Graphene-enhanced plasmonic nanohole arrays for environmental sensing in aqueous samples.

The label-free nature of surface plasmon resonance techniques (SPR) enables a fast, specific, and sensitive analysis of molecular interactions. However, detection of highly diluted concentrations and small molecules is still challenging. It is shown here that in contrast to continuous gold films, gold nanohole arrays can significantly improve the performance of SPR devices in angle-dependent measurement mode, as a signal amplification arises from localized surface plasmons at the nanostructures. This leads consequently to an increased sensing capability of molecules bound to the nanohole array surface. Furthermore, a reduced graphene oxide (rGO) sensor surface was layered over the nanohole array. Reduced graphene oxide is a 2D nanomaterial consisting of sp2-hybridized carbon atoms and is an attractive receptor surface for SPR as it omits any bulk phase and therefore allows fast response times. In fact, it was found that nanohole arrays demonstrated a higher shift in the resonance angle of 250-380% compared to a continuous gold film. At the same time the nanohole array structure as characterized by its diameter-to-periodicity ratio had minimal influence on the binding capacity of the sensor surface. As a simple and environmentally highly relevant model, binding of the plasticizer diethyl phthalate (DEP) via π-stacking was monitored on the rGO gold nanohole array realizing a limit of detection of as low as 20 nM. The concentration-dependent signal change was studied with the best performing rGO-modified nanohole arrays. Compared to continuous gold films a diameter-to-periodicity ratio (D/P) of 0.43 lead to a 12-fold signal enhancement. Finally, the effect of environmental waters on the sensor was evaluated using samples from sea, lake and river waters spiked with analytically relevant amounts of DEP during which significant changes in the SPR signal are observed. It is expected that this concept can be successfully transferred to enhance the sensitivity in SPR sensors.

Evaluation of 5-fluorouracil pharmacokinetics in cancer patients with a c.1905+1G>A mutation in DPYD by means of a Bayesian limited sampling strategy.

BACKGROUND AND OBJECTIVE: Dihydropyrimidine dehydrogenase (DPD) is the initial enzyme in the catabolism of 5-fluorouracil (5FU) and DPD deficiency is an important pharmacogenetic syndrome. So far, only very limited information is available regarding the pharmacokinetics of 5FU in patients with a (partial) DPD deficiency and no limited sampling models have been developed taking into account the non-linear pharmacokinetic behaviour of 5FU. The aim of this study was to evaluate the pharmacokinetics of 5FU and to develop a limited sampling strategy to detect decreased 5FU elimination in patients with a c.1905+1G>A-related DPD deficiency. METHODS: Thirty patients, heterozygous for the c.1905+1G>A mutation in DPYD, and 18 control patients received a dose of 5FU 300 mg/m2 and/or 5FU 450 mg/m2, followed by pharmacokinetic analysis of the 5FU plasma levels. A population pharmacokinetic analysis was performed in order to develop a compartmental pharmacokinetic model suitable for a limited sampling strategy. Clinical aspects of treating DPD-deficient patients with 5FU-based chemotherapy were assessed from the retrospectively collected clinical data. RESULTS: In a two-compartment model with Michaelis-Menten elimination, the mean maximum enzymatic conversion capacity (V(max)) value was 40% lower in DPD-deficient patients compared with controls (p < 0.001). Using a limited sampling strategy, with V(max) values calculated from 5FU concentrations at 30 or 60 minutes, significant differences were observed between DPD-deficient patients and controls at both dose levels (p < 0.001). The positive predictive value and negative predictive value for V(max), calculated from 5FU levels at 60 minutes, were 96% and 88%, respectively, in patients treated with a single dose of 5FU 300 mg/m2. All seven DPD-deficient patients (two males and five females) who had been genotyped prior to initiation of standard 5FU-containing chemotherapy developed grade 3-4 toxicity, with one case of lethal toxicity in a female patient. No grade 4 toxicity or lethal outcome was observed in 13 DPD-deficient patients treated with reduced doses of 5FU. The average dose of 5FU in DPD-deficient patients with mild toxicity (grade ≤2) was 61 ± 16% of the normal 5FU dose (n = 10). CONCLUSIONS: Profound differences in the elimination of 5FU could be detected between DPD-deficient patients and control patients. Pharmacokinetic 5FU profiling, using a single 5FU concentration at 60 minutes, may be useful for identification of DPD-deficient patients in order to reduce severe toxicity. Furthermore, treatment of DPD-deficient patients with standard 5FU-containing chemotherapy was associated with severe (lethal) toxicity.

Lymph node status and TS gene expression are prognostic markers in stage II/III rectal cancer after neoadjuvant fluorouracil-based chemoradiotherapy.

PURPOSE: According to the CAO/ARO/AIO-94 trial of the German Rectal Cancer Study Group, preoperative combined fluorouracil (FU) -based long-term chemoradiotherapy (CT/RT) is recommended for patients with International Union Against Cancer (UICC) stage II/III rectal cancer. However, despite the local benefit of neoadjuvant treatment, the overall prognostic value remains uncertain in comparison with adjuvant CT/RT. Furthermore, the prognostic value of molecular biomarkers, such as thymidylate synthase (TS), thymidine phosphorylase (TP), and dihydropyrimidine dehydrogenase (DPD), all of which are involved in the FU metabolism, is unknown in neoadjuvant settings. We assessed the impact of standardized preoperative CT/RT and intratumoral TS, TP, and DPD levels on patient outcome. PATIENTS AND METHODS: Forty patients with rectal cancer pretherapeutic UICC stage II/III, receiving preoperative FU-based CT/RT (CAO/ARO/AIO-94 trial) followed by standardized surgery, including total mesorectal excision, were investigated. Downsizing, downstaging, tumor regression, as well as TS, TP, and DPD gene expression of post-treatment surgical specimens were correlated with disease-free survival (DFS) and overall survival (OS). RESULTS: Significant downsizing (P < .001) and downstaging (P = .001) were achieved with preoperative CT/RT. During a median follow-up of 49 months (95% CI, 43 to 58 months), the cancer recurrence rate was 28.2%. DFS and OS were significantly increased in patients with downstaging (P < .001 and P = .003, respectively), compared with patients without downstaging. All patients who developed cancer recurrence had a persistent positive lymph node status after preoperative CT/RT (P < .001) and a significantly higher TS gene expression (P = .035) compared with those patients without recurrence. CONCLUSION: Persistent positive lymph node status and high intratumoral TS expression after preoperative CT/RT are predictive of an unfavorable prognosis in rectal cancer UICC stage II/III.

Prognostic value of histologic tumor regression, thymidylate synthase, thymidine phosphorylase, and dihydropyrimidine dehydrogenase in rectal cancer UICC Stage II/III after neoadjuvant chemoradiotherapy.

Histologic tumor regression (TR) in rectal cancer after preoperative chemoradiotherapy (CT/RT) may be useful as a surrogate end point for early treatment efficacy, but little is known about its prognostic value. The aim of this follow-up study was to evaluate whether TR is able to predict prognosis in rectal cancer patients. Furthermore, the prognostic value of thymidylate synthase (TS)-gene, thymidine phosphorylase (TP)-gene, and dihydropyrimidine dehydrogenase (DPD)-gene expression after neoadjuvant CT/RT was determined. Forty patients with rectal cancer cUICC stage II/III, receiving preoperative 5-fluorouracil (5-FU) based CT/RT were studied for therapy-induced TR and categorized as "responders" or "nonresponders" according to their TR-grade. Posttherapeutical TS-gene, TP-gene, and DPD-gene expression on surgical resection specimens was quantified by TaqMan real-time PCR after microdissection. During a median follow-up of 58 months, cancer recurrence occurred in 28%. A significant correlation was seen between disease-free survival and lymph node status (P<0.001). All patients, who developed cancer recurrence had a posttherapeutical positive lymph node status. The majority of patients with cancer recurrence were "responders" (91%) after CT/RT. There was a significant correlation between posttherapeutical TS-gene expression and cancer recurrence within the subgroup of "responders." TS-gene expression was significantly higher in patients with cancer recurrence than in those, who are disease-free up to date (P=0.028). In conclusion, lymph node status remains the most important prognostic marker in rectal cancer patients, whereas posttreatment TR by itself has no prognostic significance. Furthermore, measurement of posttherapeutical TS-gene expression may help to identify patients at higher risk for cancer recurrence.

Immunohistochemical analysis of thymidylate synthase, thymidine phosphorylase, and dihydropyrimidine dehydrogenase in rectal cancer (cUICC II/III): correlation with histopathologic tumor regression after 5-fluorouracil-based long-term neoadjuvant chemoradiotherapy.

In locally advanced rectal cancer, neoadjuvant 5-fluorouracil (5-FU)-based long-term chemoradiotherapy leads to marked tumor reduction and decrease of local recurrence rate. Thymidylate synthase (TS), thymidine phosphorylase (TP), and dihydropyrimidine dehydrogenase (DPD) are known to be important biomarkers to predict tumor response to 5-FU-based therapy. The aim of this study was to examine the correlation between TS, TP, and DPD protein expression and histopathologic tumor regression after neoadjuvant chemoradiotherapy. The results were compared with the recently published mRNA data. Preoperative biopsies (n = 25) and resection specimens (n = 40) from patients with rectal carcinoma (clinical UICC stage II/III) receiving neoadjuvant 5-FU-based chemoradiotherapy were studied for TS, TP, and DPD protein expression by immunohistochemistry using three different scoring systems (intensity, pattern, intensity + pattern). Results were compared with histopathologic tumor regression. A significant correlation between protein expression and tumor response was only seen when both staining intensity and staining pattern were considered. With this method, a significant association was seen between high TS expression in tumor biopsies as well as resection specimens and nonresponse of the tumor to therapy (P = 0.04). Furthermore, low TP expression in the resection specimens was significantly associated with lack of response (P = 0.02). For DPD no significant correlations were found at all. In conclusion, these results suggest that immunohistochemistry like RT-PCR is a suitable method to determine the correlation between TS, TP, and DPD expression and histopathologic tumor regression. However, precise results can only be achieved if staining intensity as well as staining pattern within the tumors are evaluated.

Thymidylate synthase, thymidine phosphorylase, dihydropyrimidine dehydrogenase expression, and histological tumour regression after 5-FU-based neo-adjuvant chemoradiotherapy in rectal cancer.

Pre-operative 5-fluorouracil (5-FU)-based chemoradiotherapy in locally advanced rectal cancer (UICC-II/III) may significantly reduce local tumour mass. Response to pre-operative treatment, however, varies significantly. Thymidylate synthase (TS), thymidine phosphorylase (TP), and dihydropyrimidine dehydrogenase (DPD) are thought to be important predictors for the efficiency of 5-FU-based treatment. The aim of this study was to determine the correlation between TS-, TP-, and DPD-gene expression and the response to 5-FU-based long-term pre-operative chemoradiotherapy assessed by histopathological tumour regression. Additionally, the predictive value of intra-tumoural TS-, TP-, and DPD-gene expression in pre-operative rectal tumour biopsies was assessed by correlation with the histopathological regression grade. Formalin-fixed, paraffin wax-embedded pre-operative biopsies (n = 14) and surgical resection specimens (n = 40) from patients with rectal carcinoma (clinical UICC stage II/III) receiving neo-adjuvant 5-FU-based chemoradiotherapy were studied for TS-, TP-, and DPD-gene expression by quantitative TaqMan real-time PCR after laser microdissection. Results were compared with standardized histopathological tumour regression analysis. There was a significant association between low TS-gene expression in pre-operative tumour biopsies and tumour response (p = 0.02). TS- and TP-gene expression was significantly lower in resection specimens of responders than of non-responders (p = 0.02) when microdissection was used. Statistical significance was even higher when TS and TP were combined (p = 0.0001). For the DPD gene, no significance was found at all. In conclusion, this study shows that TS gene expression in a pretreatment biopsy predicts the response of local rectal cancer to neo-adjuvant 5-FU-based chemoradiotherapy in a high percentage. Moreover, intra-tumoural TS- and TP-gene expression in surgical rectal specimens after neo-adjuvant chemoradiotherapy correlates significantly with histopathological tumour regression when microdissection is applied.

High-level mRNA quantification of proliferation marker pKi-67 is correlated with favorable prognosis in colorectal carcinoma.

PURPOSE: The present study retrospectively examines the expression of pKi-67 mRNA and protein in colorectal carcinoma and their correlation to the outcome of patients. METHODS: Immunohistochemistry and quantitative RT-PCR were used to analyze the expression of pKi-67 in 43 archival specimens of patients with curatively resected primary colorectal carcinoma, who were not treated with neo-adjuvant therapy. RESULTS: We determined a median pKi-67 (MIB-1) labeling index of 31.3% (range 10.3-66.4%), and a mean mRNA level of 0.1769 (DeltaC(T): range 0.01-0.69); indices and levels did not correlate. High pKi-67 mRNA DeltaC(T) values were associated with a significantly favorable prognosis, while pKi-67 labeling indices were not correlated to prognostic outcome. A multivariate analysis of clinical and biological factors indicated that tumor stage (UICC) and pKi-67 mRNA expression level were independent prognostic factors. CONCLUSION: Quantitatively determined pKi-67 mRNA can be a good and new prognostic indicator for primary resected colorectal carcinoma.

Thymidylate synthase and dihydropyrimidine dehydrogenase mRNA expression levels: predictors for survival in colorectal cancer patients receiving adjuvant 5-fluorouracil.

PURPOSE: Despite adjuvant 5-fluorouracil (5-FU) therapy, approximately 30% of patients with International Union against Cancer stage II and III colorectal cancer develop recurrence. In this study, we determined the prognostic value of thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) expression in colorectal cancer patients treated with adjuvant 5-FU. EXPERIMENTAL DESIGN: A real-time reverse transcription-PCR technique for quantitation of relative gene expression from paraffin-embedded specimen was established first. In a second step, archival paraffin-embedded primary tumor tissue of 309 patients who participated in adjuvant colorectal cancer trials was analyzed for TS and DPD mRNA expression. RESULTS: TS mRNA expression determined by real-time reverse transcription-PCR correlated with TS protein levels determined by TS immunoblot and immunohistochemistry in cultured colon cancer cell lines and paraffin-embedded primary tumor tissue. TS mRNA levels in fresh-frozen tissues also correlated with TS mRNA levels in corresponding paraffin sections. Among the patients receiving adjuvant 5-FU therapy, those with high TS survived longer than those with low TS, and in each TS subgroup, the ones with low DPD survived longer than the ones with high DPD levels. Multiple Cox regression analysis showed that besides tumor stage (P = 0.010), only the combination of TS and DPD expression turned out to be an independent prognostic factor for survival (P = 0.030). CONCLUSIONS: This suggests that TS and DPD quantitation may be helpful to evaluate prognosis of patients receiving adjuvant 5-FU and that patients with high TS and low DPD may benefit from adjuvant 5-FU chemotherapy.

Association of time to recurrence with thymidylate synthase and dihydropyrimidine dehydrogenase mRNA expression in stage II and III colorectal cancer.

Patients with International Union Against Cancer (UICC) stage IIb and III colon cancer and stage II and III rectal cancer may receive adjuvant chemotherapy with 5-fluorouracil (5-FU). High levels of thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) have been associated with resistance to 5-FU in advanced colorectal cancer. The aim of this study was to investigate the association of TS and DPD mRNA levels with recurrence-free survival in patients with colorectal cancer who are receiving adjuvant 5-FU-based chemotherapy. TS and DPD mRNA quantitation was retrospectively performed in primary colorectal cancer specimens from patients receiving adjuvant 5-FU using a reverse transcription- polymerase chain reaction technique. The median TS mRNA level in patients with a recurrence (n = 142) was 0.68, and in patients without a recurrence (n = 206) the median level was 0.80 (P < 0.01). Patients with a recurrence who had a low TS level (TS < or = 0.9; n = 102) had a median recurrence-free survival of 18 months (range 3.0 to 54 months), and those with a high TS level (TS > 0.9; n = 40) had a median recurrence-free survival of 11 months (range 1.7 to 53 months; P = 0.0024). There was no difference in the median recurrence-free survival of patients with low and high DPD mRNA levels. The TS mRNA level may be a useful marker to predict the time to recurrence in patients with colorectal cancer who are receiving adjuvant 5-FU treatment.