Laboratory realization of relativistic pair-plasma beams.

Relativistic electron-positron plasmas are ubiquitous in extreme astrophysical environments such as black-hole and neutron-star magnetospheres, where accretion-powered jets and pulsar winds are expected to be enriched with electron-positron pairs. Their role in the dynamics of such environments is in many cases believed to be fundamental, but their behavior differs significantly from typical electron-ion plasmas due to the matter-antimatter symmetry of the charged components. So far, our experimental inability to produce large yields of positrons in quasi-neutral beams has restricted the understanding of electron-positron pair plasmas to simple numerical and analytical studies, which are rather limited. We present the first experimental results confirming the generation of high-density, quasi-neutral, relativistic electron-positron pair beams using the 440 GeV/c beam at CERN's Super Proton Synchrotron (SPS) accelerator. Monte Carlo simulations agree well with the experimental data and show that the characteristic scales necessary for collective plasma behavior, such as the Debye length and the collisionless skin depth, are exceeded by the measured size of the produced pair beams. Our work opens up the possibility of directly probing the microphysics of pair plasmas beyond quasi-linear evolution into regimes that are challenging to simulate or measure via astronomical observations.

Radiation Reaction Cooling as a Source of Anisotropic Momentum Distributions with Inverted Populations.

Under the presence of strong electromagnetic fields and radiation reaction, plasmas develop anisotropic momentum distributions, characterized by a population inversion. This is a general property of collisionless plasmas when the radiation reaction force is taken into account. We study the case of a plasma in a strong magnetic field and demonstrate the development of ring momentum distributions. The timescales for ring formation are derived for this configuration. The analytical results for the ring properties and the timescales for ring formation are confirmed with particle-in-cell simulations. The resulting momentum distributions are kinetically unstable and are known to lead to coherent radiation emission in astrophysical plasmas and laboratory setups.

Prognostic value of maximum standardized uptake value measured by pretreatment 18F-FDG PET/CT in locally advanced head and neck squamous cell carcinoma

Purpose/objectives. To evaluate the prognostic impact of maximum standardized uptake value (SUVmax) in patients with locally advanced head and neck squamous cell carcinoma (HNSCC) undergoing pretreatment [F-18] fluoro-d-glucose-positron emission tomography/computed tomography (FDG PET/CT) imaging. Materials/methods. Fifty-eight patients undergoing FDG PET/CT before radical treatment with definitive radiotherapy (±concomitant chemotherapy) or surgery + postoperative (chemo)radiation were analyzed. The effects of clinicopathological factors (age, gender, tumor location, stage, Karnofsky Performance Status (KPS), and treatment strategy) including primary tumor SUVmax and nodal SUVmax on overall survival (OS), disease-free survival (DFS), locoregional control (LRC), and distant metastasis-free survival (DMFS) were evaluated. Kaplan–Meier survival curves were generated and compared with the log-rank test. Results. Median follow-up for the whole population was 31 months (range 2.3–53.5). Two-year OS, LRC, DFS and DMFS, for the entire cohort were 62.1, 78.3, 55.2 and 67.2%, respectively. Median pretreatment SUVmax for the primary tumor and lymph nodes was 11.85 and 5.4, respectively. According to univariate analysis, patients with KPS < 80% (p < 0.001), AJCC stage IVa or IVb vs III (p = 0.037) and patients undergoing radiotherapy vs surgery (p = 0.042) were significantly associated with worse OS. Patients with KPS < 80% (p = 0.003) or age ≥65 years (p = 0.007) had worse LRC. The KPS < 80% was the only factor associated with decreased DFS (p = 0.001). SUVmax of the primary tumor or the lymph nodes were not associated with OS, DFS or LRC. The KPS < 80% (p = 0.002), tumor location (p = 0.047) and AJCC stage (p = 0.025) were associated with worse cancer-specific survival (CSS). According to Cox regression analysis, on multivariate analysis KPS < 80% was the only independent parameter determining worse OS, DFS, CSS. Regarding LRC only patients with IK < 80% (p = 0.01) and ≥65 years (p = 0.01) remained statistically significant. Nodal SUVmax was the only factor associated with decreased DMFS. Patients with a nodal SUVmax > 5.4 presented an increased risk for distant metastases (HR, 3.3; 95% CI 1.17–9.25; p = 0.023). Conclusions. The pretreatment nodal SUVmax in patients with locally advanced HNSCC is prognostic for DMFS. However, according to our results primary tumor SUVmax and nodal SUVmax were not significantly related to OS, DFS or LRC. Patients presenting KPS < 80% had worse OS, DFS, CSS and LRC (AU)

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Prognostic value of maximum standardized uptake value measured by pretreatment 18F-FDG PET/CT in locally advanced head and neck squamous cell carcinoma.

PURPOSE/OBJECTIVES: To evaluate the prognostic impact of maximum standardized uptake value (SUVmax) in patients with locally advanced head and neck squamous cell carcinoma (HNSCC) undergoing pretreatment [F-18] fluoro-D-glucose-positron emission tomography/computed tomography (FDG PET/CT) imaging. MATERIALS/METHODS: Fifty-eight patients undergoing FDG PET/CT before radical treatment with definitive radiotherapy (±concomitant chemotherapy) or surgery + postoperative (chemo)radiation were analyzed. The effects of clinicopathological factors (age, gender, tumor location, stage, Karnofsky Performance Status (KPS), and treatment strategy) including primary tumor SUVmax and nodal SUVmax on overall survival (OS), disease-free survival (DFS), locoregional control (LRC), and distant metastasis-free survival (DMFS) were evaluated. Kaplan-Meier survival curves were generated and compared with the log-rank test. RESULTS: Median follow-up for the whole population was 31 months (range 2.3-53.5). Two-year OS, LRC, DFS and DMFS, for the entire cohort were 62.1, 78.3, 55.2 and 67.2%, respectively. Median pretreatment SUVmax for the primary tumor and lymph nodes was 11.85 and 5.4, respectively. According to univariate analysis, patients with KPS < 80% (p < 0.001), AJCC stage IVa or IVb vs III (p = 0.037) and patients undergoing radiotherapy vs surgery (p = 0.042) were significantly associated with worse OS. Patients with KPS < 80% (p = 0.003) or age ≥65 years (p = 0.007) had worse LRC. The KPS < 80% was the only factor associated with decreased DFS (p = 0.001). SUVmax of the primary tumor or the lymph nodes were not associated with OS, DFS or LRC. The KPS < 80% (p = 0.002), tumor location (p = 0.047) and AJCC stage (p = 0.025) were associated with worse cancer-specific survival (CSS). According to Cox regression analysis, on multivariate analysis KPS < 80% was the only independent parameter determining worse OS, DFS, CSS. Regarding LRC only patients with IK < 80% (p = 0.01) and ≥65 years (p = 0.01) remained statistically significant. Nodal SUVmax was the only factor associated with decreased DMFS. Patients with a nodal SUVmax > 5.4 presented an increased risk for distant metastases (HR, 3.3; 95% CI 1.17-9.25; p = 0.023). CONCLUSIONS: The pretreatment nodal SUVmax in patients with locally advanced HNSCC is prognostic for DMFS. However, according to our results primary tumor SUVmax and nodal SUVmax were not significantly related to OS, DFS or LRC. Patients presenting KPS < 80% had worse OS, DFS, CSS and LRC.

Transperineal biopsies of MRI-detected aggressive index lesions in low- and intermediate-risk prostate cancer patients: Implications for treatment decision.

PURPOSE: Multiparametric MRI (mpMRI) has a potential role for the identification of aggressive cancer that can be targeted for biopsy. We report the incidence and severity of discordant information between the pathology found on the transrectal ultrasound (TRUS)-guided biopsy and the mpMRI findings in patients with favorable or intermediate-risk prostate cancer referred for brachytherapy. METHODS AND MATERIALS: From March 2014 to September 2015, 10/44 consecutive patients with low- or intermediate-risk prostate cancer referred for brachytherapy presented an aggressive lesion on mpMRI and underwent an MRI-TRUS fusion-guided transperineal biopsy of the index lesion. RESULTS: A median of two intraprostatic lesions were detected by mpMRI for each patient. Three patients had bilateral disease, and seven had unilateral disease on mpMRI. The median number of cores obtained by MRI-TRUS-guided fusion of the index lesion was 3 (range 2-4). As a result of the re-evaluation consequent to additional information becoming available after the transperineal biopsy, upgrading of Gleason score occurred in 8 of the 10 patients, which changed the risk group in 9 patients. These changes resulted in modification of the proposed treatment in 8 patients. CONCLUSIONS: MpMRI-US fusion-targeted biopsy sampling allows detection and characterization of otherwise undetected aggressive disease, often placing men in higher risk groups and altering the treatment approach.

A prospective analysis of inter- and intrafractional errors to calculate CTV to PTV margins in head and neck patients

Purpose. To evaluate an institute-specific CTV–PTV margin for head and neck (HN) patients according to a 3-mm action level protocol. Methods/patients. Twenty-three HN patients were prospectively analysed. Patients were immobilized with a thermoplastic mask. Inter- and intrafractional set-up errors (in the three dimensions) were assessed from portal images (PI) registration. Digitally reconstructed radiographs (DRRs) were compared with two orthogonal PI by matching bone anatomy landmarks. The isocenter was verified during the first five consecutive days of treatment: if the mean error detected was greater than 2 mm the isocenter position was corrected for the rest of the treatment. Isocenter was checked weekly thereafter. Set-up images were obtained before and after treatment administration on 10, 20 and 30 fractions to quantify the intrafractional displacement. For the set-up errors, systematic (Σ), random (σ), overall standard deviations, and the overall mean displacement (M), were determined. CTV to PTV margin was calculated considering both inter- and intrafractional errors. Results. A total of 396 portal images was analysed in 23 patients. Systematic interfractional (Σinter) set-up errors ranged between 0.77 and 1.42 mm in the three directions, whereas the random (σ inter) errors were around 1–1.31 mm. Systematic intrafractional (Σintra) errors ranged between 0.65 and 1.11 mm, whereas the random (σ intra) errors were around 1.13–1.16 mm. Conclusions. A verification protocol (3-mm action level) provided by EPIDs improves the set-up accuracy. Intrafractional error is not negligible and contributes to create a larger CTV–PTV margin. The appropriate CTV–PTV margin for our institute is between 3 and 4.5 mm considering both inter- and intrafractional errors (AU)

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A prospective analysis of inter- and intrafractional errors to calculate CTV to PTV margins in head and neck patients.

PURPOSE: To evaluate an institute-specific CTV-PTV margin for head and neck (HN) patients according to a 3-mm action level protocol. METHODS/PATIENTS: Twenty-three HN patients were prospectively analysed. Patients were immobilized with a thermoplastic mask. Inter- and intrafractional set-up errors (in the three dimensions) were assessed from portal images (PI) registration. Digitally reconstructed radiographs (DRRs) were compared with two orthogonal PI by matching bone anatomy landmarks. The isocenter was verified during the first five consecutive days of treatment: if the mean error detected was greater than 2 mm the isocenter position was corrected for the rest of the treatment. Isocenter was checked weekly thereafter. Set-up images were obtained before and after treatment administration on 10, 20 and 30 fractions to quantify the intrafractional displacement. For the set-up errors, systematic (Σ), random (σ), overall standard deviations, and the overall mean displacement (M), were determined. CTV to PTV margin was calculated considering both inter- and intrafractional errors. RESULTS: A total of 396 portal images was analysed in 23 patients. Systematic interfractional (Σ(inter)) set-up errors ranged between 0.77 and 1.42 mm in the three directions, whereas the random (σ (inter)) errors were around 1-1.31 mm. Systematic intrafractional (Σ(intra)) errors ranged between 0.65 and 1.11 mm, whereas the random (σ (intra)) errors were around 1.13-1.16 mm. CONCLUSIONS: A verification protocol (3-mm action level) provided by EPIDs improves the set-up accuracy. Intrafractional error is not negligible and contributes to create a larger CTV-PTV margin. The appropriate CTV-PTV margin for our institute is between 3 and 4.5 mm considering both inter- and intrafractional errors.

Definitive radiotherapy for T1 glottic squamous cell carcinoma: a 15-years Cruces University Hospital experience

PURPOSE: To evaluate the treatment outcomes for T1 N0 glottic carcinoma after definitive radiotherapy. METHODS: One hundred and seventeen patients treated with radical radiotherapy from 1990 to 2006 were retrospectively reviewed. The median follow-up duration for the entire group was 92 months (range 4-227). A median dose of 70 Gy (range 63-70 Gy) was administered. We determined the rates of local control (LC), regional control, overall survival (OS) and cause-specific survival (CSS) at 5, 10 and 15 years by Kaplan-Meier product-limit method. The Cox regression analysis was performed to identify significant prognostic factors for LC and survival. The incidence of secondary malignancies is also reported. RESULTS: The 5-, 10- and 15-year LC rates for the whole group were 84, 80.2 and 80.2 %, respectively. There were 20 local recurrences, of which 19 were salvaged with laryngectomy, giving an ultimate control rate of 90.6 %. The 5-/10-/15-year OS and CSS rates were 81.2 %/66.1 %/48.3 % and 90.6 %/90.6 %/90.6 %, respectively. None of the parameters analyzed exhibited a statistically significant relationship with LC. The age ≥65 years had a statistically significant effect on OS (but not in CSS), with a hazard ratio of 2.45 (95 % confidence interval 1.29-4.66; p = 0.006). During follow-up, 26 patients (22 %) developed a secondary malignancy. Only two patients (1.7 %) presented with severe toxicity (edema and mucositis). CONCLUSIONS: Radiotherapy alone offers a high likelihood of LC and an excellent CSS rate. In addition, the surgical approach for the salvage is a successful option (AU)

Definitive radiotherapy for T1 glottic squamous cell carcinoma: a 15-year Cruces University Hospital experience.

PURPOSE: To evaluate the treatment outcomes for T1 N0 glottic carcinoma after definitive radiotherapy. METHODS: One hundred and seventeen patients treated with radical radiotherapy from 1990 to 2006 were retrospectively reviewed. The median follow-up duration for the entire group was 92 months (range 4-227). A median dose of 70 Gy (range 63-70 Gy) was administered. We determined the rates of local control (LC), regional control, overall survival (OS) and cause-specific survival (CSS) at 5, 10 and 15 years by Kaplan-Meier product-limit method. The Cox regression analysis was performed to identify significant prognostic factors for LC and survival. The incidence of secondary malignancies is also reported. RESULTS: The 5-, 10- and 15-year LC rates for the whole group were 84, 80.2 and 80.2 %, respectively. There were 20 local recurrences, of which 19 were salvaged with laryngectomy, giving an ultimate control rate of 90.6 %. The 5-/10-/15-year OS and CSS rates were 81.2 %/66.1 %/48.3 % and 90.6 %/90.6 %/90.6 %, respectively. None of the parameters analyzed exhibited a statistically significant relationship with LC. The age ≥65 years had a statistically significant effect on OS (but not in CSS), with a hazard ratio of 2.45 (95 % confidence interval 1.29-4.66; p = 0.006). During follow-up, 26 patients (22 %) developed a secondary malignancy. Only two patients (1.7 %) presented with severe toxicity (edema and mucositis). CONCLUSIONS: Radiotherapy alone offers a high likelihood of LC and an excellent CSS rate. In addition, the surgical approach for the salvage is a successful option.

Patterns of care for brachytherapy in Europe: updated results for Spain

OBJECTIVE: The aim of this follow-up pattern of care study was to evaluate current clinical practices, staffing and equipment, and to compare these results to a study performed 5 years previously. MATERIALS AND METHODS: This descriptive, pattern of care study was carried out via an online questionnaire. The survey was sent to a total of 95 cancer care centres in Spain. RESULTS: Seventy-three centres (76.8%) responded to the survey. More than half (57.5%) of responding centres offered brachytherapy (BT). A mean of 120 patients/centre were treated by BT in 2007. The most common localisations were the endometrium (29.6% of cases), prostate (29.6%), cervix uteri (14.6%), breast (12.6%), head and neck (3.6%) and vagina (2.5%). Other sites accounted for less than 2% of cases each. Most centres that offered BT (33/40 = 82.5%) were equipped with a dedicated BT operating room. The most commonly reported dosimetric method was CT dosimetry (31 of 40 centres = 77.5%), followed by plain film (30/40 = 75%), ultrasound (26/40 = 65%), MRI (8/40 = 20%), in vivo (7/40 = 17.5%) and PET-CT (5/40 = 12.5%) dosimetry. CONCLUSION: The three most common treatment sites (gynaecological, breast and prostate) remain unchanged from 2002, with prostate treatments showing large increase. Advanced dosimetric techniques (MRI, PET-CT and CT-dosimetry) continue to gain adherents. Some centres treat small numbers of patients, a finding that deserves more attention in terms of cost and quality of care. Although BT remains strong in Spain, it could be further strengthened by making modern dosimetric techniques and treatments more widely available (AU)

Brachytherapy in the United Kingdom and Spain: a subset analysis of a European pattern of care survey

PURPOSE: The aim of this pattern of care survey was to provide an overview of brachytherapy resources and practices in the United Kingdom (UK) and Spain and to identify differences that may be relevant to health-care delivery and planning. METHODS AND MATERIALS: Both countries formed part of a larger survey of European radiation oncology centres carried out in 2002. The present study includes only data from centres that perform brachytherapy and completed the questionnaire. RESULTS: Between 1997 and 2002, the number of hospitals offering brachytherapy increased by 10.2% in the UK and 21.4% in Spain. The mean number of radiotherapy patients per centre was significantly higher in the UK (2811 patients) than in Spain (1203). Gynaecological tumours accounted for most procedures (59.7% in Spain and 60.8% in the UK), followed by prostate cancer in the UK (16.7%) and breast cancer in Spain (15.5%). Significantly more procedures for breast cancer were performed in Spain (19.7 patients/centre) than in the UK (0.4 patients/centre). A significantly higher percentage of radiation oncologists in Spain performed brachytherapy, dedicating more time to brachytherapy-related work (22.2 h/week) than their colleagues in the UK (6.7 h/week). CONCLUSIONS: Brachytherapy resources and patterns of care are similar in both countries, although several notable differences exist. Radiation oncologists in Spain dedicate significantly more time to brachytherapy. Compared to the UK, brachytherapy is used more frequently in Spain as a boost in breast cancer treatments. Both countries perform more brachytherapy procedures for prostate cancer than the European average (AU)

High-dose-rate intensity modulated brachytherapy with external-beam radiotherapy improves local and biochemical control in patients with high-risk prostate cancer.

Purpose Our aim was to report the 8-year outcome of local dose escalation using high-dose-rate conformal brachytherapy combined with external irradiation for patients with high-risk prostate cancer. Material and methods From June 1998 to June 2007, 134 patients with high-risk localized prostate cancer were prospectively enrolled in the study. The median follow-up was 45 months (12-107). Only patients considered as having high-risk criteria were accepted [prostate-specific antigen (PSA) > or =20 ng/ml and/or Gleason >7 and/or stage > or =T3a or two intermediate-risk criteria: PSA 11-19 ng/ml, Gleason 7, stage T2b-c]. The total dose applied by external beam radiotherapy was 46 Gy in 200-cGy daily fractions. High-dose-rate brachytherapy was performed at the end of weeks 1 and 3 of the 5-week radiotherapy course. The doses administered in each application was 1,150 cGy. Any patient free of clinical or biochemical evidence of disease was termed b-NED. Actuarial rates of outcome were calculated by Kaplan. Meier analysis and compared using the log-rank test. Cox regression models were used to establish prognostic factors of the measures of outcome. Results Mean follow-up for the entire group was 45 months (range 12-107). The overall survival (OS) according to Kaplan-Meier estimates was 85% (+/-5) at 5 and 8 years. The 5 and 8 years for biochemical control were 80% (+/-4%) and 73% (+/-7%), respectively, whereas for failure in tumor-free survival (TFS), they were 82% (+/-3) at 5 and 8 years, respectively. The 8-year cause-specific mortality was 10% (+/-4%). The multivariate Cox regression analyses identified the number of poor prognostic factors as independent for biochemical failure. Our report includes only patients considered as high risk, and the 8-year b-NED survival rate was 83% for patients with two intermediate-risk criteria, 78% for patients with one poor prognostic factor, 56% for two and 35% for all three (p = 0.001). There were no urethral strictures and/or urinary incontinence. Gastrointestinal toxicity grade 2 was 7.5%. Conclusions The 8-year results confirm the feasibility and effectiveness of external-beam radiation therapy with conformal high-dose-rate brachytherapy boost for patients with high-risk tumor. The late toxicity rates were low, corroborating the excellent dose conformity.

High-dose-rate intensity modulated brachytherapy with external-beam radiotherapy improves local and biochemical control in patients with high-risk prostate cancer

Purpose Our aim was to report the 8-year outcome of local dose escalation using high-dose-rate conformal brachytherapy combined with external irradiation for patients with high-risk prostate cancer. Material and methods From June 1998 to June 2007, 134 patients with high-risk localized prostate cancer were prospectively enrolled in the study. The median follow-up was 45 months (12-107). Only patients considered as having high-risk criteria were accepted [prostate-specific antigen (PSA) > or =20 ng/ml and/or Gleason >7 and/or stage > or =T3a or two intermediate-risk criteria: PSA 11-19 ng/ml, Gleason 7, stage T2b-c]. The total dose applied by external beam radiotherapy was 46 Gy in 200-cGy daily fractions. High-dose-rate brachytherapy was performed at the end of weeks 1 and 3 of the 5-week radiotherapy course. The doses administered in each application was 1,150 cGy. Any patient free of clinical or biochemical evidence of disease was termed b-NED. Actuarial rates of outcome were calculated by Kaplan. Meier analysis and compared using the log-rank test. Cox regression models were used to establish prognostic factors of the measures of outcome. Results Mean follow-up for the entire group was 45 months (range 12-107). The overall survival (OS) according to Kaplan-Meier estimates was 85% (+/-5) at 5 and 8 years. The 5 and 8 years for biochemical control were 80% (+/-4%) and 73% (+/-7%), respectively, whereas for failure in tumor-free survival (TFS), they were 82% (+/-3) at 5 and 8 years, respectively. The 8-year cause-specific mortality was 10% (+/-4%). The multivariate Cox regression analyses identified the number of poor prognostic factors as independent for biochemical failure. Our report includes only patients considered as high risk, and the 8-year b-NED survival rate was 83% for patients with two intermediate-risk criteria, 78% for patients with one poor prognostic factor, 56% for two and 35% for all three (p = 0.001). There were no urethral strictures and/or urinary incontinence. Gastrointestinal toxicity grade 2 was 7.5%. Conclusions The 8-year results confirm the feasibility and effectiveness of external-beam radiation therapy with conformal high-dose-rate brachytherapy boost for patients with high-risk tumor. The late toxicity rates were low, corroborating the excellent dose conformity (AU)

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Preliminary analysis of the resources in brachytherapy in Europe and its variability of use.

PURPOSE: The main objective of the program <> is to establish a group with detailed information on brachytherapy throughout Europe. METHODS: The data was compiled by the general coordinator, the ESTRO, and the <> through a website. RESULTS: A total of 32 countries reported data from at least 50% of their centres (criteria of inclusion). Countries were grouped in three categories based on the time of incorporation to the European Union. The majority of treatments belonged to gynaecological tumours. A large spread was found regarding workload of specialists depending on centre and group. CONCLUSION: Collection of information by a website is a feasible methodology. An increase in brachytherapy treatment was observed in all 3 groups by a rate of more than 20% (year 2002 versus year 1997). These results advocate for the continuation of the PCBE study to demonstrate the development in the field, such as an increase or decrease of patient numbers per tumour category.

L-2-Oxothiazolidine-4-carboxylate reverses the tumour growth-promoting effect of interleukin-2 and improves the anti-tumour efficacy of biochemotherapy in mice bearing B16 melanoma liver metastases.

The efficacy of sequential chemoimmunotherapy involving interleukin-2 (IL2) in metastatic melanoma is limited, in part, by the severe toxicity associated with most therapeutic regimens. Glutathione (GSH), the most prevalent intracellular non-protein thiol, plays an important role in protecting against cellular injury caused by various anticancer agents. GSH is also involved in the IL2-induced proliferative activity of immune system cells and some melanoma cells expressing IL2 receptors, such as B16 melanoma cells. The present study investigated the effect of selective manipulation of GSH using the cysteine prodrug l-2-oxothiazolidine-4-carboxylate (OTZ) on the response of B16 melanoma to sequential biochemotherapy with cyclophosphamide (CY) and IL2. We found that OTZ, by depressing GSH levels, abrogates the in vitro growth-promoting effects of IL2 on B16 melanoma cells. The combination of OTZ plus IL2 in vivo also showed antitumour activity in mice bearing B16 melanoma liver metastases, significantly increasing their life span. Schedule dependency between both compounds was found; OTZ given intermittently in combination with daily IL2 administration was found to be the best therapeutic schedule. We also observed that whereas IL2 or OTZ alone added to CY resulted in a lower or non-significant improvement in the life span of the mice compared with tolerated doses of CY alone, the addition of both OTZ and IL2 to CY produced a significantly greater increase in survival than CY alone, and markedly protected mice against CY-induced toxicity, which allowed the administration of otherwise lethal doses of CY, with the CY activity/toxicity ratio being increased by four-fold.

Tunicamycin treatment reduces intracellular glutathione levels: effect on the metastatic potential of the rhabdomyosarcoma cell line S4MH.

Highly metastatic cells are known to overexpress certain Asn-linked oligosaccharides in the plasmatic membrane. Another phenotypic characteristic of malignant cells consists in the expression of high levels of intracellular glutathione (GSH). The aim of the present work was to demonstrate that the inhibition of N-glycosylation induces changes in intracellular GSH levels, and in turn participates in the inhibition of the metastatic potential of tumor cells by tunicamycin treatment. Firstly, we demonstrated that in comparison to the poorly metastatic cell line F21, the highly metastatic cells S4MH express a higher number of Asn-linked beta1-6 branched oligosaccharides and sialic acid (SA) and/or chitobiose oligosaccharides in glycoproteins involved in the regulation of the adhesion efficiency of tumor cells on endothelial cells and extracellular matrix. Our results showed that the decrease in S4MH cell adhesion efficiency on endothelial cells and extracellular matrix after the inhibition of N-glycan processing by tunicamycin treatment was caused by: (1) inhibition of the expression of N-glycan structures recognized by endothelial endogenous lectins, including beta1-6 branched oligosaccharides and SA and/or chitobiose oligosaccharides, and (2) redistribution of cell surface glycoproteins with beta1-6 branched oligosaccharides and/or SA and/or chitobiose oligosaccharides in their structures, caused by the depletion of intracellular GSH levels. The latter condition prevents the organization of these glycoproteins in the plasmatic membrane of S4MH cells necessary for anchoring to the substratum.

Effects of L-2-oxothiazolidine-4-carboxylate on the cytotoxic activity and toxicity of cyclophosphamide in mice bearing B16F10 melanoma liver metastases.

Glutathione (GSH) is the major non-protein thiol in cells that plays a critical role against damage from electrophilic agents such as alkylating drugs. Selective therapeutic GSH elevation in normal but not in tumour cells has been suggested as a means of protecting host tissues against more intense doses of chemotherapy. The present study investigated the response of B16 melanoma to treatment with the cysteine pro-drug L-2-oxothiazolidine-4-carboxylate (OTZ), alone and in combination with cyclophosphamide (CY). We found that OTZ decreased the GSH levels and proliferation rate of B16 melanoma cells in vitro, sensitizing them to the cytotoxic action of the activated metabolite of CY, acrolein (AC). In contrast to OTZ, the cysteine deliverer N-acetylcysteine (NAC) enhanced B16 melanoma cell proliferation by increasing GSH levels, and markedly decreased the sensitivity of these tumour cells to AC. In vivo studies showed the antitumoral activity of OTZ in B16 melanoma liver metastasis-induced mice, increasing their life span. We also observed that, whereas with CY treatment the GSH levels in peripheral blood mononuclear cells (PBMCs) were reduced and a dose-dependent leukopenia was produced, OTZ significantly increased PBMC GSH content, reducing toxicity and enhancing the survival of mice bearing established melanoma liver metastases treated with lethal dose CY. These results suggest a critical role for OTZ in protecting against alkylator agent-induced immunosuppression, which may allow the dose escalation of these cytostatic drugs to improve their therapeutic benefit in the treatment of malignant melanoma.

In vitro and in vivo comparison between the effects of treatment with adenosine triphosphate and treatment with buthionine sulfoximine on chemosensitization and tumour growth of B16 melanoma.

In this study we compare the effects of treatment with external sodium adenosine 5'-triphosphate (ATP) with the effects of L-buthionine-SR-sulfoximine (BSO) on B16 melanoma growth and on the modulation of the cytotoxic antimelanoma activity of cyclophosphamide (CY). We evaluated the in vitro effects of treatment with ATP or BSO on intracellular glutathione (GSH) levels, mitochondrial membrane potential (delta psi(m)) and the proliferation rate of the B16F10 melanoma cell line. Compared with untreated cells, delta psi(m) and GSH levels were already significantly decreased (25% and 57% reduction, respectively) after the first hour of incubation in culture cells exposed to 3 mM ATP. After 24 and 48 h a major reduction was observed in delta psi(m) (nearly 30%). GSH levels were also maximally depleted at 24 h (approximately 75%) and partially recovered (up to 37% of levels of control) after ATP was removed from the medium. At 24 and 48 h, the proliferation rate was decreased 1.4- and 1.7-fold, respectively, compared with control cells. Treatment with 50 microM BSO produced a time-dependent decrease in GSH levels (0.5, 21, 48 and 97.3% reduction at 1, 4, 8 and 24 h, respectively), but up to 54% of the levels of control cells was recovered after BSO was removed from the medium. In contrast to ATP, neither delta psi(m) nor proliferation rate was significantly modified in the first 24 h with BSO treatment. At 48 h, delta psi(m) was reduced by nearly 27%, and cell proliferation decreased 1.2-fold compared with controls. When the in vitro cytotoxic effect of low dose acrolein (an active metabolite of CY) in combination with BSO or ATP was analysed, a synergistic effect was found between BSO and acrolein, with a dose modification factor (DMF) of 1.98, but the antiproliferative effects of acrolein plus ATP were only approximately additive (DMF = 1.05). In addition, in in vivo studies differential effects were found between ATP and BSO. Specifically, whereas BSO alone significantly increased the survival time of mice bearing B16 melanoma liver metastases, and enhanced the cytotoxic effect of CY on this tumour model, no therapeutic benefits could be observed with ATP treatment, either alone or in combination with diethyl maleate (a GSH-depleting agent) and CY. In conclusion, our findings show that in our experimental system, both extracellular ATP and BSO have growth-inhibitory properties against B16 melanoma in vitro. In vivo, however, only BSO produces a chemosensitizing effect, whereas ATP has not proved useful as a biological modifier of chemotherapy.

Interleukin-2 increases intracellular glutathione levels and reverses the growth inhibiting effects of cyclophosphamide on B16 melanoma cells.

Glutathione (GSH) plays an essential role in the metabolism of melanoma. As changes in intracellular GSH content can modify the processes of cell proliferation and detoxification, this could determine the therapeutic response to some cancer treatment strategies. The purpose of this study was to test the effects of treatment with interleukin-2 (IL-2), alone and in combination with cyclophosphamide (CY), on survival of mice bearing B16 melanoma liver metastases, and to determine the influence of these therapeutic agents on the GSH metabolism of B16 cells. In the in vivo test system, B16 melanoma liver metastases were induced in C57BL/6 mice which were subsequently treated with IL-2, CY and CY plus IL-2. Survival time was used to determine the response to treatment. In the in vitro system, we evaluated the effects of IL-2, acrolein (an active metabolite of CY responsible for GSH depletion) and acrolein plus IL-2 on GSH levels and proliferation of B16 melanoma cells. Results indicated that, in vivo, all treatments increased mouse survival times with respect to control mice. However, the addition of IL-2 to CY therapy decreased survival time compared with treatment with CY alone. In vitro, whereas acrolein produced a GSH depletion and inhibited B16 cell proliferation, IL-2 increased GSH content and cell proliferation rate compared with untreated cells. Moreover, addition of IL-2 to cells preincubated with acrolein increased GSH levels and proliferation with respect to acrolein alone. In summary, the data suggest that GSH plays a critical role in the growth-promoting effects of IL-2 on B16F10 melanoma cells and in the antagonistic effect of IL-2 on CY inhibitory activity on these tumor cells.

Tumor-host interaction in non-random metastatic pattern distribution.

In the clinical evolution of malign tumors, prognosis depends on whether metastasis develops or not. Biologically speaking, the formation of metastasis implies the existence of tumor cells capable of successfully performing all the steps in the metastatic process: local invasion, lymphatic or hematogenous dissemination, arrest in the microvascular bed of an organ, extravasation and growth of a secondary colony. Clinical observations have demonstrated that for each primary tumor there is a colonization pattern determined by the characteristics of the microvascular endothelium and the functional environment of the target organ. Moreover, the formation of metastasis depends on at least two additional factors: a) tumor cell-tumor cell and tumor cell-host cell relations modulated by intercellular contact and/or soluble paracrine or autocrine growth factors; b) the antitumor efficiency of the immune system, mediated primarily by the action of NK/LAK cells, macrophages and cytolytic T-lymphocytes, whose activity is in turn regulated by a complex of cytokines, including interferons, tumor necrosis factors and interleukins. In this work, we first review certain aspects of tumor biology that are specifically involved in tumor cell-host cell interactions determining non-random metastatic pattern distribution, and then review the implication of certain cytokines in the regulation of tumor proliferation.