevertheless, the action of glucose 6-phosphate is most likely indirect.

Influence of the content in transcription factors on the phenotype of mouse hepatocyte-like cell lines (mhAT)

We have described new well-differentiated mouse hepatocyte-like cell lines (mhAT) derived from transgenic mice expressing simian virus 40 large T antigen under the control of antithrombin III gene promoter (Exp. Cell Res. (1992) 200, 175-185). In an attempt to understand the phenotypic variations of the different cell lines, we analyzed their content in liver-specific transcription factors at the level of both the proteins, by gel shift analysis, and the mRNA, by quantitative reverse-transcription PCR. Moreover, the transactivating ability of endogenous HNF1 alpha and C/EBP alpha was also evaluated by measuring the activity of transfected synthetic promoters consisting of DNA element homopolymers upstream of a TATA box. High levels of HNF1, HNF3, and HNF4 transcription factors were maintained in mhAT cells. In contrast, C/EBP alpha was much more variable between the different cell lines and was less abundant than it was in vivo, in the liver. We investigated the influence of HNF1 alpha and C/EBP alpha on the activity of transfected liver-specific promoters. HNF1 alpha was not limiting for the activity of transfected liver-type pyruvate kinase and albumin promoters. In contrast, the activity of the albumin promoter in the different lines was clearly dependent on the C/EBP alpha content, which seems, therefore, to be an essential factor modulating the expression of this gene in HNF1 alpha-containing cells. This work shows that the correlations between promoter activities and transacting factor contents in a panel of well-differentiated cultured cells can be used to determine the respective role of transcription factors on the strength of some promoters.

Functional properties of proximal tubule cell lines derived from transgenic mice harboring L-pyruvate kinase-SV40 (T) antigen hybrid gene

This study describes the functional characterization of two cell lines derived from the proximal convoluted (PKSV-PCT cells) and proximal straight (PKSV-PR) tubules microdissected out from kidneys of transgenic mice harboring the simian virus 40 (SV40) large T and small t antigens placed under the control of the rat L-type pyruvate kinase (L-PK) 5′ regulatory sequence. Both cell lines exhibited cellular cyclic AMP stimulated by parathormone (PTH) and calcitonin (CT) and a sodium-dependent glucose transporter. Uptake of the fluid-phase marker [3H]inulin showed that both cell lines grown on filters exhibited biphasic apical and basolateral endocytic rates. Results from Northern blot analysis indicate that the expression of the T antigen gene (Tag) is dependent on the concentration of D-glucose in the medium and show that the L-PK construct has maintained its capacity for up- or down-regulation by carbohydrates. Replacement of D-glucose by neoglucogenic substrates (lactate, oxaloacetate) blunted the expression of Tag transcripts and induced arrest of cell growth. Compared to cell grown in D-glucose-enriched medium, the hormonal sensitivities to PTH and CT and the sodium-dependent glucose uptake were unchanged whereas quiescent cells exhibited increased hydrolase content. Thus the proximal function has been preserved in these cultured cells derived from tissue-specific targeted oncogenesis in transgenic mice. As the expression of Tag transcripts is controlled by D-glucose, the structural and physiological characteristics of these cell lines can be studied in either quiescent or active growth conditions.

Establishment of renal proximal tubule cell lines by targeted oncogenesis in transgenic mice using the L-pyruvate kinase-SV40 (T) antigen hybrid gene

Targeted oncogenesis allowed us to obtain two cell lines which have been derived from the proximal tubule of kidney from transgenic mice harbouring the simian virus (SV40) large T and small t antigens placed under the control of the 5′ regulatory sequence from the rat L-type pyruvate kinase (L-PK) gene. The cell lines (PKSV-PCT and PKSV-PR cells) were derived from early (PCT) and late (Pars Recta, PR) microdissected proximal tubules grown in D-glucose-enriched medium. In such conditions of culture, both cell lines exhibited L-PK transcripts, a stable expression of SV40-encoded nuclear large T antigen, a prolonged life span but failed to induce tumors when injected sub-cutaneously into athymic (nu-nu) mice. Confluent cells, grown on plastic support or porous filters, were organized as monolayers of polarized cuboid cells with well developed apical microvilli and formed domes. Both cell lines exhibited morphological features of proximal tubule cells with villin located in the apical brush-border and substantial amounts of hydrolase activity. By immunofluorescence studies using specific antibodies, aminopeptidase N appeared restricted to the apical microvillar domain, whereas the H2 histocompatibility antigen was distributed in the cytoplasm and lateral membranes. These results demonstrate that the proximal morphological phenotype has been fully preserved in these cultured cells derived from tissue-specific targeted oncogenesis in transgenic mice.