Comprehensive Physicochemical Characterization, In Vitro Membrane Permeation, and In Vitro Human Skin Cell Culture of a Novel TOPK Inhibitor, HI-TOPK-032.

Nonmelanoma skin cancers (NMSC) are the most common skin cancers, and about 5.4 million people are diagnosed each year in the United States. A newly developed T-lymphokine-activated killer cell-originated protein kinase (TOPK) inhibitor, HI-TOPK-032, is effective in suppressing colon cancer cell growth, inducing the apoptosis of colon cancer cells and ultraviolet (UV) light-induced squamous cell carcinoma (SCC). This study aimed to investigate the physicochemical properties, permeation behavior, and cytotoxicity potential of HI-TOPK-032 prior to the development of a suitable topical formulation for targeted skin drug delivery. Techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, differential scanning calorimetry (DSC), hot-stage microscopy (HSM), X-ray powder diffraction (XRPD), Karl Fisher (KF) coulometric titration, Raman spectrometry, confocal Raman microscopy (CRM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and Fourier transform infrared microscopy were used to characterize HI-TOPK-032. The dose effect of HI-TOPK-032 on in vitro cell viability was evaluated using a 2D cell culture of the human skin keratinocyte cell line (HaCaT) and primary normal human epidermal keratinocytes (NHEKs). Transepithelial electrical resistance (TEER) at the air-liquid interface as a function of dose and time was measured on the HaCAT human skin cell line. The membrane permeation behavior of HI-TOPK-032 was tested using the Strat-M® synthetic biomimetic membrane with an in vitro Franz cell diffusion system. The physicochemical evaluation results confirmed the amorphous nature of the drug and the homogeneity of the sample with all characteristic chemical peaks. The in vitro cell viability assay results confirmed 100% cell viability up to 10 µM of HI-TOPK-032. Further, a rapid, specific, precise, and validated reverse phase-high performance liquid chromatography (RP-HPLC) method for the quantitative estimation of HI-TOPK-032 was developed. This is the first systematic and comprehensive characterization of HI-TOPK-032 and a report of these findings.

Innovative Rocuronium Bromide Topical Formulation for Targeted Skin Drug Delivery: Design, Comprehensive Characterization, In Vitro 2D/3D Human Cell Culture and Permeation.

Cutaneous squamous cell carcinoma (cSCC) is the second-most common type of non-melanoma skin cancer and is linked to long-term exposure to ultraviolet (UV) radiation from the sun. Rocuronium bromide (RocBr) is an FDA-approved drug that targets p53-related protein kinase (PRPK) that inhibits the development of UV-induced cSCC. This study aimed to investigate the physicochemical properties and in vitro behavior of RocBr. Techniques such as thermal analysis, electron microscopy, spectroscopy and in vitro assays were used to characterize RocBr. A topical oil/water emulsion lotion formulation of RocBr was successfully developed and evaluated. The in vitro permeation behavior of RocBr from its lotion formulation was quantified with Strat-M® synthetic biomimetic membrane and EpiDerm™ 3D human skin tissue. Significant membrane retention of RocBr drug was evident and more retention was obtained with the lotion formulation compared with the solution. This is the first systematic and comprehensive study to report these findings.

Structural basis for multifunctional roles of human Ints3 C-terminal domain.

Proper repair of damaged DNA is critical for the maintenance of genome stability. A complex composed of Integrator subunit 3 (Ints3), single-stranded DNA-binding protein 1 (SSB1), and SSB-interacting protein 1 (SSBIP1) is required for efficient homologous recombination-dependent repair of double-strand breaks (DSBs) and ataxia-telangiectasia mutated (ATM)-dependent signaling pathways. It is known that in this complex the Ints3 N-terminal domain scaffolds SSB1 and SSBIP1. However, the molecular basis for the function of the Ints3 C-terminal domain remains unclear. Here, we present the crystal structure of the Ints3 C-terminal domain, uncovering a HEAT-repeat superhelical fold. Using structure and mutation analysis, we show that the C-terminal domain exists as a stable dimer. A basic groove and a cluster of conserved residues on two opposite sides of the dimer bind single-stranded RNA/DNA (ssRNA/ssDNA) and Integrator complex subunit 6 (Ints6), respectively. Dimerization is required for nucleic acid binding, but not for Ints6 binding. Additionally, in vitro experiments using HEK 293T cells demonstrate that Ints6 interaction is critical for maintaining SSB1 protein level. Taken together, our findings establish the structural basis of a multifunctional Ints3 C-terminal module, allowing us to propose a novel mode of nucleic acid recognition by helical repeat protein and paving the way for future mechanistic studies.

CELF2 suppresses non-small cell lung carcinoma growth by inhibiting the PREX2-PTEN interaction.

The phosphoinositide 3-kinase (PI3-K)/Akt signaling pathway is important in the regulation of cell proliferation through its production of phosphatidylinositol 3,4,5-triphosphate (PIP3). Activation of this pathway is frequently observed in human cancers, including non-small cell lung carcinoma. The PI3-K/Akt pathway is negatively regulated by the dual-specificity phosphatase and tensin homolog (PTEN) protein. PTEN acts as a direct antagonist of PI3-K by dephosphorylating PIP3. Studies have shown that PTEN phosphatase activity is inhibited by PREX2, a guanine nucleotide exchanger factor (GEF). Multiple studies revealed that CELF2, an RNA binding protein, cooperates synergistically with PTEN as a tumor suppressor in multiple cancers. However, the underlying mechanism as to how CELF2 enhances PTEN activity remains unclear. Here, we report that CELF2 interacts with PREX2 and reduces the association of PREX2 with PTEN. Consistent with this observation, PTEN phosphatase activity is upregulated with CELF2 overexpression. In addition, overexpression of CELF2 represses both Akt phosphorylation and cell proliferation only in the presence of PTEN. In an ex vivo study, CELF2 gene delivery could significantly inhibit patient-derived xenografts (PDX) tumor growth. To further investigate the clinical relevance of this finding, we analyzed 87 paired clinical lung adenocarcinoma samples and the results showed that CELF2 protein expression is downregulated in tumor tissues and associated with poor prognosis. The CELF2 gene is located on the chromosome 10p arm, a region frequently lost in human cancers, including breast invasive carcinoma, low-grade glioma and glioblastoma. Analysis of TCGA datasets showed that CELF2 expression is also associated with shorter patient survival time in all these cancers. Overall, our work suggests that CELF2 plays a novel role in PI3-K signaling by antagonizing the oncogenic effect of PREX2.

Analysis of hydrophobic and hydrophilic moments of short penetrating peptides for enhancing mitochondrial localization: prediction and validation.

Pharmaceutical interest in targeting mitochondria is increasing because of their contribution in incurable diseases. However, the inner mitochondrial layer represents a major hurdle to overcome for most drugs. Penetrating peptides are a promising strategy for drug delivery, but the absence of standard principles and reliable prediction tools limits the design and discovery of sequences with improved organelle specificity. In our hypothesis, peptide local flexibility represents a valuable source to predict peptide performance. Here, a pool of short nonnatural peptides was designed with the same amino acid content but different positioning. Molecular dynamics and membrane-transfer simulations were used to generate the low-energy conformers in extra, intracellular, and membrane-inserted environments. The contributions of the hydrophobic and hydrophilic side chain-exposed surfaces revealed that the amino acid's relative position significantly affected the simulated peptide's dynamics. Based on the structural versatility, we predicted the peptides' behavior and the sequence with the most efficient membrane penetration and mitochondrial localization. The prediction and the improved performance of our peptides were experimentally confirmed and compared with a reported mitochondrial-targeting sequence. We demonstrated that an accurate understanding of the structural versatility is a valid aid for future works in designing sequences with improved mitochondrial targeting.-Pirisinu, M., Blasco, P., Tian, X., Sen, Y., Bode, A. M., Liu, K., Dong, Z. Analysis of hydrophobic and hydrophilic moments of short penetrating peptides for enhancing mitochondrial localization: prediction and validation.

Veratramine modulates AP-1-dependent gene transcription by directly binding to programmable DNA.

Because the transcription factor activator protein-1 (AP-1) regulates a variety of protein-encoding genes, it is a participant in many cellular functions, including proliferation, transformation, epithelial mesenchymal transition (EMT), and apoptosis. Inhibitors targeting AP-1 have potential use in the treatment of cancer and other inflammatory diseases. Here, we identify veratramine as a potent natural modulator of AP-1, which selectively binds to a specific site (TRE 5'-TGACTCA-3') of the AP-1 target DNA sequence and regulates AP-1-dependent gene transcription without interfering with cystosolic signaling cascades that might lead to AP-1 activation. Moreover, RNA-seq experiments demonstrate that veratramine does not act on the Hedgehog signaling pathway in contrast to its analogue, cyclopamine, and likely does not harbor the same teratogenicity and toxicity. Additionally, veratramine effectively suppresses EGF-induced AP-1 transactivation and transformation of JB6 P+ cells. Finally, we demonstrate that veratramine inhibits solar-ultraviolet-induced AP-1 activation in mice. The identification of veratramine and new findings in its specific regulation of AP-1 down stream genes pave ways to discovering and designing regulators to regulate transcription factor.

RSK2 phosphorylates T-bet to attenuate colon cancer metastasis and growth.

Metastasis is a major cause of cancer-related deaths. Approximately 80% of patients with colorectal cancer develop liver metastasis and 20% develop lung metastasis. We found that at different stages of colon cancer, IFNγ secretion from peripheral blood mononuclear cells was decreased compared with healthy controls. The ribosomal S6 kinase (RSK) family of kinases has multiple cellular functions, and we examined their roles in this observed IFNγ decrease. Flow cytometry analysis of wild-type (WT) and RSK2 knockout (KO) mice revealed significantly lower levels of IFNγ in the RSK2 KO mice compared with the WT mice. Since IFNγ is a component of immunity, which contributes to protection against metastatic carcinomas, we conducted a colon cancer liver metastasis experiment. We found significantly greater metastasis in RSK2 KO mice compared with WT mice. Transcription factor T-bet can directly activate Ifnγ gene transcription. In vitro kinase assay results showed that RSK2 phosphorylated T-bet at serines 498 and 502. We show that phosphorylation of T-bet by RSK2 is required for IFNγ expression, because knockdown of RSK2 expression or overexpression of mutant T-bet reduces IFNγ mRNA expression. To verify the function of the phosphorylation sites, we overexpressed a constitutively active mutant T-bet (S498E/S502E) in bone marrow. Mutant T-bet restored the IFNγ mRNA levels and dramatically reduced the metastasis rate in these mice. Overall, these results indicate that phosphorylation of T-bet is required for the inhibition of colon cancer metastasis and growth through a positive regulation of RSK2/T-bet/IFNγ signaling.

Posttranslational regulation of PGC-1α and its implication in cancer metabolism.

Deregulation of cellular metabolism is well established in cancer. The mitochondria are dynamic organelles and act as the center stage for energy metabolism. Central to mitochondrial regulatory network is peroxisome proliferator-activated receptor γ coactivator 1a (PGC-1α), which serves as a master regulator of mitochondrial proliferation and metabolism. The activity and stability of PGC-1α are subject to dynamic and versatile posttranslational modifications including phosphorylation, ubiquitination, methylation and acetylation in response to metabolic stress and other environmental signals. In this review, we describe the structure of PGC-1α. Then, we discuss recent advances in the posttranslational regulatory machinery of PGC-1α, which affects its transcriptional activity, stability and organelle localization. Furthermore, we address the important roles of PGC-1α in tumorigenesis and malignancy. Finally, we also mention the clinical therapeutic potentials of PGC-1α modulators. A better understanding of the elegant function of PGC-1α in cancer progression could provide novel insights into therapeutic interventions through the targeting of PGC-1α signaling.

Targeted therapy of the AKT kinase inhibits esophageal squamous cell carcinoma growth in vitro and in vivo.

Esophageal cancer, a leading cause of cancer death worldwide, is associated with abnormal activation of the AKT signaling pathway. Xanthohumol, a prenylated flavonoid tested in clinical trials, is reported to exert anti-diabetes, anti-inflammation and anticancer activities. However, the mechanisms underlying its chemopreventive or chemotherapeutic effects remain elusive. In the present study, we found that xanthohumol directly targeted AKT1/2 in esophageal squamous cell carcinoma (ESCC). Xanthohumol significantly inhibited the AKT kinase activity in an ATP competitive manner, which was confirmed in binding and computational docking models. KYSE70, 450 and 510 ESCC cell lines highly express AKT and knockdown of AKT1/2 suppressed proliferation of these cells. Treatment with xanthohumol inhibited ESCC cell growth and induced apoptosis and cell cycle arrest at the G1 phase. Xanthohumol also decreased expression of cyclin D1 and increased the levels of cleaved caspase-3, -7 and -PARP as well as Bax, Bims and cytochrome c in ESCC cells by downregulating AKT signaling targets, including glycogen synthase kinase 3 beta (GSK3ß), mammalian target of rapamycin, and ribosomal protein S6 (S6K). Furthermore, xanthohumol decreased tumor volume and weight in patient-derived xenografts (PDXs) that highly expressed AKT, but had no effect on PDXs that exhibited low expression of AKT in vivo. Kinase array results showed that xanthohumol treatment decreased phosphorylated p27 expression in both ESCC cell lines and PDX models. Taken together, our data suggest that the inhibition of ESCC tumor growth with xanthohumol is caused by targeting AKT. These results provide good evidence for translation toward clinical trials with xanthohumol.

Purpurogallin is a novel mitogen-activated protein kinase kinase 1/2 inhibitor that suppresses esophageal squamous cell carcinoma growth in vitro and in vivo.

Purpurogallin is a natural compound that is extracted from nutgalls and oak bark and it possesses antioxidant, anticancer, and anti-inflammatory properties. However, the anticancer capacity of purpurogallin and its molecular target have not been investigated in esophageal squamous cell carcinoma (ESCC). Herein, we report that purpurogallin suppresses ESCC cell growth by directly targeting the mitogen-activated protein kinase kinase 1/2 (MEK1/2) signaling pathway. We found that purpurogallin inhibits anchorage-dependent and -independent ESCC growth. The results of in vitro kinase assays and cell-based assays indicated that purpurogallin also strongly attenuates the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway and also directly binds to and inhibits MEK1 and MEK2 activity. Furthermore, purpurogallin contributed to S and G2 phase cell cycle arrest by reducing cyclin A2 and cyclin B1 expression and also induced apoptosis by activating poly (ADP ribose) polymerase (PARP). Notably, purpurogallin suppressed patient-derived ESCC tumor growth in an in vivo mouse model. These findings indicated that purpurogallin is a novel MEK1/2 inhibitor that could be useful for treating ESCC.

Ethyl gallate as a novel ERK1/2 inhibitor suppresses patient-derived esophageal tumor growth.

Ethyl gallate (EG) is a phenolic compound that is isolated from walnut kernels, euphorbia fischeriana, and galla rhois. It has been reported to exhibit antioxidant and anticancer activities. However, EG's effects on esophageal cancer have not yet been investigated. In the present study, we report that EG is a novel ERK1/2 inhibitor that suppresses esophageal cancer growth in vitro and in vivo. EG suppressed anchorage-dependent and -independent esophageal cancer cell growth. The results of in vitro kinase assays and cell-based assays indicated that EG directly binds to and inhibits ERK1 and ERK2 activities and their downstream signaling. Additionally, EG's inhibitory effect on cell growth is resistant to the re-activation of ERK1/2. EG increased G2/M phase cell cycle by reducing the expression of cyclin A2 and cyclin B1. The compound also stimulated cellular apoptosis through the activation of caspases 3 and 7 and inhibition of BCL2 expression. Notably, EG inhibited patient-derived esophageal tumor growth in an in vivo mouse model. These results indicate that EG is an ERK1/2 inhibitor that could be useful for treating esophageal cancer.

Aurora B kinase as a novel molecular target for inhibition the growth of osteosarcoma.

Osteosarcoma is the primary human malignant tumor affecting bone. This cancer most frequently arises in children and adolescents, with a second peak in those over the age of 50. Currently, surgery followed by radiotherapy and chemotherapy are the main treatments, but long-term positive effects are very poor. Aurora B kinase is a serine/threonine kinase that is a key regulator of cell cycle and mitosis. Tissue array analysis revealed that Aurora B kinase is overexpressed in osteosarcoma compared with normal bone tissue. We developed a compound, HOI-07 (i.e., (E)-3-((E)-4-(benzo[d] [1,3]dioxol-5-yl)-2-oxobut-3-en-1-ylidene)indolin-2-one), as a specific Aurora B kinase inhibitor and examined its effectiveness against osteosarcoma cell growth in this study. This compound inhibited Aurora B kinase activity in osteosarcoma and induced apoptosis, caused G2-M phase arrest, and attenuated osteosarcoma anchorage-independent cell growth. Moreover, knocking down the expression of Aurora B effectively reduced the sensitivity of osteosarcoma to HOI-07. Results of a xenograft mouse study indicated that HOI-07 treatment effectively suppressed the growth of 143B and KHOS xenografts, without affecting the body weight of mice. The expression of phosphorylated histone H3 (Ser10) was reduced in mice treated with HOI-07. Overall, we identified HOI-07 as a specific Aurora B kinase inhibitor for osteosarcoma treatment and this compound warrants further investigation.

Gossypin inhibits gastric cancer growth by direct targeting of AURKA and RSK2.

Gossypin is a flavone extracted from Hibiscus vitifolius, which has been reported to exhibit anti-inflammatory, antioxidant, and anticancer activities. However, the anticancer properties of gossypin and its molecular mechanism of action against gastric cancer have not been fully investigated. In the present study, we report that gossypin is an Aurora kinase A (AURKA) and RSK2 inhibitor that suppresses gastric cancer growth. Gossypin attenuated anchorage-dependent and anchorage-independent gastric cancer cell growth as well as cell migration. Based on the results of in vitro screening and cell-based assays, gossypin directly binds to and inhibits AURKA and RSK2 activities and their downstream signaling proteins. Gossypin decreased S phase and increased G2/M phase cell cycle arrest by reducing the expression of cyclin A2 and cyclin B1 and the phosphorylation of the CDC protein. Additionally, gossypin also induced intrinsic apoptosis by activating caspases and PARP and increasing the expression of cytochrome c. Our results demonstrate that gossypin is an AURKA and RSK2 inhibitor that could be useful for treating gastric cancer.

Lapachol is a novel ribosomal protein S6 kinase 2 inhibitor that suppresses growth and induces intrinsic apoptosis in esophageal squamous cell carcinoma cells.

Lapachol is a 1,4-naphthoquinone that is isolated from the Bignoniaceae family. It has been reported to exert anti-inflammatory, antibacterial, and anticancer activities. However, the anticancer activity of lapachol and its molecular mechanisms against esophageal squamous cell carcinoma (ESCC) cells have not been fully investigated. Herein, we report that lapachol is a novel ribosomal protein S6 kinase 2 (RSK2) inhibitor that suppresses growth and induces intrinsic apoptosis in ESCC cells. We found that lapachol strongly attenuates downstream signaling molecules of RSK2 in ESCC cells and also directly inhibits RSK2 activity in vitro. The RSK protein is highly activated in ESCC cells and knockdown of RSK2 significantly suppresses anchorage-dependent and anchorage-independent growth of ESCC cells. Additionally, lapachol inhibits anchorage-dependent and anchorage-independent growth of ESCC cells, and the inhibition of cell growth by lapachol is dependent on the expression of RSK2. We also found that lapachol induces mitochondria-mediated cellular apoptosis by activating caspases-3, -7, and PARP, inducing the expression of cytochrome c and BAX by inhibiting downstream molecules of RSK2. Overall, lapachol is a potent RSK2 inhibitor that might be used for chemotherapy against ESCC.

Mitochondrial network structure homeostasis and cell death.

Mitochondria are the major cellular energy-producing organelles and intracellular source of reactive oxygen species. These organelles are responsible for driving cell life and death through mitochondrial network structure homeostasis, which is determined by a balance of fission and fusion. Recent advances revealed that a number of components of the fission and fusion machinery, including dynamin-related protein 1 (Drp1), mitofusin1/2 (Mfn1/2) and Optic atrophy 1 (OPA1), that have been implicated in mitochondrial shape changes are indispensible for autophagy, apoptosis and necroptosis. Drp1 is the main regulator of mitochondrial fission and has become a key point of contention. The controversy focuses on whether Drp1 is directly involved in the regulation of cell death and, if involved, whether is it a stimulator or a negative regulator of cell death. Here, we examine the relevance of the homeostasis of the mitochondrial network structure in 3 different types of cell death, including autophagy, apoptosis and necroptosis. Furthermore, a variety of cancers often exhibit a fragmented mitochondrial phenotype. Thus, the fragmented ratio can reflect tumor progression that predicts prognosis and therapeutic response. In addition, we investigate whether the targeting of the mitochondrial fission protein Drp1 could be a novel therapeutic approach.

Therapies based on targeting Epstein-Barr virus lytic replication for EBV-associated malignancies.

In recent years, Epstein-Barr virus (EBV) lytic infection has been shown to significantly contribute to carcinogenesis. Thus, therapies aimed at targeting the EBV lytic cycle have been developed as novel strategies for treatment of EBV-associated malignancies. In this review, focusing on the viral lytic proteins, we describe recent advances regarding the involvement of the EBV lytic cycle in carcinogenesis. Moreover, we further discuss 2 distinct EBV lytic cycle-targeted therapeutic strategies against EBV-induced malignancies. One of the strategies involves inhibition of the EBV lytic cycle by natural compounds known to have anti-EBV properties; another is to intentionally induce EBV lytic replication in combination with nucleotide analogues. Recent advances in EBV lytic-based strategies are beginning to show promise in the treatment and/or prevention of EBV-related tumors.

PKCι is a target of 7,8,4'-trihydroxyisoflavone for the suppression of UVB-induced MMP-1 expression.

The soy isoflavone daidzein is bioconverted to 7,8,4'-trihydroxyisoflavone (7,8,4'-THIF) by microorganisms. Here, we investigated the matrix metalloproteinase (MMP)-1 inhibitory properties of 7,8,4'-THIF that arise through the suppression of UVB-induced MMP-1 expression. 7,8,4'-THIF reduced UVB-induced MMP-1 expression at the transcriptional level in primary human dermal fibroblasts and inhibited UVB-induced transcriptional activity of AP-1, a major activator of MMP-1 expression. Additionally, it was observed that the mitogen-activated protein kinase (MAPK) pathway, a crucial signalling cascade for MMP-1 expression, was suppressed by 7,8,4'-THIF. Protein kinase C iota (PKCι) was suspected to be a direct target of 7,8,4'-THIF. The direct interaction between 7,8,4'-THIF and PKCι was confirmed using pull-down assays and immobilized metal ion affinity-based fluorescence polarization assays. Finally, we observed that 7,8,4'-THIF inhibited UVB-induced MMP-1 expression in a human skin equivalent model. Taken together, these results suggest that 7,8,4'-THIF, a bioconversion product of daidzein, suppresses UVB-induced MMP-1 expression.

LTA4H regulates cell cycle and skin carcinogenesis.

Leukotriene A4 hydrolase (LTA4H), a bifunctional zinc metallo-enzyme, is reportedly overexpressed in several human cancers. Our group has focused on LTA4H as a potential target for cancer prevention and/or therapy. In the present study, we report that LTA4H is a key regulator of cell cycle at the G0/G1 phase acting by negatively regulating p27 expression in skin cancer. We found that LTA4H is overexpressed in human skin cancer tissue. Knocking out LTA4H significantly reduced skin cancer development in the 7,12-dimethylbenz(a)anthracene (DMBA)-initiated/12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted two-stage skin cancer mouse model. LTA4H depletion dramatically decreased anchorage-dependent and -independent skin cancer cell growth by inducing cell cycle arrest at the G0/G1 phase. Moreover, our findings showed that depletion of LTA4H enhanced p27 protein stability, which was associated with decreased phosphorylation of CDK2 at Thr160 and inhibition of the CDK2/cyclin E complex, resulting in down-regulated p27 ubiquitination. These findings indicate that LTA4H is critical for skin carcinogenesis and is an important mediator of cell cycle and the data begin to clarify the mechanisms of LTA4H's role in cancer development.

The CUG-translated WT1, not AUG-WT1, is an oncogene.

The Wilms' tumor 1 (WT1) gene is believed to act as a canonical tumor suppressor. However, it has also been reported to function as an oncogene. Germline WT1 deletion is associated with Wilms' tumor, and exogenous WT1 cDNA introduction into cells induces the transcriptional suppression of its oncogenic target genes. In contrast, high WT1 expression is associated with poor prognosis in patients with various cancers. Why WT1 acts as a tumor suppressor under certain conditions but as an oncogene under other conditions is unknown. Here, we report that CUG initiation site for WT1 protein synthesis (CUG)-translated WT1 (cugWT1), an N-terminally extended form of canonical AUG initiation site for WT1 protein synthesis (AUG)-translated WT1 (augWT1), was overexpressed in most cancer cell lines and cancer tissues and functioned as an oncogene, whereas the classical augWT1 acted as a tumor suppressor as reported previously and inhibited the function of cugWT1. Translation of cugWT1 is initiated from a CUG codon upstream and in-frame with the coding region of augWT1. cugWT1 induced cell transformation and increased the gene expression of c-myc, bcl-2 and egfr, whereas overexpression of augWT1 repressed colony formation of cancer cells and inhibited the expression of the same target genes by recruiting histone deacetylase 1 (HDAC1). In addition, we found that protein kinase B (AKT)-phosphorylated cugWT1 on Ser62 and protected cugWT1 from proteasomal degradation induced by the F-box/WD repeat-containing protein 8 (FBXW8). These results provide an important breakthrough in the field of cancer biology and contribute significantly to the resolution of the chameleon function of WT1.

Herbacetin suppresses cutaneous squamous cell carcinoma and melanoma cell growth by targeting AKT and ODC.

Herbacetin is a flavonol compound that is found in plants such as flaxseed and ramose scouring rush herb, it possesses a strong antioxidant capacity, and exerts anticancer effects on colon and breast cancer. However, the effect of herbacetin on skin cancer has not been investigated. Herein, we identified herbacetin as a dual V-akt murine thymoma viral oncogene homolog (AKT) and ornithine decarboxylase (ODC) inhibitor, and illustrated its anticancer effects in vitro and in vivo against cutaneous squamous cell carcinoma (SCC) and melanoma cell growth. To identify the direct target(s) of herbacetin, we screened several skin cancer-related protein kinases, and results indicated that herbacetin strongly suppresses both AKT and ODC activity. Results of cell-based assays showed that herbacetin binds to both AKT and ODC, inhibits TPA-induced neoplastic transformation of JB6 mouse epidermal cells, and suppresses anchorage-independent growth of cutaneous SCC and melanoma cells. The inhibitory activity of herbacetin was associated with markedly reduced NF-κB and AP1 reporter activity. Interestingly, herbacetin effectively attenuated TPA-induced skin cancer development and also exhibited therapeutic effects against solar-UV-induced skin cancer and melanoma growth in vivo. Our findings indicate that herbacetin is a potent AKT and ODC inhibitor that should be useful for preventing skin cancers.