Regiospecific Synthesis of Ring A Fused Withaferin A Isoxazoline Analogues: Induction of Premature Senescence by W-2b in Proliferating Cancer Cells

Abstract

Induction of premature senescence represents a novel functional strategy to curb the uncontrolled proliferation of malignant cancer cells. This study unveils the regiospecific synthesis of novel isoxazoline derivatives condensed to ring A of medicinal plant product Withaferin-A. Intriguingly, the cis fused products with β-oriented hydrogen exhibited excellent cytotoxic activities against proliferating human breast cancer MCF7 and colorectal cancer HCT-116 cells. The most potent derivative W-2b triggered premature senescence along with increase in senescence-associated β-galactosidase activity, G2/M cell cycle arrest, and induction of senescence-specific marker p21Waf1/Cip1 at its sub-toxic concentration. W-2b conferred a robust increase in phosphorylation of mammalian checkpoint kinase-2 (Chk2) in cancer cells in a dose-dependent manner. Silencing of endogenous Chk2 by siRNA divulged that the amplification of p21 expression and senescence by W-2b was Chk2-dependent. Chk2 activation (either by ectopic overexpression or through treatment with W-2b) suppressed NM23-H1 signaling axis involved in cancer cell proliferation. Finally, W-2b showed excellent in vivo efficacy with 83.8% inhibition of tumor growth at a dose of 25 mg/kg, b.w. in mouse mammary carcinoma model. Our study claims that W-2b could be a potential candidate to limit aberrant cellular proliferation rendering promising improvement in the treatment regime in cancer patients.

Natural withanolides, an update

“…280 Reaction of withaferin A with various N-hydroxy benzenecarboximidoyl chlorides led to the regiospecic synthesis of a series of novel isoxazoline derivatives, which were condensed into ring A (627-643). 281 Considering the steric interactions with 4,5,10-substituents, a large number of stereoisomers with a b,bring juncture were obtained. Similarly, another attempt to semisynthesize isoxazilidino withaferin was made via two-step reaction of nitrone synthesis and nitrone 1,3-dipolar cycloaddition yielding highly chemoselective and diastereoselective cisfused products (644-647).…”

Recent Advances in the Chemistry and Therapeutic Evaluation of Naturally Occurring and Synthetic Withanolides

“…In addition, acetate derivatives of WA were also more active than WA—di- and tri- acetate analogs 130e and 131 were shown to be relatively more potent, with IC 50 values ranging 0.11 μM to 0.65 μM compared to monoacetate analogs 130a , 130b , and 130c , having IC 50 values of 0.415–3.06 μM against head and neck squamous cell (HNSCC, JMAR), breast cancer cells (MDA-MB-231), melanoma (SKMEL-28) and colon cancer (DRO81-1) cells [ 114 ]. Among the A-ring-fused isoxazolines, WA analogs, the compounds having a nitro group and β,β ring juncture (e.g., 138 ), were shown to be more active than the α,α ring juncture (e.g., 139) against MCF-7 and HCT-116 cell lines [ 119 ]. A recent report from our group indicates that C4-acetylated analog ASR490 ( 116 ) of WA was significantly more potent than WA in inducing apoptosis in cancer cells.…”

“…The Faheem Rasool group synthesized novel withaferin A-ring-condensed, 2-isoxazoline derivatives [ 119 ]. The rationale for designing 2-isoxazoline-fused withanolides was that this moiety has been known as a building block for biologically active molecules and an essential precursor in organic reactions [ 120 ].…”

Ablation of apoptosis-stimulating of p53 protein 1 protects mice from acute hepatic injury and dysfunction via NF-κB pathway in CCl4-induced hepatotoxicity

“…Nuclear factor-κB (NF-κB) is an important nuclear transcription factor and is found in almost all mammalian cells, which is involved in inflammatory and immune responses and regulation of apoptosis and cellular stress [31]. Chen et al found that NF-κB activity was related to hepatocytes apoptosis [32].…”