P. Rychahou1,2, Y. Bae1,4, Y. Zaytseva1, E. Y. Lee1,3, H. L. Weiss1, B. M. Evers1,2 1University Of Kentucky,Markey Cancer Center,Lexington, KY, USA 2University Of Kentucky,Department Of Surgery,Lexington, KY, USA 3University Of Kentucky,Department Of Pathology And Laboratory Medicine,Lexington, KY, USA 4University Of Kentucky,Department Of Pharmaceutical Sciences,Lexington, KY, USA
Introduction: Colorectal cancer (CRC) is the second leading cause of cancer deaths in the US. The phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway is important for CRC progression and metastasis; inhibitors have been developed that are being evaluated in clinical trials with limited success due to systemic toxicity. The purpose of our study was to: (i) determine expression of pAkt (Ser473), Akt1 and Akt2 in primary and metastatic CRCs, and (ii) develop an effective nanocarrier for lung-selective delivery of pan-PI3K inhibitors as targeted therapy of CRC lung metastasis.
Methods: (1) To determine the expression of PI3K/Akt pathway components, we obtained primary CRCs (n=12) and CRC lung metastases (n=10). All samples were tested for pAkt (Ser473), Akt1 and Akt2 expression by immunohistochemistry (IHC) and blindly scored by a pathologist. (2) Polymeric nanoparticles were constructed and loaded with either fluorescent dye (Alexa 547) or pan-PI3K inhibitors (either PX-866 or wortmannin). Lung selective accumulation of fluorescently-labeled nanoparticles was confirmed by confocal imaging of frozen tissue sections from lung, liver and spleen. Selective PI3K inhibition in lung tissue was confirmed by western blot of protein extracts from lung, liver, spleen and kidney after intravenous administration of PX-866-loaded nanoparticles.
Results: (1) Increased pAkt (Ser473) expression was detected in 80% of primary CRCs and CRC lung metastases; 60% of the samples demonstrated markedly elevated expression of Akt2. (2) Treatment with PX-866, an irreversible pan-PI3K inhibitor currently in the clinic, inhibited cell cycle progression and induced apoptosis in patient-derived CRC organotypic cultures, CRC stem cell lines and pik3ca mutant CRC cells. (3) Importantly, in vivo treatment with pan-PI3K-loaded nanoparticles demonstrated a marked suppression of lung metastasis growth using a clinically-relevant CRC lung metastasis model.
Conclusion: We demonstrate, for the first time, safe and efficient delivery of drug-loaded nanocarriers to lung metastases, suggesting that lung selective PI3K inhibition is a viable treatment strategy for CRC lung metastasis.