LUNG-CARCINOMA IMAGING USING A SYNTHETIC LAMININ DERIVATIVE RADIOIODINATED PEPTIDE YIGSR

The synthetic laminin pentapeptide tyrosyl-isoleucyl-glycyl-seryl-argi nine (YIGSR) binds to a metastasis associated high-affinity laminin re ceptor. The aim of this study was to investigate if the radiolabeled p eptide can be considered as a basis for a potential tumor-imaging radi opharmaceutical. Methods: iodine-131-labeled YIGSR was injected in mic e inoculated with Lewis Lung carcinoma, as well as in normal controls. The experimental animals were imaged on a gamma camera 10 hr after pe ptide administration. The same peptide was also labeled with I-125 and administered to tumor-bearing and normal mice. At various time-points after peptide administration, the experimental animals were killed, a nd the radioactivity in the tumor, lung, liver and spleen was measured . Microscopic autoradiography was performed in histological sections o f the same tissues. Results: The tumor and the spleen of tumor-bearing animals were imaged on a gamma camera. No significant blood-pool back ground was detected. No other organ except urinary bladder and thyroid was imaged in normal animals. The peptide was retained on tumor and s pleen of tumor-bearing animals. Twenty-four hours after peptide admini stration, the tumor, lung, liver and spleen of animals with tumors con tained significantly more radioactivity than the same tissues of equal ly treated normal controls. The radiolabeled peptide YIGSR was detecte d by microscopic autoradiography on the surface of certain tumor cells , but not on the surface of any normal cell. Conclusion: Although exte nsive research is still required, the peptide YIGSR can be considered as a basis for the development of a receptor specific radiopharmaceuti cal useful for the in vivo estimation of the metastatic potential of t umors. This radiopharmaceutical may be helpful in staging and prognost ic-related decisions on cancer treatment.