ABSTRACT
BACKGROUND: The oxidative pentose phosphate pathway (PPP) is essential for cancer metabolism and growth. However, the contribution of 6-phosphogluconate dehydrogenase (6PGD), a key enzyme of PPP, to cervical cancer development remains largely unknown. METHODS: mRNA and protein levels of 6PGD were analyzed in cervical cancer cells and tissues derived from patients and compared to normal counterparts. Using cell culture system and xenograft mouse model, the functions of 6PGD in cervical cancer are determined and its molecular mechanism is analyzed. 6PGD inhibitor physcion and siRNA knockdown were used. RESULTS: In this work, we demonstrate that 6PGD is aberrantly upregulated and activated in cervical cancer cells and patient tissues compared to normal counterparts. Using different approaches and preclinical models, we show that 6PGD inhibition decreases growth and migration, and enhances chemosensitivity in cervical cancer. Mechanistically, inhibition of 6PGD activates AMP-activated protein kinase (AMPK) and decreases RhoA and Rac1 activities. AMPK depletion significantly reduces the effects of 6PGD inhibition in decreasing RhoA and Rac1 activities, growth and migration in cervical cancer cells. CONCLUSIONS: Our work is the first to demonstrate the aberrant expression of 6PGD and its predominant roles in cervical cancer cell growth and migration, via a AMPK-dependent activation. Our findings suggest 6PGD as a potential therapeutic target to enhance chemosensitivity in cervical cancer.
Subject(s)
AMP-Activated Protein Kinases/metabolism , Biomarkers, Tumor/antagonists & inhibitors , Phosphogluconate Dehydrogenase/antagonists & inhibitors , Uterine Cervical Neoplasms/drug therapy , Uterine Cervical Neoplasms/metabolism , rac1 GTP-Binding Protein/metabolism , rhoA GTP-Binding Protein/metabolism , AMP-Activated Protein Kinases/antagonists & inhibitors , Animals , Apoptosis/drug effects , Biomarkers, Tumor/genetics , Biomarkers, Tumor/metabolism , Cell Movement/drug effects , Cell Proliferation/drug effects , Chemotherapy, Adjuvant , Emodin/analogs & derivatives , Emodin/pharmacology , Emodin/therapeutic use , Female , Gene Expression , Humans , Mice, SCID , Paclitaxel/pharmacology , Paclitaxel/therapeutic use , Phosphogluconate Dehydrogenase/genetics , Phosphogluconate Dehydrogenase/metabolism , Tumor Cells, Cultured , Uterine Cervical Neoplasms/pathology , Xenograft Model Antitumor AssaysABSTRACT
PURPOSE: 6-phosphogluconate dehydrogenase (6PGD), a key enzyme of the oxidative pentose phosphate pathway, is involved in tumor growth and metabolism. Although high 6PGD activity has been shown to be associated with poor prognosis, its role and therapeutic value in breast cancer remain unknown. METHODS: The levels and roles of 6PGD were analyzed in breast cancer cells and their normal counterparts. The underlying mechanisms of 6PGD's roles are also analyzed. RESULTS: We found that 6PGD is aberrantly activated in breast cancer as shown by its increased transcriptional and translational levels as well as enzyme activity in breast cancer tissues and cell lines compared to normal counterparts. Although similar degree of enzyme activity inhibition was achieved in both breast cancer and normal breast cells, 6PGD inhibition by siRNA-mediated knockdown or pharmacological inhibitor physcion is more effective in inhibiting growth and survival in breast cancer than normal breast cells. Moreover, inhibiting 6PGD significantly sensitizes breast cancer response to chemotherapeutic agents in in vitro cell culture system and in vivo xenograft breast cancer model. We further show that 6PGD inhibition activates AMPK and its downstream substrate ACC1, leading to reduction of ACC1 activity and lipid biosynthesis. AMPK depletion significantly reverses the inhibitory effects of physcion in breast cancer cells, confirming that 6PGD inhibition targets breast cancer cell via AMPK activation. CONCLUSIONS: Our work provides experimental evidence on the association of 6PGD with poor prognosis in breast cancer and suggests that 6PGD inhibition may represent a potential therapeutic strategy to augment chemotherapy efficacy in breast cancer.