Modulation of cyclophosphamide activity by O 6-alkylguanine-DNA alkyltransferase

Purpose: The human medulloblastoma cell line D283 Med (4-HCR), a line resistant to 4-hydroperoxycyclophosphamide (4-HC), displays enhanced␣repair of DNA interstrand crosslinks induced by phosphoramide mustard. D283 Med (4-HCR) cells are cross-resistant to 1,3-bis(2-chloroethyl)-1-nitrosourea, but partial sensitivity is restored after elevated levels of O ⁶-alkylguanine-DNA alkyltransferase (AGT) are depleted by O ⁶-benzylguanine (O ⁶-BG). Studies were conducted to define the activity of 4-HC and 4-hydroperoxydidechlorocyclophosphamide against D283 Med (4-HCR) after AGT is depleted by O ⁶-BG. Methods: Limiting dilution and xenograft studies were conducted to define the activity of 4-HC and 4-hydroperoxydidechlorocyclophosphamide with or without O ⁶-BG. Results: The activity of 4-HC and 4-hydroperoxydidechlorocyclophosphamide against D283 Med (4-HCR) was increased after AGT depletion by O ⁶-BG preincubation. Similar studies with Chinese hamster ovary cells, with or without stable transfection with a plasmid expressing the human AGT protein, revealed that the AGT-expressing cells were significantly less sensitive to 4-HC and 4-hydroperoxydidechlorocyclophosphamide. Reaction of DNA with 4-HC, phosphoramide mustard, or acrolein revealed that only 4-HC and acrolein caused a decrease in AGT levels. Conclusions: We propose that a small but potentially significant part of the cellular toxicity of cyclophosphamide in these cells is due to acrolein, and that this toxicity is abrogated by removal of the acrolein adduct from DNA by AGT. Received: 17 February 1998 / Accepted: 20 May 1998     

Image registration of BANG gel dose maps for quantitative dosimetry verification

Background: The BANG® (product symbol SGEL, MGS Research Inc., Guilford, CT) polymer gel has been shown to be a valuable dosimeter for determining three-dimensional (3D) dose distributions. Because the proton relaxation rate (R2) of the gel changes as a function of absorbed dose, MR scans of the irradiated gel can be used to generate 3D dose maps. Previous work with the gel, however, has not relied on precise localization of the measured dose distribution. This has limited its quantitative use, as no precise correlation exists with the planned distribution. This paper reports on a technique for providing this correlation, thus providing a quality assurance tool that includes all of the steps of imaging, treatment planning, dose calculation, and treatment localization.

Methods and Materials: The BANG® gel formulation was prepared and poured into spherical flasks (15.3-cm inner diameter). A stereotactic head ring was attached to each flask. Three magnetic resonance imaging (MRI) and computed tomography (CT) compatible fiducial markers were placed on the flask, thus defining the central axial plane. A high-resolution CT scan was obtained of each flask. These images were transferred to a radiosurgery treatment-planning program, where treatment plans were developed. The gels were irradiated using our systems for stereotactic radiosurgery or fractionated stereotactic radiotherapy. The gels were MR imaged, and a relative 3D dose map was created from an R2 map of these images. The dose maps were transferred to an image-correlation program, and then fused to the treatment-planning CT scan through a rigid body match of the MRI/CT-compatible fiducial markers. The fused dose maps were imported into the treatment-planning system for quantitative comparison with the calculated treatment plans.

Results: Calculated and measured isodose surfaces agreed to within 2 mm at the worst points within the in-plane dose distributions. This agreement is excellent, considering that the pixel resolution of the MRI dose maps is 1.56 × 1.56 mm, and the treatment-planning dose distributions were calculated on a 1-mm dose grid. All points within the dose distribution were well within the tolerances set forth for commissioning and quality assurance of stereotactic treatment-planning systems. Moreover, the quantitative evaluation presented here tests the accuracy of the entire treatment-planning and delivery process, including stereotactic frame rigidity, CT localization, CT/MR correlation, dose calculation, and radiation delivery.

Conclusion: BANG® polymer gel dosimetry coupled with image correlation provides quantitative verification of the accuracy of 3D dose distributions. Such quantitative evaluation is imperative to ensure the high quality of the 3D dose distributions generated and delivered by stereotactic and other conformal irradiation systems.     

Topotecan treatment of adults with primary malignant glioma. The Brain Tumor Center at Duke

BACKGROUND: Topotecan activity was evaluated for the treatment of malignant glioma. METHODS: Sixty-three patients with newly diagnosed (n = 25) or recurrent (n = 38) malignant glioma were treated with topotecan [AU: Please verify all dosages here and throughout text.]at a dose of 2.6 mg/m2 over a 72-hour period weekly. Recurrent tumors included glioblastoma multiforme (GBM) (n = 28) and anaplastic astrocytoma (AA) (n = 10). Newly diagnosed tumors included GBM (n = 14), AA (n = 8), and anaplastic oligodendroglioma (n = 3). RESULTS: Partial responses were observed in 2 of 14 evaluable patients with newly diagnosed GBM, 1 of 8 patients with newly diagnosed AA, 3 of 10 patients with recurrent AA, and none of 28 patients with recurrent GBM. Four patients with recurrent AA and 7 patients with recurrent GBM demonstrated stable disease (range, 8-52 weeks; median, 21 weeks). Toxicity was limited to infrequent National Cancer Institute Common Toxicity Criteria Grade 3 myelosuppression. CONCLUSIONS: These results suggest that topotecan has modest activity against malignant glioma and continued evaluation of its effectiveness may be warranted when alternative schedules or combination regimens are used.     

Correlation between drug release kinetics from proteineous matrix and matrix structure: EPR and NMR study

The present study was conducted in order to probe the microstructure, microviscosity, and hydration properties of matrices containing two model drugs, naproxen sodium (NS) and naproxen (N), and egg albumin (EA) as matrix carrier. The results suggested that N release from EA matrix was controlled by a bulk erosion mechanism in combination with additional processes (crystal dissolution/crystallization rate) compared with NS matrix, which behaved as a non-erodible matrix and drug release occurred by diffusion through the gel. Using EPR technique it has been shown that incorporating NS into EA matrix strongly influences the microstructure of the protein gel, and hence the transport of the penetrant within the matrix, compared with matrices containing N. The presence of NS increased the protein chain mobility and hydration which supports our previous results showing that NS cause unfolding of EA. In contrast, N caused only marginal effect on EA chain mobility. The gel formed in EA/NS matrices was more porous compared with EA/N matrices as revealed by the lower rotational correlation time of PCA (lower microviscosity) in EA/NS matrices compared with EA/N. However, EA/N gelled matrices were more heterogeneous, i.e., containing a higher number of components having different mobility. The T(1) and T(2) relaxation studies by NMR provided an additional support for the higher chain hydration in EA/NS matrices compared with EA/N as indicated by the higher relaxation rates in the gelled matrices. Internal pH measurements by EPR revealed that the micro-pH inside 100% EA and 50/50 EA/N matrices were lower than 50/50 EA/NS matrices and in all cases lower than the penetrating buffer pH. The lower pH compartment formed in N matrices affected N solubility and crystal dissolution rate, which can explain its lower release rate compared with EA, from the same formulation. The EPR and NMR data supports our findings that NS caused unfolding of the protein, affected matrix structure, and converted it to a hydrophobic non-erodible matrix compared with EA/N matrix in which the native properties of EA were mainly retained.     

Tumors of the major salivary glands.

Tumors of the major salivary glands are reviewed according to classification, location, surgical procedure and end results. Our data of the incidence of benign and malignant tumors show that the most commonly involved area is the parotid gland and the most frequent is of the mixed variety. In the parotid region 80 percent are benign and 20 percent are malignant; whereas, in the submandibular gland, the malignant and benign tumors are equally distributed. The need for an extensive surgical attack and inclusion of contiguous structure is dictated by the nature of the malignant disease. The role of postoperative irradiation is discussed as is the indication for neck dissection. Management of the facial nerve, relative to malignant tumors of the parotid gland, is considered in detail.     

Alterations in intestinal structure, fat absorption and body weight after intestinal bypass for morbid obesity

Eleven patients underwent jejunoileal bypass for morbid obesity. Serial intestinal biopsies were obtained prior to, and at timed intervals following, operation in both fasted and fat-fed states. Villus height increased asymptotically, reaching a plateau one year after operation, with an increase of 80 per cent in mean villus length. The postbypass body weight reached a plateau at 63.9 per cent of initial body weight and correlated linearly with villus height following an asymptotic curvilinear course. The time required to attain 90 per cent of total body weight loss was 15.9 months. A study of intestinal fat absorption at both the light microscopic and ultrastructural levels showed that the enlarged villi are lined along the entire villus by functionally mature epithelium capable of transporting lipid. Villus hypertrophy is an important mechanism in the plateauing of weight loss after jejunoileal bypass for morbid obesity.     

Decreased prostaglandin E turnover in infants with essential fatty acid deficiency

Sick low birth weight infants (LBWI) are prone to develop rapid onset of essential fatty acid (EFA) deficiency. EFAs serve as precursors for prostaglandins (PGs). We measured the excretion of the major urinary metabolite of prostaglandins E1 and E2, 7alpha-hydroxy-5,11-diketotetranorprostane-1,16-dionic acid (PGE-M), in three EFA-deficient and in nine thriving neonates. There was no significant difference in PGE-M excretion between the sexes among thriving infants nor did PGE-M excretion appear to be affected by postconceptual age. However, a significant difference between the PGE-M excretion in the group of infants with EFA deficiency before and after treatment is apparent (P less than 0.05). Significant differences in PGE-M excretion were also found between the control group and the EFA-deficient infants. The severity of the EFA deficiency correlates directly with the degree of PGs excretion. The biochemical evidences of EFA deficiency and the decreased levels of PGE-M excretion are rapidly corrected when patients resume a diet containing EFA.     

General hospital services for deliberate self-poisoning: an expensive road to nowhere?

This study was designed to investigate the clinical and economic aspects of deliberate self-poisoning services in four teaching hospitals in Leeds, Leicester, Manchester and Nottingham. We investigated the management of the current self-harm episode, including direct in-hospital costs, in 456 individuals who presented to hospital on a total of 477 occasions with deliberate self-poisoning during a 4-week period in 1996. Fewer than half of the patients received specialist psychosocial assessment or follow-up. Patients were more likely to receive an assessment if they were already in contact with psychiatric services, had a history of previous overdoses, if they presented during working hours, or if they lived near the hospital. Patients who were admitted were nearly twice as likely to receive specialist assessment, and those who received a specialist assessment were nearly three times as likely to be offered follow-up. In-patient days and days on the intensive care unit accounted for 47% and 8% of the total costs, respectively. This study suggests that general hospital services are disorganised, with evidence of inequitable access to specialist assessment and after-care. This state of affairs cannot be justified on financial or clinical grounds.