The combination of intravenous Reolysin and gemcitabine induces reovirus replication and endoplasmic reticular stress in a patient with KRAS-activated pancreatic cancer
Activating mutations in RAS are present in the majority of pancreatic cancer cases and represent an ideal therapeutic target. Reolysin is a proprietary formulation of oncolytic reovirus that is currently being evaluated in multiple clinical trials due to its ability to selectively replicate in cells harboring an activated RAS pathway. Here we report for the first time the presence of reovirus replication and induction of endoplasmic reticular (ER) stress in a primary tumor specimen collected from a pancreatic cancer patient receiving intravenous Reolysin and gemcitabine.
We describe the case of a 54-year old patient diagnosed with pancreatic adenocarcinoma in February 2012. Analysis of a tumor biopsy revealed an activating KRAS mutation (G12D) and the patient was started on first-line treatment with Reolysin in combination with gemcitabine in March 2012. Stable disease was achieved with significant improvement in cancer-related pain. Following 25 cycles of treatment over 23 months, a second biopsy was collected and immunohistochemical analyses revealed the presence of reovirus replication and induction of the ER stress-related gene GRP78/BIP and the pro-apoptotic protein NOXA. Importantly, co-localization of reoviral protein and active caspase-3 was also observed in the biopsy specimen.
This is the first report of reoviral protein detection in primary tumor biopsies taken from a pancreatic cancer patient receiving intravenous Reolysin therapy. The accumulation of reoviral protein was associated with ER stress induction and caspase-3 processing suggesting that Reolysin and gemcitabine treatment exhibited direct pro-apoptotic activity against the tumor.
KeywordsReolysin Reovirus Oncolytic virus RAS Pancreatic cancer Gemcitabine ER stress NOXA
Double-stranded RNA-activated protein kinase
Eukaryotic initiation factor 2 alpha
Response Evaluation Criteria in Solid Tumors
Reolysin is a formulation of wild-type oncolytic reovirus that is currently under investigation in multiple randomized phase II clinical trials in solid tumors, including combination with taxane-based regimens for the treatment of patients with head and neck carcinoma, non-small cell lung cancer (NSCLC), prostate cancer, pancreatic cancer, and ovarian cancer [1, 2, 3, 4, 5]. Reoviruses have been reported to selectively replicate in cancer cells harboring an activated RAS pathway . The preferential replication of reovirus in cells with activated RAS is due to RAS’s ability to inhibit double-stranded RNA-activated protein kinase (PKR), a key sensor that recognizes viral particles and results in abrogation of protein synthesis by phosphorylation of eukaryotic initiation factor 2 alpha (eif2α) . Failure to activate PKR allows viral replication to continue unchecked in RAS-activated cells. Since RAS mutations are present in most patients with pancreatic cancer, Reolysin has been studied against this tumor type . Reolysin has demonstrated promising activity in preclinical models of pancreatic cancer [9, 10]. A previous Phase I study established the safety of the combination of intravenous Reolysin with gemcitabine . Subsequently, a Phase II study at our institution demonstrated a significant improvement in clinical benefit in response to Reolysin in combination with gemcitabine in patients with advanced pancreatic cancer (manuscript in preparation). However, given that pancreatic cancers are hypovascular tumors surrounded by dense desmoplastic tissue, it is postulated that chemotherapeutic agents often fail to reach the primary tumor. Therefore, it is essential to assess drug or target delivery into primary tumors and yet the identification of reovirus in primary tumor specimens and validation of biomarkers of clinical activity have not been investigated in pancreatic cancer. Here we report the first evidence of active reovirus replication in a primary tumor sample taken from a pancreatic cancer patient enrolled in the Phase II trial of intravenous Reolysin and gemcitabine. We also show induction of endoplasmic reticular (ER) stress, the pro-apoptotic BH3-only family member NOXA, and activation of caspase-3 in pancreatic tumor biopsies post-treatment.
The patient is a 54-year-old gentleman, who presented with a few months of mid-epigastric pain, nausea and vomiting with associated weight loss in February 2012. CT and MRI scans revealed a 3.3 × 3.1 cm pancreatic head mass encasing superior mesenteric artery and vein with associated mesenteric periportal lymphadenopathy. He also had sub-centimeter lung nodules presumed to be metastatic deposits. He thus had a clinical stage 4 unresectable pancreatic cancer. Genomic analysis of tumor biopsies revealed the presence of KRAS mutation (G12D) and loss of CDKN2A/B.
Toxicities were manageable and included grade 1 fever likely due to Reolysin and grade 3 thrombocytopenia and neutropenia due to gemcitabine. The patient also had a biliary obstruction, which required stenting in November 2013. He completed 27 cycles of treatment with the last one in April 2014. At this time, he presented with disease progression with ascites and jaundice.
To our knowledge, this is the first report that identified reoviral protein within a primary pancreatic tumor following systemic Reolysin therapy. These findings demonstrate that Reolysin and gemcitabine treatment may result in reovirus replication, ER stress, and apoptosis in patients treated with this regimen. Preliminary results from the Phase II study at our institution for patients with advanced pancreatic cancer treated with gemcitabine and Reolysin showed a clinical benefit with acceptable tolerability. Although this patient did not have tumor shrinkage, the patient did have prolonged stable disease for more than 2 years as well as symptomatic improvement with decreased cancer-related pain.
Since pancreatic cancers are hypovascular tumors surrounded by dense desmoplastic tissue, drug resistance may occur as chemotherapeutic agents fail to penetrate the primary tumor. This case establishes Reolysin’s ability to invade the dense desmoplastic tissue surrounding the hypovascular pancreatic cancer, suggesting that Reolysin may be an effective agent against drug resistant tumors. Since the majority of pancreatic cancers have RAS pathway activation, Reolysin serves as a potential promising active agent to overcome this barrier when combined with conventional chemotherapy .
The mechanisms of Reolysin’s anticancer activity are pleiotrophic and have been reported to include tumor lysis, ER stress, apoptosis, and stimulation of an immune response against the tumor in preclinical models [13, 14, 15, 16, 17]. Here we provide evidence in the clinical setting that the combination of Reolysin and gemcitabine displays direct anticancer effects against the primary tumor. The multitude of mechanisms by which Reolysin attacks tumor cells is an advantage that may be able to help overcome drug resistance and contribute to its ability to augment the activity of multiple conventional chemotherapeutic agents.
We have also shown significant induction of the ER stress associated markers GRP78/BIP and NOXA in the biopsy specimen analyzed following Reolysin and gemcitabine treatment. Our preclinical studies determined that induction of ER stress and the BH3-only pro-apoptotic gene NOXA are key mediators of Reolysin-induced apoptosis [9, 13]. Since cells with activated RAS are frequently under constitutive ER stress, further induction of this stress response may result in reaching a threshold where apoptosis is initiated. Additional studies combining Reolysin with other agents that trigger ER stress (i.e. bortezomib) may yield enhanced anticancer activity.
Taken together, we are the first to demonstrate reoviral protein accumulation in a primary tumor from a cancer patient treated with systemic Reolysin and gemcitabine. This treatment regimen yielded stable disease for more than 2 years in a patient with advanced pancreatic cancer, which is a significant improvement compared to the historical median survival of 6–12 months in this patient population [18, 19].
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor of this journal.
This work was supported by Oncolytics Biotech Inc., the Voelcker Fund Young Investigator Award (STN), The William and Ella Owens Foundation (STN, DM), R01CA190789 (STN), and the National Cancer Institute P30 Cancer Center Support Grant # CA054174.
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