Description

Although the majority of patients with nasopharyngeal carcinoma (NPC) do not present with overt metastases at diagnosis, a significant number succumb to disseminated disease years after the successful treatment of the primary tumor. Thus, late NPC recurrence may be the result of rare and elusive dormant cancer cells hiding in specialized niches being reactivated by specific signals. The concept of cancer dormancy has been described for the most common solid and hematological cancers; however, the dormant cancer cells in NPC remain largely uncharacterized.

Although many factors contribute toward cancer cell dormancy, recent studies have demonstrated that cancer therapy can induce cellular dormancy. Indeed, therapy-induced dormancy has been shown to lead to durable proliferation arrest, resulting in the formation of polyploid giant cancer cells (PGCCs), which are a unique sub-population of cancer cells that contribute toward the heterogeneity of solid tumors. Unlike regular-sized diploid cancer cells, PGCCs display distinct morphological features, including a large cytoplasmic area and a high genomic content contained within a single highly enlarged nucleus or multiple nuclei. Despite being present in low numbers, the frequency of PGCCs increases markedly after exposure to hypoxia and therapeutic interventions such as radiotherapy and chemotherapies.

The investigators' findings, which used a highly relevant clinical orthotopic model of imageable NPC and clinical data, suggest that autophagy inhibition (HCQ) prevents therapy-induced dormant PGCC formation and thereby prevents NPC metastasis.