Permissiveness of Human Cancer Cells to Oncolytic Bovine Herpesvirus 1 Is Mediated in Part by KRAS Activity

Abstract

Oncolytic viruses (OVs) are attractive avenues of cancer therapy due to the absence of toxic side effects often seen with current treatment modalities. Bovine herpesvirus 1 (BHV-1) is a species-specific virus that does not induce cytotoxicity in normal primary human cells but can infect and kill various human immortalized and transformed cell lines. To gain a better understanding of the oncolytic breadth of BHV-1, the NCI panel of established human tumor cell lines was screened for sensitivity to the virus. Overall, 72% of the panel is permissive to BHV-1 infection, with corresponding decreases in cellular viability. This sensitivity is in comparison to a sensitivity of only 32% for a herpes simplex virus 1 (HSV-1)-based oncolytic vector. Strikingly, while 35% of the panel supports minimal or no BHV-1 replication, significant decreases in cellular viability still occur. These data suggest that BHV-1 is an OV with tropism for multiple tumor types and is able to induce cytotoxicity independent of significant virus replication. In contrast to other species-specific OVs, cellular sensitivity to BHV-1 does not correlate with type I interferon (IFN) signaling; however, mutations in KRAS were found to correlate with high levels of virus replication. The knockdown or overexpression of KRAS in human tumor cell lines yields modest changes in viral titers; however, overexpression of KRAS in normal primary cells elicits permissivity to BHV-1 infection. Together, these data suggest that BHV-1 is a broad-spectrum OV with a distinct mechanism of tumor targeting. IMPORTANCECancer remains a significant health issue, and novel treatments are required, particularly for tumors that are refractory to conventional therapies. Oncolytic viruses are a novel platform given their ability to specifically target tumor cells while leaving healthy cells intact. For this strategy to be successful, a fundamental understanding of virus-host interactions is required. We previously identified bovine herpesvirus 1 as a novel oncolytic virus with many unique and clinically relevant features. Here, we show that BHV-1 can target a wide range of human cancer types, most potently lung cancer. In addition, we show that enhanced KRAS activity, a hallmark of many cancers, is one of the factors that increases BHV-1 oncolytic capacity. These findings hold potential for future treatments, particularly in the context of lung cancer, where KRAS mutations are a negative predictor of treatment efficacy.

Bovine herpesviruses induce different cell death forms in neuronal and glial-derived tumor cell cultures

“…Although different apoptotic forms have been described induced by BHV1 and 5 infection (Brenner et al 2012;Cardoso et al 2012Cardoso et al , 2015Delhon et al 2002;Garcia et al 2013;Geiser et al 2008;Ladelfa et al 2013;Silva-Frade et al 2010Zhu et al 2016), this particular mechanism remains unknown. Likewise, only few reports describe the susceptibility of human tumor cells to BHV1 (Cuddington and Mossman 2014). In this sense, our results demonstrated the ability of BHV1 and 5 to infect neuronal tumor cells with different rates of apoptosis and/or necroptosis.…”

“…Interestingly, BHV1 seems not to infect or cause cytotoxic effect in non-neoplasic human cells (Cuddington and Mossman 2015). Moreover, equine herpesvirus type 1 (EHV-1), another alphaherpesvirus, has been shown to infect human glioblastoma multiforme cells (Courchesne et al 2011;Cuddington and Mossman 2014).…”

Molecular Pathways: Mechanism of Action for Talimogene Laherparepvec, a New Oncolytic Virus Immunotherapy

“…In addition, hyperactive Ras may promote tumor cell replication by blocking PKR activation, thus preventing cells from detecting the stress of aberrant proliferation and terminating protein translation (3,13). Recently, a bovine herpes virus, BHV-1, was found to exhibit enhanced replication and lysis of tumor cells harboring mutations in K-RAS (14). Furthermore, there is some evidence that other oncogenic signaling factors may regulate PKR activity, although their role in mediating oncolytic virus replication remains speculative.…”

Oncoselectivity in Oncolytic Viruses against Colorectal Cancer

“…Because the entry requirements of HSV-1 have been well-characterized [74] it is an attractive candidate for rational retargeting approaches. The alphaherpesviruses encode four envelope glycoproteins necessary and sufficient for virion binding and entry into a host cell, of which the glycoprotein D (gD) is the major determinant of HSV tropism [75] [76]. The most important cognate binding partners for the HSV-1 gD are nectins 1 and 2, both of which are immunoglobulin-like cell-cell adhesion proteins [74] [77].…”