The infiltrating microbiota represents a novel cellular component of solid tumor microenvironment that can influence tumour progression and response to therapy. Adrenocortical carcinoma (ACC) is a rare and aggressive endocrine malignancy for which mitotane (MTT) treatment represents the first line therapy, though its efficacy is limited to a therapeutic window level (14-20mg/L). Novel markers able to predict those patients who would benefit from MTT therapy are urgently needed to improve patient’s management. The aim of our study was to evaluate the presence of intratumoral bacterial microbiota DNA in 26 human ACC tissues versus 9 healthy adrenals; moreover, the association between the relative bacterial composition profile, the tumor mass characteristics and MTT ability to reach high circulating levels in the early phase of treatment, was explored. We found the presence of bacterial DNA in all adrenal samples from both tumours and healthy cortex specimens, documenting significant differences in the microbial composition between malignancy and normal adrenals: in detail, the ACC tissues were characterised by a higher abundance of the Proteobacteria phylum (especially the Pseudomonas and Serratia genera). In addition, the Proteobacteria low abundance was negatively associated with tumour size, Ki67 and cortisol-secretion. Mitotane levels reached higher levels at 9 months in ACC patients with high abundance of Proteobacteria, Pseudomonas and Serratia, and with low abundance of Bacteroidota, Firmicutes and Streptococcus. These findings are the first indication that human ACCs are characterised by infiltrating bacteria and their specific abundance profile seems to influence the increase in circulating MTT levels at 9 months.

浸润微生物群代表了实体瘤微环境的一种新的细胞成分，可以影响肿瘤的进展和对治疗的反应。肾上腺皮质癌（ACC）是一种罕见的侵袭性内分泌恶性肿瘤，米托坦（MTT）治疗是一线治疗方法，但其疗效仅限于治疗窗水平（14-20mg/L）。迫切需要能够预测哪些患者将从 MTT 治疗中受益的新型标记物，以改善患者的治疗。我们研究的目的是评估 26 个人类 ACC 组织与 9 个健康肾上腺中瘤内细菌微生物群 DNA 的存在情况；此外，还探讨了相对细菌组成特征、肿瘤块特征和MTT在治疗早期达到高循环水平的能力之间的关联。我们发现肿瘤和健康皮质标本的所有肾上腺样本中都存在细菌 DNA，记录了恶性肿瘤和正常肾上腺之间微生物组成的显着差异：详细而言，ACC 组织的特征是变形菌门丰度较高（尤其是变形菌门）。假单胞菌属和沙雷氏菌属）。此外，变形菌门的低丰度与肿瘤大小、Ki67 和皮质醇分泌呈负相关。9 个月时，变形菌、假单胞菌和沙雷氏菌丰度较高，拟杆菌门、厚壁菌门和链球菌丰度较低的 ACC 患者中，米托坦水平达到较高水平。这些发现首次表明人类 ACC 具有浸润细菌的特征，其特定丰度分布似乎会影响 9 个月时循环 MTT 水平的增加。