Effects of SPARC and Possible Receptors on Colon Cancer Cell Line

Objective: The aim of this study was to observe the apoptotic/cytotoxic effects of exogenous SPARC on colon cancer cell line HT-29, then to investigate the function of stabilin-1 and integrin alpha v beta 3, which are possible receptors for SPARC in colon cancer cells and to determine the quantitation of their receptor numbers. Methods: Appropriate doses of exogenous SPARC and it's inhibitor, cilengitide added to HT-29 cell line were determined by xCELLigence Real-Time Cell Analysis system, SPARC-mediated caspase 3 expressions were measured. Using the RT-PCR system, gene expression levels of SPARC, stabilin-1 and integrin alpha v beta 3 receptors (silenced/nonsilenced with cilengitide) were detected then the numbers of receptors per cell were quantitated by flow cytometry. Results: IC50 value of SPARC was determined as 4.57 mu g/mL and IC50 value of cilengitide was determined as 50 nM. 5 mu g/mL exogenous SPARC caused increased apoptosis in the HT-29 line. Significant increase in gene expression of integrin alpha v beta 3 receptor was observed in the group incubated with 5 mu g/mL SPARC, contrarily, the addition of cilengitide decreased gene expressions. The integrin alpha v beta 3 receptor numbers increased approximately 2-fold with SPARC compared to the control. No significant changes were observed in the gene expression and receptor numbers of stabilin-1. Conclusion: Exogenous SPARC was shown to reduce proliferation and induce apoptosis in colon cancer cells. Integrin alpha v beta 3 is thought to be the possible receptor mediating SPARC in colon cancer cells. Quantification of surface receptors per cell, which we think we have done first, can be considered as a marker in the follow-up of anticancer treatments.

Automated summary

The study aimed to observe the effects of exogenous SPARC on colon cancer cell line HT-29, investigate the possible receptors stabilin-1 and integrin alpha v beta 3, and determine the receptor numbers. The appropriate doses of SPARC and its inhibitor cilengitide were determined, caspase 3 expressions were measured, and gene expression levels and receptor numbers were detected. The results showed that exogenous SPARC reduced proliferation and induced apoptosis in colon cancer cells, with integrin alpha v beta 3 considered as a possible mediating receptor for SPARC. Quantification of surface receptors per cell can be a marker for anticancer treatments.