Sensitive cytometry based system for enumeration, capture and analysis of gene mutations of circulating tumor cells.

Methods for the enumeration and molecular characterization of circulating tumor cells (CTC) have been actively investigated. However, such methods are still technically challenging. We have developed a novel epithelial cell adhesion molecule independent CTC enumeration system integrated with a sorting system using a microfluidics chip. We compared the number of CTC detected using our system with those detected using the CellSearch system in 46 patients with various cancers. We also evaluated epidermal growth factor receptor (EGFR) and PIK3CA mutations of captured CTC in a study of 4 lung cancer and 4 breast cancer patients. The percentage of samples with detected CTC was significantly higher with our system (65.2%) than with CellSearch (28.3%). The number of detected CTC per patient using our system was statistically higher than that using CellSearch (median 5, 0; P = 0.000172, Wilcoxon test). In the mutation analysis study, the number of detected CTC per patient was low (median for lung, 4.5; median for breast, 5.5); however, it was easy to detect EGFR and PIK3CA mutations in the CTC of 2 lung and 1 breast cancer patient, respectively, using a commercially available kit. Our system is more sensitive than CellSearch in CTC enumeration of various cancers and is also capable of detecting EGFR and PIK3CA mutations in the CTC of lung and breast cancer patients, respectively.

KRAS mutation confers resistance to antibody-dependent cellular cytotoxicity of cetuximab against human colorectal cancer cells.

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.

A novel flow cytometry-based cell capture platform for the detection, capture and molecular characterization of rare tumor cells in blood.

BACKGROUND: Personalized cancer treatment relies on the accurate detection of actionable genomic aberrations in tumor cells. Circulating tumor cells (CTCs) could provide an alternative genetic resource for diagnosis; however, the technical difficulties in isolating and analyzing rare CTCs have limited progress to date. In this preclinical study, we aimed to develop an improved capture system for molecular characterization of CTCs based on a novel cell sorting technology. METHODS: We developed a cell capture platform using On-chip Sort (On-Chip Biotechnologies), a novel bench-top cell sorter equipped with a disposable microfluidic chip. Spike-in experiments comprising a series of lung cancer cell lines with varying epithelial cell adhesion molecule (EpCAM) expression levels were conducted to assess the capture and purification efficiency of the platform. Samples were negatively enriched using anti-CD45-coated magnetic beads to remove white blood cells, followed by sample fixation and labeling. The enriched and labeled samples were then sorted by On-chip Sort based on cytokeratin, vimentin, and CD45 expression. Captured cells were immediately subjected to whole genome amplification followed by mutation analysis using deep targeted sequencing, and copy number analysis using quantitative polymerase chain reaction (qPCR). RESULTS: Spike-in experiments revealed an excellent overall mean capture rate of 70.9%. A 100% success rate in the detection of EGFR, KRAS and BRAF mutations from captured cells was achieved using pyrosequencing and deep sequencing. The mutant variant detection rates were markedly higher than those obtained with the CellSearch profile kit. qPCR analysis of amplified DNA demonstrated reproducible detection of copy number changes of the EGFR in captured tumor cells. CONCLUSIONS: Using a novel cell sorter, we established an efficient and convenient platform for the capture of CTCs. Results of a proof-of-principle preclinical study indicated that this platform has potential for the molecular characterization of captured CTCs from patients.

Multicolor detection of rare tumor cells in blood using a novel flow cytometry-based system.

The presence and number of circulating tumor cells (CTCs) in the blood of patients with solid tumors are predictive of their clinical outcomes. To date, the CellSearch system is the only US Food and Drug Administration-approved CTC enumeration system for advanced breast, prostate, and colon cancers. However, sensitivity issues due to epithelial cellular adhesion molecule (EpCAM)-based enrichment and limited capability for subsequent molecular analysis must be addressed before CTCs can be used as predictive markers in the clinical setting. We have developed a multicolor CTC detection system using cross-contamination-free flow cytometry, which permits the enumeration and characterization of CTCs for multiple molecular analyses. Tumor cell lines with different expression levels of EpCAM were spiked into peripheral blood obtained from healthy donors. Spike-in samples were negatively enriched using anti-CD45-coated magnetic beads to remove white blood cells, and this was followed by fixation and labeling with CD45-Alexa Fluor 700, EpCAM-phycoerythrin, cytokeratin (CK)-fluorescein isothiocyanate antibodies, and/or 7-aminoactinomycin D for nuclei staining. Excellent detection (slope = 0.760-0.888) and a linear performance (R(2) = 0.994-0.998) were noted between the observed and expected numbers of tumor cells, independent of EpCAM expression. The detection rate was markedly higher than that obtained using the CellSearch system, suggesting the superior sensitivity of our system in detecting EpCAM- tumor cells. Additionally, the incorporation of an epithelial-mesenchymal transition (EMT) marker allowed us to detect EpCAM-/CK- cells and EMT-induced tumor cells. Taken together, our multicolor CTC detection system may be highly efficient in detecting previously unrecognized populations of CTCs.

Pharmacodynamic change in plasma angiogenic proteins: a dose-escalation phase 1 study of the multi-kinase inhibitor lenvatinib.

BACKGROUND: Lenvatinib (E7080), an oral multi-kinase inhibitor, has inhibitory action on tumor cell proliferation and tumor angiogenesis in preclinical models. We evaluated correlations between pharmacodynamic (PD) biomarkers with patient clinical outcomes in a lenvatinib phase 1 dose-escalation study. METHODS: Plasma angiogenic proteins were evaluated as potential PD biomarkers of response to lenvatinib in a dose-escalation phase 1 study. Lenvatinib was administered to 27 patients by twice-daily dosing in 3-week cycles; 2 weeks of treatment followed by 1 week of rest until discontinuation. Blood samples for plasma proteins were collected on days 1 (baseline), 8, and 15 of cycle 1, and days 1, 8, and 15 of cycle 2. Selected clinical outcomes, including tumor shrinkage and adverse events (AEs), were used for correlative analyses of pharmacokinetic parameters and PD biomarkers. RESULTS: Tumor shrinkage and changes in PD biomarkers (increased vascular endothelial growth factor [VEGF] and stromal cell-derived factor 1 alpha [SDF1α] levels and decreased soluble VEGF receptor 2 [sVEGFR2] levels) significantly correlated with increasing lenvatinib exposure. Observed changes in levels of VEGF, SDF1α, and sVEGFR2 were maintained on day 15 of cycle 1, but returned to baseline during the 1-week rest period, and similar changes were induced by reinstitution of treatment in cycle 2. The worst grades of hypertension, proteinuria, and fatigue were associated with changes in VEGF and HGF at day 8 of cycle 1. Maximum tumor shrinkage was correlated with increased SDF1α levels. Decreased sVEGFR2 level was also correlated with tumor shrinkage and frequency of hypertension, proteinuria, and fatigue. Tumor shrinkage significantly correlated with the worst grade of proteinuria, but not with hypertension or fatigue. CONCLUSION: PD biomarker changes observed in plasma angiogenic proteins are correlated with lenvatinib-induced tumor shrinkage and AEs. Our findings warrant further assessment of plasma proteins associated with angiogenesis as potential biomarkers of lenvatinib activity. TRIAL REGISTRATION: ClinicalTrial.gov: NCT00280397 (January 20, 2006).

Design and synthesis of phenolic hydrazide hydrazones as potent poly(ADP-ribose) glycohydrolase (PARG) inhibitors.

Poly(ADP-ribose) polymerase (PARP) and poly(ADP-ribose) glycohydrolase (PARG) are enzymes responsible for catalyzing the formation and degradation of poly(ADP-ribose) (PAR) polymers, respectively. Activation of PARP has been shown to be involved in cell death induced by genotoxic stimuli. On the other hand, genetic disruption of PARG also leads to increased level of cell death by accumulation of PAR. Unlike PARP, where significant medicinal effort has been expended to identify potent inhibitors, PARG has been insufficiently investigated as a molecular therapeutic target. In this study, we report the design, synthesis, and biological evaluation of phenolic hydrazide hydrazones as potent PARG inhibitors. Compounds 3d, 3e, 5d, 5e, 8a, 8b and 8c showed their ability to inhibit the catalytic activity of PARG in vitro with IC50 values of 1.0, 2.1, 3.1, 3.2, 3.1, 2.8 and 1.6 µM, respectively.

Epidermal growth factor receptor variant type III markedly accelerates angiogenesis and tumor growth via inducing c-myc mediated angiopoietin-like 4 expression in malignant glioma.

BACKGROUND: Expression of the constitutively activated mutant EGFR variant III (EGFRvIII), the most common mutation in glioblastoma multiforme (GBMs), has been clinically correlated with tumor proliferation, invasion, and angiogenesis. In this study, we examined the role of EGFRvIII on the tumor microenvironment, especially on angiogenesis. METHODS: To study the role of EGFRvIII in tumor angiogenesis, we prepared LN229 glioblastoma transfected with enhanced green fluorescent protein (EGFP), wild-type EGFR, or EGFRvIII (LN229-WT or -vIII), and examined tumor growth and microvessel density in the tumors. Additionally, the potential angiogenic factors were identified by real-time PCR analysis, and the functions in LN229-vIII cells were examined. RESULTS: LN229-vIII cells showed more aggressive tumor growth and higher vascularity as compared to LN229-WT cells in vivo, although there was no significant difference in the cell growth rates in vitro. We next investigated the expression of 60 angiogenesis-related factors to clarify the mechanisms underlying the difference in vascularity between tumor xenografts of LN229-vIII and LN229-WT. We found that the mRNA and protein expressions of angiopoietin-like 4 (Angptl4), a secreted protein involved in angiogenesis and metabolism regulation, were significantly induced by EGFRvIII overexpression, both in vitro and in vivo. Constitutive knockdown of Angptl4 in LN229-vIII using shRNA significantly decreased the microvessel density in the tumor xenografts and suppressed tumor growth. To clarify the regulatory mechanisms of Angptl4 by EGFRvIII, we analyzed the signaling pathways and transcription factors by pharmacological inhibition and RNA interference. U0126, an ERK signal inhibitor dramatically suppressed Angptl4 expression. The transcription factor c-Myc, which is regulated by ERK, was activated in the LN229-vIII cells and knockdown of c-Myc using siRNA also attenuated Angptl4 expression in the LN229-vIII cells. Furthermore, chromatin immunoprecipitation (ChIP) assay revealed increased recruitment of c-Myc to the promoter region of Angptl4 in the LN229-vIII cells. CONCLUSIONS: In summary, we demonstrated that EGFRvIII induces Angptl4 expression through the ERK/c-Myc pathway and promotes tumor angiogenesis in malignant gliomas.

Silencing of poly(ADP-ribose) glycohydrolase sensitizes lung cancer cells to radiation through the abrogation of DNA damage checkpoint.

Poly(ADP-ribose) glycohydrolase (PARG) is a major enzyme that plays a role in the degradation of poly(ADP-ribose) (PAR). PARG deficiency reportedly sensitizes cells to the effects of radiation. In lung cancer, however, it has not been fully elucidated. Here, we investigated whether PARG siRNA contributes to an increased radiosensitivity using 8 lung cancer cell lines. Among them, the silencing of PARG induced a radiosensitizing effect in 5 cell lines. Radiation-induced G2/M arrest was largely suppressed by PARG siRNA in PC-14 and A427 cells, which exhibited significantly enhanced radiosensitivity in response to PARG knockdown. On the other hand, a similar effect was not observed in H520 cells, which did not exhibit a radiosensitizing effect. Consistent with a cell cycle analysis, radiation-induced checkpoint signals were not well activated in the PC-14 and A427 cells when treated with PARG siRNA. These results suggest that the increased sensitivity to radiation induced by PARG knockdown occurs through the abrogation of radiation-induced G2/M arrest and checkpoint activation in lung cancer cells. Our findings indicate that PARG could be a potential target for lung cancer treatments when used in combination with radiotherapy.

Efficacy of everolimus, a novel mTOR inhibitor, against basal-like triple-negative breast cancer cells.

Patients with triple-negative breast cancers (TNBCs) typically have a poor prognosis because such cancers have no effective therapeutic targets, such as estrogen receptors for endocrine therapy or human epidermal growth factor receptor 2 (HER2) receptors for anti-HER2 therapy. As the phosphatidylinositol 3' kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) cascade is activated in TNBCs, mTOR is a potential molecular target for anticancer therapy. In this study, we investigated the antitumor activities of everolimus, an oral mTOR inhibitor, in nine TNBC cell lines. Everolimus effectively inhibited cell growth at concentrations under 100 nM (IC(50)) in five cell lines and even in the 1-nM range in three of the five cell lines. To identify specific characteristics that could be used as predictive markers of efficacy, we evaluated the expressions of proteins in the mTOR cascade, basal markers, and cancer stem cell markers using western blotting, fluorescent in situ hybridization (FISH), or immunohistochemistry. All five of the sensitive cell lines were categorized as a basal-like subtype positive for either epidermal growth factor receptor (EGFR) or CK5/6, although resistant cell lines were not of this subtype and tended to exhibit the characteristics of cancer stem cells, with decreased E-cadherin and the increased expression of Snail or Twist. In vivo assays demonstrated antitumor activity in a mouse xenograft model of basal-like breast cancer, rather than non-basal breast cancer. These results suggest that everolimus has favorable activity against basal-like subtypes of TNBCs. Epidermal growth factor receptor and CK5/6 are positive predictive markers of the TNBC response to everolimus, while cancer stem cell markers are negative predictive markers.

Hypoxia induces gefitinib resistance in non-small-cell lung cancer with both mutant and wild-type epidermal growth factor receptors.

Somatic mutations in the epidermal growth factor receptor (EGFR) gene, such as exon 19 deletion mutations, are important factors in determining therapeutic responses to gefitinib in non-small-cell lung cancer (NSCLC). However, some patients have activating mutations in EGFR and show poor responses to gefitinib. In this study, we examined three NSCLC cell lines, HCC827, PC9, and HCC2935, that expressed an EGFR exon 19 deletion mutation. All cells expressed mutant EGFR, but the PC9 and HCC2935 cells also expressed wild-type EGFR. The HCC827 cells were highly sensitive to gefitinib under both normoxia and hypoxia. However, the PC9 and HCC2935 cells were more resistant to gefitinib under hypoxic conditions compared to normoxia. Phosphorylation of EGFR and ERK was suppressed with gefitinib treatment to a lesser extent under hypoxia. The expression of transforming growth factor-α (TGFα) was dramatically upregulated under hypoxia, and the knockdown of TGFα or hypoxia-inducible factor-1α (HIF1α) reversed the resistance to gefitinib in hypoxic PC9 and HCC2935 cells. Finally, introduction of the wild-type EGFR gene into the HCC827 cells caused resistance to gefitinib under hypoxia. This phenomenon was also reversed by the knockdown of TGFα or HIF1α. Our results indicate that hypoxia causes gefitinib resistance in EGFR-mutant NSCLC through the activation of wild-type EGFR mediated by the upregulation of TGFα. The presence of wild-type and mutant EGFR along with tumor hypoxia are important factors that should be considered when treating NSCLC patients with gefitinib.

Circulating endothelial cells and other angiogenesis factors in pancreatic carcinoma patients receiving gemcitabine chemotherapy.

BACKGROUND: Pancreatic carcinoma is a significant cause of cancer-related death in developed countries. As the level of circulating endothelial cells (CECs) is known to increase in response to various cancers, we investigated the predictive potential of CEC levels and the association of these levels with the expression of proangiogenic factors in pancreatic carcinoma patients. METHODS: Pancreatic carcinoma patients receiving gemcitabine chemotherapy were prospectively assigned to this study. CEC levels were measured using the CellTracks system, and the plasma levels of several angiogenesis factors were measured using multiplex immunoassay. Associations between clinical outcomes and the levels of these factors were evaluated. RESULTS: Baseline CEC levels were markedly higher in pancreatic carcinoma patients (n = 37) than in healthy volunteers (n = 53). Moreover, these high CEC levels were associated with decreased overall survival (median, 297 days versus 143 days, P < 0.001) and progression-free survival (median, 150 days versus 64 days, P = 0.008), as well as with high vascular endothelial growth factor, interleukin (IL)-8, and IL-10 expression in the pancreatic carcinoma patients. CONCLUSIONS: Several chemokines and proangiogenic factors correlate with the release of CECs, and the number of CECs detected may be a useful prognostic marker in pancreatic carcinoma patients undergoing gemcitabine chemotherapy. TRIAL REGISTRATION: UMIN000002323.

Transcriptomic profiling of single circulating tumor cells provides insight into human metastatic gastric cancer.

Transcriptome analysis of circulating tumor cells (CTCs), which migrate into blood vessels from primary tumor tissues, at the single-cell level offers critical insights into the biology of metastasis and contributes to drug discovery. However, transcriptome analysis of single CTCs has only been reported for a limited number of cancer types, such as multiple myeloma, breast, hepatocellular, and prostate cancer. Herein, we report the transcriptome analysis of gastric cancer single-CTCs. We utilized an antigen-independent strategy for CTC isolation from metastatic gastric cancer patients involving a size-dependent recovery of CTCs and a single cell isolation technique. The transcriptomic profile of single-CTCs revealed that a majority of gastric CTCs had undergone epithelial-mesenchymal transition (EMT), and indicated the contribution of platelet adhesion toward EMT progression and acquisition of chemoresistance. Taken together, this study serves to employ CTC characterization to elucidate the mechanisms of chemoresistance and metastasis in gastric cancer.

Sunitinib inhibits lymphatic endothelial cell functions and lymph node metastasis in a breast cancer model through inhibition of vascular endothelial growth factor receptor 3.

INTRODUCTION: Metastasis is a common event and the main cause of death in cancer patients. Lymphangiogenesis refers to the formation of new lymphatic vessels and is thought to be involved in the development of metastasis. Sunitinib is a multi-kinase inhibitor that blocks receptor tyrosine kinase activity, including that of vascular endothelial growth factor receptors (VEGFRs). Although sunitinib is a clinically available angiogenesis inhibitor, its effects on lymphangiogenesis and lymph node metastasis remain unclear. The purpose of this study was to investigate the effects of sunitinib on vascular endothelial growth factor receptor 3 (VEGFR-3) and a related event, lymphangiogenesis. METHODS: The effects of sunitinib on the degree of phosphorylation of VEGFR-2/3 and other signaling molecules was examined in lymphatic endothelial cells (LECs) treated with the drug; VEGF-induced LEC growth, migration, and tube formation were also examined. For the in vivo study, luciferase-expressing breast cancer cells were transplanted into mammary fat pads of mice; the microvessel and lymphatic vessel density was then measured after treatment with sunitinib and anti-VEGFR-2 antibody. RESULTS: First, in human LECs, sunitinib blocked both VEGFR-2 and VEGFR-3 phosphorylation induced by VEGF-C or VEGF-D, and abrogated the activation of the downstream molecules extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt. Furthermore, sunitinib attenuated the cell-proliferation activity induced by VEGF-C/D and prevented VEGF-C-induced migration and tube formation of the LECs; however, anti-VEGFR2 treatment shows only a partial effect on the growth and functions of the LECs. We used a breast cancer cell line expressing luciferase as a metastatic cancer model. Sunitinib treatment (40 mg/kg/day) inhibited the growth of the primary tumor transplanted in the mammary fat pad of the mice and significantly reduced the number of blood and lymphatic vessels in the tumor. Furthermore, the development of axillary lymph node metastasis, detected by bioluminescent imaging, was markedly suppressed. This effect of sunitinib was more potent than that of DC101, an anti-mouse VEGFR-2 antibody. CONCLUSIONS: The results suggest that sunitinib might be beneficial for the treatment of breast cancer by suppressing lymphangiogenesis and lymph node metastasis, through inhibition, particularly important, of VEGFR-3.

Efficacy of RAD001 (everolimus) against advanced gastric cancer with peritoneal dissemination.

Peritoneal dissemination occurs frequently in patients with unresectable advanced-stage gastric cancer. In this study, we tested the efficacy of the mTOR inhibitor RAD001 (everolimus) against advanced gastric cancer with peritoneal dissemination. Using the two cell lines, 58As1, a cell line exhibiting a high propensity for peritoneal metastasis, and its parental cell line, HSC-58, a human scirrhous gastric cancer cell line, we first examined the growth-inhibitory activity of everolimus in vitro. Methylene blue assay demonstrated a moderate inhibitory effect of the drug on both cell lines under normal culture conditions (maximal inhibitory effect: 50.5% at 1 µM, HSC-58, 65.3%, 58As1). However, under the hypoxic condition (1% O(2)), while the growth-inhibitory activity of everolimus was greatly reduced in the HSC-58 cell line, the degree of reduction of the inhibitory activity was much smaller in the 58As1 cell line. Western blotting revealed that the degree of phosphorylation of mTOR and its downstream signaling molecules, p70S6K and 4E-BP1, was decreased under hypoxic conditions in HSC-58. On the other hand, phospho-p70S6K and phospho-4E-BP1 remained active under hypoxic conditions in 58As1, the molecular activity was suppressed by everolimus. Cell-cycle analysis showed that hypoxia-induced G1 arrest was not manifested in the 58As1 cells, unlike in the HSC-58 cells. Separately, an in vivo orthotopic mouse model of 58As1 revealed that everolimus significantly reduced peritoneal dissemination as evaluated by the quantitative photon counting method. Taken together, our results suggest that everolimus may have favorable activity against gastric cancer, particularly in cases with peritoneal dissemination.

Cancer antineovascular therapy with liposome drug delivery systems targeted to BiP/GRP78.

Angiogenesis is crucial for tumor growth and hematogenous metastasis. Specifically expressed and functional protein molecules in angiogenic endothelial cells, especially on the plasma membrane, may be molecular targets for antiangiogenic drugs and drug delivery systems (DDS) in cancer therapy. To discover such target molecules, we performed subcellular proteome analysis of human umbilical vein endothelial cells (HUVECs) treated with or without vascular endothelial growth factor (VEGF) using 2-dimensional difference in-gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). Among the identified proteins, BiP/GRP78, a molecular chaperone, was highly expressed in the membrane/organelle fraction of HUVECs after VEGF treatment. The involvement of BiP in VEGF-induced angiogenesis was examined by RNA interference. BiP knockdown significantly suppressed VEGF-induced endothelial cell proliferation and VEGF-induced phosphorylation of extracellular-regulated kinase 1/2, phospholipase C-γ, and VEGF receptor-2 in HUVECs. Cell surface biotinylation analysis revealed that the cell surface expression of BiP was elevated in VEGF-activated HUVECs. Aiming to apply BiP to a target molecule in liposomal DDS, we developed liposomes modified with the WIFPWIQL peptide, which has been shown to bind to BiP, and investigated its potential for cancer therapy. The WIFPWIQL-modified liposomes (WIFPWIQL liposomes) were significantly taken up by VEGF-activated HUVECs as compared to peptide-unmodified liposomes. WIFPWIQL liposomes appeared to accumulate in tumor endothelial cells in vivo. WIFPWIQL liposomes containing doxorubicin significantly suppressed tumor growth and prolonged the survival of colon26 NL-17 carcinoma cell-bearing mice. In summary, BiP may regulate VEGF-induced endothelial cell proliferation through VEGFR-2-mediated signaling and be an effective target molecule for cancer antineovascular therapy.

Synergistic interactions between the synthetic retinoid tamibarotene and glucocorticoids in human myeloma cells.

Tamibarotene (TM411) is a synthetic retinoic acid receptor-alpha/-beta selective retinoid that is chemically more stable than all-trans retinoic acid. This study was designed to evaluate the activity of TM411 in multiple myeloma (MM) and the effects of TM411 combined with a glucocorticoid (GC). In vitro, five human myeloma cells were treated with TM411 alone, GC alone, or TM411 + GC. Cell survival was analyzed by the tetrazolium dye assay and the Hoechst 33342/propidium iodide double-staining method. The effect of TM411 + GC was assessed by the isobologram method. In vivo, the growth-inhibitory effects of the drugs on RPMI-8226 cell xenografts established in SCID mice were examined. The effects of the agents on IL-6-mediated signaling pathways were also analyzed by Western blotting. TM411 was 2- to 10-fold more potent, in terms of its growth-inhibitory effect, than all-trans retinoic acid. The combination of TM411 and GC was found to show a markedly synergistic interaction. While increased expressions of the IL-6 receptor, phosphorylated MAPK, and Akt were observed after exposure to GC, TM411 attenuated this increase in the expressions, suggesting that such modification of the effect of GC by TM411 might be the possible mechanism underlying the synergistic interaction. Furthermore, TM411 + GC showed a supra-additive inhibitory effect in a xenograft model as compared with TM411 or GC alone. These results imply that the combination of TM411 + GC might be highly effective against MM, and suggest the need for clinical evaluation of TM411 + GC for the treatment of MM.

MicroRNA-500 as a potential diagnostic marker for hepatocellular carcinoma.

We identified that microRNA expression changed dynamically during liver development and found that miR-500 is an oncofetal miRNA in liver cancer. miR-500 was abundantly expressed in several human liver cancer cell lines and 45% of human hepatocellular carcinoma (HCC) tissue. Most importantly, an increased amount of miR-500 was found in the sera of the HCC patients. In fact, miR-500 levels in sera of the HCC patients returned to normal after the surgical treatment in three HCC patients. Our findings reveal that diverse changes of miRNAs occur during liver development and, one of these, miR-500 is an oncofetal miRNA relevant to the diagnosis of human HCC.

Dysfunction of Poly (ADP-Ribose) Glycohydrolase Induces a Synthetic Lethal Effect in Dual Specificity Phosphatase 22-Deficient Lung Cancer Cells.

Poly (ADP-ribose) glycohydrolase (PARG) is the main enzyme responsible for catabolism of poly (ADP-ribose) (PAR), synthesized by PARP. PARG dysfunction sensitizes certain cancer cells to alkylating agents and cisplatin by perturbing the DNA damage response. The gene mutations that sensitize cancer cells to PARG dysfunction-induced death remain to be identified. Here, we performed a comprehensive analysis of synthetic lethal genes using inducible PARG knockdown cells and identified dual specificity phosphatase 22 (DUSP22) as a novel synthetic lethal gene related to PARG dysfunction. DUSP22 is considered a tumor suppressor and its mutation has been frequently reported in lung, colon, and other tumors. In the absence of DNA damage, dual depletion of PARG and DUSP22 in HeLa and lung cancer A549 cells reduced survival compared with single-knockdown counterparts. Dual depletion of PARG and DUSP22 increased the apoptotic sub-G1 fraction and upregulated PUMA in lung cancer A549, PC14, and SBC5 cells, and inhibited the PI3K/AKT/mTOR pathway in A549 cells, suggesting that dual depletion of PARG and DUSP22 induced apoptosis by upregulating PUMA and suppressing the PI3K/AKT/mTOR pathway. Consistently, the growth of tumors derived from double knockdown A549 cells was slower compared with those derived from control siRNA-transfected cells. Taken together, these results indicate that DUSP22 deficiency exerts a synthetic lethal effect when combined with PARG dysfunction, suggesting that DUSP22 dysfunction could be a useful biomarker for cancer therapy using PARG inhibitors. SIGNIFICANCE: This study identified DUSP22 as a novel synthetic lethal gene under the condition of PARG dysfunction and elucidated the mechanism of synthetic lethality in lung cancer cells.

Synergistic antitumor activity of the novel SN-38-incorporating polymeric micelles, NK012, combined with 5-fluorouracil in a mouse model of colorectal cancer, as compared with that of irinotecan plus 5-fluorouracil.

The authors reported in a previous study that NK012, a 7-ethyl-10-hydroxy-camptothecin (SN-38)-releasing nano-system, exhibited high antitumor activity against human colorectal cancer xenografts. This study was conducted to investigate the advantages of NK012 over irinotecan hydrochloride (CPT-11) administered in combination with 5-fluorouracil (5FU). The cytotoxic effects of NK012 or SN-38 (an active metabolite of CPT-11) administered in combination with 5FU was evaluated in vitro in the human colorectal cancer cell line HT-29 by the combination index method. The effects of the same drug combinations was also evaluated in vivo using mice bearing HT-29 and HCT-116 cells. All the drugs were administered i.v. 3 times a week; NK012 (10 mg/kg) or CPT11 (50 mg/kg) was given 24 hr before 5FU (50 mg/kg). Cell cycle analysis in the HT-29 tumors administered NK012 or CPT-11 in vivo was performed by flow cytometry. NK012 exerted more synergistic activity with 5FU compared to SN-38. The therapeutic effect of NK012/5FU was significantly superior to that of CPT-11/5FU against HT-29 tumors (p = 0.0004), whereas no significant difference in the antitumor effect against HCT-116 tumors was observed between the 2-drug combinations (p = 0.2230). Cell-cycle analysis showed that both NK012 and CPT-11 tend to cause accumulation of cells in the S phase, although this effect was more pronounced and maintained for a more prolonged period with NK012 than with CPT-11. Optimal therapeutic synergy was observed between NK012 and 5FU, therefore, this regimen is considered to hold promise of clinical benefit, especially for patients with colorectal cancer.

Antitumor activity of cetuximab against malignant glioma cells overexpressing EGFR deletion mutant variant III.

Anti-epidermal growth factor receptor (EGFR) monoclonal antibody, cetuximab, is a promising targeted drug for EGFR-expressing tumors. Glioblastomas frequently overexpress EGFR including not only the wild type but also a deletion mutant form called 'variant III (vIII)', which lacks exon 2-7, does not bind to ligands, and is constitutively activated. In this study, we investigated the antitumor activity of cetuximab against malignant glioma cells overexpressing EGFRvIII. For this purpose, we transfected human malignant glioma cell lines with the retroviral vector containing cDNA for EGFRvIII, and analyzed the mode of cetuximab-induced action on the EGFRvIII in the cells. Immunoprecipitation and immunofluorescence revealed binding of cetuximab to EGFRvIII. Notably, immunoblotting analyses showed that cetuximab treatment resulted in reduced expression levels of the EGFRvIII. However, cetuximab alone did not exhibit a growth-inhibitory effect against the EGFRvIII-expressing cells. On the other hand, an assay for antibody-dependent cell-mediated cytotoxicity (ADCC) demonstrated cetuximab-induced cytolysis in the presence of human peripheral blood mononuclear cells in a dose-dependent manner. These results suggest that deletion mutant EGFRvIII can be a target of cetuximab and that ADCC activity substantially contributes to the antitumor efficacy of cetuximab against the EGFRvIII-expressing glioma cells. Thus, cetuximab could be a promising therapy in malignant gliomas that express EGFRvIII.