A dose escalation study of gemcitabine plus oxaliplatin in combination with imatinib for gemcitabine-refractory advanced pancreatic adenocarcinoma

BACKGROUND

Targeting platelet-derived growth factor receptor-β (PDGFR-β) is a potential strategy to reduce tumour-related interstitial fluid pressure, enhance cytotoxic drug uptake and reduce chemoresistance. This study aimed to define safe doses of gemcitabine plus oxaliplatin when combined with imatinib (potent PDGFR-β inhibitor) in patients with advanced gemcitabine-refractory pancreatic cancer (PC).

PATIENTS AND METHODS

Using a 3 + 3 dose escalation design, patients of performance status zero or one were entered into five sequential dose levels (DLs) of gemcitabine [day 1, from 400 (DL1) to 1000 mg/m(2) (DL4)] and oxaliplatin [day 2, 85 (DL1-4) and 100 mg/m(2) (DL5)] two weekly. Imatinib 400 mg od was given for 7 days (day minus 2-5) each cycle.

RESULTS

Twenty-seven patients received 168 cycles in total. Median age was 61 years (44-74 years). Dose-limiting toxicities occurred in two of two patients at DL5 (G4 thrombocytopenia, G3 lethargy), defined as the maximum tolerated dose and one of six patients at DL4 (G3 lethargy). DL4 was expanded. There were 2 of 27 partial responses and 14 of 27 stable disease [disease control 52%, 95% confidence interval (CI) 32% to 71%]. Median progression-free survival and overall survival were 4.6 (95% CI 2.1-7.0) and 5.6 months (95% CI 2.5-8.7), respectively.

CONCLUSION

In gemcitabine-refractory PC, gemcitabine (1000 mg/m(2)) and oxaliplatin (85 mg/m(2)) can be safely combined with imatinib given on a 7 days on and 7 days off intermittent schedule.

Characterization of putative stem cells in isolated human colonic crypt epithelial cells and their interactions with myofibroblasts

Colonic epithelial stem cells are believed to be located at the crypt base where they have previously been shown to express musashi-1. The colonic stem cell niche, which includes extracellular matrix and myofibroblasts (together with other cell types), is likely to be important in maintaining the function of the progenitor cells. The aims of our studies were to characterize stem cells in isolated and disaggregated human colonic crypt epithelial cells and investigate their interactions with monolayers of primary human colonic myofibroblasts. In unfractionated preparations of disaggregated colonic crypts, musashi-1 positive cells preferentially adhered to colonic myofibroblasts, despite the presence of excess blocking anti-beta(1)-integrin antibody. These adherent epithelial cells remained viable for a number of days and developed slender processes. Cells with side population characteristics (as demonstrated by ability to expel the dye Hoechst 33342) were consistently seen in the isolated colonic crypt epithelial cells. These side population cells expressed musashi-1, beta(1)-integrin, BerEP4, and CD133. Sorted side population crypt epithelial cells also rapidly adhered to primary colonic myofibroblasts. In conclusion, in preparation of isolated and disaggregated human colonic crypts, cells with stem cell characteristics preferentially adhere to primary human colonic myofibroblasts in a beta(1)-integrin-independent fashion.

The effect of component size and orientation on the concentrations of metal ions after resurfacing arthroplasty of the hip

Increased concentrations of metal ions after metal-on-metal resurfacing arthroplasty of the hip remain a concern. Although there has been no proven link to long-term health problems or early prosthetic failure, variables associated with high metal ion concentrations should be identified and, if possible, corrected. Our study provides data on metal ion levels from a series of 76 consecutive patients (76 hips) after resurfacing arthroplasty with the Articular Surface Replacement. Chromium and cobalt ion concentrations in the whole blood of patients with smaller (<or= 51 mm) femoral components were significantly higher than in those with the larger (>or= 53 mm) components (p < 0.01). Ion concentrations in the former group were significantly related to the inclination (p = 0.01) and anteversion (p = 0.01) of the acetabular component. The same relationships were not significant in the patients with larger femoral components (p = 0.61 and p = 0.49, respectively). Accurate positioning of the acetabular component intra-operatively is essential in order to reduce the concentration of metal ions in the blood after hip resurfacing arthroplasty with the Articular Surface Replacement implant.

Essential role of toxin A in C. difficile 027 and reference strain supernatant-mediated disruption of Caco-2 intestinal epithelial barrier function

Clostridium difficile induces mucosal inflammation via secreted toxins A and B and initial interactions between the toxins and intestinal epithelial cells (which lead to loss of barrier function) are believed to be important in disease pathogenesis. Secreted toxin-specific antibodies may inhibit such interactions. Using the Caco-2 epithelial cell line, we have investigated the use of an anti-toxin A monoclonal antibody (ATAA) in providing protection against toxin A-mediated disruption of epithelial barrier function (assessed by measurement of transepithelial electrical resistance and luminal to basolateral flux of labelled dextran). In contrast to free antibody, ATAA conjugated to sepharose beads was more effective in neutralizing the activity of purified toxin A. Sepharose bead-conjugated ATAA was subsequently used to investigate the contribution of toxin A in epithelial injury mediated by C. difficile supernatant samples (containing toxins A, B and other products). Loss of barrier function mediated by apical application of supernatant samples of reference and epidemic 027 strains of C. difficile was abrogated by neutralization of toxin A. However, this was not the case when the supernatant samples were applied to the basal surface of epithelial monolayers. In conclusion, our studies have shown that (i) sepharose bead-conjugated ATAA is more effective in neutralizing toxin A than free antibody and (ii) when the apical (luminal) surface of epithelial monolayers is exposed to the secretory products of reference and 027 strains of C. difficile, toxin A is required for the initial injury that leads to loss of barrier function.