Intensive Immunofluorescence Staining Methods for Low Expression Protein: Detection of Intestinal Stem Cell Marker LGR5

Continuous formation of small clusters with LGR5-positive cells contributes to tumor growth in a colorectal cancer xenograft model

New cancer characteristics can be discovered by focusing on the process of tumor formation. Cancer stem cells (CSCs) are a key subpopulation, as they are theorized to be at the apex of the tumor hierarchy. We can better understand their function in the tumor hierarchy by using sectioned samples to observe the growth of tumors from their origins as CSCs. In this study, we evaluated the growth of moderate differentiated colorectal cancer from LGR5-positive cells, which is a CSC marker of colorectal cancer, using xenograft and three-dimensional culture models spatiotemporally. These cells express LGR5 at high levels and show CSC phenotypes. To detect them, we used a previously generated antibody that specifically targets LGR5, and were therefore able to observe LGR5-positive cells aggregating into small clusters (sCLs) over the course of tumor growth. Because these LGR5-expressing sCLs formed continuously during growth mainly in the invasive front, we concluded that the structure must contribute significantly to the expansion of CSCs and to tumor growth overall. We confirmed the formation of sCLs from gland structures using a three-dimensional culture model. In addition, sCLs exhibited upregulated genes related to stress response and partial/hybrid epithelial-mesenchymal transition (EMT), as well as genes reported to be prognosis factors. Finally, sCLs with high LGR5 expression were identified in clinical samples. Based on these results, we elucidate how sCLs are an important contributors to tumor growth and the expansion of CSCs.

Three-dimensional culture models mimic colon cancer heterogeneity induced by different microenvironments

Colorectal cancer demonstrates intra-tumour heterogeneity formed by a hierarchical structure comprised of cancer stem cells (CSCs) and their differentiated progenies. The mechanism by which CSCs are maintained and differentiated needs to be further elucidated, and there is evidence that the tumour microenvironment governs cancer stemness. Using PLR123, a colon cancer cell line with CSC properties, we determined the culture conditions necessary to establish a pair of three-dimensional (3D) culture models grown in Matrigel, designated stemCO and diffCO. The conditions were determined by comparing the phenotypes in the models with PLR123 mouse xenografts colonising lung and liver. StemCO resembled LGR5-positive undifferentiated tumours in the lung, and diffCO had lumen structures composed of polarised cells that were similar to the ductal structures found in differentiated tumours in the liver. In a case using the models for biomedical research, treatment with JAG-1 peptide or a γ-secretase inhibitor modified the Notch signaling and induced changes indicating that the signal participates in lumen formation in the models. Our results demonstrate that culture conditions affect the stemness of 3D culture models generated from CSCs and show that comparing models with different phenotypes is useful for studying how the tumour environment regulates cancer.

New Insight into the Role of Nitric Oxide Pathways in Pancreas

Nitric oxide (NO) is generated by a family of enzymes termed NO synthases (NOS) that convert L-arginine to NO and citrulline. The role of NO as an important biological mediator and recognition of the pathophysiological significance of superoxides/NO interaction has led to an intensive research and development of therapies based on the interception of the NO signaling cascade in the pancreatitis course. However, the presence and localization of the NO-generating enzymes in various organs including pancreas are subject to controversy. We assumed that this controversy might reflect rather the diversity of experimental approaches and an insufficient sensitivity of the methods used. Applying tyramide signal amplification (TSA) immunohistochemical technology, we were able detect all three NOS isoforms both in exocrine and endocrine compartments and in the vasculature in the normal pancreas and in pancreatitis. This also allowed us to demonstrate that oxidative stress runs ahead of NOS up-regulation, which implies that the NO enhancement in the course of pancreatitis is likely to be an adaptive mechanism aimed at maintaining the homeostatic cellular level of the bioactive NO. The aims of this minireview are to describe normal intrapancreatic NO pathways and the role of NO in the pancreatitis course.

A simple method for histopathological evaluation of organoids

In vitro-cultured 3D structures called organoids have become important tools for biological research, but there is little information concerning simple and efficient methods to evaluate organoid morphology. To address this issue, we attempted to establish a simple method by applying conventional histopathology that enables observation of multiple organoids on a single cross section, maintains good morphology, and is applicable to various histopathological stains. By centrifugation in unsolidified agarose solution, we were able to accumulate the organoids onto a single plane. The morphology was well preserved, and the various morphological types and sizes of organoid structures were identified. This method was also applicable for special staining, immunohistochemistry, and immunofluorescence staining. This method makes it possible to utilize the advantages of conventional pathological methods when studying organoids.