MUTYH-associated polyposis - colorectal phenotype and management.

AIM: The aim was to determine the presentation, management and outcomes of MUTYH-associated polyposis (MAP). METHOD: A prospectively maintained database was used to identify patients with MAP. Demographic data and data on germline mutation, surgical management, histopathology of tumours and endoscopic surveillance were collected. RESULTS: In all, 134 patients with MAP were identified. The majority presented symptomatically (n = 83). Sixty-eight patients developed cancer (seven synchronous, 12 metachronous). The median age at diagnosis of first colorectal cancer was 47 years (range 33-74 years). Cancers occurred in the context of a few adenomas (< 10). The majority of patients (n = 108) had surgery as the first line management. One patient received palliative care. Twenty-five patients had endoscopic surveillance as first line management; no cancers occurred in this group. Patients who had segmental resection and postoperative surveillance still appeared to be at risk of metachronous cancer (5/30, 17%). CONCLUSIONS: MUTYH testing should be considered even in the context of cancers occurring with fewer than 10 adenomas. In cases of primary colorectal cancers, extended surgery should be considered if patients do not have access to high quality endoscopic surveillance postoperatively. For some patients, endoscopic therapy is an appropriate and safe option in expert hands.

Outcomes following laparoscopic rectal cancer resection by supervised trainees.

BACKGROUND: The aim was to evaluate the applicability of laparoscopic surgery in the treatment of primary rectal cancer in a training unit. METHODS: A cohort analysis was undertaken of consecutive patients undergoing elective surgery for primary rectal cancer over a 7-year interval. Data on patient and operative details, and short-term clinicopathological outcomes were collected prospectively and analysed on an intention-to-treat basis. RESULTS: A total of 306 patients (213 men, 69·6 per cent) of median (i.q.r.) age 67 (58-73) years with a median body mass index of 26·6 (23·9-29·9) kg/m(2) underwent surgery. Median tumour height was 8 (6-11) cm from the anal verge, and 46 patients (15·0 per cent) received neoadjuvant radiotherapy. Seven patients (2·3 per cent) were considered unsuitable for laparoscopic surgery and underwent open resection; 299 patients (97·7 per cent) were suitable for laparoscopic surgery, but eight were randomized to open surgery as part of an ongoing trial. Some 291 patients (95·1 per cent) underwent a laparoscopic procedure, with conversion required in 29 (10·0 per cent). Surgery was partially or completely performed by trainees in 72·4 per cent of National Health Service patients (184 of 254), whereas private patients underwent surgery primarily by consultants. Median postoperative length of stay for all patients was 6 days and the positive circumferential resection margin rate was 4·9 per cent (15 of 306). CONCLUSION: Supervised trainees can perform routine laparoscopic rectal cancer resection.

An analysis of the accuracy of computed tomography colonography when defining anatomy for novel full-thickness colonic excision techniques in early colonic neoplasia.

AIM: Full-thickness laparo-endoscopic excision (FLEX) is a new technique developed for the full-thickness excision of colonic adenomas and, potentially, early cancer, avoiding the need for colectomy. FLEX requires accurate preoperative characterization of three key morphological features of the tumour, including its relation to the mesenteric border, its diameter and the circumferential extent of involvement of the bowel wall. This study evaluated the accuracy of CT colonography (CTC) for the assessment of these features in early colonic tumours. METHOD: Consecutive patients undergoing CTC prior to colonic resection for complex benign polyps or UICC Stage 1 cancer were retrospectively analysed by two specialist gastrointestinal radiologists blinded to the subsequent histopathological findings. The location of the tumour in relation to the mesenteric border, its maximum diameter and the circumferential extent of involvement of the colonic wall were correlated with the histopathological examination of the surgical resection specimen. Pearson's correlation coefficient (r) and Kappa agreement (κ) were used to compare the maximum diameter and the circumferential extent of involvement of the colonic wall. RESULTS: Twenty-eight patients with early colonic neoplasia were included. All had had a surgical segmental resection. Four had a benign adenoma and 24 had a TNM Stage 1 cancer. Histopathological assessment of the resected surgical specimen showed that 21 of the 28 lesions were located on the mesenteric border. The median diameter was 35 (interquartile range 28-42) mm; 13 lesions involved less than one-third of the circumference, 11 between one and two-thirds and four more than two-thirds. CTC correctly identified the location of the lesion in relation to the mesenteric border in all 28 cases. Correlation between CTC and histopathology was good for the assessment of the maximum diameter of the lesion (r = 0.81) and the circumferential extent of involvement of the colonic wall (κ = 0.76). CONCLUSION: CTC can accurately assess the key morphological features for the selection of patients with early colonic neoplasia for full-thickness laparo-endoscopic excision.

Role of SMAD proteins in colitis-associated cancer: from known to the unknown.

Small mothers against decapentaplegic (SMAD) proteins are a family of signal transduction molecules in transforming growth factor ß (TGFß) ligand pathways that have been found to have a key role in the pathogenesis of inflammatory bowel disease (IBD). Long standing IBD predisposes individuals to colitis-associated colorectal cancer (CAC), an entity that possess unique characteristics compared to hereditary and sporadic cancer. The ligands of the TGFß super family along with SMADs have also been implicated in several aspects of colorectal cancer formation. SMAD proteins are shown to be involved in a number of potentially carcinogenic mechanisms such as altering gene transcription, controlling stem cell differentiation to causing epigenetic changes. Modulation of these proteins has emerged as a novel therapeutic intervention for IBD although its effect on carcinogenesis remains elusive. This account reviews available evidence linking SMAD proteins to CAC and explores the potential areas for future research in this area.

Inhibition of COX-2 with NS-398 decreases colon cancer cell motility through blocking epidermal growth factor receptor transactivation: possibilities for combination therapy.

UNLABELLED: The use of non-steroidal anti-inflammatory drugs has proved of great interest in the prevention and treatment of colorectal cancer, although their precise mechanisms of action remain unclear. Overexpression of cyclooxygenase-2 (COX-2) and subsequent prostaglandin production promote metastasis and have been shown to increase cell motility in vitro. OBJECTIVE: We have aimed to elucidate whether specific inhibition of COX-2 with NS-398 (NS-398 is a selective inhibitor of COX-2) would be able to inhibit motility of colorectal cancer cells and whether this was modulated through epidermal growth factor receptor (EGFR) transactivation. MATERIALS AND METHODS: A transwell filter assay was used to study cell motility. Expression of COX-2, EGFR phosphorylation and prostaglandin E(2) (PGE(2)) receptors were assessed by Western blot analysis and reverse transcriptase-polymerase chain reaction. PGE(2) concentrations after NS-398 treatment were estimated by enzyme immunoassay. RESULTS: Treatment with NS-398 significantly reduced PGE(2) levels and reduced cell migration in the HT29 and HCA7 colorectal carcinoma cell lines and this effect was rescued by addition of PGE(2). Furthermore, specific inhibition of COX-2 with NS-398 reduced EGFR phosphorylation in colorectal cancer cells. Direct inhibition of EGFR activity with AG1478 reduced PGE(2)-stimulated motility, clearly demonstrating that PGE(2 )acts via the EGFR-signalling pathway. The novel combination of NS-398 and AG1478 dramatically reduced migration of colorectal cancer cells. CONCLUSION: The data presented indicate that the use of NS-398 in chemoprevention and adjuvant therapy for colorectal cancer may work in part, through the inhibition of cell motility. Furthermore, our data suggest that the combined use of non-steroidal anti-inflammatory drugs with EGFR antagonists could be explored further for future use in the clinic.

A pilot study to assess near infrared laparoscopy with indocyanine green (ICG) for intraoperative sentinel lymph node mapping in early colon cancer.

BACKGROUND: Previous attempts at sentinel lymph node (SLN) mapping in colon cancer have been compromised by ineffective tracers and the inclusion of advanced disease. This study evaluated the feasibility of fluorescence detection of SLNs with indocyanine green (ICG) for lymphatic mapping in T1/T2 clinically staged colonic malignancy. METHODS: Consecutive patients with clinical T1/T2 stage colon cancer underwent endoscopic peritumoral submucosal injection of indocyanine green (ICG) for fluorescence detection of SLN using a near-infrared (NIR) camera. All patients underwent laparoscopic complete mesocolic excision surgery. Detection rate and sensitivity of the NIR-ICG technique were the study endpoints. RESULTS: Thirty patients mean age = 68 years [range = 38-80], mean BMI = 26.2 (IQR = 24.7-28.6) were studied. Mesocolic sentinel nodes (median = 3/patient) were detected by fluorescence within the standard resection field in 27/30 patients. Overall, ten patients had lymph node metastases, with one of these patients having a failed SLN procedure. Of the 27 patients with completed SLN mapping, nine patients had histologically positive lymph nodes containing malignancy. 3/9 had positive SLNs with 6 false negatives. In five of these false negative patients, tumours were larger than 35 mm with four also being T3/T4. CONCLUSION: ICG mapping with NIR fluorescence allowed mesenteric detection of SLNs in clinical T1/T2 stage colonic cancer. CLINICALTRIALS.GOV: ID: NCT01662752.

Basiliximab for the treatment of steroid-resistant ulcerative colitis: further experience in moderate and severe disease.

BACKGROUND: Preliminary data have suggested that interleukin-2 receptor blockade with basiliximab may increase steroid sensitivity. We have previously reported a small case series demonstrating the potential of basiliximab as a novel agent for the treatment of steroid-resistant ulcerative colitis. AIM: To report further experience of the efficacy and safety of treatment with the interleukin-2 receptor blocking monoclonal antibody basiliximab, in addition to steroids, for the treatment of severe and moderate steroid-resistant ulcerative colitis. METHODS: Twenty patients were enrolled - 13 patients with moderate steroid-resistant ulcerative colitis (Ulcerative Colitis Symptom Score: >or=6) and seven patients with severe steroid-resistant ulcerative colitis. All were given a single dose of 40 mg basiliximab plus standard steroid therapy in an open-label, uncontrolled trial. Primary end point was clinical remission within 8 weeks (Ulcerative Colitis Symptom Score:

Increased p53-dependent apoptosis by the insulin-like growth factor binding protein IGFBP-3 in human colonic adenoma-derived cells.

We investigated the expression of insulin-like growth factor binding protein 3 (IGFBP-3) in normal human colonic epithelium and whether IGFBP-3 is involved in the induction of apoptosis in colonic epithelial cells. A gradient of IGFBP-3 protein expression was observed within the normal colonic crypt, and increased IGFBP-3 expression was coincident with the region of increased differentiation and apoptosis. Treatment of human colonic tumor cell lines with IGFBP-3 alone was shown to have no effect on growth. However, an increase in p53-dependent apoptosis was observed in the presence of 100 ng/ml IGFBP-3 24 h after the induction of DNA damage by gamma-irradiation. These results suggest that IGFBP-3 enhances the p53-dependent apoptotic response of colorectal cells to DNA damage.

BCL-2 expression in human colorectal adenomas and carcinomas.

As BCL-2 oncoprotein has been implicated as a survival factor in a number of tissues, we examined colorectal tumour specimens and cell lines for BCL-2 expression. BCL-2 protein was expressed in 19/22 adenocarcinomas and 12/13 adenomas. 6/9 carcinoma cell lines and 7/8 adenoma cell lines were also BCL-2 positive. BCL-2 expression was retained in metastases to the regional lymph nodes (3/3 specimens) and in the cell line SW620, derived from a lymph node metastasis. These studies suggest a role for BCL-2 in promoting cell survival of benign and malignant colorectal tumours and that BCL-2 deregulation may be a relatively early event in colorectal carcinogenesis. The retention of BCL-2 expression in the carcinomas and lymph node metastases may explain the resistance of colorectal tumours to chemotherapeutic treatment.

Characterisation of adherens and tight junctional molecules in normal animal larynx; determining a suitable model for studying molecular abnormalities in human laryngopharyngeal reflux.

BACKGROUND: The disruption of intercellular junctions in the larynx is a pathological feature of laryngopharyngeal reflux (LPR). Good experimental models are necessary to gain greater insight into the molecular mechanisms and alterations that result from abnormal exposure of the laryngeal epithelium to acid refluxate. AIMS: To characterise laryngeal tissues from different species to determine the most suitable for use in experimental studies of LPR. METHODS: Human and non-human laryngeal tissues (mouse, rat, guinea pig, porcine, and rabbit) were studied. Histological characterisation was performed by light microscopy. The expression and subcellular localisation of adherens junctional molecules (E-cadherin and beta catenin) was evaluated by immunohistochemistry, and tight junction molecules (occludin and zonula occludens 1 (ZO-1)) by western blotting. The ultrastructural features of porcine and human tissue were assessed by electron microscopy. RESULTS: Porcine tissue revealed both respiratory-type and stratified squamous epithelium, as seen in the human larynx. The expression and subcellular localisation of the E-cadherin-catenin complex was detected in all species except mouse and rat. The pattern of ZO-1 and occludin expression was preserved in all species. CONCLUSION: The expression of intercellular junctional complexes in porcine epithelium is similar to that seen in humans. These results confirm the suitability of these species to study molecular mechanisms of LPR in an experimental system.

Sulindac enhances cell proliferation in DMH-treated mouse colonic mucosa.

In a previous study we reported that the NSAID sulindac had a marked inhibitory effect on the development of colonic tumours in mice treated with the carcinogen 1,2-dimethylhydrazine (DMH). In this study we examined the effects of sulindac in respect of cell-kinetic changes in mouse colonic mucosa as determined by flash labelling with the thymidine analogue bromodeoxyuridine (BrdUrd) at varying intervals during the process of colonic carcinogenesis. We also investigated the possibility that these changes may be modulated by misoprostol a prostaglandin E1 analogue. Four groups of 36 mice each were treated for 18 weeks with the following drug/s respectively: (1) DMH; (2) DMH and sulindac; (3) DMH, sulindac and misoprostol; and (4) DMH and misoprostol. Three animals from each group were killed each week between the sixth week and the eighteenth week after the start of the experiment. A 1-h flash label technique was employed and paraffin sections of colonic mucosa were examined. For each animal a total of 50 perfect axially cut crypts were chosen and the following parameters determined: crypt length, labelling index and labelling index distribution: the data were analysed using the computer program GLIM. For each of the four groups, crypt lengths increased significantly with the duration of treatment with no significant difference between the groups. In sulindac-treated animals the labelling index for all positions increased with duration of treatment whereas for animals not treated with sulindac there was no significant difference in labelling index with respect to duration of treatment. The administration of misoprostol did not appear to significantly alter the effects of sulindac. It is postulated that the observed increase in cell proliferation could be a compensatory phenomenon occurring secondary to loss of crypt epithelial cells by apoptosis induced by sulindac. Also the finding of an increase in labelling index mediated by a chemopreventive agent indirectly questions the rationale behind the therapeutic manipulation of crypt cell proliferation in order to reduce the risk of colon cancer.

Modulation by verapamil of vincristine pharmacokinetics and sensitivity to metaphase arrest of the normal rat colon in organ culture.

The in-vitro pharmacokinetics of vincristine (VCR) in normal rat colonic mucosa were studied. Two complementary approaches were adopted using an explant organ-culture system. Firstly [G-3H]vincristine (3HVCR) accumulation, retention and efflux were characterized under basal conditions and compared with measurements made either under energy-depleted conditions, or in the presence of VRP. Secondly, a histological method--the postmetaphase index (PMI)--was used to compare the sensitivity of explants to VCR in the presence or absence of verapamil (VRP). This latter technique involves the measurement, by counting, of the proportion of mitotic figures escaping from metaphase arrest. The studies yielded the following results: 3HVCR accumulation in colonic mucosa showed no evidence of saturability up to the maximum dose studied (130 nM), at a dose of 52 nM accumulation was enhanced in energy-depleted conditions by a factor of 1.8, and in the presence of VRP (6.6 microM) by a factor of 1.4. In the presence of VRP (6.6 microM) retention of 3HVCR was increased by a factor of 1.3 and efflux was reduced by a factor of 0.8 after 2 hr. VRP (6.6 microM) reduced the PMI of colonic mucosal epithelial cells exposed to 11 nM VCR from 18.8% to 11.4% (i.e. 40% reduction) indicating sensitization of the cells to this property of VCR. These results provide evidence that the sensitivity of normal colonic mucosa to vincristine is, at least in part, regulated by drug transport. Qualitatively our observations resemble those described in multidrug resistance. Given that P-glycoprotein has been demonstrated by several groups in colonic mucosal cells, the results support a normal role for this membrane transport molecule in the protection of intestinal cells from plant alkaloids and other xenobiotic agents ingested in the diet.

Basiliximab (anti-CD25) in combination with steroids may be an effective new treatment for steroid-resistant ulcerative colitis.

BACKGROUND: Steroid resistance represents a major clinical problem in the treatment of ulcerative colitis. In vitro, interleukin-2 renders lymphocytes steroid resistant. AIM: To explore the therapeutic potential of interleukin-2 receptor blockade in steroid-resistant ulcerative colitis with both in vitro measures and a pilot in vivo study. METHODS: Ten patients with steroid-resistant ulcerative colitis received a single bolus of 40 mg of intravenous basiliximab plus steroid treatment in an open-label, uncontrolled, 24-week study. The outcome was assessed using the Ulcerative Colitis Symptom Score, rectal biopsy and Inflammatory Bowel Disease Questionnaire. Lymphocyte steroid sensitivity was measured in vitro in 39 subjects in the presence or absence of basiliximab. RESULTS: Nine of the 10 patients achieved clinical remission within 8 weeks. At 24 weeks, seven patients were in clinical remission. Marked improvement in the Ulcerative Colitis Symptom Score was seen by 1 week (P = 0.004) and on rectal biopsy and Inflammatory Bowel Disease Questionnaire by 2 weeks (both P < 0.05). Improvements persisted to 24 weeks (Ulcerative Colitis Symptom Score, Inflammatory Bowel Disease Questionnaire, both P < 0.005). Eight of the nine responders relapsed (median, 9 weeks), but remission was re-achieved with further corticosteroids and the addition of azathioprine. At 24 weeks, seven patients were in full clinical remission, five off all steroid therapy. In vitro measurement of lymphocyte steroid sensitivity demonstrated steroid resistance in 22% of subjects. All were rendered steroid sensitive in the presence of basiliximab. CONCLUSIONS: Basiliximab appears to be effective at inducing remission in steroid-resistant ulcerative colitis. In vitro, basiliximab also produced a dramatic increase in lymphocyte steroid sensitivity in healthy subjects. Confirmation in randomized controlled studies is required.

c-erbB-2 overexpression in the dysplasia/carcinoma sequence of Barrett's oesophagus.

AIMS--To investigate overexpression of the oncoprotein c-erbB-2 in the dysplasia/carcinoma sequence of Barrett's columnar-lined oesophagus (CLO). METHODS--Immunohistochemical staining was performed using the monoclonal antibody NCL-CB-11 on formalin fixed tissue from 31 cases of Barrett's carcinoma, 20 cases of cancer associated dysplastic CLO, seven cases of dysplastic CLO without cancer, and 20 cases of non-dysplastic CLO. Membranous staining was regarded as positive for c-erbB-2 overexpression; cytoplasmic staining was recorded separately as its significance is uncertain. RESULTS--Membranous c-erbB-2 overexpression was observed in eight of 31 (26%) carcinomas and in none of the cases of dysplastic CLO. Variable cytoplasmic staining was seen in four of 31 (13%) tumours and seven of 27 (26%) cases of dysplastic CLO. No staining was observed in non-dysplastic CLO. CONCLUSIONS--C-erbB-2 overexpression is a relatively late event in the development of some Barrett's carcinomas and is unlikely to be involved in the early stages of neoplastic transformation of CLO.

Upper gastrointestinal cancer pathology reporting: a regional audit to compare standards with minimum datasets.

AIMS: Accurate pathological (pTNM) staging of oesophageal and gastric cancer provides important prognostic information. The aim of this study was to compare the standard of pathology reporting of oesophageal and gastric cancer resections from a cancer network with standards set by the Royal College of Pathologists. METHODS: All reports for oesophageal and gastric cancer resections from the five hospitals in the cancer network in 2001 were collected. Individual items of information were compared with minimum datasets provided by the Royal College of Pathologists. Items were classified as "complete", "partially complete", or "absent". RESULTS: One hundred and ten reports were audited (54 oesophageal and 56 gastric). Fourteen gastric and 17 oesophagectomy reports were over 75% complete. Clinically important missing data occurred most frequently for the pM component of TNM staging (pMx omitted in 87 reports) and completeness of resection expressed as a bold statement (absent in 50 reports). Twelve reports could not be classified because the specimen contained no residual tumour after neoadjuvant treatment. CONCLUSION: The use of a standard proforma for reporting upper gastrointestinal cancers based on a minimum dataset provided by the Royal College of Pathologists is recommended, with modifications to allow for specimens with no tumour after neoadjuvant treatment.

Primary yolk sac tumour of the liver in adulthood.

Primary yolk sac tumour of the liver is exceedingly rare. A 28 year old woman presented with a cystic liver mass and a markedly raised serum alpha-fetoprotein concentration. She underwent a partial hepatectomy for a suspected hepatocellular carcinoma but histological examination of the tumour revealed the classical morphological and immunohistochemical features of a yolk sac tumour. There was no evidence of an extrahepatic primary source. Review of this case, together with the six previously reported adult cases of primary yolk sac tumours of the liver, revealed several features of the tumour that may aid differentiation from hepatocellular carcinoma, with potential therapeutic implications.

Epidermal growth factor receptors in colorectal carcinoma.

Nineteen samples of primary colorectal carcinoma and adjacent mucosa were examined for EGFr expression using radioligand binding assays and immunohistochemical staining with the monoclonal antibody EGFR1. Radioligand binding experiments showed expression of EGFr in both tumour and mucosa in all cases. In tumour samples EGFr levels ranged between 4 and 79 fmole per mg membrane protein (Kd = 0.1-0.4 X 10(-9) M). There was no significant difference in the level of EGFr expression between tumour and mucosa overall. Immunohistochemical staining with the EGFR1 antibody was useful in localising EGFr to epithelial elements although it was less sensitive than ligand binding assays.

Cost-effective strategy for the serological investigation of coeliac disease.

Increased numbers of requests for serological investigation of coeliac disease, and a local trend to request both anti-gliadin antibodies (AGA) and anti-endomysium antibodies (AEA) simultaneously, resulted in cost pressures that prompted a review of our practice. Serology results from all patients (771 children, 511 adults) investigated for coeliac disease over a 3-year period were compared with small intestine histology where available. IgG AGA and IgA AGA were measured by enzyme-linked immunosorbent assay (in-house), IgA AEA by immunofluorescence (send-away contract). Overall diagnostic performance was as follows: AGA sensitivity 84%, specificity 88%, positive predictive value (PPV) 24%, negative predictive value (NPV) 99%; AEA sensitivity 88%, specificity 97%, PPV 65%, NPV 99%. Results showed AGA, with its high NPV, to be a suitable first-line test to exclude coeliac disease. The high specificity of AEA makes it a suitable confirmatory test when AGA is positive. Introduction of this step-wise approach to coeliac disease investigation resulted in cost savings of at least Pound Sterling 5000 per year without detriment to the clinical service.

Plexiform neurofibroma of the small bowel infiltrated with metastatic adenocarcinoma.

Neurofibromatosis Type 1 (NF1) is not classically associated with gastrointestinal manifestations although these patients are at increased risk of several GI complications. We describe the ultrasound, CT and barium findings in a patient with NF1 who had a huge benign plexiform neurofibroma of the ileum that was infiltrated with metastatic adenocarcinoma.

The proapoptotic BH3-only protein Bim is downregulated in a subset of colorectal cancers and is repressed by antiapoptotic COX-2/PGE(2) signalling in colorectal adenoma cells.

Overexpression of cyclooxygenase-2 (COX-2) and elevated levels of its enzymatic product prostaglandin E2 (PGE(2)) occur in the majority of colorectal cancers and have important roles in colorectal tumorigenesis. However, despite the established prosurvival role of PGE(2) in cancer, the underlying mechanisms are not fully understood. Here, we have shown that PGE(2) suppresses apoptosis via repression of the proapoptotic BH3-only protein Bim in human colorectal adenoma cells. Repression of Bim expression was dependent upon PGE(2)-mediated activation of the Raf-MEK-ERK1/2 pathway, which promoted Bim phosphorylation and proteasomal degradation. Reduction of Bim expression using RNA interference reduced spontaneous apoptosis in adenoma cells and abrogated PGE(2)-dependent apoptosis suppression. Treatment of COX-2-expressing colorectal carcinoma cells with COX-2-selective NSAIDs-induced Bim expression, suggesting that Bim repression via PGE(2) signalling may be opposed by COX-2 inhibition. Examination of Bim expression in two established in vitro models of the adenoma-carcinoma sequence revealed that downregulation of Bim expression was associated with tumour progression towards an anchorage-independent phenotype. Finally, immunohistochemical analyses revealed that Bim expression is markedly reduced in approximately 40% of human colorectal carcinomas in vivo. These observations highlight the COX-2/PGE(2) pathway as an important negative regulator of Bim expression in colorectal tumours and suggest that Bim repression may be an important step during colorectal cancer tumorigenesis.