Role of nitric oxide in the pathogenesis of Barrett’s-associated carcinogenesis

Inflammation as a driver of hematological malignancies

Hematopoiesis is a tightly regulated process that produces all adult blood cells and immune cells from multipotent hematopoietic stem cells (HSCs). HSCs usually remain quiescent, and in the presence of external stimuli like infection or inflammation, they undergo division and differentiation as a compensatory mechanism. Normal hematopoiesis is impacted by systemic inflammation, which causes HSCs to transition from quiescence to emergency myelopoiesis. At the molecular level, inflammatory cytokine signaling molecules such as tumor necrosis factor (TNF), interferons, interleukins, and toll-like receptors can all cause HSCs to multiply directly. These cytokines actively encourage HSC activation, proliferation, and differentiation during inflammation, which results in the generation and activation of immune cells required to combat acute injury. The bone marrow niche provides numerous soluble and stromal cell signals, which are essential for maintaining normal homeostasis and output of the bone marrow cells. Inflammatory signals also impact this bone marrow microenvironment called the HSC niche to regulate the inflammatory-induced hematopoiesis. Continuous pro-inflammatory cytokine and chemokine activation can have detrimental effects on the hematopoietic system, which can lead to cancer development, HSC depletion, and bone marrow failure. Reactive oxygen species (ROS), which damage DNA and ultimately lead to the transformation of HSCs into cancerous cells, are produced due to chronic inflammation. The biological elements of the HSC niche produce pro-inflammatory cytokines that cause clonal growth and the development of leukemic stem cells (LSCs) in hematological malignancies. The processes underlying how inflammation affects hematological malignancies are still not fully understood. In this review, we emphasize the effects of inflammation on normal hematopoiesis, the part it plays in the development and progression of hematological malignancies, and potential therapeutic applications for targeting these pathways for therapy in hematological malignancies.

BMP4 promotes a phenotype change of an esophageal squamous epithelium via up-regulation of KLF4

INTRODUCTION

Barrett's esophagus is a metaplastic lesion. However, the cellular and molecular mechanisms involved are poorly understood. The aim of this study was to investigate the roles of KLF4 and BMP4 in the pathogenesis of Barrett's epithelium.

MATERIALS AND METHODS

Immunohistochemistry was used to analyse the expression of KLF4, BMP4, CDX2, MUC2 and MUC5AC in human esophageal specimens. Human esophageal squamous epithelial cells were subjected to bile acid treatment and used in transfection experiments. Quantitative real-time PCR and Western blot analysis were used to detect the expression of KLF4, BMP4, CDX2, MUC2 and MUC5ac.

RESULTS

In human tissues, Barrett's epithelium strongly expressed BMP4, p-Smad1/5/8 and KLF4. Furthermore, bile acids increased the expression of BMP4, KLF4, p-Smad1/5/8, CDX2, MUC2 and MUC5ac in esophageal epithelial cells in a time-dependent manner. Moreover, we found that BMP4 up-regulated the expression of KLF4, CDX2, MUC2 and MUC5ac, but Noggin, a specific BMP4 antagonist, can block the expression of KLF4, CDX2, MUC2 and MUC5ac induced by BMP4. However, BMP4 cannot induce the expression of CDX2, MUC2 and MUC5ac in cells with KLF4 siRNA, and Noggin cannot block the expression of KLF4, CDX2, MUC2 and MUC5ac in cells transfected with the KLF4 expression vector.

CONCLUSION

Our results demonstrate that BMP4 promotes a phenotype change of an esophageal squamous epithelium via up-regulation of KLF4.

The esophageal microbiota in health and disease

The esophageal mucosa is among the sites colonized by human microbiota, the complex microbial ecosystem that colonizes various body surfaces and is increasingly recognized to play roles in several physiological and pathological processes. Our understanding of the composition of the esophageal microbiota in health and disease is challenged by the need for invasive sampling procedures and by the dynamic nature of the esophageal environment and remains limited in comparison with the information available for other body sites. Members of the genus Streptococcus appear to be the major components of the microbiota of the healthy esophagus, although the presence of several other taxa has also been reported. Dysbiosis, consisting of enrichment in some Gram-negative taxa (including Veillonella, Prevotella, Haemophilus, Neisseria, Campylobacter, and Fusobacterium), has been reported in association with gastroesophageal reflux disease and is hypothesized to contribute to the evolution of this condition toward Barrett's esophagus (which is the most common esophageal precancerous lesion) and, eventually, adenocarcinoma. Some Campylobacter species (mostly C. concisus) are also putatively involved in the progression of disease toward adenocarcinoma. However, variable findings have recently been reported in additional studies. Causative relationships between dysbiosis or specific bacterial species and esophageal diseases remain controversial and warrant further investigations.