Abstract LB-85: Real-time molecular imaging of cathepsins for rapid detection of cancer in human breast lumpectomy specimens.
Authors: Vykhovanets Eugene , Gilmore Hannah , Blum Galia , Bogyo Matthew , Basilion James 
Published: August 2014

Objectives: Successful breast cancer surgery relies on the rapid and accurate localization of the residual tumor cells/tissues positioned to close to the surface of the lumpectomy specimen. Presence of cancerous cells/tissue inside of the surgical margin may lead to secondary surgeries creating an enormous burden in time, cost and patient anxiety. Recent studies have demonstrated the ability of near infrared fluorescent smart imaging probes to target tumor proteases in small animal models of cancers. These probes are extremely selective, robust, and useful for imaging tumor-expressed proteases in human tumor tissue xenografts implanted in mice. The high target selectivity, cellular permeability, and rapid kinetics have prompted us to utilize these probes to identify cancer at or near the surface of lumpectomy specimens during breast conserving surgeries.

Material and Method: To determine the feasibility of using these probes for rapid detection of cancer cells in lumpectomy margins, we characterized the ability of ex vivo topically applied quenched activity based probe, GB119, to: 1) interact with tumor associated proteases; 2) become activated by human breast cancer tissues; 3) penetrate normal human breast tissue; and 4) “find” cancerous tissues residing within normal breast tissues.

Results: Specifically we found that: 1) In vitro incubation of GB119 and breast cancer cell lysates resulted in cathepsin-dependent activation of GB119 and fluorescence in 3-6 min; 2) GB119 was activated and accumulated in lysosomes of MCF-7 breast cancer cell culture in vitro; 3) Human breast cancer xenografts could be detected under 2-mm layer of normal breast tissue in 5-10 min by topical application of GB119 onto the breast tissue indicating high levels of permeability of the normal breast tissue for the probe. The broad-spectrum suicide cysteine protease inhibitor K11777 abrogated the ability of the probe to detect breast cancer xenograft implying a high specificity of the GB119/cathepsin-dependent fluorescent signal. 4) IHC analysis confirmed the presence of GB119’s fluorochrome, Cy5, both at the surface and inside (up to 1-mm) of the breast cancer xenograft which was separated from the probe by 2-mm layer of the normal breast tissue. 5) Pathology data confirm that GB119/tumor cathepsin-dependent fluorescence on the surface of the human lumpectomy specimens pretreated with GB119 correlates with presence of breast cancer in surgical margin.

Conclusions: Topical application of GB119 onto surgically removed lumpectomy specimens may be a new tool to rapidly and completely assess cancer infiltrates in the lumpectomy margins essential to improve outcomes for breast cancer patients.

Citation Format: Eugene Vykhovanets, Hannah Gilmore, Galia Blum, Matthew Bogyo, James Basilion. Real-time molecular imaging of cathepsins for rapid detection of cancer in human breast lumpectomy specimens. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-85. doi:10.1158/1538-7445.AM2013-LB-85