Re-sensitization of 5-FU resistance by SPARC through negative regulation of glucose metabolism in hepatocellular carcinoma.

Secreted protein, acidic and rich in cysteine (SPARC), a calcium-binding matricellular glycoprotein, is implicated in the progression of many cancers. Currently, there is growing evidence for important functions of SPARC in a variety of cancers and its role in cancer depends on tumor types. In this study, we reported SPARC negatively regulated glucose metabolism in hepatocellular carcinoma (HCC). Overexpression of SPARC inhibited glucose uptake and lactate product through downregulation of key enzymes of glucose metabolism. On the other hand, knock down of SPARC reversed the phenotypes. Meanwhile, exogenous expression of SPARC in HepG2 cells resulted in tolerance to low glucose and was correlated with AMPK pathway. Interestingly, the 5-fluorouracil (5-FU)-resistant HepG2 cells showed increased glucose metabolism and downregulated SPARC levels. Finally, we reported the overexpression of SPARC re-sensitize 5-FU-resistant cells to 5-FU through inhibition of glycolysis both in vitro and in vivo. Our study proposed a novel function of SPARC in the regulation of glucose metabolism in hepatocellular carcinoma and will facilitate the development of therapeutic strategies for the treatments of liver tumor patients.

Netrin-1 promoted pancreatic cancer cell proliferation by upregulation of Mdm2.

Netrin-1 displays proto-oncogenic activity in several cancers, which is thought to result from the ability of netrin-1 secretions to stimulate survival when bound to associated receptors. The objective of this study was to determine the role of netrin-1 in pancreatic cancer cell proliferation in vitro. Our results revealed that netrin-1 overexpression promoted while its silence inhibited two pancreatic cancer cell lines. At the molecular level, we found that netrin-1 promoted cell proliferation by upregulation of murine double minute 2 (Mdm2). As a result, p53 protein contents were reduced in cells overexpressing netrin-1. Therefore, our data suggests the presence of a previously unknown network in the proliferation and progression of pancreatic cancer cells.

MiR-199a suppresses the hypoxia-induced proliferation of non-small cell lung cancer cells through targeting HIF1α.

Deregulated microRNAs (miRNAs) are small noncoding RNAs that are involved in the carcinogenesis of various cancers, including lung cancer. HIF1a has been suggested to be a master regulator of hypoxia-induced cell proliferation. The relationship between HIF1a expression and the progression of non-small cell lung cancer (NSCLC) is not fully understood, and whether HIF1a expression is regulated by miRNAs in this process remains unclear. In this study, we found that the upregulation of HIF1a expression and the reduction in miR-199a levels were highly associated with NSCLC progression. NSCLC cells derived from cancer tissues with low miR-199a levels showed high HIF1a expression and high proliferation capacity. Moreover, HIF1a and glycolysis inhibitors suppress the proliferation of NSCLC cells. MiR-199a overexpression suppressed the hypoxia-induced proliferation of NSCLC cells through targeting elevated HIF1a and blocking the downstream upregulation of PDK1 without affecting AKT activation. Together, these results indicate that downregulation of miR-199a is essential for hypoxia-induced proliferation through derepressing the expression of HIF1a expression and affecting HIF1a mediated glycolytic pathway in NSCLC progression.

SPARC regulates ferroptosis induced by sorafenib in human hepatocellular carcinoma.

BACKGROUND: Secreted protein acidic and rich in cysteine (SPARC) is implicated in cancer progression, but its role and associated molecular mechanism in the sorafenib sensitivity of hepatocellular carcinoma cells (HCC) remains elusive. METHODS: Human HCC cell lines Hep3B and HepG2 were treated with sorafenib alone or combined with activator or inhibitor of ferroptosis. Cell viability assay, reactive oxygen species (ROS) assay, lactate dehydrogenase (LDH) assay and western blot were used to study the regulatory mechanism of SPARC on HCC cells. RESULTS: Overexpression of SPARC enhanced the cytotoxic effect of sorafenib in Hep3B and HepG2 cells compared with parental cells. Depletion of SPARC decreased the cytotoxic effect of sorafenib in Hep3B and HepG2 cells compared with parental cells. Moreover, overexpression of SPARC significantly induced LDH release, whereas depletion of SPARC suppressed the release of LDH in Hep3B and HepG2 cells. Inhibition of ferroptosis exerted a clear inhibitory role against LDH release, whereas activation of ferroptosis promoted the release of LDH in HCC cells, as accompanied with deregulated expression of ferroptosis-related proteins. Furthermore, overexpression of SPARC induced oxidative stress, whereas depletion of SPARC suppressed the production of ROS. Deferoxamine (DFX)-induced inhibition of ferroptosis suppressed the production of ROS, while activation of ferroptosis promoted the contents of ROS in HCC cells exposed to sorafenib. CONCLUSION: Our findings give a better understanding of ferroptosis and its molecular mechanism in HCC cells that is regulated by SPARC in response to sorafenib.

MicroRNA-153 promotes Wnt/ß-catenin activation in hepatocellular carcinoma through suppression of WWOX.

Persistent activation of Wnt/ß-catenin signaling plays crucial roles in the development of human cancers, including hepatocellular carcinoma (HCC). Here, we performed a MicroRNA-based genetic screen, which revealed a novel diversion in ß-catenin signaling triggered by MicroRNA-153 (miR-153). Overexpression of miR-153 was able to promote ß-catenin transcriptional activity, leading to cell-cycle progression, proliferation and colony formation of HCC cells. Additionally, systemic administration of miR-153 antigomir suppressed hepatocellular carcinogenesis in a murine liver cancer model. At the molecular level, we found that miR-153 inhibited protein level of WWOX, a tumor suppressor and inhibitor of ß-catenin signaling, through targeting its 3'-untranslated region. Therefore, our study highlights the importance of MicroRNA-153/WWOX/ß-catenin regulatory axis in the HCC tumorigenesis.

HIF1-regulated ATRIP expression is required for hypoxia induced ATR activation.

The ATR-ATRIP protein kinase complex plays a crucial role in the cellular response to replication stress and DNA damage. Recent studies found that ATR could be activated in response to hypoxia and be involved in hypoxia-induced genetic instability in cancer cells. However, the underlying mechanisms for ATR activation in response to hypoxic stress are still not fully understood. We reported that ATRIP is a direct target of HIF-1. Silencing the expression of HIF-1α in cancer cells by RNA interference abolished hypoxia-induced ATRIP expression. Silencing the expression of ATRIP by RNA interference abolished hypoxia induced ATR activation and CHK1 phosphorylation in cancer cells. Taken together, these data shed novel insights on the mechanism of hypoxia-induced activation of the ATR pathway.