Microcystin-LR induces anoikis resistance to the hepatocyte uptake transporter OATP1B3-expressing cell lines
Hiroyuki Takano1, Shota Takumi2, Satoshi Ikema1
1Division of Food and Chemical Biology, Faculty of Fisheries, Kagoshima University, Kagoshima 890-0056, Japan.
Abstract:
Microcystin-LR is a cyclic peptide released by several bloom-forming cyanobacteria. Understanding the mechanism of microcystin-LR toxicity is important, because of the both potencies of its acute cytotoxicity and tumor-promoting activity in hepatocytes of animals and humans. Recently, we have reported that the expression of human hepatocyte uptake transporter OATP1B3 was critical for the selective uptake of microcystin-LR into hepatocytes and for induction of its fatal cytotoxicity. In this study, we demonstrated a novel function of microcystin-LR which induced bipotential changes including anoikis resistance and cytoskeleton reorganization to OATP1B3-transfected HEK293 cells (HEK293-OATP1B3). After exposure to microcystin-LR, HEK293-OATP1B3 cells were divided to the floating cells and remaining adherent cells. After collection and reseeding the floating cells into a fresh flask, cells were confluently proliferated (HEK293-OATP1B3-FL) under the microcystin-LR-free condition. Both the proliferated HEK293-OATP1B3-FL and remaining adherent HEK293-OATP1B3-AD cells changed the character with down- and up-regulation of E-cadherin, respectively. Additionally, these cells acquired resistance to microcystin-LR. These results suggest that microcystin-LR could be associated with not only tumor promotion, but also epithelial-mesenchymal transition-mediated cancer metastasis. Furthermore, microcystin-LR might induce the cytoskeleton reorganization be accompanied epithelial-mesenchymal transition.
Insights
Microcystin-LR induces changes in cells expressing the OATP1B3 transporter, promoting anoikis resistance and cytoskeleton reorganization. This suggests a role in tumor promotion and epithelial-mesenchymal transition-mediated metastasis.
Area of Science:
- Toxicology
- Cell Biology
- Biochemistry
Background:
- Microcystin-LR is a potent cyclic peptide toxin from cyanobacteria.
- Its toxicity and tumor-promoting activity in hepatocytes are significant concerns.
- OATP1B3 transporter expression is critical for microcystin-LR uptake and cytotoxicity in hepatocytes.
Purpose of the Study:
- To investigate the novel functions of microcystin-LR in OATP1B3-transfected HEK293 cells.
- To explore microcystin-LR's role in cellular changes beyond cytotoxicity.
- To assess the potential link between microcystin-LR, cancer metastasis, and epithelial-mesenchymal transition.
Main Methods:
- HEK293 cells transfected with OATP1B3 (HEK293-OATP1B3) were exposed to microcystin-LR.
- Floating and adherent cell populations were separated and cultured.
- Changes in cell characteristics, including E-cadherin expression and microcystin-LR resistance, were analyzed.
Main Results:
- Microcystin-LR induced anoikis resistance and cytoskeleton reorganization in HEK293-OATP1B3 cells.
- Separated cell populations (HEK293-OATP1B3-FL and HEK293-OATP1B3-AD) exhibited altered E-cadherin expression.
- Both cell populations acquired resistance to microcystin-LR after proliferation.
Conclusions:
- Microcystin-LR may be associated with tumor promotion and cancer metastasis via epithelial-mesenchymal transition.
- Microcystin-LR can induce cytoskeleton reorganization, potentially accompanying epithelial-mesenchymal transition.
- The study reveals a novel function of microcystin-LR involving cellular plasticity and resistance mechanisms.
