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Intracellular trafficking as a determinant of AS-DACA cytotoxicity in rhabdomyosarcoma cells
Steven J Wolf1, Tony Huynh, Nicole S Bryce
1Biospecimens Research and Tumour Bank, Children's Cancer Research Unit, The Children's Hospital at Westmead, Westmead, NSW 2774, Australia.
Background:
Rhabdomyosarcoma (RMS) is a malignant soft tissue sarcoma derived from skeletal muscle precursor cells, which accounts for 5-8% of all childhood malignancies. Disseminated RMS represents a major clinical obstacle, and the need for better treatment strategies for the clinically aggressive alveolar RMS subtype is particularly apparent. Previously, we have shown that the acridine-4-carboxamide derivative AS-DACA, a known topoisomerase II poison, is potently cytotoxic in the alveolar RMS cell line RH30, but is 190-fold less active in the embryonal RMS cell line RD. Here, we investigate the basis for this selectivity, and demonstrate in these RMS lines, and in an AS-DACA- resistant subclone of RH30, that AS-DACA-induced cytotoxicity correlates with the induction of DNA double strand breaks.
Results:
We show that inhibition of the multidrug-resistance associated protein (MRP1) has no effect on AS-DACA sensitivity. By exploiting the pH-dependent fluorescence properties of AS-DACA, we have characterized its intracellular distribution, and show that it concentrates in the cell nucleus, as well as in acidic vesicles of the membrane trafficking system. We show that fluorescence microscopy can be used to determine the localization of AS-DACA to the nuclear and cytoplasmic compartments of RMS cells grown as spheroids, penetrance being much greater in RH30 than RD spheroids, and that the vesicular signal leads the way into the spheroid mass. EEA1 and Rab5 proteins, molecular markers expressed on early-endosomal vesicles, are reduced by >50% in the sensitive cell lines.
Conclusion:
Taking the evidence as a whole, suggests that endosomal vesicle trafficking influences the toxicity of AS-DACA in RMS cells.
Insights
The chemotherapy drug AS-DACA shows selective toxicity in rhabdomyosarcoma (RMS) cells, with its effectiveness linked to DNA double-strand breaks and influenced by endosomal vesicle trafficking. This finding may lead to improved treatments for this childhood cancer.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Rhabdomyosarcoma (RMS) is a significant childhood cancer.
- Alveolar RMS is an aggressive subtype requiring better therapies.
- The drug AS-DACA shows differential cytotoxicity in RMS cell lines.
Purpose of the Study:
- Investigate the basis for AS-DACA's selective toxicity in RMS.
- Determine the correlation between AS-DACA's effects and DNA damage.
- Explore the role of cellular mechanisms in AS-DACA sensitivity.
Main Methods:
- Utilized RMS cell lines (RH30 and RD) and a resistant subclone.
- Assessed AS-DACA cytotoxicity and induction of DNA double-strand breaks.
- Investigated AS-DACA's intracellular distribution using pH-dependent fluorescence and microscopy.
- Examined the effect of multidrug-resistance associated protein (MRP1) inhibition.
- Quantified early-endosomal vesicle markers (EEA1, Rab5).
Main Results:
- AS-DACA-induced cytotoxicity correlates with DNA double-strand breaks.
- Multidrug-resistance associated protein (MRP1) inhibition does not affect AS-DACA sensitivity.
- AS-DACA concentrates in the nucleus and acidic vesicles within RMS cells.
- AS-DACA penetrance is greater in sensitive RH30 spheroids, with vesicular signal preceding nuclear entry.
- Sensitive cell lines show a significant reduction in early-endosomal markers (EEA1, Rab5).
Conclusions:
- Endosomal vesicle trafficking significantly influences AS-DACA toxicity in RMS cells.
- The cellular uptake and distribution, particularly via endosomal pathways, are critical for AS-DACA's anti-cancer effects.
- Findings suggest potential therapeutic strategies targeting vesicle trafficking to enhance AS-DACA efficacy.
