Complications and survival after hybrid and fully minimally invasive oesophagectomy.

BACKGROUND: Minimally invasive oesophagectomy (MIO) is reported to produce fewer respiratory complications than open oesophagectomy. This study assessed differences in postoperative complications between MIO and hybrid MIO (HMIO) employing thoracoscopy and laparotomy, along with the influence of co-morbidities on postoperative outcomes. METHODS: Patients with oesophageal cancer undergoing three-stage MIO or three-stage HMIO between 1999 and 2018 were identified from a prospectively developed database, which included patient demographics, co-morbidities, preoperative therapies, and cancer stage. The primary outcome was postoperative complications in the two groups. Secondary outcomes included duration of operation, blood transfusion requirement, duration of hospital stay, and overall survival. RESULTS: There were 828 patients, of whom 722 had HMIO and 106 MIO, without significant baseline differences. Median duration of operation was longer for MIO (325 versus 289 min; P < 0.001), but with less blood loss (median 250 versus 300 ml; P < 0.001) and a shorter hospital stay (median 12 versus 13 days; P = 0.006). Respiratory complications were not associated with operative approach (31.1 versus 35.2 per cent for MIO and HMIO respectively; P = 0.426). Anastomotic leak rates (10.4 versus 10.2 per cent) and 90-day mortality (1.0 versus 1.7 per cent) did not differ. Cardiac co-morbidity was associated with more medical and surgical complications. Overall survival was associated with AJCC stage and co-morbidities, but not operative approach. CONCLUSION: MIO had a small benefit in terms of blood loss and hospital stay, but not in operating time. Oncological outcomes were similar in the two groups. Postoperative complications were associated with pre-existing cardiorespiratory co-morbidities rather than operative approach.

Baseline neutrophil-lymphocyte ratio holds no prognostic value for esophageal and junctional adenocarcinoma in patients treated with neoadjuvant chemotherapy.

BACKGROUND: Several studies have reported that neutrophil-lymphocyte ratio (NLR) can predict survival in esophageal and gastroesophageal junction adenocarcinoma, as it reflects systemic inflammation. Hence, we aimed to determine whether baseline NLR holds prognostic value for esophageal adenocarcinoma patients treated with neoadjuvant chemotherapy (nCT) followed by surgery. METHODS: We studied the data of 139 patients that received nCT before undergoing esophagectomy with curative intent, all identified from a prospectively maintained database (1998-2016). Pretreatment hematology reports were used to calculate the baseline NLR. A receiver operating characteristic curve (ROC-curve) was plotted to determine an optimal cutoff value. NLR quartiles were used to display possible differences between groups in relation to overall survival (OS) and disease-free survival (DFS) using the method of Kaplan-Meier. Cox regression analysis was performed to assess the prognostic value of NLR. RESULTS: The median OS and DFS times were 46 months (interquartile range [IQR]: 19-166) and 30 months (IQR: 13-166], respectively, for the entire cohort. The ROC-curve showed that NLR has no discriminating power for survival status (area under the curve = 0.462) and therefore no optimal cutoff value could be determined. There were no statistically significant differences in median OS times for NLR quartiles: 65 (Q1), 32 (Q2), 45 (Q3), and 46 months (Q4) (P = 0.926). Similarly, DFS showed no difference between quartile groups, with median survival times of 27 (Q1), 19 (Q2), 36 (Q3), and 20 months (Q4) (P = 0.973). Age, pN, pM, and resection margin were independent prognostic factors for both OS and DFS. On the contrary, NLR was not associated with OS or DFS in univariable and multivariable analyses. CONCLUSION: Baseline NLR holds no prognostic value for esophageal and gastroesophageal junction adenocarcinoma patients treated with nCT in this study, in contrast to other recently published papers. This result questions the validity of NLR as a reliable prognostic indicator and its clinical usefulness in these patients.

Impact of postoperative morbidity on long-term survival after oesophagectomy.

BACKGROUND: Oesophageal malignancy is a disease with a poor prognosis. Oesophagectomy is the mainstay of curative treatment but associated with substantial morbidity and mortality. Although mortality rates have improved, the incidence of perioperative morbidity remains high. This study assessed the impact of postoperative morbidity on long-term outcomes. METHODS: A prospective database was designed for patients undergoing oesophagectomy for malignancy from 1998 to 2011. An observational cohort study was performed with these data, assessing intraoperative technical complications, postoperative morbidity and effects on overall survival. RESULTS: Some 618 patients were included, with a median follow-up of 51 months for survivors. The overall complication rate was 64·6 per cent (399 of 618), with technical complications in 124 patients (20·1 per cent) and medical complications in 339 (54·9 per cent). Technical complications were associated with longer duration of surgery (308 min versus 293 min in those with no technical complications; P = 0·017), greater operative blood loss (448 versus 389 ml respectively; P = 0·035) and longer length of stay (22 versus 13 days; P < 0·001). Medical complications were associated with greater intraoperative blood loss (418 ml versus 380 ml in those with no medical complications; P = 0·013) and greater length of stay (16 versus 12 days respectively; P < 0·001). Median overall and disease-free survival were 41 and 43 months. After controlling for age, tumour stage, resection margin, length of tumour, adjuvant therapy, procedure type and co-morbidities, there was no effect of postoperative complications on disease-specific survival. CONCLUSION: Technical and medical complications following oesophagectomy were associated with greater intraoperative blood loss and a longer duration of inpatient stay, but did not predict disease-specific survival.

Prognostic value of maximum standardized uptake values from preoperative positron emission tomography in resectable adenocarcinoma of the esophagus treated by surgery alone.

Preoperative staging for esophageal adenocarcinoma is suboptimal for predicting outcomes when compared with pathological data. The aim of this study was to assess if the quantitative values obtained by preoperative 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) are independent prognostic indicators for survival in patients with resectable adenocarcinoma of the esophagus undergoing surgical treatment without neoadjuvant therapy. Patients were identified from a prospective database, survival analyses were undertaken using log rank and Cox method. The median follow-up was 44 months (range 18-61 months). Between November 2002 and November 2005, 45 consecutive patients underwent FDG-PET followed by surgery. The median age was 72 years (range 38-82 years). On univariate analysis of overall survival and disease-free survival, preoperative FDG-PET maximum standardized uptake value (SUV(max); P= 0.008 and P= 0.015, respectively) and postoperative pathological stage (P= 0.001 and P= 0.001, respectively) as well as postoperative histological grade (P= 0.001 and P= 0.001, respectively) were significantly associated with outcome. Multivariate analysis demonstrated that only the postoperative pathological variables were independent predictors of outcome (Wald 11.81, P= 0.001). Preoperative FDG-PET SUV(max) is associated with outcome after esophageal adenocarcinoma resection but remains less accurate than postoperative variables. A high FDG-PET SUV(max) could be used to identify a high-risk population who would benefit most from neoadjuvant therapies.

Positron emission tomography and pathological evidence of response to neoadjuvant therapy in adenocarcinoma of the esophagus.

Our aim was to determine if fluorodeoxyglucose positron emission tomography (FDG-PET) could be correlated with a pathological response in patients with esophageal adenocarcinoma receiving neoadjuvant chemotherapy and/or chemoradiation therapy. Patients with resectable, histologically proven adenocarcinoma of the esophagus were entered in the study. Preoperative chemotherapy comprised two cycles of cisplatin and 5-fluorouracil. Radiation therapy commenced with the second cycle on day 22. FDG-PET images were obtained pre-treatment and on completion of intended neo-adjuvant treatment. Quantification was achieved by the calculation of both standardized uptake values (SUV) and tumor/liver ratios (TLR). Evidence of histopathological response was identified according to the Mandard tumor regression scoring system. There were 45 patients, 22 receiving neoadjuvant chemotherapy and 23 chemoradiation therapy. Forty patients underwent surgical resection. Seven patients (16%) had a histopathological response. The mean percentage change in SUV in the histological responders group was -56.8% (SD 29) and in the non-responders -27.8% (SD 32.1) (P = 0.035). The mean percentage change in TLR was -49.1% (SD 44.8) in the responders and in the non-responders -27.3% (SD 31.3) (P = 0.128). There was no difference between the two methods of assessment, however there was less variation with SUV. There was no correlation between the FDG-PET response and the histopathological response. Presently an FDG-PET scan performed 3-6 weeks after neoadjuvant therapy for adenocarcinoma of the esophagus should not be used as a marker of the potential result of the treatment. The optimal timing of a second FDG-PET remains unclear.

Combined effects of obesity, acid reflux and smoking on the risk of adenocarcinomas of the oesophagus.

OBJECTIVE: To measure the relative risks of adenocarcinomas of the oesophagus and gastro-oesophageal junction associated with measures of obesity, and their interactions with age, sex, gastro-oesophageal reflux symptoms and smoking. DESIGN AND SETTING: Population-based case-control study in Australia. PATIENTS: Patients with adenocarcinomas of the oesophagus (n = 367) or gastro-oesophageal junction (n = 426) were compared with control participants (n = 1580) sampled from a population register. MAIN OUTCOME MEASURE: Relative risk of adenocarcinoma of the oesophagus or gastro-oesophageal junction. RESULTS: Risks of oesophageal adenocarcinoma increased monotonically with body mass index (BMI) (p(trend) <0.001). Highest risks were seen for BMI >or=40 kg/m2 (odds ratio (OR) = 6.1, 95% CI 2.7 to 13.6) compared with "healthy" BMI (18.5-24.9 kg/m2). Adjustment for gastro-oesophageal reflux and other factors modestly attenuated risks. Risks associated with obesity were substantially higher among men (OR = 2.6, 95% CI 1.8 to 3.9) than women (OR = 1.4, 95% CI 0.5 to 3.5), and among those aged <50 years (OR = 7.5, 95% CI 1.7 to 33.0) than those aged >or=50 years (OR = 2.2, 95% CI 1.5 to 3.1). Obese people with frequent symptoms of gastro-oesophageal reflux had significantly higher risks (OR = 16.5, 95% CI 8.9 to 30.6) than people with obesity but no reflux (OR = 2.2, 95% CI 1.1 to 4.3) or reflux but no obesity (OR = 5.6, 95% 2.8 to 11.3), consistent with a synergistic interaction between these factors. Similar associations, but of smaller magnitude, were seen for gastro-oesophageal junction adenocarcinomas. CONCLUSIONS: Obesity increases the risk of oesophageal adenocarcinoma independently of other factors, particularly among men. From a clinical perspective, these data suggest that patients with obesity and frequent symptoms of gastro-oesophageal reflux are at especially increased risk of adenocarcinoma.

Outcomes from salvage esophagectomy post definitive chemoradiotherapy compared with resection following preoperative neoadjuvant chemoradiotherapy.

Chemoradiotherapy (CRT) as a definitive treatment for esophageal cancer, is being used with increasing frequency and as a result, surgeons will be required to assess more patients who have residual or recurrent local malignancy. This article aimed to assess outcomes after esophagectomy following definitive CRT (dCRT) and compare any difference between them and patients who had preoperative neoadjuvant CRT (nCRT) using a similar regimen of chemotherapy. From a prospective database the details of patients who had a resection following nCRT and dCRT were analyzed. The main therapeutic difference between the groups was the dose of radiotherapy (35 vs 60 Gy) and the timing of the resection following completion of the CRT (median 4 vs 28 weeks). Fourteen patients had an esophagectomy following a dCRT and 53 had one following a nCRT. Preoperatively, the dCRT group had worse respiratory function and more ECG abnormalities. Preoperative tumor length, pathological TNM staging and R0 resection rates were the same in both groups. Post resection, the dCRT group had greater morbidity than the nCRT group, spending longer in the intensive care unit (median 48 vs 24 h), more days in hospital (median 31 vs 13) and having more severe respiratory complications (37%vs 6%). The operative mortality was higher in the dCRT group (7%vs 0%). The three-year survival was 24% after dCRT. Patients selected for salvage esophagectomy following dCRT are a major challenge in postoperative care. However, some patients survive for a reasonable period of time, making resection a worthwhile option.

Minimally invasive esophagectomy: short- and long-term outcomes.

BACKGROUND: We aimed to assess the outcomes including the effect on quality of life (QoL) of a group of patients having a minimally invasive esophagectomy (MIE). METHODS: Patients with esophageal cancer were offered MIE over a 22-month period. Data on outcomes were collected prospectively, including formal quality-of-assessments. RESULTS: There were 25 patients offered MIE. Two patients were converted to a laparotomy to improve the lymphadenectomy. There were no deaths. Respiratory problems (pneumonia, 28%) were the most common in the 64% of patients who had a complication. The median blood loss was 300 ml, time of surgery 330 min, and time to discharge 11 days. There was a decrease in the measured QoL both in general and specifically for the esophageal patients, taking 18-24 months to return to baseline. CONCLUSIONS: MIE was performed with morbidity similar to other approaches. There were no clear benefits shown in this group of patients with respect to postoperative recovery or short- to medium-term QoL.

Symptomatic and functional outcome after laparoscopic reoperation for failed antireflux surgery.

BACKGROUND: The aim was to determine symptomatic and functional outcome after reoperative antireflux surgery for recurrent reflux, persistent dysphagia and severe gas bloat, using a primarily laparoscopic surgical approach. METHODS: This was a retrospective analysis of prospectively collected data from 118 patients, of whom 70 had reoperative surgery for recurrent reflux, 35 for dysphagia and 13 for gas bloat. DeMeester scores before and 1 year after surgery, functional symptoms after surgery and overall patient satisfaction were analysed. RESULTS: Reoperation was completed laparoscopically in 101 patients (85.6 per cent), in 28 after previous open hiatal surgery. The operation was converted from an initial laparoscopic approach to open surgery in 17 patients. One-year follow-up data were available for 104 patients (88.1 per cent). After reoperation for recurrent reflux, 84 per cent had a DeMeester heartburn score of zero or one, and 87 per cent had a regurgitation score of zero or one. After reoperation for dysphagia, 21 of 32 patients had a dysphagia score of zero or one, with improvement observed in 25. All patients undergoing reoperation for severe gas bloat were satisfied with the outcome 1 year after operation. CONCLUSION: Revisional surgery for recurrent reflux using a laparoscopic approach offered high rates of success and patient satisfaction. Swallowing returned to normal in two-thirds of patients after reoperation.

Chemoradiation therapy is effective for the palliative treatment of malignant dysphagia.

Between 1993 and 2001, 106 patients with esophageal cancer were reviewed at a multidisciplinary clinic and treated with palliative intent by chemoradiation therapy. This study assesses the palliative benefit on dysphagia and documents the toxicity of this treatment. The study population comprised 72 men and 34 women with a median age of 69 years. Patients were treated with a median radiation dose of 35 Gy in 15 fractions with a concurrent single course of 5 FU-based chemotherapy. Dysphagia was measured at the beginning and completion of treatment and at monthly intervals until death, using a modified DeMeester (4-point) score. Treatment was well tolerated, with only 5% of patients failing to complete therapy. The treatment-related mortality was 6%. The median survival for the study population was 7 months. The median baseline score at presentation was 2 (difficulty with soft food). Following treatment, 49% of patients were assessed as having a dysphagia score of 0 (no dysphagia). Seventy-eight per cent had an improvement of at least one grade in their dysphagia score after treatment. Only 14% of patients showed no improvement with treatment. Fifty-one per cent maintained improved swallowing until the time of last follow-up or death. This single-institution study shows that chemoradiation therapy administered for the palliation of malignant dysphagia is well tolerated and produces a sustainable normalization in swallowing for almost half of all patients.

Current concepts of tumour metastasis.

BACKGROUND: Tumour metastasis remains the principal cause of treatment failure and poor prognosis in patients with cancer. Recent advances in our understanding of the biology of metastasis are providing novel potential targets for anti-cancer therapies. AIM: This paper reviews the current concepts in tumour metastasis. METHODS: A review of Medline publications relating to the molecular biology and therapy of human tumour metastasis was conducted. RESULTS AND DISCUSSION: Early metastasis models were based upon the premise of uninterrupted tumour growth, with the inevitable formation of distant metastases and eventual death of the patient. However, current research suggests that metastasis is an inefficient process governed by several rate-limiting steps, and that failure to negotiate these steps can lead to tumour dormancy. Successful metastatic tumour growth depends upon appropriate tumour-host microenvironment interactions and, ultimately, the development of vascularised metastases post-extravasation in the target organ. An understanding of the molecular mechanisms involved in this dynamic process will aid in the identification of therapeutic targets that may allow earlier diagnosis and more specific therapies for patients with metastasis.

Early reoperation for acute dysphagia following laparoscopic fundoplication.

BACKGROUND: A small number of patients develop acute severe dysphagia for which reoperation is necessary within 10 days of laparoscopic fundoplication. The aim of this study was to identify clinical variables that might predict the likelihood of this condition occurring, such that it could be avoided in the future. METHODS: This was a prospective cohort study from three tertiary referral centres, using reoperation for acute dysphagia as the main outcome variable. Gastrointestinal symptom rating scale, and psychological well-being index questionnaires were undertaken before laparoscopic fundoplication, and dysphagia scores were determined before operation and 1 year later. Standard preoperative assessment included gastroscopy, oesophageal manometry and pH studies. RESULTS: Twelve (1.9 per cent) of the 617 patients suffered acute dysphagia, which was predicted by older age and female sex, and resulted in a longer duration of hospital stay. This condition was not predicted by any other demographic, clinical, investigative or operative variables. CONCLUSION: The study did not identify useful criteria by which severe acute dysphagia could be anticipated and thereby avoided following laparoscopic fundoplication.

Human trypsinogen in colorectal cancer.

Trypsinogen (TRY), the precursor to the serine protease trypsin, is found in the pancreas and mediates digestive proteolysis in the small intestine. Differential display of cDNAs expressed by human colorectal tumor tissues compared with adjacent normal colonic mucosa identified an isoform of TRY (TRY2) up-regulated in colorectal cancers. Northern blot analysis of RNA isolated from a series of 28 malignant colon tumors and corresponding normal mucosa showed that TRY transcripts were up-regulated 2- to 33-fold in 29% of tumors. Further, TRY mRNA was expressed in 6 colorectal cancer cell lines, with highest levels detected in the metastatic tumor lines SW620 and HT29. Immunostaining for TRY protein expression showed intense immunoreactivity in the supranuclear cytoplasm of colon tumors in 16% of tissue specimens. To evaluate the relative contributions of 2 isoforms of TRY, TRY1 and TRY2, to total TRY mRNA expression, a semi-quantitative multiplex RT-PCR assay was developed. TRY2 mRNA was detected in all 6 colorectal tumor cell lines, whereas TRY1 mRNA was expressed only in the metastatic tumor lines, showing that the high levels of TRY expression in the metastatic tumor lines are likely due to up-regulation of TRY1. Evaluation of TRY1 and TRY2 mRNA expression by multiplex RT-PCR in a series of 20 colon tumor tissues representative of the range of tumor progression showed that TRY2 mRNA was expressed much more commonly than TRY1 mRNA in normal mucosa (26% vs. 6%) as well as in primary tumor tissues (65% vs. 15%). These data demonstrate that TRY2 is the dominant TRY in colon tissue and suggest that up-regulation of TRY1 expression in colon tumors may be associated with a metastatic phenotype.

Thoracoscopic mobilization of the esophagus. A 6 year experience.

BACKGROUND: Traditionally, esophageal resection has been performed using a thoracotomy to access the intrathoracic esophagus. With the aim to avoid the potential morbidity of the open thoracic approach, mobilization of the esophagus under direct vision recently has been described. We report our experience at attempting thoracoscopic mobilization of the esophagus in 162 patients during a 6-year period. METHODS: Patients with malignancy or end-stage benign disease of the esophagus considered suitable for a three-stage esophagectomy underwent a thoracoscopy with a view to endoscopic mobilization of the esophagus. Of the 162 patients in whom the procedure was attempted, it was abandoned in 9 patients (6%), and the procedure was converted to open surgery in 11 patients (7%). RESULTS: In the patients whose esophagus was mobilized, the average blood loss was 165 ml, and the average time for the thoracoscopic segment of the surgery was 104 min. In the 133 patients who underwent a resection for invasive malignancy, a limited mediastinal nodal dissection retrieved an average of 11 nodes, and the median survival was 29 months. The 30-day mortality was 3.3% and the in-hospital mortality 5.3%. CONCLUSIONS: Thoracoscopic mobilization can be performed safely with satisfactory outcomes in a center performing a large volume of esophageal surgery and possessing advanced endoscopic surgery skills. Further assessment of this technique and comparisons with traditional open procedures are needed to assess this approach further as an appropriate oncologic procedure.

Chronic dysphagia following laparoscopic fundoplication.

BACKGROUND: Many surgeons practise tailored laparoscopic antireflux surgery in an attempt to prevent postoperative dysphagia. The aim of this study was to determine the effect of 360 degrees fundoplication (Nissen) or 270 degrees fundoplication (Toupet), and the influence of abnormal oesophageal peristalsis, upon postoperative dysphagia. METHODS: This was a cohort study from three tertiary referral centres, using dysphagia before laparoscopic fundoplication and 1 year after operation as the main outcome variable. Preoperative oesophageal manometry was performed on all patients. RESULTS: Some 761 patients underwent Nissen and 85 underwent Toupet fundoplication. Only 2 per cent reported severe postoperative dysphagia. There was a significant selection bias towards the Toupet operation for patients with abnormal oesophageal motility (P < 0.001). For patients whose oesophageal manometric findings were normal there was a significant improvement in dysphagia after Nissen fundoplication (P = 0.02), and no significant change following Toupet fundoplication. There was no significant change in the rate of dysphagia following either method of fundoplication amongst other subgroups in which oesophageal manometry was stratified as non-specific motor disorder, low-amplitude peristalsis, or aperistalsis. CONCLUSION: A tailored approach to the degree of fundoplication is unnecessary as patients with dysmotility suffer no more dysphagia after full laparoscopic Nissen fundoplication than those who have a partial Toupet wrap.

Grantsmanship: achieving success in research funding.

High-quality research is seldom feasible without skillful grantsmanship. Like most skills it is learnt and then improved by practice. Fortunately, there is a consistent formula to constructing a research grant, provided certain guidelines are followed. The grant application need not be a significant barrier between a good idea and its realization in improvements to patient care. This paper outlines the essential principles in the construction of the successful research grant application.

Two novel mucin genes down-regulated in colorectal cancer identified by differential display.

Epithelial mucins are large, secreted and cell surface glycoproteins involved in epithelial cell protection, adhesion modulation, and signaling. Using differential display, we have identified two novel mucin cDNAs (dd34 and dd29), hereafter designated MUC11 and MUC12, respectively, that are down-regulated in colorectal cancers. Northern blots demonstrated polydisperse signals characteristic of mucin transcripts in RNA from normal colon that were absent in colorectal cancer. Both cDNAs were mapped by fluorescence in situ hybridization to chromosome band 7q22, the location of the MUC3 mucin gene, thus suggesting that there may be a cluster of mucin genes at this locus. The sequences of both differential display clones were extended by a combination of screening libraries and PCR. The 2.8-kb MUC11 cDNA composite encoded 35 serine/threonine-rich, mucin-like degenerate 28 amino acid tandem repeats. The MUC12 cDNA composite encoded a putative transmembrane mucin containing two extracellular cysteine-rich, EGF-like domains, a coiled-coil region, and a mucin-like domain consisting of 28 amino acid degenerate tandem repeats. Distinct patterns of expression of MUC11, MUC12, and MUC3 mRNAs were observed in a range of normal human tissues. MUC12 mRNA was not expressed in any of six colorectal cancer cell lines examined and was down-regulated or absent in 6 of 15 (40%) tumors compared with matched normal colonic tissue. In contrast, MUC11 showed a different pattern of mRNA expression, with four of these lines showing low levels and the other two lines showing relatively high levels of MUC11 transcripts. Expression of MUC11 was down-regulated in the tumors of 12 of 15 (80%) paired samples. Structural homology of MUC12 with rat, mouse, and human MUC3 and human and rat MUC4/ASGP2 indicate that there is a distinct subfamily of transmembrane mucins with conserved epidermal growth factor domains. The homology of MUC12 with epidermal growth factor-like growth factors and its down-regulation in colorectal cancers, together with known interactions between rat MUC4 and c-erbB-2 growth factor receptors, suggests that MUC12 may be involved in epithelial cell growth regulation.

The MUC3 gene encodes a transmembrane mucin and is alternatively spliced.

Epithelial mucins are a family of secreted and cell surface glycoproteins expressed by epithelial tissues and implicated in epithelial cell protection, adhesion modulation and signaling. The gene encoding human MUC3 (hMUC3), localised to chromosome 7q22, is most highly expressed in the small intestine. It has previously been reported to be a non-transmembrane mucin with minimal homology to its suggested orthologues from rat (rMuc3) and mouse (mMuc3). RT-PCR was performed to investigate the carboxyl terminus of the published sequence of hMUC3 from normal colon and small intestine tissues and also from a series of 10 colorectal cancer cell lines. Two distinct PCR products were identified. In contrast to the previously published hMUC3 sequence, which terminates shortly after a single cysteine-rich EGF-like domain, conceptual protein translation of the dominant and largest PCR product identified two extracellular cysteine-rich EGF-like domains separated by an N-glycosylation-rich domain and a potential coiled-coil region, followed by a putative transmembrane region and a 75 amino acid cytoplasmic tail. The smaller of the two PCR products was found to be an alternative splice variant of MUC3 including the first EGF-like domain but lacking part of the second EGF-like domain and the transmembrane region. Nine out of 10 colorectal cancer cell lines were found to express MUC3. Interestingly, one of the cell lines, LoVo, expressed predominantly the alternative splice form lacking a transmembrane domain. Structural homology of the new protein sequence of hMUC3 with rMuc3 and mMuc3 indicates it is closely related to the rodent proteins and is likely to be involved in ligand-binding and intracellular signaling. The new finding that MUC3 encodes a transmembrane molecule presents a new paradigm for the structure of this mucin and the manner in which it may function.

Down-regulation of the down-regulated in adenoma (DRA) gene correlates with colon tumor progression.

The down-regulated in adenoma (DRA) gene was originally identified as a gene that was down-regulated in colon tumors. It encodes a protein with anion transporter function that is expressed predominantly in the mucosa of the lower gastrointestinal tract. In this study, expression of DRA and its cellular distribution have been investigated in a series of benign adenomatous polyps and malignant colorectal tumors and in corresponding normal colonic mucosa. We show that DRA mRNA and protein are expressed in all normal colonic tissue specimens with the protein restricted primarily to the terminally differentiated columnar epithelium and some goblet cells. Apical membrane localization was especially apparent in the columnar epithelium. The levels of DRA mRNA transcripts were down-regulated in all colon tumors examined relative to matched normal mucosa, with most specimens showing undetectable levels of DRA mRNA (77 of 104 tumors). DRA down-regulation was positively associated with colonic tumor progression according to Dukes' stage and was particularly significant in the early transition from normal mucosa to polyp to adenocarcinoma. DRA expression does not appear to be strictly associated with colonic cell differentiation; rather, its absence and down-regulation were associated with the proliferating component of the crypt epithelium and with neoplastic transformation, respectively.

Expression of antisense CD44 variant 6 inhibits colorectal tumor metastasis and tumor growth in a wound environment.

Up-regulation of CD44 variant isoforms has been linked to the progression of epithelial tumors and the metastatic phenotype. Here we report a functional role for CD44 variant isoforms in colorectal cancer metastasis. An antisense mRNA approach was used to down-regulate CD44 variant isoforms containing CD44 variant 6 (v6) in the metastatic colorectal tumor cell line HT29. Cell lines stably expressing antisense CD44 exon 10 (v6) showed reduced expression of alternatively spliced CD44 variant isoforms but no significant change in expression of CD44 core protein, as judged by immunohistochemical analysis using CD44 domain-specific monoclonal antibodies. Expression of antisense exon 10 (v6) had no effect on HT29 tumor cell proliferation in vitro or the ability of the cells to bind immobilized hyaluronan, but it resulted in a reduced capacity to form liver metastases in nude mice following intrasplenic injection. Metastases were not detected in nude mice inoculated with antisense CD44 exon 10 (v6)-expressing cell lines after 4 months, against a background of a 30% metastasis rate in the control HT29 parental and vector alone transfected lines. Furthermore, whereas 82% of mice intrasplenically injected with control HT29 parental and vector alone cell lines developed tumors in incisional wound sites, none of the mice injected with antisense exon 10 expressing HT29 cells developed similar tumors. This is the first demonstration that antisense RNA can be used to selectively inhibit expression of specific domains of a molecule generated through alternative mRNA splicing while allowing expression of core domains to remain unaffected. Furthermore, these results provide direct evidence for a functional role of CD44 variant isoforms in the metastasis of human colorectal tumor cells and may suggest a critical role for CD44 variants in promoting cell growth specifically in the cytokine/growth factor-enriched environment of a wound site.