Parise Robert A, Egorin Merrill J, Kanterewicz Beatriz, Taimi Mohammed, Petkovich Martin, Lew April M, Chuang Samuel S, Nichols Mark, El-Hefnawy Talal, Hershberger Pamela A
The University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA.
Int J Cancer. 2006 Oct 15;119(8):1819-28. doi: 10.1002/ijc.22058.
1Alpha,25-dihydroxyvitamin D3 (1,25D3) displays potent antiproliferative activity in a variety of tumor model systems and is currently under investigation in clinical trials in cancer. Studies were initiated to explore its potential in nonsmall cell lung cancer (NSCLC), as effective approaches to the treatment of that disease are needed. In evaluating factors that may affect activity in NSCLC, the authors found that CYP24 (25-hydroxyvitamin D3-24-hydroxylase), the enzyme that catabolizes 1,25D3, is frequently expressed in NSCLC cell lines but not in the nontumorigenic bronchial epithelial cell line, Beas2B. CYP24 expression by RT-PCR was also detected in 10/18 primary lung tumors but in only 1/11 normal lung tissue specimens. Tumor-specific CYP24 upregulation was confirmed at the protein level via immunoblot analysis of patient-matched normal lung tissue and lung tumor extracts. Enzymatically active CYP24 is expected to desensitize NSCLC cells to 1,25D3. The authors therefore implemented a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) assay for 1,25D3 and its CYP24-generated metabolites to determine whether NSCLC cells express active enzyme. Analysis of NSCLC cell cultures revealed time-dependent loss of 1,25D3 coincident with the appearance of CYP24-generated metabolites. MK-24(S)-S(O)(NH)-Ph-1, a specific inhibitor of CYP24, slowed the loss of 1,25D3 and increased 1,25D3 half-life. Furthermore, combination of 1,25D3 with MK-24(S)-S(O)(NH)-Ph-1 resulted in a significant decrease in the concentration of 1,25D3 required to achieve maximum growth inhibition in NSCLC cells. These data suggest that increased CYP24 expression in lung tumors restricts 1,25D3 activity and support the preclinical evaluation of CYP24 inhibitors for lung cancer treatment.
1α,25 - 二羟基维生素D3（1,25D3）在多种肿瘤模型系统中显示出强大的抗增殖活性，目前正在癌症临床试验中进行研究。由于需要有效的非小细胞肺癌（NSCLC）治疗方法，因此开展了相关研究以探索其在NSCLC中的潜力。在评估可能影响NSCLC活性的因素时，作者发现CYP24（25 - 羟基维生素D3 - 24 - 羟化酶），即分解代谢1,25D3的酶，在NSCLC细胞系中经常表达，但在非致瘤性支气管上皮细胞系Beas2B中不表达。通过逆转录 - 聚合酶链反应（RT - PCR）检测发现，18例原发性肺肿瘤中有10例存在CYP24表达，但在11例正常肺组织标本中仅有1例表达。通过对患者匹配的正常肺组织和肺肿瘤提取物进行免疫印迹分析，在蛋白质水平证实了肿瘤特异性CYP24上调。具有酶活性的CYP24预计会使NSCLC细胞对1,25D3脱敏。因此，作者采用高效液相色谱 - 串联质谱（HPLC - MS/MS）分析法检测1,25D3及其由CYP24产生的代谢产物，以确定NSCLC细胞是否表达活性酶。对NSCLC细胞培养物的分析显示，1,25D3随时间的流失与CYP24产生的代谢产物的出现一致。CYP24的特异性抑制剂MK - 24(S)-S(O)(NH)-Ph - 1减缓了1,25D3的流失并延长了1,25D3的半衰期。此外，1,25D3与MK - 24(S)-S(O)(NH)-Ph - 1联合使用导致在NSCLC细胞中实现最大生长抑制所需的1,25D3浓度显著降低。这些数据表明，肺肿瘤中CYP24表达增加会限制1,25D3的活性，并支持对CYP24抑制剂用于肺癌治疗的临床前评估。
