Advertisement
Journal of Clinical Oncology  
Search for:
Limit by:
  Browse by Subject or Issue
Home Search or Browse JCO My JCO Subscriptions Customer Service Site Map

Journal of Clinical Oncology, Vol 25, No 11 (April 10), 2007: pp. 1451-1453
© 2007 American Society of Clinical Oncology.
DOI: 10.1200/JCO.2006.09.2023
This Article
Right arrow Full Text (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a colleague
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Save to my personal folders
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bozzetti, C.
Right arrow Articles by Ardizzoni, A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bozzetti, C.
Right arrow Articles by Ardizzoni, A.

CORRESPONDENCE

p73 and p53 Pathway in Human Breast Cancers

Cecilia Bozzetti, Rita Nizzoli, Antonino Musolino

Medical Oncology Unit, University Hospital, Parma, Italy

Eugenia M. Martella, Pellegrino Crafa, Costanza A. Lagrasta

Pathology Department, University Hospital, Parma, Italy

Roberta Camisa

Medical Oncology Unit, University Hospital, Parma, Italy

Antonio Bonati

Department of Clinical Sciences, University of Parma, Italy; Unit of Hematology, University Hospital, Parma, Italy

Paolo Lunghi

Department of Clinical Sciences, University of Parma, Italy

Andrea Ardizzoni

Medical Oncology Unit, University Hospital, Parma, Italy

To the Editor:

We read with interest the study by Domìnguez et al1 aimed to evaluate the expression of TAp73 and {Delta}TAp73 variants in patients with colon and breast cancer and their possible associations with E2F-1, p53, and K-ras status. The clinical relevance of alterations in these genes was also assessed. In their breast cancer series, TAp73 suppressor and the {Delta}TAp73 oncogenic isoforms {Delta}Ex2p73 and {Delta}Np73 were significantly coupregulated (P = .031 and P = .019, respectively). Statistical associations were also observed between wild-type p53 status and overexpression of the {Delta}Np73 variant (P = .04), overexpression of E2F-1 and some TP73 forms, and upregulation of {Delta}TAp73 variants ({Delta}Ex2p73, {Delta}Ex2/3p73, and {Delta}Np73) and some tumor pathologic markers (vascular invasion and hormone receptor status).

The expression levels of TAp73 and {Delta}TAp73 were determined by quantitative real-time reverse transcriptase polymerase chain reaction. Furthermore, 14 of the 60 breast cancer cases were also analyzed for TAp73 and {Delta}Np73 protein expression by immunohistochemistry. TAp73 and {Delta}Np73 were considered positive in tissue samples exhibiting nuclear staining in more than 10% of the epithelial cells. TAp73 and {Delta}Np73 immunoreactivity was observed in 21% and 30% of the 14 breast cancer cases, respectively. TAp73 and {Delta}Np73 nuclear protein expression correlated with mRNA quantification in 12 (86%) and 11 (79%) of the 14 breast samples, respectively.

The significant association between expression of wild-type p53 and upregulation of {Delta}Np73 observed by Domìnguez et al led the authors to postulate that redundant alterations affecting the same pathway may not confer extra growth advantages on tumor cells during carcinogenesis and thereby alleviate the selective pressure on those cells harboring both alterations.

Our experience refers to the immunocytochemical evaluation of TAp73, {Delta}Np73, p53, and other biologic variables on 73 fine needle aspirates from primary breast cancer patients. Immunocytochemical analyses were performed on cytospin preparations using the same reagent used by Domìnguez et al: a monoclonal TAp73 antibody (clone 5B429; this antibody recognizes the TAp73 isoforms but does not detect the {Delta}Np73 variant or p53), a monoclonal {Delta}Np73 antibody (clone 38C674; this antibody does not cross react with any TAp73 isoform or p53), and a revelation system (LSA; DAKO, Glostrup, Denmark) using diaminobenzidine chromogen as substrate. A monoclonal antibody to p53 (D0-7; Dako Corp, Carpinteria, CA) was used. TAp73 and {Delta}Np73 immunoreactivity was evaluated in a semiquantitative way. Cells were classified as positive for TAp73 and {Delta}Np73 when nuclei or cytoplasm or both were scored as 2+ or 3+ in more than 10% of tumor cells. Cells were classified as p53 positive when 10% of the nuclei showed specific nuclear staining. Immunostaining of TAp73 protein was detected in 25 (47%) of 53 carcinomas examined. Staining was confined to the cell nucleus in 10 (40%) of 25 cases and to the cytoplasm in 14 (56%) of 25 cases. One case (4%) showed both cytoplasmic and nuclear TAp73 localization. {Delta}Np73 immunostaining was detected in 30 (45%) of 67 samples. {Delta}Np73 staining was cytoplasmic in 28 (93%) of 30 cases and nuclear in two cases (Fig 1). NB4 and K562 cell lines were tested by immunocytochemistry as positive controls for TAp73 and {Delta}Np73 expression. TAp73 and {Delta}Np73 expression was confirmed on tumor samples and cell lines by Western blot analysis.


Figure 1
View larger version (92K):
[in this window]
[in a new window]
[PowerPoint Slide for Teaching]
  		Fig 1. {triangleup}Np73 expressing tumor cells show strong (3+) cytoplasmic staining.

 
Our results suggest that TAp73 localization may be confined to the cytoplasm and to the nucleus of tumor cells, while {Delta}Np73 is predominantly cytoplasmic. In this regard, we read with interest the study of Inoue et al2 in which a nuclear localization signal and a nuclear export signal were identified in p73, suggesting that p73 localization is controlled by both nuclear import and export and that the overall distribution of p73 is likely to result from the balance between these two processes. Proper control of nuclear import and export is therefore an important regulatory determinant of p73. In contrast, immunostaining of p73 protein was reported to be confined only to the cell nucleus in 41% and 32% of cholangiocellular and hepatocellular carcinomas of the liver, respectively.3,4 In a more recent report on buccal squamous cell carcinomas, only nuclear p73 expression was considered as positive staining.5 With regard to the cytoplasmic {Delta}Np73 localization observed in our series, the same finding was reported by Uramoto et al6 that found that positive expression of {Delta}Np73 was mainly in the cytoplasm of tumor cells in 77 (58.3%) of 132 patients with lung cancer. In a study on human thyroid cancers,7 TAp73 and {Delta}Np73 expression was predominantly nuclear, although in sporadic cases some cytoplasmic staining was detected. Based on these findings, we suggest that both nuclear and cytoplasmic TAp73 and {Delta}Np73 staining are considered in tissue sample assessment.

In our series, no correlation was found between TP73 isoforms and estrogen and progesterone receptor status, Ki67 growth fraction, and HER-2/neu amplification whereas, like in the series by Domìnguez et al, a significant correlation between TAp73 and {Delta}Np73 (P < .05) was observed (Table 1).


View this table:
[in this window]
[in a new window]

  		Table 1. Associations Between {Delta}Np73 and Biological Characteristics in Breast Cancer Patients

 
Positive p53 immunostaining, suggesting TP53 mutations, was observed in the series by Domìnguez et al1 in 23 (38%) of 60 breast cancer patients and a statistical association was reported between wild-type status and overexpression of the {Delta}Np73 variant (P = .04). The fact that in our series, conversely to that of Domìnguez et al, we found a significant correlation between p53 positivity and {Delta}Np73 expression (P < .05; Table 1) suggests that both alteration, TP53 mutation, and upregulation of the TP73 oncogenic isoform {Delta}Np73, may not be mutually exclusive, and could confer additional growth advantage on cancer cells.

Significantly, {Delta}Np73 overexpression was observed in NB4 and K562 leukemia cell lines carrying an inactive p538 and {Delta}Np73 transcript and protein were detectable in different subtypes of primary acute myelogenous leukemia (AML) blasts.9,10 In AML, TP53 mutations are quite rare (5% to 10%), but murine double minute 2, its principal negative regulator, has been found to be frequently overexpressed in AML and to inactivate p5311-13 suggesting that both alterations, inactivation of wild-type p53 protein and {Delta}Np73 expression, can cooperate in the leukemic process.

In addition, a trend but no significance between overexpression of dominant-negative forms of p73 and concomitant wild-type p53 status on a set of 30 tumors was observed.14

These findings together with our results suggest that more samples in various type of tumors need to be analyzed to fully clarify the relationship between p53 status, p53 activity, and {Delta}Np73 protein levels. Finally, further functional studies are needed to elucidate the mechanisms that differentially control TA and {Delta}Np73 localization, activity, protein stability, and p73-protein interactions, and the role that they play in breast carcinogenesis.

AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST

The authors indicated no potential conflicts of interest.

REFERENCES

1. Dominguez G, Garcia JM, Pena C, et al: DeltaTAp73 upregulation correlates with poor prognosis in human tumors: Putative in vivo network involving p73 isoforms, p53, and E2F-1. J Clin Oncol 24:805-815, 2006[Abstract/Free Full Text]

2. Inoue T, Stuart J, Leno R, et al: Nuclear import and export signals in control of the p53-related protein p73. J Biol Chem 277:15053-15060, 2002[Abstract/Free Full Text]

3. Tannapfel A, Engeland K, Weinans L, et al: Expression of p73, a novel protein related to the p53 tumour suppressor p53, and apoptosis in cholangiocellular carcinoma of the liver. Br J Cancer 80:1069-1074, 1999[CrossRef][Medline]

4. Tannapfel A, Wasner M, Krause K, et al: Expression of p73 and its relation to histopathology and prognosis in hepatocellular carcinoma. J Natl Cancer Inst 91:1154-1158, 1999[Abstract/Free Full Text]

5. Chen YK, Huse SS, Lin LM: Differential expression of p53, p63 and p73 proteins in human buccal squamous-cell carcinomas. Clin Otolaryngol Allied Sci 28:451-455, 2003[CrossRef][Medline]

6. Uramoto H, Sugio K, Oyama T, et al: Expression of deltaNp73 predicts poor prognosis in lung cancer. Clin Cancer Res 10:6905-6911, 2004[Abstract/Free Full Text]

7. Frasca F, Vella V, Aloisi A, et al: P73 tumor-suppressor activity is impaired in human thyroid cancer. Cancer Res 63:5829-5837, 2003[Abstract/Free Full Text]

8. Lunghi P, Costanzo A, Levrero M, et al: Treatment with arsenic trioxide (ATO) and MEK1 inhibitor activates the p73–p53AIP1 apoptotic pathway in leukemia cells. Blood 104:519-525, 2004[Abstract/Free Full Text]

9. Rizzo MG, Giombini E, Diverio D, et al: Analysis of p73 expression pattern in acute myeloid leukemias: Lack of DeltaN-p73 expression is a frequent feature of acute promyelocytic leukemia. Leukemia 18:1804-1809, 2004[CrossRef][Medline]

10. Lunghi P, Costanzo A, Salvatore L, et al: MEK1 inhibition sensitizes primary acute myelogenous leukemia to arsenic trioxide-induced apoptosis. Blood 107:4549-4553, 2006[Abstract/Free Full Text]

11. Hu G, Zhang W, Deisseroth AB: p53 gene mutations in acute myelogenous leukaemia. Br J Haematol 81:489-494, 1992[Medline]

12. Bueso-Ramos CE, Yang Y, deLeon E, et al: The human MDM-2 oncogene is overexpressed in leukemias. Blood 82:2617-2623, 1993[Abstract/Free Full Text]

13. Kojima K, Konopleva M, Samudio IJ, et al: MDM2 antagonists induce p53-dependent apoptosis in AML: Implications for leukemia therapy. Blood 106:3150-3159, 2005[Abstract/Free Full Text]

14. Zaika AI, Slade N, Erster SH, et al: DeltaNp73, a dominant-negative inhibitor of wild-type p53 and TAp73, is up-regulated in human tumors. J Exp Med 196:765-780, 2002[Abstract/Free Full Text]





This Article
Right arrow Full Text (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a colleague
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Save to my personal folders
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bozzetti, C.
Right arrow Articles by Ardizzoni, A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bozzetti, C.
Right arrow Articles by Ardizzoni, A.

About
JCO		 Editorial
Roster		 Advertising
Information		 Librarians &
Institutions		 Rights &
Permissions		 PDA Services

Copyright © 2007 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
Terms and Conditions of Use
  HighWire Press HighWire Press™ assists in the publication of JCO Online