Tier 3 — preclinical

Fisetin and polymeric micelles encapsulating fisetin exhibit potent cytotoxic effects towards ovarian cancer cells

Xiao X, Zou J, Fang Y, Meng Y, Xiao C, Fu J, Liu S, Bai P, Yao Y
BMC Complementary and Alternative Medicine 2018 Volume 18, article 91

Bibliography

PubMed
PMID 29544480
PubMed Central
PMC5855937
DOI
10.1186/s12906-018-2127-7
Funding
National Nature Science Foundations of China (grant no. 81202387); Sichuan Province Science and Technology Plan Project (grant nos. 2013JY0013/2014JY0213); Scientific Research Foundation of Sichuan University for Outstanding Young Scholars (grant no. 2013SCU04A22); Seventh New Century Education Reform Project sponsored by Sichuan University (grant no. SCUY7093); Demonstration Project of Chengdu Science and Technology (grant no. 2015-HM02-00075-SF).
Competing interests
The authors declare that they have no competing interests.

Study snapshot

DesignIn vitro cytotoxicity, apoptosis and mechanistic assays in ovarian cancer cell lines, plus an in vivo SKOV3 xenograft mouse tumour model comparing free fisetin against mPEG-PCL polymeric micelle-encapsulated fisetin.
ModelHuman ovarian cancer cell line SKOV3 (primary model); comparator cell lines CASKi, HEC-1A, HepG2; normal human bronchial epithelial cells, ovarian surface epithelial cells and vascular smooth muscle cells as controls; BALB/c athymic nude mice bearing SKOV3 xenograft tumours.
SampleIn vitro assays in triplicate; in vivo xenograft study used 8 treatment/control groups of n=5 mice each, repeated across two experimental sets.
InterventionFree fisetin or mPEG-PCL polymeric micelle-encapsulated fisetin (fisetin:mPEG-PCL 1:9 w/w, self-assembly method; particle size 22.4 ± 3.0 nm, encapsulation efficiency 98.53 ± 0.02%, drug loading 9.88 ± 0.14%) at concentrations up to 300 µM in vitro; in vivo intraperitoneal fisetin or fisetin micelles at 50 or 100 mg/kg, 5 days on/2 days off for 2 weeks.
DurationIn vitro exposures up to 48 hours; in vivo dosing over 2 weeks with tumour follow-up to 21 days.
EndpointsCell viability and IC50 (SKOV3 and comparator cell lines); Apoptosis (TEM ultrastructure, TUNEL, Annexin V/PI flow cytometry); Apoptotic signalling proteins (Bax, Bcl-2, caspase-3/9, PARP cleavage); Xenograft tumour volume and weight; Tumour angiogenesis (ultrasound microvessel density, CD31/VEGF/VEGFR2 immunohistochemistry)

What the study showed, in plain terms

Fisetin is a promising natural anti-cancer compound, but it barely dissolves in water, which limits how well the body can absorb and use it. This Sichuan University team built a nanoparticle version — fisetin packaged inside tiny mPEG-PCL polymer 'micelles' — to see if this improves its cancer-fighting power against ovarian cancer, one of the deadliest gynaecological cancers.

Both plain fisetin and the fisetin micelles killed ovarian cancer (SKOV3) cells in a dose- and time-dependent way, while leaving normal human cells largely untouched. The micelle version was somewhat more potent (lower IC50: about 48 µM vs 61 µM for plain fisetin) and triggered slightly more apoptosis (programmed cell death) via the classic mitochondrial pathway — more Bax, less Bcl-2, and activation of caspase-3/9.

In mice carrying real ovarian tumours, injected fisetin shrank tumours by about 54%, and the micelle version by about 71%, over three weeks. The micelles also appeared to reduce tumour blood vessel formation slightly more than plain fisetin.

The authors' explanation for the micelles' edge is pharmacokinetic: the nanoparticle shell releases fisetin more slowly and steadily and appears to penetrate the leaky, disorganised blood vessels of tumour tissue more efficiently than free fisetin — a known phenomenon in cancer nanomedicine sometimes called the enhanced permeability and retention effect.

Key findings

  • Fisetin and fisetin micelles both reduced SKOV3 ovarian cancer cell viability in a dose- and time-dependent manner, with no meaningful cytotoxicity to normal bronchial, ovarian surface or vascular smooth muscle cells.
  • IC50 against SKOV3 cells was 61.2 µM for free fisetin versus 48.2 µM for fisetin micelles (approximately 21% lower), with tumour growth inhibition of 34.8% versus 48.7% respectively in vitro.
  • Both treatments induced classic mitochondrial apoptosis: increased Bax, decreased Bcl-2, cleavage of procaspase-3/9 to active caspase-3/9, and PARP cleavage, all in a dose-dependent manner; up to 73-80% of cells showed early apoptosis at the highest concentrations tested.
  • In an SKOV3 xenograft mouse model, fisetin at 50 mg/kg gave 53.6% tumour growth inhibition after 21 days, while fisetin micelles gave approximately 70.7% inhibition — a modestly stronger effect than free fisetin at the same nominal dose.
  • Ultrasound and immunohistochemistry suggested reduced tumour vasculature (fewer, smaller blood vessels and reduced CD31/VEGFR2 signal) in fisetin- and fisetin-micelle-treated tumours compared with controls.

What this study can and cannot tell us

This is a preclinical cell-culture and mouse xenograft study; there is no human ovarian cancer data on fisetin or fisetin micelles. In vivo dosing was by intraperitoneal injection, not oral administration, so it does not reflect how an oral fisetin supplement would behave.

The angiogenesis findings (ultrasound microvessel density, VEGF/VEGFR2/CD31 staining) were reported as directionally reduced but some comparisons did not reach statistical significance (P > 0.05 in the ultrasound vessel-density analysis), so the anti-angiogenic claim is weaker than the direct cytotoxicity/apoptosis findings.

The nanoparticle formulation used here (mPEG-PCL polymeric micelles) is a laboratory research formulation, not a marketed or clinically tested product, and its relevance to any commercial fisetin supplement is indirect at best.

Editorial review

Reviewed by the Biohack Blueprint research team

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Dr. Khaled Mahmoud, MBBChCritical Care Medicine, Longevity Science & Editorial Direction Dr. Amr Yasser, PhDCardiometabolic, Musculoskeletal, Gut & Bioavailability Dr. Abdulla Mostafa, PhDCellular Senescence, Neurological, Mitochondrial & Brain-Ageing Biology