To elucidate mechanisms of resistance to chemotherapies currently used in the first-line treatment of advanced colorectal cancer, we have developed a panel of HCT116 p53 wild-type (p53 ؉/؉ ) and null (p53 ؊/؊ ) isogenic colorectal cancer cell lines resistant to the antimetabolite 5-fluorouracil (5-FU), topoisomerase I inhibitor irinotecan (CPT-11), and DNA-damaging agent oxaliplatin. These cell lines were generated by repeated exposure to stepwise increasing concentrations of each drug over a period of several months. We have demonstrated a significant decrease in sensitivity to 5-FU, CPT-11, and oxaliplatin in each respective resistant cell line relative to the parental line as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis, with increases in IC 50 (72 h) concentrations ranging from 3-to 65-fold. Using flow cytometry, we have also demonstrated compromised apoptosis and cell cycle arrest in 5-FU-, oxaliplatin-, and CPT-11-resistant cell lines compared with the parental lines after exposure to each drug. In addition, we found that resistance to 5-FU and oxaliplatin was higher in parental p53 ؊/؊ cells compared with parental p53 ؉/؉ cells, with an ϳ5-fold increase in IC 50 (72 h) for each drug. In contrast, the IC 50 (72 h) doses for CPT-11 were identical in the p53 wild-type and null cell lines. Furthermore, apoptosis after treatment with 5-FU and oxaliplatin, but not CPT-11, was significantly reduced in parental p53 ؊/؊ cells compared with parental p53 ؉/؉ cells. These data suggest that p53 may be an important determinant of sensitivity to 5-FU and oxaliplatin but not CPT-11. Using semiquantitative reverse transcription-PCR, we have demonstrated down-regulation of thymidine phosphorylase mRNA in both p53 ؉/؉ and p53 ؊/؊ 5-FU-resistant cells, suggesting that decreased production of 5-FU active metabolites may be an important resistance mechanism in these lines. In oxaliplatin-resistant cells, we noted increased mRNA levels of the nucleotide excision repair gene ERCC1 and ATP-binding cassette transporter breast cancer resistance protein. In CPT-11-resistant cells, we found reduced mRNA levels of carboxylesterase, the enzyme responsible for converting CPT-11 to its active metabolite SN-38, and topoisomerase I, the SN-38 target enzyme. In addition, we noted overexpression of breast cancer resistance protein in the CPT-11-resistant lines. These cell lines are ideal tools with which to identify novel determinants of drug resistance in both the presence and absence of wild-type p53.

Expression of class II major histocompatibility complex (MHC) on monocytes is a prerequisite for effective antigen presentation and processing, an important component of the immune response to infection. It has been reported that the level of monocyte class II expression may identify patients who go on to develop infective complications following trauma. In the present study, flow cytometry was used to measure MHC class II (human leucocyte antigen (HLA)-DR) expression on circulating monocytes and T cells in 36 patients undergoing elective major resectional surgery, of whom 12 developed septic complications. The percentage of HLA-DR positive monocytes fell significantly on the first day after operation in both groups (P < 0.001) but was significantly higher in those without than in those with sepsis on days 1, 3 and 5 (P < 0.05). In contrast, the level of T cell HLA-DR expression rose significantly on the first day after operation (P < 0.05) in patients without sepsis to a level higher than in those who developed infection (P < 0.05). These findings have important implications, as predictive biological elements and for biological response modification, in patients at risk of developing sepsis after surgery.

ObjectiveThe authors described their experience with laparoscopic-assisted colorectal resection for colorectal carcinoma, both curative and palliative, with emphasis on patient selection. The techniques of the operations were described. Summary Background Data ResultsFourteen of 83 patients eventually required conversion to open surgery. The median operative time was 180 minutes. The patients could return to a normal diet in a median of 4 days. The median number of doses of analgesics required was two, and the median hospital stay was 6 days. The morbidity rate was 12%, and there was no deaths attributable to the procedure. There were four distant recurrences and one pelvic recurrence. ConclusionsLaparoscopic-assisted colorectal resection for selected patients is feasible, and early postoperative results are encouraging. This procedure does not appear to be associated with an excessive recurrence rate, and long-term follow-up is necessary for late survival figures.170