Abstract
Background: Although mechanistic target of rapamycin (mTOR) inhibitors, such as temsirolimus, show promise in treating bladder cancer, acquired resistance often hampers efficacy. This study evaluates mechanisms leading to resistance. Methods: Cell growth, proliferation, cell cycle phases, and cell cycle regulating proteins were compared in temsirolimus resistant (res) and sensitive (parental—par) RT112 and UMUC3 bladder cancer cells. To evaluate invasive behavior, adhesion to vascular endothelium or to immobilized extracellular matrix proteins and chemotactic activity were examined. Integrin α and β subtypes were analyzed and blocking was done to evaluate physiologic integrin relevance. Results: Growth of RT112res could no longer be restrained by temsirolimus and was even enhanced in UMUC3res, accompanied by accumulation in the S- and G2/M-phase. Proteins of the cdk-cyclin and Akt-mTOR axis increased, whereas p19, p27, p53, and p73 decreased in resistant cells treated with low-dosed temsirolimus. Chemotactic activity of RT112res/UMUC3res was elevated following temsirolimus re-exposure, along with significant integrin α2, α3, and β1 alterations. Blocking revealed a functional switch of the integrins, driving the resistant cells from being adhesive to being highly motile. Conclusion: Temsirolimus resistance is associated with reactivation of bladder cancer growth and invasive behavior. The α2, α3, and β1 integrins could be attractive treatment targets to hinder temsirolimus resistance.
Highlights
Bladder cancer represents the second most prevalent genitourinary malignancy [1] and is the ninth most common malignancy worldwide [2]
Proliferation of UMUC3par and RT112par was significantly diminished after exposure to temsirolimus, whereas UMUC3res and RT112res proliferation was not affected by temsirolimus, each compared to untreated controls (Figure 1C,D)
We found a strong increase of cyclin D1 in temsirolimus resistant tumor cells accompanied by a considerable reduction of p73
Summary
Bladder cancer represents the second most prevalent genitourinary malignancy [1] and is the ninth most common malignancy worldwide [2]. Current treatments for non-muscle-invasive disease confer a 5 years cancer-specific survival rate of about 90%. Muscle-invasive, recurrent, or metastatic bladder cancer is associated with a poor prognosis [3,4,5]. First-line treatment of metastatic disease is commonly based on a cisplatin-containing chemotherapy, with MVAC (methotrexate, vinblastine, doxorubicin, cisplatin) or GC (gemcitabine, cisplatin) [6]. These agents have improved patient outcome, median survival is still limited to Cancers 2019, 11, 777; doi:10.3390/cancers11060777 www.mdpi.com/journal/cancers. Methods: Cell growth, proliferation, cell cycle phases, and cell cycle regulating proteins were compared in temsirolimus resistant (res) and sensitive (parental—par) RT112 and UMUC3 bladder cancer cells. Results: Growth of RT112res could no longer be restrained by temsirolimus and was even enhanced in UMUC3res, accompanied by accumulation in the S- and G2/M-phase
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
