The Radiosensitization Mechanism Study Of The PLK1 Inhibitor HS-10159 In NSCLC

Objectives The key steps during the process of mitosis include G2/M transition, the maturation of cellular organelles, the repair of genetic materials, etc. PLK1 plays an important regulatory role during mitosis and has become a hot research topic given its high expression in tumor and worse prediction for patient’s prognosis. Our study analyzed the expression of PLK1 in clinical pathologic tissues and their prognosis in NSCLC and brain metastasis, observed the change of cell cycle, apoptosis and protein expression in NSCLC with radiotherapy alone or combined with PLK1 inhibitor HS-10159. We further explored the radiosensitization molecular mechanism of the PLK1 inhibitor HS-10159 in NSCLC, providing a theoretical basis for the clinical application of targeted small molecule inhibitors of PLK1 HS-10159 treatment of NSCLC together with radiotherapy.Method 1. The expression of PLK1 was detected in NSCLC tissues and adjacent paired tissues as well as brain metastases by immunohistochemistry. We assessed the expression of PLK1 and clinical pathology parameters, follow-up the prognosis of patients using the SPSS statistical software as the Kaplan-Meier survival curve test and log-rank test. 2. NSCLC cell lines of A549, SPC, LTEP were tested for cell growth and proliferation and colony formation. Radiosensitization was observed in cells treated with PLK1 inhibitor HS-10159 by MTS and colony formation assays. 3. To detect the expression of PLK1 and P-PLK1 in cell lines A549, SPC, LTEP by Western blot and the change of cell cycle, apoptosis was analyzed by flow cytometric in single drug treatment, single radiotherapy and combined treatment of NSCLC cell.Results 1. The PLK1 expression from 44 NSCLC, 19 adjacent tissues, 41 brain metastases showed that PLK1 protein was upregulated in NSCLC compared to adjacent tissue; The NSCLC patients with negative PLK1 expression had longer OS than those with positive PLK1 expression. No significant difference was found between primary lung cancer patients and brain metastases. 2. PLK1 inhibitor HS-10159 significantly inhibits the proliferation of NSCLC cells, P-PLK1 expression was significantly inhibited within 0.5h-6h in cells treated with HS-10159, then increased to higher level within 6h-24 h post HS-10159 treatment. 3. PLK1 inhibitor HS-10159 inhibits NSCLC tumor cell colony formation, and significantly increases radiation sensitivity of A549 cells, with no significant radiation sensitization for LTEP and SPC cells. 4. With the single radiation dose increases, P-PLK1 expression increased in NSCLC cells, PLK1 inhibitor HS-10159 inhibits P-PLK1 expression in NSCLC cells.The drug inhibits the increase of P-PLK1 protein caused by radiotherapy. 5. PLK1 inhibitor HS-10159 in combination with radiotherapy significantly increased G2/M phase arrest in cells. Either HS-10159 or combined therapy increased cell death and apoptosis compared with the control group. However, the drug combined with radiotherapy didn’t significantly increase apoptotic cell death compared with drug alone.Conclusion 1. Analysis of clinical data showed that PLK1 protein expression is significantly correlated to the prognosis of NSCLC, indicating PLK1 may be used as prognostic marker for NSCLC patients. 2. PLK1 inhibitor HS-10159 inhibit the NSCLC cellular proliferation and colony formation in a cell type-dependent manner. 3. The radiation increased acute P-PLK1 expression in NSCLC cells, PLK1 inhibitor HS-10159 alleviates the induction of P-PLK1 protein caused by radiotherapy. PLK1 inhibitor HS-10159 in combination with radiotherapy significantly increased G2/M arrest in NSCLC cells, the drug combined with radiotherapy failed to show synergetic effect on increasing apoptotic cell death. The molecular mechanism of the PLK1 inhibitor HS-10159 sensitizing radiation therapy in NSCLC needs to be further explored.