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NIH, National Cancer Institute, Biological Research Laboratory [S. A. A., A. J. F.] and Developmental Therapeutics Program [T. G. M.], Bethesda, Maryland 20892; Frederick Cancer Research Facility, Frederick, Maryland 21702 [D. S.]; and The Burnham Institute, La Jolla, California 92037 [S. K., J. C. R.]
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ABSTRACT |
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INTRODUCTION |
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TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Although expression at the protein level (4) may be a more accurate predictor of activity in the cell, mRNA expression can be a very useful end point for comparison between cell lines. When mRNA levels are informative, their measurement would have the practical advantage of requiring a relatively small sample as well as being more quantitative, rapid, and sensitive. It is also possible to use RNA analysis for newly identified target genes in advance of antibody availability. Microarray technologies promise to yield quantitative measurement of thousands of mRNA levels at once (5 , 6) , which paves the way for such applications as molecular tumor profiling and precise tailoring of individual chemotherapy regimens.
Accurate measurements of relative basal mRNA levels in human cancer
cell lines may provide insight into mechanisms of molecular regulation,
interactions, and drug action when this information is considered in
the context of the other data in the NCI-ACDS. For instance, our
laboratory recently identified a subset of the p53 wild-type cell lines
with reduced or absent induction of GADD45 after
-irradiation (7)
. When the NCI-ACDS database was
searched for differential sensitivity of this subset of cell lines to
cytotoxic drugs, topoisomerase II inhibitors were found to be
significantly less toxic in the cell lines with defective
GADD45 induction (P < 0.0001). This difference was confirmed by the demonstration that
etoposide 16 toxicity and DNA-protein cross-links were decreased
when GADD45 expression was blocked with an antisense vector
and led to discovery of a role for Gadd45 in regulating chromatin
accessibility (8)
. This example demonstrates how
mechanistic insight can be gained by exploring hypotheses suggested
from analysis of a large, complex, but well-controlled biological
survey.
We have performed a careful quantitation of the relative basal levels of 10 transcripts chosen for their known roles in cellular damage responses or cancer biology and as potential modifiers of toxicity (O6AT, CIP1/WAF1, GADD34, GADD45, GADD153, cMYC, MDM2, BAX, BCL2, and BCL-XL) in the 60 cell lines of the NCI-ACDS and looked for correlations between levels of these transcripts, p53 status, and cytotoxicity of the tested compounds in the NCI-ACDS database. Many statistically significant and interesting associations with existing molecular target profiles were observed. In this report, we highlight those we found most provocative, but other correlations can be explored.5 One of the most striking findings in the present study was the overall negative correlation between BCL-X levels and sensitivity to the 122 "standard" chemotherapy agents with the exception of one group of antimetabolites. This correlation was stronger than the positive correlation with cytotoxicity previously reported for p53 across diverse mechanisms of drug action (9) and suggests the importance of endogenous BCL-X levels in the cellular response to chemotherapeutic agents, independent of p53 status.
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MATERIALS AND METHODS |
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Quantitative Expression Analysis.
mRNA was isolated by the guanidine thiocyanate method of
Chomczynski and Sacchi (10)
, followed by poly(A)
purification using oligodeoxythymidylate cellulose as previously
described (11)
. cDNA probes for GADD34,
GADD45, and GADD153 were obtained by excising the
insert from pHu34B (12)
, pHul45 (12)
, and
pHul75 (13)
, respectively. Other cDNA plasmids were
obtained from Oncor (c-MYC) or were generously provided by
B. Vogelstein of The Johns Hopkins University, Baltimore, MD
(MDM2), S. Korsmeyer of the Washington University School of
Medicine, St. Louis, MO (BAX and BCL2), W.
El-Deiry of the University of Pennsylvania School of Medicine,
Philadelphia, PA (CIP1/WAF1), and L. Boise of the University
of Miami School of Medicine, Miami, FL (BCL-X). The
cDNA inserts were labeled with 32P using the
PrimeIt RT system (Stratagene) according to the directions of the
supplier. Twofold serial dilutions of the mRNAs were fixed on nylon
membranes, with six copies of each filter being made from the same RNA
dilution at one time. For each transcript, hybridization to the labeled
cDNA probe was carried out on a complete filter set (which included RNA
samples from all of the cell lines in the screen) in the same
hybridization mix. High-stringency hybridization and wash conditions
were as previously described (11)
. Hybridization was
quantitated on a phosphorimager (Molecular Dynamics). Relative signal
levels, normalized to the poly(A) content of each sample, were
determined using the RNA Analysis program as previously described
(14)
. Relative protein levels of
Bcl-XL and Bax were measured using standard
Western blotting techniques as previously described (15)
.
Statistical Methods.
Growth inhibition patterns (IC50 values for 60
human tumor cell lines) were those available from the NCI Developmental
Therapeutics Program.5
Values were reexpressed as potency
values by using the negative log of the molar concentration calculated
in the NCI screen. The dependence of drug potency on gene expression
levels was gauged using either the Spearman correlation coefficient for
continuous value gene expression measurements, such as
GADD45 expression, or the Wilcoxon Rank Sum test for binary
gene expression measurements, such as Mer-/Mer+ or p53
wild-type/mutant. Positive correlations occurred when relatively high
levels of gene expression were found in relatively sensitive cell
lines. Negative correlations occurred when relatively high levels of
gene expression were found in resistant cell lines.
Partial correlations were calculated using SAS Proc Corr (SAS Institute, Cary, NC); e.g., to find the residual correlation between chemosensitivity and BCL-X after "removing" any contributions attributable to a correlation between chemosensitivity and measured doubling time, Proc Corr was executed with drug potency and BCL-X levels listed as the variables to test correlation and with doubling time listed as the partial variable. In this way, the potential role of previously demonstrated sensitivity factors ("molecular targets") as underlying factors responsible for the present observed correlations could be examined statistically.
To visualize a large number of correlation or Wilcoxon test results simultaneously, we first calculated the asymptotic P from the test statistic for each test using normal approximation and then plotted the results for all of the tests in a histogram or color-coded table. The histogram reveals the number of drug sensitivity correlations that would have been considered statistically significant had each drug’s correlation with gene expression been evaluated alone. The same histogram can reveal positive or negative trends that might not have been detected by a simple count of individual results above a particular significance threshold. The colorized matrix (or in some cases a single column) of P also highlights the statistical significance of correlation test results as well as positive or negative trends but allows the display of results according to a logical (drug mechanism of action) or empirical (cluster) order.
The P reported here correspond to the single-tailed test, in
which the alternative hypothesis is that the correlation is negative
and the null hypothesis is that the correlation is zero. As such, a
significant negative correlation (
= 0.05) will be
reported on our one-sided P scale as 0.05, whereas a
significant positive correlation ( = 0.05) will be
reported as 0.95. The latter case can be understood as there being a
95% probability of finding a more negative correlation by chance,
whereas more positive correlations happen because of chance alone only
5% of the time, indicating with reasonable certainty that the
correlation is positive.
Unidrug Pattern Data Set.
To reduce the bias in the drug screen database toward the
overrepresentation of some chemical structure and activity classes, a
k-means, algorithm-based clustering process was
developed.6
A series of iterative clustering optimizations was performed on the
NCI-ACDS IC50 patterns to find 1200 clusters that
were well populated but maximally diverse in pattern. Exemplar
compounds, nonconfidential compounds closest to the center of each
cluster, were taken to represent the entire database. In theory and as
first demonstrated by early applications of the COMPARE
program7
and many examples since, highly correlated groups of compounds will
share the same physicochemical properties and more importantly, often
share mechanism of action properties. This phenomenon was named by the
late Ken Paull the "COMPARE effect." Appropriately, the sets of
compounds represented by the database exemplars are termed compare
effect clusters. When a molecular target pattern comprising some cell
characteristic measured in the NCI-ACDS is used to search for
correlating activity patterns, a search against the redundancy-reduced
set of compare effect cluster exemplars is expected to provide a more
concise and accurate survey of the molecular target’s role in measured
cytotoxicity.
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RESULTS |
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In previous studies with inducible genes (21, 22, 23)
our laboratory has developed an accurate and rapid approach for
comparative measurements of low-abundance transcripts (11)
that is less labor intensive than RNase protection and that avoids the
problems of normalization inherent in Northern blot analysis of weakly
expressed transcripts. Serial dilutions of poly(A) RNA are hybridized
to a radioactive probe and used to generate a standard calibration
curve. This compensates for the nonlinearity (pseudo-first-order
kinetics) of signal to mRNA content, which can be encountered in
hybridizations, such as when the probe is not in excess
(11
, 24)
. Replicate membranes made with the same serially
diluted RNA samples are hybridized to a polyuridylic acid probe to
control for differences in the poly(A) RNA content between different
samples or for any loading differences between lanes. The poly(A)
content of different samples is generally within 
25%, although
greater variations did sometimes occur between different cell lines.
Hybridization to a polyuridylic acid probe effectively corrects for
such variations (14)
. This method is also much more
reliable than normalization to so-called housekeeping genes, such as
GAPDH or ß-actin, which can show considerable variability
between different cell lines. Overall, this technique has been shown to
yield accurate determinations of low-abundance transcripts (on the
order of 1/105
) and to reliably detect
differences of 1.5-fold or greater (11
, 14
, 25)
with
results comparable with those of RNase protection (26)
.
Such sensitivity and accuracy are critical for the meaningful
comparison of uninduced basal levels of transcripts in different cell
lines and exceed the degree of accuracy possible for measurements of
relative protein levels or for many other methods of measuring relative
mRNA levels, including most array applications. Using this approach, we
determined the relative basal levels of the mRNAs for the genes
GADD34, GADD45, GADD153, BAX, BCL2,
BCL-XL, MDM2, CIP1/WAF1, O6AT, and
cMYC in the 60 human cancer cell lines of the NCI-ACDS. RNA
samples from all of the 60 cell lines were hybridized together at high
stringency in the same hybridization mix at the same time to avoid
variations in hybridization conditions. The results of quantitative
hybridization of these 10 transcripts are presented in Table 1
as basal levels relative to the levels in BT549 or in the case of
BCL2, which was not detectable in this cell line, relative
to the levels in MDA-N. Although some transcripts were more
variable than others, in most cases variation was less than 10-fold
across the NCI-ACDS.
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gives an additional indication of the
robust nature of our measurements. As might be expected, there is a
strong positive correlation between these two measurements where
relative protein levels are available for comparison (BAX:
r = 0.41, P = 0.001; BCL-XL: r = 0.55, P = 0.000006). These mRNA and protein
level measurements are in good agreement, but there is also substantial
variation in the protein level that is not explained by the mRNA
measurements. Some of this unexplained variation may be attributable to
posttranslational protein regulation, whereas some may reflect the
different sources of error in the very different quantitation
techniques necessarily used and the inherent difficulties in
normalizing relative protein content. Although mRNA levels may not be a
direct substitute for protein measurements, they can nonetheless be of
predictive value.
Correlations between Basal RNA Levels of Different Genes.
We first looked for correlations between the basal mRNA levels of the
10 genes measured in the cell lines of the NCI-ACDS. The strongest
correlation between these targets is for CIP1/WAF1 and
BAX (Fig. 2
; r = 0.687; P = 0.0001). CIP1/WAF1 basal levels also correlated well with
the basal levels of GADD45 (r = 0.471; P = 0.0001), a gene similarly
regulated during cell growth arrest and stress responses
(27)
. This may suggest that when both of these genes are
expressed in a cell, they tend to maintain a relatively constant ratio
with respect to each other. Previous experiments had suggested a
compensatory mechanism whereby under stress conditions, a cell could
offset a lack of GADD45 induction with an unusually
prolonged and large magnitude CIP1/WAF1 response
(7)
. Because the basal levels of these two genes correlate
positively with each other rather than negatively, such compensation
would appear to be engaged only during stress response, however, not
during normal growth. The basal levels of the three major
GADD genes as measured here also correlate with each other
(GADD45 and GADD153: r = 0.36; P = 0.004; GADD45 and
GADD34: r = 0.42;
P = 0.0007; GADD153 and
GADD34: r = 0.52;
P < 0.00005), suggesting coordinate
regulation of these genes under normal growth conditions and during
stress response (12)
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Relationship of Basal RNA Levels to p53 Status.
The most significant relationship between p53 status and any of the
basal mRNA levels measured here was for CIP1/WAF1
(P = 0.002; Fig. 3A
). Induction of CIP1/WAF1 by ionizing radiation
previously has been shown to be dependent on wild-type p53 function
(30
, 31) . p53 may also play an important role in the basal
regulation of CIP1/WAF1, because among p53 mutant cell
lines, basal expression was extremely low in most cases. Basal levels
of BAX, another gene with p53-regulated stress response
(32
, 33)
, also tended to be higher among p53 wild-type
cell lines (P = 0.003; Fig. 3B
).
Interestingly, no significant correlation was found between p53 status
and basal levels of GADD45, despite the dependence of
ionizing radiation induction of this gene on wild-type p53 function
(34
, 35)
and the positive correlation of basal levels of
GADD45 with those of CIP1/WAF1. Induction of
GADD45 by other DNA-damaging stresses, such as UV radiation
or alkylating agents, is regulated by both p53-dependent and
-independent pathways (34
, 36)
. The present results
perhaps suggest a greater role for p53-independent mechanisms in
maintenance of basal GADD45 levels.
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-rays was measured previously for these three genes in the
60 cell lines of the NCI-ACDS (9)
. Comparing the basal
levels of these genes with their absolute induced levels (the product
of the basal level and the relative fold-induction in each line) there
is a trend of increased absolute induced levels with increasing basal
expression both within the p53 wild-type subset of cell lines (Fig. 4)
and across the entire NCI-ACDS panel (GADD45:
r = 0.71; CIP1/WAF1:
r = 0.63; MDM2:
r = 0.94; all P < 0.00005), despite the relative lack of induction in the p53 mutant cell
lines. This indicates that the stress response of these genes does not
compensate for their variations in basal expression. Rather, the
relative basal expression levels of these genes are an important
determinant of absolute stress-induced expression levels, regardless of
the fold-induction in a particular cell line. The finding that the
relative relationship of gene expression levels among the cell lines is
similar before and after genotoxic stress, irrespective of p53 status,
supports the use of basal expression level data as an informative
marker for predicting genotoxic response.
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. Loss of detectable expression of O6AT at either the mRNA or
protein level is estimated to occur in 15–25% of primary human
tumors (39)
, resulting in the Mer- phenotype. A slightly
higher fraction, 18/60 (30%), of the cell lines in the NCI-ACDS panel
expressed undetectable levels of O6AT in our study (Table 1)
. To test
the ability of our gene expression measurements to identify mechanisms
of drug action, we first examined the correlation of Mer+/Mer-
phenotype with activity of O6
-alkylating agents
(r = -0.44; P < 0.05). This contrasted with the lack of correlation between the Mer
phenotype and toxicity of other alkylators (r = -0.04). This would be expected because the O6AT DNA repair
protein is specific for the reversal of the O6
lesions generated by these agents but is not active against other
lesions or other mechanisms of toxicity (Fig. 5A and B)
. As a specific example, a comparison of
the GI50 values for PCNU, one of the agents in
this mechanistic class, is illustrated in Fig. 5C
for cell
lines expressing (Mer+) or not expressing (Mer-) O6AT.
Expression of O6AT has previously been shown to be a good predictor of
sensitivity of a cell line to nitrosourea compounds such as this
(39)
. These results provide a positive control
illustrating the identification of drugs by mechanism of action through
informatic analysis of RNA expression data and provide a validation of
the methodology used here.
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. This pattern is almost an exact mirror image of the
pattern of drug sensitivities correlated with p53 status (Fig. 6B
; an overall positive correlation of 0.23; Ref.
9
). Bcl-XL is a member of the Bcl2
family of apoptosis-regulating proteins, which has been shown to
protect against p53-mediated apoptosis (40
, 41)
. An
alternately spliced form of the same transcript codes for
Bcl-XS, which antagonizes the activity of the
major Bcl-XL protein to promote apoptosis
(42)
, but this message is expressed at very low levels in
most cell lines examined. Overexpression of BCL-X in murine
lymphoid cells has been reported to have a protective effect against
the toxicity of diverse agents including cyclosporin A, rapamycin,
FK-506 (43)
, bleomycin, cisplatin, etoposide,
vincristine, hygromycin B, mycophenolic acid (44)
,
vinblastine, teniposide, methotrexate, fluorouracil, hydroxyurea, and
-irradiation (45)
. Conversely, suppression of
Bcl-XL levels in a human cancer cell line by use
of either BCL-X antisense or overexpression of its
antagonist Bak was found to sensitize the cells to apoptosis after
treatment with 5-fluorouracil or cisplatin (46)
.
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, possibly
indicating Bcl-XL as a more important regulator
of cell death. In addition, levels of BAX, which codes for
an apoptosis-promoting protein, do not show a comprehensive correlation
with drug toxicity across the NCI-ACDS (Fig. 6D)
as might
have been expected. This may suggest that Bax-independent mechanisms of
Bcl-XL action may play a predominant role in
determining the survival of cancer cells exposed to chemotherapeutic
agents. On the other hand, because only basal expression levels were
measured here, we cannot exclude the possibility that drug-inducible
levels of BAX or BCL-2 may correlate with tumor
cell line responses to anticancer compounds. The pattern of
correlations between BCL-X basal expression and cytotoxicity
does appear to be specific to expression of this gene, however, and not
merely a general hallmark of apoptosis-regulating genes.
Because BCL-X previously had been shown to be induced by
ionizing radiation in a small subset of cancer cell lines
(49)
, we measured -ray induction of this gene in an
additional 31 of the 60 cell lines (data not shown). We found a
relationship between basal and absolute induced levels similar to
(r = 0.79; P < 0.0001) that found for the previously measured genes GADD45,
CIP1/WAF1, and MDM2 discussed above, indicating that
the relative relationship of BCL-X levels are also very
similar before and after treatment. The relative inductions of
BCL-X were furthermore not predictive of cytotoxicity in
either the Standard set of 122 agents or the larger Unidrug
set.8
Previous measurements of doubling time for the cell lines of the
NCI-ACDS (9)
also show a significant negative correlation
across all of the drug classes examined (Fig. 6E)
. This
indicates, as might be expected, general increased chemoresistance the
more slowly a cell divides. This pattern was similar to that found for
BCL-X, so it was possible that BCL-X expression
levels were acting as a marker for cellular growth rate rather than
chemosensitivity. The correlation between doubling time and
BCL-X expression is not significant, however
(P > 0.05). Furthermore, examining the
partial correlation of BCL-X levels and drug sensitivity by
"removing" the statistical effect of doubling time still
demonstrates a highly significant effect for BCL-X (Fig. 6F)
, indicating an effect independent of doubling time.
Similarly, the protective effect of BCL-X also appears to be
independent of p53 status because there was no difference in
distribution of BCL-X levels among the p53 wild-type and p53
mutant cell lines in the NCI-ACDS. The significance of correlations
between drug sensitivities and BCL-X expression was also
unaffected by p53 status of the cell lines, as demonstrated by either
partial correlation (Fig. 6G)
or by the exclusion of the p53
wild-type cell lines in determining the drug sensitivity correlations
(Fig. 6H)
.
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DISCUSSION |
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TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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It is interesting that the protective effect of
Bcl-XL extends across all of the cancer cell
types in the NCI-ACDS panel and is not restricted to lymphoid and
myeloid cell lines, which are especially prone to undergo apoptosis.
BCL-XL induction by ionizing radiation
previously has been shown to occur primarily in cell lines with both
wild-type p53 function and a propensity to undergo rapid
radiation-induced apoptosis (49)
. In contrast to the
specificity of cell type required for BCL-X induction, the
protective effect of high basal levels of BCL-X extends
across the NCI-ACDS, depending neither on wild-type p53 function, nor
on cell type. In a smaller set of cell lines, relatively low basal
levels of BCL-XL have been shown to
correlate with a greater degree of -ray-induced apoptosis
(49)
, suggesting the protective effect of high basal
levels may extend also to ionizing radiation. Although no quantitative
measurement of radiation-induced apoptosis has been made for the 60
cell lines of the NCI-ACDS, a comparison of the basal BCL-X
levels in the lymphoid/myeloid panel (lines very prone to apoptosis;
mean, 0.34 ± 0.10) with levels in all of the other cell
lines (mean, 0.93 ± 0.08) indicates a similar trend.
This implies that basal levels of BCL-X can play a major
role in the determination of cellular response to a wide variety of
chemotherapeutic agents, perhaps through modulation of apoptosis.
Unlike the sensitizing effect on cell killing previously seen for
wild-type p53 (9)
, the protective effect of
BCL-X extends beyond the more classical cancer therapeutics.
This is illustrated with the "Unidrug 1247," a set of 1247 agents
from the NCI-ACDS database having maximally diverse activity patterns,
and in theory, 1247 distinguishable biochemical mechanisms of cell
killing.6
Although the dependence of toxicity on p53
status is no longer evident in this larger survey of agents, the
(inverse) association between toxicity and BCL-X expression
(Fig. 7, A and B)
remains essentially unchanged from that seen across
the smaller set of drug mechanisms. A similar pattern of correlations
is also observed between drug activity and measurements of
Bcl-XL protein expression (Fig. 7, C and D)
. A 
2 comparison of the drug
activity patterns in the Unidrug 1247 for Bcl-XL
measured as mRNA versus protein had a P < 0.0001, again indicating good agreement between the two
measurements. In contrast, comparison between BAX expression
at either the mRNA or protein level and sensitivity to this larger drug
set shows no pattern of overall correlation (data not shown),
consistent with the results in the initial set of 122 agents (Fig. 6C)
. Unlike the case with BCL-X, when the bias
introduced by multiple drugs sharing a small number of cytotoxic
mechanisms is removed by considering the diverse mechanisms included in
the Unidrug set, the strongly significant dependence of drug toxicity
on wild-type p53 status (as seen in Fig. 6B
) is no longer
strikingly apparent (Fig. 7E)
, indicating that the
protective effect of BCL-X expression may be much broader
than the sensitization by wild-type p53.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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1 Supported in part by NIH Grants GM60554 and
CA78040 (to J. C. R. and S. K.). 
2 To whom requests for reprints should be
addressed, at NIH, National Cancer Institute, 37 Convent Drive,
Building 37, Room 5C09, Bethesda, MD 20892.
3 Present address: Large Scale Proteomics Corp.,
Rockville, MD 20850.
4 The abbreviations used are: NCI-ACDS, National
Cancer Institute’s anticancer drug screen; GI50, 50%
growth-inhibitory concentration; GADD, growth arrest and DNA
damage-inducible; poly(A), polyadenylate; PCNU,
1-(2-chloroethyl)3-(2,6-dioxo-3-piperidyl)-1-nitrosourea.
5 Internet address to access the NCI-ACDS database
and the NCI Developmental Therapeutics Program:
http://dtp.nci.nih.gov/.
6 T. G. Myers, unpublished results.
Details are available at http://www.chemodb.org.
7 Written by K. Paull in the DTP of the NCI.
Details are available at
http://dtp.nci.nih.gov/docs/compare/compare.html.
8 Details are available at
http://rex.nci.nih.gov/RESEARCH/basic/lbc/fornace.html and
http://www.chemodb.org.
Received 2/25/00. Accepted 8/24/00.
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-irradiation in many wild-type p53 human melanoma lines. Cancer Res., 56: 840-847, 1996.-ray response of GADD45. Cancer Res., 54: 2755-2760, 1994.-ray response of BCL-XL depends on normal p53 function. Oncogene, 13: 2287-2293, 1996.[Medline]
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 S. Trudel, Z. H. Li, J. Rauw, R. E. Tiedemann, X. Y. Wen, and A. K. Stewart Preclinical studies of the pan-Bcl inhibitor obatoclax (GX015-070) in multiple myeloma Blood, June 15, 2007; 109(12): 5430 - 5438. [Abstract] [Full Text] [PDF]
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G. N.C. Chiu, L. A. Edwards, A. I. Kapanen, M. M. Malinen, W. H. Dragowska, C. Warburton, G. G. Chikh, K. Y.Y. Fang, S. Tan, J. Sy, et al. Modulation of cancer cell survival pathways using multivalent liposomal therapeutic antibody constructs Mol. Cancer Ther., March 1, 2007; 6(3): 844 - 855. [Abstract] [Full Text] [PDF]
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 I. V. Lebedeva, I. Washington, D. Sarkar, J. A. Clark, R. L. Fine, P. Dent, D. T. Curiel, N. J. Turro, and P. B. Fisher Strategy for reversing resistance to a single anticancer agent in human prostate and pancreatic carcinomas PNAS, February 27, 2007; 104(9): 3484 - 3489. [Abstract] [Full Text] [PDF]
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A. R. Jazirehi, M. I. Vega, and B. Bonavida Development of Rituximab-Resistant Lymphoma Clones with Altered Cell Signaling and Cross-Resistance to Chemotherapy Cancer Res., February 1, 2007; 67(3): 1270 - 1281. [Abstract] [Full Text] [PDF]
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A. R. Shoemaker, A. Oleksijew, J. Bauch, B. A. Belli, T. Borre, M. Bruncko, T. Deckwirth, D. J. Frost, K. Jarvis, M. K. Joseph, et al. A Small-Molecule Inhibitor of Bcl-XL Potentiates the Activity of Cytotoxic Drugs In vitro and In vivo. Cancer Res., September 1, 2006; 66(17): 8731 - 8739. [Abstract] [Full Text] [PDF]
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D. Alfano, I. Iaccarino, and M. P. Stoppelli Urokinase Signaling through Its Receptor Protects against Anoikis by Increasing BCL-xL Expression Levels J. Biol. Chem., June 30, 2006; 281(26): 17758 - 17767. [Abstract] [Full Text] [PDF]
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L. Ming, P. Wang, A. Bank, J. Yu, and L. Zhang PUMA Dissociates Bax and Bcl-XL to Induce Apoptosis in Colon Cancer Cells J. Biol. Chem., June 9, 2006; 281(23): 16034 - 16042. [Abstract] [Full Text] [PDF]
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 M. I. Vega, A. R. Jazirehi, S. Huerta-Yepez, and B. Bonavida Rituximab-Induced Inhibition of YY1 and Bcl-xL Expression in Ramos Non-Hodgkin's Lymphoma Cell Line via Inhibition of NF-{kappa}B Activity: Role of YY1 and Bcl-xL in Fas Resistance and Chemoresistance, Respectively J. Immunol., August 15, 2005; 175(4): 2174 - 2183. [Abstract] [Full Text] [PDF]
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 P. S. Adusumilli, B. M. Stiles, M.-K. Chan, T.-C. Chou, R. J. Wong, V. W. Rusch, and Y. Fong Radiation Therapy Potentiates Effective Oncolytic Viral Therapy in the Treatment of Lung Cancer Ann. Thorac. Surg., August 1, 2005; 80(2): 409 - 417. [Abstract] [Full Text] [PDF]
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K. Bagrintseva, S. Geisenhof, R. Kern, S. Eichenlaub, C. Reindl, J. W. Ellwart, W. Hiddemann, and K. Spiekermann FLT3-ITD-TKD dual mutants associated with AML confer resistance to FLT3 PTK inhibitors and cytotoxic agents by overexpression of Bcl-x(L) Blood, May 1, 2005; 105(9): 3679 - 3685. [Abstract] [Full Text] [PDF]
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 R. Pal, A. Datta, A. J. Fornace Jr, M. L. Bittner, and E. R. Dougherty Boolean relationships among genes responsive to ionizing radiation in the NCI 60 ACDS Bioinformatics, April 15, 2005; 21(8): 1542 - 1549. [Abstract] [Full Text] [PDF]
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T. Syrovets, J. E. Gschwend, B. Buchele, Y. Laumonnier, W. Zugmaier, F. Genze, and T. Simmet Inhibition of I{kappa}B Kinase Activity by Acetyl-boswellic Acids Promotes Apoptosis in Androgen-independent PC-3 Prostate Cancer Cells in Vitro and in Vivo J. Biol. Chem., February 18, 2005; 280(7): 6170 - 6180. [Abstract] [Full Text] [PDF]
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A. R. Jazirehi, S. Huerta-Yepez, G. Cheng, and B. Bonavida Rituximab (Chimeric Anti-CD20 Monoclonal Antibody) Inhibits the Constitutive Nuclear Factor-{kappa}B Signaling Pathway in Non-Hodgkin's Lymphoma B-Cell Lines: Role in Sensitization to Chemotherapeutic Drug-induced Apoptosis Cancer Res., January 1, 2005; 65(1): 264 - 276. [Abstract] [Full Text] [PDF]
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 A J M Watson Apoptosis and colorectal cancer Gut, November 1, 2004; 53(11): 1701 - 1709. [Full Text] [PDF]
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P. A. Svingen, D. Loegering, J. Rodriquez, X. W. Meng, P. W. Mesner Jr., S. Holbeck, A. Monks, S. Krajewski, D. A. Scudiero, E. A. Sausville, et al. Components of the Cell Death Machine and Drug Sensitivity of the National Cancer Institute Cell Line Panel Clin. Cancer Res., October 15, 2004; 10(20): 6807 - 6820. [Abstract] [Full Text] [PDF]
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A. R. Jazirehi, M. I. Vega, D. Chatterjee, L. Goodglick, and B. Bonavida Inhibition of the Raf-MEK1/2-ERK1/2 Signaling Pathway, Bcl-xL Down-Regulation, and Chemosensitization of Non-Hodgkin's Lymphoma B Cells by Rituximab Cancer Res., October 1, 2004; 64(19): 7117 - 7126. [Abstract] [Full Text] [PDF]
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 C. L. Galindo, A. A. Fadl, J. Sha, and A. K. Chopra Microarray Analysis of Aeromonas hydrophila Cytotoxic Enterotoxin-Treated Murine Primary Macrophages Infect. Immun., September 1, 2004; 72(9): 5439 - 5445. [Abstract] [Full Text] [PDF]
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P.-F. Cartron, L. Oliver, P. Juin, K. Meflah, and F. M. Vallette The p18 Truncated Form of Bax Behaves Like a Bcl-2 Homology Domain 3-only Protein J. Biol. Chem., March 19, 2004; 279(12): 11503 - 11512. [Abstract] [Full Text] [PDF]
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S. Wu, H. Zhu, J. Gu, L. Zhang, F. Teraishi, J. J. Davis, D. A. Jacob, and B. Fang Induction of Apoptosis and Down-Regulation of Bcl-XL in Cancer Cells by a Novel Small Molecule, 2[ [3-(2,3-Dichlorophenoxy)propyl]amino]ethanol Cancer Res., February 1, 2004; 64(3): 1110 - 1113. [Abstract] [Full Text] [PDF]
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R. L. Hayward, J. S. Macpherson, J. Cummings, B. P. Monia, J. F. Smyth, and D. I. Jodrell Enhanced oxaliplatin-induced apoptosis following antisense Bcl-xl down-regulation is p53 and Bax dependent: Genetic evidence for specificity of the antisense effect Mol. Cancer Ther., February 1, 2004; 3(2): 169 - 178. [Abstract] [Full Text] [PDF]
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G. Stassi, M. Todaro, M. Zerilli, L. Ricci-Vitiani, D. Di Liberto, M. Patti, A. Florena, F. Di Gaudio, G. Di Gesu, and R. De Maria Thyroid Cancer Resistance to Chemotherapeutic Drugs via Autocrine Production of Interleukin-4 and Interleukin-10 Cancer Res., October 15, 2003; 63(20): 6784 - 6790. [Abstract] [Full Text] [PDF]
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D. M. Gascoyne, R. M. Kypta, and M. d. M. Vivanco Glucocorticoids Inhibit Apoptosis during Fibrosarcoma Development by Transcriptionally Activating Bcl-xL J. Biol. Chem., May 9, 2003; 278(20): 18022 - 18029. [Abstract] [Full Text] [PDF]
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 O. S. Frankfurt and A. Krishan Microplate Screening for Apoptosis with Antibody to Single-Stranded DNA Distinguishes Anticancer Drugs from Toxic Chemicals J Biomol Screen, April 1, 2003; 8(2): 185 - 190. [Abstract] [PDF]
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D. R. Mercatante, J. L. Mohler, and R. Kole Cellular Response to an Antisense-mediated Shift of Bcl-x Pre-mRNA Splicing and Antineoplastic Agents J. Biol. Chem., December 13, 2002; 277(51): 49374 - 49382. [Abstract] [Full Text] [PDF]
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J. Hildesheim and A. J. Fornace Jr. Gadd45a: An Elusive Yet Attractive Candidate Gene in Pancreatic Cancer : Commentary re: K. Yamasawa et al., Clinicopathological Significance of Abnormalities in Gadd45 Expression and Its Relationship to p53 in Human Pancreatic Cancer. Clin. Cancer Res., 8: 2563-2569, 2002 Clin. Cancer Res., August 1, 2002; 8(8): 2475 - 2479. [Full Text] [PDF]
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K. Yamasawa, Y. Nio, M. Dong, K. Yamaguchi, and M. Itakura Clinicopathological Significance of Abnormalities in Gadd45 Expression and Its Relationship to p53 in Human Pancreatic Cancer Clin. Cancer Res., August 1, 2002; 8(8): 2563 - 2569. [Abstract] [Full Text] [PDF]
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C. Wiese, A. J. Pierce, S. S. Gauny, M. Jasin, and A. Kronenberg Gene Conversion Is Strongly Induced in Human Cells by Double-strand Breaks and Is Modulated by the Expression of BCL-xL Cancer Res., March 1, 2002; 62(5): 1279 - 1283. [Abstract] [Full Text] [PDF]
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) and mutant (
) p53
function as previously determined 
, cell lines with wild-type p53; 
, cell lines
with mutant p53. B, ranked order of relative expression
levels of BAX mRNA in exponentially growing, untreated
cells. 
