Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Okadaic acid (OA), a potent mouse skin tumor promoter and inhibitor of the protein phosphatases 1 and 2A, was investigated for its effects on the expression of tumor-associated early and secondary response genes in mouse keratinocytes. Adult mice were treated topically with 12.5 nmol of OA, and the steady-state levels of various gene transcripts in the skin were determined at different times after treatment. The nuclear proto-oncogenes c-fos and c-jun are referred to as early response genes because the classical tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) induces their expression to maximal levels within 2 h after treatment. OA induced the expression of c-fos 2-72 h after treatment, with two peaks at 6 and 48 h. The steady-state level of expression of c-jun was relatively high in untreated skin, and OA induced a slight increase in its expression from 12 to 48 h after treatment. Transin and plasminogen-activator (PA) urokinase, whose induced expression peaks at least 4 h after TPA treatment, are referred to as secondary response genes. OA induced their expression more slowly than TPA. In mouse papilloma cell line 308, OA induced higher and more sustained steady-state levels of c-jun and c-fos than an equimolar dose of TPA. Transin and PA-urokinase were induced to similar levels by TPA and OA in 308 cells; however, the induction of these genes by OA was slower than induction by TPA. The existence of different patterns of induced expression of early and secondary response genes by OA and TPA suggests that these tumor promoters affect gene expression in mouse keratinocytes through different pathways.
Mol Carcinog 1992
PMID:Okadaic acid induces the expression of both early and secondary response genes in mouse keratinocytes. 154 37

A single topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA) to mouse skin decreased 125I-labeled epidermal growth factor (EGF) binding in epidermal membrane preparations within 1 h while 1,8-dihydroxy-3-methyl-9-anthrone (chrysarobin) gradually reduced binding with maximum inhibition at 15 h. Subsequently, 125I-EGF binding increased to approximately 200% of control in epidermal membrane preparations from both TPA- and chrysarobin-treated mice. A single application of TPA but not chrysarobin resulted in a rapid translocation of protein kinase C (PKC) to the membrane; however, treatment with both promoters ultimately led to a time-dependent loss of PKC activity in both membrane and cytosol fractions. The initial inhibition of 125I-EGF binding was sustained for at least 24 h after single and multiple treatments with both promoting agents. Acid washing restored EGF binding to control levels in membrane preparations obtained 24 h after a single application, whereas acid washing of membrane preparations obtained 24 h after a second application of TPA or chrysarobin increased binding (2.5-fold and 1.5-fold that of the control, respectively). The presence of increased amounts of ligands for the EGF receptor in tumor promoter-treated epidermis was initially confirmed in 125I-EGF binding competition experiments using NRK-49F cells. A single topical application of TPA or chrysarobin induced elevated levels of transforming growth factor-alpha (TGF-alpha) mRNA at 6 h or 15-24 h, respectively. Elevated levels of a TGF-alpha precursor (21 kDa) were subsequently observed in cytosol and membrane preparations after single and multiple applications of TPA or chrysarobin. These results suggest that repeated topical application of tumor promoters may lead to sustained loss of a negative-feedback mechanism involving phosphorylation at Thr-654 of the EGF receptor by PKC. The concomitant elevation of ligands, such as TGF-alpha, may provide a mechanism for sustained cell proliferation essential for skin tumor promotion.
Mol Carcinog 1991
PMID:Evidence for autocrine/paracrine growth stimulation by transforming growth factor-alpha during the process of skin tumor promotion. 200 35

The study presented here was designed to further investigate the role of transforming growth factor-alpha (TGF alpha) in skin tumor promotion by examining the ability of 12-O-tetradecanoylphorbol-13-acetate (TPA) and several non-phorbol ester promoters to alter TGF alpha mRNA and protein levels in mouse epidermis. Total RNA was isolated from SENCAR mouse epidermis at various times after single topical treatments with TPA (3.4 nmol), chrysarobin (220 nmol), okadaic acid (2.5 nmol), and thapsigargin (8.5 nmol). Northern analyses of these isolated RNA samples revealed that all four tumor promoters transiently elevated TGF alpha mRNA levels. Whereas TPA, okadaic acid, and thapsigarin elevated TGF alpha mRNA levels over similar time courses (peak at 4-8 h), chrysarobin elevated TGF alpha mRNA levels with a markedly delayed time course (peak at 24-48 h). More detailed studies with TPA also revealed that multiple treatments (four over a 2-wk period) transiently elevated TGF alpha mRNA in both the epidermis and the dermis. The time courses for changes in TGF alpha mRNA after multiple TPA treatments were similar for both tissues. To facilitate studies of altered TGF alpha mRNA expression in mouse epidermis and possibly other mouse tissues, a semiquantitative reverse transcriptase-polymerase chain reaction method was developed. This method faithfully revealed changes in TGF alpha mRNA levels with all four tumor-promoting agents similar to those determined by northern blot analyses. Immunofluorescence analysis of frozen sections from promoter-treated skin revealed elevated TGF alpha protein levels in both epidermis and dermis, although staining was most intense in the epidermal layer. Immunofluorescence analysis of epidermal hyperplasia adjacent to a full-thickness wound also demonstrated significant epidermal TGF alpha staining. Collectively, these results indicate that mechanistically diverse tumor promoter stimuli elevate TGF alpha mRNA and protein in SENCAR mouse epidermis. Elevated levels of TGF alpha may play an essential role in mitogenic stimulation during tumor promotion by diverse promoting stimuli.
Mol Carcinog 1995 Apr
PMID:Elevation of transforming growth factor-alpha mRNA and protein expression by diverse tumor promoters in SENCAR mouse epidermis. 772 44

The activation of ras proto-oncogenes by point mutation in a broad spectrum of clinical malignancies and experimentally induced tumors suggests their critical role in cancer induction. To determine whether the activation of ras proto-oncogenes by point mutation also contributes to ultraviolet B radiation (UVB)-induced skin tumorigenesis and whether this event is responsible for the different tumorigenic potentials of UVB radiation in different mouse strains, we analyzed the skin tumors induced by UVB in SKH-1 hairless and C3H mice for specific mutations in the Ha-, Ki-, and N-ras oncogenes. With the same UVB irradiation protocol, the latency period for tumor appearance was longer in C3H mice than in SKH-1 hairless mice. In addition, tumor incidence and multiplicity were also significantly higher (P<0.001, chi square and Wilcoxon rank sum tests) in SKH-1 hairless mice compared with C3H mice. None of the 30 skin tumor specimens (15 from each mouse strain) analyzed by polymerase chain reaction (PCR) amplification of specific codons followed by dot-blot hybridization with specific probes contained mutation in codons 13 of Ha-ras; 12, 13, and 61 of Ki-ras; or 12 and 13 of N-ras. However, three of the 15 tumors in SKH-1 hairless mice showed either a G35-->A or G35-->T transition at second position of Ha-ras codon 12. Interestingly, one of these tumors (with a G35-->A transition) also harbored an A182-->G mutation at second position of Ha-ras codon 61. None of the tumors from C3H mice showed mutations in codons 12 or 61 of the Ha-ras oncogene. With regard to codon 61 of the N-ras oncogene, six tumors from SKH-1 hairless mice and 10 tumors from C3H mice showed an A183-->T transversion. While G35-->A or G35-->T transition detected by PCR and dot-blot hybridization was confirmed by sequencing, the mutations identified similarly at codon 61 in either the Ha- or N-ras oncogenes could not be verified by sequencing of PCR-amplified products subcloned into plasmid vectors. With the exception of the low incidence of Ha-ras oncogene mutations at codon 12 in SKH-1 hairless mouse skin tumors induced by UVB, the striking absence of mutations in the Ha-, Ki-, and N-ras oncogenes in UVB-induced mouse skin tumors suggests that ras oncogene mutations are rare and thus are not an initiating event in photocarcinogenesis.
Mol Carcinog 1996 Feb
PMID:Mutations in ras oncogenes: rare events in ultraviolet B radiation-induced mouse skin tumorigenesis. 859 84

Many studies have shown that all trans retinoic acid (RA) exhibits significant protective effects against mouse skin tumor promotion and spontaneous as well as enhanced malignant conversion. In a recently completed study, we showed that under treatments in which papillomas on SENCAR mouse skin are induced at low and high probabilities to convert to malignant carcinomas, RA affords significant protection against both tumor promotion and subsequent malignant conversion. More than 95% of these mouse skin papillomas and carcinomas have been shown to contain point mutation at the 61 codon of Ha-ras oncogene. The ras oncogene encodes a p21 protein that, in its mutated form, transforms mammalian cells only when p21 is at the inner surface of the plasma membrane, by a series of enzymatic reactions in which the initial step is catalyzed by farnesyltransferase (FTase). In this study, we assessed whether the protective effect of RA against malignant conversion involves the inhibition of ras p21 processing in those tumors that contain the activated ras oncogene. The FTase activity and the levels of cytosolic and membrane-bound Ha-ras p21 were determined in all papillomas and carcinomas obtained from acetone- or RA-treated animals. No matter how the data were analyzed and what comparisons were considered, in all the protocols used, compared with controls, papillomas and carcinomas obtained from RA-treated groups showed significantly decreased (P < 0.01-0.001) FTase activity. Furthermore, the tissue samples from RA-treated groups in different protocols also showed significantly diminished membrane localization of Ha-ras p21, with a concomitant increase in cytosolic Ha-ras p21 levels. The analysis of these data also showed that in all the protocols used, the increased FTase activity and membrane localization of Ha-ras p21 were associated with the induction of papillomas and their subsequent malignant conversion to squamous cell carcinomas. Taken together, these results indicate a strong correlation between the inhibition of ras p21 farnesylation because of a decrease in FTase activity by RA and its protective effect against malignant conversion of papillomas to carcinomas. Based on the results of this study, it is tempting to suggest that clinical trials evaluating the preventive or therapeutic potential of retinoids may be directed more toward those clinical malignancies that are known to contain the activated ras oncogene.
Mol Carcinog 1996 Sep
PMID:Protection against malignant conversion in SENCAR mouse skin by all trans retinoic acid: inhibition of the ras p21-processing enzyme farnesyltransferase and Ha-ras p21 membrane localization. 887 71

To examine the possible role of gap junctions in mouse skin tumor progression, we generated a panel of mouse skin tissue samples exhibiting normal, hyperplastic, or neoplastic changes and characterized the expression of the gap-junction genes connexin 43 (Cx43) and connexin 26 (Cx26) by in situ hybridization and immunohistochemical analyses. In normal skin, these two gap junction genes were differentially expressed; Cx43 was found predominantly in the less differentiated lower spinous layers, whereas Cx26 was found in terminally differentiating upper spinous and granular layers. In hyperplastic epidermis exhibiting an expansion of the differentiated upper layer, i.e., epidermis with a thickened granular layer or in which the granular layer was replaced with keratinocytes exhibiting tricholemmal differentiation, expression of Cx43 and Cx26 remained segregated in the lower and upper spinous layers, respectively. However, in papillomas, Cx26 was localized in the lower but not upper spinous layer, an expression pattern identical to that of Cx43. In addition, the overall expression levels of both Cx43 and Cx26 appeared to be greatly elevated in the papillomas. It is interesting that such marked alteration in the pattern of Cx26 expression occurred within the context of hyperplastic changes histologically identical to those seen in the nonpapillomous hyperplasias. Interestingly, in neoplastic skin lesions containing a squamous cell carcinoma, Cx43 and Cx26 expression was extinguished. Moreover, expression of Cx43 was also significantly reduced in adjacent apparently nonneoplastic tissues. Overall, these observations show that perturbations in gap-junction gene expression are associated with skin hyperplasia and neoplasia. Such findings suggest a possible role for gap junctions in the malignant conversion of mouse epidermal cells.
Mol Carcinog 1996 Oct
PMID:Perturbation in connexin 43 and connexin 26 gap-junction expression in mouse skin hyperplasia and neoplasia. 889 Sep 53

Okadaic acid (OA), a specific inhibitor of protein phosphatases 1 and 2A, is also a potent mouse skin tumor promoter. The effects of OA on regulation of c-jun/activator protein-1 (AP-1) transcriptional activation were investigated in mouse keratinocytes. AP-1 DNA binding to the jun 12-O-tetradecanoylphorbol-13-acetate-response element (TGACATCA) as determined by gel shift analysis was strongly induced by OA (100 ng/mL) at 6 and 12 h. Preincubation of nuclear extracts with anti-c-jun antibody demonstrated that c-jun was a major component of the DNA-bound AP-1 complex induced by OA in 308 cells. Transfection of a c-jun promoter-reporter construct demonstrated that AP-1 transactivation was induced by OA. The mRNA level of the c-jun proto-oncogene was dramatically increased by 6 and 12 h of OA treatment. Furthermore, a significant induction of c-jun protein was stimulated by 6 and 12 h of OA treatment. Upon further analysis, it was found that OA induced a significant accumulation of Ser 73-phosphorylated c-jun protein in 308 cells. In summary, our data suggest that skin tumor promotion by OA is due at least in part to increased AP-1 DNA binding and transactivation mediated by c-jun hyperphosphorylation.
Mol Carcinog 1997 Jan
PMID:Activation of AP-1 by okadaic acid in mouse keratinocytes associated with hyperphosphorylation of c-jun. 902 11

Cyclins and cyclin-dependent kinases (Cdks) are central to regulation of the cell cycle. Their abnormal expression may cause loss of cell-cycle control and result in autonomous cell growth, a critical feature of neoplasias. In this study, using immunoblotting, we analyzed the protein levels of several G1/S cyclins (cyclins D1, D2, D3, A, and E) and their respective Cdks (Cdk 2, 4, and 6) in 17 mouse squamous cell carcinomas (SCCs) and 18 mouse skin tumor cell lines. Overexpression of these cell cycle-related genes was frequent in tumors and cell lines. Of special interest was the fact that a group of cell lines that became more aggressive after animal passaging expressed more cyclins D2 and D3 than their respective parental lines did. In addition, SCCs had higher cyclin D3 expression levels than papillomas, and metastases had higher levels than the respective primary tumors, indicating that overexpression of cyclin D3 may be associated with increased aggressiveness of mouse SCC. Interestingly, overexpression of cyclin E was seen in most SCCs induced by a complete carcinogenesis protocol with benzo[a]pyrene (B(a)P) and only in a few SCCs induced by a two-stage carcinogenesis protocol using 7,12-dimethylbenz[a]anthracene as initiator. In contrast, more of the latter tumors overexpressed cyclin D1 and D2 than those induced by B(a)P. Thus, it is possible that different components of the cell-cycle machinery are involved in proliferative dysfunctions that take place during tumor development with different carcinogenesis protocols. Taken together, these results indicate that overexpression of G1 cyclins and their related Cdks is a significant molecular abnormality that could be involved in the process of tumor progression.
Mol Carcinog 1997 Mar
PMID:Increased expression of G1 cyclins and cyclin-dependent kinases during tumor progression of chemically induced mouse skin neoplasms. 911 84

Transforming growth factor-alpha (TGF alpha) can stimulate keratinocyte proliferation and function as an autocrine tumor promoter in 7,12-dimethylbenz[a]anthracene (DMBA)-initiated TGF alpha-transgenic mouse skin. In this study, we examined the effect of ectopic TGF alpha transgene expression on skin tumor growth and progression after DMBA initiation in the presence of 12-O-tetradecanoylphorbol-13-acetate (TPA). Both the multiplicity and size of skin tumors arising in TGF alpha-transgenic mice were significantly higher than those of the nontransgenic parental CD-1 strain. There were more dysplastic papillomas and squamous cell carcinomas (SCCs) in the transgenic animals as well. ProTGF alpha protein was expressed in transgenic papillomas, but mature TGF alpha was not detected. The epidermal growth factor receptor (EGFR) appeared to be downregulated and was associated with enhanced tyrosine phosphorylation of several substrates in TGF alpha-transgenic mouse tumors. Characteristic codon 61 mutations in the Ha-ras gene were found in most of the papillomas and SCCs induced by DMBA and TPA in transgenic as well as nontransgenic mice. However, no p53 gene mutations were found in any skin tumors from either transgenic or control animals. Analysis of cellular proliferation in both DMBA-TPA-induced papillomas and in skin 48 h after TPA treatment alone revealed significantly more DNA synthesis in TGF alpha-transgenic mice relative to controls. These results demonstrate that TGF alpha, through EGFR overstimulation, can act synergistically with TPA to induce the formation, growth, and development of DMBA-initiated skin tumors containing classic Ha-ras gene mutations but not p53 gene inactivation.
Mol Carcinog 1997 Mar
PMID:Enhanced sensitivity to tumor growth and development in multistage skin carcinogenesis by transforming growth factor-alpha-induced epidermal growth factor receptor activation but not p53 inactivation. 911 86

We previously isolated the 5' upstream sequences of the mouse P-cadherin gene, in which putative binding sites for several transcription factors were identified between nt-101 and +30. In the study reported here, the promoter activity of the postulated 5' cis-acting sequences of the P-cadherin promoter, and the activity of the proximal E-cadherin promoter were investigated in several murine keratinocyte cell lines showing different levels of P- and E-cadherin expression as well as different morphology and tumorigenic behavior. Cell-type specificity and optimal activity of P-cadherin expression in murine keratinocytes was conferred by 5' sequences located between nt -200 and +30, and the GC-rich region (nt -101 to +80) and a CCAAT box element (nt -65) had a major regulatory role. The cell-type specificity of the E-cadherin promoter, on the other hand, was mediated by a combination of positive regulatory elements, a GC-rich region (nt -58 to -24), and a CCAAT box (nt -65) and repressor elements inside the E-pal sequence. Interestingly, the maximum repressor effect of the E-pal element was observed in non-expressing undifferentiated spindle cells. In vitro binding studies indicated that the GC-rich region of the P-cadherin promoter was mainly recognized by Sp1-related nuclear factors, whereas both AP2- and Sp1-related factors were involved in the interaction of the GC-rich region of the E-cadherin promoter. Common factors (probably related to the CP1 family) seemed also to be involved in the recognition of the CCAAT-box element of both the E- and P-cadherin promoters, but additional specific factors participated in the interaction with the CCAAT box of the E-cadherin promoter. Our studies also support the hypothesis that loss or modification of some of the regulatory factors occurs during mouse skin tumor progression.
Mol Carcinog 1997 Sep
PMID:Analysis of the E-cadherin and P-cadherin promoters in murine keratinocyte cell lines from different stages of mouse skin carcinogenesis. 932 34


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