Abstract
Liver cancer exhibits the fourth most common cause of cancer-associated mortality worldwide. Due to the rapid growth, solid tumors undergo severe hypoxia and produce high levels of extracellular adenosine to maintain homeostasis. A previous study indicated that the hypoxic condition in liver cancer increased hepatic adenosine, which is known to facilitate cancer survival and proliferation. Extracellular adenosine has been revealed to regulate pathological and physiological processes in cells and tissues. However, its pathophysiological role in liver cancer remains undetermined. Emerging evidence has indicated that the adenosine A2B receptor promotes the progression of liver cancer. Therefore, it was hypothesized that HIF-1α is a transcriptional regulator of A2B in human liver cancer. The current study determined A2B expression of a number of liver cancer cell lines and performed functional studies of HIF-1α as a master transcriptional regulator of hepatic A2B signaling during hypoxic conditions. The current study aimed to identify the promoter region of A2B, which has a hypoxia response element, by performing luciferase assays. The present study demonstrated that reduced HIF-1α expression is associated with low expression of A2B, and HIF-1α overexpression is associated with A2B induction. Furthermore, the siRNA-mediated downregulation of A2B inhibited the growth and proliferation of HepG2, which is a liver cancer cell line. The relationship between HIF-1α and A2B expression was also identified in human liver cancer specimens. In conclusion, the current study indicated that A2B is induced by the HIF-1α transcriptional regulator during hypoxia, and it may be a potential pharmacologic and therapeutic target for the treatment of patients with liver cancer.