Protein Kinase C未 Is a Therapeutic Target in Malignant Melanoma with NRAS Mutation
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- 作者：Asami Takashima ; Brandon English ; Zhihong Chen ; Juxiang Cao ; Rutao Cui ; Robert M. Williams ; Douglas V. Faller
- 刊名：ACS Chemical Biology
- 出版年：2014
- 出版时间：April 18, 2014
- 年：2014
- 卷：9
- 期：4
- 页码：1003-1014
- 全文大小：642K
- 年卷期：v.9,no.4(April 18, 2014)
- ISSN：1554-8937
文摘
NRAS is the second most frequently mutated gene in melanoma. Previous reports have demonstrated the sensitivity of cancer cell lines carrying KRAS mutations to apoptosis initiated by inhibition of protein kinase C未 (PKC未). Here, we report that PKC未 inhibition is cytotoxic in melanomas with primary NRAS mutations. Novel small-molecule inhibitors of PKC未 were designed as chimeric hybrids of two naturally occurring PKC未 inhibitors, staurosporine and rottlerin. The specific hypothesis interrogated and validated is that combining two domains of two naturally occurring PKC未 inhibitors into a chimeric or hybrid structure retains biochemical and biological activity and improves PKC未 isozyme selectivity. We have devised a potentially general synthetic protocol to make these chimeric species using Molander trifluorborate coupling chemistry. Inhibition of PKC未, by siRNA or small molecule inhibitors, suppressed the growth of multiple melanoma cell lines carrying NRAS mutations, mediated via caspase-dependent apoptosis. Following PKC未 inhibition, the stress-responsive JNK pathway was activated, leading to the activation of H2AX. Consistent with recent reports on the apoptotic role of phospho-H2AX, knockdown of H2AX prior to PKC未 inhibition mitigated the induction of caspase-dependent apoptosis. Furthermore, PKC未 inhibition effectively induced cytotoxicity in BRAF mutant melanoma cell lines that had evolved resistance to a BRAF inhibitor, suggesting the potential clinical application of targeting PKC未 in patients who have relapsed following treatment with BRAF inhibitors. Taken together, the present work demonstrates that inhibition of PKC未 by novel small molecule inhibitors causes caspase-dependent apoptosis mediated via the JNK-H2AX pathway in melanomas with NRAS mutations or BRAF inhibitor resistance.