Evaluation of Volumetric Response Assessment From SABR for Renal Cell Carcinoma (RCC)

PURPOSE

SABR is increasingly used to treat renal cell carcinoma (RCC). However, the optimal method to assess treatment response is unclear. We aimed to quantify changes in both volume and maximum linear size of tumors after SABR and evaluate the utility of the 2 approaches in treatment response assessment.

METHODS AND MATERIALS

We retrospectively studied patients with RCC treated with SABR at our institution between 2013 and 2020. All available follow-up computed tomography scans were aligned, and tumors were contoured on all scans. Volume and maximum linear size were measured at each follow-up, relative to these measurements at the time of computed tomography simulation.

RESULTS

Twenty-four patients with 25 tumors were included. Median follow-up was 32 months (range, 16-67). Nineteen tumors (76%) had 30% volumetric response at a median time of 7 months after SABR, and 12 tumors (48%) had 30% decrease in maximum linear size at a median time of 16 months. Eighteen tumors (72%) decreased in volume on first follow-up scan and continued to shrink, and 5 tumors (20%) displayed transient growth after SABR (average 24% increase in volume). Compared with T1a tumors, T1b or larger tumors were more likely to have transient growth (8% vs 33%; P = .16) and had higher average relative volume 24 months after SABR (0.47 vs 0.8; P = .022).

CONCLUSIONS

Volume measurement results in more pronounced and earlier change compared with linear size measurement when assessing response to SABR. These findings may provide guidance when assessing treatment response for patients with RCC treated with SABR.

Evaluation of Volumetric Response Assessment from Stereotactic Ablative Radiotherapy (SABR) for Renal Cell Carcinoma (RCC)

PURPOSE/OBJECTIVE(S)

SABR has recently been proven to be a safe, effective treatment for RCC. However, long term follow-up assessment can be challenging as traditional methods of assessment such as RECIST may not identify tumor response, and delayed responses to SABR are common. The purpose of this study was to quantify SABR response using volumetric changes from baseline throughout follow-up.

MATERIALS/METHODS

We conducted a single-center retrospective study including all patients treated with SABR for RCC from 2013 to 2020. Patients were included if they had no metastatic disease, no resection after SABR, and had follow-up imaging available for at least 12 months following SABR. All available follow-up CT scans were collected and aligned, and tumors were contoured on all follow-up scans to measure volume and maximum linear dimension. Response to SABR was assessed by comparing tumor volume at follow-up to the initial tumor volume at the time of CT simulation.

RESULTS

Twenty-four patients with 25 tumors were included. The dose was between 25Gy and 42Gy in 1-5 fractions; 64% of tumors received 35Gy in 5 fractions. Follow-up time was between 16 and 67 months; median follow-up was 32 months. A total of 164 follow-up scans were contoured. The relative volume and standard deviation (compared to baseline) at 3, 6, 9, 12, 24, 36, and 48 months was 0.76 (SD 0.22), 0.80 (SD 0.27), 0.76 (SD 0.32), 0.75 (SD 0.26), 0.61 (SD 0.33), 0.53 (SD 0.41), and 0.34 (SD 0.22) respectively. One tumor (4%) showed continued growth after SABR, while 24 of 25 tumors (96%) had durable volumetric response after SABR. Eighteen of 25 tumors (72%) decreased in volume on first follow-up scan and continued to shrink, while 6 of 25 tumors (24%) displayed growth after SABR (average 33% increase in volume) before shrinking below their initial volume. The median time to any volumetric response was 3.5 months (range 2-19 months). Nineteen tumors (76%) had 30% volumetric response. Median time to 30% volumetric response was 7 months (range 3-55 months). In contrast, 12 tumors (48%) had 30% decrease in maximum linear size, with median time to 30% linear response of 16 months (range 4-42 months). Thirteen tumors (52%) had 50% volumetric response; median time to 50% volumetric response was 11 months (range 4-37 months). Among tumors for which contrast-enhanced scans were available, 15 of 22 tumors (68%) displayed arterial enhancement at their most recent follow-up scan, at a median time of 24 months after SABR.

CONCLUSION

SABR is a highly effective treatment for RCC, achieving durable local control in 96% of cases. Initial growth after SABR is common before volumetric response occurs. Volumetric response is more frequent and occurs earlier than decrease in maximum linear dimension, even with persistent arterial contrast enhancement following SABR.

Universal evaluation of MLC models in treatment planning systems based on a common set of dynamic tests

PURPOSE

To demonstrate the feasibility of characterising MLCs and MLC models implemented in TPSs using a common set of dynamic beams.

MATERIALS AND METHODS

A set of tests containing synchronous (SG) and asynchronous sweeping gaps (aSG) was distributed among twenty-five participating centres. Doses were measured with a Farmer-type ion chamber and computed in TPSs, which provided a dosimetric characterisation of the leaf tip, tongue-and-groove, and MLC transmission of each MLC, as well as an assessment of the MLC model in each TPS. Five MLC types and four TPSs were evaluated, covering the most frequent combinations used in radiotherapy departments.

RESULTS

Measured differences within each MLC type were minimal, while large differences were found between MLC models implemented in clinical TPSs. This resulted in some concerning discrepancies, especially for the HD120 and Agility MLCs, for which differences between measured and calculated doses for some MLC-TPS combinations exceeded 10%. These large differences were particularly evident for small gap sizes (5 and 10 mm), as well as for larger gaps in the presence of tongue-and-groove effects. A much better agreement was found for the Millennium120 and Halcyon MLCs, differences being within ± 5% and ± 2.5%, respectively.

CONCLUSIONS

The feasibility of using a common set of tests to assess MLC models in TPSs was demonstrated. Measurements within MLC types were very similar, but TPS dose calculations showed large variations. Standardisation of the MLC configuration in TPSs is necessary. The proposed procedure can be readily applied in radiotherapy departments and can be a valuable tool in IMRT and credentialing audits.

Differentiation of patient-specific void urine-derived human induced pluripotent stem cells to fibroblasts and skeletal muscle myocytes

Cell-based therapy is a major focus for treatment of stress urinary incontinence (SUI). However, derivation of primary cells requires tissue biopsies, which often have adverse effects on patients. A recent study used human induced pluripotent stem cells (iPSC)-derived smooth muscle myocytes for urethral sphincter regeneration in rats. Here, we establish a workflow using iPSC-derived fibroblasts and skeletal myocytes for urethral tissue regeneration: (1) Cells from voided urine of women were reprogrammed into iPSC. (2) The iPSC line U1 and hESC line H9 (control) were differentiated into fibroblasts expressing FSP1, TE7, vinculin, vimentin, αSMA, fibronectin and paxillin. (3) Myogenic differentiation of U1 and H9 was induced by small molecule CHIR99021 and confirmed by protein expression of myogenic factors PAX7, MYOD, MYOG, and MF20. Striated muscle cells enriched by FACS expressed NCAM1, TITIN, DESMIN, TNNT3. (4) Human iPSC-derived fibroblasts and myocytes were engrafted into the periurethral region of RNU rats. Injected cells were labelled with ferric nanoparticles and traced by Prussian Blue stain, human-specific nuclear protein KU80, and human anti-mitochondria antibody. This workflow allows the scalable derivation, culture, and in vivo tracing of patient-specific fibroblasts and myocytes, which can be assessed in rat SUI models to regenerate urethral damages and restore continence.

A pilot study of stereotactic boost for malignant epidural spinal cord compression: clinical significance and initial dosimetric evaluation

Purpose

Metastatic epidural spinal cord compression (MESCC) is a devastating complication of advanced malignancy, which can result in neurologic complications and significant deterioration in overall function and quality of life. Most patients are not candidates for optimal surgical decompression and as a result, receive urgent 3D conformal radiotherapy (3DCRT) to prevent or attempt to reverse neurologic progression. Multiple trials indicate that response and ambulatory rates after 3DCRT are inferior to surgery. The advent of stereotactic body radiation therapy (SBRT) has created a method with which a “radiosurgical decompression” boost may facilitate improve outcomes for MESCC patients.

Methods

We are conducting a pilot study to investigate SBRT boost after urgent 3D CRT for patients with MESCC. The aim of the study is to establish feasibility of this two-phase treatment regimen, and secondarily to characterize post-treatment ambulation status, motor response, pain control, quality of life and survival.

Discussion

We describe the study protocol and present a case report of one patient. A quality assurance review was conducted after the first seven patients, and resultant dose-constraints were revised to improve safety and feasibility of planning through more conservative organ at risk constraints. There have been no severe adverse events (grade 3–5) to date. We have illustrated clinical and dosimetric data of an example case, where a patient regained full strength and ambulatory capacity.

Conclusions

Our study aims to determine if SBRT is a feasible option in addition to standard 3DCRT for MESCC patients, with the goal to consider future randomized trials if successful. Having a robust quality assurance process in this study ensures translatability going forward if future trials with multicenter and increased patient representation are to be considered.

Trial registration

clinicaltrials.gov; registration no. NCT03529708; https://clinicaltrials.gov/ct2/show/NCT03529708; First posted May 18, 2018.

A Randomized Phase II Trial of Prostate Boost Irradiation With Stereotactic Body Radiotherapy (SBRT) or Conventional Fractionation (CF) External Beam Radiotherapy (EBRT) in Locally Advanced Prostate Cancer: The PBS Trial (NCT03380806)

Standard therapy for high-risk (HR) prostate cancer (PrCa) involves androgen deprivation therapy (ADT) and pelvic conventional fractionation (CF) external beam radiotherapy (EBRT) followed by boost CF-EBRT treatment to prostate for a total of 78 to 80 Gy in 39 to 40 fractions. This is a long and inconvenient treatment for patients. Brachytherapy boost treatment studies indicate that escalation of biological dose of radiotherapy (RT) can improve outcomes in HR-PrCa. However, brachytherapy is an invasive treatment associated with increased toxicity and requires specialized resources. Stereotactic body radiotherapy (SBRT) is a promising, non-invasive alternative to brachytherapy. However, its impact on patient quality of life (QoL) and RT-associated toxicity has not been investigated in a randomized setting. In this study, we investigate SBRT as a boost treatment, following pelvic CF-EBRT, in patients with HR-PrCa treated with ADT. One hundred patients with locally advanced PrCa will be randomized to receive daily CF-EBRT of 45 to 46 Gy in 23 to 25 fractions followed by either daily CF-EBRT of 32 to 33 Gy in 15 to 16 fractions (control arm) or SBRT boost treatment of 19.5 to 21 Gy in 3 fractions (1 fraction per week) (experimental arm). The primary objective of the PBS trial is early bowel and urinary QoL (expanded prostate index composite [EPIC], up to 6 months after RT). This phase II randomized study (PBS) provides an appropriate setting to investigate effectively the impact of SBRT boost on QoL and toxicity in patients with HR-PrCa, before this modality can be compared against the current standard of care in larger phase III protocols.

COMP Report: CPQR technical quality control guidelines for CyberKnife® Technology

The Canadian Organization of Medical Physicists (COMP), in close partnership with the Canadian Partnership for Quality Radiotherapy (CPQR) has developed a series of Technical Quality Control (TQC) guidelines for radiation treatment equipment. These guidelines outline the performance objectives that equipment should meet in order to ensure an acceptable level of radiation treatment quality. This particular TQC contains detailed performance objectives and safety criteria for CyberKnife^® Technology. The quality control recommendations in this document are based upon previously published guidelines and the collective experience of all Canadian sites using this technology. This TQC guideline has been field tested at the newest Canadian CyberKnife installation site and includes recommendations for quality control of the Iris™ and InCise™ MLC collimation systems.

The Technique, Resources and Costs of Stereotactic Body Radiotherapy of Prostate Cancer: A Comparison of Dose Regimens and Delivery Systems

Robotic system has been used for stereotactic body radiotherapy (SBRT) of prostate cancer. Arc-based and fixed-gantry systems are used for hypofractionated regimens (10-20 fractions) and the standard regimen (39 fractions); they may also be used to deliver SBRT. Studies are currently underway to compare efficacy and safety of these systems and regimens. Thus, we describe the technique and required resources for the provision of robotic SBRT in relation to the standard regimen and other systems to guide investment decisions. Using administrative data of resource volumes and unit prices, we computed the cost per patient, cost per cure and cost per quality adjusted life year (QALY) of four regimens (5, 12, 20 and 39 fractions) and three delivery systems (robotic, arc-based and fixed-gantry) from a payer's perspective. We performed sensitivity analyses to examine the effects of daily hours of operation and in-room treatment delivery times on cost per patient. In addition, we estimated the budget impact when a robotic system is preferred over an arc-based or fixed-gantry system. Costs of SBRT were $6333/patient (robotic), $4368/patient (arc-based) and $4443/patient (fixed-gantry). When daily hours of operation were varied, the cost of robotic SBRT varied from $9324/patient (2 hours daily) to $5250/patient (10 hours daily). This was comparable to the costs of 39 fraction standard regimen which were $5935/patient (arc-based) and $7992/ patient (fixed-gantry). In settings of moderate to high patient volume, robotic SBRT is cost effective compared to the standard regimen. If SBRT can be delivered with equivalent efficacy and safety, the arc-based system would be the most cost effective system.

Poster - Thurs Eve-36: Use of multileaf collimator as a replacement of physical missing tissue compensator

Missing tissue compensators are used to improve dose uniformity for some patients undergoing radiation therapy. Currently, our practice is to machine compensators out of lead alloy plate. Replacing this physical filter with a segmented multileaf collimator (MLC) delivery sequence is beneficial in terms of work flow and delivery efficiency. The purpose of this work is to compare the dose uniformity achieved by fields that are either (A) conventionally compensated, compensated by segmenting the physical compensator thickness map into either (B) step-and-shoot or (C) dynamic MLC delivery sequences using an in-house sequencer, (D) compensated using Pinnacle sequencer, or (E) compensated using IMRT optimization. A computer program was developed to construct both step-and-shoot and dynamic MLC sequence files from mechanical thickness maps of our current compensators. In addition, the Pinnacle sequencer and IMRT optimization were used to generate step-and-shoot MLC sequences. Planar doses were measured for each at the isocenter depth with an ion chamber array to compare the five methods. A comparison of the relative dose distribution shows that the compensation achieved by method (E) is in close agreement with that achieved using method (A), that is, dose uniformity within 4%. Method (D) resulted in the shortest delivery time and achieved dose uniformity to within 5%. Methods (B) and (C) need additional refinement to be of practical use. The results support the feasibility of replacing physical compensators with MLC delivery sequences. Compensation by MLC segments provides more flexibility and efficiency in design and delivery than by physical compensators while maintaining or improving the uniformity of dose to the plane of compensation.

Erythropoietin receptor expression in biopsy specimens from patients with uterine cervix squamous cell carcinoma

Hypoxia, an important mechanism of radioresistance, is a strong stimulus for erythropoietin (EPO) production. The stimulatory effects of EPO are mediated through the activation of its receptors, EPO receptors (EPORs). The objective of this study is to determine whether EPORs are expressed in biopsy specimens of patients with squamous cell carcinoma of the cervix. Eighteen biopsy specimens were studied after obtaining Institutional Review Board-approved consent. Standard immunohistochemistry techniques were utilized. Expression of EPORs was present in 16 out of 18 (88.9%) specimens. The intensity (qualitative) and the frequency (semiquantitative) of EPORs expression showed a statistically significant correlation (P= 0.00379). Statistical analysis was performed to determine whether EPORs expression is related to other parameters such as age, FIGO stage, histologic grade, and hemoglobin levels. Only age showed a statistically significant correlation with EPORs frequency of expression (P= 0.00878). Currently, work is in progress in our laboratory to study the radiobiologic effects of EPO on the radiation response of cultured cancer cell lines in vitro.

Functional analysis of a recurrent missense mutation in Notch3 in CADASIL

BACKGROUND

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited vascular dementia characterised by recurrent ischemic strokes in the deep white matter. Mutations in the gene encoding the cell surface receptor, Notch3, have been identified in CADASIL patients, and accumulation of the extracellular domain of Notch3 has been demonstrated in affected vessels. Almost all CADASIL mutations alter the number of cysteine residues in the epidermal growth factor (EGF)-like repeats in the extracellular domain of the protein.

OBJECTIVES

To understand the functional consequences of a recurrent CADASIL mutation on furin processing, cell surface expression, ligand binding, and activation of a downstream effector CBF1 by the Notch3 receptor.

METHODS

We expressed wild type and mutant Notch3 receptors in cultured cells and examined cell surface expression of the proteins. We also applied a new flow cytometry based approach to semi-quantitatively measure binding to three Notch ligands. Additionally, we used a well characterised co-culture system to examine ligand dependent activation of transcription from a CBF1-luciferase reporter construct.

RESULTS

These studies revealed subtle abnormalities in furin processing of the mutant receptor, although both heterodimeric and full length receptors are present on the cell surface, are capable of interacting with soluble forms of three ligands, Delta1, Delta4, and Jagged1, and retain the ability to activate CBF1 in a ligand dependent manner.

CONCLUSIONS

By comparison with other mutant forms of Notch3, these data indicate that individual CADASIL mutations can have disparate effects on Notch3 expression and function.

Molecular defects in the β-globin gene identified in different ethnic groups/populations during prenatal diagnosis for β-thalassemia: a Malaysian experience

Beta-thalassemia is the most-common genetic disorder of hemoglobin synthesis in Malaysia, and about 4.5% of the population are heterozygous carriers of the disorder. Prenatal diagnosis was performed for 96 couples using the Amplification Refractory Mutation System and Gap-Polymerase Chain Reaction. We identified 17 beta-globin defects-initiation codon for translation (T-G), -29 (A-G), -28 (A-G), CAP +1 (A-C), CD 8/9 (+G), CD 15 (G-A), CD 17 (A-T), CD 19 (A-G), Hb E (G-A), IVS1-1 (G-T), IVS1-5 (G-C), CD 41/42 (-CTTT), CD 71-72 (+A), IVS2-654 (CT), poly A(A-G), 100-kb Ggamma(Agammadeltabeta) degrees and 45-kb Filipino deletions. The 192 beta-alleles studied comprised Chinese (151 patients), Malay (21), Orang Asli from East Malaysia (15), Filipino (1), Indian (1), Indonesian Chinese (2), and Thai (1). In the Chinese, 2 beta-globin defects at CD 41/42 and IVS2-654 were responsible for 74% of beta-thalassemia. beta-mutations at CD 19, IVS1-1 (G-T), IVS1-5, poly A, and hemoglobin E caused 76% of the hemoglobin disorders in the Malays. The Filipino 45-kb deletion caused 73.3% of bthalassemia in the Orang Asli. Using genomic sequencing, the rare Chinese beta-mutation at CD 43 (G-T) was confirmed in 2 Chinese, and the Mediterranean mutation IVS1-1 (G-A) was observed in a Malay beta-thalassemia carrier. The beta-globin mutations confirmed in this prenatal diagnosis study were heterogenous and 65 (68%) couples showed a different globin defect from each other. The use of specific molecular protocols has allowed rapid and successful prenatal diagnosis of beta-thalassemia in Malaysia.

A brief case report and review of ciguatera poisoning

Although ciguatera fish poisoning is generally a mild, self-limited disease, both life-threatening acute reactions and troublesome chronic symptoms can occur. Because ciguatera has been largely confined to tropical locations, a relative lack of recognition exists among many US physicians. As access to tropical locations has increased, so has the distribution of ciguatera. Herein, we present a case report and review the current literature on ciguatera.

Progesterone oxidation by cytochrome P450 2D isoforms in the brain

The existence of cytochrome P450 2D isoforms in the brain has been demonstrated, although their physiological functions remain to be elucidated. In this study we demonstrated that recombinant rat cytochrome P450 2D1 and 2D4 and human cytochrome P450 2D6 possess progesterone 6 beta- and 16 alpha- hydroxylation activities; 2 beta- and 21-hydroxylation activities; and 2 beta-, 6 beta-, 16 alpha- and 21-hydroxylation activities, respectively. Cytochrome P450 2D4 had the lowest K(m) value and the highest maximum velocity value toward these activities. Progesterone 2 beta- and 21-hydroxylation activities were also detected in rat brain microsomes, and these activities were completely inhibited by anticytochrome P450 2D antibodies. The presence of endogenous 2 beta- and 21-hydroxyprogesterones in rat brain tissues was also demonstrated. The mRNAs of cytochrome P450 2D4, CYP11A, and 3 beta-hydroxysteroid dehydrogenase were detected in the rat brain, suggesting that progesterone was generated from cholesterol by CYP11A and 3 beta-hydroxysteroid dehydrogenase and then underwent hydroxylation to hydroxyprogesterones by cytochrome P450 2D4 in rat brain. Collectively, our findings support the idea that cytochrome P450 2D may be involved in the regulation (metabolism and/or synthesis) of endogenous neuroactive steroids, such as progesterone and its derivatives, in brain tissues.

Identification of hydroxylamino-dinitroso-1,3,5-triazine as a transient intermediate formed during the anaerobic biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine

The metabolic fate of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in a mixed culture incubated under methanogenic conditions was studied. Analysis by high-performance liquid chromatography (HPLC) confirmed the loss of RDX and the formation of mono-, di-, and trinitroso-RDX as transient biodegradation intermediates. An additional peak observed in the HPLC chromatograms was identified by liquid chromatography-mass spectrometry as hydroxylamino-dinitroso-1,3,5-triazine. This is the first report identifying hydroxylamino-dinitroso-1,3,5-triazine as a transient intermediate produced during the anaerobic biodegradation of RDX.

Orbitofrontal and anterior cingulate cortex neurofibrillary tangle burden is associated with agitation in Alzheimer disease

Few studies evaluate neuropathological correlates of behavioral changes in Alzheimer disease (AD). We identified 31 autopsy patients with a diagnosis of definite AD. Behavioral changes were assessed with the Neuropsychiatric Inventory. Brain sections were collected from bilateral orbitofrontal and left anterior cingulate, superior temporal, inferior parietal, occipital, and hippocampal cortices for quantification of neurofibrillary tangles (NFTs) and diffuse and neuritic plaques. Sections from frontal, cingulate, and hippocampal cortices were reviewed for the presence of Lewy bodies (LBs). Hypothesis-driven correlational analyses were performed by the bootstrap method. Subgroup analyses contrasted a group with high scores of one specific behavior to a group with low scores after equating groups for other behaviors. NFT burden in the left orbitofrontal cortex across all 31 patients significantly correlated with agitation scores (r = 0.41, p < 0.015) and NFTs correlated significantly (r = 0.66, p = 0.004) with higher agitation scores in the subgroup analysis. Left anterior cingulate NFTs, although not within our hypotheses, also showed a significant relationship to agitation within the subgroups (r = 0.76, p = 0.0003; Bonferroni p = 0.02). Seven patients, including three in the agitation subgroup, had cortical LBs. Aberrant motor behavior and NFT density in the left orbitofrontal cortex showed a significant relationship for the entire group (r = 0.38, p < 0.03) and for subgroups (r = 0.49, p = 0.04), whereas apathy and left anterior cingulate NFTs showed a significant relationship only for the entire group (r = 0.25, p < or = 0.01). These observations suggest that agitation and aberrant motor behavior are correlates of greater NFT pathology in the orbitofrontal cortex in AD, whereas increasing apathy may relate to greater NFT burden in the anterior cingulate.

A new role for P-selectin in shear-induced platelet aggregation

BACKGROUND

P-selectin, expressed on platelets on activation, mediates rolling of platelets on endothelial cells, but its role in shear-induced platelet aggregation is not known.

METHODS AND RESULTS

Platelets were exposed to either a single pulse (30 seconds) or 3 pulses (10 seconds) of high shear stress (150 to 200 dynes/cm(2)) each followed by low shear stress (10 dynes/cm(2)) for 4.5 minutes or 90 seconds, respectively, at 37 degrees C to resemble more closely in vivo conditions such as those in stenotic arteries. Under these conditions, platelet aggregation was significantly increased compared with low or high shear stress alone. Monoclonal anti-P-selectin antibodies inhibited shear-induced platelet aggregation, especially when induced by the combination of high and low shear stress, by approximately 70% and had an additive effect on the inhibition by abciximab (anti-glycoprotein (GP) IIb/IIIa antibody). However, anti-P-selectin antibody inhibited shear-induced platelet aggregation only at 37 degrees C, not at 22 degrees C, whereas abciximab inhibited shear-induced platelet aggregation at both 22 degrees C and 37 degrees C. This differential effect of anti-P-selectin antibody is explained by the finding that shear-induced P-selectin expression on platelets was observed mainly at 37 degrees C.

CONCLUSIONS

These results indicate that pulsatile shear stress, which resembles flow conditions in stenotic arteries, induces significantly more platelet aggregation at 37 degrees C than monophasic shear stress. Under these conditions, we show a novel role for P-selectin in platelet aggregation distinct from that of GP IIb/IIIa, which may be of importance in the initiation of thrombosis associated with atherosclerotic lesions.

Translational upregulation of X-linked inhibitor of apoptosis (XIAP) increases resistance to radiation induced cell death

Inhibitory regulators of apoptosis play a critical role in the responsiveness of tumour cells to cytotoxic agents. The X-linked inhibitor of apoptosis protein (XIAP) is a member of a novel family of Inhibitor of Apoptosis (IAP) proteins. Here we show that acute low dose ionizing irradiation results in the translational upregulation of XIAP that correlates with an increased resistance to radiation in non-small cell lung carcinoma. This upregulation is mediated by an internal ribosome binding mechanism via an IRES element located within a XIAP 5' UTR. Transient overexpression of XIAP rendered human carcinoma cells resistant to low dose gamma-irradiation. By contrast, the antisense targeting of XIAP resulted in increased cell death following irradiation advocating a distinct role for XIAP in radiation resistant phenotype of human cancers. Oncogene (2000) 19, 4174 - 4177

Pedophilia and temporal lobe disturbances

Paraphilias may occur with brain disease, but the nature of this relationship is unclear. The authors report 2 patients with late-life homosexual pedophilia. The first met criteria for frontotemporal dementia; the second had bilateral hippocampal sclerosis. Both were professional men with recent increases in sexual behavior. In both, 18-fluorodeoxyglucose positron emission tomography revealed prominent right temporal lobe hypometabolism. These cases and the literature suggest that bilateral anterior temporal disease affecting right more than left temporal lobe can increase sexual interest. A predisposition to pedophilia may be unmasked by hypersexuality from brain disease. These observations have potential implications for all neurologically based paraphilias.

Isoform-selective metabolism of mianserin by cytochrome P-450 2D

The involvement of cytochrome P-450 (CYP) 2D isoforms in the metabolism of mianserin and the stereoselectivity of their catalytic activities were investigated by using five CYP2D isoforms (CYP2D1, 2D2, 2D3, 2D4, and 2D6). Using RS-mianserin as a substrate, we found that five CYP2D isoforms had similar levels of 8-hydroxylation activity. However, N-demethylation activity differed among the isoforms; CYP2D3 and 2D4 efficiently demethylated RS-mianserin compared with the other three isoforms. N-Oxidation activity was specific to CYP2D1 although its level was relatively low. Another metabolite, assigned as 8-hydroxy-N-desmethylmianserin by liquid chromatography/mass spectrometry analysis, was formed by CYP2D4 and 2D6. The metabolism exhibited stereoselectivity. CYP2D1 and 2D4 selectively 8-hydroxylated the R(-)-enantiomer, and CYP2D6 predominately N-demethylated R(-)-enantiomer. N-Oxidation by CYP2D1 was specific to R(-)-enantiomer. In conclusion, CYP2D isoforms are involved in several metabolic pathways of mianserin acting in an isoform-specific manner. Stereoselectivity of the catalytic activities was clearly observed in the reactions of CYP2D1, 2D4, and 2D6.

Antiarrhythmic drug therapy in patients with renal failure, liver failure, and congestive heart failure

Commonly prescribed antiarrhythmic agents--and several recently developed agents--are reviewed with respect to their use in patients with renal failure, hepatic failure, and congestive heart failure. Because removal of electrophysiologically active agents from the systemic circulation in most cases depends on either renal elimination, hepatic metabolism, or both, patients with preexisting kidney or liver disease may be at increased risk of treatment-related drug toxicity, including proarrhythmia. These susceptibilities should be anticipated, with drug selection and/or dosage modified accordingly. Patients with left ventricular dysfunction and heart failure also are at increased risk of treatment-related complications, including proarrhythmia and hemodynamic intolerance. In addition, the metabolism of antiarrhythmic drugs may be impaired in these patients. Preference should be given to drugs with a proven safety profile, such as amiodarone, in patients with heart failure.

Developmental changes in the catalytic activity and expression of CYP2D isoforms in the rat liver

Developmental changes in bufuralol 1'-hydroxylation activity, which is known as a typical activity of cytochrome P-450 (CYP)2D isoforms, in the liver of rats were investigated. The catalytic activities of hepatic microsomes increased with development especially from 3 to 7 weeks. Eadie-Hofstee plots of bufuralol 1'-hydroxylation were obtained for monophasic kinetics (Km: 0.037 microM) at 1 week and for biphasic kinetics (Km: 0.051 and 6.4 microM) at 7 weeks of age. Quinine completely inhibited bufuralol 1'-hydroxylation activity of hepatic microsomes of 1- and 7-week-old rats. These results indicated that at least two kinds of CYP2D isoforms, which differ markedly in their affinity for bufuralol, were present at 7 weeks of age and that the CYP2D isoform that had low affinity for bufuralol was expressed with development. To assess the affinity of CYP2D isoforms for bufuralol, the kinetic properties of CYP2D1, 2D2, 2D3, and 2D4 expressed in yeast cells were investigated. The Km value of CYP2D2, 0.044 microM, was extremely small compared with that of the other rat CYP2D isoforms. We further investigated developmental changes of CYP2D isoform mRNA by reverse transcription-polymerase chain reaction. CYP2D3 mRNA increased with development although CYP2D1 and 2D2 mRNA were not changed. The CYP2D4 mRNA was not detected. These findings indicated that CYP2D2, which had high affinity for bufuralol, was expressed in immature and mature rats, but CYP2D3, which had low affinity for bufuralol, was expressed only in mature rats.