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R Lotan

Publications and source records attributed to R Lotan.

At least 109 records · Page 6Linked to original sources
PubMed1997

Progressive decrease in nuclear retinoic acid receptor beta messenger RNA level during breast carcinogenesis.

Some of the nuclear retinoic acid receptors (RARs) alpha, beta, and gamma and retinoid X receptors (RXRs) alpha, beta, and gamma are thought to mediate the effects of retinoids on cell growth, differentiation, and apoptosis and thereby prevent breast carcinogenesis. We analyzed the expression of mRNAs for the three RARs and RXR-alpha in histological sections of specimens from 70 breast cancer patients, which included adjacent normal tissue, ductal carcinoma in situ, and invasive cancer, using in situ hybridization. RARs alpha, beta, and gamma and RXR-alpha were expressed in 98.1, 98.0, 93.0, and 100% of the adjacent normal tissues. Significant decreases in the number of cases expressing RAR-beta were observed among ductal carcinoma in situ (83.1%) and invasive carcinomas (51.6%), especially among the poorly differentiated cases (77.4 and 35.7 %, respectively). No relationship was found between the expression of estrogen receptor and RAR-beta. These results implicate decreases in RAR-beta expression in breast cancer development and suggest that they are independent of estrogen receptor status.

Breast↗
PubMed1997

Differential effects of synthetic nuclear retinoid receptor-selective retinoids on the growth of human non-small cell lung carcinoma cells.

Retinoids are promising agents for cancer chemoprevention and therapy. Nuclear retinoic acid receptors (RARs; RARalpha, -beta, and -gamma) and retinoid X receptors (RXRs; RXRalpha, -beta, and -gamma) are thought to mediate most of retinoids' effects on cell growth and differentiation. Because the majority of human non-small cell lung carcinoma (NSCLC) cell lines are resistant to all-trans-retinoic acid, we searched for more potent retinoids. Therefore, we examined the effects of 37 natural and synthetic retinoids that exhibit specific binding to and transactivation of individual RARs or RXRs on the proliferation of eight human NSCLC cell lines. All of these cells expressed mRNAs of the three RXRs; however, they expressed varying levels of RARalpha and RARgamma, and only three of the eight cell lines expressed RARbeta mRNA. Cellular retinoic acid-binding proteins (CRABPs) I and II were detected in one and three of the eight cell lines, respectively. Only 8 of the 37 retinoids exhibited growth-inhibitory activity (IC50, < 10 microM) against at least two of the eight NSCLC cell lines. The active retinoids included one (TD550) of five RARalpha-selective, one (Ch55) of three RARbeta-selective, three (CD437, CD2325, and SR11364) of six RARgamma-selective, and one (CD271) of four RARbeta/gamma-selective retinoids. The potency of these retinoids was low (IC50, > 1 microM), except for CD437, which was very potent (IC50, 0.1-0.5 microM). The six RXR-selective retinoids were mostly inactive even at 10 microM. However, combinations of RAR-selective and RXR-selective retinoids exhibited additive effects. There appeared to be no simple correlation among the histological type of the NSCLC (adeno- or squamous), the levels of nuclear receptors or CRABPs, and the response of the cells to the growth-inhibitory effects of retinoids. Nevertheless, in contrast with former studies with natural retinoids, these results suggest that several synthetic retinoids do exhibit inhibitory activity against NSCLC cells, and some of them may be useful clinically.

Antineoplastic Agents↗
PubMed1997

Enhancement of Calu-1 human lung carcinoma cell growth in serum-free medium by retinoids: dependence on AP-1 activation, but not on retinoid response element activation.

Many lung cancer cell lines are resistant to the growth inhibitory effects of retinoids. However, some small-cell lung cancer cell lines were inhibited by all trans-retinoic acid (ATRA) in serum-free medium. We compared the responses of seven non-small cell lung cancer (NSCLC) cell lines to ATRA in serum-free medium and in medium supplemented with delipidized serum. Whereas the growth of four cell lines was inhibited more in serum-free medium, the growth of the Calu-1 cell line was stimulated by ATRA in a dose-dependent fashion with a maximum at 10(-8) M. Delipidized serum (>2.5%) but not bovine serum albumin (0.15%) suppressed growth stimulation by ATRA. Transcripts of RA receptors RARalpha and RARgamma but not of RARbeta were detected in Calu-1 cells. Receptor expression, the formation of a complex among receptors and a RA-responsive element (RARE), and the transcriptional activation RARE were not suppressed by serum. Natural retinoids and synthetic receptor class- or subtype-selective retinoid agonists, which activated RARs and RXRs for gene transcription from a RARE, and a RAR antagonist (CD2366), which was unable to do so, stimulated the growth of Calu-1 cells in serum-free medium but not in serum-containing medium. Both ATRA and CD2366 enhanced the transcriptional activation of an Activator Protein-1 (AP-1)-luciferase reporter construct in serum-free medium but not in delipidized serum. Transcriptional activation of the RARE by ATRA occurred both in the presence or absence of delipidized serum. These results demonstrate that retinoid-induced growth stimulation of Calu-1 cells is associated with enhanced AP-1 transactivation but not with RARE transactivation.

Antineoplastic Agents↗
PubMed1997

Involvement of reactive oxygen species in N-(4-hydroxyphenyl)retinamide-induced apoptosis in cervical carcinoma cells.

BACKGROUND: The inhibitory effects of N-(4-hydroxyphenyl)retinamide (4HPR) on tumorigenesis and tumor growth may result from its ability to induce apoptosis (programmed cell death). Since antioxidants inhibit 4HPR-induced apoptosis, experiments were planned to determine whether the levels of reactive oxygen species increase in cells undergoing apoptosis after exposure to 4HPR. METHODS: Cells of the human cervical carcinoma cell line C33A and normal human cervical epithelial cells were treated with 4HPR and analyzed for survival, induction of apoptosis, generation of reactive oxygen species, and expression of the apoptosis-related proteins Bcl-2 and Bax. RESULTS: Treatment with 4HPR decreased C33A cell number by inducing apoptosis in a time- and dose-dependent fashion. DNA fragmentation typical of apoptosis was observed in cells exposed to 4HPR at concentrations of 3 microM or higher for 6-24 hours. The generation of reactive oxygen species was enhanced by 1.85-fold to 4.5-fold after a 1.5-hour treatment with 0.4-10 microM 4HPR. Pyrrolidine dithiocarbamate, an oxygen radical scavenger, suppressed the rate of generation of reactive oxygen species and inhibited 4HPR-induced apoptosis. 4HPR failed to modulate cellular levels of the Bcl-2 and Bax proteins. N-(4-Methoxyphenyl)retinamide, the major 4HPR metabolite, and several other retinoids that bind to nuclear retinoic acid receptors or retinoid X receptors failed to enhance the generation of reactive oxygen species and to induce apoptosis. 4HPR was much less effective in generating reactive oxygen species and in inducing apoptosis in normal human cervical epithelial cells than in C33A cervical carcinoma cells. CONCLUSIONS: Enhancement of the generation of reactive oxygen species may be involved in apoptotic pathway induction by 4HPR.

Antioxidants↗
PubMed1997

Expression of the endogenous galactose-binding protein galectin-3 correlates with the malignant potential of tumors in the central nervous system.

BACKGROUND: The 31-kilodalton beta-galactoside-binding protein galectin-3 has been associated with cellular transformation and metastasis. Because neural tissues contain large amounts of glycoconjugates, and endogenous carbohydrate-binding proteins have been described in the human brain, the authors examined the expression of galectin-3 in human brain tumors and metastases to the central nervous system. METHODS: Brain tumors were categorized by the World Health Organization system and galectin-3 expression by immunoperoxidase staining using a quantitative staining score. RESULTS: Glioblastomas (Grade 4 astrocytomas) all stained strongly for galectin-3, whereas low grade astrocytomas (Grade 2) did not express the endogenous lectin. Anaplastic astrocytomas (Grade 3) exhibited intermediate expression. The staining score was significantly associated with tumor grade (P < 0.001). Normal brain tissue and benign tumors did not express galectin-3, whereas metastases to the brain were all positive for galectin-3 expression. Metastases expressed significantly more galectin-3 than the primary tumors from which they were derived (P = 0.003). CONCLUSIONS: Galectin-3 expression correlates with the malignant potential of tumors in the central nervous system.

Antigens, Differentiation↗
PubMed1997

Suppression of retinoic acid receptor beta in non-small-cell lung cancer in vivo: implications for lung cancer development.

BACKGROUND: Retinoids, analogues of vitamin A, are required for the normal growth and differentiation of human bronchial epithelium. They are also able to reverse premalignant lesions and prevent second primary tumors in some patients with non-small-cell lung cancer (NSCLC). These effects are thought to result from modulation of cell growth, differentiation, or apoptosis (programmed cell death). When certain retinoid receptors in the cell nucleus (i.e., retinoic acid receptors [RARs] and retinoid X receptors [RXRs]), which mediate most retinoid actions, are suppressed, abnormal activity may result that could enhance cancer development. PURPOSE: This study was designed to determine whether there are abnormalities in the expression of retinoid receptors in surgical specimens from patients with NSCLC. METHODS: Transcripts of nuclear retinoid receptors were detected in formalin-fixed, paraffin-embedded specimens by use of digoxigenin-labeled riboprobes specific for RAR alpha, RAR beta, RAR gamma, RXR alpha, RXR beta, and RXR gamma for in situ hybridization to histologic specimens from 79 patients with NSCLC and as control from 17 patients with non-lung cancer. The quality and specificity of the digoxigenin-labeled probes were determined by northern blotting, and the specificity of the binding of antisense riboprobes was verified by use of sense probes as controls. RESULTS: All receptors were expressed in at least 89% of control normal bronchial tissue specimens from 17 patients without a primary lung cancer and in distant normal bronchus specimens from patients with NSCLC. RAR alpha, RXR alpha, and RXR gamma were expressed in more than 95% of the NSCLC specimens. In contrast, RAR beta, RAR gamma, and RXR beta expression was detected in only 42%, 72%, and 76% of NSCLC, respectively. CONCLUSIONS: These data suggest that the expression of RAR alpha, RXR alpha, and RXR gamma is not altered in NSCLC; however, expression of RAR beta and possibly also of RAR gamma and RXR beta is suppressed in a large percentage of patients with lung cancer. IMPLICATIONS: The loss of expression of one or more of these nuclear retinoid receptors may be associated with lung carcinogenesis.

Adenocarcinoma↗
PubMed1997

Frequent inactivation of p16INK4a in oral premalignant lesions.

Head and neck carcinogenesis is believed to be a multistep process, whereby genetic events accumulate in the carcinogen-exposed field at risk, resulting in distinct phenotypic premalignant changes that eventually evolve into invasive cancer. Frequent loss of heterozygosity (LOH) at the chromosome 9p21 region and inactivation of p16(INK4a) by different mechanisms have been described in head and neck squamous cell carcinoma (HNSCC). Recently, we reported that loss of 9p21 is also frequent in oral premalignant lesions. To investigate potential inactivation of p16(INK4a) in these premalignant lesions, we analysed 74 biopsies from 36 patients by immunohistochemistry (IHC) for expression of the p16 protein. Loss of p16 expression was found in 28 (38%) of the lesion biopsies from 17 patients (47%). LOH at the D9s171, a marker in the 9p21 region, was observed in 19 lesion biopsies from 12 cases and correlated with absence of p16 by IHC in 11 (92%) of the 12 comparable cases and 15 (79%) of 19 lesion biopsies. By direct sequencing of ten lesion biopsies from ten individuals with LOH at D9s171 for p16(INK4a) exon 2, one non-sense mutation at codon 88 (GGA-->TGA) was identified. Our data suggest that inactivation of p16(INK4a) may play an important role in early head and neck cancer development.

Biopsy↗
PubMed1997

Molecular epidemiology and retinoid chemoprevention of head and neck cancer.

Head and neck cancer is a major worldwide health problem; it has been estimated that approximately 900,000 people were diagnosed with this disease in 1995. Patients are generally treated with surgery and/or radiation therapy. Treatment, especially of patients with early stage (I or II) head and neck squamous cell carcinoma, is often successful. A serious concern, however, is the fact that these patients subsequently develop second primary tumors at an annual rate of 4%-7%. Molecular analyses of premalignant and malignant tissues have produced strong evidence that clonal genetic alterations occur during the early stage of aerodigestive tract carcinogenesis. Although the roles of tobacco and diet in head and neck carcinogenesis have been the subjects of epidemiologic investigations for many years, it has only recently become possible to integrate information regarding genetic susceptibility factors into the development of comprehensive risk models for these cancers. The molecular and epidemiologic studies provide the foundation on which clinical trials can be designed to evaluate the role of retinoids and other compounds in the reversal of premalignancy and the prevention of second primary tumors (i.e., in chemoprevention). This translational approach has led to studies of the utility of intermediate end point markers, such as the nuclear retinoic acid receptors, in chemoprevention strategies. Given the rapid advances occurring in this area of research, it may soon be possible to use these biomarkers to identify patients who are most at risk for developing head and neck cancer and who are most likely to benefit from chemopreventive interventions.

Biomarkers, Tumor↗
PubMed1997

Induction of apoptosis in human non-small cell lung carcinoma cells by the novel synthetic retinoid CD437.

Retinoids are promising agents for the prevention and treatment of several human malignancies including lung cancer. However, many lung cancer cell lines are resistant to the growth inhibitory effects of all-trans-retinoic acid (ATRA). Recently, we found that a new synthetic retinoid, 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437), which binds selectively to nuclear RA receptor gamma, was the most effective inhibitor of the growth of human non-small cell lung carcinoma (NSCLC) cells among 37 retinoids tested. After a 4-day treatment with CD437 the growth of 8 NSCLC cell lines was inhibited with an IC50 ranging from 0.13 to 0.53 microM. In contrast, ATRA failed to inhibit the growth of any of these cell lines by more than 43% after a 7-day treatment even at 10 microM. The presence of detached rounded cells in treated cultures indicated that CD437 may induce apoptosis. Indeed, this was confirmed by the presence of 20-57% cells with a sub-G1 DNA content and by an enzyme-linked immunosorbent assay (ELISA) of apoptosis. Two retinoids, CD2366 and CD2665, which are antagonists of nuclear retinoid receptor activation, failed to inhibit the effect of CD437 on the growth of the NSCLC cell lines. CD437 failed to suppress the transcriptional activation of the activator protein-1 (AP-1) reporter. These results demonstrate that CD437 can induce apoptosis in NSCLC cells that are resistant to ATRA and that this effect is mediated by a mechanism that may be independent of transactivation of retinoid receptors or transrepression of AP-1.

Adamantane↗
PubMed1997

Growth inhibition of cultured human gastric cancer cells by 9-cis-retinoic acid with induction of cdk inhibitor Waf1/Cip1/Sdi1/p21 protein.

The effect of 9-cis-retinoic acid (9-cis-RA) on the growth of eight gastric cancer cell lines was related to their transcription levels of mRNAs for retinoid receptors. Northern blot analysis showed that seven (TMK-1, MKN-1, -28, -45, -74, HSC-39, KATO-III) out of eight gastric cancer cell lines synthesized mRNAs for retinoic acid receptors (RARs) and retinoid X receptor-alpha (RXR-alpha). MKN-7 cells did not transcribe either RARs or RXR-alpha at the mRNA level although they appeared to have no alterations at the gene level. The growth of all of the cell lines except for MKN-7 cells was inhibited by 1 x 10(-6) M 9-cis-RA. Cell cycle distribution analysis revealed that G0-G1 arrest was not induced by exposure to 9-cis-RA in the sensitive TMK-1 and KATO-III cells or the resistant MKN-7 cells. Interestingly, 9-cis-RA temporarily increased the amount of the cyclin dependent kinase (cdk) inhibitor, Waf1/Cip1/Sdi1/p21 protein, and also reduced the amount of cdk-7, epidermal growth factor receptor (EGFR) and cyclin D1 proteins, followed by reduction in phosphorylation of the product of the retinoblastoma tumor suppressor gene (Rb) in the sensitive TMK-1 cells, but not in the resistant MKN-7 cells. These results suggest that 9-cis-RA has a cytostatic effect on gastric cancer cells that synthesize the receptor molecules through cell cycle regulatory machinery.

Adenocarcinoma↗
PubMed1997

A gene for arthrogryposis multiplex congenita neuropathic type is linked to D5S394 on chromosome 5qter.

Arthrogryposis multiplex congenita (AMC) is a heterogeneous-symptom complex characterized by joint contractures at birth that involve more than one part of the body. We performed a genetic-linkage study of one large Israeli-Arab inbred kindred showing autosomal recessive inheritance of AMC neuropathic type that had been recently investigated by our group. After analysis of approximately 80% of the genome, D5S1456, which showed no increased homozygosity, showed increased genotype sharing in affected individuals. Linkage analysis in all family members revealed linkage between AMC and D5S1456 on chromosome 5qter (maximum LOD score 5.3 at recombination fraction .001). Analysis of additional markers in this region places the gene causing AMC in this family between D5S1456 and D5S498.

Arabs↗
PubMed1997

Roles of retinoids and their nuclear receptors in the development and prevention of upper aerodigestive tract cancers.

Vitamin A analogs (retinoids) suppress oral and lung carcinogenesis in animal models and prevent the development of second primary tumors in head, neck, and lung cancer patients. These effects result from changes in the expression of genes that regulate cell growth and differentiation. Retinoic acid receptors (RARs; -alpha, -beta, and -gamma) and retinoid X receptors (RXRs; -alpha, -beta, and, -gamma) are retinoid-activated transcription factors, which mediate effects of retinoids on gene expression. Therefore, alterations in receptor expression or function could interfere with the retinoid signaling pathway and thereby enhance cancer development. We found that the expression of RAR beta was suppressed in more than 50% of oral and lung premalignant lesions in individuals without cancer and in dysplastic lesions adjacent to cancer and in malignant oral and lung carcinomas. The expression of the other receptors was not different among normal, dysplastic, and malignant oral tissues. However, the expression of RAR gamma and RXR beta was somewhat decreased in lung cancers. These results show that RAR beta expression is lost at early stages of carcinogenesis in the aerodigestive tract and support the hypothesis that the loss of RAR beta expression may facilitate the development of some of these cancers.

Head and Neck Neoplasms↗
PubMed1997

Polyamine measurements in the uterine cervix.

Cervical cancer remains a significant health problem. New strategies based on the molecular aspects of cervical carcinogenesis are needed. Chemoprevention represents a novel strategy for cervical cancer prevention. Our group plans phase I and II trials using alpha-difluoromethylornithine, a suicide inhibitor of ornithine decarboxylase and potent antiproliferative chemopreventive agent. We conducted a study to identify which polyamines in tissue could best serve as surrogate endpoint biomarkers for future trials. Thirty patients with biopsy-proven cervical intraepithelial neoplasia grade 3 underwent colposcopically directed biopsies of normal and abnormal areas of the uterine cervix for analysis of polyamine synthesis biomarkers. Statistically significant differences were found in the ornithine decarboxylase value and the spermidine:spermine ratio between normal and abnormal areas of the cervix. In general, the ranges in measurements varied widely. Differences in polyamine synthesis biomarkers between colposcopically normal and abnormal areas can be demonstrated. However, studies using polyamine synthesis biomarkers in the cervix would require large numbers of patients to achieve significance.

Cervix Uteri↗
PubMed1997

Accumulation of p53 protein and retinoic acid receptor beta in retinoid chemoprevention.

Although retinoids have proven to be effective as chemopreventive agents in reversing premalignant oral lesions and preventing second primary tumors, their mechanisms of chemopreventive efficacy in clinical settings have not been established. To better define this mechanism, we studied p53 protein and retinoic acid receptor beta (RAR-beta) expression in 52 baseline biopsy samples taken from premalignant oral lesions. We then studied p53 expression in 39 matched samples and RAR-beta expression in 38 matched samples before and after treating them with isotretinoin. The study results were then compared with clinical responses. To detect p53 protein expression, 4-micrometer sections of formalin-fixed, paraffin-embedded tissue specimens were used for immunohistochemical analysis with a monoclonal anti-p53 antibody, and levels of p53 expression were recorded with a labeling index (LI). Expression of RAR-beta mRNA was determined using nonradioactive in situ hybridization, and the staining intensity of RAR-beta mRNA was semiquantitated using scores from 0 (no expression) to 3+ (highest expression). p53 protein was detected in 85% of all lesions. High p53 protein expression (LI >/= 0.2) was detected in 25% of the lesions at baseline and in 18% of the lesions after isotretinoin therapy. The clinical response was 65% for lesions having low p53 expression (LI < 0.2) and 27% for lesions having high p53 expression (P = 0.027). Expression of RAR-beta mRNA was detected in 40% of the patients at baseline and increased to 90% of the patients after isotretinoin therapy (P < 0. 001). Seventy-two percent of the patients having low p53 expression had no RAR-betamRNA expression at baseline, whereas 22% of the patients having high p53 expression had no RAR-beta expression, which suggests that patients having low p53 expression tended to lose RAR-beta mRNA expression in their tissues. Eighty-three percent of patients having low p53 expression had up-regulation of RAR-beta mRNA after isotretinoin therapy, compared with 22% of patients with high p53 expression (P = 0.003). We correlated baseline p53 protein expression with RAR-beta modulation and clinical responses to isotretinoin therapy. The patients with low p53 protein expression at baseline and up-regulation of RAR-beta after isotretinoin therapy achieved a 70% rate of major response. The patients with low p53 protein expression and either no change or down-regulation of RAR-beta or with high p53 expression and up-regulation of RAR-beta had a response rate of 50%. The patients with high p53 protein expression and either no change or down-regulation of RAR-beta had a response rate of only 14% to isotretinoin therapy. The basic mechanisms underlying the association between clinical responses and these two biomarkers need to be explored.

Adult↗
PubMed1996

Telomerase activity in head and neck squamous cell carcinoma and adjacent tissues.

The primary function of telomerase is the synthesis of telomeric DNA, which is the main pathway by which telomere length is maintained in the human germline and stem cells. Activation of telomerase is associated with elongation of telomeres and cell immortalization. Recently, telomerase activity has been detected in tissues from many human cancers but not in the majority of normal tissues, suggesting that telomere stabilization and telomerase activation may play a role in tumorigenesis. To explore telomerase activity in head and neck neoplastic and preneoplastic tissues, we studied 16 head and neck squamous cell carcinoma (HNSCC) cell lines and 60 specimens from 29 patients with HNSCC for telomerase activity. We precisely compared telomerase activity with histological features in adjacent tissue sections. We detected telomerase activity in 16 of 16 (100%) HNSCC cell lines, 26 of 29 (90%) invasive tumors, 7 of 7 (100%) dysplastic lesions, and 5 of 5 (100%) hyperplastic lesions, whereas 0 of 17 normal tissues or 2 hyperkeratotic lesions had detectable telomerase activity. Our data indicate that activation of telomerase activity is frequent in HNSCC and may occur early in the tumorigenesis process. The reactivation of telomerase may be a useful marker for cancer risk assessment in the oral cavity.

Aged↗