Factors influencing local control after MR-guided stereotactic body radiotherapy (MRgSBRT) for adrenal metastases

Purpose

Stereotactic body radiotherapy (SBRT) is an effective treatment for adrenal gland metastases, but it is technically challenging and there are concerns about toxicity. We performed a multi-institutional pooled retrospective analysis to study clinical outcomes and toxicities after MR-guided SBRT (MRgSBRT) using for adrenal gland metastases.

Methods and Materials

Clinical and dosimetric data of patients treated with MRgSBRT on a 0.35 T MR-Linac at 11 institutions between 2016 and 2022 were analyzed. Local control (LC), local progression-free survival (LPFS), distant progression-free survival (DPFS) and overall survival (OS) were estimated using Kaplan-Meier method and log-rank test.

Results

A total of 255 patients (269 adrenal metastases) were included. Metastatic pattern was solitary in 25.9 % and oligometastatic in 58.0 % of patients. Median total dose was 45 Gy (range, 16-60 Gy) in a median of 5 fractions, and the median BED10 was 100 Gy (range, 37.5-132.0 Gy). Adaptation was done in 87.4 % of delivered fractions based on the individual clinicians' judgement. The 1- and 2- year LPFS rates were 94.0 % (95 % CI: 90.7-97.3 %) and 88.3 % (95 % CI: 82.4-94.2 %), respectively and only 2 patients (0.8 %) experienced grade 3 + toxicity. No local recurrences were observed after treatment to a total dose of BED10 > 100 Gy, with single fraction or fractional dose of > 10 Gy.

Conclusions

This is a large retrospective multi-institutional study to evaluate the treatment outcomes and toxicities with MRgSBRT in over 250 patients, demonstrating the need for frequent adaptation in 87.4 % of delivered fractions to achieve a 1- year LPFS rate of 94 % and less than 1 % rate of grade 3 + toxicity. Outcomes analysis in 269 adrenal lesions revealed improved outcomes with delivery of a BED10 > 100 Gy, use of single fraction SBRT and with fraction doses > 10 Gy, providing benchmarks for future clinical trials.

Outcomes of MR-Guided Stereotactic Body Radiotherapy (MRgSBRT) for Adrenal Metastases: A Multi-Institutional Pooled Analysis

PURPOSE/OBJECTIVE(S)

Stereotactic body radiotherapy (SBRT) is an effective treatment for adrenal metastases, but it is technically challenging and there are concerns about toxicity due to the proximity of organs at risk. We hypothesized that MR-guided SBRT (MRgSBRT) using a 0.35 T MR-Linac for adrenal metastases can achieve durable local control (LC) with a low probability of toxicity.

MATERIALS/METHODS

In an ethics-approved study, we analyzed clinical and dosimetric data of patients treated with MRgSBRT at 10 institutions between 2016-2022. LC, local progression-free survival (LPFS), distant progression-free survival (DPFS) and overall survival (OS) were estimated using Kaplan-Meier method and log-rank test. Responses were evaluated using RECIST criteria. Toxicity was graded according to CTCAE (v4.0). OS and DPFS were calculated on a per-patient basis, while LC and LPFS were calculated on a per-lesion basis.

RESULTS

A total of 249 patients (260 adrenal lesions) were included; median age was 65 years (range 28-91), 65.5% were male, 83.9% had ECOG PS 0-1. The most common primary tumor was lung cancer (69.1%). Adrenal metastases were synchronous, metachronous, oligoprogressive or oligopersistent in 20%, 41.5%, 35.8% and 2.7% of patients, respectively. Metastatic pattern was solitary in 26.9%, oligometastatic in 57.3% and polymetastatic in 15.8% of patients. Right-sided metastases comprised 40%, left-sided 51.5% and lesions were bilateral in 8.5%. Chemotherapy and immunotherapy were administered in 67.1% and 60.6% of patients, respectively. Median gross tumor volume was 21.8 cc (range 1.1-383.2) and median planning target volume was 36.9 cc (range 3.6-516.9). Median total dose was 45 Gy (range 16-60), median fraction number was 5 (range 1-8) and median fraction dose used was 10 Gy (range 5-24). Median BED10 was 100 Gy (range 37.5-132); 87.8% of fractions used adapted plans. At a median follow-up was 17.7 months (IQR 5.5-21.7), local responses were scored as complete response (CR), partial response (PR), stable disease (SD) or progressive disease (PD) in 36.9%, 28.2%, 25.7%, and 9.1%, respectively. Median OS was 30.4 months, with 1- and 2- year OS rates of 75.3% and 57.1%, respectively. On multivariate analysis, significantly higher OS rates were seen in patients achieving a CR (p = 0.007, HR 0.50) and with ECOG scores of 0-1 (p = 0.001, HR 0.43). One- and 2- year LPFS rates were 94.5% and 88.8%, respectively. No local recurrences were observed after treatment to a BED10>100 or with single fraction (range 16-24 Gy). Only 2 patients (0.8%) had ≥grade 3 chronic toxicity.

CONCLUSION

This multi-institutional study of MRgSBRT outcomes for adrenal metastases revealed a 2-year LPFS of 89%, with a <1% risk of ≥grade 3 toxicity. Daily adaptation was performed in 90% of plans, indicating a beneficial role for MR guidance.

Randomized Trial of Five or Two MRI-guided Adaptive Radiotherapy Treatments for Prostate Cancer (FORT)

PURPOSE/OBJECTIVE(S)

The objective of this randomized clinical trial is to demonstrate that 2 treatments of real-time MRI-guided radiotherapy (RT) does not significantly increase patient-reported GI and GU symptoms compared to 5 treatments of RT 2 years after treatment completion (24 months).

MATERIALS/METHODS

Key Eligibility Criteria: Inclusion Criteria 1. Men aged > 18 with histologically confirmed low or intermediate risk prostate cancer per NCCN guidelines. 2. ECOG 0 - 1 3. IPSS < 18 4. Ability to receive MRI-guided radiotherapy. 5. Ability to complete the Expanded Prostate Cancer Index Composite (EPIC) questionnaire. Exclusion Criteria 1. Prior history of receiving pelvic RT. 2. Patient with history of IBD. 3. Hip replacements. 4. History of bladder neck or urethral stricture. 5. TURP < 8 weeks prior to RT 6. Metastatic (pelvic nodal or distant) disease on CT, Bone, and/or PSMA PET scan. Study Design/Endpoints: This is a randomized phase II non-inferiority trial comparing 2 fractions of ultrahypofractionated RT (25 Gy total with optional PSMA/MRI boost to 28 Gy) versus 5 fractions of ultra-hypofractionated RT (37.5 Gy total with optional PSMA/MRI boost to 45 Gy) in the definitive setting for prostate cancer. Subjects will be stratified based on pre-specified stratification factors and randomized 1:1 to receive 2 or 5 fractions using permuted block randomization. The primary endpoint is the change in patient-reported GI and GU symptoms as measured by EPIC at 2 years from end of treatment. Secondary endpoints will include both the safety endpoints including change in GI and GU symptoms at 3, 6, 12 and 60 months from end of treatment, and multiple efficacy endpoints including time to progression, prostate cancer specific survival and overall survival.

SAMPLE SIZE

The sample size is calculated based on a non-inferiority design. The non-inferiority margins are set to be a change score of 6 points for the GI symptoms and 5 points for the GU symptoms. The standard deviations of the change scores are assumed to be 13.2 for the GI symptoms and 10.5 for the GU symptoms based on estimates generated in RTOG 0415 trial. This level of change in scores are deemed as clinically meaningful. For example, 6 points of change score for GI symptoms corresponds to two symptoms worsening by 1 level (i.e., loose stools and frequency of bowel movements change from "no problem" to "very small problem") or one of the symptoms worsening by 2 levels (i.e., loose stool change from "no problem" to "small problem"). A sample size of 122 with 61 in each arm will ensure 80% power for GI endpoint and 83% power for GU endpoint to detect non-inferiority using a one-sided two-sample t-test at the significance level of 0.05. Adjusting for a projected 10% EPIC/non-compliance rate, 136 patients (68 per arm) will be randomized. Stratification Factors: Patients will be stratified according to baseline EPIC bowel and urinary domain scores and country of treatment. Enrollment: Twenty patients.

RESULTS

To be determined.

CONCLUSION

To be determined.

A randomized phase II trial of MR-guided prostate stereotactic body radiotherapy administered in 5 or 2 fractions for localized prostate cancer (FORT)

BACKGROUND

Ultra-hypofractionated regimens for definitive prostate cancer (PCa) radiotherapy are increasingly utilized due in part to promising safety and efficacy data complemented by greater patient convenience from a treatment course requiring fewer sessions. As such, stereotactic body radiation therapy (SBRT) is rapidly emerging as a standard definitive treatment option for patients with localized PCa. The commercially available magnetic resonance linear accelerator (MR-LINAC) integrates MR imaging with radiation delivery, providing several theoretical advantages compared to computed tomography (CT)-guided radiotherapy. MR-LINAC technology facilitates improved visualization of the prostate, real-time intrafraction tracking of prostate and organs-at-risk (OAR), and online adaptive planning to account for target movement and anatomical changes. These features enable reduced treatment volume margins and improved sparing of surrounding OAR. The theoretical advantages of MR-guided radiotherapy (MRgRT) have recently been shown to significantly reduce rates of acute grade ≥ 2 GU toxicities as reported in the prospective randomized phase III MIRAGE trial, which compared MR-LINAC vs CT-based 5 fraction SBRT in patients with localized PCa (Kishan et al. JAMA Oncol 9:365-373, 2023). Thus, MR-LINAC SBRT-utilizing potentially fewer treatments-is warranted and clinically relevant for men with low or intermediate risk PCa electing for radiotherapy as definitive treatment.

METHODS/DESIGN

A total of 136 men with treatment naïve low or intermediate risk PCa will be randomized in a 1:1 ratio to 5 or 2 fractions of MR-guided SBRT using permuted block randomization. Randomization is stratified by baseline Expanded PCa Index Composite (EPIC) bowel and urinary domain scores. Patients undergoing 5 fractions will receive 37.5 Gy to the prostate over 10-14 days and patients undergoing 2 fractions will receive 25 Gy to the prostate over 7-10 days. The co-primary endpoints are GI and GU toxicities as measured by change scores in the bowel and urinary EPIC domains, respectively. The change scores will be calculated as pre-treatment (baseline) score subtracted from the 2-year score.

DISCUSSION

FORT is an international, multi-institutional prospective randomized phase II trial evaluating whether MR-guided SBRT delivered in 2 fractions versus 5 fractions is non-inferior from a gastrointestinal (GI) and genitourinary (GU) toxicity standpoint at 2 years post-treatment in men with low or intermediate risk PCa.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT04984343 . Date of registration: July 30, 2021.

PROTOCOL VERSION

4.0, Nov 8, 2022.

Randomized trial of five or two MRI-guided adaptive radiotherapy treatments for prostate cancer (FORT)

TPS399

Background: The objective of this randomized clinical trial is to demonstrate that 2 treatments of real-time MRI-guided radiotherapy (RT) does not significantly increase patient-reported GI and GU symptoms compared to 5 treatments of RT 2 years after treatment completion (24 months). Methods: Key Eligibility Criteria: Inclusion Criteria 1. Men aged > 18 with histologically confirmed low or intermediate risk prostate cancer per NCCN guidelines. 2. ECOG 0 – 1 3. IPSS < 18 4. Ability to receive MRI-guided radiotherapy. 5. Ability to complete the Expanded Prostate Cancer Index Composite (EPIC) questionnaire. Exclusion Criteria 1. Prior history of receiving pelvic RT. 2. Patient with history of IBD. 3. Hip replacements. 4. History of bladder neck or urethral stricture. 5. TURP < 8 weeks prior to RT 6. Metastatic (pelvic nodal or distant) disease on CT, Bone, and/or PSMA PET scan. Study Design/Endpoints: This is a randomized phase II non-inferiority trial comparing 2 fractions of ultrahypofractionated RT (25 Gy total with optional PSMA/MRI boost to 28 Gy) versus 5 fractions of ultra-hypofractionated RT (37.5 Gy total with optional PSMA/MRI boost to 45 Gy) in the definitive setting for prostate cancer. Subjects will be stratified based on pre-specified stratification factors and randomized 1:1 to receive 2 or 5 fractions using permuted block randomization. The primary endpoint is the change in patient-reported GI and GU symptoms as measured by EPIC at 2 years from end of treatment. Secondary endpoints will include both the safety endpoints including change in GI and GU symptoms at 3, 6, 12 and 60 months from end of treatment, and multiple efficacy endpoints including time to progression, prostate cancer specific survival and overall survival. Sample Size: The sample size is calculated based on a non-inferiority design. The non-inferiority margins are set to be a change score of 6 points for the GI symptoms and 5 points for the GU symptoms. The standard deviations of the change scores are assumed to be 13.2 for the GI symptoms and 10.5 for the GU symptoms based on estimates generated in RTOG 0415 trial. This level of change in scores are deemed as clinically meaningful. For example, 6 points of change score for GI symptoms corresponds to two symptoms worsening by 1 level (i.e., loose stools and frequency of bowel movements change from “no problem” to “very small problem”) or one of the symptoms worsening by 2 levels (i.e., loose stool change from “no problem” to “small problem”). A sample size of 122 with 61 in each arm will ensure 80% power for GI endpoint and 83% power for GU endpoint to detect non-inferiority using a one-sided two-sample t-test at the significance level of 0.05. Adjusting for a projected 10% EPIC/non-compliance rate, 136 patients (68 per arm) will be randomized. Stratification Factors: Patients will be stratified according to baseline EPIC bowel and urinary domain scores and country of treatment. Enrollment: Eleven patients. Clinical trial information: NCT04984343 .

Intensity-modulated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): 2-year toxicity results from an open-label, randomised, phase 3, non-inferiority trial

BACKGROUND

Localised prostate cancer is commonly treated with external beam radiotherapy and moderate hypofractionation is non-inferior to longer schedules. Stereotactic body radiotherapy (SBRT) allows shorter treatment courses without impacting acute toxicity. We report 2-year toxicity findings from PACE-B, a randomised trial of conventionally fractionated or moderately hypofractionated radiotherapy versus SBRT.

METHODS

PACE is an open-label, multicohort, randomised, controlled, phase 3 trial conducted at 35 hospitals in the UK, Ireland, and Canada. In PACE-B, men aged 18 years and older with a WHO performance status 0-2 and low-risk or intermediate-risk histologically-confirmed prostate adenocarcinoma (Gleason 4 + 3 excluded) were randomly allocated (1:1) by computerised central randomisation with permuted blocks (size four and six), stratified by centre and risk group to control radiotherapy (CRT; 78 Gy in 39 fractions over 7·8 weeks or, following protocol amendment on March 24, 2016, 62 Gy in 20 fractions over 4 weeks) or SBRT (36·25 Gy in five fractions over 1-2 weeks). Androgen deprivation was not permitted. Co-primary outcomes for this toxicity analysis were Radiation Therapy Oncology Group (RTOG) grade 2 or worse gastrointestinal and genitourinary toxicity at 24 months after radiotherapy. Analysis was by treatment received and included all patients with at least one fraction of study treatment assessed for late toxicity. Recruitment is complete. Follow-up for oncological outcomes continues. The trial is registered with ClinicalTrials.gov, NCT01584258.

FINDINGS

We enrolled and randomly assigned 874 men between Aug 7, 2012, and Jan 4, 2018 (441 to CRT and 433 to SBRT). In this analysis, 430 patients were analysed in the CRT group and 414 in the SBRT group; a total of 844 (97%) of 874 randomly assigned patients. At 24 months, RTOG grade 2 or worse genitourinary toxicity was seen in eight (2%) of 381 participants assigned to CRT and 13 (3%) of 384 participants assigned to SBRT (absolute difference 1·3% [95% CI -1·3 to 4·0]; p=0·39); RTOG grade 2 or worse gastrointestinal toxicity was seen in 11 (3%) of 382 participants in the CRT group versus six (2%) of 384 participants in the SBRT group (absolute difference -1·3% [95% CI -3·9 to 1·1]; p=0·32). No serious adverse events (defined as RTOG grade 4 or worse) or treatment-related deaths were reported within the analysis timeframe.

INTERPRETATION

In the PACE-B trial, 2-year RTOG toxicity rates were similar for five fraction SBRT and conventional schedules of radiotherapy. Prostate SBRT was found to be safe and associated with low rates of side-effects. Biochemical outcomes are awaited.

FUNDING

Accuray.

Clinical adoption patterns of 0.35 Tesla MR-guided radiation therapy in Europe and Asia

Background

Magnetic resonance-guided radiotherapy (MRgRT) utilization is rapidly expanding, driven by advanced capabilities including better soft tissue imaging, continuous intrafraction target visualization, automatic triggered beam delivery, and the availability of on-table adaptive replanning. Our objective was to describe patterns of 0.35 Tesla (T)-MRgRT utilization in Europe and Asia among early adopters of this novel technology.

Methods

Anonymized administrative data from all 0.35T-MRgRT treatment systems in Europe and Asia were extracted for patients who completed treatment from 2015 to 2020. Detailed treatment information was analyzed for all MR-linear accelerators (linac) and -cobalt systems.

Results

From 2015 through the end of 2020, there were 5796 completed treatment courses delivered in 46,389 individual fractions. 23.5% of fractions were adapted. Ultra-hypofractionated (UHfx) dose schedules (1–5 fractions) were delivered for 63.5% of courses, with 57.8% of UHfx fractions adapted on-table. The most commonly treated tumor types were prostate (23.5%), liver (14.5%), lung (12.3%), pancreas (11.2%), and breast (8.0%), with increasing compound annual growth rates (CAGRs) in numbers of courses from 2015 through 2020 (pancreas: 157.1%; prostate: 120.9%; lung: 136.0%; liver: 134.2%).

Conclusions

This is the first comprehensive study reporting patterns of utilization among early adopters of a 0.35T-MRgRT system in Europe and Asia. Intrafraction MR image-guidance, advanced motion management, and increasing adoption of on-table adaptive RT have accelerated a transition to UHfx regimens. MRgRT has been predominantly used to treat tumors in the upper abdomen, pelvis and lungs, and increasingly with adaptive replanning, which is a radical departure from legacy radiotherapy practices.

Based on 0.35 T magnetic resonance-guided radiotherapy, what are the nonisotropic PTV margins required for conventional prostate radiotherapy?

This study aims to calculate planning target volume (PTV) margins for the prostate and seminal vesicles (SVs) from the use of magnetic resonance-guided radiation therapy (MRgRT). And whether nonisotropic PTV margins are beneficial for these structures. Organ motion is linked to the displacement of the prostate and SVs. From the use of MRgRT, the nearby organs at risk (OAR) can be visualized both inter- and intrafraction. This study looked to determine if there is a correlation between interfractional OAR changes and displacements to the prostate and SVs. Inter- and intrafractional data from 20 consecutive prostate cancer patients treated using extreme hypofractionated 0.35 T MRgRT indicated prostate and SV motion during treatment. Tracking points (TPs) on 2D sagittal cine-MRI enabled assessment of this intrafractional motion. To determine a correlation between rectal changes and target displacements, the rectal diameter (RD) changes were compared against the displacement differences (DDs) at the prostate and SVs. Eighty percent of patients required intrafractional imaging corrections during radiotherapy, including 16/100 fractions due to rectal volume increases and 24/100 fractions due to bladder volume increases. The frequency of ≥3 mm intrafraction displacement was considerably greater in TPs in the SV than in the prostate. A moderate positive correlation (R² = 0.417) was shown between RD changes and DDs at the level of the prostate and SVs. The PTV margins required for 90% of the patient cohort for prostate and SVs are nonuniform in different directions, and the margin is larger for SVs. Organ motion contributed toward prostate and SV displacements and showed the importance of a robust bladder and rectal-filling protocol.

Implementation of Stereotactic MRI-Guided Adaptive Radiotherapy (SMART) for Hepatobiliary and Pancreatic Cancers in the United Kingdom - Fifty in Five

The first MRIdian® MR linear accelerator (MR-Linac; ViewRay, Oakwood Village, Ohio) in the United Kingdom went live in December 2019 following a record installation time. Stereotactic MRI-guided Adaptive Radiotherapy (SMART) has since been implemented and has advantages of excellent soft tissue definition of both target and organs at risk (OARs), real-time target and OAR visualisation on cine-MRI, daily recontouring of target and critical OARs with live online plan adaptation/re-optimisation, and automatic respiratory-gated treatment delivery. We present a multi-disciplinary narrative and technical description of how this innovative technique was implemented for hepatobiliary (HPB) cancers. In particular, we explain how a collaborative approach and desire to push the boundaries and improve outcomes enabled 50 patients to be treated in the first five months, many with technically challenging tumours not always deliverable on other platforms. Physics, dosimetry, radiographer, and clinician perspectives on implementing SMART are presented. MRIdian® single fraction lung stereotactic ablative radiotherapy (SABR) will shortly be implemented along with innovative research in conjunction with our academic partners.

Harnessing the potential of multimodal radiotherapy in prostate cancer

Radiotherapy in combination with androgen deprivation therapy (ADT) is a standard treatment option for men with localized and locally advanced prostate cancer. However, emerging clinical evidence suggests that radiotherapy can be incorporated into multimodality therapy regimens beyond ADT, in combinations that include chemotherapy, radiosensitizing agents, immunotherapy and surgery for the treatment of men with localized and locally advanced prostate cancer, and those with oligometastatic disease, in whom the low metastatic burden in particular might be treatable with these combinations. This multimodal approach is increasingly recognized as offering considerable clinical benefit, such as increased antitumour effects and improved survival. Thus, radiotherapy is becoming a key component of multimodal therapy for many stages of prostate cancer, particularly oligometastatic disease.

Stereotactic body radiotherapy for moderately central and ultra-central oligometastatic disease: Initial outcomes

BACKGROUND

Delivery of SBRT to central thoracic tumours within 2 cm of the proximal bronchial tree (PBT), and especially ultra-central tumours which directly abut the PBT, has been controversial due to concerns about high risk of toxicity and treatment-related death when delivering high doses close to critical mediastinal structures. We present dosimetric and clinical outcomes from a group of oligometastatic patients treated with a risk-adapted SBRT approach.

METHODS

Between September 2015 and October 2018, 27 patients with 28 central thoracic oligometastases (6 moderately central, 22 ultra-central) were treated with 60 Gy in 8 fractions under online CBCT guidance. PTV dose was compromised where necessary to meet mandatory OAR constraints. Patients were followed up for toxicity and disease status.

RESULTS

Mandatory OAR constraints were met in all cases; this required PTV coverage compromise in 23 cases, with V100% reduced to <70% in 11 cases. No acute or late toxicities of Grade ≥ 3 were reported. One and 2 year in-field control rates were 95.2% and 85.7% respectively, progression-free survival rates were 42.8% and 23.4% respectively, and overall survival rates were 82.7% and 69.5% respectively. No significant differences were seen in control or survival rates by extent of PTV underdosage or between moderately and ultra-central cases.

CONCLUSION

It appears that compromising PTV coverage to meet OAR constraints allows safe and effective delivery of SBRT to moderately and ultra-central tumours, with low toxicity rates and high in-field control rates. This treatment can be delivered on standard linear accelerators with widely available imaging technology.

ToxNav germline genetic testing and PROMinet digital mobile application toxicity monitoring: Results of a prospective single-center clinical utility study-PRECISE study

INTRODUCTION

In this study (PRECISE), we assess the clinical utility of a germline DNA sequencing-based test (ToxNav) for mutations in DPYD and ENOSF1 genes to alter clinician-prescribed fluoropyrimidine doses and the use of a digital application (PROMinet) to record patient-reported chemotherapy toxicity.

MATERIALS AND METHODS

Adult patients with a histological diagnosis of colorectal cancer (CRC) who consented to fluoropyrimidine-based chemotherapy were recruited prospectively and given a digital application to monitor and record associated toxicities. Patient samples were analyzed for 18 germline coding variants in DPYD and 1 ENOSF1 variant.

RESULTS

Genetic testing was performed for 60 patients and identified one patient at increased risk of fluoropyrimidine-based toxicities. Uptake of genetic testing was high and results were available on average 17 days from initial clinical encounter. Patient-reported chemotherapy toxicity identified differences in 5-fluorouracil vs capecitabine regime profiles and identified profiles associated with subsequent need for chemotherapy dose reduction and hospital admission.

DISCUSSION

The PRECISE clinical trial demonstrated that a germline DNA sequencing-based test can provide clinically relevant information to alter clinicians' fluoropyrimidine prescription. The study also obtained high volume, high granularity patient-reported toxicity data that might allow the improvement and personalization of chemotherapy management.

Chemotherapy induced Hyponatraemia

We present a case report of chemotherapy induced renal salt wasting syndrome (RSWS) that was initially diagnosed and managed as syndrome of inappropriate secretion of antidiuretic hormone (SIADH), based on osmolality values as well as hydration status. The patient was receiving chemotherapy for metastatic testicular cancer. Progressive deterioration of electrolyte balance prompted the diagnosis of RSWS. This was confirmed by a high urinary sodium concentration, a simple but important investigation which is rarely requested in the initial investigation of hyponatraemia. Urine sodium concentration is high in RSWS but normal in SIADH. With chemotherapy playing such an important role in cancer management, the correct diagnosis of hyponatraemia in an oncology patient is vital in order to allow appropriate management. Although the distinctions between SIADH and RSWS can be very subtle, the management of these two distinct clinical situations is very different-namely, fluid restriction versus salt replacement.

Electrophoretic manipulation of single DNA molecules in nanofabricated capillaries

We demonstrate the use of nanofabricated capillaries, integrated as part of a microfluidic structure, to study the electrophoretic behaviour of single, fluorescently-labelled, molecules of DNA as a function of capillary size. The nanocapillaries, fabricated using a focused ion beam, have cross-sections down to 150 x 180 nm. Control of single-molecule direction and velocity was achieved using voltage manipulation. DNA mobility was found to increase with decreasing cross-section, which we interpret in terms of reduced electro-osmotic counter-flow. Such nanofabricated capillaries as part of larger fluidic structures have great potential for biotechnology, particularly single molecule manipulation and analysis.

Novel spermine-based cationic gemini surfactants for gene delivery

Two types of spermine-based gemini surfactants have been synthesised; structure-activity studies have shown one type to be far superior in gene transection than the other.

Analysis of N-linked oligosaccharides: progress towards the characterisation of glycoprotein-linked carbohydrates

The covalent attachment of carbohydrate to proteins is a very common co- or post-translational event in the biosynthesis of glycoproteins. The type and heterogeneity of these oligosaccharides can affect a range of physico-chemical and biological properties of a glycoprotein. Thus the development of sensitive, reliable and robust analytical methods for carbohydrate analysis is important in the pharmaceutical industry, especially in the recombinant production of experimental and therapeutic glycoproteins. In this report we have reviewed methodology for the in-gel enzymatic release of N-linked oligosaccharides from glycoproteins separated by electrophoresis. These oligosaccharides are derivatised by reductive amination using 3-acetamido-6-aminoacridine (AA-Ac), a novel, highly fluorescent probe. A major advantage of this technique is that glycan derivatives are amenable to analysis by an array of chromatographic and mass spectrometric methods, allowing the resolution and characterisation of a wide variety of glycan structures. It is hoped that in due course the methodology described will be applied to proteomics studies, especially in identifying the role of carbohydrate in protein function and disease.

Determination of carbohydrate structures N-linked to soluble CD154 and characterization of the interactions of CD40 with CD154 expressed in Pichia pastoris and Chinese hamster ovary cells

CD40-CD154 (CD40 ligand) interactions are essential for the development of protective immunity. Previous studies have described the CD40 binding site as a shallow groove formed between two monomers of CD154. However, these studies have not examined the structure or biological function of the carbohydrate on CD154. Human CD154 contains a single N-linked glycosylation site at asparagine 240. We have characterized the interactions between CD40 and soluble (s) CD154 in which sCD154 contains different types of carbohydrates. Detailed carbohydrate analysis revealed high-mannose structures on sCD154 purified from Pichia pastoris, whereas CD154 purified from Chinese hamster ovary E1A contained heterogeneous populations of complex carbohydrates. sCD154 purified from either system was trimeric, it bound to CD40 with similar affinities of 10-30 nM, and it functionally induced CD69 and CD95 expression on primary B cells. Together, these results indicate that the presence of varied types of N-linked glycans on asparagine 240 of CD154 does not play a significant role in the CD40-CD154 interactions.

Sialylation of human IgG-Fc carbohydrate by transfected rat alpha2,6-sialyltransferase

A recombinant IgG3 antibody with Phe-243 replaced by Ala (FA243) was expressed in a CHO-K1 parental cell line. The resulting IgG-Fc-linked carbohydrate was significantly alpha2,3-sialylated (53% of glycans), as indicated by normal- and reverse-phase HPLC analyses. Following transfection of a rat alpha2,6-sialyltransferase gene into this parental cell line, IgG-Fc-linked glycans were sialylated (60% of glycans) such that the ratio of alpha2,6- to alpha2,3-linked sialic acid was 0.9:1.0. By comparison, the wild-type IgG3 (F243) is minimally sialylated (2-3% alpha2,3-linked), thus suggesting that sialylation is controlled primarily by the protein structure local to the carbohydrate and that the two sialyltransferases compete to sialylate the nascent oligosaccharide. The additional alpha2,6-sialylation affected the function of the recombinant antibody. FA243 IgG3 having both alpha2,6 and alpha2,3-sialylation restored recognition to wild-type IgG3 levels for human FcgammaRI, FcgammaRII, and target cell lysis by complement. We discuss how sialylation linkage could modulate IgG function.

Rational approaches to the design of cationic gemini surfactants for gene delivery

We report a new class of amphiphilic gemini surfactants as vehicles for gene delivery into cells, and the beginnings of a systematic structure-activity study. Preliminary results suggest that combining gemini surfactants with dioleoylphosphatidylethanolamine (DOPE) should allow the preparation of liposomes of various sizes and lipid compositions. Control of such colloidal changes could be as significant as the changes in the molecular composition of the gemini surfactants in delivering optimum gene expression in animal models.

Characterization of the glycosylation profiles of Alzheimer's beta -secretase protein Asp-2 expressed in a variety of cell lines

Amyloid 39-42 beta -peptides are the main components of amyloid plaques found in the brain of Alzheimer's disease patients. Amyloid 39-42 beta-peptide is formed from amyloid precursor protein by the sequential action of beta- and gamma-secretases. Asp-2 is a transmembrane aspartic protease expressed in the brain, shown to have beta-secretase activity. Mature Asp-2 has four N-glycosylation sites. In this report we have characterized the carbohydrate structures in this glycoprotein expressed in three different cell lines, namely Chinese hamster ovary, CV-1 origin of SV40, and baculovirus-infected SF9 cells. Biantennary and triantennary oligosaccharides of the "complex" type were released from glycoprotein expressed in the mammalian cells, whereas mannose-rich glycans were identified from glycoprotein synthesized in the baculovirus-infected cells. Site-directed mutagenesis of the asparagine residues at amino acid positions 153, 172, 223, and 354 demonstrate that the protease activity of Asp-2 is dependent on its glycosylation.

Neutron reflection from a dimyristoylphosphatidylcholine monolayer adsorbed on a hydrophobised silicon support

Neutron specular reflection has been used to study the structure of a monolayer of dimyristoylphosphatidylcholine (DMPC) deposited using the Langmuir-Blodgett technique onto a silicon oxide substrate. A self-assembled monolayer of octadecyltrichlorosilane with a deuterated alkyl chain (d-OTS) had been previously bonded onto this silicon oxide substrate which rendered it hydrophobic. In the system under study, the alkyl chains of the phospholipid were found to penetrate extensively into the d-OTS layer with the mixed chain region (d-OTS and DMPC) having a total thickness of 30.5 A. This mixed region was divided into two halves for analysis; the 'lower half' (nearest to the substrate surface) was found to comprise anchored d-OTS chains mixed with the lipid chains in the volume ratio approx. 0.60:0.35. The corresponding volume ratio in the 'upper half' of this region was determined to be approx. 0.50:0.40. The thicknesses of these regions were found to be 17.9 A (incorporating approx. 6% solvent) and 12.6 A (incorporating approx. 9% solvent) for the lower and upper halves respectively. The DMPC head groups were found to be confined to the most external layer (furthest away from the silicon substrate). This layer was found to have a thickness of 9.4 A and included a small fraction of the lipid alkyl chains with approx. 47% solvent.

A comparative study of the asparagine-linked oligosaccharides on siglec-5, siglec-7 and siglec-8, expressed in a CHO cell line, and their contribution to ligand recognition

The siglecs (sialic acid-binding immunoglobulin-like lectins) mediate sialic acid-dependent cellular interactions and may in some cases signal through SH2-binding domains. In addition to the previously characterized siglecs, sialoadhesin, CD22, CD33 and myelin-associated glycoprotein, several new ones, siglec-5, siglec-7 and siglec-8, have recently been cloned. Although these novel receptors have generated considerable interest as therapeutic targets because of their expression pattern on immune cells, very little is known about how their lectin activity is regulated. Previous studies with sialoadhesin, CD22 and CD33 have shown that siglec glycosylation has significant effects on binding. To determine any differences in the glycan composition of siglec-5, siglec-7 and siglec-8 that may modify their function, we released and characterized the N-linked oligosaccharide distribution in these three glycoproteins. The glycan pools from siglec-5 and siglec-7 contained a larger proportion of sialylated and core-fucosylated biantennary, triantennary and tetra-antennary oligosaccharides, whereas the carbohydrate mixture released from siglec-8 is noticeably less sialylated and is more abundant in 'high-mannose'-type glycans. In addition, we show that, in contrast with CD22 and CD33, mutating the conserved potentially N-linked glycosylation site in the first domain has no effect on binding mediated by siglec-5 or siglec-7.

Sugar-based tertiary amino gemini surfactants with a vesicle-to-micelle transition in the endosomal pH range mediate efficient transfection in vitro

Novel reduced sugar gemini amphiphiles linked through their tertiary amino head groups via alkyl spacers of 4 or 6 carbons, and with varying (unsaturated) alkyl tail lengths of 12--18, have been synthesized and tested for transfection in vitro in an adherent Chinese hamster ovary cell line (CHO-K1). Transfection efficiencies peaked at 2.7 times that of the commercial standard Lipofectamine Plus/2000 for pure solutions of the compound bearing unsaturated (oleyl) alkyl tails. For those compounds bearing saturated alkyl tails, transfection efficiency peaked at a tail length of 16, at a level similar to Lipofectamine Plus/2000. All of the amphiphiles formed bilayer vesicles at physiological pH. Some of the amino groups at the surface were protonated, and vesicles therefore bore a positive charge. Increased protonation with reduced pH resulted in greatly increased monomer solubility and a morphology change from vesicle to micelle at characteristic pH values, dependent on the tail length. For the compounds promoting high transfection efficiency, this characteristic pH was within the range found in the endosomal compartment (7.4--4.0). Formation of mixed micelles between gemini surfactant and membrane phospholipids at reduced pH may therefore provide a method of endosome rupture and subsequent escape of entrapped DNA, thus discarding the need for extra fusogenic or endosomolytic agents. The positive charge on the vesicles at physiological pH drives the colloidal association with DNA. Small angle X-ray scattering measurements indicate that lamellar aggregates are formed, which have a d spacing of 48--54 A. Preliminary differential scanning calorimetric measurements suggest that reduction of pH causes a disordering of the hydrocarbon region of the DNA-surfactant complex.

Immobilisation of antibodies in gels allows the improved release and identification of glycans

Human IgG and IgM, bovine IgM and three therapeutic IgG monoclonal antibodies have been separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Carbohydrates were then released from these immobilised proteins by direct enzymatic digestion, derivatised with a highly fluorescent probe and analysed by high performance liquid chromatography and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. This procedure not only allowed measurement of the purity of the intact antibodies but also provided detailed analysis of the complex mixtures of oligosaccharides covalently attached to these glycoproteins. The methodology out-lined allows the simultaneous processing of a number of glycoproteins separated on one single gel. In contrast to the release of carbohydrate from glycoproteins in solution, this procedure can also be conveniently applied when only impure glycoprotein is available.

Facile sequencing of oligosaccharides by matrix-assisted laser desorption/ionisation on a hybrid quadrupole orthogonal acceleration time-of-flight mass spectrometer

N-Linked oligosaccharide mixtures released from a number of standard glycoproteins were derivatised with 3-acetylamino-6-acetylaminoacridine (AA-Ac) using reductive amination. Analysis of these mixtures using an experimental matrix-assisted laser desorption/ionisation (MALDI) hybrid quadrupole orthogonal acceleration time-of-flight (Q-TOF) mass spectrometer provided detailed information about the mass distribution of the glycan derivatives. Collision-induced dissociation of the singly protonated [M + H](+) ions also gave rise to a number of product ions produced by the sequential cleavage of the glycosidic linkages. As fragmentation of the positively charged species occurred predominantly in one direction, i.e., from the non-reducing end of the glycan to the AA-Ac moiety, a considerable amount of information could be obtained with ease about the sequence in which the sugar residues were attached to one another. This derivatisation procedure and mass spectrometric methodology were applied successfully to neutral and acidic glycans released from proteins separated by gel electrophoresis.

Principal component analysis of mass spectra of peptides generated from the tryptic digestion of protein mixtures

Principal component analysis (PCA) has been used to analyse mass spectral peptide profiles obtained from the enzymatic digestion of standard protein mixtures. Scores and loadings plots clearly revealed peptide fragments that differentiated one protein mixture from another. Peptide map search results identified with a high degree of certainty any additional proteins in these mixtures. As a proof-of-concept this methodology was applied to hepatic protein mixtures obtained from rats treated with two hepatotoxic compounds: methapyriline and SB-219994. Liver proteins were extracted, pre-separated by one-dimensional polyacrylamide gel electrophoresis, subjected to tryptic digestion and analysed by mass spectrometry. Two up-regulated proteins, glutathione S-transferase with methapyrilene and peroxisomal bifunctional enzyme with SB-219994, were identified in this manner.

High resolution of oligosaccharide mixtures by ultrahigh voltage micellar electrokinetic capillary chromatography

Oligosaccharide mixtures released from ribonuclease B and human IgG have been separated using micellar electrokinetic capillary chromatography operated at 100 kV. The resolution of these closely related analytes at this high voltage was found to be superior to that obtained at 20 kV, a voltage which is ordinarily used in most capillary electrophoresis separations.

Analysis of N-linked oligosaccharides released from glycoproteins separated by two-dimensional gel electrophoresis

Protocols have been developed for the characterization of carbohydrate covalently attached (N-linked) to an asparagine residue in glycoproteins, after separation by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). Mixtures of proteins (each at a level from 0.5 to 50 microg) were resolved in the first dimension according to their isoelectric points (pI), followed by separation in the orthogonal axis on the basis of their molecular weights. Glycans were released directly from excised gel spots after digestion with PNGase F, with or without prior treatment with trypsin. In a third method, glycoproteins were electroblotted onto poly(vinylidene difluoride) before glycans were released by PNGase F. For all these procedures profiles of the neutral and sialic acid-containing oligosaccharide mixtures were obtained after derivatization with 3-acetamido-6-aminoacridine, and analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and/or high-performance liquid chromatography. Potential applications to proteomics are discussed.

Capillary electrophoresis in the pharmaceutical industry: applications in discovery and chemical development

Over the last 10 to 15 years capillary electrophoresis (CE) has become an extensively used separation technique in the pharmaceutical industry. The attraction of the various modes of operation of CE to analysts is their complementarity to other more established methodology, in particular high-performance liquid chromatography. CE methods have been developed not only for the resolution of drug substances that vary widely in their structure, size and stereochemistry, but also for the determination of the physico-chemical constants of analytes, such as pKa and isoelectric point (pI) values, binding and complexation constants, and octanol-water partition coefficients.

Early indication of effects of puromycin aminonucleoside using a fluorimetric assay of 2-aminoacridone-derivatized carbohydrates in urine

This paper describes a novel noninvasive method to study the changes in free carbohydrates excreted in urine as a result of toxicity in the rat induced by the administration of puromycin aminonucleoside (PAN). Urine samples were collected for 24 h prior to dosing and at 8, 24, and 32 h postdosing. For each sample, free carbohydrates were extracted from the urine using a graphitized carbon column and then labeled with 2-aminoacridone (2-AMAC) prior to analysis by hydrophilic interaction liquid chromatography (HILC). Dramatic changes were seen in the profile of the carbohydrates at the 8- and 24-h time points. These changes in carbohydrate profiles may be useful as early indicators of toxicity.

Phenotyping apolipoprotein E*3-leiden transgenic mice by two-dimensional polyacrylamide gel electrophoresis and mass spectrometric identification

Apolipoprotein E (ApoE) plays an important role in cholesterol and triglyceride metabolism, being one of the major structural components of chylomicrons and very low density lipoprotein (VLDL) remnants. ApoE functions as a ligand in the receptor-mediated uptake of these remnants from the blood by the liver. A variant form of ApoE, apolipoprotein E*3-Leiden, shows reduced affinity for the low density lipoprotein (LDL) receptor, and results in the dominant expression of type III hyperlipoproteinemia. Two-dimensional electrophoresis (2-DE) has been used to characterise protein expression in serum samples from control and transgenic mice expressing the human ApoE*3-Leiden mutation, fed a cholesterol-rich diet, and transgenic mice fed a normal diet. For the identification of proteins, single silver-stained spots were excised from the 2-DE gels and subjected to in-gel enzymatic digestion. Extracted peptides were analysed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). This proteomic approach has enabled the ApoE*3-Leiden variant to be positioned in a 2-DE separation of serum proteins, and has identified changes in the expression of haptoglobin, indicating that this protein may provide a marker for the potential onset of atherosclerosis.

Enantiospecific analysis by capillary electrophoresis: applications in drug metabolism and pharmacokinetics

Enantiospecific analysis has an important role in drug metabolism and pharmacokinetic investigations and its now no longer acceptable to determine total drug, or metabolite, concentrations following the administration of a racemate. Inspite of the fact that capillary electrophoresis (CE) has become an essential technique in pharmaceutical and enantiospecific analysis, the chromatographic methodologies remain the most commonly used approach for the determination of the enantiomeric composition of drugs in biological fluids. The application of CE to bioanalysis has been slow, which is in part associated with the complexity of biological matrices together with the relatively poor concentration limits of detection achievable. However, as a result of its versatility, high separation efficiency, minimal sample requirements, speed of analysis and low consumable expense CE is likely to play an increasingly significant role in the area. This review present an overview of enantiospecific CE in bioanalysis in which the approaches to enantiomeric resolution and the problems associated with biological matrices are briefly discussed. The application of enantiospecific CE to samples of biological origin is illustrated using examples where the methodology has either solved an analytical problem, or provided a useful alternative to the currently available chromatographic methods. Such improvements in methodology are associated with either the high separation efficiency and/or microanalytical capabilities of the technique. Enantiospecific CE will not replace the chromatographic methodologies but does provide the bioanalyst with a useful addition to his armamentarium.

A probe for the versatile analysis and characterization of N-linked oligosaccharides

A novel fluorescent probe, 3-(acetylamino)-6-aminoacridine (AA-Ac), has been synthesized and its applicability to the analysis of picomole levels of N-linked glycans investigated. AA-Ac was found to be an excellent derivatization reagent for N-linked glycans, giving at least twice the intensity of fluorescence as its predecessor 2-aminoacridone. AA-Ac-labeled glycans were analyzed by both normal and reversed-phase HPLC. They were also amenable to enzymatic sequencing and analysis by MALDI-TOF mass spectrometry, free zone capillary electrophoresis, and capillary electrophoresis/electrospray ionization mass spectrometry.

Analysis of oligosaccharides by microbore high-performance liquid chromatography

A 1-mm microbore hydrophilic interaction column has been used for the separation of 2-aminoacridone (2-AMAC)-derivatized glycan mixtures, released from naturally occurring and recombinant proteins. Primary structure identification of the 2-AMAC glycan derivatives was carried out by HPLC using fluorescence and mass spectrometric detection. In some cases, enzymatic digestion of the 2-AMAC glycans was applied to confirm glycan structure. This strategy is considerably more rapid than methods normally used in glycan analysis, which involves manual collection of separated oligosaccharide derivatives and analysis of individual fractions by mass spectrometry.

Development of a protocol for the automated analysis of amino acids in brain tissue samples and microdialysates

An automated precolumn derivatisation method has been developed for the measurement of fourteen amino acids in brain tissue and microdialysate samples. The method involves labelling amino acids with naphthalene-2,3-dicarboxaldehyde (NDA) in the presence of cyanide (CN-). The resulting highly stable N-substituted 1-cyanobenz[f]isoindole (CBI) derivatives were separated using a binary gradient elution profile and detected fluorometrically. The order of elution of the derivatised amino acids was confirmed by using liquid chromatography with fluorescence and mass spectrometric detection in tandem. Linear calibration plots were obtained for all amino acids in the range studied (0.2-12.5 microM). The limit of detection for CBI derivatives of amino acids was in the range 5-20 fmol (S/N=2) using a 5 microl injection volume. The method has been used for the measurement of amino acids in microdialysates from rat brain and tissue homogenates from different regions of mouse brain.

Carbohydrate release from picomole quantities of glycoprotein and characterisation of glycans by high-performance liquid chromatography and mass spectrometry

Samples of 5 to 20 microg of human IgG were subjected to dithiothreitol treatment to reduce disulphide bridges, followed by tryptic digestion. Glycans released from the tryptic peptide mixture by PNGase F digestion were then derivatised with 2-aminoacridone. Labelled oligosaccharides were separated by normal-phase high-performance liquid chromatography and individual components were collected for matrix-assisted laser desorption ionization time-of-flight and electrospray mass spectrometric analysis.

A detailed analysis of neutral and acidic carbohydrates in human milk

Reverse- and normal-phase chromatography have been used to separate a number of standard human milk oligosaccharides derivatized via a reductive amination reaction with 2-aminoacridone (2-AMAC). Analytes were detected by spectrofluorimetry and injected simultaneously with a hydrolyzed dextran ladder derivatized with methyl-4-aminobenzoate. The latter probe does not fluoresce at the wavelength of emission by the 2-AMAC derivatives, and the derivatized, hydrolyzed dextran components were visualized by their ultraviolet absorbance. This procedure gave precise measurements of the "size" of 2-AMAC oligosaccharides in terms of their glucose equivalent values. Analytical amounts of 2-AMAC oligosaccharide standards were also isolated for further characterization by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and electrospray ionization (ESI) mass spectrometry. MS-MS was also used to provide information on oligosaccharide sequences. This methodology was used successfully to characterize mixtures of neutral and acidic oligosaccharides from samples of human milk. This approach could be usefully applied to the study of glycoforms from a variety of samples such as those released from glycoproteins/glycolipids; these have been reported to be altered in a number of diseases, for example, cancer, cystic fibrosis, and autoimmune disease such as rheumatoid arthritis.

Structural characterisation of N-linked glycan mixtures by precursor ion scanning and tandem mass spectrometric analysis

2-Aminoacridone (2-AMAC) labelled N-linked glycan pools were analysed directly by a hybrid quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-Tof) in the precursor ion scanning and tandem mass spectrometry (MS/MS) modes. The use of a precursor ion scanning strategy on this instrument provides a rapid and sensitive method of screening glycan mixtures, without prior separation by chromatographic methods. It allows facile and preliminary characterisation of glycans into different classes, for example, high-mannose or complex glycans. Preliminary sequencing information for each glycan is obtained in the initial precursor ion scanning mode, but further sequencing information of selected glycans can be obtained using the MS/MS mode. Copyright 1999 John Wiley & Sons, Ltd.