Unfavourable prognosis associated with K-ras gene mutation in pancreatic cancer surgical margins.

BACKGROUND: Despite intent to cure surgery with negative resection margins, locoregional recurrence is common in pancreatic cancer. AIMS: To determine whether detection of K-ras gene mutation in the histologically negative surgical margins of pancreatic cancer reflects unrecognised disease. PATIENTS: Seventy patients who underwent curative resection for pancreatic ductal adenocarcinoma were evaluated. METHODS: All patients had surgical resection margins (pancreatic transection and retroperitoneal) that were histologically free of invasive cancer. DNA was extracted from these paraffin embedded surgical margins and assessed by quantitative real time polymerase chain reaction to detect the K-ras gene mutation at codon 12. Detection of K-ras mutation was correlated with standard clinicopathological factors. RESULTS: K-ras mutation was detected in histologically negative surgical margins of 37 of 70 (53%) patients. A significant difference in overall survival was demonstrated between patients with margins that were K-ras mutation positive compared with negative (median 15 v 55 months, respectively; p = 0.0008). By univariate and multivariate analyses, detection of K-ras mutation in the margins was a significant prognostic factor for poor survival (hazard ratio (HR) 2.8 (95% confidence interval (CI) 1.5-5.3), p = 0.0009; and HR 2.8 (95% CI 1.4-5.5), p = 0.004, respectively). CONCLUSIONS: Detection of cells harbouring K-ras mutation in histologically negative surgical margins of pancreatic cancer may represent unrecognised disease and correlates with poor disease outcome. The study demonstrates that molecular-genetic evaluation of surgical resection margins can improve pathological staging and prognostic evaluation of patients with pancreatic ductal adenocarcinoma.

Hypophosphorylated retinoblastoma protein is associated with G2 arrest in esophageal squamous cell carcinoma.

Hypophosphorylated retinoblastoma (Rb) gene product binds critical transcription factors, leading to G1 arrest in a number of conditions, including following DNA damage. We have previously shown that irradiated esophageal squamous cell carcinoma (ESSC) cells undergo predominantly G2 arrest, with increases in inhibitors of Rb phosphorylation. We thus hypothesized that this G2 arrest would be accompanied by increases in hypophosphorylated Rb protein (pRb). We sequenced the Rb genes of three human ESSC lines (KYSE) following reverse transcription polymerase chain reaction of exons A-E. Western gels were performed on protein extracts for pRb. Cells were irradiated at 6 Gy, and protein was extracted at 6 h. ELISA was used to measure hypophosphorylated pRb in radiated versus control cells. Student's t test was used to compare results. All lines had wild-type Rb genes. Western gels confirmed the presence of pRb. There were significant increases in hypophosphorylated pRb in all three lines following irradiation (no line with less than a 100% increase). We have thus shown that irradiation-induced G2 arrest occurs in association with wild-type Rb genes and that there is associated hypophosphorylation of pRb. This supports our data describing a further role for other G1 mediators, such as p21, in G2 arrest. Further investigations into therapies to expoit this cell cycle checkpoint are warranted and planned.