Equivalence of cell survival data for radiation dose and thermal dose in ablative treatments: analysis applied to essential tremor thalamotomy by focused ultrasound and gamma knife.

Thermal dose and absorbed radiation dose have historically been difficult to compare because different biological mechanisms are at work. Thermal dose denatures proteins and the radiation dose causes DNA damage in order to achieve ablation. The purpose of this paper is to use the proportion of cell survival as a potential common unit by which to measure the biological effect of each procedure. Survival curves for both thermal and radiation doses have been extracted from previously published data for three different cell types. Fits of these curves were used to convert both thermal and radiation dose into the same quantified biological effect: fraction of surviving cells. They have also been used to generate and compare survival profiles from the only indication for which clinical data are available for both focused ultrasound (FUS) thermal ablation and radiation ablation: essential tremor thalamotomy. All cell types could be fitted with coefficients of determination greater than 0.992. As an illustration, survival profiles of clinical thalamotomies performed by radiosurgery and FUS are plotted on a same graph for the same metric: fraction of surviving cells. FUS and Gamma Knife have the potential to be used in combination to deliver a more effective treatment (for example, FUS may be used to debulk the main tumour mass, and radiation to treat the surrounding tumour bed). In this case, a model which compares thermal and radiation treatments is valuable in order to adjust the dose between the two.

Androgen receptor degradation by the E3 ligase CHIP modulates mitotic arrest in prostate cancer cells.

The androgen receptor (AR) has a vital role in the onset and progression of prostate cancer by promoting G1-S progression, possibly by functioning as a licensing factor for DNA replication. We here report that low dose 2-methoxyestradiol (2-ME), an endogenous estrogen metabolite, induces mitotic arrest in prostate cancer cells involving activation of the E3 ligase CHIP (C-terminus of Hsp70-interacting protein) and degradation of the AR. Depletion of the AR by small interfering RNA (siRNA) eliminates 2-ME-induced arrest and introducing AR into PC3-M cells confers 2-ME-induced mitotic arrest. Knockdown of CHIP or MDM2 (mouse homolog of double minute 2 protein) individually or in combination reduced AR degradation and abrogated M phase arrest induced by 2-ME. Our data link AR degradation via ubiquitination to mitotic arrest. Targeting the AR by activating E3 ligases such as CHIP represents a novel strategy for the treatment of prostate cancer.

Disruption of spermatogenesis and Sertoli cell structure and function by the indenopyridine CDB-4022 in rats.

The present studies were undertaken to determine the testicular cell type(s) affected by the antispermatogenic indenopyridine CDB-4022. At the oral threshold dose (2.5 mg/kg), CDB-4022 induced infertility in all males. CDB-4022 did not alter (P > 0.05) Leydig cell function as assessed by circulating testosterone, seminal vesicle, and ventral prostate weights or body weight gain compared to controls. Conversely, CDB-4022 reduced (P < 0.05) testicular weight, spermatid head counts, and percentage of seminiferous tubules undergoing spermatogenesis. In a second study, adult male rats received a maximally effective oral dose of CDB-4022 (12.5 mg/kg), dipentylphthalate (DPP; 2200 mg/kg; a Sertoli cell toxicant), or vehicle and were necropsied 3, 6, or 12 h after dosing to determine acute effects. Serum inhibin B levels were suppressed (P < 0.05) by 6 h after CDB-4022 or DPP treatment, but epididymal androgen-binding protein (ABP) levels were not altered (P > 0.05), compared to controls. CDB-4022 and DPP increased (P < 0.05) the percentage of tubules with apoptotic germ cells, particularly differentiating spermatogonia and spermatocytes, by 12 h after dosing. Microscopic examination of the testis indicated a greater degree of vacuolation in Sertoli cells and initial signs of apical germ cell sloughing/shedding by 3 or 12 h after CDB-4022 or DPP treatment, respectively. In a third study, prepubertal male rats were treated with vehicle, 12.5 mg/kg of CDB-4022, or 2200 mg/kg of DPP, and the efferent ducts of the right testis were ligated 23 h before necropsy. Seminiferous tubule fluid secretion (difference in weight of testes), serum inhibin B levels, and ABP levels in the unligated epididymis were reduced (P < 0.05) at 24 and 48 h after dosing in CDB-4022- and DPP-treated rats compared to controls. Collectively, these data suggest that CDB-4022 disrupts spermatogenesis by inducing apoptosis in early stage germ cells via a direct action on the Sertoli cell.

Histone H1 and H3 dephosphorylation are differentially regulated by radiation-induced signal transduction pathways.

We recently demonstrated that linker histone H1, which is thought to have a fundamental role in higher-order chromatin structure, becomes transiently dephosphorylated after ionizing radiation (IR) in a mutated ataxia telangiectasia (ATM) dependent manner. To establish whether H1 dephosphorylation was a component of a damage-response pathway that included dephosphorylation of other histones, we asked whether H3 was dephosphorylated in response to IR in a manner similar to H1. H1 and H3 are maximally phosphorylated in metaphase and both are dephosphorylated after IR. However, the duration of IR-induced H3 dephosphorylation is significantly longer than that of IR-induced H1 dephosphorylation. Moreover, H1 dephosphorylation is ATM-dependent, whereas H3 dephosphorylation is ATM-independent. These observations suggest that the damage-sensing pathways regulating H3 and H1 dephosphorylation diverge upstream of ATM.

Circulating concentrations of the antiprogestins CDB-2914 and mifepristone in the female rhesus monkey following various routes of administration.

The overall aim of these studies was to investigate the oral and i.m. bioavailability of CDB-2914 in intact female rhesus monkeys, and to compare the serum concentrations of CDB-2914 with that of mifepristone following oral administration. In the first study, a 50 mg bolus of CDB-2914 per monkey was administered intravenously, orally or intramuscularly. The area under the serum concentration-time curve for 72 h (AUC(0-72)) following i.v. injection was 18 320 +/- 2718 ng/ml*h, and that for oral administration was 10 464 +/- 3248 ng/ml*h. Thus, the oral bioavailability of CDB-2914 equivalents was 56%. The AUC(0-168 h) following i.m. injection was 11 226 +/- 1130 ng/ml*h. Therefore, the i.m. bioavailability of CDB-2914 equivalents was 62%. In the second study, the serum concentrations of CDB-2914 and mifepristone equivalents were compared following an oral bolus dose in two different formulations. When administered at 5 mg/kg in aqueous suspending vehicle (ASV), the mean peak serum concentration (C(max)) of CDB-2914 equivalents (192 +/- 64 ng/ml) occurred at 5 +/- 1 h, whereas the C(max) of mifepristone equivalents (82 +/- 25 ng/ml) occurred at 3 +/- 1 h. Following administration in gelatin capsules (35 mg/monkey), the C(max) of CDB-2914 equivalents (129 +/- 24 ng/ml) occurred at 5 +/- 1 h, while the C(max) of mifepristone equivalents (31 +/- 8 ng/ml) occurred at 3 +/- 1 h. The serum concentration (AUC(0-120 h)) of CDB-2914 equivalents was 4.7- or 5. 3-fold greater than that of mifepristone equivalents when administered orally in ASV or gelatin capsules respectively. The serum protein binding characteristics of CDB-2914 were also studied. CDB-2914 bound to human alpha(1)-acid glycoprotein (AAG), but not with as high an affinity as mifepristone. In contrast, neither CDB-2914 nor mifepristone bound with high affinity to AAG, corticosteroid binding globulin or sex hormone binding globulin in monkey serum. Collectively, these results indicated that CDB-2914 was more efficiently absorbed than mifepristone following oral administration to female rhesus monkeys.

The tumor suppressor p53 can reduce stable transfection in the presence of irradiation.

The tumor suppressor p53 is believed to play an essential role in maintaining genome stability. Although it is currently unknown how p53 is involved in this important biological safeguard, several previous publications indicate that p53 can help to maintain genome integrity through the recombination-mediated DNA repair process. The integration of linearized plasmid DNA into the host chromosome utilizes the same repair process, and the frequency can be measured by clonogenic assays in which cells that were stably transfected by plasmid integration can be scored by their colony-forming abilities. To gain insight into whether p53 has a direct role in plasmid integration into the host chromosome, we determined the frequency of stable transfection with CHO cells expressing either wild-type or mutant p53 in the presence and absence of irradiation. We found that low-dose irradiation ( approximately 50 to 100 cGy) increased stable transfection frequencies in CHO cells regardless of their p53 status. However, the increase of transfection frequency was significantly lower in CHO cells expressing wild-type p53. Our data thus suggest that wild-type p53 can suppress plasmid DNA integration into the host genome. This p53 function may play a direct and significant role in maintaining genome stability.

Histone H1 dephosphorylation is mediated through a radiation-induced signal transduction pathway dependent on ATM.

Ionizing radiation is known to activate multiple signal transduction pathways, but the targets of these pathways are poorly understood. Phosphorylation of histone H1 is thought to have a role in chromatin condensation/decondensation, and we asked whether ionizing radiation (IR) would alter H1 phosphorylation. Our data demonstrate that low doses of IR result in a dramatic, but transient, dephosphorylation of H1 isoforms. The in vivo IR-induced dephosphorylation of H1 is completely blocked by wortmannin and is abrogated in ataxia telangiectasia cells. Furthermore, we measured radiation-induced inhibition of cyclin dependent kinase activity and activation of histone H1 phosphatase activity. Both activities were affected by radiation-induced signals in an ATM-dependent manner. Thus, the rapid IR-induced dephosphorylation of H1 involves a pathway including ATM and a wortmannin-sensitive step leading to both inhibition of cyclin-dependent kinase activities as well as activation of H1 phosphatase(s).

The radiation-induced S-phase checkpoint is independent of CDKN1A.

We recently demonstrated that, in response to radiation, replication is down-regulated at the level of individual origins throughout S phase of the cell cycle. Since several in vitro studies demonstrate that CDKN1A (formerly known as p21) down-regulates replication by inhibiting PCNA, and since CDKN1A can retard progression of cells through S phase in vivo, the question arises whether CDKN1A is involved in the S-phase damage-sensing pathway. In the present study we analyzed the effect of ionizing radiation on CDKN1A+/+ and CDKN1A-/- cells derived from the HCT 116 cell line. Neither progression of cells through S phase nor survival after exposure to ionizing radiation is influenced by CDKN1A status in either synchronous or asynchronous cells. These results establish that CDKN1A is not necessary for the acute S-phase damage-sensing pathway that functions to prevent firing of replication origins during S phase.

Third ventricular lesion masquerading as suprasellar disease.

We discuss the case of a patient who presented with a bitemporal visual field disturbance thought to arise from chiasmatic compression secondary to a suprasellar mass. The patient was ultimately diagnosed with medulloblastoma with diffuse intraventricular disease. Careful review of magnetic resonance (MR) findings in this case demonstrate the apparent suprasellar mass to be within the suprachiasmatic recess of the third ventricle. The role of MR imaging in distinguishing between suprasellar disease involving the third ventricle and primary third ventricular lesions is discussed.

Radiation down-regulates replication origin activity throughout the S phase in mammalian cells.

An asynchronous culture of mammalian cells responds acutely to ionizing radiation by inhibiting the overall rate of DNA replication by approximately 50% for a period of several hours, presumably to allow time to repair DNA damage. At low and moderate doses, this S phase damage-sensing (SDS) pathway appears to function primarily at the level of individual origins of replication, with only a modest inhibition of chain elongation per se. We have shown previously that the majority of the inhibition observed in an asynchronous culture can be accounted for by late G1cells that were within 2-3 h of entering the S period at the time of irradiation and which then fail to do so. A much smaller effect was observed on the overall rate of replication in cells that had already entered the S phase. This raised the question whether origins of replication that are activated within S phase per se are inhibited in response to ionizing radiation. Here we have used a two-dimensional gel replicon mapping strategy to show that cells with an intact SDS pathway completely down-regulate initiation in both early- and late-firing rDNA origins in human cells. We also show that initiation in mid- or late-firing rDNA origins is not inhibited in cells from patients with ataxia telangiectasia, confirming the suggestion that these individuals lack the SDS pathway.

Effects of two progestin-only contraceptives, Depo-Provera and Norplant-II, on the vaginal epithelium of rhesus monkeys.

The objective of this study was to determine whether progestin-only contraceptives induce thinning of the vaginal epithelium in nonhuman primates. Eight intact rhesus monkeys (four per group) were treated with either a single intramuscular injection of 30 mg of Depo-Provera or a subcutaneous insertion of Norplant-II (2 x 75 mg rods; day 0). Norplant-II rods were removed 90 days after insertion. Vaginal biopsies were obtained during a pretreatment menstrual cycle and following treatment on days 10, 30, 60, 118, and 146. Formalin-fixed vaginal biopsies were evaluated for epithelial thickness and the degree of keratinization. The circulating levels of estradiol, progesterone, medroxyprogesterone acetate (MPA), or levonorgestrel (LNG) were monitored throughout the study by specific radioimmunoassays. Circulating levels of estradiol and progesterone confirmed the stage of the menstrual cycle in which pretreatment biopsies were obtained. Following treatment with Depo-Provera, serum levels of MPA increased to 2.3 +/- 0.6 ng/ml (x +/- SE, n = 4) within 24 hr. Serum levels of MPA were maximal on day 14 (5.5 +/- 0.9 ng/ml), dropped below 1 ng/ml by day 50, and were nondetectable by day 70. Circulating levels of LNG were elevated 24 hr after insertion of Norplant-II (5.8 +/- 3.0 ng/ml), peaked on day 2 (7.6 +/- 4.2 ng/ml), remained between 1.4 and 6.2 ng/ml from days 14 to 90, and were nondetectable by day 118, the first serum sample after removal of Norplant-II. There were no significant differences (p > 0.05) in the epithelial thickness (microm), number of epithelial cell layers, or type of epithelium present in vaginal biopsies obtained during the follicular or luteal phases of the pretreatment menstrual cycle. Conversely, a pronounced effect of progestin treatment was observed on the vaginal epithelium. There were no significant differences (p > 0.05) between the two progestin treatment groups, but a significant effect (p < 0.05) over time was observed (two-way ANOVA). Compared with pretreatment menstrual cycle controls, the vaginal epithelial thickness was decreased (p < 0.05) by day 30 or 60 following Norplant-II insertion or Depo-Provera injection, respectively. The number of epithelial cell layers was also decreased (p < 0.05) on days 30 and/or 60 in progestin-treated monkeys compared with pretreatment control cycles. Following removal of Norplant-II or metabolic excretion of MPA, the vaginal epithellium regenerated and the thickness was no longer different (p > 0.05) from the pretreatment control cycle. These data demonstrate that progestin-only contraceptives induced thinning of the vaginal epithelium in rhesus monkeys, and this effect was rapidly reversible following physical or metabolic removal of the progestin.

A p53-independent damage-sensing mechanism that functions as a checkpoint at the G1/S transition in Chinese hamster ovary cells.

In response to a moderate dose of radiation, asynchronous mammalian cell populations rapidly and transiently down-regulate the rate of DNA synthesis to approximately 50% of preirradiation values. We show here that only half of the reduction in overall replication rate can be accounted for by direct inhibition of initiation at origins in S-phase cells. The other half results from the operation of a newly defined cell cycle checkpoint that functions at the G1/S transition. This checkpoint senses damage incurred at any time during the last 2 hr of G1 and effectively prevents entry into the S period. The G1/S and S-phase checkpoints are both p53-independent and, unlike the p53-mediated G1 checkpoint, respond rapidly to radiation, suggesting that they may represent major damage-sensing mechanisms connecting the replication machinery with DNA repair pathways.

Cloning and characterization of Chinese hamster p53 cDNA.

We have cloned and sequenced Chinese hamster p53 cDNA and have compared the p53 sequence in different Chinese hamster cell lines to several relevant phenotypes. Our results indicate that a mutation in CHO cells that changes Thr211 to Lys211 abrogates the ability to arrest in G1 and apparently renders cells capable of amplifying DNA. However, this mutation has no effect on the G2 checkpoint or on acute down-regulation of DNA replication after a radiation challenge.

S phase damage sensing checkpoints in mammalian cells.

Mammalian cells have evolved multiple responses for dealing with DNA damage. One response is to acutely downregulate DNA synthesis at the initiation step. Essentially nothing is known about the initial signal that activates this SDS pathway or the macromolecules involved in transducing the signal into the final inhibitory step at origins. Determining whether any radiation induced changes in known proteins involved in cell cycle regulation or in other signal transduction pathways are primary or secondary responses to DNA damage constitutes a major challenge to identifying members of the pathway. It may turn out to be easier to identify the final mediator in the pathway, namely the protein(s) whose interaction with origins is ultimately affected by radiation. Hopefully, mutations in SDS genes in genetically tractable systems such as S cerevisiae or Schizosaccharomyces pombe will allow the identification of homologous genes in mammals. Most tumour cells are TP53 negative, and yet it is not clear that TP53 status influences radiation sensitivity. The SDS pathway may therefore represent an important protective mechanism that stands in the way of effective tumour cell killing by radiation therapy. It is hoped that an understanding of this pathway will provide opportunities for developing novel antineoplastic targets and/or radiation sensitizers.

Desmoplastic fibroma: a role for radiotherapy?

Desmoplastic fibroma is a rare, locally aggressive, benign tumor that is considered the skeletal counterpart of the desmoid tumor of soft tissues. Although the treatment of choice of desmoplastic fibroma is surgical excision, radiation therapy should be considered when surgery is not a viable option.

Extradural failure in glioblastoma multiforme: MRI demonstration.

Glioblastoma multiforme is invariably associated with intracranial failure following conventional therapy. Extracranial as well as metastatic failure are rarely seen. Subtle extracranial abnormalities in most patients with glioblastoma multiforme are not indicative of convexity failure. However, in patients with high p53 and Ki67 immunoreactivity and in whom the dura was not closed at the time of craniotomy, the possibility of early extradural failure should be considered.

Definitive radiotherapy for T1 and T2 squamous cell carcinoma of the tonsil.

BACKGROUND: To assess whether survival or local control of early squamous cell carcinoma of the tonsil has been compromised by a moderate-dose approach. METHODS: Between 1970 and 1989, 185 patients with SCCa of the tonsil were seen at our institution. Fifty-three patients with T1 (30) and T2 (23) lesions treated with definitive radiotherapy were reviewed. Median follow-up was 60 months. The effects of total dose and site of the primary on survival and local regional control were analyzed. RESULTS: Three-year determinate survival was 77%. Mean total dose was 63.1 Gy. Site of the primary significantly affected survival (86% for fossa, 54% for pillars, p < 0.025). Local control at 2 years was 81% and was independent of dose > or = 63 Gy or site of the primary. Grade 4 complications defined by the RTOG/EORTC Acute Morbidity criteria occurred in three patients. CONCLUSIONS: Tumor doses on the order of 63 Gy or less result in excellent local control and survival rates for T1 and T2 carcinomas of the tonsil. Local control rates are better for fossa lesions than for pillar lesions.

A phase 1-2 trial of superselective carboplatin, low-dose infusional 5-fluorouracil and concurrent radiation for high-grade gliomas.

Recent trials have suggested that low-dose infusional 5-FU is more efficacious when given during radiotherapy than is bolus 5-FU. Additionally, intra-arterial cisplatin for brain tumors has been shown to be associated with both high response rates as well as significant toxicity. A dose escalation study was therefore performed using superselective carboplatin, a cisplatin analogue with a favorable CNS toxicity profile in combination with 6 weeks of infusional 5-FU at 225 mg/m2 and concurrent radiotherapy. Eight patients were treated at the starting dose of 200 mg/m2 carboplatin and 11 patients were treated at 300 mg/m2. No toxicity was observed that was attributable to infusional 5-FU. However, two ischemic events related to the superselective delivery of carboplatin were observed, and one patient was noted to have asymptomatic retinal toxicity from the carboplatin. Of 19 patients, 5 had objective responses with 25% or greater reduction in tumor volumes. Continuous infusional 5-FU can be given in combination with partial brain radiotherapy without significant toxicity. Superselective carboplatin delivery is associated with a low incidence of stroke, but no significant retinal toxicity.

Esthesioneuroblastoma. Long-term outcome and patterns of failure--the University of Virginia experience.

BACKGROUND: Esthesioneuroblastoma is a rare tumor arising from olfactory epithelium. This retrospective review analyzed the patterns of failure and long term outcome of patients with esthesioneuroblastoma evaluated at a single institution. METHODS: Forty patients with esthesioneuroblastoma were evaluated at the University of Virginia, with a median follow-up of 130 months. In most cases, treatment consisted of combined-modality therapy, including radiotherapy and surgery for Stages A and B disease and the addition of chemotherapy for Stage C disease. Fifteen patients received chemotherapy that included cyclophosphamide plus vincristine. Thirty-eight patients received radiotherapy, with a median dose of 50 Gy. Initial surgery for 23 patients included craniofacial resection, whereas the remainder had less extensive surgery (3 had no initial surgery). Five patients were salvaged with high dose chemotherapy and autologous bone marrow transplantation (CTX/BMT). RESULTS: Actuarial survivals at 5, 10, and 15 years are 78%, 71%, and 65% respectively. Fifty-five percent of patients failed therapy, and 68% of the failures were locoregional. Thirty-nine percent of recurrences occurred later than 5 years from diagnosis. Three of the five patients were successfully salvaged with CTX/BMT compared with four of seventeen patients who underwent conventional salvage therapy. CONCLUSIONS: Esthesioneuroblastoma is associated with long term survival and late recurrences. Multimodality therapy should be used initially. Durable remissions of failures can be achieved with CTX/BMT: