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MINI 35 - Biology (ID 161)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
MINI35.13 - Targeting Cancer Stem Cell Factor BMI1 to Sensitize Non-Small Cell Lung Cancer to Chemotherapy and Radiation Therapy (ID 502)
18:30 - 20:00 | Author(s): H. Cheng
Lung cancer is known to be the most frequent disease and the leading cause of cancer-related death in men and women worldwide. Despite treatment advances, patient outcomes remain dismal and overall survival at 5 years is only 15%. The resistance mechanisms for concurrent chemoradiation therapy are poorly studied. Cancer stem cells have been proposed to be the driver for many cancers including lung cancer and may be also responsible for therapy resistance.
We sought therefore to identify therapy resistance pathways in lung cancer by using genome-wide RNAi high-throughput screen via a shRNA viral library pool containing approx. 60,000 individual shRNAs targeting alomost 80% of human genome on a human lung adenocarcinoma cell line (PC9) treated with cisplatin alone, radiation alone and combined radiation and cisplatin.
From the cisplatin and radiation screen, analysis of top 100 potential hits interestingly showed several cancer stem cells markers including Sox, Lrg6, and members of the Hedgehog signaling pathway Patched and Bmi1. FACS analysis showed increased stem cell markers CD133, ABCG2 and CXCR4 expression on PC9 cells treated multiple times with cisplatin and radiation compared to non-treated cells, pointing towards acquired stemness of lung cancer cells after treatmentent and subsequently resistanve to treatment. Further FACS and real time PCR analysis revealed evlevated EMT marker such as CD44 and SNAIL and decreased expression of E-Cadherin and Vementin in treated cells compared to non-treated cells. Cells treated with cisplatin and radiation in combination with PTC-209 showed increased cleaved-PARP staining compared to cells treated with combined chemoradiation. We further determined the effects of Bmi1 on therapy resistance with survival assays by treating PC9 cells with Bmi1 inhibitor PTC-09. MTT cell survival and colonogenic assays was performed by treating PC9 cells with PTC-09 in triplicate and then treated with increasing dosage of cisplatin (0.1, 1 and 10 µM) or X-ray radiation (2, 4 and 6 Gy). Significantly decreased cell survival was observed in PTC-09 treated PC9 cells treated with cisplatin or radiation compared to control and cisplatin or radiation alone treated cells. Further colonogenic assay of PC9 cells treated with 2Gy+1 um cisplatin and increasing dosage of PTC-09 showed significant decrease in the ability of cells to form colonies compared to control.
By performing an unbiased genome wide RNAi screen for therapeutic resistance, we have successfully identified and validated a molecular regulator of cancer stem cell pathway which enabled us to successfully test the revelance of the cancer stem cell model in lung cancer. Our study provides evidence for the concept that targeting cancer stem cells can be therapeutically beneficial. We are further evaluating effect of Bmi1 using CRISPR knock out model and downstream target.
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