Histone deacetylase inhibitor-induced cancer stem cells exhibit high pentose phosphate pathway metabolism.

// Bisrat G. Debeb 1, 5 , Lara Lacerda 1, 5 , Richard Larson 1, 5 , Adam R. Wolfe 1, 5 , Savitri Krishnamurthy 2, 5 , James M. Reuben 3, 5 , Naoto T. Ueno 4, 5 , Michael Gilcrease 2 , Wendy A. Woodward 1, 5 1 Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA 2 Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA 3 Department of Hematopathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA 4 Department of Breast Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA 5 MD Anderson Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, Houston, TX 77030, USA Correspondence to: Wendy A. Woodward, email: wwoodward@mdanderson.org Bisrat G. Debeb, email: bgdebeb@mdanderson.org Keywords: HDAC inhibitors, cancer stem cells, pentose phosphate pathway, G6PD Received: September 24, 2015 Accepted: March 16, 2016 Published: April 07, 2016 ABSTRACT Purpose: We recently demonstrated that histone deacetylase (HDAC) inhibitors can “reprogram” differentiated triple-negative breast cancer cells to become quiescent stem-like cancer cells. We hypothesized that the metabolic state of such cells differs from that of their differentiated progeny. Results: In untreated cells, glucose uptake was higher in ALDH + cells than in ALDH – cells ( p = 0.01) but lactate production was not different; treating ALDH – or ALDH + cells with VA or SAHA similarly increased glucose uptake without changing lactate production but upregulated G6PD, a rate-limiting enzyme in pentose phosphate pathway metabolism. NADPH production was higher in HDAC inhibitor-treated stem-like cells than in vehicle-treated cells ( p < 0.05). Two G6PD inhibitors, 6-aminonicotinamide and dehydroepiandrosterone, decreased mammosphere formation efficiency and ALDH activity and 6-aminonicotinamide reduced the VA-induced increase in ALDH + cells. Finally, patients expressing high G6PD mRNA had significantly worse overall survival ( p < 0.001), and patients with high G6PD protein showed a similar trend towards worse disease-specific survival ( p = 0.06). Methods: Glucose consumption, lactate and NADPH production, and reactive oxygen species generation were compared in aldehyde dehydrogenase (ALDH)-positive and –negative cells in the presence or absence of the HDAC inhibitors valproic acid (VA) or suberoylanilide hydroxamic acid (SAHA). Glucose-6-phosphate dehydrogenase (G6PD) expression was evaluated in a tissue microarray from 94 patients with node-positive invasive breast carcinoma and in two publically available databases and correlated with overall survival. Conclusions: Energy metabolism in HDAC inhibitor-induced stem-like cancer cells differed sharply from that of differentiated cell types. HDAC inhibitor-induced dedifferentiation promoted metabolic reprogramming into the pentose phosphate pathway, which is targeted effectively by G6PD inhibition. These findings highlight a potential dual-therapy approach to targeting bulk differentiated cells with HDAC inhibitors and CSCs with G6PD inhibitors.