Background

Nasopharyngeal carcinoma (NPC) is a malignant tumor involving the head and neck areas. Unlike other head and neck cancers, NPC is characterized by increased invasiveness and metastasis [1]. Survival outcomes are significantly better in patients with early-stage NPC than in those with late-stage NPC [1, 2]. Although NPC is rare in most parts of the world, it has a high regional incidence in Asia, with that in Southern China and Southeast Asia ranking among the highest in the world [2]. Generally, there are three main types of NPC according to the World Health Organization (WHO), which include keratinizing squamous cell carcinoma, non-keratinizing carcinoma and undifferentiated carcinoma [3]. Epstein-Barr virus (EBV) has been shown to be a risk factor for NPC, especially for non-keratinizing and undifferentiated carcinoma [3,4,5]. The earliest evidence of NPC associated with EBV was identified in 1973 [6]. Although EBV is detected in most patients with NPC, cases of EBV-negative NPC have also been reported [4, 7]. Other lifestyle-associated risk factors and/or host genetic variants may interact with EBV to play roles in the carcinogenesis of NPC [5, 8, 9]. Obesity can occur due to unhealthy lifestyle habits and has been associated with an increased risk for various cancers, including breast, esophageal, pancreatic, and colorectal cancers [10,11,12,13]. Interestingly, several epidemiological studies have shown that patients with NPC have higher BMI, implying that overweight or obese people are tended to have a greater risk of NPC [14,

Conclusions

In summary, we conducted a study to understand the effects of leptin on NPC by combining a small-scale clinical analysis, in vitro, in vivo and in silico methods. Our small-scale clinical findings indicated that elevated intra-tumoral leptin was associated with more advanced tumors and poor prognosis of NPC. Our data also suggested that leptin was involved in alteration of diverse molecules related to pathways that regulate EMT and cell proliferation. These results supported the idea that leptin facilitates nasopharyngeal cell survival, proliferation and invasion by influencing the expression levels of EMT-, cell proliferation- and glycolysis-related proteins, which are key to tumor invasiveness and metastasis and the shortened survival of patients with cancer. Similarly, these results may also explain the findings of our clinical research, as well as our mouse model of tumor growth, considering the cancer-promoting effects of leptin in our assays. Furthermore, we utilized in silico miRNA-target prediction to identify miR-874-3p as a novel regulator of leptin and rigorously validated this prediction experimentally. Our data suggests that miR-874-3p targets leptin mRNA to reduce cell survival and proliferation in NPC cells. Overall, this study provides insights into how leptin is involved in the carcinogenesis of NPC with a focus on potential pathological effects of leptin and therapeutic targeting of leptin expression, which may potentially be applied in future clinical settings.