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Updated: Sep 18, 2025
In Vitro and In Vivo Evaluation of Photocontrolled Biologically Active Compounds - Potential Drug Candidates for Cancer Photopharmacology
Published on: September 29, 2023
Photoswitchable Stat3 inhibitors: design, synthesis and anticancer activity study on 2D and 3D breast cancer cell
Satyajit Bera1, Subhankar Bose2, Nilakshi Paul1
1Department of Chemistry, University of Calcutta 92 A.P.C. Road Kolkata 700009 West Bengal India sschem@caluniv.ca.in.
Abstract:
Stat3 protein is known to be hyperactive in many human cancer cells, including leukaemia, lymphoma, breast, ovarian, lung, and prostate cancer cells. The treatment of most of these cancer types relies on chemotherapy, which encounters various side effects owing to off-target effects of the drugs. Photopharmacology promises to eliminate such off-target effects with the use of photoswitchable drugs. Based on a potent Stat3 inhibitor, in this study, we developed two azobenzene-based photoswitchable inhibitors 2 and 3. Ambient light-exposed compound 2 contained 90% trans isomer, which upon irradiation with a 365 nm light, isomerized to 81% cis isomer, that showed t 1/2 of >38 h at 37 °C. Back-irradiation of the cis-enriched PSS with a 475 nm light yielded 79% trans-enriched PSS. Interestingly, cis- and trans-enriched PSSs showed 1.3-1.5 times higher anticancer potencies against the MDA-MB-231 breast cancer cell line than the parent Stat3 inhibitor 1, except the trans-enriched PSS of 2 (1.2 times less activity). In the 2D cell culture study, the cis-enriched PSS of 2 (IC50 of 4.8 ± 0.5 μM) was found to be 1.7-fold more potent than its trans-enriched PSS. Notably, the 3D cell spheroid culture study displayed a better photopharmacological response, in which the cis-enriched PSS induced 2.5-fold higher spheroid growth inhibition than the trans-enriched PSS. Cell cycle analysis demonstrated the arrest of the cell cycle in the G1 phase, which occurred more efficiently using the cis isomer than the trans isomer. An immunoblot assay confirmed the inhibition of Stat3 activation. These experimental results agreed with the in silico docking performed on the SH2 domain of Stat3.
Insights
We developed novel photoswitchable Stat3 inhibitors for cancer therapy. The cis isomer demonstrated enhanced potency and cell cycle arrest, offering a promising photopharmacology approach to minimize chemotherapy side effects.
Area of Science:
- Medicinal Chemistry
- Photopharmacology
- Cancer Biology
Background:
- Signal transducer and activator of transcription 3 (Stat3) is hyperactive in numerous human cancers.
- Conventional chemotherapy for Stat3-associated cancers causes side effects due to off-target drug activity.
- Photopharmacology offers a strategy to mitigate off-target effects using light-activated drugs.
Purpose of the Study:
- To develop novel azobenzene-based photoswitchable Stat3 inhibitors.
- To evaluate the anticancer efficacy and photopharmacological response of these novel compounds.
Main Methods:
- Synthesis of two azobenzene-based photoswitchable Stat3 inhibitors (compounds 2 and 3).
- Photochemical isomerization studies (365 nm and 475 nm light).
- In vitro anticancer activity assessment in 2D and 3D cell cultures (MDA-MB-231 breast cancer cells).
- Cell cycle analysis and immunoblot assays to confirm Stat3 inhibition.
- In silico docking studies on the Stat3 SH2 domain.
Main Results:
- Compounds 2 and 3 exhibited reversible photoisomerization between trans and cis forms.
- The cis-enriched isomer of compound 2 showed significantly higher potency (1.7-fold in 2D, 2.5-fold in 3D cultures) and induced G1 cell cycle arrest.
- Stat3 activation was confirmed to be inhibited by the developed compounds.
- In silico docking supported the experimental findings.
Conclusions:
- Azobenzene-based photoswitchable inhibitors represent a promising photopharmacological approach for Stat3-targeted cancer therapy.
- The cis isomer demonstrated superior anticancer activity, highlighting the potential for light-controlled drug delivery.
- This strategy could lead to more targeted cancer treatments with reduced side effects.
