COX-2/PGE2 Axis Regulates HIF2α Activity to Promote Hepatocellular Carcinoma Hypoxic Response and Reduce the Sensitivity of Sorafenib Treatment.

Purpose: Hypoxia-inducible factor-2α (HIF2α) is regarded as a preferential target for individualized hepatocellular carcinoma (HCC) treatment and sorafenib resistance. Our study aimed to identify the regulatory mechanisms of HIF2α activity under hypoxic conditions. We sought to determine whether the COX-2/PGE2 axis is involved in the regulatory mechanisms of HIF2α activity and of sorafenib resistance in hypoxic HCC cells.Experimental Design: The cell viability, migration, and invasion abilities were measured to analyze the effects of HIF2α on hypoxic HCC cells. Both in vitro and in vivo HCC models were used to determine whether the COX-2/PGE2 axis is a driver of HIF2α level and activity, which then reduces the sensitivity of sorafenib treatment in hypoxic HCC cells.Results: Under hypoxic conditions, the COX-2/PGE2 axis effectively stabilized HIF2α and increased its level and activity via decreasing von Hippel-Lindau protein (p-VHL) level, and also enhanced HIF2α activity by promoting HIF2α nuclear translocation via MAPK pathway. The activation of HIF2α then led to the enhanced activation of VEGF, cyclin D1, and TGFα/EGFR pathway to mediate HCC development and reduce the sensitivity of sorafenib. More importantly, COX-2-specific inhibitors synergistically enhanced the antitumor activity of sorafenib treatment.Conclusions: Our data obtained demonstrate that the COX/PGE2 axis acts as a regulator of HIF2α expression and activity to promote HCC development and reduce sorafenib sensitivity by constitutively activating the TGFα/EGFR pathway. This study highlights the potential of COX-2-specific inhibitors for HCC treatment and particularly for enhancing the response to sorafenib treatment. Clin Cancer Res; 24(13); 3204-16. ©2018 AACR.

Association between hyperhomocysteinemia and stroke with atherosclerosis and small artery occlusion depends on homocysteine metabolism-related vitamin levels in Chinese patients with normal renal function.

This study was conducted to investigate the role of different homocysteine metabolism-related vitamin (HMRV) levels in the correlation between hyperhomocysteinemia (HHCY) and ischemic stroke (IS) subtypes. Three hundred and forty-eight IS patients manifesting different vascular subtypes were subclassified on the basis of HMRV deficiencies. Correlation between HHCY and IS subtypes was investigated in all the subgroups. In this study, HHCY was significantly correlated with the IS subtypes in large artery atherosclerosis (OR 1.126, 95%CI: 1.051 ~ 1.206, P = 0.001) and small artery occlusion (OR 1.105, 95%CI: 1.023 ~ 1.193, P = 0.012). Subgroup analysis revealed a correlation between HHCY and IS subgroup (OR 1.201, 1.178, 95%CI: 1.081 ~ 1.334, 1.058 ~ 1.313, P = 0.001, P = 0.003, respectively) in HMRV deficiency, but not significantly with the IS subgroup in normal HMRV levels. Serum vitamin B12 concentrations are inversely correlated with both IS subtypes in HMRV deficiency subgroups (OR 0.992, 0.995, 95%CI: 0.987 ~ 0.996, 0.991 ~ 0.999, P < 0.001, P = 0.007, respectively), which may contribute to HHCY incidence in these populations. The correlation between HHCY and IS subtypes is affected by HMRV levels in this case-control study. Our findings are helpful to understand the inconsistency in prior homocysteine studies. Serum vitamin B12 levels may play a critical role in HHCY incidence in this Chinese population.Cerebrovascular disease has emerged as the leading cause of disability and mortality in both urban and rural areas of China (Neurology branch of Chinese Medical Association 2015). Ischemic stroke (IS) constitutes 60% to 80% of all cerebrovascular disease (Neurology branch of Chinese Medical Association 2014). Among a variety of risk factors, hyperhomocysteinemia (HHCY) has been closely correlated with IS due to intracranial small-vessel disease and extracranial large-artery disease (Selhub et al. 1995; Eikelboom et al. 2000; Alvarez et al. 2012; Jeon et al. 2014). However, the failure to lower homocysteine (HCY) via homocysteine metabolism-related vitamin (HMRV, including folic acid and vitamin B12 but not vitamin B6 in this study) supplementation to reduce stroke morbidity questions the role of HCY as a risk factor for stroke (Lonn et al. 2006; Hankey et al. 2010). Theoretically, HMRV supplementation merely lowers the incidence of stroke induced by HHCY resulting from HMRV deficiency, whereas HHCY-induced stroke concomitant with normal HMRV levels may be refractory to treatment. The correlation between HCY varying with HMRV levels and IS subtypes is still unclear. In this study, we investigated the impact of variation in HMRV levels on the correlation between HHCY and IS subtypes in 348 acute IS patients with large and small vessel diseases. We sought to determine the factors underlying the conflicting results associated with lowering HCY by HMRV supplementation to reduce stroke incidence.