Abstract: 509

SOMATOSTATIN AFFECTS TOPOISOMERASE II LEVELS IN SYNCHRONIZED LNCaP CELLS.

Laura A. Favetta¹ , Fabiana Cillo¹ , Chiara Agradi¹ , Marcella Motta¹ , Tiziana A.L Brevini-Gandolfi^{1 *}
Department of Endocrinology, University of Milan, via G. Balzaretti 9, 20133 Milan, Italy ¹

We have previously demonstrated the ability of Somatostatin (S) to inhibit the growth of the human prostatic cancer cell line LNCaP. The molecular mechanism, possibly involved in the hormone antiproliferative action needs to be further elucidated. Using RNA differential display (dd)PCR, we recently reported that S affects LNCaP cell gene transcription. In particular, we identified up-regulation of a 170 bp fragment, showing a 91% degree of homology with Topoisomerase II deposited sequence. To investigate the physiological impact of this finding, we evaluated the effect of the hormone on the corresponding protein in synchronized LNCaP cells. To this purpose, cells were synchronized by the double thymidine block in G1, S, G2 and M phase respectively. Each cell group was treated with S used at the antiproliferative concentration. In control groups S was omitted. We then extracted LNCaP cell constitutive proteins and separated them on a 8-15% SDS PAGE. Proteins were blotted onto nitrocellulose filtres and probed for the levels of Topoisomerase II protein, using a specific monoclonal antibody. The results obtained indicate that S interacts with the availability of Topoisomerase II in LNCaP cells. More in details, the hormone appears to alter the correct concentration of the enzyme in G2/M phase, preventing cells to enter M phase and accomplish mitosis. Considering that Topoisomerase II is a key molecule regulating cell cycle and that its levels as well as its timing of expression are crucial for the correct completion of cell division, we may postulate that S might affect LNCaP cell proliferation directly, interferring with the expression of this enzyme and, therefore, with the correct cell cycle dynamic in LNCaP cells. (Supported by AIRC and by MURST).

    This abstract is being presented on Tuesday, August 3 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.