PDV Cells Research Articles

Essential Oil of Mentha aquatica var. Kenting Water Mint Suppresses Two-Stage Skin Carcinogenesis Accelerated by BRAF Inhibitor Vemurafenib.

The v-raf murine sarcoma viral homolog B1 (BRAF) inhibitor drug vemurafenib (PLX4032) is used to treat melanoma; however, epidemiological evidence reveals that it could cause cutaneous keratoacanthomas and squamous cell carcinoma in cancer patients with the most prevalent HRASQ61L mutation. In a two-stage skin carcinogenesis mouse model, the skin papillomas induced by 7,12-dimethylbenz[a]anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA) (DT) resemble the lesions in BRAF inhibitor-treated patients. In this study, we investigated the bioactivity of Mentha aquatica var. Kenting Water Mint essential oil (KWM-EO) against PDV cells, mouse keratinocytes bearing HRASQ61L mutation, and its effect on inhibiting papilloma formation in a two-stage skin carcinogenesis mouse model with or without PLX4032 co-treatment. Our results revealed that KWM-EO effectively attenuated cell viability, colony formation, and the invasive and migratory abilities of PDV cells. Induction of G2/M cell-cycle arrest and apoptosis in PDV cells was also observed. KWM-EO treatment significantly decreased the formation of cutaneous papilloma further induced by PLX4032 in DT mice (DTP). Immunohistochemistry analyses showed overexpression of keratin14 and COX-2 in DT and DTP skin were profoundly suppressed by KWM-EO treatment. This study demonstrates that KWM-EO has chemopreventive effects against PLX4032-induced cutaneous side-effects in a DMBA/TPA-induced two-stage carcinogenesis model and will be worth further exploration for possible application in melanoma patients.

The PPARγ Agonist Rosiglitazone Suppresses Syngeneic Mouse SCC (Squamous Cell Carcinoma) Tumor Growth through an Immune-Mediated Mechanism.

Recent evidence suggests that PPARγ agonists may promote anti-tumor immunity. We show that immunogenic PDV cutaneous squamous cell carcinoma (CSCC) tumors are rejected when injected intradermally at a low cell number (1 × 106) into immune competent syngeneic hosts, but not immune deficient mice. At higher cell numbers (5 × 106 PDV cells), progressively growing tumors were established in 14 of 15 vehicle treated mice while treatment of mice with the PPARγ agonist rosiglitazone resulted in increased tumor rejection (5 of 14 tumors), a significant decrease in PDV tumor size, and a significant decrease in tumor cell Ki67 labeling. Rosiglitazone treatment had no effect on tumor rejection, tumor volume or PDV tumor cell proliferation in immune deficient NOD.CB17-PrkdcSCID/J mice. Rosiglitazone treatment also promoted an increase in tumor infiltrating CD3+ T-cells at both early and late time points. In contrast, rosiglitazone treatment had no significant effect on myeloid cells expressing either CD11b or Gr-1 but suppressed a late accumulation of myeloid cells expressing both CD11b and Gr-1, suggesting a potential role for CD11b+Gr-1+ myeloid cells in the late anti-tumor immune response. Overall, our data provides evidence that the PPARγ agonist rosiglitazone promotes immune-mediated anti-neoplastic activity against tumors derived from this immunogenic CSCC cell line.

SMAD3 is essential for transforming growth factor-β1-induced urokinase type plasminogen activator expression and migration in transformed keratinocytes

Transforming growth factor-β1 (TGF-β1) stimulates the extracellular matrix degrading proteases expression and cell migration in order to enhance cancer cells malignancy. In the present study, we analysed the role of TGF-β1-induced Smad3 activation in the urokinase type plasminogen activator (uPA) production, as well as in cell migration and E-cadherin downregulation in transformed PDV keratinocyte cell line. TGF-β1 signalling was interfered by the chemical inhibitor of the TGF-β1-receptor 1 (ALK5), SB505124, and the specific Smad3 inhibitor, SiS3. Our results showed that TGF-β1 stimulates uPA expression directly through ALK5 activation. The inhibition of Smad3 strongly reduced the capacity of TGF-β1 to stimulate uPA expression, in parallel decreasing the uPA inhibitor plasminogen activator inhibitor type 1 (PAI-1) expression. In addition, the transient expression of dominant negative Smad3 mutant inhibited the TGF-β1-induced uPA promoter transactivation. Moreover, Smad3−/− mouse embryonic fibroblasts were refractory to the induction of uPA by TGF-β1. The inhibition of both ALK5 and Smad3 dramatically blocked the TGF-β1-stimulated E-cadherin downregulation, F-actin reorganisation and migration of PDV cells. Taken together, our results suggest that the TGF-β1-induced activation of Smad3 is the critical step for the uPA upregulation and E-cadherin downregulation, which are the key events preceding the induction of cell migration by TGF-β1 in transformed cells.

SKIP is required for TGF-β1-induced epithelial mesenchymal transition and migration in transformed keratinocytes

Transforming growth factor-β1 (TGF-β1) potently induces the epithelial-mesenchymal transition (EMT) during tumoral progression. Although Sky-interacting protein (SKIP) regulates TGF-β1-induced Smad activation, its role in the induction of cell malignance remains uncertain. We found that TGF-β1 increases SKIP expression in PDV cells. In cells stably transfected with SKIP antisense, AS-S, Smad3 activation decreased, along with an inhibition of TGF-β1-induced EMT, and the cells were sensitized to the TGF-β1-dependent inhibition of proliferation. Also, AS-S cells showed a weaker migration and invasion response. Moreover, TGF-β1-induced urokinase-type plasminogen activator expression was inhibited, concomitantly with a TGF-β1-independent increment of the plasminogen-activator inhibitor-1 expression. Thus, these results suggest that SKIP is required for EMT and invasiveness induced by TGF-β1 in transformed cells.

Spred2 inhibits TGF‐β1‐induced urokinase type plasminogen activator expression, cell motility and epithelial mesenchymal transition

TGF-beta1 is a potent inductor of malignance in cancer cells. TGF-beta1 stimulates the expression of extracellular matrix degrading proteases, cell migration and it is also involved in the epithelial-mesenchymal transition (EMT). In the present work, we analyzed the role of Spred2 in the urokinase-type plasminogen activator (uPA) stimulation, EMT and cell migration by TGF-beta1. We found that both the expression of mRNA and the protein level of Spred2 were lower in transformed keratinocytes PDV compared with immortalized keratinocytes MCA-3D. The transient ectopic expression of Spred2 in PDV cells inhibited the TGF-beta1-transactivated SRE-Luc reporter which is related with the ERK1,2 signal. The stable ectopic expression of Spred2 in PDV cells (SP cells) led to the loss of ERK 1,2 activation by TGF-beta1, although Smad2 activation was not affected, and the knockdown of Spred2 enhanced the activation of ERK1,2 signal by TGF-beta1. The increment of uPA expression induced by TGF-beta1 was suppressed in SP cells. In contrast, the stimulus on PAI-1 expression was not affected and comparable to parental PDV cells. SP cells under TGF-beta1 treatment were unable to display the EMT, since the overexpression of Spred2 abolished the TGF-beta1-induced disruption of the E-cadherin cell to cell interactions, reorganization of the actin cytoskeleton and upregulation of the mesenchymal marker vimentin. Finally, SP cells could not respond to the TGF-beta1 stimulus on cell migration. Taken together, the data in the present study suggests that Spred2 is a regulator of TGF-beta1-induced malignance in transformed keratinocytes.

The Progression in the Mouse Skin Carcinogenesis Model Correlates With ERK1/2 Signaling

The ras family of proto-oncogenes encodes for small GTPases that play critical roles in cell-cycle progression and cellular transformation. ERK1/2 MAP kinases are major ras effectors. Tumors in chemically treated mouse skin contain mutations in the Ha-ras proto- oncogene. Amplification and mutation of Ha-ras has been shown to correlate with malignant progression of these tumors. Cell lines isolated from mouse skin tumors represent the stages of tumor development, such as the PDV:PDVC57 cell line pair and B9 squamous carcinoma and A5 spindle cells. PDVC57 cells were selected from PDV cells, which were transformed with dimethyl-benzanthracene (DMBA) in vitro and then transplanted in adult syngeneic mice. The PDV:PDVC57 pair contains ratio of normal:mutant Ha-ras 2:1 and 1:2, respectively. This genetic alteration correlates with more advanced tumorigenic characteristics of PDVC57 compared to PDV. The squamous carcinoma B9 cell clone was isolated from the same primary tumor as A5 spindle cell line. The mutant Ha-ras allele, also present in B9, is amplified and overexpressed in A5 cells. Therefore these cell line pairs represent an in vivo model for studies of Ha-ras and ERK1/2 signaling in mouse tumorigenesis. The ERK1/2 status in the above mouse cell lines was examined by using various molecular techniques. For the study of the tumorigenic properties and the role of the ras/MEK/ERK1/2 pathway in the cell lines mentioned, phenotypic characteristics, colony formation assay, anchorage-independent growth, and gelatin zymography were assessed, after or without treatment with the MEK inhibitor, PD98059. ERK1/2 phosphorylation was found to be increased in PDVC57 when compared to PDV. This also applies to A5 spindle carcinoma cells when compared to squamous carcinoma and papilloma cells. The above finding was reproduced when transfecting human activated Ha-ras allele into PDV, thus demonstrating that Ha-ras enhances ERK1/2 signaling. To further test whether ERK1/2 activation was required for growth we used the MEK-1 inhibitor, PD98059. The latter inhibited cell proliferation and anchorage-independent growth of squamous and spindle cells. In addition, PD98059 treatment partially reverted the spindle morphology of A5 cells. These data suggest, for the first time, that oncogenicity and the degree of progression in the mouse skin carcinogenesis model correlates with ERK1/2 signaling.

Blockade of Smad4 in transformed keratinocytes containing a Ras oncogene leads to hyperactivation of the Ras-dependent Erk signalling pathway associated with progression to undifferentiated carcinomas.

Smad4 functions as a transcription factor in TGF-beta signalling. We have investigated the role of Smad4 in the TGF-beta1 cell responses of transformed PDV keratinocytes, which contain a Ras oncogene, and of non-tumorigenic MCA3D keratinocytes, by transfecting both cell lines with a dominant-negative Smad4 construct. Smad4 mediates TGF-beta1-induced up-regulation of p21Cip1 and growth arrest in MCA3D cells. However, in PDV keratinocytes, Smad4 is only partially involved in TGF-beta1-induced growth inhibition, and does not mediate enhancement of p21Cip1 levels by the growth factor. TGF-beta1 activates Ras/Erk signalling activity in both cell lines. PD098059, a specific inhibitor of MEK, disminishes TGF-beta1-induced p21Cip1 levels in PDV but not in MCA3D cells, suggesting an involvement of Erk in up-regulation of p21Cip1 by TGF-beta1 in PDV cells. PDV dominant-negative Smad4 cell transfectants, but not MCA3D transfectants, showed constitutive hyperactivation of the Ras/Erk signalling pathway, increased secretion of urokinase, higher motility properties, and a change to a fibroblastoid cell morphology associated in vivo with the transition from a well differentiated to a poorly differentiated tumour phenotype. Infection of MCA3D control and dominant negative Smad4 cell transfectants with retroviruses carrying a Ras oncogene led to enhanced p21Cip1 and urokinase secreted levels, independently of TGF-beta1 stimulation, that were reduced by PD098059. These results suggest that Smad4 acts inhibiting Ras-dependent Erk signalling activity in Ras-transformed keratinocytes. Loss of Smad4 function in these cells results in hyperactivation of Erk signalling and progression to undifferentiated carcinomas. Oncogene (2000) 19, 4134 - 4145

Involvement of the Ras/MAPK Signaling Pathway in the Modulation of Urokinase Production and Cellular Invasiveness by Transforming Growth Factor-β1 in Transformed Keratinocytes

Transformed PDV keratinocytes respond to TGF-β1 by stimulating cell motility and invasiveness concomitantly to enhancement of the urokinase-type plasminogen activator (uPA) expression/secretion. Depletion of extracellular signal-regulated kinase (ERK1, 2) proteins by treatment of PDV cells with antisense oligonucleotides reduced basal uPA production and abolished stimulation of uPA secreted levels and cell motility by TGF-β1. PD098059, an inhibitor of mitogen-activated protein kinase (MAPK) kinase (MEK), decreased TGF-β1-induced uPA mRNA expression, secreted activity in a dose-dependent manner, and abrogated TGF-β1-stimulated cell motility and invasiveness. PDV-derived dominant-negative RasN17 cell transfectants secreted similar amounts of uPA and exhibited similar invasive abilities as the parental cells or control clones, but were unable to respond to TGF-β1 for stimulation of uPA-secreted levels and invasiveness. These results suggest that a Ras/MAPK transduction pathway is involved in the invasive response of transformed keratinocytes to TGF-β1.

Urokinase expression and binding activity associated with the transforming growth factor ?1-induced migratory and invasive phenotype of mouse epidermal keratinocytes

Transforming growth factor beta1(TGF-beta1) is a stimulator of malignant progression in mouse skin carcinogenesis. TGF-beta1 exerts a differential effect on cultured nontumorigenic (MCA3D cell line) and transformed (PDV cell line) keratinocytes. Whereas MCA3D cells are growth arrested and committed to die in the presence of the factor, it induces a reversible epithelial-fibroblastic conversion in PDV cells. This conversion is associated in vivo with a squamous-spindle cell carcinoma transition. Here we have investigated the role of urokinase (uPA) during malignant progression of transformed epidermal keratinocytes. We show that the levels of uPA expression/secretion, and the uPA binding activity to the cell surface, correlate with the invasive and malignant potentials of mouse epidermal cell lines. TGF-beta1 enhanced uPA production, the number of uPA cell surface binding sites, and the expression of the plasminogen activator inhibitor PAI-1, in transformed PDV cells, but had no major effect on nontumorigenic MCA3D keratinocytes. Increased uPA production depended on the presence of the factor in the culture medium and occurred concomitantly to the stimulation of the migratory and invasive abilities of PDV cells. Synthetic peptides containing the amino terminal sequence of the mature mouse uPA inhibited the binding of uPA to the cell surface and decreased TGF-beta1-induced cell motility and invasiveness. These results demonstrate that the uPA system mediates at least part of the migratory and invasive phenotype induced by TGF-beta1 in transformed keratinocytes, and suggest a role for uPA on the changes that lead to the appearance of spindle carcinomas.

Cadherin/catenin complexes in murine epidermal keratinocytes: E-cadherin complexes containing either beta-catenin or plakoglobin contribute to stable cell-cell contacts.

The cadherin/catenin complexes expressed by a murine epidermal keratinocyte cell line PDV, expressing E- and P-cadherin, have been analysed using a combination of biochemical and confocal microscopy analysis. Two types of E-cadherin complexes, containing beta-catenin or plakoglobin and alpha-catenin, were detected in PDV cells as in other cell types, while P-cadherin was mainly detected in complexes containing beta-catenin and alpha-catenin in PDV and other murine epidermal keratinocytes. Biotin-labelling studies have shown that both types of E-cadherin complexes are present at the surface of confluent cells. Furthermore, confocal microscopy analysis indicated that E-cadherin/plakoglobin complexes are located in stable cell-cell contacts at the middle lateral membranes and associated with alpha-catenin and the actin cytoskeleton, with a similar distribution to that to the E-cadherin/beta-catenin complexes. In addition, E-cadherin/plakoglobin complexes not associated with alpha-catenin or the actin cytoskeleton were detected in lower planes of the lateral contacting membranes as well as E-cadherin non-associated with catenins in the more basal planes. These studies support that in murine epidermal keratinocytes both beta-catenin- and plakoglobin-containing E-cadherin complexes contribute to the maintenance of stable cell-cell contacts and suggest a differential role of the plakoglobin containing complexes in different epithelial cell types.

Changes in Keratin Expression during Malignant Progression of Transformed Mouse Epidermal Keratinocytes

We have studied in this report the expression of keratins in mouse epidermal keratinocytes transformed in culture by a chemical carcinogen (PDV) and in cell lines (PDVCM1, PDVCM2, PDVCV1, and PDVC57) derived by tumor transplantation of PDV cells in syngeneic C57BI/6 mice. PDV, PDVCM1, PDVCM2, and PDVCV1 cell lines are weakly to moderately tumorigenic, giving rise to squamous cell carcinomas, although not at all injection points, whereas PDVC57 cells are more malignant, inducing highly anaplastic carcinomas at 100% of injection sites. All the cell lines synthesize anomalously simple epithelial keratins, substantial amounts of K8, and minor quantities of K18 and K19, but the level of expression is increased in PDVC57. We have found that in PDVC57 cells upregulation of K8 is linked to down-regulation of the normal keratins produced by epidermal keratinocytes in culture (i.e., K5, K6, K14, and K17). On the other hand, K8 does not generally colocalize with K13, a keratin also aberrantly expressed by epidermal cell cultures when induced to differentiate by high Ca 2+ medium. K13, normally synthesized in internal stratified epithelia, is anomalously induced in mouse epidermal tumors and has been used as an early marker of carcinoma progression. In tumors induced by the cell lines upon injection in mice, K8 is found in the less differentiated regions as opposite to K13, restricted to the differentiating areas of the tumors. In PDV, PDVCM1, PDVCM2, and PDVCV1 carcinomas the overall expression of K13 is higher than that of K8. However, this relation is inverted in tumors induced by PDVC57 cells, in a good correlation with the tumoral phenotypes produced by the cell lines. Our results suggest that upregulation of the simple epithelial keratin K8, as found in transformed epidermal cell lines and tumors, is a late marker of malignant progression and is associated with the loss of the differentiated phenotype.

Caffeine inhibition of postreplication repair of UV-damaged DNA in mouse epidermal cells

The effect of caffeine (0.25–1.5 mM) on UV-irradiated (5 and 10 J/m 2) primary cultures of mouse epidermal cells (EPD) and an in vitro transformed cell line (PDV) was studied at the cellular and molecular levels. A synergistic reduction in cell survival induced by caffeine with UV-irradiation was found in the PDV cells at 10 J/m 2 but not at 5 J/m 2. When conversion of low molecular weight newly-synthesized DNA to high molecular weight DNA was studied in both cell types, caffeine at 1.5 mM had no effect on this conversion in unirradiated cultures. At 5 J/m 2, caffeine had a transitory inhibitory effect on this conversion. However, at 10 J/m 2 caffeine had a strong permanent inhibitory effect on this conversion at doses higher than 0.5 mM in PDV cells and higher than 0.25 mM in EPD cells. This apparent inhibition of elongation by caffeine in irradiated cells could not be accounted for by an effect on the rate of DNA synthesis. In PDV cells there was a direct correlation in terms of effective caffeine dose level between synergistic reduction in cell survival after UV and the effect on DNA elongation. Irradiated EPD cells were more sensitive to the inhibitory effect of caffeine on DNA elongation.