A hallmark of malignancy cells is the ability to survive and proliferate when challenged with stressors such as growth element insufficiency. improved phosphorylation and inactivation of the cell cycle Ginsenoside Rd inhibitor pRb. Consistent with these results, serum-starved cells with high ST6Gal-I manifestation maintain a greater number of S phase cells compared with low ST6Gal-I expressors, reflecting enhanced proliferation. Finally, selective enrichment in clonal variants with high ST6Gal-I manifestation is observed upon long term serum deprivation, assisting the concept that ST6Gal-I confers a survival advantage. Collectively, these results implicate a functional part for ST6Gal-I in fostering tumor cell survival within the serum-depleted tumor microenvironment. main ovarian tumors (16). Contrarily, ST6Gal-I manifestation is negligible in the differentiated epithelium of normal colon, pancreas, and ovary (15, 16), whereas, Ginsenoside Rd notably, a subset of cells with high ST6Gal-I manifestation is found within the base of colon crypts, a stem cell market (15). ST6Gal-I is also highly indicated in additional epithelium-related stem cell compartments (15, 16) as well as in embryonic and Rabbit polyclonal to HSD17B13 induced pluripotent stem cells (15, 18,C20). Consistent with a potential function in conferring stem cell-like properties, we recently reported that ST6Gal-I promotes a malignancy stem cell (CSC) phenotype (16). ST6Gal-I manifestation correlates with additional CSC markers, including ALDH1 and CD133 (15), and ST6Gal-I activity is critical for CSC behaviors such as tumor spheroid growth, chemoresistance and tumor-initiating potential (16). Additionally, ST6Gal-I up-regulation in tumor cells induces the manifestation of important CSC-associated transcription factors, including Sox9 and Slug (16). We hypothesize that one Ginsenoside Rd of the main functions of ST6Gal-I in malignancy cells, including CSCs, is to protect against varied cytotoxic stimuli through sialylation-dependent modulation of cell surface receptors. For example, 2-6 sialylation of the Fas receptor inhibits apoptosis by avoiding Fas internalization, a requisite step in apoptotic signaling (12). Furthermore, 2-6 sialylation of TNFR1 blocks TNF-stimulated cell death (13), whereas 2-6 sialylation of particular integrins impedes apoptosis induced by galectins (21, 22), a family of galactose-binding lectins. In immune cells, ST6Gal-I-mediated sialylation of CD45 helps prevent galectin-dependent CD45 clustering and subsequent apoptosis (23). Finally, 2-6 sialylation of the platelet endothelial cell adhesion molecule receptor prevents endothelial cell death (24). In this study, we describe a new survival-associated function for ST6Gal-I: safety against serum growth factor insufficiency. Using ovarian and pancreatic malignancy cell models with ST6Gal-I overexpression or knockdown, we display that ST6Gal-I facilitates the survival of cells cultivated under serum-depleted tradition conditions. Serum-starved cells with high ST6Gal-I manifestation maintain activation of prosurvival signaling nodes, including Akt and NFB, and retain proliferative capacity via ST6Gal-I-dependent up-regulation of cyclin D2. These findings highlight a novel part for the tumor glycome in sustaining the viability of tumor cells exposed to serum-depleted environments, such as those found within hypovascularized regions of large, solid tumors. Results Cells with Large ST6Gal-I Manifestation Are Resistant to Cytotoxic Stress Induced by Serum Deprivation To interrogate the part of ST6Gal-I in safety against serum withdrawal, ST6Gal-I was stably overexpressed in the OV4 ovarian malignancy cell collection, which is one of the few tumor lines that lack detectable ST6Gal-I protein (Fig. 11% FBS cultures; however, serum-starved KD cells showed evidence of cytotoxicity and cell detachment (Fig. 1and densitometric analyses of three self-employed blots in Fig. 2EV cultures cultivated in 10% FBS, suggesting that ST6Gal-I enhances basal activation of these molecules. Consistent with these results, serum-starved BxPC3 cells with ST6Gal-I knockdown experienced reduced levels of pAkt and cIAP2 compared with EV cells (representative blots in Fig 2and densitometry in Fig. 2 0.05. For Akt, pAkt and total Akt were each normalized to -tubulin, and then data were plotted as pAkt/total Akt ( 0.05. Other studies from our group have suggested that cytotoxic stimuli can exert selective pressure, leading to the development of clonal variants with high ST6Gal-I manifestation. For example, cell lines developed to grow continually in the presence of the chemotherapeutics cisplatin or irinotecan have up-regulated ST6Gal-I (15, 25). Accordingly, we investigated whether prolonged exposure to serum-depleted culture conditions would select for cells with high ST6Gal-I manifestation. OV4 EV and OE cells were cultivated in 10% or.