Romidepsin is a cyclic molecule that inhibits histone deacetylases. It is Food and Drug Administration-approved for treatment of cutaneous and peripheral T-cell lymphoma, but its precise mechanism of action against malignant T cells is unknown. To better understand the biological effects of romidepsin in these cells, we exposed PEER and SUPT1 T-cell lines, and a primary sample from T-cell lymphoma patient (Patient J) to romidepsin. We then examined the consequences in some key oncogenic signaling pathways. Romidepsin displayed IC 50 values of 10.8, 7.9 and 7.0 nM in PEER, SUPT1 and Patient J cells, respectively. Strong inhibition of histone deacetylases and demethylases, increased production of reactive oxygen species and decreased mitochondrial membrane potential were observed, which may contribute to the observed DNA-damage response and apoptosis. The stressactivated protein kinase/c-Jun N-terminal kinase signaling pathway and unfolded protein response in the endoplasmic reticulum were activated, whereas the phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) and β-catenin pro-survival pathways were inhibited. The decreased level of β-catenin correlated with the upregulation of its inhibitor SFRP1 through romidepsin-mediated hypomethylation of its gene promoter. Our results provide new insights into how romidepsin invokes malignant T-cell killing, show evidence of its associated DNA hypomethylating activity and offer a rationale for the development of romidepsin-containing combination therapies.

Purpose: Intensity‐modulated proton therapy (IMPT) has a great potential to further advance proton therapy. However, it is widely accepted that IMPT is very sensitive to uncertainties. The worst‐case analysis (WA) originally proposed by Lomax has been adopted in our institute to evaluate IMPT plan sensitivity to range and setup uncertainties. Here, we propose an evaluation method by exhaustively sampling uncertainties and apply it to validate WA. Methods: A series of perturbations to modify proton beam ranges and to shift the iso‐center in x‐, y‐ and z‐directions were sampled for 500 times to generate the probability distribution of plan qualities. The magnitude of a perturbation was assigned randomly following a normal distribution with specified standard deviations in each perturbation dimension. Perturbed dose was calculated for each sampling and compared to the WA dose. Dose‐volume‐histograms (DVH) were obtained for all perturbed doses. The distribution of DVHs and dose‐volume indices were examined. Prostate and head/neck cases were selected for demonstration. Results: In both cases, the DVHs of 500 perturbed doses spread over bands with various widths, and the DVH curves of WA lie within these bands and near the “worst” edges. for CTV, 97.6% in the prostate case and 97% in the head/neck case of the perturbed doses show a D95 value higher than the value given by WA. For normal tissues, at least 96.4% of the perturbed doses show lower dose‐volume indices (e.g. V70 of rectum and bladder) than the ones by WA. Conclusions: After exhaustively sampling the possible uncertainties, we verified that the worst‐case analysis may reasonably evaluate the IMPT plan sensitivity to setup and range uncertainties without considerably over‐ or under‐estimating it. The exhaustively sampling approach proposed here could offer a great outset toward comprehensively evaluating the IMPT plan sensitivity to a broader spectrum of planning and delivery uncertainties.

Multifocal ERGs (MERGs) of 5 adult monkeys (Macaca mulatta) with inner retinal defects caused by laser-induced glaucoma were compared to MERGs from 3 monkeys with inner retinal activity suppressed pharmacologically. MERGs were recorded with DTL fiber electrodes from anesthetized monkeys. Stimuli consisted of 103 equal size hexagons within 17 degrees of the fovea. Stimuli at each location passed through a typical VERIS m-sequence of white (200 cd/m2) and black (12 cd/m2) presentations. In animals with laser-induced glaucoma, visual field sensitivity was assessed by static perimetry using the Humphrey C24-2 full-threshold program modified for animal behavior. Inner retinal (amacrine and ganglion cell) activity was suppressed by intravitreal injection of TTX (4.7-7.6 microM) and NMDA (1.6-5 mM). In normal eyes the first order response (1st order kernel) was larger and more complex, with more distinct oscillations (>60 Hz) in central than in peripheral locations. The 2nd order kernel also was dominated by oscillatory activity. There were naso-temporal variations in both kernels. Pharmacological suppression of inner retinal activity reduced or eliminated the oscillatory behavior, and naso-temporal variations. The 1st order kernel amplitude was increased most and was largest at the fovea. Removed inner retinal responses also were largest at the fovea. The 2nd order kernel was greatly reduced at all locations. In eyes with advanced glaucoma, the effects were similar to those produced by suppressing inner retinal activity, but the later portion of the 1st order kernel waveform was different, lacking a dip after the large positive wave. Visual sensitivity losses and MERG changes both increased over the timecourse of glaucoma, with changes in the MERG being more diffusely distributed across the visual field. We conclude that 1st and 2nd order responses of the primate MERG can be identified that originate from inner retina and are sensitive indicators of glaucomatous neuropathy.

Purpose: For intensity‐modulated proton therapy (IMPT), spots (high dose regions around the Bragg peaks of beamlets) for a set of energies are arranged on a grid in the target volume. The spot spacing can have a significant impact on the quality and efficiency of an IMPT plan. The purpose of this research is to optimize spot spacing and lateral margin for IMPT. Method and Materials: Multiple treatment plans were generated for a group of prostate patients, varying spot spacing (2.5–10mm) and margin size (0–12mm). All plans employed two opposing fields which were individually optimized for uniform target coverage. Dose Volume Histograms were compared to evaluate rectal sparing and target dose homogeneity. Spot‐weight histograms were used to investigate the impact of delivery system constraints on low MUs per spot, on plan quality and robustness, and on optimization efficiency. Results: Dose homogeneity decreases with lateral margin size for a given spot spacing, with 5mm spacing showing comparable performance to current treatment protocols (10mm spacing and 12mm margin). Rectal dose increases with margin size and decreases with spot spacing. For small spot spacing and margin combinations, a large fraction of the spots are close to the minimum MU limit for the delivery system. Many of the spots below this limit are discarded during optimization. This effect decreases significantly above about 5mm spacing and margin. Conclusion: Lateral margins and spot spacing must be chosen to balance target dose homogeneity against avoidance of critical structures. While decreased spot spacing increases target dose homogeneity and lowers rectal dose, it also results in a large number of low‐intensity spots, decreasing plan robustness and optimization efficiency and increasing calculation time. The optimum combination that improves rectal sparing while maintaining comparable dose homogeneity, calculation time, and plan robustness is 5mm for spot spacing with 5mm for lateral margins.

Purpose: The passive scattering proton therapy (PSPT) technique is the commonly used radiotherapy technique for craniospinal irradiation (CSI). However, PSPT involves many numbers of junction shifts applied over the course of treatment to reduce the cold and hot regions caused by field mismatching. In this work, we introduced a robust planning approach to develop an optimal and clinical efficient techniques for CSI using intensity modulated proton therapy (IMPT) so that junction shifts can essentially be eliminated. Methods: The intra‐fractional uncertainty, in which two overlapping fields shift in the opposite directions along the craniospinal axis, are incorporated into the robust optimization algorithm. Treatment plans with junction sizes 3,5,10,15,20,25 cm were designed and compared with the plan designed using the non‐robust optimization. Robustness of the plans were evaluated based on dose profiles along the craniospinal axis for the plans applying 3 mm intra‐fractional shift. The dose intra‐fraction variations (DIV) at the junction are used to evaluate the robustness of the plans. Results: The DIVs are 7.9%, 6.3%, 5.0%, 3.8%, 2.8% and 2.2%, for the robustly optimized plans with junction sizes 3,5,10,15,20,25 cm. The DIV are 10% for the non‐robustly optimized plans with junction size 25 cm. The dose profiles along the craniospinal axis exhibit gradual and tapered dose distribution. Using DIVs less than 5% as maximum acceptable intrafractional variation, the overlapping region can be reduced to 10 cm, leading to potential reduced number of the fields. The DIVs are less than 5% for 5 mm intra‐fractional shifts with junction size 25 cm, leading to potential no‐junction‐shift for CSI using IMPT. Conclusion: This work is the first report of the robust optimization on CSI based on IMPT. We demonstrate that robust optimization can lead to much efficient carniospinal irradiation by eliminating the junction shifts.