Abstract This study evaluated the potential contribution of the APC gene to malignant transformation in patients with renal cell carcinoma. We tested 36 human renal cell carcinoma samples and 18 adjacent normal kidney tissues for the expression of APC protein, both wild and truncated types, by western blot using antibodies that recognize ei- ther the carboxy or the amino epitope of the APC protein. The same tumor samples together with autologous periph- eral blood were also analyzed at the DNA level. Using specific oligonucleotide primers for exons 11 and 15, gene instability was followed by polymerase chain reaction/loss of heterozygosity (LOH) (on the basis of restriction frag- ment length polymorphism). Molecular data were also compared to pathohistological diagnosis, TNM stage, and patient’s age using multivariate statistical methods. All normal renal tissues revealed expression of the wild-type APC protein. Neither wild nor mutant type proteins were found in 36% (13/36) of tumor samples; the rest of tumor tissues expressed the wild-type protein (312 kDa). Mutat- ed APC protein, with a molecular weight of 117 kDa, was found in only one tumor sample. From 36 tumor samples 16 (44.4%) were informative for RsaI exon 11 polymor- phic site, while only half of these (8/16) demonstrated LOH. From 13 tumor samples that had no detectable pro- tein product by western blot analysis eight were homozy- gous for the exon 11 polymorphism and were tested for another polymorphic site, MspI/exon 15. The overall pro- portion of LOH cases for both polymorphisms tested was 52.9% (9/17). Pathohistological diagnosis and molecular data showed no correlation. However, multivariate analysis determined a stage strong positive correlation of age and TNM with the presence of LOH and the absence of the wild-type APC protein. Out results suggest that the APC tumor suppressor gene plays a role in renal carcinogenesis. Alterations in this gene are responsible for tumor evolu- tion and progression, but cannot be considered as a first event in tumor initiation. Key words APC gene/protein · Loss of heterozygosity · Renal cell carcinomas Abbreviations APC Adenomatous polyposis coli · LOH Loss of heterozygosity · RCC Renal cell carcinoma · RFLP Restriction fragment length polymorphism · TBS Tris-buffered saline Nives Pećina-Šlaus 1 · Krešimir Pavelić · Jasminka Pavelić ( ✉ ) Division of Molecular Medicine, Rud – er Bošković Institute, Bijenička 54, HR-10000 Zagreb, Croatia e-mail: pavelic@rudjer.irb.hr, Tel.: +385-1-4680094/4561114, Fax: +385-1-4680094 1 Present address: Department of Biology, School of Medicine, University of Zagreb, Šalata 3, HR-10 000 Zagreb, Croatia J Mol Med (1999) 77: 446–453 © Springer-Verlag 1999 ORIGINAL ARTICLE Nives Pećina-Šlaus · Krešimir Pavelić Jasminka Pavelić Loss of heterozygosity and protein expression of APC gene in renal cell carcinomas Received: 20 May 1998 / Accepted: 23 November 1998 NIVES PEćINA-ŠLAUS graduated in 1990. Working in the Division of Molecular Med- icine at Ruder Bošković Insti- tute, she received her Masters Degree in 1992. She attended two scholarships in the United States, at Cold Spring Harbor Laboratory and at Georgetown University. In 1998 she re- ceived her Ph.D. in oncogenes and tumor suppressor genes, which are her field of interest. JASMINKA PAVELIć received a Ph.D. in experimen- tal hematology from the Uni- versity of Zagreb. She is pres- ently an Full Professor of Molecular Biology and Chief of the Laboratory for Molecular Oncology at the Division of Molecular Medicine at Rud – er Bošković Institute. Her major research interest include molec- ular biology aspects of genes/oncogenes/oncosuppres- sor genes and human gene ther- apy.