Melanoma is one of the fastest growing cancers in the United States and is accompanied with a poor prognosis owing to tumors being resistant to most therapies. Atypical protein kinase Cs (aPKC) are involved in malignancy in many cancers. We previously reported that aPKCs play a key role in melanoma's cell motility by regulating cell signaling pathways which induce epithelial-mesenchymal Transition (EMT). We tested three novel inhibitors; [4-(5-amino-4-carbamoylimidazol-1-yl)-2,3-dihydroxycyclopentyl] methyl dihydrogen phosphate (ICA-1T) along with its nucleoside analog 5-amino-1-((1R,2S,3S,4R)-2,3-dihydroxy-4-methylcyclopentyl)-1H-imidazole-4-carboxamide (ICA-1S) which are specific to protein kinase C-iota (PKC-ι) and 8-hydroxy-1,3,6-naphthalenetrisulfonic acid (ζ-Stat) which is specific to PKC-zeta (PKC-ζ) on cell proliferation, apoptosis, migration and invasion of two malignant melanoma cell lines compared to normal melanocytes. Molecular modeling was used to identify potential binding sites for the inhibitors and to predict selectivity. Kinase assay showed >50% inhibition for specified targets beyond 5 μM for all inhibitors. Both ICA-1 and ζ-Stat significantly reduced cell proliferation and induced apoptosis, while ICA-1 also significantly reduced migration and melanoma cell invasion. PKC-ι stimulated EMT via TGFβ/Par6/RhoA pathway and activated Vimentin by phosphorylation at S39. Both ICA-1 and ζ-Stat downregulate TNF-α induced NF-κB translocation to the nucleus there by inducing apoptosis. Results suggest that PKC-ι is involved in melanoma malignancy than PKC-ζ. Inhibitors proved to be effective under in-vitro conditions and need to be tested in-vivo for the validity as effective therapeutics. Overall, results show that aPKCs are essential for melanoma progression and metastasis and that they could be used as effective therapeutic targets for malignant melanoma.

中文翻译：

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致癌PKC-1在黑色素瘤的上皮-间质转化过程中激活波形蛋白。基于PKC-1和PKC-ζ特异性抑制剂的研究。

黑色素瘤是美国发展最快的癌症之一，并且由于肿瘤对大多数疗法有抵抗力，因此预后较差。非典型蛋白激酶Cs（aPKC）参与许多癌症的恶性肿瘤。我们先前曾报道aPKCs通过调节诱导上皮-间质转化（EMT）的细胞信号通路在黑素瘤的细胞运动中起关键作用。我们测试了三种新型抑制剂。[4-（5-氨基-4-氨基甲酰咪唑-1-基）-2,3-二羟基环戊基]磷酸二氢甲酯（ICA-1T）及其核苷类似物5-氨基-1-（（（1R，2S，3S， 4R）-2,3-二羟基-4-甲基环戊基）-1H-咪唑-4-羧酰胺（ICA-1S）对蛋白激酶C-iota（PKC-1）和8-羟基-1,3,6具有特异性-萘三磺酸（ζ-Stat）对细胞增殖，凋亡，PKC-ζ（PKC-ζ）具有特异性，与正常黑色素细胞相比，两个恶性黑色素瘤细胞系的迁移和侵袭。使用分子建模来识别抑制剂的潜在结合位点并预测选择性。激酶分析显示，对于所有抑制剂，对于超过5μM的特定目标，抑制率均大于50％。ICA-1和ζ-Stat均显着降低细胞增殖并诱导凋亡，而ICA-1也显着降低迁移和黑色素瘤细胞侵袭。PKC-1通过TGFβ/ Par6 / RhoA途径刺激EMT，并通过在S39处的磷酸化激活波形蛋白。ICA-1和ζ-Stat均通过诱导细胞凋亡而下调TNF-α诱导的NF-κB转运至细胞核。结果表明，PKC-1比PKC-ζ参与黑素瘤恶性肿瘤。抑制剂在体外条件下被证明是有效的，因此需要进行体内测试以作为有效疗法的有效性。总体而言，结果表明，aPKC对于黑色素瘤的进展和转移至关重要，并且可以用作恶性黑色素瘤的有效治疗靶标。