Biomedical subjects

S X Hu

Publications and source records attributed to S X Hu.

At least 37 records · Page 2Linked to original sources

PubMed1997

Deletion of three distinct regions on chromosome 13q in human non-small-cell lung cancer.

We examined loss of heterozygosity (LOH) at the retinoblastoma susceptibility gene (RB1) locus on chromosome 13q14 in 20 non-small-cell lung cancers (NSCLCs) using polymorphic markers. The expression of RB protein was examined by immunohistochemical analysis of paraffin-embedded specimens of the same tumors. The results revealed that 10 of 16 informative cases showed an LOH at the RB1 locus, whereas only 2 of the 10 tumors lost expression of the RB protein. These 2 tumors had mutations in the remaining RB1 allele. Thus, inactivation of the RB1 gene appears to be involved in a small subset of NSCLCs only. To elucidate the presence of tumor-suppressor genes other than RB1 on 13q, heterozygosity at 15 different loci was investigated. Of 20 tumors analyzed, 15 showed an LOH at least at one locus, and the regions 13q12.1-qter, 13q12.2-14.2 and 13q14.1-q14.3, including the RB1 locus, were deleted in significant numbers of the tumors. Our results suggest that, in addition to the RB1 gene, abnormalities of other tumor-suppressor genes on chromosome 13q are involved in the development of human NSCLCs.

Carcinoma, Non-Small-Cell Lung↗

PubMed1997

Differential retinoblastoma protein expression in neuroendocrine tumors of the lung. Potential diagnostic implications.

Neuroendocrine lung tumors have been considered by some to be a continuum ranging from relatively benign typical carcinoids to highly malignant small-cell carcinomas. Histopathological diagnosis may sometimes be difficult because of their overlapping features. Correct classification, however, carries important prognostic and therapeutic significance. To determine the clinicopathological implications of retinoblastoma (RB) protein expression in these neoplasms, we examined the RB status in a series of neuroendocrine tumors by immunohistochemical analysis of paraffin-embedded tissue sections. A total of 105 tumors were studied. All 44 typical and 15 atypical carcinoids, one of which was initially misdiagnosed as a small-cell carcinoma, manifested a heterogeneous RB-positive staining pattern. Atypical carcinoids in general showed an increase in the number of tumor cells with strong nuclear staining compared to typical carcinoids. In contrast, all 40 small-cell and 6 large-cell neuroendocrine carcinomas failed to show RB staining in any tumor nuclei, indicating loss of RB function. Our results suggest that RB status as measured by immunohistochemical staining can be used as a marker to distinguish typical and atypical carcinoids from small-cell and large-cell neuroendocrine carcinomas.

Carcinoid Tumor↗

PubMed1996

Expression of the retinoblastoma (RB) tumor suppressor gene inhibits tumor cell invasion in vitro.

To determine if replacement of the retinoblastoma (RB) tumor suppressor gene could inhibit invasion of RB-defective tumor cells, the capacity of tumor cells to migrate or invade was quantitated by the Boyden chamber assay. The studies were done in a diverse group of stable RB-reconstituted human tumor cell lines, including those derived from the osteosarcoma and carcinomas of the lung, breast and bladder. The expression of the exogenous wild-type RB protein in these tumor cell lines was driven by either a constitutively active promoter or an inducible promoter. It was found that significantly more tumor cells from the parental RB-defective cell lines and the RB revertants than from the RB-reconstituted RB+ cell lines penetrated through the Matrigel (P<0.001, two-tailed t-test), although both RB+ and RB- cells migrated at approximately the same rate on uncoated polycarbonate filters in the Boyden chambers. Of note, the inhibition of invasiveness of various RB-defective tumor cells by RB replacement was apparently well correlated with suppression of their tumorigenicity in vivo. In contrast, although either functional RB or p53 re-expression effectively suppressed tumor formation in nude mice of the RB-/p53null osteosarcoma cell line, Saos-2, replacement of the wild-type p53 gene had much less impact on their invasiveness as compared to the RB gene. These studies provided an insight into the broader biological basis of the RB-mediated tumor suppression in RB-defective tumor cells.

Animals↗

PubMed1996

p53, Rb, and cyclin D1 expression in human oral verrucous carcinomas.

BACKGROUND: The verrucous carcinoma (VC), a tumor with low grade malignancy, appears to be associated with tobacco and human papillomavirus. The pathobiology of these tumors has not been extensively studied, and molecular genetic alterations have not been reported. In this study we investigated by immunohistochemistry the expression of p53, Rb, and cyclin D1 in a series of well-defined oral VC. Changes in the expression of these genes have been commonly reported in a variety of human tumors. METHODS: We studied 29 cases of VC, fixed in formalin and embedded in paraffin. Immunohistochemistry was carried out using the avidin-biotin immunoperoxidase technique. Polyclonal antibody CM-1 was used for p53, a rabbit polyclonal human RB antibody, Rb-WL-1 antibody for Rb and a rabbit polyclonal human cyclin D antibody for cyclin D1. RESULTS: Positive p53 expression (protein accumulation) was detected in 15 of the 29 VC analyzed. In some cases, p53-positive areas were small foci but in most of the cases extensive positive areas were observed. None of the cases studied showed alterations of Rb protein. The expression of cyclin D1 was determined in 18 cases of VC. Positive nuclear immunostaining was seen in 11 cases. CONCLUSIONS: p53 protein accumulation is frequently observed in these tumors suggesting possible mutations of this gene in VC. Overexpression of cyclin D1 but no alterations of Rb staining were also observed in this low grade tumor suggesting that Rb may be functionally inactivated by overexpression of cyclin D1 or HPV infection.

Adult↗

PubMed1996

Enhanced tumor suppressor gene therapy via replication-deficient adenovirus vectors expressing an N-terminal truncated retinoblastoma protein.

The preclinical studies presented here demonstrate that treatment of human non-small cell lung carcinoma and bladder carcinoma cells by a recombinant adenovirus vector, AdCMVpRB94, expressing the N-terminal truncated retinoblastoma (RB) protein (pRB94) completely suppressed the tumorigenicity of the treated tumor cells in nude mice. Furthermore, gene therapy of established human RB- and RB+ bladder xenograft cancers in nude mice by AdCMVpRB94 resulted in regression of the treated tumors. Of note, although both the full-length and the truncated forms of the RB protein, when overexpressed in tumor cells via replication-deficient adenovirus vectors, were capable of suppression of tumor growth, the pRB94 was evidently more potent than the full-length RB protein.

Adenoviruses, Human↗

PubMed1996

Retinoblastoma protein inhibits IFN-gamma induced apoptosis.

Regulation of apoptosis (programmed cell death) is critical for maintaining tissue homeostasis. Recent studies indicate a tight coupling between cellular proliferation and apoptosis as cell cycle regulators such as Cyclin D, E1A and E7 appear to influence both events. Each of these modulators is able to bind to and inhibit the function of the retinoblastoma tumor suppressor protein (RB). RB functions, in part, by binding to and inactivating E2F transcription factors, preventing expression of E2F-activated genes associated with G1/S cell-cycle progression. Loss of functional RB deregulates E2F activity and, depending on cell type and environmental factors, promotes tumorigenesis or apoptotic death. To determine the effect of RB on IFN-gamma induced apoptosis, we treated RB-defective carcinoma cell lines and their respective RB-constituted sister clones with IFN-gamma and examined the cells for alterations characteristic of apoptosis. We observed that RB-defective cells, but not the RB-reconstituted clones, decreased in size following IFN-gamma treatment. IFN-gamma treatment caused increased cell detachment in the RB-defective lines but did not affect adherence of the RB-reconstituted clones. Assays for DNA fragmentation revealed lower molecular weight DNA and the apoptosis-associated oligo-nucleosomal ladder following IFN-gamma treatment of the RB-defective cells while higher molecular weight DNA was present in the IFN-gamma treated, RB-reconstituted lines. IFN gamma-induced apoptosis in RB-defective cells was enhanced by serum stimulation, which is also characteristic of p53-dependent E2F-1-mediated apoptosis. However, IFN-gamma induced apoptosis in RB-defective lines does not require wild-type p53 suggesting that, upon IFN-gamma induction, deregulated E2F-mediated apoptosis can also proceed via p53-independent pathways.

Antineoplastic Agents↗

PubMed1996

Apoptosis-independent retinoblastoma protein rescue of HLA class II messenger RNA IFN-gamma inducibility in non-small cell lung carcinoma cells. Lack of surface class II expression associated with a specific defect in HLA-DRA induction.

Work from our laboratory indicates that HLA class II induction by IFN- gamma in the retinoblastoma (RB) protein-defective breast carcinoma line MDA-468-S4 (S4) requires reconstitution of functional RB. To determine whether RB is required for HLA class 11 expression in multiple tumor types, the RB-defective non-small cell lung carcinoma line H2009 and its RB-reconstituted subclones were examined for class II inducibility. Surface HLA-DR (DR) was not inducible by IFN-gamma in H2009. However, unlike the RB-reconstituted subclones of S4, DR surface expression was not detected in the H2009 RB-positive subclones. IFN-gamma induction of CIITA, a major regulator of class II transcription, suggested that H2009 retained at least part of the IFN-gamma signaling pathway leading to class II expression. Examination of class II mRNA indicated that IFN-gamma induction of RB was rescued in the RB-positive subclones of H2009, confirming the requirement for RB for HLA class II inducibility and revealing that RB is required for inducibility in developmentally distinct tumor types. However, DRA inducibility was not rescued in the H2009 RB-positive subclones, which explained the lack of surface DR induction in the RB-positive H2009 subclones. DPA and DPB were also only weakly inducible in the RB-reconstituted H2009 subclones, compared with the previously described, S4 RB-positive subclones. Finally, data reported here indicates that RB's ability to inhibit IFN-gamma-induced apoptosis is not a viable explanation for why RB expression rescues DRB inducibility in H2009.

Apoptosis↗

PubMed1996

Prognostic value of p53 in muscle-invasive bladder cancer treated with preoperative radiotherapy.

OBJECTIVES: The relationship of p53 mutations as analyzed immunohistochemically to radiation response and therapeutic outcome was examined in a cohort of 301 patients with muscle-invasive transitional cell carcinoma of the bladder treated relatively uniformly with preoperative radiotherapy (50 Gy in 25 fractions) 4 to 6 weeks prior to radical cystectomy. METHODS: Adequate formalin-fixed paraffin-embedded archival tissue for the immunohistochemical staining of p53 using antibody DO1 was obtained in 109 patients. The median follow-up for those living was 91 months. RESULTS: Overall, p53 staining was positive in 56% of the cases, with 60% positive in Stage T2 (n = 48), 42% in Stage T3a (n = 31), and 63% in Stage T3b (n = 30). Overexpression of p53 did not correlate with actuarial local control, distant metastasis freedom, disease freedom, or overall survival. However, significant associations were seen when these analyses were limited to patients with clinical Stage T3b disease. In this subgroup, the actuarial 5-year rates for patients with p53 positively and negatively stained tumors were 55% and 100%, respectively, for distant metastasis freedom (P = 0.01), 51% and 91% for disease freedom (P = 0.04), and 32% and 91% for overall survival (P = 0.006). Cox proportional hazards models that included p53 staining and other prognostic factors of significance in the univariate analyses revealed p53 to be independently predictive of survival for patients with Stage T3b disease. CONCLUSIONS: The prognostic value of p53 immunostaining rested with Stage T3b patients. Although no correlations were found with radiation response, p53 positivity in this subgroup was associated with a higher rate of distant metastasis and reduced overall survival. For these patients, p53 negativity would indicate that aggressive local treatment (that is, preoperative radiotherapy and cystectomy) is sufficient, whereas p53 positivity would indicate that multiagent chemotherapy is required because of the increased risk of distant metastasis.

Carcinoma, Transitional Cell↗

PubMed1996

Transfusion-associated graft-versus-host disease diagnosed by polymerase chain reaction analysis of DNA microsatellites: an autopsy case with immunohistochemical investigation.

An autopsy case of transfusion-associated graft-versus-host disease (TA-GVHD) is reported with immunohistochemical investigation and polymerase chain reaction (PCR) analysis. In a 58-year-old male, esophagectomy for carcinoma was performed with a transfusion of 4 units of fresh whole blood. Diarrhea, fever, erythematous rash, pain and leukopenia occurred with an onset 11 days after the operation. He died of sudden dyspnea 29 days after the operation. At autopsy, histological examinations revealed lichenoid lesion in the skin, injury of mucosal epithelia in the digestive tract and damage of interlobular bile ducts in the liver. Immunohistochemical investigation suggested the association between these lesions and CD8-positive T lymphocytes. Severe disturbances of bone marrow and lymphoid organs were accompanied with gram-positive cocci infection in the lungs, esophagus and small intestine. PCR analysis of DNA at microsatellite loci, human growth hormone (HGH) and apolipoprotein B (Apo B), showed DNA chimerism and established the definitive diagnosis of TA-GVHD.

Antigens, CD↗

PubMed1996

Altered retinoblastoma and p53 protein status in non-small cell carcinoma of the lung: potential synergistic effects on prognosis.

Routinely processed pathological specimens from 119 patients with stage I and II adenocarcinomas or squamous cell carcinomas were examined by immunohistochemical analysis for altered retinoblastoma (RB) and/or p53 protein expression. Absent RB nuclear staining (RB-) indicating loss of RB function occurred in 19 (16%) of the cases studied, whereas expression of a putative mutant p53 nuclear protein (p53(+)) was found in 54 (45%) of the tumors. The median survival was 39 versus 12 months for patients with RB+ and RB- tumors, respectively (P = 0.05 by log rank analysis). Similarly, the median survival was 41 months for patients whose tumors had no expression of mutant p53 (p53(-)) compared with 24 months for individuals with p53 (+) tumors (P = 0.01). These differences in survival, however, were not statistically significant by multivariate analysis. Nevertheless, individuals with RB-/p53(+) tumors had a significantly shorter median survival (12 months) than those with RB+/p53(-) tumors (41 months), as determined by both log rank and multivariate analyses (P = 0.005 and 0.03, respectively). In addition, 66 large cell carcinomas from all stages were examined. Again, a more significant difference in survival (48 versus 8 months) was found between patients with RB+/p53(-) versus RB-/p53(+) tumors (P = 0. 006). These results suggest that RB and p53 status might be used synergistically as prognostic factors in a subset of non-small cell lung carcinomas.

Adult↗

PubMed1995

Genetic disparity between morphologically benign cysts contiguous to ovarian carcinomas and solitary cystadenomas.

BACKGROUND: Ovarian carcinomas occasionally contain large, histologically benign cysts contiguous to the clearly malignant areas (cystadenocarcinomas). The question of whether such cysts are remnants of pre-existing benign tumors (cystadenomas) or constitute integral components of the carcinomas is important in clarifying the role of cystadenomas in ovarian carcinogenesis. It is also important for our general understanding of tumor heterogeneity, a phenomenon thought to result from the gradual accumulation of genetic abnormalities in initially homogeneous tumors. This question is also pertinent to the clinical management of ovarian cystadenomas, which are frequent in women of childbearing age and are usually treated surgically based on the possibility that they may give rise to carcinomas. PURPOSE: Reasoning that molecular markers of ovarian malignancy would be confined to the histologically malignant portions of cystadenocarcinomas if the morphologically benign portions are in fact pre-existing typical cystadenomas, we sought to verify that mutations in the p53 tumor suppressor gene are markers of malignancy in ovarian tumors and to determine the distribution of such mutations in cystadenocarcinomas. METHODS: We used immunohistochemical and DNA-sequencing techniques to analyze 46 ovarian carcinomas, 21 ovarian tumors of low malignant potential, and 16 solitary cystadenomas for the presence of p53 mutations. We then used similar techniques to examine the distribution of such mutations in different portions of cystadenocarcinomas. The observed differences in mutation frequencies were analyzed by the two-tailed Fisher's exact test. RESULTS: Mutations in the p53 gene were present in 24 (52%) of the 46 carcinomas, but they were absent in the 21 tumors of low malignant potential (P < .0001) and the 16 solitary cystadenomas (P = .0002). Six of six cystadenocarcinomas with p53 mutations showed the presence of the same mutations in the adjacent, histologically benign cysts. The mutations were seen not only in cells immediately adjacent to the carcinomas, but also throughout the morphologically benign cysts. Twenty (83%) of the 24 cases showing mutation of one p53 allele also showed loss of genetic heterozygosity, suggesting that the other p53 allele was deleted. Such allelic loss, if present in morphologically malignant portions of cystadenocarcinomas, was also observed in the contiguous cysts. CONCLUSIONS: Ovarian carcinomas can be distinguished from ovarian cystadenomas and tumors of low malignant potential by p53 mutations. The fact that the mutations were present in histologically benign cysts contiguous to ovarian carcinomas suggests that such cysts are not typical cystadenomas and may carry a genetic predisposition to carcinogenesis that is not present in ordinary cystadenomas.

Carcinoma↗

PubMed1995

Retinoblastoma-like phenotype expressed in medulloblastomas.

The previous demonstration of rod-opsin and S-antigen (S-Ag), a protein which arrests visual phototransduction, in retinoblastomas and in a subgroup of medulloblastomas has suggested a relationship between these tumors. We examined 17 medulloblastomas for the presence of a retinoblastoma-like phenotype. Overall 41% of the tumors were immunoreactive for S-Ag. Two tumors with well-differentiated Flexner-Wintersteiner rosettes were also immunoreactive for S-Ag, but not for epithelial membrane antigen (EMA). In contrast, most ependymal rosettes in two ependymomas stained positive for EMA along the luminal surface, consistent with a previous study, and were negative for S-Ag. Because calcification in areas of necrosis is a near constant finding in retinoblastomas, the medulloblastomas were evaluated for the presence of calcification, using Von Kossa staining. Forty-one percent showed calcification in areas of necrosis and 29% were positive for both calcification and S-Ag immunoreactivity. There was a statistically significant concordance between calcification and S-Ag immunoreactivity in the medulloblastomas (p < 0.05). Despite similar phenotypic features, a shared mechanism of tumori-genesis for retinoblastomas and the subgroup of medulloblastomas with photoreceptor differentiation could not be identified since all 17 medulloblastomas were found to express functional Rb protein, as indicated by positive nuclear immunoreactivity.

Adolescent↗

PubMed1995

The loss of retinoblastoma gene in association with c-myc and transforming growth factor-beta 1 gene expression in human bladder cancer.

PURPOSE: We investigate the roles and possible interactions of the retinoblastoma, transforming growth factor-beta 1 and c-myc genes in bladder cancer. MATERIALS AND METHODS: The expression of these 3 genes was examined in 38 biopsy specimens of human bladder cancer by immunohistochemical analysis or Northern blotting. RESULTS: Loss of the retinoblastoma protein expression was most significantly correlated with high grade cancer. Over expression of c-myc or expression of transforming growth factor-beta 1 was less associated with tumor grade or stage, although c-myc over expression defined stage Ta against other stage tumors, since no stage Ta lesions had increased c-myc expression. Finally, loss of retinoblastoma gene function did not correlate with either c-myc or transforming growth factor-beta 1 expression. CONCLUSIONS: These results further support that retinoblastoma gene inactivation is an important factor in the progression of bladder cancer, and suggest that transforming growth factor-beta 1 and c-myc are not regulators or are not regulated by retinoblastoma gene expression.

Gene Expression Regulation, Neoplastic↗

PubMed1995

Growth-factor stimulation reveals two mechanisms of retinoblastoma gene inactivation in human myelogenous leukemia cells.

Mutation or deletion of the retinoblastoma tumor suppressor gene (Rb) or abnormal Rb protein expression is found in many types of human solid tumors. Low or absent levels of Rb protein are usually found in the leukemic cells of patients with acute myelogenous leukemia (AML) who have an extremely poor prognosis. The absence of Rb protein in these AML cells could result from defects in the Rb gene or from abnormal cell cycle regulation that affects Rb expression. To test these possibilities and to examine whether a low level of Rb protein in AML cells could be up-regulated, we studied the effect that growth factors interleukin 3 (IL3) and granulocyte-macrophage colony stimulating factor (GM-CSF) had on the levels of Rb protein and Rb phosphorylation in AML cells from patients with low Rb or no Rb protein expression. We observed three responses to growth factor-stimulation in leukemic cells taken from patients with AML: (1) some AML cell samples entered a proliferative phase, and Rb protein levels increased with the appearance of normally phosphorylated forms of Rb protein and positive nuclear staining for Rb protein; (2) some AML cell samples became more proliferative, but the levels of Rb protein remained low or absent; and (3) some AML cell samples showed no response. These results indicate that at least two different mechanisms may be responsible for the lack of Rb protein in the leukemic cells of some patients with AML.

Gene Expression Regulation, Leukemic↗

PubMed1995

Loss of heterozygosity occurs centromeric to RB without associated abnormalities in the retinoblastoma gene in tumors from patients with metastatic renal cell carcinoma.

Tumor suppressor genes have been found to have loss of function in a number of malignancies. This loss of function is believed to contribute to malignant transformation or metastatic spread. In the present study, expression of the retinoblastoma (RB) tumor suppressor gene was examined in cell lines and tumor tissue obtained from primary renal and metastatic sites in patients with metastatic renal cell carcinoma. Three of fifteen (20%) of informative renal carcinoma cell lines had loss of heterozygosity (LOH) in the RB gene (intron 20) detected by polymerase chain reaction analysis. Using restriction fragment length polymorphism (RFLP) analysis, 7 of 22 (32%) informative cell lines had LOH centromeric to the RB gene at the D13S1 locus. No LOH (0 of 7) was seen telomeric to the RB gene at the D13S2 locus. None of the 28 cell lines examined had decreased RB mRNA expression compared with short-term cultures of proximal renal tubular cells. Western blotting demonstrated phosphorylated and unphosphorylated forms of RB protein of expected molecular weight in all 41 cell lines (33 primary and 8 metastatic) examined. Twenty-nine primary cell lines and 6 metastatic cell lines all demonstrated normal immunohistochemical staining. Loss of RB immunohistochemical staining in paraffin-embedded tissue was detected in none of the primary tumors (0 of 30) or metastatic tumors (0 of 12). The absence of abnormalities of RB expression detected in these renal cell carcinomas suggests that abnormalities of the RB gene are not central to malignant transformation or progression in this tumor type; however, another tumor suppressor gene centromeric to the RB locus may be important in renal cell carcinogenesis.

Base Sequence↗

PubMed1994

Enhanced tumor cell growth suppression by an N-terminal truncated retinoblastoma protein.

The retinoblastoma (RB) gene encodes a nuclear phosphoprotein of 928 amino acids (pRB). Thus far, much effort in RB research has been focused on both the viral oncoprotein-binding domains and the C-terminal domain, whereas little is known about the N-terminal moiety of the protein. We report here that an N-terminal truncated RB protein of approximately 94 kDa (pRB94) exerts more potent cell growth suppression as compared to the full-length pRB protein in a diversity of tumor cell lines examined, including those having a normal endogenous RB gene. Tumor cells transfected with the pRB94-expressing plasmids displayed multiple morphological changes frequently associated with cellular senescence and/or apoptosis. They failed to enter S phase and rapidly died. The pRB94 expressed in recipient tumor cells had a longer half-life than the full-length pRB protein and tended to remain in an active un- or hypophosphorylated form. Since it has also been found that N-terminal truncated RB proteins often accumulated in growth-arrested and/or differentiated tumor cells, we suggest that N-terminal truncation of pRB may be one of the cellular mechanisms modulating the RB protein function in cell-cycle control.

Animals↗

PubMed1994

Deletions of chromosome 13q, mutations in Retinoblastoma 1, and retinoblastoma protein state in human hepatocellular carcinoma.

Twenty-one tumors from 18 patients (two independent tumors were obtained from each of three patients) with hepatocellular carcinomas were examined for loss of heterozygosity (LOH) at loci on chromosome 13q, using 15 polymorphic nucleotide sequences of microsatellites as genetic markers. The results revealed LOH in a common region between the centromeric D13S127 locus (13q12.2-q14.1) and the telomeric D13S137 (13q14.3) locus, including the RB1 locus, in nine of 21 tumors. Immunohistochemical staining of paraffin-embedded tumor sections indicated loss of retinoblastoma (RB) protein expression in all tumors showing LOH except one. Absence of RB protein expression was also observed in three of 12 tumors without LOH. Single-strand conformation polymorphism analysis of polymerase chain reaction products using primers flanking all 27 exons of the RB1 gene, as well as nucleotide sequencing, revealed tumor-specific small deletions of the RB1 coding region in the remaining RB1 allele of two tumors having LOH at the RB1 locus with concomitant loss of RB protein expression. Our results indicate that the loss of a region of chromosome 13q including the RB1 locus significantly (P < 0.006) correlates with loss of RB protein in hepatocellular carcinomas. However, tumor-specific mutations of the RB1 gene were detected in only two of 13 tumors with LOH and/or lack of RB protein expression, indicating that analysis of the RB1 status at the protein level in these tumors may be more sensitive than the actual mutational analysis.

Base Sequence↗

PubMed1994

Aberrant RB gene expression in routinely processed, archival tumor tissues determined by three different anti-RB antibodies.

The retinoblastoma (RB) susceptibility gene encodes a nuclear phosphoprotein which is likely involved in cell cycle control and cell differentiation. The RB protein is mutated or absent in a variety of human malignancies. Its role as a molecular marker for clinical tumor behavior is under extensive investigation. However, studies on the status of the RB protein in primary or metastatic tumors and their precursor lesions have been slowed by the lack of availability of a sensitive, reliable assay which allows examination of RB expression in selected cell populations within archival tissues. Thus far, meaningful immunohistochemical analysis of RB protein in formalin-fixed, paraffin-embedded specimens has been achieved only with the polyclonal antibody RB-WL-I. We now describe a method which produced excellent staining results in formalin-fixed, routinely processed tissues, using commercially available monoclonal antibodies (MAbs) in conjunction with an antigen-retrieval step. The resulting stains were superior to those on frozen sections and comparable to those obtained with RB-WL-I. Twelve of 51 random invasive bladder cancers (24%) had abnormal expression of the RB gene, as determined by immunohistochemistry. Smaller cohorts of breast, prostate and lung carcinomas had incidences of aberrant RB gene expression ranging from 9% to 24%. Since the staining method was widely applicable to essentially all formalin-fixed, archival tissues, it may expedite studies on the biological and clinical significance of altered RB expression in human neoplasia.

Antibodies, Monoclonal↗