Cancer stem cells (CSCs) are considered to be responsible for recurrence, metastasis, and resistance to treatment in many types of cancers; therefore, new treatment strategies targeting CSCs are attracting attention. In this study, we fabricated a polyethylene glycol-tagged microwell device that enabled spheroid formation from human oral squamous carcinoma cells. HSC-3 and Ca9-22 cells cultured in the microwell device aggregated and generated a single spheroid per well within 24–48 h. The circular shape and smooth surface of spheroids were maintained for up to five days, and most cells comprising the spheroids were Calcein AM-positive viable cells. Interestingly, the mRNA expression of CSC markers (Cd44, Oct4, Nanog, and Sox2) were significantly higher in the spheroids than in the monolayer cultures. CSC marker-positive cells were observed throughout the spheroids. Moreover, resistance to cisplatin was enhanced in spheroid-cultured cells compared to that in the monolayer-cultured cells. Furthermore, some CSC marker genes were upregulated in HSC-3 and Ca9-22 cells that were outgrown from spheroids. In xenograft model, the tumor growth in the spheroid implantation group was comparable to that in the monolayer culture group. These results suggest that our spheroid culture system may be a high-throughput tool for producing uniform CSCs in large numbers from oral cancer cells.

高悪性度転化（high-grade transformation：HGT）は，腺様囊胞癌（adenoid cystic carcinoma：AdCC）ではまれな現象であり，HGTにより悪性度の高い状態となり，典型的なAdCCと比較して，頸部リンパ節転移や遠隔転移を生じる傾向が高い。患者は69歳女性で，口蓋正中部の腫脹の精査を主訴に受診した。初診時，口蓋正中やや左側寄りに30×15mm大の広基性腫瘤を認めた。生検の結果，口蓋腺より発生した唾液腺悪性腫瘍との診断であったが，確定診断には至らなかった。そのため，全身麻酔下に全切除術を施行した。初診から切除までの間にも腫瘍は著明な増大を示した。切除標本は，定型的なAdCCの部分と，それに接して存在するHGT部分の2つの要素で構成されており，急速に増大した部分は，病理組織学的にHGT-AdCCで占められていた。切除標本にて断端陽性の所見を認めたため，術後放射線照射を行い，局所においては占拠性病変の出現はなかったが，その後の画像評価にて転移性肺腫瘍を認め，同時化学放射線療法を施行するも，死亡の転帰をとった。