Abstract A68: Penfluridol suppresses triple-negative breast cancer metastasis to brain by inhibiting integrin signaling

Breast cancer is the second leading cause of cancer related deaths in US. Breast tumor metastasis to brain is major 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 current study, we evaluated penfluridol, a first generation, highly potent 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 24 hours of treatment with penfluridol. We also observed that penfluridol treatment induced significant apoptosis in 4T1, MDA-MB-231 and HCC-1806, TNBC cells as exbited 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 integrinα6β4 resulted in apoptosis which was further increased by penfluridol treatment. On the other hand, activation of integrins by TGFβ treatment and Laminin reduced induction of apoptosis by penfluridol confirming the role of integrins. We further evaluated the efficacy of penfluridol in three independent invivo experiments. In the first experiment, we implanted 4T1, breast cancer cells in the mammary fats of female mice and started treatment once tumor size was around 50 mm3 with 10 mg/kg penfluridol by oral gavage everyday till day 27. 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 next day of cells injection. Our result demonstrated that the tumor growth in the brain of penfluridol treated mice was reduced by 72% as compared to control. Further 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 metastasis of breast cancer cells to brain by 90%. The tumors obtained from PF treated mice from all the three different in vivo experiments exhibited reduced integrinβ4 and increased apoptosis. In addition, chronic administration of PF failed to exhibit any serious toxicity or behavioral side effects in mice. Taken together, our result indicate that PF is effective in reducing the growth of primary TNBC tumor as well as metastatic growth in brain by inhibiting integrin signaling. Citation Format: Alok Ranjan, Parul Gupta, Sanjay K. Srivastava. Penfluridol suppresses triple-negative breast cancer metastasis to brain by inhibiting integrin signaling. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr A68.