High-altitude hypoxia exacerbates chemotherapy-induced myelosuppression by lowering serum G-CSF/GM-CSF and regulating apoptosis and proliferation.

The unique hypoxic environment in high-altitude regions is increasingly drawing attention for its impact on the health of residents, particularly in patients post-chemotherapy. This study aimed to investigate the effects and potential mechanisms of high-altitude hypoxia on myelosuppression following chemotherapy, with the goal of providing a theoretical basis for clinical treatment. A retrospective clinical study of 80 patients with breast cancer revealed that patients in the plateau exhibited a significantly higher incidence of grade 3 or higher neutropenia and any level of neutropenia post-chemotherapy than those in the plain, with propensity score matching (PSM) confirming these associations. Animal experiments revealed that high-altitude hypoxia reduced the white blood cell (WBC) count, granulocyte count, lymphocyte count, and number of bone marrow nucleated cells (BMNCs) in cyclophosphamide (CTX)-treated mice. Additionally, high-altitude hypoxia induced a significant reduction in the proliferation index and an elevation in apoptosis rates in BMNCs. High-altitude hypoxia also significantly reduced serum levels of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Transcriptomic analysis of BMNCs demonstrated that high-altitude hypoxia might modulate the hematopoietic function in CTX-induced myelosuppression mice through pathways related to hematopoiesis, such as porphyrin metabolism, hematopoietic cell lineage, ECM-receptor interaction, and PI3K-Akt signaling pathway. Our results suggest that high-altitude hypoxia exacerbates chemotherapy-induced myelosuppression, possibly through reducing the serum level of G-CSF/GM-CSF and regulating apoptosis and proliferation by PI3K-Akt signaling pathway, highlighting that cancer patients undergoing chemotherapy in hypoxic environments may require enhanced supportive care to mitigate these adverse effects.