Abstract
Zoledronic acid (ZOL), a third-generation bisphosphonate that strongly inhibits osteoclast activity, is widely used for the treatment of bone metastasis from a variety of malignancies, including renal cell carcinoma (RCC). We previously reported that zoledronic acid (ZOL) clinically potentiates antitumor effects of radiotherapy (RT) on bone metastases from RCC. To date, however, it remains unknown whether ZOL radiosensitizes RCC and if it does, how. Here, we demonstrated that ZOL directly radiosensitizes RCC cells independent of osteoclast activity by potentiating the caspase-3-mediated apoptosis pathway. The radiosensitization by ZOL was observed in 786-O, A-498, and ACHN cells but not in Caki-1 cells. As its underlying molecular mechanism, we found that the signal transducer and activator of transcription 1 (STAT1) plays a key role. The three RCC cell lines, in which ZOL exerted a radiosensitizing effect, expressed STAT1 abundantly but Caki-1 cells did not. ZOL downregulated endogenous STAT1 expression in 786-O, A-498, and ACHN cells by a post-transcriptional modification. We confirmed that knockdown of endogenous STAT1 by siRNA sensitized 786-O cells to RT equivalently to ZOL, and that introduction of exogenous STAT1 rendered Caki-1 cells more RT-resistant. This is the first study to clarify the molecular mechanism by which ZOL directly radiosensitizes tumor cells. Because tumor cells commonly overexpress STAT1 and ZOL reportedly radiosensitizes various types of tumor cells, ZOL warrants further clinical and translational studies as a potent radiosensitizer against RT-resistant tumors overexpressing STAT1.
Highlights
The standard of care for localized renal cell carcinoma (RCC) is surgical excision of the primary tumor
Based on the clinical efficacy of the combination therapy with Zoledronic acid (ZOL) and RT against bone metastases from RCC, we hypothesized that ZOL sensitizes RCC to RT directly and/or through modifying osteoclast activity
The current study clearly demonstrated that 10 mM of ZOL exerts radiosensitizing effects directly on RCC cells by enhancing RT-induced caspase-3 activation
Summary
The standard of care for localized renal cell carcinoma (RCC) is surgical excision of the primary tumor. ZOL as a single agent reportedly decreased the risk of SREs and prolonged the SRE-free survival in RCC patients with bone metastases, the objective response rate was quite low (7%) and more than half of the patients eventually experienced SREs [10]. We and another group reported that ZOL potentiates RT effects on bone metastases from RCC [11,12]. As its underlying molecular mechanism, ZOL post-transcriptionally downregulates the signal transducer and activator of transcription 1 (STAT1), which is responsible for the radiosensitization of RCC cells
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: 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.