Investigating cancer stem cell sphere explosion via bubbling cell death

Abstract

Bubbling cell death (BCD) is defined as "formation of a bubble from the nucleus per cell and release of this swelling bubble from the cell surface to extracellular space that causes cell death" WW domain-containing oxidoreductase known as WWOX is essential for UV/cold shock-induced nuclear damage and bubbling death Tumor suppressor WWOX with Ser14 phosphorylation is shown to accumulate in the tumor lesions but functional significance of this regard is largely unknown We have previously demonstrated that breast cancer 4T1 stem cells undergo shrinkage and then explosion with dead cells in response to UV/cold shock at room temperature as determined by time-lapse microscopy Here we investigated how breast cancer stem cell sphere explosion occurs via the mechanisms of BCD Ceritinib an anaplastic lymphoma kinase (ALK) inhibitor for lung cancer caused toxicity in breast cancer 4T1 cells When breast cancer 4T1 stem cell spheres were treated with ceritinib the spheres fully exploded with dead cells via BCD Ceritinib downregulated the expression of phosphorylated ERK IκB? and pS14-WWOX and upregulated pY33-WWOX UV/cold shock treatment also showed the same result Treatment of the WWOX7-21 antibody resulted in significantly inhibition of ceritinib-mediated 4T1 sphere explosion In contrast synthetic WWOX7-21 peptides enhanced 4T1 sphere death by ceritinib Notably when Ser14-phosphorylated WWOX peptide was used to treat the 4T1 spheres cells significantly acquired resistance to ceritinib Ceritinib induced ERK and WWOX protein translocation into nucleus Immunofluorescent microscopy revealed that pS14-WWOX antibody pretreatment enhanced ceritinib-mediated nuclear translocation of endogenous ERK By F?rster resonance energy transfer (FRET) microscopy we observed that ceritinib reduced the WWOX/ERK/IκB? complex formation In summary phosphorylation at Ser14 turns WWOX from tumor suppressor into tumor promoter and regulates the cancer stem cell sphere explosion WWOX/ERK/IκB? complex also plays a role in ceritinib-dependent cancer stem cell explosion

Date of Award	2018 Aug 29
Original language	English
Supervisor	Nan-Shan Chang (Supervisor)