Monte Carlo dose calculations for high-dose-rate brachytherapy using GPU-accelerated processing

PURPOSE

Current clinical brachytherapy dose calculations are typically based on the Association of American Physicists in Medicine Task Group report 43 (TG-43) guidelines, which approximate patient geometry as an infinitely large water phantom. This ignores patient and applicator geometries and heterogeneities, causing dosimetric errors. Although Monte Carlo (MC) dose calculation is commonly recognized as the most accurate method, its associated long computational time is a major bottleneck for routine clinical applications. This article presents our recent developments of a fast MC dose calculation package for high-dose-rate (HDR) brachytherapy, gBMC, built on a graphics processing unit (GPU) platform.

METHODS AND MATERIALS

gBMC-simulated photon transport in voxelized geometry with physics in (192)Ir HDR brachytherapy energy range considered. A phase-space file was used as a source model. GPU-based parallel computation was used to simultaneously transport multiple photons, one on a GPU thread. We validated gBMC by comparing the dose calculation results in water with that computed TG-43. We also studied heterogeneous phantom cases and a patient case and compared gBMC results with Acuros BV results.

RESULTS

Radial dose function in water calculated by gBMC showed <0.6% relative difference from that of the TG-43 data. Difference in anisotropy function was <1%. In two heterogeneous slab phantoms and one shielded cylinder applicator case, average dose discrepancy between gBMC and Acuros BV was <0.87%. For a tandem and ovoid patient case, good agreement between gBMC and Acruos BV results was observed in both isodose lines and dose-volume histograms. In terms of the efficiency, it took ∼47.5 seconds for gBMC to reach 0.15% statistical uncertainty within the 5% isodose line for the patient case.

CONCLUSIONS

The accuracy and efficiency of a new GPU-based MC dose calculation package, gBMC, for HDR brachytherapy make it attractive for clinical applications.

Cytoplasmic neuropilin 2 is associated with metastasis and a poor prognosis in early tongue cancer patients

Neuropilin 2 (Nrp2) plays an important role in regulating lymphangiogenesis. Nrp2 expression in early tongue cancer was investigated to predict lymph node metastasis and the long-term prognosis. The relationships between clinicopathological variables of cT1-T2N0 tongue squamous cell carcinoma (SCC) and overexpression of Nrp2, vascular endothelial growth factor C (VEGFC), vascular endothelial growth factor receptor 3 (VEGFR3), and semaphorin 3F (Sema3F) were analyzed. Expression levels were compared using oral SCC cell lines. The Nrp2 gene was silenced to determine the impact of Nrp2. Cytoplasmic Nrp2 overexpression predicted regional metastasis with sensitivity and specificity of 90.3% and 42.1%, respectively. Cytoplasmic Nrp2 overexpression (P<0.001) and VEGFC overexpression (P=0.006) were significantly related to regional metastasis (Student t-test). However, only cytoplasmic Nrp2 overexpression was an independent prognostic factor for both disease-free survival (DFS; P=0.008) and overall survival (OS; P=0.016) (Cox regression); the risk of recurrence was 12-times higher (P=0.015) and risk of mortality was 8-times higher (P=0.016). Co-localization of Nrp2 and VEGFC was greater within the cytoplasm of aggressive cell lines (HN12 and RCa-T). Nrp2 plays a role in tumourigenesis; VEGFC supplementation cannot rescue the biological function of Nrp2 in Nrp2-depleted cell lines. Cytoplasmic Nrp2 overexpression is associated with decreased OS and DFS. Cytoplasmic Nrp2 overexpression may be a reliable diagnostic and prognostic marker for early tongue SCC.

Ultrasound hyperthermia induces apoptosis in head and neck squamous cell carcinoma: An in vitro study

Background

Hyperthermia is considered an efficient complement in the treatment of head and neck squamous cell carcinoma (HNSCC). Hyperthermia induces cell apoptosis in a temperature- and time-dependent manner. However, the molecular mechanism of hyperthermia remains unclear. The aim of this study was to investigate the mechanism of apoptosis induced by ultrasound hyperthermia in HNSCC cell lines HN-30 and HN-13.

Material and Methods

We examined the dynamic changes of early apoptosis and secondary necrosis in HN-30 and HN-13 cells treated by hyperthermia at 42°C for 10 min. We further examined mitochondrial membrane potential in vitro by ultrasound hyperthermia for different heating temperatures (38-44°C, 10 min) and heating times (42°C, 10-50 min). After heating by ultrasound at 42°C for 10 min, the apoptosis index achieved its highest level at 8 h after treatment, decreased rapidly and remained constant at a reduced level at 12 h.

Results

The level of secondary necrosis increased with the level of early apoptosis but remained at a higher level until 14 h. The level of secondary necrosis correlated with the level of early apoptosis (HN-13: r=0.7523, P=0.0030; HN-30: r=0.6510, P=0.016). The fractions of cells with low mitochondrial membrane potential (Δψ) in the heating-temperature grads group and heating-time grads group decreased significantly over time. Therefore, HN-30 and HN-13 cells developed apoptosis after ultrasound hyperthermia treatment with decreases in the mitochondrial transmembrane potential level.

Conclusions

Ultrasound hyperthermia induces apoptosis in HN-30 and HN-13 cells, possibly via the mitochondrial caspase pathway.

Key words:Head and neck squamous cell carcinoma, apoptosis, mitochondrial membrane potential, ultrasound hyperthermia.

Serological biomarkers as risk factors of SLE-associated pulmonary arterial hypertension: a systematic review and meta-analysis

Objective This article aims to determine the serological biomarkers which can be considered as risk factors of systemic lupus erythematosus (SLE)-associated pulmonary arterial hypertension by a systematic review and meta-analysis. Methods This study was conducted in accordance with the PRISMA statement. The search database included MEDLINE, EMBASE, Cochrane Library and Scopus. The Newcastle-Ottawa scale was used for the quality assessment. The odds ratio was the primary measure of effect of the risk factors. Results Twelve studies were included in this meta-analysis. The results identified the anti-RNP antibody and anti-Sm antibody as risk factors for SLE-associated pulmonary arterial hypertension with the pooled odds ratios 3.68 (95% confidence interval 2.04-6.63, P < 0.0001) and 1.71 (95% confidence interval 1.06-2.76, P = 0.03), respectively. Conclusion Pulmonary arterial hypertension is a serious complication of SLE with a worse prognosis than SLE patients without pulmonary arterial hypertension. The early recognition of pulmonary arterial hypertension with transthoracic echocardiography routinely performed in SLE patients with risk factors is necessary, especially in Asian patients.

The increased expression of TCF3 is correlated with poor prognosis in Chinese patients with nasopharyngeal carcinoma

OBJECTIVES

Regulatory factors controlling stem cell identity and self-renewal are often active in aggressive cancers and are thought to promote cancer growth and progression. B-cell-specific transcription factor 3 (TCF3/E2A) is a member of the T-cell factor/lymphoid enhancer factor (TCF/LEF) transcription factor family that is central to regulating epidermal and embryonic stem cell identity. It has been reported that TCF3 was connected with the development and progression of a number of human cancers. In this study, we aimed to identify the expression of TCF3 in human nasopharyngeal carcinoma (NPC) and evaluate its clinical significance.

DESIGN

To investigate the expression of TCF3 in NPC and its relationship to prognosis.

SETTING

An in vitro study.

MAIN OUTCOME MEASURES

We analysed the expression of TCF3 in NPC and in non-tumourous nasopharyngeal tissues by quantitative RT-PCR and Western blotting. The expression patterns of TCF3 in 117 archived paraffin-embedded NPC specimens were characterised by immunohistochemistry, and the correlation between the TCF3 protein expression and the clinicopathological features of NPC was analysed.

RESULTS

We observed that TCF3 had a higher expression in NPC than in non-tumourous nasopharyngeal tissues of 117 archived paraffin-embedded NPC specimens, and 80 (68.4%) biopsy tissues revealed high levels of TCF3 expression. Furthermore, statistical analyses demonstrated that the increased expression of TCF3 was closely related to clinical stage, locoregional recurrence and distant metastasis of NPC. NPC patients with high levels of TCF3 expression had a shorter survival time, whereas patients with lower levels of TCF3 expression survived longer. Moreover, multivariate analysis suggested that the upregulation of TCF3 was a critical prognostic factor for NPC.

CONCLUSIONS

Our observations suggest, for the first time, that TCF3 is significantly associated with the development and progression of NPC, which can be used as an important prognostic marker for patients with NPC and may be an effective target for the treatment of NPC.

[Analysis of clinical characteristics and outcome of patients with very high risk primary immunoglobulin light-chain amyloidosis]

目的

探讨极高危原发性轻链型淀粉样变（pAL）患者的临床特征及其预后。

方法

回顾性分析2009年1月至2016年2月在北京协和医院确诊的205例pAL患者的临床资料，将梅奥2004分期Ⅲb期或梅奥2012分期4期的患者定义为极高危患者。

结果

34例（16.6%）为极高危pAL患者，中位年龄57（20~84）岁，男性22例（64.7%）。所有患者均有心脏受累，15例（44.1%）患者的受累脏器≥ 3个。27例（81.8%）患者的心功能分级为3~4级，中位血清肌钙蛋白I为0.25（0.08~1.23）µg/L，中位血清N末端B型利钠肽前体为11 733（1 892~103 277）ng/L，中位血清游离轻链差值为403.0（18.1~1 911.6）mg/L，8例（24.2%）患者的骨髓浆细胞比例≥0.100。16例（47.1%）患者采用硼替佐米为主的化疗方案，总体血液学缓解率为58.3%。中位随诊27（1~40）个月，14例（41.2%）患者在诊断后3个月内死亡，中位生存时间仅为4个月。3、6、12和24个月的预期生存率分别为51.3%、44.0%、35.2%和29.6%。一线化疗后获得血液学缓解、未获得血液学缓解以及姑息治疗的患者1年预计存活率分别为90.9%、11.1%及0（P<0.001）。

结论

极高危pAL患者的预后极差，早期病死率高，获得血液学缓解的pAL患者有着明显更好的预后。

Molecular characterization and functional analysis of pheromone binding protein 1 from Cydia pomonella (L.)

A full-length cDNA encoding Cydia pomonella pheromone binding protein 1 (CpomPBP1) was cloned and characterized. CpomPBP1, possessing the typical characteristics of lepidopteran odorant binding proteins, was detected to be specifically expressed in the antennae of male and female moths at the mRNA and protein level. Soluble recombinant CpomPBP1 was subjected to in vitro binding to analyse its binding properties and to search for potentially active semiochemicals. A competitive binding assay showed that three 12-carbon ligands, codlemone, 1-dodecanol and E,E-2,4-dodecadienal, were able to bind to CpomPBP1 in decreasing order of affinity. Moreover, unlike the wild-type CpomPBP1, the C-terminus truncated CpomPBP1 exhibited high affinity to ligands even in an acidic environment, suggesting that the C-terminus plays a role in preventing ligands from binding to CpomPBP1 in a lower pH environment.

Slater to Mott Crossover in the Metal to Insulator Transition of Nd_{2}Ir_{2}O_{7}

We present an angle-resolved photoemission study of the electronic structure of the three-dimensional pyrochlore iridate Nd_{2}Ir_{2}O_{7} through its magnetic metal-insulator transition. Our data reveal that metallic Nd_{2}Ir_{2}O_{7} has a quadratic band, touching the Fermi level at the Γ point, similar to that of Pr_{2}Ir_{2}O_{7}. The Fermi node state is, therefore, a common feature of the metallic phase of the pyrochlore iridates. Upon cooling below the transition temperature, this compound exhibits a gap opening with an energy shift of quasiparticle peaks like a band gap insulator. The quasiparticle peaks are strongly suppressed, however, with further decrease of temperature, and eventually vanish at the lowest temperature, leaving a nondispersive flat band lacking long-lived electrons. We thereby identify a remarkable crossover from Slater to Mott insulators with decreasing temperature. These observations explain the puzzling absence of Weyl points in this material, despite its proximity to the zero temperature metal-insulator transition.

Innate lymphoid cells as novel regulators of obesity and its-associated metabolic dysfunction

The increased prevalence of obesity worldwide has been accompanied by increases in risk and rates of obesity-associated metabolic dysfunctions, such as insulin resistance. The chronic, low-grade inflammatory condition of obesity highlights the pathophysiological link between the immune system and the metabolic system, which has yet to be fully understood. Recent studies of obesity have started to uncover potential regulatory roles for the innate lymphoid cells (ILCs), which under normal conditions serve to regulate development of lymphoid tissue and function of the mucosal immune system. The ILCs are a newly identified immune cell population with complicated composition and subsequently diverse and dynamic functions. Studies to determine the distribution profile of the various ILCs in adipose tissue provide intriguing clues as to their regulatory capacity in obesity and its associated metabolic dysfunctions. Here, we review the recent findings supporting a role for ILCs as regulators of obesity or its associated insulin resistance, and discuss the potential underlying molecular mechanism as well as its promise as a therapeutic target for clinical applications. © 2016 World Obesity.

Bioinformatics-based design of novel antigenic B-cell linear epitopes of Deinagkistrodon acutus venom

OBJECTIVE

With the help of bioinformatics analysis, we wished to develop a novel antivenom against the Deinagkistrodon (D.) acutus snake venom using B-cell linear epitopes of three primary toxins (serine protease, metalloprotease, and phospholipase A2).

MATERIALS AND METHODS

cDNA sequences of three toxins of D. acutus venom were retrieved from the NCBI database. B-cell linear epitopes were predicted using DNAStar and the website server software provided by IEDB. Then, the sequences of the predicted epitopes were artificially synthesized and inserted into the vector pET-32a-c(+). Recombinant antigen peptide was expressed and purified. BALB/c mice were immunized with the recombinant antigen peptide. The immunoprotective effect of this novel antivenom was measured by neutralization of venom haemorrhagic activity.

RESULTS

Six epitopes were obtained by bioinformatics analysis. ELISA analysis showed that antibody titre was >8,000 against snake venom and >64,000 against the recombinant peptide. Neutralization assays confirmed that the developed antivenom could effectively reduce the haemorrhagic activity of snake venom.

CONCLUSIONS

Six B-cell linear epitopes of D. acutus snake venom were predicted by bioinformatics analysis and successfully utilized to produce a novel antivenom.