The hedgehog pathway in hematopoiesis and hematological malignancy

Area of Science:

• Oncology
• Hematology
• Molecular Biology

Background:

• The Hedgehog (HH) pathway is implicated in hematological malignancies, with activation linked to relapse and poor outcomes.
• HH pathway inhibitors, such as glasdegib targeting Smoothened (SMO), are being investigated and have received FDA approval for specific acute myeloid leukemia (AML) cases.
• The precise mechanism of action for SMO inhibitors (SMOi) in AML remains unclear, with hypotheses focusing on cancer stem cells (CSCs) or stromal cells.

Purpose of the Study:

• To review the role of the HH pathway in hematopoiesis and hematological malignancies.
• To highlight preclinical and clinical evidence supporting HH pathway inhibition as a therapeutic strategy.
• To explore the hypothesis that SMOi's clinical benefit is mediated by stromal cells protecting AML CSCs.

Main Methods:

• Literature review of HH pathway in hematopoiesis and malignancy.
• Analysis of preclinical and clinical trial data for HH inhibitors.
• Exploration of evidence for stromal cell involvement in HH pathway-mediated CSC protection.

Main Results:

• The HH pathway is a validated therapeutic target in hematological malignancies.
• Clinical activity of SMOi suggests a mechanism beyond direct CSC targeting.
• Evidence supports the hypothesis that stromal cells in the tumor microenvironment mediate SMOi's effects on CSCs.

Conclusions:

• HH pathway inhibitors represent a promising therapeutic avenue for hematological malignancies.
• The clinical benefit of SMOi may be primarily mediated through the tumor microenvironment, specifically stromal cells.
• Further research is needed to elucidate the exact mechanisms and optimize therapeutic strategies targeting the HH pathway in AML and other blood cancers.