Abstract
OBJECTIVE: We aimed to characterize a potential role for phosphatidylinositol 3-kinase (PI3k) in leading to accelerated postoperative metastatic tumor growth. BACKGROUND: PI3k enhances tumor cell survival in part by phosphorylating Akt and reducing apoptosis. Postoperatively, apoptosis is reduced within local recurrences and distant metastases. This reduction is associated with the phenomenon of accelerated postoperative tumor growth. METHODS: Balb/c mice underwent a tail vein injection of 1x10 metastatic murine mammary adenocarcinoma 4T1 cells. Animals were divided into the following treatment groups (n=10/group): group A, controls; group B, DMSO intraperitoneally (IP) daily from days 14 to 21; group C, IP LY294002 daily from days 14 to 21; group D, laparotomy only; group E, laparotomy followed by IP DMSO for 7 days; and group F, laparotomy followed by LY294002 IP for 7 days. All laparotomies were performed on day 14. Animals were killed at day 28. Metastatic tumor burden was assessed using the lung/body weight ratio and a histologic metastatic index. Mitotic counts and apoptotic indices were established using a combination of hematoxylin and eosin histology and TUNEL immunohistochemistry. A parallel survival study was performed, and PI3k activity was assessed using western blots for phospho-Akt. RESULTS: Laparotomy was associated with increased systemic tumor burden (P=0.001). Postoperatively, LY294002 significantly attenuated metastatic tumor growth (P<0.001). Effective PI3k inhibition was confirmed by demonstrating a reduced Akt phosphorylation. Moreover, PI3k inhibition led to reduced proliferation, increased apoptosis (P<0.001), and enhanced postoperative survival (P<0.001). CONCLUSIONS: Targeting PI3k with postoperative LY294002 significantly attenuates the acceleration in postoperative metastatic tumor growth seen following laparotomy.