PAMAM-Camptothecin Conjugate Inhibits Proliferation and Induces Nuclear Fragmentation in Colorectal Carcinoma Cells

To synthesize and characterize a poly (amido amine) dendrimer-camptothecin (PAMAM-CPT) conjugate and evaluate its activity on human colorectal carcinoma cells (HCT-116). The attachment of CPT to amine-terminated PAMAM was facilitated through a succinic acid-glycine linker. The conjugate was characterized for absence of small molecular weight impurities, size and drug content. Stability of the conjugate in PBS and growth media and its in vitro activity on HCT-116 were studied. Cell cycle arrest and nuclear fragmentation upon PAMAM-CPT treatment were investigated. The conjugate was stable under physiological pH (7.4) in PBS and in growth media (with 10% FBS) with minimal release of 4% and 6% drug, respectively, at 48 h. PAMAM-CPT inhibited proliferation of HCT-116 cells with an IC50 value of 1.6 +/- 0.3 A mu M. The conjugate induced signs of cell cycle arrest with up to 68% of cells blocked in the G(2) phase. Confocal images of cells treated with PAMAM-CPT suggest nuclear fragmentation and formation of apoptotic bodies. Results show that the PAMAM-CPT conjugate was active against colorectal cancer cells in vitro, inhibiting their growth and inducing nuclear fragmentation. Coupled with the ability to target macromolecular therapeutics to tumors, this conjugate shows promise for cancer chemotherapy.