ATRA, in combination with sorafenib

decreased the activity of the metabolic pathways of HCC cells, and contributes to the increased sensitivity to apoptosis. Combination of anti-cancer drugs with ATRA will be useful for anti-tumor therapy for HCC by regulating cancer cell metabolism. Disclosures: The following people have nothing to disclose: Goshi Shiota, Keita Kanki Introduction: Sorafenib is standard of care for advanced hepatocellular carcinoma (HCC). however, response is often transient with development of resistance. We have recently found that sorafenib CHIR99021 treatment increased hypoxia and induced SDF1α and CXCR4 expression in HCCs – leading to tumor desmoplasia and Gr1+ myeloid suppressor cell recruitment. Anti-mouse

PD1 antibody (αPD1) treatment has been shown to boost immune response in other malignancies that are characterized by PD1/PD1L upregulation. Methods: We used an orthotopic murine HCC model – HCA1 tumor grafts in syngeneic C3H mice. HCC tumor growth was monitored by ultrasound. HCC tumor growth was monitored by small animal ultrasound. When tumor volume reached approximately 14mm3 (3×3×3mm), the mice were randomized to 4 groups of treatment (n=6): (1) control (CTRL); (2) sorafenib, 50mg/ kg/daily gavage (SOR); (3) sorafenib plus the CXCR4 inhibitor AMD3100 (10mg/kg/s.c. minipump) (SOR+AMD); and (4) SOR+AMD plus aPD1 (5 × 100μg i.p. injections every 3 days) (SOR/AMD/PD1). MK-2206 research buy Tumor growth was evaluated for 28 days. Results: At the endpoint, tumor volume was significantly smaller in the SOR/AMD and SOR/AMD/PD1 groups versus CTRL (CTRL: 240mm3 vs. SOR: 151mm3 vs. SOR/AMD: 116mm3 vs. SOR/AMD/αPD1: 79mm3). Sorafenib treatment alone resulted in accumulation of intratumoral T-regulatory cells and M2-type macrophages. Inhibition of CXCR4 by AMD3100 prevented these effects and led to inhibition of tumor metastasis and primary tumor growth. However, combination treatment of SOR/AMD did not increase the number of CD8+ T-cells. Addition of aPD1 synergized with SOR/AMD in delaying tumor growth and reducing

metastasis. aPD1 treatment significantly 6-phosphogluconolactonase increased intratumoral infiltration of cytotoxic CD8+ T cells and their activation (as demonstrated by elevated levels of IL-2, TNF-α and IFN-γ expression). CD8+ T-cells co-localized with caspase-3 positive apoptotic HCC cells. Conclusion: Modulation and activation of immune responses by combining AMD3100 and aPD1 may be a novel approach to inhibit local and distant tumor evasion from sorafenib treatment in HCC. Disclosures: Thomas Reiberger – Grant/Research Support: Roche, Gilead, MSD, Phenex; Speaking and Teaching: Roche, Gilead, MSD Rakesh K. Jain – Board Membership: XTuit, H&Q Healthcare Investors, H&Q Life Sciences Investors; Consulting: Enlight Biosciences, Noxxon, Zyngenia; Grant/ Research Support: Dyax, MedImmune, Roche; Stock Shareholder: Enlight Biosciences, SynDevRx, XTuit Dan G.