| Colorectal cancer (CRC), which represents the second leading cause of cancer deaths in the western countries, is one of the major healthcare problems worldwide. Each year, more than one million new cases are diagnosed with this malignancy worldwide and approximately 50% of these patients die of it. In terms of incidence, among males CRC is the third most common cancer after lung and prostate cancers; among females it follows breast cancer, occupying the second place. At present, surgical resection is the cornerstone treatment for early-stage colorectal cancer and chemotherapy is the first adjuvant option for metastatic CRC. Despite new treatment strategies developed in the past decade, the prognosis of patients with metastatic CRC still remains poor, with an average survival of less than 30 months. Therefore, it is necessary to elucidate the underlying molecular mechanisms of CRC and identify new molecular involved in its development and progression.Colon tumours arising at the splenic flexure are relatively rare and represent only 2-8% of all colon cancers treated by surgery]. They tend to more frequently be obstructive and to present at a more advanced stage, thus resulting in a poorer prognosis than that for tumours arising at other sites in the left colon. The topography of the splenic flexure is ill-defined, and the blood supply and lymphatic drainage show heterogeneity. The extent of resection chosen by surgeon is often arbitrary rather than based on evidence; to avoid this, lymph road mapping has been proposed as a method to better target the extent of resection, particularly to avoid unnecessary resection of the middle colic artery. However, although of potential value for colonic flexure tumours, this technique has not been widely adopted due to the procedure being labourintensive. The most appropriate surgical approach continues to be debated; one option is to perform an extended right colectomy which, in most cases, allows a tension-free ileo-colic anastomosis to be made, and provides the anastomosis with a good blood supply. The alternative is a left colectomy, consisting of either a high tie of the inferior mesenteric artery and ligation of the left branch of the middle colic artery, followed by a transverse-rectal anastomosis, or the selective ligation of the left colic artery with a transverse-sigmoid anastomosis. However, for extended left colectomies, a right colonic transposition may be necessary to achieve a tension-free anastomosis. The evidence in the literature regarding the advantages and disadvantages of either approach is sparse. The aim of this study was to investigate if there is a difference in the short- and long-term outcomes for patients with splenic flexure cancers treated by left (LC) versus extended right (RC) colectomyColorectal (CRA) or coloanal (CAA) anastomoses are routinely performed in colorectal surgery; to minimize the risk of anastomotic leakage, the lowered colon should be well-vascularized and of adequate length to ensure a tension-free anastomosis.1 To achieve these goals, the following surgical maneuvers may be helpful:the complete mobilization of the splenic flexure extended to the root of the transverse mesocolon until the duodenojejunal junction, the division of the inferior mesenteric vein under the pancreas or the high ligation of the inferior mesenteric artery with a section of the upper left colonic artery proximal to its division, leaving the colon perfused by the middle colic artery via the marginal artery.2 However, in several circumstances, such as left colectomy extended to the transverse colon or to the rectum, or in case of iterative colonic resection, the above-mentioned procedures may be insufficient to take down a well-vascularized colon into the pelvis and perform a tension-free anastomosis. In these cases,2 additional surgical techniques can be used as an alternative to total colectomy with ileorectal or ileoanal anastomosis:the transmesenteric lowering of the colon which consists of taking down the proximal colon through an avascular window in the terminal part of the ileal mesentery,3 and the Deloyers procedure comprising an anastomosis between the right or the transverse colon and the rectum or anus after a complete colonic mobilization and rotation while preserving the ileocolic junction and the ileocolic artery. In November 1963, Prof Deloyers reported the first series of 11 patients operated on according to his technique. These patients underwent surgery for ulcerative colitis, megacolon, dolichocolon with chronic constipation, and polyposis involving the left and transverse colon. Since this publication,4 studies including a total of 32 patients have reported the results of the Deloyers procedure, and all have focused on Hirshsprung disease and severe chronic constipation. After an extended left colectomy, the remaining colon stump is unable to reach the rectal stump without undue tension. To overcome this problem, the surgeon can complete the colectomy and perform an ileorectal anastomosis. However, the functional results after total colectomy are poorer than after a segmental colectomy. You et al. reported a median of five daily stools after ileorectal anastomosis, despite dietary restrictions and medication. In contrast, Manceau reported a median number of three bowel movements per day and night after right colonic transposition. The ileocaecal junction functions as a sphincter and the colon slows down transit time considerably. Thus, colonic rotation to perform a tension-free colorectal anastomosis could be an alternative to a total colectomy with an ileorectal anastomosis.MicroRNAs (miRNAs or miRs) are a class of endogenous small, non-protein coding, single stranded RNAs with about 22 nucleotides that are capable to regulate gene expression at the post-transcriptional level. miRNAs negatively regulate protein expression usually by binding to the 3’-untranslated regions (UTR) of target mRNAs, resulting in their degradation or translational repression. As partial pairing between an miRNA and a target site is often sufficient, a given miRNA may regulate multiple mRNAs and a given mRNA might also be targeted by multiple miRNAs. A lot of miRNAs are aberrantly expressed in CRC and involved in its development and progression, suggesting that miRNAs may play pivotal roles in its diagnosis and therapy. Thus, it is of great importance to indentify some novel miRNAs and explore their roles in CRC.MiR-503 is an intragenic miRNA clustered with miR-424 on chromosomal location Xq26.3 and was first identified in human retinoblastoma tissues using the microRNA microarray technique. Aberrant expression of miR-503 and its role in several human cancers have been reported recently. For example, Peng et al found that miR-503 expression is reduced in gastric cancer cell lines and that miR-503 inhibits gastric cancer cell proliferation, migration and invasion. Chong et al observed that miR-503 was down-regulated in osteosarcoma cell lines and primary tumor samples, and the restoration of miR-503 reduced cell proliferation, migration and invasion. Zhang et al showed that the expression of miR-503 was significantly decreased in glioblastoma multiforme tissues and cell lines, and overexpression of miR-503 suppressed cell proliferation through inducing apoptosis by targeting IGF-1R. However, miR-503 expression and its role in CRC is still unknown.The aim of our study was:(1) The outcomes for patients with splenic flexure tumours treated by left versus extended right colectomy; (2) Curative effect comparison in different ways of colonic anastomosis in extended left colectomy; (3) To investigate the expression and function of miR-503 in CRC.。Part 1:The outcomes for patients with splenic flexure tumours treated by left versus extended right colectomyMethods:Stage Ⅰ-Ⅲ splenic flexure tumours, treated either by extended right colectomy or left colectomy between 2001 and 2014, were identified in a prospective database, and the outcomes compared.Results:A total of 21 (44%) splenic flexure tumours were resected by left colectomy and 28 (56%) by right colectomy. In terms of surgical quality surrogates, the number of harvested lymph nodes and R0 rate were similar in the RC and LC groups. The proportion of patients with more than 12 lymph nodes harvested was not significantly different (P<0.05). The rate of primary anastomosis without a stoma and the leak rate were similar between the LC and RC groups. The anastomotic complication rate was 10.2% and was not significantly different between right colonic transposition and anastomosis after the mesentery of small intestine (10.7% vs 9.5%, P=0.89). With respect to the long-term survival outcomes, In the univariate analysis, the 5-year overall survival (x2=2.146,P=0.143) showed a trend towards a non-significant survival benefit for left colectomy. There are no significant differences in the short-or long-term outcomes between patients treated with left colectomy and extended right colectomy for splenic flexure tumours.Conclusion:Since the extended right colectomy is a more radical operation with regard to resection of the middle colic artery, one would have expected a higher lymph node yield in the RC group. In addition, the fact that the T3 case with positive margins was laparoscopically resected may support our personal experience that the left-sided laparoscopic approach is technically more challenging, especially the selective dissection of the left-sided branch of the middle colic artery; this carries the potential risk of compromising the radicality. The small number of laparoscopic procedures performed in our study was due to the fact that, as already mentioned, laparoscopic resections of splenic flexure tumours are technically demanding, and the procedure has only been practiced in our centre more recently. More RC cases seemed to be unsuitable for laparoscopy due to massive bowel dilatation or perforation in cases of emergency presentation. As already mentioned, this may be explained by the central dissection of the middle colic artery and associated lymph node clearance achieved by RC. With respect to the long-term survival outcomes, the type of procedure was not a significant predictor even when adjusted for other influencing factors like the age, tumour stage, urgency and year of surgery in the multivariate analysis.Part 2:Options and outcome for reconstruction after extended left hemicolectomyObjective:A tension-free anastomosis is required to minimize anastomotic leakage after an extended left colectomy when the residual transverse colon is too short to spontaneously reach the pelvis. To resolve this problem, colonic rotation with a right colonic transposition or anastomosis after the mesentery of small intestine is mandatory. This study compared these two techniques.Methods:Between January 2001 and 2014,38 patients had undergone right colonic transposition (n=11) or anastomosis after the mesentery of small intestine (n=27) after an extended left colectomy. All anastomotic complications had been recorded during the follow up. An extended left colectomy was defined as a colectomy removing atleast the splenic flexure, the descending colon and the sigmoid.Results:No differences were found between right colonic transposition and anastomosis after the mesentery of small intestine in terms of patient characteristics, surgical indications, therapeutic features and risk factors for anastomotic leakage (sex, diabetes, bevacizumab use, colorectal anastomotic level or protective stoma use). Ligature of the middle colic artery was significantly more frequent with right colonic transposition than with anastomosis after the mesentery of small intestine (90.9% vs 14.8%; P<0.05). An additional colonic resection tended to be required more often in the right colonic transposition group than in the anastomosis after the mesentery of small intestine group. The anastomotic complication rate was 13.2% and was not significantly different between right colonic transposition and anastomosis after the mesentery of small intestine (18.1% vs 11.1%, P=0.60).Conclusion:Both colonic rotation and anastomosis after the mesentery of small intestine techniques are feasible and safe. The right colonic transposition and anastomosis techniques after the mesentery of small intestine yielded similar results in terms of colorectal anastomotic complications, but right colonic transposition required ligature of the middle colic artery and additional colonic resection tended to be required more frequently.Part 3:Curative effect comparison in two ways of colonic anastomosis in extended left colectomyObjective:To study and comparise in two ways of colonic anastomosis of extended left colectomy.Methods:The clinical and follow-up data of 28 patients who underwent extended left colectomy from July 2000 to august 2013 in our hospital were retrospectively analyzed. The patients were divided into two groups. The way of colonic anastomosis in Ⅰ group(n=15) was ahead small intestine. (n=51). In II group(n=13),8 patients were underwent colonic anastomosis after the small intestine through the mesentery,5 patients were underwent colonic anastomosis after the mesentery of small intestine.The complications, operation time, flatus passage and estimated blood loss were compared between the two groups.Results:The mean operation time was 165.1 minutes for I group and 173.7 minutes for Ⅱ group. Two groups of postoperative complication rates were 46.7%,23.1% respectively (P< 0.05). The incidence of postoperative complications of high small intestinal obstruction in I group was 26.7%and in II group was 0.0%(P<0.05). The incidence of postoperative anastomotic fistula was 6.7%(I group) and 7.7%(Ⅱ group) (P>0.05). The time of flatus passage, Length of stay and time to resume regular diet were significantly lower in I group than in II group (P<0.05).Conclusion:colonic anastomosis in extended left colectomy through small mesenteric rear or small mesentery can effectively avoid oppression jejunum to intestinal obstruction and its postoperative result is superior to anter small intestinal anastomosis.Part 4:miR-503 inhibits cell proliferation and induces apoptosis in colorectal cancer cells by targeting E2F3Objective:Colorectal cancer (CRC) is one of the major healthcare problems worldwide. A lot of miRNAs are aberrantly expressed in CRC and involved in its development and progression. The purpose of this study was to investigate the expression and function of miR-503 in CRC.Methods:miR-503 expression was detected in CRC tissues and cell lines by Quantitative real-time PCR. Cell proliferation was assessed by MTT assay. Cell apoptosis and cell cycle distribution were measured by flow cytometry. Moreover, luciferase reporter assay and western blot were performed to determine the potential target of miR-503 in CRC cells.Results:miR-503 was significantly decreased in CRC tissues and cell lines in comparison with controls. Overexpression of miR-503 in CRC cells remarkably inhibited cell proliferation and induced apoptosis. Furthermore, E2F3 was identified as a direct target of miR-503 in CRC cells and down-regulation of E2F3 had a similar effect as miR-503 overexpression on CRC cells. In addition, the expression of E2F3 was negatively correlated with miR-503 level in CRC tissues.Conclusion:we first observed that the expression level of miR-503 is significantly down-regulated in colorectal cancer tissues and cell lines, when compared with paired adjacent normal tissues and normal colonic cell line FHC, which indicates that miR-503 may play important role in the development of CRC. Next, we investigated the biological function of miR-503 in CRC and found that overexpression of miR-503 markedly suppressed cell proliferation, induces apoptosis and G0/G1 arrest in SW480 cells. These results indicate that miR-503 may act as a tumor suppressor in the development of CRC.Then, we identified E2F transcription factor 3 (E2F3), an important transcription factor involved in the proliferation and cell cycle distribution, as a direct target of miR-503 by luciferase report assay and western blot. Functional assays showed that down-regulation of E2F3 not only inhibited proliferation but also induced apoptosis and G0/G1 arrest in SW480 cells, which mimics the effect of miR-503 on CRC cells. However, restoration of E2F3 partially attenuates the effects of miR-503 on CRC cells proliferation and apoptosis. Moreover, we detected that E2F3 expression level is significantly increased in CRC tissues and inversely correlated with miR-503 in CRC. The above findings suggest that miR-503 plays its suppressive role in CRC by direct targeting E2F3.Taken together, our study demonstrated for the first time that miR-503 is significantly down-regulated in colorectal cancer tissues and cell lines in comparison with controls. In addition, miR-503 inhibits proliferation, induces apoptosis and G0/G1 arrest by directly targeting E2F3. Our findings suggest that miR-503 may serve as a novel molecule for the diagnosis and therapy of patients with colorectal cancer. |
PDF Full Text Request