The effect of intermittent hypoxia and fecal microbiota of OSAS on genes associated with colorectal cancer

Jia Gao,Hailong Cao,Bangmao Wang,Qiang Zhang

doi:10.1007/s11325-020-02204-z

Abstract

PurposeColorectal cancer (CRC) is one of the common causes of cancer death worldwide. Obstructive sleep apnea syndrome (OSAS), sharing many risk factors in common with CRC, is prevalent among CRC patients. OSAS may promote the CRC development independently but the mechanism is still unknown. Intermittent hypoxia (IH) is one of the characteristics of OSAS, and hypoxia may influence the genes associated with CRC. Intestinal microbiota plays important role in CRC carcinogenesis, and OSAS patients have been shown to have intestinal microbiota dysbiosis. We hypothesized that IH and intestinal microbiota dysbiosis may be involved for CRC in patients with OSAS.MethodsWe established precancerous cell models of CRC with Immorto-Min colonic epithelial (IMCE) cells. First, the cells were exposed to IH in a special chamber for 4 h, 8 h, and 12 h. Feces from 6 patients with OSAS and 6 healthy controls were collected and made into sterile fecal fluid for incubation with IMCE cells for 12 h. The cells were then exposed to IH for 4 h, 8 h, and 12 h. After IH exposure, the expressions of genes and inflammation cytokines associated with CRC, such as β-catenin, STAT3, HIF-1α, IL-6, TNF-α, c-myc, and cyclinD1, were tested.ResultsIH activated the expression of HIF-1α and STAT3 both in mRNA and protein level (HIF-1α: P = 0.015 for mRNA level, P = 0.027 for protein level; STAT3: P = 0.023 for mRNA level, P = 0.023 for protein level), and promoted p-STAT3 shifting to the nucleus (P = 0.023). The mRNA of β-catenin (P = 0.022) and cyclinD1 (P = 0.023) was elevated, but there was no change for the β-catenin protein in the nucleus. Gut microbiota of OSAS patients promoted the expression of STAT3 (protein level: 0 h: P = 0.037; 4 h: P = 0.046; 8 h: P = 0.049; 12 h: P = 0.037), promoted p-STAT3 (4 h: P = 0.049; 8 h: P = 0.046; 12 h: P = 0.046) shifting to the nucleus, and also elevated the expression of IL-6 and TNF-α in mRNA level at 4 h (IL-6: P = 0.037, TNF-α: P = 0.037) and 8 h (IL-6: P = 0.037, TNF-α: P = 0.037). The protein of β-catenin in the nucleus was not affected by IH and gut microbiota from OSAS.ConclusionsOur study demonstrated that IH and gut microbiota of patients with OSAS activated HIF-1α expression and STAT3 pathway in IMCE cells, with no influence on β-catenin pathway, which suggested that IH, STAT3 pathway, chronic inflammation, and intestinal microbiota dysbiosis may be involved in CRC carcinogenesis correlated with OSAS These findings must be interpreted cautiously and further research is necessary to clarify the causative steps in CRC development.

Highlights

Colorectal cancer (CRC) is very common worldwide, which lists third in morbidity and second in mortality overall worldwide [1], and the trend is still uprising in many countries, such as Russia, China, and Brazil
Our study demonstrated that Intermittent hypoxia (IH) and gut microbiota of patients with Obstructive sleep apnea syndrome (OSAS) activated hypoxia-induced factor (HIF)-1α expression and STAT3 pathway in Immorto-Min colonic epithelial (IMCE) cells, with no influence on β-catenin pathway, which suggested that IH, STAT3 pathway, chronic inflammation, and intestinal microbiota dysbiosis may be involved in CRC carcinogenesis correlated with OSAS These findings must be interpreted cautiously and further research is necessary to clarify the causative steps in CRC development
We could observe that the mRNA level of HIF-α was significantly elevated after 8 h and 12 h IH treatment compared with the control group (C group) (P < 0.05, F = 27.819), and increased during the longer IH exposure, but there were no statistically significant differences in the levels between 4 and 8 h IH groups (Fig. 1)

Summary

Introduction

Colorectal cancer (CRC) is very common worldwide, which lists third in morbidity and second in mortality overall worldwide [1], and the trend is still uprising in many countries, such as Russia, China, and Brazil. Twenty percent emergence of CRC could be referred to genetic background, such as hereditary non-polyposis colorectal cancer (HNPCC or Lynch syndrome), hamartomatous polyposis syndrome, and familial adenomatous polyposis (FAP), with characteristic of family history. Insufficient intake of dietary fiber, high consumption of red or processed meat, body fatness, alcohol drinks, gut microbiota disorder [3], and ulcerative colitis [4] have been proved to have the relationship with CRC. People with these characteristics usually have obesity problem and many metabolism abnormalities, and together with sleep apnea problems. Sleep apnea is prevalent among colorectal cancer patients [5]

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