Effect of lanthanum chloride on tumor growth and apoptosis in human ovarian cancer cells and xenograft animal models

Ovarian cancer is the leading cause of mortality resulting from gynecologic cancer. A common anti-ovarian tumor drug is cisplatin; however, repeated use of cisplatin causes severe resistance and leads to poor long-term survival rate in ovarian cancer patients. Recently, it was reported that lanthanum chloride (LaCl₃) may inhibit tumor growth and induce apoptosis in certain cancer cells. In the present study, the effect of LaCl₃ on ovarian cancer was determined in vivo and in vitro. A cisplatin-sensitive human ovarian cancer cell line, COC1, was used in the current study. A xenograft animal model of ovarian cancer was established injecting COC1 or cisplatin-resistant COC1 cells (COC1/DDP) cells into mice. A TUNEL assay was used to determine the apoptosis of the COC1 or COC1/DDP cells and a immunohistochemical assay was conducted to measure the expression of B-cell lymphoma-2, Ki67, breast cancer 1 (BRCA)1, BRCA2 and excision repair cross-complementation group 1 in COC1 or COC1/DDP cells. It was observed that LaCl₃ promoted apoptosis in COC1 and COC1/DDP cells. In addition, LaCl₃ plus cisplatin led to further increase in the expression levels of tumor suppressor genes and decrease in the expression of oncogenes. Furthermore, application of LaCl₃ and cisplatin inhibited tumor growth in vivo in a xenograft animal model. These results indicated the synergistic role of LaCl₃ on cisplatin-induced inhibition of cancer cell proliferation and tumor growth, providing a potential and effective candidate for the treatment of ovarian tumors.

Label free quantitative proteomics analysis on the cisplatin resistance in ovarian cancer cells

Quantitative proteomics has been made great progress in recent years. Label free quantitative proteomics analysis based on the mass spectrometry is widely used. Using this technique, we determined the differentially expressed proteins in the cisplatin-sensitive ovarian cancer cells COC1 and cisplatin-resistant cells COC1/DDP before and after the application of cisplatin. Using the GO analysis, we classified those proteins into different subgroups bases on their cellular component, biological process, and molecular function. We also used KEGG pathway analysis to determine the key signal pathways that those proteins were involved in. There are 710 differential proteins between COC1 and COC1/DDP cells, 783 between COC1 and COC1/DDP cells treated with cisplatin, 917 between the COC1/DDP cells and COC1/DDP cells treated with LaCl3, 775 between COC1/DDP cells treated with cisplatin and COC1/DDP cells treated with cisplatin and LaCl3. Among the same 411 differentially expressed proteins in cisplatin-sensitive COC1 cells and cisplain-resistant COC1/DDP cells before and after cisplatin treatment, 14% of them were localized on the cell membrane. According to the KEGG results, differentially expressed proteins were classified into 21 groups. The most abundant proteins were involved in spliceosome. This study lays a foundation for deciphering the mechanism for drug resistance in ovarian tumor.