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Clinical Investigations |
Department of Medicine, Section of Oncology [S. G., P. E. L., D. F. H.], Departments of Surgery [T. A.], and Pathology The Gade Institute [L. A. A.], Haukeland University Hospital, Department of Molecular Biology [Ø. F., D. F. H., J. R. L.], University of Bergen, N-5021, Bergen, and Department of Genetics, The Norwegian Radiumhospital, N-0310 Oslo [H. J., A-L. B-D.], Norway
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ABSTRACT |
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 Top ABSTRACT INTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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INTRODUCTION |
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TopABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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The merging understanding of the key role of apoptosis to the effects of chemotherapy (2) has led to a focus on defects in the apoptotic machinery as a cause of chemoresistance. Thus, in vitro (3) and animal in vivo (4) studies have found defects in the TP53 function to predict for resistance to chemotherapy. Several studies have evaluated alterations in p53 (the protein encoded by the TP53 gene) in relation to chemosensitivity in breast cancer as well as in other malignancies. Studies determining p53 status by immunostaining have, with a few exceptions (5 , 6) , failed to show a predictive value for response to different chemotherapy regimens in breast cancer patients. This is the case both in the adjuvant as well as in the "neoadjuvant" or the metastatic setting (7, 8, 9, 10, 11, 12, 13, 14, 15) . However, not all TP53 mutations cause increased expression of a p53 protein detectable by immunostaining (16 , 17) . In addition, it has been shown that detection of TP53 alterations at the gene level is superior to immunostaining as a prognostic factor when both analyses were performed in parallel on the same group of breast cancer patients (18) .
Studies evaluating the predictive value of p53 immunostaining to chemotherapy sensitivity in different solid tumors have reported conflicting results (19, 20, 21, 22, 23, 24) . In contrast, studies detecting TP53 gene defects by DNA sequencing have reported mutations to predict for chemoresistance in hematological malignancies (25, 26, 27, 28) .
Several other factors, such as expression of P-glycoprotein, alterations in glutathione status, or expression of topoisomerase II (29, 30, 31, 32) , have been proposed to be involved in chemoresistance in breast cancer. However, mutations in the TP53 gene and overexpression of c-erbB-2 (also known as HER-2), the human homologue of the murine neu oncogene (33) , are the only two parameters thus far with substantial evidence of being linked to chemoresistance (15 , 17 , 34) . Although some authors have claimed expression of c-erbB-2 to be correlated to p53 alterations (35 , 36) , a recent large study reported expression of c-erbB-2 to be independent of p53 expression (15) .
We reported in 1996 the preliminary results from a neoadjuvant study revealing mutations in the TP53 gene and, in particular, those affecting or disrupting the L2/L3 loop domains of the protein (codons 163–195 and 236–251, respectively), to predict for resistance to doxorubicin monotherapy in 63 patients treated for locally advanced breast cancer (17) . This protocol is now closed. We here give the mature data reporting the predictive value of TP53 mutations, p53 immunostaining, and TP53 LOH3 together with protein expression data on c-erbB-2, bcl-2, and histological grading to the response to doxorubicin monotherapy in 90 patients. We also evaluated the prognostic impact of each of these parameters with respect to relapse-free and breast cancer-specific survival with a median follow-up time from enrollment in the study of 62.5 months.
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PATIENTS AND METHODS |
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TopABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Tumor Type.
Of the 93 tumor samples, two tumors consisted mainly of ductal carcinoma in situ with minor invasive components. These two tumors were excluded from any further statistical analysis. Of the residual 91 invasive tumor samples, 76 were invasive ductal carcinomas, 8 were lobular carcinomas, and 7 were classified as other histological types (mucinous carcinoma, papillary carcinoma, and poorly differentiated carcinoma). Histological grading was performed using the criteria of Elston and Ellis (37)
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Tissue Sampling.
Prior to therapy, tissue was obtained by an open biopsy for snap-freezing (liquid nitrogen in the theater) in addition to formaldehyde fixation and paraffin embedding. Similarly, a second sample was snap-frozen in nitrogen in patients having surgery after their chemotherapy.
Treatment Protocol.
The study protocol was approved by the local ethical committee, and the patients gave their informed consent. Primary treatment consisted of weekly doxorubicin (14 mg/m2) scheduled for 16 weeks (17)
with 4-weekly assessment of clinical response according to the Union International Contre Cancer criteria (38)
. Thus, responses were classified as a CR (complete disappearance of all tumor lesions), a PR (reduction 
50% in the sum of all lesions, calculated for each as the product of the largest diameter and the one perpendicular to it), PD (increase in the diameter product of any individual tumor lesion by 25%), and StbD (anything between a PR and a PD). The terms StbD and a PR are pragmatic terms that describe a status of tumor "growth arrest" with or without a certain degree of macroscopic reduction in tumor size; the discrimination may often be arbitrary (several patients having a modest reduction in size of their tumors). On the other hand, tumors that are progressing lack sensitivity to treatment. The PD tumors are distinctive, and easily discriminated clinically from the other groups. To analyze for the predictive value of the different parameters, we compared tumors with PD to the combined group of tumors with StbD/PR/CR. Therapy was terminated immediately in case of PD.
The clinical response to doxorubicin treatment could not be classified in one patient harboring an invasive carcinoma for technical reasons (patient 25), leaving 90 patients for response evaluation to doxorubicin and 79 for follow-up analysis (excluding all patients with distant metastases at diagnosis but including patient 25).
Initially, the study protocol involved 12 weeks of postoperative chemotherapy in patients with a PR and no signs of distant metastasis (not any of the other patients). However, several patients refused such treatment because of side effects, and it was subsequently deleted from the protocol.
Median follow-up time was defined from inclusion in the study up to December 31, 1998. Deaths attributable to other causes than breast cancer were treated as censored observations. Patient identity numbers refer to all patients referred for locally advanced breast cancer (whether eligible for study or not).
Genetic Analysis.
Mutations in the TP53 gene were initially analyzed by CDGE as described elsewhere (17
, 39
, 40)
with primers covering the evolutionary conserved regions of the gene covering exons 5–8. In addition, samples from all tumors expressing PD during chemotherapy were sequenced using cDNA. Because of the fact that one sample (tumor 26, Table 1
; see also "Results") had a mutation detected by sequencing that could not be seen on CDGE, all samples were analyzed with an improved method (TTGE) as described elsewhere.4
The method involves use of primers covering the regions (exons and introns) from exons 2 to 11. All samples with aberrantly migrating bands on TTGE were submitted to direct sequencing of PCR products with standard dideoxy sequencing reaction using the Dye Terminator Cycle Sequencing kit with AmpliTag FS on an ABI 373 sequencer (Perkin-Elmer). Samples with known TP53 mutations in each of the exons were included in the analysis as positive controls. To further test the sensitivity of the TTGE method, direct sequencing using cDNA was also performed on tumor samples from 32 of our patients, including all of the 9 with a clinical PD (5 mutated and 4 without mutations) and an additional 23 tumors (5 of which had mutations detected by TTGE). Tumor mRNA was prepared by use of the Quick Prep Micro Purification kit (Pharmacia Biotech), followed by cDNA synthesis, with the use of the Gene Amp RNA-PCR Core kit (Perkin-Elmer) and sequencing.
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Immunohistochemistry.
Immunohistochemical examination of p53 protein expression was performed on formaldehyde-fixed and paraffin-embedded material using the avidin-biotin complex method with the antibody DO-7 (Dako, Copenhagen, Denmark), dilution 1:100, with incubation at room temperature for 1 h after microwave pretreatment of the slides. Antigen localization was achieved by the peroxidase method. Negative controls were incubated as described, omitting the primary antibody, and no positive staining was observed. The examiner was blinded to the treatment outcome. Nuclear staining was recorded using a semiquantitative and subjective grading, considering both the intensity of staining and the proportion of tumor cells showing an unequivocal positive reaction. Intensity was recorded as 0 (no staining) to 3 (strong staining), and the amount of positive cells was recorded as: 0 (no tumor cells positive); 1 (positive staining in <10% of the tumor cells); 2 (positive staining in 10–50% of the tumor cells); or 3 (positive staining in >50% of the tumor cells). A staining index was calculated as the product of staining intensity and staining area.
The c-erbB-2 status was evaluated immunohistochemically on frozen tissue sections using the monoclonal antibody OP15 (Oncogene Science, Manhasset, NY) as described previously (43) . In accordance with previous studies, membrane staining was graded by intensity (0–3), rating a membrane staining of 2 and 3 as positive.
bcl-2 immunohistochemical staining was performed on formaldehyde-fixed, paraffin-embedded tissue according to an indirect avidin-biotin complex procedure using the antibody 124 obtained from Dako in dilution 1:50. After microwave pretreatment, slides were incubated for 3 h at room temperature, followed by incubation overnight at 4°C. The complex was detected with the peroxidase method. Negative controls were incubated as described, omitting the primary antibody, and no staining was recorded. Normal lymphocytes in the peritumoral tissue were present in several cases and presented as a positive internal control for bcl-2 immunostaining. Cytoplasmic staining was recorded as described above for p53 nuclear staining.
Statistical Analysis.
Mutations of the TP53 gene, LOH for the TP53 gene, histological grading, and the different immunohistochemical stainings were correlated to response to chemotherapy and to each other with use of the 
2 method. Comparison between the fractions of patients with TP53 missense and nonsense/splice/deletion mutations that did not show immunoreactivity was performed with the Fisher exact test (because of the small number). Because the L2 and L3 domains of the p53 protein play a critical role in DNA binding (44)
and mutations affecting these domains predict a poor prognosis in breast cancer (39)
, we analyzed separately the predictive value of mutations affecting these domains (total and missense), as well as "non-missense" mutations (deletions/splice and stop codons) in the total material.
Relapse-free and breast cancer-specific survival were analyzed by the log-rank test. Factors found to predict outcome (P < 0.05) in univariate analysis (histological grade, TP53 mutations, and expression of bcl-2) were further analyzed by the Cox multivariate proportional hazards model.
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RESULTS |
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TopABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. The 32 samples sequenced from cDNA gave the same results.
Of the 26 mutations, 16 were missense mutations (4 transversions and 12 transitions), 6 were deletions/splices, and 4 were nonsense mutations. Nineteen of these mutations (9 of the missense and all of the nonsense and deletions/splice mutations) affected or disrupted the L2 and/or L3 domains of the p53 protein. The same TP53 mutation profile was obtained after treatment in all but one patient (no. 75, Table 1
), whose sample taken after treatment did not give any conclusive result for technical reasons.
The clinical response to therapy could not be determined in one patient. Table 2
shows the clinical responses to doxorubicin therapy classified according to the Union International Contre Cancer criteria (38)
and stratified with respect to predictive factors in the remaining 90 patients. Detailed characteristics of patients with primary PD are presented in Table 3
. Although TP53 mutations in total were nonsignificantly associated with PD (P = 0.063), TP53 mutations affecting or disrupting the L2/L3 domains (n = 19) and non-missense mutations (n = 10; including nonsense, splice, deletion, and frame shift mutations) predicted for resistance to doxorubicin (P = 0.008 and P = 0.025, respectively). Although a significant statistical correlation between p53 immunostaining and TP53 mutations was found (Table 4
; P < 0.001), p53 immunostaining did not predict resistance to therapy (Table 2)
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; P = 0.021 and P = 0.031) but did not predict chemoresistance (Table 2)
. Among 14 patients harboring TP53 mutations affecting the L2/L3 domains of the p53 protein for whom allelic imbalance could be determined, only one of five and one of six of the patients who obtained a PR or a StbD, respectively, and zero of three with PD had retained the normal TP53 allele (Table 5)
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) because of technical reasons. Eight tumors expressing LOH in the first biopsy were found to express the normal allele in the second sample. One tumor expressing the normal allele in the first biopsy demonstrated LOH in the second sample. In addition to TP53 mutations, high histological grade (P = 0.023), expression of c-erbB-2 (P = 0.041), and lack of expression of bcl-2 (P = 0.018) all predicted for primary resistance to therapy.
Table 4
summarizes the correlations between the different parameters. As mentioned above, we observed a strong statistical correlation between TP53 mutations and expression of the p53 protein evaluated by immunostaining. However, not all patients with TP53 mutations expressed immunostaining of the p53 protein. Regarding a p53 staining index of 6 or above as positive, 11 of 26 mutated tumors did not stain (Table 1)
; of those, 9 had a staining index of 0 or 1. Lack of staining was preferentially seen in tumors harboring a nonsense mutation or a splice/deletion; thus, 7 of 10 of these tumors did not stain, compared with 4 of 16 tumors harboring a missense mutation (P = 0.032). Thus, three of the five tumors that progressed on therapy and harbored a TP53 mutation were negative for p53 immunostaining (Table 1)
. Although a positive immunostaining for c-erbB-2 was associated with TP53 mutations (P < 0.001), we found no statistical significant association between immunostaining for p53 and c-erbB-2. Interestingly, of the four patients with PD who also showed positive immunostaining for c-erbB-2, three were found to harbor a TP53 mutation affecting the L2/L3 domains (Table 3)
. Expression of c-erbB-2 was also associated with lack of expression of bcl-2 (P = 0.001) but revealed no association to any of the other parameters examined. Lack of expression of bcl-2 was also associated with TP53 mutations (P = 0.003).
Relapse-free and breast cancer-specific survival among patients with no evidence of distant metastasis at diagnosis (n = 79) is depicted in Figs. 1
and 2
. TP53 mutations (total and those affecting or disrupting the L2/L3 domains), a high histological grade, and lack of bcl-2 expression (but not TP53 LOH) all predicted for a poor relapse-free and breast cancer-specific survival by univariate analysis. Among the patients without distant metastasis who obtained a PR on chemotherapy, no difference in relapse-free or overall survival between those receiving 12 weeks of chemotherapy (n = 19) versus fewer than 12 courses (n = 3) versus no chemotherapy (n = 10) after surgery was observed (data not shown). Multivariate analysis was performed including bcl-2 expression, histological grade, and TP53 mutations. This revealed only histological grade to be predictive for relapse-free (P = 0.01) as well as breast cancer-specific (P = 0.0007) survival, independent of whether TP53 status was evaluated as mutated versus wild type or whether mutations affecting or disrupting the L2/L3 domains were handled as a separate group.
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DISCUSSION |
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TopABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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The literature regarding the predictive value of p53 alterations to chemoresistance in breast cancer is conflicting, with a substantial number of papers reporting negative findings (7, 8, 9, 10, 11, 12, 13, 14, 15
, 47
, 48)
. However, all these studies evaluated p53 status by immunohistochemistry. Many antibodies do not discriminate between normal and mutated proteins. In addition, 
30% of the tumors harboring TP53 mutations are recorded as negative by immunostaining (16)
. In contrast, after our report in 1996 (17)
, we are aware of another four studies (49, 50, 51, 52)
reporting a correlation between TP53 mutations and therapy resistance in breast cancer. Although the study of Berns et al. (53)
reported a significant correlation between TP53 mutations and lack of response to tamoxifen in 202 patients, each of these studies contained a smaller number of patients evaluable for resistance to chemotherapy compared with our preliminary report (63 patients). Although the results of these studies in general concurred with our original observations, the results are not directly comparable with ours. With the exception of one treatment arm in the study by Kandioler-Eckerberger et al. (49)
who used paclitaxel monotherapy, these studies all used combined drug regimens, making a direct evaluation of possible mechanisms of resistance to individual drugs difficult. Two of the studies also differed with respect to treatment principles or statistical analysis. Formenti et al. (51)
administered chemotherapy and radiotherapy in concert, thus making it difficult to interpret which treatment modality TP53 status predicted response to. Lizard Nacol et al. (50)
combined TP53 mutation status and LOH in their statistical analysis stating that "alterations in the TP53 gene" predict for chemoresistance. Although the study of Berns et al. (53)
could not observe a statistically significant correlation between TP53 mutation and response to combined chemotherapy, the number of patients evaluated in this subgroup was only 41.
This report extends and strengthens our previous finding regarding the predictive value of TP53 mutations affecting or disrupting the L2 and/or L3 domains of the p53 protein with respect to primary resistance to doxorubicin therapy in breast cancer. To our knowledge, this is the largest study thus far directly relating response to chemotherapy to TP53 alterations in breast cancer patients.
In the present study, we show that p53 immunostaining did not predict for chemoresistance, whereas TP53 mutation status did. A large number of tumors harboring TP53 mutations showed absent or minimal immunoreactivity, despite the fact that we used an antibody directed against epitopes located in the NH2-terminal domain of the protein. Lack of immunostaining was particularly frequent in tumors with nonsense mutations and among those who progressed on therapy. This selectivity may explain the lack of predictive value of p53 evaluated by immunostaining to treatment outcome, despite a strong statistical correlation between p53 staining and TP53 mutation status.
Mutations in the TP53 gene may have different biological effects. Although mutations often are associated with loss of function, some mutated p53 proteins still bind to DNA to a variable degree (52) . Other mutant proteins may exert a dominant-negative effect by driving normal p53 into a mutant conformation (54) , exert a "gain-of-function" by binding to alternative DNA sites (55) , or act by mechanisms possibly independent of DNA binding (56 , 57) . Although these biological effects have been observed for many mutants in vitro, their importance as mechanisms to chemoresistance in vivo is incompletely understood. The L2 and L3 domains together chelate a zinc atom and are critical to DNA binding (44) . Interestingly, another study showed that mutations affecting these domains were associated with a particularly poor prognosis in breast cancer (39 , 58) .
Although our data suggest that mutations in these domains also may be of particular importance predicting resistance to doxorubicin therapy, this hypothesis is based on a limited number of observations and should be confirmed in other studies. The possibility also exists that another grouping of mutants based on functional status may further improve the predictive value of certain TP53 mutations. Thus, in addition to demonstrating the importance of gene sequencing instead of immunostaining to evaluate the biological effects of TP53 alterations, our data underline the importance of reporting individual mutations in detail for comparison between different studies and combined analysis.
Considering definitions of the L2 and L3 domains, there may be some inconsistency as to whether the border codons (L2 nos. 163 and 194; L3 nos. 236 and 251) should be included (44)
. Here, we used a conservative approach including these nucleotides in the domains. To exclude them would mean to change the classification of one tumor (no. 15, Table 1
). This tumor harbored a point mutation at codon 163 and was classified as a mutation affecting or disrupting the L2/L3 domains. It responded to therapy (PR), and the patient is currently relapse free 79.1 months after diagnosis. To classify this tumor as one not affecting or disturbing the L2/L3 domains would strengthen our hypothesis with respect to response as well as survival.
Similar to what we observed here, a correlation between TP53 mutations affecting the DNA-binding domains of the p53 protein and LOH has been reported in head and neck cancers (59)
. Thus, an interesting question is whether concomitant TP53 LOH plays a key role in the mechanism of chemoresistance. Although our data should be interpreted with caution because of the limited number of events and the heterogeneity of the TP53 mutation spectrum, it is tempting to speculate about how these mutations fit in with current hypotheses regarding their biological effects. All our patients harboring TP53 mutations affecting or disrupting the L2/L3 domain with PD and for whom information about allelic imbalance was available also had TP53 LOH (n = 3). However, this was also the case for 9 of 11 patients with L2/L3-affecting mutations who obtained a PR or StbD during doxorubicin therapy (Table 5)
. Although the possibility exists that preservation of a normal TP53 allele could be a rescue mechanism in some patients with TP53 mutations, it does not seem to be a major discriminator for response to therapy in this patient group. On the other hand, our findings are consistent with the hypothesis that redundant mechanisms may exist, because many patients with loss of TP53 function (mutation with LOH) still may respond to initial chemotherapy. Although one patient (no. 11) with PD had a stop codon at 204, another three patients (nos. 100, 101, and 109) with stop codons in the 136–213 area (two with documented LOH) all obtained a PR to doxorubicin therapy, and one of them is still relapse free. Our results do not exclude the possibility that some of the missense mutations may cause a gain-of-function p53 protein, but the results are more consistent with the hypothesis that other gene alterations may operate in concert with TP53 mutations and LOH to cause primary chemoresistance to doxorubicin.
Although the same TP53 mutation profile was revealed in all but one tumor investigated before and after chemotherapy, LOH status changed in nine tumors. Interestingly, the one tumor showing LOH in the second sample but not in the first sample (no. 104, Table 3
) had a particular clinical course. This tumor showed some initial regression but then started to regrow after 12 weeks on chemotherapy, suggesting that there could have been a selection of resistant clones during therapy. Considering the eight tumors that revealed LOH prior to chemotherapy but not afterward, one possible explanation could be a reduced number of tumor cells compared with normal tissue in some of these samples. However, this change occurred in patients with StbD (n = 3) and PD (n = 1) in addition to those having a PR (n = 4).
In addition to TP53 mutations, we also found expression of c-erbB-2 to predict for chemoresistance. However, although we were able to reproduce the data of Thor et al. (15) showing lack of correlation between expression of c-erbB-2 and p53 detected by immunostaining, comparing c-erbB-2 expression with TP53 mutational status revealed a different picture. Thus, our finding of a strong correlation between TP53 mutations and c-erbB-2 expression but not between p53 immunostaining and c-erbB-2 underlines the lack of specificity when using immunostaining as a surrogate marker for TP53 mutations. Notably, among our patients with primary PD, there was only one tumor of four with positive c-erbB-2 immunostaining that did not harbor a TP53 mutation affecting the L2/L3 domains. Although our observations do not allow any conclusive statement regarding the predictive value of TP53 mutations versus c-erbB-2 staining, our data question the hypothesis of an independent role for TP53 and c-erbB-2 with respect to chemoresistance (15) . Thus, it is mandatory for future studies evaluating the predictive value of c-erbB-2 expression to chemoresistance to also include proper sequence analysis of the TP53 gene. Notably, response rates to herceptin (humanized specific antibody to c-erbB-2) in patients with high expression of c-erbB-2 are in the range of 10–25% only (60 , 61) ; one explanation could be that TP53 mutations may predict for resistance to this type of therapy as well.
Our findings that expression of bcl-2 was associated with a better response to chemotherapy may be somewhat surprising, associating this gene with antiapoptotic activity (62) . The finding is consistent with the results of Makris et al. (13) but contrasts those of Bonetti et al. (9) , who found bcl-2 expression to predict for resistance. However, these studies used different treatment regimens than the present. Other studies have shown that the biological effect of bcl-2 depends on its interaction with other proteins of this gene family, such as bax (63 , 64) . bcl-2 has been shown to be down-regulated by wild-type p53 in breast cancer cells (65) and probably had little effect on chemoresistance on its own in our patients.
Although TP53 mutations affecting or disrupting the L2/L3 domains (but not p53 immunostaining), histological grading, and expression of c-erbB-2 all predicted for a poor relapse-free as well as breast cancer-specific survival in patients with no sign of distant metastasis at diagnosis in univariate analysis, histological grade was the only factor predicting relapse-free as well as breast cancer-specific survival in multivariate analysis. Notably, time to relapse and death not only depends on treatment effect but also on tumor growth rate and metastatic potential, which may be controlled by other factors than those regulating apoptosis.
In summary, our data confirm that TP53 mutations affecting certain domains of the p53 protein are associated with primary resistance to doxorubicin therapy in breast cancer patients. They may further explain the conflicting results in the literature with respect to the predictive value of TP53 mutations versus p53 protein expression and confirm a strong association between TP53 mutations and expression of c-erbB-2. The finding that different TP53 mutations concomitant with LOH were present in patients with PD but also in patients responding to drug therapy suggests that redundant mechanisms may compensate for loss of TP53 function. This is consistent with the hypothesis that other gene defects in addition to loss of p53 function may occur in breast cancers resistant to doxorubicin therapy.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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1 Supported by grants from the Norwegian Cancer Society. 
2 To whom requests for reprints should be addressed, at Department of Medicine, Section of Oncology, Haukeland University Hospital, N-5021, Bergen, Norway.
3 The abbreviations used are: LOH, loss of heterozygosity; CR, complete response; PR, partial response; PD, progressive disease; StbD, stable disease; CDGE, constant denaturant gel electrophoresis; TTGE, temporal temperature gel electrophoresis.
4 T. Sørlie, S. Lystad, H. Johnsen, P. Vu, A. L. Borresen-Dale, Protocol for mutation screening of the TP53 gene by Temporal Temperature Gradient Gel Electrophoresis (TTGE), submitted for publication.
Received 1/26/00. Accepted 1/31/01.
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TopABSTRACTINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONREFERENCES |
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 F. Le Calvez, A. Ahman, N. Tonisson, J. Lambert, S. Temam, P. Brennan, D. G. Zaridze, A. Metspalu, and P. Hainaut Arrayed Primer Extension Resequencing of Mutations in the TP53 Tumor Suppressor Gene: Comparison with Denaturing HPLC and Direct Sequencing Clin. Chem., July 1, 2005; 51(7): 1284 - 1287. [Full Text] [PDF]
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V. N. Kristensen, T. Sorlie, J. Geisler, A. Langerod, N. Yoshimura, R. Karesen, N. Harada, P.E. Lonning, and A.-L. Borresen-Dale Gene Expression Profiling of Breast Cancer in Relation to Estrogen Receptor Status and Estrogen-Metabolizing Enzymes: Clinical Implications Clin. Cancer Res., January 15, 2005; 11(2): 878s - 883s. [Abstract] [Full Text] [PDF]
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 M. A. Troester, K. A. Hoadley, T. Sorlie, B.-S. Herbert, A.-L. Borresen-Dale, P. E. Lonning, J. W. Shay, W. K. Kaufmann, and C. M. Perou Cell-Type-Specific Responses to Chemotherapeutics in Breast Cancer Cancer Res., June 15, 2004; 64(12): 4218 - 4226. [Abstract] [Full Text] [PDF]
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V. Staalesen, B. Leirvaag, J. R. Lillehaug, and P. E. Lonning Genetic and Epigenetic Changes in p21 and p21B Do Not Correlate with Resistance to Doxorubicin or Mitomycin and 5-Fluorouracil in Locally Advanced Breast Cancer Clin. Cancer Res., May 15, 2004; 10(10): 3438 - 3443. [Abstract] [Full Text] [PDF]
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 S. H. Giordano Update on Locally Advanced Breast Cancer Oncologist, December 1, 2003; 8(6): 521 - 530. [Abstract] [Full Text] [PDF]
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S. Geisler, A.-L. Borresen-Dale, H. Johnsen, T. Aas, J. Geisler, L. A. Akslen, G. Anker, and P. E. Lonning TP53 Gene Mutations Predict the Response to Neoadjuvant Treatment with 5-Fluorouracil and Mitomycin in Locally Advanced Breast Cancer Clin. Cancer Res., November 15, 2003; 9(15): 5582 - 5588. [Abstract] [Full Text] [PDF]
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T. Sorlie, R. Tibshirani, J. Parker, T. Hastie, J. S. Marron, A. Nobel, S. Deng, H. Johnsen, R. Pesich, S. Geisler, et al. Repeated observation of breast tumor subtypes in independent gene expression data sets PNAS, July 8, 2003; 100(14): 8418 - 8423. [Abstract] [Full Text] [PDF]
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K. Ott, H. Vogelsang, J. Mueller, K. Becker, M. Muller, U. Fink, J. R. Siewert, H. Hofler, and G. Keller Chromosomal Instability Rather Than p53 Mutation Is Associated with Response to Neoadjuvant Cisplatin-based Chemotherapy in Gastric Carcinoma Clin. Cancer Res., June 1, 2003; 9(6): 2307 - 2315. [Abstract] [Full Text] [PDF]
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M. Phelps, M. Darley, J. N. Primrose, and J. P. Blaydes p53-independent Activation of the hdm2-P2 Promoter through Multiple Transcription Factor Response Elements Results in Elevated hdm2 Expression in Estrogen Receptor {alpha}-positive Breast Cancer Cells Cancer Res., May 15, 2003; 63(10): 2616 - 2623. [Abstract] [Full Text] [PDF]
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H. Bonnefoi, S. Diebold-Berger, P. Therasse, A. Hamilton, M. van de Vijver, G. MacGrogan, L. Shepherd, N. Amaral, C. Duval, R. Drijkoningen, et al. Locally advanced/inflammatory breast cancers treated with intensive epirubicin-based neoadjuvant chemotherapy: are there molecular markers in the primary tumour that predict for 5-year clinical outcome? Ann. Onc., March 1, 2003; 14(3): 406 - 413. [Abstract] [Full Text] [PDF]
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A. Moliterni, S. Menard, P. Valagussa, E. Biganzoli, P. Boracchi, A. Balsari, P. Casalini, G. Tomasic, E. Marubini, S. Pilotti, et al. HER2 Overexpression and Doxorubicin in Adjuvant Chemotherapy for Resectable Breast Cancer J. Clin. Oncol., February 1, 2003; 21(3): 458 - 462. [Abstract] [Full Text] [PDF]
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 A. Langerod, I. R. K. Bukholm, A. Bregard, P. E. Lonning, T. I. Andersen, T. O. Rognum, G. I. Meling, R. A. Lothe, and A.-L. Borresen-Dale The TP53 Codon 72 Polymorphism May Affect the Function of TP53 Mutations in Breast Carcinomas but not in Colorectal Carcinomas Cancer Epidemiol. Biomarkers Prev., December 1, 2002; 11(12): 1684 - 1688. [Abstract] [Full Text] [PDF]
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P. S. Bernard and C. T. Wittwer Real-Time PCR Technology for Cancer Diagnostics Clin. Chem., August 1, 2002; 48(8): 1178 - 1185. [Abstract] [Full Text] [PDF]
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H. Millward, W. Samowitz, C. T. Wittwer, and P. S. Bernard Homogeneous Amplification and Mutation Scanning of the p53 Gene Using Fluorescent Melting Curves Clin. Chem., August 1, 2002; 48(8): 1321 - 1328. [Abstract] [Full Text] [PDF]
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T. Sorlie, C. M. Perou, R. Tibshirani, T. Aas, S. Geisler, H. Johnsen, T. Hastie, M. B. Eisen, M. van de Rijn, S. S. Jeffrey, et al. Gene expression patterns of breast carcinomas distinguish tumor subclasses with clinical implications PNAS, September 11, 2001; 98(19): 10869 - 10874. [Abstract] [Full Text] [PDF]
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A. N. Jain, K. Chin, A.-L. Borresen-Dale, B. K. Erikstein, P. E. Lonning, R. Kaaresen, and J. W. Gray Quantitative analysis of chromosomal CGH in human breast tumors associates copy number abnormalities with p53 status and patient survival PNAS, July 3, 2001; 98(14): 7952 - 7957. [Abstract] [Full Text] [PDF]
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