1. 二次突变 作为 BRCA2 突变癌症铂类耐药的一种机制 乳腺中心实验室 许会影 2015.3.15

2. Background: 1. Function: Tumor suppressor gene. HR 2. BRCA1/2-deficient Increasing risk of developing cancer in the breast and ovary. These cancer cells are hypersensitive to platinum but eventually develop platinum resistance. 3.The mechanism What is the mechanism of acquired cisplatin resistance of BRCA2-mutated cancer? About BRCA:

3. Design of experiment: 12 human breast cancer cell lines Canpan-1 5 recurrent Ovarian cancer patients with BRCA2 mutation HCC1428 Sequencing Function( siRNA) 14 cisplatin-resistant Canpan-1 clones Sequencing Function(RAD51) Sequencing UW3548

4. 在 Ab-1,HCC1428 没有观测到 BRCA2 蛋白条带。 Ab-1 full-length undetectable ☞ 实验结果 : 1

5. HCC1428 Ab-1 undetectable (BRCA2) Ab-2 detectabl HCC1428 BRCA2 蛋白缺失 中间片段。 推测 Capan-1

6. 有一个 BRC 重复序列加上 DNA 结 合区域以及核定位序列就可以有 效发挥 BRCA2 的功能。

7. 顺铂化疗 + 二次突变 = 顺铂耐药？ ？ siRNA 转染

8. Result2:

13. 3. Result3:

14. Conclusion: First, in a cisplatin-resistant BRCA2-mutated breast-cancer cell line, HCC1428, a secondary genetic change in BRCA2 rescued BRCA2 function. Second, cisplatin selection of a BRCA2-mutated pancreatic cancer cell line, Capan-1 (refs 3, 4), led to five different secondary mutations that restored the wild-type BRCA2 reading frame. All clones with secondary mutations were resistant both to cisplatin and to a poly(ADP-ribose) polymerase (PARP) inhibitor (AG14361). Finally, we evaluated recurrent cancers from patients whose primary BRCA2-mutated ovarian carcinomas were treated with cisplatin. The recurrent tumour that acquired cisplatin resistance had undergone reversion of its BRCA2 mutation.

15. 2.Treatment with cisplatin could facilitate secondary mutations by increasing the mutation rate via DNA damaging effects. 1.secondary mutations that restore the wild-type BRCA2 reading frame may be a major clinical mediator of acquired resistance to platinum-based chemotherapy.

16. Outlook 1.A larger clinical study is warranted to determine the prevalence and clinical significance of in vivo secondary mutations in BRCA2 in human tumors. 2.Testing for secondary mutations in platinum-treated BRCA2-mutated cancers may be clinically important, because tumors with secondary mutations are likely to be resistant to both cisplatin and PARP inhibitors. 3. It will be important to explore mechanisms for restoring drug sensitivity.