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Originally published as Ann Surg Oncol Early Release 10.1245/ASO.2003.02.004 on September 8, 2003

Annals of Surgical Oncology 10:876-881 (2003)
© 2003 Society of Surgical Oncology
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ORIGINAL ARTICLES

Intratumoral Heterogeneity in Microsatellite Alterations in BRCA1 and PTEN Regions in Sporadic Colorectal Cancer

Jose M. Garcia, MD, Rufo Rodriguez, MD, Javier Silva, PhD, Concepción Muñoz, MD, Gemma Dominguez, PhD, Jose M. Silva, PhD, Enric Carcereny, MD, Mariano Provencio, MD, Pilar España, MD and Félix Bonilla, MD

From the Department of Medical Oncology (JMG, JS, GD, JMS, EC, MP, PE, FB), Hospital Universitario Puerta de Hierro, Madrid, Spain; and Departments of Pathology (RR) and Gastroenterology (CM), Hospital Virgen de la Salud, Toledo, Spain.

Correspondence: Address correspondence and reprint requests to: Felix Bonilla, MD, Department of Medical Oncology, Hospital Universitario Puerta de Hierro, C/San Martin de Porres 4, E-28035 Madrid, Spain; Fax: 34-91-373-7667; E-mail: felixbv{at}stnet.es


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Background: Chromosome regions 17q21 (BRCA1) and 10q23 (PTEN) have been found deleted in colorectal cancer.

Methods: We studied the frequency of loss of heterozygosity (LOH) in these 2 regions in 214 patients with only 1 sample per tumor and in 100 patients with several samples per tumor. Three microsatellite markers of each region were used for the LOH test. The polymerase chain reaction product was electrophoresed in 8% polyacrylamide gels, and band intensity was shown by silver staining.

Results: The proportions of LOH in the two regions were 38.4% for 17q21 and 30.8% for 10q23 in the group of 214 and were 47.7% for 17q21 and 34.7% for 10q23 in the group of 100. We found a high correlation between the LOH in both regions (P < .001), where 81% of LOH in 10q23 region was matched by concomitant LOH in 17q21. In the group of tumors with several samples (group of 100), 39% and 68% did not present LOH in the 17q21 and 10q23 regions, respectively, in all of their tumor samples. However, in the 20 patients with LOH in both regions in the group of 100 (several samples per tumor), all samples with LOH in 10q23 also had LOH in 17q21, whereas not all samples with LOH in 17q21 had LOH in 10q23.

Conclusions: These results show that colorectal cancer is highly heterogeneous, at least for these tumors markers, and suggest a sequential acquisition pattern of these anomalies during tumor growth, in which changes in 17q21 could occur before those in 10q23.

Key Words: Colorectal cancer • LOH • BRCA1 • PTEN • Tumor heterogeneity


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Studies of the pathogenesis of colorectal cancer (CRC) have reported loss of heterozygosity (LOH) in numerous chromosomal regions. The regions most commonly deleted in CRC are located at 17p, which is affected in >75% of these carcinomas1,2; 18q, which shows allelic losses in >70%1,3; and, occasionally, 5q.4,5 Additionally, other allelic losses are involved in the pathogenesis of various carcinomas, such as region 17q21, which harbors the BRCA1 gene,6–9 and region 10q23, which contains the tumor-suppressor gene PTEN.10 Both genes have also been related sporadically to CRC.11–15

The product encoded by the PTEN gene has sequence homology with dual-specificity phosphatases, which can dephosphorylate serine/threonine and tyrosine residues. It also has extensive homology with auxilin and tensin, cytoskeletal proteins that interact with actin filaments.16–18

Mutations in the PTEN gene have been found in three related human autosomal dominant disorders: Cowden disease, Lhermitte-Duclos disease, and Bannayan-Zonana syndrome.19 These are characterized by developmental defects and tumor susceptibility, as well as gastric hamartomas, juvenile polyposis, and colonic adenoma, at least in Cowden disease.20

PTEN is also mutated in sporadic tumors, such as those in brain, breast, endometrium, kidney, and prostate.16–18 Although only 1.4% of unselected sporadic colon cancers have been associated with mutations in the PTEN gene,14 allelic losses occur in CRC close to the PTEN locus at a frequency of approximately 30%.15 Further, 19% of mutations in the PTEN gene are associated with microsatellite instability,21 and up to 60% are linked with transforming growth factor-ß receptor II mutations and microsatellite instability.22

BRCA1 is a large gene with many functional domains, each with different biological features. The C-terminal region is associated with the transactivation region of the protein,23 and residues 758 to 1064 are associated with binding to Rad51,24 thus acting as a repair complex of the doubled-stranded DNA breaks and in recombination-linked repair. BRCA1 has also been related to the coactivation of p53.25 Moreover, the presence of truncating mutations in the first two thirds of the BRCA1 gene may significantly increase the risk of ovarian cancer (more than that of breast cancer).26 This may indicate that the inactivation mechanism of the gene depends on the tissue type.

Higher rates of CRC have been found in families linked to the BRCA1 gene than in other families.11–13 Mutations on this gene in stomach and colon cancers are associated with the microsatellite mutator phenotype.27 Additionally, we found a high percentage (49%) of LOH in region 17q21 in sporadic CRC.9

Defects in BRCA1 repair mechanisms may thus be involved in tumorigenic processes other than breast carcinomas. Similarly, alterations to normal PTEN functions secondary to mutations or changes in expression levels may be associated with a broad spectrum of human cancers, including CRC. Here we examine allelic losses in regions 17q21 and 10q23 in two series of CRC patients, and on the basis of the results, we suggest an acquisition pattern of these alterations.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Tumor Samples and DNA Extraction
Samples from two separate groups of patients were examined. In the first group, 1 tumor sample and 1 healthy tissue sample were taken from 214 patients: 63 samples were formalin-fixed and paraffin-embedded, and the other 151 were snap-frozen. In the other group of 100 patients, an average of three noncontiguous samples were taken from each tumor and snap-frozen along with the matching healthy tissue. All specimens underwent histological examination to confirm the diagnosis of adenocarcinoma and the presence of at least 75% tumor cells. We did not have microdissection techniques at our disposal, and the LOH rate may be slightly underestimated as a result. Patients belonging to families with familial adenomatosis coli or those that fit the standard criteria for hereditary nonpolyposis CRC28 were excluded. DNA was extracted from formalin-fixed, paraffin-embedded tissues by using chelatin resin or from snap-frozen tissues by using a nonorganic method (S-4520 kit; Oncor Inc., Gaithersburg, MD).

Polymerase Chain Reaction Conditions, Primers, and LOH Assay
Allelic deletions were detected with LOH analysis by using the microsatellite markers D17S1323, D17S1322, and D17S855, which localize to introns 12, 19, and 20, respectively, of the BRCA1 gene for region 17q2129; D10S541 and D10S583, which flank the PTEN gene; and D10S2491, which is intragenic to PTEN, for region 10q23.30 Polymerase chain reaction (PCR) was performed in 25-µL volumes with .2 U of Taq Gold DNA polymerase and 1x PCR buffer (Promega, Madison WI), 200 µM of dNTP, 30 pmol of each primer, and a range of concentrations of KCl and MgCl2, depending on the polymorphic markers used. PCR was performed in a thermocycler (PerkinElmer Cetus, Foster City, CA). Each sample was denatured at 94°C for 11 minutes and subjected to 30 cycles (denaturation at 94°C for 30 seconds, annealing at 56°C for 40 seconds, and elongation at 72°C for 30 seconds) followed by a final 12-minute extension at 72°C. The amplified products were mixed with 6 µL of loading buffer (.02% xylene cyanol and .02% bromophenol blue) and run on nondenaturing 8% polyacrylamide gels for 4 hours at 500 V. Allelic band intensity was then revealed by silver staining. We analyzed the allele intensities by densitometry. The gel image was captured with a GS-690 Imaging Densitometer (Bio-Rad Laboratories, Hercules, CA), digitized at 400 dpi, and analyzed with Multianalyst/PC (Bio-Rad). An allele was considered to be lost when its signal was reduced by >50% with respect to that observed on the normal counterpart DNA. In the cases with more than one sample per tumor, LOH was assigned if at least one of the samples had lost the allele (Fig. 1).



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  		FIG. 1. Photographs of gels taken under normal light after staining with the (NO3)Ag method. (A) Examples of loss of heterozygosity (LOH) at different loci studied in regions 17q21 and 10q23; (B) patient 89, showing LOH in two of three tumor samples studied for region 17q21 (microsatellite marker D17S855) but in only one of them in the 10q23 region (microsatellite marker D10S2491). The almost complete loss of one allele in 17q21 in sample Tb demonstrates the practically complete absence of normal cell contamination in that sample, suggesting that retention of heterozygosity in 10q23 is not due to normal cell contamination.

 
Statistical Analysis
The variables analyzed were contrasted by means of the {chi}2 test with the Yates correction. Statistical analysis was performed with SPSS version 10.0 (SPSS Inc., Chicago, IL).


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
LOH Analysis
In the series of 214 patients with CRC, 164 (76.6%) were informative for at least 1 marker of region 17q21, and 162 (75.7%) were informative for the 10q23 region. The LOH frequency was 38.4% (63 of 164) for 17q21 and 30.8% (50 of 162) for 10q23 (Table 1). A total of 39 (61.9%) of the 63 tumors with LOH in 17q21 were informative for at least 2 of the 3 markers used, and 29 of these (74.3%) showed LOH in all of them. Similarly, we found 27 (54%) of 50 tumors with 2 or 3 informative markers and LOH in region 10q23, and 19 of these (70.3%) showed all markers lost.


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  		TABLE 1. Informative (INF) patients and loss of heterozygosity (LOH) for each of the studied regions
 
To examine the relation between LOH in the 2 regions, we selected 129 (60.3%) patients who were informative for these 2 regions simultaneously. In this case, we found 49 (38%) patients with LOH in 17q21 and 36 (27.9%) with LOH in 10q23. The distribution was as follows: 27 (20.9%) patients with concomitant LOH, 22 (17.1%) with LOH in 17q21 alone, 9 (7%) with LOH in 10q23 alone, and 71 (55%) without LOH in either region (Table 2). These results are highly significant (P < .001): 75% (27 of 36) of cases with LOH in 10q23 appeared among those with LOH in 17q21, whereas 25% (9 of 36) appeared in cases without LOH in 17q21.


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  		TABLE 2. Distribution of patients regarding the regions of losses and the statistical results in 129 patients informative for the 2 regions studied at same time and only 1 sample per tumor, and in 66 informative patients for both regions and multiple samples per tumor
 
In these 129 patients, we explored the possible relation between allelic losses and clinicopathologic data (Table 3). The parameters age, sex, tumor side, stage, and recurrence rate were obtained from medical records. The distribution of LOH in the two regions did not show significant differences regarding age, sex, tumor side, or stage. However, the recurrence rate was significantly higher in patients with double LOH than in those without LOH.


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  		TABLE 3. Relationship between allelic losses concomitantly at the 17q21 and 10q23 regions and clinicopathologic data in 129 informative cases for both regions
 
Intratumoral Heterogeneity Analysis
In the second group (100 patients, who provided an average of 3 samples per tumor), 86 were informative for region 17q21, of which 41 (47.7%) showed LOH in some marker of this region in at least 1 sample. For 10q23, we found 72 informative patients, 25 of whom (34.7%) showed LOH in some marker of this region in at least 1 of their tumor samples.

Sixty-six of these 100 patients were informative for the 2 regions simultaneously and were selected for the correlation study. We considered that there was LOH when at least one of the samples of each tumor presented it. We found 33 tumors (50%) with LOH in region 17q21 and 22 tumors (33.3%) with LOH in region 10q23. When we compared the presence or absence of LOH in 17q21 with the presence or absence of LOH in 10q23, we found a highly significant difference (P < .001). The distribution was as follows: 20 (30.3%) of 66 tumors showed concomitant LOH in both regions, 13 (19.7%) showed LOH only in 17q21, 2 (3%) showed LOH only in 10q23, and, finally, 31 (47%) did not show LOH in either region (Table 2). Whereas 91% (20 of 22) of tumors with LOH in 10q23 also showed LOH in 17q21, only 9% (2 of 22) had LOH in 10q23 but not in 17q21 in any of their samples.

In the group of 20 patients with concomitant LOH, there were 5 with losses in both regions in all their tumor samples. Among the other 15, there were samples without LOH in either region, patients with LOH in both regions but in only some of the samples, and samples with LOH only in 17q21. The other possible combination, LOH in 10q23 but not in 17q21, was not found in any of the 15 cases (Table 4). Among the 66 patients informative for the 2 regions, the tumor stages of the 20 patients with concomitant LOH did not display any significant difference compared with the other 46 patients.


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  		TABLE 4. Representative outline of losses in the 17q21 and 10q23 regions in the 20 patients with multiple tumoral samples and concomitant LOH in both regions
 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
We found a highly significant correlation (P < .001) in the pattern of LOH in the two regions. The losses in the 10q23 region were significantly higher among patients with LOH in the 17q21 region. These results show that the LOHs in 10q23 are not random and may be linked to the losses in 17q21. Moreover, it may be assumed that if BRCA1, located in 17q21, acts as a caretaker gene controlling the integrity of the genome,31 cells that harbor alterations in it could present alterations in other genes more frequently than cells with intact caretaker genes. This may explain the high frequency of LOH in the PTEN gene region found among the tumors with LOH in the BRCA1 gene region.

We recently reported clonal heterogeneity in these markers in colon tumors, which could explain some findings in extracellular tumor DNA in plasma.32 In this study, we examined whether the correlation found among the LOH of the two regions persisted among the different samples of the same tumor. We gathered an average of 3 samples of the surgical tumor specimens from 100 new patients. We found tumors with LOH in some of the regions studied, but not in all their fragments.

A monoclonal origin for sporadic colon cancer has been reported.33 Therefore, the observed intratumoral heterogeneity could be due to anomalies acquired during tumor growth rather than primary genetic alterations, because tumor cells are unlikely to lose chromosome fragments and recover them later. Indeed, one cell could repair the deletion and recover the allele, for example, by homologous recombination.34 However, the existing allele and its corresponding microsatellite polymorphic markers would be duplicated, but the lost allele and its corresponding polymorphic microsatellite marker would not be found.

Similarly, in the group of 100 patients, LOH in 10q23 was preferentially distributed in the tumors that presented LOH in 17q21 (P < .001). Here we also found that in the group with concomitant LOH in both regions, there were fragments with LOH in 17q21 but not in 10q23, although the opposite pattern was never found. If we assume a polyclonal origin for these tumors or assume that they were the product of fusion of several adjacent synchronous tumors, we should have found fragments with LOH only in 10q23. The fact that we did not, together with the highly significant correlation between the losses in the two regions, led us to propose a sequential pattern for the acquisition of these molecular anomalies. LOH in region 17q21 may confer an evolutionary advantage to the cell, because it is frequent in this type of tumor. Offspring of such a cell may then have an additional loss in region 10q23. This could explain the distribution of LOH in the two regions.

The frequency of LOH in each region was higher in the second part of the study than in the first: 47.7% vs. 38.4% for 17q21 and 34.7% vs. 30.8% for 10q23. This difference could be attributed to the fact that only a small fraction of the tumor was analyzed, so possible losses in other parts of the tumor would not have been detected. Undetected losses could explain the disagreement in the results obtained by different groups in studies of allelic losses in this type of tumor.

The timing of the appearance of molecular anomalies during tumorigenesis is difficult to establish, because it is impossible to ascertain the evolutionary state of the tumor at the moment of extirpation, at least for sporadic CRC. Our knowledge of the chronology of molecular anomalies is deduced from statistical data from different tumoral series, in which a range of molecular changes are detected. For example, it is inferred that the losses in 17p are acquired in the step from adenoma to carcinoma, because of their low frequency in the former versus 75% in the latter.33 The differential detection of the anomalies in the two regions studied suggests three stages in the incorporation of the alterations. It may also increase the precision with which we time the appearance of other anomalies, such as point mutations in tumor-suppressor genes or oncogenes.


   ACKNOWLEDGMENTS
 
The acknowledgments are available online at www.annalssurgicaloncology.org.

The authors thank the patients who participated in this study and Robin Rycroft for his assistance with English. Supported by grants from the Fundacion Banco Santander Central Hispano, Sociedad Española de Oncología Médica, and Aventis Pharma, S.A.


   FOOTNOTES
 
Colorectal tumors showed a high correlation between loss of heterozygosity (LOH) in the 17q21 region (BRCA1) and LOH in the 10q23 region (PTEN; P < .001), and 81% of the LOH in the 10q23 region was matched by concomitant LOH in 17q21.

Received for publication February 5, 2003. Accepted for publication June 23, 2003.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Watanabe T, Wu T-T, Catalano PJ, et al. Molecular predictors of survival after adjuvant chemotherapy for colon cancer. N Engl J Med 2001; 344: 1196–206.[Abstract/Free Full Text]
  2. Diep CB, Thorstensen L, Meling GI, Skovlund E, Rognum TO, Lothe RA. Genetic tumor markers with prognostic impact in Dukes’ stages B and C colorectal cancer patients. J Clin Oncol 2003; 21: 820–9.[Abstract/Free Full Text]
  3. Martinez-Lopez E, Abad A, Font A, et al. Allelic loss on chromosome 18q as a prognostic marker in stage II colorectal cancer. Gastroenterology 1998; 114: 1180–7.[CrossRef][Medline]
  4. Solomon E, Voss R, Hall V, et al. Chromosome 5 allele loss in human colorectal carcinomas. Nature 1987; 328: 616–9.[CrossRef][Medline]
  5. Ashton-Rickardt PG, Dunlop MG, Nakamura Y, et al. High frequency of APC loss in sporadic colorectal carcinoma due to breaks clustered in 5q21–22. Oncogene 1989; 4: 1169–74.[Medline]
  6. Silva JM, Gonzalez R, Provencio M, et al. Loss of heterozygosity in BRCA1 and BRCA2 markers and high-grade malignancy in breast cancer. Breast Cancer Res Treat 1999; 53: 9–17.[CrossRef][Medline]
  7. Gao X, Zacharek A, Grignon DJ, Sakr W, Porter AT, Honn KV. Loss of heterozygosity of the BRCA1 and other loci on chromosome 17q in human prostate cancer. Cancer Res 1995; 55: 1002–5.[Abstract/Free Full Text]
  8. Mori T, Aoki T, Matsubara T, et al. Frequent loss of heterozygosity in the region including BRCA1 on chromosome 17q in squamous cell carcinomas of the esophagus. Cancer Res 1994; 54: 1638–40.[Abstract/Free Full Text]
  9. García-Patiño E, Gomendio B, Lleonart M, et al. Loss of heterozygosity in the region including the BRCA1 gene on 17q in colon cancer. Cancer Genet Cytogenet 1998; 104: 119–23.[CrossRef][Medline]
  10. Ali IU, Schriml LM, Dean M. Mutational spectra of PTEN/MMAC1 gene: a tumor suppressor with lipid phosphatase activity. J Natl Cancer Inst 1999; 91: 1922–32.[Abstract/Free Full Text]
  11. Porter DE, Cohen BB, Wallace MR, et al. Breast cancer incidence, penetrance and survival in probable carriers of BRCA1 gene mutations in families linked to BRCA1 on chromosome 17q12–21. Br J Surg 1994; 81: 1512–5.[Medline]
  12. Ford D, Easton D, Bishop D, Narod S, Goldgard D, and the Breast Cancer Research Linkage Consortium. Risk of cancer in BRCA1-mutation carriers. Lancet 1994; 343: 692–5.[CrossRef][Medline]
  13. Cropp CS, Nevanlinna HA, Pyrhonen S, et al. Evidence for involvement of BRCA1 in sporadic breast carcinoma. Cancer Res 1994; 54: 2548–51.[Abstract/Free Full Text]
  14. Wang ZJ, Taylor F, Churchman M, Norbury G, Tomlinson I. Genetic pathways of colorectal carcinogenesis rarely involve the PTEN and LKB1 genes outside the inherited hamartoma syndromes. Am J Pathol 1998; 153: 363–6.[Abstract/Free Full Text]
  15. Frayling IM, Bodmer WF, Tomlinson IP. Allele loss in colorectal cancer at the Cowden disease/juvenile polyposis locus on 10q. Cancer Genet Cytogenet 1997; 97: 64–9.[CrossRef][Medline]
  16. Li DM, Sun HI. TEP1, encoded by a candidate tumor suppressor locus, is a novel protein tyrosine phosphatase regulated by transforming growth factor beta. Cancer Res 1997; 57: 2130–6.[Abstract/Free Full Text]
  17. Steck PA, Pershouse MA, Jasser SA, et al. Identification of a candidate tumor suppressor gene, MMAC1, at chromosome 10q23.3 that is mutated in multiple advanced cancers. Nat Genet 1997; 15: 356–62.[CrossRef][Medline]
  18. Li J, Yen C, Liaw D, et al. PTEN, a putative protein tyrosine phosphatase gene mutated in human brain, breast, and prostate cancer. Science 1997; 275: 1943–7.[Abstract/Free Full Text]
  19. Liaw D, Mash DJ, Li J, et al. Germline mutations of the PTEN gene in Cowden’s disease, an inherited breast and thyroid cancer syndrome. Nat Genet 1997; 16: 64–7.[CrossRef][Medline]
  20. Chi SG, Kim HJ, Park BJ, et al. Mutational abrogation of the PTEN/MMAC1 gene in gastrointestinal polyps in patients with Cowden disease. Gastroenterology 1998; 115: 1084–9.[CrossRef][Medline]
  21. Guanti G, Resta N, Simone C, et al. Involvement of PTEN mutations in the genetic pathways of colorectal cancerogenesis. Hum Mol Genet 2000; 9: 283–7.[Abstract/Free Full Text]
  22. Dicuonzo G, Angeletti S, Garcia-Foncillas J, et al. Colorectal carcinomas and PTEN/MMAC1 gene mutations. Clin Cancer Res 2001; 12: 4049–53.
  23. Chapman MS, Verma IM. Transcriptional activation by BRCA1. Nature 1996; 382: 678–9.[CrossRef][Medline]
  24. Scully R, Chen J, Plug A, et al. Association of BRCA1 with Rad51 in mitotic and meiotic cells. Cell 1997; 88: 265–75.[CrossRef][Medline]
  25. Ouchi T, Monteiro ANA, August A, Aaronson SA, Hanafusa H. BRCA1 regulates p53-dependent gene expression. Proc Natl Acad Sci U S A 1998; 95: 2302–6.[Abstract/Free Full Text]
  26. Gayther SA, Warren W, Mazoyer S, et al. Germline mutations of the BRCA1 gene in breast cancer families provide evidence for a genotype-phenotype correlation. Nat Genet 1995; 11: 428–33.[CrossRef][Medline]
  27. Yamamoto H, Sawai H, Perucho M. Frameshift somatic mutations in gastrointestinal cancer of the microsatellite mutator phenotype. Cancer Res 1997; 57: 4420–6.[Abstract/Free Full Text]
  28. Vasen HF, Macklin JP, Meera-Khan P, Lynch HT. The International Collaborative Group on Hereditary Non-Polyposis Colorectal Cancer (ICG-HNPCC). Dis Colon Rectum 1991; 34: 424–5.[CrossRef][Medline]
  29. Smith TM, Lee MK, Szabo CI, et al. Complete genomic sequence and analysis of 117 kb of human DNA containing the gene BRCA1. Genome Res 1996; 6: 1029–49.[Abstract/Free Full Text]
  30. García JM, Silva JM, Dominguez G, et al. Allelic loss of the PTEN region (10q23) in breast carcinomas of poor pathophenotype. Breast Cancer Res Treat 1999; 57: 237–43.[CrossRef][Medline]
  31. Kinzler KW, Vogelstein B. Gatekeepers and caretakers. Nature 1997; 386: 761–3.[CrossRef][Medline]
  32. García JM, Silva JM, Dominguez G, Silva J, Bonilla F. Heterogeneous tumor clones as an explanation of discordance between plasma DNA and tumor DNA alterations. Genes Chromosomes Cancer 2001; 31: 300–301.[CrossRef][Medline]
  33. Fearon ER, Hamilton SR, Vogelstein B. Clonal analysis of human colorectal tumors. Science 1987; 238: 193–6.[Abstract/Free Full Text]
  34. Khanna KK, Jackson SP. DNA double-strand breaks: signaling, repair and the cancer connection. Nat Genet 2001; 27: 247–54.[CrossRef][Medline]



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