The protective role of manganese superoxide dismutase against adriamycin-induced acute cardiac toxicity in transgenic mice.

Adriamycin (ADR) is a potent anticancer drug known to cause severe cardiac toxicity. Although ADR generates free radicals, the role of free radicals in the development of cardiac toxicity and the intracellular target for ADR-induced cardiac toxicity are still not well understood. We produced three transgenic mice lines expressing increased levels of human manganese superoxide dismutase (MnSOD), a mitochondrial enzyme, as an animal model to investigate the role of ADR-mediated free radical generation in mitochondria. The human MnSOD was expressed, functionally active, and properly transported into mitochondria in the heart of transgenic mice. The levels of copper-zinc SOD, catalase, and glutathione peroxidase did not change in the transgenic mice. Electron microscopy revealed dose-dependent ultrastructural alterations with marked mitochondrial damage in nontransgenic mice treated with ADR, but not in the transgenic littermates. Biochemical analysis indicated that the levels of serum creatine kinase and lactate dehydrogenase in ADR-treated mice were significantly greater in nontransgenic than their transgenic littermates expressing a high level of human MnSOD after ADR treatment. These results support a major role for free radical generation in ADR toxicity as well as suggesting mitochondria as the critical site of cardiac injury.

Antitumor activity of picolinic acid in CBA/J mice.

The growth of a solid tumor induced by im implantation of Ehrlich ascites tumor cells in inbred CBA/J mice was retarded by treatment with an iron chelator, picolinic acid (PLA). Survival of the mice was also significantly increased after PLA treatment. However, the iron chelator deferoxamine had no such effects; tumor growth was slightly enhanced, and survival was decreased.

Lowered superoxide dismutase activity in distant organs of tumor-bearing mice.

Solid tumors were induced by implantation of 5 X 10(6) Ehrlich carcinoma cells im into the right flank of 8- to 12-week-old female CBA/J mice. Tumor-bearing mice were killed at 0, 2, 4, 10, or 24 days after im implantation of the tumor cells, and superoxide dismutase (SOD) activities were determined in liver, spleen, kidneys, lungs, and leg muscle. Depressed SOD activities were seen in all organs studied. In liver, spleen, and kidneys, the manganese SOD (MnSOD) activities were depressed at some point after implantation, even though microscopic examination revealed no evidence of metastases in these organs. Cytochrome c oxidase activity was not diminished in any of the tissues studied, indicating that the decline in MnSOD was not due to a decline in the number of mitochondria or to a general decline in mitochondrial enzymes. When the tumor cells were dialyzed against 0.9% saline, the dialysate contained a factor that when injected im also inhibited SOD activity.

Possible role of glutathione in the antitumor effect of a copper-containing synthetic superoxide dismutase in mice.

The effect of glutathione and a glutathione reductase inhibitor on the antitumor effect of Cu(II)(3,5-diisopropylsalicylate)2 (CuDIPS) was studied. CuDIPS is a low-molecular-weight copper coordination compound that exhibits superoxide dismutase-like activity. CuDIPS had antitumor activity against intraperitoneal Ehrlich ascites carcinoma in Swiss mice. A single ip injection of glutathione partially eliminated the antitumor effect of CuDIPS, whereas a single ip injection of 1,3-bis(2-chloroethyl)-1-nitrosourea enhanced the antitumor effect of CuDIPS. These results are consistent with the hypothesis that CuDIPS exerts part of its antitumor effect by producing H2O2.

Antitumor effect of a copper coordination compound with superoxide dismutase-like activity.

Growth of Ehrlich carcinomas in inbred CBA mice was retarded by im administration of Cu(II)(3,5-diisopropylsalicylate)2 (CuDIPS). CuDIPS is a low molecular weight (mol wt = 503) copper coordination compound that exhibits superoxide dismutase (SOD)-like activity. It has been used as an anti-inflammatory agent and is lipid-soluble. This property enables the compound to penetrate membranes, thus becoming an intracellular O2- scavenger. In the tumor system studied, the amounts of both copper- and zinc-containing SOD (CuZnSOD) and manganese-containing SOD are reduced. Injection of Orgotein (CuZnSOD from bovine liver) had no significant effect on tumor growth and host survival. When CuDIPS was administered at various doses, reduction in tumor size, delay of metastasis, and a significant increase in survival of the hosts were observed.

Redox-mediated effects of selenium on apoptosis and cell cycle in the LNCaP human prostate cancer cell line.

The effects of selenium exposure were studied in LNCaP human prostate cancer cells, and this same cell line adapted to selenium over 6 months to compare acute versus chronic effects of sodium selenite, the latter most closely resembling human clinical trials on the effects of selenium in cancer prevention and therapy. Our results demonstrated that oxidative stress was induced by sodium selenite at high concentrations in both acute and chronic treatments, but outcomes were different. After acute exposure to selenite, cells exhibited mitochondrial injury and cell death, mainly apoptosis. After chronic exposure to selenite, cells showed growth inhibition caused by cell cycle arrest, increased numbers of mitochondria and levels of mitochondrial enzymes, and only minimal induction of apoptosis. Immunoblotting analysis revealed that multiple proteins were up-regulated by chronic exposure to selenite. Among them, only up-regulation of manganese superoxide dismutase and the cyclin-dependent kinase inhibitor p21(Waf1/Cip1), proteins known to be redox sensitive and to have cell cycle regulatory functions, correlated with cell growth inhibition. Our results in selenite-adapted cells suggest that selenium may exert its effects in human prostate cancer cells by altering intracellular redox state, which subsequently results in cell cycle block.

Morphological and immunohistochemical studies of the estrogen-induced Syrian hamster renal tumor: probable cell of origin.

Chronic natural or synthetic estrogen treatment of Syrian golden hamsters leads to the development of malignant renal neoplasms. In the present study, morphological and immunohistochemical studies were performed to further characterize the estrogen-induced hamster renal tumors. The neoplasms were composed of two distinct cell populations: a large-cell component that appeared highly epithelial, and a poorly differentiated small-cell component. Importantly, both cell types had epithelial characteristics, since they contained desmosomes at their cell surfaces. However, the large-cell component possessed additional epithelial features such as microvilli, intracytoplasmic lumens, and cilia. Comparative studies of renal tumors and developing renal tissue from fetal and newborn hamsters revealed remarkable histological similarities. Morphologically, the large tumor cells resembled early metanephric tubules and the small tumor cells were very similar to the blastemal cells of the developing kidney. The earliest tumor foci were found after 4.5 months of treatment. They were consistently found in the kidney interstitium in proximity to large arteries. Immunohistochemical staining for intermediate filaments in developing fetal and newborn kidneys demonstrated cytokeratin in renal tubules, desmin in blastemal cells, and vimentin in stromal cells. Estrogen-induced renal tumor cells uniquely possessed reactivity for all three intermediate filaments, clearly demonstrating their epithelial and mesenchymal characteristics. Based on their morphological resemblance to developing embryonic kidney cells and the presence of both epithelial and mesenchymal intermediate filaments, our findings provide strong evidence that the cell of origin of this malignant tumor is a precursor cell that is committed to an epithelial differentiation pathway.

Dietary intervention at middle age: caloric restriction but not dehydroepiandrosterone sulfate increases lifespan and lifetime cancer incidence in mice.

Dietary manipulations to prevent cancer and other diseases of aging have drawn broad public and scientific attention. One indicator of this interest is that dehydroepiandrosterone (DHEA) supplements are widely consumed by those who hope that this hormone may keep them "younger longer." However, key data to support this belief are lacking. For example, the influence of DHEA treatment on spontaneous cancer and life span in healthy, long-lived strains of mice or rats is unknown. This is in contrast to the situation for caloric restriction (CR), which is known to oppose cancer development and increase maximum life span in rodents. To address this issue, we assigned 300 middle age (12-month-old) male C57BL/6 mice to one of four groups (n = 75 for each group) and evaluated them for longevity and spontaneous disease patterns. Two groups were fed a normal diet (ND), and two others were fed a calorie-restricted diet (RD). One ND group and one RD group were also given 25 microg/ml DHEA sulfate (DHEAS) in their drinking water. Although urine samples from DHEAS-treated mice contained 10-fold more DHEA and DHEAS than did samples from unsupplemented mice, DHEAS administration did not affect body weight, life span, or cancer patterns. The RD lowered body weight by 26% and increased maximum life span by approximately 15%. The incidence of the most prevalent cancer, plasma cell neoplasm, was higher in RD mice (66%) than in ND mice (41%). Thus, DHEAS, as administered here, influenced neither cancer nor longevity at two caloric intakes. In contrast, CR from middle age increased longevity, the age at which tumor-bearing mice died, and the percentage of mice dying with cancers, suggesting that CR may retard promotion and/or progression of existing lymphoid cancers.

Carcinogenic activities of various steroidal and nonsteroidal estrogens in the hamster kidney: relation to hormonal activity and cell proliferation.

The therapeutic use of estrogens has been associated with an increased risk of some of the most predominant, as well as less prevalent, cancers in women. The estrogen-induced renal tumor is one of the primary animal models to evaluate the carcinogenic properties of estrogens. Correlations were made with various estrogens by using parameters of estrogenicity end points such as competitive binding, progesterone receptor induction, and alterations in prolactin levels; in vitro renal proximal cell proliferation; and in vivo estrogen-induced carcinogenicity. The most potent estrogens were Moxestrol (MOX), diethylstilbestrol (DES), and 17 beta-estradiol, followed by indenestrol B, 16 alpha-hydroxyestrone, and 11 beta-methoxyestradiol with moderate estrogenic activities, whereas 11 beta-methylestradiol, 17 alpha-estradiol, indanestrol, and deoxoestrone were all relatively weaker. As expected, hydrolyzed Premarin (unconjugated estrogens) was strongly estrogenic. Of the estrogens tested, MOX was the most potent carcinogenic estrogen in the hamster kidney. Both 16 alpha-hydroxyestrone and 11 beta-methoxyestradiol induced intermediate tumor incidences with distinctly lower frequencies of renal tumor foci compared to the most potent carcinogenic estrogens. However, hamsters treated for 9.0 months with 11 beta-methylestradiol, 17 alpha-estradiol, deoxoestrone, and indanestrol exhibited no tumors. In contrast, treatment with estrone, equilin plus d-equilenin, and hydrolyzed Premarin for the same time period resulted in 100% renal tumor incidences and numerous tumor foci. Cell proliferation studies of cultured hamster kidney proximal tubule cells were carried out at varying estrogen concentrations (0.01-100 nM). Exposure to MOX resulted in consistently high renal cell proliferative response over a concentration range of 0.1-10 nM. Strongly carcinogenic estrogens such as estrone had a maximal renal cell proliferation response (2.4-fold above untreated control levels) between 0.1 and 10 nM, DES and 17 beta-estradiol responded at 1.0 nM, and 4-hydroxyestradiol responded at 10 nM. Interestingly, exposure to ethinylestradiol, a potent estrogen, at similar or higher doses as those used for DES and 17 beta-estradiol, yielded only a 10% renal tumor incidence and induced only a 1.7-fold increase in proximal tubule cell proliferation. In contrast, 17 alpha-estradiol, deoxoestrone, indanestrol, and 11 beta-methylestradiol, all weakly estrogenic and noncarcinogenic agents, had relatively little effect on tubule cell proliferation. The hydrolyzed Premarin exhibited a maximal 2.0-fold cell proliferative response at 10 nM. The present results provide clear evidence that, in the hamster kidney, the degree of carcinogenicity of a given estrogen correlates with its ability to induce proximal tubule cell proliferation in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of human uroepithelial cells immortalized in vitro by simian virus 40.

Normal human uroepithelial cells (HUC) were transformed with simian virus 40 (SV40) in vitro. SV40-transformed HUC (SV-HUC) were selected by their ability to survive senescence which normally occurs in HUC between passages 4 and 6. At passage 6, 100% of SV-HUC stained positive for SV40 T-antigen. The epithelial nature of SV-HUC was confirmed by positive staining for human cytoplasmic keratins in all cells. SV-HUC have altered growth characteristics compared to HUC including the capacity to grow on plastic, independent of a collagen-gel substrate; loss of the dependence on medium supplements for optimal growth, loss of the dependence on feeder cells for growth at clonal density, and an apparently unlimited lifespan in culture (greater than 2 years). Although SV-HUC have an increased percentage of viable cells and increased saturation density compared to HUC, the generation time of SV-HUC during log phase is similar to that of HUC. Cultures of SV-HUC are epithelial in appearance and show some morphological heterogeneity in cell size and shape. At the ultrastructural level, SV-HUC have numerous alterations such as, irregularly shaped nuclei and nucleoli, pleomorphic microvilli, and the lack of a glycocalyx on the cell surface. In addition, SV-HUC does not stratify in culture, suggesting an inability to differentiate. Unlike HUC, SV-HUC are capable of growth in soft agarose, a property which increased with serial passage. Yet, through at least P50, SV-HUC remained nontumorigenic as determined by the inability to form tumors in athymic nude mice. This cell line of human epithelial origin may be suitable for studying the conversion of cells to tumorigenicity by subsequent treatment with another oncogenic agent.

Suppression of fibrosarcoma metastasis by elevated expression of manganese superoxide dismutase.

A mouse fibrosarcoma cell line (FSa-II), which exhibits low endogenous levels of manganese superoxide dismutase, was transfected with a human manganese superoxide dismutase complementary DNA. Fifty clones were screened for manganese superoxide dismutase activity by the superoxide dismutase activity gel assay. Activity of the positive clones was measured by the nitro blue tetrazolium-reduction assay in the presence of cyanide. Three cell lines exhibiting a range of activity were chosen to be transplanted into syngeneic mice. The results indicated that the metastasis rate for all transfected cells was significantly less than that of control cells.

Comparison of effects of two polymorphic variants of manganese superoxide dismutase on human breast MCF-7 cancer cell phenotype.

Two polymorphic variants of manganese superoxide dismutase (MnSOD), with either Ile or Thr at amino acid 58, (Ile58MnSOD or Thr58MnSOD), have been found in the human population. The MnSOD activity of these two variants and their effects on the malignant phenotype of human breast cancer MCF-7 cells were compared. It was demonstrated that MnSOD-overexpressing clones obtained from transfection of the two MnSOD cDNAs into MCF-7 cells had increased MnSOD immunoreactive protein and increased MnSOD activity. Cells overexpressing Ile58MnSOD had 3-fold higher MnSOD activity than cells overexpressing Thr58MnSOD in vivo at an equal MnSOD protein level. Tumor-suppressive effects of MnSOD-overexpressing cells were indicated by: (a) decreased plating efficiency; (b) elongated cell population doubling time; (c) lower clonogenic fraction in soft agar; and (d) complete inhibition or delayed onset of tumor formation in nude mice. When compared on the same activity basis, the suppressive effects of Ile58MnSOD were similar to those of Thr58MnSOD. However, far more Thrs58MnSOD protein was required to obtain the same amount of MnSOD activity, making the Thr58MnSOD far less effective. A dose-response suppressive effect was observed when the increase of MnSOD activity was moderate. We conclude that MnSOD is a tumor suppressor in human breast cancer, but the Thr58 form of the protein is a much less effective tumor suppressor than the Ile58 form of the protein.

Cell culture of human colon adenomas and carcinomas.

Cell lines were established from colon adenomas, including tubular and villous polyps, primary adenocarcinomas, and metastases arising in patients with colon adenocarcinomas. The protocol for cultivating these diverse tissues includes primary cultivation of tissue explants on a type I collagen gel followed by nonenzymatic subculture of the epithelial outgrowth. All early passages were accomplished using low subculture ratios. Cultured cells elaborate morphological structures which are similar to features present in the tissues from which they were cultivated. Specifically, all structural features of colon epithelial cells were identified, including junction formation, prominent microvilli, and mucin secretion, in several cell lines. Five cell lines cultured from colonic neoplasms at different stages of cancer progression were selected for detailed characterization. Cells grown from two tubular polyps had normal human karyotypes. Cells from a villous polyp and all adenocarcinomas were aneuploid with stable marker chromosomes. The established cell lines exhibit distinct phenotypes based on growth characteristics in vitro and in athymic mice; and it is suggested that these cell lines represent useful models for studying the evolution of colon cancer from a benign to an aggressive cell type.

Characterization of early kidney lesions in estrogen-induced tumors in the Syrian hamster.

Syrian hamsters were treated with diethylstilbestrol (DES), a potent estrogen and kidney carcinogen, or ethinyl estradiol (EE), a strong estrogen but weak carcinogen, for 1-9 months. At monthly intervals their kidneys were studied using light, immunoperoxidase, and electron microscopic techniques. At 5 months, DES-treated animals exhibited interstitial lesions composed of small round cells with a high nuclear:cytoplasmic ratio. Immunoperoxidase and ultrastructural studies showed these cells to be similar to cells in fully formed tumors at 9 months. Early lesions in EE-treated animals (seen as early as 1 month) were dissimilar, these lesions appeared in the deep cortex adjacent to the renal pelvis, where proximal tubules underwent hyperplastic changes, showing columnar cells with large nuclei, occasional mitoses, and sloughing of apical cytoplasm. Cells in early lesions of EE-treated animals did not resemble the fully developed tumor in either immunoperoxidase or ultrastructural features; although with longer treatment these tubular lesions progressed to dysplasia (3-5 months) and severe dysplasia/carcinoma in situ (7 months), they did not form grossly visible tumors during the 9-month study. Both early lesions identified were specific, inasmuch as they were not observed in control animals and animals treated with beta-dienestrol and 17 alpha-estradiol (noncarcinogenic weak estrogens). Animals given a combination of DES and EE showed tubular hyperplasia but not interstitial lesions; this finding was of particular interest because hamsters given this combination of estrogens do not develop gross renal tumors. These results strongly implicate the primitive interstitial cell in the hamster kidney as the cell of origin of the DES-induced neoplasm.

The role of cellular glutathione peroxidase redox regulation in the suppression of tumor cell growth by manganese superoxide dismutase.

Manganese-containing superoxide dismutase (MnSOD) is an essential primary antioxidant enzyme that converts superoxide radical to hydrogen peroxide and molecular oxygen within the mitochondrial matrix. Cytosolic glutathione peroxidase (GPX) converts hydrogen peroxide into water. MnSOD is reduced in a variety of tumor types and has been proposed to be a new kind of tumor suppressor gene, but the mechanism(s) by which MnSOD suppresses malignancy is unclear. According to the enzymatic reactions catalyzed by MnSOD and cytosolic GPX, change in the cellular redox status, especially change attributable to accumulation of hydrogen peroxide or other hydroperoxides, is a possible reason to explain the suppression of tumor growth observed in MnSOD-overexpressing cells. To test this possible mechanism, we transfected human cytosolic GPX cDNA into human glioma cells overexpressing MnSOD. The results showed that GPX overexpression not only reversed the tumor cell growth inhibition caused by MnSOD overexpression but also altered the cellular contents of total glutathione, reduced glutathione, oxidized glutathione, and intracellular reactive oxygen species. Overexpression of GPX also inhibited degradation of the inhibitory subunit alpha of nuclear factor-KB. These results suggest that hydrogen peroxide or other hydroperoxides appear to be key reactants in the tumor suppression by MnSOD overexpression, and growth inhibition correlates with the intracellular redox status. This work suggests that manipulations that inhibit peroxide removal should enhance the tumor suppressive effect of MnSOD overexpression.

Expression of manganese superoxide dismutase reduces tumor control radiation dose: gene-radiotherapy.

This study investigated the in vitro and in vivo radiation response of tumor cells transfected with human manganese superoxide dismutase (MnSOD) cDNA. A major objective was to test the potential tumor suppressive effect of MnSOD in vivo. Tumor cells studied were an in vitro line derived from a murine spontaneous fibrosarcoma, FSa-II, which expressed an undetectable MnSOD activity. These cells were transfected with pSV2-NEO plasmid (NEO line) or cotransfected with MnSOD plasmid plus pSV2-NEO plasmid (SOD lines) as described previously. The cell lines used were SOD-L and SOD-H, which expressed, respectively, low and high MnSOD activities after transfection, and NEO and parental FSa-II controls. Both SOD-L and SOD-H cell lines were slightly more resistant to ionizing radiation than were the two control cell lines when irradiated in vitro in the presence of oxygen. The dose-modifying factors calculated at the survival level of 0.01 were 1.13 and 1.15 for the SOD-L and SOD-H cells, respectively. To investigate potential tumor suppressive effects, animal tumors of 4 mm diameter were irradiated in vivo under hypoxic conditions, and the radiation dose to control one-half of the irradiated tumors (TCD50) was determined for each tumor. The TCD50S obtained on the basis of the tumor control rate in 120 days after irradiation were substantially lower for the SOD-H and SOD-L tumors compared to the NEO tumors. They were 22.9, 28.6, and 47.5 Gy for SOD-H, SOD-L and NEO tumors, respectively. To analyze these data, survival curves were obtained for hypoxic cells by irradiating NEO and SOD-H tumors under hypoxic conditions in vivo and assaying in vitro. Analysis of these curves suggests that the decrease in the TCD50S of SOD tumors is attributable to the reduced tumorigenicity in these tumors. The hypoxic cell survival curves also showed that SOD did not protect cells from radiation in the absence of oxygen. Electron microscopy showed no morphological differences between these cells. These results suggest that the fraction of tumorigenic cells could be reduced by expression of MnSOD, resulting in a substantial decrease in the TCD50.

Transgenic mice overexpressing protein kinase C epsilon in their epidermis exhibit reduced papilloma burden but enhanced carcinoma formation after tumor promotion.

To determine the role that protein kinase C epsilon (PKCepsilon) may play in skin growth, differentiation, and tumor promotion, transgenic mice were generated that overexpressed an epitope-tagged protein kinase C epsilon (T7-PKCepsilon) in their epidermis using the human keratin 14 promoter. Three independent mouse lines that overexpressed the T7-PKCepsilon in their epidermis were produced. The three independent lines 206, 224, and 215 exhibited a 3-, 6-, and 18-fold elevation, respectively, in the level of PKCepsilon immunoreactive protein. Line 215 exhibited a 19-fold greater phosphatidylserine and 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulated kinase activity than line 224. Line 206 exhibited a low basal T7-PKCepsilon activity, which failed to be stimulated by phosphatidylserine and TPA. All of the line 215 transgenic mice (F0 to the F2 generation) displayed phenotypic changes in the skin. The phenotypic changes progressed gradually, starting around 4-5 months of age, with mild dryness of the tail accompanied by hair loss and inflammation at the base of the tail. Hyperproliferation and ulceration of the affected regions were observed around 7-8 months of age. The hyperproliferative epidermis from the affected regions exhibited an expansion of the suprabasal epidermal cells. Inflammation and/or ulceration were also observed in the dorsal skin, the ears, and around the eyes. The line 215 mice, which expressed the highest level of PKCepsilon, were evaluated for sensitivity to mouse skin tumor promotion by TPA. Tumors were elicited by the initiation (7,12-dimethylbenz[a]anthracene, 100 nmol)-promotion (TPA, 5 nmol/twice weekly) protocol. The papilloma burden was reduced by 95-96% for male and female T7-PKCepsilon mice compared to wild-type controls. However, carcinomas developed rapidly in the T7-PKCepsilon mice treated with 7, 12-dimethylbenz[a]anthracene and TPA. These carcinomas appeared to form independently of prior papilloma development. These results demonstrate that PKCepsilon is an important regulator of skin tumor development.

Transgenic mice overexpressing protein kinase Cdelta in the epidermis are resistant to skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate.

To determine the role of protein kinase Cdelta in mouse skin carcinogenesis, we have developed transgenic FVB/N mouse lines expressing in the epidermis an epitope-tagged protein kinase Cdelta (T7-PKCdelta) regulated by the human keratin 14 promoter. The untreated T7-PKCdelta mice displayed excessive dryness in the skin of the tail with a variable penetrance over time. Histologically, the tail skin showed hyperplasia with evidence of hyperkeratosis. The epidermis of the rest of the T7-PKCdelta mouse was unremarkable. Despite this mild phenotype, the effects of PKCdelta overexpression on mouse skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA) were dramatic. Two independent lines of T7-PKCdelta mice (16 and 37) expressing the T7-PKCdelta transgene were examined for responsiveness to skin tumor promotion by 7,12-dimethylbenz[a]anthracene and TPA. By immunoblot analysis, the T7-PKCdelta-16 and T7-PKCdelta-37 mice showed an 8- and 2-fold increase of PKCdelta protein. The T7-PKCdelta-16 mice averaged 300% more T7-PKCdelta activity than the T7-PKCdelta-37 mice did. The T7-PKCdelta-37 mice did not manifest any difference in tumor burden or incidence. However, the reduction in papilloma burden at 25 weeks of promotion for the T7-PKCdelta-16 mice relative to wild-type mice averaged 72 and 74% for males and females, respectively. The T7-PKCdelta-16 mice reached 50% papilloma incidence between 12 and 13 weeks of promotion compared with 8 weeks for wild-type mice. Furthermore, the carcinoma incidence was also reduced in T7-PKCdelta-16 mice. Carcinoma incidence at 25 weeks of promotion treatment was: wild-type females, 78%; T7-PKCdelta16 females, 37%; wild-type males, 45%; and T7- PKCdelta-16 males, 7%. Thus, PKCdelta when expressed at sufficient levels can suppress skin tumor promotion by TPA.

Protein kinase C-epsilon transgenic mice: a unique model for metastatic squamous cell carcinoma.

Squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) are the most common forms of human skin cancer. BCC is slow growing and mostly localized, whereas SCC metastasizes to the regional lymph nodes and subsequently to distal organs. In murine skin carcinogenesis models for SCC, the incidence of metastasis is very low. We report here that FVB/N transgenic mice, which overexpress (approximately 18-fold) epitope-tagged protein kinase C-epsilon (T7-PKCepsilon) protein in the epidermis provide a unique murine model system for highly malignant/metastatic SCC. Skin tumors were developed by the initiation-promotion protocol (initiation with 100 nmol 7,12-dimethyl-benz[a]anthracene; promotion with 5 nmol 12-O-tetradecanoylphorbol-13-acetate twice weekly). T7-PKCepsilon transgenic mice showed 92% suppression of papilloma development compared with wild-type littermates after 23 weeks of tumor promotion. However, within 15-20 weeks of 12-O-tetradecanoylphorbol-13-acetate promotion, 40% of T7-PKCepsilon mice developed at least one carcinoma compared with 7% of the wild-type mice. All carcinomas from T7-PKCepsilon mice appeared without prior papilloma formation. Interestingly, 7,12-dimethyl-benz[a]anthracene alone resulted in the development of squamous cell carcinomas in 22% of T7-PKCepsilon mice, whereas wild-type littermates developed no tumors. Histopathological analysis of tumors from multiple T7-PKCepsilon mice revealed moderately differentiated SCC invading the dermal region with neoplasia appearing to originate and invade from the hair follicle. Carcinomas of T7-PKCepsilon mice rapidly metastasized to regional lymph nodes within 3 weeks of appearance. In wild-type mice, the grade of the invading tumors, originating from interfollicular epidermis, was pathologically categorized as well-differentiated SCC and remained localized to the dermis. The T7-PKCepsilon transgenic mice may provide a rapid and unique in vivo model to investigate metastatic SCC.

Overexpression of manganese superoxide dismutase suppresses tumor formation by modulation of activator protein-1 signaling in a multistage skin carcinogenesis model.

Manganese superoxide dismutase (MnSOD) is a nuclear encoded primary antioxidant enzyme localized in mitochondria. Because expression of MnSOD plays a major role in maintaining cellular redox status and reactive oxygen species are known to play a role in signal transduction and carcinogenesis, we investigated the role of MnSOD in the development of cancer using a two-stage [7,12-dimethylbenz(a)-anthracene plus 12-O-tetradecanoylphorbol-13-acetate (TPA)] skin carcinogenesis model. Female transgenic mice expressing the human MnSOD gene in the skin and their nontransgenic counterparts were used in this study. Pathological examination demonstrated significant reduction of papilloma formation in transgenic mice. Quantitative analysis of 4-hydroxy-2-nonenal-modified proteins showed greater accumulation of oxidative damage products in nontransgenic compared with transgenic mice, and this oxidative damage was demonstrated to be present in both mitochondria and nucleus. TPA increased activator protein-1 (AP-1) binding activity within 6 h in nontransgenic mice, but increased AP-1 binding activity was delayed in the transgenic mice. Electrophoretic mobility shift assay, transcription of the target genes, and Western analysis studies indicated that the increased AP-1 binding activity was attributable to induction of the Jun but not the Fos protein families. Overexpression of MnSOD selectively inhibited the TPA-induced activation of protein kinase Cepsilon and prevented subsequent activation of c-Jun NH(2)-terminal kinase in response to TPA. Overall, these results indicate that MnSOD regulates both cellular redox status and selectively modulates PKCepsilon signaling, thereby delaying AP-1 activation and inhibiting tumor promotion, resulting in reduction of tumors in MnSOD transgenic mice.