Phosphorylation of STAT1 serine 727 enhances platinum resistance in uterine serous carcinoma.

Uterine serous carcinoma (USC) is a highly aggressive histological subtype of endometrial cancers harboring highly metastatic and chemoresistant features. Our previous study showed that STAT1 is highly expressed in USC and acts as a key molecule that is positively correlated with tumor progression, but it remains unclear whether STAT1 is relevant to the malicious chemorefractory nature of USC. In the present study, we investigated the regulatory role of STAT1 toward platinum-cytotoxicity in USC. STAT1 suppression sensitized USC cells to increase cisplatin-mediated apoptosis (p < 0.001). Furthermore, phosphorylation of STAT1 was prominently observed on serine-727 (pSTAT1-Ser727), but not on tyrosine-701, in the nucleus of USC cells treated with cisplatin. Mechanistically, the inhibition of pSTAT1-Ser727 by dominant-negative plasmid elevated cisplatin-mediated apoptosis by increasing intracellular accumulation of cisplatin through upregulation of CTR1 expression. TBB has an inhibitory effect on casein kinase 2 (CK2), which phosphorylate STAT1 at serine residues. Sequential treatment with TBB and cisplatin on USC cells greatly reduced nuclear pSTAT1-Ser727, enhanced intracellular accumulation of cisplatin, and subsequently increased apoptosis. Tumor load was significantly reduced by combination therapy of TBB and cisplatin in in vivo xenograft models (p < 0.001). Our results collectively suggest that pSTAT1-Ser727 may play a key role in platinum resistance as well as tumor progression in USC. Thus, targeting the STAT1 pathway via CK2 inhibitor can be a novel method for attenuating the chemorefractory nature of USC.

Immune checkpoint inhibition in ovarian cancer.

Recent studies have shown that tumor cells acquire escape mechanisms to evade host immunity in the tumor microenvironment. Two key immune checkpoint pathways mediated by immunosuppressive co-signaling, the first via programmed cell death 1 (PD-1) and PD-1 ligand 1 (PD-1/PD-L1) and the second via CTLA-4 and B7 (CTLA-4/B7), have been previously described. Several clinical trials have revealed an outstanding anti-tumor efficacy of immune checkpoint inhibitors (anti-CTLA-4 antibody, anti-PD-1 antibody and/or anti-PD-L1 antibody) in patients with various types of solid malignancies, including non-small cell lung cancer, melanoma, renal cell cancer and ovarian cancer. In this review, we examine pre-clinical studies that described the local immune status and immune checkpoint signals in ovarian cancer, highlight recent clinical trials that evaluated immune checkpoint inhibitors against ovarian cancer and discuss the clinical issues regarding immune checkpoint inhibitors.

Sorafenib efficacy in ovarian clear cell carcinoma revealed by transcriptome profiling.

The purpose of this study was to investigate a new modality of therapy against ovarian clear cell carcinoma (OCCC), a chemoresistant subtype of ovarian cancer. Microarray datasets of ovarian cancer cell lines and cancer tissues were analyzed using bioinformatic tools. The gene expression profile of OCCC was similar to that of renal cell carcinoma (RCC). This similarity was at least partially due to hepatocyte nuclear factor 1 pathway activation common to both malignancies. In addition, oncogenic pathway alterations were characteristic of OCCC including hypoxia inducible factor 1 alpha subunit and relatively high Ras activities. Therefore, we predicted that the multi-kinase inhibitor sorafenib, which is approved for RCC and suppresses Ras activity, would also be effective against OCCC. Orally administered sorafenib (40 mg/kg per day) significantly inhibited tumor growth in nude mice when it was given after inoculation with the OCCC cell line RMG-2 (P = 0.002). Furthermore, sorafenib significantly reduced tumor size when it was administered to established RMG-2 tumors (P = 0.0002), while intraperitoneal injection of cisplatin (5 mg/kg per week) did not. In conclusion, the prominent anti-tumor effect of sorafenib against OCCC indicates that sorafenib is a promising candidate drug and supports the need for clinical trials using sorafenib against OCCC. This report demonstrates a method to utilize genome-wide information to facilitate translational research for treatments against less common subtypes of cancers.