Reversible squamous cell characteristics induced by vitamin A deficiency in a small cell lung cancer cell line

A cultured small cell lung cancer cell line (Lu-134-B-S) established from a xenotransplanted tumor in a nude mouse, which had originated from a primary focus of small cell lung cancer, showed morphological changes when the medium was changed from RPMI 1640 supplemented with 10% fetal calf serum to RPMI 1640 supplemented with 10% delipidized fetal calf serum. That is, it consisted of "classic" small cells in the former medium, but after eight passages in the latter medium many cells became squamous cells, possessing abundant eosinophilic cytoplasm and intercellular bridges. Immunohistochemically, they reacted to antikeratin and antiinvolucrin antibodies. Electron microscopically, well developed desmosomes and associated tonofibrils were noted, and electrophoretically, the amount of medium (Mr 57,000 and 59,000) and large-sized (Mr 67,000) keratins were found to increase with the change of the medium. These changes reversed to the original small cell morphology within 4 weeks after addition of vitamin A (retinoic acid) to the medium. These findings suggested that deficiency of vitamin A caused the change of the cell from small to squamous cell and vice versa.     

Cell specific differences in O6-methylguanine-DNA methyltransferase activity and removal of O6-methylguanine in rat pulmonary cells

Previous studies have demonstrated that cell specificity existsfor the alkylation of DNA from lung cells following treatmentof rats with the tobacco specific carcinogen 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone(NNK). The concentration of the promutagenic adduct O⁶-methylguanine(O⁶MG) was found to be greatest in Clara cells followed by macrophages,type II cells and alveolar small cells. The purpose of thisstudy was to measure the activity of the repair protein O⁶-methylguanine-DNAmethyltransferase (O⁶MGMT) and to determine whether differencesexist for the removal of O⁶MG among pulmonary cell types. Constitutiveactivity of O⁶MGMT was 2-fold greater in macrophages and typeII cells than alveolar small cells and Clara cells. Treatmentfor 4 days with NNK (10 mg/kg/day) had no effect on O⁶MGMT activityin macrophages, but decreased activity in alveolar small cellsand type II cells by 57 and 84%, respectively. O⁶MGMT activitywas reduced to below limits of detection in Clara cells followingtreatment with NNK. The effect of NNK on O⁶MGMT activity wasconsistent with rates of removal of O⁶MG in macrophages andClara cells. The loss of O⁶MG from DNA of macrophages followedfirst order kinetics (t = 48 h) while very little loss of thisadduct was observed in Clara cells over an 8 day period followingcessation of carcinogen treatment. Even though O⁶MGMT activitywas reduced in alveolar small cells and type II cells, 90% ofthe O⁶MG bound to DNA in these cell types was removed within8 days after treatment was discontinued. The loss of O⁶MG frompulmonary cells appears to result largely from the removal ofthis adduct by O⁶MGMT since rates of cell turnover were verylow (0.5–1.5%/day) in the lung and were not affected bytreatment with NNK. This study indicates that the activity ofO⁶MGMT and the rate of resynthesis of this repair enzyme differconsiderably among pulmonary cells following the methylationof DNA. The high concentration of O⁶MG in Clara cells and thelow rate of repair of this promutagenic adduct may be criticalfactors in the potent pulmonary carcinogenicity induced by thetobacco specific carcinogen NNK.     

Effect of Human Epidermal Growth Factor on Cell Growth and Its Receptor in Human Gastric Carcinoma Cell Lines

The effect of human epidermal growth factor (hEGF) on the growthof various histological types of six human gastric carcinomacell lines was examined. The cell lines had relatively highaffinity EGF receptors (dissociation constant Kd = 10^–9to 10^–10 M). One gastric cancer cell line, MKN-74 (welldifferentiated adenocarcinoma) showed no response to hEGF, incell growth, DNA synthesis or ¹²⁵I-hEGF cell binding. Therewere no apparent correlations between histological type andcell growth, DNA synthesis or number of EGF receptors in thesecells. The number of EGF receptors and the Kd value of the gastriccarcinoma cell lines varied with their internal and externalenvironments. hEGF concentrations corresponding to maximum stimulationin DNA synthesis varied between cell lines. The results suggestsome gastric carcinoma cells to have EGF receptors and theirgrowth seemingly to be stimulated by EGF in vitro. There are,however, no obvious correlations between the effect of hEGFon the growth of human gastric carcinoma cell lines or theirhistological type.     

The usefulness of human tumor cell lines in the study of chemosensitivity. A study of malignant melanomas

The chemosensitivity of human melanoma cells has been studied before and after continuous in vitro culture. Altogether, nine cell lines were studied, two derived from patients' biopsies, and seven from xenografts in athymic mice. The sensitivity to the agents DTIC (Dacarbazine), CCNU (Lomustine), procarbazine, vinblastine, abrin and ricin was assayed. Furthermore, in five cases the chemosensitivity of the cell lines was compared to that of tumors obtained by injecting the cell lines into athymic mice. In all cases the sensitivity was measured in an in vitro soft agar assay. Upon cultivation in vitro, two of the cell lines, one derived from a patient's metastasis and one from a xenograft in athymic mice, showed marked increases in sensitivity to some of the drugs, whereas sensitivity to other drugs showed little or no change. For the other cell lines small, but definite increases or decreases in chemosensitivity were observed. Permanent cultures showed the same chemosensitivity as early subcultures. The tumors formed by injecting the cell lines into athymic mice showed moderate changes in chemosensitivity, as compared to the cell lines in vitro. The data indicate that considerable changes in chemosensitivity may occur when cells are brought from in vivo to in vitro conditions and vice versa and that such changes may be highly specific. Therefore, although cell lines may be useful in some respects, they should be used with caution in attempts to evaluate quantitatively the sensitivity of human tumors to cancerostatic drugs.     

Conversion of platelet-derived growth factor-dependent cells to growth factor-independent cells during chemical carcinogenesis in vitro

The growth responses of hamster dermal fibroblasts (HDF cells)to platelet-derived growth factor (PDGF) during chemical carcinogenesisin vitro were investigated. Normal HDF cells grew in mediumwith whole blood serum (WBS), but not in medium with plasma-derivedserum (PDS). However, they grew in PDS medium when PDGF wasadded. In contrast to control cultures which finally stoppedproliferating, 7 out of 8 cell strains treated with 4-nitroquinoline-1-oxide(4NQO) or N-methyl-N'-nitro-nitrosoguanidine changed to celllines. Later, 5 of these 7 cell lines became able to grow inPDS medium in association with ability to grow in soft agar.When clonal cell lines were isolated at early stages of carcinogenesiswhile parental cell lines were still PDGF-dependent, most ofthem gradually became PDGF-independent as well. Dialysed celllysates of transformed HDF cells showed strong growth stimulatingactivity on normal HDF cells in PDS medium. Thus, this conversionof PDGF-dependent cells to PDGF-independent cells was correlatedwith the appearance of a growth factor(s) produced specificallyby transformed HDF cells.     

The Variation of Cell Type Distribution in Lung Cancer: A Study of 10,910 Cases at a Medical Center in Taiwan between 1970 and 1993

The rise in the incidence of lung cancer has been associatedwith shifts in histologic distribution. A study was conductedto investigate changes in the cell type distribution in lungcancer in relation to age, sex, and smoking history, based ona retrospective analysis of 10,910 proven cases of lung cancerat the Veterans General Hospital-Taipei during the period from1970 to 1993. The diagnosis in each case was substantiated byhistologic samples from the original tumor site in the lung.Detailed smoking histories were obtaind by personal interviewat the time of the first admission. Adenocarcinoma (38.3%) wasthe most common type of lung cancer, followed by squamous cellcarcinoma (37.1%) and small cell carcinoma (12.2%). Over thestudy period, the incidence of squamous cell carcinoma decreasedfrom 46.4% to 36.2% in men (P < 0.005), adenocarcinoma increasedfrom 30% to 36% in men (P = 0.001) and 50.7% to 64.8% in women(P = 0.008), and small cell carcinoma increased from 7% to 14%in men but showed no significant change in women. Adenocarcinomaexhibited a marked increase in both men and women, and surpassedsquamous cell carcinoma as the most frequent type of lung cancer.Lung cancer among younger men, and among non-smoking older menand women, was more often adenocarcinoma. Small cell carcinomashowed a significant increase among males, differing from thetrend for squamous cell carcinoma in men, though both are stronglyassociated with smoking. These findings suggest factors otherthen cigarette smoking could influence the development and distributionof lung cancer.     

Development and Elongation of Neurite–like Outgrowth on Small Cell Lung Cancer Cell Lines

One (Lu–134A) of nine human small cell lung cancer cell lines which grow as floating cell aggregates changed its morphology dramatically when cells were cultured on a coverslip coated with poly–ethylenimine or extracellular matrix of human lung adenocarcinoma cell line PC–9 cells. The Lu–134A cells adhered to the substrate and developed elongated cytoplasmic processes which gradually grew into long neuronal–like processes. These processes developed to a length of more than 10 times the cell body length after 20 days of culture. Addition of dibutyryl cyclic adenosine 3', 5 –monophosplmte to the cells on these substrates remarkably promoted the development and elongation of the processes, which grew into a netlike arrangement. The characteristics of these elongated neuronal–like processes were studied using immunocytochemical and electron microscopical methods. The processes reacted intensely with monoclonal antibodies against β –tubulin and microtubule–associated protein–2. The swelling portions of the distal tips of these processes reacted strongly with polyclonal antibody against synaptophysin. Neurosecretory granules and bundles of microtuhules were observed within processes. These findings suggested that this human small cell lung cancer cell line (Lu–134A) differentiated into neuronal cells, and indicated that attachment of cells to a substrate is the key to the development of long neurite–like outgrowths.     

Use of HT-29, a cultured human colon cancer cell line, to study the effect of fermented milks on colon cancer cell growth and differentiation

Epidemiological and in vivo and in vitro experimental studieshave suggested that fermented milks may interfere with the emergenceand/or the development of colon cancer. The results, however,remain inconclusive. This prompted us to develop a new approachbased on the use of HT-29, a cultured human colon cancer cellline, to study at the cellular level the effect of fermentedmilks on colon cancer cell growth and differentiation characteristics.Undifferentiated HT-29 cells have been grown in the continuouspresence of milks fermented by one of the following bacterialpopulations: Lactobacillus helveticus, Bifido-bacterium, L.acidophilusor a mix of Streptococcus thermo-philus and Lbulgaricus. PenicilinG was added to the cell culture medium, resulting in a completeblockade of bacterial growth without significant effect on bacterialviability. One out of the four bacteria species studied, namelyL.acidophilus, was without effect on both cell growth and differentiation.The three other bacterial strains induced a significant, althoughvariable, reduction in the growth rate of HT-29 cells, whichresulted in a 10–50% decrease in the cell number at steady-state(i.e. at cell confluency). The most efficient strains in loweringthe HT-29 growth rate were L.helveticus and Bifidobacterium.Concomitantly, the specific activities of dipeptidyl peptidaseIV (DPP IV), a sensitive and specific marker of HT-29 cell differentiation,and that of three other brush border enzymes (sucrase, aminopeptidaseN and alkaline phosphatase) were significantly increased, thussuggesting that these cells may have entered a differentiationprocess. Altogether, these results indicate that the use ofcultured colon cancer cells may be a useful tool to furtherstudy the effect of fermented milks on colon cancer and thatbacterial strains may exert a different and specific effecton cancer cell growth and differentiation when used in fermentedmilk products.     

Chemosensitivity Test for Human Small Cell Lung Cancer Cell Lines In Vitro

The in vitro response to seven chemotherapeutic drugs of threeestablished human small cell lung cancer (SCLC) cell lines (NCIH69, H 128, N231) was tested by a double soft agar clonogenicassay. Colony formation by the three cell lines was universallyreduced more than 50% by continuous exposure to peak plasmaconcentrations of all the drugs. However by exposure to one-tenthof the peak plasma concentrations, the colony growth of H69was reduced to 25.6% and 37.7% by etoposide and teniposide,respectively, and that of N231 was reduced to 46.7%, 39.0%,27.5% by carboplatin, etoposide and tenipo side, respectively.On the other hand colony formation by the three cell lines wasnot suppressed more than 50% by one-hour exposure to any ofthe drugs tested at one-tenth of the peak plasma concentrations.By one-hour exposure to drugs at the peak plasma concentrations,colony formation by H69, H128 and N23 I was reduced more than50% by cisplatin, etoposide, teniposide and nimustin, by adriamycin,tenoposide and ACNU, and by adriamycin, etoposide, teniposideand nimustin, respectively. It was concluded that these threecell lines have similar sensitivity to seven drugs commonlyused against small cell lung cancer.     

The Establishment of a Cell Strain (PC-1) from a Human Lung Cancer

A human lung cancer cell strain (PC-1) was established in vitroand maintained in continuous growth for more than two and ahalf years. The material used for explanation was a metastaticlymph node of a case of poorly differentiated epidermoid carcinomaconsisting predominantly of small anaplastic cells of a polygonalcell type. The cultured cell grew attached to a glass surfacein layered heaps and were epidermoid ultrastructurally. Chromosomal analysis of the cells at the 7th passage culturerevealed that all mitotic cells with the chromosome number of46 or more exhibited the karyotypic abnormality of Dp⁺. Tumorsdeveloped after hetcrotransplantation of the cultured cellsinto the hamster's cheek pouch showed features of epidermoidcarcinoma with keratinization indicating neoplastic cell originof the strain. Doubling time of the total cell population was72 hours. Histogenesis of the small cell anaplastic carcinoma was discussed.     

Expression of C-terminal src Kinase in Human Colorectal Cancer Cell Lines

C-terminal src kinase (CSK) is a cytoplasmic protein which decreasesactivities of the Src family protein-tyrosine kinases. We produceda polyclonal antibody specific for CSK and analyzed the expressionof CSK by immunoblotting in two human colorectal normal celllines and eighteen cancer cell lines. CSK was detected in boththe two normal and all the eighteen cancer cell lines. The expressionof CSK obtained from human colorectal cancer cell lines wasgreater than that from human colorectal normal cell lines inmost cases. The elevated expression of CSK in human colorectalcancer cell lines appeared to correspond to the elevated p60^c-src(c-Src) and p62^c-yes (c-Yes) protein-tyrosine kinase activitiesfound in other studies. Thus, CSK may not have an anti-oncogenicrole to play through the negative regulation of Src family kinasesin colorectal carcinogenesis     

Type I collagen inhibits differentiation and promotes a stem cell-like phenotype in human colorectal carcinoma cells

Background:

Human colorectal cancer is caused by mutations and is thought to be maintained by a population of cancer stem cells. Further phenotypic changes occurring at the invasive edge suggest that colon cancer cells are also regulated by their microenvironment. Type I collagen, a promoter of the malignant phenotype in pancreatic carcinoma cells, is highly expressed at the invasive front of human colorectal cancer.

Methods:

This study investigates the role of type I collagen in specifying the colorectal cancer cell phenotype. The effect of type I collagen on morphology, localisation of cell–cell adhesion proteins, differentiation and stem cell-like characteristics was examined in a panel of human colorectal carcinoma cell lines.

Results:

Human colorectal carcinoma cells grown on type I collagen in serum-free medium show an epithelial–mesenchymal-like transition (EMT-like), assuming a more flattened less cohesive morphology. Type I collagen downregulates E-cadherin and β-catenin at cell–cell junctions. Furthermore, type I collagen inhibits differentiation, increases clonogenicity and promotes expression of stem cell markers CD133 and Bmi1. Type I collagen effects were partially abrogated by a function-blocking antibody to α2 integrin.

Conclusion:

Together, these results indicate that type I collagen promotes expression of a stem cell-like phenotype in human colorectal cancer cells likely through α2β1 integrin.     

High dietary retinoic acid prevents malignant conversion of skin papillomas induced by a two-stage carcinogenesis protocol in female SENCAR mice

We have previously reported that high dietary retinoic acid(RA; 30 µg/g diet) inhibits carcinoma formation in a twostageskin carcinogenesis protocol, using 7,12-dimethylbenz[a]anthracene(DMBA) as the initiator and 12-O-tetradecanoyl phorbol-13-acetate(TPA) as the tumorpromoter in female SENCAR mice. We next askedwhether switching the diets from high to control levels of RAand vice versa would influence carcinoma formation. Mice at3 weeks of age were initiated with DMBA (20     

Morphological transformation of immortalized hamster dermal fibroblasts following treatment with simple alkylating carcinogens

We have examined the mechanism of transformation of a line ofimmortalized hamster dermal fibroblasts (4DH2 cells) followingtreatment with the simple alkylating agents, N-methyl-N-nitrosourea(MNU), N-ethyl-N-nitrosourea (ENU) and dimethyl sulphate (DMS).Treatment of 4DH2 cells with the potent point mutagens MNU andENU gave rise to a spectrum of foci of different sizes, includingprogressively growing large foci and compact small foci. Incontrast, treatment with the weak point mutagen DMS producedmostly large foci. The ability of cell lines derived from morphologicallytransformed foci to grow in soft agar in general reflects theiroriginal size. Thus most cell lines derived from large focigrew in soft agar while most lines derived from small foci didnot. Transfection of cellular DNAs into the parent 4DH2 cellline and into NIH3T3 mouse fibroblasts has revealed the presenceof dominantly acting transforming genes in the chemically transformedcell lines. Thus DNA from five of six cell lines derived byculturing large foci and from one of three cell lines derivedby culturing small foci induced efficient morphological transformationof the recipient cells. Southern analyses of DNA from primaryand secondary transfectants showed that several of the transforminggenes transferred in these experiments were not closely relatedto H-ras, K-ras or N-ras     

Overexpression of c-K-ras, c-N-ras and transforming growth factor {beta} co-segregate with tumorigenicity in morphologically transformed C3H 10T1/2 cell lines

Morphologic transformation and tumorigenicity are separate cellularphenotypes in transformed 1OT1/2 cells. We have investigatedthe levels of expression of genes for c-myc, c-H-ras, c-K-ras,c-N-ras, TGFß and Rb in 42 morphologically transformed1OT1/2 cell lines, in an attempt to define the molecular mechanisntsgoverning morphologic transformation and tumorigenicity in the1OT1/2 cell system. The 101 1/2 cell lines investigated generallyoverexpressed mRNAs for c-myc, c-H-ras, and TGFß relativeto the levels expressed by wild- type 10T1 cells (levels ofexpression >1.5-fold that of wild- type 1011/2 cells). Incontrast, only half of these cell lines overexpressed mRNAsfor c-N-ras and/or Rb relative to wild- type 1OT1/2 cells, andonly 25%; overexpressed c-K-ras mRNA. The mean levels of mRNAexpression for each of c-K-ras, c-N-ras and TGFß genesin tumorigenic cell lines were significantly greater than themean levels of expression in non-tumorigenic cell lines, suggestingan association between twnorigenicity and the levels of expressionof these specific genes. In contrast, levels of expression forc-myc, c-H-ras and Rb genes were not correlated with tumorigenicity.Cell lines that coexpressed high levels of c-K-ras, c-N-rasand TGFß genes were likely to be tumorigenic (11/12cell lines were tumorigenic), whereas cell lines that coexpressedlow levels of these genes were unlikely to be tumorigenlc (1/10cell lines were tumorigenic). High expression of TGFßwas sufficient for tumorigenicity in the absence of high levelsof expression of c-K-ras and c-N-ras (5/5 cell lines were tumorigenic).Elevated expression of either c-K-ras or c-N-ras alone was Insufficientfor tumorlgenlclty, however, coordinate overexpresslon of bothc-K-ras and c-ras was associated with tumorigenicity irrespectiveof the expression status for TGFß (13/15 cell lineswere tuinorigenic). These results suggest that overexpresslonof c-ras, c-H-ras and TGFß are conunonly associatedwith, and possibly mechanistically related to, the process ofmorphologic transformation in 1OTI/2 cells. In addition, theseresults suggest that progression from morphologic transformationto tumorigenicity in 1011/2 cell lines is frequently accompaniedby overexpression of c-K-ras and c-N-ras, and by enhancementof the level of overexpresslon of TGFß     

Predicting the Correlation of EZH2 and Cancer Stem Cell Markers in Esophageal Squamous Cell Carcinoma

Background

Enhancer of zeste homolog 2 (EZH2), a stemness factor, plays roles in regulation of cell differentiation and embryonic development as well as cancer progression. Deregulation of EZH2 in cancers is correlated with tumor cell invasiveness, metastasis, and the patients’ poor outcome. However, the mechanistic role of EZH2 in cancer is ambiguous. In this study, we aimed to inhibit the expression of EZH2 in a cancer cell line, and evaluate consequence changes in gene expression pattern.

Materials and methods

Using specific retroviral shRNA-EZH2, EZH2 gene was silenced in the KYSE30 cell line. Relative comparative real-time PCR was used to confirm silencing of EZH2 and evaluate expression pattern of selected markers.

Results

Inhibition of EZH2 expression in KYSE30 cells caused significant changes in different genes. Indeed, HIWI and HEY1 genes were over- and underexpressed in KYSE30 cells, respectively, following EZH2 silencing. Other selected cancer stem cell markers were not changed significantly.

Conclusion

To the best our knowledge, there are variety of small molecule inhibitors to target EZH2 in cancer cells as a treatment candidate; therefore, our data in this study helps the researchers to select EZH2 for cancer therapy based on its mechanism and correlation with other markers.

     

Immunocytochemical Expression of Microtubule-associated Protein-2 (MAP-2) in Small Cell Lung Cancer Cell Lines with Neuronal-like Processes

Five of six human small cell lung cancer (SCLC) cell lines changed morphologically into cells with neuronal-like processes on the extracellular matrix of human lung adenocarcinoma cell line PC-9 cells (PC-9/ECM substrate). The features of the neuronal-like processes of these SCLC cell lines were examined immunocytochemically using monoclonal antibodies against p-chains of tubulin and microtubule-associated protein-2 (MAP-2), which is somatodendritic MAP of neurons. It was observed that β-chains of tubulin and MAP-2 were expressed along the neuronal-like processes of SCLC cell lines. These findings suggest that the β-chains of tubulin and MAP-2 are expressed functionally in SCLC cell lines in association with the development of dendrite-like processes on PC-9/ECM substrate.     

An oncogenic cell line inducing transplantable metastasizing adenocarcinomas in Xenopus borealis

Three epithelioid cell lines were initiated from stage 35 tadpolesof Xenopus borealis. Cell strain XB693-M1 was obtained by incubationof one of these cell lines in MNNG. The strain is hypotetraploidwith a modal chromosome number of 62. It is tumorigenic when4 ? 10⁶ cells are injected into hosts belonging to a partiallyhistocompatible family. The tumors are very invasive, metastazingadenocarcinomas that kill the host within 5 to 38 weeks. Thetumor can be propagated in vivo by serial transplantation.     

Effects of anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene on human small airway epithelial cells and the protective effects of myo-inositol

Benzo[a]pyrene (B[a]P), a tobacco-derived carcinogen, induceslung tumors in rodents through its carcinogenic metabolite,anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene(B[a]PDE). Tumorigenesis is inhibited by dietary myo-inositolin the post-initiation phase. However, little is known abouthow B[a]PDE and myo-inositol affect normal human lung cells.We addressed this question using untransformed human small airwayepithelial (SAE) cells. SAE cell viability decreased <50%in parallel to an increase of apoptotic cells (>20%) 2 daysafter the cells were treated for 1 h with B[a]PDE (>100 nM).In contrast, the cell number and viability were not alteredin A549 human lung cancer cells by B[a]PDE treatment up to 10µM with <5% apoptotic cells and <10 U/l LDH in themedium. SAE cells retain the features of basal cells in serum-free,low Ca²⁺ (4 nM) medium up to 4–5 passages, but in serum-supplementedor serum-free, high Ca²⁺(1 mM) cultures, they differentiateinto non-ciliated epithelial cells expressing Clara cell secretoryprotein (CCSP). A non-toxic, physiologically relevant dose ofB[a]PDE (1 nM) partially inhibited serum and Ca²⁺-induced SAEcell differentiation. This effect was abolished by wortmannin,a phosphatidylinositol-3 kinase (PI-3K) inhibitor, and PD98059,a mitogen activated protein kinase (MAPK) kinase-1 (MEK1) inhibitor,but not by SB202190, a p38 MAPK inhibitor, or melittin, a proteinkinase C inhibitor. Myo-inositol (10–100 µM) didnot alter growth or differentiation of untreated SAE or A549cells, but reversed the inhibitory effect of B[a]PDE on serumand Ca²⁺-induced SAE cell differentiation when supplementedto the culture after B[a]PDE treatment. This myo-inositol actionwas not altered by PD98059, wortmannin or melittin, but waspartially suppressed by SB202190. Collectively, these resultsindicate that B[a]PDE inhibits serum-induced SAE cell differentiation,possibly involving activating signals through a PI-3K/MEK1 mediatedMAPK pathway, whereas myo-inositol protects SAE cells againstthis inhibitory effect of B[a]PDE perhaps through both PI-3K/MEK1and p38 MAPK pathways.