Abstract 5504: Penfluridol suppresses triple negative breast cancer metastasis to brain by inhibiting α6β4 integrins

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Breast cancer is the second leading cause of cancer related deaths in the United States. Breast tumor metastasis to brain is primary cause of deaths. Brain metastasis of triple negative breast cancer cells (TNBC) is highly resistant to current therapies and is a cause of reduced survival rates in patients. In the current study, we evaluated the anti-cancer effects of penfluridol, a first generation antipsychotic drug against three different highly aggressive TNBC cell line. The IC50 of penfluridol was around 6 μM in 4T1, MDA-MB-231 and HCC-1806, breast cancer cells respectively. Our result showed that the expression of integrinβ4, integrinα6, Fak, Paxillin, Rac1/2/3 and ROCK1 was significantly reduced after treatment with penfluridol for 24 hours. Penfluridol treatment induced significant apoptosis in 4T1, MDA-MB-231 and HCC-1806 cells as exhibited by cleavage of caspase 3. Interestingly, integrin signaling is known to play significant role in breast cancer metastasis, and integrinα6β4 are overexpressed in breast tumors. Integrinα6 and β4 were silenced in breast cancer cells using shRNA and siRNA respectively. Silencing of integrinα6β4 resulted in apoptosis which was further increased by penfluridol treatment. On the other hand, activation of integrins by TGFβ treatment reduced the induction of apoptosis by penfluridol, confirming the role of integrins. Efficacy of penfluridol was evaluated in three in vivo experiments. In the first experiment, 4T1, breast cancer cells were implanted in the mammary fat pads of female mice and the mice were treated with 10 mg/kg penfluridol by oral gavage everyday till day 27, once the tumor size reached 50 mm3. Penfluridol treatment suppressed breast tumor growth by 50% as compared to control. In the second experiment, 4T1 luciferase transfected breast cancer cells were injected intracranially into the brain. The growth of 4T1-luc cells was monitored non-invasively using IVIS caliper and the mice started getting treatment with 10 mg/kg penfluridol by oral gavage the very next day of tumor cell injection. Our result demonstrated that the tumor growth in the brain of penfluridol treated mice was reduced by 85% as compared to control. Furthermore, anti-metastatic effect of penfluridol was determined by intracardiac injection of 4T1-luc breast tumor cells into the left ventricle of mouse heart. Once breast cancer cells lodged in the brain, mice were treated with 10 mg/kg penfluridol for 12 days. Our results showed that penfluridol treatment suppressed the growth of metastatic breast cancer cells in brain by 90%. The metastatic tumors from penfluridol treated mice exhibited reduced expression of integrins. Taken together, our result indicate that penfluridol is effective in reducing the growth of primary TNBC tumor as well as metastatic growth in brain by inhibiting integrin signaling. [Supported in part by R01 grant CA129038, awarded by National Cancer Institute, NIH]. Citation Format: Alok Ranjan, Parul Gupta, Sanjay Srivastava. Penfluridol suppresses triple negative breast cancer metastasis to brain by inhibiting α6β4 integrins. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5504. doi:10.1158/1538-7445.AM2015-5504