Neuronatin is related to keratinocyte differentiation by up-regulating involucrin.

BACKGROUND: Neuronatin (Nnat), which is a neuronal developmental and differentiation molecule, is expressed in the endoplasmic reticulum of non-neuronal cells and is involved in insulin secretion from pancreatic ß-cells by plausibly modulating their intracellular calcium concentration. However, the role of Nnat in keratinocyte differentiation remains unclear. OBJECTIVE: To unveil a possible integration of Nnat in controlling the keratinocyte differentiation markers such as involucrin, cytokeratin1, filaggrin, loricrin and S100A7. METHODS: Immunohistological staining was done using psoriasis, chronic eczema, lichen planus and normal skin. Immunofluorescence staining, Western blotting and semi-quantitative real-time PCR were performed for detecting Nnat, involucrin, cytokeratin1, filaggrin, loricrin and S100A7 using human keratinocytes with or without Nnat gene transfection. Small interference RNA was applied to knockdown the Nnat gene expression. RESULTS: Nnat existed in normal human epidermis and cultured keratinocytes. In the hyperplastic epidermis of psoriasis, chronic eczema and lichen planus, over-expression of Nnat was evident along with involucrin and cytokeratin1 expression. Coordinate up-regulation of Nnat and involucrin, but not cytokeratin1, was demonstrated in cultured keratinocytes under differentiation stimuli such as extracellular calcium elevation, exposure to phorbol myristate acetate, and increased cell density. Transfection of small intereference RNA for Nnat decreased the mRNA levels of Nnat and involucrin, but not of cytokeratin1. Furthermore, a gene transfection assay showed increased involucrin expression in the Nnat-transfected keratinocytes than in mock-transfected counterparts, without any appreciable influence on cytokeratin1, filaggrin, loricrin and S100A7 expression. CONCLUSION: These data indicate that Nnat is related to keratinocyte differentiation by up-regulating involucrin expression.

Hematopoietic progenitor kinase 1, mitogen-activated protein/extracellular signal-related protein kinase kinase kinase 1, and phosphomitogen-activated protein kinase kinase 4 are overexpressed in extramammary Paget disease.

The c-Jun amino-terminal kinase (JNK) pathway seems to play important roles in the pathogenesis of several tumors, but its significance in extramammary Paget disease (EMPD) has not been investigated yet. The purpose of the study was to investigate the potential contribution of the JNK-associated molecules, such as hematopoietic progenitor kinase 1 (HPK1), mitogen-activated protein/extracellular signal-related protein kinase kinase kinase1 (MEKK1), transforming growth factor-ß activated kinase 1 (TAK1), and phosphomitogen-activated protein kinase kinase 4 (p-MKK4) to the development of EMPD. Thirty-five paraffin-embedded EMPD specimens were subjected to immunohistochemical staining for HPK1, MEKK1, TAK1, and p-MKK4. All the 35 EMPD, including 13 dermal invasive EMPD and 2 lymph node metastasis, showed cytoplasmic overexpression of HPK1, MEKK1, and p-MKK4. The expression (%positive cells) of HPK1, MEKK1, and p-MKK4 in EMPD (92.3% ± 8.6%, 92.9% ± 8.6%, and 92.7% ± 7.4%, respectively) were significantly higher than in normal eccrine sweat gland cells (51.6% ± 10.4%, 44.7% ± 11.7%, 0% ± 0%). In addition, the expression of HPK1-, MEKK1-, and p-MKK4 in invasive EMPD was significantly higher than in noninvasive EMPD. Meanwhile, the expression of TAK1 was basically low and no significantly different between EMPD and normal controls. In conclusion, these results indicate that JNK pathway may play a role in the pathogenesis of EMPD.

Nerve growth factor, brain-derived neurotrophic factor and their high-affinity receptors are overexpressed in extramammary Paget's disease.

BACKGROUND: Neurotrophin (NT) systems appear to play important roles in the pathogenesis of several tumors, but their expression in extramammary Paget's disease (EPD) has not been investigated. METHODS: Thirty-four paraffin-embedded EPD specimens (32 primary EPD and 2 metastatic to lymph nodes) were subject to immunohistochemical staining for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), NT3, NT4, their high-affinity receptors (TrkA, TrkB and TrkC) and the common low-affinity receptor, p75 NT receptor (p75). RESULTS: All 34 EPD specimens, including 2 metastatic to lymph nodes, showed cytoplasmic overexpression of NGF, BDNF, TrkA and TrkB. The expression (% positive cells) of NGF, BDNF, NT3, NT4, TrkA and TrkB (81.6 ± 14.9, 86.0 ± 10.4, 89.6 ± 14.9, 87.8 ± 17.9, 83 ± 14.4 and 86.2 ± 11.7%) in EPD was significantly higher than in normal skin (21.6 ± 6.5, 27.6 ± 4.5, 19.7 ± 10.1, 8.2 ± 10.0, 25.0 ± 5.3 and 25.4 ± 6.4%), and the expression of these factors in invasive EPD was significantly higher than in noninvasive EPD. Interestingly, Paget cells were negative for p75 and TrkC in all the 34 EPD specimens. CONCLUSIONS: These results suggest that overexpression of NGF, BDNF and their high-affinity receptors (TrkA and TrkB) might play a role in the pathogenesis of EPD.

Aberrant expression of tenascin-c and neuronatin in malignant peripheral nerve sheath tumors.

Development of neurofibroma (NF) and its malignant counterpart, malignant peripheral nerve sheath tumor (MPNST), is a hallmark of type I neurofibromatosis (NF1). Newly identified glycoprotein neuronatin (Nnat) is predominantly expressed in the fetal central and peripheral nervous systems and is gradually diminished according to the neural maturation. However, its expression in NFs and MPNSTs is unknown. Since an overexpression of tenascin-C (Tn-C), an extracellular matrix component, has been observed in neural malignancies, we investigated the immunohistological expressions of Nnat and Tn-C in NFs and MPNSTs, and compared their expression with that of the proliferation marker Ki-67 to possibly distinguish MPNSTs from ordinal NFs. Standard immunohistological procedure was performed for Nnat, Tn-C and Ki-67 in 9 sporadic NFs, 15 diffuse NFs (NF1), 15 plexiform NFs (NF1) and 6 MPNSTs (NF1), as well as 5 normal skins. All of the MPNSTs showed positive staining for Nnat, Tn-C and Ki-67, in sharp contrast to completely negative staining in all sporadic or NF-1-derived NFs. The aberrant expression of Nnat and Tn-C was a useful marker for distinguishing MPNSTs from benign NFs.