Cancer stem cells and radiotherapy

Area of Science:

• Cancer Stem Cell Biology
• Radiation Oncology
• Radiobiology

Background:

• Cancer stem cells (CSCs) play a pivotal role in tumor development, metastasis, and treatment resistance.
• Understanding CSCs is critical for advancing radiation oncology and radiobiological research.
• Distinguishing true stemness from mere clonogenicity in cancer cells is an ongoing challenge.

Purpose of the Study:

• To summarize the historical and current research status of cancer stem cells in radiobiology and clinical radiation oncology.
• To differentiate the concepts of clonogenicity and stemness in cancer cells.
• To evaluate the role of cancer stem cells in radiation resistance.

Main Methods:

• Review of historical and current research on cancer stem cells in radiobiology.
• Discussion of quantitative transplantation assays (e.g., TD50) for assessing stemness.
• Exploration of new technologies for CSC isolation, including surface marker expression (e.g., CD133, CD44, CD29).

Main Results:

• Quantitative transplantation assays (TD50) are the gold standard for verifying stemness.
• New technologies enable selection of CSC-enriched subpopulations based on surface markers.
• Current data, particularly for glioma stem cells (CD133+), do not provide firm evidence for differential radiosensitivity between CSCs and non-stem cells.

Conclusions:

• Cancer stem cells have been a significant research focus in radiooncology for five decades.
• Despite advancements in marker-based assays, challenges remain regarding marker specificity, animal models, and in vitro assays.
• Clonogenic assays may not accurately reflect stemness, hindering investigations into CSC radioresistance.
• Combining stem cell markers with radiobiological assays holds promise for translational research in radiation oncology.