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Biomedical subjects

W F Benedict

Publications and source records attributed to W F Benedict.

At least 73 records · Page 4Linked to original sources
PubMed1992

Altered expression of retinoblastoma protein and known prognostic variables in locally advanced bladder cancer.

BACKGROUND: The clinical behavior of the tumor in patients with locally advanced bladder carcinoma is unpredictable. Current predictors of clinical behavior include depth of muscle invasion, presence of vascular invasion, proliferation rate, and loss of blood group antigens. Treatment selection would be facilitated by the development of a reliable marker of tumor progression. Functional retinoblastoma (RB) gene loss has been reported to occur in bladder carcinoma, but the significance of this loss is unknown. PURPOSE: We have evaluated the frequency of functional loss of the RB gene in locally advanced bladder carcinoma and have compared the results to known prognostic factors in the same cohort. METHODS: Forty-three study patients with pathologically well-characterized, locally advanced bladder carcinoma, who were placed in a protocol incorporating surgery and chemotherapy, were studied for known clinical and pathological prognostic indicators as well as for their Rb status. Formalin-fixed and paraffin-embedded archival primary tumor tissues were used for histological and immunohistochemical analyses. RESULTS: Altered Rb protein expression was documented in 37% of the tumor specimens. The high rate of altered Rb expression found in this cohort with advanced urothelial tumors strongly suggests that RB functional loss may be associated with tumor progression in this malignancy. Altered Rb protein expression was found to be independent of other known prognostic variables. A significantly poorer tumor-free survival rate also was noted for those patients who had a tumor with an altered Rb protein with or without vascular invasion. CONCLUSION: The high frequency of Rb alteration in locally advanced bladder carcinomas, plus the fact that a significant correlation could not be found between the Rb status and other known prognostic markers in this preliminary study, suggests that altered RB expression may be an independent prognostic marker of tumor progression in bladder cancer.

Gene Expression Regulation, Neoplastic↗
PubMed1992

Altered RB expression is a prognostic clinical marker involved in human bladder tumorigenesis.

We are now beginning to understand the development of bladder cancer at the molecular level. Tumor evolution involves the interaction of both oncogenes and tumor suppressor genes. One of the key tumor suppressor genes in this process is the retinoblastoma (RB) gene. Much has been learned recently about the role of this gene in the tumor progression and prognosis of bladder cancer, although several questions are still unanswered. The progress made on this subject in our laboratory as well as others will be the focus of this report.

Biomarkers, Tumor↗
PubMed1991

Inactivation of the retinoblastoma gene in human bladder and renal cell carcinomas.

The retinoblastoma (RB) gene was the first tumor suppressor gene isolated and its inactivation is associated with the pathogenesis of several types of human cancer. In this study, we investigated the involvement of the RB gene in bladder and renal cell carcinomas by determining the loss of heterozygosity (LOH) at the RB locus and by DNA, RNA, and protein analysis of the RB gene. Whenever possible, the latter included Western blotting and immunohistochemical staining of the RB protein. In bladder carcinoma, 2 of the 8 cell lines we studied had an inactivated RB gene; one cell line lacked RB expression without a gross RB deletion, whereas the other cell line expressed only the underphosphorylated form of the RB protein. None of 16 low-grade noninvasive bladder carcinomas showed an alteration in RB protein by direct Western blot analysis, whereas 2 of 14 high-grade, invasive tumors had no RB protein as measured by both Western blotting and immunohistochemical staining. This suggests that the loss of RB function may be more important in the progression of bladder cancer than in its initiation, although more extensive studies are required. LOH within the RB locus was observed in 5 of 27 informative cases of primary bladder, ureter, or renal pelvis carcinoma. However, none of the 5 cases with LOH at the RB locus had a functional loss of RB protein expression. In renal cell carcinoma, one of the 12 cell lines had a gross homozygous deletion of the RB gene, and 2 of 32 primary tumors were negative for RB protein expression. LOH at the RB locus also was found in only 2 of 30 informative cases, one of which lacked RB expression. These results are the first to demonstrate the involvement of RB inactivation in the development of advanced primary bladder carcinoma and suggest that RB loss could have a role in certain renal cell carcinomas. Our data, however, show no correlation between LOH at the RB locus in bladder cancer and actual inactivation of the RB gene at the protein level. This may suggest that there is a second tumor suppressor or recessive cancer gene on chromosome 13 in bladder cancer and/or that the mechanism of RB inactivation in bladder cancer frequently involves independent mutations of each RB allele.

Base Sequence↗
PubMed1991

Intraocular tumor formation of RB reconstituted retinoblastoma cells.

It has been reported that replacement of a functional retinoblastoma (RB) gene in RB defective WERI-27 retinoblastoma cells results in complete loss of their tumorigenic potential in nude mice following s.c. injection. We have repeated the identical studies and found that although tumors did not develop s.c., the RB reconstituted cells, either soon after RB virus infection or after long term cultivation, consistently produced tumors when injected intraocularly. These tumor cells, when reestablished in culture, were found to retain a normal RB protein as determined by direct Western blotting and immunocytochemical staining. The tumors, however, occurred with a longer average latency period and with less frequency compared to those produced by the parental RB defective cells. Our results suggest that reintroduction of the RB gene into WERI-27 cells reduces but does not completely suppress their tumorigenic potential. Since retinoblastoma is an eye tumor it also provides further documentation that the use of an orthotopic injection site can be critical when determining the tumorigenicity of a given cell type.

Animals↗
PubMed1991

The retinoblastoma gene functions as a growth and tumor suppressor in human bladder carcinoma cells.

The product of the human retinoblastoma gene (RB) is a nuclear phosphoprotein that is thought to function as a tumor suppressor. Mutations of RB frequently occur in human bladder carcinoma. To investigate the significance of the functional loss of this gene in bladder cancer, an RB expression plasmid (pBARB) under control of the human beta-actin promoter was transfected into the bladder carcinoma cell line HTB9, which lacks RB expression. Marker-selected transfectants that expressed RB protein were identified by immunoblotting and immunohistochemical staining. In selected clones, stable RB expression has persisted over 1 yr under standard culture conditions with 10% serum. However, RB expression caused major alterations of HTB9 growth properties both in vitro and in vivo. RB+ transfectants lacked the ability to form colonies in semi-solid medium, and their growth rate was significantly decreased in 3% serum. In addition, the tumorigenicity of these transfectants was markedly decreased. Tumors that formed in nude mice were much smaller and had a longer latency period but were indistinguishable microscopically from those produced by parental cells. Slower growing tumors were RB+, as measured by nuclear staining of their RB protein and by a normal RB protein pattern on immunoblots. These findings support the concept that the RB gene acts as both a growth and tumor suppressor in bladder cancer cells.

Actins↗
PubMed1991

Absence of retinoblastoma protein expression in primary non-small cell lung carcinomas.

Retinoblastoma (RB) protein expression was examined in paraffin and frozen tissue sections of 36 primary non-small cell lung carcinomas (NSCLC) using immunohistochemistry with confirmation by direct Western blotting. A normal RB protein staining pattern was present in 24 and absent in 10 NSCLC. Two additional RB positive primary tumors have major foci in which all tumor cells showed no RB protein staining. Significantly more high-stage (stages III and IV) NSCLC had altered RB protein expression than those with low-stage (stages I and II) tumors (P less than 0.05). The results suggest that absence of the RB expression may be associated with the initiation and/or progression of many NSCLC. This is the first report of successful RB staining in paraffin sections.

Blotting, Northern↗
PubMed1991

Lack of nuclear RB protein staining in G0/middle G1 cells: correlation to changes in total RB protein level.

Functional loss of the retinoblastoma (RB) gene has been implicated in a diverse group of human malignancies. The potential clinical importance of such loss demands a reproducible RB cell staining method to distinguish RB+ from RB- tumors. We report that normal and known RB+ tumor cells either in culture or in vivo display a mosaic RB staining pattern with variable proportions of cells having unstained nuclei which are indistinguishable from truly RB- tumor cells. We also show that the apparent lack of nuclear staining corresponds to RB+ cells which are in the G0 or middle G1 phase, where as much as 10-fold decrease in total cellular RB protein occurs compared to their G2/M phase counterparts. These findings not only provide new clues to RB protein function in cell growth and differentiation, but also need to be considered when evaluating the RB status in primary malignancies for its role in tumor initiation/progression or as a prognostic parameter.

Animals↗
PubMed1991

Characterization of intragenic deletions in two sporadic germinal mutation cases of retinoblastoma resulting in abnormal gene expression.

Two gross intragenic deletions of the retinoblastoma (RB) gene from patients with sporadic hereditary disease were analysed in detail. This study was undertaken to determine whether there were common mechanisms for these deletions and whether changes found in the tumors were identical to those found in the constitutional cells. Short repeats at the deletion breakpoints were found in both tumors, one resulting in a 2.0 kb deletion including exons 21 and 22, and the other producing a 3.7 kb deletion including exons 14-17. In addition, the identical sequence changes documented in genomic DNAs and transcripts of these tumors were also observed in the constitutional cells. Both deletions were in-frame and resulted in a truncated transcript and protein identical to the expected size based on the exons deleted. These studies provide further documentation of the events which represent the actual 'two hits' originally hypothesized to be responsible for retinoblastoma development.

Base Sequence↗
PubMed1990

Preferential retention of paternal alleles in human retinoblastoma: evidence for genomic imprinting.

The origins of the initial mutations in sporadic retinoblastoma were explored using polymorphic markers from chromosome 13q. The paternal chromosome was maintained in 3 of 3 informative bilateral tumors which had undergone reduction to homozygosity for regions of this chromosome. The paternal chromosome was maintained in 7 of 8 informative unilateral tumors which likewise demonstrated a reduction of homozygosity. These data are in contrast to previously published studies of chromosome retention in unilateral retinoblastoma [Dryja, T. P., Mukai, S., Petersen, R., Rapaport, J. M., Walton, D., and Yandel, D. W. Nature (Lond.), 339: 556-558, 1989; Zhu, Z., Dunn, J. M., Phillips, R. A., Goddard, A. D., Paton, K. E., Becker, A., and Gallie, B. L. Nature (Lond.), 340: 312-313, 1989] and provide the first evidence that genomic imprinting may play a role in this disease.

Alleles↗
PubMed1989

Evaluation of response to chemotherapy in retinoblastoma heterotransplanted to the eyes of nude mice.

The role of chemotherapy in the treatment of retinoblastoma (RB) is unsatisfactory and clinical research is severely limited. A xenograft model for testing chemotherapeutic and other agents has been developed by the heterotransplantation of human RB cells into the anterior chamber of the nude mouse eye. A grading system for visually monitored tumor growth was designed to allow serial observations and documentation of the response to therapy in the model. This method of monitoring compared favorably with histopathologic, photographic, or other criteria in the reproducible, sequential evaluation of tumor status. Six chemotherapeutic agents [vincristine (VCR), doxorubicin (DOX), actinomycin D (ACT-D), dimethyltriazeno-imidazole carboxamide (DTIC), cyclophosphamide (CPM), and diaziquone (AZQ)] were then tested in the model against a patient-derived xenograft line. Results were expressed as the delay in tumor progression judged by serial grading. CPM produced a consistent response in all treated tumors, as did DTIC to a lesser, more variable extent. In 3 of 10 tumors treated with CPM and in 1 of 18 treated with DTIC, complete responses were maintained for at least 20 weeks. VCR, DOX, and ACT-D were ineffective, producing patterns of tumor progression no different from those in the control group. AZQ was most effective, producing responses far exceeding those of conventional agents. The model allows quantitative documentation of the response to therapy in heterotransplanted human RB. Further testing of new agents and combinations is warranted. AZQ may be active against RB.

Animals↗
PubMed1989

The retinoblastoma susceptibility gene product: a characteristic pattern in normal cells and abnormal expression in malignant cells.

Immunoprecipitation and Western immunoblotting studies were undertaken using purified high-affinity antibodies against a synthetic peptide corresponding to a portion of the deduced retinoblastoma (RB) protein. On SDS-PAGE, normal human cells showed an RB protein pattern consisting of a lower sharp band with a Mr of 110 kD and a more variable region above this band with a Mr ranging from 110 kD to 116 kD. The 110 kD band represents the unphosphorylated Rb protein whereas the broader, less well defined region is the phosphorylated RB protein in which molecular mass heterogenicity results from varying amount of phosphorylation. This pattern repeats once at a lower Mr in which a 98 kD band and 98-104 kD variable region can be visualized. This latter conformation seems to represent the unphosphorylated and phosphorylated RB protein translated from the second AUG codon of the RB mRNA. Cellular RB mRNA extracted from normal fibroblasts was translated in vitro reinforcing the usage of this second start codon. A higher ratio of phosphorylated to unphosphorylated Rb protein was seen in cells growing in log phase compared to those arrested in G1 phase. Our present studies also detected two candidates for RB-associated cellular proteins with a Mr of 124 kD and 55 kD respectively. In addition, shortened versions of RB-isoantigenic proteins were found in retinoblastoma and osteosarcoma cell lines.

Antibodies, Neoplasm↗
PubMed1988

The gene responsible for the development of retinoblastoma and osteosarcoma.

The gene responsible for the formation of both retinoblastoma and osteosarcoma recently has been isolated. This represents the first human recessive cancer gene ever cloned. Structural deletions within one or both retinoblastoma gene alleles were commonly noted in the retinoblastomas and an osteosarcoma. Whether or not changes were observed at the DNA level there was either no expression or an abnormal expression of the gene in the tumor. The fact that we could detect changes in the fibroblasts of some patients with the hereditary form of retinoblastoma also indicates that the gene can be used for diagnostic purposes.

DNA, Neoplasm↗
PubMed1988

Simultaneous determination of ascorbic acid and dehydroascorbic acid in cultures of C3H/10T1/2 cells.

A reproducible method is described for the separation and quantification of ascorbic acid and dehydroascorbic acid by ion-pairing reverse-phase high performance liquid chromatography and detection by absorbance at 232 nm. Lowest detectable concentrations with a linear response of detection were 5 nmol for ascorbic acid and 50 nmol for dehydroascorbic acid. This method was applied to the analysis of C3H/10T1/2 cells and culture medium after influx or efflux experiments and single or multiple treatments with ascorbic acid. Subsequent measurement of the radioactivity in the eluted fractions increased the detectability of both ascorbic acid and dehydroascorbic acid to 10 to 20 pmol.

Ascorbic Acid↗
PubMed1988

Altered expression of the retinoblastoma (RB) gene in small-cell carcinoma of the lung.

Nine lung small-cell carcinoma (SCC) cell lines and 9 lung non-SCC cell lines were examined for structural changes of the retinoblastoma (RB) gene as well as its expression using a complementary DNA probe. The RB protein product was investigated using an anti-RB antibody which we produced. Although homozygosity or hemizygosity of the RB gene was suggested in 8 of 9 SCCs and one of 2 large cell carcinomas (LCCs) by Southern blot analysis using an RB cDNA probe and polymorphic DNA markers for chromosome 13, no obvious structural changes of the RB gene were detected in these 18 cell lines. However, RB transcripts were either markedly reduced in quantity or abnormal in length in 3 of 9 SCCs. The specific 115 kD protein was not immunoprecipitated by the anti-RB antibody in all 9 SCCs with either normal or abnormal size RB mRNA. Three of 4 adenocarcinomas (AdCs), all 3 squamous cell carcinomas, and one of 2 LCCs expressed normal size RB mRNA, and the 115 kD protein was immunoprecipitated by the anti-RB antibody. The 115 kD protein was also absent in one of 2 LCCs with shortened RB mRNA and in one of 4 AdCs with low level of RB mRNA expression. These results strongly suggest that inactivation of the RB gene might be involved in the development of lung cancers, especially of SCCs.

Adenocarcinoma↗
PubMed1987

Complete or partial homozygosity of chromosome 13 in primary retinoblastoma.

Sixteen retinoblastomas were examined with chromosome 13 polymorphic probes to determine the frequency of homozygosity for the chromosome in the tumors. Each of the tumors had two cytogenetically normal appearing No. 13 chromosomes. Nontumorous cells from the same patients were heterozygous for the various polymorphic chromosome 13 probes used. At least partial homozygosity for a single chromosome 13 was observed in 75% of the tumors. These studies confirm and extend previous studies which suggest that homozygosity or hemizygosity at RBI occurs in the majority of retinoblastomas. We also demonstrate in an additional tumor that rapid clonal evolution from hemizygosity to homozygosity can occur in the tumor.

Cells, Cultured↗