Expression and localisation of insulin receptor substrate 2 in normal intestine and colorectal tumours. Regulation by intestine-specific transcription factor CDX2.

BACKGROUND AND AIMS: Self-renewal and differentiation of intestinal epithelium is a tightly regulated process, whose perturbations are implicated in human colorectal tumourigenesis. The insulin/insulin-like growth factor (IGF) signalling pathway may play an important role in intestinal epithelium homeostasis. Insulin receptor substrate 2 (IRS2) is a poorly characterised component in this pathway. METHODS: Using complementary in vitro and in vivo human and murine models, expression (mRNA and protein levels), localisation (immunohistochemistry) and regulation of IRS2 were investigated in the normal intestine and colorectal tumours. In silico analysis of the human IRS2 promoter was performed together with reporter and chromatin immunoprecipitation assays. RESULTS: Significant IRS2 expression was detected in the intestine, with specific protein localisation in the villus region of the ileum and in the surface epithelium of the colon. In human HT29 and Caco2 cells, IRS2 mRNA levels increased with spontaneous and induced differentiation, together with CDX2 (caudal-related homeobox protein 2), P21 and KLF4 (Krüppel-like factor 4). Adenoviral infection with human CDX2 induced IRS2 expression in APC- (adenomatous polyposis coli) and beta-catenin-mutated cells. On the other hand, IRS2 downregulation was observed in differentiated enterocytes after adenoviral infection with short hairpin CDX2 (shCDX2), in the intestine of CDX2 heterozygous mice and in colorectal tumours of Apc(Min/+) and patients with familial adenomatous polyposis (FAP). The human IRS2 promoter region presents several CDX2-binding sites where CDX2 immunoprecipitated in vivo. IRS2 reporters were functionally activated via CDX2 and blocked via a dominant-negative CDX2 protein. CONCLUSIONS: Combining gain- and loss-of-function approaches, an intriguing scenario is presented whereby IRS2 is significantly expressed in the apical intestinal compartment and is directly controlled by CDX2 in normal intestine and tumours.

[Rectal cancer: locoregional recurrence in relation to surgical and complementary treatment]. / Il cancro del retto: le recidive locoregionali in rapporto alle terapie chirurgiche e complementari adottate.

Much recent data have been published on the risk of local recurrence (LR) following curative surgery for rectal cancer and the impact of adjuvant therapy. On the other hand, improvements in surgical techniques, as the total mesorectal excision, have apparently reduced the risk of LR. Furthermore, in selected cases, neoadjuvant therapy seems to reduce much more the incidence of LR. A list of prognostic factors which affect the onset of LR, other than the different procedures, was considered. To investigate such evidences a retrospective analysis was undertaken in our series, focusing on examination of the employed techniques as potential predictors of local recurrence. Thus, in a 18-yr-period (1986-2003), two hundred and ninety-five patients who had undergone elective curative surgical resection of rectal cancer were included in the study. The demographic, operative and follow-up data were collected retrospectively. All patients underwent total mesorectal excision, whereas neoadjuvant therapy was performed in a selected series of patients, according to defined entry criteria patterns. Results evidenced LR in 7.1% of patients and occurred between 6 months to 8 year following surgery. Comparisons were made between patients who had different surgical procedures; indeed sphyncter saving procedures correlated with a higher incidence of LR rather than abdomino-perineal resection. Pelvic recurrences were observed more frequently compared to the anastomotic ones. A limited number of patients with LR underwent surgery due to the associated condition of metastatic lesions; the follow-up related to such series evidenced a mortality rate of 57% within 3 year from reoperation. A low local recurrence rate can be achieved after total mesorectal excision (TME) without preoperative radiotherapy. Our results suggest that preoperative radiotherapy may be employed only for those patients who are at a higher risk for local recurrence.