Biomedical subjects

R Lotan

Publications and source records attributed to R Lotan.

At least 19 recordsLinked to original sources

PubMed1992

Suppression of melanoma cell motility factor receptor expression by retinoic acid.

beta-All-trans-retinoic acid (RA) has been shown to inhibit the growth, enhance the differentiation, and suppress the transformed and metastatic properties of certain human and murine melanoma cells. This study examined the effect of RA on the level of a cell surface receptor (M(r) 78,000) (gp78) for an autocrine motility factor, which has been implicated in invasion and metastasis. Treatment of murine melanoma cell lines S91-C2, B16-F1, and K1735-P with RA (10 microM) for 5 days decreased the level of gp78 by 37, 72, and 92%, respectively, as revealed by immunoblotting with monoclonal antibodies raised against gp78. In contrast, RA had only a limited effect on gp78 levels in melanoma cell clones or variant cell lines that are resistant to the growth-inhibitory effects of RA (S91-C154, B16-F10, and K1735-Cl19). Further studies with K1735-P, the most sensitive cell line with respect to modulation of gp78, showed that the decrease in gp78 level required at least 1 microM RA and 4 to 5 days of treatment. The binding of anti-gp78 antibodies to the surface of intact RA-treated cells and to intracellular gp78 in permeabilized cells was also lower than in untreated cells. Furthermore, RA treatment decreased the induction of cell motility, on colloidal gold-coated glass coverslips, by anti-gp78 antibodies, which mimic the effect of autocrine motility factor. The RA-induced decrease in antibody-enhanced cell motility was similar to the time- and RA concentration-dependent decrease in the amount of gp78, suggesting that the two events are related. These results raise the possibility that the previously reported suppression by RA of tumor cell invasion and metastasis may be related, at least in part, to suppression of cell motility resulting from the decreased level of the autocrine motility factor receptor.

Animals↗

PubMed1992

Determination of biomarkers for intermediate end points in chemoprevention trials.

Renewed interest is being directed toward chemoprevention as a means of reducing cancer mortality. To overcome the inherent problems associated with using cancer development as a study end point, there has recently been a great surge of interest in defining the biomarkers associated with specific stages of the carcinogenic process as intermediate end points. We have detailed the evidence supporting the concept of field cancerization, a concept of general importance that is probably applicable to carcinogenesis and chemoprevention at many organ sites in humans, and presented results of tests of the potentially useful biomarkers proliferating cell nuclear antigen and blood group antigen. Because microassay techniques are more readily applicable to small biopsy samples, further expansion of these studies and exploration of panels of additional biomarkers are expected to generate exciting results in the field of chemoprevention.

ABO Blood-Group System↗

PubMed1992

Differential glycosylation and cell surface expression of lysosomal membrane glycoproteins in sublines of a human colon cancer exhibiting distinct metastatic potentials.

Changes in the glycosylation of asparagine-linked oligosaccharides have been shown in various tumor cells, including human colon cancer. Attempts were made to elucidate the difference in Asn-linked oligo-saccharides attached to lysosomal membrane glycoproteins isolated from sublines of human colon carcinoma exhibiting high and low metastatic potentials in nude mice. Lysosomal membrane glycoproteins (lamp) 1 and 2 were immunoprecipitated from the cells after labeling with radioactive sugars, and the glycopeptides prepared were fractionated by serial lectin affinity chromatography employing immobilized concanavalin A, Datura stramonium agglutinin, and tomato lectin. Comparison of Asn-linked oligosaccharides from the different colonic carcinoma cells revealed the following features. First, the highly metastatic carcinoma cells express more poly-N-acetyllactosaminyl side chains with branched galactose residues than cells with low metastatic potential. Second, sialylation is more significant in the highly metastatic carcinoma cells than in the poorly metastatic ones. Conversely, N-acetyllactosamine units are less fucosylated in the highly metastatic cells than in poorly metastatic cells. These structural changes were apparently caused by the increase in sialyltransferase and the decrease in alpha 1----3 fucosyltransferase in the highly metastatic cells. The results also suggest that highly metastatic carcinoma cells express more sialyl Lex structures at the termini of poly-N-acetyllactosaminyl side chains than poorly metastatic carcinoma cells. Further, highly metastatic cells were found to express more lamp-1 and lamp-2 on the cell surface. These results were found to be correlated to the increased expression of sialyl Lex structures with high affinity binding of anti-sialyl Lex antibody on highly metastatic cells. Increased expression of sialyl Lex in the poly-N-acetyllactosamines of the cell surface may contribute to the metastatic behavior of the cells, assuming that this structure can serve as a better ligand for selectins present on endothelial cells and platelets.

Antibodies↗

PubMed1992

Identification of a new squamous cell differentiation marker and its suppression by retinoids.

Rabbit tracheobronchial epithelial cells (RbTE) can undergo squamous cell differentiation under defined culture conditions and, therefore, have been used as a model to study the regulation of squamous cell differentiation markers. In the present study, we identified a 20-kDa protein, designated rSQ20, in the serum-free growth medium conditioned by RbTE cells undergoing squamous cell differentiation. The protein was also found in extracts of squamous differentiated cells. rSQ20 was labeled by cells incubated with [35S]methionine but not with [3H]glucosamine, suggesting that it is not a glycoprotein. Undifferentiated cells did not produce this protein. rSQ20 was detected in the conditioned medium of RbTE cells after they reached a confluent and growth-arrested state, and thereafter its level increased markedly and concurrently with an increase in type I (epidermal) transglutaminase, an established marker of squamous cell differentiation. rSQ20 found in concentrated conditioned medium of squamous differentiated RbTE cells was eluted from a gel filtration column as a protein of 20 kDa, similar to that found by gel electrophoresis under denaturing conditions, suggesting that it is not a multimeric protein. A protein with an apparent molecular weight of 16 kDa (rSQ16), probably the product of partial proteolysis of rSQ20, was often found in various amounts in the conditioned medium of differentiated RbTE cells. beta-All-trans retinoic acid and other vitamin A analogues (retinoids), which suppress squamous cell differentiation, inhibited the expression of rSQ20 in RbTE cells. RbTE cells immortalized by transfection with SV40 large T antigen as well as malignantly transformed derivatives obtained from the immortalized cells by further transfection with v-Ha-ras secreted SQ20 and SQ16 when grown to high cell densities although their squamous differentiation was impaired. An analogous protein with an apparent molecular weight of 16 kDa, designated hSQ16, was detected in the medium of differentiated normal human bronchial epithelial (NHBE) cells and normal human epidermal keratinocytes (NHEK). No such protein could be detected in the medium in which undifferentiated NHBE or NHEK cells were grown. These results suggest that rSQ20 and hSQ16 are new markers of squamous cell differentiation.

Animals↗

PubMed1992

Expression of a preprorelaxin-like gene during squamous differentiation of rabbit tracheobronchial epithelial cells and its suppression by retinoic acid.

Squamous cell differentiation in tracheobronchial epithelial cells is accompanied by many biochemical and molecular changes. One of the molecular changes in rabbit tracheal epithelial (RbTE) cells is the differential expression of a squamous cell-specific mRNA encoded by the complementary DNA SQ10. In this study, we sequenced SQ10 complementary DNA and showed that this gene encodes a preprorelaxin-like protein. The DNA sequence of the coding region of SQ10 has 68% identity with the human preprorelaxin mRNA, whereas the deduced amino acid sequence exhibits 46% identity with human preprorelaxin. An antiserum (pepIV-Ab) was raised against a synthetic 22-amino acid oligopeptide of the protein encoded by SQ10. Immunoblot analysis of cellular extracts of squamous-differentiated cells showed that this antiserum reacted with proteins of 22 and 20 kilodaltons, possibly constituting prepro- and proforms of this protein. These proteins were undetectable in undifferentiated RbTE cells. In agreement with these observations, PepIV-Ab specifically stained the cytosol of squamous-differentiated RbTE cells but failed to stain undifferentiated cells. PepIV-Ab recognized a 20 and 16 kilodalton polypeptide in medium conditioned by squamous-differentiated RbTE cells, indicating that the prorelaxin-like protein is secreted. The amino acid sequences of three peptides that were obtained after tryptic digestion of the secreted 16 kilodalton protein were identical to sequences encoded by SQ10. Retinoids which have been shown to inhibit squamous differentiation suppressed the induction of SQ10 protein as well as mRNA in a concentration-dependent manner. The concentration at which retinoic acid caused a 50% inhibition of SQ10 mRNA levels was approximately 5 nM.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1992

Suppression by retinoic acid of epidermal growth factor receptor autophosphorylation and glycosylation in cultured human head and neck squamous carcinoma cells.

The epidermal growth factor receptor (EGF-R) gene is overexpressed or amplified in various human squamous cell carcinomas, including those of the head and neck (HNSCC). Earlier we found that beta-all-trans-retinoic acid (RA) inhibited the growth and suppressed the aberrant squamous cell differentiation of several cultured HNSCC cell lines. Here we examined the effects of RA on the expression and function of EGF-R in two HNSCC cell lines, 1483 and 183, which exhibit distinct states of squamous cell differentiation, EGF-R mRNA levels, and responses to the growth inhibitory effects of RA. Treatment with RA (1 microM, 7 days) of the RA-sensitive 1483 cells decreased the level of EGF-R mRNA two- to four-fold and the binding of 125I-EGF to the cell surface by 30%-35%. In contrast, RA treatment of the 183 cells did not alter the EGF-R mRNA level or the binding of 125I-EGF. Other effects of RA on EGF-R structure and function were similar in both cell lines. RA did not alter the amount of immunoprecipitable [35S]methionine-labeled cellular EGF-R, 125I-cell surface labeled EGF-R, EGF-R internalization, or transforming growth factor alpha (TGF-alpha) mRNA. More important, RA treatment of both cell lines decreased EGF-R autophosphorylation activity detected in immune-complex-kinase assay by about three- and five-fold in the 1483 and 183 cells, respectively. Likewise, RA decreased the glycosylation of EGF-R in both cell lines. In the 1483 cells, RA suppressed the incorporation of either glucosamine or fucose by about 50%, whereas in the 183 cells RA suppressed the incorporation of fucose by about 80%. These results demonstrate that RA can modify the structure of the EGF-R by decreasing its glycosylation and suggest that these changes may suppress the autophosphorylation activity of the receptor kinase. The RA-induced changes in EGF-R do not correlate with the effect of RA on the growth of the cells but may be related to the suppression of squamous cell differentiation in the 1483 cells.

Carcinoma, Squamous Cell↗

PubMed1991

Lactose-binding lectin expression in human colorectal carcinomas. Relation to tumor progression.

Lactose-binding lectins having Mr values of approximately 14,000 (L-14.5) and approximately 35,000 Da have been found in a variety of vertebrate tissues, including normal intestine and colon, and in several types of tumors such as colon carcinomas. To determine the clinical relevance of such lectins in human colon cancer, specimens from 46 patients with colorectal carcinoma of identified Dukes' stages were selected and analyzed for the presence and amount of lactose-binding lectins by immunoblotting using a polyclonal, rabbit anti-lectin antibody followed by binding of 125I-labeled anti-rabbit IgG. The amount of a lectin having an Mr value of approximately 31,000 Da (L-31) varied among the specimens. The levels of L-31 lectin in colorectal cancer specimens from primary tumors of patients with distant metastases (Dukes' stage D) were significantly higher than were those from patients without detectable metastases (Dukes' stages B1 and B2). In contrast, among the various specimens the variation in the level of the L-14.5 lectin was smaller, and there was no correlation between the amount of this lectin and cancer stage. Immunohistochemical staining of thin sections of colorectal tumor specimens using antibodies specific for either L-31 or L-14.5 lectin revealed that the two were located at different places, the L-31 lectin primarily within the cytoplasm of carcinoma cells, and the L-14.5 lectin associated with secreted material. These results indicated that the relative amount of the L-31 lectin increases as the colorectal cancer progresses to a more malignant stage.

Colorectal Neoplasms↗

PubMed1991

Retinoic acid suppression of squamous differentiation in human head-and-neck squamous carcinoma cells.

Retinoids (vitamin A analogues) inhibit the squamous differentiation of normal and malignant epithelial cells. This study investigated the ability of the head-and-neck squamous-cell carcinoma (HNSCC) cell line 1483 to undergo squamous differentiation in the absence and presence of beta-all-trans retinoic acid (RA). The growth of these cells in culture is accompanied by an increase in keratinocyte transglutaminase, involucrin and keratin KI, 3 established markers of squamous cell differentiation. Higher levels of these differentiation markers were detected in cells cultured in delipidized serum (DLS), from which endogenous retinoids have been extracted, than in cells cultured in fetal bovine serum (FBS), which contains retinoids. Treatment with I microM RA decreased the levels of the various differentiation markers in cells cultured in either FBS or DLS as revealed by immunofluorescent labelling of permeabilized cells and by immunoblotting of cell extracts using specific monoclonal or polyclonal antibodies. The cells' ability to cross-link proteins to form envelopes under the plasma membrane was stimulated in the presence of calcium ionophore but inhibited by RA. These results indicate that the malignant 1,483 HNSCC cells recapitulate the main characteristics of normal squamous-cell differentiation in culture and that RA suppresses this differentiation as it does in normal keratinizing epithelial cells.

Calcium↗

PubMed1991

Increased content of an endogenous lactose-binding lectin in human colorectal carcinoma progressed to metastatic stages.

The quantity and localization of two lactose-binding lectins with molecular weights of 31,000 and 14,500 in human colorectal carcinoma tissue specimens obtained by surgical resection have been studied using specific polyclonal antibodies. Electrophoretic separation and blotting of detergent extracts of tumor tissues (48 specimens), followed by the binding of an antibody that recognizes both of these lectins, demonstrated that the contents of Mr 31,000 and 14,500 lectins vary from one specimen to another. The Mr 31,000 lectin content was higher in tumor specimens classified as Dukes' stage D than in those from other stages. A significant correlation was found between Mr 31,000 lectin levels and the levels of carcinoembryonic antigen in the patients' sera at the time of surgery. Immunohistochemical staining with antibodies specific for each lectin was performed with 20 colon carcinoma tissues and 5 colonic adenoma tissues. The results showed that the Mr 31,000 lectin localizes in the cytoplasm of colorectal carcinoma cells and normal epithelial cells, whereas antibody binding to Mr 14,500 lectin is observed in a limited number of carcinoma specimens and is mainly associated with luminal surfaces and secretory products. Adenoma cells were reactive with Mr 14,500 anti-lectin antibody at their luminal surfaces or cytoplasms, but they did not stain with Mr 31,000 anti-lectin antibody. These results suggest that a correlation exists among the level of the Mr 31,000 lectin, the serum level of carcinoembryonic antigen, and the stage of progression of colorectal carcinomas.

Analysis of Variance↗

PubMed1991

Developmental changes in ventricular action potential properties in guinea-pigs are modulated by age-related changes in the thyroid state.

Previous studies have demonstrated that in different cardiac preparations action potential duration (APD) increases with age. As in various species, thyroid hormone levels increase developmentally, and since hyperthyroidism shortens APD while hypothyroidism prolongs it, we hypothesized that developmental changes in APD result from age-related variations in the thyroid state. The hypothesis was tested by analysing ventricular action potentials and total T4 (TT4) levels in guinea-pigs in the age range of 0 days to 3 months (adult), and in hyperthyroid and hypothyroid newborns (0-5 days old). We found that APD50 increased exponentially with age with a time constant of 6.7 days, from 100.6 +/- 3.4 ms in newborns (0-5 days old) to 147.4 +/- 5.2 ms in adults (P less than 0.001). TT4 decreased exponentially with age with a time constant of 4.8 days, from 3.9 +/- 0.4 micrograms/dl in newborns to less than 1.0 microgram/dl in adults. In the age range studied, APD50 and TT4 were linearly correlated: Y = -12.13X + 142, r - 0.865. In contrast to the marked changes in APD, resting potential and action potential amplitude were age-independent, and Vmax only slightly increased with age. Alterations in the thyroid state in newborns affected ventricular action potentials as predicted by the hypothesis. In euthyroid (TT4 = 3.9 +/- 0.4 micrograms/dl), hypothyroid (TT4 = 1.6 +/- 0.4 micrograms/dl) and hyperthyroid (TT4 = 39.8 +/- 10.8 micrograms/dl) newborns, APD50 was: 100.6 +/- 3.4 ms, 117.7 +/- 4.2 ms and 63.7 +/- 7.4 ms, respectively (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMed1991

Nuclear receptors for retinoids: mediators of retinoid effects on normal and malignant cells.

Retinoids are a group of natural and synthetic vitamin A analogues that possess the unique ability to modulate the growth and differentiation of normal, premalignant and malignant epithelial and mesenchymal cells in vitro and in vivo. Naturally occurring retinoids act as physiologic regulators of embryonal development and maintain the proper differentiation of many epithelial tissues in the adult. Retinoids also act pharmacologically to restore regulation of differentiation and growth in certain premalignant and malignant cells in vitro and in vivo. Consequently, these compounds are being evaluated clinically for cancer prevention and therapy. There are strong indications that retinoids exert their diverse effects by regulating the expression of specific genes. The mechanism of this action is beginning to be unraveled following the discovery that nuclear receptors for retinoic acid are present in many cells and tissues. These receptors belong to the large family comprising steroid, thyroid hormone, and vitamin D3 receptors, which are DNA-binding proteins that function as trans-acting transcription modulating factors. We review here some of the properties of these receptors, their interactions with responsive elements in the promoter region of specific genes, and the recent demonstration of their involvement as mediators of the effects of retinoids on growth and differentiation.

Cell Differentiation↗

PubMed1991

Effects of hypo or hyper-thyroidism on growth hormone-binding protein.

OBJECTIVE: Growth hormone (GH) receptors are influenced by the thyroidal state of experimental animals. It has been suggested that GH-binding protein (BP) might serve as an indirect measure of the GH receptors. The present study was undertaken to investigate the growth hormone binding protein in patients with hypo or hyperthyroidism. PATIENTS: Patients included 42 adults with untreated hyperthyroidism (FT4 greater than 25 pmol/l; TSH less than 0.15 mU/l) and 29 adults and three children with untreated hypothyroidism (FT4 less than 10 pmol/l; TSH greater than 15 mU/l). MEASUREMENTS: Growth hormone binding protein was measured by a binding assay with dextran-coated charcoal separation. The specific binding of 125I-human GH (1 ng) obtained with 50 microliters serum was expressed as a percentage of the total c.p.m. RESULTS: Growth hormone binding protein specific binding in hypothyroid adults and children was significantly lower than in their respective controls in both adults and children (P less than 0.001). In patients with FT4 levels greater than 40 pmol/l, the mean (+/- SEM) growth hormone specific binding (12.89 +/- 0.59%) was higher than in controls (P less than 0.05). However, in 15 hyperthyroid patients with levels of FT4 of 25-40 pmol/l, the mean growth hormone binding protein specific binding (11.22 +/- 0.76%) was not different from that in normal human subjects. The affinity constants (Ka) obtained by Scatchard analysis for the hypothyroid and hyperthyroid patients' sera were not significantly different from that for normal human sera. Binding capacity for the hypothyroid sera was significantly lower (P less than 0.02), while that of hyperthyroid sera was increased (P less than 0.001). CONCLUSIONS: Growth hormone binding protein correlates positively with the thyroid status. It can be indirectly deduced that this reflects a similar relationship with the human GH receptor.

Adult↗

PubMed1991

Recent advances in cancer chemoprevention.

The CCPC 90 conference and workshop included presentations by basic scientists describing the key in vitro and in vivo model systems used to study epithelial carcinogenesis and its associated biochemical and molecular alterations. A major conference theme was the identification of markers identifying specific carcinogenic stages. Current work focuses on defining the biology of preneoplasia, the critical specific molecular events in multistep carcinogenesis, and the dynamic interplay between viral, behavioral, dietary, and genetic factors in human carcinogenesis. Studies of molecular epidemiology and genetic susceptibility are identifying new risk groups and contributing to preventive strategies. Another major theme of the conference was the concept of field carcinogenesis and the study of carcinogen-exposed tissue "at risk" for the development of cancer. A specific example discussed by several investigators was the issue of SPT development in head and neck and lung cancers. Novel studies of biologic markers for use in early detection and as intermediate end points were described. The latter application, if validated in human trials, may allow short-term screening of chemopreventive agents and determinations of optimal doses/schedules for phase III chemoprevention trials. These biomarker trials may serve as a bridge between preclinical work and full-scale randomized trials. The status of the major phase III clinical trials was presented. Major problems in chemoprevention trials include (1) selection of agents, doses, and schedules, (2) lack of pharmacologic and pharma quality control, (5) adherence (drop-out and drop-in), and (6) trial-specific feasibility/recruitment, issues.

Animals↗

PubMed1991

Role of thyroid state in age-dependent cardiac effects of ouabain in guinea pigs.

We tested the hypothesis that the decrease in the thyroid state, with age, contributes to the age-related increase in myocardial responsiveness to cardiac glycosides. Thyroid hormone levels (reflecting the thyroid state): total T4 (microgram/dl) and total T3 (ng/dl) in the 3 groups of guinea pigs were (mean +/- SEM): adults (3 months old): less than 1.0 and 22.6 +/- 1.1; euthyroid newborns (0-5 days old): 3.9 +/- 0.4 and 56.5 +/- 11.9; hypothyroid newborns, (0-5 days old): 1.5 +/- 0.3 and 26.5 +/- 9.8. In euthyroid newborns, T4 and T3 levels were significantly higher than in adults (p less than 0.01 for T4 and p less than 0.05 for T3) and in hypothyroid newborns (p less than 0.05). Isometric twitch was recorded from right ventricular papillary muscles by means of a force transducer. Ouabain 10(-6) M increased isometric twitch tension in adults (tension = 0.66 +/- 0.18 g/mm2) by 123.6 +/- 18.2%, in euthyroid newborns (tension = 0.19 +/- 0.04 g/mm2) by 83.6 +/- 14.5%, and in hypothyroid newborns (tension = 0.12 +/- 0.01 g/mm2) by 170.9 +/- 33.8% (p less than 0.01). Ouabain dose-response curve in the range of 10(-7) M-0.5 x 10(-5) M was significantly different (compared by two-way ANOVA) between euthyroid newborns and hypothyroid newborns (p less than 0.01), and between euthyroid newborns and adults (p less than 0.01). Toxic effects of ouabain reflected by the generation of aftercontractions were also age related and were augmented by hypothyroidism in newborns.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1991

Retinoids as modulators of tumor cells invasion and metastasis.

Retinoids, natural and synthetic analogues of vitamin A, have demonstrated promising results in pre-clinical and clinical trials of cancer prevention and therapy. This chapter reviews the ability of retinoids to suppress tumor growth and metastasis in vivo and to inhibit invasion in vitro. The mechanisms of these effects include suppression of growth and enhancement of differentiation of malignant cells, inhibition of their ability to produce degradative enzymes required for invasion, suppression of migration, inhibition of neovascularization, and augmentation of host anti-tumor immune responses.

Animals↗

PubMed1990

Modulation of lysosomal-associated membrane glycoproteins during retinoic acid-induced embryonal carcinoma cell differentiation.

Differentiation of the murine embryonal carcinoma (EC) cell lines F-9 and PC-13, induced by beta-all transretinoic acid (RA) resulted in an increased level of two lysosomal-associated membrane glycoproteins (LAMP-1 and LAMP-2). After differentiation, the levels of both LAMPs in the EC cells were comparable to those found in visceral and parietal endoderm cell lines (PSA-5E and PYS-2, respectively). RA treatment of the EC cells also resulted in an increase in the apparent Mr of both LAMPs apparently due to increased glycosylation because the deglycosylated LAMP-1 from undifferentiated and from differentiated cells had a similar electrophoretic migration. Indeed, the binding of 125I-labeled L-phytohemagglutinin (L-PHA) to glycoproteins with Mr or 90,000-130,000 increased after differentiation and about 24 times more 125I-labeled L-PHA bound to LAMP-1 isolated by immunoprecipitation from extracts of RA-treated F-9 cells than to LAMP-1 from undifferentiated cells. The increased level of the LAMPs was detected in F-9 cells treated with greater than 10(-7) M RA and required greater than 48 h of treatment as did the increased expression of the B1 chain of laminin, an established marker for differentiation in this system. LAMP-1- and L-PHA-reactive glycoproteins were localized by fluorescence techniques to intracellular vesicles, presumably lysosomes, and to the cell surface and both increased after RA treatment. LAMP-2 was barely detectable intracellularly in undifferentiated cells but could be detected clearly after differentiation. In contrast, no LAMP-2 could be detected on the cell surface either before or after differentiation of F-9 cells. The increased level and glycosylation of both LAMP-1 and LAMP-2 was observed also in cells treated with a synthetic chalcone carboxylic acid analog of RA and by combination of either retinoid with dibutyryl cyclic AMP. These results demonstrate that differentiation of EC cells is accompanied by changes in the synthesis and glycosylation of LAMP glycoproteins and that these changes are specific for the cell type that results after differentiation.

Animals↗

PubMed1990

Prevention of second primary tumors with isotretinoin in squamous-cell carcinoma of the head and neck.

BACKGROUND: Patients with head-and-neck cancers who are free of disease after local therapy remain at high risk for both recurrent and second primary tumors. Retinoids have proved efficacious in the treatment of premalignant oral lesions and are promising agents for the prevention of epithelial carcinogenesis. METHODS: We prospectively studied 103 patients who were disease-free after primary treatment for squamous-cell cancers of the larynx, pharynx, or oral cavity. After completion of surgery or radiotherapy (or both), these patients were randomly assigned to receive either isotretinoin (13-cis-retinoic acid) (50 to 100 mg per square meter of body-surface area per day) or placebo, to be taken daily for 12 months. RESULTS: There were no significant differences between the two groups in the number of local, regional, or distant recurrences of the primary cancers. However, the isotretinoin group had significantly fewer second primary tumors. After a median follow-up of 32 months, only 2 patients (4 percent) in the isotretinoin group had second primary tumors, as compared with 12 (24 percent) in the placebo group (P = 0.005). Multiple second primary tumors occurred in four patients, all of whom were in the placebo group. Of the 14 second cancers, 13 (93 percent) occurred in the head and neck, esophagus, or lung. CONCLUSIONS: Daily treatment with high doses of isotretinoin is effective in preventing second primary tumors in patients who have been treated for squamous-cell carcinoma of the head and neck, although it does not prevent recurrences of the original tumor.

Adult↗

PubMed1990

Increased fucosylation of high-molecular-weight glycoproteins accompanies retinoic-acid-induced differentiation of F-9 embryonal carcinoma cells.

Retinoic acid (RA) treatment of F-9 embryonal carcinoma cells resulted in cell flattening and increased production of laminin B1 chain, both indicating differentiation to endoderm-like cells. In addition, RA caused a time- and dose-dependent decrease in growth rate in monolayer culture and a dose-dependent decrease in the ability of the cells to form colonies in soft agarose. Differentiation was accompanied by an increase in the fucosylation of specific high-molecular-weight cellular and cell-surface glycoproteins. The fucosylation of glycoproteins of Mr 175,000 (gp175), 250,000 (gp250), and 400,000 (gp400) increased as early as 24 hr after the addition of 5 x 10(-6) M RA to the culture medium. These changes preceded both growth inhibition and the induction of laminin B1 expression, which were detected 48 to 72 hr after addition of RA. The increased fucosylation of these glycoproteins showed a distinct dose-response relationship. Both gp175 and gp250 showed the greatest increase in fucosylation at 10(-5) M, which was also the dose at which RA induced laminin maximally, while the fucosylation of gp400 was greatest at 10(-8) M RA and declined at higher concentrations. The overall synthesis of large fucosylated glycopeptides decreased in RA-treated cells, in spite of the increases in the fucosylation of specific cellular glycoproteins. RA-induced differentiation of F-9 cells was also accompanied by a time- and dose-dependent increase in fucosyltransferase activity. Although the functions of these glycoproteins are not currently known, the early increase in their fucosylation can be considered as a marker of differentiation in this system.

Animals↗