Alicia Hurtado

Using sindbis viral vectors for specific detection and suppression of advanced ovarian cancer in animal models.

We studied the therapeutic value of Sindbis vectors for advanced metastatic ovarian cancer by using two highly reproducible and clinically accurate mouse models: a SCID xenograft model, established by i.p. inoculation of human ES-2 ovarian cancer cells, and a syngenic C57BL/6 model, established by i.p. inoculation of mouse MOSEC ovarian cancer cells. We demonstrate through imaging, histologic, and molecular data that Sindbis vectors systemically and specifically infect/detect and kill metastasized tumors in the peritoneal cavity, leading to significant suppression of the carcinomatosis in both animal models. Use of two different bioluminescent genetic markers for the IVIS Imaging System permitted demonstration, for the first time, of an excellent correlation between vector delivery and metastatic locations in vivo. Sindbis vector infection and growth suppression of murine MOSEC tumor cells indicate that Sindbis tumor specificity is not attributable to a species difference between human tumor and mouse normal cells. Sindbis virus is known to infect mammalian cells using the Mr 67,000 laminin receptor. Immunohistochemical staining of tumor cells indicates that laminin receptor is elevated in tumor versus normal cells. Down-regulated expression of laminin receptor with small interfering RNA significantly reduces the infectivity of Sindbis vectors. Tumor overexpression of the laminin receptor may explain the specificity and efficacy that Sindbis vectors demonstrate for tumor cells in vivo. We show that incorporation of antitumor cytokine genes such as interleukin-12 and interleukin-15 genes enhances the efficacy of the vector. These results suggest that Sindbis viral vectors may be promising agents for both specific detection and growth suppression of metastatic ovarian cancer.

The Transition of the 37-Kda Laminin Receptor (Rpsa) to Higher Molecular Weight Species: Sumoylation or Artifact?

Abstract The 37-kDa laminin receptor (37LRP or RPSA) is a remarkable, multifaceted protein that functions in processes ranging from matrix adhesion to ribosome biogenesis. Its ability to engage extracellular laminin is further thought to contribute to cellular migration and invasion. Most commonly associated with metastatic cancer, RPSA is also increasingly found to be important in other pathologies, including microbial infection, neurodegenerative disease and developmental malformations. Importantly, it is thought to have higher molecular weight forms, including a 67-kDa species (67LR), the expression of which is linked to strong laminin binding and metastatic behavior. The composition of these larger forms has remained elusive and controversial. Homo- and heterodimerization have been proposed as events capable of building the larger species from the monomeric 37-kDa precursor, but solid evidence is lacking. Here, we present data suggesting that higher molecular weight species require SUMOylation to form. We also comment on the difficulty of isolating larger RPSA species for unambiguous identification and demonstrate that cell lines stably expressing tagged RPSA for long periods of time fail to produce tagged higher molecular weight RPSA. It is possible that higher molecular weight species like 67LR are not derived from RPSA.

Systemically Administered Sindbis Virus in Combination with Immune Checkpoint Blockade Induces Curative Anti-tumor Immunity

Oncolytic viruses represent a promising form of cancer immunotherapy. We investigated the potential of Sindbis virus (SV) for the treatment of solid tumors expressing the human cancer testis antigen NYESO-1. NYESO-1 is an immunogenic antigen frequently expressed in numerous cancers, such as ovarian cancer. We show that SV expressing the tumor-associated antigen NYESO-1 (SV-NYESO1) acts as an immunostimulatory agent, inducing systemic and rapid lymphocyte activation, leading to a pro-inflammatory environment. SV-NYESO1 treatment combined with anti-programmed death 1 (anti-PD-1) markedly augmented the anti-tumor immunity in mice over the course of treatment, resulting in an avid systemic and intratumoral immune response. This response involved reduced presence of granulocytic myeloid-derived suppressor cells in tumors and an increase in the activation of splenic and tumor-infiltrating T cells. Combined therapy also induced enhanced cytotoxic activity of T cells against NYESO-1-expressing tumors. These results were in line with an observed inverse correlation between T cell activation and tumor growth. Finally, we show that combined therapy resulted in complete clearance of NYESO-1-expressing tumors in vivo and led to long-term protection against recurrences. These findings provide a rationale for clinical studies of SV-NYESO1 combined with immune checkpoint blockade anti-PD-1 to be used in the treatment of NYESO-1-expressing tumors.

ATM kinase is activated by sindbis viral vector infection

Sindbis virus is a prototypic member of the Alphavirus genus, Togaviridae family. Sindbis replication results in cellular cytotoxicity, a feature that has been exploited by our laboratory for treatment of in vivo tumors. Understanding the interactions between Sindbis vectors and the host cell can lead to better virus production and increased efficacy of gene therapy vectors. Here we present studies investigating a possible cellular response to genotoxic effects of Sindbis vector infection. The Ataxia Telangiectasia Mutated (ATM) kinase, a sentinel against genomic and cellular stress, was activated by Sindbis vector infection at 3h post infection. ATM substrates, Mcm3 and the γH2AX histone, were subsequently phosphorylated, however, substrates involved with checkpoint arrest of DNA replication, p53, Chk1 and Chk2, were not differentially phosphorylated compared with uninfected cells. The ATM response suggests nuclear pertubation, resulting from cessation of host protein synthesis, as an early event in Sindbis vector infection.