Potential binding of cryptotanshinone with hemoglobin and antimetastatic effects against breast cancer cells through alleviating the expression of MMP-2/-9

Abstract

As a naturally occurring quinone molecule, cryptotanshinone (C19H20O3) has demonstrated a variety of pharmacological actions through diverse molecular processes. However, the interactions of cryptotanshinone with the major blood proteins and the signaling pathways that contribute to the antimetastatic effect of cryptotanshinone against cancer cells remain largely unknown. The binding of cryptotanshinone to human hemoglobin (Hb) was therefore examined in this study using different spectroscopic techniques such as fluorescence and circular dichroism (CD). To further study the binding interaction at atomic level, molecular docking analysis was also performed. Additionally, cellular assays were performed to assess the anticancer and antimetastatic effects of cryptotanshinone on MCF-7 cells. These assays included cell viability, qPCR, and ELISA assays to measure cell growth as well as mRNA and protein expression of Bax, Bcl-2, matrix metalloproteinase-2 (MMP-2) and MMP-9. According to experimental findings, cryptotanshinone was able to reduce the intrinsic fluorescence [tryptophan (Trp-37)] intensity of hemoglobin (Hb) by a static quenching process, mostly made possible by hydrogen bonding interaction, with no appreciable effects on Hb's secondary structure. Cellular assay showed that cryptotanshinone with a IC50 concentration of 17.5 µg/ml can mitigate the breast cancer MCF-7 cell viability through induction of apoptosis (overexpression of Bax/Bcl-2 at both mRNA and protein levels) as well as antimetastatic activity (downexpression of MMP-2/-9 at both mRNA and protein levels). In conclusion, we discovered that cryptotanshinone exhibits the potential ability to bind Hb and may be regarded as a promising bioactive anticancer substance, which requires additional in vitro research in future studies.