Effects of beta-all-trans retinoic acid on growth, proliferation, and cell death in a multicellular tumor spheroid model for squamous carcinomas

Flow cytometry after bromodeoxyuridine labeling to measure S and G2+M phase durations plus doubling times in vitro and in vivo

This protocol describes methods for calculating the proliferative parameters of cell populations. The basis of the technique is to label cells, either in vitro or in vivo, with halogenated thymidine analogs, such as bromodeoxyuridine (BrdU). Bivariate DNA-BrdU flow cytometry is used to analyze the BrdU-labeled and unlabeled cells. The enumeration of specific cohorts of cells that either have or have not divided in the interval between labeling and cell/tissue sampling permits the calculation of the potential doubling time (T(pot)) of the population, plus the durations of DNA synthesis (T(S)) and the G2+M phase (T(G2+M)) of the cell cycle. The method provides information that is not otherwise available, namely inhibition of DNA synthesis and the separate evaluation of cell-cycle effects in BrdU-labeled and unlabeled subpopulations. Ethanol-fixed samples take 1 d to prepare and stain, and reliable parameter estimates might be obtained from measurements made at a single time point after labeling.

Mitochondrial permeability transition and release of cytochrome c induced by retinoic acids

Retinoic acids, structurally related to vitamin A, inhibit the in vitro proliferation of different types of normal and neoplastic cells. The effects of all-trans, 9-cis, and 13-cis retinoic acids were tested on mitochondria isolated from rat liver. All the compounds were able to induce the membrane permeability transition observed as swelling and decrease in membrane potential, but 13-cis retinoic acid appeared to be the most effective. The latter was also shown to stimulate the release of cytochrome c from mitochondria, suggesting a potential target of retinoids in the induction of cell apoptosis. Interestingly, EGTA and cyclosporin A, which strongly inhibit the permeability transition induced by 13-cis retinoic acid, were without effect on the release of cytochrome c from the mitochondrial intermembrane space.

RARalpha antagonist Ro 41-5253 inhibits proliferation and induces apoptosis in breast-cancer cell lines

Ro 41-5253 is a RARalpha-selective antagonist that binds RARalpha but does not induce transcriptional activation and does not influence RAR/RXR heterodimerization and DNA binding. This retinoid inhibits proliferation and induces apoptosis in MCF-7 and ZR-75.1 estrogen-receptor-positive breast-carcinoma cells in a dose-dependent way. The anti-proliferative effect is more evident in ZR-75.1 cells than in MCF-7 cells and is probably mediated by anti-AP1 activity, a mechanism known to be implied in the action of several retinoids. In the induction of apoptosis also ZR-75.1 cells are more sensitive to treatment with Ro 41-5253 than MCF-7 cells. In ZR-75.1 cells an apoptotic/hypodiploid DNA peak is already evident after 2 days of incubation, whereas in MCF-7 cells it appears only after 4 days. The highest percentage of apoptotic cells, for both cell lines, is reached after 6 days of treatment. The apoptosis pathway is p53-independent and bcl-2 downregulation seems to be correlated with an increase in TGF-beta1 protein. The MDA-MB-231 estrogen-receptor-negative cell line is poorly responsive to Ro 41-5253 treatment, both in terms of proliferation inhibition and apoptosis induction. Ro 41-5253 has proliferation-inhibiting and apoptosis-inducing properties that are not mediated by transcriptional activation from retinoic-acid response elements. This retinoid antagonist seems to be a compound that exerts an anti-tumor activity but does not induce the toxic side effects of retinoids and might, therefore, be considered as a candidate for cancer therapy.

Fenretinide-induced apoptosis of human head and neck squamous carcinoma cell lines

BACKGROUND

Squamous cell carcinoma of the head and neck (HNSCC) has a high incidence of recurrence and associated second primary malignancy. The retinoid 13-cis-retinoic acid has been shown to be effective as both a chemopreventive and chemotherapeutic agent for HNSCC, but often with treatment-limiting toxicity. The synthetic retinoid fenretinide (N-(4-hydroxyphenyl)retinamide) (HPR) has significant antiproliferative activity against a number of animal and human malignancies and has been used in clinical trials as a chemopreventive agent in patients with breast and prostate cancer and oral leukoplakia. HPR has been shown to have a toxicity profile lower than that for other retinoids used in clinical trials.

PURPOSE

The aim of this study was to investigate the effect of HPR on the growth of HNSCC cell lines in vitro.

METHODS

Four HNSCC cell lines (JHU-011-SCC, JHU-020-SCC, JHU-022-SCC, and FaDu) were treated with a range of concentrations of HPR for various times. After HPR exposure, cell viability was determined by tetrazolium dye (MTT) colorimetric assay, comparing cell survival with that of untreated control cells. HPR-induced apoptosis was determined by flow-cytometric deoxyribonucleic acid cell-cycle analysis, ultrastructural analysis with electron microscopy, and deoxyribonucleic acid fragmentation detected by gel electrophoresis.

RESULTS

HPR caused significant growth inhibition in three of the four HNSCC cell lines in a dose- and time-dependent fashion. In two cell lines (JHU-011-SCC, JHU-020-SCC) a significant antiproliferative effect was achieved between 1 and 2.5 micromol/L HPR after 72 hours of treatment. By deoxyribonucleic acid cell-cycle analysis, electron microscopy, and gel electrophoresis, HPR was shown to induce apoptosis in the JHU-011-SCC and JHU-020-SCC cell lines, but not in the FaDu cell line, which was insensitive to the growth inhibitory effect of HPR.

CONCLUSIONS

This study has demonstrated that HPR reduces cell viability in HNSCC cells in vitro at clinically relevant doses, with the growth inhibition occurring through the induction of apoptosis.

Effects of all-trans-retinoic acid and 13-cis-retinoic acid on breast-cancer cell lines: growth inhibition and apoptosis induction

Interest has been increasingly focused on all-trans-retinoic acid (tRA) and 13-cis-retinoic acid (13cRA) in cancer chemoprevention and treatment. We have examined the in vitro effects of these 2 retinoic acids (RAs) on human breast-cancer cell lines MCF-7 and ZR-75.1 (both estrogen-receptor-positive, ER+) and MDA-MB-231 (estrogen-receptor-negative, ER-), in terms of inhibition of proliferation and induction of apoptosis. Both retinoic acids exerted an evident dose-dependent growth inhibition, although in the ER- cell line the anti-proliferative effect was obtained only with the highest concentration used; the anti-proliferative activity of tRA was more evident than 13cRA on all 3 tested cell lines. tRA and 13cRA induced apoptosis in MCF-7 and MDA-MB-231 cell lines, but not in ZR-75.1. The apoptotic phenomenon was clearly time-dependent, and in our experience it was not related to the arrest in a specific phase of cell cycle. After treatment with RAs the levels of bcl-2 were reduced in MCF-7, while in ZR-75.1 and in MDA-MB-231 no treatment-related modifications were observed. An analysis of estrogen-receptor status, used as a marker of differentiation, demonstrated that after treatment with RAs the levels of estrogen receptor (ER) decreased in ZR-75.1 only. Our study indicates that the anti-proliferative effects of RAs are sustained by induction of apoptosis in MCF-7 and MDA-MB-231 cells, while in ZR-75.1 cells an induction of differentiation without apoptosis was the prevalent mechanism of growth inhibition. Our results encourage further studies on in vivo effects of these retinoids in breast cancer.

Effects of extracellular calcium on cholesteatoma migration and adhesion in vitro

Cholesteatoma matrix and tympanic epithelia share the unique property of en mass migratory locomotion in vitro. Although this migratory behavior is not well understood, it is thought to be a major contributor to the pathogenesis and pathophysiology of cholesteatoma disease. We have surmised that en mass migration depends on tight calcium-dependent intercellular and substrate cellular adhesions. The purpose of this investigation was to determine the effects of a diminished extracellular calcium level on cholesteatoma migration and adhesion. Cholesteatoma matrixes obtained intraoperatively from patients undergoing mastoidectomies for chronic ear disease were cut into small fragments and grown in culture. When cultured specimens were exposed to low-calcium medium (0.14 mmol/L calcium), a greater than 10-fold reduction in the rate of migration was observed when compared with control values (1.8 mmol/L calcium). This reduction of migration returned to normal within 48 hours after extracellular calcium was replenished. Substrate cellular adhesion was also significantly reduced when cholesteatoma cells were grown in low-calcium medium. These observations were further supported by histomorphologic findings. Our findings suggest that calcium-dependent intercellular and substrate cellular adhesions are essential for cholesteatoma migration and adhesion. These studies further our understanding of the pathophysiology of cholesteatoma disease and may provide clues on how to better treat patients with this disease.

Enhancement of glycosylation of cellular glycoconjugates in the squamous carcinoma cell line MDA886Ln by beta-all-trans retinoic acid

Retinoids have been shown to inhibit the growth and modulate the glycosylation of head and neck squamous cell carcinoma (HNSCC) cells including the MDA886Ln cells. To examine the effects of beta-all-trans retinoic acid (RA) on glycoconjugates in HNSCC MDA886Ln cells, the cells were grown in the absence or presence of 1 microM RA and then labeled with tritiated monosaccharides, extracted and analysed by polyacrylamide gel electrophoresis and fluorography. RA increased markedly the incorporation of [3H]-glucosamine, [3H]-galactose, and [3H]-mannose into numerous cellular glycoconjugates, however, the incorportion of [3H]-fucose and [3H]-leucine was almost unaffected by RA. RA increased the incorporation of glucosamine and galactose but not mannose into high molecular weight (HMW) glycoconjugates of about 220 and 500-600 kDa. To analyse the steady state level of glycoconjugates by lectin blotting, extracts of unlabeled cells were separated by gel electrophoresis and the gels were probed with 125I-labeled wheat germ agglutinin (WGA) and Maackia amurensis (MA) agglutinin. Both lectins were found to bind to numerous glycoconjugates including the HMW glycoconjugates, whereas 125I-peanut agglutinin bound only to the HMW glycoconjugates RA treatment increased the binding of all three lectins to the HMW glycoconjugates. These findings demonstrate that RA enhanced the incorporation of specific monosaccharides into a variety of glycoconjugates and in particular into HMW mucin-like glycoconjugates. This effect of RA may be the result of induction of a more normal differentiation state of the HNSCC cells.

Influence of benzylisothiocyanate and 13-cis-retinoic acid on micronucleus formation induced by benzo[a]pyrene

The purpose of this study was to investigate the influence of benzylisothiocyanate (BIT) and 13-cis-retinoic acid (RA) upon the genotoxic potential of benzo[a]pyrene (BaP) to induce micronucleus formation in the bone marrow of mice. Eighty-two male mice were divided into 10 groups. One group served as a negative control (olive oil intubation). Four groups received an oral intubation of various concentrations of BIT (15 to 120 mg/kg) and i.p. injections of BaP (185 mg/kg). Another four groups were treated identically, but received RA (20 to 150 mg/kg) in place of BIT. Finally, one group received only i.p. injection of BaP (185 mg/kg). The results showed that both BIT and RA significantly reduced the frequency of micronucleus formation in the bone marrow of the BaP treated animals. BIT was found to be effective at all the tested concentrations. RA was effective only at three of the four tested concentrations (40, 75 and 150 mg/kg). These findings indicate that both BIT and RA may reduce the genotoxic effects of benzo[a]pyrene in the mice under the test conditions utilized.

Inhibition of Cholesteatoma Migration in vitro with all-Trans Retinoic Acid

Retinoids have recently become of interest to clinicians because of their ability to inhibit migration and proliferation of premalignant squamous cells while enhancing growth and proliferation of normal cells. An in vitro investigation was undertaken to determine whether retinoic acid exhibits similar inhibitory effects on cholesteatoma cells. Cholesteatoma specimens were obtained intraoperatively from 10 patients undergoing mastoidectomy or revision mastoidectomy for chronic ear disease. Cholesteatoma explant growth and en mass migration were observed daily, and topographic maps were constructed at various time intervals to quantify rate and direction of expiant migration in the presence or absence of all- trans retinoic acid. Before all- trans retinoic acid administration, explants migrated very rapidly (1 to 2 mm/day). A maximum threefold inhibition of migratory rate occurred, with explants exposed to 0.1 μmol/L retinoic acid when compared with controls. A sixfold maximum inhibition was observed at higher retinoic acid concentrations (5 μmol/L). On removal of all- trans retinoic acid, twofold and fourfold increases in migratory rates were observed. The direction of explant migration varied significantly for long periods of time and appeared not to be affected by retinoic acid. This investigation suggests that all- trans retinoic acid has an inhibitory effect on cholesteatoma cell migration. Retinoids may have a role in controlling cholesteatoma disease in the future.

Cell, tissue and organ culture as in vitro models to study the biology of squamous cell carcinomas of the head and neck

In vitro models are currently being used to study head and neck squamous cell carcinoma (HNSCC). Several hundred HNSCC cell lines have been established by various investigators and used to study a broad spectrum of questions related to head and neck cancer. The head and neck model with respect to multistage carcinogenesis is now complete. Several techniques exist for the culture of normal epithelial cells from the upper aerodigestive tract (UADT). The biology of these UADT cells (oral cavity, oropharynx, hypopharynx and larynx) is being studied. Successful culture of premalignant lesions (dysplastic mucosa, leukoplakia, erythroplakia) has resulted in establishment of a limited number of premalignant cell lines and cell cultures. HPV infection of normal oral epithelial cells for immortalization (approximately premalignant cells) coupled with transformation with carcinogens (malignant cells) has established an experimental model for progression. Two in vivo models for oral carcinogenesis, the 7,12 dimethylbenz(a)anthracene-induced hamster cheek pouch model and the 4-nitroquinoline-N-oxide rat oral model, have been established in culture. Thus, multistage carcinogenesis models have been established from both human tissues and animal models and include cultures of normal, premalignant and malignant cells. Culture techniques for growing dissociated primary tumor cells for short term experimental analysis are being used. The culture of normal or tumor tissue as organ/explant cultures allows for the maintenance of normal cell-cell and cell-matrix interaction, but limits experimentation since these cultures cannot be propagated. Several three dimensional model systems are being used to obtain this histological complexity but allow for experimentation. The ability to culture normal, premalignant and malignant cells coupled with the use of a variety of culture techniques, should allow for the continued growth and experimentation in head and neck cancer research.

Modulation of growth and proliferation in squamous cell carcinoma by retinoic acid: a rationale for combination therapy with chemotherapeutic agents

We have previously shown that beta-all trans retinoic acid (RA) inhibits macrocellular growth of a multicellular tumor spheroid model for squamous carcinoma, as measured by spheroid size, but allows for continuing DNA synthesis and cell cycle progression, the two being reconciled by a cell death effect. DNA synthesis in the presence of growth inhibition suggested a rationale for examining combination chemotherapy with RA-inhibited cells. To this aim, we have extended this observation to a series of 8 squamous carcinoma cell lines. Cells were treated with 1 microM RA for 7 days and cell growth parameters monitored. Although growth inhibition ranged from 0% (A431) to approx. 80% (MDA 886Ln), [3H]-thymidine incorporation (cpm/microgram protein) and percent S-phase (by flow cytometry) in 7-day RA-treated cells was equal or higher than in their control vehicle-treated cells in 7/8 SCC cell lines. Thus RA-induced growth inhibition is not just cytostasis. Combination therapy was examined with MDA 886Ln, MDA 686Ln, 1483 and A431 cells pre-treated for 7 days with 1 microM RA followed by cisplatin or 5-fluorouracil treatment. An increased effectiveness for the combination was shown using 5-day tetrazolium dye (MTT) growth assays when cells were growth-inhibited by RA. Computerized analysis of data using median-effect and isobologram techniques indicated that the interaction of RA with these chemotherapeutic agents was synergistic. With squamous carcinoma, RA treatment inhibits growth while allowing for continuing DNA synthesis, and these RA-treated, growth-inhibited cells exhibit increased sensitivity to chemotherapeutic agents.

Interaction of liposome-associated all-trans-retinoic acid with squamous carcinoma cells

Because of their antiproliferative and differentiation-inducing properties, retinoids have been used clinically as therapeutic and chemopreventive agents against squamous-cell carcinomas (SCC). As is the case for many therapeutic agents, however, the administration of retinoids is associated with toxic effects. Because encapsulation of certain drugs in lipid vesicles (liposomes) has been shown to result in reduced toxic effects, we studied the in vitro interaction of liposome-encapsulated all-trans-retinoic acid (L-ATRA) with a SCC line (MDA 886Ln) and its multicellular tumor spheroid (MTS) model. Various L-ATRA formulations were tested for incorporation of retinoic acid, toxic effects against human red blood cells, uptake and retention by tumor cells, and antiproliferative effects against SCC. Of the different formulations tested, L-ATRA containing diphosphatidyl palmitoylcholine (DPPC) and stearylamine (SA; 9:1, w/w) showed optimal drug incorporation, high stability, and minimal toxicity toward red blood cells and was highly efficacious in delivering ATRA and, thus, in inhibiting the growth of MDA 886Ln and its MTS model. DPPC: SA L-ATRA inhibited the expression of the enzyme keratinocyte transglutaminase in epidermal cells as effectively as did the free drug. These results suggest that liposomes can serve as an effective carrier system for the delivery of retinoids to SCC.

Antiproliferative effects of free and liposome-encapsulated retinoic acid in a squamous carcinoma model: monolayer cells and multicellular tumor spheroids

Antiproliferative effects of free retinoic acid (RA) and liposome-encapsulated RA (RAlp) were compared in a squamous carcinoma system using both monolayer cells and multicellular tumor spheroids (MTS), an in-vivo-like model with three-dimensional histological structure. Initial studies examined the effect of lipid composition on the efficiency of RA encapsulation and on the subsequent toxicity of RAlp to red blood cells. In 5-day growth assays for monolayer cells, RA and RAlp (1 microM-0.1 nM) produced similar growth inhibition. In 6-day growth assays for MTS, RAlp was shown to have increased effectiveness. Liposomal uptake by the squamous carcinoma cells was examined by culturing monolayers and MTS with fluorescence-tagged liposomes and examining them under fluorescence microscopy between days 1 and 6. Phagocytosed liposomes were present, but their low levels suggested that other mechanisms of drug delivery such as adsorption, fusion or direct lipid transfer probably occurred for RAlp. Histological examination of MTS showed that RA and RAlp produced similar alterations. In this squamous carcinoma system, liposomes are effective in delivering retinoic acid and in producing biological effects in monolayer cells and within the three-dimensional structure of MTS.