Short Communication Genetic and Immunohistochemical Analyses of p53 Independently Predict Regional Metastasis of Gastric Cancers 1 Yih-Horng Shiao, 2 Domenico Palli, Neil E. Caporaso, W. Gregory Alvord, Andrea Amorosi, Gabriella Nesi, Calogero Saieva, Giovanna Masala, Joseph F. Fraumeni, Jr., and Jerry M. Rice Laboratory of Comparative Carcinogenesis [Y-H. S.] and Data Management Services, Inc. [W. G. A.], National Cancer Institute, Frederick Cancer Research and Development Center, NIH, Frederick, Maryland 21702; Epidemiology Unit, Centro per lo Studio e la Prevenzione Oncologica, A.O. Careggi, 50131 Florence, Italy [D. P., C. S., G. M.]; Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland 20892 [N. E. C., J. F. F.]; Department of Pathology, University of Florence, 50134 Florence, Italy [A. A., G. N.]; and International Agency for Research on Cancer, 69372 Lyon Cedex 08, France [J. M. R.] Abstract Either p53 gene mutation or immunohistochemical detection of p53 protein has not been consistently shown to have prognostic significance in human cancers, including gastric carcinomas. One hypothesis to explain this inconsistency is that some p53 mutations and p53 protein accumulation are not indicative of tumor progression. To test this hypothesis, we categorized p53 status in 105 gastric carcinomas according to types of mutations, numerical scores of immunohistochemical staining (IHC), or combinations thereof. The p53 status was then correlated with metastasis to liver or peritoneum. Gastric cancers with no p53 mutations were significantly less likely to metastasize than tumors with mutations. Intermediate IHC scores were inversely associated with metastasis. A substantial number of gastric cancers (31 of 105) showed positive p53 immunostaining without detectable mutations (p53/IHC), which suggested an accumulation of wild- type p53 protein, and also a significantly lower risk for metastasis. After adjusting for depth of invasion and lymph node involvement, the p53/IHC combination predicted low metastatic risk better than either p53 or IHC with intermediate scores. These findings suggest that an accumulation of wild-type p53 protein occurs in gastric cancer cells and represents a stress-response mechanism that lowers metastatic potential. Introduction Mutations of the p53 tumor suppressor gene can result in a loss of function of the wild-type gene product to regulate cell cycle progression and apoptosis (programmed cell death; Refs. 1, 2). p53-knockout mice that lack functional p53 are prone to certain tumors and are less responsive to chemo- or radiotherapy (1, 2), which suggests that p53 mutation is an indicator of poor cancer prognosis. Most but not all mutant p53 proteins have a prolonged half-life and accumulate in tissues and can be directly detected by IHC 3 (3). Therefore, p53 protein accumulation is commonly in- terpreted as indicative of the presence of p53 mutations. The prognostic value of p53 mutations or p53 protein accumulation has not been consistently demonstrated in many human neoplasms, including gastric cancer (4, 5). Both positive and negative findings have been reported in studies with vari- ous sample sizes, which indicates that inadequate statistical power alone, as suggested by an early observation (6), cannot entirely explain the discrepancy. It has been shown that p53 mutations vary in their biological effects (7). Some mutated p53 proteins behave like the wild-type counterpart, whereas others are correlated with tumor aggressiveness. In addition, an accu- mulation of p53 protein may not necessarily indicate the pres- ence of a p53 mutation, because not all mutated p53 proteins yield positive immunohistochemical staining, and wild-type protein can also accumulate in response to stress stimulants, such as DNA damage (1, 4). Because of the biological varia- bility of p53 mutations and the diverse causes of p53 protein accumulation, either parameter alone may fail to predict prog- nosis consistently. In this study, we categorized p53 changes into various groups according to types of mutations, scores of immunohis- tochemical staining, or combinations thereof, and then corre- lated these changes with the presence of regional metastases of gastric cancers. The possible biological functions and implica- tions for regional metastasis are discussed. Materials and Methods Subjects. One hundred and five gastric carcinoma patients (41 females, 64 males; mean age, 62 years; range, 34 –76 years) were selected from a population-based case-control study con- ducted in central Italy, as described previously (8). Formalin- fixed paraffin-embedded tissues were retrieved from archives at the Department of Pathology, University of Florence, Italy. Demographic and clinicopathological information was ab- stracted from our population-based database, and staging was carried out for each case by the TNM classification at the time of surgery. For this study, “metastasis” refers to hepatic and/or peritoneal spread from the primary site. No systematic docu- mentation of metastasis to other sites was available. Data on p53 gene mutations were obtained from a previous study (8). p53 IHC. Dewaxed 5-m formalin-fixed paraffin-embedded sections were subjected to an antigen retrieval method by Received 9/8/99; revised 3/22/00; accepted 3/28/00. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 Supported in part by Regione Toscana, Florence, Italy. 2 To whom requests for reprints should be addressed, at Building 538, Room 205, National Cancer Institute, Frederick Cancer Research and Development Center, National Institutes of Health, Frederick, MD 21702. Phone: (301) 846-1246; Fax: (301) 846-5946; E-mail: Shiao@mail.ncifcrf.gov. 3 The abbreviations used are: IHC, immunohistochemistry/immunohistochemical staining; p53+, p53 (gene) mutation; p53-, without detectable p53 mutations; p53-/IHC+, positive p53 immunostaining without detectable mutations. 631 Vol. 9, 631– 633, June 2000 Cancer Epidemiology, Biomarkers & Prevention on July 12, 2021. © 2000 American Association for Cancer Research. cebp.aacrjournals.org Downloaded from