Synergistic cytotoxicity of radiation and oncolytic Lister strain vaccinia in V600D/EBRAF mutant melanoma depends on JNK and TNF-α signaling

Abstract

Melanoma is an aggressive skin cancer that carries an extremely poor prognosis when local invasion, nodal spread or systemic metastasis has occurred. Recent advances in melanoma biology have revealed that RAS-RAF-MEK-ERK signalling plays a pivotal role in governing disease progression and treatment resistance. Proof-of-concept clinical studies have shown that direct BRAF inhibition yields impressive responses in advanced disease but these are short-lived as treatment resistance rapidly emerges. Therefore, there is a pressing need to develop new targeted strategies for BRAF mutant melanoma.As such, oncolytic viruses represent a promising cancer-specific approach with significant activity in melanoma.This study investigated interactions between genetically-modified vaccinia virus (GLV1h68) and radiotherapy in melanoma cell lines with BRAF mutant, Ras mutant or wildtype genotype. Pre-clinical studies revealed that GLV-1h68 combined with radiotherapy significantly increased cytotoxicity and apoptosis relative to either single agent in V600D BRAF/ V600E BRAF mutant melanoma in vitro and in vivo. The mechanism of enhanced cytotoxicity with GLV-1h68/radiation was independent of viral replication and due to attenuation of JNK, p38 and ERK MAPK phosphorylation specifically in BRAF mutant cells. Further studies showed that JNK pathway inhibition sensitized BRAF mutant cells to GLV-1h68-mediated cell death, mimicking the effect of radiation. GLV1h68 infection activated MAPK signalling in V600D BRAF/ V600E BRAF mutant cell lines and this was associated with TNF-α secretion which, in turn, provided a prosurvival signal.Combination GLV-1h68/radiation (or GLV-1h68/JNK inhibition) caused abrogation of TNF-α secretion. These data provide a strong rationale for combining GLV-1h68 with irradiation in V600D/E BRAF mutant tumors.3

Phase I Trial of Intravenous Oncolytic Vaccinia Virus (GL-ONC1) with Cisplatin and Radiotherapy in Patients with Locoregionally Advanced Head and Neck Carcinoma

“…In particular, viral infection increases the S-phase and sub-G 1 cells and induces apoptosis via activated caspase-3/7 (19). Furthermore, it has been shown that the combination of radiation with genetically modified vaccinia increases cytotoxicity and apoptosis due to attenuation of the JNK pathway and ERK MAPK phosphorylation in BRAF-mutant melanoma cells (20). These studies support the hypothesis that the oncolytic effects of vaccinia could be enhanced in the presence of chemoradiotherapy.…”

“…Preclinical evidence indicates that viral therapies can have a direct oncolytic effect on tumor cells. In addition, oncolytic viruses can improve tumor regression when combined with radiation and chemotherapy (19)(20)(21)(22). Replication of viruses in tumor cells can also elicit a beneficial immune response, representing a novel avenue of oncolysis (25).…”

“…The cytotoxic effect of GL-ONC1 is also enhanced when combined with radiation or chemotherapy. In preclinical studies (17), the addition of radiation or chemotherapy to GL-ONC1 resulted in enhanced cell kill and increased viral replication in irradiated tumors (17)(18)(19)(20)(21)(22). In particular, viral infection increases the S-phase and sub-G 1 cells and induces apoptosis via activated caspase-3/7 (19).…”

Oncolytic viruses as platform for multimodal cancer therapeutics: a promising land

“…A recent study has found that synergistic cytotoxicity of radiation and oncolytic Lister strain vaccinia virus to BRAF mutant melanoma depends on JNK and TNF-α signaling. 8 The virus GLV-1h68 combined with radiotherapy significantly increased cytotoxicity and apoptosis relative to either single agent in V600D BRAF/ V600E BRAF mutant melanoma cells in vitro and in vivo. The mechanism of enhanced cytotoxicity from the combination was independent of viral replication but due to attenuation of JNK, p38 and ERK MAPK phosphorylation specifically in BRAF mutant cells.…”

Chemical Induction of Unfolded Protein Response Enhances Cancer Cell Killing through Lytic Virus Infection

“…For example, treatments with biological agents or chemicals or the physical induction of stress sensitizes tumor cells to be killed by oncolytic viruses (6,7). In some instances, stress induction leads to the inhibition of virus replication; for example, radiation therapy attenuates vaccinia virus infection (8). Alternatively, inhibition of cell stress can enhance oncolysis; for example, blockage of endoplasmic reticulum (ER) stress augments rhabdovirus oncolysis (9).…”