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1.  Genetic inactivation or pharmacological inhibition of Pdk1 delays development and inhibits metastasis of BrafV600E::Pten−/− melanoma 
Oncogene  2013;33(34):4330-4339.
Phosphoinositide-dependent kinase-1 (PDK-1) is a serine/threonine protein kinase that phosphorylates members of the conserved AGC kinase superfamily, including AKT and PKC, and is implicated in important cellular processes including survival, metabolism and tumorigenesis. In large cohorts of nevi and melanoma samples, PDK1 expression was significantly higher in primary melanoma, compared with nevi, and was further increased in metastatic melanoma. PDK1 expression suffices for its activity, due to auto-activation, or elevated phosphorylation by phosphoinositide 3'-OH-kinase (PI 3-K). Selective inactivation of Pdk1 in the melanocytes of BrafV600E::Pten−/− or BrafV600E::Cdkn2a−/−::Pten−/− mice delayed the development of pigmented lesions and melanoma induced by systemic or local administration of 4-HT. Melanoma invasion and metastasis were significantly reduced or completely prevented by Pdk1 deletion. Administration of the PDK1 inhibitor GSK2334470 (PDKi) effectively delayed melanomagenesis and metastasis in BrafV600E::Pten−/− mice. Pdk1−/− melanomas exhibit a marked decrease in the activity of AKT, P70S6K and PKC. Notably, PDKi was as effective in inhibiting AGC kinases and colony forming efficiency of melanoma with Pten WT genotypes. Gene expression analyses identified Pdk1-dependent changes in FOXO3a-regulated genes and inhibition of FOXO3a restored proliferation and colony formation of Pdk1−/− melanoma cells. Our studies provide direct genetic evidence for the importance of PDK1, in part through FOXO3a-dependent pathway, in melanoma development and progression.
PMCID: PMC3955742  PMID: 24037523
PDK1; FOXO3a; melanoma; Braf; Pten; GSK2334470
2.  SUMOylation inhibits FOXM1 activity and delays mitotic transition 
Oncogene  2013;33(34):4316-4329.
The forkhead box transcription factor FOXM1 is an essential effector of G2/M phase transition, mitosis and the DNA damage response. As such, it is frequently deregulated during tumorgenesis. Here we report that FOXM1 is dynamically modified by SUMO1 but not SUMO2/3 at multiple sites. We show that FOXM1 SUMOylation is enhanced in MCF-7 breast cancer cells in response to treatment with epirubicin and mitotic inhibitors. Mutation of 5 consensus conjugation motifs yielded a SUMOylation deficient mutant FOXM1. Conversely, fusion of the E2 ligase Ubc9 to FOXM1 generated an auto-SUMOylating mutant (FOXM1-Ubc9). Analysis of wild-type FOXM1 and mutants revealed that SUMOylation inhibits FOXM1 activity, promotes translocation to the cytoplasm, and enhances APC/Cdh1-mediated ubiquitination and degradation. Further, expression of the SUMOylation-deficient mutant enhanced cell proliferation compared to wild-type FOXM1 whereas the FOXM1-Ubc9 fusion protein resulted in persistent cyclin B1 expression and slowed the time from mitotic entry to exit. In summary, our findings suggest that SUMOylation attenuates FOXM1 activity and causes mitotic delay in cytotoxic drug response.
PMCID: PMC4096495  PMID: 24362530
FOXM1; SUMO; Chemotherapy; Drug Resistance; Breast Cancer; Cell Cycle
3.  miR-93-directed down-regulation of DAB2 defines a novel oncogenic pathway in lung cancer 
Oncogene  2013;33(34):4307-4315.
The disabled homolog 2 (DAB2) gene was recently identified as a tumor suppressor gene with its expression down-regulated in multiple cancer types. The role of DAB2 in lung tumorigenesis, however, is not fully characterized, and the mechanisms of DAB2 dysregulation in lung cancer are not defined. Here we show that low DAB2 levels in lung tumor specimens are significantly correlated with poor patient survival, and that DAB2 over-expression significantly inhibits cell growth in cultured lung cancer cells, indicating its potent tumor suppressor function. We next identify that microRNA miR-93 functions as a potent repressor of DAB2 expression by directly targeting the 3′UTR of the DAB2 mRNA. Using in vitro and in vivo approaches, we demonstrate that miR-93 over-expression plays an important role in promoting lung cancer cell growth, and that its oncogenic function is primarily mediated by down-regulating DAB2 expression. Our clinical investigations further indicate that high tumor levels of miR-93 are correlated with poor survival of lung cancer patients. The correlations of both low DAB2 and high miR-93 expression with poor patient survival strongly support the critical role of the miR-93/DAB2 pathway in determining lung cancer progression.
PMCID: PMC4281941  PMID: 24037530
DAB2; miRNA; miR-93; lung cancer
4.  ASCL1 and RET expression defines a clinically relevant subgroup of lung adenocarcinoma characterized by neuroendocrine differentiation 
Oncogene  2013;33(29):3776-3783.
ASCL1 is an important regulatory transcription factor in pulmonary neuroendocrine (NE) cell development, but its value as a biomarker of NE differentiation in lung adenocarcinoma (AD) and as a potential prognostic biomarker remains unclear. We examined ASCL1 expression in lung cancer samples of varied histologic subtype, clinical outcome and smoking status and compared with expression of traditional NE markers. ASCL1 mRNA expression was found almost exclusively in smokers with AD, in contrast to non-smokers and other lung cancer subtypes. ASCL1 protein expression by immunohistochemical (IHC) analysis correlated best with synaptophysin compared with chromogranin and CD56/NCAM. Analysis of a compendium of 367 microarray-based gene expression profiles in stage I lung adenocarcinomas identified significantly higher expression levels of the RET oncogene in ASCL1-positive tumors (ASCL1+) compared with ASCL1− tumors (q-value <10−9). High levels of RET expression in ASCL1+ but not in ASCL1− tumors was associated with significantly shorter overall survival (OS) in stage 1 (P = 0.007) and in all AD (P = 0.037). RET protein expression by IHC had an association with OS in the context of ASCL1 expression. In silico gene set analysis and in vitro experiments by ASCL1 shRNA in AD cells with high endogenous expression of ASCL1 and RET implicated ASCL1 as a potential upstream regulator of the RET oncogene. Also, silencing ASCL1 in AD cells markedly reduced cell growth and motility. These results suggest that ASCL1 and RET expression defines a clinically relevant subgroup of ∼10% of AD characterized by NE differentiation.
PMCID: PMC4329973  PMID: 24037524
prognostic biomarker; MASH1; lung cancer; neuroendocrine; microarray
5.  Human skin neural crest progenitor cells are susceptible to BRAFV600E-induced transformation 
Kumar, SM | Dai, J | Li, S | Yang, R | Yu, H | Nathanson, KL | Liu, S | Zhou, H | Guo, J | Xu, X
Oncogene  2013;33(7):832-841.
Adult stem cells are multipotent and persist in small numbers in adult tissues throughout the lifespan of an organism. Unlike differentiated cells, adult stem cells are intrinsically resistant to senescence. It is unclear how adult stem cells in solid organs respond to oncogenic stimulation and whether these cells have a role in tumor initiation. We report here that expression of BRAFV600E in human neural crest progenitor cells (hNCPCs) did not induce growth arrest as seen in human melanocytes, but instead, increased their cell proliferation capacity. These cells (hNCPCsV600E) acquired anchorage-independent growth ability and were weakly tumorigenic in vivo. Unlike in human melanocytes, BRAFV600E expression in hNCPCs did not induce p16INK4a expression. BRAFV600E induced elevated expression of CDK2, CDK4, MITF and EST1/2 protein in hNCPCs, and also induced melanocytic differentiation of these cells. Furthermore, overexpression of MITF in hNCPCsV600E dramatically increased their tumorigenicity and resulted in fully transformed tumor cells. These findings indicate that hNCPCs are susceptible to BRAFV600E-induced transformation, and MITF potentiates the oncogenic effect of BRAFV600E in these progenitor cells. These results suggest that the hNCPCs are potential targets for BRAFV600E-induced melanocytic tumor formation.
PMCID: PMC3695032  PMID: 23334329
melanoma; neural crest; transformation; melanocytes; BRAFV600E
6.  ELF3 is a Repressor of Androgen Receptor Action in Prostate Cancer Cells 
Oncogene  2013;33(7):862-871.
The androgen receptor (AR) plays a critical role in the development and progression of prostate cancer (PC) and is a major therapeutic target in this disease. The transcriptional activity of AR is modulated by the co-regulators with which it interacts and consequently deregulation of cofactor expression and/or activity impacts the expression of genes whose products can play a role in PC pathogenesis. Here we report that ELF3, a member of the ETS family of transcription factors, is a repressor of AR transcriptional activity. Exogenous expression of ELF3 represses AR transcriptional activity when assessed using reporter-based transfection assays or when evaluated on endogenous AR target genes. Conversely, ELF3 knockdown increases the AR transcriptional activity. Biochemical dissection of this activity indicates that it results from the physical interaction between ELF3 and AR and that this interaction inhibits the recruitment of AR to specific androgen response elements within target gene promoters. Significantly, we observed that depletion of ELF3 expression in LNCaP cells promotes cell migration while increased ELF3 expression severely inhibits tumor growth in vitro and in a mouse xenograft model. Taken together, these results suggest that modulation of ELF3 expression and/or AR/ELF3 interaction may have utility in the treatment of PC.
PMCID: PMC4103030  PMID: 23435425
ETS factor; ChIP; nuclear receptor; LNCaP cells; xenograft
7.  EIF3i Promotes Colon Oncogenesis by Regulating COX-2 Protein Synthesis and β-Catenin Activation 
Oncogene  2013;33(32):4156-4163.
Translational control of gene expression has recently been recognized as an important mechanism controlling cell proliferation and oncogenesis and it mainly occurs in the initiation step of protein synthesis that involves multiple eukaryotic initiation factors (eIFs). Many eIFs have been found to have aberrant expression in human tumors and the aberrant expression may contribute to oncogenesis. However, how these previously considered house-keeping proteins are potentially oncogenic remains elusive. In this study, we investigated the expression of eIF3i in human colon cancers, tested its contribution to colon oncogenesis, and determined the mechanism of eIF3i action in colon oncogenesis. We found that eIF3i expression was up-regulated in both human colon adenocarcinoma and adenoma polyps as well as in model inducible colon tumorigenic cell lines. Over-expression of ectopic eIF3i in intestinal epithelial cells causes oncogenesis by directly up-regulating synthesis of COX-2 protein and activates the β-catenin/TCF4 signaling pathway that mediates the oncogenic function of eIF3i. Together, we conclude that eIF3i is a proto-oncogene that drives colon oncogenesis by translationally up-regulating COX-2 and activating β-catenin signaling pathway. These findings imply that protooncogenic eIFs likely exert their tumorigenic function by regulating/altering the synthesis level of down-stream tumor suppressor or oncogenes.
PMCID: PMC3962800  PMID: 24056964
eIF3i; COX-2; β-catenin; translational control; colon cancer; RNA-binding
8.  FOXM1 targets NBS1 to regulate DNA damage-induced senescence and epirubicin resistance 
Oncogene  2013;33(32):4144-4155.
FOXM1 is implicated in genotoxic drug resistance but its mechanism of action remains elusive. We show here that FOXM1-depletion can sensitize breast cancer cells and MEFs into entering epirubicin-induced senescence, with the loss of long-term cell proliferation ability, the accumulation of γH2AX foci, and the induction of senescence-associated β-galactosidase activity and cell morphology. Conversely, reconstitution of FOXM1 in FOXM1-deficient MEFs alleviates the accumulation of senescence-associated γH2AX foci. We also demonstrate that FOXM1 regulates NBS1 at the transcriptional level through an FHRE on its promoter. Like FOXM1, NBS1 is overexpressed in the epirubicin-resistant MCF-7EpiR cells and its expression level is low but inducible by epirubicin in MCF-7 cells. Consistently, overexpression of FOXM1 augmented and FOXM1 depletion reduced NBS1 expression and epirubicin-induced ATM phosphorylation in breast cancer cells. Together these findings suggest that FOXM1 increases NBS1 expression and ATM phosphorylation, possibly through increasing the levels of the MRN(MRE11/RAD50/NBS1) complex. Consistent with this idea, the loss of P-ATM induction by epirubicin in the NBS1-deficient NBS1-LBI fibroblasts can be rescued by NBS1 reconstitution. Resembling FOXM1, NBS1 depletion also rendered MCF-7 and MCF-7EpiR cells more sensitive to epirubicin-induced cellular senescence. In agreement, the DNA repair-defective and senescence phenotypes in FOXM1-deficent cells can be effectively rescued by overexpression of NBS1. Moreover, overexpression of NBS1 and FOXM1 similarly enhanced and their depletion downregulated HR DNA repair activity. Crucially, overexpression of FOXM1 failed to augment HR activity in the background of NBS1 depletion, demonstrating that NBS1 is indispensable for the HR function of FOXM1. The physiological relevance of the regulation of NBS1 expression by FOXM1 is further underscored by the strong and significant correlation between nuclear FOXM1 and total NBS1 expression in breast cancer patient samples, further suggesting that NBS1 as a key FOXM1 target gene involved in DNA damage response, genotoxic drug resistance and DNA damage-induced senescence.
PMCID: PMC3969838  PMID: 24141789
FOXM1; senescence; DNA damage; NBS1; epirubicin; resistance; breast cancer
9.  Syntaxin 6-mediated Golgi translocation plays an important role in nuclear functions of EGFR through microtubule-dependent trafficking 
Oncogene  2013;33(6):756-770.
Receptor tyrosine kinases (RTKs) are cell surface receptors that initiate signal cascades in response to ligand stimulation. Abnormal expression and dysregulated intracellular trafficking of RTKs have been shown to be involved in tumorigenesis. Recent evidence shows that these cell surface receptors translocate from cell surface to different cellular compartments, including the Golgi, mitochondria, endoplasmic reticulum (ER) and the nucleus, to regulate physiological and pathological functions. Although some trafficking mechanisms have been resolved, the mechanism of intracellular trafficking from cell surface to the Golgi is not yet completely understood. Here we report a mechanism of Golgi translocation of epidermal growth factor receptor (EGFR) in which EGF-induced EGFR travels to the Golgi via microtubule-dependent movement by interacting with dynein and fuses with the Golgi through syntaxin 6-mediated membrane fusion. We also demonstrate that the microtubule- and syntaxin 6-mediated Golgi translocation of EGFR is necessary for its consequent nuclear translocation and nuclear functions. Thus, together with previous studies, the microtubule- and syntaxin 6-mediated trafficking pathway from cell surface to the Golgi, ER and the nucleus defines a comprehensive trafficking route for EGFR to travel from cell surface to the Golgi and the nucleus.
PMCID: PMC3874427  PMID: 23376851
EGF receptor; Golgi and nuclear translocation; microtubules; syntaxin 6
10.  Site Specific Activation of AKT Protects Cells from Death Induced by Glucose Deprivation 
Oncogene  2013;33(6):745-755.
The serine/threonine kinase AKT is a key mediator of cancer cell survival. We demonstrate that transient glucose deprivation modestly induces AKT phosphorylation at both Thr308 and Ser473. In contrast, prolonged glucose deprivation induces selective AKTThr308 phosphorylation and phosphorylation of a distinct subset of AKT downstream targets leading to cell survival under metabolic stress. Glucose deprivation-induced AKTThr308 phosphorylation is dependent on PDK1 and PI3K but not EGFR or IGF1R. Prolonged glucose deprivation induces the formation of a complex of AKT, PDK1, and the GRP78 chaperone protein, directing phosphorylation of AKTThr308 but AKTSer473. Our results reveal a novel mechanism of AKT activation under prolonged glucose deprivation that protects cells from metabolic stress. The selective activation of AKTThr308 phosphorylation that occurs during prolonged nutrient deprivation may provide an unexpected opportunity for the development and implementation of drugs targeting cell metabolism and aberrant AKT signaling.
PMCID: PMC3874430  PMID: 23396361
glucose deprivation; site specific AKT phosphorylation; substrate specific AKT activation; cell survival
11.  HAI-2 suppresses the invasive growth and metastasis of prostate cancer through regulation of matriptase 
Oncogene  2013;33(38):4643-4652.
Dysregulation of cell surface proteolysis has been strongly implicated in tumorigenicity and metastasis. In this study, we delineated the role of hepatocyte growth factor activator inhibitor-2 (HAI-2) in prostate cancer (PCa) cell migration, invasion, tumorigenicity and metastasis using a human PCa progression model (103E, N1, and N2 cells) and xenograft models. N1 and N2 cells were established through serial intraprostatic propagation of 103E human PCa cells and isolation of the metastatic cells from nearby lymph nodes. The invasion capability of these cells was revealed to gradually increase throughout the serial isolations (103E
PMCID: PMC4314694  PMID: 24121274
prostate cancer; hepatocyte growth factor activator inhibitor-2; cancer cell invasion; tumorigenicity and metastasis
PMCID: PMC3962713  PMID: 24037531
Oncogene  2009;28(37):3296-3306.
The tyrosine kinase receptor anaplastic lymphoma kinase (ALK) and its ligand, the growth factor pleiotrophin (PTN), are highly expressed during the development of the nervous system and have been implicated in the malignant progression of different tumor types. Here, we describe human single-chain variable fragment (scFv) antibodies that target the ligand-binding domain (LBD) in ALK and show the effect in vitro and in vivo. The ALK LBD was used as a bait in a yeast two-hybdrid system to select human scFv from a library with randomized complementarity-determining region 3 domains. Surface plasmon resonance showed high-affinity binding of the selected scFv. The anti-ALK scFv competed for binding of PTN to ALK in intact cells and inhibited PTN-dependent signal transduction through endogenous ALK. Invasion of an intact endothelial cell monolayer by U87MG human glioblastoma cells was inhibited by the anti-ALK scFv. In addition, the growth of established tumor xenografts in mice was reversed after the induction of the conditional expression of the anti-ALK scFv. In archival malignant brain tumors expression levels of ALK and PTN were found elevated and appear correlated with poor patient survival. This suggests a rate-limiting function of the PTN/ALK interaction that may be exploited therapeutically.
PMCID: PMC4312131  PMID: 19633684
ALK; growth factor; PTN; single-chain antibody; tyrosine kinase receptor
Oncogene  2013;33(14):1872-1876.
Most GISTs contain KIT or PDGFRA kinase gain-of-function mutations, and therefore respond clinically to imatinib and other tyrosine kinase inhibitor (TKI) therapies. However, clinical progression subsequently results from selection of TKI-resistant clones, typically containing secondary mutations in the KIT kinase domain, which can be heterogeneous between and within GIST metastases in a given patient. TKI-resistant KIT oncoproteins require HSP90 chaperoning and are potently inactivated by HSP90-inhibitors, but clinical applications in GIST patients are constrained by the toxicity resulting from concomitant inactivation of various other HSP90 client proteins, beyond KIT and PDGFRA. To identify novel targets responsible for KIT oncoprotein function, we performed parallel genome-scale short hairpin RNA (shRNA)-mediated gene knockdowns in KIT-mutant GIST-T1 and GIST882. GIST cells were infected with a lentiviral shRNA pooled library targeting 11 194 human genes, and allowed to proliferate for 5~7 weeks, at which point assessment of relative hairpin abundance identified the HSP90-cofactor, CDC37, as one of the top six GIST-specific essential genes. Validations in treatment-naïve (GIST-T1, GIST882) vs. imatinib-resistant GISTs (GIST48, GIST430) demonstrated that: 1) CDC37 interacts with oncogenic KIT; 2) CDC37 regulates expression and activation of KIT and downstream signaling intermediates in GIST; and 3) unlike direct HSP90 inhibition, CDC37 knockdown accomplishes prolonged KIT inhibition (>20 days) in GIST. These studies highlight CDC37 as a key biologic vulnerability in both imatinib-sensitive and imatinib-resistant GIST. CDC37 targeting is expected to be selective for KIT/PDGFRA and a subset of other HSP90 clients, and thereby represents a promising strategy for inactivating the myriad KIT/PDGFRA oncoproteins in TKI-resistant GIST patients.
PMCID: PMC4310725  PMID: 23584476
CDC37; HSP90; GIST; targeted therapy; functional genomics; shRNA library
Oncogene  2013;33(46):5370-5378.
Dysregulation of the Hedgehog (Hh)-Gli signaling pathway is implicated in a variety of human cancers, including basal cell carcinoma (BCC), medulloblastoma (MB), and embryonal rhabdhomyosarcoma (eRMS), three principle tumors associated with human Gorlin syndrome. However, the cellular origins of these tumors, including eRMS, remain poorly understood. In this study, we explore the cell populations that give rise to Hh-related tumors by specifically activating Smoothened (Smo) in both Hh-producing and -responsive cell lineages in postnatal mice. Interestingly, we find that unlike BCC and MB, eRMS originates from the stem/progenitor populations that do not normally receive active Hh signaling. Furthermore, we find that the myogenic lineage in postnatal mice is largely Hh quiescent and that Pax7-expressing muscle satellite cells are not able to give rise to eRMS upon Smo or Gli1/2 over-activation in vivo, suggesting that Hh-induced skeletal muscle eRMS arises from Hh/Gli quiescent non-myogenic cells. In addition, using the Gli1 null allele and a Gli3 repressor allele, we demonstrate the genetic requirement for Gli proteins in Hh-induced eRMS formation and provide molecular evidence for the involvement of SoxC factors in Hh-dependent eRMS cell survival and differentiation.
PMCID: PMC4309268  PMID: 24276242
Oncogene  2013;33(30):3959-3969.
The p53 tumor suppressor protein is a major sensor of cellular stresses, and upon stabilization, activates or represses many genes that control cell fate decisions. While the mechanism of p53-mediated transactivation is well established, several mechanisms have been proposed for p53-mediated repression. Here, we demonstrate that the CDK inhibitor p21 is both necessary and sufficient for the downregulation of known p53-repression targets, including survivin, CDC25C and CDC25B in response to p53 induction. These same targets are similarly repressed in response to p16 overexpression, implicating the involvement of the shared downstream retinoblastoma (RB)-E2F pathway. We further show that in response to either p53 or p21 induction, E2F4 complexes are specifically recruited onto the promoters of these p53 repression targets. Moreover, abrogation of E2F4 recruitment via the inactivation of RB pocket proteins, but not by RB loss of function alone, prevents the repression of these genes. Finally, our results indicate that E2F4 promoter occupancy is globally associated with p53 repression targets, but not with p53 activation targets, implicating E2F4 complexes as effectors of p21 dependent p53-mediated repression.
PMCID: PMC4067464  PMID: 24096481
p53; p21; E2F4; RB; p130; transcriptional repression
Oncogene  2013;33(30):3980-3991.
The processes that control the progression of ductal carcinoma in situ (DCIS) to invasive breast cancer remain poorly understood. Epidermal growth factor receptor 2 (ErbB2) over expression is common in DCIS, as is disruption of the retinoblastoma tumor suppressor (RB) pathway. Here we examined the cooperative impact of ErbB2 and RB deregulation on facets of disease progression. Our studies demonstrate that RB deficiency altered the expression of key molecules needed for proper cellular organization and epithelial cell-cell adhesion as part of a program related to the epithelial to mesenchymal transition (EMT). An increase in the invasive potential of ErbB2 over expressing cells was observed upon RB depletion. Furthermore, stable knockdown of RB resulted in invasive lesions in orthotopic xenograft assays, compared to DCIS-like lesions developing from RB-proficient cells. Conversely, the invasive phenotype observed in ErbB2-positive cancer models was inhibited through CDK4/6 inhibition in an RB-dependent manner. Lastly, in a cohort of DCIS cases, we show that while elevated levels of ErbB2 are associated with increased risk of a subsequent DCIS recurrence, it is not associated with progression to invasive disease. In contrast, RB loss in ErbB2 positive DCIS cases was associated with increased risk for invasive breast cancer. Taken together, these data demonstrate a key role for the RB-pathway in invasion associated with breast tumor progression, and shed light on the key molecular events that promote the progression of DCIS to invasive disease.
PMCID: PMC4150690  PMID: 24121271
Tumor Suppressor; Epithelial to Mesenchymal Transition; Cyclin Dependent Kinase; Cell Cycle; E2F; CDK4/6; PD-0332991
Oncogene  2011;31(7):858-868.
Glioblastoma is the most frequent brain tumor in adults and is the most lethal form of human cancer. Despite the improvements in treatments, survival of patients remains poor. In order to identify microRNAs (miRs) involved in glioma tumorigenesis, we evaluated, by a miRarray, differential expression of miRs in the tumorigenic glioma LN-18, LN-229 and U87MG cells compared with the non-tumorigenic T98G cells. Among different miRs we focused our attention on miR-221 and -222. We demonstrated the presence of a binding site for these two miRs in the 3′ untranslated region of the protein tyrosine phosphatase μ (PTPμ). Previous studies indicated that PTPμ suppresses cell migration and is downregulated in glioblastoma. Significantly, we found that miR-221 and -222 over-expression induced a downregulation of PTPμ as analyzed by both western blot and real-time PCR. Furthermore, miR-222 and -221 induced an increase in cell migration and growth in soft agar in glioma cells. Interestingly, the re-expression of PTPμ gene was able to revert the miR-222 and -221 effects on cell migration. Furthermore, we found an inverse correlation between miR-221 and -222 and PTPμ in human glioma cancer samples. In conclusion, our results suggest that miR-221 and -222 regulate glioma tumorigenesis at least in part through the control of PTPμ protein expression.
PMCID: PMC4299860  PMID: 21743492
Glioma; microRNA; tumorigenesis; apoptosis
Oncogene  2013;33(29):3784-3793.
Increased expression of HBEGF in ER negative breast tumors is correlated with enhanced metastasis to distant organ sites and more rapid disease recurrence upon removal of the primary tumor. Our previous work has demonstrated a paracrine loop between breast cancer cells and macrophages in which the tumor cells are capable of stimulating macrophages through the secretion of CSF-1 while the tumor associated macrophages (TAMs) in turn aid in tumor cell invasion by secreting EGF. To determine how the autocrine expression of EGFR ligands by carcinoma cells would affect this paracrine loop mechanism, and in particular whether tumor cell invasion depends on spatial ligand gradients generated by TAMs, we generated cell lines with increased HBEGF expression. We find that autocrine HBEGF expression enhanced in vivo intravasation and metastasis, and resulted in a novel phenomenon in which macrophages were no longer required for in vivo invasion of breast cancer cells. In vitro studies revealed that expression of HBEGF enhanced invadopodium formation, thus providing a mechanism for cell autonomous invasion. The increased invadopodium formation was directly dependent on EGFR signaling, as demonstrated by a rapid decrease in invadopodia upon inhibition of autocrine HBEGF/EGFR signaling as well as inhibition of signaling downstream of EGFR activation. HBEGF expression also resulted in enhanced invadopodium function via upregulation of MMP2 and MMP9 expression. We conclude that high levels of HBEGF expression can short-circuit the tumor cell/macrophage paracrine invasion loop, resulting in enhanced tumor invasion that is independent of macrophage signaling.
PMCID: PMC3950352  PMID: 24013225
HBEGF; breast cancer invasion; EGFR; metastasis
Oncogene  2013;33(29):3861-3868.
Kcnq1, which encodes for the pore-forming alpha subunit of a voltage-gated potassium channel, was identified as a gastrointestinal (GI) tract cancer susceptibility gene in multiple Sleeping Beauty DNA transposon-based forward genetic screens in mice. To confirm that Kcnq1 has a functional role in GI tract cancer we created ApcMin mice that carried a targeted deletion mutation in Kcnq1. Results demonstrated that Kcnq1 is a tumor suppressor gene as Kcnq1 mutant mice developed significantly more intestinal tumors, especially in the proximal small intestine and colon, some of these tumors progressed to become aggressive adenocarcinomas. Gross tissue abnormalities were also observed in the rectum, pancreas and stomach. Colon organoid formation was significantly increased in organoids created from Kcnq1 mutant mice compared with wildtype littermate controls, suggesting a role for Kcnq1 in regulation of the intestinal crypt stem cell compartment. To identify gene expression changes due to loss of Kcnq1 we carried out microarray studies in colon and proximal small intestine. We identified altered genes involved in innate immune responses, goblet and Paneth cell function, ion channels, intestinal stem cells, EGFR and other growth regulatory signaling pathways. We also found genes implicated in inflammation and in cellular detoxification. Pathway analysis using Ingenuity Pathway Analysis (IPA) and gene set enrichment analysis (GSEA) confirmed the importance of these gene clusters and further identified significant overlap with genes regulated by MUC2 and CFTR, two important regulators of intestinal homeostasis. To investigate the role of KCNQ1 in human colorectal cancer (CRC) we measured protein levels of KCNQ1 by immunohistochemistry in tissue microarrays containing samples from CRC patients with liver metastases who had undergone hepatic resection. Results showed that low expression of KCNQ1 expression was significantly associated with poor overall survival (OS).
PMCID: PMC3935979  PMID: 23975432
colorectal cancer; KCNQ1; tumor suppressor
PMCID: PMC4295628  PMID: 23604120
PMCID: PMC4294274  PMID: 23416980
PMCID: PMC4294546  PMID: 18679417
PMCID: PMC4292929  PMID: 23474764
PMCID: PMC4292930  PMID: 21625215

Results 1-25 (1559)