e17560 Background: Ovarian cancer (OC) ranks fifth among cancer deaths in women and remains the deadliest of all gynecological cancers. OncoTherad is a nanostructured complex developed by University of Campinas/Brazil, which exhibits immunomodulatory and antitumor properties. Erythropoietin (EPO) can exert non-hematopoietic functions and the association of immunotherapy and EPO is a reality in anemic patients due to cancer or chemotherapy who may use immunotherapies. We evaluated the effects of OncoTherad and EPO, alone or in combination, on PD-1/PDL-1 and CTLA-4 checkpoints, pro-angiogenic (VEGF) and anti-angiogenic (Endostatin) markers, and microvessel density (CD31-labeled capillaries) in chemically induced ovarian cancer in rats. Methods: Thirty-five Fischer rats were distributed into groups: Control (Sham surgery); Cancer (7,12-dimethylbenzoanthracene – DMBA injection in the ovarian bursa, 1.25 mg/kg); OncoTherad (20mg/kg); EPO (8.4 µg/kg); and OncoTherad+EPO (same doses of the isolated treatments). Intraperitoneal doses were administered twice a week for 4 weeks. Immunohistochemistry was analyzed as total immunoreactivity and intensity of immunoreaction. Results: The Cancer group showed an increase (p < 0.05) in microvascular density and histopathological lesions, predominantly high-grade dysplasias with non-metastatic phenotype, which was related to the little involvement of PD-1/PD-L1 and CTLA-4 checkpoints in this carcinogenesis stage. The treatments altered the frequency of ovarian lesions, especially OncoTherad promoted a significant reduction of cystic lesions, while in the EPO group there was marked hyperplasia of the interstitial tissue and the associated treatment led to intermediate results. OncoTherad immunotherapy was effective in reducing angiogenesis, promoting a decrease (p < 0.05) in VEGF immunostaining and microvessel count, and an increase (p < 0.05) in endostatin immunoreactivity. EPO treatment decreased (p < 0.05) endostatin levels in comparison with OncoTherad group and led to a weaker (p < 0.05) immunoreaction intensity of PD-1/PD-L1 and CTLA-4 compared to the Cancer group. These effects might be related to the modification of the tumor microenvironment modulated by EPO with a decrease in the population of immune cells with immunosuppressive phenotype as well as histopathological alterations including reduction of folliculogenesis and luteogenesis. Conclusions: OncoTherad was able to prevent histopathological lesions and reduce the angiogenesis involved in the ovarian carcinogenesis. EPO treatment decreased endostatin, which possibly had effects on angiogenic activity. However, EPO also modulated the OC microenvironment by reducing PD-1/PD-L1 and CTLA-4. The association of OncoTherad+EPO might have triggered a compensatory effect between the isolated treatments.

e17602 Background: Ovarian cancer (OC) has the most devastating death rate of gynecological cancers with only 44% of women surviving 5 years after diagnosis. Toll-like receptors (TLRs) signaling can play an important role in the OC treatment. TLR activation in immune cells can help activate an effective antitumor response. In this scenario, a new perspective is represented by combined OncoTherad (MRB-CFI-1) immunotherapy and Platelet Rich Plasma (PRP). OncoTherad (MRB-CFI-1) leads to the distinct stimulation of the innate immune system mediated by TLR2 and TLR4, resulting in an increased activation of the IFN signaling pathway. Also, PRP acts on immune activation and exerts antitumor effects. This study characterized the histopathological and molecular effects of the OncoTherad associated with PRP in the treatment of OC chemically induced in rats and described the possible mechanisms of action of this association involving the TLRs 2 and 4 signaling pathways. Methods: Fischer 344 female rats were divided into 5 groups (n = 7 animals per group): Control (Sham surgery) group; Cancer (7,12 dimethylbenzoanthracene – DMBA injection in the ovarian bursa, 1.25 mg/kg) group; OncoTherad (20mg/kg) group; PRP (328.103 – 549.103 platelets/mm3) group and; OncoTherad+PRP (same doses of the isolated treatments) group. Intraperitoneal doses were administered twice a week for 4 weeks. Immunohistochemistry was analyzed as total immunoreactivity and intensity of immunoreaction. Results: Our results showed serous type ovarian carcinoma, follicular atresia, absence of corpora lutea and hyperplasia of the germinal epithelium and tunica albuginea in the Cancer group. The histopathological changes in the PRP group were similar as Cancer group. In contrast, the animals treated with OncoTherad singly or in combination with PRP showed decrease of ovarian neoplastic lesions and histopathological recovery. TLR4 and IL-6 immunoreactivities were significantly lower (p < 0.05) in the Cancer group. PRP treatment reduced (p < 0.05) TLR2. In the Oncotherad+PRP group, the immunoreactivities of TLR4, MyD88, IRF-3 and TNF-α were lower. OncoTherad treatment alone led to stimulation of the innate immune system mediated by TLR2 and TLR4, resulting in an increased activation of the MyD88 signaling pathway (intensified IL-6 and TNF-α immunoreactivities). Conclusions: OncoTherad immunotherapy was able to reduce ovarian lesions and stimulated the TLR2 and 4 signaling pathways in the OC microenvironment, leading to antitumor effects by activating the production of inflammatory cytokines. Thus, OncoTherad immunotherapy could be considered an important therapeutic strategy for OC.