Insulin-like Growth Factor-1 (IGF-1) Regulates Pheochromocytoma cellular proliferation in vitro and in vivo.

FERNANDEZ MARIA CELIA, ; VENARA MARCELA,; NOWICKI SUSANA, ; ALVAREZ SEDó CRISTIAN, ; CHEMES HECTOR, ; BARONTINI MARTA,; PENNISI PATRICIA

Boston

Congreso; 93rd Annual Meeting & Expo of The Endocrine Society; 2011

The Endocrine Society

We have previously shown that IGF-1R expression is increased in malignant compared to benign human pheochromocytoma, and that the mouse pheochromocytoma cell  line MPC4/30 expresses a functional IGF-1R. Herein, we demonstrate that MPC4/30 cellular proliferation and BrdU incorporation after 5 days in culture increased significantly with rhIGF-1 stimulation (15±4.5 vs 30.3±2.6 x104cells p<0.05 tTest; 25.7±5.8% vs 34.7±6.0% positive nuclei p<0.01 M.Whitney Test, respectively) while the percentage of apoptotic cells was significantly lower (35.8±2.7% vs 10.8±1.3% cleaved caspase 3 positive cells; 21.3±2.7 vs 6.8±1.3 % of positive cells for TUNEL assay, p<0.01 M.Whitney Test). MPC4/30 cells migration was also stimulated by rhIGF-1 (12±1 vs 18±1 p<0.01, M.Whitney Test). Additionally, MPC4/30 cells formed colonies in soft agar and stimulation with rhIGF-1 increased the number and size of colonies (11±3 vs 26± 3 p<0.01; 217±13ìm vs 288±69ìm p<0.01 tTest). To evaluate the impact of IGF-1 on pheochromocytoma cellular proliferation in vivo, we generated a mouse model of pheochromocytoma by subcutaneous injection of MPC4/30 cells to control and liver IGF-1 deficient (LID) mice that exhibit 75% reduction in serum IGF-1 levels. We found that six weeks after MPC4/30 cells injection all control mice developed subcutaneous tumors, while only 40% of LID mice showed noticeable tumors. LID mice harboring MPC4/30 and treated daily with 2 mg/kg rhIGF-1 developed tumors as controls. The latency period for tumor growth increased in LID mice as compared to both control and LID mice treated with rhIGF-1 [Median Survival Ratio 2.2 95%CI 1.59-2.81, Chi2  136.5; 1.83 95%CI 1.35-2.32, Chi2 53.17 respectively, p<0.0001 Logrank Test]. LID mice had 10 times lower probability for developing tumors as compared to controls (Hazard Ratio 0.1 95%CI 0.02-0.27), and rhIGF-1 treatment increased this risk 8 times (Hazard Ratio 7.98 95%CI 1.60-67.06). Our data clearly show that cellular proliferation of pheochromocytoma is regulated by IGF-1 both in vitro and in vivo. IGF-1 enhanced proliferation, migration and cell’s ability to grow unattached.