Adjuvant oncolytic virotherapy for personalized anti-cancer vaccination.

By conferring systemic protection and durable benefits, cancer immunotherapies are emerging as long-term solutions for cancer treatment. One such approach that is currently undergoing clinical testing is a therapeutic anti-cancer vaccine that uses two different viruses expressing the same tumor antigen to prime and boost anti-tumor immunity. By providing the additional advantage of directly killing cancer cells, oncolytic viruses (OVs) constitute ideal platforms for such treatment strategy. However, given that the targeted tumor antigen is encoded into the viral genomes, its production requires robust infection and therefore, the vaccination efficiency partially depends on the unpredictable and highly variable intrinsic sensitivity of each tumor to OV infection. In this study, we demonstrate that anti-cancer vaccination using OVs (Adenovirus (Ad), Maraba virus (MRB), Vesicular stomatitis virus (VSV) and Vaccinia virus (VV)) co-administered with antigenic peptides is as efficient as antigen-engineered OVs and does not depend on viral replication. Our strategy is particularly attractive for personalized anti-cancer vaccines targeting patient-specific mutations. We suggest that the use of OVs as adjuvant platforms for therapeutic anti-cancer vaccination warrants testing for cancer treatment.

SOCS1 inhibits migration and invasion of prostate cancer cells, attenuates tumor growth and modulates the tumor stroma.

BACKGROUND: The suppressor of cytokine signaling 1 (SOCS1) gene is repressed in prostate cancer (PCa) by epigenetic silencing and microRNA miR30d. Increased expression of the SOCS1-targeting miR30d correlates with higher biochemical recurrence, suggesting a tumor suppressor role of SOCS1 in PCa, but the underlying mechanisms are unclear. We have shown that SOCS1 inhibits MET receptor kinase signaling, a key oncogenic pathway in cancer progression. Here we evaluated the role of SOCS1 in attenuating MET signaling in PCa cells and tumor growth in vivo. METHODS: MET-overexpressing human DU145 and PC3 PCa cell lines were stably transduced with SOCS1, and their growth, migration and invasion of collagen matrix were evaluated in vitro. Cells expressing SOCS1 or the control vector were evaluated for tumor growth in NOD.scid.gamma mice as xenograft or orthotopic tumors. RESULTS: HGF-induced MET signaling was attenuated in SOCS1-expressing DU145 and PC3 cells. Compared with vector control cells, SOCS1-expressing cells showed reduced proliferation and impaired migration following HGF stimulation. DU145 and PC3 cells showed marked ability to invade the collagen matrix following HGF stimulation and this was attenuated by SOCS1. As xenografts, SOCS1-expressing PCa cells showed significantly reduced tumor growth compared with vector control cells. In the orthotopic tumor model, SOCS1 reduced the growth of primary tumors and metastatic spread. Intriguingly, the SOCS1-expressing DU145 and PC3 tumors showed increased collagen deposition, associated with increased frequency of myofibroblasts. CONCLUSIONS: Our findings support the tumor suppressor role of SOCS1 in PCa and suggest that attenuation of MET signaling is one of the underlying mechanisms. SOCS1 in PCa cells also appears to prevent the tumor-promoting functions of cancer-associated fibroblasts.

Suppressor of cytokine signaling 1-dependent regulation of the expression and oncogenic functions of p21(CIP1/WAF1) in the liver.

The SOCS1 gene coding for suppressor of cytokine signaling 1 is frequently repressed in hepatocellular carcinoma (HCC), and hence SOCS1 is considered a tumor suppressor in the liver. However, the tumor-suppressor mechanisms of SOCS1 are not yet well understood. SOCS1 is known to inhibit pro-inflammatory cytokine production and signaling and to promote activation of the p53 tumor suppressor. However, we observed that SOCS1-deficient mice developed numerous and large liver tumor nodules following treatment with the hepatocarcinogen diethylnitrosamine (DEN) without showing increased interleukin-6 production or activation of p53. On the other hand, the livers of DEN-treated Socs1-null mice showed elevated levels of p21(CIP1/WAF1) protein (p21). Even though p21 generally functions as a tumor suppressor, paradoxically many cancers, including HCC, are known to express elevated levels of p21 that correlate with poor prognosis. We observed elevated p21 expression also in the regenerating livers of SOCS1-deficient mice and in cisplatin-treated Socs1-null hepatocytes, wherein the p21 protein showed increased stability. We show that SOCS1 interacts with p21 and promotes its ubiquitination and proteasomal degradation. Besides, the DEN-treated livers of Socs1-null mice showed increased nuclear and cytosolic p21 staining, and the latter was associated with growth factor-induced, phosphatidylinositol 3-kinase-dependent phosphorylation of p21 in SOCS1-deficient hepatocytes. Cytosolic p21 is often associated with malignancy and chemo-resistance in many cancers. Accordingly, SOCS1-deficient hepatocytes showed increased resistance to apoptosis that was reversed by shRNA-mediated p21 knockdown. In the regenerating livers of Socs1-null mice, increased p21 expression coincided with elevated cyclinD levels. Correspondingly, SOCS1-deficient hepatocytes showed increased proliferation to growth factor stimulation that was reversed by p21 knockdown. Overall, our findings indicate that the tumor-suppressor functions of SOCS1 in the liver could be mediated, at least partly, via regulation of the expression, stability and subcellular distribution of p21 and its paradoxical oncogenic functions, namely, resistance to apoptosis and increased proliferation.

Induction of autoimmune diabetes in non-obese diabetic mice requires interleukin-21-dependent activation of autoreactive CD8⁺ T cells.

Non-obese diabetic (NOD) mice lacking interleukin (IL)-21 or IL-21 receptor do not develop autoimmune type 1 diabetes (T1D). We have shown recently that IL-21 may promote activation of autoreactive CD8(+) T cells by increasing their antigen responsiveness. To investigate the role of IL-21 in activating diabetogenic CD8(+) T cells in the NOD mouse, we generated IL-21-deficient NOD mice expressing the highly pathogenic major histocompatibility complex (MHC) class-I-restricted 8.3 transgenic T cell receptor (TCR). IL-21 deficiency protected 8.3-NOD mice completely from T1D. CD8(+) T cells from the 8.3-NOD.Il21(-/-) mice showed decreased antigen-induced proliferation but displayed robust antigen-specific cytolytic activity and production of effector cytokines. IL-21-deficient 8.3 T cells underwent efficient homeostatic proliferation, and previous antigen stimulation enabled these cells to cause diabetes in NOD.Scid recipients. The 8.3 T cells that developed in an IL-21-deficient environment showed impaired antigen-specific proliferation in vivo even in IL-21-sufficient mice. These cells also showed impaired IL-2 production and Il2 gene transcription following antigen stimulation. However, IL-2 addition failed to reverse their impaired proliferation completely. These findings indicate that IL-21 is required for efficient initial activation of autoreactive CD8(+) T cells but is dispensable for the activated cells to develop effector functions and cause disease. Hence, therapeutic targeting of IL-21 in T1D may inhibit activation of naive autoreactive CD8(+) T cells, but may have to be combined with other strategies to inhibit already activated cells.