Low-dose phthalates promote breast cancer stem cell properties via the oncogene ΔNp63α and the Sonic hedgehog pathway.

BACKGROUND: The omnipresence of human phthalate (PAE) exposure is linked to various adverse health issues, including breast cancer. However, the effects of low-dose PAE exposure on breast cancer stem cells (BCSCs) and the underlying mechanism remain unexplored. METHODS: BCSCs from breast cancer cell lines (MDA-MB-231 and MCF-7) were enriched using a tumorsphere formation assay. Gene and protein expression was detected by measurement of quantitative real-time reverse transcription PCR, western blot, and immunofluorescence assays. Transient transfection assays were used to evaluate the involvement of Gli1, a signaling pathway molecule and ΔNp63α, an oncogene in influencing the PAE-induced characteristics of BCSCs. RESULTS: PAE (butylbenzyl phthalate, BBP; di-butyl phthalate, DBP; di-2-ethylhexyl phthalate, DEHP) exposure of 10-9 M significantly promoted the tumorsphere formation ability in BCSCs. Breast cancer spheroids with a 10-9 M PAE exposure had higher levels of BCSC marker mRNA and protein expression, activated sonic hedgehog (SHH) pathway, and increased mRNA and protein levels of an oncogene, ΔNp63α. Furthermore, suppression of the SHH pathway attenuated the effects of PAEs on BCSCs. And the overexpression of ΔNp63α enhanced PAE-induced characteristics of BCSCs, while low expression of ΔNp63α inhibited the promotion effects of PAEs on BCSCs and the SHH pathway. CONCLUSION: Low-dose PAE exposure promoted the stem cell properties of BCSCs in a ΔNp63α- and SHH-dependent manner. The influence of low-dose exposure of PAEs and its relevance for the lowest observed effect concentrations requires further investigation, and the precise underlying mechanism needs to be further explored.

ΔNp63α mediates sulforaphane suppressed colorectal cancer stem cell properties through transcriptional regulation of Nanog/Oct4/Sox2.

Cancer stem cells (CSCs) play a key role in cancer initiation, development, metastasis, and recurrence. Previously, we found that sulforaphane (SFN), a natural compound obtained from cruciferous vegetables, inhibited colorectal CSCs via the downregulation of TAp63α. However, the role of ΔNp63α, another critical isoform of p63 which has been considered to contribute to cancer progression, in SFN-mediated colorectal CSCs inhibition remains unclear. Here, we showed that ΔNp63α expression was enhanced in sphere-forming colorectal cancer cells. Overexpression of ΔNp63α promoted the properties of CSCs, while downregulation of ΔNp63α suppressed those properties. Besides, ΔNp63α was found to activate the transcription of core CSCs genes including Nanog, Oct4, and Sox2. Furthermore, in vitro and in vivo experiments illustrated the regulatory effects of SFN on ΔNp63α and colorectal CSCs. These findings suggested for the first time that ΔNp63α activated the transcription of Nanog, Oct4, Sox2 and mediated the interventional effects of SFN on colorectal CSCs, thus providing a novel mechanism by which SFN inhibits colorectal CSCs.

Adverse effects of iron deficiency anemia on pregnancy outcome and offspring development and intervention of three iron supplements.

Iron deficiency anemia (IDA) is a common micronutrient deficiency among pregnant women with severe consequences including impaired immuno-inflammatory system, premature birth, fetal death etc. The present study aimed to investigate the effects of three iron supplements on IDA female rats and their offspring. The IDA female rat model was established with low iron diet and the rats were then mated. After pregnancy, rats were fed diets containing different iron supplements (iron polysaccharide complex, iron protein succinylate and ferrous sulfate) until their offspring were 42 days old. Pregnancy outcomes, haematological, iron metabolism, physical and neurological development indexes were determined. The results showed that all three iron supplements improved the levels of hematological parameters of both mother and offspring rats. After iron supplementation, serum iron, transferrin saturation and serum ferritin levels were increased compared with the IDA group. The level of ferritin light chain in the liver and spleen of both mother and offspring rats in iron supplemented groups was significantly higher than that of the IDA group. The average number of born alive per litter in the iron treatment groups was significantly higher than that in the IDA group. Iron supplements also improved the physical growth and neurobehavioral development of offspring rats. It was also found that iron supplementation improved the expression of ferritin light chain and the synaptic growth associated proteins in the brain and hippocampus. No significant difference was found in the efficacy of three iron supplements. These results suggest that pregnant and postpartum IDA affects pregnancy outcomes, offspring physical development and causes neural impairment. Sufficient iron supplementation can significantly improve IDA and its adverse effects on both mother and offspring.

TAp63α targeting of Lgr5 mediates colorectal cancer stem cell properties and sulforaphane inhibition.

Cancer stem cells (CSCs) have an established role in cancer progression and therapeutic resistance. The p63 proteins are important transcription factors which belong to the p53 family, but their function and mechanism in CSCs remain elusive. Here, we investigated the role of TAp63α in colorectal CSCs and the effects of sulforaphane on TAp63α. We found that TAp63α was upregulated in spheres with stem cell properties compared to the parental cells. Overexpression of TAp63α promoted self-renewal capacity and enhanced CSC markers expression in colorectal sphere-forming cells. Furthermore, we showed that TAp63α directly bound to the promoter region of Lgr5 to enhance its expression and activate its downstream ß-catenin pathway. Functional experiments revealed that sulforaphane suppressed the stemness of colorectal CSCs both in vitro and in vivo. Upregulation of TAp63α attenuated the inhibitory effect of sulforaphane on colorectal CSCs, indicating the role of TAp63α in sulforaphane suppression of the stemness in colorectal cancer. The present study elucidated for the first time that TAp63α promoted CSCs through targeting Lgr5/ß-catenin axis and participated in sulforaphane inhibition of the stem cell properties in colorectal cancer.

Sulforaphane inhibits epithelial-mesenchymal transition by activating extracellular signal-regulated kinase 5 in lung cancer cells.

Epithelial-mesenchymal transition (EMT) contributes to the initiation, invasion, metastasis and drug resistance of cancer. The function of extracellular signal-regulated kinase 5 (ERK5) in lung cancer progression remains elusive. In this study, we investigated the effect of sulforaphane (SFN) on lung cancer EMT and the role of ERK5 in its effect. Wound healing and Transwell assays were applied to examine the migratory and invasive capacity in vitro. Quantitative real-time polymerase chain reaction and immunoblotting analysis were performed to investigate the expression of mRNA and protein levels. Small-interfering RNA was used to silence ERK5. Xenograft model was used to confirm the effect of SFN in vivo. Enhanced EMT and decreased ERK5 activation were observed in lung cancer cells in comparison with normal human bronchial epithelial cells. SFN diminished the migratory and invasive capacity of lung cancer cells. Additionally, significantly increased expression of epithelial markers (E-cadherin and ZO-1), decreased expression of mesenchymal markers (N-cadherin and Snail1) and activation of ERK5 were observed after SFN treatment. The inhibitory effect of SFN on lung cancer cell EMT was attenuated by ERK5 silencing. SFN-induced EMT suppression and ERK5 activation were further confirmed in lung cancer xenograft mouse model. The present study illustrated for the first time that ERK5 activation mediates SFN suppression of lung cancer cell EMT. These findings could provide new insights into the function of ERK5 in EMT regulation and the potential therapeutic application of SFN in cancer intervention.

Genistein inhibits nasopharyngeal cancer stem cells through sonic hedgehog signaling.

Genistein, a soy derived isoflavanoid compound, exerts anticancer effects in various cancers. Nasopharyngeal cancer stem cells (NCSCs) are a small subpopulation of cancer cells which are responsible for initiation, progression, metastasis, and recurrence of nasopharyngeal cancer. The present study aimed to investigate the suppressive effects of genistein on NCSCs and its underlying mechanism. NCSCs were enriched from human nasopharyngeal cancer cell lines CNE2 and HONE1 through tumorsphere-forming assay. It was shown that genistein inhibited the tumorsphere formation capacity, decreased the number of EpCAM+ cells, downregulated the expression of NCSCs markers, suppressed cell proliferation, and induced apoptosis of NCSCs. Genistein suppressed the activity of Sonic hedgehog (SHH) signaling, which was important for the maintenance of NCSCs, while activation of SHH signaling by purmorphamine diminished the inhibitory effects of genistein on NCSCs. Our data suggested that genistein inhibited NCSCs through the suppression of SHH signaling. These findings support the use of genistein for targeting NCSCs.

MAPK/AP-1 pathway regulates benzidine-induced cell proliferation through the control of cell cycle in human normal bladder epithelial cells.

Bladder cancer is the most common malignancy of the urinary tract. Long-term exposure to benzidine is one of the major causes of bladder cancer. However, the mechanism of benzidine-induced bladder cancer is not yet sufficiently characterized. Dysregulated cell proliferation serves a critical role in cancer initiation and development; whether benzidine promotes cell proliferation, and the role of MAPKs in this process, have not previously been investigated. The present study aimed to investigate the benzidine-induced modulation of intracellular mitogen-activated protein kinases (MAPKs) and activator protein-1 (AP-1) signaling cascades on cell proliferation in SV-40 immortalized human uroepithelial cells (SV-HUC-1). It was identified that benzidine exposure enhanced the proliferation of SV-HUC-1 cells, promoted the transition of cells from G1 to S phase and altered the expression level of cell cycle-associated genes at the mRNA and protein levels. Furthermore, exposure of the SV-HUC-1 cells to benzidine was associated with the activation of MAPKs, including extracellular regulated protein kinases 1 and 2, p38 and Jun N-terminal kinase. The downstream target of MAPKs, AP-1 monomers, was also activated. Benzidine-induced proliferation was reversed by MAPK-specific inhibitors. Thus, the present study demonstrated that benzidine enhances the proliferation of bladder cells via activating the MAPK/AP-1 pathway, which may provide novel insights into the molecular mechanisms of benzidine-initiated bladder tumorigenesis, as well as cancer prevention.

Phenethyl isothiocyanate inhibits colorectal cancer stem cells by suppressing Wnt/ß-catenin pathway.

Cancer stem cells (CSCs) are considered to play essential roles in the process of origination, proliferation, migration, and invasion of cancer, and their properties are regulated by Wnt/ß-catenin pathway. Phenethyl isothiocyanate (PEITC) is a natural product obtained from cruciferous vegetables with anticancer activities. The present study aimed to investigate the inhibitory effect and the underlying mechanisms of PEITC on colorectal CSCs. In this study, we found that PEITC can significantly reduce the size and number of colorectal cancer cell spheroids in serum-free medium. With increasing PEITC concentrations (10-40 µM), the number of spheroids was reduced to about 10% of the control group, and the percentage of CD133+ cells was decreased by about 3-16 folds. PEITC also decreased the expression of CSC markers. Meanwhile, inhibition of proliferation as well as induction of apoptosis of colorectal CSCs was observed after PEITC treatment. Furthermore, through activating Wnt/ß-catenin pathway with LiCl, the inhibitory effects of PEITC on colorectal CSCs were diminished. Our data suggested that PEITC can be an effective inhibitor of colorectal CSCs by targeting Wnt/ß-catenin pathway.

Correction to: Wnt/ß-catenin signaling mediates the suppressive effects of diallyl trisulfide on colorectal cancer stem cells.

Unfortunately, the online published article has error in Figure 4. The correct Figure 4 is given here.

Wnt/ß-catenin signaling mediates the suppressive effects of diallyl trisulfide on colorectal cancer stem cells.

PURPOSE: Cancer stem cells (CSCs) are responsible for colorectal cancer (CRC) initiation, growth, and metastasis. Garlic-derived organosulfur compound diallyl trisulfide (DATS) possesses cancer suppressive properties. Wnt/ß-catenin signaling is a key target for CSCs inhibition. However, the interventional effect of DATS on colorectal CSCs has not been clarified. We aimed to illustrate the regulation of Wnt/ß-catenin in DATS-induced colorectal CSCs inhibition. METHODS: Serum-free medium culture was used to enrich colorectal CSCs. SW480 and DLD-1 sphere-forming cells were treated with different concentrations of DATS for 5 days; LiCl and ß-catenin plasmids were used to stimulate the activity of Wnt/ß-catenin pathway. The size and number of colonspheres were detected by tumorsphere formation assay; the expression of colorectal CSCs-related genes was detected by Western blotting and qRT-PCR; the capacities of colorectal CSCs proliferation and apoptosis were detected by Cell Counting Kit-8, Hoechst 33258 cell staining and flow cytometry, respectively. RESULTS: The levels of colorectal CSCs markers were elevated in the tumorspheres cells. DATS efficiently suppressed the activity of colorectal CSCs, as evidenced by reducing the size and number of colonspheres, decreasing the expression of colorectal CSCs markers, promoting apoptosis and inhibiting the proliferation of colorectal CSCs. Moreover, DATS suppressed the activity of Wnt/ß-catenin pathway, while upregulation of Wnt/ß-catenin diminished the inhibitory effect of DATS on colorectal CSCs. CONCLUSIONS: Wnt/ß-catenin pathway mediates DATS-induced colorectal CSCs suppression. These findings support the use of DATS for targeting colorectal CSCs.

(-)-Epigallocatechin-3-Gallate Inhibits Colorectal Cancer Stem Cells by Suppressing Wnt/ß-Catenin Pathway.

The beneficial effects of tea consumption on cancer prevention have been generally reported, while (-)-Epigallocatechin-3-gallate (EGCG) is the major active component from green tea. Cancer stem cells (CSCs) play a crucial role in the process of cancer development. Targeting CSCs may be an effective way for cancer intervention. However, the effects of EGCG on colorectal CSCs and the underlying mechanisms remain unclear. Spheroid formation assay was used to enrich colorectal CSCs from colorectal cancer cell lines. Immunoblotting analysis and quantitative real-time polymerase chain reaction were used to measure the alterations of critical molecules expression. Immunofluorescence staining analysis was also used to determine the expression of CD133. We revealed that EGCG inhibited the spheroid formation capability of colorectal cancer cells as well as the expression of colorectal CSC markers, along with suppression of cell proliferation and induction of apoptosis. Moreover, we illustrated that EGCG downregulated the activation of Wnt/ß-catenin pathway, while upregulation of Wnt/ß-catenin diminished the inhibitory effects of EGCG on colorectal CSCs. Taken together, this study suggested that EGCG could be an effective natural compound targeting colorectal CSCs through suppression of Wnt/ß-catenin pathway, and thus may be a promising agent for colorectal cancer intervention.

Curcumin Suppresses Lung Cancer Stem Cells via Inhibiting Wnt/ß-catenin and Sonic Hedgehog Pathways.

Cancer stem cells (CSCs) are highly implicated in the progression of human cancers. Thus, targeting CSCs may be a promising strategy for cancer therapy. Wnt/ß-catenin and Sonic Hedgehog pathways play an important regulatory role in maintaining CSC characteristics. Natural compounds, such as curcumin, possess chemopreventive properties. However, the interventional effect of curcumin on lung CSCs has not been clarified. In the present study, tumorsphere formation assay was used to enrich lung CSCs from A549 and H1299 cells. We showed that the levels of lung CSC markers (CD133, CD44, ALDHA1, Nanog and Oct4) and the number of CD133-positive cells were significantly elevated in the sphere-forming cells. We further illustrated that curcumin efficiently abolished lung CSC traits, as evidenced by reduced tumorsphere formation, reduced number of CD133-positive cells, decreased expression levels of lung CSC markers, as well as proliferation inhibition and apoptosis induction. Moreover, we demonstrated that curcumin suppressed the activation of both Wnt/ß-catenin and Sonic Hedgehog pathways. Taken together, our data suggested that curcumin exhibited its interventional effect on lung CSCs via inhibition of Wnt/ß-catenin and Sonic Hedgehog pathways. These novel findings could provide new insights into the potential therapeutic application of curcumin in lung CSC elimination and cancer intervention. Copyright © 2017 John Wiley & Sons, Ltd.

Cigarette smoke extract induces the proliferation of normal human urothelial cells through the NF-κB pathway.

Bladder cancer is a common genitourinary malignant disease worldwide. Convincing evidence shows that cigarette smoke (CS) is a crucial risk factor for bladder cancer, yet the role of the NF-κB signaling pathway in the development of CS-associated bladder cancer has not been fully elucidated. In the present study, we found that exposure to cigarette smoke extract (CSE) induced proliferation and triggered the transition of normal human urothelial cells from G1 to S phase. Moreover, CSE exposure enhanced the expression of cyclin D1 and proliferating cell nuclear antigen (PCNA) and decreased the expression of p21 in SV-HUC-1 cells. Furthermore, the levels of nuclear NF-κB p65/p50 were significantly elevated by CSE. Pre-treatment with the NF-κB inhibitor (PDTC) reversed CSE-triggered cell proliferation. Taken together, our study revealed that CSE induced proliferation of normal human urothelial cells through the NF-κB pathway, and these data enhance our understanding of the CSE-related carcinogenesis of bladder cancer.

Curcumin reverses benzidine-induced cell proliferation by suppressing ERK1/2 pathway in human bladder cancer T24 cells.

Bladder cancer is one of the leading causes of cancer-related death in the world. Prolonged exposure to benzidine is a known cause of bladder cancer. Curcumin has been clinically used in chemoprevention and treatment of cancer. However, it remains unknown whether mitogen-activated protein kinase (MAPK) pathways are involved in curcumin-mediated protection from benzidine-associated promotive effects on bladder cancer. In our study, we found that benzidine increased the proliferation of human bladder cancer T24 cells, triggered transition of the cells from G1 to S phase, elevated the expression of cyclin D1 and proliferating cell nuclear antigen (PCNA) and decreased p21 expression. Meanwhile, exposure of T24 cells to benzidine resulted in activation of extracellular regulated protein kinases 1 and 2 (ERK1/2) pathway as well as activator protein 1 (AP-1) proteins. Treatment with ERK1/2 inhibitor U0126 or curcumin effectively abrogated benzidine-triggered cell proliferation and ERK1/2/AP-1 activation. These results suggested for the first time that curcumin in low concentrations played a protective role in benzidine-induced ERK1/2/AP-1 activation and proliferation of bladder cancer cells, therefore providing new insights into the pathogenesis and chemoprevention of benzidine-associated bladder cancer.

Benzidine induces epithelial-mesenchymal transition in human uroepithelial cells through ERK1/2 pathway.

Prolonged benzidine exposure is a known cause of urothelial carcinoma (UC). Benzidine-induced epithelial-to-mesenchymal transition (EMT) is critically involved in cell malignant transformation. The role of ERK1/2 in regulating benzidine-triggered EMT has not been investigated. This study was to investigate the regulatory role of ERK1/2 in benzidine-induced EMT. By using wound healing and transwell chamber migration assays, we found that benzidine could increase SV-HUC-1 cells invasion activity, western blotting and Immunofluorescence showed that the expression levels of Snail, ß-catenin, Vimentin, and MMP-2 were significantly increased, while, the expression levels of E-cadherin, ZO-1 were decreased. To further demonstrate the mechanism in this process, we found that the phosphorylation of ERK1/2, p38, JNK and AP-1 proteins were significantly enhanced compared to the control group (*P < 0.05). Afterward, treated with MAPK pathways inhibitors, only ERK inhibitor（U0126）could reduce the expression of EMT markers in SV-HUC-1 cells, but not p38 and JNK inhibitor（SB203580, SP600125）, which indicated that benzidine induces the epithelial-mesenchymal transition in human uroepithelial cells through ERK1/2 pathway. Taken together, findings from this study could provide into the molecular mechanisms by which benzidine exerts its bladder-cancer-promoting effect as well as its target intervention.

Oxidative injury in the lungs of neonatal rats following short-term exposure to ultrafine iron and soot particles.

Greater risk of adverse effects from particulate matter (PM) has been noted in susceptible subpopulations, such as children. However, the physicochemical components responsible for these biological effects are not understood. As critical constituents of PM, transition metals were postulated to be involved in a number of pathological processes of the respiratory system through free radical-medicated damage. The purpose of this study was to examine whether oxidative injury in the lungs of neonatal rats could be induced by repeated short-term exposure to iron (Fe) and soot particles. Sprague Dawley rats 10 d of age were exposed by inhalation to two different concentrations of ultrafine iron particles (30 or 100 microg/m(3)) in combination with soot particles adjusted to maintain a total particle concentration of 250 microg/m(3). Exposure at 10 d and again at 23 d of age was for 6 h/d for 3 d. Oxidative stress was observed at both Fe concentrations in the form of significant elevations in glutathione disulfide (GSSG) and GSSG/glutathione (GSH) ratio and a reduction in ferric/reducing antioxidant power in bronchoalveolar lavage. A significant decrease in cell viability associated with significant increases in lactate dehydrogenase (LDH) activity, interleukin-1-beta (IL-1beta), and ferritin expression was noted following exposure to particles containing the highest Fe concentration. Iron from these particles was shown to be bioavailable in an in vitro assay using the physiologically relevant chelator, citrate. Data indicate that combined Fe and soot particle exposure induces oxidative injury, cytotoxicity and pro-inflammatory responses in the lungs of neonatal rats.

NF-kappaB inhibition is involved in tobacco smoke-induced apoptosis in the lungs of rats.

Apoptosis is a vital mechanism for the regulation of cell turnover and plays a critical role in tissue homeostasis and development of many disease processes. Previous studies have demonstrated the apoptotic effect of tobacco smoke; however, the molecular mechanisms by which tobacco smoke triggers apoptosis remain unclear. In the present study we investigated the effects of tobacco smoke on the induction of apoptosis in the lungs of rats and modulation of nuclear factor-kappa B (NF-kappaB) in this process. Exposure of rats to 80 mg/m(3) tobacco smoke significantly induced apoptosis in the lungs. Tobacco smoke resulted in inhibition of NF-kappaB activity, noted by suppression of inhibitor of kappaB (IkappaB) kinase (IKK), accumulation of IkappaBalpha, decrease of NF-kappaB DNA binding activity, and downregulation of NF-kappaB-dependent anti-apoptotic proteins, including Bcl-2, Bcl-xl, and inhibitors of apoptosis. Initiator caspases for the death receptor pathway (caspase 8) and the mitochondrial pathway (caspase 9) as well as effector caspase 3 were activated following tobacco smoke exposure. Tobacco smoke exposure did not alter the levels of p53 and Bax proteins. These findings suggest the role of NF-kappaB pathway in tobacco smoke-induced apoptosis.

Environmental tobacco smoke suppresses nuclear factor-kappaB signaling to increase apoptosis in infant monkey lungs.

RATIONALE: Exposure to environmental tobacco smoke in early life has adverse effects on lung development. Apoptosis plays an essential role in development; however, the molecular mechanisms of pulmonary apoptosis induced by environmental tobacco smoke is unknown. OBJECTIVES: To investigate the mechanistic role of nuclear factor (NF)-kappaB, a critical cell survival pathway, in the developing lungs exposed to environmental tobacco smoke. METHODS: Timed-pregnant rhesus monkeys and their offspring were exposed to filtered air or to aged and diluted sidestream cigarette smoke as a surrogate to environmental tobacco smoke (a total suspended particulate concentration of 0.99 mg/m(3) for 6 h/d, 5 d/wk) from 45-50 d gestational age to 72-77 d postnatal age (n = 4/group). MEASUREMENTS AND MAIN RESULTS: NF-kappaB-DNA binding activity, regulated anti-apoptotic genes, and apoptosis were measured in lung tissues. Exposure to environmental tobacco smoke significantly suppressed NF-kappaB activation pathway and activity. Environmental tobacco smoke further down-regulated NF-kappaB-dependent anti-apoptotic genes and induced activation of caspases, cleavage of cellular death substrates (poly(ADP)-ribose polymerase and caspase-activated DNase) and an increase in the rate of apoptosis in the lung parenchyma. No significant alterations were observed for activator protein 1, p53 or Akt activity. CONCLUSIONS: Our results indicate that exposure to low levels of environmental tobacco smoke during a critical window of maturation in the neonatal nonhuman primate may compromise lung development with potential implications for future lung growth and function. These findings support our hypothesis that NF-kappaB plays a key role in the regulation of the apoptotic process.

MAPK/AP-1 signal pathway in tobacco smoke-induced cell proliferation and squamous metaplasia in the lungs of rats.

Overwhelming evidence has demonstrated tobacco smoke (TS) is causally associated with various types of cancers, especially lung cancer. Sustained epithelial cell hyperplasia and squamous metaplasia are considered as preneoplastic lesions during the formation of lung cancer. The cellular and molecular mechanisms leading to lung cancer due to TS are not clear. Mitogen-activated protein kinases (MAPK)/activator protein-1 (AP-1) can be activated by various stimuli and play a critical role in the control of cell proliferation and differentiation. To date, information on the response of the MAPK/AP-1 pathway during hyperplasia and squamous metaplasia induced by TS is lacking. We therefore investigated the effects of TS on the development of epithelial hyperplasia and squamous metaplasia, regulation of MAPK/AP-1 activation, and expression of AP-1-regulated cell cycle proteins and differentiation markers in the lungs of rats. Exposure of rats to TS (30 mg/m(3) or 80 mg/m(3), 6 h/day, 3 days/week for 14 weeks) dramatically induced cell proliferation and squamous metaplasia in a dose-dependent manner, effects that paralleled the activation of AP-1-DNA binding activity. Phosphorylated ERK1/2, JNK, p38 and ERK5 were significantly increased by exposure to TS, indicating the activation of these MAPK pathways. Expression of Jun and Fos proteins were differentially regulated by TS. TS upregulated the expression of AP-1-dependent cell cycle proteins including cyclin D1 and proliferating cell nuclear antigen (PCNA). Among the AP-1-dependent cell differentiation markers, keratin 5 and 14 were upregulated, while loricrin, filaggrin and involucrin were downregulated following TS exposure. These findings suggest the important role of MAPK/AP-1 pathway in TS-induced pathogenesis, thus providing new insights into the molecular mechanisms of TS-associated lung diseases including lung cancers.