Fig. 2

Elevated XIAP protein levels prior to neoadjuvant radio chemotherapy indicate resistance to therapy in rectal cancer patients. Biopsy tissue samples of 29 rectal cancer patients were obtained at colonoscopy or rigid sigmoidoscopy. a Representative Western blot images for 6 patients (3 RCPath A, 2 RCPath B and 1 RCPath C) are shown in Fig. 2a. The expression levels of XIAP and Smac in tumour (T) and matched normal tissue (N) were determined by quantitative Western blotting. Beta Actin was used as a loading control. HeLa cells were used as a standard. b Protein expression levels for all 29 patients were then correlated with tumour regression grade. Levels of XIAP protein increased in accordance with radio chemotherapy resistance (p = 0.025) in tumour tissue. XIAP protein levels are also significantly raised in the tumour tissue compared to the matched normal tissue in RCPath C patients (p = 0.007). c Smac protein was not differentially expressed in RCPath grades. Furthermore there was no significant difference in Smac expression in tumour and matched normal tissue. (d, e) Expression levels of cIAP-1 (d) and cIAP-2 (e) were also determined by quantitative Western blotting in 14 biopsy tissues and then correlated with tumour regression grade. Neither protein was differentially expressed in RCPath grades nor was there a significant difference in expression in tumour and matched normal tissue