The PI3K/mTOR dual inhibitor NVP-BEZ235 reduces the growth of ovarian clear cell carcinoma

Abstract

Abstract.Patients with clear cell carcinoma of the ovary (OCCC) have poor survival due to resistance to standard chemotherapy. OCCC has frequent activating mutations of the PIK3CA gene. The present study was conducted to clarify the efficacy of the inhibition of the PI3K-AKT-mTOR pathway in OCCC. We used 8 OCCC cell lines and 5 ovarian serous adenocarcinoma (OSAC) cell lines. The mutation status of the PIK3CA and KRAS genes was examined by direct sequencing. The IC 50 values of NVP-BEZ235 (BEZ235) and temsirolimus were determined by WST-8 assay. Protein expression levels of PI3K-AKT-mTOR pathway molecules were examined by western blotting. Cell cycle distribution was analyzed by flow cytometry. Annexin V staining was used for detecting apoptosis. We also investigated the effects of BEZ235 on OCCC tumor growth in a nude mouse xenograft model. Four of the 8 OCCC cell lines showed a PIK3CA mutation while none of the 5 OSAC cell lines showed a mutation. The IC 50 values of BEZ235 for the OCCC cell lines were lower than these values for the OSAC cell lines. The IC 50 value of temsirolimus was higher than BEZ235 in the OCCC cell lines. The PIK3CA mutation was more frequently noted in OCCC than OSAC cells, but the sensitivity of these cell lines to BEZ235 or temsirolimus was not related to the mutation status. pHER3 and pAkt proteins were expressed more frequently in OCCC compared with OSAC. However, protein expression levels were distributed widely, and were not related to the sensitivity. Treatment with BEZ235 suppressed expression of pAkt, although treatment with temsirolimus did not. OCCC cells exhibited G 1 phase arrest after treatment with BEZ235 and apoptosis with a higher concentration of the agent. BEZ235 significantly inhibited tumor growth in mice bearing OVISE and TU-OC-1 cell tumors. The present study indicated that the PI3K-AKT-mTOR pathway is a potential target for OCCC, and that BEZ235 warrants investigation as a therapeutic agent. IntroductionClear cell carcinoma of the ovary (OCCC) is recognized in the World Health Organization classification of ovarian tumors as a distinct histological entity. Its clinical behavior is distinctly different from other epithelial ovarian cancers (1). OCCC accounts for 3.7-12.1% of epithelial ovarian cancers (2,3). We found that response rates for platinum-based chemotherapy were 11.1% for OCCC and 72.5% for serous adenocarcinoma (SAC), suggesting that OCCC resists conventional platinumbased chemotherapy (4). A novel therapeutic strategy is needed to improve the prognosis of patients with OCCC.PIK3CA is located at the 3q26.3 locus and encodes the catalytic subunit of the phosphatidylinositol 3-kinase (PI3K), p110α (5). In response to an extracellular signal, the activated p110α phosphorylates PIP2 to generate PIP3. The PIP3 recruits AKT to the plasma membrane, where it is phosphorylated and activated by phosphatidylinositol-dependent kinase 1 (PDK1) and PDK2. Activated AKT can directly activate the mammalian target of rapamycin (mTOR) by phosphorylation at Ser2448. mTOR ...

Dual blockade of PI3K/AKT/mTOR (NVP-BEZ235) and Ras/Raf/MEK (AZD6244) pathways synergistically inhibit growth of primary endometrioid endometrial carcinoma cultures, whereas NVP-BEZ235 reduces tumor growth in the corresponding xenograft models

“…These results are in accordance with the results of Shoji et al and Oishi et al, who used commercial EC cell lines and ovarian clear cell carcinoma cell lines, respectively [17,30]. In hepatocellular carcinoma, however, Kirstein et al indicated that NVP-BKM120 has a higher antitumor activity compared to RAD001 (mTORC1 inhibitor) and NVP-BEZ235 [31].…”

Ovarian clear cell carcinoma, outcomes by stage: The MSK experience

“…This is in contrast to HGSCs, which are characterized by frequent mutations of TP53 – up to 96% as reported in The Cancer Genome Atlas (TCGA) [26]. A trial of NVP-BEZ235, a dual PI3K/mTOR inhibitor, showed promise in OCCC cell lines [27], and may warrant further investigation. There is an ongoing phase II GOG trial for dasatinib (GOG 283) in recurrent/persistent OCCC and endometrial CCC characterized for retention or loss of BAF250a expression, a protein encoded by ARID1A .…”

Emerging strategies for targeting PI3K in gynecologic cancer

“…Numerous in vitro and in vivo studies have investigated the activity of direct PI3K and mTOR inhibition and have found significant activity in clear cell, mucinous and high grade serous ovarian cancer models [61][62][63][64]. While the frequency of PIK3A gene mutation was highest in ovarian clear cell carcinomas, this alteration did not appear to associate with response to PI3K or mTOR inhibitors [61,[65][66][67]. A recent study utilized a model of endometrioid ovarian carcinoma finding that the greatest effects of mTOR or AKT inhibition were derived in the setting of concurrent conventional cyctotoxic chemotherapy [12].…”