Abstract 2351: Down-regulation of Fibulin-5 in invasive growing primary prostate cancer cells
Authors: Unteregger Gerhard , Jung Volker , Hach Carolin , Kamradt Joern , Saar Matthias , Stoeckle Michael 
Published: June 2012

Introduction: Aside from its normal function in the embryonic development fibulin-5 seems to be involved in tumor formation by controlling proliferation and cell motility. In several malignancies including those from prostate, lung, breast and kidney predominantly down regulation of fibulin-5 was reported. But even enhanced expression in some minor cell populations was published. Since fibulin-5 mediates Epithelial-Mesenchymal Transition (EMT) in mammary epithelial cells its function during invasion seems to be likely. To evaluate the role of this matrix-protein in tumor progression we analyzed fibulin-5 expression in primary prostate cancer samples cultivated in our previously published 3D-invasion model.

Experimental procedures: Fresh biopsies from 11 radical prostatectomies were subjected to our 3D-invasion model which allows for an expansion of the invading growing cell population. Expression of fibulin-5 was assessed by qRT- PCR in non-invading (top) and invasive growing (bottom) tumor cells. To investigate the role of Fibulin-5 on tumor cell migration, Fluoroblock® membranes were coated with 3 different Fibulin-5 peptides: two NH2-terminal peptides harbouring the RGD motif and one C-terminal peptide without this sequence. PC-3, LNCaP, DU-145 and A549 cells were applied onto these inserts and migration was quantified after 24 hrs by fluorescence reading using calcein staining.

Results: No fibulin-5 signals were revealed by qRT-PCR and immunostaining in LNCaP and PC-3 cell lines. In contrast, the expression in DU-145 was comparable to A 549, a lung carcinoma cell line which serves as a positive control. Invasive growing primary prostate tumor cells exhibit in all cases lower fibulin-5 expression as compared to the non-invasive cell population. After coating with fibulin-5 peptides migration of the cell lines was inhibited differentially with the most pronounced effect in LNCaP and Du145; migration of PC-3 and A 549 were not affected. Migration was less inhibited in all cell lines by the C-terminal peptide.

Conclusion: Our results confirmed the down regulation of fibulin-5 in prostate cancer samples in our 3D- invasion model. Interestingly, we observed differences in the expression of this matrix protein between the non-invading cell population and the more aggressive invading tumor cells, both originating from the same biopsy sample. Since all invasive cells exhibit a reduced fibulin-5 expression as compared to the non-invading cells we conclude that down-regulation of fibulin-5 expression favors tumor invasion and metastasis. This assumption is supported by the results of the migration experiments. Thus, the expression profile of fibulin-5 may reflect the invasive potential of individual tumor cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2351. doi:10.1158/1538-7445.AM2011-2351