CYTOSKELETON ALTERATIONS INDUCED BY Geodia corticostylifera CYCLIC PEPTIDES IN BREAST CANCER CELLS.

RANGEL M. (1,2) PFISTER S.C. (1) PRADO M.P. (1) FERREIRA R.A.S. (1) FREITAS J.C. (3) KONNO K. (2) SANTELLI G.M.M. (1).

(1) Depto. de Biologia Celular e do Desenvolvimento, Instituto de Ciências Biomédicas da USP, São Paulo, Brazil; (2) Lab. Especial de Toxinologia Aplicada, Instituto Butantan, São Paulo, Brazil; (3) Depto. de Fisiologia, Instituto de Biociências da USP.

The cyclic peptides geodiamolides A, B, H and I (1–4) from the sponge G. corticostylifera have anti-proliferative activity against human breast cancer cell lines (T47D and MCF7). Using fluorescence techniques and confocal microscopy, we found evidence that the geodiamolides A, B, H and I act by disorganizing actin filaments of T47D and MCF7 cancer cells, in a way similar to other depsipeptides (such as jaspamide and dolastatins), keeping the normal microtubule organization. The cytoskeleton proteins of normal cells lines (primary culture human fibroblasts and BRL3A rat liver epithelial cells) were not affected by the treatment as tumor cells were, thus indicating the biomedical potential of these compounds. At the present work we also investigated if the cytoskeleton alterations induced by sponge depsipeptides are associated with changes of connexin 43 (a membrane protein that form gap junction channels) assembly or degradation.

Normal liver (BRL3A) and hepatocarcinoma (HTC) cell lines were submitted to treatment with peptide solutions at different conditions. Immunofluorescence reactions and Lucifer Yellow assays by Scrape Loading and Dye Transfer (SL/DT) of the cells were analyzed under a confocal laser scanning microscope. The geodiamolides showed a probable role in enhancing or preserving GJC both in BRL3A and in HTC-transfected cells, however, the actin filaments disruption was more apparent in tumor cells than in normal ones. The treatment with proteasomal inhibitors enhanced gap junction plaques (GJP). Therefore, the geodiamolides could interfere with the delivery of connexins to the degradation structures, stabilizing connexins assembled and the accumulation of GJP.

KEY WORDS: cancer cell, cytoskeleton, marine sponge, geodiamolide, connexin, gap junction channels.

FINANCIAL SUPPORT: FAPESP and CNPq.

CORRESPONDENCE TO: Marisa Rangel Laboratorio Especial de Toxinologia Aplicada, Instituto Butantan, Av. Vital Brasil, 1500, CEP 05503-900 Sao Paulo,SP, Brazil. Phone: +55 11 37261024; fax: +55 11 37261024. E-mail: mrangel@butantan.gov.br