Soft Agar Cloning Assay Research Articles

Immortalized Mesenchymal Stem Cells: A Safe Cell Source for Cellular or Cell Membrane-Based Treatment of Glioma.

Mesenchymal stem cells (MSCs) have emerged as putative therapeutic tools due to their intrinsic tumor tropism, and anti-tumor and immunoregulatory properties. The limited passage and self-differentiation abilities of MSCs in vitro hinder preclinical studies on them. In this study, we focused on the safety of immortalized mesenchymal stem cells (im-MSCs) and, for the first time, studied the feasibility of im-MSCs as candidates for the treatment of glioma. The im-MSCs were constructed by lentiviral transfection of genes. The proliferative capacity of im-MSCs and the proliferative phenotype of MSCs and MSCs co-cultured with glioma cells (U87) were measured using CCK-8 or EdU assays. After long-term culture, karyotyping of im-MSCs was conducted. The tumorigenicity of engineered MSCs was evaluated using soft agar cloning assays. Next, the engineered cells were injected into the brain of female BALB/c nude mice. Finally, the cell membranes of im-MSCs were labeled with DiO or DiR to detect their ability to be taken up by glioma cells and target in situ gliomas using the IVIS system. Engineered cells retained the immunophenotype of MSC; im-MSCs maintained the ability to differentiate into mesenchymal lineages in vitro; and im-MSCs showed stronger proliferative capacity than unengineered MSCs but without colony formation in soft agar, no tumorigenicity in the brain, and normal chromosomes. MSCs or im-MSCs co-cultured with U87 cells showed enhanced proliferation ability, but did not show malignant characteristics in vitro. Immortalized cells continued to express homing molecules. The cell membranes of im-MSCs were taken up by glioma cells and targeted in situ gliomas in vivo, suggesting that im-MSCs and their plasma membranes can be used as natural drug carriers for targeting gliomas, and providing a safe, adequate, quality-controlled, and continuous source for the treatment of gliomas based on whole-cell or cell membrane carriers.

KIR2DL4 promotes the proliferation of RCC cell associated with PI3K/Akt signaling activation

BackgroundKiller cell immunoglobulin-like receptor 2DL4 (KIR2DL4) is a transmembrane glycoprotein that is expressed by natural killer (NK) cells and certain subsets of T cells. However, its expression profiles and functions in solid tumor progression remain poorly defined. MethodsIn the present study, using bioinformatics analysis, immunohistochemistry, immunoblotting, MTT cell viability assay, soft agar colony formation assay and a human renal cell carcinoma (RCC) cell xenograft model in nude mice, we examined whether KIR2DL4 is expressed by RCC and its possible roles in RCC progression. ResultsWe confirmed that KIR2DL4 is overexpressed by RCC cells. MTT and soft agar cloning assays showed that KIR2DL4 knockdown delayed cell proliferation and viability in RCC cell lines, Caki-1 and 769-P, in vitro. By contrast, KIR2DL4 overexpression promoted Caki-1 cell proliferation both in vitro and in vivo, which was observed in a BALB/c-nu/nu xenograft mouse model. Moreover, RNA sequencing data demonstrated that the differentially expressed genes found between parallel-controlled and Caki-1 cells overexpressing KIR2DL4 were highly associated with cancer development, of which those related to the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) signaling pathway were particularly enriched, immunoblotting data showed that the level of AKT phosphorylation was higher or lower in KIR2DL4 overexpressing or KIR2DL4 knocking-down Caki-1 cells compared with that in the parallel-controlled cells. In addition, PI3K inhibitor wortmannin treatment and KIR2DL4-shRNA transfection further deregulated the levels of phosphorylated AKT and Caki-1 cell proliferation. ConclusionsOur results indicate that KIR2DL4 is also expressed by RCC cells, which promotes RCC progression associated with PI3K/AKT activation.

Biological roles of filamin a in prostate cancer cells.

ABSTRACTObjective This study aims to investigate the association of filamin A with the function and morphology of prostate cancer (PCa) cells, and explore the role of filamin A in the development of PCa, in order to analyze its significance in the evolvement of PCa.Materials and Methods A stably transfected cell line, in which filamin A expression was suppressed by RNA interference, was first established. Then, the effects of the suppression of filamin A gene expression on the biological characteristics of human PCa LNCaP cells were observed through cell morphology, in vitro cell growth curve, soft agar cloning assay, and scratch test.Results A cell line model with a low expression of filamin A was successfully constructed on the basis of LNCaP cells. The morphology of cells transfected with plasmid pSilencer-filamin A was the following: Cells were loosely arranged, had less connection with each other, had fewer tentacles, and presented a fibrous look. The growth rate of LNCap cells was faster than cells transfected with plasmid pSilencer-filamin A (P <0.05). The clones of LNCap cells in the soft agar cloning assay was significantly fewer than that of cells stably transfected with plasmid pSilencer-filamin A (P <0.05). Cells stably transfected with plasmid pSilencer-filamin A presented with a stronger healing and migration ability compared to LNCap cells (healing rate was 32.2% and 12.1%, respectively; P <0.05).Conclusion The expression of the filamin A gene inhibited the malignant development of LNCap cells. Therefore, the filamin A gene may be a tumor suppressor gene.

Abstract 5328: RNF12 inhibits the proliferation of hepatocellular carcinoma through c-Myc and p21

Abstract Purpose: RNF12/RLIM, a RING E3 ubiquitin ligase, plays an important role in the epigenetic regulation of sex-specific nurturing tissues in female mice. Recently, a few studies demonstrated a correlation between RNF12 and the proliferation of multiple cancers. The role of RNF12 in hepatocellular carcinoma is incompletely understood. The purpose of this study is to investigate the effect of RNF12 on the proliferation of human hepatocellular carcinoma cells. RNF12 is also known to interact with a number of nuclear proteins, including CLIM, HDAC2, and Smad4. We also explored whether c-Myc and p21, an oncogene and tumor suppressor essential to liver tumorigenesis, were affected by RNF12. Methods: Immunohistochemistry of RNF12 and c-Myc was performed on surgically dissected human hepatocellular carcinoma tissues. The soft-agar cloning, flow cytometry and Transwell invasion assays were carried out to investigate the role of RNF12 in SK-Hep1 cell proliferation, cell cycle and invasiveness. Real-time quantitative PCR and Western blotting were used to examine the mRNA and protein levels of RNF12 and related proteins in SK-Hep1 cells. Results: We found that the level of RNF12 was lower in hepatocellular carcinoma, compared with the surrounding non-cancerous tissues, while the c-Myc expression was higher. Using a SK-Hep1 cell line stably expressing RNF12, we showed that RNF12 over-expression inhibited cell proliferation and induced cell cycle arrest at G1 phase. Furthermore, we showed that RNF12 over-expression decreased the level of oncoprotein c-Myc, while not much affecting its mRNA level. Co-immunoprecipitation demonstrated that RNF12 and c-Myc associated with each other, suggesting a direct protein-protein interaction. RNF12 over-expression also markedly increased the mRNA and protein levels of p21, a tumor suppressor and the downstream target of p53, c-Myc and many other cancer-related regulators. Consistently, silencing of RNF12 reduced p21 mRNA and protein levels and increased c-Myc protein. Conclusion: Our study demonstrated reduced expression of RNF12 in hepatocellular carcinoma, and RNF12 over-expression inhibited the proliferation and cell cycle progression of SK-Hep1 cells. Mechanistically, RNF12 may directly regulate the level of c-Myc, similarly as other transcription factors such as CLIM and Smad4. The mechanisms underlying the increased expression of p21 is being investigated. Taken together, RNF12 may serve as a tumor suppressor in hepatocellular carcinoma, partly through oncoprotein c-Myc and tumor suppressor p21. Note: This abstract was not presented at the meeting. Citation Format: Meng Nie, Yongsheng Huang, Lin Wang. RNF12 inhibits the proliferation of hepatocellular carcinoma through c-Myc and p21 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5328. doi:10.1158/1538-7445.AM2017-5328

Abstract B46: Rac1 inhibition as a therapeutic strategy in breast cancer

Abstract Over the past few decades, targeted therapies have accounted for most of the therapeutic advances in breast cancer. The purpose of this approach is to discover new, actionable therapeutic strategies for breast cancer. We previously used a forward genomic screening approach to identify novel genes capable of cooperating with HER2, and found that loss of HACE1 was prevalent in breast cancer, identifying it as a tumor suppressor gene. HACE1 had significantly lower expression in breast cancer patients compared to normals. HACE1 is an E3 ubiquitin ligase that ubiquitinates Rac1, marking it for degradation. Rac1, a Rho GTPase, is a central component of key signaling pathways in breast cancer. While we identified HACE1 in a HER2 cooperating screen, the observation that HACE1 levels were consistently low across different subtypes of breast cancer led us to suggest that Rac1 is commonly hyperactivated in breast cancer and therefore has potential as a therapeutic target. We tested a Rac1 inhibitor, EHT 1864, on 8 different breast cancer cell lines, starting with an initial soft agar assay screen for sensitivity versus resistance and found that 4 cells lines were sensitive to the Rac1 inhibitor in soft agar cloning assays (MCF7, T47D, BT549, and BT474), while 4 other cell lines were resistant (MDA231, MDA436, MDA468, HS578T). These results were confirmed in 2D proliferation assays. The majority of the cell lines that were resistant to Rac1 inhibition overexpressed EGFR, suggesting that overexpression of EGFR confers resistance to Rac1 inhibition via the MAP Kinase pathway. Isogenic cell lines (MCF7) that express multiple activating proteins of the MAPK signaling pathway including EGFR, HER2, and MEK were treated with EHT1864 to determine if MAPK signaling was capable of overcoming Rac1 inhibition. Interestingly, the expression of EGFR conferred resistance to the Rac1 inhibitor. We further showed that molecular knockdown of EGFR in HS578T cells (EGFR-overexpressing, Rac1 inhibitor-resistant cells) resensitizes this cell line to Rac1 inhibition. Pharmalogical inhibition of EGFR using Gefitinib, an EGFR tyrosine kinase inhibitor, demonstrated the same resensitization to the Rac1 inhibitor. Our results suggest that Rac1 inhibition may be a therapeutic strategy in the treatment of breast cancer, as a single agent alone or in the case of EGFR overexpressing (triple-negative) breast cancers, in combination with EGFR targeted therapies. Citation Format: Dana Senderoff, Georges Azzi, Erik Goka, Marc Lippman. Rac1 inhibition as a therapeutic strategy in breast cancer. [abstract]. In: Proceedings of the Fourth AACR International Conference on Frontiers in Basic Cancer Research; 2015 Oct 23-26; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2016;76(3 Suppl):Abstract nr B46.

Abstract 2719: TCRP1 gene promotes NIH/3T3 cell transformation by over-activating PDPK1 and Akt

Abstract TCRP-1 (Tongue Cancer Resistance-related Protein-1) gene was recently cloned from the multidrug resistance tongue cancer cell (Tca8113/PYM) which developed by ourselves team (GeneBank accession number: EF36480). Subsequently we found that the gene can mediate tongue cancer cells to specific cisplatin chemotherapy tolerance and radiotherapy tolerance, and its mechanism may be caused at least in part by TCRP1 induced activation of the PI3K/Akt/NF-κB signaling pathway and promotes cell survival. Recently, using real-time quantitative PCR and immunohistochemical method to detect various types of tumors and control normal tissue, we found that expression of TCRP1 in lung cancer, ovarian cancer and glioma were significantly higher than that of normal tissue. These results suggest that TCRP1 gene may be closely related to the carcinogenesis. In the present study we constructed a lentiviral vector expressing TCRP1 to transfect NIH/3T3 cells, and found proliferation rate of NIH/3T3/TCRP1 cells was significantly improved compared with NIH/3T3 cells and NIH/3T3/vector cells by detection with the CellTiter-Glo Assay. Clonogenic capacity of NIH/3T3/TCRP1 cells was 5.39 times and 20.18 times higher than the control group in plate cloning and soft agar cloning assay. Subcutaneous tumorigenicity experiment with self-controlled in 10 nude mice found only the injected site of NIH/3T3/TCRP1 cell emergence nodular masses about 1cm diameter after 3 weeks, and the tumorigenic rate was 90%. Pathological diagnosis of mass was fibrosarcoma. These results suggest that TCRP1 gene own an oncogene-like effect. In order to study the TCRP1 tumorigenic mechanisms, gene chips were used and showed that expression of total of 1894 genes were up-regulated and 3626 genes were down-regulated. Among these genes, the verification results of PDPK1, Akt, GSK3β and cyclinD1 were consistent with microarray results. Co-immunoprecipitation assay indicate that TCRP1 interact with PDPK1; FRET(Fluorescence Resonance Energy Transfer)experiments shows that TCRP1 can directly bind to PDPK1. On the other hand, the growth rate and in vitro colony forming ability of NIH/3T3/TCRP1 cells was significantly inhibited after using PDPK1 inhibitor AR-12 and TCRP1 interference. These data suggest that TCRP1 mediated PI3K/Akt pathway to the excessive activation by recruiting recruitment and activating of PDPK1, resulting in a series of growth and proliferation and cell transformation related factor expression or activation of its downstream. This may be the possible mechanism of cell malignant transformation induced by TCRP1. {This study was supported by grant from National Natural Science Foundation (81472184) of China.} Citation Format: Chengkun Wang, Xiaorong Liu, Qinwei Qiu, Zhijie Zhang, Jiang Yin, Guopei Zheng, Zhimin He. TCRP1 gene promotes NIH/3T3 cell transformation by over-activating PDPK1 and Akt. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2719. doi:10.1158/1538-7445.AM2015-2719

Dominant negative Ubiquitin-conjugating enzyme E2C sensitizes cervical cancer cells to radiation

Purpose: To find the radiation sensitivity of human cervical carcinoma cell lines and to investigate the effect of the dominant negative-Ubiquitin-conjugating enzyme E2C (DN-UBE2C) on cell proliferation and radiation response.Materials and methods: Radiation sensitivities of human cervical cell lines (SiHa, HeLa, BU25TK, ME 180, and C33A) were analyzed by assessing their cell survival after irradiation by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. Soft agar cloning assay, growth curve and radiation response of DN-UBE2C stably transfected SiHa and HeLa cell lines were assessed by MTS assay and Clonogenic assay.Results: Difference in sensitivity to radiation was observed among the cervical cancer cell lines studied. SiHa was found to be the most resistant cell line whereas C33A cells were the most sensitive. The growth rate of SiHa and HeLa transfected with DN-UBE2C was significantly reduced compared to vector control. Furthermore, DN-UBE2C-mediated radiosensitivity was correlated with a significant decrease in resistance to radiation by SiHa and HeLa cells after transfection with the DN-UBE2C when compared to control cultures.Conclusion: These results suggested that the Ubiquitin-conjugating enzyme E2C (UBE2C) gene is a potential therapeutic target for cervical cancer treatment.

Glycoprotein transmembrane nmb: An androgen‐downregulated gene attenuates cell invasion and tumorigenesis in prostate carcinoma cells

Glycoprotein transmembrane nmb (GPNMB) gene was originally identified in osteoblasts and belongs to the pmel-17/nmb family. The function or regulation of GPNMB in the human prostate remains unknown. The expression of GPNMB in prostate carcinoma cells were determined by real-time reverse transcription-polymerase chain reaction (RT-qPCR) and immunoblot assays. Effects of ectopic GPNMB overexpression on cell proliferation, invasion, and tumorigenesis were determined by (3) H-thymidine incorporation, matrigel invasion, soft agar cloning assays, and murine xenograft study. Effects of GPNMB, p53, and androgen on target gene were assessed using RT-PCR, immunoblotting, and transient gene expression assays. In vitro analysis using several prostate cell lines suggested that expression of GPNMB may be relevant to the extent of neoplasia. Ectopic overexpression of GPNMB significantly attenuated cell proliferation and invasion and exerted antitumorigenic activity on PC-3 cells in vitro and in vivo. GPNMB overexpression induced the gene expressions of N-myc downstream regulated gene 1 (Ndrg1) and maspin in PC-3 cells. Doxorubicin treatment or transient overexpression of p53 increased GPNMB expression. Androgen (R1881) treatment has a divergent effect on gene expression of prostate-specific antigen (PSA) and GPNMB in LNCaP cells. Androgen treatment enhanced cell proliferation but downregulated GPNMB protein expression in stably overexpressed androgen receptor (AR) CA-HPV-10 cells. Together these results suggest that GPNMB gene is a p53- and androgen-dysregulated gene and should be regarded as an anti-tumor gene for prostate cancer. The enhancement of Ndrg1 and maspin gene expressions may account for the anti-proliferative and anti-invasive function of GPNMB in PC-3 cells.

Abstract 5015: Hcasz5, CASZ1 gene transcript variant 2 with 5 zinc fingers functions as a tumor suppressor in Neuroblastoma

Abstract Neuroblastoma (NB) is a common childhood malignant tumor of the sympathetic nervous system. The human homolog of the Drosophila neural fate determination gene CASZ1, a zinc-finger transcription factor, maps to chromosome 1p36.22, a region implicated in NB tumorigenesis. We have previously reported that human CASZ1 gene encodes two major mRNA species, hcasz5 (CASZ1 gene transcript variant 2) and hcasz11 (CASZ1 gene transcript variant 1) because the predicted proteins have 5 and 11 zinc fingers, respectively. Quantitative PCR analysis showed that low expression of total CASZ1 is significantly correlated with decreased survival probability (p=0.0009). Functional in vitro and in vivo studies on the full length CASZ1 - hcasz11 show that it has tumor suppressor activity. To date the function of the short isoform - hcasz5 is unknown. In this study quantitative PCR analysis was performed using isoform specific primers that only recognize hcasz5. Low hcasz5 expression is significantly associated with older age (&amp;gt;18 months), high-risk disease, 1p LOH, MYCN amplification and an undifferentiated histopathology (all p&amp;lt;0.005). Using CASZ1 antibody that recognizes both hcasz5 and hcasz11 isoforms, we found hcasz5 and hcasz11 protein are co-expressed in the nucleus of all cell lines and mouse tissues examined. Retinoic acid (RA), a key embryonic morphogen, coordinately regulates hcasz5 and hcasz11 expression; moreover, the epigenetic modification agents 5-Aza-dC and HDAC inhibitors also induce both hcasz5 and hcasz11 expression. Bio-informatic analysis indicates that hcasz5 and hcasz11 utilize the same promoter and enhancer regulatory regions. However, the steady-state level of hcasz11 is higher than hcasz5 indicating different post-transcriptional mechanisms regulate specific isoforms. Frequently different isoforms have distinct functions or act as dominant negatives. However, expression profiling reveals that the majority of hcasz5 target genes overlap with hcasz11 targets and are also involved in cell movement, proliferation and developmental processes. Analysis of target gene expression revealed that neither hcas5 nor hcasz11 functioned synergistically or acted as a dominant negative when co-expressed in vitro. Functionally, specific restoration of hcasz5 in NB cells enhanced cell adhesion, inhibited migration and suppressed cell growth similar to the functional effects when hcasz11 expression is restored in NB cells. This study indicates that while both hcas5 and hcasz11 are lost in poor prognosis NB patient samples, the functional restoration of either isoform is sufficient to suppress tumor growth by MTS assay and soft agar cloning assay in vitro. We argue that the redundant expression and largely overlapping functions of hcasz5 and hcasz11 isoforms indicate that expression of the CASZ1 gene is an important regulator of neuroblast growth and differentiation during development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5015.

Thymidylate synthase gene expression in solid tumors predicts for response to pemetrexed in vitro

13058 Background: Pemetrexed (P) is a novel antifolate which targets thymidilate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT). The aim of the present study was to identify gene expression thresholds for these enzymes in human tumor specimens in order to separate P-sensitive from P-resistant patients. Methods: Soft-agar cloning assays were performed on freshly biopsied tumor cells exposed one hour to clinically achievable concentrations of P. In parallel, RNA was isolated, transcribed to cDNA and subsequently used for multiplex real-time PCR. Gene expression data were normalized against beta-actin transcripts followed by correlation against cloning assay results. Iterative calculations (fourfold analysis) were done for each enzyme separately to find the best cutoff for prediction of sensitivity to P. Results: Sensitive and resistant tumor samples were statistically significant different in gene expression of TS, DHFR, and GARFT (p &lt; 0.003). 81% of all tumors with a TS copy number &lt; 144 (related to 104 copies β-actin) were sensitive to P in vitro. (specificity = 0.69; chi2 = 14.14). Statistical tests demonstrated that gene expression of TS, DHFR, and GARFT are dependent variables and that TS transcription is the leading variable. The combination of TS, DHFR, and GARFT expression data was not superior to TS alone. Conclusions: TS expression is the most meaningful predictor for sensitivity (≤ 144 copies) or resistance (&gt; 144 copies) to Pemetrexed in fresh tumor tissue. This observation forms a rationale for clinical trials using TS expression as predictor for clinical response. No significant financial relationships to disclose.

Investigation of HMN-176 anticancer activity in human tumor specimens in vitro and the effects of HMN-176 on differential gene expression

HMN-176, (E)-4-(2-[2-(N-[4-methoxybenzene-sulfonyl]amino)phenyl]ethenyl) pyridine 1-oxide, is a stilbene derivative which inhibits mitosis without significant effect on tubulin polymerization and displays potent cytotoxicity against a variety of human tumor cell lines. The present study evaluated the activity profile of the antineoplastic agent HMN-176 in an ex-vivo soft agar cloning assay (human tumor colony-forming assay) in a panel of 132 human tumor specimens under 14-day continuous exposure at 0.1, 1.0, and 10.0 microg/ml. Thirty percent of specimens in the different treatment groups (39/132 in 0.1 and 1.0 test groups; 40/132 in 10.0 test group) were assessable, falling within the negative and positive control parameters. At these dose levels, responses were observed in 32% (11/34), 62% (21/34), and 71% (25/35) of assessable specimens, respectively. HMN-176 demonstrated activity towards 75% of the breast cancer specimens (6/8) treated with 1.0 microg/ml, 67% of non small-cell lung (4/6) and 57% of ovarian (4/7) cancer specimens treated with 10 microg/ml. Low levels of cross-resistance to cisplatin, cyclophosphamide, 5-fluorouracil, and etoposide were also observed. There was a positive relationship between HMN-176 concentration and effect, demonstrating greatest overall activity at 10.0 microg/ml. Evaluation of differential gene expression in drug-sensitive (A2780) and drug-resistant (A2780cp) ovarian carcinoma cell lines exposed to 0.1 microg/ml HMN-176 up to 48 h using cDNA microarrays with 1,154 known human genes revealed significant drug effects on tumor associated genes, including upregulation of tissue inhibitor matrix metalloproteinases gene (TIMP) in both cell lines, suggesting that HMN-176 could potentially overcome tumor drug resistance. In conclusion, in vitro responses demonstrate efficacy at pharmacologically relevant concentrations, which suggests that HMN-176 deserves further evaluation in clinical trials.

AMD473 (ZD0473) exhibits marked in vitro anticancer activity in human tumor specimens taken directly from patients.

AMD473 (ZD0473; cis-amminedichloro[2-methylpyridine]platinum [II]) is a new generation anticancer agent that, in preclinical studies, shows evidence of an extended spectrum of antitumor activity and overcomes platinum resistance mechanisms. Here we evaluate the activity of AMD473 (ZD0473) in a panel of 120 human tumor specimens using a soft agar cloning assay (human tumor colony-forming assay). When tumor cells were treated with 1.0, 4.0 or 16.0 microg/ml AMD473 (ZD0473) for 2 h, in vitro responses were observed in 18% (9/51), 33% (17/51) and 44% (19/43) of assessable specimens. Treatment of tumor cells with the same concentrations of AMD473 (ZD0473) for 24 h resulted in responses of 33% (16/48), 63% (30/48) and 85% (35/41). AMD473 (ZD0473) (16 microg/ml; 24 h) demonstrated activity towards 100% of the non-small cell lung (5/5) and ovarian (8/8) cancer specimens and 73% (8/11) of the breast cancer specimens treated. Low levels of cross-resistance to cisplatin cyclophosphamide, 5-flurouracil, etoposide and gemcitabine were observed. There was a positive relationship between AMD473 (ZD0473) concentration and effect, and a significant difference between response to 2- versus 24-h exposure to 4 or 16 microg/ml (p=0.003 and p=0.001, respectively). These responses demonstrate efficacy at pharmacologically relevant concentrations, suggesting AMD473 (ZD0473) deserves further evaluation.

Activity of SCH 66336, a tricyclic farnesyltransferase inhibitor, against human tumor colony-forming units

The ras gene product regulates transduction of growth-proliferative signals from the membrane to the nucleus. Mutationally-activated Ras is the oncogene most frequently found in human tumors. In order to perform its function in cell signaling, Ras must be farnesylated on the CAAX motif present on the carboxyl terminus of the ras protein. This reaction is catalysed by farnesyl protein transferase. In the present study, SCH 66336, an orally bioavailable nonpeptide tricyclic farnesyltransferase inhibitor, was tested against a large variety of human tumors to define its preclinical activity profile, utilizing the human tumor cloning assay. A soft agar cloning assay was used to determine the in vitro effects of SCH 66336 against primary human tumor specimens taken directly from patients. A total of 70 evaluable specimens were exposed to SCH 66336 for 14-day continuous exposure at concentrations ranging from 0.1 to 2.5 microM. In vitro responses were defined as an inhibition > or = 50% of human tumor colony forming units at a given concentration. There was a positive relationship between concentration and response to SCH 66336. With the highest concentration (2.5 microM), response was demonstrated in 50% (three of six) of breast tumors, 40% (6 of 15) of ovarian tumors, and 38% (5 of 13) of non-small-cell lung tumor colony forming units. Among the 69 specimens tested at the concentration of 2.5 microM, SCH 66336 had activity in 27% of tumor specimens that were resistant to doxorubicin, 38% of tumor specimens resistant to cisplatin, 33% of tumor specimens resistant to paclitaxel, and 27% of tumor specimens resistant to etoposide. The broad spectrum of soft agar growth inhibition by SCH 66336 in the human tumor cloning assay, and its efficacy at physiologically relevant concentrations in animal models, suggest that SCH 66336 may deserve future clinical trials in patients with ovarian, breast and non-small-cell lung cancer.

In vitro antitumor activity of the novel marine agent, Ecteinascidin-743 (ET-743, NSC-648766) against human tumors explanted from patients

Ecteinascidin-743 (ET-743), a member of the ecteinascidin family selected for clinical development, is a tetrahydroisoquinolone alkaloid isolated from the marine ascidian, Ecteinascidia turbinata. This novel compound is a minor groove binding, guanine-specific alkylating agent which also interacts with the microtubule network and blocks cell cycle progression at late S/G2. A soft agar cloning assay was used to determine the in vitro effects of ET-743 against primary human tumor specimens taken directly from patients. A total of 93 evaluable specimens were exposed to ET-743 for one-hour (n = 25) and/or 14-day continuous exposure (n = 92) at concentrations ranging from 0.1 nM to 1 microM. In vitro responses were defined as an inhibition > or = 50% of human tumor colony forming units at a given concentration. One-hour exposure to ET-743 at concentrations of 0.1 nM, 1 nM, 10 nM, 100 nM and 1 microM induced in vitro responses in 0% (0/17), 6% (1/17), 16% (4/25), 13% (1/8), and 25% (2/8) of specimens, respectively. Continuous exposure to ET-743 at concentrations of 0.1 nM, 1 nM, 10 nM, 100 nM and 1 microM, inhibited 0% (0/16), 13% (2/16), 49% (44/90), 62% (47/76), and 77% (58/75) of tumor specimens, respectively. Tumor-specific responses and concentration-dependent relationships were observed with a continuous exposure to ET-743. At 100 nM, the compound inhibited 79% (11/14) breast, 69% (9/13) non-small-cell lung, 58% (7/12) ovary, and 88% (7/8) melanoma specimens. At 1 microM, ET-743 inhibited 100% (14/14) breast specimens, 85% (11/13) non-small-cell lung, 67% (8/12) ovary and 86% (6/7) melanoma specimens. Activity of ET-743 at and above 10 nM was also observed against sarcoma and kidney tumors. At 10 nM concentration and continuous exposure ET-743 demonstrated incomplete cross-resistance with paclitaxel, alkylating agents, doxorubicin and cisplatin. Our data from the cloning assay indicate that the duration of exposure to ET-743 is an important factor in human tumors. Therefore, long-term exposure to ET-743 may be preferred in future clinical trials. The activity of ET-743 in breast, non-small-cell lung, and ovarian cancers as well as in melanoma may deserve further clinical evaluations. The potential of ET-743 in sarcoma and renal tumors might also be considered. In addition, our data indicate that a plasma concentration of 100 nM of ET-743 must be considered as a target during the clinical development of the compound; also the concept of continuous/protracted exposure in clinical trials with ET-743 has to be taken into account.

Differential expression and biological activity of the heparin-binding growth-associated molecule (HB-GAM) in lung cancer cell lines.

The growth of human lung cancer cells is regulated positively and negatively by a variety of growth factors through autocrine as well as paracrine mechanisms. In the present report, we studied the differential role and expression of a neuropolypeptide growth factor in 26 lung cancer cell lines. Expression of the heparin-binding growth-associated molecule (HB-GAM) in 12 small cell lung cancer (SCLC) cell lines was compared to that in 14 non-small cell lung cancer (NSCLC) cell lines. HB-GAM mRNA was expressed in 9 of 12 SCLC and 3 of 14 NSCLC cell lines as determined by RT-PCR analyses. Normal human bronchial epithelial cells were used as negative controls. All cell lines which expressed HB-GAM mRNA produced HB-GAM protein as well. Western blot analysis showed that the tumor cells secreted HB-GAM into the media. HB-GAM, purified from lung cancer cell lines, exerted biological activity on fibroblasts, endothelial cells and SW13 cells as determined by thymidine incorporation and soft agar cloning assays. In addition, the biological activity of HB-GAM was blocked by a specific antibody in a dose-dependent way. Our findings suggest that HB-GAM may serve as a marker for SCLC cell lines and that it may function as a paracrine growth factor in human lung cancer. HB-GAM may be a further member of the network of growth factors involved in proliferation, angiogenesis and metastasis of lung tumors.

Activity of TER286 against human tumor colony-forming units.

Glutathione S-transferase (GST) isozymes have been shown to be elevated in many human cancer types as compared to normal tissues. TER286, one in a class of glutathione-based GST-activated cytotoxins, was tested in a soft agar cloning assay to determine its in vitro activity against primary human tumor colony-forming units. Breast and lung specimens from patients who had received prior therapy and those who were previously untreated were exposed to TER286 at concentrations of 1, 10 and 50 microM using both 1 h and continuous exposures. Overall in vitro responses (50% or less survival compared to untreated controls) were observed in 0% (0/14), 14% (2/14) and 29% (4/14), respectively, in specimens exposed to TER286 for 1 h, and in 5% (2/41), 10% (4/41) and 61% (25/41), respectively, in specimens exposed to TER286 continuously. TER286 has cytotoxic activity against both breast and lung cancer colony-forming units, and demonstrates a concentration-response effect. At 50 microM, there is a significant difference between 1 h and continuous exposures in head-to-head comparisons. These data suggest that TER286 can be activated in human tumor colony-forming units and should be pursued as a treatment candidate for patients whose tumors are resistant to drug treatment based on up-regulation of GST.

Species Differences in the Clonal Expansion of Hepatocytes in Response to the Coaction of Epidermal Growth Factor and Nafenopin, a Rodent Hepatocarcinogenic Peroxisome Proliferator

Species Differences in the Clonal Expansion of Hepatocytes in Response to the Coaction of Epidermal Growth Factor and Nafenopin, a Rodent Hepatocarcinogenic Peroxisome Proliferator. James, N.H. and Roberts, R. A. (1995). Fundam. Appl. Toxicol. 26, 143-149.Peroxisome proliferators are members of the nongenotoxic family of rodent hepatocarcinogens. There exist substantial species differences in response to peroxisome proliferators among mammalian species. We have reported previously that peroxisome proliferators can synergize with epidermal growth factor (EGF) to promote the clonal expansion of rat hepatocytes associated with the early stages of hepatocarcinogenesis. The aim of the present study was to determine whether responsiveness in this in vitro assay reflected the known species differences in response to peroxisome proliferators. The process of tumorigenicity was modeled in the soft agar cloning assay since growth in soft agar is thought to reflect the early stages of tumorigenesis. This is because clonal expansion under these conditions requires the cells to survive, to undergo mitosis, and to escape from the contact-dependent growth associated with normal cell behavior. The data presented here show that mouse hepatocytes are able to undergo clonal expansion in soft agar in response to nafenopin and EGF giving a three to fourfold increase in colony numbers over control. This result is comparable to the fivefold increase in rat hepatocyte colony numbers that we have reported previously. In contrast, hamster, guinea pig, and human hepatocytes did not respond to the concerted action of EGF and nafenopin despite their ability to respond to EGF as a mitogen in monolayer culture. These data demonstrate that the clonal expansion of rodent hepatocytes in soft agar in response to peroxisome proliferators and EGF displays the same species differences as other pleiotropic responses to these compounds and is likely therefore to be relevant to the process of hepatocarcinogenesis.

Activity of the morpholino anthracycline 3'-deamino-3'-morpholino-13-deoxo-10-hydroxycarminomycin (MX2) against human tumor colony-forming units in vitro.

In several preclinical systems, the morpholino anthracycline MX2 has greater antitumor activity than doxorubicin, is less cardiotoxic, and is effective against multidrug resistant cancer cells. We used a human tumor soft-agar cloning assay to test the cytotoxicity of MX2 against single cell suspensions from freshly obtained human tumors. Tumor cells were exposed to MX2 at 0.05 and 0.5 micrograms/ml either for 1 hour (2-1 specimens; 77 [38%] assessable) or continuously (231 specimens; 91 [39%] assessable). Superior antitumor activity was observed with continuous exposure (19% in vitro response at 0.05 micrograms/ml and 69% at 0.5 micrograms/ml) than with 1-hour exposure (1.3% at 0.05 micrograms/ml and 12% at 0.5 micrograms/ml). Activity was seen against all types of cancer tested including renal (91%), melanoma (88%), ovarian (73%), breast (71%) and non-small-cell lung (67%) cancer at a MX2 concentration of 0.5 micrograms/ml after continuous exposure. If appropriate plasma levels can be achieved in patients, MX2 could have significant clinical activity with those tumors.

Species Differences in the Clonal Expansion of Hepatocytes in Response to the Coaction of Epidermal Growth Factor and Nafenopin, a Rodent Hepatocarcinogenic Peroxisome Proliferator

Peroxisome proliferators are members of the nongenotoxic family of rodent hepatocarcinogens. There exist substantial species differences in response to peroxisome proliferators among mammalian species. We have reported previously that peroxisome proliferators can synergize with epidermal growth factor (EGF) to promote the clonal expansion of rat hepatocytes associated with the early stages of hepatocarcinogenesis. The aim of the present study was to determine whether responsiveness in this in vitro assay reflected the known species differences in response to peroxisome proliferators. The process of tumorigenicity was modeled in the soft agar cloning assay since growth in soft agar is thought to reflect the early stages of tumorigenesis. This is because clonal expansion under these conditions requires the cells to survive, to undergo mitosis, and to escape from the contact-dependent growth associated with normal cell behavior. The data presented here show that mouse hepatocytes are able to undergo clonal expansion in soft agar in response to nafenopin and EGF giving a three- to fourfold increase in colony numbers over control. This result is comparable to the fivefold increase in rat hepatocyte colony numbers that we have reported previously. In contrast, hamster, guinea pig, and human hepatocytes did not respond to the concerted action of EGF and nafenopin despite their ability to respond to EGF as a mitogen in monolayer culture. These data demonstrate that the clonal expansion of rodent hepatocytes in soft agar in response to peroxisome proliferators and EGF displays the same species differences as other pleiotropic responses to these compounds and is likely therefore to be relevant to the process of hepatocarcinogenesis.

Activity of Intoplicine (RP60475), a New DNA Topoisomerase I and II Inhibitor, Against Human Tumor Colony-Forming Units In Vitro

Intoplicine (RP60475) is the most active analogue evaluated in the 7H-benzo[e]-pyrido-[4,3-b]-indole series of antineoplastic compounds. It exerts its activity through inhibition of DNA topoisomerase I and II. This study was planned to determine plasma concentrations of intoplicine necessary for optimal clinical antitumor activity, as well as to pinpoint possible responsive tumor types that can be included in phase II clinical studies. Tumor specimens were collected from patients as part of routine clinical measures. Single-cell suspensions were prepared from freshly obtained solid tumor biopsy specimens and were exposed to intoplicine either for 1 hour or continuously. The sensitivity of these specimens to intoplicine was evaluated in a human tumor soft-agar cloning assay. Response was considered positive when the colony-forming unit count in drug-treated samples was 50% or less than the response of control tumor samples treated with saline. With 1-hour exposure to intoplicine at final concentrations of 2.5 micrograms/mL and 10.0 micrograms/mL, 26% and 54% of the assessable specimens showed positive in vitro responses, respectively. With continuous exposure to intoplicine at concentrations of 0.25 micrograms/mL and 2.5 micrograms/mL, 16% and 71% of the assessable specimens showed positive responses, respectively. Activity was seen against breast (71%), non-small-cell lung (69%), and ovarian (45%) cancer colony-forming units at a intoplicine concentration of 10.0 micrograms/mL after 1-hour exposure. Incomplete cross-resistance with doxorubicin, cisplatin, fluorouracil, 4-hydroperoxycyclophosphamide, vinblastine, and etoposide was also observed. Intoplicine appears to be active in vitro against a variety of human tumors, including a subgroup of tumors insensitive in vitro to standard antineoplastic compounds. If plasma levels of 10.0 micrograms/mL can be achieved in subjects in ongoing clinical trials, intoplicine could have significant clinical activity. These data indicate that further investigation of intoplicine is warranted.