Effects of oxalate exposure on Madin-Darby canine kidney cells in culture: renal prothrombin fragment-1 mRNA expression

It has been suggested that renal tubular cell damage induced by oxalic acid, one of the components of urinary calculi, may be involved in a variety of ways in the development of urolithiasis. During our study on a calculus related protein, renal prothrombin fragment-1 (RPTF-1), we noted that this is an inflammation related substance that mediates an acute inflammatory reaction, one of the original roles of prothrombin. RPTF-1 is a part of prothrombin that is a coagulation factor known to be expressed in the renal tubule. We examined whether oxalic acid may cause cytotoxic effects on tubular epithelial cells and whether such chemical stimulation may promote the translation of RPTF-1 mRNA into RPTF-1 proteins. We used Madin-Darby canine kidney (MDCK) cells derived from the distal tubule of a dog kidney. In this study, the effects of oxalic acid in culture solution at different concentrations on cytotoxicity were assessed using a MTT assay. The location of active oxygen species was identified using dichlorofluorescein diacetate. After the prothrombin sequence of RPTF-1 was confirmed in MDCK cells, RPTF-1 mRNA expression was determined by RT-PCR. The gene sequence of the same promoter area was ligated, and a luciferase sequence was inserted downstream of the vector. The target sequence was transfected into MDCK cells and the relation between oxalic acid and prothrombin promoter was examined. In addition, the variable expression of RPTF-1 mRNA was quantitatively compared depending on oxalic acid concentrations using real-time PCR. When cytotoxicity was investigated, cells were not damaged but, by contrast, were stimulated and activated under oxalic acid below a certain concentration. The relation between cytotoxicity on the cultured MDCK cell membrane and active oxygen species was confirmed. Luminescence in MDCK cells containing the luciferase gene was detected by the addition of oxalic acid, which activated the prothrombin promoter. A part of the prothrombin gene sequence in the MDCK cells was detected and an increase in the expression of RPTF-1 mRNA in MDCK cells by the addition of oxalic acid was confirmed using real-time PCR. Increased expression of prothrombin by adding oxalic acid has already been demonstrated in previous studies. In this study, however, RPTF-1 mRNA was promoted by oxalic acid and a direct association between oxalic acid and RPTF-1 is indicated. This finding shows that increased oxalic acid in urine induces the expression of RPTF-1 in tubular epithelial cells and thereby causes the generation of active oxygen species.     

Different progression of tumor xenografts between mucin-producing and mucin-non-producing mammary adenocarcinoma-bearing mice

Previously, we found that MUC2 mucins could activate monocytes/macrophages through a scavenger receptor leading to cyclooxygenase (COX) 2 induction and overproduction of prostaglandin E2 (PGE2). To investigate the role of mucins in the tumor-bearing state, we compared s.c. tumor formation by using mucin-producing (TA3-Ha) and mucin-non-producing (TA3-St) cloned variants of mouse mammary adenocarcinomas. Expression of COX2 mRNA and protein and production of PGE2 were elevated in peritoneal macrophages stimulated with epiglycanin, which is a mucin-like glycoprotein produced by TA3-Ha cells. S.c. tumor tissues comprising TA3-Ha cells grew much faster than tissues comprising TA3-St cells. COX2 protein and vascular endothelial growth factor in TA3-Ha tumor tissues were elevated compared with the TA3-St tumor tissues. Although similar numbers of macrophages were observed immunochemically in the two types of tumor tissues, COX2 was induced prominently in the infiltrating macrophages in TA3-Ha tumor tissues but only faintly in TA3-St tumor tissues. Furthermore, angiogenesis progressed remarkably in TA3-Ha tumor tissues but only slightly in TA3-St tumor tissues. Epiglycanin-induced overproduction of PGE2 down-regulated interleukin-12 production by macrophages. IFN-gamma-producing CD4 T cells in spleens obtained from TA3-Ha tumor-bearing mice were significantly reduced compared with TA3-St tumor-bearing mice, suggesting that mucins cause PGE2-mediated immune suppression. Actually, the tumor growth of a TA3-Ha cell xenograft was suppressed effectively by oral administration of a COX2 inhibitor but that of a TA3-St cell one was not. These results suggest that mucins play an important role in tumor progression through overproduction of PGE2.     

Triplet chemotherapy for malignant pericardial mesothelioma: a case report

Malignant pericardial mesothelioma (MPM) is a relatively rare neoplasm in Japan, and no standard treatment regimens have been established for this disease. A 47-year-old woman with MPM presenting with cardiac tamponade was treated using four cycles of chemotherapy consisting of cisplatin (CDDP) 40 mg/m2, gemcitabine (GEM) 800 mg/m2 and vinorelbine (VNR) 20 mg/m2 on days 1 and 8 every 4 weeks after pericardial drainage alone. The diagnosis of MPM was confirmed by an immunohistochemical procedure using either positive or negative markers of malignant mesothelioma in addition to conventional cytological examinations using pericardial effusion. The patient experienced no severe non-hematological or hematological toxicities except for grade 3 neutropenia. The patient has returned to her usual activities and has remained well for 24 months after the last chemotherapy without any evidence of disease progression.     

Methodological aspects of current problems in target-based anticancer drug development

Differently from the conventional antineoplastic agents, target-based drugs are designed a priori, based on our knowledge of various physiological molecules that has been obtained by the development of molecular biology. This “Copernican revolution” in drug development may imply a paradigm shift in this field. However, contrary to the initial expectations, many drugs developed by this approach are now faced with difficulties, mainly because of the fundamental and theoretical limits of this approach. All of the physiological functions are not always known in all target molecules. In low-molecular-weight drugs, i.e., “inhibitors,” targets disperse, due to the structural similarities in physiological molecules. This double-faced “out-of-focusing” causes many problems in various steps of drug development, drug design, clinical trials, and administration to patients. Many drugs are now being abandoned because of unexpectedly lower response rates or unforeseeable adverse effects, and the variety of the drugs exhibits a kaleidoscopic appearance. The double-faced “out-of-focusing” derives from the methodological limits in molecular biology, i.e., elementalism, and limits in our techniques for drug development. To overcome these currently inevitable limits, it appears essential to elucidate the specific changes in target molecules that chiefly promote tumor growth and, consequently, strongly predict response to the administered drugs. Precise and efficient detection of responder populations is the key to the development and establishment of target-based anticancer therapies.