University of Hawaii Cancer Center, 701 Ilalo Street, Honolulu, HI 96813, United States.
University of Guam Cancer Research Center, Mangilao, GU, United States.
Environ Int. 2021 Mar;148:106381. doi: 10.1016/j.envint.2021.106381. Epub 2021 Jan 19.
Areca nut/betel quid (AN/BQ) chewing, a prevalent practice in parts of the Pacific and Asia, is an independent cause of cancers of the oral cavity and esophagus and may be linked to liver cancer. The mechanisms of AN/BQ-associated carcinogenesis are unclear. In a Guam population, we previously demonstrated that AN/BQ chewing alters the oral bacterial microbiome including in chewers with oral premalignant lesions. Enrichment of specific taxa, including Cyanobacteria, was observed.
We undertook an investigation to evaluate Areca catechu and/or Piper betle plants as potential sources of Cyanobacteria and cyanotoxins in AN/BQ chewers in Guam.
We evaluated bacterial 16S rRNA with Illumina MiSeq in 122 oral samples and 30 Areca catechu nut and Piper betle leaf samples. Cyanobacteria sequences were interrogated using the NCBI database to identify candidate species and their reference sequences were evaluated for secondary metabolite toxins using AntiSMASH 5.0. Selected toxins were measured by ELISA in extracts from 30 plant samples and in a subset of 25 saliva samples.
Cyanobacteria was the predominant taxa in Areca catechu and Piper betle plants, comprising 75% of sequences. Cyanobacteria was detected at low levels in oral samples but 90-fold higher in current AN/BQ chewers compared to former/never chewers (p = 0.001). Microcystin/nodularin was detected in saliva (15 of 25 samples) and Piper betle leaves (6 of 10 samples). Cylindrospermopsin was detected in all saliva and leaf samples and 7 of 10 nut/husks. Salivary cylindrospermopsin levels were significantly higher in current chewers of betel quid (i.e., crushed Areca catechu nut wrapped in Piper betle leaf) compared to those chewing Areca nut alone. Anabaenopeptin was detected in saliva (10 of 25 samples), all leaf samples, and 7 of 10 nut/husks. Salivary anabaenopeptin concentration was weakly, albeit significantly, correlated with oral Cyanobacteria relative abundance.
Our study demonstrates that Cyanobacteria can contaminate AN/BQ plants and expose chewers to potent hepatotoxins. With worldwide increases in climate-related overgrowth of Cyanobacteria, our findings have broad implications for cancer risk across populations.
槟榔（Areca nut/ betel quid，AN/BQ）咀嚼在太平洋和亚洲部分地区非常普遍，是口腔和食管癌症的独立病因，可能与肝癌有关。槟榔相关致癌作用的机制尚不清楚。在关岛人群中，我们之前的研究表明，槟榔咀嚼改变了口腔细菌微生物组，包括在有口腔癌前病变的咀嚼者中。观察到特定类群的丰度增加，包括蓝藻。
我们进行了一项研究，以评估关岛槟榔咀嚼者的槟榔和荖叶是否可能是蓝藻和蓝藻毒素的潜在来源。
我们使用 Illumina MiSeq 评估了 122 个口腔样本和 30 个槟榔果和荖叶样本中的细菌 16S rRNA。使用 NCBI 数据库对蓝藻序列进行了查询，以鉴定候选种，并用 AntiSMASH 5.0 评估其参考序列中的次级代谢毒素。通过 ELISA 在 30 个植物样本的提取物和 25 个唾液样本的子集中测量了选定的毒素。
蓝藻是槟榔和荖叶植物中的主要类群，占序列的 75%。蓝藻在口腔样本中的检出水平较低，但在当前槟榔咀嚼者中比以前/从不咀嚼者高 90 倍（p=0.001）。微囊藻毒素/节球藻毒素在唾液（25 个样本中的 15 个）和荖叶（10 个样本中的 6 个）中均有检出。柱孢藻毒素存在于所有唾液和叶片样本中，10 个槟榔果/果壳样本中有 7 个。咀嚼含荖叶的槟榔（即，压碎的槟榔果包裹在荖叶中）的当前咀嚼者的唾液中柱孢藻毒素水平明显高于单独咀嚼槟榔果的咀嚼者。在唾液（25 个样本中的 10 个）、所有叶片样本和 10 个槟榔果/果壳样本中均检测到拟柱孢藻肽。唾液中拟柱孢藻肽浓度与口腔蓝藻相对丰度呈弱相关，但具有统计学意义。
我们的研究表明，蓝藻可以污染槟榔/荖叶植物，并使咀嚼者接触到有效的肝毒素。随着与气候相关的蓝藻过度生长在全球范围内的增加，我们的发现对不同人群的癌症风险具有广泛的影响。
