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The serine-threonine mitogen-activated protein kinase kinase family member T-LAK cell-originated protein kinase (TOPK/PBK) is heavily involved in tumor development, cancer growth, apoptosis, and inflammation. Despite the identification of TOPK as a promising novel therapeutic target, no inhibitor of TOPK has yet been reported. In this study, we screened 36 drug candidates using an in vitro kinase assay and identified the novel TOPK inhibitor HI-TOPK-032. In vitro, HI-TOPK-032 strongly suppressed TOPK kinase activity but had little effect on extracellular signal-regulated kinase 1 (ERK1), c-jun-NH 2 -kinase 1, or p38 kinase activities. HI-TOPK-032 also inhibited anchorage-dependent and -independent colon cancer cell growth by reducing ERK-RSK phosphorylation as well as increasing colon cancer cell apoptosis through regulation of the abundance of p53, cleaved caspase-7, and cleaved PARP. In vivo, administration of HI-TOPK-032 suppressed tumor growth in a colon cancer xenograft model. Our findings therefore show that HI-TOPK-032 is a specific inhibitor of TOPK both in vitro and in vivo that may be further developed as a potential therapeutic against colorectal cancer. Cancer Res; 72(12); 3060-8. Ó2012 AACR.

PURPOSE Common treatment modalities for non-small cell lung cancer (NSCLC) involve the epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) like gefitinib and erlotinib. However, the vast majority of treated patients acquire resistance to EGFR-TKIs, due in large part to secondary mutations in EGFR or amplification of the MET gene. Our purpose was to test ubiquitin-specific peptidase 8 (USP8) as a potential therapeutic target for gefitinib-resistant and -sensitive non-small cell lung cancer (NSCLC). EXPERIMENTAL DESIGN Testing the effect of knockdown of USP8 and use of a synthetic USP8 inhibitor to selectively kill gefitinib-resistant (or -sensitive) NSCLCs with little effect on normal cells in cell culture and a xenograft mouse model. RESULTS Knockdown of ubiquitin-specific peptidase 8 (USP8) selectively kills gefitinib-resistant NSCLCs, while having little toxicity toward normal cells. Genetic silencing of USP8 led to the down-regulation of several receptor tyrosine kinases (RTKs), including EGFR, ERBB2, ERBB3, and MET. We also determined that a synthetic USP8 inhibitor markedly decreased the viability of gefitinib-resistant and -sensitive NSCLC cells by decreasing RTK expression, while having no effect on normal cells. Moreover, treatment with a USP8 inhibitor led to significant reductions in tumor size in a mouse xenograft model using gefitinib-resistant and -sensitive NSCLC cells. CONCLUSIONS Our results demonstrate for the first time that the inhibition of USP8 activity or reduction in USP8 expression can selectively kill NSCLC cells. We propose USP8 as a potential therapeutic target for gefitinib-resistant and -sensitive NSCLC cells.

Ultraviolet (UV) irradiation is the most important factor contributing to the development of skin cancer. The use of chemopreventive agents, especially naturally occurring plant products, to prevent skin cancer caused by UV might an effective therapeutic or preventive intervention. Using in silico virtual screening of the Chinese Medicine Library, we identified norathyriol as a potential ERK2 inhibitor. Norathyriol is a metabolite of mangiferin, which is found in mango, Hypericum elegans, and Tripterospermum lanceolatum, and has potent anticancer-promoting activity. Here, we show that norathyriol inhibits ERK1/2 kinase activities and attenuates UVB-induced phosphorylation of the mitogen-activated protein kinase (MAPK) cascades. Direct binding of norathyriol with ERK2 was confirmed by a co-crystal structure. The norathyriol xanthone moiety acts as an adenine mimeric and anchors the compound by hydrogen bonds to the hinge region of the protein ATP-binding site. Norathyriol inhibited cell growth in mouse skin epidermal JB6 P+ cells by inducing G2-M phase arrest. Mouse skin tumorigenesis data clearly showed that treatment with norathyriol significantly suppressed solar UV-induced skin carcinogenesis in vivo. Results also indicated that norathyriol exhibits a potent chemopreventive activity through the inhibition of transcription factor AP-1 and NF-κB by targeting ERKs in UV-induced skin carcinogenesis.

Previous investigations have shown that ibuprofen inhibits the second wave of platelet aggregation and blocks the conversion of 14 C-arachidonic acid to thromboxane. However, the influence of the drug on platelet function and cyclooxygenase is transitory, lasting only 24 hours. The present study has taken advantage of the shortlived influence of ibuprofen to study its interaction with the long-term effects of aspirin. As expected, both aspirin and ibuprofen supressed platelet cyclooxygenase activity and function, but addition of aspirin to ibuprofen-treated platelets did not increase the degree of inhibition in vitro. Platelet function and prostaglandin synthesis recovered completely 26 hours following ingestion of ibuprofen, but remained compromised 26 hours after taking aspirin. When 650 mg of aspirin was administered after ibuprofen, platelet function and cyclooxygenase activity recovered as completely at 26 hours as did platelets which had been exposed to ibuprofen alone. Thus, prior exposure to ibuprofen in vivo completely protected cyclooxygenase from the irreversible effects of aspirin. Our findings indicate that ibuprofen-like indomethacin and other nonsteroidal antiinf lammatory drugs react with the heme group of cyclooxygenase to prevent arachidonic acid conversion. Since ibuprofen completely blocks the effects of aspirin in platelets in vitro and in vivo, aspirin's primary influence on inhibition of cyclooxygenase must also be through action on the heme portion of the enzyme, rather than acetylation of the protein. 12 Investigations into its mechanism of action several years ago 3 " 5 suggested that it suppressed conversion of arachidonic acid by acetylating the enzyme cyclooxygenase. Other potent inhibitors of prostaglandin formation, however, are incapable of acetylating proteins and must block cyclooxygenase in some other manner.6 " 14 Studies in our laboratory using a cell-free system demonstrated that inhibitors of prostaglandin synthesis (including aspirin, indomethacin, tolmetin, and ibuprofen) prevented arachidonic acid oxidation by interfering with the action of ferrous iron or

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Non-small cell lung cancer (NSCLC) is the leading cause of cancer mortality worldwide. Despite progress in developing chemotherapeutics for the treatment of NSCLC, primary and secondary resistance limits therapeutic success. NSCLC cells exhibit multiple mutations in the epidermal growth factor receptor (EGFR), which cause aberrant activation of diverse cell signaling pathways. Therefore, suppression of the inappropriate amplification of EGFR downstream signaling cascades is considered to be a rational therapeutic and preventive strategy for the management of NSCLC. Our initial molecular target-oriented virtual screening revealed that the ginger components, including [6]-shogaol, [6]-paradol and [6]-gingerol, seem to be potential candidates for the prevention and treatment of NSCLC. Among the compounds, [6]-shogaol showed the greatest inhibitory effects on the NSCLC cell proliferation and anchorage-independent growth. [6]-Shogaol induced cell cycle arrest (G1 or G2/M) and apoptosis. Furthermore, [6]-shogaol inhibited Akt kinase activity, a downstream mediator of EGFR signaling, by binding with an allosteric site of Akt. In NCI-H1650 lung cancer cells, [6]-shogaol reduced the constitutive phosphorylation of signal transducer and activator of transcription-3 (STAT3) and decreased the expression of cyclin D1/3, which are target proteins in the Akt signaling pathway. The induction of apoptosis in NCI-H1650 cells by [6]-shogaol corresponded with the cleavage of caspase-3 and caspase-7. Moreover, intraperitoneal administration of [6]-shogaol inhibited the growth of NCI-H1650 cells as tumor xenografts in nude mice. [6]-Shogaol suppressed the expression of Ki-67, cyclin D1 and phosphorylated Akt and STAT3 and increased terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positivity in xenograft tumors. The current study clearly indicates that [6]-shogaol can be exploited for the prevention and/or treatment of NSCLC.