Elevation of spermine remodels immunosuppressive microenvironment through driving the modification of PD-L1 in hepatocellular carcinoma.

BACKGROUND: Spermine is frequently elevated in tumor tissues and body fluids of cancer patients and is critical for cancer cell proliferation, migration and invasion. However, the immune functions of spermine in hepatocellular carcinoma progression remains unknown. In the present study, we aimed to elucidate immunosuppressive role of spermine in hepatocellular carcinoma and to explore the underlying mechanism. METHODS: Whole-blood spermine concentration was measured using HPLC. Human primary HCC tissues were collected to examine the expression of CaSR, p-Akt, ß-catenin, STT3A, PD-L1, and CD8. Mouse model of tumorigenesis and lung metastasis were established to evaluate the effects of spermine on hepatocellular carcinoma. Western blotting, immunofluorescence, real time PCR, digital Ca2+ imaging, and chromatin immunoprecipitation assay were used to investigate the underlying mechanisms by which spermine regulates PD-L1 expression and glycosylation in hepatocellular carcinoma cells. RESULTS: Blood spermine concentration in the HCC patient group was significantly higher than that in the normal population group. Spermine could facilitate tumor progression through inducing PD-L1 expression and decreasing the CD8+ T cell infiltration in HCC. Mechanistically, spermine activates calcium-sensing receptor (CaSR) to trigger Ca2+ entry and thereby promote Akt-dependent ß-catenin stabilization and nuclear translocation. Nuclear ß-catenin induced by spermine then activates transcriptional expression of PD-L1 and N-glycosyltransferase STT3A, while STT3A in turn increases the stability of PD-L1 through inducing PD-L1 protein N-glycosylation in HCC cells. CONCLUSIONS: This study reveals the crucial function of spermine in establishing immune privilege by increasing the expression and N-glycosylation of PD-L1, providing a potential strategy for the treatment of hepatocellular carcinoma. Video Abstract.

O-Sulfation disposition of curcumin and quercetin in SULT1A3 overexpressing HEK293 cells: the role of arylsulfatase B in cellular O-sulfation regulated by transporters.

Extensive phase II metabolic reactions (i.e., glucuronidation and sulfation) have resulted in low bioavailability and decreased biological effects of curcumin and quercetin. Compared to glucuronidation, information on the sulfation disposition of curcumin and quercetin is limited. In this study, we identified that BCRP and MRP4 played a critical role in the cellular excretion of curcumin-O-sulfate (C-O-S) and quercetin-O-sulfate (Q-O-S) by integrating chemical inhibition with transporter knock-down experiments. Inhibited excretion of sulfate (C-O-S and Q-O-S) caused significant reductions in cellular O-sulfation of curcumin (a maximal 74.4% reduction) and quercetin (a maximal 76.9% reduction), revealing a strong interplay of sulfation with efflux transport. It was further identified that arylsulfatase B (ARSB) played a crucial role in the regulation of cellular O-sulfation by transporters. ARSB overexpression significantly enhanced the reduction effect of MK-571 on the cellular O-sulfation (fmet) of the model compound (38.8% reduction for curcumin and 44.2% reduction for quercetin). On the contrary, ARSB knockdown could reverse the effect of MK-571 on the O-sulfation disposition of the model compound (29.7% increase for curcumin and 47.3% increase for quercetin). Taken together, ARSB has been proven to be involved in cellular O-sulfation, accounting for transporter-dependent O-sulfation of curcumin and quercetin. A better understanding of the interplay beneath metabolism and transport will contribute to the exact prediction of in vivo drug disposition and drug-drug interactions.

HGF/c-MET pathway contributes to cisplatin-mediated PD-L1 expression in hepatocellular carcinoma.

Cisplatin has been reported to promote the expression of programmed cell death ligand-1 (PD-L1) in some cancer cells. However, the underlying mechanism through which PD-L1 is transcriptionally regulated by cisplatin in hepatocellular carcinoma (HCC) cells remains largely unknown. In the present study, we found that the expression of hepatocyte growth factor (HGF), p-Akt, p-ERK, and PD-L1 was increased in cisplatin-treated SNU-368 and SNU-739 cells. HGF stimulation also increased PD-L1 expression in these cells. Moreover, Inhibition of HGF/c-MET, PI3K/Akt, and MEK/ERK signaling pathways can dramatically block cisplatin or HGF-induced PD-L1 expression in SNU-368 and SNU-739 cells. In vivo, combination PHA665752 with cisplatin significantly reduced tumor weight with increased infiltration of CD8+ T cells in the tumor. Taken together, our study suggested that HGF/c-Met axis-induced the activation of PI3K/Akt and MEK/ERK pathways contributes to cisplatin-mediated PD-L1 expression. These findings may provide an alternative avenue for the treatment of HCC.