N-Myc Downstream Regulated Gene-1 May Play an Important Role in the Prognosis of Ovarian Cancer, in Its Association with Beta-Catenin

NDRG1 is a nickel- and calcium-inducible gene that plays important roles in the primary growth of malignant tumors, as well as in invasion and metastasis. This study investigated the associations of NDRG1 expression with cell adhesion and other clinicopathological factors in ovarian cancer. The clinical records of 123 women who underwent surgery for ovarian cancer in our institute were reviewed retrospectively. The expression of NDRG1, E-cadherin, and beta-catenin in surgical specimens were evaluated immunohistochemically. The NDRG1 expression level was significantly associated with beta-catenin expression, peritoneal metastasis outside the pelvic cavity, lymph node metastasis, and FIGO stages. The Kaplan-Meier analysis showed a significant association between the NDRG1 expression level and progression-free survival: high NDRG1 expression was related to poor survival. Our results suggest that the increased expression of NDRG1 is associated with cell adhesion and may be a poor prognostic indicator in women with ovarian cancer.

AXL/CDCP1/SRC axis confers acquired resistance to osimertinib in lung cancer

Osimertinib, a third-generation EGFR-TKI, has nowadays been applied to non-small cell lung cancer harboring activated EGFR mutation with or without T790M, but ultimately develop resistance to this drug. Here we report a novel mechanism of acquired resistance to osimertinib and the reversal of which could improve the clinical outcomes. In osimertinib-resistant lung cancer cell lines harboring T790M mutation that we established, expression of multiple EGFR family proteins and MET was markedly reduced, whereas expression of AXL, CDCP1 and SRC was augmented along with activation of AKT. Surprisingly, AXL or CDCP1 expression was induced by osimertinib in a time-dependent manner up to 3 months. Silencing of CDCP1 or AXL restored the sensitivity to osimertinib with reduced activation of SRC and AKT. Furthermore, silencing of both CDCP1 and AXL increased the sensitivity to osimertinib. Either silencing of SRC or dasatinib, a SRC family kinase (SFK) inhibitor, suppressed AKT phosphorylation and cell growth. Increased expression of AXL and CDCP1 was observed in refractory tumor samples from patients with lung cancer treated with osimertinib. Together, this study suggests that AXL/SFK/AKT and CDCP1/SFK/AKT signaling pathways play some roles in acquired osimertinib resistance of non-small cell lung cancer.

NDRG1 activates VEGF-A-induced angiogenesis through PLCγ1/ERK signaling in mouse vascular endothelial cells

Many diseases, including cancer, have been associated with impaired regulation of angiogenesis, of which vascular endothelial growth factor (VEGF)-A is a key regulator. Here, we test the contribution of N-myc downstream regulated gene 1 (NDRG1) to VEGF-A-induced angiogenesis in vascular endothelial cells (ECs). Ndrg1^−/− mice exhibit impaired VEGF-A-induced angiogenesis in corneas. Tumor angiogenesis induced by cancer cells that express high levels of VEGF-A was also reduced in a mouse dorsal air sac assay. Furthermore, NDRG1 deficiency in ECs prevented angiogenic sprouting from the aorta and the activation of phospholipase Cγ1 (PLCγ1) and ERK1/2 by VEGF-A without affecting the expression and function of VEGFR2. Finally, we show that NDRG1 formed a complex with PLCγ1 through its phosphorylation sites, and the inhibition of PLCγ1 dramatically suppressed VEGF-A-induced angiogenesis in the mouse cornea, suggesting an essential role of NDRG1 in VEGF-A-induced angiogenesis through PLCγ1 signaling.

Kosuke Watari et al. show that N-myc downstream-regulated gene 1 (NDRG1) stimulates new blood vessel formation that is induced by VEGF-A, using Ndrg1 knockout mice. They find that PLCγ1/ERK signaling mediates this regulation, providing mechanistic insights into how vascular endothelial cells form new vessels.

Targeting Phosphorylation of Y-Box-Binding Protein YBX1 by TAS0612 and Everolimus in Overcoming Antiestrogen Resistance

Nuclear expression of Y-box-binding protein (YBX1) is closely correlated with clinical poor outcomes and drug resistance in breast cancer. Nuclear translocation of YBX1 is facilitated by YBX1 phosphorylation at serine 102 by AKT, p70S6K, and p90RSK, and the phosphorylated YBX1 (pYBX1) promotes expression of genes related to drug resistance and cell growth. A forthcoming problem to be addressed is whether targeting the phosphorylation of YBX1 overcomes antiestrogen resistance by progressive breast cancer. Here, we found that increased expression of pYBX1 was accompanied by acquired resistance to antiestrogens, fulvestrant and tamoxifen. Forced expression of YBX1/S102E, a constitutive phosphorylated form, resulted in acquired resistance to fulvestrant. Inversely, YBX1 silencing specifically overcame antiestrogen resistance. Furthermore, treatment with everolimus, an mTORC1 inhibitor, or TAS0612, a novel multikinase inhibitor of AKT, p70S6K, and p90RSK, suppressed YBX1 phosphorylation and overcame antiestrogen resistance in vitro and in vivo IHC analysis revealed that expression of pYBX1 and YBX1 was augmented in patients who experienced recurrence during treatment with adjuvant endocrine therapies. Furthermore, pYBX1 was highly expressed in patients with triple-negative breast cancer compared with other subtypes. TAS0612 also demonstrated antitumor effect against triple-negative breast cancer in vivo Taken together, our findings suggest that pYBX1 represents a potential therapeutic target for treatment of antiestrogen-resistant and progressive breast cancer.

Bidirectional Regulation between NDRG1 and GSK3β Controls Tumor Growth and Is Targeted by Differentiation Inducing Factor-1 in Glioblastoma

The development of potent and selective therapeutic approaches to glioblastoma (GBM), one of the most aggressive primary brain tumors, requires identification of molecular pathways that critically regulate the survival and proliferation of GBM. Previous studies have reported that deregulated expression of N-myc downstream regulated gene 1 (NDRG1) affects tumor growth and clinical outcomes of patients with various types of cancer including glioma. Here, we show that high level expression of NDRG1 in tumors significantly correlated with better prognosis of patients with GBM. Loss of NDRG1 in GBM cells upregulated GSK3β levels and promoted cell proliferation, which was reversed by selective inhibitors of GSK3β. In contrast, NDRG1 overexpression suppressed growth of GBM cells by decreasing GSK3β levels via proteasomal degradation and by suppressing AKT and S6 cell growth signaling, as well as cell-cycle signaling pathways. Conversely, GSK3β phosphorylated serine and threonine sites in the C-terminal domain of NDRG1 and limited the protein stability of NDRG1. Furthermore, treatment with differentiation inducing factor-1, a small molecule derived from Dictyostelium discoideum, enhanced NDRG1 expression, decreased GSK3β expression, and exerted marked NDRG1-dependent antitumor effects in vitro and in vivo. Taken together, this study revealed a novel molecular mechanism by which NDRG1 inhibits GBM proliferation and progression. Our study thus identifies the NDRG1/GSK3β signaling pathway as a key growth regulatory program in GBM, and suggests enhancing NDRG1 expression in GBM as a potent strategy toward the development of anti-GBM therapeutics. SIGNIFICANCE: This study identifies NDRG1 as a potent and endogenous suppressor of glioblastoma cell growth, suggesting the clinical benefits of NDRG1-targeted therapeutics against glioblastoma.

Abstract 183: N-myc downstream regulated gene 1 (NDRG1) is indispensable for VEGF-A-induced tumor angiogenesis through PLCγ/ERK signaling activation in vascular endothelial cells

[Background] Vascular endothelial growth factor (VEGF)-A is a key regulator of tumor angiogenesis that is essential for tumor growth and progression. The unraveling of the precise mechanisms behind VEGF-A-induced tumor angiogenic process will further contribute to development of novel and potent anti-cancer therapeutics. N-myc downstream regulated gene 1 (NDRG1) has been shown to play essential roles in multiple biological processes including embryogenesis, tissue development, cell growth, differentiation, and tumorigenesis. We previously reported that NDRG1 expression levels in cancer cells are closely correlated with tumor angiogenesis and growth (Hosoi et al., Cancer Res., 2009; Murakami et al., J Biol Chem., 2013), and also that NDRG1 promotes tumor angiogenesis through enhanced VEGF-A production by tumor-associated macrophages (Watari et al., Sci Rep., 2016). However, it remains unclear whether NDRG1 expression in vascular endothelial cells (ECs) plays any crucial role in VEGF-A-induced tumor angiogenesis. In our present study, we further ask whether and how NDRG1 in ECs could specifically regulate tumor angiogenesis. We also present our finding of intrinsic importance that NDRG1 functions as an essential factor for VEGF-A-induced angiogenesis.

[Methods] NDRG1 deficient mice: The NDRG1 deficient mice on C57BL6 background were purchased from Laboratory Animal Resource Bank, National Institutes of Biomedical Innovation, Health and Nutrition (Osaka, Japan). Isolation of mouse endothelial cells: CD31+ endothelial cells were isolated from mouse lung by magnetic sorting using CD31 MicroBeads. Aortic ring assay: 1 mm mouse aortic rings were embedded in 3-dimensional growth factor reduced Matrigel, treated with or without FGF-2 (50 ng/mL) or VEGF (25 ng/ml), and incubated at 37°C. Vascular length and branching point were measured at day 7.

[Results] [1] Analysis of TCGA datasets revealed that NDRG1 expression was positively correlated with VEGF-A expression in patients with various cancer types. [2] In breast cancer patients in Kurume University hospital, NDRG1 was expressed in both cancer cells and ECs. In NDRG1 deficient mice, we observed following experimental results. [3] Both tumor growth and angiogenesis were all suppressed in syngeneic tumors. [4] VEGF-A-induced angiogenesis was specifically impaired in corneal micropocket assay and aortic ring assay, whereas FGF-2 could induce angiogenesis in both assays. [5] NDRG1 formed a complex with PLC-γ, and this complex formation was requisite for the VEGF-A-induced PLCγ/ERK activation in ECs.

[Conclusion] We first present an indispensable role of NDRG1 in VEGF-A-induced angiogenesis through PLCγ/ERK activation in ECs. The NDRG1 could be a novel candidate target for development of therapeutics for VEGF-A-induced tumor angiogenesis and other vascular diseases.

Citation Format: Kosuke Watari, Tomohiro Shibata, Ai Shinoda, Hideyuki Abe, Akihiko Kawahara, Yuichi Murakami, Eiji Oki, Jun Akiba, Yoshihiko Maehara, Michihiko Kuwano, Mayumi Ono. N-myc downstream regulated gene 1 (NDRG1) is indispensable for VEGF-A-induced tumor angiogenesis through PLCγ/ERK signaling activation in vascular endothelial cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 183.

Abstract 3011: Overcoming endocrine therapy resistance by drugs targeting YBX1 activation pathway in breast cancer

[Background] Endocrine therapies effectively improve the outcomes of patients with estrogen receptor alpha (ERα)-positive breast cancer. However, the emergence of drug-resistant tumors is a serious challenge. Our previous studies have demonstrated that YBX1 plays pivotal roles in acquisition of endocrine therapy resistance through downregulation of ERα and upregulation of HER2/ErbB2 in breast cancer patients (Shibata et al., Cancer Res., 2017). Furthermore, many laboratories have consistently demonstrated that YBX1 expression is correlated with poor outcomes of breast cancer patients, but the mechanism underlying why YBX1 expression leads to a poor outcome has yet to be revealed. Herein, our present findings demonstrate the critical role of YBX1, and also novel approach to overcome resistance to endocrine therapy.

[Methods] We searched a TCGA database for top 500 genes that are positively or negatively correlated with YBX1 and with ESR1 in breast cancer patients. Furthermore, we established fulvestrant resistant breast cancer cell lines in which AKT/mTORC1/S6K signaling pathway is activated.

[Results] Based on our finding, YBX1 expression is consistently correlated with reduced expression of ERα and its effector genes, conferring breast cancer cells resistance to endocrine therapy. [1] The enhanced expression of YBX1 is negatively correlated with ESR1 and its effector genes in tumors, and also with poor outcomes in breast cancer patients (TCGA and patients in our hospital). [2] Enhanced expression of YBX1 and pYBX1 is closely correlated with recurrence and resistance to endocrine therapy in patients. [3] Breast cancer cells resistant to fulvestrant or tamoxifen showed markedly enhanced expression of pYBX1 and treatment with mTORC1 inhibitors almost completely overcame above resistance in vitro and in vivo. [4] Constitutive activation of YBX1 by the mutant construct induced resistance to fulvestrant, indicating that YBX1 phosphorylation is crucial for the acquired drug resistance. Enhanced expression of YBX1 and also pYBX1 is thus closely associated with endocrine therapy resistance, and also with malignant progression in breast cancer.

[Conclusion] Based on both basic and clinical findings, we will present our novel concept that activation of the oncogenic transcriptional activity by YBX1 phosphorylation is crucial for acquired resistance to endocrine therapy and also poor outcomes in breast cancer. The YBX1 activation by PI3K/AKT/mTOR and RAF/MEK/ERK signaling pathways could be useful candidates for development of overcoming drugs. We will discuss overcoming effects of mTORC1 inhibitors.

Citation Format: Tomohiro Shibata, Kosuke Watari, Akihiko Kawahara, Tomoya Sudo, Yuichi Murakami, Eriko Tokunaga, Nami Yamashita, Eiji Oki, Yoshihiko Maehara, Jun Akiba, Yoshito Akagi, Maki Tanaka, Michihiko Kuwano, Mayumi Ono. Overcoming endocrine therapy resistance by drugs targeting YBX1 activation pathway in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3011.

Oncogenic Y-box binding protein-1 as an effective therapeutic target in drug-resistant cancer

Y-box binding protein-1 (YBX1), a multifunctional oncoprotein containing an evolutionarily conserved cold shock domain, dysregulates a wide range of genes involved in cell proliferation and survival, drug resistance, and chromatin destabilization by cancer. Expression of a multidrug resistance-associated ATP binding cassette transporter gene, ABCB1, as well as growth factor receptor genes, EGFR and HER2/ErbB2, was initially discovered to be transcriptionally activated by YBX1 in cancer cells. Expression of other drug resistance-related genes, MVP/LRP, TOP2A, CD44, CD49f, BCL2, MYC, and androgen receptor (AR), is also transcriptionally activated by YBX1, consistently indicating that YBX1 is involved in tumor drug resistance. Furthermore, there is strong evidence to support that nuclear localization and/or overexpression of YBX1 can predict poor outcomes in patients with more than 20 different tumor types. YBX1 is phosphorylated by kinases, including AKT, p70S6K, and p90RSK, and translocated into the nucleus to promote the transcription of resistance- and malignancy-related genes. Phosphorylated YBX1, therefore, plays a crucial role as a potent transcription factor in cancer. Herein, a novel anticancer therapeutic strategy is presented by targeting activated YBX1 to overcome drug resistance and malignant progression.

The augmented expression of the cytidine deaminase gene by 5-azacytidine predicts therapeutic efficacy in myelodysplastic syndromes

5-Azacytidine (5AC), a hypomethylating agent, is clinically used for the treatment of patients with myelodysplastic syndromes (MDS). Cytidine deaminase (CDA) is a key enzyme in the detoxification of 5AC. We investigated whether the CDA expression could predict response to 5AC in MDS. Among leukemia-derived cell lines, MDS-L, an MDS-derived cell line with a relatively low CDA expression level, was found to be the most sensitive to 5AC. Combination with tetrahydrouridine, an inhibitor of CDA, synergistically potentiated the cytotoxic effect of 5AC. Treatment with 5AC markedly enhanced the expression level of CDA mRNA and showed demethylation at CpG sites in the 5′-flanking region of the CDA gene. We further compared the protein expression levels of CDA in matched clinical samples before and after treatment with 5AC in bone marrow cells from 8 MDS patients by an immunohistochemical analysis. The CDA expression level showed an approximately 2- to 3-fold increase after 5AC treatment in 3 of these cases, and these three patients with relatively higher CDA expression levels after 5AC treatment all showed better clinical responses to 5AC. In contrast, the 5 remaining patients, whose CDA expression showed no augmentation, observed no clinical benefit. Taken together, the optimized determination of the CDA expression levels before and after 5AC treatment, and the methylation status at CpG sites of 5′-flanking region of the CDA gene, may contribute to the development of precise 5AC therapy for MDS.

Y-box binding protein YBX1 and its correlated genes as biomarkers for poor outcomes in patients with breast cancer

The enhanced expression of the Y-box binding protein YBX1 is consistently correlated with poor outcomes or reduced survival of breast cancer patients. However, the mechanism underlying the association between increased YBX1 expression and poor outcomes has yet to be revealed. We searched a database for the top 500 genes that are positively or negatively correlated with YBX1 and with ESR1 in breast cancer patients. We further examined the association between YBX1-correlated genes and breast cancer outcomes in patients at Kyushu University Hospital. More than 60% of genes that are positively correlated with YBX1 are also negatively correlated with ESR1. The enhanced expression levels of the top 20 positively correlated genes mostly predict negative outcomes, while the enhanced expression levels of the top 20 negatively correlated genes mostly predict positive outcomes. Furthermore, in breast cancer patients at Kyushu University Hospital, the expression levels of YBX1 and YBX1-positively correlated genes were significantly higher and the expression levels of genes negatively correlated with YBX1 were significantly lower in patients who relapsed after their primary surgery than in those who did not relapse. The expression of YBX1 together with the expression of its positively or negatively correlated genes may help to predict outcomes as well as resistance to endocrine therapies in breast cancer patients. Determining the expression of YBX1 and its closely correlated genes will contribute to the development of precision therapeutics for breast cancer.

Phosphorylation of mTOR Ser2481 is a key target limiting the efficacy of rapalogs for treating hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Although recent studies facilitate the identification of crucial genes and relevant regulatory pathways, therapeutic approaches against advanced HCC are insufficiently effective. Therefore, we aimed here to develop potent therapeutics to provide a reliable biomarker for the therapeutic efficacy in patients with HCC. To this end, we first compared the cytotoxic effects of various anti-cancer drugs between well differentiated (HAK-1A) and poorly differentiated (HAK-1B) cell lines established from a single HCC tumor. Of various drug screened, HAK-1B cells were more sensitive by a factor of 2,000 to the mTORC1 inhibitors (rapalogs), rapamycin and everolimus, than HAK-1A cells. Although rapalogs inhibited phosphorylation of mTOR Ser2448 in HAK-1A and HAK-1B cells, phosphorylation of mTOR Ser2481 was specifically inhibited only in HAK-1B cells. Silencing of Raptor induced apoptosis and inhibited the growth of only HAK-1B cells. Further, three other cell lines established independently from the tumors of three patients with HCC were also approximately 2,000-fold times more sensitive to rapamycin, which correlated closely with the inhibition of mTOR Ser2481 phosphorylation by rapamycin. Treatment with everolimus markedly inhibited the growth of tumors induced by poorly differentiated HAK-1B and KYN-2 cells and phosphorylation of mTOR Ser2481 in vivo. To our knowledge, this is the first study showing that the phosphorylation of mTOR Ser2481 is selectively inhibited by rapalogs in mTORC1-addicted HCC cells and may be a potential reliable biomarker for the therapeutic efficacy of rapalogs for treating HCC patients.

The activation of SRC family kinases and focal adhesion kinase with the loss of the amplified, mutated EGFR gene contributes to the resistance to afatinib, erlotinib and osimertinib in human lung cancer cells

Second- and third-generation inhibitors of epidermal growth factor receptor (EGFR) tyrosine kinase activity (EGFR-TKIs) are improving the treatment of patients with non-small cell lung cancer. Here we established two sublines (BR1-8 and BR2-3) resistant to a second-generation inhibitor, afatinib, from the human lung cancer cell line HCC827 that harbors a mutation that activates the tyrosine kinase activity of EGFR. These afatinib-resistant sublines were resistant to first-generation EGFR-TKIs, gefitinib and erlotinib, and a third-generation EGFR-TKI, osimertinib. These resistant sublines showed markedly reduced levels of multiple EGFR family proteins, including the activated mutant EGFR, and complete loss of EGFR amplification as compared with their parental HCC827 cells harboring amplification of EGFR gene. Treatment with the multikinase inhibitor dasatinib or transfection with a SRC small interfering RNA inhibited cell survival and AKT phosphorylation in drug-resistant sublines to a greater extent compared with HCC827 cells. Further, the migration of drug-resistant cells was greater compared with that of HCC827 cells and was inhibited by dasatinib or an FAK inhibitor. These findings indicate that compensatory activation of SRC family kinases (SFKs) and FAK supports the survival and migration of afatinib-resistant cells when the expression of multiple EGFR family proteins was mostly abrogated. Combinations of potent drugs that target SFKs and FAK may overcome the resistance of lung cancer cells to second-generation TKIs.

Breast Cancer Resistance to Antiestrogens Is Enhanced by Increased ER Degradation and ERBB2 Expression

Endocrine therapies effectively improve the outcomes of patients with estrogen receptor (ER)-positive breast cancer. However, the emergence of drug-resistant tumors creates a core clinical challenge. In breast cancer cells rendered resistant to the antiestrogen fulvestrant, we defined causative mechanistic roles for the transcription factor YBX1 and the levels of ER and the ERBB2 receptor. Enforced expression of YBX1 in parental cells conferred resistance against tamoxifen and fulvestrant in vitro and in vivo Furthermore, YBX1 overexpression was associated with decreased and increased levels of ER and ERBB2 expression, respectively. In antiestrogen-resistant cells, increased YBX1 phosphorylation was associated with a 4-fold higher degradation rate of ER. Notably, YBX1 bound the ER, leading to its accelerated proteasomal degradation, and induced the transcriptional activation of ERBB2. In parallel fashion, tamoxifen treatment also augmented YBX1 binding to the ERBB2 promoter to induce increased ERBB2 expression. Together, these findings define a mechanism of drug resistance through which YBX1 contributes to antiestrogen bypass in breast cancer cells. Cancer Res; 77(2); 545-56. ©2016 AACR.

Nuclear Y-Box-binding Protein-1 Expression Predicts Poor Clinical Outcome in Stage III Colorectal Cancer

BACKGROUND/AIM

Y-Box-binding protein-1 (YB-1), a DNA/RNA-binding protein, is an important oncogenic transcription and translation factor. We aimed to evaluate the relationships between nuclear YB-1 expression, epidermal growth factor receptor (EGFR) status, and poor clinical outcomes in patients with colorectal cancer (CRC).

MATERIALS AND METHODS

Nuclear YB-1 expression was immunohistochemically analyzed in CRC tissues obtained from 124 patients who underwent curative resection between 2005 and 2008. Correlations between nuclear YB-1 expression, various clinicopathological characteristics, EGFR status, and prognostic factors were evaluated.

RESULTS

High-grade nuclear YB-1 expression was detected in 62.9% of cases and was found to be an independent predictor of poorer overall survival (p<0.001) and relapse-free survival (p<0.001). A trend was also observed towards a positive correlation between nuclear YB-1 expression and EGFR status (p=0.051).

CONCLUSION

Nuclear YB-1 expression is a useful prognostic biomarker that correlates with EGFR status in patients with CRC.

Overcoming drug resistance to receptor tyrosine kinase inhibitors: Learning from lung cancer

There are various receptor tyrosine kinase (TK)-targeted drugs that are currently used in the treatment of patients with non-small cell lung cancer (NSCLC). Among them, the epidermal growth factor receptor (EGFR) TK inhibitors (TKIs) are the most extensively studied. Receptor TKIs including EGFR TKIs have shown dramatic therapeutic efficacies in malignant tumors, which harbor activating mutations in the EGFR gene. However, within 1 or 2years after treatment, patients harboring these mutations often develop resistance to TKI therapy. This review article is aimed at drawing attention to the fact that we must first understand how receptor TKI resistance is acquired to develop strategies for overcoming resistance to TKIs. Furthermore, an insight into the specific molecules or signaling pathways that mediate resistance is a key factor for understanding and overcoming acquired drug resistance. Finally, we present our views on the continuing battle against "drug resistance," and provide further guidelines and strategies on how to minimize the development of drug-resistant tumors.

Impaired differentiation of macrophage lineage cells attenuates bone remodeling and inflammatory angiogenesis in Ndrg1 deficient mice

N-myc downstream regulated gene 1 (NDRG1) is a responsible gene for a hereditary motor and sensory neuropathy-Lom (Charcot–Marie–Tooth disease type 4D). This is the first study aiming to assess the contribution of NDRG1 to differentiation of macrophage lineage cells, which has important implications for bone remodeling and inflammatory angiogenesis. Ndrg1 knockout (KO) mice exhibited abnormal curvature of the spine, high trabecular bone mass, and reduced number of osteoclasts. We observed that serum levels of macrophage colony-stimulating factor (M-CSF) and macrophage-related cytokines were markedly decreased in KO mice. Differentiation of bone marrow (BM) cells into osteoclasts, M1/M2-type macrophages and dendritic cells was all impaired. Furthermore, KO mice also showed reduced tumor growth and angiogenesis by cancer cells, accompanied by decreased infiltration of tumor-associated macrophages. The transfer of BM-derived macrophages from KO mice into BM-eradicated wild type (WT) mice induced much less tumor angiogenesis than observed in WT mice. Angiogenesis in corneas in response to inflammatory stimuli was also suppressed with decreased infiltration of macrophages. Taken together, these results indicate that NDRG1 deficiency attenuates the differentiation of macrophage lineage cells, suppressing bone remodeling and inflammatory angiogenesis. This study strongly suggests the crucial role of NDRG1 in differentiation process for macrophages.

Abstract C13: Direct binding of ERα to YB-1 suppresses HER2 expression in human breast cancer

[Background] ERα and HER2 are two major biomarkers of therapeutic efficacy in breast cancer patients. Y-box binding protein YB-1 is an oncoprotein involved in breast cancer and a transcription factor for HER2/ErbB2. However, regulatory mechanisms of ERα and HER2 expression by YB-1 are largely unknown. In our present study, we examined how nuclear YB-1 regulates expression of HER2 and ERα in breast cancer cells.

[Materials and methods] We established YB-1/Tet-On system in which nuclear YB-1 expression was induced by doxycycline, and examined how YB-1 could modulate expression of HER2 and ERα in breast cancer cells. Furthermore, we established the ERα/Tet-On system, in which ERα expression was markedly induced after treatment with doxycycline. To assess whether the YB-1-HER2-ERα correlation was affected by menopause, we analyzed biopsy samples of 116 premenopausal and 114 postmenopausal patients, who had not received any therapeutic drugs, by IHC.

[Results] We first examined whether YB-1 regulates expression of ERα and HER2 by using various human breast cancer cell lines, and observed following findings. (1) Nuclear YB-1 overexpression increased HER2 expression and decreases ERα expression, while HER2 expression was suppressed by estradiol and enhanced by anti-estrogen drugs. (2) ERα binding to YB-1 suppressed YB-1 binding to the HER2 promoter region. Furthermore, binding of YB-1 to ERα was enhanced by estradiol and suppressed by anti-estrogen drugs. (3) YB-1 induced proteasomal degradation of ERα when both interact directly.

We have next examined whether expression of HER2, nuclear YB-1, and ERα are significantly associated by IHC analysis of biopsy samples of breast cancers. In breast cancers of postmenopausal, but not premenopausal patients, nuclear YB-1 expression was positively correlated with HER2 expression and negatively correlated with ERα expression.

[Conclusions] In our study, we presented a new finding that YB-1 promoted proteasomal degradation of ERα by direct interaction and that YB-1-induced HER2 expression was suppressed by ERα. Furthermore, in breast tumors of postmenopausal patients, nuclear YB-1 expression was positively correlated with HER2 expression and negatively correlated with ERα expression. Therefore, this study could contribute to further development of optimized endocrine- and HER2- targeted therapeutics against breast cancer.

Citation Format: Tomohiro Shibata, Kosuke Watari, Hiroto Izumi, Akihiko Kawahara, Satoshi Hattori, Chihiro Fukumitsu, Yuichi Murakami, Ryuji Takahashi, Uhi Toh, Ken-ichi Ito, Maki Tanaka, Masayoshi Kage, Michihiko Kuwano, Mayumi Ono. Direct binding of ERα to YB-1 suppresses HER2 expression in human breast cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C13.

Abstract B199: Novel anti-angiogenic cancer therapeutic strategy by targeting differentiated macrophage lineage cells through N-myc downstream regulated gene 1 (NDRG1)

[Background] Angiogenesis is essential for malignant progression of cancer. Over the last couple of decades, it was highlighted that the progenitor cells derived from bone marrow (BM) differentiated, became part of the tumor stroma, and involved in tumor angiogenesis. In particular, macrophages, which differentiated into tumor-associated macrophages in tumor microenvironment, are known to play crucial roles in tumor angiogenesis. However, the specific molecules and markers of these “angiogenesis-supporting macrophages” have not been fully defined (Qian and Pollard, Cell. 2010). N-myc downstream regulated gene 1 (NDRG1), a gene responsible for a hereditary motor and sensory neuropathy (Lon-Charcot-Marie disease), plays pleiotropic roles in cell proliferation, development, differentiation, and tumorigenesis. We have previously reported that NDRG1 expression levels in cancer cells were closely correlated with tumor angiogenesis (Maruyama et al., Cancer Res. 2006; Hosoi et al., Cancer Res. 2009; Ureshino et al., PLoS One. 2012; Murakami et al., J Biol Chem. 2013). However, how NDRG1 could affect tumor angiogenesis remains unclear. In this study, we asked how NDRG1 could specifically modulate tumor angiogenesis through its differentiation control of macrophage lineage cells by using NDRG1 knock out (KO) mice.

[Material and methods] NDRG1 KO mice: The NDRG1 KO mice on C57BL6 background have been kindly donated by Dr. Toshiyuki Miyata (National Cerebral and Cardiovascular Center) (Okuda et al., Mol Cell Biol., 2004). Preparation of BM derived macrophages (BMDMs): BMDMs were obtained by flushing mouse femurs from mice. Cells were seeded in dishes and washed twice 3 hours later. Adherent cells were incubated in DMEM supplemented with 10% FBS and 20ng/ml M-CSF for 7 days. Matrigel plug assay in BM suppression mice: wild type (WT) recipient mice were exposed to 3-Gy sublethal whole-body irradiation to suppress BM and temporarily deplete leukocytes. Seven days after the irradiation, the mice were injected subcutaneously with growth factor-reduced Matrigel containing B16/BL6 cells, with or without BMDMs from WT or NDRG1 KO mice.

[Results] In NDRG1 KO mice as compared to their WT counterparts, [1] serum levels of M-CSF and macrophage-related cytokines were all decreased, and BM cells showed much slower growth rates in response to M-CSF in vitro; [2] trabecular bone mass and number of osteoclasts were decreased in vivo; [3] tumor growth and angiogenesis were markedly suppressed, accompanying by decreased infiltration of tumor-associated macrophages; [4] the transfer of BMDMs from KO mice into BM-eradicated WT mice induced much less tumor angiogenesis than observed in WT mice; [5] VEGF-A expression in BMDMs from KO mice were much less than those in cells from WT mice when stimulated by LPS or IL-1β.

[Conclusion] We discovered the central role of NDRG1 in differentiation of macrophage lineage cells, which affected bone remodeling and tumor angiogenesis. We will discuss which molecules are specifically regulated by NDRG1 during differentiation processes of monocytes/macrophages into angiogenesis-supporting macrophages, and whether these molecules in macrophages could have potentially important target for anti-angiogenesis cancer therapeutics.

Citation Format: Kosuke Watari, Tomohiro Shibata, Hiroshi Nabeshima, Ai Shinoda, Yuichi Fukunaga, Akihiko Kawahara, Kazuyuki Karasuyama, Jun-ichi Fukushi, Yuichi Murakami, Michihiko Kuwano, Mayumi Ono. Novel anti-angiogenic cancer therapeutic strategy by targeting differentiated macrophage lineage cells through N-myc downstream regulated gene 1 (NDRG1). [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B199.

Abstract 1688: Overcoming drug resistance to gemcitabine in pancreas cancer cells by targeting activated PI3K/mTOR pathway

Pancreas cancer is one of the most difficult neoplasms to treat curatively and 5-year survival rate is only 5%. Gemcitabine, a difluorinated deoxycitidine, has been first reported to improve pancreas cancer both response rate and median overall survival of patients with pancreas cancer. Treatment with combination of gemcitabine and erlotinib was reported to prolong survival compared with gemcitabine alone against pancreas ductal adenocarcinoma, but its benefit is modest. Further development of potent combination therapeutics with gemcitabine should be very useful for treatment of pancreas cancer.

In our present study, we examined whether the cytotoxic effect of gemcitabine could be potentiated when combined with other anticancer drugs including molecular targeted drugs and cytotoxic anticancer agents, and also whether such combination could overcome drug resistance to gemcitabine. We observed following findings [1]We first screened various anticancer agents that could synergistically potentiate cytotoxic effect of gemcitabine against pancreas cancer cell lines in culture, and observed that mTOR inhibitors, such as rapamycin, everolimus and AZD8055, synergistically enhanced the anti-proliferative effect of gemcitabine. [2] PI3K/mTOR/S6K-driven signaling pathway for de novo pyrimidine biosynthesis was markedly blocked when combined with gemcitabine and mTOR inhibitors. [3] We also observed that mTOR/S6K-driven de novo pyrimidine synthetic pathway was markedly activated in drug-resistant cancer cells as compared to their parental cell line. [4] Immunohistochemical analysis of clinical samples derived from resected pancreas tumors showed that mTOR was highly expressed in progressive pancreas cancer. Combination of gemcitabine and drugs targeting mTOR-driven signaling pathway will further provide potent therapeutics against both gemcitabine-sensitive and -resistant pancreas cancer. Furthermore, personalized therapeutics against pancreas cancer patients by this combination will be discussed based on expression levels of activated PI3K/mTOR/S6K in tumors.

Citation Format: Yuichi Murakami, Ai Shinoda, Kosuke Watari, Hiroshi Nabeshima, Akihiko Kawahara, Daisuke Nagayama, Yoshiki Naito, Koichi Higaki, Masako Inoue, Michihiko Kuwano, Mayumi Ono. Overcoming drug resistance to gemcitabine in pancreas cancer cells by targeting activated PI3K/mTOR pathway. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1688. doi:10.1158/1538-7445.AM2014-1688

Chemical Composition of the Essential Oil of Mastic Gum and their Antibacterial Activity Against Drug-Resistant Helicobacter pylori

Mastic gum is derived from the tree named Pistacia lentiscus that is grown only in Island Hios of Greek. Since Mastic was first reported to kill Helicobacter pylori (H. pylori) in 1998, there has been no further study to elucidate which component of mastic specifically shows the antimicrobial activity against H. pylori. In this study, we examined which component of mastic gum was responsible for anti-H. pylori activity. We prepared the essential oil of mastic gum and identified 20 constituents by GC-MS analysis. Ten standard components were assayed for anti-H. pylori activity, and it clarified that α-terpineol and (E)-methyl isoeugenol showed the anti-H. pylori activity against four different H. pylori strains that were established from patients with gastritis, gastric ulcer and gastric cancer. These components could be useful to overcome the drug-resistance H. pylori growth in stomach.

Tumor-derived interleukin-1 promotes lymphangiogenesis and lymph node metastasis through M2-type macrophages

Tumors formed by a highly metastatic human lung cancer cell line are characterized by activated signaling via vascular endothelial growth factor (VEGF)-C through its receptor (VEGFR-3) and aggressive lymph node metastasis. In this study, we examined how these highly metastatic cancers acquired aggressive lymph node metastasis. Compared with their lower metastatic counterparts, the highly metastatic tumors formed by this cell line expressed higher amounts of interleukin (IL)-1α, with similarly augmented expression of IL-1α and IL-1β by tumor stromal cells and of VEGF-A and VEGF-C by tumor-associated macrophages. These tumor-associated macrophages were mainly of the M2 type. Administration of a macrophage-targeting drug suppressed the production of these potent angiogenic and lymphangiogenic factors, resulting in decreased tumor growth, angiogenesis, lymphangiogenesis, and lymph node metastasis. In Matrigel plug assays, the highly metastatic cells formed tumors that were extensively infiltrated by M2-type macrophages and exhibited enhanced angiogenesis and lymphangiogenesis. All of these responses were suppressed by the IL-1 receptor (IL-1R) antagonist anakinra. Thus, the IL-1α-driven inflammatory activation of angiogenesis and lymphangiogenesis seems to provide a highly metastatic tumor microenvironment favorable for lymph node metastasis through cross-talk with macrophages. Accordingly, the IL-1R/M2-type macrophage axis may be a good therapeutic target for patients with this form of lung cancer.

Nuclear Y-box-binding protein-1 is a poor prognostic marker and related to epidermal growth factor receptor in uterine cervical cancer

OBJECTIVE

Y-box binding protein-1 (YB-1) is a member of the cold shock protein family and functions in transcription and translation. Many studies indicate that YB-1 is strongly expressed in tumor cells and is considered a marker of tumor aggressiveness and clinical prognosis. Overexpression of epidermal growth factor receptor (EGFR) has been associated with poor outcomes in cervical cancer. Clinical trials of EGFR family-base therapy are currently being initiated in cervical cancer. Nuclear YB-1 expression correlates with EGFR expression in various types of cancer. However, the clinical significance of nuclear YB-1 expression in different settings, the correlation with EGFR, and the prognostic implications of YB-1 expression in cervical cancer remain elusive.

PATIENTS AND METHODS

Nuclear YB-1 expression was immunohistochemically analyzed in tissue specimens obtained from 204 patients with cervical cancer who underwent surgery. Associations of nuclear YB-1 expression with clinicopathological factors such as survival, EGFR expression, and human epidermal growth factor receptor 2 (HER2) expression were investigated.

RESULTS

Nuclear YB-1 expression was found in 41 (20.2%) of 204 cases of cervical cancer and correlated with disease stage, tumor diameter, stromal invasion, and lymph-node metastasis. Nuclear YB-1 expression also correlated with EGFR expression (P=0.0114) as well as HER2 expression (P=0.0053). Kaplan-Meier survival analysis showed that nuclear YB-1 expression was significantly associated with poor progression-free survival (P=0.0033) and overall survival (P=0.0003), respectively.

CONCLUSION

Nuclear YB-1 expression is a prognostic marker and correlates with EGFR expression in cervical cancer.

Erlotinib resistance in lung cancer cells mediated by integrin β1/Src/Akt-driven bypass signaling

EGF receptor (EGFR) kinase inhibitors, including gefitinib and erlotinib, exert potent therapeutic efficacy in non-small cell lung cancers harboring EGFR-activating mutations. However, most patients ultimately develop resistance to these drugs. Here, we report a novel mechanism of acquired resistance to EGFR tyrosine kinase inhibitors and the reversal of which could improve clinical outcomes. In erlotinib-resistant lung cancer cells harboring activating EGFR mutations that we established, there was increased expression of Src, integrin β1, α2, and α5 along with enhanced cell adhesion activity. Interestingly, RNAi-mediated silencing of integrin β1 restored erlotinib sensitivity and reduced activation of Src and Akt after erlotinib treatment. Furthermore, Src silencing inhibited Akt phosphorylation and cell growth, with this inhibitory effect further augmented by erlotinib treatment. Increased expression of integrin β1, α5, and/or α2 was also observed in refractory tumor samples from patients with lung cancer treated with erlotinib and/or gefitinib. Together, our findings identify the integrin β1/Src/Akt signaling pathway as a key mediator of acquired resistance to EGFR-targeted anticancer drugs.

N-myc downstream-regulated gene 1 promotes tumor inflammatory angiogenesis through JNK activation and autocrine loop of interleukin-1α by human gastric cancer cells

The expression of N-myc downstream-regulated gene 1 (NDRG1) was significantly correlated with tumor angiogenesis and malignant progression together with poor prognosis in gastric cancer. However, the underlying mechanism for the role of NDRG1 in the malignant progression of gastric cancer remains unknown. Here we examined whether and how NDRG1 could modulate tumor angiogenesis by human gastric cancer cells. We established NU/Cap12 and NU/Cap32 cells overexpressing NDRG1 in NUGC-3 cells, which show lower tumor angiogenesis in vivo. Compared with parental NU/Mock3, NU/Cap12, and NU/Cap32 cells: 1) induced higher tumor angiogenesis than NU/Mock3 cells accompanied by infiltration of tumor-associated macrophages in mouse dorsal air sac assay and Matrigel plug assay; 2) showed much higher expression of CXC chemokines, MMP-1, and the potent angiogenic factor VEGF-A; 3) increased the expression of the representative inflammatory cytokine, IL-1α; 4) augmented JNK phosphorylation and nuclear expression of activator protein 1 (AP-1). Further analysis demonstrated that knockdown of AP-1 (Jun and/or Fos) resulted in down-regulation of the expression of VEGF-A, CXC chemokines, and MMP-1, and also suppressed expression of IL-1α in NDRG1-overexpressing cell lines. Treatment with IL-1 receptor antagonist (IL-1ra) resulted in down-regulation of JNK and c-Jun phosphorylation, and the expression of VEGF-A, CXC chemokines, and MMP-1 in NU/Cap12 and NU/Cap32 cells. Finally, administration of IL-1ra suppressed both tumor angiogenesis and infiltration of macrophages by NU/Cap12 in vivo. Together, activation of JNK/AP-1 thus seems to promote tumor angiogenesis in relationship to NDRG1-induced inflammatory stimuli by gastric cancer cells.

Abstract LB-220: The Integrinβ1/Src/Akt-driven bypass signaling pathway contributes to Erlotinib resistance in lung cancer

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) such as gefitinib and erlotinib have improved therapeutic efficacies on non-small cell lung cancer (NSCLC) harboring activating EGFR mutations. However, appearance of drug resistant mutation limits patients' outcome. A secondary T790M mutation and MET amplification are two major mechanisms of acquired EGFR-TKI resistance.

To develop novel therapeutics to overcome drug resistant tumors, we should further understand other mechanisms at molecular basis of intrinsic importance.

We established erlotinib or gefitinib resistant cell lines from PC9 cells that harbor an activating EGFR deletion mutation by chronic exposure to these TKIs. We have previously identified that loss of PTEN or loss of activated EGFR gene allele is responsible for acquired resistance (Cancer Res., 2010; Nat Med., 2011; PLoS ONE, 2012; Cancer Sci., 2013). In our present study, one erlotinib-resistant subline from PC9 cells revealed following interesting characteristics;

[1] The increased expression of integrins β1, α2, and α5 was observed, along with enhanced adhesion and migratory activity in the resistant sublines.

[2] The increased expression and activation of Src was also observed.

[3] Interestingly, integrinβ1 knockdown markedly restored sensitivity to erlotinib and reduced the activation of Src and Akt upon treatment with erlotinib.

[4] Furthermore, Src knockdown suppressed Akt phosphorylation and cell growth, and this inhibitory effect was further augmented by erlotinib.

[5] The expression of integrins β1 and α5 was also observed in a refractory tumor sample from a lung cancer patient treated with erlotinib. Together, we will present our novel concept that integrinβ1/Src/Akt pathway represents a novel a bypass effector pathway for the acquisition of resistance to EGFR-TKIs.

Citation Format: Mayumi Ono, Rina Kanda, Kosuke Watari, Akihiko Kawahara, Masayoshi Kage, Hidetaka Uramoto, Michihiko Kuwano. The Integrinβ1/Src/Akt-driven bypass signaling pathway contributes to Erlotinib resistance in lung cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-220. doi:10.1158/1538-7445.AM2013-LB-220

Sorting nexin 2-mediated membrane trafficking of c-Met contributes to sensitivity of molecular-targeted drugs

The sorting nexin (SNX) family is a diverse group of cytoplasmic and membrane-associated proteins that are involved in membrane-trafficking steps within the endocytotic network. SNX1 and SNX2 are components of the mammalian retromer complex and they also play critical roles in the membrane trafficking of growth factor receptors including epidermal growth factor receptor (EGFR) and c-Met. The human lung cancer cell lines, which harbor activating mutations in the kinase domain of EGFR gene, are sensitive to EGFR-targeted drugs gefitinib or erlotinib. However, a lung cancer cell line harboring gene amplification of c-Met is sensitive to the c-Met-targeted drug SU11274 but not to EGFR-targeted drugs. C-Met overexpression is identified as one of the bypass mechanisms for acquired resistance to EGFR-targeted drugs. Here we show that the siRNA-mediated knockdown of SNX2 decreases the cell-surface localization of c-Met, but not that of EGFR, resulting in lysosomal degradation of the c-Met protein. SNX2 specifically interacts with c-Met and treatment with lysosomal inhibitors almost completely annihilates downregulation of c-Met protein by SNX2 knockdown. Therefore, silencing of SNX2 markedly alters sensitivity to anticancer drugs targeted to c-Met (SU11274) and EGFR (gefitinib and erlotinib) through promotion of compensatory activation of the EGFR pathway in lung cancer cells. These findings suggest that development of drugs targeting SNX2 could be useful in overcoming drug resistance to EGFR-targeted drugs in lung cancer cells harboring c-Met gene amplification.

Activation of the human multidrug resistance-1 (mdr1) gene promoter in response to inhibitors of DNA topoisomerases

The multidrug resistance (MDR1) gene encodes a Mr 170,000 energy-dependent membrane efflux pump termed P-glycoprotein, and the P-glycoprotein is often expressed in various human tumors before and after cancer chemotherapy. In this study, we have established a human cancer KB cell line (Kst-6) which stably expressed the CAT gene (pMDRCAT1) driven by the human MDR1 promoter. Exposure to inhibitors of DNA topoisomerase I (camptothecin: CPT-11) and II (etoposide: VP-16 and teniposide: VM-26) could efficiently induce CAT activities in both time- and dose-dependent manners. However, CAT activity could not be significantly induced when treated with an ATP-antagoist, novobiocin. Northern blot analysis showed about 5-fold increase in CAT mRNA levels in Kst-6 cells treated with CPT-11 or VP-16, but not with novobiocin. Proximal MDR1 promoter-binding activities of transacting factor were augmented in nuclear extracts from KB cells treated with CPT-11, VM-26, and VP-16.

N-myc downstream regulated gene 1 (NDRG1) promotes metastasis of human scirrhous gastric cancer cells through epithelial mesenchymal transition

Our recent study demonstrated that higher expression of N-myc downregulated gene 1 (NDRG1) is closely correlated with poor prognosis in gastric cancer patients. In this study, we asked whether NDRG1 has pivotal roles in malignant progression including metastasis of gastric cancer cells. By gene expression microarray analysis expression of NDRG1 showed the higher increase among a total of 3691 up-regulated genes in a highly metastatic gastric cancer cell line (58As1) than their parental low metastatic counterpart (HSC-58). The highly metastatic cell lines showed decreased expression of E-cadherin, together with enhanced expression of vimentin and Snail. This decreased expression of E-cadherin was restored by Snail knockdown in highly metastatic cell lines. We next established stable NDRG1 knockdown cell lines (As1/Sic50 and As1/Sic54) from the highly metastatic cell line, and both of these cell lines showed enhanced expression of E-cadherin and decreased expression of vimentin and Snail. And also, E-cadherin promoter-driven luciferase activity was found to be increased by NDRG1 knockdown in the highly metastatic cell line. NDRG1 knockdown in gastric cancer cell showed suppressed invasion of cancer cells into surround tissues, suppressed metastasis to the peritoneum and decreased ascites accumulation in mice with significantly improved survival rates. This is the first study to demonstrate that NDRG1 plays its pivotal role in the malignant progression of gastric cancer through epithelial mesenchymal transition.

Abstract 1199: Sorting nexin 2 (SNX2) controls drug sensitivity to molecular targeted anticancer agents through membrane trafficking of c-Met protein in cancer cell

Various molecular targeted anticancer drugs are often developed by targeting activated growth factor receptors that are expressed on plasma membrane of cancer cells. Expression of such active receptors on the cell surface is essential to limit the drug sensitivity to molecular targeted drugs in lung cancer cells and others. The sorting nexin (SNX) family is a diverse group of cytoplasmic and membrane-associated proteins that are involved in membrane-trafficking steps within the endocytotic network. Human SNX family proteins comprise about 34 proteins with wide range of biological functions, which play specialized and/or generalized roles in the regulation of protein trafficking, including endosomal trafficking of membrane receptors and transporters. SNX1 and SNX2 are components of the mammalian retromer complex. In this study, we show that the small-interfering RNA (siRNA)-mediated knockdown of SNX2 decreased the cell-surface localization of c-Met, but not that of EGFR, resulting in degradation of the c-Met protein. Knockdown of SNX2 markedly altered sensitivity to anticancer drugs targeting c-Met and EGFR through promotion of compensatory activation of the EGFR pathway in lung cancer cells. Furthermore, SNX2 knockdown also specifically decreased c-Met expression, and altered drug sensitivity to c-Met-targeted drug in gastric cancer cells. These findings suggest that SNX2 is a key protein that regulates c-Met-driven growth-signalling pathways, affecting the therapeutic efficacy of growth factor receptor-targeted drugs in lung and gastric cancer patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1199. doi:1538-7445.AM2012-1199

The antitumor effect of a novel angiogenesis inhibitor (an octahydronaphthalene derivative) targeting both VEGF receptor and NF-κB pathway

Development of a novel type of angiogenesis inhibitor will be essential for further improvement of therapeutics against cancer patients. We examined whether an octahydronaphthalene derivative, AMF-26, which was screened as an inhibitor of intercellular adhesion molecule-1 (ICAM-1) production stimulated by inflammatory stimuli in vascular endothelial cells, could block angiogenesis in response to vascular endothelial growth factor (VEGF) and/or inflammatory cytokines. Low dose AMF-26 effectively inhibited the tumor necrosis factor-α (TNF-α)- or the interleukin-1β (IL-1β)-induced production of ICAM-1 in human umbilical vascular endothelial cells (HUVECs). We found that the TNF-α-induced phosphorylation of nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBα) and nuclear translocation of p65 were impaired by AMF-26 in both endothelial cells and cancer cells. AMF-26 was found to inhibit the phosphorylation of VEGF receptor 1 (VEGFR1), VEGFR2 and the downstream signaling molecules Akt, extracellular signal-regulated kinase (ERK)1/2 stimulated by VEGF in HUVECs. Therefore, the VEGF-induced proliferation, migration and tube formation of vascular endothelial cells was highly susceptible to inhibition by AMF-26. Oral administration of AMF-26 significantly blocked VEGF- or IL-1β-induced angiogenesis in the mouse cornea, and also tumor angiogenesis and growth. Together, our results indicate that AMF-26 inhibits angiogenesis through suppression of both VEGFR1/2 and nuclear factor-κB (NF-κB) signaling pathways when stimulated by VEGF or inflammatory cytokines. AMF-26 could be a promising novel candidate drug for cancer treatments.

Macrophage infiltration predicts a poor prognosis for human ewing sarcoma

Ewing sarcoma-primitive neuroectodermal tumor (EWS) is associated with the most unfavorable prognosis of all primary musculoskeletal tumors. The objective of the present study was to investigate whether tumor-associated macrophages (TAMs) affect the development of EWS. TAMs were isolated from mouse xenografts using CD11b magnetic beads and examined for their cytokine expression and osteoclastic differentiation. To evaluate the role of TAMs in xenograft formation, liposome-encapsulated clodronate was used to deplete TAMs in mice. Macrophage infiltration and tumor microvascular density were histologically evaluated in 41 patients with EWS, and association with prognosis was examined using Kaplan-Meier survival analysis. In mouse EWS xenografts, TAMs expressed higher concentrations of cytokines including interleukin-6, keratinocyte-derived chemokine, and monocyte chemotactic protein-1. TAMs were more capable than normal monocytes of differentiating into tartrate-resistant acid phosphatase-positive giant cells. Depleting macrophages using liposome-encapsulated clodronate significantly inhibited development of EWS xenografts. In human EWS samples, higher levels of CD68-positive macrophages were associated with poorer overall survival. In addition, enhanced vascularity, increase in the amount of C-reactive protein, and higher white blood cell counts were also associated with poor prognosis and macrophage infiltration. TAMs seem to enhance the progression of EWS by stimulating both angiogenesis and osteoclastogenesis. Further investigation of the behavior of TAMs may lead to development of biologically targeted therapies for EWS.

YB-1 bridges neural stem cells and brain tumor-initiating cells via its roles in differentiation and cell growth

The Y-box binding protein 1 (YB-1) is upregulated in many human malignancies including glioblastoma (GBM). It is also essential for normal brain development, suggesting that YB-1 is part of a neural stem cell (NSC) network. Here, we show that YB-1 was highly expressed in the subventricular zone (SVZ) of mouse fetal brain tissues but not in terminally differentiated primary astrocytes. Conversely, YB-1 knockout mice had reduced Sox-2, nestin, and musashi-1 expression in the SVZ. Although primary murine neurospheres were rich in YB-1, its expression was lost during glial differentiation. Glial tumors often express NSC markers and tend to loose the cellular control that governs differentiation; therefore, we addressed whether YB-1 served a similar role in cancer cells. YB-1, Sox-2, musashi-1, Bmi-1, and nestin are coordinately expressed in SF188 cells and 9/9 GBM patient-derived primary brain tumor-initiating cells (BTIC). Silencing YB-1 with siRNA attenuated the expression of these NSC markers, reduced neurosphere growth, and triggered differentiation via coordinate loss of GSK3-β. Furthermore, differentiation of BTIC with 1% serum or bone morphogenetic protein-4 suppressed YB-1 protein expression. Likewise, YB-1 expression was lost during differentiation of normal human NSCs. Consistent with these observations, YB-1 expression increased with tumor grade (n = 49 cases). YB-1 was also coexpressed with Bmi-1 (Spearmans 0.80, P > 0.001) and Sox-2 (Spearmans 0.66, P > 0.001) based on the analysis of 282 cases of high-grade gliomas. These proteins were highly expressed in 10/15 (67%) of GBM patients that subsequently relapsed. In conclusion, YB-1 correlatively expresses with NSC markers where it functions to promote cell growth and inhibit differentiation.

N-myc downstream regulated gene1/Cap43 overexpression suppresses tumor growth by hepatic cancer cells through cell cycle arrest at the G0/G1 phase

N-myc downstream regulated gene-1 (NDRG1)/Cap43 regulates tumor growth and metastasis in various carcinomas. In this study we examined whether and how NDRG1/Cap43 modulates tumor growth by human hepatocellular carcinoma (HCC) cells. NDRG1/Cap43 cDNA was used to transfect HCC cell lines (KIM-1), and stable transfectants overexpressing NDRG1/Cap43 (KIM-1/Cap43) were obtained. Cell cycle analysis showed that KIM-1/Cap43 cells were arrested in the G0/G1 phase. Western blot analysis demonstrated an increase in p21 in KIM-1/Cap43 cells in culture under full confluency as compared with KIM-1/Mock. When KIM-1 cells, which are very low in NDRG1/Cap43 expression, were treated with mimosine, a G0/G1 cell cycle blocker, expression of NDRG1/Cap43 was induced in a dose dependent manner, together with p21 induction and CDK4 reduction. In vivo, KIM-1/Cap43 cells showed markedly decreased tumor growth rates compared with those of KIM-1/Mock. Immunohistochemical staining demonstrated markedly higher p21 labeling index in the KIM-1/Cap43 tumor than KIM-1/Mock tumor, and lower CDK4 and Ki-67 labeling index in the KIM-1/Cap43 than KIM-1/Mock. In order to confirm suppressive effects of NDRG1/Cap43, we further established a stable transfectant expressing NDRG1/Cap43 (HAK-1B/Cap43) using another HCC cell line, HAK-1B. Western blot analysis demonstrated an increase in p21 and a decrease in CDK4 in HAK-1B/Cap43 cells in culture under full confluency as compared with HAK-1B/Mock. HAK-1B/Cap43 also showed decreased tumor growth rates as compared with its control counterpart in vivo. NDRG1/Cap43 overexpression thus induced cell cycle arrest at the G0/G1 phase accompanied by increased p21 and decreased CDK4 expression in HCC cells. NDRG1/Cap43 might play a key role in the cell cycle control of G0/G1 in HCC cells.

Abstract LB-101: Y-box binding protein-1 (YB-1) inhibition triggers differentiation of normal and cancer stem cells from the brain

The Y-box-binding protein-1 (YB-1) is up-regulated in many human malignancies including glioblastoma (GBM). It is also essential for normal brain development, suggesting that YB-1 is part of a neural stem cell (NSC) network. Here we show that YB-1 was highly expressed in the subventricular zone (SVZ) of mouse fetal brain tissues but not in terminally differentiated primary astrocytes. Conversely, YB-1 knock-out mice had reduced Sox-2, nestin and musashi expression in the SVZ. While primary murine neurospheres were rich in YB-1, its expression was lost during glial differentiation. Likewise, YB-1, Sox-2, mushashi, Bmi-1 and nestin are coordinately expressed in SF188 cells and 9/9 GBM patient-derived primary CSCs. Silencing YB-1 with small interfering RNA attenuated the expression of these NSC markers, reduced neurosphere growth and triggered differentiation via coordinate loss of GSK3-β. Further, differentiation of CSCs with 1% serum or bone morphogenetic protein-4 (BMP-4) suppressed YB-1 protein expression. Likewise, YB-1 expression was lost during differentiation of normal human NSCs. Consistent with these observations, YB-1 was preferentially expressed in highly undifferentiated primary gliomas based on the analysis of WHO grade 1-IV tumors (n=49 cases). YB-1 was also co-expressed with Bmi-1 (Spearmans 0.80, p&gt;0.001) and Sox-2 (Spearmans 0.66, p&gt;0.001) based on the analysis of 282 cases of high-grade gliomas. These CSC markers were also highly expressed in 10/15 (67%) of GBM patients that subsequently relapsed. In conclusion, YB-1 is a key feature of stem cells where it functions to suppress differentiation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-101. doi:10.1158/1538-7445.AM2011-LB-101

Mechanism of HSV infection through soluble adapter-mediated virus bridging to the EGF receptor

Herpes simplex virus entry into cells requires the binding of envelope glycoprotein D (gD) to an entry receptor. Depending on the cell, entry occurs by different mechanisms, including fusion at the cell surface or endocytosis. Here we examined the entry mechanism through a non-HSV receptor mediated by a soluble bi-specific adapter protein composed of recognition elements for gD and the EGF receptor (EGFR). Virus entered into endosomes using either EGF or an EGFR-specific single chain antibody (scFv) for receptor recognition. Infection was less efficient with the EGF adapter which could be attributed to its weaker binding to a viral gD. Infection mediated by the scFv adapter was pH sensitive, indicating that gD-EGFR bridging alone was insufficient for capsid release from endosomes. We also show that the scFv adapter enhanced infection of EGFR-expressing tumor tissue in vivo. Our results indicate that adapters may retarget HSV infection without drastically changing the entry mechanism.

Nuclear expression of N-myc downstream regulated gene 1/Ca(2+)-associated protein 43 is closely correlated with tumor angiogenesis and poor survival in patients with gastric cancer

Expression of N-myc downstream regulated gene 1 (NDRG1)/Ca(2+)-associated protein 43 (Cap43) in cancer cells is a predictive marker of good or poor prognosis depending on tumor type. In this study, we examined whether NDRG1/Cap43 is a marker of good or poor prognosis in gastric cancer patients, and whether it is associated with tumor stromal responses, including angiogenesis and macrophage infiltration. The expression levels of NDRG1/Cap43, the number of CD68-positive macrophages and the CD34-positive microvessel density were analyzed by immunohistochemistry in 129 gastric cancer patients, including 65 with the intestinal type and 64 with the diffuse type. The expression of NDRG1/Cap43 in the nucleus and the membrane was evaluated. Nuclear NDRG1/Cap43 expression was found in 20/65 (30.8%) patients with the intestinal type and in 9/64 (14.1%) patients with the diffuse type of gastric cancer. Nuclear NDRG1/Cap43 expression was significantly associated with pathological stage in the intestinal type (P=0.002), but not in the diffuse type (P=0.039). Nuclear NDRG1/Cap43 expression was also closely associated with infiltrating macrophages (P=0.001) and tumor angiogenesis (P=0.001) in the intestinal type. Furthermore, nuclear NDRG1/Cap43 expression was associated with poor prognosis in both the intestinal (P=0.001) and the diffuse types of gastric cancer (P=0.047). By contrast, membranous NDRG1/Cap43 expression was not associated with the overall survival of gastric cancer patients with either the intestinal or diffuse type of gastric cancer. The expression of NDRG1/Cap43 in the nucleus may be a predictive biomarker for malignant progression in the intestinal type of gastric cancer, preferable to the expression of NDRG1/Cap43 in the membrane.

Expression of selected gene for acquired drug resistance to EGFR-TKI in lung adenocarcinoma

BACKGROUND

Individualized treatment is an attractive challenge that may allow for more effective and safer treatment of human disease. Activating mutations in the epidermal growth factor receptor (EGFR) gene in lung adenocarcinoma are associated with a dramatic clinical response to EGFR-tyrosine kinase inhibitors (TKIs). However, patients often experience a relapse after treatment with EGFR-TKIs, even when the tumors are initially highly sensitive. However, the "whole picture" regarding acquired resistance remains unclear.

METHODS

Tumor specimens were collected from 11 lung adenocarcinoma patients before and after treatment with gefitinib. The status of the EGFR and K-ras genes were investigated by PCR-based analyses. Immunohistochemistry and real-time PCR assays were used to evaluate the MET gene in terms of its tyrosine phosphorylation and amplification, respectively. The expression of HGF, PTEN, and EGR-1, and changes in the epithelial-mesenchymal transition (EMT) status including the expression of E-cadherin and gamma-catenin as epithelial markers, and vimentin and fibronectin as mesenchymal markers, were evaluated by immunohistochemistry.

RESULTS

Seven (64%) of the gefitinib refractory tumors exhibited a secondary threonine-to-methionine mutation at codon 790 in EGFR (T790M). All of the tumors had wild type K-ras gene expression. No MET amplification was detected in any of the samples, nor was there phosphorylation of MET detected in any of the resistant samples. Neither MET gene amplification, nor the overexpression of HGF was observed in samples without the T790M mutation. A strong expression of HGF was detected in 6 of 8 specimens with the T790M mutation. Three (38%) of 8 cases showed a loss of PTEN in samples with the T790M mutation. A loss of EGR-1 was detected in 2 (29%) of 7 cases, including one tumor without PTEN. Four (57%) of 7 cases showed positive expression of phosphorylated Akt (p-Akt). A change in the EMT status between pre-and post-treatment was observed in 4 (44%) of 9 cases. In all examined samples cases, some alterations of gene or proteins were observed.

CONCLUSIONS

The current results showed that these alterations in gene or protein expression can account for all resistant mechanisms. This phenomenon suggests the existence of complicated relationships among acquired resistance-related genes.

N-myc downstream-regulated gene 1/Cap43 expression promotes cell differentiation of human osteosarcoma cells

The N-myc downstream regulated gene 1 (NDRG1)/Cap43 is closely associated with cell differentiation, and its expression is induced by hypoxia and increasing intracellular calcium levels. Whether the NDRG1/Cap43 expression in cancer cells is a predictive marker of good or poor prognosis in patients, depends upon tumor types and differentiation status. In this study, we examined whether the NDRG1/Cap43 expression was involved in the differentiation of osteosarcoma cells, using three osteosarcoma cell lines, MG63, U2OS and SaOS2. The NDRG1/Cap43 expression in MG63 and U2OS was significantly enhanced by vitamin D3, which also induced the production of osteocalcin, a differentiation marker of osteoblasts. The knockdown of NDRG1/Cap43 using small interfering RNA also suppressed the production of osteocalcin and enhanced cell proliferation, accompanied by the suppression of p21 expression. Furthermore, the acquired invasiveness of osteosarcoma cells during the invasion in Matrigel resulted in the decreased expression of NDRG1/Cap43. On the basis of these results, our proposed role for NDRG1/Cap43 would be in the capacity of differentiation and invasion in osteosarcoma cells.

Loss of PTEN expression by blocking nuclear translocation of EGR1 in gefitinib-resistant lung cancer cells harboring epidermal growth factor receptor-activating mutations

Gefitinib (Iressa) and erlotinib (Tarceva), which target the epidermal growth factor receptor (EGFR), are approved for treatment of patients with advanced non-small cell lung cancer (NSCLC). Patients whose tumors harbor mutations in the EGFR gene, including delE746-A750 in exon 19 and L858R in exon 21, may benefit in particular from gefitinib treatment. However, acquired resistance to gefitinib has been a serious clinical problem, and further optimization is needed for application of EGFR-targeted drugs in lung cancer patients. In this study, we established gefitinib-resistant NSCLC cells from PC-9 cell line, which harbors the delE746-A750 mutation, by exposing the cell line to gefitinib for over 7 months. Gefitinib-resistant PC-9/GEFs cell lines showed a marked downregulation of PTEN expression and increased Akt phosphorylation. In revertant, gefitinib-sensitive clones (PC-9/Rev) derived from PC-9/GEF1-1 and PC-9/GEF2-1, PTEN expression, as well as sensitivity to gefitinib and erlotinib, was restored. Knockdown of PTEN expression using small interfering RNA specific for PTEN in PC-9 cells resulted in drug resistance to gefitinib and erlotinib. Nuclear translocation of the EGR1 transcription factor, which regulates PTEN expression, was shown to be suppressed in resistant clones and restored in their revertant clones. Reduced PTEN expression was also seen in tumor samples from a patient with gefitinib-refractory NSCLC. This study thus strongly suggests that loss of PTEN expression contributes to gefitinib and erlotinib resistance in NSCLC. Our findings reinforce the therapeutic importance of PTEN expression in the treatment of NSCLC with EGFR-targeted drugs.