BACKGROUND Cisplatin-based chemotherapy often results in ovarian cancer (OC) chemical resistance and treatment failure. The combination of natural compounds with platinum-based agents is a new strategy for overcoming cisplatin resistance. At present, the synergistic effects and mechanism of combination of shikonin and cisplatin to overcome cisplatin resistance in OC are still unknown. PURPOSE This study was to evaluate the synergistic effects of shikonin and cisplatin on cisplatin-resistant OC cells and to assess the underlying molecular basis for these effects. METHODS Cell counting kit-8 assay, colony-formation assay, proteomic analysis, reactive oxygen species (ROS) detection, lipid peroxidation (LPO) detection, Fe2+ detection, western blot, and quantitative real-time reverse transcription PCR (qRT-PCR) were performed to evaluate the effects of shikonin and cisplatin on cisplatin-resistant OC cells. Underlying mechanisms of action were investigated in vitro using small molecule inhibitors and siRNA. In vivo, the effect of shikonin and cisplatin combination on tumor growth in BALB/c nude mice was evaluated, with tumor immunohistochemical (IHC) staining performed to detect ferroptosis-related proteins. RESULTS In vitro, shikonin and cisplatin were shown to synergistically reduce the viability of cisplatin-resistant OC cells. Proteomic results demonstrated that the combination of the two drugs induced a ferroptotic process, as evidenced by increased levels of ROS, LPO, and Fe2+, with downregulation of glutathione peroxidase 4 (GPX4). Heme oxygenase 1 (HMOX1) inhibition and siRNA interference attenuated the combined effect of the two drugs on cell viability. Accumulation of Fe2+ was attenuated by siRNA interference of HMOX1. In vivo, combination treatment significantly inhibited the growth of subcutaneous tumors in BALB/c nude mice and increased the expression of ferroptosis-related proteins in tumor tissue. CONCLUSION We report for the first time that the co-treatment of shikonin and cisplatin overcomes cisplatin resistance in OC through ferroptosis. Mechanistic analysis reveals the co-treatment induces ferroptosis through upregulation of HMOX1 that promotes Fe2+ accumulation.

Aim: To investigate the expression of long intergenic noncoding RNA 00515 (LINC00515) in high-grade serous ovarian cancer (HGSOC) and its potential correlation with platinum resistance. Patients & methods: Expression of LINC00515 in HGSOC (n = 115) and normal (n = 19) tissues was detected via quantitative real-time PCR (qRT-PCR). We further explored the statistical significance of the relationship between LINC00515 expression and platinum resistance in HGSOC. Results: LINC00515 was gradually downregulated in the order of normal > platinum-sensitive > platinum-resistant tissue (p < 0.05). Results demonstrated that LINC00515 downregulation was correlated with platinum resistance and relapse-free survival (RFS) of HGSOC (p < 0.05). Conclusion: LINC00515 downregulation is correlated with HGSOC development, platinum resistance and RFS, supporting its utility as a potential biomarker to predict platinum resistance and prognosis of RFS.

Objective To detect the frequency of BRAF/ KRAS and PIK3CA mutations in the small cell lung cancer (SCLC) specimens from a large population of Chinese patients and to analyze the gene mutation and clinical characteristics. Methods A total of 557 samples were collected from SCLC patients from 2009 to 2014.BRAF,KRAS,PIK3CA,NRAS and MEK1 gene mutations were detected by the dideoxy sequencing. Chi-square test was adopted to analyze the correlation between clinical factors and gene mutation. Kaplan-Meier method was utilized for survival analysis. Cox model was used for multivariate prognostic analysis. Results BRAF mutations were detected in 13 out of 557 specimens. The mutation types included V600E (n= 5) ,V600A (n= 2) ,V600M (n= 1) ,D594G (n= 1),G464E (n= 1),K601R (n= 2) and S605N (n= 1).KRAS mutation was detected in 6 cases including G12C (n= 3),G12A (n= 1),G12D (n=1) andG13D (n= 1).PIK3CA mutation was observed in 4 samples including E545G (n= 2) and H1047R (n= 2).Besides,NRAS mutation (Q61R) was detected in 1 case and MEK1 mutation (D61Y) was noted in 1 case. These gene mutations were not significantly correlated with the age, gender, smoking status and clinical staging of the patients. Univariate survival analysis demonstrated the median survival time of patients with gene mutation was (10.30±0. 751) months (95％CI:8. 829-11. 771 months),significantly shorter than (12.80±0. 543) months (95％CI:11. 736-13. 864 months) of their counterparts without gene mutation (P=0. 011). Conclusions BRAF/ KRAS and PIK3CA gene mutation is detected in a small proportion of SCLC patients. These gene mutations are not significantly correlated with the clinical characteristics. Univariate survival analysis demonstrates that negative these gene mutations are negatively correlated with the clinical prognosis of SCLC patients.