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Updated: Jul 30, 2025
Intratibial Osteosarcoma Cell Injection to Generate Orthotopic Osteosarcoma and Lung Metastasis Mouse Models
Published on: October 28, 2021
Targeting RNA Polymerase I Transcription Activity in Osteosarcoma: Pre-Clinical Molecular and Animal Treatment
Chang-Won Kang1, Anneke C Blackburn1, Amos Hong Pheng Loh2
1The Division of Genome Science and Cancer, The John Curtin School of Medical Research, The Australian National University, Acton, Canberra 2601, Australia.
Abstract:
The survival rate of patients with osteosarcoma (OS) has not improved over the last 30 years. Mutations in the genes TP53, RB1 and c-Myc frequently occur in OS and enhance RNA Polymerase I (Pol I) activity, thus supporting uncontrolled cancer cell proliferation. We therefore hypothesised that Pol I inhibition may be an effective therapeutic strategy for this aggressive cancer. The Pol I inhibitor CX-5461 has demonstrated therapeutic efficacy in different cancers in pre-clinical and phase I clinical trials; thus, the effects were determined on ten human OS cell lines. Following characterisation using genome profiling and Western blotting, RNA Pol I activity, cell proliferation and cell cycle progression were evaluated in vitro, and the growth of TP53 wild-type and mutant tumours was measured in a murine allograft model and in two human xenograft OS models. CX-5461 treatment resulted in reduced ribosomal DNA (rDNA) transcription and Growth 2 (G2)-phase cell cycle arrest in all OS cell lines. Additionally, tumour growth in all allograft and xenograft OS models was effectively suppressed without apparent toxicity. Our study demonstrates the efficacy of Pol I inhibition against OS with varying genetic alterations. This study provides pre-clinical evidence to support this novel therapeutic approach in OS.
Insights
RNA Polymerase I (Pol I) inhibition effectively suppressed osteosarcoma growth in preclinical models. This novel therapeutic strategy shows promise for treating this aggressive cancer by reducing tumor proliferation and cell cycle progression.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Therapeutics
Background:
- Osteosarcoma (OS) survival rates have stagnated for decades.
- Frequent mutations in TP53, RB1, and c-Myc drive OS proliferation by enhancing RNA Polymerase I (Pol I) activity.
Purpose of the Study:
- To investigate the therapeutic potential of Pol I inhibition in osteosarcoma.
- To evaluate the efficacy of the Pol I inhibitor CX-5461 in preclinical OS models.
Main Methods:
- Characterization of ten human OS cell lines using genome profiling and Western blotting.
- In vitro assessment of RNA Pol I activity, cell proliferation, and cell cycle progression.
- In vivo evaluation of CX-5461 efficacy in murine allograft and human xenograft OS models.
Main Results:
- CX-5461 treatment reduced ribosomal DNA (rDNA) transcription and induced G2-phase cell cycle arrest in all tested OS cell lines.
- Significant suppression of tumor growth was observed in all tested allograft and xenograft models.
- No apparent toxicity was detected in the in vivo models.
Conclusions:
- Pol I inhibition is a viable therapeutic strategy for osteosarcoma, irrespective of genetic mutations.
- CX-5461 demonstrates significant preclinical efficacy against osteosarcoma.
- These findings provide a strong rationale for advancing Pol I inhibitors into clinical trials for osteosarcoma treatment.
