NHE7 upregulation potentiates the uptake of small extracellular vesicles by enhancing maturation of macropinosomes in hepatocellular carcinoma

BACKGROUND

Small extracellular vesicles (sEVs) mediate intercellular communication that contributes to hepatocellular carcinoma (HCC) progression via multifaceted pathways. The success of cell entry determines the effect of sEV on recipient cells. Here, we aimed to delineate the mechanisms underlying the uptake of sEV in HCC.

METHODS

Macropinocytosis was examined by the ability of cells to internalize dextran and sEV. Macropinocytosis was analyzed in Na(+)/H(+) exchanger 7 (NHE7)-knockdown and -overexpressing cells. The properties of cells were studied using functional assays. pH biosensor was used to evaluate the intracellular and endosomal pH. The expression of NHE7 in patients' liver tissues was examined by immunofluorescent staining. Inducible silencing of NHE7 in established tumors was performed to reveal the therapeutic potential of targeting NHE7.

RESULTS

The data revealed that macropinocytosis controlled the internalization of sEVs and their oncogenic effect on recipient cells. It was found that metastatic HCC cells exhibited the highest efficiency of sEV uptake relative to normal liver cells and non-metastatic HCC cells. Attenuation of macropinocytic activity by 5-(N-ethyl-N-isopropyl)-amiloride (EIPA) limited the entry of sEVs and compromised cell aggressiveness. Mechanistically, we delineated that high level of NHE7, a sodium-hydrogen exchanger, alkalized intracellular pH and acidized endosomal pH, leading to the maturation of macropinosomes. Inducible inhibition of NHE7 in established tumors developed in mice delayed tumor development and suppressed lung metastasis. Clinically, NHE7 expression was upregulated and linked to dismal prognosis of HCC.

CONCLUSIONS

This study advances the understanding that NHE7 enhances sEV uptake by macropinocytosis to promote the malignant properties of HCC cells. Inhibition of sEV uptake via macropinocytosis can be exploited as a treatment alone or in combination with conventional therapeutic approaches for HCC.

Intratumoral microbiome impacts immune infiltrates in tumor microenvironment and predicts prognosis in esophageal squamous cell carcinoma patients

Background

Different intratumoral microbiotaexist in different tumors and play a crucial function in carcinogenesis. However, whether they impact clinical outcomes in esophageal squamous cell carcinoma (ESCC) and their mechanism remain unclear.

Methods

16S rDNA amplicon sequencing was performed on surgically resected samples from 98 ESCC patients to analyze intratumoral microbiome abundance and composition. Multiplex fluorescent immunohistochemistry staining was used to profile the phenotypes of immune infiltrates in the tumor microenvironment (TME).

Results

Patients with higher intratumoral Shannon index had significantly worse surgical outcomes. When patients were divided into short-term survivors and long-term survivors based on the median survival time, both intratumoral alpha-diversity and beta-diversity were found to be significantly inconsistent, and the relative abundance of Lactobacillus and Leptotrichia emerged as the two microorganisms that probably influenced the survival of ESCC patients. Only Lactobacillus in ESCC was validated to significantly worsen patients' prognoses and to be positively correlated with the Shannon index. Multivariate analysis revealed that the intratumoral Shannon index, the relative abundance of Lactobacillus, and the pathologic tumor-node-metastasis (pTNM) stage were independently associated with patients' overall survival. Furthermore, the relative abundance of both Lactobacillus and Shannon index was positively correlated with the proportions of PD-L1⁺ epithelial cells (ECs) and tumor-associated macrophages (TAMs). The Shannon index was negatively correlated with the proportions of natural killer (NK) cells in the TME.

Conclusions

A high abundance of intratumoral Lactobacillus and bacterial alpha-diversity was associated with the formation of the immunosuppressive TME and predicted poor long-term survival in ESCC patients.