Growth factor involvement in the carcinogenesis cascade is centered on the promotionary events of clonal expansion. These proliferative factors first appear early on in tumor development at sites of premalignant lesions or carcinoma in situ. Thus, a rational approach for defining early markers and target sites of cancer intervention is achieved by identifying the specific growth factors of promotion. We have used this investigative strategy as the primary focus of our experimental studies. Two approaches have been utilized to accomplish our investigative goals which include 1) growth of human tumor cell lines in serum- free/hormone-free medium (RO) and the characterization (molecular/biochemical) of the autocrine growth factors generated under these conditions, and 2) defining biologically relevant peptides with a potential for growth promoting activity based on the presence of alpha- amidated carboxy-terminal amino acids. We have developed a new molecular detection technique, in situ PCR, geared to identifying low frequency message or DNA mutational events in paraffin embedded archival material. With this assay system, we have been successful in demonstration the expression of mRNA from transferrin (Tf), insulin-like growth factor-1 (IGF-1), gastrin-releasing peptide receptor (GRPR) and adrenomedullin (AM) in human lung tumors taken from pathological specimens. Interestingly, by immunohistochemical and in situ PCR analysis, we have found that Tf and Tf receptor (TfR) are co-expressed in pulmonary malignancies but are absent in quiescent normal bronchial epithelium. Additionally, AM has been identified in colon and ovary carcinomas but undetectable in the normal counterpart tissue. From our initial screening data it appears that Tf/TfR and AM may be unique markers of tumor formation in regionally distinct organs. We will extend these initial studies to cover a variety of human tumors supplied by outside collaborators, including lung (University of Pittsburgh), pancreas (Mayo Clinic), breast (University of Texas), and ovary (NNMC). Using these tissues, we will evaluate growth factor expression in normal, premalignant and tumor specimens.
