Murtha Timothy D, Brown Taylor C, Rubinstein Jill C, Haglund Felix, Juhlin C Christofer, Larsson Catharina, Korah Reju, Carling Tobias
Yale Department of Surgery & Yale Endocrine Neoplasia Laboratory, Yale School of Medicine, New Haven, CT.
Department of Oncology-Pathology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
Surgery. 2017 Jun;161(6):1667-1674. doi: 10.1016/j.surg.2016.11.036. Epub 2017 Jan 7.
Cytochrome P450-mediated metabolism of chemotherapeutic agents contributes to chemotherapy resistance in multiple malignancies. Adrenocortical carcinoma is known to have a poor response to adjuvant therapies; however, the mechanism remains unknown. Recent comprehensive genetic analyses of adrenocortical carcinomas demonstrated recurrent copy number gains in multiple cytochrome P450 genes prompting investigation into whether cytochrome P450 overexpression potentiates adrenocortical carcinoma chemoresistance.
We determined the expression patterns of 6 cytochrome P450 genes (CYP2A6, CYP2A7, CYP2A13, CYP2B6, CYP2S1, and CYP4F2) predicted to be amplified in adrenocortical carcinoma (n = 29) relative to normal adrenal cortex (n = 10). Gene copy numbers were determined with the TaqMan copy number assay. Gene silencing was performed via small interfering RNA (siRNA) in the adrenocortical carcinoma cell line NCI-H295R and treated with mitotane and cisplatin.
Of the 6 cytochrome P450 genes tested, CYP2A6 was overexpressed with a 55-fold mean increase compared to normal adrenal samples (P < .05). Immunohistochemical analysis confirmed protein overexpression. Copy gains of CYP2A6 were found in 26% (7/27) of adrenocortical carcinoma specimens. Silencing of CYP2A6 in NCI-H295R cells resulted in decreased cell viability and increased chemosensitivity (P < .05).
Frequent upregulation in adrenocortical carcinomas and the reversal of chemoresistance in adrenocortical carcinoma cells via enforced silencing suggest a role for CYP2A6 in adrenocortical malignancy.
细胞色素P450介导的化疗药物代谢导致多种恶性肿瘤产生化疗耐药性。已知肾上腺皮质癌对辅助治疗反应不佳；然而，其机制尚不清楚。最近对肾上腺皮质癌的全面基因分析表明，多个细胞色素P450基因存在反复的拷贝数增加，这促使人们研究细胞色素P450过表达是否会增强肾上腺皮质癌的化疗耐药性。
我们测定了预计在肾上腺皮质癌（n = 29）中相对于正常肾上腺皮质（n = 10）会扩增的6个细胞色素P450基因（CYP2A6、CYP2A7、CYP2A13、CYP2B6、CYP2S1和CYP4F2）的表达模式。用TaqMan拷贝数测定法确定基因拷贝数。在肾上腺皮质癌细胞系NCI-H295R中通过小干扰RNA（siRNA）进行基因沉默，并用米托坦和顺铂处理。
在所检测的6个细胞色素P450基因中，与正常肾上腺样本相比，CYP2A6过表达，平均增加55倍（P <.05）。免疫组织化学分析证实了蛋白过表达。在26%（7/27）的肾上腺皮质癌标本中发现了CYP2A6的拷贝增加。在NCI-H295R细胞中沉默CYP2A6导致细胞活力下降和化疗敏感性增加（P <.05）。
肾上腺皮质癌中CYP2A6频繁上调，并且通过强制沉默可逆转肾上腺皮质癌细胞的化疗耐药性，这表明CYP2A6在肾上腺皮质恶性肿瘤中发挥作用。
