Glutaminase inhibitors induce thiol-mediated oxidative stress and radio-sensitization in treatment resistant cervical cancers

• Published in: Molecular cancer therapeutics 2020-10, Vol.19 (12), p.2465-2475
• Main Authors: Rashmi, Ramachandran, Jayachandran, Kay, Zhang, Jin, Menon, Vishnu, Muhammad, Naoshad, Zahner, Michael, Ruiz, Fiona, Zhang, Sisi, Cho, Kevin, Wang, Yuting, Huang, Xiaojing, Huang, Yi, McCormick, Michael L., Rogers, Buck E., Spitz, Douglas R., Patti, Gary J., Schwarz, Julie K.
• Format: Article
• Language: English
• ISSN: 1535-7163; 1538-8514
• DOI: 10.1158/1535-7163.MCT-20-0271

The purpose of the study was to determine if radiation resistant cervical cancers are dependent upon glutamine metabolism driven by activation of the PI3K pathway and test whether PI3K pathway mutation predicts radio-sensitization by inhibition of glutamine metabolism. Cervical cancer cell lines with and without PI3K pathway mutations, including SiHa and SiHa PTEN −/− cells engineered by CRISPR/Cas9, were used for mechanistic studies performed in vitro in the presence and absence of glutamine starvation and the glutaminase inhibitor, telaglenastat (CB-839). These studies included cell survival, proliferation, quantification of oxidative stress parameters, metabolic tracing with stable isotope labeled substrates, metabolic rescue and combination studies with L-buthionine sulfoximine (BSO), auranofin (AUR), and radiation (RT). In vivo studies of telaglenastat ± RT were performed using CaSki and SiHa xenografts grown in immune compromised mice. PI3K activated cervical cancer cells were selectively sensitive to glutamine deprivation through a mechanism that included thiol-mediated oxidative stress. Telaglenastat treatment decreased total glutathione pools, increased the percent glutathione disulfide, and caused clonogenic cell killing that was reversed by treatment with the thiol antioxidant, N-acetylcysteine. Telaglenastat also sensitized cells to killing by glutathione depletion with BSO, thioredoxin reductase inhibition with AUR, and RT. Glutamine dependent PI3K activated cervical cancer xenografts were sensitive to telaglenastat monotherapy, and telaglenastat selectively radio-sensitized cervical cancer cells in vitro and in vivo . These novel preclinical data support the utility of telaglenastat for glutamine dependent radio-resistant cervical cancers and demonstrate that PI3K pathway mutations may be used as a predictive biomarker for telaglenastat sensitivity.