Role of the abnormal HIF‐1α‐glycolysis‐aerobic oxidation pathway in non‐Hodgkin lymphoma and the intervention study

Abstract

Introduction: Diffuse large B-cell lymphoma is a highly heterogeneous entity with varied clinical manifestation and prognosis. Although the immunochemotherapy improves treatment responses, approximately 40% of the patients still eventually endure refractory/relapsed diseases. So how can we identify patients who are unlikely to be cured with conventional therapy and thus to optimize the strategy have become extremely meaningful. The metabolic reprogramming is a remarkably distinct character of tumor cells and is linked to proliferation, drug resistance, survival advantages, and tumor progression. Malignant tumor cells prefer glycolysis rather than aerobic oxidation even under aerobic surroundings. Furthermore, this altered metabolism is an active adjustment regulated by hypoxia inducible factor 1α (HIF-1α) in a reversible manner. The aim of this study is to clarify the role of the balance between glycolysis and aerobic oxidation in DLBCL and to explore the potential of targeting abnormal metabolic phenotype for NHL. Methods: Expressions of HIF-1α, key enzymes of glycolysis pathway hexokinase II (HKII), and aerobic oxidation pathway succinate dehydrogenase (SDHA) in lymphoma samples from DLBCL patients were detected by immunohistochemistry, and the association between expression levels and clinical outcomes were analyzed. SU-DHL-4 cells and Raji cells were stably transfected with lentiviral vectors carried with short hairpin RNA targeting either HIF-1α gene or HKII gene and control vectors encoding a nonmammalian shRNA. Results: Retrospective analysis of the 83 newly diagnosed DLBCL patients showed that HIF-1α+, HKIIhigh and SDHAlow were significantly correlated with inferior PFS and OS. A small subset of patients was identified that the H-H-S group (HIF-1α+HKIIhighSDHAlow), representing that critical regulator and enzymes of glycolysis-aerobic oxidation pathway are all abnormaly expressed, had significantly inferior PFS (3-year PFS, 14.3% vs 78.3%, P = .001) and OS (3-year OS, 14.3% vs 89.9%, P < .001) compared to the non–H-H-S group. Prognostic factors such as LDH, Ki67, SUVmax, IPI, and non-GCB subtype significantly differed between H-H-S group and non–H-H-S group. Furthermore, H-H-S group was demonstrated as an independent prognostic factor. HKII gene silencing significantly suppressed proliferation and abnormal glycolytic metabolism of lymphoma cells as well as enhanced cell apoptosis and sensitivity to chemotherapeutic drugs. Same phenomena were found while HIF-1α was interfered by specific shRNA. Conclusions: The abnormal HIF-1α-glycolysis-aerobic oxidation pathway might act as a prognostic indicator in DLBCL. Knocking down either HIF-1α gene or HKII gene could rescue malignant biological phenotypes of lymphoma cells, suggesting that targeting malignant metabolic phenotype may be a promising approach for refractory/relapsed lymphoma. Keywords: diffuse large B-cell lymphoma (DLBCL); prognostic indices; R-CHOP