Radiation Damage to Tumor Vasculature Initiates a Program That Promotes Tumor Recurrences.

Area of Science:

• Oncology
• Radiation Biology
• Immunology

Background:

• Radiation therapy can induce tumor recurrence by promoting blood vessel regrowth.
• This pathway involves hypoxia-inducible factor-1 (HIF-1), stromal cell-derived factor-1 (SDF-1/CXCL12), and tumor-associated macrophages (TAMs).
• The process is not tumor-specific and aids in normal tissue repair.

Purpose of the Study:

• To review preclinical evidence of a radiation-induced pathway that promotes tumor vascularization and recurrence.
• To explore therapeutic strategies targeting this pathway to improve radiation therapy outcomes.
• To assess the potential of pathway inhibitors in protecting normal tissues from radiation damage.

Main Methods:

• Review of preclinical data on radiation-induced tumor response.
• Analysis of the molecular mechanisms involving HIF-1, CXCL12, and TAMs.
• Evaluation of preclinical models treated with inhibitors of monocytes/macrophages, HIF-1, CXCL12, CXCR4, and CSF-1R.

Main Results:

• Radiation therapy upregulates HIF-1 and CXCL12, attracting proangiogenic M2-polarized TAMs that restore tumor vasculature.
• Inhibitors of this pathway significantly enhance the radiation response in various preclinical tumor models.
• These inhibitors also protect normal tissues from radiation-induced damage.

Conclusions:

• Targeting the radiation-induced pathway involving HIF-1, CXCL12, and TAMs offers a promising strategy to improve cancer radiation therapy.
• Inhibitors of this pathway demonstrate dual efficacy: enhancing tumor response and protecting normal tissues.
• Clinical trials, including those with CXCR4 inhibitors like plerixafor, show encouraging results and support further investigation.