Evaluation of p53 protein expression as a marker for long-term prognosis in colorectal carcinoma.

Mutation of the p53 gene is reported to be of prognostic importance in colorectal carcinomas. Immunohistochemical staining of the accumulated p53 gene product may be a simple alternative for p53 mutation analysis. Previous studies addressing the prognostic importance of p53 expression, however, yielded contradictory results. Therefore, we evaluated the importance of p53 expression as a marker for long-term prognosis in a well-characterised study population of 109 colorectal carcinomas. After antigen retrieval with target unmasking fluid (TUF), immunostaining of p53 was performed with both monoclonal antibody DO7 and polyclonal antibody CM1. Objective quantification of the p53 signal was assessed by a computerised image analyser. p53 expression was higher in non-mucinous tumours than in mucinous tumours (p53 labelling index = 30% and 17% respectively, P = 0.05), and in metastatic tumours compared with non-metastatic tumours (p53 labelling index = 37% and 22% respectively, P = 0.05). Other histopathological features were not related to p53 expression. In multivariate analysis, Dukes' stage (P = 0.02) and histological grade (P = 0.05) stood out as independent markers for prognosis. p53 expression was not an independent marker for prognosis. At present, p53 expression is not a useful marker for long-term prognosis. Further insight into the relationship between p53 mutations and p53 expression is needed to elucidate more precisely the clinical relevance of p53 alterations

25 kHz narrow spectral bandwidth of a wavelength tunable diode laser with a short waveguide-based external cavity

We report on the spectral properties of a diode laser with a tunable external cavity in integrated optics. Even though the external cavity is short compared to other small-bandwidth external cavity lasers, the spectral bandwidth of this tunable laser is as small as 25 kHz (FWHM), at a side-mode suppression ratio (SMSR) of 50 dB. Our laser is also able to access preset wavelengths in as little as 200 us and able to tune over the full telecom C-band (1530 nm - 1565 nm).Comment: 8 pages, 7 figure

Clinical and pathological associations with p53 tumour-suppressor gene mutations and expression of p21WAF1/Cip1 in colorectal carcinoma.

Inactivation of the p53 tumour-suppressor gene is common in a wide variety of human neoplasms. In the majority of cases, single point mutations in the protein-encoding sequence of p53 lead to positive immunohistochemistry (IHC) for the p53 protein, and are accompanied by loss of the wild-type allele. Recently, the WAF1/Cip1 gene was identified as one of the genes induced by wild-type p53, and increased expression of p21WAF1/Cip1 has been found to reflect the status of the p53 tumour-suppressor pathway. We investigated the inactivation of p53 in a relatively small, but well-characterised, group of 46 colorectal carcinomas that were previously studied for allelic alterations, ras oncogene mutations and DNA aneuploidy. Alterations in p53 were identified by IHC, loss of 17p and DNA sequence analysis of exons 5-8, whereas p21WAF1/Cip1 protein expression was determined by IHC. p53 mutations were identified in 19 of the 46 tumours (41%), whereas positive IHC for p53 was found in 21 of the 46 tumours (46%). Positive IHC for p21WAF1/Cip1 was detected in 16 of 42 cases (38%). We found no relationship between p21WAF1/Cip1 staining and p53 protein expression or p53 mutational status. Inactivating mutations in the p53 gene correlated with LOH at 17p but not with LOH at 5q or 18q, Dukes' stage, tumour grade or DNA ploidy. There was a higher survival rate independent of Dukes' stage in the group with no alterations in p53 compared with those with evidence of dysfunction of p53, but the difference was not statistically significant. We conclude that inactivation of p53 and altered expression of p21WAF1/Cip1 are common in colorectal carcinoma but do not correlate with each other or with the clinical or pathological parameters investigated

Nuclear DDX3 expression predicts poor outcome in colorectal and breast cancer

Purpose: DEAD box protein 3 (DDX3) is an RNA helicase with oncogenic properties that shuttles between the cytoplasm and nucleus. The majority of DDX3 is found in the cytoplasm, but a subset of tumors has distinct nuclear DDX3 localization of yet unknown biological significance. This study aimed to evaluate the significance of and mechanisms behind nuclear DDX3 expression in colorectal and breast cancer. Methods: Expression of nuclear DDX3 and the nuclear exporter chromosome region maintenance 1 (CRM1) was evaluated by immunohistochemistry in 304 colorectal and 292 breast cancer patient samples. Correlations between the subcellular localization of DDX3 and CRM1 and the difference in overall survival between patients with and without nuclear DDX3 were studied. In addition, DDX3 mutants were created for in vitro evaluation of the mechanism behind nuclear retention of DDX3. Results: DDX3 was present in the nucleus of 35% of colorectal and 48% of breast cancer patient samples and was particularly strong in the nucleolus. Nuclear DDX3 correlated with worse overall survival in both colorectal (hazard ratio [HR] 2.34, P<0.001) and breast cancer (HR 2.39, P=0.004) patients. Colorectal cancers with nuclear DDX3 expression more often had cytoplasmic expression of the nuclear exporter CRM1 (relative risk 1.67, P=0.04). In vitro analysis of DDX3 deletion mutants demonstrated that CRM1-mediated export was most dependent on the N-terminal nuclear export signal. Conclusion: Overall, we conclude that nuclear DDX3 is partially CRM1-mediated and predicts worse survival in colorectal and breast cancer patients, putting it forward as a target for therapeutic intervention with DDX3 inhibitors under development in these cancer types

Modeling of mode-locking in a laser with spatially separate gain media

We present a novel laser mode-locking scheme and discuss its unusual properties and feasibility using a theoretical model. A large set of single-frequency continuous-wave lasers oscillate by amplification in spatially separated gain media. They are mutually phase-locked by nonlinear feedback from a common saturable absorber. As a result, ultra short pulses are generated. The new scheme offers three significant benefits: the light that is amplified in each medium is continuous wave, thereby avoiding issues related to group velocity dispersion and nonlinear effects that can perturb the pulse shape. The set of frequencies on which the laser oscillates, and therefore the pulse repetition rate, is controlled by the geometry of resonator-internal optical elements, not by the cavity length. Finally, the bandwidth of the laser can be controlled by switching gain modules on and off. This scheme offers a route to mode-locked lasers with high average output power, repetition rates that can be scaled into the THz range, and a bandwidth that can be dynamically controlled. The approach is particularly suited for implementation using semiconductor diode laser arrays.Comment: 13 pages, 5 figures, submitted to Optics Expres

Shot noise limited heterodyne detection of CARS signals

We demonstrate heterodyne detection of CARS signals using a cascaded phase-preserving chain to generate the CARS input wavelengths and a coherent local oscillator. The heterodyne amplification by the local oscillator reveals a window for shot noise limited detection before the signal-to-noise is limited by amplitude fluctuations. We demonstrate an improvement in sensitivity by more than 3 orders of magnitude for detection using a photodiode. This will enable CARS microscopy to reveal concentrations below the current mMolar range

On the absence of bound-state stabilization through short ultra-intense fields

We address the question of whether atomic bound states begin to stabilize in the short ultra-intense field limit. We provide a general theory of ionization probability and investigate its gauge invariance. For a wide range of potentials we find an upper and lower bound by non-perturbative methods, which clearly exclude the possibility that the ultra intense field might have a stabilizing effect on the atom. For short pulses we find almost complete ionization as the field strength increases.Comment: 34 pages Late

On the Influence of Pulse Shapes on Ionization Probability

We investigate analytical expressions for the upper and lower bounds for the ionization probability through ultra-intense shortly pulsed laser radiation. We take several different pulse shapes into account, including in particular those with a smooth adiabatic turn-on and turn-off. For all situations for which our bounds are applicable we do not find any evidence for bound-state stabilization.Comment: 21 pages LateX, 10 figure

Ionization Probabilities through ultra-intense Fields in the extreme Limit

We continue our investigation concerning the question of whether atomic bound states begin to stabilize in the ultra-intense field limit. The pulses considered are essentially arbitrary, but we distinguish between three situations. First the total classical momentum transfer is non-vanishing, second not both the total classical momentum transfer and the total classical displacement are vanishing together with the requirement that the potential has a finite number of bound states and third both the total classical momentum transfer and the total classical displacement are vanishing. For the first two cases we rigorously prove, that the ionization probability tends to one when the amplitude of the pulse tends to infinity and the pulse shape remains fixed. In the third case the limit is strictly smaller than one. This case is also related to the high frequency limit considered by Gavrila et al.Comment: 16 pages LateX, 2 figure

Significant variation in histopathological assessment of endoscopic resections for Barrett's neoplasia suggests need for consensus reporting:propositions for improvement

Endoscopic resection (ER) is an important diagnostic step in management of patients with early Barrett's esophagus (BE) neoplasia. Based on ER specimens, an accurate histological diagnosis can be made, which guides further treatment. Based on depth of tumor invasion, differentiation grade, lymphovascular invasion, and margin status, the risk of lymph node metastases and local recurrence is judged to be low enough to justify endoscopic management, or high enough to warrant invasive surgical esophagectomy. Adequate assessment of these histological risk factors is therefore of the utmost importance. Aim of this study was to assess pathologist concordance on these histological features on ER specimens and evaluate causes of discrepancy. Of 62 challenging ER cases, one representative H&E slide and matching desmin and endothelial marker were digitalized and independently assessed by 13 dedicated GI pathologists from 8 Dutch BE expert centers, using an online assessment module. For each histological feature, concordance and discordance were calculated. Clinically relevant discordances were observed for all criteria. Grouping depth of invasion categories according to expanded endoscopic treatment criteria (T1a and T1sm1 vs. T1sm2/3), ≥1 pathologist was discrepant in 21% of cases, increasing to 45% when grouping diagnoses according to the traditional T1a versus T1b classification. For differentiation grade, lymphovascular invasion, and margin status, discordances were substantial with 27%, 42%, and 32% of cases having ≥1 discrepant pathologist, respectively. In conclusion, histological assessment of ER specimens of early BE cancer by dedicated GI pathologists shows significant discordances for all relevant histological features. We present propositions to improve definitions of diagnostic criteria