Probes for LGR5

During human gastric carcinogenesis, intestinal metaplasia (IM) is frequently seen in the atrophic stomach. In mice, a distinct type of metaplasia known as spasmolytic polypeptide-expressing metaplasia (SPEM) is found in several inflammatory and genetically engineered models. Given the diversity of long- and short-term models of mouse SPEM, it remains unclear whether all models have a shared or distinct molecular mechanism. The origin of SPEM in mice is currently under debate. It is postulated that stem or progenitor cells acquire genetic alterations that then supply metaplastic cell clones, while the possibility of transdifferentiation or dedifferentiation from mature gastric chief cells has also been suggested. In this study, we report that loss of chief cells was sufficient to induce short-term regenerative SPEM-like lesions that originated from chief cell precursors in the gastric neck region. Furthermore, Lgr5+ mature chief cells failed to contribute to both short- and long-term metaplasia, whereas isthmus stem and progenitor cells efficiently contributed to long-term metaplasia. Interestingly, multiple administrations of high-dose pulsed tamoxifen induced expansion of Lgr5 expression and Lgr5-CreERT recombination within the isthmus progenitors apart from basal chief cells. Thus, we conclude that short-term SPEM represents a regenerative process arising from neck progenitors following chief cell loss, whereas true long-term SPEM originates from isthmus progenitors. Mature gastric chief cells may be dispensable for SPEM development.

Abstract

Colon cancer stem cells (CSCs) are closely related to tumorigenesis and treatment response, and LGR5 is currently the most robust and reliable CSC marker in colorectal cancer (CRC). However, LGR5 expression in CRC tumor budding (TB) is not well understood. We examined the clinicopathological and prognostic significance of LGR5 in CRC TB. LGR5 expression was evaluated by RNAscope, a newly developed RNA in situ hybridization technique, using a tissue microarray consisting of 55 patient samples of TB in colon adenocarcinoma (CA) selected from the medical archives at our hospital. Patients were stratified into negative and positive LGR5 expression groups. Inflammatory cell infiltration was weaker and histological grade was lower in the LGR5-positive group compared with the LGR5-negative group (P = 0.0407 and P = 0.0436, respectively). There was a significant difference in OS between the LGR5-positive group and LGR5-negative group (log-rank test, P = 0.0088). Cox proportional hazards models revealed that the LGR5-positive group (Overall survival (OS) = 0.37, 95% CI: 0.17–0.79, P = 0.0101) had better OS. LGR5 expression may be affected by inflammatory cell infiltration in the budding area of CA and is an important potential marker of prognosis.

In mice, the incisors grow throughout the animal's life, and this continuous renewal is driven by dental epithelial and mesenchymal stem cells. Sox2 is a principal marker of the epithelial stem cells that reside in the mouse incisor stem cell niche, called the labial cervical loop, but relatively little is known about the role of the Sox2+ stem cell population. In this study, we show that conditional deletion of Sox2 in the embryonic incisor epithelium leads to growth defects and impairment of ameloblast lineage commitment. Deletion of Sox2 specifically in Sox2+ cells during incisor renewal revealed cellular plasticity that leads to the relatively rapid restoration of a Sox2-expressing cell population. Furthermore, we show that Lgr5-expressing cells are a subpopulation of dental Sox2+ cells that also arise from Sox2+ cells during tooth formation. Finally, we show that the embryonic and adult Sox2+ populations are regulated by distinct signaling pathways, which is reflected in their distinct transcriptomic signatures. Together, our findings demonstrate the heterogeneity of the Sox2+ population and reinforce its importance for incisor homeostasis.

Absorptive and secretory cells of the small intestine are derived from a single population of Lgr5-expressing stem cells. While key genetic pathways required for differentiation into specific lineages have been defined, epigenetic programs contributing to this process remain poorly characterized. Members of the BET family of chromatin adaptors contain tandem bromodomains that mediate binding to acetylated lysines on target proteins to regulate gene expression. In this study, we demonstrate that mice treated with a small molecule inhibitor of BET bromodomains, CPI203, exhibit greater than 90% decrease in tuft and enteroendocrine cells in both crypts and villi of the small intestine, with no changes observed in goblet or Paneth cells. BET bromodomain inhibition did not alter the abundance of Lgr5-expressing stem cells in crypts, but rather exerted its effects on intermediate progenitors, in part through regulation of Ngn3 expression. When BET bromodomain inhibition was combined with the chemotherapeutic gemcitabine, pervasive apoptosis was observed in intestinal crypts, revealing an important role for BET bromodomain activity in intestinal homeostasis. Pharmacological targeting of BET bromodomains defines a novel pathway required for tuft and enteroendocrine differentiation and provides an important tool to further dissect the progression from stem cell to terminally differentiated secretory cell.