Astroprincin (FAM171A1, C10orf38): A Regulator of Human Cell Shape and Invasive Growth.

Our group originally found and cloned cDNA for a 98-kDa type 1 transmembrane glycoprotein of unknown function. Because of its abundant expression in astrocytes, it was called the protein astroprincin (APCN). Two thirds of the evolutionarily conserved protein is intracytoplasmic, whereas the extracellular domain carries two N-glycosidic side chains. APCN is physiologically expressed in placental trophoblasts, skeletal and hearth muscle, and kidney and pancreas. Overexpression of APCN (cDNA) in various cell lines induced sprouting of slender projections, whereas knockdown of APCN expression by siRNA caused disappearance of actin stress fibers. Immunohistochemical staining of human cancers for endogenous APCN showed elevated expression in invasive tumor cells compared with intratumoral cells. Human melanoma cells (SK-MEL-28) transfected with APCN cDNA acquired the ability of invasive growth in semisolid medium (Matrigel) not seen with control cells. A conserved carboxyterminal stretch of 21 amino acids was found to be essential for APCN to induce cell sprouting and invasive growth. Yeast two-hybrid screening revealed several interactive partners, of which ornithine decarboxylase antizyme-1, NEEP21 (NSG1), and ADAM10 were validated by coimmunoprecipitation. This is the first functional description of APCN. These data show that APCN regulates the dynamics of the actin cytoskeletal and, thereby, the cell shape and invasive growth potential of tumor cells.

Ornithine decarboxylase antizyme inhibitor 2 (AZIN2) is a signature of secretory phenotype and independent predictor of adverse prognosis in colorectal cancer.

Ornithine decarboxylase (ODC) is the rate-limiting enzyme of polyamine synthesis. The two ODC antizyme inhibitors (AZIN1) and (AZIN2) are regulators of the catalytic activity of ODC. While AZIN1 is a regulator of cell proliferation, AZIN2 is involved in intracellular vesicle transport and secretion. There are no previous reports on the impact of AZIN2 expression in human cancer. We applied immunohistochemistry with antibodies to human AZIN2 on tissue micro- arrays of colorectal cancers (CRC) from 840 patients with a median follow-up of 5.1 years (range 0-25.8). The 5-year disease-specific survival rate was 58.9% (95% Cl 55.0-62.8%). High AZIN2 expression was associated with mucinous histology (p = 0.002) and location in the right hemicolon (p = 0.021). We found no association with age, gender, stage, or histological tumor grade. High tumor expression of AZIN2 predicted an unfavorable prognosis (p<0.0001, log-rank test), compared to low AZIN2 expression. Cox multivariable analysis identified AZIN2 as an independent factor of an unfavorable prognosis in CRC. The strongest AZIN2 expression was seen in invasive tumor cells having morphological features of epithelial-mesenchymal transition (EMT). Induction of EMT in HT-29 CRC cells lead to upregulated expression of endogenous AZIN2. Given that AZIN2 is a regulator of vesicle transport and secretion, we overexpressed human AZIN2 cDNA in T84 CRC cells, and found strongly enhanced accumulation of CD63-positive exosomes in the culture medium. These findings indicate that AZIN2 expression is a signature of EMT-associated secretory phenotype that is linked to an adverse prognosis in CRC.

Hypoxic preconditioning induces neuroprotective stanniocalcin-1 in brain via IL-6 signaling.

BACKGROUND AND PURPOSE: Exposure of animals for a few hours to moderate hypoxia confers relative protection against subsequent ischemic brain damage. This phenomenon, known as hypoxic preconditioning, depends on new RNA and protein synthesis, but its molecular mechanisms are poorly understood. Increased expression of IL-6 is evident, particularly in the lungs of animals subjected to hypoxic preconditioning. Stanniocalcin-1 (STC-1) is a 56-kDa homodimeric glycoprotein originally discovered in bony fish, where it regulates calcium/phosphate homeostasis and protects against toxic hypercalcemia. We originally reported expression of mammalian STC-1 in brain neurons and showed that STC-1 guards neurons against hypercalcemic and hypoxic damage. METHODS: We treated neural Paju cells with IL-6 and measured the induction of STC-1 mRNA. In addition, we quantified the effect of hypoxic preconditioning on Stc-1 mRNA levels in brains of wild-type and IL-6 deficient mice. Furthermore, we monitored the Stc-1 response in brains of wild-type and transgenic mice, overexpressing IL-6 in the astroglia, before and after induced brain injury. RESULTS: Hypoxic preconditioning induced an upregulated expression of Stc-1 in brains of wild-type but not of IL-6-deficient mice. Induced brain injury elicited a stronger STC-1 response in brains of transgenic mice, with targeted astroglial IL-6 expression, than in brains of wild-type mice. Moreover, IL-6 induced STC-1 expression via MAPK signaling in neural Paju cells. CONCLUSIONS: These findings indicate that IL-6-mediated expression of STC-1 is one molecular mechanism of hypoxic preconditioning-induced tolerance to brain ischemia.

Hypoxic preconditioning induces elevated expression of stanniocalcin-1 in the heart.

Animals exposed for a few hours to low oxygen content (8%) develop resistance against further ischemic myocardial damage. The molecular mechanism(s) behind this phenomenon, known as hypoxic preconditioning (HOPC), is still incompletely understood. Stanniocalcin-1 (STC-1) is an evolutionarily conserved glycoprotein originally discovered in fish, in which it regulates calcium/phosphate homeostasis and protects against toxic hypercalcemia. Our group originally reported expression of mammalian STC-1 in brain neurons and showed that STC-1 is a prosurvival factor that guards neurons against hypercalcemic and hypoxic damage. This study investigates the involvement of STC-1 in HOPC-induced cardioprotection. Wild-type mice and IL-6-deficient (Il-6(-/-)) mice were kept in hypoxic conditions (8% O(2)) for 6 h. Myocardial Stc-1 mRNA expression was quantified during hypoxia and after recovery. HOPC triggered a biphasic upregulation of Stc-1 expression in hearts of wild-type mice but not in those of Il-6(-/-) mice. Treatment of cardiomyocyte cells in culture with hypoxia or IL-6 elicited an Stc-1 response, and ectopically expressed STC-1 in HL-1 cells localized to the mitochondria. Our findings indicate that IL-6-induced expression of STC-1 is one molecular mechanism behind the ischemic tolerance generated by HOPC in the heart.