FOXP3 is a direct target of miR15a/16 in umbilical cord blood regulatory T cells.

Exact mechanism of action of umbilical cord blood (CB)-derived regulatory T cells (Tregs) in the prevention of GVHD remains unclear. On the basis of selective overexpression of peptidase inhibitor 16 in CB Tregs, we explored the related p53 pathway, which has been shown to negatively regulate miR15a/16 expression. Significantly lower levels of miR15a/16 were observed in CB Tregs when compared with conventional CB T cells (Tcons). In a xenogeneic GVHD mouse model, lower levels of miR15a/16 were also found in Treg recipients, which correlated with a better GVHD score. Forced overexpression of miR15a/16 in CB Tregs led to inhibition of FOXP3 and CTLA4 expression and partial reversal of Treg-mediated suppression in an allogeneic mixed lymphocyte reaction that correlated with the reversal of FOXP3 demethylation in CB Tregs. On the other hand, miR15a/16 knockdown in CB Tcons led to expression of FOXP3 and CTLA4 and suppression of allogeneic lymphocyte proliferation. Using a luciferase-based mutagenesis assay, FOXP3 was determined to be a direct target of miR15a and miR16. We propose that miR15a/16 has an important role in mediating the suppressive function of CB Tregs and these microRNAs may have a 'toggle-switch' function in Treg/Tcon plasticity.

Ex vivo expansion of umbilical cord blood for transplantation.

Umbilical cord blood (UCB) has become an important source of hematopoietic stem cell transplant (HSCT) for hematologic malignancies in adults. Its ready availability, allowance of higher HLA disparity and lower incidence of graft-versus-host disease (GVHD) makes it a very attractive source especially for minority populations. The major limitation to a wider use of this source of HSCT is the relative low number of progenitor cells in the graft. For this reason, adult UCB transplants are usually associated with delayed engraftment and increased rates of infectious complications. CB ex vivo expansion holds the promise of delivering higher cell doses and improved outcomes. Here we discuss different methods of expansion, their shortcomings and future directions.

Oestrogen-receptor-alpha gene polymorphism affects response in bone mineral density to oestrogen in post-menopausal women.

OBJECTIVE: An oestrogen-receptor-alpha (ERalpha) gene polymorphism has been variably reported to be related to bone mass. To investigate whether this ERalpha gene polymorphism is associated with a functional difference, we assessed the response in bone mineral density (BMD) to oestrogen therapy in post-menopausal women in relation to ERalpha gene polymorphism. PATIENTS AND MEASUREMENTS: Subjects consisted of 124 Thai post-menopausal women. Sixty-three of the women were less than 6 years post-menopausal and 61 were more than 10 years post-menopausal with vertebral or femoral osteoporosis as defined by BMD T-score less than - 2.5. Subjects were randomly allocated to receive 0.3 mg (n = 67) or 0.625 mg (n = 57) of conjugated equine oestrogen (CEE). All subjects also took 5 mg medroxyprogesterone acetate. Vertebral and femoral neck BMD were measured at baseline and 1 year after treatment. Data were expressed as mean +/- SEM. Capital P represents the absence of the restriction site while lower-case p indicates the presence of the restriction site. RESULTS: For subjects on 0.625 mg CEE, BMD at L2-4 increased significantly after 1 year in those with pp (n = 20) Pp (n = 29) and PP genotypes (n = 8) (P < 0.001). However, in subjects on 0.3 mg CEE, BMD at L2-4 increased significantly after 1 year in subjects with Pp (n = 34, + 7.6 +/- 1.5%, P < 0.001) and PP genotypes (n = 13, + 6. 9 +/- 1.0%, P < 0.001), but not in those with pp genotype (n = 20, + 2.3 +/- 2.1%, P = NS). After adjusting for age and years since menopause, the change in vertebral BMD was still lower in those without the P allele compared to those with the P allele (P < 0.05). Femoral BMD did not significantly change regardless of dose of CEE and genotype. CONCLUSIONS: We conclude that ERalpha gene polymorphism affects skeletal response to oestrogen in post-menopausal women. The effect of ERalpha gene polymorphism appears to be site-specific and does not relate to biochemical markers of bone turnover. Determination of ERalpha genotype may help identify post-menopausal women who will have more skeletal benefit from oestrogen therapy.

Prevention of postmenopausal bone loss by low and conventional doses of calcitriol or conjugated equine estrogen.

OBJECTIVES: Estrogen deficiency is the most common cause of postmenopausal osteoporosis and estrogen replacement is well known to retard postmenopausal bone loss. Calcium supplement alone is generally considered to be insufficient for the prevention of bone loss associated with estrogen deficiency while the role of calcitriol is unclear. In the present study we examined the efficacy different doses of estrogen or calcitriol in the prevention of postmenopausal bone loss in Thais. METHODS: The subjects consisted of 146 Thai women no more than 6 years postmenopausal. The subjects were randomly allocated to receive 750 mg supplemental calcium alone, calcium and conjugated equine estrogen (CEE) at 0.3 or 0.625 mg, calcium and calcitriol at 0.25 or 0.5 microg daily. Those receiving CEE also took 5 mg medrogestone for 12 days each month. BMD at L2-4 and femoral neck were measured at baseline 1 year and 2 years after treatments. Data were expressed as mean +/- S.E. RESULTS: Subjects on supplemental calcium alone had approximately 2.5% decreases in L2-4 (P < 0.05) and femoral BMD (P < 0.01) at 2 years. CEE (0.3 mg) resulted in 3.20 +/- 1.2% increase in vertebral BMD (P < 0.05) while no significant change in BMD was demonstrated at the femoral neck. Likewise, 0.625 mg of CEE induced 5.4 +/- 1.4% increase in vertebral BMD at 2 years (P < 0.001) without change in the femoral BMD. In regard to calcitriol, no significant change in vertebral or femoral BMD was demonstrated with either 0.25 or 0.5 microg calcitriol. CONCLUSION: We concluded that calcitriol is effective in the prevention of early postmenopausal bone loss in Thais. It represents an option for the prevention of osteoporosis in postmenopausal women who are contraindicated for estrogen replacement.

Comparison of miniature multileaf collimation (MMLC) with circular collimation for stereotactic treatment.

PURPOSE: A prototype Miniature Multi-Leaf Collimator (MMLC) designed specifically for radiosurgery and small field radiotherapy has been fabricated and evaluated at the University of Texas M. D. Anderson Cancer Center (UTMDACC). This work demonstrates the advantages of a computer-controlled MMLC vs. conventional circular collimation for the treatment of an irregularly shaped target volume in the brain. METHODS AND MATERIALS: Two patient treatments were selected for this comparison from 38 intracranial tumors treated with radiosurgery at UTMDACC from 8/6/91 to 5/10/94. Target contours and critical structures defined for one of the patients was used to create a simulated target volume and critical structures in a spherical head phantom. Computer simulations were performed using traditional single isocenter treatment with a circular collimator for a set of six arcs. The same arc paths were used to compute the dose distribution for the MMLC and conformed beam geometries were defined using a three-dimensional (3D) treatment planning system with beam's eye view capabilities. Then, the calculated dose distribution for a single isocenter, conformal treatment was delivered to the spherical head phantom under static conditions by shaping the MMLC to conform the target volume shape projected as a function of couch rotation and gantry angle. Planar dose distributions through the target volume were measured using therapy verification film located in the phantom. The measurements were used to verify that the 3D treatment planning system was capable of simulating the MMLC technique. For the second patient with a peanut-shaped tumor, the 3D treatment planning calculations were used to compare dose distributions for the MMLC and for traditional single and multiple isocenter treatments using circular collimators. The resulting integral dose-volume histograms (DVHs) for the target volume, normal brain, and critical structures for the three treatment techniques were compared. RESULTS: (a) Analysis of the film dosimetry data exemplified the degree of conformation of the high-dose region to the target shape that is possible with a computer-controlled MMLC. (b) Comparison of measured and calculated dose distributions indicates that the 3D treatment planning system can simulate the MMLC treatment. (c) Comparison of DVHs from the single isocenter MMLC and circular collimator treatments shows similar coverage of the target volume with increased dose to the brain for circular collimation (4). Comparison of DVHs from the single isocenter MMLC with the multiple isocenter circular collimator treatment approach shows a more inhomogeneous dose distribution through the target volume and increased dose to the brain for the latter. CONCLUSION: Dosimetry data for single isocenter treatments using computer-controlled field shaping with a MMLC demonstrate the ability to conform the dose distribution to an irregularly shaped target volume. DVHs validated that the single isocenter MMLC treatment is preferable to both single and multiple isocenter, circular collimator treatment because it provides a more uniform dose distribution to an irregularly shaped target volume and reduces the dose to surrounding brain tissue for the example cases.

Dosimetric evaluation of lead and tungsten eye shields in electron beam treatment.

PURPOSE: The purpose of this study is to report that commercially available eye shields (designed for orthovoltage x-rays) are inadequate to protect the ocular structures from penetrating electrons for electron beam energies equal to or greater than 6 MeV. Therefore, a prototype medium size tungsten eye shield was designed and fabricated. The advantages of the tungsten eye shield over lead are discussed. METHODS AND MATERIALS: Electron beams (6-9 MeV) are often used to irradiate eyelid tumors to curative doses. Eye shields can be placed under the eyelids to protect the globe. Film and thermoluminescent dosimeters (TLDs) were used within a specially constructed polystyrene eye phantom to determine the effectiveness of various commercially available internal eye shields (designed for orthovoltage x-rays). The same procedures were used to evaluate a prototype medium size tungsten eye shield (2.8 mm thick), which was designed and fabricated for protection of the globe from penetrating electrons for electron beam energy equal to 9 MeV. A mini-TLD was used to measure the dose enhancement due to electrons backscattered off the tungsten eye shield, both with or without a dental acrylic coating that is required to reduce discomfort, permit sterilization of the shield, and reduce the dose contribution from backscattered electrons. RESULTS: Transmission of a 6 MeV electron beam through a 1.7 mm thick lead eye shield was found to be 50% on the surface (cornea) of the phantom and 27% at a depth of 6 mm (lens). The thickness of lead required to stop 6-9 MeV electron beams is impractical. In place of lead, a prototype medium size tungsten eye shield was made. For 6 to 9 MeV electrons, the doses measured on the surface (cornea) and at 6 mm (lens) and 21 mm (retina) depths were all less than 5% of the maximum dose of the open field (4 x 4 cm). Electrons backscattered off a tungsten eye shield without acrylic coating increased the lid dose from 85 to 123% at 6 MeV and 87 to 119% at 9 MeV. For the tungsten eye shield coated with 2-3 mm of dental acrylic, the lid dose was increased from 85 to 98.5% at 6 MeV and 86 to 106% at 9 MeV. CONCLUSION: Commercially available eye shields were evaluated and found to be clearly inadequate to protect the ocular structures for electron beam energies equal to or greater than 6 MeV. A tungsten eye shield has been found to provide adequate protection for electrons up to 9 MeV. The increase in lid dose due to electrons backscattered off the tungsten eye shield should be considered in the dose prescription. A minimum thickness of 2 mm dental acrylic on the beam entrance surface of the tungsten eye shield was found to reduce the backscattered electron effect to acceptable levels.

Comprehensive analysis of electron beam central axis dose for a radiotherapy linear accelerator.

This work evaluates the application of AAPM task group 25 (TG25) methodology for determination of central axis depth dose for a radiotherapy linear accelerator, whose dual scattering foil system and applicators were recently modified. The percent depth dose (%DD) and the dose output factor have been measured for square and rectangular fields at 100- and 110-cm source-to-surface distance (SSDs). At 100-cm SSD, results showed that %DD for a specific energy and field size can vary with applicator, the largest variation being for the 20-MeV, 10 x 10-cm field where a spread of +/- 2.5% or +/- 3 mm about the mean %DD is observed. The square-root method determines rectangular field %DD within 1%. Output factors for rectangular fields are calculated from square field values more accurately using a square-root method than the equivalent-square method recommended by TG25. At 110-cm SSD, the %DD calculated from that at 100-cm SSD using an inverse square factor does not agree with measured values for all fields. The maximum difference observed for the 20-MeV, 6 x 6-cm field was 5.5% or 10 mm. Output data at the 110-cm SSD show that the square-root method is suitable for determination of the air-gap correction factors of rectangular fields. In summary, the recommendations of TG25 work reasonably well for central axis electron beam dosimetry for this version of a radiotherapy linear accelerator, except in limited cases where applicator-scattered electrons apparently cause minor but clinically significant discrepancies.

Dosimetric evaluation of total scalp irradiation using a lateral electron-photon technique.

PURPOSE: To evaluate the radiation dosimetry of a new technique for total scalp irradiation. METHODS AND MATERIALS: A treatment technique described by Akazawa (1989) has been studied. During each fraction, two electron and two photon fields are treated. While most of the lateral scalp is treated with the electron fields, a rind of scalp close to the midsagittal plane is irradiated by parallel-opposed lateral photon fields. A wax bolus is used to build up skin dose and to protect the brain from electron dose. The dose distribution and dose-volume histograms were evaluated for different field arrangements using a 3-dimensional treatment planning system. After modifying the technique, in-vivo thermoluminescent dosimetry were used to evaluate the dose distributions for the first two patients. RESULTS: To compensate for the lack of dose from the opposed photon field at the junction, the technique was modified using overlapped fields instead of abutting fields. A field overlap of 3 to 4 mm between the electron and photon fields was found optimal. When used with the field junction shift of 1 cm midway through the treatment, this scheme resulted in a dose uniformity of -5% to +15% of the prescribed dose in the region of abutment. Results of the 3-dimensional dose calculation were supported by in-vivo thermoluminescent dosimetry on two patients. CONCLUSION: On the basis of computer dose calculations and in-vivo dosimetry. Akazawa's technique for scalp irradiation can be improved by using a 3 to 4 mm overlap of electron and photon fields. This modified technique is practical and produces clinically acceptable dosimetry.