ABSTRACT
The tumor promoter 12-O-tetra-decanoylphorbol-13-acetate (TPA) has been defined by its ability to promote tumorigenesis on carcinogen-initiated mouse skin. Activation of Wnt/ß-catenin signaling has a decisive role in mouse skin carcinogenesis, but it remains unclear how TPA activates Wnt/ß-catenin signaling in mouse skin carcinogenesis. Here, we found that TPA could enhance Wnt/ß-catenin signaling in a casein kinase 1 (CK1) ε/δ-dependent manner. TPA stabilized CK1ε and enhanced its kinase activity. TPA further induced the phosphorylation of LRP6 at Thr1479 and Ser1490 and the formation of a CK1ε-LRP6-axin1 complex, leading to an increase in cytosolic ß-catenin. Moreover, TPA increased the association of ß-catenin with TCF4E in a CK1ε/δ-dependent way, resulting in the activation of Wnt target genes. Consistently, treatment with a selective CK1ε/δ inhibitor SR3029 suppressed TPA-induced skin tumor formation in vivo, probably through blocking Wnt/ß-catenin signaling. Taken together, our study has identified a pathway by which TPA activates Wnt/ß-catenin signaling.
Subject(s)
Carcinogens/toxicity , Casein Kinase 1 epsilon/metabolism , Casein Kinase Idelta/metabolism , Skin Neoplasms/pathology , Tetradecanoylphorbol Acetate/toxicity , Wnt Signaling Pathway/drug effects , Animals , Axin Protein/metabolism , Carcinogenesis/chemically induced , Carcinogenesis/pathology , Casein Kinase 1 epsilon/antagonists & inhibitors , Casein Kinase Idelta/antagonists & inhibitors , Cell Line, Tumor , Disease Models, Animal , Fibroblasts , HEK293 Cells , Humans , Low Density Lipoprotein Receptor-Related Protein-6/metabolism , Mice , Phosphorylation , Protein Stability/drug effects , Purines/pharmacology , Skin Neoplasms/chemically induced , Transcription Factor 4 , Wnt Proteins/metabolism , beta Catenin/metabolismABSTRACT
We investigated the effect of thalidomide on cachexia and TNF-α serum levels during experimental skin carcinogenesis in mice. Female mice were divided into four groups: 1) DMBA (dissolved in acetone) induced tumorigenesis; 2) DMBA and Thalidomide (dissolved in DMSO); 3) DMBA and DMSO; and 4) Acetone. Body weight was measured once a week. Euthanasia was performed 14 weeks later, when blood was collected for the dosage of TNF-α serum levels. Mice with DMBA induced tumorigenesis had a significant loss of body weight when compared to acetone treated animals, starting at the third week and lasting the whole experiment. But there was no difference among Thalidomide treated and the others DMBA control animals, regarding body weight. High TNF-α serum levels were associated with the development of cachexia in mice during the process of experimental skin tumorigenesis. However, there was not a significant difference in the TNF-α serum levels when compared control mice and thalidomide treated mice. These results suggest that thalidomide does not interfere with skin tumorigenesis, cachexia and serum TNF-α levels in Balb/C mice. In addition, high TNF-α serum levels are associated to weight loss during experimental carcinogenesis.
