Smad4 inactivation predicts for worse prognosis and response to fluorouracil-based treatment in colorectal cancer.

AIMS: To determine whether expression of Smad4, a tumour suppressor found to be absent in 10% of colorectal cancer (CRC), is associated with outcomes in patients with CRC. METHODS: Tumour samples from 241 consecutive patients with CRC who underwent upfront colon resection between 2005 and 2009 were obtained. Triplicate tissue cores from resected primary colon tumours and matched normal controls were used to construct the tissue microarrays (TMAs). We examined the expression of Smad4 using immunohistochemistry. Clinicopathological records were obtained for all patients. TMAs were reviewed by two pathologists and scored as either 'positive' or 'negative' for nuclear staining. In total, 21 of 241 tumours (8.6%) were Smad4 negative. RESULTS: Loss of Smad4 expression correlated with significantly worse overall survival (OS) (p=0.011) and disease-free survival (DFS) (p=0.024). Patients with loss of Smad4 expression had a median OS of 31 months compared with 89 months positive Smad4 expression. Loss of Smad4 remained significant on multivariate analysis for OS (p=0.0097). In patients with node-positive disease, loss of Smad4 predicts for worse DFS (p=0.012). In patients with metastatic and recurrent disease, Smad4 loss predicts for worse OS (p=0.012). Of the patients that received capecitabine over the course of their treatment, those with Smad4 loss (n=13) had significantly worse DFS (p=0.003) and OS (p=0.0007). CONCLUSIONS: Loss of Smad4 expression is associated with worse DFS and OS in multiple subsets of patients with CRC. Further studies are required to validate our findings and ascertain the role of Smad4 status in the management of this disease.

A disposable tear glucose biosensor-part 1: design and concept testing.

BACKGROUND: Tear glucose has been suggested previously as a potential approach for the noninvasive estimation of blood glucose. While the topic remains unresolved, an overview of previous studies suggests the importance of a tear sampling approach and warrants new technology development. A concept device is presented that meets the needs of a tear glucose biosensor. METHODS: Three approaches to chronoamperometric glucose sensing were evaluated, including glucose oxidase mediated by potassium ferricyanide or oxygen with a hydrogen peroxide catalyst, Prussian blue, and potassium ferricyanide-mediated glucose dehydrogenase. For tear sampling, calcium alginate, poly(2-hydroxyethyl methacrylate), and polyurethane foam were screened as an absorbent tear sampling material. A quantitative model based on the proposed function of concept device was created. RESULTS: For glucose sensing, it was found that potassium ferricyanide with glucose dehydrogenase was ideal, featuring oxygen insensitivity, long-term stability, and a lower limit of detection of 2 muM glucose. Polyurethane foam possessed all of the required characteristics for tear sampling, including reproducible sampling from a hydrogel-simulated, eye surface (4.2 +/- 0.5 microl; n = 8). It is estimated that 100 microM of glucose tear fluid would yield 135 nA (14.9% relative standard deviation). CONCLUSION: A novel concept device for tear glucose sampling was presented, and the key functions of this device were tested and used to model the performance of the final device. Based on these promising initial results, the device is achievable and within reach of current technical capabilities, setting the stage for prototype development.

A disposable tear glucose biosensor-part 2: system integration and model validation.

BACKGROUND: We presented a concept for a tear glucose sensor system in an article by Bishop and colleagues in this issue of Journal of Diabetes Science and Technology. A unique solution to collect tear fluid and measure glucose was developed. Individual components were selected, tested, and optimized, and system error modeling was performed. Further data on prototype testing are now provided. METHODS: An integrated fluidics portion of the prototype was designed, cast, and tested. A sensor was created using screen-printed sensors integrated with a silicone rubber fluidics system and absorbent polyurethane foam. A simulated eye surface was prepared using fluid-saturated poly(2-hydroxyethyl methacrylate) sheets, and the disposable prototype was tested for both reproducibility at 0, 200, and 400 microM glucose (n = 7) and dynamic range of glucose detection from 0 to 1000 microM glucose. RESULTS: From the replicated runs, an established relative standard deviation of 15.8% was calculated at 200 microM and a lower limit of detection was calculated at 43.4 microM. A linear dynamic range was demonstrated from 0 to 1000 microM with an R(2) of 99.56%. The previously developed model predicted a 14.9% variation. This compares to the observed variance of 15.8% measured at 200 microM glucose. CONCLUSION: With the newly designed fluidics component, an integrated tear glucose prototype was assembled and tested. Testing of this integrated prototype demonstrated a satisfactory lower limit of detection for measuring glucose concentration in tears and was reproducible across a physiological sampling range. The next step in the device design process will be initial animal studies to evaluate the current prototype for factors such as eye irritation, ease of use, and correlation with blood glucose.