title: Elucidation of the anticancer potential and tubulin isotype-specific interactions of β-sitosterol.
abstract: Beta-sitosterol (β-SITO), a phytosterol present in many edible vegetables, has been reported to possess antineoplastic properties and cancer treatment potential. We have shown previously that it binds at a unique site (the 'SITO-site') compared to the colchicine binding site at the interface of α- and β-tubulin. In this study, we investigated the anticancer efficacy of β-SITO against invasive breast carcinoma using MCF-7 cells. Since 'isotypes' of β-tubulin show tissue-specific expression and many are associated with cancer drug resistance, using computer-assisted docking and atomistic molecular dynamic simulations, we also examined its binding interactions to all known isotypes of β-tubulin in αβ-tubulin dimer. β-SITO inhibited MCF-7 cell viability by up to 50%, compared to vehicle-treated control cells. Indicating its antimetastatic potential, the phytosterol strongly inhibited cell migration. Immunofluorescence imaging of β-SITO-treated MCF-7 cells exhibited disruption of the microtubules and chromosome organization. Far-UV circular dichroism spectra indicated loss of helical stability in tubulin when bound to β-SITO. Docking and MD simulation studies, combined with MM-PBSA and MM-GBSA calculations revealed that β-SITO preferentially binds with specific β-tubulin isotypes (βIIand βIII) in the αβ-tubulin dimer. Both these β-tubulin isotypes have been implicated in drug resistance against tubulin-targeted chemotherapeutics. Our data show the tubulin-targeted anticancer potential of β-SITO, and its potential clinical utility against βIIand βIIIisotype-overexpressing neoplasms.
authors.affiliation: a Experimental Cancer Therapeutics and Chemical Biology, UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai Kalina Campus , Santacruz (E), Mumbai 400098 , India.
authors.forename: Madhura
authors.initials: M
authors.lastname: Pradhan
authors.affiliation: b Biotechnology and Bioinformatics , Jaypee University of Information Technology , Waknaghat, Solan 173234 , Himachal Pradesh , India.
authors.forename: Charu
authors.initials: C
authors.lastname: Suri
authors.affiliation: a Experimental Cancer Therapeutics and Chemical Biology, UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai Kalina Campus , Santacruz (E), Mumbai 400098 , India.
authors.forename: Sinjan
authors.initials: S
authors.lastname: Choudhary
authors.affiliation: c School of Life Sciences, Sambalpur University , Jyoti Vihar, Sambalpur 768019 , Odisha , India.
authors.forename: Pradeep Kumar
authors.initials: PK
authors.lastname: Naik
authors.affiliation: a Experimental Cancer Therapeutics and Chemical Biology, UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai Kalina Campus , Santacruz (E), Mumbai 400098 , India.
authors.forename: Manu
authors.initials: M
authors.lastname: Lopus
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D061986:MCF-7 Cells; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D011485:Protein Binding; D000072417:Protein Domains; D055503:Protein Multimerization; D012855:Sitosterols / Q000737:chemistry* / Q000378:metabolism; D014404:Tubulin / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D012855:Sitosterols; D014404:Tubulin; C025473:gamma-sitosterol
keywords: breast cancer; microtubule; molecular dynamic simulations; β-sitosterol; β-tubulin isotypes