ABSTRACT
OBJECTIVE To explored the potential of pharmacological stabilization and reactivation of p53 for targeted cancer therapies. METHODS The cytotoxicity of a potent Cyclophilin A (CypA) inhibitor HL001 was tasted against a panel of cancer cell lines. The genotypes and activation of p53 were compared with the cytotoxicity profile of HL001. Two-dimensional (2D) PAGE analysis was performed to investigate differentially expressed proteins that involves in the anti-proliferation effects of HL001. Pull-down and Co-IP were used to confirmed the new identified PPI between CypA and G3BP1 and orthotopic animal model of lung cancer was used to tested the anti- tumor activity of HL001 in vivo. RESULTS We identify a novel CypA small molecule inhibitor HL001 that induces non-small cell lung cancer (NSCLC) cell cycle arrest and apoptosis via restoring p53 expression. We find that HL001 stabilizes p53 through inhibiting the MDM2-mediated p53 ubiquitination. Further mechanistic studies reveal that the downregulation of G3BP1 and the induction of reactive oxygen species and DNA damage by HL001 contribute to p53 stabilization. Surprisingly, HL001 selectively suppresses tumor growth in p53 wildtype NSCLC harboring Arg72 homozygous alleles (p53- 72R) through disrupting interaction between MDM2 and p53-72R in a CypA dependent manner. Moreover, combining HL001 with cisplatin synergistically enhance tumor regression in orthotopic NSCLC mouse model. CONCLUSION Pharma?cologic inhibition of CypA offers a potential therapeutic strategy via specific activation of p53-72R in NSCLC.
ABSTRACT
OBJECTIVE Leukotriene B4 (LTB4) biosynthesis and subsequently neutrophilic inflam?mation may provide a potential strategy for the treatment of acute lung injury (ALI) or idiopathic pulmonary fibrosis (IPF). To provide a potential strategy for the treatment of ALI or IPF, we identified potent inhibi?tors of Leukotriene A4 hydrolase (LTA4H), a key enzyme in the biosynthesis of LTB4. METHODS In this study, we identified two known histone deacetylase (HDAC) inhibitors, suberanilohydroxamic acid (SAHA) and its analogue 4-(dimethylamino)-N-〔7-(hydroxyamino)-7-oxoheptyl〕benzamide (M344), as effective inhibitors of LTA4H using enzymatic assay, thermofluor assay, and X- ray crystallographic investigation. We next tested the effect of SAHA and M344 on endogenous LTB4 biosynthesis in neutrophils by ELISA and neutrophil migration by transwell migration assay. A murine experimental model of ALI was induced by lipopolysaccharide(LPS) inhalation. Histopathological analysis of lung tissue using H&E staining revealed the serious pulmonary damage caused by LPS treatment and the effect of the SAHA. We next examined mRNA and protein levels of pro-inflammatory cytokines in lung tissue and bronchoalveolar lavage fluid using qRT- PCR and ELISA to further investigate the underlying mechanisms of anti-inflammatory activities by SAHA. We also investigated the effects of SAHA and M344 on a murine experimental model of bleomycin (BLM)-induced IPF model. RESULTS The results of enzymatic assay and X-ray crystallography showed that both SAHA and M344 bind to LTA4H, signif?icantly decrease LTB4 levels in neutrophil, and markedly diminish early neutrophilic inflammation in mouse models of ALI and IPF under a clinical safety dose. CONCLUSION Collectively, SAHA and M344 would provide promising agents with well-known clinical safety for potential treatment in patients with ALI and IPF via pharmacologically inhibiting LAT4H and blocking LTB4 biosynthesis.