Demonstration of electron acceleration in a laser-driven dielectric microstructure.

The enormous size and cost of current state-of-the-art accelerators based on conventional radio-frequency technology has spawned great interest in the development of new acceleration concepts that are more compact and economical. Micro-fabricated dielectric laser accelerators (DLAs) are an attractive approach, because such dielectric microstructures can support accelerating fields one to two orders of magnitude higher than can radio-frequency cavity-based accelerators. DLAs use commercial lasers as a power source, which are smaller and less expensive than the radio-frequency klystrons that power today's accelerators. In addition, DLAs are fabricated via low-cost, lithographic techniques that can be used for mass production. However, despite several DLA structures having been proposed recently, no successful demonstration of acceleration in these structures has so far been shown. Here we report high-gradient (beyond 250 MeV m(-1)) acceleration of electrons in a DLA. Relativistic (60-MeV) electrons are energy-modulated over 563 ± 104 optical periods of a fused silica grating structure, powered by a 800-nm-wavelength mode-locked Ti:sapphire laser. The observed results are in agreement with analytical models and electrodynamic simulations. By comparison, conventional modern linear accelerators operate at gradients of 10-30 MeV m(-1), and the first linear radio-frequency cavity accelerator was ten radio-frequency periods (one metre) long with a gradient of approximately 1.6 MeV m(-1) (ref. 5). Our results set the stage for the development of future multi-staged DLA devices composed of integrated on-chip systems. This would enable compact table-top accelerators on the MeV-GeV (10(6)-10(9) eV) scale for security scanners and medical therapy, university-scale X-ray light sources for biological and materials research, and portable medical imaging devices, and would substantially reduce the size and cost of a future collider on the multi-TeV (10(12) eV) scale.

Generation of stable, low-divergence electron beams by laser-wakefield acceleration in a steady-state-flow gas cell.

Laser-driven, quasimonoenergetic electron beams of up to approximately 200 MeV in energy have been observed from steady-state-flow gas cells. These beams emitted within a low-divergence cone of 2.1+/-0.5 mrad FWHM display unprecedented shot-to-shot stability in energy (2.5% rms), pointing (1.4 mrad rms), and charge (16% rms) owing to a highly reproducible gas-density profile within the interaction volume. Laser-wakefield acceleration in gas cells of this type provides a simple and reliable source of relativistic electrons suitable for applications such as the production of extreme-ultraviolet undulator radiation.

Targeting of human p53-overexpressing tumor cells by an HLA A*0201-restricted murine T-cell receptor expressed in Jurkat T cells.

A potent anti-human (hu) p53 CD8+ CTL response develops in HLA A*0201 transgenic (Tg) mice after immunization with peptides corresponding to HLA A*0201 motifs from hu p53. Mice immunized with the hu P53(149-157) peptide develop a CTL response that is of moderately high affinity and is capable of recognizing hu tumor cells expressing mutated p53. In this report, the mRNAs encoding the predominantly expressed T-cell receptor (TCR) sequences were molecularly cloned from a murine (mu) CTL clone derived from immunized Tg mice, which recognized endogenously processed hu p53 restricted by HLA A*0201. The separate A and B chain TCR cDNAs were transfected in the corresponding TCR A- and B- Jurkat-CD3- mutant T-cell lines, and each rescued CD3 surface expression. Both TCR chains were simultaneously introduced into Jurkat-CD3+ cells, and the transfected Jurkat cells recognized hu T2 cells sensitized with the p53(149-157) CTL epitope but not T2 cells sensitized with a nonspecific CTL epitope. Breast, pancreatic, and sarcoma tumor cell lines, which overexpress endogenous mutated p53, were recognized in the presence of anti-CD28 costimulation, only if they also expressed HLA A*0201. Normal hu fibroblasts established from skin cultures were not recognized. These results represent the first time that a p53-specific TCR capable of recognizing hu cancer cells was heterologously expressed in a naive recipient cell, converting that cell to one recognizing hu tumor cells with mutated p53. This TCR represents a candidate molecule for a genetic strategy in combating hu cancer by an adoptive immunotherapy approach, which uses the strong xenorecognition of hu p53 in mice.

Contralateral prophylactic mastectomy improves the outcome of selected patients undergoing mastectomy for breast cancer.

BACKGROUND: Risk factors for contralateral breast cancer (CBC) may indicate a benefit for contralateral prophylactic mastectomy (CPM) at the time of unilateral mastectomy for breast cancer. The purpose of this study is to evaluate the efficacy of CPM in preventing CBC. METHODS: sixty-four patients undergoing CPM and a control group of 182 patients not undergoing CPM and matched for age, stage, surgery, chemotherapy, and hormonal therapy were retrospectively compared for CBC rate, disease-free survival, and overall survival. RESULTS: Thirty-six CBCs occurred in the control group. In the CPM group, 3 CBCs were found at the time of prophylactic mastectomy, but none occurred subsequently (P = 0.005). Disease-free survival at 15 years in the CPM group was 55% (95% confidence interval [CI] 38% to 69%) versus 28% (95% CI 19% to 36%) in the control group (P = 0.01). Overall survival at 15 years was 64% (95% CI 45% to 78%) CPM versus 48% (95% CI 39% to 58%) in controls (P = 0.26). CONCLUSION: CPM prevented CBC and significantly prolonged disease-free survival. Future studies will need to address risk assessment and contralateral breast cancer prevention in patients treated for early breast cancer.

Immunotherapy of bladder cancer targeting P53.

PURPOSE: Superficial bladder cancer is often responsive to immunotherapy with bacillus Calmette-Guerin (BCG). However, some tumors progress despite BCG treatment, and most of these have mutations in the p53 tumor suppressor gene resulting in its over-expression. Overexpressed p53 is therefore a potential target for immunotherapy. The objective of this study was to demonstrate whether human bladder cancer xenografts in SCID mice could be eliminated by cytotoxic T cells (CTL) which recognize over-expressed p53. MATERIALS AND METHODS: Murine CTL which are specific for human p53 were previously generated in our laboratory by peptide immunization of HLA A2.1 transgenic mice. These CTL recognize and lyse human tumor cell lines which over-express p53 in the context of HLA A2.1. The p53 over-expressing HLA A2.1+ human bladder cancer cell line J82 was used to establish subcutaneous or intravesicular tumors in SCID mice. The mice were then administered tail vein injections of 5 x 10(7) p53-specific CTL, control CTL, or phosphate buffered saline (PBS). RESULTS: The subcutaneous tumor mean volume at 5 weeks for the p53-specific CTL treatment group was significantly lower than for both the control CTL or the PBS group (32 mm.3 versus 185 mm.3, p = 0.04 and 32 mm.3 versus 418 mm.3, p = 0.0001). In the mice with intravesicular tumors, a reduction to nonpalpable tumor size in vivo was seen with specific CTL therapy (14% palpable) versus control CTL treatment (86% palpable), the final tumor volume at necropsy was 127 mm.3 versus 246 mm.3 (N.S.). CONCLUSION: The overall response of the human bladder tumors in the SCID mouse model suggests the possibility of targeting p53 in patients with bladder cancer.

An orthotopic in vivo model of human pancreatic cancer.

BACKGROUND: Pancreatic cancer is a highly lethal disease that frequently presents in advanced stages. For most patients, treatment with great clinical efficacy does not exist. Relevant in vivo models to test novel therapies are highly desirable. METHODS: The human pancreatic ductal adenocarcinoma cell line Panc-1 was injected intraperitoneally into SCID mice. The pattern of the resulting peripancreatic as well as metastatic disease was examined. Survival experiments after chemotherapy with gemcitabine or doxorubicin, and after immunotherapy with p53-specific cytotoxic T lymphocytes were performed. RESULTS: All animals developed isolated pancreatic tumor implants within 48 hours after injection. After the formation of invasive pancreatic tumor nodules, peripancreatic and portal adenopathy developed, causing biliary obstruction. All tumor-bearing animals died of disease within 5 to 12 weeks. Survival after gemcitabine treatment and after p53-CTL injection was significantly prolonged, with some animals remaining tumor-free. Doxorubicin treatment did not yield extended survival, but led to significant toxicity. CONCLUSION: Intraperitoneal injection of Panc-1 cells into SCID mice produces a quasi-orthotopic tumor development model that shares many characteristics with human pancreatic cancer. The ease of cell injection, avoidance of cumbersome surgical intervention with its resulting mortality, and the reliable development of obstructive jaundice as a dependent comorbid factor render this a useful model for in vivo testing of novel therapeutic approaches to pancreatic cancer. Our initial therapeutic studies demonstrate that in vitro antitumor efficacy against Panc-1 cancer cells does not necessarily predict the in vivo response, highlighting the preclinical experimental value of this model.

Targeting p53 for adoptive T-cell immunotherapy.

p53 gene mutations occur in most human cancers and result in an altered protein product that accumulates within the cell. Although the observed endogenous human CTL response to p53 is weak, high-affinity, human p53-specific CTLs have been generated from HLA A2.1 transgenic mice immunized with human CTL epitope peptides. In this study, we examine the ability of HLA A2.1-restricted and human p53-specific CTLs from HLA A2.1 transgenic mice to suppress the growth of p53-overexpressing human tumors in severe combined immunodeficient (SCID) mice. In vitro, murine p53(149-157)-specific CTLs selectively lysed the p53-overexpressing pancreatic carcinoma cell line Panc-1 but did not recognize HLA A2.1- tumor cells or HLA A2.1+ normal human fibroblasts. Furthermore, in vivo, the growth of established human tumor xenografts in SCID mice was significantly reduced and survival was prolonged after the administration of p53-specific CTLs but not after the administration of control CTLs or PBS alone. Following treatment with p53(149-157)-specific CTLs, regressing Panc-1 tumors were infiltrated by the CD8+ CTLs, as demonstrated by immunohistochemistry. These findings suggest that p53(149-157)-specific and HLA A2.1-restricted murine CTLs suppress the growth of established Panc-1 tumors following adoptive transfer into SCID hosts and prolong their survival.

Intraductal neoplasms of the pancreas.

BACKGROUND: Since 1980 a group of pancreatic tumors have been termed intraductal papillary mucinous tumors (IPMT). Because these tumors occupy an intraductal position they are demonstrated by pancreatography to reside in the main pancreatic duct (MPD) or side branch ducts (SBD). Lesions of IPMT result in abdominal pain or pancreatitis symptoms because mucin production or papillary growth results in ductal obstruction. Only 104 cases had been reported in the literature by 1996 but more are being presented in abstract form. We reviewed our own 33 cases to assist defining operative decision-making criteria. METHODS: All cases of IPMT between 1989 and 1997 were reviewed for clinical presentation, anatomy by endoscopic retrograde cholangiopancreatography and computed tomography, histologic findings, and long-term outcomes. RESULTS: Our cases were older (65 years) and presented with disease centered mainly in the head of the gland. Clinical presentation was epigastric pain (82%), pancreatitis (56%), weight loss (36%), diabetes (27%), and jaundice (9%). Operations were pancreatectomy in 31 (Whipple n = 15, total n = 5, distal n = 10, local n = 1), bypass only (n = 1), and no operation (n = 1). Malignancy was found in 14 of 33 (42%). Factors significantly associated (P <0.05 Fisher exact test) with malignancy were history of alcohol abuse or death from disease. Jaundice or presence in both MPD and SBD approached a significant association with malignancy but not abdominal pain, weight loss, diabetes, preoperative serum elevations of amylase, SGOT, CA-19-9, or CEA; diffuse MPD dilation, gland region, gross mucus in ducts or filling defects, cytology, calcifications, or a pancreatic mass. In 31 resected patients after a follow-up of 37 months (1 to 103) death had occurred in 6 of 13 malignant cases and 0 of 18 with benign disease. Three-year actuarial survival was 82% (all) and 56% (malignant). Symptom recurrence after resection was found in 6 of 31 at a mean of 13 months postoperatively and was associated with death from disease (P <0.05) or presence of pain preoperatively. CONCLUSION: Malignancy is common with IPMT and is more likely to be present with the clinical history of alcohol abuse or jaundice and if the tumor involves both the MPD and the SBD. The prognosis after resection is better than pancreatic cancer but the 19% recurrence of symptoms was equally seen with benign or malignant cases owing to residual disease in pancreatic remnants. The amount of resection should be extensive in patients likely to have malignancy (alcohol, jaundice, MPD+SBD). In those likely to redevelop symptoms, ie, those with preoperative pain, a careful assessment should be made via imaging studies for extent of disease.

Malignant melanoma of the head and neck: effect of treatment on survival.

This study compared outcomes for intermediate-thickness (1.5 to 3.99 mm) head and neck melanomas treated with or without elective lymph node dissection (ELND). The records of all head and neck melanomas treated at Virginia Mason Medical Center from 1974 through 1995 were reviewed and analyzed for outcome by stage and elective or therapeutic lymph node dissection. One hundred seventy-four patients with head and neck melanomas were treated in the study period, of which only 25% had intermediate-thickness lesions. Of 38 clinically node-negative patients with intermediate-thickness lesions followed more than 3 years, 10 underwent ELND, yielding two positive dissections (20%). The rate of distant metastases and the mortality rate were 44% and 35% lower in patients undergoing ELND compared with stage II patients who did not undergo ELND, but the difference did not achieve statistical significance (P = 0.12 and 0.21, respectively). The role of ELND in head and neck melanoma is uncertain. This retrospective study is limited by the small number of intermediate-thickness lesions, yet there appears to be a survival advantage to ELND in head and neck melanoma, even in negative dissections. Conventional histologic stains miss micrometastases detected by immunohistological and polymerase chain techniques. Removal of such micrometastases may explain the improved outcome. A multicenter prospective trial in head and neck melanomas, incorporating the latest techniques of sentinel node biopsy and immunohistological staining of node specimens, is needed to clarify definitive therapy for this increasingly common diagnosis.