KCTD1 mutants in scalp­ear­nipple syndrome and AP­2α P59A in Char syndrome reciprocally abrogate their interactions, but can regulate Wnt/ß­catenin signaling.

Potassium­channel tetramerization-domain-containing 1 (KCTD1) mutations are reported to result in scalp­ear­nipple syndrome. These mutations occur in the conserved broad­complex, tramtrack and bric a brac domain, which is associated with inhibited transcriptional activity. However, the mechanisms of KCTD1 mutants have not previously been elucidated; thus, the present study aimed to investigate whether KCTD1 mutants affect their interaction with transcription factor AP­2α and their regulation of the Wnt pathway. Results from the present study demonstrated that none of the ten KCTD1 mutants had an inhibitory effect on the transcriptional activity of AP­2α. Co­immunoprecipitation assays demonstrated that certain mutants exhibited changeable localization compared with the nuclear localization of wild­type KCTD1, but no KCTD1 mutant interacted with AP­2α. Almost all KCTD1 mutants, except KCTD1 A30E and H33Q, exhibited differential inhibitory effects on regulating TOPFLASH luciferase reporter activity. In addition, the interaction region of KCTD1 to the PY motif (amino acids 59­62) in AP­2α was identified. KCTD1 exhibited no suppressive effects on the transcriptional activity of the AP­2α P59A mutant, resulting in Char syndrome, a genetic disorder characterized by a distinctive facial appearance, heart defect and hand abnormalities, by altered protein cellular localization that abolished protein interactions. However, the P59A, P60A, P61R and 4A AP­2α mutants inhibited TOPFLASH reporter activity. Moreover, AP­2α and KCTD1 inhibited ß­catenin expression levels and SW480 cell viability. The present study thus identified a putative mechanism of disease­related KCTD1 mutants and AP­2α mutants by disrupting their interaction with the wildtype proteins AP­2α and KCTD1 and influencing the regulation of the Wnt/ß­catenin pathway.

AP-2ß inhibits hepatocellular carcinoma invasion and metastasis through Slug and Snail to suppress epithelial-mesenchymal transition.

Transcription factor AP-2ß plays an important role in human cancer, but its clinical significance in hepatocellular carcinogenesis is largely unknown. Methods: AP-2ß expression was detected in human hepatocellular cancer (HCC) tissues and cell lines. The effects of AP-2ß on HCC proliferation, migration, invasion, tumor formation and metastasis were evaluated by MTT, colony formation and transwell assays in vitro and mouse experiments in vivo. The association between AP-2ß and miR-27a/EMT markers in HCC cell lines and tissues was analyzed. Results: AP-2ß expression was decreased in HCC tissues and cell lines. Reduced expression of AP-2ß was significantly associated with more advanced tumor stages and larger tumor sizes. The overexpression of AP-2ß reduced HCC proliferation, migration, invasion, tumor formation and metastasis in vitro and in vivo. Additionally, AP-2ß overexpression increased the sensitivity of HCC cells to cisplatin. Moreover, AP-2ß modulates the levels of EMT markers through Slug and Snail in HCC cell lines and tissues. Furthermore, oncogenic miR-27a inhibits AP-2ß expression by binding to the AP-2ß 3' untranslated region (UTR) and reverses the tumor suppressive role of AP-2ß. Conclusion: These results suggested that AP-2ß is lowly expressed in HCC by inhibiting EMT signaling to regulate HCC cell growth and migration. Therefore, AP-2ß in the novel miR-27a/AP-2ß/Slug/EMT regulatory axis enhances the chemotherapeutic drug sensitivity of HCC and might represent a potential target for evaluating the treatment and prognosis of human HCC.

Transcription factor AP-2ß suppresses cervical cancer cell proliferation by promoting the degradation of its interaction partner ß-catenin.

Transcription factor AP-2ß mediates the transcription of a number of genes implicated in mammalian development, cell proliferation, and carcinogenesis. Although the expression pattern of AP-2ß has been analyzed in cervical cancer cell lines, the functions and molecular mechanism of AP-2ß are unknown. Here, we found that AP-2ß significantly inhibits TCF/LEF reporter activity. Moreover, AP-2ß and ß-catenin interact both in vitro through GST pull-down assays and in vivo by co-immunoprecipitation. We further identified the interaction regions to the DNA-binding domain of AP-2ß and the 1-9 Armadillo repeats of ß-catenin. Moreover, AP-2ß binds with ß-TrCP and promotes the degradation of endogenous ß-catenin via the proteasomal degradation pathway. Immunohistochemistry analysis revealed a negative correlation between the two proteins in cervical cancer tissues and cell lines. Finally, functional analysis showed that AP-2ß suppresses cervical cancer cell growth in vitro and in vivo by inhibiting the expression of Wnt downstream genes. Taken together, these findings demonstrated that AP-2ß functions as a novel inhibitor of the Wnt/ß-catenin signaling pathway in cervical cancer.

AP-2α inhibits hepatocellular carcinoma cell growth and migration.

Transcription factor AP-2α is involved in many types of human cancers, but its role in hepatocellular carcinogenesis is largely unknown. In this study, we found that expression of AP-2α was low in 40% of human hepatocellular cancers compared with adjacent normal tissues by immunohistochemical analysis. Moreover, AP-2α expression was low or absent in hepatocellular cancer cell lines (HepG2, Hep3B, SMMC-7721 and MHHC 97-H). Human liver cancer cell lines SMMC-7721 and Hep3B stably overexpressing AP-2α were established by lentiviral infection and puromycin screening, and the ectopic expression of AP-2α was able to inhibit hepatocellular cancer cell growth and proliferation by cell viability, MTT assay and liquid colony formation in vitro and in vivo. Furthermore, AP-2α overexpression decreased liver cancer cell migration and invasion as assessed by wound healing and Transwell assays, increasing the sensitivity of liver cancer cells to cisplatin analyzed by MTT assays. Also AP-2α overexpression suppressed the sphere formation and renewed the ability of cancer stem cells. Finally, we found that AP-2α is epigenetically modified and modulates the levels of phosphorylated extracellular signal-regulated protein kinase (ERK), ß-catenin, p53, EMT, and CD133 expression in liver cancer cell lines. These results suggested that AP-2α expression is low in human hepatocellular cancers by regulating multiple signaling to affect hepatocellular cancer cell growth and migration. Therefore, AP-2α might represent a novel potential target in human hepatocellular cancer therapy.