Penfluridol: An Antipsychotic Agent Suppresses Metastatic Tumor Growth in Triple-Negative Breast Cancer by Inhibiting Integrin Signaling Axis

Abstract

Metastasis of breast cancer, especially to the brain, is the major cause of mortality. The inability of anti-cancer agents to cross the blood-brain-barrier represents a critical challenge for successful treatment. In the current study, we investigated the anti-metastatic potential of penfluridol (PF), an antipsychotic drug frequently prescribed for schizophrenia with anti-cancer activity. We show that PF induced apoptosis and reduced the survival of several metastatic triple negative breast cancer (TNBC) cell lines. Additionally, PF treatment significantly reduced the expression of integrinα6, integrin β4, Fak, Paxillin, Rac1/2/3, and ROCK1 in vitro. We further evaluated the efficacy of PF in three different in vivo tumor models. We demonstrate that PF administration to an orthotopic model of breast cancer suppressed tumor growth by 49%. On the other hand, PF treatment inhibited the growth of metastatic brain tumors introduced by intracardiac or intracranial injection of breast cancer cells by 90% and 72%, respectively. PF-treated tumors from all three models exhibited reduced integrinβ4 and increased apoptosis. Moreover, chronic administration of PF failed to elicit significant toxic or behavioral side effects in mice. Taken together, our result indicate that PF effectively reduces the growth of primary TNBC tumors and especially metastatic growth in the brain by inhibiting integrin signaling, and prompt further preclinical investigation into repurposing PF for the treatment of metastatic TNBC.

Penfluridol Represses Integrin Expression in Breast Cancer through Induction of Reactive Oxygen Species and Downregulation of Sp Transcription Factors

“…Many of the effects observed in breast and other cancer cell lines treated with penfluridol and other phenothiazine derivatives are similar to that observed after knockdown of Sp transcription factors Sp1, Sp3 or Sp4 or after treatment with agents that target Sp TFs (10–18). For example, knockdown of Sp1, Sp3 or Sp4 individually or combined decreased proliferation and migration/invasion of breast (MDA-MB-231 and SKBR3) and other cancer cell lines (12) and similar results were observed for drugs that repress Sp TF expression (13–18).…”

“…Phenothiazine-derived antipsychotic drugs such as thioridazine and chlorpromazine exhibit anticarcinogenic activity in several different cancer cell lines (3–9). More recent studies have demonstrated that penfluridol, another antipsychotic drug, also inhibits breast and pancreatic cancer cell growth (9,10). For example, in pancreatic cancer a series of phenothiazene analogs induced apoptosis and inhibited clonogenic growth and colony formation, and more detailed studies with penfluridol indicated that induction of protein phosphatase 2A (PP2A) was a key effect of this compound (9).…”

“…For example, in pancreatic cancer a series of phenothiazene analogs induced apoptosis and inhibited clonogenic growth and colony formation, and more detailed studies with penfluridol indicated that induction of protein phosphatase 2A (PP2A) was a key effect of this compound (9). Penfluridol exhibited antimetastatic activity in triple negative breast cancer cells and inhibited tumor growth and brain metastasis in three different in vivo models and the key elements were inhibition of α6- and β4-integrin expression (10). However, the mechanisms of the penfluridol-induced responses were not well defined, and this limits potential clinical applications of the compound.…”

“…For example, knockdown of Sp1, Sp3 or Sp4 individually or combined decreased proliferation and migration/invasion of breast (MDA-MB-231 and SKBR3) and other cancer cell lines (12) and similar results were observed for drugs that repress Sp TF expression (13–18). Moreover, the effects of penfluridol and other phenothazines on inhibition of several genes including cyclin D1, bcl-2, vascular endothelial growth factor (VEGF) receptors, myc and activation/cleavage caspase-3/PARP (3–10) have also been observed after Sp knockdown (10–18). It was recently reported that the antimetastatic activity of penfluridol in triple negative breast cancer cells was related to downregulation of α6- and β4-integrin expression (10); however, since both integrin gene promoters are GC-rich, it is possible that Sp1 and other Sp TFs may regulate expression of α6- and β4-integrins as well as α5-integrin (19–21).…”

Penfluridol induces endoplasmic reticulum stress leading to autophagy in pancreatic cancer

“…In our previous study, we have established the anti-cancer effects of penfluridol against breast cancer and its metastasis to brain through inhibition of integrin signaling, whereas Wu et al 24 observed dysregulation of cholesterol homeostasis by penfluridol in breast cancer. 17 ER plays critical role in synthesis and secretion of transmembrane and secretary proteins. The adaptive response to ER stress is unfolded protein response (UPR).…”