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Biomedical subjects

T G Myers

Publications and source records attributed to T G Myers.

At least 19 recordsLinked to original sources
PubMed2001

Thymidylate synthase as a molecular target for drug discovery using the National Cancer Institute's Anticancer Drug Screen.

Thymidylate synthase (TS) is a critical cellular target for cancer chemotherapeutics, particularly the fluoropyrimidine and antifolate classes of antineoplastic agents. One of the primary mechanisms of clinical insensitivity to these agents is through the overexpression of the target enzyme, TS. Thus, there is a need for the development of agents which selectively target TS-overexpressing malignant cells. To this end, we conducted a search for agents which potentially selectively target TS-overexpressing cells using two separate algorithms for identifying such compounds in the NCI Drug Repository by comparing cytotoxicity profiles of 30000 compounds with the TS expression levels measured by Western blot analysis in 53 cell lines. Using the traditional COMPARE analysis we were unable to identify compounds which maintain a selective ability to kill high TS-expressing cells in a subsequent four cell line validation assay. A new algorithm, termed COMPARE Effect Clusters analysis, enabled the identification of a particular drug cluster which contained compounds that maintained a selective ability to kill TS-overexpressing cell lines in the validation assay. While the identified compounds were selectively cytotoxic to TS-overexpressing cells, we found that they were not specifically targeting TS as a mechanism of action. Apparently, the overexpression of TS was providing a marker for sensitivity. This identified class of compounds which appears to be selectively cytotoxic against cells which overexpress TS may be useful for the development of therapeutics for those whose cancers overexpress TS de novo.

Antineoplastic Agents↗
PubMed2001

Wild-type p53 marginally induces endogenous MDR-1 mRNA without causing a measurable drug resistance in human cancer cells.

The notion that wt p53 downregulates MDR-1 links p53 mutations to multidrug resistant phenotype. Alternatively, it has been envisioned that wt p53 protects cells against DNA damaging drugs by inducing MDR-1. Opposing conclusions on the relationship between MDR-1 and p53 have been predominantly based on the effects of p53 on MDR-1 promoter-constructs. We found that introduction of wt p53 slightly induced MDR-1 mRNA in three cell lines having endogenous mt p53. Wt p53-mediated induction of endogenous MDR-1 may represent a rudiment of cellular protection against toxic compounds earlier in evolution. Marked induction of p21WAF1/CIP1 (p21) mRNA was observed in all cell lines; and lower levels of wt p53 were required to induce p21 than MDR-1. Pgp was undetectable and wt p53 did not increase resistance to an MDR-1 substrate, suggesting the changes in MDR-1 mRNA may be functionally insignificant. Unlike endogenous MDR-1, the expression of an MDR-1 promoter (-434/+147 fragment) - luciferase construct was unchanged or even inhibited by wt p53 that may be secondary to wt p53-mediated cytotoxicity. Thus, partial promoter constructs may not accurately represent endogenous MDR-1.

Adenoviridae↗
PubMed2001

Screening for and identification of novel agents directed at renal cell carcinoma.

We were interested in identifying novel agents for renal cell carcinoma (RCC) by screening for activities that model renal tumor biology. Searching for relative renal cell sensitivity and leukemia insensitivity among cytotoxicity profiles in the NCI Drug Screen database, we identified 16 potential agents with renal selectivity. We evaluated the agents in 10 RCC cell lines (of primary and metastatic origin) isolated from 5 patients. The 50% inhibitory concentrations (IC50) in these cell lines ranged from 0.019 +/- 0.013 to 11.4 +/- 0.55 microM and were comparable with values obtained with renal cell lines in the NCI Drug Screen panel. Because RCC are slowly growing tumors, we evaluated the compounds on rapidly (27% S phase) or slowly (6% S phase) growing cells. In contrast to doxorubicin, where cytotoxicity was restricted to rapidly proliferating cells, three compounds (NSC 280074, 281613, and 281817) were more cytotoxic in slowly proliferating cells. NSC 72151 and 268965 were equitoxic for both populations. NSC 94889, 638850, and 630938 were more cytotoxic in rapidly growing cells. In in vitro time exposure studies, four compounds, NSC 268965, 280074, 281613, and 281817, were maximally cytotoxic with as little as 3 h exposure time. From an analysis comparing the p53 genotype of the 60 cell lines of the National Cancer Institute (NCI) Drug Screen with the cytotoxicity profiles for the 16 putative renal compounds, 13 compounds were classified as likely to be indifferent to p53 status. We also developed a panel specificity detection method for the NCI Drug Screen database to evaluate the prevalence of renal sensitive compounds. Of the 16 studied compounds, 14 were among those identified as renal sensitive by the statistical analysis. Lastly, we found reduced tumor growth in mice with established renal human tumor xenografts after treatment with two of the renal active compounds. These studies describe compounds with potential renal activity that are candidates for preclinical development for renal cell carcinoma.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

An informatics approach identifying markers of chemosensitivity in human cancer cell lines.

We have used a sensitive and reproducible method of measuring mRNA expression to compare basal levels of 10 transcripts in the 60 cell lines of the National Cancer Institute's in vitro anticancer drug screen (NCI-ACDS) under conditions of exponential growth. The strongest correlation among these target genes was between levels of CIP1/WAF1 and BAX. Levels of the three major growth arrest and DNA damage-inducible gene transcripts, (GADD34, GADD45, and GADD153), which are coordinately regulated in response to many stresses, were also correlated across the 60 cell lines. Although the stress induction of several of the transcripts studied here has been shown to be dependent on wild-type p53 status, basal levels of only CIP1/WAF1 and BAX were found to correlate with p53 status. As expected, basal expression of O6 alkyl guanine alkyl-transferase correlated well with resistance to O6-alkylating agents (r = -0.44) but not with resistance to alkylators with different mechanisms of action (r = -0.04). When basal expression levels of the 10 genes across the NCI-ACDS panel were compared with sensitivities to a panel of 122 standard chemotherapy agents, the most striking relationship was a strong negative correlation (r = -0.3) between basal BCL-X levels and sensitivity to drugs in all of the mechanistic classes except one class of antimetabolites. Sensitivities to a maximally diverse sample of 1200 from 70,000 compounds tested in the NCI-ACDS of agents were also negatively correlated with BCL-X levels. A novel application of factor analysis revealed that the newly discovered associations were independent of previously demonstrated sensitivity factors such as p53 mutation status and native population doubling time. A similar pattern of correlation was seen for Bcl-X(L) protein levels. Conversely, BAX and BCL2, two other genes associated with regulation of apoptosis, showed no overall correlation with drug sensitivities. This suggests that BCL-X may play a unique role in general resistance to cytotoxic agents, with the cell lines demonstrating relative resistance to 70,000 cytotoxic agents in the NCI-ACDS being characterized by high BCL-X expression.

Biomarkers, Tumor↗
PubMed2000

Systematic variation in gene expression patterns in human cancer cell lines.

We used cDNA microarrays to explore the variation in expression of approximately 8,000 unique genes among the 60 cell lines used in the National Cancer Institute's screen for anti-cancer drugs. Classification of the cell lines based solely on the observed patterns of gene expression revealed a correspondence to the ostensible origins of the tumours from which the cell lines were derived. The consistent relationship between the gene expression patterns and the tissue of origin allowed us to recognize outliers whose previous classification appeared incorrect. Specific features of the gene expression patterns appeared to be related to physiological properties of the cell lines, such as their doubling time in culture, drug metabolism or the interferon response. Comparison of gene expression patterns in the cell lines to those observed in normal breast tissue or in breast tumour specimens revealed features of the expression patterns in the tumours that had recognizable counterparts in specific cell lines, reflecting the tumour, stromal and inflammatory components of the tumour tissue. These results provided a novel molecular characterization of this important group of human cell lines and their relationships to tumours in vivo.

Breast↗
PubMed2000

A gene expression database for the molecular pharmacology of cancer.

We used cDNA microarrays to assess gene expression profiles in 60 human cancer cell lines used in a drug discovery screen by the National Cancer Institute. Using these data, we linked bioinformatics and chemoinformatics by correlating gene expression and drug activity patterns in the NCI60 lines. Clustering the cell lines on the basis of gene expression yielded relationships very different from those obtained by clustering the cell lines on the basis of their response to drugs. Gene-drug relationships for the clinical agents 5-fluorouracil and L-asparaginase exemplify how variations in the transcript levels of particular genes relate to mechanisms of drug sensitivity and resistance. This is the first study to integrate large databases on gene expression and molecular pharmacology.

Antineoplastic Agents↗
PubMed1999

DT-Diaphorase expression and tumor cell sensitivity to 17-allylamino, 17-demethoxygeldanamycin, an inhibitor of heat shock protein 90.

BACKGROUND: To our knowledge, 17-allylamino,17-demethoxygeldanamycin (17AAG) is the first inhibitor of heat shock protein 90 (Hsp90) to enter a phase I clinical trial in cancer. Inhibition of Hsp90, a chaperone protein (a protein that helps other proteins avoid misfolding pathways that produce inactive or aggregated states), leads to depletion of important oncogenic proteins, including Raf-1 and mutant p53 (also known as TP53). Given its ansamycin benzoquinone structure, we questioned whether the antitumor activity of 17AAG was affected by expression of the NQO1 gene, which encodes the quinone-metabolizing enzyme DT-diaphorase. METHODS: The antitumor activity of 17AAG and other Hsp90 inhibitors was determined by use of a sulforhodamine B-based cell growth inhibition assay in culture and by the arrest of xenograft tumor growth in nude mice. DT-diaphorase activity was determined by use of a spectrophotometric assay, and protein expression was determined by means of western immunoblotting. RESULTS: In two independent in vitro human tumor cell panels, we observed a positive relationship between DT-diaphorase expression level and growth inhibition by 17AAG. Stable, high-level expression of the active NQO1 gene transfected into the DT-diaphorase-deficient (by NQO1 mutation) BE human colon carcinoma cell line resulted in a 32-fold increase in 17AAG growth-inhibition activity. Increased sensitivity to 17AAG in the transfected cell line was also confirmed in xenografts. The extent of depletion of Raf-1 and mutant p53 protein confirmed that the Hsp90 inhibition mechanism was maintained in cells with high and low levels of DT-diaphorase. 17AAG was shown to be a substrate for purified human DT-diaphorase. CONCLUSION: These results suggest that the antitumor activity and possibly the toxicologic properties of 17AAG in humans may be influenced by the expression of DT-diaphorase. Careful monitoring for NQO1 polymorphism and the level of tumor DT-diaphorase activity is therefore recommended in clinical trials with 17AAG.

Antibiotics, Antineoplastic↗
PubMed1999

Gadd45, a p53-responsive stress protein, modifies DNA accessibility on damaged chromatin.

This report demonstrates that Gadd45, a p53-responsive stress protein, can facilitate topoisomerase relaxing and cleavage activity in the presence of core histones. A correlation between reduced expression of Gadd45 and increased resistance to topoisomerase I and topoisomerase II inhibitors in a variety of human cell lines was also found. Gadd45 could potentially mediate this effect by destabilizing histone-DNA interactions since it was found to interact directly with the four core histones. To evaluate this possibility, we investigated the effect of Gadd45 on preassembled mononucleosomes. Our data indicate that Gadd45 directly associates with mononucleosomes that have been altered by histone acetylation or UV radiation. This interaction resulted in increased DNase I accessibility on hyperacetylated mononucleosomes and substantial reduction of T4 endonuclease V accessibility to cyclobutane pyrimidine dimers on UV-irradiated mononucleosomes but not on naked DNA. Both histone acetylation and UV radiation are thought to destabilize the nucleosomal structure. Hence, these results imply that Gadd45 can recognize an altered chromatin state and modulate DNA accessibility to cellular proteins.

Animals↗
PubMed1999

The complexity of radiation stress responses: analysis by informatics and functional genomics approaches.

Molecular responses to genotoxic stress are complex and are mediated by a variety of regulatory pathways. One key element in cellular response is the stress gene transcription factor p53, which can regulate nearly 100 genes that have already been identified. Although p53 plays a central role in the cellular response to DNA-damaging agents such as ionizing radiation (IR), other pathways can also have important roles. One example is the transcriptional responses associated with IR-induced apoptosis, where induction of some genes is limited to p53 wild-type (wt) cells that also have the ability to undergo rapid apoptosis after irradiation. In contrast, other genes are triggered after IR in lines undergoing rapid apoptosis regardless of p53 status. From this and other examples, it is apparent that the pattern of stress gene expression is cell type specific in both primary and transformed lines. The premise will be developed that such differences in stress gene responsiveness can be employed as molecular markers using a combination of informatics and functional genomics approaches. An example is given using the panel of lines of the NCI anticancer drug screen where both the p53 status and sensitivity to a large collection of cytotoxic agents have been determined. The utility of cDNA microarray hybridization to measure IR-stress gene responses has recently been demonstrated and a large number of additional IR-stress genes have been identified. The responses of some of these genes to IR and other DNA-damaging agents varied widely in cell lines from different tissues of origin and different genetic backgrounds, highlighting the importance of cellular context to genotoxic stress responses; this also highlights the need for informatics approaches to discover and prioritize hypotheses regarding the importance of particular cellular factors. The aim of this review is to demonstrate the utility of combining an informatics approach with functional genomics in the study of stress responses.

Animals↗
PubMed1998

Roles for p53 in growth arrest and apoptosis: putting on the brakes after genotoxic stress.

The tumor suppressor gene p53 plays a major role in regulation of the mammalian cellular stress response, in part through the transcriptional activation of genes involved in cell cycle control, DNA repair, and apoptosis. Many factors contribute to control of the activation of p53, and the downstream response to its activation may also vary depending on the cellular environment or other modifying factors in the cell. The complexity of the p53 response makes this an ideal system for application of newly emerging rapid throughput analysis techniques and informatics analysis.

Animals↗
PubMed1998

Cytotoxic activities of Mannich bases of chalcones and related compounds.

Various Mannich bases of chalcones and related compounds displayed significant cytotoxicity toward murine P388 and L1210 leukemia cells as well as a number of human tumor cell lines. The most promising lead molecule was 21 that had the highest activity toward L1210 and human tumor cells. In addition, 21 exerted preferential toxicity to human tumor lines compared to transformed human T-lymphocytes. Other compounds of interest were 38, with a huge differential in cytotoxicity between P388 and L1210 cells, and 42, with a high therapeutic index when cytotoxicity to P388 cells and Molt 4/C8 T-lymphocytes were compared. In general, the Mannich bases were more cytotoxic than the corresponding chalcones toward L1210 but not P388 cells. A ClusCor analysis of the data obtained from the in vitro human tumor screen revealed that the mode of action of certain groups of compounds was similar. For some groups of compounds, cytotoxicity was correlated with the sigma, pi, or molar refractivity constants in the aryl ring attached to the olefinic group. In addition, the IC50 values in all three screens correlated with the redox potentials of a number of Mannich bases. X-ray crystallography and molecular modeling of representative compounds revealed various structural features which were considered to contribute to cytotoxicity. While a representative compound 15 was stable and unreactive toward glutathione (GSH) in buffer, the Mannich bases 15, 18, and 21 reacted with GSH in the presence of the pi isozyme of glutathione S-transferase, suggesting that thiol alkylation may be one mechanism by which cytotoxicity was exerted in vitro. Representative compounds were shown to be nonmutagenic in an intrachromosomal recombination assay in yeast, devoid of antimicrobial properties and possessing anticonvulsant and neurotoxic properties. Thus Mannich bases of chalcones represent a new group of cytotoxic agents of which 21 in particular serves as an useful prototypic molecule.

Animals↗
PubMed1998

Mining the National Cancer Institute Anticancer Drug Discovery Database: cluster analysis of ellipticine analogs with p53-inverse and central nervous system-selective patterns of activity.

The United States National Cancer Institute conducts an anticancer drug discovery program in which approximately 10,000 compounds are screened every year in vitro against a panel of 60 human cancer cell lines from different organs. To date, approximately 62,000 compounds have been tested in the program, and a large amount of information on their activity patterns has been accumulated. For the current study, anticancer activity patterns of 112 ellipticine analogs were analyzed with the use of a hierarchical clustering algorithm. A dramatic coherence between molecular structures and their activity patterns could be seen from the cluster tree: the first subgroup (compounds 1-66) consisted principally of normal ellipticines, whereas the second subgroup (compounds 67-112) consisted principally of N2-alkyl-substituted ellipticiniums. Almost all apparent discrepancies in this clustering were explainable on the basis of chemical transformation to active forms under cell culture conditions. Correlations of activity with p53 status and selective activity against cells of central nervous system origin made this data set of special interest to us. The ellipticiniums, but not the ellipticines, were more potent on average against p53 mutant cells than against p53 wild-type ones (i.e., they seemed to be "p53-inverse") in this short term assay. This study strongly supports the hypothesis that "fingerprint" patterns of activity in the National Cancer Institute in vitro cell screening program encode incisive information on the mechanisms of action and other biological behaviors of tested compounds. Insights gained by mining the activity patterns could contribute to our understanding of anticancer drugs and the molecular pharmacology of cancer.

Antineoplastic Agents↗
PubMed1998

Expression and location of pro-apoptotic Bcl-2 family protein BAD in normal human tissues and tumor cell lines.

The BAD protein is a pro-apoptotic member of the Bcl-2 family whose ability to heterodimerize with survival proteins such as Bcl-X(L) and to promote cell death is inhibited by phosphorylation. Monoclonal antibodies were generated against the human BAD protein and used to evaluate its expression by immunoblotting and immunohistochemistry in normal human tissues and by immunoblot analysis of the National Cancer Institute anti-cancer drug screening panel of 60 human tumor cell lines. BAD protein was detectable by immunoblotting in many normal tissues, with testis, breast, colon, and spleen being among those with the highest steady-state levels. Immunostaining of tissues revealed many examples of cell-type-specific expression of BAD, suggesting dynamic regulation of BAD protein levels in vivo. In many types of normal cells, BAD immunoreactivity was associated with cytosolic organelles resembling mitochondria, suggesting that BAD is often heterodimerized with other Bcl-2 family proteins in vivo. The relative levels of BAD protein varied widely among established human tumor cell lines, with colon, lung, and melanomas generally having the highest expression. As a group, hematopoietic and lymphoid lines contained the least BAD protein. The BAD protein derived from 11 of 41 tumor lines that expressed this pro-apoptotic protein migrated in gels as a clear doublet, consistent with the presence of hyperphosphorylated BAD protein. Taken together, these findings define for the first time the normal cell-type-specific patterns of expression and intracellular locations of the BAD protein in vivo and provide insights into the regulation of this pro-apoptotic Bcl-2 family protein in human tumors.

Antibodies, Monoclonal↗
PubMed1997

Identification of epidermal growth factor receptor and c-erbB2 pathway inhibitors by correlation with gene expression patterns.

BACKGROUND: Growth factor receptor-signaling pathways are potentially important targets for anticancer therapy. The interaction of anticancer agents with specific molecular targets can be identified by correlating target expression patterns with cytotoxicity patterns. We sought to identify new agents that target and inhibit the activity of the epidermal growth factor (EGF) receptor and of c-erbB2 (also called HER2 or neu), by correlating EGF receptor, transforming growth factor (TGF)-alpha (a ligand for EGF receptor), and c-erbB2 messenger RNA (mRNA) expression levels with the results of cytotoxicity assays of the 49000 compounds in the National Cancer Institute (NCI) drug screen database. METHODS: The levels of mRNAs were measured and used to generate a molecular target database for the 60 cell lines of the NCI anticancer drug screen. The computer analysis program, COMPARE, was used to search for cytotoxicity patterns in the NCI drug screen database that were highly correlated with EGF receptor, TGF-alpha, or c-erbB2 mRNA expression patterns. The putative EGF receptor-inhibiting compounds were tested for effects on basal tyrosine phosphorylation, in vitro EGF receptor tyrosine kinase activity, and EGF-dependent growth. Putative ErbB2-inhibiting compounds were tested for effects on antibody-induced ErbB2 tyrosine kinase activity. RESULTS: EGF receptor mRNA and TGF-alpha mRNA levels were highest in cell lines derived from renal cancers, and c-erbB2 mRNA levels were highest in cells derived from breast, ovarian, and colon cancers. Twenty-five compounds with high correlation coefficients (for cytotoxicity and levels of the measured mRNAs) were tested as inhibitors of the EGF receptor or c-erbB2 signaling pathways; 14 compounds were identified as inhibitors of these pathways. The most potent compound, B4, inhibited autophosphorylation (which occurs following activation) of ErbB2 by 50% in whole cells at 7.7 microM. CONCLUSIONS: Novel EGF receptor or c-erbB2 pathway inhibitors can be identified in the NCI drug screen by correlation of cytotoxicity patterns with EGF receptor or c-erbB2 mRNA expression levels.

Antineoplastic Agents↗
PubMed1997

Characterization of the p53 tumor suppressor pathway in cell lines of the National Cancer Institute anticancer drug screen and correlations with the growth-inhibitory potency of 123 anticancer agents.

In the present study, we report the characterization of the p53 tumor suppressor pathway in the 60 cell lines of the National Cancer Institute (NCI) anticancer drug screen, as well as correlations between the integrity of this pathway and the growth-inhibitory potency of 123 anticancer agents in this screen. Assessment of p53 status in these lines was achieved through complete p53 cDNA sequencing, measurement of basal p53 protein levels and functional assessment of (a) transcriptional activity of p53 cDNA from each line in a yeast assay, (b) gamma-ray-induced G1 phase cell cycle arrest, and (c) gamma-ray-induced expression of CIP1/WAF1, GADD45, and MDM2 mRNA. Our investigations revealed that p53 gene mutations were common in the NCI cell screen lines: 39 of 58 cell lines analyzed contained a mutant p53 sequence. cDNA derived from almost all of the mutant p53 cell lines failed to transcriptionally activate a reporter gene in yeast, and the majority of mutant p53 lines studied expressed elevated basal levels of the mutant p53 protein. In contrast to most of the wild-type p53-containing lines, cells containing mutant p53 sequence were also deficient in gamma-ray induction of CIP1/WAF1, GADD45, and MDM2 mRNA and the ability to arrest in G1 following gamma-irradiation. Taken together, these assessments provided indications of the integrity of the p53 pathway in the 60 cell lines of the NCI cell screen. These individual p53 assessments were subsequently used to probe a database of growth-inhibitory potency for 123 "standard agents," which included the majority of clinically approved anticancer drugs. These 123 agents have been tested against these lines on multiple occasions, and a proposed mechanism of drug action had previously been assigned to each agent. Our analysis revealed that cells with mutant p53 sequence tended to exhibit less growth inhibition in this screen than the wild-type p53 cell lines when treated with the majority of clinically used anticancer agents: including DNA cross-linking agents, antimetabolites, and topoisomerase I and II inhibitors. Similar correlations were uncovered when we probed this database using most of the other indices of p53 status we assessed in the lines. Interestingly, a class of agents that differed in this respect was the antimitotic agents. Growth-inhibitory activity of these agents tended, in this assay, to be independent of p53 status. Our characterization of the p53 pathway in the NCI cell screen lines should prove useful to researchers investigating fundamental aspects of p53 biology and pharmacology. This information also allows for the large-scale analysis of the more than 60,000 compounds tested against these lines for novel agents that might exploit defective p53 function as a means of preferential toxicity.

Antineoplastic Agents↗
PubMed1997

Reduced folate carrier gene (RFC1) expression and anti-folate resistance in transfected and non-selected cell lines.

Methotrexate transport deficiency due to decreased reduced folate carrier (RFC) activity has been observed in several cell lines selected for resistance to methotrexate (MTX). Since MTX resistance is multifactorial, however, it is difficult to quantify the relative importance of changes in RFC activity in selected cell lines and even more so to determine the relative contribution of naturally occurring RFC activity in the MTX sensitivity of non-selected cell lines. We examined the role of RFC in MTX resistance by studying a transport-deficient cell line transfected with the gene for human RFC, RFC1, and by correlating relative RFC1 expression with MTX and trimetrexate (TMTX) growth inhibition (GI50) in a panel of cell lines used in the NCI Anticancer Drug Screen. Clones of transport-deficient, MTX-resistant ZR-75-1 human breast cancer cells (MTX(R) ZR-75-1) transfected with RFC1 were 250-fold more sensitive to MTX and 300-fold more resistant to TMTX than control cell clones, showing that restoration of RFC activity has a significant impact on MTX and TMTX cytotoxicity. We also surveyed 40 of the 60 cell lines in the NCI drug screen panel for RFCI RNA levels by a quantitative RT-PCR assay. RFCI RNA levels varied over a range of 15-fold, with only 1 cell line found to be null in expression. Using data from the 6-day drug exposure assay, RFC1 correlated positively with MTX and negatively with TMTX cytotoxicity. As predicted by transfection studies, the calculated difference between MTX and TMTX potency was even more strongly correlated with RFC1 RNA levels of the cell lines. In addition, compounds in the NCI Anticancer Drug Screen database with cytotoxicity profiles which correlated with RFC1 RNA levels or with the calculated difference in MTX-TMTX potency were examined for MTX uptake inhibition and cytotoxicity in the RFC1-transfected MTX(R) ZR-75-1 cell line. Overall, our data demonstrate the importance of RFC1 in MTX resistance both as a transgene and as a constitutively expressed gene in non-selected cell lines.

Antineoplastic Agents↗
PubMed1997

An information-intensive approach to the molecular pharmacology of cancer.

Since 1990, the National Cancer Institute (NCI) has screened more than 60,000 compounds against a panel of 60 human cancer cell lines. The 50-percent growth-inhibitory concentration (GI50) for any single cell line is simply an index of cytotoxicity or cytostasis, but the patterns of 60 such GI50 values encode unexpectedly rich, detailed information on mechanisms of drug action and drug resistance. Each compound's pattern is like a fingerprint, essentially unique among the many billions of distinguishable possibilities. These activity patterns are being used in conjunction with molecular structural features of the tested agents to explore the NCI's database of more than 460,000 compounds, and they are providing insight into potential target molecules and modulators of activity in the 60 cell lines. For example, the information is being used to search for candidate anticancer drugs that are not dependent on intact p53 suppressor gene function for their activity. It remains to be seen how effective this information-intensive strategy will be at generating new clinically active agents.

Algorithms↗