Role of microphthalmia transcription factor (Mitf) in melanoma differentiation

We transfected the melanocyte-specific Mitf-M isoform into the aggressive melanoma UISO-Mel-6 cell lines. Our data show that Mitf decreases cell proliferation and results in cells which grow in clusters. By analyzing the expression of the markers of differentiation, we demonstrate that Mitf favored increased expression of tyrosinase and tyrosinase-related protein-1. In addition, Mitf induces Bcl-2 expression following transfection of UISO-Mel-6 cells. We also showed that Mitf gene affects cell-cycle distribution by resting cells preferentially in G2/G1 phase, and inducing the expression of p21 and p27. Moreover, we performed in vivo studies using subcutaneous injection of UISO-Mel-6 and UISO-Mel-6-Mitf in Balb/c nude mice. Our data show that Mitf inhibits tumor growth and decreases Ki67 expression. Tumors induced by UISO-Mel-6 cells were ulcerated and resulted in metastases to liver. None of the mice injected with UISO-Mel-6(Mitf+) cells harbored liver metastases. Our results suggest that Mitf is involved in melanoma differentiation and leads to a less aggressive phenotype.     

Role of integrins in regulating epidermal adhesion,growth and differentiation

Mammalian epidermis is renewed throughout life by proliferation of a multipotential stem cell population and terminal differentiation of stem cell progeny. In recent years, extracellular matrix receptors of the integrin family have been identified as important regulators of epidermal homeostasis, influencing the balance between stem cell renewal and differentiation. Integrin expression is altered when the epidermis is damaged or diseased, and there is good evidence that specific integrins can contribute positively or negatively to pathogenesis. In this review I summarize what is known about the expression and function of epidermal integrins, and highlight the challenges for future research.     

Role of N-glycans in growth factor signaling

Secreted proteins and membrane proteins are frequently post-translationally modified by oligosaccharides. Therefore, many glycoproteins are involved in signal transduction. One example is growth factor receptors, which are membrane proteins that often contain oligosaccharides. The oligosaccharides in those growth factor receptors play crucial roles in receptor functions. An analysis of glycosyltransferase-transfectants revealed that the branching structures of oligosaccharide also serve as important determinants. For example, N-glycans of epidermal growth factor receptor (EGFR) are involved in receptor sorting, ligand binding and dimerization. The addition of a bisecting GlcNAc to N-glycans increases the endocytosis of EGFR. N-glycans of Trk, a high affinity nerve growth factor receptor, also affect its function. Thus, oligosaccharides play an important role in growth factor signaling. Published in 2004. This revised version was published online in August 2006 with corrections to the Cover Date.     

Dynamics of expression of growth differentiation factor 15 in normal and PIN development in the mouse

Growth differentiation factor (GDF15) is a distant member of the transforming growth factor-beta superfamily, a diverse group of structurally related proteins that exert multiple effects on cell fate such as on cell growth and differentiation but little is known about GDF15 in these processes. Previously we observed the mature GDF15 to be associated with human prostate carcinogenesis hence prompting us to study GDF15 further. Here we report gdf15 expression both at the RNA and protein levels, in normal prostatic tissues of wild type (wt) and prostatic intraepithelial neoplasia (PIN) of transgenic (Tg) 12T-7s model mice during embryonic, postnatal, and adult prostate formation up to 15 weeks after birth. Dynamic changes in expression, at both the mRNA and protein level, correlated with cell proliferation and differentiation during distinct phases of normal mouse prostate development and alterations in the dynamics of gdf15 expression correlated with the changes in development resulting in PIN formation. Most notably mature gdf15 protein was significantly elevated during hyperplasia and PIN development. Changes in the protein levels did not always correlate well with the mRNA levels. This was more prominent during PIN than during normal prostate development suggesting that this may also be an indicator of disturbed regulation of gdf15 in PIN. We propose that gdf15 is a growth factor with dual function either promoting proliferation or growth arrest and differentiation due most likely to differences in cellular differentiation. Because of the differentiation defect in PIN its epithelium no longer responds to gdf15 by cellular growth arrest as does the normal epithelium and gdf may even stimulate proliferation. The data supports our hypothesis that GDF15 plays a role in the early stages of human prostate cancer.     

CircRNA fibroblast growth factor receptor 3 promotes tumor progression in non-small cell lung cancer by regulating Galectin-1-AKT/ERK1/2 signaling

The dysregulation of circular RNA (circRNA) expression is involved in the progression of several cancers, including non-small cell lung cancer (NSCLC). However, the role and underlying molecular mechanisms of circRNA FGFR3 (circFGFR3) in NSCLC progression remains unknown. Here, we used quantitative real-time polymerase chain reaction to validate that circFGFR3 expression was higher in NSCLC tissues than in the paratumor tissues. Furthermore, our study indicated that the forced circFGFR3 expression promoted NSCLC cell invasion and proliferation. Mechanistically, we found that circFGFR3 promoted NSCLC cell invasion and proliferation via competitively combining with miR-22-3p to facilitate the galectin-1 (Gal-1), p-AKT, and p-ERK1/2 expressions. Clinically, we revealed that the high circFGFR3 expression correlates with the poor clinical outcomes in patients with NSCLC. Together, these data provide mechanistic insights into the circFGFR3-mediated regulation of both the AKT and ERK1/2 signaling pathways by sponging miR-22-3p and increasing Gal-1 expression.