Therapeutic Target In Human Cancer Research Articles

The E3 Ligase RING1 Targets p53 for Degradation and Promotes Cancer Cell Proliferation and Survival.

As a component of the transcriptional repression complex 1 (PRC1), the ring finger protein RING1 participates in the epigenetic regulation in cancer. However, the contributions of RING1 to cancer etiology or development are unknown. In this study, we report that RING1 is a critical negative regulator of p53 homeostasis in human hepatocellular and colorectal carcinomas. RING1 acts as an E3 ubiquitin (Ub) ligase to directly interact with and ubiquitinate p53, resulting in its proteasome-dependent degradation. The RING domain of RING1 was required for its E3 Ub ligase activity. RING1 depletion inhibited the proliferation and survival of the p53 wild-type cancer cells by inducing cell-cycle arrest, apoptosis, and senescence, with only modest effects on p53-deficient cells. Its growth inhibitory effect was partially rescued by p53 silencing, suggesting an important role for the RING1-p53 complex in human cancer. In clinical specimens of hepatocellular carcinoma, RING1 upregulation was evident in association with poor clinical outcomes. Collectively, our results elucidate a novel PRC1-independent function of RING1 and provide a mechanistic rationale for its candidacy as a new prognostic marker and/or therapeutic target in human cancer.Significance: These results elucidate a novel PRC1-independent function of RING1 and provide a mechanistic rationale for its candidacy as a new prognostic marker and/or therapeutic target in human cancer. Cancer Res; 78(2); 359-71. ©2017 AACR.

Therapeutic relevance of the PP2A-B55 inhibitory kinase MASTL/Greatwall in breast cancer.

PP2A is a major tumor suppressor whose inactivation is frequently found in a wide spectrum of human tumors. In particular, deletion or epigenetic silencing of genes encoding the B55 family of PP2A regulatory subunits is a common feature of breast cancer cells. A key player in the regulation of PP2A/B55 phosphatase complexes is the cell cycle kinase MASTL (also known as Greatwall). During cell division, inhibition of PP2A-B55 by MASTL is required to maintain the mitotic state, whereas inactivation of MASTL and PP2A reactivation is required for mitotic exit. Despite its critical role in cell cycle progression in multiple organisms, its relevance as a therapeutic target in human cancer and its dependence of PP2A activity is mostly unknown. Here we show that MASTL overexpression predicts poor survival and shows prognostic value in breast cancer patients. MASTL knockdown or knockout using RNA interference or CRISPR/Cas9 systems impairs proliferation of a subset of breast cancer cells. The proliferative function of MASTL in these tumor cells requires its kinase activity and the presence of PP2A-B55 complexes. By using a new inducible CRISPR/Cas9 system in breast cancer cells, we show that genetic ablation of MASTL displays a significant therapeutic effect in vivo. All together, these data suggest that the PP2A inhibitory kinase MASTL may have both prognostic and therapeutic value in human breast cancer.

Abstract 5074: Therapeutic targeting of bromodomain and extra-terminal proteins degradation in triple-negative breast cancer

Abstract Triple negative breast cancer represents the most clinically challenging subtypes of breast cancer for which targeted therapeutics are still lacking. BET proteins have emerged as new therapeutic targets for human cancer and other diseases.We have developed a highly potent BET degrader, BETd-246, with an exceptional selectivity based upon a new class of BET inhibitor, BETi-211, and investigated its therapeutic potential and mechanisms of action in TNBC. BETd-246 induces degradation of BET proteins at low nanomolar concentrations within 1 hour, leading to potent anti-proliferative activity and strong apoptosis induction in the majority of TNBC cell lines, and is much more effective than the BETi-211 treatment. RNA-seq analysis reveals that degradation of BET proteins by BETd-246 elicits distinct transcriptional response than BET BD inhibition in TNBC cell lines. Transcriptomic analysis also shows a number of proliferation and survival-related genes were differentially regulated by BETd-246 and BETi-211 which were confirmed by quantitative RT-PCR. Mechanistically, down-regulation of MCL1 by BETd-246 plays a key role in the robust apoptosis induction in TNBC cell lines. In in vivo models, BETd-246 effectively degrades BET proteins and suppresses MCL1 expression in xenograft tumor tissues and exhibits a strong antitumor activity at well-tolerated dose-schedules in mice. Our data strongly suggest that targeting BET protein degradation is an exciting therapeutic strategy for TNBC. Citation Format: Longchuan Bai, Bing Zhou, Chao-Yie Yang, Jiao Ji, Donna McEachern, Sally Przybranowski, Shaomeng Wang. Therapeutic targeting of bromodomain and extra-terminal proteins degradation in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5074. doi:10.1158/1538-7445.AM2017-5074

Abstract 1127: Aberrant nuclear expression of GSK-3beta in human head and neck carcinoma

Abstract Background: Recurrent/metastatic head and neck squamous cell carcinoma (SCCHN) and salivary gland malignancies are difficult to treat with limited standard of care options at the present time. Glycogen Synthase Kinase-3beta (GSK-3beta), a serine/threonine protein kinase, has been implicated as a potential therapeutic target in human cancer. Our in vivo studies demonstrated that our novel GSK-3 inhibitors significantly potentiated the effects of conventional chemotherapy in patient-derived xenograft models of glioblastoma and breast cancer leading to regression of tumors. In order to develop a rationale to test our novel GSK-3 inhibitors in head and neck (H&N) malignancies, we evaluated the expression pattern of GSK-3beta in human H&N benign tissue and malignant tumors. Methods: We used immunohistochemical staining of H&N tumor tissue Microarray (TMA), 48 total cases (20 benign tissues, 28 malignant), to study the expression pattern of GSK-3beta. GSK-3beta nuclear accumulation was defined as positive staining of more than 50% of cancer cell nuclei throughout the tumor regardless of cytoplasmic staining. Results: Of the 20 malignant H&N samples (15 SCCHN, 1 nasopharyngeal and 5 other histology), 13 (65%) were found to have aberrant nuclear accumulation of GSK-3beta. Amongst SCCHN, 73% (11 of 15 samples) had aberrant nuclear accumulation of GSK-3beta. In contrast, none (0%) of the 11 benign non-salivary H&N tissue showed detectable expression of GSK-3beta. Of interest, 60% of salivary adenoid cystic carcinoma specimens and 44% of benign salivary gland tissue showed GSK-3beta expression. Conclusions: Our results demonstrate for the first time, that there is aberrant nuclear expression of GSK-3beta in SCCHN. This finding supports further exploring of our novel GSK-3beta inhibitor as a potential therapeutic target for recurrent/metastatic SCCHN and also, as a potential prognostic and predictive biomarker for risk of recurrent disease and chemo- or radio-resistance. Its role in salivary gland malignancies requires further studying. Citation Format: Maria Matsangou, Andrey Ugolkov, Timothy J. Taxter, Sandeep Samant, Andrew P. Mazar, Francis J. Giles. Aberrant nuclear expression of GSK-3beta in human head and neck carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1127. doi:10.1158/1538-7445.AM2017-1127

PET-Guided Evaluation and Optimization of Internalized Antibody-Drug Conjugates Targeting Erythropoietin-Producing Hepatoma A2 Receptor.

The erythropoietin-producing hepatoma A2 receptor (EphA2) is a tyrosine kinase overexpressed by tumor stroma and cancer cells. A high expression level of EphA2 predicts poor prognosis, correlating with disease progression and metastasis. Therefore, EphA2 is a relevant therapeutic target for human cancer. Antibodies, selectively bound to EphA2, can induce rapid receptor phosphorylation that results in antibody internalization and degradation. This internalization mechanism has been exploited with the development of antibody-drug conjugates (ADCs) for cancer chemotherapy. In this study, we used PET imaging to study the pharmacokinetics and tumor delivery of a panel of anti-EphA2 monoclonal antibodies (mAbs) with and without drug conjugates. Methods: A library of human anti-EphA2 mAbs were screened and evaluated for EphA2 internalization rate, binding affinity, epitope binding, and hydrophobicity. We chose 3 of these antibodies, denoted as 1C1, 3B10, and 2H7, which recognize different epitopes, for further evaluation. ADCs were generated by S239C mutation to give a ratio of 2 drug molecules per antibody. Native mAbs and ADCs were characterized, after conjugation to a DFO chelator and 89Zr radiolabeling, in assays including cell uptake, internalization, hydrophobicity, and in vivo imaging using PET. Results: All 3 mAbs had high affinities for EphA2 but exhibited different internalization rates following the order of 1C1 > 3B10 > 2H7. Internalization rate is only 1 factor that affects in vitro cell uptake and in vivo tumor accumulation. Interestingly, the hydrophobicity of the mAbs, which followed the order of 2H7 > 1C1 > 3B10, had a strong correlation with in vivo tumor uptake measured by PET, with the least hydrophobic antibody, 3B10, showing the highest tumor uptake. ADC significantly reduced the in vivo uptake of all 3 mAbs. Conclusion: Tumor uptake of mAb is a complex process that is affected by multiple parameters, including internalization, hydrophobicity, and chemical modification. Our results suggest that the addition of drug molecules to mAb increases the clearance of the mAb presumably due to the increased hydrophobicity. Understanding the complexity of antibody-based tumor delivery may help improve ADC engineering for better tumor targeting and reduced side effects.

LSD1 demethylates HIF1α to inhibit hydroxylation and ubiquitin-mediated degradation in tumor angiogenesis.

Lysine-specific demethylase 1 (LSD1), which has been considered as a potential therapeutic target in human cancer, has been known to regulate many biological functions through its non-histone substrates. Although LSD1-induced hypoxia-inducible factor alpha (HIF1α) demethylation has recently been proposed, the effect of LSD1 on the relationship between HIF1α post-translational modifications (PTMs) and HIF1α-induced tumor angiogenesis remains to be elucidated. Here, we identify a new methylation site of the HIF1α protein antagonized by LSD1 and the interplay between HIF1α protein methylation and other PTMs in regulating tumor angiogenesis. LSD1 demethylates HIF1α at lysine (K) 391, which protects HIF1α against ubiquitin-mediated protein degradation. LSD1 also directly suppresses PHD2-induced HIF1α hydroxylation, which has a mutually dependent interplay with Set9-mediated HIF1α methylation. Moreover, the HIF1α acetylation that occurs in a HIF1α methylation-dependent manner is inhibited by the LSD1/NuRD complex. HIF1α stabilized by LSD1 cooperates with CBP and MTA1 to enhance vascular endothelial growth factor (VEGF)-induced tumor angiogenesis. Thus, LSD1 is a key regulator of HIF1α/VEGF-mediated tumor angiogenesis by antagonizing the crosstalk between PTMs involving HIF1α protein degradation.

AKT Inhibition in Solid Tumors With AKT1 Mutations.

Purpose AKT1 E17K mutations are oncogenic and occur in many cancers at a low prevalence. We performed a multihistology basket study of AZD5363, an ATP-competitive pan-AKT kinase inhibitor, to determine the preliminary activity of AKT inhibition in AKT-mutant cancers. Patients and Methods Fifty-eight patients with advanced solid tumors were treated. The primary end point was safety; secondary end points were progression-free survival (PFS) and response according to Response Evaluation Criteria in Solid Tumors (RECIST). Tumor biopsies and plasma cell-free DNA (cfDNA) were collected in the majority of patients to identify predictive biomarkers of response. Results In patients with AKT1 E17K-mutant tumors (n = 52) and a median of five lines of prior therapy, the median PFS was 5.5 months (95% CI, 2.9 to 6.9 months), 6.6 months (95% CI, 1.5 to 8.3 months), and 4.2 months (95% CI, 2.1 to 12.8 months) in patients with estrogen receptor-positive breast, gynecologic, and other solid tumors, respectively. In an exploratory biomarker analysis, imbalance of the AKT1 E17K-mutant allele, most frequently caused by copy-neutral loss-of-heterozygosity targeting the wild-type allele, was associated with longer PFS (hazard ratio [HR], 0.41; P = .04), as was the presence of coincident PI3K pathway hotspot mutations (HR, 0.21; P = .045). Persistent declines in AKT1 E17K in cfDNA were associated with improved PFS (HR, 0.18; P = .004) and response ( P = .025). Responses were not restricted to patients with detectable AKT1 E17K in pretreatment cfDNA. The most common grade ≥ 3 adverse events were hyperglycemia (24%), diarrhea (17%), and rash (15.5%). Conclusion This study provides the first clinical data that AKT1 E17K is a therapeutic target in human cancer. The genomic context of the AKT1 E17K mutation further conditioned response to AZD5363.

CYP4A in tumor-associated macrophages promotes pre-metastatic niche formation and metastasis

Tumor-associated macrophages (TAMs) play an essential role in metastasis. However, what enables TAMs to have a superior capacity to establish pre-metastatic microenvironment in distant organs is unclear. Here we have begun to uncover the effects of cytochrome P450 (CYP) 4A in TAMs on lung pre-metastatic niche formation and metastasis. CYP4A+ TAM infiltration was positively associated with metastasis, pre-metastatic niche formation and poor prognosis in breast cancer patients. The pharmacological inhibition of CYP4A reduced lung pre-metastatic niche formation (evidenced by a decrease in vascular endothelial growth factor receptor 1 positive (VEGFR1+) myeloid cell recruitment and pro-metastatic protein expression) and metastatic burden, accompanied with TAM polarization away from the M2 phenotype in spontaneous metastasis models of 4T1 breast cancer and B16F10 melanoma. Co-implantation of 4T1 cells with CYP4A10high macrophages promoted lung pre-metastatic niche formation and metastasis. Depletion of TAMs disrupted lung pre-metastatic niches and thereby prevented metastasis. Treatment with the CM from CYP4A10high M2 macrophages (M2) increased pre-metastatic niche formation and metastatic burden in the lungs, whereas CYP4A inhibition attenuated these effects. In vitro TAM polarization away from the M2 phenotype induced by CYP4A inhibition decreased VEGFR1+ myeloid cell migration and fibronectin expression, accompanied with downregulation of STAT3 signaling. Conversely, overexpression of CYP4A or exogenous addition of 20-hydroxyeicosatetraenoic acid promoted M2 polarization and cytokine production of macrophages and thereby enhanced migration of VEGFR1+ myeloid cells, which were reversed by siRNA or pharmacological inhibition of STAT3. Importantly, a combined blocking M2 macrophage-derived factors TGF-β, VEGF and SDF-1 abolished VEGFR1+ myeloid cell migration and fibroblast activation induced by CYP4A. In summary, CYP4A in TAMs is crucial for lung pre-metastatic niche formation and metastasis, and may serve as a potential therapeutic target in human cancer.

Sclareol inhibits cell proliferation and sensitizes cells to the antiproliferative effect of bortezomib via upregulating the tumor suppressor caveolin-1 in cervical cancer cells.

The anticancer effect of sclareol has long been reported, however, the exact mechanisms underlying the antitumorigenic effect of sclareol in cervical carcinoma remain to be fully elucidated. The present study analyzed cell proliferation and cell apoptosis by MTT and FITC-Annexin V assays. The protein levels of caveolin-1 (Cav-1) and copper-zinc superoxide dismutase (SOD)1 were determined by western blotting, and the interaction of Cav1 and HSC70 was investigated by co-immunoprecipitation experiments. The present study found that sclareol inhibited cell proliferation and induced apoptosis in HeLa cells. Two cancer-associated proteins, Cav1 and SOD1 were identified as potential targets of sclareol in HeLa cells. The expression of Cav1 increased when the cells were treated with sclareol, and the protein level of SOD1 was negatively correlated with Cav1. The overexpression of Cav1 enhanced the sensitivity of the HeLa cells to sclareol treatment and downregulated the protein level of SOD1, which exhibited potential associations between Cav1 and SOD1. In addition, sclareol significantly sensitized several cancer cells to the anticancer effect of bortezomib by targeting Cav1 and SOD1. Taken together, the results of the present study demonstrated that sclareol inhibited tumor cell growth through the upregulation of Cav1, and provides a potential therapeutic target for human cancer.

Anti-helminthic niclosamide inhibits Ras-driven oncogenic transformation via activation of GSK-3.

Despite the importance of Ras oncogenes as a therapeutic target in human cancer, their ‘undruggable’ tertiary structures limit the effectiveness of anti-Ras drugs. Canonical Wnt signaling contributes to Ras activity by glycogen synthase kinase 3 (GSK-3)-dependent phosphorylation at the C-terminus and subsequent degradation. In the accompanying report, we show that the anti-helminthic niclosamide directly binds to GSK-3 and inhibits Axin functions in colon cancer cells, with reversion of Snail-mediated epithelial-mesenchymal transition. In this study, we report that niclosamide effectively suppresses Ras and nuclear NFAT activities regardless of the mutational status of Ras at nM levels. Mechanistically, niclosamide increased endogenous GSK-3 activity, shortening the half-life of mutant Ras. Further, niclosamide activates Raf-1 kinase inhibitory protein, a downstream target of Snail repressor. Niclosamide treatment attenuates Ras-induced oncogenic potential in vitro and in vivo. These findings provide a clinically available repositioned Ras inhibitor as well as a novel strategy for inhibiting the Ras via GSK-3.

Promising therapeutic role of miR-27b in tumor.

MicroRNAs are small nonprotein-encoding RNAs ranging from 18 to 25 nucleotides in size and regulate multiple biological pathways via directly targeting a variety of associated genes in cancers. MicroRNA-27b is a highly conserved MicroRNA throughout vertebrates and there are two homologs (hsa-miR-27a and hsa-miR-27b) in humans. MicroRNA-27b is an intragenic microRNA located on chromosome 9q22.1 within the C9orf3 gene, clustering with miR-23b and miR-24-1 in human. As a frequently dysregulated microRNA in human cancers, microRNA-27b could function as a tumor suppressor or an oncogenic microRNA. More and more studies indicate that microRNA-27b is involved in affecting various biological processes, such as angiogenesis, proliferation, metastasis, and drug resistance, and thus may act as a promising therapeutic target in human cancers. In this review, we discuss the role of microRNA-27b in detail and offer novel insights into molecular targeting therapy for cancers.

Long noncoding RNA activated by transforming growth factor-β promotes cancer development and is a prognostic marker in cervical cancer.

Long noncoding RNAs (lncRNAs) have been highlighted as crucial elements in cancer biology. LncRNA activated by transforming growth factor-β (ATB) was identified to promote the development of multiple cancers and may serve as a potential therapeutic target in human cancers. However, to the best of our knowledge, the functional role of ATB in cervical cancer has not been verified yet. The expression of lncRNA ATB was evaluated by quantitative reverse transcriptase-polymerase chain reaction assay in cervical cancer cell lines and clinical specimens. The clinical significance of ATB was statistically evaluated by analyzing the relationship between ATB overexpression and the clinicopathological characteristics of cervical cancer patients. Moreover, Kaplan-Meier analysis and log-rank test were conducted to investigate the role of ATB in the overall survival (OS) and progression-free survival (PFS) of cervical cancer patients or subgroup patients. Furthermore, univariate and multivariate analyses were adopted to identify the risk factors of OS and PFS of cervical cancer patients. LncRNA ATB was upregulated in cervical cancer cell lines and tissues (P < 0.05). Statistical analysis revealed that ATB overexpression was correlated with higher squamous cell carcinoma antigen level, larger tumor size, lymph node metastasis, and more advanced International Federation of Gynecology and Obstetrics (FIGO) stage of cervical cancer patients (P < 0.05). In addition, survival analysis showed that ATB upregulation was associated with poorer OS in cervical cancer patients and in subgroup patients without/with lymph node metastasis and with FIGO Stage I/II (P < 0.05). Furthermore, high ATB expression was defined as an independent risk factor of poorer OS and early recurrence of cervical cancer patients (P < 0.05). LncRNA ATB correlates with the malignant phenotypes and poor prognosis of cervical cancer. ATB may serve as a promising prognostic marker and therapeutic target of cervical cancer patients.

PRL2 Phosphatase Is a Key Mediator of Oncogenic Cytokine Signaling in Leukemia Stem Cells

Acute myeloid leukemia (AML) is a heterogeneous disease with multiple signaling pathways contributing to its pathogenesis. Mutations in receptor tyrosine kinase KIT and FLT3 are found in approximately 40% of AML patients and targeted therapies for inhibiting KIT and FLT3 have failed, thus new targets for therapeutic intervention need to be identified. The phosphatase of regenerating liver (PRL) family of phosphatases, consisting of PRL1, PRL2, and PRL3, represents an intriguing group of proteins being validated as biomarkers and therapeutic targets in human cancer. While PRL2 is highly expressed in some subtypes of human AML, including AML1-ETO+ AML and AML with mixed lineage leukemia (MLL) translocations, its role in AML is largely unknown. To determine the role of PRL2 in the pathogenesis of AML, we utilized two murine models of human AML induced by transducing mouse HSCs with AML1-ETO or MLL-AF9. We found that PRL2 is important for the progression and maintenance of leukemia induced by AML1-ETO or MLL-AF9 through enhancing leukemia stem cell (LSC) self-renewal. To elucidate the mechanisms by which PRL2 promotes LSC maintenance, we performed genome wide RNA-seq analysis of MLL-AF9+ LSCs. Gene Set Enrichment Analysis (GESA) indicates that PRL2 deficiency alters the MLL-AF9 signature essential for LSC self-renewal.We have recently identified PRL2 to be important for the proliferation and self-renewal of hematopoietic stem cells (HSCs) through the regulation of KIT signaling. Notably, PRL2 null hematopoietic progenitor cells showed decreased KIT phosphorylation as well as ERK phosphorylation following SCF stimulation, suggesting that PRL2 is important for KIT activation. Given that KIT inactivation could be mediated by removal from the cell surface and intracellular degradation, we reasoned that PRL2 may regulate KIT receptor internalization and stability. That was indeed the case. We found that the KIT protein half-life in PRL2 null hematopoietic progenitor cells (Kit+) was significantly decreased compared to WT cells. Furthermore, PRL2 null progenitor cells showed enhanced KIT ubiquitination compared to WT cells and less KIT was found on the surface of PRL2 null progenitor cells compared to WT cells following SCF stimulation. We also found that loss of PRL2 in human AML cells resulted in enhanced internalization of KIT. These observations demonstrate that PRL2 deficiency results in less KIT on the cell surface and a lower global KIT level in the cell.Upon SCF stimulation, KIT binds to and induces the phosphorylation of CBL proteins, which in turn act as E3 ligases, mediating the ubiquitination and degradation of KIT. To understand how PRL2 modulates the turnover of KIT in hematopoietic cells, we performed GST-pulldown assays and found that the substrate-trapping mutant PRL2/CS-DA showed an increased association with KIT and CBL compared to wild-type PRL2 in Kasumi-1 cells, suggesting that KIT and CBL may be PRL2 substrates. Furthermore, we found that PRL2/CS-DA mutant showed enhanced association with FLT3 and CBL compared to wild-type PRL2 in MV4-11 cells. Our data suggest that PRL2 dephosphorylates CBL and inhibits CBL activity toward KIT and FLT3, leading to sustained activation of downstream signaling pathways.To determine the functional significance of PRL2 in human AML with KIT and FLT3 mutations, we utilized two well-established murine model of myeloproliferative neoplasms (MPN) induced by KITD814V or FLT3-ITD. We found that loss of Prl2 decreased the ability of oncogenic KITD814V and FLT3-ITD to promote mouse hematopoietic stem and progenitor cell (HSPC) proliferation in vitro andthe development of MPN in vivo. Furthermore, we found that genetic and pharmacological inhibition of PRL2 decreased the proliferation and survival of human AML cells bearing KIT or FLT3 mutations.Taken together, we demonstrate that PRL2 promotes leukemia stem cell (LSC) self-renewal and maintenance through sustaining the activity of oncogenic KIT and FLT3 signals. Our findings suggest that pharmacological inhibition of PRL2 holds potential as a novel therapy for acute myeloid leukemia, and might also be applicable to the treatment of other human cancers. DisclosuresNo relevant conflicts of interest to declare.

PinX1: structure, regulation and its functions in cancer.

PIN2/TRF1-interacting telomerase inhibitor 1 (PinX1) is a novel cloned gene located at human chromosome 8p23, playing a vital role in maintaining telomeres length and chromosome stability. It has been demonstrated to be involved in tumor genesis and progression in most malignancies. However, some researches showed opposing molecular status of PinX1 gene and its expression patterns in several other types of tumors. The pathogenic mechanism of PinX1 expression in human malignancy is not yet clear. Moreover, emerging evidence suggest that PinX1 (especially its TID domain) might be a potential new target cancer treatment. Therefore, PinX1 may be a new potential diagnostic biomarker and therapeutic target for human cancers, and may play different roles in different human cancers. The functions and the mechanisms of PinX1 in various human cancers remain unclear, suggesting the necessity of further extensive works of its role in tumor genesis and progression.

Roles and epigenetic regulation of epithelial-mesenchymal transition and its transcription factors in cancer initiation and progression.

The epithelial-mesenchymal transition (EMT) is a crucial developmental process by which epithelial cells undergo a mesenchymal phenotypic change. During EMT, epigenetic mechanisms including DNA methylation and histone modifications are involved in the regulation of EMT-related genes. The epigenetic gene silencing of the epithelial marker E-cadherin has been well characterized. In particular, three major transcriptional repressors of E-cadherin, Snail, ZEB, and Twist families, also known as EMT-inducing transcription factors (EMT-TFs), play a crucial role in this process by cooperating with multiple epigenetic modifiers. Furthermore, recent studies have identified the novel epigenetic modifiers that control the expression of EMT-TFs, and these modifiers have emerged as critical regulators of cancer development and as novel therapeutic targets for human cancer. In this review, the diverse functions of EMT-TFs in cancer progression, the cooperative mechanisms of EMT-TFs with epigenetic modifiers, and epigenetic regulatory roles for the expression of EMT-TFs will be discussed.

Utilization of Microarray Analysis to Determine Therapeutic Targets in Human Cancers

Utilization of Microarray Analysis to Determine Therapeutic Targets in Human Cancers

The histone demethylase LSD1 is a novel oncogene and therapeutic target in oral cancer

The histone demethylase LSD1 functions as a key pro-oncogene and attractive therapeutic target in human cancer. Here we sought to interrogate the oncogenic roles of LSD1 in OSCC tumorigenesis and therapeutic intervention by integrating chemical-induced OSCC model, genetic and pharmacological loss-of-function approaches. Our data revealed that aberrant LSD1 overexpression in OSCC was significantly associated with tumor aggressiveness and shorter overall survival. Increased abundance of LSD1 was detected along with disease progression in DMBA- or 4NQO-induced OSCC animal models. LSD1 depletion via siRNA-mediated knockdown in OSCC cells resulted in impaired cell proliferation, migration/invasion, tumorsphere formation and reduced xenograft growth while inducing cell apoptosis and enhancing chemosensitivity to 5-FU. Moreover, treatments of LSD1 chemical inhibitors (pargyline and tranylcypromine) induced its protein reduction probably via enhanced protein degradation and produced similar phenotypic changes resembling LSD1 silencing in OSCC cells. Pharmacological inhibition of LSD1 by intraperitoneal delivery of these inhibitors resulted in impaired xenograft overgrowth. Taken together, our data reveal the tumorigenic roles of LSD1 and identified LSD1 as a novel biomarker with diagnostic and prognostic significance, and also establish that targeting LSD1 by chemical inhibitors is a viable therapeutic strategy against OSCC.

Knockdown of TMEM16A suppressed MAPK and inhibited cell proliferation and migration in hepatocellular carcinoma.

TMEM16A plays an important role in cell proliferation in various cancers. However, less was known about the expression and role of TMEM16A in hepatocellular carcinoma. We screened the expression of TMEM16A in patients’ hepatocellular carcinoma tissues, and also analyzed the biological function of hepatocellular carcinoma cells by knockdown of TMEM16A, as well as the expression of MAPK signaling proteins, including p38, p-p38, ERK1/2, p-ERK1/2, JNK, and p-JNK, and cell cycle regulatory protein cyclin D1 in TMEM16A siRNA-transfected SMMC-7721 cells by Western blot. Our results showed that TMEM16A was overexpressed in hepatocellular carcinoma tissues. Inhibition of TMEM16A suppressed the cell proliferation, migration, and invasion, and cell cycle progression but did not influence the cell apoptosis. TMEM16A siRNA-suppressed cancer cell proliferation and tumor growth were accompanied by a reduction of p38 and ERK1/2 activation and cyclin D1 induction, and were not influenced by other tested MAPK signaling proteins. In addition, inhibition of TMEM16A suppressed tumorigenicity in vivo. TMEM16A is overexpressed in hepatocellular carcinoma, and that inhibition of TMEM16A suppressed MAPK and growth of hepatocellular carcinoma. TMEM16A could be a potentially novel therapeutic target for human cancers, including hepatocellular carcinoma.

A High Affinity hRpn2-Derived Peptide That Displaces Human Rpn13 from Proteasome in 293T Cells.

Rpn13 is a proteasome ubiquitin receptor that has emerged as a therapeutic target for human cancers. Its ubiquitin-binding activity is confined to an N-terminal Pru (pleckstrin-like receptor for ubiquitin) domain that also docks it into the proteasome, while its C-terminal DEUBAD (DEUBiquitinase ADaptor) domain recruits deubiquitinating enzyme Uch37 to the proteasome. Bis-benzylidine piperidone derivatives that were found to bind covalently to Rpn13 C88 caused the accumulation of polyubiquitinated proteins as well as ER stress-related apoptosis in various cancer cell lines, including bortezomib-resistant multiple myeloma lines. We find that a 38-amino acid peptide derived from the C-terminus of proteasome PC repeat protein hRpn2/PSMD1 binds to hRpn13 Pru domain with 12 nM affinity. By using NMR, we identify the hRpn13-interacting amino acids in this hRpn2 fragment, some of which are conserved among eukaryotes. Importantly, we find the hRpn2-derived peptide to immunoprecipitate endogenous Rpn13 from 293T cells, and to displace it from the proteasome. These findings indicate that this region of hRpn2 is the primary binding site for hRpn13 in the proteasome. Moreover, the hRpn2-derived peptide was no longer able to interact with endogenous hRpn13 when a strictly conserved phenylalanine (F948 in humans) was replaced with arginine or a stop codon, or when Y950 and I951 were substituted with aspartic acid. Finally, over-expression of the hRpn2-derived peptide leads to an increased presence of ubiquitinated proteins in 293T cells. We propose that this hRpn2-derived peptide could be used to develop peptide-based strategies that specifically target hRpn13 function in the proteasome.

Urothelial cancer associated 1: a long noncoding RNA with a crucial role in cancer.

Urothelial cancer associated 1 (UCA1) is a long noncoding RNA (lncRNA) which has gained more attention in recent years due to its aberrant expression in embryogenesis and a broad range of cancer tissues and cells. Importantly, multiple studies have shown that UCA1 plays oncogenic roles in tumor growth and metastasis, and it may act as a potential biomarker and therapeutic target for human cancers. However, the molecular mechanism of UCA1 in cancer initiation, progression and metastasis remains incompletely understood. Thus, gaining a better understanding of the functional mechanism of UCA1 in cancer onset and progression is of the utmost significance for evaluating the potential application of UCA1. In this review, we discuss UCA1 expression profiling, isoform, expression regulation, biological role and mechanism for UCA1 tumor-promoting effect. We further discuss the potential clinical application of UCA1 as a promising diagnostic biomarker or therapeutic target for human cancers. UCA1 functions as an oncogenic lncRNA in several malignancies, and it might become a potential biomarker or therapeutic target for human cancers.