Bitter melon prevents the development of 4-NQO-induced oral squamous cell carcinoma in an immunocompetent mouse model by modulating immune signaling

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide, and tobacco is one of the most common factors for HNSCC of the oral cavity. We have previously observed that bitter melon (Momordica charantia) extract (BME) exerts antiproliferative activity against several cancers including HNSCC. In this study, we investigated the preventive role of BME in 4-nitroquinoline 1-oxide (4-NQO) carcinogen-induced HNSCC. We observed that BME feeding significantly reduced the incidence of 4-NQO-induced oral cancer in a mouse model. Histologic analysis suggested control 4- NQO-treated mouse tongues showed neoplastic changes ranging from moderate dysplasia to invasive squamous cell carcinoma, whereas no significant dysplasia was observed in the BME-fed mouse tongues. We also examined the global transcriptome changes in normal versus carcinogen- induced tongue cancer tissues, and following BME feeding. Gene ontology and pathway analyses revealed a signature of biological processes including "immune system process" that is significantly dysregulated in 4-NQO- induced oral cancer. We identified elevated expression of proinflammatory genes, s100a9, IL23a, IL1β and immune checkpoint gene PDCD1/PD1, during oral cancer development. Interestingly, BME treatment significantly reduced their expression. Enhancement of MMP9 ("ossification" pathway) was noted during carcinogenesis, which was reduced in BME-fed mouse tongue tissues. Our study demonstrates the preventive effect of BME in 4-NQO-induced carcinogenesis. Identification of pathways involved in carcinogen-induced oral cancer provides useful information for prevention strategies. Together, our data strongly suggest the potential clinical benefits of BME as a chemopreventive agent in the control or delay of carcinogen-induced HNSCC development and progression.