Asporin modulates tissue microenvironment, invasive growth and bone metastasis of breast cancer

Konference: 2011 7. Sympozium a workshop molekulární patologie a histo-cyto-chemie

Kategorie: Nádorová biologie/imunologie/genetika a buněčná terapie

Téma: Postery

Číslo abstraktu: 005p

Autoři: MUDr. Gvantsa Kharaishvili; MUDr. Magdalena Čížková; MUDr. Kateřina Bouchalová (Špačková), Ph.D.; Mgr. Eva Sedláková; prof. MUDr. Zdeněk Kolář, CSc.; Mgr. Jan Bouchal

Introduction: In an earlier publication we identified asporin as a novel cancer related protein (BMC Cancer 2007, 7:55), also reported among bone metastasis specific genes (Cancer Letters 2009, 276:212–220). Asporin is a member of the class I small leucine-rich repeat proteoglycan family and besides affinity to collagen, it binds calcium and initiates collagen mineralization. Asporin is abundantly expressed in tissues with high remodeling rate (e.g. periodontal ligament) whereas extremely high turnover of matrix proteins is also associated with invasive cancer.

Material and methods: Formalin-fixed paraffin-embedded tissues [invasive ductal (101) and lobular (39) carcinomas classified according to hormone receptors and Her2; 5 bone metastases from autopsies] were immunohistochemically stained with in-house polyclonal peptide antibody against asporin. The antibody was validated on uterus tissue as a positive control together with a commercial antibody (Abcam). Data were evaluated by non-parametric Mann-Whitney U test and Spearman correlation coefficient. Expression of asporin in both tissues and cell lines was also queried in databases Gene Expression Omnibus, ArrayExpress and Oncomine. Expression of asporin was further tested by RT-PCR in selected breast cancer cell lines. Migration and invasion of MDA-MB-231 cells were tested using real-time cell analysis Xcelligence system (Roche). Transwells were coated by solidifying collagen for 6 hours (with or without recombinant asporin). Starved cells were seeded on the collagen in transwells while FBS was used as a chemoattractant in bottom wells.

Results: Levels of asporin were significantly higher in invasive lobular carcinomas than ductal ones (p<0.001). Asporin was also highly expressed in all bone metastases. Asporin expression positively correlated with tumor grade within the triple negative subgroup (Rs 0.4, p<0.05) but not in luminal and Her2 subtypes. Expression of asporin in invasive breast carcinomas was also confirmed in other public datasets (e.g. Karnoub breast and Hess breast in Oncomine database). Surprisingly, we found no breast cancer cell line overexpressing asporin, which underlines the importance of the tumor microenvironment in vivo. MDA-MB-231 cells migrated faster through collagen I with recombinant asporin.

Conclusion: Asporin is expressed by both invasive breast carcinomas and bone metastases. Mechanistically, asporin may affect extracellular matrix structure and promote invasive growth of breast cancer cells. Further investigation of the role of asporin in metastasis to bone is additionally justified given its affinity for calcium.

Acknowledgements: This work was supported by grants NS 9956-4 from the Czech Ministry of Health, MSM 6198959216 from the Czech Ministry of Education and EU infrastructure support CZ.1.05/2.1.00/01.0030. Gvantsa Kharaishvili was also supported by LF_2010_006.

Datum přednesení příspěvku: 29. 4. 2011