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Supplementary Figure Legends from Activation of the PI3K/Akt/mTOR and MAPK Signaling Pathways in Response to Acute Solar-Simulated Light Exposure of Human Skin

Supplementary Figure 1. Box plot graphs of protein expression in sun-protected skin after 2, 2,5, and 3 MED (x-axis) of SSL-irradiation (SSL) with baseline (green bars), 5 minutes (orange bars), 1 hour (blue bars), 5 hours (red bars), and 24 hours (grey bars) post SSL on the y-axis. Supplementary Figure 2. Box plot graphs of protein expression in sun-protected skin after 2, 2,5, and 3 MED (x-axis) of SSL-irradiation (SSL) with baseline (green bars), 5 minutes (orange bars), 1 hour (blue bars), 5 hours (red bars), and 24 hours (grey bars) post SSL on the y-axis. Supplementary Figure 3. Box plot graphs of protein expression in sun-protected skin after 2, 2,5, and 3 MED (x-axis) of SSL-irradiation (SSL) with baseline (green bars), 5 minutes (orange bars), 1 hour (blue bars), 5 hours (red bars), and 24 hours (grey bars) post SSL on the y-axis.

The incidence of skin cancer is higher than all other cancers and continues to increase, with an average annual cost over $8 billion in the United States. As a result, identifying molecular pathway alterations that occur with UV exposure to strategize more effective preventive and therapeutic approaches is essential. To that end, we evaluated phosphorylation of proteins within the PI3K/Akt and MAPK pathways by immunohistochemistry in sun-protected skin after acute doses of physiologically relevant solar-simulated ultraviolet light (SSL) in 24 volunteers. Biopsies were performed at baseline, 5 minutes, 1, 5, and 24 hours after SSL irradiation. Within the PI3K/Akt pathway, we found activation of Akt (serine 473) to be significantly increased at 5 hours while mTOR (serine 2448) was strongly activated early and was sustained over 24 hours after SSL. Downstream, we observed a marked and sustained increase in phospho-S6 (serine 235/S236), whereas phospho-4E-BP1 (threonines 37/46) was increased only at 24 hours. Within the MAPK pathway, SSL-induced expression of phospho-p38 (threonine 180/tyrosine 182) peaked at 1 to 5 hours. ERK 1/2 was observed to be immediate and sustained after SSL irradiation. Phosphorylation of histone H3 (serine 10), a core structural protein of the nucleosome, peaked at 5 hours after SSL irradiation. The expression of both p53 and COX-2 was increased at 5 hours and was maximal at 24 hours after SSL irradiation. Apoptosis was significantly increased at 24 hours as expected and indicative of a sunburn-type response to SSL. Understanding the timing of key protein expression changes in response to SSL will aid in development of mechanistic-based approaches for the prevention and control of skin cancers. Cancer Prev Res; 8(8); 720–8. ©2015 AACR.

The incidence of skin cancer is higher than all other cancers and continues to increase, with an average annual cost over $8 billion in the United States. As a result, identifying molecular pathway alterations that occur with UV exposure to strategize more effective preventive and therapeutic approaches is essential. To that end, we evaluated phosphorylation of proteins within the PI3K/Akt and MAPK pathways by immunohistochemistry in sun-protected skin after acute doses of physiologically relevant solar-simulated ultraviolet light (SSL) in 24 volunteers. Biopsies were performed at baseline, 5 minutes, 1, 5, and 24 hours after SSL irradiation. Within the PI3K/Akt pathway, we found activation of Akt (serine 473) to be significantly increased at 5 hours while mTOR (serine 2448) was strongly activated early and was sustained over 24 hours after SSL. Downstream, we observed a marked and sustained increase in phospho-S6 (serine 235/S236), whereas phospho-4E-BP1 (threonines 37/46) was increased only at 24 hours. Within the MAPK pathway, SSL-induced expression of phospho-p38 (threonine 180/tyrosine 182) peaked at 1 to 5 hours. ERK 1/2 was observed to be immediate and sustained after SSL irradiation. Phosphorylation of histone H3 (serine 10), a core structural protein of the nucleosome, peaked at 5 hours after SSL irradiation. The expression of both p53 and COX-2 was increased at 5 hours and was maximal at 24 hours after SSL irradiation. Apoptosis was significantly increased at 24 hours as expected and indicative of a sunburn-type response to SSL. Understanding the timing of key protein expression changes in response to SSL will aid in development of mechanistic-based approaches for the prevention and control of skin cancers. Cancer Prev Res; 8(8); 720–8. ©2015 AACR.

Elisabeth L. Bair, Man Ling Chen, Kathy McDaniel, Kiyotoshi Sekiguchi, Anne E. Cress, Raymond B. Nagle, and George Timothy Bowden, "Membrane Type 1 Matrix Metalloprotease Cleaves Laminin-10 and Promotes Prostate Cancer Cell Migration", Neoplasia, Vol. 7 (4), pp. 380-389, Elsevier, 2005, Disruption of the extracellular matrix by proteases is crucial for tumor invasion. Laminin-10 (Ln-10) has previously been identified as a substrate for cell migration and cell adhesion, and is present in the basal lamina (BL) of both normal prostate and prostate cancer. Here, we investigate a role for membrane type 1 matrix metalloprotease (MT1-MMP) in modifying this Ln-10-rich BL. MT1-MMP is a transmembrane member of the MMP family that has been demonstrated to be upregulated as prostate cancer progresses from normal to prostate intraepithelial neoplasia to invasive cancer, suggesting a role for MT1-MMP in the invasion of prostate cancer. We show that MT1-MMP cleaves the α5 chain of purified human Ln-10 from its 350-kDa form into 310-, 190-, 160-, and 45-kDa fragments. This cleavage causes a decrease in DU-145 prostate cancer cell adhesion to purified Ln-10, and an increase in transmigration of DU-145 cells through cleaved Ln-10. We also show that prostate cancer cells expressing membrane-bound MT1-MMP cleave the α5 chain of Ln-10. Ln α5-chain cleavage is also observed in human prostate cancer tissues. These findings suggest that prostate cancer cells expressing high levels of MT1-MMP have increased invasive potential through their ability to degrade and invade Ln-10 barriers.

Solar ultraviolet (UV) light is a major etiological factor in skin carcinogenesis, with solar UV-stimulated signal transduction inducing pathological changes and skin damage. The primary sensor of solar UV-induced cellular signaling has not been identified. We use an experimental system of solar simulated light (SSL) to mimic solar UV and we demonstrate that Fyn is a primary redox sensor involved in SSL-induced signal transduction. Reactive oxygen species (ROS) generated by SSL exposure directly oxidize Cys488 of Fyn, resulting in increased Fyn kinase activity. Fyn oxidation was increased in mouse skin after SSL exposure, and Fyn knockout (Fyn−/−) mice formed larger and more tumors compared to Fyn wildtype mice when exposed to SSL for an extended period of time. Murine embryonic fibroblasts (MEFs) lacking Fyn as well as cells in which Fyn expression was knocked down were resistant to SSL-induced apoptosis. Furthermore, cells expressing mutant Fyn (C448A) were resistant to SSL-induced apoptosis. These findings suggest that Fyn acts as a regulatory nexus between solar UV, ROS and signal transduction during skin carcinogenesis.

The MMP, matrilysin. (20MMP-7), has been shown to be overexpressed in prostate cancer cells and to increase prostate cancer cell invasion. Prostate stromal fibroblasts secrete factor(s), including fibroblast growth factor-1. (20FGF-1) that induces promatrilysin expression in LNCaP cells. In the present study, we investigated the signal transduction pathway involved in the FGF-1-induced expression of promatrilysin. FGF-1 treatment significantly increased the activation of extracellular signal-regulated kinases 1 and 2. (20ERK1 and ERK2). This induction was time-dependent and was sustained until 24 hours after treatment. Treating the cells with MEK1/2 inhibitor. (20PD98059) eliminated ERK activation completely and blocked FGF-1-mediated induction of promatrilysin expression. Transient transfection studies with human matrilysin promoter resulted in a four-to-five-fold increase in reporter luciferase enzyme activity that was blocked by the MEK1/2 inhibitor. (20PD98059). Serine phosphorylation of signal transducer and activator of transcription 3. (20STAT3) was observed after FGF-1 treatment and pretreatment with 20 µM PD98059 abolished STAT3 phosphorylation. Transient transfection with dominant negative STAT3 inhibited FGF-1-induced transactivation of the matrilysin promoter indicating that STAT3 plays an important role in FGF-1-induced matrilysin expression. We propose that the FGF-1-induced signaling pathway that leads to promatrilysin expression is ERK-dependent and leads to phosphorylation of Ser-727 on STAT3, phosphorylated STAT3, then binds and transactivates the matrilysin promoter. Our results demonstrate that ERK-MAP kinase and transcription factor STAT3 are important components of FGF-1-mediated signaling, which induce promatrilysin expression in LNCaP cells.

Matrix metalloproteinases (MMPs) degrade extracellular matrix proteins, and there is evidence that they play a role in tumor cell growth, invasion and metastasis. Matrilysin (MMP-7) is over-expressed in prostate cancer cells and increases prostate cancer cell invasion. Prostate stromal fibroblasts secrete a factor(s), including fibroblast growth factor-1 (FGF-1), which induces promatrilysin expression in the prostate carcinoma cell line LNCaP but not in normal prostate epithelial cells (PrECs). Since FGF-1 is present in the prostate, an altered sensitivity to FGF-1 might explain the up-regulation of matrilysin expression in prostate cancer cells compared to normal prostate epithelium. FGF receptor-1 (FGFR-1) is not normally expressed by normal prostate epithelial cells; however, aberrant expression of this receptor has been reported in prostate cancer cells, including the LNCaP cell line. We hypothesized that aberrant expression of FGFR-1 in PrECs would render them sensitive to induction of promatrilysin expression by recombinant FGF-1. To test this hypothesis, we transiently transfected PrECs with an FGFR-1 expression vector, which resulted in over-expression of FGFR-1 protein in approximately 40% of cells. FGF-1 increased promatrilysin expression in FGFR-1-transfected PrECs 4-fold over mock-transfected cells, and this induction was inhibited by a specific FGFR-1 inhibitor, SU5402, and by co-expression of a dominant negative FGFR-1 protein. Our results demonstrate that aberrant FGFR-1 expression, an epigenetic phenomenon that has been associated with prostate cancer progression, allows induction of promatrilysin expression by FGF-1 in PrECs.

Previously, our laboratory showed that interleukin-1beta (IL-1beta) secreted by lipopolysaccharide-activated monocytes induces promatrilysin expression in the prostate carcinoma cell line, LNCaP. We now demonstrate that IL-1beta-induced promatrilysin expression is mediated by an indirect mechanism that requires nuclear factor Kappa B (NFkappaB)-dependent synthesis of IL-6. Inhibition of protein synthesis with cycloheximide blocked IL-1beta-mediated induction of matrilysin mRNA suggesting that synthesis of one or more additional factors is required for IL-1beta-induced promatrilysin protein expression. Blockage of NFkappaB transactivation activity abrogated IL-1beta-induced promatrilysin expression to baseline levels suggesting that NFkappaB transactivation activity is necessary. Inhibition of IL-6 activity attenuated IL-1beta-induced promatrilysin, but not NFkappaB transactivation activity indicating that IL-6 acts downstream of NFkappaB in potentiation of IL-1beta-mediated promatrilysin expression. Inhibition of protein synthesis with cycloheximide did not alter IL-6-induced induction of matrilysin mRNA indicating that, contrary to the mechanism by which IL-1beta regulates promatrilysin expression, IL-6-mediated matrilysin mRNA expression does not require new protein synthesis. Transient transfection with dominant negative STAT3 inhibited IL-1beta- and IL-6-induced promatrilysin. These data provide evidence that NFkappaB-mediated IL-6 synthesis is required for IL-1beta-induced promatrilysin expression, and IL-6 signaling through STAT3 plays a role in IL-1beta-induced promatrilysin expression.

By performing in vitro kinase assays we found in papilloma producing 308 mouse keratinocytes that okadaic acid elevated activities of extracellular signal-regulated kinase (ERK) 1/2, c-Jun N-terminal kinases (JNKs) and p38 mitogen-activated protein kinases (MAPKs). This okadaic acid mediated activation of MAP kinases correlated with increased AP-1 binding to a consensus TPA responsive element (TRE) and elevated TRE dependent transcription. To determine the role of p38 MAP kinases in these processes we employed the specific p38 MAP kinase inhibitor SB 203580. Using orthophosphate labeling we showed a decrease in phosphorylation of MAPK activated protein kinase-2 (MAPKAP-K2) indicating reduced activity of p38 MAPKs utilizing this kinase as substrate. In contrast, we found that SB 203580 raised activities of ERK-1/2 and JNKs. Electrophoretic mobility shift assays revealed an increase in TRE binding activity in response to SB 203580 most likely resulting from increased expression of the major TRE binding components JunD and FosB as indicated by Western blot analyses. Increased TRE DNA binding failed to lead to increased transactivation correlating with the inability of SB 203580 to increase phosphorylation of these AP-1 proteins. These data indicate that SB 203580 sensitive p38 MAP kinases are not involved in okadaic acid mediated increases in TRE DNA binding and transactivation.

Repeated doses of beta-radiation in the mouse skin model have been reported to produce carcinomas and sarcomas with equal frequency. Among sarcomas, fibrosarcomas and osteosarcomas have been the predominant reported histologies. In this report we describe the beta-radiation induction of rhabdomyosarcoma (RMS), a histology previously undescribed with tumor induction protocols using ionizing radiation in an animal model. Radiation-induced RMS is often seen as a secondary tumor following therapeutic irradiation for retinoblastoma in children. In our experiment the backs of 50 CD-1 mice were irradiated 3 times weekly for 35 weeks using a 90Sr source. The initial dose was 5.5 Gy/application, which was later reduced to 3 Gy after 15 weeks due to severe skin reactions. In all, 27 skin and subcutaneous tumors were seen and collected. Of 12 sarcomas seen, 9 had a rhabdoid histology; cell lines from 3 such tumors as well as a squamous-cell carcinoma (SCC) and a malignant fibrous histiocytoma (MFH) were established. Immunohistochemical analysis of their parent tumors showed that the rhabdoid tumors expressed desmin, which established the diagnosis of RMS. Two-dimensional gel electrophoresis and Western analysis of insoluble protein extracts confirmed that the cell lines from RMS tumors expressed desmin. A screen for molecular alterations identified a mutant p53 phenotype for RMS and MFH cell lines. These radiation-induced RMS cell lines provide a unique opportunity to study the molecular biology of this tumor in an animal model and will help provide insight into the mechanisms of radiation-induced RMS in humans.

Sulforaphane (SFN) is a natural compound that has been investigated as a chemopreventive agent. SFN has been shown to inhibit the activator-protein-1 (AP-1) transcription factor and may be effective for inhibition of ultraviolet (UV) induced skin carcinogenesis. This study was designed to investigate the stability of SFN as a function of pH, temperature and in various solvents and formulations.Stability was analyzed using high-performance liquid chromatography. A potential lead formulation was identified and evaluated in vivo.SFN was determined to undergo apparent first-order degradation kinetics for the conditions explored. It was observed that SFN undergoes base catalyzed degradation. Buffer species and solvent type impacts stability as well. SFN was found to be very sensitive to temperature with degradation rate changing by a factor of nearly 3.1 for every 10 °C change in temperature (at pH 4.0). SFN completely degraded after 30 days in a conventional pharmaceutical cream formulation. Improved stability was observed in organic formulation components. Stability studies were conducted on two nonaqueous topical formulations: a polyethylene glycol (PEG) ointment base and an organic oleaginous base.Topically applied SFN in the PEG base formulation significantly reduced AP-1 activation after UV stimulation in the skin of a transgenic mouse model, indicating that SFN in this formulation retains efficacy in vivo.

The matrix metalloproteinase, matrilysin, is thought to play an important role in the early steps of tumor progression. We determined the chromosome location of the matrilysin gene (MMP7) by Southern and PCR analysis of two different panels of somatic cell hybrids and in situ hybridization of metaphase chromosomes. Matrilysin maps to the region, 11q21→q22, adding MMP7 to the cluster of matrix metalloproteinase genes that have already mapped to this region.

It has been hypothesized that tumor promotion in mouse skin involves clonal expansion of initiated cells with activated c-Harvey (Ha)-ras oncogene to give rise to benign tumors. We have used the two stage mouse skin carcinogenesis model using 7,12-dimethylbenz[a]anthracene (DMBA) as the initiator and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) as the tumor promoter to quantitate the number of mutated c-Ha-ras alleles in mouse epidermal DNA. Epidermal samples were harvested over a 12-week period before the appearance of papillomas. Three 61st codon (i.e. CAA) c-Ha-ras mutations, CTA (T2), CGA (G2) and CAT (T3) were quantitated by newly developed nested PCR/RFLP assays. During TPA promotion the number of T2 mutant copies showed a progressive increase starting at 4 weeks after initiation and the number of T3 mutant alleles showed an increase starting at 6 weeks. By 12 weeks after initiation, TPA-promoted mouse epidermis averaged approximately 8x10(5) T2 mutant alleles per epidermis while the number of T3 mutant alleles averaged 3x10(4) per epidermis. The best-fit lines for the quantitation of mutant alleles derived from DMBA/TPA-treated mice from 4 to 12 weeks after initiation were exponential. These results were consistent with clonal expansion of epidermal cells carrying these mutations during tumor promotion. The slopes of the best-fit lines for the mutant copies indicated a trend in which cells with the T2 mutations had a growth advantage during TPA promotion over cells with the T3 mutation.

Matrilysin is a metalloproteinase expressed in a variety of tumors as well as in some types of normal tissue. In addition to regulating normal tissue remodelling, metalloproteinases are believed to play a role in tumor cell invasion and metastasis by degrading components of the extracellular matrix, for example the highly insoluble fibronectin fibrils found in the interstitial stroma. In this study we examined whether matrilysin can degrade fibronectin fibrils produced by human foreskin fibroblasts and characterized the degradation products of soluble fibronectin. Using indirect immunofluorescence microscopy, we demonstrate for the first time degradation of the fibronectin fibrils upon incubation with 15 nM active matrilysin. Removal of matrilysin resulted in regrowth of the fibrils, suggesting that matrilysin was not cytotoxic. Immunoblotting with specific monoclonal antibodies revealed initial degradation of soluble fibronectin within 1 h. Further degradation occurred over a period of 20 h. Degradation of soluble fibronectin resulted in one fragment of 58 kDa containing the gelatin-binding domain, two fragments of 37 and 38 kDa, which were part of the cell attachment domain, and three fragments of 36, 33, and 30 kDa recognized by an antibody raised against the C-terminal heparin-binding domain. In addition to most of these fragments, several intermediates and unique fragments of 31 and 34 kDa could be found in the conditioned medium of human foreskin fibroblasts treated with matrilysin. Isolation of these fragments may allow further studies to determine their influences on cell migration, attachment, and signal transduction, which are expected to be different from the effects of undegraded fibronectin.

The purpose of this study was to characterize stromal-epithelial interactions that result in induction of protease gene expression in squamous cell carcinoma of the skin. Coculture of the human squamous cell carcinoma cell line II4 with primary human foreskin fibroblasts was observed to induce mRNA expression of urokinase-type plasminogen activator (uPa), matrilysin, 92-kDa type IV collagenase, and c-ets, a transcriptional activator of several genes within the serine and matrix metalloprotease families. uPA and c-ets induction were localized to the fibroblast cell population. uPa induction was found to be dependent upon cell-cell contact with the tumor cell population, whereas c-ets induction was due to a combination of cell-cell contact and a tumor cell-derived soluble factor. In contrast, matrilysin induction localized to the tumor cells and was shown by Northern and Western analyses to occur in response to a fibroblast-derived soluble factor. These data demonstrate that both paracrine factors and cell-cell contact between stromal fibroblasts and epithelial tumor cells can influence protease gene expression.

Efficient secondary prevention methods for non-melanoma skin cancers are needed to supplement primary prevention in high-risk individuals. Pharmacologic effects in UV-induced keratinocyte signaling may predict efficacy of new drugs. In order to understand effects of solar light on signal transduction networks in human skin, we exposed buttocks skin of healthy volunteers to solar-simulated light (SSL) at doses 2x-3x of minimum erythemal dose (MED) using a Multiport UV Solar Simulator (Solar Light Co.). Punch biopsies (6 mm) were collected at baseline, 5 min, 1 hr, 5 hr, and 24 hr post-exposure. Biopsies were split with half fixed in formalin and half snap-frozen for Reverse Phase Protein Microarray (RPMA) analysis to identify relevant signaling networks activated by SSL exposure. 24 subjects ≥ 18 y.o. with Fitzpatrick skin type II or III, with no concurrent illness, cancer, or use of photosensitizing drugs were recruited. 12 were exposed to SSL at 2x MED, 6 at 2.5x MED, and 6 at 3x MED. The activation/phosphorylation or total levels of 128 key signaling proteins and drug targets were measured for each sample. Coordinate network-based analysis was performed on specific signaling pathways that included PI3k/Akt/mTOR, Ras/Raf/MEK/Erk, and Fyn/RSK2. Analyte levels were compared at baseline to those at 5 min, 1 hr, 5 hr, and 24 hr after SSL exposure. Unsupervised and supervised statistical analysis was used with Bonferroni multiple comparison adjustment (p < 0.01). Pathway activation maps were constructed using p values to indicate time-dependence of pathway activation. Differences in MED did not significantly affect expression, so all 24 subjects were analyzed independent of SSL dose. Most pathway modulation occurred within the first 5 hr, with cell death and apoptosis-related endpoints maximal at 24 hr. Many kinases were activated within 5 min and activity increased at 1-5 hr before reversing to baseline or lower at 24 hr. Early and sustained activation of p38/SAPK/ ERK pathways started at 5 min, continued through 5 hr and was sustained at 24 hr. Systemic AKT-mTOR pathway activation was observed from 5 min-1 hr, sustained through 5 hr, and decreased at 24 hr. EGFR-HER3 activation followed a similar pattern. COX2 expression increased at 1 hr and was sustained through 24 hr. AMPK was activated early and sustained through 24 hr since LKB1, the dominant AMPK kinase was activated within 5 min-1hr and sustained. Correlation-based network maps were generated and revealed time-dependent SSL induced pathway activation linkages. This work shows that protein pathway activation mapping of phosphorylated proteins in relevant signaling pathways can be used in future studies to determine pharmacodynamic activity of selective topical agents administered in a test area exposed to SSL to determine drug-induced modification of skin carcinogenesis pathways. Citation Format: Steven P. Stratton, Clara Curiel-Lewandrowski, Janine G. Einspahr, Valerie Calvert, Chengcheng Hu, Yira Bermudez, David S. Alberts, George T. Bowden, Emanuel F. Petricoin. Mapping of functional protein pathway modulations in non-sun exposed skin of healthy volunteers using solar simulated light: A new model for pharmacodynamic testing of skin cancer chemopreventive drugs. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3246. doi:10.1158/1538-7445.AM2014-3246

Background Matrix metalloproteinases (MMPs) are involved in tumor progression. Matrilysin (MMP-7) has been shown to be upregulated in prostatic carcinomas and can increase the invasive capacity of DU-145 cells. Because of the heterogenous nature of prostatic tumors, we examined promatrilysin expression in cocultures containing two different prostatic carcinoma cell lines, DU-145 and LNCaP. Methods Using enzyme linked immunosorbent assay (ELISA) analyses, promatrilysin expression was measured in DU-145/LNCaP cocultures and conditioned media cross-cultures. The effects of blocking IL-6 on promatrilysin expression were examined by pretreating conditioned media with IL-6 neutralizing antibody. Results A significant induction of promatrilysin expression was observed in DU-145/LNCaP cocultures compared to LNCaP cells alone. In addition, DU-145 conditioned medium induced the same fold induction of promatrilysin as was observed in the cocultures. LNCaP cell conditioned medium did not induce promatrilysin expression in DU-145 cells. Neutralization of IL-6 with neutralizing antibody abrogated DU-145 conditioned media induced promatrilysin expression to baseline levels. Conclusions IL-6 secreted by DU-145 cells can induce promatrilysin expression in LNCaP cells. IL-6, in vivo, may act as a paracrine signaling factor that regulates matrix metalloproteinase expression. Therefore, IL-6 may play a role in invasive metastatic processes of a prostate carcinoma. Prostate 48:206–209, 2001. © 2001 Wiley-Liss, Inc.

Objective: Previously we have shown that a malignant mouse keratinocyte cell line, 10Gy5, has elevated AP-1 transactivation and reduced JunB protein levels compared to its parental benign cell line, 308, and that the tumorigenicity in the 10Gy5 cells could be blocked by a dominant negative c-Jun mutant protein. We wished to determine whether the change in JunB protein levels could account for the elevated AP-1 activity and whether re-expression of JunB in malignant 10Gy5 cells altered their proliferative capacity. Design: In the current study, we reduced JunB expression in benign 308 cells with antisense oligonucleotides and increased JunB expression in malignant 10Gy5 cells by stable transfection of a JunB expression vector. Results: Increased AP-1 activity was detected after treatment of the benign 308 cell line with JunB antisense oligonucleotides that reduced JunB protein levels. Stably JunB-transfected clones of malignant 10Gy5 cells showed decreased AP-1 activity, slowed in vitro cell proliferation and reduced tumor growth when xenografted to athymic nude mice. Conclusion: These findings suggest that expression of JunB protein has a negative effect on malignant tumor cell proliferation in part through its ability to inhibit AP-1 transactivation.

The shellfish toxin, okadaic acid (OA), is a potent tumor promoter that induces expression of the proto-oncogene junB in mouse keratinocyte 308 cells. Here we show, through deletion analysis of the junB promoter, that sequences near the TATA box conferred transcriptional induction by OA. Transient transfections of luciferase constructs bearing the junB promoter with single mutations in various cis elements demonstrated that a promoter containing a mutated CCAAT box could not be induced by OA. When this CCAAT box was inserted into a heterologous promoter construct, OA induction was dependent on an intact CCAAT box. Flanking cis elements located near the CCAAT box, although not required for OA inducibility, did play a role in the basal level of transcription. NF-Y was shown by EMSA to bind to the CCAAT box. OA induction from the junB CCAAT box was blocked by dominant negative NF-YA as well as the CCAAT box-dependent anticancer drug, ET-473. Expression of a lexA/NF-YA chimeric protein demonstrated that OA induction was dependent on the binding of NF-Y family members. These studies demonstrate that OA can mediate transcriptional activation of junB through the classical CCAAT box and that transcription factor NF-Y plays a functional role in the induction.

The effects of p38 MAP kinase and ERK on UVB induced c-fos gene expression were studied in a human keratinocyte cell line, FL30. UVB significantly increased c-fos gene expression at both the transcriptional and protein levels. p38 and ERK were also significantly activated after UVB irradiation. Treating the cells with p38 inhibitor SB202190 inhibited p38 activation, but not ERK; treating the cells with MEK-1 inhibitor PD98059 inhibited ERK activation without suppressing p38 activation. The kinase activation was determined by Western blots using phospho-p38 or ERK antibodies, or an in vivo p38 activity assay. Further studies demonstrated that blocking p38 almost completely abrogated UVB induced c-fos gene transcription and c-Fos protein synthesis. Inhibiting ERK partially abrogated UVB induced c-fos transcriptional and protein levels. Suppression of both p38 and ERK not only completely blocked UVB induced c-fos expression, but also decreased c-fos gene basal expression. Our data indicated that p38 may play a more important role than ERK in UVB induced c-fos expression in human keratinocytes. Since c-fos expression may play an important role in UVB induced AP-1 activation, and AP-1 activation is known to play a role in tumor promotion, both p38 and ERK could be potential targets for chemoprevention of skin cancer.

Green tea polyphenols have been shown to inhibit cancer in a variety of tumor models, including ultraviolet B (UVB)-induced non-melanoma skin cancer. In green tea extracts, the major dry mass constituent is the family of catechins, of which (-)-epigallocatechin-(3)-gallate (EGCG) is considered to be important for the chemopreventive activity. EGCG has been shown to have antioxidant properties, but there has been little progress toward identifying the specific targets and mechanisms of its action. Using cultured human keratinocytes, we show that UVB-induced AP-1 activity is inhibited by EGCG in a dose range of 5.45 nM to 54.5 microM. EGCG is effective at inhibiting AP-1 activity when applied before, after or both before and after UVB irradiation. EGCG also inhibits AP-1 activity in the epidermis of a transgenic mouse model. This work begins to define a mechanism by which EGCG could be acting to inhibit UVB-induced tumor formation.

Overexpression of the matrix metalloproteinase matrilysin and the absence of beta 4 integrin are two features characteristic of human prostate carcinoma. In the following study we demonstrate that the beta 4 integrin, but not the alpha 6 or beta 1 integrin subunits, is cleaved by matrilysin in vitro. A specific fragment of 90 kDa is generated using matrilysin, which is not observed with other proteases. Two putative cleavage sites for matrilysin within the extracellular domain of the beta 4 integrin at residues 107 (isoleucine, prior to the ligand-binding region) and 417 (leucine, prior to cysteine-rich region) are identified by sequence comparisons with known matrilysin substrates. The selective cleavage of the beta 4 integrin by matrilysin may partly explain the loss of beta 4 integrin expression in invasive prostate carcinoma.

Compelling evidence indicates that p53 acts as a transcription factor and that this activity is regulated by several factors including subcellular localization and phosphorylation status of the protein. To learn more about how these two processes determine whether p53 becomes activated, we studied the temperature sensitive murine p53, p53val135. At nonpermissive temperatures, p53val135 remains sequestered in the cytoplasm of cells which express it. Electrophoretic mobility shift assays demonstrated that, under these conditions, the protein lacked DNA binding activity. However, by shifting to the permissive temperature, p53val135 became concentrated in the nucleus, hyperphosphorylated, and had acquired the ability to bind DNA in a sequence specific manner. This was accompanied by the induction of two p53 regulated genes, mdm2 and p21waf1, which indicated that p53val135 had become an active transcription factor. Two dimensional gel electrophoresis and tryptic peptide mapping showed that entry into the nucleus resulted in the appearance of new phosphorylated isoforms and that the protein had become extensively phosphorylation at the N-terminus. Notably, phosphorylation at the N-terminus occurred only in the nucleus, whereas phosphorylation at the C-terminus could occur in both the cytoplasm and the nucleus. Based on these observations, we suggest that phosphorylation of p53's N-terminus is compartmentally restricted.

The expression of extracellular-matrix (ECM)-degrading proteases has been shown to be necessary for invasion of tumor cells into surrounding tissue. For several tumor types, overexpression of these proteases is dependent upon interactions with adjacent fibroblast cell populations. We previously demonstrated activation of matrix metalloprotease (MMP) and urokinase-type plasminogen activator (uPa) expression in a coculture model consisting of squamous cell carcinoma cells (SCC) with dermal fibroblasts. In the present study we have examined whether melanocytes, which are known to interact closely with keratinocytes of the basal epidermal layer, might influence ECM-degrading protease expression in SCC cells as well. Upon coculture of the human SCC cell line II-4 with the nontumorigenic mouse melanocyte cell line Melan-a or treatment of II-4 cells with Melan-a conditioned media, induction of expression of the MMP matrilysin and uPa was observed. In contrast, no induction was observed for stromelysin-1 or 92-kDa type IV collagenase. Matrilysin/uPa-inducing activity was found to act at the level of gene transcription for both matrilysin and uPa and was ubiquitously expressed among six different human melanocytic cell strains/lines, ranging from primary normal melanocytes to cell lines established from metastatic melanoma lesions. These data demonstrate that melanocytic cells can exert a paracrine influence in SCC cells on the expression of specific proteases involved in ECM turnover and tumor invasiveness.

Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are the most common types of cancers. Since most BCC and SCC develop on sun-exposed areas of the body, chronic sun exposure is considered the main etiologic factor of these tumors. In vitro and in vivo studies have identified PI3K/Akt/mTOR signaling pathway as a solar light-activated pathway. However, little work has been done on studying the expression profiles of this pathway in humans. In the study herein, we evaluate the modulation of solar light-activated PI3K/Akt/mTOR signaling pathway in normal human skin and solar simulated light (SSL)-irradiated human skin to determine the expression profiles of upstream and downstream phosphorylated proteins Akt (Ser473), mTOR (Ser2448), S6 ribosomal protein (Ser235/236), and 4E-BP1 (Thr37/46). The study population consisted of individuals 18 years or older in general good health with skin types II-III. SSL irradiation at 2, 2.5, and 3 times minimal erythema dose (MED) were applied to unexposed skin. Punch biopsies were taken at baseline, 5 minutes, 1 h, 5 h, and 24 h post-irradiation and immediately fixed in 10% formalin. Tissues were evaluated by immunohistochemistry for the expression of phosphorylated proteins. Proliferating cell nuclear antigen (PCNA) and cleaved caspase 3 (Asp175) were evaluated as markers for keratinocyte proliferation and apoptosis, respectively. Induction of phosphorylated Akt was seen at 5 hours with a 2-fold increase in expression when compared to baseline. Expression of phosphorylated mTOR gradually increased with a peak at 24 hours (3-fold). Significant induction of phosphorylated S6 ribosomal protein was seen at 1 h (3-fold), 5 h (7-fold), and 24 h (10-fold) post SSL irradiation. Induction of phosphorylated 4E-BP1 was limited to the 24 h time point with an increase of 2-fold when compared to baseline. Our data corroborate in vitro and in vivo studies finding, which allow for better understanding of the expression profile patterns of phosphorylated proteins in the PI-3 kinase/Akt/mTOR pathway during exposure of physiological relevant solar-simulated light. Identification of key proteins in this pathway could lead to the use of these proteins as biomarkers and/or specific targets for the prevention and control of skin tumors. Citation Format: Yira Bermudez, Steve P. Stratton, Clara Curiel-Lewandrowski, Chengcheng Hu, George T. Bowden, Kathylynn Saboda, David S. Alberts, Janine G. Einspahr. PI3K/Akt/mTOR signaling modulation in solar UV-induced skin carcinogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4264. doi:10.1158/1538-7445.AM2013-4264

Chronic sun exposure is considered the main etiologic agent of non-melanoma skin cancer (NMSC). Inactivation of tumor suppressor p53 and activation of key oncogenic signaling pathways important in cell proliferation and transformation are considered crucial steps in the development of NMSC. Therefore, our overall hypothesis is that topically administered small molecule drugs can modulate specific targets in ultraviolet (UV)-induced signaling cascades resulting in attenuation or reversal of carcinogenic events in human skin. In the study herein, we evaluate the modulation of solar light-activated mTOR and Fyn/RSK2 signaling pathways in normal human skin and solar simulated light (SSL)-irradiated human skin to determine the expression profiles of upstream and downstream phosphorylated proteins p38 (Thr180/Tyr182), p44/42 MAPK (Thr202/Tyr204), histone H3 (Ser10), p90RSK (Thr359/Ser363), Akt (Ser473), mTOR (Ser2448), S6 ribosomal protein (Ser235/236), and 4E-BP1 (Thr37/46). The study population consisted of individuals 18 years or older in general good health with skin types II-III. SSL irradiation at various doses ranging from two to four times the minimal erythema dose (MED) was applied to unexposed skin. Punch biopsies were taken at baseline, 5 minutes, 1 h, 5 h, and 24 h post-irradiation and immediately fixed in 10% formalin. Tissues were evaluated by immunohistochemistry for the expression of phospho-proteins. Proliferating cell nuclear antigen (PCNA) and cleaved caspase 3 (Asp175) were evaluated as markers for keratinocyte proliferation and apoptosis, respectively. Marked SSL-induced changes in human epidermis were seen in the expression of phosphorylated histone H3, S6 ribosomal protein, and 4E-BP1 at 1 h, 5 h, and 24 h post-SSL as compared to control. A linear increase in phosphorylated p44/42 MAPK expression was observed at 1 h, 5 h, and 24 h post-SSL as compared to control. Phosphorylated Akt expression increased post-SSL, and appears dependent on duration and intensity of SSL exposure. Ultimately, the expression profile patterns of phosphorylated proteins in the mTOR and Fyn/Rsk2 pathways will be used to determine activity of new and selective chemoprevention agents being developed to target these SSL-induced skin carcinogenesis pathways. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3673. doi:10.1158/1538-7445.AM2011-3673

The progression of target stem cells through a premalignant to a malignant state during either chemical or radiation carcinogenesis is accompanied by a variety of biochemical, cytological, and morphological changes. These phenotypic alterations result in turn from either qualitative alterations in the encoded gene product or changes in the level of expression of the cellular gene. There are three classes of cellular genes that are known to be altered during carcinogenesis and are thought to play a functional role in tumor formation. One of these classes are the cellular protooncogenes (Bishop 1983; Land et al. 1983; Bowden 1985) that are activated by mutation and encode for products that are involved in growth factor signal transduction. Another class are the tumor suppressor genes (Klein 1987) whose products are involved in regulating cellular growth, differentiation, and senescence. During tumor formation these tumor suppressor genes are inactivated, presumably through mutational events. The third class of genes are effector genes (Zarbl et al. 1991) that are regulated by the oncogenes or the tumor suppressor genes and whose altered expression plays a role in induction or maintainence of various tumor phenotypes. Both chemical carcinogens and ionizing radiation are known to induce the types of activating mutations seen in oncogenes and the inactivating mutations observed in tumor suppressor genes. These mutations can lead to structural changes in encoded gene products or loss of normal control of expression of these genes. An important unanswered question is whether these carcinogens directly induce the mutations found in these critical genes or whether the carcinogens are indirectly involved, perhaps in selection for cells containing spontaneously induced target gene mutations.

The boundary between promotion and progression in experimental carcinogenesis can be operationally defined as long as stable intermediate stages of tumor formation can be identified. Once operational definitions have been made, investigators can and should pursue questions of molecular mechanisms to explain phenotypic changes that occur during promotion and progression. This paper deals with the identification and characterization of molecular markers (i.e., differentially expressed cellular genes) that identify different stages of mouse skin tumor formation. These marker genes whose steady state levels of messenger are elevated at specific stages in skin tumor formation can serve to define the stages of promotion and progression. There is also the possibility that overexpression of one or a number of these genes actually plays a functional role in tumor formation.

Currently prostate cancer is the most commonly diagnosed visceral neoplasm in the male population and the second largest cancer killer of men in the US. While the detection rate of prostate cancer has greatly increased using serum PSA as a screening test, Gleason sum scores and pathologic staging are useful prognostic indicators but cannot accurately predict at the time of biopsy those tumors that will behave aggressively and prove fatal through metastatic dissemination versus those that will remain organ-confined for many years. An important step in metastatic progression of cancer is the remodeling of the extracellular matrix (ECM). Matrix metalloproteases are a family of zinc-dependent enzymes that degrade the components of the ECM in tumor invasion thereby creating a path for migration of neoplastic cells through the basal lamina and into the surrounding stroma. The membrane-type-1 matrix metalloproteases (MT1-MMP), a member of the transmembrane metalloproteases, is found to possess proteolytic activity for ECM proteins including gelatin, fibronectin, K-elastin, vitronectin, collagens and laminin-5 and has been demonstrated to be upregulated in the progression of prostate cancer. In situ hybridization (ISH) techniques have been applied increasingly to localize gene expression at the cytological level. Using reverse-transcriptase polymerase chain reaction (RT-PCR), TOPO cloning, and in vitro synthesis of a unique sequence of MT1-MMP, our aim is to detect its localized expression within prostate cancer sections. Future plans including detecting cadherin and laminin expression patterns on prostate tissue sections.

A complex network of proteins having attachment sites with DNA are known to exist in mammalian cells and have been referred to as a nuclear cage, matrix, scaffold and nucleoid. Since ionizing radiation is known to induce DNA--protein crosslinks as well as DNA single- and double-stranded breaks, an investigation of the sedimentation of the nucleoid in Chinese hamster ovary (CHO)* cells before, during and after treatments with ionizing radiation was undertaken. Using neutral sucrose gradient sedimentation, it was possible to reproducibly separate the protein and DNA components of interphase nucleoids. Under conditions of radiation damage, the DNA and protein components of the nucleoid were shifted to a coincident position in the gradients consistent with the generation of single- and double-stranded DNA scissions. During DNA damage repair, an apparent recruitment of protein to the nucleoid occurred and a rearrangement of the protein sedimentation was observed as the repair of DNA progressed. These data suggest that the protein component of the nucleoid was dynamic under conditions of DNA damage repair.

The damage to hepatic cell DNA caused by i.p. administration of 1,2-dibromoethane (EDB) was studied in male Swiss Webster mice. Three hours after treatment, hepatic nuclei were isolated and damage to DNA assessed by the alkaline elution technique. The method for isolation of the nuclei preserved the integrity of the DNA and in addition it was found that the purified nuclei could be frozen for at least 1 week with no detectable damage to the DNA. EDB administration (25-75 mg/kg) resulted in a dose-dependent increase in DNA single-strand breaks. More DNA single-strand breaks were detected when lysed nuclei were preincubated in the alkaline eluting solution prior to analysis. The presence of these alkali-labile sites suggests that the DNA strand breaks result, in part, from the lability of DNA sites alkylated by EDB. There was no evidence of EDB induced DNA-DNA cross-links or DNA-protein cross-links. The use of isolated hepatic nuclei as a sample for alkaline elution analysis may be a useful technique for studying the nature of DNA damage induced in vivo by carcinogens.

SummaryThe pH step alkaline elution and alkaline sucrose gradient techniques were utilized to evaluate alterations in DNA replication (initiation and elongation) induced by heat and low dose X-irradiation in synchronized Chinese hamster ovary cells. The initiation and elongation processes of DNA synthesis were radioresistant at the G1/S boundary (4 hours after mitosis) while in mid S phase (9 hours after mitosis) DNA initiation and elongation were sensitive to X-irradiation. The initiation and elongation processes of DNA synthesis which were radiation resistant at the G1/S boundary could be inhibited by a hyperthermia treatment (43°C for 1 hour beginning at 4 hours after mitosis). The impairment of initiation in the heated cells was maintained through late S phase while that of elongation was reversible as judged by full recovery at 15 hours after mitosis. These data suggest that the known synergistic lethality of heat and radiation may be mediated by an impairment of initiation of DNA synthesis.

The metabolism, hepatotoxicity, and hepatic DNA damage of 1,2-dibromoethane (EDB) and tetradeutero-1,2-dibromoethane (d 4 EDB) were compared in male Swiss-Webster mice. In vitro studies that measured bromide ion released from the substrate to monitor the rate of metabolism showed that the hepatic microsomal metabolism of EDB was significantly reduced by deuterium substitution, while metabolism by the hepatic glutathione S -transferases was unaffected. Three hours after ip administration of EDB or d 4 EDB (50 mg/kg), there was 42% less bromide in the plasma of d 4 EDB-treated mice than in the plasm of EDB-treated mice. This difference demonstrates a significant deuterium isotope effect on the metabolism of EDB in vivo . Although the metabolism of d 4 EDB was less than that of EDB 3 hr after exposure, the DNA damage caused by both analogs was not significantly different at this time point. At later time points (8, 24, and 72 hr), d 4 EDB caused significantly greater DNA damage than EDB. Since the decreased metabolism of d 4 EDB was apparently due to a reduced rate of microsomal oxidation, these data support the hypothesis that conjugation with GSH is responsible for the genotoxic effects of EDB.

Chinese hamster V79 cells were treated with either (±)-7 β ,8 α -dihydroxy-9 α , 10 α -epoxy-7,8,9,10-tetrahydrobenzo[ a ]pyrene (B[ a ]P-diol epoxide I) or (±)-7 β , 8 α -dihydroxy-9 β ,10 β -epoxy-7,8,9,10-tetrahydrobenzo[ a ]pyrene (B[ a ]P-diol epoxide II) and the nascent DNA was labeled with [ Me - 3 H]thymidine. The cells were harvested for determination of cytotoxicity, sister-chromatid exchanges (SCE), ouabiin-resistant (O r ) mutations and the size of newly synsthesized daughter-strand DNA. Both isomers caused dose-dependent decreases in survival of cells and in the size of nascent DNA. Increases in the frequencies of SCE and of O r mutation were found in cells treated with either isomer. However, B[ a ]P-diol epoxide I caused 10–20-fold more O r mutations and 50–100% more SCE than did B[ a ]P-diol epoxide II at equal molar dose levels. In contrast to the marked difference in the frequencies of both SCE and O r mutations caused by both compounds, the isomers induced similar reductions in the size of the nascent DNA at equal dose levels. In comparing the molecular and biological effects of the two isomers the reduction in the size of nascent DNA was more closely related to cytotoxicity than to the induction of SCE or O r mutations.

The relationship between the direct (i.e., within the target cell itself) induction by tumor promoters of DNA double or single strand scissions and late-stage promotion of a selected tumor cell phenotype in JB6 mouse epidermal cells was investigated. These cells have been shown to respond to late-stage tumor promoters with an irreversible induction of anchorage independent growth. Mezerein, a late-stage tumor promoter in mouse skin, stimulated promotion of anchorage independent growth of JB6 cells without detectable concomitant induction of DNA double or single strand breaks. A single treatment of JB6 cells with benzoyl peroxide, a complete tumor promoter, or H2O2, a weak complete tumor promoter but an efficient Stage I tumor promoter, did not induce anchorage independent growth but did induce DNA single strand scissions. The lack of induction of detectable DNA strand scissions by mezerein, an active promoter of anchorage independent growth, and the existence of promoters which induce DNA strand scissions but not promotion of anchorage independent growth after a single treatment, suggest that direct induction of DNA strand scissions is unrelated to the late-stage promotion of tumor cell phenotype in JB6 cells.

An important feature of the development of many human and animal tumours is the appearance of pre-malignant benign lesions, some of which undergo further changes during progression to malignancy. Many of the currently accepted concepts of multi-stage carcinogenesis have been developed using an experimental model based on the chemical induction of tumours in mouse skin. In this system, many of the premalignant papillomas which arise are promoter-dependent, and appear to regress if promoter treatment is interrupted, whereas others progress to form autonomous benign lesions and, in some cases, malignant carcinomas. Although the number and nature of the events leading to malignancy are not known, DNA transfection experiments have led to the identification of several genes which may be qualitatively altered in tumour cells (see ref. 6 for review). We have previously shown that DNA from transplantable mouse skin carcinomas induced by chemical carcinogens has the ability to transform NIH/3T3 cells, and that the gene responsible for the transformation is an activated form of the mouse cellular Harvey-ras gene (c-rasH). We have now investigated the stage of carcinogenesis at which the proto-oncogene acquires transforming activity. We demonstrate that primary papillomas induced by chemical carcinogens in two different mouse strains have an activated c-rasH gene. This constitutes the first report of a benign tumour which contains DNA with detectable transforming activity. In addition, steady-state levels of c-rasH gene transcripts are elevated in the papillomas as compared with normal epidermis.

Chemical carcinogenesis in mouse skin has been divided into the process of initiation, promotion and progression. Recently we have shown that ionizing radiation acts as an initiator in this model system. In this paper we describe a three-stage experiment using ionizing radiation in the third stage of mouse skin carcinogenesis. CD-1 mice were initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) followed by biweekly promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). After 20 weeks of promotion, the animals were treated with either acetone, TPA (twice a week for 2 weeks) or eight fractions of 1 MeV electrons (1 Gy/fraction over a period of 10 days). The conversion of papillomas to squamous cell carcinomas was 80% for animals treated with ionizing radiation compared with 25% for tumor-bearing animals treated with TPA. Ionizing radiation increased the number of cumulative carcinomas per group. The lack of an increase in the number of cumulative papillomas per group due to ionizing radiation suggests that the dose and fractionation protocol used in this study enhanced the progression of pre-existing papillomas.

The effect of tumor promoters on the in vivo expression of tumor-associated, overexpressed genes was studied. Two of the tumor-associated genes, mal 1 and mal 2 were overexpressed already in the benign papilloma stage of mouse skin carcinogenesis. Overexpression of the other two genes, mal 4 and transin, was specific for the malignant state. Treatment of the normal adult epidermis with the complete tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) and the incomplete, second-stage promoter 12-O-retinylphorbol-13-acetate (RPA) enhanced transiently the expression of the mal sequences and transin. Fractionation of the adult epidermis on Percoll gradients into basal cells and differentiated, suprabasal cells showed that expression of the mal sequences was enhanced by TPA in both basal and differentiated cells. In contrast, transin expression, which was undetectable in cells of the normal epidermis, was enhanced in only the basal cells of the TPA-treated epidermis. The non-tumor-promoting hyperplastic agent, ethylphenyl propiolate (EPP), applied to the skin at a hyperplastic dose level did not enhance the expression of the mal 4 or transin sequences in the epidermis and had only a slight enhancing effect on the levels of mal 1 and mal 2 transcripts in the epidermis. Our results suggest that the observed stimulated expression of mal 1 and mal 2 is related to proliferative processes, whereas stimulated expression of mal 4 and transin reflects tumor-promoter-specific responses.

Vero cells treated with various concentrations of (+/-)7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy, 7,8,9,10-dihydrobenzo(a)pyrene (BP-diol epoxide I) exhibited dose-dependent inhibition in both the rate of DNA synthesis and in the size of nascent DNA. The maximum inhibition was seen 2--3 h after addition of BP-diol epoxide I. A recovery in both the rate of synthesis and size of nascent DNA was observed 5--10 h after treatment. The pH step alkaline elution assay which separates different nascent DNA replication intermediates was used to investigate whether the inhibition and recovery noted above could be accounted for by alterations in DNA replication initiation (DNA synthesis within a replicon) or elongation (rejoining of replicons). At lowest dose studied (0.166 muM BP-diol epoxide I) a reversible inhibition in DNA initiation was observed. At the higher dose levels (0.66 muM and 1.66 muM BP-diol epoxide I) inhibition of both DNA initiation and elongation were observed and inhibition of elongation predominated. The inhibition in elongation was detected by an increase in the relative amount of low molecular weight nascent DNA associated with DNA synthesis within a replicon and a relative decrease in the higher molecular weight elongated DNA. A reversal in the inhibition of both initiationmore » and elongation was noted.« less

The effect of caffeine on Chinese hamster V79 cells after treatment with the highly mutagenic (+/-)-7 beta,8 alpha-dihydroxy-9 alpha, 10 alpha-7,8,9,10-tetrahydrobenzo[a]pyrene, and the weaker mutagen (+/-)-7 beta,8 alpha-dihydroxy-9 beta,10 beta-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, B[a]P-deiol-epoxide II, was studied at both the biological and molecular levels. Caffeine, at nontoxic dose levels, caused a synergistic reduction in cell survival induced by both isomers and also inhibited DNA elongation as measured by alkaline sucrose-gradient analysis of nascent DNA. However, caffeine did not affect the induction of either ouabain-resistant mutants or sister-chromatid exchanges by either isomer. These results suggest that enhanced cell killing by caffeine in benzo[a]pyrene-diol-epoxide treated V79 cells may be related to caffeine's inhibitory effect on DNA elongation. However, inhibition of DNA elongation by caffeine did not influence the resulting induced levels of mutagenesis or sister-chromatid exchanges.

Induction of DNA synthesis by the tumor promoter tetradecanoyl phorbol acetate (TPA) was studied in a line of cultured rat fibroblasts (Rat-1) and their Rous sarcoma virus-transformed derivative (Rat-1 (RSV)). Following serum deprivation for 54 h to achieve quiescence, semiconservative DNA replication was measured by incubation of cells in BrdUrd and FdUrd after serum stimulation in the presence or absence of TPA. Optimal concentrations of TPA (0.1--0.5 microgram/ml) in serum-free medium induced a small increase (10--15%) in the amount of DNA made over a 30-h period in both Rat-1 and Rat-1 (RSV) cells. When Rat-1 cells were stimulated by a 4-h serum pulse, 30% of the DNA was replicated by 30 h. If the serum pulse was followed by TPA addition, 70% DNA replication was observed. If the serum pulse was preceded by TPA addition, the onset of DNA synthesis was delayed by several houses, but stimulation of DNA synthesis occurred. In contrast, the Rat-1 (RSV) cells did not show an increased in DNA synthesis induced by TPA in similar protocols, but the serum-induced onset of DNA synthesis was delayed by several hours in the presence of TPA. Therefore, TPA acts as a co-inducer of DNA synthesis in the Rat-1 but not in the Rat-1 (RSV) cells. The parent alcohol, phorbol, was inactive in Rat-1 cells, but delayed the onset of DNA synthesis in the Rat-1 (RSV) cells. We conclude that the co-inducing and delaying activities of TPA on DNA synthesis appear to be distinct and to act a different points in the G1 phase of the cell cycle.

Evidence is presented to support our previously proposed hypothesis that the hyperplastic effect of tumor promoters is related to their ability to alter existing physiological levels of growth factors in target tissues. Epidermal growth factor and phorbol ester tumor promoters acted synergistically at low (0.001-0.05 ng/ml) but not high (greater than 0.1 ng/ml) EGF concentrations to induce DNA synthesis in cultured Rat-1 fibroblast cells. The degree of synergism correlated with the tumor-promoting ability of the compound. The tumor promoters decreased 125I-EGF binding to cellular receptors in a dose-dependent manner that also correlated with the tumor-promoting ability of the compound. The inhibition of EGF binding by phorbol ester compounds resulted in a decrease in the amount of EGF degraded as compared to control cultures. At limiting EGF concentrations, the sparing of EGF degradation resulted in an increase in the amount of EGF remaining in the culture medium after 12 h of incubation and a concomitant increase in the amount of EGF bound to phorbol ester-treated cells at this time as compared to control cultures. The ability of a phorbol ester compound to alter EGF degradation and to stimulate DNA synthesis synergistically with EGF correlated with the tumor-promoting ability of the compound and occurred only a low EGF concentrations.

The mechanisms by which tumor promoters exert their effects on target tissues are not clearly understood. Recent studies have demonstrated that phorbol ester tumor promoters induce an oxidative burst in phagocytes and DNA single-strand breaks (SSB) in leukocytes. The purpose of the research presented here was to investigate the clastogenic effects of tumor promoters in the target cell population, primary mouse epidermal cells co-incubated with leukocytes. Using the alkaline elution assay to detect DNA SSB, it was demonstrated that tumor promoters induce DNA SSB in primary mouse epidermal cells incubated in the presence of leukocytes. By increasing the ratio of leukocytes to epidermal cells from 1:2 to 10:1, in the presence of 1.6 X 10(-6) M 12-O-tetradecanoylphorbol-13-acetate (TPA), a ratio dependent increase in DNA SSB was observed (from 9 X 10(-2) to 121 DNA SSB per 10(6) nucleotides). A dose response in DNA SSB was seen with TPA over a concentration range of 4 X 10(-9)-1.6 X 10(-6) M. Mezerein, a second stage tumor promoter, induced similar levels of DNA SSB to that of TPA. 4-O-Methyl TPA, a first stage tumor promoter, induced significantly fewer DNA SSB than either TAP or mezerein at similar concentrations. The induction of DNA SSB in epidermal cells treated with TPA and co-incubated with leukocytes was inhibited by catalase but not superoxide dismutase. These data indicate that tumor promoters can act indirectly on target epidermal cells by stimulating the release of a clastogenic factor from leukocytes through a mechanism involving H2O2.

We investigated the ability of retinoic acid (RA) to alter the binding of epidermal growth factor (EGF) to Rat-1 and Swiss mouse 3T3 cells, the EGF-related induction of ornithine decarboxylase (ODC) activity and DNA synthesis. Pretreatment of 3T3 cells with 10 −10 –10 −5 M RA produced a dose-dependent increase in EGF binding. The increased EGF binding appeared to result from an increased number of EGF receptors and did not occur in Rat-1 cells which, unlike 3T3 cells, possessed measureable amounts of cellular retinoic acid binding protein (CRABP). Both cell lines responded to RA pretreatment with an increase in EGF- and TPA-induced ODC activity, without a concomitant increase in DNA synthesis in either cell line. We suggest that the increase in EGF binding induced by RA in 3T3 cells is apparently unrelated to alterations in EGF-induced biological responses and to the presence of CRABP.

Ionizing radiation appears to crosslink nuclear DNA with chromosomal proteins. Important cellular processes such as transcription and DNA replication are likely to be compromised as a result of the DNA crosslinking. Heat treatment (43/sup o/C) of mouse leukemia cells (L1210) before X irradiation (50 Gy) was found to cause a doubling of the radiation-induced DNA crosslinking as measured by alkaline elution technique. By using proteinase K, a very active protease, to eliminate DNA-protein crosslinking in the alkaline elution assay, it was shown that the thermally enhanced DNA crosslinking was attributed to an increase in DNA-protein crosslinking. However, utilizing a protein radiolabel technique under conditions of increased DNA-protein crosslinking, the amount of protein left on the filter in the elution assay was not increased. These data suggest that qualitative rather than large quantitative differences in the crosslinked chromosomal proteins exist between irradiated cells and cells treated with heat prior to irradiation.