Contribution of galectin-1, a glycan-binding protein, to gastrointestinal tumor progression

Gastrointestinal cancer is a group of tumors that affect multiple sites of the digestive system, including the stomach, liver, colon and pancreas. These cancers are very aggressive and rapidly metastasize, thus identifying effective targets is crucial for treatment. Galectin-1(Gal-1) belongs to a family of glycan-binding proteins, or lectins, with the ability to cross-link specific glycoconjugates. A variety of biological activities have been attributed to Gal-1 at different steps of tumor progression. Herein, we summarize the current literature regarding the roles of Gal-1 in gastrointestinal malignancies. Accumulating evidence shows that Gal-1 is drastically up-regulated in human gastric cancer, hepatocellular carcinoma, colorectal cancer and pancreatic ductal adenocarcinoma tissues, both in tumor epithelial and tumor-associated stromal cells. Moreover, Gal-1 makes a crucial contribution to the pathogenesis of gastrointestinal malignancies, favoring tumor development, aggressiveness, metastasis, immunosuppression and angiogenesis. We also highlight that alterations in Gal-1-specific glycoepitopes may be relevant for gastrointestinal cancer progression. Despite the findings obtained so far, further functional studies are still required. Elucidating the precise molecular mechanisms modulated by Gal-1 underlying gastrointestinal tumor progression, might lead to the development of novel Gal-1-based diagnostic methods and/or therapies.

Hierarchical and selective roles of galectins in hepatocarcinogenesis, liver fibrosis and inflammation of hepatocellular carcinoma

Hepatocellular carcinoma(HCC)represents a global health problem.Infections with hepatitis B or C virus,non-alcoholic steatohepatitis disease,alcohol abuse,or dietary exposure to aflatoxin are the major risk factors to the development of this tumor.Regardless of the carcinogenic insult,HCC usually develops in a context of cirrhosis due to chronic inflammation and advanced fibrosis.Galectins are a family of evolutionarily-conserved proteins defined by at least one carbohydrate recognition domain with affinity forβ-galactosides and conserved sequence motifs.Here,we summarize the current literature implicating galectins in the pathogenesis of HCC.Expression of"proto-type"galectin-1,"chimera-type"galectin-3 and"tandem repeat-type"galectin-4 is up-regulated in HCC cells compared to their normal counterparts.On the other hand,the"tandemrepeat-type"lectins galectin-8 and galectin-9 are downregulated in tumor hepatocytes.The abnormal expression of these galectins correlates with tumor growth,HCC cell migration and invasion,tumor aggressiveness,metastasis,postoperative recurrence and poor prognosis.Moreover,these galectins have important roles in other pathological conditions of the liver,where chronic inflammation and/or fibrosis take place.Galectin-based therapies have been proposed to attenuate liver pathologies.Further functional studies are required to delineate the precise molecular mechanisms through which galectins contribute to HCC.

MicroRNAs contribute to ATP-binding cassette transporter-and autophagy-mediated chemoresistance in hepatocellular carcinoma

Hepatocellular carcinoma(HCC) has an elevated mortality rate, largely because of high recurrence and metastasis. Additionally, the main obstacle during treatment of HCC is that patients usually develop resistance to chemotherapy.Cancer drug resistance involves many different mechanisms, including alterations in drug metabolism and processing, impairment of the apoptotic machine, activation of cell survival signaling, decreased drug sensitivity and autophagy, among others. Nowadays, miRNAs are emerging as master regulators of normal physiology-and tumor-related gene expression. In HCC,aberrant expression of many miRNAs leads to chemoresistance. Herein, we particularly analyzed miRNA impact on HCC resistance to drug therapy. Certain miRNAs target ABC(ATP-binding cassette) transporter genes. As most of these miRNAs are downregulated in HCC, transporter levels increase and intracellular drug accumulation decrease, turning cells less sensitive to death. Others miRNAs target autophagy-related gene expression, inhibiting autophagy and acting as tumor suppressors. Nevertheless, due to its downregulation in HCC, these miRNAs do not inhibit autophagy or tumor growth and, resistance is favored.Concluding, modulation of ABC transporter and/or autophagy-related gene expression or function by miRNAs could be determinant for HCC cell survival under chemotherapeutic drug treatment. Undoubtedly, more insights on the biological processes, signaling pathways and/or molecular mechanisms regulated by miRNAs are needed. Anyway, miRNA-based therapy together with conventional chemotherapeutic drugs has a great future in cancer therapy.