White (WAT) and brown (BAT) adipose tissue are tissues of energy storage and energy dissipation, respectively. Experimental evidence suggests that brown and white preadipocytes are differentially determined, but so far not much is known about the genetic control of this determination process. The aim of this study was to identify differentially expressed genes involved in brown and white preadipocyte development. Using representational difference analysis (cDNA RDA) and DNA microarray screening, we identified four genes with higher expression in white preadipocytes (three different complement factors and ␦-6 fatty acid desaturase) and seven genes with higher expression levels in brown preadipocytes, of which three are structural genes implicated in cell adhesion and cytoskeleton organization (fibronectin, ␣-actinin-4, metargidin) and four that might function in gene transcription and protein synthesis (vigilin, necdin, snRNP polypeptide A, and a homolog to human hepatocellular carcinomaassociated protein). The expression profile of these genes was analyzed during preadipocyte differentiation, upon -adrenergic stimulation, and in WAT and BAT tissue in vivo compared with references genes such as peroxisome proliferatoractivated receptor-␥ (PPAR␥), uncoupling protein 1 (UCP1), cytochrome c oxidase. adipocyte differentiation; thermogenesis; preadipocyte marker genes; uncoupling protein; cDNA representational-difference analysis; DNA microarray analysis WHITE AND BROWN ADIPOSE TISSUES represent counter actors in energy partitioning, channeling lipid energy either to accumulation in white fat (WAT) or to oxidation, i.e., dissipation in brown fat (BAT) a highly thermogenic tissue (23). Throughout the last years considerable progress has been made in elucidating the molecular mechanisms of adipocyte differentiation which involves sequential activation of numerous transcription factors from several families like different members of the CCAAT/enhancer binding proteins (C/ EBP) and peroxisome proliferator-activated receptors (PPAR) (1,15,30,44,52). However, most of these studies focused on differentiation of white preadipocytes using established white preadipocyte cell lines such as 3T3-L1 and 3T3-F442A cells (37). One of the remaining questions is how and at which stage of development the differentiation of BAT vs. WAT is regulated, of which very little is currently known. Brown and white adipocytes show distinct morphological and biochemical phenotypes in vivo (9). When differentiated in vitro, brown adipocytes show a higher respiratory capacity than white adipocytes and express the BAT specific uncoupling protein 1 (UCP1), which is considered to be a marker for brown adipocytes (21). It is still not clear whether BAT and WAT derive from the same adipose precursor cells or arise independently from distinct mesenchymal stem cells (44), although recently PGC-1, a coactivator of PPAR␥, has been identified, which induces genes important in the development of brown adipocyte phenotype (41).We have performed parallel culture...
For this purpose we developed MAb U36, recognizing a 2 d kDa antigen expressed on the outer cell surface of squamouscell carcinomas and their normal counterparts. Clinical radioimmunoscintigraphy (RIS) and biodistribution studies have shown that the MAb-U36-defined antigen is a suitable target molecule for antibody-based therapy of head-and-neck cancer. In the present study we further characterized the antigen by cDNA cloning. The cDNA was isolated by expression cloning in COS-7 cells. Sequence analysis and database searching revealed that the MAb-U36-defined antigen is identical to the squamous-cellspecific CD44 splice variant epican. The epitope recognized by Squamous-cell carcinoma is the major histological type among tumors of the head and neck. The early stages arc treated with either surgery or radiotherapy, and advanccd stages with combined surgery and radiotherapy. In patients with advanced disease (stages Ill and IV), locoregional recurrences develop in 50 to 60% of the cases after primary therapy, and 15 to 25% of the patients develop distant metastases . The actual incidence of distant metastases in HNSCC patients is probably even higher, since autopsy studies report an incidence of 40 to 57% . These data indicate that there is an urgent need for an effective adjuvant therapy for the eradication of (minimal) residual disease after initial treatment, to prevent thc eventual development of locoregional recurrences and/or distant metastases. The high expectations raised by chemotherapy have not been fulfillcd, and its application is in general limited to palliation. We therefore have decided to exploit the tumor-targeting capacity of monoclonal antibodies for delivery of radionuclides to the remaining tumor deposits. A panel of MAbs directed against squamous-cell-carcinoma-associated antigens was selected by in vitro techniques and evaluated in in vivo models of tumor-bearing nude mice . The antibodies selected by this procedure were tested in RIS and biodistribution studies in patients with HNSCC De Bree el al., 1995). MAb U36 appeared to be the most promising antibody for specific targeting of HNSCC in patients. Immunohistochemical evaluation showed that in 1881196 (96%) of the HNSCC tumors, at least 50% of the tumor cells were intensely stained by MAb U36, indicating that the antigen is very homogeneously expressed (De Bree etal., 1994). Moreover, extensive biodistribution and RIS studies in HNSCC patients have shown that W"Tc-labcled U36 IgG accumulates selectively and to a high level in these tumors (De Brce et al., 1995), and during a follow-up of 3 years no adverse reactions have been observed. These data showed that the MAb-U36-defined antigen is a suitable target moleculc for antibody-based adjuvant therapy of squamous-cell carcinoma of the head and neck. The antibody recognizes a 200-kDa cell-surface antigen highly expressed by human normal squamous epithelia and squamouscell carcinomas of distinct sites of origin: head and neck, lung, esophagus, cervix and epidermis (Schrijvers et al., 1993)....
CD44 splice variants, especially those containing the v6 domain, are assumed to play a critical role in the malignant progression of many human tumors. This concept was based on (i) the aberrant expression of CD44v6 in malignant cells, often encoded by alternatively spliced transcripts, and (ii) the absence of CD44v6 expression in corresponding normal tissues. Remarkably, data on CD44v6 expression in squamous cells do not support this hypothesis: the v6 domain is highly expressed in normal squamous tissues and down‐regulation has been described in the majority of squamous‐cell carcinomas of the head and neck (HNSCC). In this study, we have compared the expression of v6 in normal oral mucosa and HNSCC in a qualitative and quantitative way. Immuno‐histochemistry was performed with 3 different anti‐v6 antibodies (U36, U39 and VFF18) on a large panel of HNSCC cell lines and tumors. The v6‐encoding splice variants were characterized by screening a cDNA library of a human HNSCC cell line and by RT‐PCR on HNSCC cell lines, microdissected normal mucosa and primary as well as metastatic HNSCC tissue. The results revealed that there is no, or only marginal, down‐regulation of CD44v6 in HNSCC. About 97% of the primary HNSCC tumors exhibited a high and homogeneous staining pattern (U36, 270/277; U39, 268/277 tumors with more than 50% positive cells). Furthermore, the v6‐containing CD44 splice variants present in HNSCC primary tumors and metastases were identical to those expressed in normal mucosa. Our data indicate that v6‐containing CD44 splice variants do not play a role in the malignant progression of HNSCC. Int. J. Cancer 82:837–845, 1999. © 1999 Wiley‐Liss, Inc.
For this purpose we developed MAb U36, recognizing a 2 d kDa antigen expressed on the outer cell surface of squamouscell carcinomas and their normal counterparts. Clinical radioimmunoscintigraphy (RIS) and biodistribution studies have shown that the MAb-U36-defined antigen is a suitable target molecule for antibody-based therapy of head-and-neck cancer. In the present study we further characterized the antigen by cDNA cloning. The cDNA was isolated by expression cloning in COS-7 cells. Sequence analysis and database searching revealed that the MAb-U36-defined antigen is identical to the squamous-cellspecific CD44 splice variant epican. The epitope recognized by Squamous-cell carcinoma is the major histological type among tumors of the head and neck. The early stages arc treated with either surgery or radiotherapy, and advanccd stages with combined surgery and radiotherapy. In patients with advanced disease (stages Ill and IV), locoregional recurrences develop in 50 to 60% of the cases after primary therapy, and 15 to 25% of the patients develop distant metastases . The actual incidence of distant metastases in HNSCC patients is probably even higher, since autopsy studies report an incidence of 40 to 57% . These data indicate that there is an urgent need for an effective adjuvant therapy for the eradication of (minimal) residual disease after initial treatment, to prevent thc eventual development of locoregional recurrences and/or distant metastases. The high expectations raised by chemotherapy have not been fulfillcd, and its application is in general limited to palliation. We therefore have decided to exploit the tumor-targeting capacity of monoclonal antibodies for delivery of radionuclides to the remaining tumor deposits. A panel of MAbs directed against squamous-cell-carcinoma-associated antigens was selected by in vitro techniques and evaluated in in vivo models of tumor-bearing nude mice . The antibodies selected by this procedure were tested in RIS and biodistribution studies in patients with HNSCC De Bree el al., 1995). MAb U36 appeared to be the most promising antibody for specific targeting of HNSCC in patients. Immunohistochemical evaluation showed that in 1881196 (96%) of the HNSCC tumors, at least 50% of the tumor cells were intensely stained by MAb U36, indicating that the antigen is very homogeneously expressed (De Bree etal., 1994). Moreover, extensive biodistribution and RIS studies in HNSCC patients have shown that W"Tc-labcled U36 IgG accumulates selectively and to a high level in these tumors (De Brce et al., 1995), and during a follow-up of 3 years no adverse reactions have been observed. These data showed that the MAb-U36-defined antigen is a suitable target moleculc for antibody-based adjuvant therapy of squamous-cell carcinoma of the head and neck. The antibody recognizes a 200-kDa cell-surface antigen highly expressed by human normal squamous epithelia and squamouscell carcinomas of distinct sites of origin: head and neck, lung, esophagus, cervix and epidermis (Schrijvers et al., 1993)....
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.