A Systematic Algorithm for Metabolically Based Sensitization to Cisplatin in Head and Neck Squamous Cell Carcinoma

Abstract

Cisplatin is the most commonly utilized systemic agent in the setting of head and neck squamous cell carcinoma (HNSCC). Despite nearly half a century of clinical use, our understanding of cisplatin activity in HNSCC and the primary drivers of its effectiveness or lack thereof, remains limited. Here we undertook a systematic evaluation of cisplatin processing and effects on HNSCC cell death in order to develop a broadly applicable approach for chemo-sensitization. Established HNSCC cell lines were chosen to represent the relative frequency of oncogenic events common to HNSCC (ie, TP53 mutation, HPV activation, NOTCH mutation). In vivo experiments were carried out using a xenograft murine model. Induction coupled plasma mass spectrometry was used to measure cisplatin transport and DNA-binding. DNA damage secondary to oxidative stress was measured using quantitative gammaH2AX phosphorylation and foci formation. Cisplatin effects on cell death were measured using individual assays for senescence, apoptosis, mitotic catastrophe, as well as the clonogenic survival assay. Cisplatin-generated metabolic shifts were measured using both steady-state metabolomics interrogation and 13C kinetic experiments. HNSCC cells import cisplatin in a dose- and time-dependent fashion but only a small fraction of cisplatin is bound to DNA following acute exposure. Cisplatin generated oxidative stress is a critical driver of cisplatin toxicity in HNSCC across molecular backgrounds. Mechanisms of cell death vary by genomic background and are not predictive of relative cisplatin sensitivity. Cisplatin transport, neutralization by thiol moieties, and DNA-damage repair are dependent on energy (ATP) and reducing equivalents (NADH, NADPH). Cisplatin exposure triggers measurable changes in central carbon flux, particularly in the conversion of pyruvate into lactate due to NADH depletion; compensatory changes in the citric acid cycle and pentose phosphate pathway are insufficient to restore reducing equivalent levels and are not consistent across molecular backgrounds. Direct measurements of intratumoral pyruvate and lactate correlate with relative cisplatin toxicity under in vivo conditions. Targeted inhibition of glycolytic flux potentiates cisplatin toxicity through (1) altered transport, (2) prolonged oxidative stress, and (3) decreased DNA repair (via PARP). Cisplatin toxicity in HNSCC is largely driven by non-specific oxidative stress across molecular backgrounds. Lactate dehydrogenase (LDH) activity appears to be both a marker of cisplatin toxicity and a potentially suitable target for metabolic targeting in HNSCC resistant to cisplatin. Conversely, metabolic targeting of non-glycolytic metabolic pathways is unlikely to be successful in sensitizing HNSCC cells to cisplatin across molecular backgrounds.