Expression of L-type amino acid transporter 1 in various skin lesions.

L-type amino acid transporter 1 (LAT1) is a Na(+)-independent neutral amino acid transporter that has an essential role in cell proliferation. Although the involvement of LAT1 in human carcinogenesis has been investigated by immunohistochemistry in various organs, LAT1 expression in skin has not been reported yet. Therefore, in the present study, immunohistochemistry for LAT1 was performed in 15 keratoacanthoma (KA), 10 seborrheic keratosis, 16 Bowen's disease, 11 basal cell carcinoma (BCC), and 9 squamous cell carcinoma (SCC) cases as well as 61 normal epidermis as control. It was demonstrated that LAT1 expression limited to the basal layer was occasionally observed in normal epidermis while its expression was significantly decreased in the epithelium of seborrheic keratosis and Bowen's disease (P<0.05). By contrast, a significantly higher rate of LAT1 expression was observed in the epithelium of KA, BCC, and SCC than in normal epidermis (P<0.05). Although LAT1 expression was limited to the basal layer or rim of the nests in KA, LAT1 expression was also observed in the center of the nests in BCC and SCC (P<0.001). Thus, LAT1 is differentially expressed in various skin lesions and may be an especially useful marker to distinguish KA from SCC.

Divergent expression of L-type amino acid transporter 1 during uterine cervical carcinogenesis.

L-type amino acid transporter 1 (LAT1) is a Na⁺-independent neutral amino acid transporter that has an essential role in cell proliferation. Although LAT1 expression is observed in various tumor cell lines and immunohistochemical expression of LAT1 has been investigated in carcinomas of various organs, LAT1 expression in uterine cervical neoplasm has not been reported. Therefore, in the present study, we immunohistochemically analyzed LAT1 expression along with the well-known markers of cervical carcinogenesis Ki-67 and p16 in normal uterine cervical mucosa (49 specimens) as well as cervical intraepithelial neoplasia (17 mild or moderate dysplasias and 19 severe dysplasias or carcinomas in situ) and invasive carcinomas (17 squamous cell carcinomas and 9 adenocarcinomas). LAT1 expression was limited to the basal layer of normal squamous epithelium, and it was significantly decreased in cervical intraepithelial neoplasia (P < .001), generally paralleled by increased expression of Ki-67 and p16. Interestingly, in invasive squamous cell carcinoma, LAT1 expression again increased especially at the invasive fronts (P < .001), whereas Ki-67 and p16 expressions were almost unchanged relative to noninvasive neoplasia. Although virtually no LAT1 expression was demonstrated in normal uterine cervical glands, LAT1 expression was observed in some adenocarcinomas (P < .001). The present study suggests that LAT1 expression decreases because of human papillomavirus infection as reflected by p16 overexpression in cervical intraepithelial neoplasia, whereas LAT1 expression in invasive carcinoma is associated with acquired malignant potential.

Dual myeloperoxidase-antineutrophil cytoplasmic antibody- and antiglomerular basement membrane antibody-positive cases associated with prior pulmonary fibrosis: a report of four cases.

BACKGROUND: Both myeloperoxidase-associated antineutrophil cytoplasmic antibody (MPO-ANCA) and antiglomerular basement membrane antibody (anti-GBM Ab) positivity have been demonstrated in patients with rapidly progressive glomerulonephritis (RPGN), either with or without pulmonary hemorrhage; however, the implications of these antibodies in such patients have not yet been elucidated. The cases with dual positive antibodies were studied clinically, serologically, and pathologically, and the implications of antibodies are discussed here. PATIENTS AND METHODS: Four patients with prior pulmonary fibrosis, who subsequently developed RPGN and pulmonary hemorrhage, were studied clinically, serologically, and pathologically. The clinical data were reviewed extensively and the dual positive antibodies were detected by enzyme-linked immunosorbent assays. Pathological studies were performed with a renal biopsy in one patient, a gastric biopsy in another patient, and autopsy materials in the remaining 2 patients. RESULTS: All 4 patients had prior pulmonary fibrosis before the symptoms of RPGN when the dual positivity of MPO-ANCA and anti-GBM Ab was detected. Three cases were accompanied by pulmonary hemorrhage around the time of RPGN whereas the remaining case demonstrated pulmonary hemorrhage a few years later. Renal tissue specimens in 3 cases showed circumferential crescents and linear immunoglobulin G deposits along the glomerular capillary loops in glomeruli. Two autopsy specimens revealed vasculitis of the small arteries and arterioles of the kidney, and one of them showed similar vasculitic findings in both the gastrointestinal tract walls and the adipose tissues of the adrenal glands. Additionally, a case with pulmonary hemorrhage occurring after remission was associated with re-elevated MPO-ANCA levels but without anti-GBM Ab positivity. A gastric biopsy was unremarkable and non-contributory for the diagnosis, but this case showed vasculitic symptoms of peripheral neuritis and retinal hemorrhage. Taken together, all 4 cases demonstrated prior pulmonary fibrosis and dual positivity of MPO-ANCA as well as anti-GBM Abs at the time of RPGN, and were associated with either pulmonary hemorrhage or its occurrence thereafter. CONCLUSION: Four cases that showed prior pulmonary fibrosis as well as subsequent RPGN and pulmonary hemorrhage were both MPO-ANCA- and anti-GBM Ab-positive at the time of RPGN. The glomeruli disclosed features compatible with anti-GBM Ab disease, but the clinical and pathological vasculitic manifestations, including prior pulmonary fibrosis that might be an early manifestation of ANCA disease, suggested the occurrence of MPO-ANCA-associated vasculitis. Furthermore, 1 case subsequently showed repetitive pulmonary hemorrhage with re-elevated MPO-ANCA positivity but without anti-GBM Ab positivity, and this event was possibly due to MPO-ANCA-associated alveolar capillaritis. As anti-GBM Ab disease is generally thought not to manifest the clinical and pathological features of vasculitis excluding the kidney, MPO-ANCA might be a key factor regarding the occurrence of this dual positive disease.

Identification of MPO-positive capillaries of the pleura by immunohistochemistry in MPO-ANCA associated vasculitis.

We present a case of a middle-aged woman with myeloperoxidase anti-neutrophil cytoplasmic autoantibody (MPO-ANCA)-associated vasculitis that demonstrated immunohistochemically positive MPO capillaries of the pleura. The patient initially presented with proteinuria and microscopic hematuria at the age of 38. Acute progressive glomerulonephritis and pulmonary hemorrhage occurred 4 years later, and a high serum titer of MPO-ANCA was detected therefore a diagnosis of microscopic polyangiitis was made. Steroid-pulse therapy was performed and the pulmonary shadow improved, but the renal failure did not improve, thus, hemodialysis was initiated. Thereafter, an 18-year asymptomatic phase followed, but high serum levels of MPO-ANCA persisted during this period. Chronic pulmonary hemorrhage was discovered at the age of 60, and video-assisted thoracoscopic surgery was performed. Resected tissue revealed diffuse aloveolar hemorrhage accompanied by marked hemosiderin deposition, whereas MPO-immunopositive capillaries were identified only in the pleura. To our knowledge, this is the first report demonstrating MPO-positive capillaries in a disease other than glomerulonephritis. Judging from this unique case, MPO-positive endothelial cells may appear only during the hyperacute stage before hemorrhage, and may diminish thereafter, thus, may be associated with the trigger of microscopic polyangiitis.

Expression of stem cell factor (SCF), a KIT ligand, in gastrointestinal stromal tumors (GISTs): a potential marker for tumor proliferation.

Gastrointestinal stromal tumors (GISTs) show a high incidence of gain-of-function mutations of the c-kit gene, which encodes a receptor tyrosine kinase KIT. This mutation is seen independently of metastasis and/or recurrence of tumors; thus, the factors involved in tumor proliferation rate and malignancy are still not known. Some mesenchymal and epithelial tumors have been reported to co-express KIT and its ligand, stem cell factor (SCF), for autonomous proliferation by the autocrine mechanism. The purpose of this study is to clarify whether GIST cells produce SCF, despite mutated KIT with constitutive activation. Immunohistochemically, we examined the co-expression of KIT and SCF in 36 GIST cases. All cases were found to be KIT-positive, and of these, 21 cases, including four recurrent or metastatic GISTs, showed co-expression of SCF. MIB-1 labeling index was significantly higher, and the average tumor size was larger in SCF-positive cases. By confocal microscopy, KIT was expressed on the cellular membrane, around which SCF was distributed less densely. Western blot analysis revealed that the membrane-bound SCF of 31 kDa was found to be approximately 10 times more abundant than the soluble SCF of 18.5 kDa, suggesting continuous KIT activation. These results indicate that proliferation of GIST cells can be caused not only by the gain-of-function mutation of c-kit, but also by the autocrine mechanism of the SCF/KIT system. Thus, SCF expression would be a useful marker for tumor proliferation.