Colonic immune cells in irritable bowel syndrome: A systematic review and meta-analysis.

BACKGROUND & AIMS: Increases in mucosal immune cells have frequently been observed in irritable bowel syndrome (IBS) patients. However, this finding is not completely consistent between studies, possibly due to a combination of methodological variability, population differences and small sample sizes. We performed a meta-analysis of case-control studies that compared immune cell counts in colonic biopsies of IBS patients and controls. METHODS: PubMed and Embase were searched in February 2017. Results were pooled using standardized mean difference (SMD) and were considered significant when zero was not within the 95% confidence interval (CI). Heterogeneity was assessed based on I2 statistics where I2  ≤ 50% and I2  > 50% indicated fixed and random effect models, respectively. KEY RESULTS: Twenty-two studies on 706 IBS patients and 401 controls were included. Mast cells were increased in the rectosigmoid (SMD: 0.38 [95% CI: 0.06-0.71]; P = .02) and descending colon (SMD: 1.69 [95% CI: 0.65-2.73]; P = .001) of IBS patients. Increased mast cells were observed in both constipation (IBS-C) and diarrhea predominant IBS (IBS-D). CD3+ T cells were increased in the rectosigmoid (SMD: 0.53 [95% CI: 0.21-0.85]; P = .001) and the descending colon of the IBS patients (SMD: 0.79, 95% CI [0.28-1.30]; P = .002). This was possibly in relation to higher CD4+ T cells in IBS (SMD: 0.33 [95% CI: 0.01-0.65]; P = .04) as there were no differences in CD8+ T cells. CONCLUSIONS & INFERENCES: Mast cells and CD3+ T cells are increased in colonic biopsies of patients with IBS vs non-inflamed controls. These changes are segmental and sometimes IBS-subtype dependent. The diagnostic value of the quantification of colonic mucosal cells in IBS requires further investigation.

The miR-487b-3p/GRM3/TGFß signaling axis is an important regulator of colon cancer tumorigenesis.

Molecular targeting is an import strategy to treat advanced colon cancer. The current study demonstrates that expression of GRM3, a metabotropic glutamate receptor mainly expressed in mammalian central nervous system, is significantly upregulated in majority of human colonic adenocarcinomas tested and colon cancer cell lines. Knockdown of GRM3 expression or inhibition of GRM3 activation in colon cancer cells reduces cell survival and anchorage-independent growth in vitro and inhibits tumor growth in vivo. Mechanistically, GRM3 antagonizes TGFß-mediated activation of protein kinase A and inhibition of Protein kinase B (AKT). In addition, TGFß signaling increases GRM3 protein stability and knockdown of GRM3 enhances TGFß-mediated tumor suppressor function. Further studies indicate that miR-487b-3p directly targets GRM3. Overexpression of miR-487b-3p mimics the effects of GRM3 knockdown and suppresses the tumorigenicity of colon cancer cells in vivo. Expression of miR-487b-3p is decreased in colon adenocarcinomas and inversely correlates with GRM3 expression. Taken together, these studies indicate that upregulation of GRM3 expression is a functionally important molecular event in colon cancer, and that GRM3 is a promising molecular target for colon cancer treatment. This is particularly interesting and important from a therapeutic standpoint because numerous metabotropic glutamate receptor antagonists are available, many of which have been found unsuitable for treatment of neuropsychiatric disorders for reasons such as inability to readily penetrate blood brain barriers. As GRM3 is upregulated in colon cancer, but rarely expressed in normal peripheral tissues, targeting GRM3 with such agents would not likely cause adverse neurological or peripheral side effects, making GRM3 an attractive and specific molecular target for colon cancer treatment.

MicroRNA-587 antagonizes 5-FU-induced apoptosis and confers drug resistance by regulating PPP2R1B expression in colorectal cancer.

Drug resistance is one of the major hurdles for cancer treatment. However, the underlying mechanisms are still largely unknown and therapeutic options remain limited. In this study, we show that microRNA (miR)-587 confers resistance to 5-fluorouracil (5-FU)-induced apoptosis in vitro and reduces the potency of 5-FU in the inhibition of tumor growth in a mouse xenograft model in vivo. Further studies indicate that miR-587 modulates drug resistance through downregulation of expression of PPP2R1B, a regulatory subunit of the PP2A complex, which negatively regulates AKT activation. Knockdown of PPP2R1B expression increases AKT phosphorylation, which leads to elevated XIAP expression and enhanced 5-FU resistance; whereas rescue of PPP2R1B expression in miR-587-expressing cells decreases AKT phosphorylation/XIAP expression, re-sensitizing colon cancer cells to 5-FU-induced apoptosis. Moreover, a specific and potent AKT inhibitor, MK2206, reverses miR-587-conferred 5-FU resistance. Importantly, studies of colorectal cancer specimens indicate that the expression of miR-587 and PPP2R1B positively and inversely correlates with chemoresistance, respectively, in colorectal cancer. These findings indicate that the miR-587/PPP2R1B/pAKT/XIAP signaling axis has an important role in mediating response to chemotherapy in colorectal cancer. A major implication of our study is that inhibition of miR-587 or restoration of PPP2R1B expression may have significant therapeutic potential to overcome drug resistance in colorectal cancer patients and that the combined use of an AKT inhibitor with 5-FU may increase efficacy in colorectal cancer treatment.

MicroRNA-192 suppresses liver metastasis of colon cancer.

Metastasis causes most deaths from colon cancer yet mechanistic understanding and therapeutic options remain limited. Here we show that expression of microRNA (miR)-192 is inversely correlated with metastatic potential of colon cancer cells. Ectopic expression of miR-192 sensitizes colon cancer cells to growth factor deprivation stress-induced apoptosis, whereas inhibition of miR-192 confers resistance. Overexpression of miR-192 inhibits metastatic colonization to the liver in an orthotopic mouse model of colon cancer. Alterations associated with the metastatic phenotype in the primary tumors include increased apoptosis, decreased proliferation and angiogenesis. Further studies indicate that miR-192 downregulates expression of Bcl-2, Zeb2 and VEGFA in vitro and in vivo, which is responsible for enhanced apoptosis, increased expression of E-cadherin and decreased angiogenesis in vivo, respectively. Finally, studies performed on human colonic adenocarcinoma show that expression of miR-192 is significantly reduced in neoplastic cells as compared with normal colonic epithelium. Importantly, there is a significant decrease in miR-192 expression in stage IV tumors when compared with stage I or II lesions. These findings indicate that miR-192 has an important role in colon cancer development and progression. Our studies underscore the clinical relevance and prognostic significance of miR-192 expression in colon cancer. Therefore, a major implication of our studies is that restoration of miR-192 expression or antagonism of its target genes (Bcl-2, Zeb2 or VEGFA) may have considerable therapeutic potential for anti-metastatic therapy in patients with colon cancer.

Sequential histologic changes in the healing process in small bowel allografts treated for acute cellular rejection.

INTRODUCTION: Acute cellular rejection (ACR) is a common complication seen in small intestinal transplant patients. Once diagnosed, follow-up endoscopy/biopsies may be performed to assess for response to therapy and the pathologist is often asked to determine whether the findings are compatible with treated/resolving or ongoing ACR. To this end, the sequence of resolution of ACR's changes in biopsies is important. METHODS: We retrospectively reviewed the clinical histories and hematoxylin and eosin-stained slides from 16 cases of ACR patients who underwent isolated small bowel or combined liver/small bowel/pancreas transplants. Selected cases were new diagnoses of mild ACR with prior negative biopsies in the preceding 2 months, treatment for rejection based on the ACR diagnosis, and biopsies in the following 4 weeks diagnosed as "treated ACR" or "normal." The presence of ACR diagnostic features (epithelial injury, lamina propria [LP] inflammation with resident cell population, and crypt apoptotic body [AB] quantification) were evaluated. A series of 15 age-matched screening intestinal allograft biopsies were used as controls. RESULTS: After treatment, epithelial injury as manifested by mucin depletion resolved by 2 week. LP inflammation was significantly reduced by 1 week after therapy, with a marked decrease in activated lymphocytes and eosinophils, and completely returned to control levels by week 3. Apoptosis fell below the diagnostic threshold for rejection (<6 AB/10 crypts) by week 2 and was equivalent to control biopsies at week 3. CONCLUSION: Knowledge of the sequence of the resolution of the histologic features of ACR after treatment may provide useful information to pathologists evaluating follow-up biopsies. These data show that both LP inflammation and crypt epithelial injury are reduced by 1 week after anti-rejection therapy and their persistence may signify ongoing rejection.

Quantification of intraepithelial lymphocytes in normal pediatric small intestinal allograft and native ilea.

BACKGROUND: The small bowel acts as one of the first lines of defense against intraluminal infections and antigenic stimuli. Pediatric small bowel transplant patients are at particular risk from such agents, especially viral enteridities. Quantification of intraepithelial lymphocytes (IEL) in architecturally normal small intestinal mucosal biopsies plays an important role in the diagnosis of conditions such as celiac disease and some viral infections. No studies to date have been done to quantify IEL numbers in pediatric small bowel allografts and in native pediatric ilea. Our study investigated the IEL:enterocyte (EC) ratio in pediatric allograft and native ilea. METHODS: Hematoxylin and eosin slides from 50 surveillance endoscopic biopsies of small bowel allografts taken from patients <8 years of age and 50 terminal ileal biopsies from aged-matched control populations were reviewed. IEL:EC ratios were averaged from five well-oriented villi in each case. IEC numbers were compared between biopsies from proximal (afferent) and distal (efferent) limbs of double-barrel allograft stomas, as well as native terminal ilea. RESULTS: Within small bowel allografts, the average number of villus tip IELs was 1.3/20 ECs (standard deviation [SD] 0.6) in the proximal limb and 1.0/20 ECs in the distal (SD 0.6 P < .01). This value was significantly lower than in the control ilea (2.1/20 EC [SD 0.6]; P < .01, each). The overall distribution of lymphocytes was in a similar pattern throughout the villus with IEL:EC ratios on villus sides from proximal allografts, distal allografts, and native ilea being 1:20, 0.8:20, and 2:20, respectively. CONCLUSIONS: The results suggest that approximately one to two IEL per 20 ECs at villus tips may represent a "normal" intraepithelial inflammatory cell population in small bowel allografts. The value is lower than that seen in age-matched native ileal biopsies. IEL numbers are significantly higher in the proximal limb compared to the distal limb of double-barrel stomas.

Histologic features of cytomegalovirus enteritis in small bowel allografts.

BACKGROUND: Cytomegalovirus (CMV) is one of the most common viral infections to affect solid organ transplant patients, most frequently owing to reactivation of a latent infection as a result of immunosuppression. CMV enteritis (CE) may enter into the differential diagnosis of acute rejection in biopsies of small bowel (SB) allografts, where differentiation is important due to disparate therapies. OBJECTIVE: The aim of this study was to identify histologic features in SB allografts that may suggest CE. METHODS: The case files for a single institution were queried for all cases of SB mucosal biopsies with cells positive by CMV immunoperoxidase staining. Morphologic and clinical information was reviewed. RESULTS: Six biopsies demonstrating immunoperoxidase-confirmed CE were identified in a retrospective review of the records of a single institution. A common predisposing factor was the administration of high-dose steroids within a month before CE diagnosis. Most cases (66%) displayed a demarcated area of villous/crypt loss with an abundance of plasma cells and lymphocytes and a paucity of eosinophils. One case showed an acute enteritis-like pattern of injury, corresponding with a higher number of CMV-positive cells. CMV inclusions were visible on hematoxylin-eosin stains in all but 1 case. In no case were histologic criteria for acute cellular rejection met. CONCLUSIONS: The presence of circumscribed area of mucosal injury with few eosinophils or an acute enteritis pattern should prompt the identification of viral inclusions or the acquisition of a CMV immunostain.

Mitochondrial changes in cidofovir therapy for BK virus nephropathy.

Polyoma (BK) virus nephropathy (BKVN) is often treated with the nucleotide analog cidofovir. An adverse effect of this drug class is proximal tubular toxicity, and ultrastructural abnormalities in proximal tubular mitochondria have been observed in patients treated with similar drugs for other viral infections. We report similar changes in biopsies from BKVN treated with cidofovir. Renal allograft biopsies showing BKVN, on which electron microscopy was performed, were categorized into 3 groups: initial diagnosis (BD), postcidofovir treatment (CT), and posttreatment with immunosuppression reduction (IR). Nineteen cases from each group were randomly selected. Mitochondrial changes were present in 6 biopsies from patients receiving CT therapy (31.5%), ranging from diffuse mitochondrial swelling to profound morphologic changes. No similar abnormalities were seen in other groups. In those with atypical mitochondria, the mean number of cidofovir doses was 2.67, with an average interval between last dose and biopsy of 2.17 weeks. CT patients without mitochondrial changes had a mean of 4.6 doses and an average interval between last dose and biopsy of 27.2 weeks. Some renal transplant patients treated with cidofovir display alterations in proximal tubular mitochondria akin to those seen with similar drugs. The findings support the mitochondrial toxicity of nucleotide analogs.