Interaction of stattic, a STAT3 inhibitor with human serum albumin: spectroscopic and computational study

Chitosan-Coated-PLGA Nanoparticles Enhance the Antitumor and Antimigration Activity of Stattic – A STAT3 Dimerization Blocker

Purpose

The use of nanocarriers to improve the delivery and efficacy of antimetastatic agents is less explored when compared to cytotoxic agents. This study reports the entrapment of an antimetastatic Signal Transducer and Activator of Transcription 3 (STAT3) dimerization blocker, Stattic (S) into a chitosan-coated-poly(lactic-co-glycolic acid) (C-PLGA) nanocarrier and the improvement on the drug’s physicochemical, in vitro and in vivo antimetastatic properties post entrapment.

Methods

In vitro, physicochemical properties of the Stattic-entrapped C-PLGA nanoparticles (S@C-PLGA) and Stattic-entrapped PLGA nanoparticles (S@PLGA, control) in terms of size, zeta potential, polydispersity index, drug loading, entrapment efficiency, Stattic release in different medium and cytotoxicity were firstly evaluated. The in vitro antimigration properties of the nanoparticles on breast cancer cell lines were then studied by Scratch assay and Transwell assay. Study on the in vivo antitumor efficacy and antimetastatic properties of S@C-PLGA compared to Stattic were then performed on 4T1 tumor bearing mice.

Results

The S@C-PLGA nanoparticles (141.8 ± 2.3 nm) was hemocompatible and exhibited low Stattic release (12%) in plasma. S@C-PLGA also exhibited enhanced in vitro anti-cell migration potency (by >10-fold in MDA-MB-231 and 5-fold in 4T1 cells) and in vivo tumor growth suppression (by 33.6%) in 4T1 murine metastatic mammary tumor bearing mice when compared to that of the Stattic-treated group. Interestingly, the number of lung and liver metastatic foci was found to reduce by 50% and 56.6%, respectively, and the average size of the lung metastatic foci was reduced by 75.4% in 4T1 tumor-bearing mice treated with S@C-PLGA compared to Stattic-treated group (p < 0.001).

Conclusion

These findings suggest the usage of C-PLGA nanocarrier to improve the delivery and efficacy of antimetastatic agents, such as Stattic, in cancer therapy.

Investigation on the binding interaction of rhodamine B with human serum albumin: effect of metal ions

The binding of rhodamine B (RB) to human serum albumin (HSA) in the absence and presence of Cu²⁺ or Fe³⁺ under simulated physiological conditions was studied by using various biophysical methods for the first time. The results showed that the interaction between HSA and RB could spontaneously result in the formation of HSA-RB complex (namely, static quenching mechanism) through hydrophobic interactions and hydrogen bonds irrespective of the absence or presence of metal ions. The presence of metal ions led to the reduction of binding affinity of RB to HSA compared with no metal ions, which might result from the conformational change of HSA caused by the binding of metal ions. Furthermore, the analysis of UV-vis absorption, circular dichroism, synchronous fluorescence and three-dimensional fluorescence experiments demonstrated that the addition of RB induced conformational and microenvironmental changes of HSA without and with metal ions. In short, this work will be helpful to in-depth understand the transport mechanism and biological effect of RB and the effect of metal ions on the interaction of HSA-RB in vivo.

Suppression of STAT3 Phosphorylation and RelA/p65 Acetylation Mediated by MicroRNA134 Plays a Pivotal Role in the Apoptotic Effect of Lambertianic Acid

As p300-mediated RelA/p65 hyperacetylation by signal transducers and activators of transcription 3 (STAT3) is critical for NF-κB activation, in the current study, the apoptotic mechanism of lambertianic acid (LA) was explored in relation to STAT3 phosphorylation and RelA/p65 acetylation in MCF-7, DU145, PC-3, and MDA-MB-453 cells. LA significantly increased the cytotoxicity, sub G 1 population, and the cleavage of poly (ADP-ribose) polymerase (PARP) in MDA-MB-453 or PC-3 cells (STAT3 mutant), more than in the MCF-7 or DU145 cells (STAT3 wild). Consistently, LA inhibited the phosphorylation of STAT3 and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and disrupted the interaction between p-STAT3, p300, NF-κB, and RelA/p65 acetylation (Ac-RelA/p65) in the MCF-7 and DU145 cells. Also, LA reduced the nuclear translocation of STAT3 and NF-κB via their colocalization, and also suppressed the protein expression of XIAP, survivin, Bcl-2, Bcl-xL, vascular endothelial growth factor (VEGF), Cox-2, c-Myc and mRNA expression of interleukin 6 (IL-6), and tumor necrosis factor-α (TNF-α) in MCF-7 cells. Conversely, IL-6 blocked the ability of LA to suppress the cytotoxicity and PARP cleavage, while the depletion of STAT3 or p300 enhanced the PARP cleavage of LA in the MCF-7 cells. Notably, LA upregulated the level of miRNA134 and so miRNA134 mimic attenuated the expression of pro-PARP, p-STAT3, and Ac-RelA, while the miRNA134 inhibitor reversed the ability of LA to reduce the expression of Ac-RelA and pro-PARP in MCF-7 cells. Overall, these findings suggest that LA induced apoptosis via the miRNA-134 mediated inhibition of STAT3 and RelA/p65 acetylation.

Spectroscopic evaluation of synthesized 5β-dihydrocortisol and 5β-dihydrocortisol acetate binding mechanism with human serum albumin and their role in anticancer activity

Our study focus on the biological importance of synthesized 5β-dihydrocortisol (Dhc) and 5β-dihydrocortisol acetate (DhcA) molecules, the cytotoxic study was performed on breast cancer cell line (MCF-7) normal human embryonic kidney cell line (HEK293), the IC₅₀ values for MCF-7 cells were 28 and 25 μM, respectively, whereas no toxicity in terms of cell viability was observed with HEK293 cell line. Further experiment proved that Dhc and DhcA induced 35.6 and 37.7% early apoptotic cells and 2.5, 2.9% late apoptotic cells, respectively, morphological observation of cell death through TUNEL assay revealed that Dhc and DhcA induced apoptosis in MCF-7 cells. The complexes of HSA-Dhc and HSA-DhcA were observed as static quenching, and the binding constants (K) was 4.7 ± .03 × 10⁴ M^-1 and 3.9 ± .05 × 10⁴ M^-1_, and their binding free energies were found to be -6.4 and -6.16 kcal/mol, respectively. The displacement studies confirmed that lidocaine 1.4 ± .05 × 10⁴ M^-1 replaced Dhc, and phenylbutazone 1.5 ± .05 × 10⁴ M^-1 replaced by DhcA, which explains domain I and domain II are the binding sites for Dhc and DhcA. Further, FT-IR, synchronous spectroscopy, and CD results revealed that the secondary structure of HSA was altered in the presence of Dhc and DhcA. Furthermore, the atomic force microscopy and transmission electron microscopy showed that the dimensions like height and molecular size of the HSA-Dhc and HSA-DhcA complex were larger compared to HSA alone. Detailed analysis through molecular dynamics simulations also supported greater stability of HSA-Dhc and HSA-DhcA complexes, and root-mean-square-fluctuation interpreted the binding site of Dhc as domain IB and domain IIA for DhcA. This information is valuable for further development of steroid derivative with improved pharmacological significance as novel anti-cancer drugs.