Biomedical subjects

R Lotan

Publications and source records attributed to R Lotan.

At least 37 records · Page 2Linked to original sources

PubMed2001

Inactivation of retinoic acid receptor beta by promoter CpG hypermethylation in gastric cancer.

Inactivation of nuclear retinoic acid receptor beta (RARbeta) expression is implicated in tumorigenesis. We hypothesized that loss of RARbeta in gastric cancer cells may occur as a result of multiple factors, including epigenetic modifications which alter RARbeta promoter chromatin structure. We examined hypermethylation of CpG islands present in the RARbeta promoter by methylation-specific PCR and the expression of RARbeta in gastric cancer cell lines and tissues. Three (MKN-28, -45 and -74) out of eight gastric cancer cell lines had a loss of RAR expression associated with promoter methylation. RARbeta expression was retrieved in these cell lines by treatment with 5-azacytidine or by the histone deacetylase inhibitor trichostatin A. Promoter hypermethylation was detected in 64% (7/11) of gastric carcinoma tissues with reduced expression of RARbeta, whereas it was detected in 22% (2/9) of tumors with retained RARbeta expression. To investigate the functions of exogenous RARbeta in gastric cancer cells, we transfected a retroviral RARbeta expression vector (LNSbeta) into MKN-28 cells that have hypermethylation of the RARbeta promoter. Overexpression of RAR in MKN-28 cells appeared to regulate the expression of DNA methyltransferase and DNA demethylase and the acetylation of hitone H4. These results suggest that the transcriptional inactivation of the RARbeta by promoter CpG hypermethylation is frequently associated with gastric carcinoma. Our data also suggests that DNA methylation plays a pivotal role in establishing and maintaining an inactive state of RARbeta by rendering the chromatin structure inaccessible to the transcription machinery.

Aged↗

PubMed2001

All-trans-retinoic acid enhances the effect of adenovirus-mediated wild-type p53 gene transfer in head and neck squamous cell carcinoma.

OBJECTIVES: Adenovirus-mediated p53 (AdCMVp53) gene therapy for cancer is currently undergoing phase III clinical trials. One problematic aspect of this therapy is that the current protocols result in low transduction of the therapeutic virus in vivo. To search new modalities that can enhance the effect of AdCMVp53 gene therapy, we focused on retinoids. METHODS: To study the effect of ATRA in combination with AdCMVp53 gene therapy, we pretreated head and neck squamous cell carcinoma (HNSCC) cells for 72 hours with a low-dose All-trans-retinoic acid (ATRA) (10-7 M-10-8 M) which will not affect the in vitro cell growth, and then infected the cells with low MOI (30MOI) AdCMVp53. In vitro cell proliferation assays, cell cycle assays were performed. Expression of p53 and p53-related gene products, BAX and p21, were examined. RESULTS: The combined treatment with ATRA and Ad-p53 suppressed cell growth and induced apoptosis significantly more than AdCMVp53 treatment alone (P <.05). p53 expression significantly increased more after the combined treatment than after either treatment alone, at both the transcription and protein levels. In addition, increased expression of p21 and BAX, which are downstream gene products of p53, was observed in the combination. ATRA also enhanced the expression of green fluorescent protein (GFP) transduced by an adenovirus-cytomegalovirus (CMV)-GFP vector suggesting ATRA enhances adenovirus-CMV-promoted vectors through transcription. CONCLUSIONS: Our results indicate that ATRA enhances AdCMVp53 expression through transcriptional mechanisms and can synergistically induce apoptosis in HNSCC cells. ATRA has a potential to enhance the effect of adenovirus-mediated p53 gene therapy for HNSCC.

Adenoviridae↗

PubMed2001

Overexpression of retinoic acid receptor beta induces growth arrest and apoptosis in oral cancer cell lines.

Expression of retinoic acid receptor beta (RARbeta) is reported to be absent or down-regulated in oral squamous cell carcinomas. Recently, we found that the growth-inhibitory effect of 9-cis-retinoic acid (9CRA) on oral squamous cell carcinoma may depend on the expression levels of endogenous RARbeta. In order to clarify the role of RARbeta in growth and differentiation, we transfected RARbeta expression vector into oral squamous carcinoma cell lines, HSC-4 and Ho-1-N-1. Both RARbeta-transfected cell lines displayed growth inhibition. Moreover, RARbeta-transfected clones underwent morphological changes, and RARbeta-transfected HSC-4 clones underwent apoptosis even in the absence of 9CRA treatment. In contrast, RARbeta-transfected Ho-1-N-1 clones exhibited cell cycle arrest without undergoing apoptosis initially; however, apoptosis was induced in these cells after 6 days of 9CRA treatment. RARalpha and RARgamma expression was reduced at both the protein and mRNA levels in RARbeta transfectants, whereas the expression of retinoid X receptor alpha (RXRalpha) was not altered. RARb transfectants exhibited alterations in the levels of cell cycle-associated proteins, histone acetyltransferase (HAT) and apoptosis-associated proteins. After 6 days of 9CRA treatment, RARbeta transfectants overexpressed Waf1 / Cip1 / Sdi1 / p21, Kip1 / p27, chk1, p300 / CBP, BAX, Bak, Apaf 1, caspase 3 and caspase 9. Conversely, E2F1, cdc25B and HDAC1 were down-regulated in these transfectants. In addition, histone H4 acetylation was induced in RARb transfectants. These findings suggest that histone acetylation mediated by histone acetyltransferase and p300 / CBP may play a role in the growth arrest and apoptosis induced by RARbeta transfection in oral squamous cell carcinoma.

Alitretinoin↗

PubMed2001

Autofluorescence microscopy of fresh cervical-tissue sections reveals alterations in tissue biochemistry with dysplasia.

Fluorescence spectroscopy offers an effective, noninvasive approach to the detection of precancers in multiple organ sites. Clinical studies have demonstrated that fluorescence spectroscopy can provide highly sensitive, specific and cost-effective diagnosis of cervical precancers. However, the underlying biochemical mechanisms responsible for differences in the fluorescence spectra of normal and dysplastic tissue are not fully understood. We designed a study to assess the differences in autofluorescence of normal and dysplastic cervical tissue. Transverse, fresh tissue sections were prepared from colposcopically normal and abnormal biopsies in a 34-patient study. Autofluorescence images were acquired at 380 and 460 nm excitation. Results showed statistically significant increases in epithelial fluorescence intensity (arbitrary units) at 380 nm excitation in dysplastic tissue (106 +/- 39) relative to normal tissue (85 +/- 30). The fluorophore responsible for this increase is possibly reduced nicotinamide adenine dinucleotide. Stromal fluorescence intensities in the dysplastic samples decreased at both 380 nm (102 +/- 34 [dysplasia] vs 151 +/- 44 [normal]) and 460 nm excitation (93 +/- 35 [dysplasia] vs 137 +/- 49 [normal]), wavelengths at which collagen is excited. Decreased redox ratio (17-40% reduction) in dysplastic tissue sections, indicative of increased metabolic activity, was observed in one-third of the paired samples. These results provide valuable insight into the biological basis of the differences in fluorescence of normal and precancerous cervical tissue.

Adult↗

PubMed2001

Identification of effective retinoids for inhibiting growth and inducing apoptosis in bladder cancer cells.

PURPOSE: Retinoids modulate the growth and differentiation of normal and malignant epithelial cells in vitro and in vivo, and inhibit bladder carcinogenesis in animal models. Retinoid analogs have been used in several clinical chemoprevention trials of superficial bladder cancer recurrence. There is a clear need to identify new effective retinoids and develop novel approaches for the chemoprevention and treatment of superficial bladder cancer. We investigated the effects of various retinoids on growth inhibition and apoptosis induction in bladder cancer cell lines. MATERIALS AND METHODS: Ten grades 1 to 3 bladder cancer cell lines and the 4 retinoids all-trans-retinoic acid, 9-cis retinoic acid, 4-(N-hydroxyphenyl) retinamide (4HPR) and LGD1069 were used in the study. We compared the ability of these retinoids to inhibit growth, induce apoptosis, affect the expression of nuclear retinoid receptors and modulate apoptosis related genes. RESULTS: Most bladder cancer cell lines did not express retinoic acid receptor beta and were resistant to the effect of all-trans-retinoic acid and 9-cis retinoic acid on growth inhibition and apoptosis induction, even at a concentration of 10(-5) M. The 2 cell lines that expressed retinoic acid receptor beta were constitutively sensitive to the growth inhibitory effect of all-trans-retinoic acid. 4HPR inhibited cell growth by about 90% in all but 1 cell line and induced apoptosis at a concentration of 10(-5) M after a 24-hour treatment. LGD1069 had virtually no effect. All-trans-retinoic acid and 4HPR induced retinoic acid receptor beta expression in 1 bladder cancer cell line. However, the effect of 4HPR on cell growth and apoptosis were not related to the constitutive expression of retinoic acid receptor beta. 4HPR decreased bcl-2 expression in 6 of 8 bladder cancer cell lines but did not change p53 gene expression. CONCLUSIONS: The results demonstrate that 4HPR is the most potent growth inhibitor and apoptosis inducer of the retinoids tested. Lack of retinoic acid receptor beta expression may be responsible for cell resistance to all-trans-retinoic acid but not to the other retinoids.

Apoptosis↗

PubMed2001

Cyclooxygenase-2 overexpression is a marker of poor prognosis in stage I non-small cell lung cancer.

Cyclooxygenase-2 (COX-2), the enzyme that converts arachidonic acid to prostaglandins, is overexpressed in a variety of different tumors, including those of the colon, pancreas, lung, and head and neck. We used in situ hybridization with a digoxgenin-labeled COX-2 antisense riboprobe to assess the presence of strong or intermediate versus weak or absent COX-2 expression in specimens from 160 patients with stage I non-small cell lung cancer (NSCLC). Of these, 3 specimens had strong expression, 69 had intermediate expression of COX-2, 24 had weak expression, and 64 had no detectable COX-2. The strength of COX-2 expression was associated with a worse overall survival rate (P = 0.001) and a worse disease-free survival rate (P = 0.022). The median survival times for the strong, intermediate or weak, and null COX-2 expressors were 1.04, 5.50, and 8.54 years, respectively. Interestingly, all three specimens with strong COX-2 expression came from patients who died within 18 months. Retinoic acid receptor beta (RAR-beta) is a nuclear retinoid receptor whose expression is frequently lost in aerodigestive tract carcinogenesis. We previously demonstrated that expression of RAR-beta in stage I NSCLC indicates a poor prognosis. Retinoids have been shown to prevent induction of COX-2 by mitogens and tumor promoters. Expression of COX-2 correlated with RAR-beta expression (P = 0.053), but not with k-ras mutational status, vascular endothelial growth factor, basic fibroblast growth factor, interleukin 8 levels, or other markers of angiogenesis, invasion, and metastases. Thus, like RAR-beta positivity, COX-2 overexpression appears to portend a shorter survival among patients with early stage non-small cell lung cancer. Future studies of RAR-beta and COX-2 regulation in NSCLC should further the development of prevention and therapy interventions with retinoids and/or COX-2 antagonists in this patient population.

Biomarkers, Tumor↗

PubMed2001

Effects of novel phenylretinamides on cell growth and apoptosis in bladder cancer.

Superficial bladder cancer is a major target for chemoprevention. Retinoids are important modulators of epithelial differentiation and proliferation and are effective in the treatment and prevention of several epithelial cancers. One class of compounds, the retinamides, is structurally similar to other retinoids but have the added feature of being potent apoptosis inducers. Among these, fenretinide (N-[4-hydroxyphenyl]retinamide), or 4HPR, has promise for bladder cancer chemoprevention and is currently under Phase III study in this setting. In addition to 4HPR, there are several new structurally related phenylretinamides bearing hydroxyl, carboxyl, or methoxyl residues on carbons 2, 3, and 4 of the terminal phenylamine ring [designated N-(2-hydroxyphenyl)retinamide, N-(3-hydroxyphenyl)retin amide, N-(2-carboxyphenyl)retin- amide, N-(3-carboxyphenyl)retin amide, N-(4-carboxy- phenyl)retinamide, and N-(4-methoxyphenyl)retinamide, respectively]. The objective of this study was to compare the growth inhibitory and apoptotic effects of these phenylretinamides with 4HPR in human bladder transitional cell cancer-derived cell lines of varying histological grade (RT4, grade 1; UM-UC9 and UM-UC10, grade 3; and UM-UC14, grade 4) by cell counting, cell cycle fluorescence-activated cell sorter analysis and a dual stain apoptosis assay. All of the seven phenylretinamides reduced cell number, altered the cell cycle distribution, and induced apoptosis when administered at a concentration of 10 microM, which is within the pharmacologically achievable range. Although the relative potencies of the phenylretinamides varied depending on the cell line, N-(3-hydroxy phenyl)retin- amide was the most active with significantly greater growth inhibition than 4HPR in all of the four cell lines. These in vitro findings warrant further study of these novel phenylretinamides, which may have potential as preventive or therapeutic agents in transitional cell cancer.

Anticarcinogenic Agents↗

PubMed2001

Identification of retinamides that are more potent than N-(4-hydroxyphenyl)retinamide in inhibiting growth and inducing apoptosis of human head and neck and lung cancer cells.

The synthetic retinoid, N-(4-hydroxyphenyl)retinamide (4HPR), which is currently being evaluated in clinical trials for cancer prevention and therapy, inhibits the growth of a variety of malignant cells through induction of apoptosis. However, in the majority of tumor cells, this inhibitory effect of 4HPR requires high concentrations (>1 microM), which exceed the peak plasma level measured in humans. In the present study, we compared and contrasted the effects of several synthetic retinamides on the growth of human lung and head and neck cancer cells in vitro. We found that some retinamides, especially N-(2-carboxyphenyl)retinamide (2CPR), exhibited better growth inhibitory effects than 4HPR in some of the cell lines. 2CPR exerted potent growth inhibitory effects in 5 of 10 head and neck cancer cell lines and in 1 of 10 lung cancer cell lines (IC(50), <0.8 microM). 2CPR (1 microM) induced apoptosis ranging from 10 to 60% in four of five cell lines, whereas 4HPR was ineffective at the same concentration. Unlike 4HPR, 2CPR (up to 10 microM) failed to induce reactive oxygen species production in these sensitive cell lines but could activate caspases 3 and 7 as well as increase poly(ADP-ribose)polymerase cleavage. Interestingly, the effect of 2CPR on cell growth could be suppressed by the specific retinoic acid receptor pan antagonist AGN193109. Our results suggest that 2CPR acts via retinoic acid receptors and may be a good candidate for prevention and treatment of some head and neck and lung cancers.

Anticarcinogenic Agents↗

PubMed2001

A randomized clinical trial of 4-hydroxyphenylretinamide for high-grade squamous intraepithelial lesions of the cervix.

PURPOSE: Previous trials of topical trans-retinoic acid treatment of cervical intraepithelial neoplasia (CIN) grades 2 and 3 led to a statistically significant regression of CIN 2, but not CIN 3. We tested N-(4-hydroxyphenyl)retinamide (4-HPR), a promising oral retinoid that has been shown to induce apoptosis through nonretinoic receptor acid-mediated pathways, for its toxicity and efficacy against CIN 2/3. EXPERIMENTAL DESIGN: In a blinded randomized trial, 4-HPR at 200 mg/day for 6 months (with a 3-day/month drug holiday) was compared with placebo in patients with biopsy-proven CIN-2/3 [high-grade squamous intraepithelial lesions (HGSILs)]. Patients were treated with placebo or 4-HPR for 6 months, biopsied, and then followed for an additional 6 months. At the 12-month end point, they underwent either loop excision if a histological lesion was present or a biopsy from the original area of the lesion if no lesion was present. RESULTS: An interim analysis of blinded data showed a significantly worse prognosis at 12 months for one group. When the code was broken because of the poorer outcomes, we discovered that the 4-HPR treatment arm was performing more poorly than was the placebo at 6 and 12 months (25 versus 44% response rates at 6 months; 14 versus 50% at 12 months). Toxicity was not significant in either arm. CONCLUSIONS: 4-HPR at 200 mg/day with a 3-day/month drug holiday is not active compared with placebo in the treatment of HGSIL. Because 4-HPR is active in the laboratory, the lack of effect in our trial may indicate that higher doses are needed in patients to achieve comparable results.

Adult↗

PubMed2000

15-Lipoxygenase-1 mediates nonsteroidal anti-inflammatory drug-induced apoptosis independently of cyclooxygenase-2 in colon cancer cells.

We previously found (I. Shureiqi et al., Carcinogenesis (Lond.), 20: 1985-1995, 1999; I. Shureiqi et al, J. Natl. Cancer Inst., 92: 1136-1142, 2000) that (a) 15-lipoxygenase-1 (15-LOX-1) protein and its product 13-S-hydroxyoctadecadienoic acid (13-S-HODE) are decreased; and (b) nonsteroidal anti-inflammatory drug (NSAID)-induced 15-LOX-1 expression is critical to NSAID-induced apoptosis in colorectal cancer cells expressing cyclooxygenase-2 (COX-2). We used the NSAIDs sulindac sulfone (COX-2-independent) and NS-398 (a COX-2 inhibitor) to assess NSAID upregulation of 15-LOX-1 in relation to COX-2 inhibition during NSAID-induced apoptosis in the DLD-1 (COX-2-negative) colon cancer cell line. We found that: (a) NSAIDs up-regulated 15-LOX-1, which preceded apoptosis; and (b) 15-LOX-1 inhibition blocked NSAID-induced apoptosis, which was restored by 13-S-HODE but not by its parent, linoleic acid. NSAIDs can induce apoptosis in colon cancer cells via up-regulation of 15-LOX-1 in the absence of COX-2.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2000

Augmentation of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis by the synthetic retinoid 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437) through up-regulation of TRAIL receptors in human lung cancer cells.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis via the death receptors DR4 and DR5 in different transformed cells in vitro and exhibits potent antitumor activity in vivo with minor side effects. The synthetic retinoid CD437 is a potent inducer of apoptosis in cancer cells through increased levels of death receptors. We demonstrate that treatment of human lung cancer cells with a combination of suboptimal concentrations of CD437 and TRAIL enhanced induction of apoptosis in tumor cell lines with wild-type p53 but not in normal lung epithelial cells. CD437 up-regulated DR4 and DR5 expression. The CD437 and TRAIL combination enhanced activation of caspase-3, caspase-7, caspase-8, and caspase-9 and the subsequent cleavage of poly(ADP-ribose) polymerase and DNA fragmentation factor 45. Caspase inhibitors blocked the induction of apoptosis by this combination. Moreover, this combination induced Bid cleavage and increased cytochrome c release from mitochondria. These results suggest that the mechanism of enhanced apoptosis by this combination involves p53-dependent increase of death receptors by CD437, activation of these receptors by TRAIL, enhanced Bid cleavage, release of cytochrome c, and activation of caspase-3, caspase-7, caspase-8, and caspase-9. These findings suggest a novel strategy for the prevention and treatment of human lung cancer with the CD437 and TRAIL combination.

Antineoplastic Agents↗

PubMed2000

Induction of Fas expression and augmentation of Fas/Fas ligand-mediated apoptosis by the synthetic retinoid CD437 in human lung cancer cells.

The synthetic retinoid 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437) induces apoptosis in a variety of cancer cells. Recently, we demonstrated that CD437 induces apoptosis in human non-small cell lung cancer (NSCLC) cells expressing wild-type p53 by increasing the level of the death domain-containing cell surface receptor Killer/DR5. In the present study, we investigated whether CD437 induced the expression of Fas (CD95/APO-1), a cell surface protein belonging to the tumor necrosis factor receptor superfamily, which induces apoptosis upon interaction with Fas ligand (FasL) or agonistic antibodies. We found that CD437 increased the level of Fas mRNA in a time- and concentration-dependent manner in NSCLC H460 cells. The increased Fas expression was also identified at the protein level. CD437 induced Fas expression in three NSCLC cell lines with wild-type p53 but not in six NSCLC cell lines containing mutant p53. Moreover, enhanced degradation of wild-type p53 protein in NSCLC cells expressing human papillomavirus-16 E6 oncoprotein blocked CD437-induced Fas expression. These results implicate the involvement of wild-type p53 in CD437-induced Fas expression in human NSCLC cells. CD437 did not change Fas mRNA stability, and actinomycin D abolished CD437-induced expression of Fas mRNA, suggesting that CD437 induces Fas expression at the transcriptional level. The combination of CD437 and FasL or CD437 and agonistic anti-Fas antibody caused synergistic induction of apoptosis. Furthermore, CD437 augmented Fas/ FasL-induced apoptosis in cell lines with wild-type p53 but not in cell lines having mutant p53, indicating that a p53-dependent mechanism is also involved in this effect. Taken together, these results demonstrate that increased Fas expression may play an important role in CD437-induced, p53-dependent apoptosis in human NSCLC cells.

Antineoplastic Agents↗

PubMed2000

Implication of multiple mechanisms in apoptosis induced by the synthetic retinoid CD437 in human prostate carcinoma cells.

The synthetic retinoid 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437) induces apoptosis in several types of cancer cell. CD437 inhibited the growth of both androgen-dependent and -independent human prostate carcinoma (HPC) cells in a concentration-dependent manner by rapid induction of apoptosis. CD437 was more effective in killing androgen-independent HPC cells such as DU145 and PC-3 than the androgen-dependent LNCaP cells. The caspase inhibitors Z-VAD-FMK and Z-DEVD-FMK blocked apoptosis induced by CD437 in DU145 and LNCaP cells, in which increased caspase-3 activity and PARP cleavage were observed, but not in PC-3 cells, in which CD437 did not induce caspase-3 activation and PARP cleavage. Thus, CD437 can induce either caspase-dependent or caspase-independent apoptosis in HPC cells. CD437 increased the expression of c-Myc, c-Jun, c-Fos, and death receptors DR4, DR5 and Fas. CD437's potency in apoptosis induction in the different cell lines was correlated with its effects on the expression of oncogenes and death receptors, thus implicating these genes in CD437-induced apoptosis in HPC cells. However, the importance and contribution of each of these genes in different HPC cell lines may vary. Because CD437 induced the expression of DR4, DR5 and Fas, we examined the effects of combining CD437 and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and Fas ligand, respectively, in HPC cells. We found synergistic induction of apoptosis, highlighting the importance of the modulation of these death receptors in CD437-induced apoptosis in HPC cells. This result also suggests a potential strategy of using CD437 with TRAIL for treatment of HPC. Oncogene (2000) 19, 4513 - 4522.

Androgens↗

PubMed2000

15-LOX-1: a novel molecular target of nonsteroidal anti-inflammatory drug-induced apoptosis in colorectal cancer cells.

BACKGROUND: Nonsteroidal anti-inflammatory drugs (NSAIDs) appear to act via induction of apoptosis-programmed cell death-as potential colorectal cancer chemopreventive agents. NSAIDs can alter the production of different metabolites of polyunsaturated fatty acids (linoleic and arachidonic acids) through effects on lipoxygenases (LOXs) and cyclooxygenases. 15-LOX-1 is the main enzyme for metabolizing colonic linoleic acid to 13-S-hydroxyoctadecadienoic acid (13-S-HODE), which induces apoptosis. In human colorectal cancers, the expression of this enzyme is reduced. NSAIDs can increase 15-LOX enzymatic activity in normal leukocytes, but their effects on 15-LOX in neoplastic cells have been unknown. We tested the hypothesis that NSAIDs induce apoptosis in colorectal cancer cells by increasing the protein expression and enzymatic activity of 15-LOX-1. METHODS: We assessed 15-LOX-1 protein expression and enzymatic activity, 13-S-HODE levels, and 15-LOX-1 inhibition in association with cellular growth inhibition and apoptosis induced by NSAIDs (primarily sulindac and NS-398) in two colorectal cancer cell lines (RKO and HT-29). All P values are two-sided. RESULTS: Sulindac and NS-398 progressively increased 15-LOX-1 protein expression in RKO cells (at 24, 48, and 72 hours) in association with subsequent growth inhibition and apoptosis. Increased 13-S-HODE levels and the formation of 15-hydroxyeicosatetraenoic acid on incubation of the cells with the substrate arachidonic acid confirmed the enzymatic activity of 15-LOX-1. Inhibition of 15-LOX-1 in RKO cells by treatment with caffeic acid blocked NS-398-induced 13-S-HODE production, cellular growth inhibition, and apoptosis (P =. 007, P<.0001, and P<.0001, respectively); growth inhibition and apoptosis were restored by adding exogenous 13-S-HODE (P<.0001 for each) but not its parent compound, linoleic acid (P = 1.0 for each). Similar results occurred with other NSAIDs and in HT-29 cells. CONCLUSIONS: These data identify 15-LOX-1 as a novel molecular target of NSAIDs for inducing apoptosis in colorectal carcinogenesis.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2000

Evidence that retinoic acid receptor beta induction by retinoids is important for tumor cell growth inhibition.

Retinoic acid receptor beta (RARbeta) is thought to be involved in suppressing cell growth and tumorigenicity. Many premalignant and malignant cells exhibit a reduced RARbeta expression. However, in some of these cells (e.g. H157 human squamous cell carcinoma cells), RARbeta can be induced by retinoids (e.g. all-trans-retinoic acid, ATRA) because its promoter contains a retinoic acid response element. To examine the hypothesis that RARbeta induction is important for inhibition of cell proliferation by retinoids, we blocked ATRA-induced RARbeta expression in H157 cells using a retroviral vector harboring multiple copies of antisense RARbeta2 sequences. Antisense RARbeta-transfected cells showed not only decreased expression of ATRA-induced RARbeta protein but also reduced ATRA-induced RARE binding activity and transactivation. Importantly, all antisense RARbeta transfectants of H157 cells were less responsive than vector-transfected cells to the growth inhibitory effects of the retinoids ATRA and Ch55 in vitro. These results demonstrate that RARbeta induction may play an important role in mediating growth inhibitory effects of retinoids in cancer cells.

Base Sequence↗

PubMed2000

Differential regulation of constitutive and retinoic acid-induced galectin-1 gene transcription in murine embryonal carcinoma and myoblastic cells.

Galectin-1 (gal-1), a galactoside-binding lectin, is found in many vertebrate tissues and its expression is regulated during development. We had found that gal-1 expression is increased in F9 murine embryonal carcinoma cells concurrently with induction of differentiation by all-trans retinoic acid (RA). In contrast, gal-1 expression was constitutively high in murine myoblastic C2C12 cells. Therefore, we used these two cell types as models to begin to understand the mechanisms underlying constitutive and RA-induced gal-1 expression. We transfected transiently into F9 cells a series of reporter constructs containing different deletions of the 5' upstream region of the gal-1 gene promoter placed upstream of the chloramphenicol acetyltransferase reporter cDNA and evaluated the activation of transcription by RA treatment. The results indicate that the induction of gal-1 by RA is regulated at least partially at the level of transcription. A strong RA responsiveness region was found within the sequence from -1578 to -1448 upstream of the transcription start site (+1). In contrast, the high constitutive gal-1 expression in C2C12 cells appeared to be mediated by a sequence within the promoter region from -62 to +1, which contains an Sp1 consensus sequence. A gel electrophoretic mobility shift assay indicated that the transcription factor SP1 bound to the gal-1 Sp1 site and mutagenesis of this Sp1 site abolished both the binding of nuclear proteins to the mutated Sp1 site and the high constitutive expression of the gal-1 gene. The results demonstrate that gal-1 expression is cell type-specific and suggest that different factors regulate constitutive and RA-induced gal-1 expression.

Animals↗

PubMed2000

Effect of 9-cis-retinoic acid on oral squamous cell carcinoma cell lines.

Retinoic acid (RA) has been shown to be effective in suppressing premalignant lesions and preventing second primary malignancies in patients cured of squamous cell carcinoma of the head and neck. However, the precise mechanisms of these effects are still uncertain. In the present study, we examined the effect of 9-cis-RA on the growth of six oral cancer cell lines (HSC-2, HSC-3, HSC-4, Ca9-22, Ho-1-N-1 and Ho-1-u-1). In addition, the relationship among growth and differentiation of tumor cells, RA responsiveness and the expression of nuclear retinoic acid receptors were also investigated. Among the six cell lines examined, five (HSC-2, HSC-3, HSC-4, Ca9-22 and Ho-1-u-1) displayed growth inhibition after treatment with 1x10(-6) M 9-cis-RA, while Ho-1-N-1 cells were resistant to 9-cis-RA. The expression level of RARbeta in 9-cis-RA resistant Ho-1-N-1 cells was very low in comparison with the sensitive cell lines. On the other hand, all of the six the cell lines expressed RARalpha, RARgamma, and RXRalpha at various levels. 9-cis-RA induced accumulation of cell population in G1 phase in HSC-3 cells on the 6th day of the treatment, followed by a marked reduction in the levels of hyperphosphorylated pRB, whereas p53 level was not altered. Interestingly, 9-cis-RA induced transiently the expression of p21(Waf1/Cip1), p27(Kip1), p300, CBP, BAX, Bak and bcl-2 proteins, respectively. This effect was associated with reduction of cyclin D1, cdk4 and CDK-activating kinase (cyclin H and cdk7) protein in HSC-3 cells. These results suggest that the growth inhibitory effect of 9-cis-RA on oral squamous cell carcinoma may depend on the expression levels of RARs, especially RARbeta proteins and RXRalpha proteins, and that 9-cis-RA may provide a powerful therapeutic agent for head and neck cancers.

Alitretinoin↗

PubMed2000

Effects of sodium butyrate on growth, differentiation, and apoptosis in head and neck squamous carcinoma cell lines.

BACKGROUND: Biologic agents that reverse early changes in the aerodigestive tract mucosa have potential treatment applications for patients with field cancerization of the upper aerodigestive tract. Sodium butyrate (BA) is a normal dietary constituent that induces differentiation and inhibits growth in several malignant cell types in vitro, but its effect on head and neck squamous cell carcinoma (HNSCC) has not been evaluated. METHODS: Using five HNSCC cell lines, the effects of BA on cell proliferation and apoptosis were examined by colorimetric and fluorescence-labeling methods, and the expression of differentiation markers and apoptosis-related proteins were analyzed using Western and Northern blotting, flow cytometry, and cell cycle analysis. RESULTS: BA-induced growth inhibition and apoptosis in HNSCC cells at millimolar concentrations. Apoptosis induction did not depend on the p53 status of the cell lines or on expression of members of the Bcl-2/Bax family. CONCLUSIONS: These results demonstrate that butyrate has activity against HNSCC in vitro and may have clinical applications for management of HNSCC patients.

Apoptosis↗