Senji Shirasawa

Fukuoka University, Hukuoka, Fukuoka, Japan

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Publications (138)826.41 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Docking protein 2 (Dok2) is an adapter protein which is involved in hematopoiesis. However, it still remains unclear how Dok2 functions in regulation of transcription of hematopoietic genes. To address this issue, we knocked-down Dok2 mRNA in mouse erythroleukemia cells which highly express Dok2 intrinsically.
    Anticancer research 08/2014; 34(8):4561-7. · 1.71 Impact Factor
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    ABSTRACT: We have previously reported the crucial roles of oncogenic Kirsten rat sarcoma viral oncogene homolog (KRAS) in inhibiting apoptosis and disrupting cell polarity via the regulation of phosphodiesterase 4 (PDE4) expression in human colorectal cancer HCT116 cells in three-dimensional cultures (3DC). Herein we evaluated the effects of resveratrol, a PDE4 inhibitor, on the luminal cavity formation and the induction of apoptosis in HCT116 cells.
    Anticancer research 08/2014; 34(8):4551-5. · 1.71 Impact Factor
  • Keiko Doi, Shuhei Ishikura, Senji Shirasawa
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    ABSTRACT: ZFAT (zinc-finger gene in AITD susceptibility region), originally identified as a candidate susceptibility gene for autoimmune thyroid disease, has been reported to be involved in various cellular processes and several common diseases including multiple sclerosis. Recent studies revealed that mouse Zfat is a novel critical regulator for both thymocyte differentiation and peripheral T-cell homeostasis. Zfat deficiency at early thymocyte developmental stages results in the inhibition of the development of CD4(+)CD8(+) thymocytes with an impaired positive selection. Zfat deficiency in peripheral T-cells results in a reduction in the number of T-cells with decreased expression of the interleukin-7 receptor-α (IL-7Rα) that is critical for T-cell homeostasis. In addition, T-cell antigen receptor stimulation-induced responses of Zfat-deficient T-cells are also impaired, with reduced IL-2Rα expression. This review highlights and discusses the roles of Zfat in thymocyte differentiation of T-cells and in the homeostasis of naive T-cells with recent work.
    Anticancer research 08/2014; 34(8):4489-4495. · 1.71 Impact Factor
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    ABSTRACT: There are currently no approved targeted therapies for advanced KRAS mutant (KRASMT) colorectal cancer (CRC). Using a unique systems biology approach, we identified JAK1/2-dependent activation of STAT3 as the key mediator of resistance to MEK inhibitors in KRASMT CRC in vitro and in vivo. Further analyses identified acute increases in c-MET activity following treatment with MEK inhibitors in KRASMT CRC models, which was demonstrated to promote JAK1/2-STAT3-mediated resistance. Furthermore, activation of c-MET following MEK inhibition was found to be due to inhibition of the ERK-dependent metalloprotease ADAM17, which normally inhibits c-MET signaling by promoting shedding of its endogenous antagonist, soluble "decoy" MET. Most importantly, pharmacological blockade of this resistance pathway with either c-MET or JAK1/2 inhibitors synergistically increased MEK-inhibitor-induced apoptosis and growth inhibition in vitro and in vivo in KRASMT models, providing clear rationales for the clinical assessment of these combinations in KRASMT CRC patients.
    Cell reports. 06/2014;
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    ABSTRACT: The KRAS oncogene influences angiogenesis, metastasis and chemoresistance in colorectal cancers (CRCs), and these processes are all enhanced in hypoxic conditions. To define functional activities of mutant KRAS in a hypoxic microenvironment, we first performed cDNA microarray experiments in isogenic DKs5 and DKO3 colon cancer cell lines that differ only by their expression of mutant KRAS (K-ras(D13) ). Adrenomedullin (ADM) was identified as one of the most significantly upregulated genes in DKs5 cells that express the KRAS oncogene in hypoxia (3.2-fold, p = 1.47 × 10(-5) ). Ectopic expression of mutant KRAS (K-ras(V12) ) in Caco-2 cells (K-ras(WT) ) induced ADM, whereas selective knockdown of mutant KRAS alleles (K-ras(D13) or K-ras(V12) ) in HCT116, DLD1 and SW480 colon cancer cells suppressed the expression of ADM in hypoxia. Knockdown of ADM in colon tumor xenografts blocked angiogenesis and stimulated apoptosis, resulting in tumor suppression. Furthermore, ADM also regulated colon cancer cell invasion in vitro. Among 56 patients with CRC, significantly higher expression levels of ADM were observed in samples harboring a KRAS mutation. Collectively, ADM is a new target of oncogenic KRAS in the setting of hypoxia. This observation suggests that therapeutic targets may differ depending upon the specific tumor microenvironment.
    International Journal of Cancer 05/2014; 134(9):2041-50. · 6.20 Impact Factor
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    ABSTRACT: KRAS is mutated in ∼40% of colorectal cancer (CRC), and there are limited effective treatments for advanced KRAS mutant CRC. Therefore, it is crucial that downstream mediators of oncogenic KRAS continue to be studied. We identified p190RhoGAP as being phosphorylated in the DLD1 CRC cell line, which expresses a heterozygous KRAS G13D allele, and not in DKO4 in which the mutant allele has been deleted by somatic recombination. We found that a ubiquitous binding partner of p190RhoGAP, p120RasGAP (RasGAP), is expressed in much lower levels in DKO4 cells compared to DLD1, and this expression is regulated by KRAS. Rescue of RasGAP expression in DKO4 rescued Rho pathway activation and partially rescued tumorigenicity in DKO4 cells, indicating that the combination of mutant KRAS and RasGAP expression is crucial to these phenotypes. We conclude that RasGAP is an important effector of mutant KRAS in CRC.
    PLoS ONE 01/2014; 9(1):e86103. · 3.73 Impact Factor
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    ABSTRACT: Cetuximab is a chimeric IgG1 monoclonal antibody (mAb) that targets the extracellular domain of epidermal growth factor receptor (EGFR). Oncogenic KRAS mutations in tumors have been shown to be a negative predictor of the response of colorectal cancer (CRC) to cetuximab treatment. Cetuximab exerts its therapeutic effects through several mechanisms including antibody-dependent cellular cytotoxicity (ADCC). However, the influence of KRAS mutations on cetuximab-mediated ADCC is not fully understood. Here, we investigated cetuximab-mediated ADCC in two pairs of isogenic CRC cells with or without a KRAS mutation. Peripheral blood mononuclear cells (PBMCs) from healthy volunteers and NK92, a natural killer (NK) cell line that exogenously expresses FcγRIIIa (CD16a), were used as effector cells. In an ADCC assay, perforin-dependent target cell lysis was not affected by the KRAS mutation status. On the other hand, perforin-independent ADCC was observed only in CRC cells with wild-type KRAS, but not in cells with mutant KRAS. Neutralizing experiments revealed that the Fas-Fas ligand (FasL) interaction was responsible for the induction of apoptosis and perforin-independent ADCC. Furthermore, the presence of effector cells clearly enhanced the growth-inhibitory effect of cetuximab only in CRC cells with wild-type KRAS, but not in those with mutant KRAS. These findings suggest that ADCC is an important mode of action of cetuximab and that KRAS mutation impairs the therapeutic effect exerted by cetuximab-mediated ADCC. © 2013 Wiley Periodicals, Inc.
    International Journal of Cancer 10/2013; · 6.20 Impact Factor
  • Toshiyuki Tsunoda, Senji Shirasawa
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    ABSTRACT: A zinc-finger gene in autoimmune thyroid disease susceptibility region (ZFAT) was originally identified as a highly conserved immune-related transcriptional regulator containing one adenosine-thymidine (AT)-hook and 18 C2H2-type zinc-finger domains. Subsequently, roles of ZFAT in development, primitive haematopoiesis, angiogenesis, immune responses and several common diseases, such as multiple sclerosis, hypertension and cancer, have been demonstrated. Previously, we recorded a ZFAT protein expression in MOLT-4 human acute T-lymphoblastic leukaemia cells, while ZFAT knockdown activated caspases and induced apoptosis in these cells. Hence, the precise functions of ZFAT are of particular interest in cancer research. In this article, we have reviewed investigations on the roles of ZFAT in haematopoietic and angiogenesis, and discussed the possible involvement of ZFAT in haematopoietic malignancies.
    Anticancer research 07/2013; 33(7):2833-7. · 1.71 Impact Factor
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    ABSTRACT: We previously reported that Tespa1 (thymocyte-expressed, positive selection-associated gene 1) protein expressed in lymphocytes physically interacts with IP3R (Inositol 1,4,5-trisphosphate receptor), a Ca(2+) channel protein spanning endoplasmic reticulum (ER) membrane. However, the biochemical characterization of Tespa1 protein remains unknown. In this study, we have found that Tespa1 protein was posttranslationally modified upon intracellular Ca(2+) increase in thymocytes. Through the analyses using various inhibitors, store-operated Ca(2+) entry (SOCE) was found to be an essential factor for the Tespa1 protein modification induced by TCR-stimulation. Remarkably, the Ca(2+)-dependent Tespa1 protein modification was restored by in vitro protein phosphatase treatment, indicating that this modification was due to phosphorylation. Moreover, we examined whether Ca(2+)-dependent phosphorylation of Tespa1 protein would affect the physical association between Tespa1 and IP3R proteins, revealing that physical association of these proteins is maintained regardless of the presence or absence of phosphorylation of Tespa1. In addition, KRAP protein which represents substantial amino acid sequence homology to Tespa1 was also posttranslationally phosphorylated by intracellular Ca(2+) increase in HCT116 human colon cancer cells and HEK293 human embryonic kidney cells, suggesting that common signaling mechanism(s) may contribute to the molecular modification of Tespa1 and KRAP in different cellular processes. All these results suggested a novel molecular modification of Tespa1 and the existence of the regulatory pathway that SOCE affects the Tespa1-IP3R molecular complex.
    Biochemical and Biophysical Research Communications 03/2013; · 2.41 Impact Factor
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    ABSTRACT: Regulation of intracellular Ca(2+) concentration is critical in numerous biological processes. Inositol 1,4,5-trisphosphate receptor (IP3R) functions as the Ca(2+) release channel on endoplasmic reticulum (ER) membranes. Much attention has been dedicated to mitochondrial Ca(2+) uptake via mitochondria-associated ER membranes (MAM) which is involved in intracellular Ca(2+) homeostasis; however, the molecular mechanisms that link the MAM to mitochondria still remain elusive. We previously reported that Tespa1 (thymocyte-expressed, positive selection-associated gene 1) expressed in lymphocytes physically interacts with IP3R. In this study, we first performed double-immunocytochemical staining of Tespa1 with a mitochondrial marker or an ER marker on an acute T lymphoblastic leukemia cell line, Jurkat cells, by using anti-ATP synthase or anti-calnexin antibody, respectively, and demonstrated that Tespa1 was localized very close to mitochondria and the Tespa1 localization was overlapped with restricted portion of ER. Next, we examined the effects of Tespa1 on the T cell receptor (TCR) stimulation-induced Ca(2+) flux by using Ca(2+) imaging in Jurkat cells. Reduction of Tespa1 protein by Tespa1-specific siRNA diminished TCR stimulation-induced Ca(2+) flux into both mitochondria and cytoplasm through the analyses of the mitochondrial Ca(2+) indicator (Rhod-2) and the cytoplasmic Ca(2+) indicator (Fluo-4), respectively. Furthermore, co-immunoprecipitation assay in HEK293 cells revealed that exogenous Tespa1 protein physically interacted with a MAM-associated protein, GRP75 (glucose-regulated protein 75), but not with an outer mitochondrial membrane protein, VDAC1 (voltage-dependent anion channel 1). All these results suggested that Tespa1 will participate in the molecular link between IP3R-mediated Ca(2+) release and mitochondrial Ca(2+) uptake in the MAM compartment.
    Biochemical and Biophysical Research Communications 03/2013; · 2.41 Impact Factor
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    ABSTRACT: Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is one of several pro-angiogenic factors, and represents a possible therapeutic target for patients with triple-negative breast cancer (TNBC). However, the role of HB-EGF in promoting tumor aggressiveness in TNBC remains unclear. In order to investigate specific genes and pathways involved in TNBC tumorigenesis, we profiled gene expression changes in two TNBC cell lines under two-dimensional culture (2DC) and three-dimensional culture (3DC) and in a tumor xenograft model. We identified simultaneous upregulation of HB-EGF, vascular endothelial growth factor A (VEGFA) and angiopoietin-like 4 (ANGPTL4) in 3DC and tumor xenografts, compared with 2DC. We show that HB-EGF regulates the expression of VEGFA or ANGPTL4 via transcriptional regulation of hypoxia inducible factor-1 alpha and nuclear factor kappa B. Furthermore, suppression of VEGFA or ANGPTL4 expression enhanced HB-EGF expression, highlighting a unique regulatory loop underlying this angiogenesis network. Targeted knockdown of HB-EGF significantly suppressed tumor formation in a TNBC xenograft model, compared with individual knockdown of either VEGFA or ANGPTL4, by reducing the expression of both VEGFA and ANGPTL4. In patients with TNBC, VEGFA or ANGPTL4 expression was also significantly correlated with HB-EGF expression. Low concentrations of exogenously added HB-EGF strongly activated the proliferation of endothelial cells, tube formation and vascular permeability in blood vessels, in a similar fashion to high doses of VEGFA and ANGPTL4. Taken together, these results suggest that HB-EGF plays a pivotal role in the acquisition of tumor aggressiveness in TNBC by orchestrating a molecular hierarchy regulating tumor angiogenesis.
    Molecular Cancer Research 02/2013; · 4.35 Impact Factor
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    ABSTRACT: The human ZFAT gene was originally identified as a susceptibility gene for autoimmune thyroid disease. Mouse Zfat is a critical transcriptional regulator for primitive hematopoiesis and required for peripheral T cell homeostasis. However, its physiological roles in T cell development remain poorly understood. Here, we generated Zfat (f/f)-LckCre mice and demonstrated that T cell-specific Zfat-deletion in Zfat (f/f)-LckCre mice resulted in a reduction in the number of CD4(+)CD8(+)double-positive (DP) cells, CD4(+)single positive cells and CD8(+)single positive cells. Indeed, in Zfat (f/f)-LckCre DP cells, positive selection was severely impaired. Defects of positive selection in Zfat-deficient thymocytes were not restored in the presence of the exogenous TCR by using TCR-transgenic mice. Furthermore, Zfat-deficient DP cells showed a loss of CD3ζ phosphorylation in response to T cell antigen receptor (TCR)-stimulation concomitant with dysregulation of extracellular signal-related kinase (ERK) and early growth response protein (Egr) activities. These results demonstrate that Zfat is required for proper regulation of the TCR-proximal signalings, and is a crucial molecule for positive selection through ERK and Egr activities, thus suggesting that a full understanding of the precise molecular mechanisms of Zfat will provide deeper insight into T cell development and immune regulation.
    PLoS ONE 01/2013; 8(10):e76254. · 3.73 Impact Factor
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    ABSTRACT: In order to assess the consequences of endogenous mutant KRas, we analyzed the signaling and biological properties of a small panel of isogenic cell lines. These include the cancer cell lines DLD1, HCT116 and Hec1A, in which either the WT or mutant KRas allele has been disrupted, and SW48 colorectal cancer cells and HMECs in which a single copy of mutant KRas was introduced at its endogenous genomic locus. We find that single copy mutant KRas causes surprisingly modest activation of downstream signaling to ERK and Akt. In contrast, a negative feedback signaling loop to EGFR and NRas occurs in some, but not all, of these cell lines. Mutant KRas also had relatively minor effects on cell proliferation and cell migration, but more dramatic effects on cell transformation as assessed by growth in soft agar. Surprisingly, knockout of the wild type KRas allele consistently increased growth in soft agar, suggesting tumor suppressive properties of this gene under these conditions. Finally, we examined the effects of single copy mutant KRas on global gene expression. While transcriptional programs triggered by mutant KRas were generally quite distinct in the different cell lines, there was a small number of genes that were consistently overexpressed, and these could be used to monitor KRas inhibition in a panel of human tumor cell lines. We conclude that there are conserved components of mutant KRas signaling and phenotypes, but that many depend on cell context and environmental cues.
    Journal of Biological Chemistry 11/2012; · 4.65 Impact Factor
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    Takahiro Fujimoto, Senji Shirasawa
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    ABSTRACT: KRAS-induced actin-interacting protein (KRAP), originally identified as one of the deregulated genes expressed in colorectal cancer, participates under physiological conditions in the regulation of systemic energy homeostasis and of the exocrine system. We have recently found that KRAP is a molecule associated with inositol 1,4,5-trisphosphate receptor (IP3R) and is critical for the proper subcellular localization of IP3R in the liver and the pancreas. However, the expression of KRAP and its precise function in other tissues remain elusive. In this study, we aimed to identify the KRAP-expressing cells in mouse stomach and kidneys and to examine the relevance of KRAP expression in the regulation of IP3R localization in these tissues. In the stomach, double immunohistochemical staining for KRAP and IP3R demonstrated that KRAP was expressed along with the apical regions in the mucous cells and the chief cells, and IP3R3 was dominantly co-localized with KRAP in these cells. Furthermore, IP3R2 was also co-localized with IP3R3 in the chief cells. It is of note that the proper localization of IP3R3 and IP3R2 in the chief cells and of IP3R3 in the mucous cells were significantly abrogated in KRAP-deficient mice. In the kidneys, KRAP was expressed in both the apical and the basal regions of the proximal tubular cells. Intriguingly, KRAP deficiency abrogated the localization of IP3R1 in the proximal tubular cells. Finally, co-immunoprecipitation study in the stomachs and the kidneys validated the physical association of KRAP with IP3Rs. These findings demonstrate that KRAP physically associates with IP3Rs and regulates the proper localization of IP3Rs in the mucous cells and the chief cells of the stomach and in the proximal tubular cells of the kidneys.
    International Journal of Molecular Medicine 09/2012; · 1.96 Impact Factor
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    ABSTRACT: It has been suggested that P-glycoprotein (P-gp), the product of multidrug resistance 1 (MDR1) gene, regulates the brain entry of various xenobiotics. Impaired function of P-gp may be associated with an increased risk of Parkinson's disease (PD). The aim of this study was to investigate the impact of a MDR1 C3435T polymorphism on PD risk alone or in combination with environmental factors. A total of 238 patients with PD and 368 controls were genotyped for the MDR1 C3435T polymorphism. Subjects with the TT genotype of the C3435T polymorphism showed a nonsignificantly increased risk of PD (odds ratio (OR) = 1.49, 95% confidence interval (CI) =0.85 - 2.25) compared with those with the CC genotype. A gene-environment interaction was suggested, with a combination of at least one T allele and ever drinking conferring significantly higher risk (OR = 1.83, 95% CI = 1.07 - 3.15, P = 0.029), compared with the CC genotype and never drinking. No significant interaction of smoking or occupational pesticide use with the C3435T polymorphism was observed. Our results suggest that the C3435T polymorphism may not play an important role in PD susceptibility in Japanese. Evidence of an interaction between the C3435T polymorphism and alcohol consumption was suggested.
    Drug Metabolism and Pharmacokinetics 09/2012; · 2.07 Impact Factor
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    ABSTRACT: We previously established a three-dimensional (3-D) colonic crypt model using HKe3 cells which are human colorectal cancer (CRC) HCT116 cells with a disruption in oncogenic KRAS, and revealed the crucial roles of oncogenic KRAS both in inhibition of apoptosis and in disruption of cell polarity; however, the molecular mechanism of KRAS-induced these 3-D specific biological changes remains to be elucidated. Among the genes that were upregulated by oncogenic KRAS in this model, we focused on the phosphodiesterase 4B (PDE4B) of which expression levels were found to be higher in clinical tumor samples from CRC patients in comparison to those from healthy control in the public datasets of gene expression analysis. PDE4B2 was specifically overexpressed among other PDE4 isoforms, and re-expression of oncogenic KRAS in HKe3 cells resulted in PDE4B overexpression. Furthermore, the inhibition of PDE4 catalytic activity using rolipram reverted the disorganization of HCT116 cells into the normal physiologic state of the epithelial cell polarity by inducing the apical assembly of ZO-1 (a tight junction marker) and E-cadherin (an adherens junction marker) and by increasing the activity of caspase-3 (an apoptosis marker) in luminal cavities. Notably, rolipram reduced the AKT phosphorylation, which is known to be associated with the disruption of luminal cavity formation and CRC development. Similar results were also obtained using PDE4B2-shRNAs. In addition, increased expression of PDE4B mRNA was found to be correlated with relapsed CRC in a public datasets of gene expression analysis. These results collectively suggested that PDE4B is upregulated by oncogenic KRAS, and also that the inhibition of PDE4 catalytic activity can induce both epithelial cell polarity and luminal apoptosis in CRC, thus highlighting the utility of our 3-D culture (3 DC) model for the KRAS-induced development of CRC in 3-D microenvironment. Indeed, using this model, we found that PDE4B is a promising candidate for a therapeutic target as well as prognostic molecular marker in CRC. Further elucidation of the signaling network of PDE4B2 in 3 DC would provide a better understanding of CRC in vivo.
    Molecular Cancer 07/2012; 11:46. · 5.13 Impact Factor
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    ABSTRACT: Mutation of RAS genes is one of the most common oncogenic alterations in cancer and acquisition of activating RAS mutations has been demonstrated to cause progression of colorectal adenoma to cancer. The aim of this study was to identify changes in the proteome of the intermediate-stage colorectal cancer cell line Caco2, induced by ectopic expression of two distinct RAS proteins, KRAS(V12) and HRAS(V12), in their mutated, constitutively active form. Using 2D-gel electrophoresis, followed by LC-MS/MS we identified almost 200 differentially expressed proteins in pair-wise comparisons of Caco2 vs Caco2-KRAS(V12) and Caco2 vs Caco2-HRAS(V12). Although many of the affected proteins were unique for each pair, there were also substantial similarities. Interestingly, transformation by the mutant KRAS(V12) gene resulted in elevated expression levels and activity of endogenous H-ras protein. Silencing the latter with a specific RNAi reversed several proteomic changes observed in KRAS(V12)-transformed cells, suggesting that oncogenic K-ras partly exerts its effects through endogenous H-ras activation. Alterations in the expression of cytoskeletal and cell adhesion proteins, caused by HRAS siRNA treatment, correlated with a reduction in the invasive properties of Caco2-KRAS(V12) cells. Our data suggest a novel interplay between K-ras and H-ras, with possible implications for colorectal carcinogenesis.
    Journal of proteomics 07/2012; 75(17):5356-69. · 5.07 Impact Factor
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    ABSTRACT: Activation of phosphatidylinositol 3-kinase (PI3K)/Akt signaling is associated with tumorigenesis and metastasis of colorectal cancer (CRC). The mammalian target of rapamycin (mTOR) kinase, a downstream effector of PI3K/Akt signaling, regulates tumorigenesis and metastasis of CRCs, indicating that mTOR inhibition may have therapeutic potential. Notwithstanding, many cancers, including CRC, demonstrate resistance to the antitumorigenic effects of rapamycin. In this study, we show that inhibition of mTORC1 with rapamycin leads to feedback activation of PI3K/Akt and Ras-MAPK signaling, resulting in cell survival and possible contribution to rapamycin resistance. Combination with the multikinase inhibitor, sorafenib, abrogates rapamycin-induced activation of PI3K/Akt and Ras-MAPK signaling pathways. Combination of rapamycin with sorafenib synergistically inhibits proliferation of CRC cells. CRCs harboring coexistent KRAS and PIK3CA mutations are partially sensitive to either rapamycin or sorafenib monotherapy, but highly sensitive to combination treatment with rapamycin and sorafenib. Combination with sorafenib enhances therapeutic efficacy of rapamycin on induction of apoptosis and inhibition of cell-cycle progression, migration and invasion of CRCs. We demonstrate efficacy and safety of concomitant treatment with rapamycin and sorafenib at inhibiting growth of xenografts from CRC cells with coexistent mutations in KRAS and PIK3CA. The efficacy and tolerability of combined treatment with rapamycin and sorafenib provides rationale for use in treating CRC patients, particularly those with tumors harboring coexistent KRAS and PIK3CA mutations.
    Carcinogenesis 06/2012; 33(9):1782-90. · 5.64 Impact Factor
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    ABSTRACT: Inhibition of the PI3K (phosphoinositide 3-kinase)/Akt/mTORC1 (mammalian target of rapamycin complex 1) and Ras/MEK [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase]/ERK pathways for cancer therapy has been pursued for over a decade with limited success. Emerging data have indicated that only discrete subsets of cancer patients have favourable responses to these inhibitors. This is due to genetic mutations that confer drug insensitivity and compensatory mechanisms. Therefore understanding of the feedback mechanisms that occur with respect to specific genetic mutations may aid identification of novel biomarkers that predict patient response. In the present paper, we show that feedback between the PI3K/Akt/mTORC1 and Ras/MEK/ERK pathways is cell-line-specific and highly dependent on the activating mutation of K-Ras or overexpression c-Met. We found that cell lines exhibited differential signalling and apoptotic responses to PD184352, a specific MEK inhibitor, and PI103, a second-generation class I PI3K inhibitor. We reveal that feedback from the PI3K/Akt/mTORC1 to the Ras/MEK/ERK pathway is present in cancer cells harbouring either K-Ras activating mutations or amplification of c-Met but not the wild-type counterparts. Moreover, we demonstrate that inhibition of protein phosphatase activity by OA (okadaic acid) restored PI103-mediated feedback in wild-type cells. Together, our results demonstrate a novel mechanism for feedback between the PI3K/Akt/mTORC1 and the Ras/MEK/ERK pathways that only occurs in K-Ras mutant and c-Met amplified cells but not the isogenic wild-type cells through a mechanism that may involve inhibition of a specific endogenous phosphatase(s) activity. We conclude that monitoring K-Ras and c-Met status are important biomarkers for determining the efficacy of PI103 and other PI3K/Akt inhibitors in cancer therapy.
    Bioscience Reports 06/2012; 32(4):413-22. · 1.88 Impact Factor
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    ABSTRACT: We previously found that oncogenic KRAS induces increased expression of microRNAs (miRNAs), such as miR-200c and miR-221/222, in human colorectal cancer (CRC) HCT116 cells in a three-dimensional (3D)-specific manner, however, the regulation of miRNA expression through oncogenic KRAS in other types of CRC remains unclear. The differential expression of 94 cancer-related miRNAs was examined in DLD-1 and DKO-4 cells (DLD-1 cells with a disrupted oncogenic KRAS) in 3D cultures. Increased miR-15b, miR-16, miR-23a, miR-24, miR-103 and miR-222 expression was observed in 3D and in 2D cultures. Of note, increased miR-181a, miR-200c and miR-210 expression was only observed in 3D cultures. Furthermore, miR-181a and miR-210 were significantly overexpressed in DLD-1 cells in 3D culture compared with those in HCT116 cells, and were significantly overexpressed in human CRC specimens. Oncogenic KRAS regulates 3D-specific miRNAs that are possibly associated with CRC development in vivo.
    Anticancer research 06/2012; 32(6):2271-5. · 1.71 Impact Factor

Publication Stats

4k Citations
826.41 Total Impact Points

Institutions

  • 2007–2014
    • Fukuoka University
      • Faculty of Medicine
      Hukuoka, Fukuoka, Japan
  • 2011
    • Tokyo Kasei University
      Edo, Tōkyō, Japan
  • 2007–2011
    • Dalhousie University
      Halifax, Nova Scotia, Canada
  • 1991–2011
    • Kyushu University
      • • Department of Neurology
      • • Graduate School of Medical Sciences
      • • Medical Institute of Bioregulation - MIB Hospital
      Fukuoka-shi, Fukuoka-ken, Japan
  • 2009
    • Massachusetts General Hospital
      • Department of Medicine
      Boston, MA, United States
    • National Research Institute for Child Health and Development, Tokyo
      Edo, Tōkyō, Japan
  • 2003–2007
    • Montefiore Medical Center
      • Department of Oncology
      New York City, NY, United States
  • 2005
    • Virginia Commonwealth University
      • Department of Radiation Oncology
      Richmond, VA, United States
    • Harvard Medical School
      • Department of Neurobiology
      Boston, MA, United States
  • 2003–2004
    • Albert Einstein Medical Center
      Philadelphia, Pennsylvania, United States
  • 2001–2004
    • Dana-Farber Cancer Institute
      Boston, Massachusetts, United States
  • 2000
    • Howard Hughes Medical Institute
      Maryland, United States
  • 1997
    • University of Washington Seattle
      • Department of Medicine
      Seattle, WA, United States