Molecular dosimetry of DNA adducts in the medaka small fish model

Small fish models are being used with increasing frequency for carcinogenicity testing and comparative cancer research in the US, Canada and Europe. However, there is a need to further define the early biochemical events of carcinogenesis in these species. Identification and quantitation of DNA adducts can integrate all of the various factors involved in chemical exposure, uptake, distribution and biotransformation of a putative carcinogen. In the present study, Japanese medaka (Oryzias latipes) were exposed to the alkylating agent, diethylnitrosamine (DEN), in the ambient water. Liver DNA was analyzed for O6-ethylguanine (O6EG), O4-ethylthymidine (O4ET) and O2- ethylthymidine (O2ET) by the immuno-slot-blot technique, using monoclonal antibodies against each adduct of interest. While fish exposed to 10 p.p.m. DEN had liver DNA adduct concentrations at or only slightly higher than background levels, those exposed to 100 p.p.m. DEN averaged 34 and 53 pmol O6EG/micromol guanine, 15 and 41 pmol O2ET/micromol thymidine and 2 and 6 pmol O4ET/micromol thymidine at 0 and 24 h post-exposure, respectively. The results of this study show that, under these short-term exposure conditions, ethyl-DNA adducts appear to accumulate in medaka liver tissue in a sublinear (i.e. non- linear) fashion after aqueous exposure to DEN. Thus, critical DNA repair enzymes such as O6-alkylguanine DNA alkyltransferase, which are relatively efficient at lower carcinogen levels, are probably saturated at the 100 p.p.m. concentration level of DEN.      

小野剂量学临床实践指南

小野剂量学是立体定向放射治疗、立体定向放射外科手术以及调强放疗等精确放疗技术中小照射野物理剂量精确性的理论基础。相比于常规射野,小野的应用增加了临床剂量的不确定度,而且剂量误差较常规射束大。为了确保小野剂量学和探测器标准化使用,在国家癌症中心/国家肿瘤质控中心的组织领导下,多家医疗单位共同参与,结合国内临床需求以及加速...     

Microencapsulation of small intestinal neuroendocrine neoplasm cells for tumor model studies

Basic cancer research is dependent on reliable in vitro and in vivo tumor models. The serotonin (5‐HT) producing small intestinal neuroendocrine tumor cell line KRJ‐1 has been used in in vitro proliferation and secretion studies, but its use in in vivo models has been hampered by problems related to the xeno‐barrier and tumor formation. This may be overcome by the encapsulation of tumor cells into alginate microspheres, which can function as bioreactors and protect against the host immune system. We used alginate encapsulation of KRJ‐1 cells to achieve long‐term functionality, growth and survival. Different conditions, including capsule size, variations in M/G content, gelling ions (Ca²⁺/Ba²⁺) and microcapsule core properties, and variations in KRJ‐1 cell condition (single cells/spheroids) were tested. Viability and cell growth was evaluated with MTT, and confocal laser scanner microscopy combined with LIVE/DEAD viability stains. 5‐HT secretion was measured to determine functionality. Under all conditions, single cell encapsulation proved unfavorable due to gradual cell death, while encapsulation of aggregates/spheroids resulted in surviving, functional bioreactors. The most ideal spheroids for encapsulation were 200–350 μm. Long‐term survival (>30 days) was seen with solid Ca²⁺/Ba²⁺ microbeads and hollow microcapsules. Basal 5‐HT secretion was increased (sixfold) after hollow microcapsule encapsulation, while Ca²⁺/Ba²⁺ microbeads was associated with normal basal secretion and responsiveness to cAMP/PKA activation. In conclusion, encapsulation of KRJ‐1 cells into hollow microcapsules produces a bioreactor with a high constitutively activate basal 5‐HT secretion, while Ca²⁺/Ba²⁺ microbeads provide a more stable bioreactor similar to non‐encapsulated cells. Alginate microspheres technology can thus be used to tailor different functional bioreactors for both in vitro and in vivo studies. (Cancer Sci 2012; 103: 1230–1237)     

Postal dosimetry audit test for small photon beams

Background and purpose

Small radiation beams (<4 cm width) are being increasingly used in the delivery of advanced techniques as Intensity Modulated Radiotherapy (IMRT) and Stereotactic Radiosurgery (SRS). Dose measurements in small beams present challenges not encountered for larger beams. A postal audit with Thermoluminiscent Dosimeters (TLD) was developed to check the doses in small photon beams. A validation test in real conditions was carried out in fourteen centres.

Material and methods

The TLD postal audit employs very small chips (1 × 1 × 1 mm³) of TLD-100 inserted at 5 and 10 cm of depth in a cylindrical PMMA phantom designed for this purpose. This experimental system is mailed to the audited centres to be irradiated with beams of 1 and 3 cm of side or diameter. The prescribeddose is 1.5 Gy at 10 cm. The properties of this system were studied experimentally and by Monte Carlo (MC) simulation, before the external test.

Results

Deviations between the prescribed and measured absorbed doses are below 5% for 69% (1 × 1 cm² beam) and 64% (3 × 3 cm² beam) of the audited centres. When deviations are above 5%, their causes have been investigated and led to corrections.

Conclusion

The developed postal audit is suitable to verify the absorbed doses in small photon beams with an accuracy of 2.9% (1s).     

A functional role for tumor cell heterogeneity in a mouse model of small cell lung cancer

Small cell lung cancer (SCLC) is the lung neoplasia with the poorest prognosis, due to its high metastatic potential and chemoresistance upon relapse. Using the previously described mouse model for SCLC, we found that the tumors are often composed of phenotypically different cells with either a neuroendocrine or a mesenchymal marker profile. These cells had a common origin because they shared specific genomic aberrations. The transition from neuroendocrine to mesenchymal phenotype could be achieved by the ectopic expression of oncogenic Ras(V12). Crosstalk between mesenchymal and neuroendocrine cells strongly influenced their behavior. When engrafted as a mixed population, the mesenchymal cells endowed the neuroendocrine cells with metastatic capacity, illustrating the potential relevance of tumor cell heterogeneity in dictating tumor properties.     

Differences in biodistribution between 99mTc-depreotide, 111In-DTPA-octreotide, and 177Lu-DOTA-Tyr3-octreotate in a small cell lung cancer animal model

AIM: (177)Lu-DOTA-Tyr(3)-octreotate is a candidate radiopharmaceutical for the therapy of somatostatin receptor (sstr)-positive small cell lung cancer (SCLC). Scintigraphy of lung tumors is made with 2 alternative somatostatin analogs, (111)In-DTPA-octreotide or (99m)Tc-depreotide. The aim of this study was to compare the biodistribution of these 3 radiopharmaceuticals in SCLC xenografted to nude mice. METHODS: Nude mice, bearing tumors from the human SCLC cell line NCI-H69, were intravenously injected with 10 MBq (2.4 microg) (99m)Tc-depreotide and 2 MBq (0.5 microg) (111)In-DTPA-octreotide simultaneously. The activity concentration (%IA/g) was measured in tumor and normal tissue at 2, 4, and 24 hours postinjection (hpi). The results were compared with earlier published biodistribution data of 3 MBq (0.7 microg) (177)Lu-DOTA-Tyr(3)-octreotate in the same animal model. RESULTS: The activity concentration of (111)In-DTPAoctreotide in tumor was higher than the activity concentration of (99m)Tc-depreotide at 2-24 hpi, p < 0.05. The highest tumor uptake at 24 hpi was, however, found for (177)Lu-DOTA-Tyr(3)-octreotate. The activity concentration of (99m)Tc-depreotide was significantly higher in the heart, lungs, liver, the salivary glands, spleen, and bone marrow than for (111)In-DTPA-octreotide at 2-24 hpi. Saturation of the somatostatin receptors may have influenced the uptake in tumor and sstr-positive normal tissues. CONCLUSION: The low tumor-to-lung and tumor-to-liver activity concentration ratios for (99m)Tc-depreotide could result in a lower detection rate of SCLC with this compound versus (111)In-DTPA-octreotide. (177)Lu-DOTA-Tyr(3)-octreotate gave the highest tumor-activity concentration, and has, thus, the best properties for therapy.     

Crypt residing bacteria and proximal colonic carcinogenesis in a mouse model of Lynch syndrome

Colorectal cancer is a multifactorial disease involving inherited DNA mutations, environmental factors, gut inflammation and intestinal microbiota. Certain germline mutations within the DNA mismatch repair system are associated with Lynch syndrome tumors including right-sided colorectal cancer with mucinous phenotype and presence of an inflammatory infiltrate. Such tumors are more often associated with bacterial biofilms, which may contribute to disease onset and progression. Inflammatory bowel diseases are also associated with colorectal cancer and intestinal dysbiosis. Herein we addressed the question, whether inflammation can aggravate colorectal cancer development under mismatch repair deficiency. MSH2^{loxP/loxP Vill-cre} mice were crossed into the IL-10^−/− background to study the importance of inflammation and mucosal bacteria as a driver of tumorigenesis in a Lynch syndrome mouse model. An increase in large bowel tumorigenesis was found in double knockout mice both under conventional housing and under specific pathogen-free conditions. This increase was mostly due to the development of proximal tumors, a hotspot for tumorigenesis in Lynch syndrome, and was associated with a higher degree of inflammation. Additionally, bacterial invasion into the mucus of tumor crypts was observed in the proximal tumors. Inflammation shifted fecal and mucosal microbiota composition and was associated with enrichment in Escherichia-Shigella as well as Akkermansia, Bacteroides and Parabacteroides genera in fecal samples. Tumor-bearing double knockout mice showed a similar enrichment for Escherichia-Shigella and Parabacteroides. Lactobacilli, Lachnospiraceae and Muribaculaceae family members were depleted upon inflammation. In summary, chronic inflammation aggravates colonic tumorigenesis under mismatch repair deficiency and is associated with a shift in microbiota composition.     

Dosimetry of 131I-labeled anti-ferritin in hepatoma: a model for radioimmunoglobulin dosimetry

Dosimetric studies are reported for four hepatoma patients treated with ¹³¹I-labeled anti-ferritin following combination radiation and chemotherapy. Administered activities of radiolabeled antibody ranged from 93 to 157 mCi. Studies included liver and tumor volume calculations from sequences of computerized axial tomographic (CAT) scan slices, in-vivo gnantitation of radiolabeled antibody in the liver and tumor, determination of kinetic parameters of radioimmmioglubulin for liver, tumor, and the total body, and computation of dose rates (rad/boor) and dose (rad) for these tissues. Tumor volumes for these patients prior to the administration of radiolabeled antibody ranged from 370 to 920 cm³ and liver volumes from 900 to 1980 cm³. In-vivo quantitation, carried out 4 to 8 days following infusion of ¹³¹I-labeled anti-ferritin, demonstrated tumor-to-liver ratios of about 2:1 for the deposition of radioimmunoglobuBn in these tissues. Mean values of the effective half-life for radiolabeled antibody in the liver and tumor were 7.4 days and for total-body activity 3.6 days, respectively. For the four patients, the calculated ¹³¹I radiation dose for tumor tissue ranged from 1500 to 2200 rad, for liver tissue from 400 to 1000 rad, and for total-body irradiation (TBI) from 110 to 220 rad.     

A Monte Carlo approach for small electron beam dosimetry.

BACKGROUND AND PURPOSE: In treatments where it is necessary to conform the field shape yielding a very small effective beam area, dosimetry and conventional treatment planning may be inaccurate. The Monte Carlo (MC) method can be an alternative to verify dose calculations. A conjunctival mucosa-associated lymphoid tissues lymphoma is presented, to show the importance of an independent assessment in critical situations. MATERIALS AND METHODS: In this work, the MC technique has been employed using the program BEAM (based on EGS4 code). Electron beam simulation has been performed and the results have been compared with those obtained with films. The patient dose distribution has been obtained by two methods: the full Monte Carlo (FMC) simulation and a conventional planning system (PLATO). RESULTS: Concerning dosimetry, some differences have been observed in the comparison of profiles obtained with film and those obtained with the MC method. Moreover, significant differences were found in the patient isodose distribution between both calculation methods. CONCLUSIONS: The results highlight that, in treatments where small beams are needed, conventional dosimetry and planning systems have some limitations. Therefore, an independent and more accurate assessment, such as MC, would be desirable.     

Study of a new commercial film for high energy photon dosimetry]

Dosimetric properties of a new film, the Extended Dose Range-EDR2, manufactured by Kodak, have been studied. We have established the response of the film versus dose and compared it with that of X-OMAT V films. We found a linear response with dose, for the range from 0.5 to 4 Gy. No dependence of this curve with beam quality and with depth is observed. EDR2 films are useful for dosimetric study of high-energy photon beam, especially when high dose gradient occurs such as for Intensity Modulated Radiotherapy Treatment.     

"PCL" a new automatic fast reader suitable for in vivo dosimetry.

The authors present a new automatic TLD reader specially designed for medical dosimetric applications, which allow considerable time-saving. The "PCL" reader is based on an isothermal heating kinetics and can be used with TL material of any nature and any shape (powder, microrods, pellets). Doses from 1 microGy to 10 Gy can be measured, or higher doses by interposing an optical absorber in front of the PM. The readout system is controlled by an IBM compatible personal computer. Results can be printed under the form defined by the users and then can be straightly stored in a patient sheet or an experience book. Tests performed with LiF chips TLD 100 and 700 (HARSHAW), Li2B4O7:Mn discs LiB (ALNOR), LiF powder PTL 717 (DESMARQUET) and Li2B4O7:Cu powder (CEN-FAR) are presented. They show a good reproducibility and interesting dosimetric properties.     

SL12 murine T-lymphoma: a new model for tumor cell heterogeneity

It has been observed that subclones from the spontaneous murine AKR/J T-lymphoma cell line SL12 with similar in vitro growth characteristics exhibit stable differences in tumorigenicity. The cell line is composed of at least three distinct cloned cell types that are highly, moderately, or poorly tumorigenic in syngeneic host animals. When healthy, young, syngeneic host animals were given iv injections with the same number of viable growth phase cells, each cloned cell type had a different tumor incidence, latent period, and pattern of tumor spread. The unusual stability of the cloned cell lines is shown by a similar incidence, latency, and spread of the tumors when studied after more than 1 year of continuous in vitro culture. The SL12 clones also differ in several phenotypic characteristics commonly used to classify thymocyte maturation, e.g., a) the expression of three of seven surface antigens examined, b) the cellular response to glucocorticoid hormone, and c) the expression of terminal deoxynucleotidyl transferase.     

Technetium-99m tetrofosmin SPECT predicts chemotherapy response in small cell lung cancer.

The multidrug resistance gene 1 encoding human P-glycoprotein (Pgp) is thought to play an important role in the multidrug resistance of lung cancer. The purpose of this study was to predict chemotherapy response by technetium-99m tetrofosmin (Tc-99m TF) lung single photon emission computed tomography (SPECT) and compare Pgp expression in patients with untreated small cell lung cancer (SCLC). Forty patients with untreated SCLC received Tc-99m TF lung SPECT prior to chemotherapy. The chemotherapy response was evaluated in the 3rd month after completion of treatment. Immunohistochemical staining of Pgp expression was performed on multiple nonconsecutive sections of biopsy specimens. By quantitative analyses, tumor to background ratios were 1.86 +/- 0.27 and 1.17 +/- 0.26 for patients with a good and poor response, respectively (p < 0.05). All of the 20 patients with a good chemotherapy response also had a positive Tc-99m TF lung SPECT and negative Pgp expression. In contrast, only 4 of the 20 patients with a poor chemotherapy response had a positive Tc-99m TF lung SPECT. Moreover, 10 of the 20 patients with a poor chemotherapy response also had negative Pgp expression (p < 0.05). Therefore, we concluded that Tc-99m TF lung SPECT can accurately predict the chemotherapy response, and Tc-99m TF lung SPECT findings can be partially compatible with Pgp expression in patients with untreated SCLC.     

胃泌素释放肽前体作为小细胞肺癌标记物的临床研究

目的 评价胃泌素释放肽前体(progastrin-releasing peptide，ProGRP)作为小细胞肺癌(SCLC)新标记物的临床意义。方法 回顾性分析经病理证实的55例SCLC初治患者血清中ProGRP水平，并观察其与肿瘤分期、治疗效果的关系。结果 ProGRP诊断SCLC的灵敏度为80．0％，特异度为97．0％；进展期SCLC患者血清ProGRP平均水平显著高于局限期患者，二者分别为820.Ong/L和205.86ng/L(P=0．0003)；临床治疗有效的SCLC患者，治疗后ProGRP水平较治疗前明显下降，而治疗无效病例则无下降甚至升高。结论 ProGRP作为SCLC新的标记物，具有敏感性高、特异性强的特点，并可准确反映SCLC病情及对化疗的反应。     

Physical dosimetry of 125I seeds of a new design for interstitial implant

The physical characteristics of a new ¹²⁵I seed, consisting of radioactive iodine adsorbed on a silver wire and contained in a sealed titanium shell, have been measured. Advantages of the new seed design are: increased radiopacity, possible determination of seed orientation in an implant for dosimetric calculations, and source strength specification traceable to the National Bureau of Standards. Spectroscopic analysis of the new seed using an intrinsic Ge detector revealed the 27.4, 31.4 and 35.5kev photons from the decay of ¹²⁵I, and in addition, 22.1 and 25.2kev fluorescent X ray from the silver wire. Measured and calculated relative dose distribution along the perpendicular bisector of the new seed is similar to that of the existing seed, with a slightly more rapid fall-off due to the existence of the lower energy photons. The measured angular distributions of the seeds of the two designs are similar, exhibiting significant anisotropy. A protocol of source strength specification, choice of effective gamma constant value and dose calculation relative to ¹²⁵I implants is suggested.     

肠系膜淋巴结滤泡树突细胞肉瘤1例报告并文献复习

目的探讨滤泡树突细胞肉瘤的临床病理特征、诊断和鉴别诊断。方法对1例肠系膜淋巴结滤泡树突细胞肉瘤进行光镜和免疫组化观察,结合文献进行讨论。结果镜下肿瘤由旋涡状、束状排列的胖梭形、卵圆形或多边形瘤细胞和大量混杂的淋巴细胞组成。免疫表型瘤细胞表达CD35和CD23,弱阳性表达CD68、S-100和EMA;淋巴细胞表达CD45RO和CD3。结论淋巴结滤泡树突状细胞肉瘤是一种罕见的免疫辅助细胞中度恶性肿瘤,其诊断依靠组织病理学和免疫组化,治疗以手术切除为主,必要时辅以化疗和(或)放疗。     

The dose-area product, a new parameter for the dosimetry of narrow photon beams

In the dosimetry of narrow photon fields with side lengths of the order of 1 cm, the traditional parametrisation via the absolute dose on the beam axis and the relative lateral dose distribution has to deal with the difficulty to find sufficiently small detectors and to adjust them accurately on the narrow-beam axis. This can be avoided by reconsidering the parametrisation, using as normalization factor the surface integral of the dose in the plane perpendicular to the beam axis, abbreviated as the "dose-area product" (DAP). We investigated and confirmed the ability of a large-area parallel-plate ionisation chamber, with a sensitive volume shaped as a flat cylinder of 81.6 mm diameter and 2 mm thickness, to perform the integration over the full lateral dose profile of narrow photon beams with side lengths up to 5 cm. The lateral adjustment of this large-area detector relative to a narrow photon beam is not critical. The large-area ionisation chamber was calibrated in terms of the DAP by reference to a 0.3 cm3 ionisation chamber. A field-size dependent "modified output factor" was defined as the ratio of the DAP measured at 5 cm phantom depth for 100 cm SSD, and the monitor reading. A prominent phenomenon of narrow photon fields is the field-size and source-distance independence of the relative axial profile of the DAP as function of the thickness of a pre-absorber or of the depth in a phantom. For narrow-beam treatment planning in IMRT, the DAP is combined with the energy- and field size-dependent relative lateral dose distribution which is represented, for example, by a Gaussian convolution kernel. Another useful feature of the DAP is the possibility of its direct control during patient irradiation by means of an on-line monitor with spatial resolution, arranged in the accessory holder.     

~(99m)Tc-MIBI肺显像测定非小细胞肺癌P-糖蛋白表达

目的　研究99mTc MIBI(甲氧基乙丁基异腈 )肺显像定性检测非小细胞肺癌P 糖蛋白 (P GP)及与化疗效果对比。方法　采用二时相平面显像 ,以病灶处99mTc MIBI的潴留指数 (RI)为P GP定性指标 ,RI <0为P GP阳性 ,以WHO标准将疗效分为完全或者部分缓解 (CR、PR)无变化 (NC) ,进展 (PD) ,将P GP定性结果与疗效比较。结果　 3 2例非小细胞肺癌中 2 1例 ( 6 5 .6 % )P GP表达阳性 ,化疗有效率为 9.5 % ,11例 ( 3 4.4% )P GP表达阴性 ,化疗有效率为 81.8% ,两组化疗有效率有显著性差异 (P <0 .0 1)。结论　99mTc MIBI肺显像可作为肺癌P GP非组织学测定方法 ,可预测化疗敏感性 ,指导临床治疗。