Marco Chilosi

The homeodomain-containing transcription factor pancreatic duodenal homeobox 1 (PDX-1) plays a key role in pancreatic development and β-cell function. It is a major regulator of transcription in pancreatic cells, and transactivates the insulin gene by binding to a specific DNA motif in its promoter region. Glucose also regulates insulin gene transcription through PDX-1. It has been shown that PDX-1 is required for maintaining pancreatic islet functions by activating gene expression and has a dual role in pancreatic development. It initially contributes to pancreatic formation during embryogenesis and subsequently regulates the pancreatic islet cell physiology in mature islet cells. Because of this key role in the embryologic development of the pancreas, PDX-1 expression has been investigated in pancreatic cancer cell lines and human tumors. Moreover, a few reports have described expression of PDX-1 in other human neoplasms and have investigated its potential role in differential diagnosis, but data on normal human tissues are lacking. Understanding the molecular mechanisms of pancreas formation, and especially the function of PDX-1, may contribute to the improved treatment and prevention of debilitating diseases such as diabetes, insulinomas and pancreatic carcinomas. Nevertheless, further studies are needed concerning its possible application in routine practice.

Crohn's disease is a chronic inflammatory bowel disease, whose aetiology and pathogenesis are still unknown. The occurrence of epithelioid granulomas is one characteristic feature of the disease since these lesions are found in the bowel wall in 50-87% of colectomy specimens. Although granulomas are not pathognomonic, their identification is considered a relevant element for diagnosis. Cathepsin-k, a papain-like cysteine protease, is involved in bone remodelling, and has been widely used as a immunohistochemical marker for the in situ detection of osteoclasts. Interestingly, the expression of this potent protease is also significantly increased in stimulated tissue macrophages, epithelioid cells and granulomas, but is not expressed in resident tissue macrophages. In the present study, we evaluated Cathepsin-k expression as a diagnostic tool in the identification of small granulomas in Crohn's disease. Formalin-fixed and paraffin-embedded samples of 10 cases of Crohn's disease were collected from surgical ileo-colic resections followed by comparison of Cathepsin-k and CD68 immunoreactivity. Granulomas were identified in 4 of 10 cases examined in haematoxylin & eosin preparations. Cathepsin-k enabled the identification of small granulomas (with a diameter between 100 and 200 microm) in 6 of 10 cases, mainly localized within the submucosa and muscular layers. When compared to CD68, Cathepsin-k immunoreactivity was generally absent or only weakly expressed in resting tissue macrophages, thus allowing better identification of activated epithelioid cells. Based on these results, Cathepsin-k appears to be a reliable tool for the precise and rapid identification of small epithelioid granulomas in Crohn's disease.

At present, no studies have evaluated the role of bronchoscopic transbronchial lung biopsy (TBLB) in the diagnosis of diffuse drug-induced lung disease (DILD), and there is no consensus for a definite diagnostic workup approach for this rare clinical entity. The aim of the present study was to evaluate the clinical usefulness of TBLB in diffuse DILD. This study was a retrospective analysis of patients with diffuse DILD, who underwent bronchoscopy. The role of TBLB was assessed to determine whether the histological results are useful for the final diagnosis. Over a 5-yr period, 44 patients underwent bronchoscopy, and all had a bronchoalveolar lavage (BAL). Thirty-three of the 44 patients underwent TBLB (75%), and the results of TBLB were diagnostically helpful in 25 (75.7%) of the procedures. No histopathologic abnormality was identified in 6 (18%) of the 33 patients. In 2 patients (6%) the obtained samples were not adequate, since no lung parenchyma was obtained. No severe complications related to bronchoscopic procedures occurred. In conclusion, TBLB is a safe procedure, and is diagnostically helpful in the majority of cases of patients with diffuse DILD. Histological data obtained by TBLB further corroborate clinical, laboratory, radiologic and BAL results for a definitive diagnosis of diffuse DILD.

The p63 gene has high homology with p53, but more complex physiologic functions, including the regulation of the maintenance of basal cells in stratified epithelia. These cells in fact express high levels of the deltaN-terminal truncated isoforms of the p63 gene that can act as dominant-negative inhibiting the activity of p53. Basal cells in human bronchi and bronchioli seem to use the same strategy, since they constitutively express high levels of p63, at variance with alveolar pneumocytes. Over-expression of these isoforms in airway basal cells can inhibit important functions of the p53-pathway, including cell cycle arrest and apoptosis. This finding underlines the key role of p63 in epithelial renewal in human lung, with important implications in the understanding of the mechanisms of tissue remodelling occurring in diffuse lung diseases.

Evidence has recently been provided to support a role for genomic imprinting in the regulation of embryonic implantation and development and placental growth, as well as in the pathogenesis of proliferative trophoblastic diseases. The cyclin-dependent kinase inhibitor p57KIP2 has recently been recognized as a maternally imprinted gene. We investigated p57KIP2 expression in first-trimester normal placentas from interrupted pregnancy, spontaneous abortions, and different types of proliferative trophoblastic diseases using single- and double-marker immunohistochemical techniques. In normal placenta, nuclear p57KIP2 expression was observed at high frequency (up to 100%) in extravillous trophoblast, cytotrophoblast, and implantation-site interstitial trophoblast, but was absent in syncytiotrophoblast. p57KIP2 was also expressed in the stromal cells of maternal decidua, which was one of the few adult tissues retaining p57KIP2 expression (most other adult tissues investigated were negative). p57KIP2 expression was either absent or low in all cases of diploid/tetraploid complete moles (20 cases) and in three cases of gestational choriocarcinoma. On the other hand, all spontaneous abortions (12 cases) and triploid partial moles (19 cases) showed p57KIP2 levels comparable to those observed in normal placenta. These findings are in line with the hypothesis that deregulation of genomic imprinting, particularly the loss of cell-cycle inhibitors such as p57KIP2, is involved in the abnormal development of androgenetic trophoblastic proliferations. In addition, this simple immunohistochemical analysis could provide a useful diagnostic marker in difficult cases.