In Vitro Organoid-Based Assays Reveal SMAD4 Tumor-Suppressive Mechanisms for Serrated Colorectal Cancer Invasion.

Colon cancer is the third most prominent cancer and second leading cause of cancer-related deaths in the United States. Up to 20% of colon cancers follow the serrated tumor pathway driven by mutations in the MAPK pathway. Loss of SMAD4 function occurs in the majority of late-stage colon cancers and is associated with aggressive cancer progression. Therefore, it is important to develop technology to accurately model and better understand the genetic mechanisms behind cancer invasion. Organoids derived from tumors found in the Smad4KO BRAFV600E/+ mouse model present multiple phenotypes characteristic of invasion both in ex vivo and in vivo systems. Smad4KO BRAFV600E/+ tumor organoids can migrate through 3D culture and infiltrate through transwell membranes. This invasive behavior can be suppressed when SMAD4 is re-expressed in the tumor organoids. RNA-Seq analysis reveals that SMAD4 expression in organoids rapidly regulates transcripts associated with extracellular matrix and secreted proteins, suggesting that the mechanisms employed by SMAD4 to inhibit invasion are associated with regulation of extracellular matrix and secretory pathways. These findings indicate new models to study SMAD4 regulation of tumor invasion and an additional layer of complexity in the tumor-suppressive function of the SMAD4/Tgfß pathway.

Acute appendicitis secondary to Entamoeba histolytica infestation.

Acute appendicitis secondary to amoebic infestation is a rare possibility, especially in endemic areas. If left untreated, significant postoperative morbidity and mortality can result from the spread of amoebic trophozoites and subsequent tissue reaction. Histopathological examination of the resected appendix with demonstration of invasion by the parasite is mandatory for establishing a diagnosis. Careful examination of the specimen is thus of paramount importance.

Anatomical mapping of the biliary tree during laparoscopic cholecystectomy by using indocyanine green dye.

Background: Fluorescent cholangiography using intravenous indocyanine green (ICG) is a noninvasive technique that enables real-time intraoperative imaging of biliary anatomy. The objective of this study was to visualise the biliary anatomy in routine and complicated cases of laparoscopic cholecystectomy (LC). Methods: This was a prospective observational study of patients undergoing LC for various indications. After obtaining consent, 5 mg/1 ml of ICG dye was administered intravenously in each patient, 2 h before the incision time. LC was performed by standard critical view of the safety technique. The biliary tree was visualised using near-infrared (NIR) view before clipping any structure. Intra-operative findings, visibility of ducts in the NIR view, conversion, adverse reactions to ICG and post-operative outcomes in all patients were recorded. Results: Out of 43 patients undergoing LC, 24 had cholelithiasis, 10 had acute cholecystitis, 3 had chronic cholecystitis, 1 had mucocele of the gall bladder, 1 had gall bladder polyp and 4 cases had common bile duct (CBD) stone clearance with endoscopic retrograde cholangiopancreatography. Cystic duct (CD) and CBD were visualised in 100% of cases among all groups except for those with acute cholecystitis where CD and CBD were visualised in 90% and 80% of cases, respectively, and in chronic cholecystitis CD and CBD were visualised in 66.6% and 80% of patients, respectively. There was one elective conversion in the chronic cholecystitis group due to dense adhesions and non-progression. Only the CBD was visualised in this case. There were no cases of CBD injury or any allergic reactions to the dye. Conclusions: Fluorescent cholangiography during LC is a safe and non-invasive method, allowing superior anatomical visualisation of the biliary tree in comparison to simple laparoscopy. This method can correct misinterpretation errors and detect aberrant duct anatomy, thus increasing the confidence of the operating surgeon enabling safe dissection. This simple technique has the potential to become standard practice to avoid bile duct injury during LC.

SMAD4 is critical in suppression of BRAF-V600E serrated tumorigenesis.

BRAF-driven colorectal cancer is among the poorest prognosis subtypes of colon cancer. Previous studies suggest that BRAF-mutant serrated cancers frequently exhibit Microsatellite Instability (MSI) and elevated levels of WNT signaling. The loss of tumor-suppressor Smad4 in oncogenic BRAF-V600E mouse models promotes rapid serrated tumor development and progression, and SMAD4 mutations co-occur in human patient tumors with BRAF-V600E mutations. This study assesses the role of SMAD4 in early-stage serrated tumorigenesis. SMAD4 loss promotes microsatellite stable (MSS) serrated tumors in an oncogenic BRAF-V600E context, providing a model for MSS serrated cancers. Inactivation of Msh2 in these mice accelerated tumor formation, and whole-exome sequencing of both MSS and MSI serrated tumors derived from these mouse models revealed that all serrated tumors developed oncogenic WNT mutations, predominantly in the WNT-effector gene Ctnnb1 (ß-catenin). Mouse models mimicking the oncogenic ß-catenin mutation show that the combination of three oncogenic mutations (Ctnnb1, Braf, and Smad4) are critical to drive rapid serrated dysplasia formation. Re-analysis of human tumor data reveals BRAF-V600E mutations co-occur with oncogenic mutations in both WNT and SMAD4/TGFß pathways. These findings identify SMAD4 as a critical factor in early-stage serrated cancers and helps broaden the knowledge of this rare but aggressive subset of colorectal cancer.