KRAS mutations are prevalent in 40-45% of patients with colorectal cancer (CRC) and targeting this gene has remained elusive. Reovirus is an endogenous double-stranded RNA virus with specificity for KRAS -mutated CRC. Using peripheral blood mononuclear cells (PBMC) and serum samples from patients with metastatic CRC (mCRC) post reovirus treatment in combination with FOLFIRI and bevacizumab (a phase 1 clinical study), we demonstrate that administration of reovirus results in immunomodulatory changes across genomic, protein and cellular levels. These changes include alterations in expression of several genes including KRAS, VEGFA and CXCR2; sustained reductions in exosomal and cellular levels of miR-29a-3p (a microRNA upregulated in CRC and associated with decreased expression of the tumor suppressor WWOX gene); increases in serum anti-tumorigenic cytokines GM-CSF, IL-15 and IL-12p40 and IL-12p70; reductions in serum pro-tumorigenic cytokines VEGF, RANTES and IL-8; increases in the population of dendritic cells, CD4+ and CD8+ T-cells; increased expression of granzyme B a marker CD8+T activation. These data lend valuable insight into the potential of reovirus as an adjuvant when administered with established chemotherapy regimens in patients with KRAS-mutated mCRC. The findings warrant further study of reovirus in other cancers.SIGNIFICANCE: Reovirus has profound immunomodulatory properties that span the genomic, protein and immune cell distribution levels. This is the first study with reovirus in cancer patients that demonstrates these multi-layered effects, demonstrating how reovirus can function as an immune stimulant (augmenting the efficacy of immuno-chemo-therapeutic drugs), and an oncolytic agent.

Background: KRAS mutations are prevalent in 40-45% of patients with colorectal cancer (CRC) and targeting this gene has remained elusive. Viruses are well known immune sensitizing agents. The therapeutic efficacy of oncolytic reovirus in combination with chemotherapy is underway in a phase 1 study of metastatic CRC. This study evaluates the nature of immune response by determining the cytokine expression pattern in peripheral circulation along with the distribution of antigen presenting cells (APCs) and activated T lymphocytes. Further the study evaluates the alterations in exosomal and cellular microRNA levels along with the effect of reovirus on leukocyte transcriptome.Methods: Reovirus was administered as a 60-minute intravenous infusion for 5 consecutive days every 28 days, at a tissue culture infective dose (TCID50) of 3x1010. Peripheral blood mononuclear cells (PBMC) were isolated from whole blood prior to reovirus administration and post-reovirus on days 2, 8, and 15. The expression profile of 25 cytokines in plasma was assessed (post PBMC isolation) on an EMD Millipore multiplex Luminex platform. Exosome and cellular levels of miR-29a-3p was determined in pre and post reovirus treated samples. Peripheral blood mononuclear cells were stained with fluorophore labelled antibodies against CD4, CD8, CD56, CD70, and CD123, fixed and evaluated by flow cytometry. The expression of granzyme B was determined on core biopsy of one patient. Finally, Clariom D Assay, was used to determine the expression of 847 immune-related genes when compared to pre reovirus treatment by RNA sequencing analysis. A change was considered if the expression level either doubled or halved and the significance was determined at a p value of 0.001.Results:Cytokine assay indicated upregulation at day 8 for IL-12p40 (2.95; p=0.05); day 15 for GM-CSF (3.56; p=0.009), IFN-Ƴ (1.86; p=0.0004) and IL-12p70 (2.42; p=0.02). An overall reduction in IL-8, VEGF and RANTES/CCL5 was observed over the 15-day period. Statistically significant reductions were observed at Day 15 for IL-8 (0.457-fold, 53.3% reduction; p=0.03) and RANTES/CC5 (0.524-fold, 47.6% reduction; p=0.003). An overall increase in IL-6 was observed, with statistical significance at day 8 (1.98- fold; 98% increase, p=0.00007). APCs were stimulated within 48 hours and activated (CD8+ CD70+) T cells within 168 hours as determine by flow cytometry. Sustained reductions in exosomal and cellular levels of miR-29a-3p (a microRNA upregulated in CRC and associated with decreased expression of the tumor suppressor WWOX gene) was documented. Reovirus administration further resulted in increases in KRAS (33x) , IFNAR1 (20x), STAT3(5x), and TAP1 (4x) genes after 2 days; FGCR2A (23x) and CD244 (3x) after 8 days; KLRD1 (14x), TAP1 (2x) and CD244(2x) after 15 days. Reductions (>0.5x) were observed in VEGFA (2x) after 2 days; CXCR2 (2x), ITGAM (3x) after 15 days.Conclusions: Reovirus has profound immunomodulatory properties that span the genomic, protein and immune cell distribution levels. This is the first study with reovirus in cancer patients that demonstrates these multi- layered effects, demonstrating how reovirus can function as an immune stimulant (augmenting the efficacy of immuno-chemo-therapeutic drugs), and an oncolytic agent. Reovirus thus functions bimodally as an oncolytic agent causing lysis of tumor cells, and facilitator of immune-mediated recognition and destruction of tumor cells.

Background KRAS mutations are prevalent in 40-45% of patients with colorectal cancer (CRC) and targeting this gene has remained elusive. Viruses are well known immune sensitizing agents. The therapeutic efficacy of oncolytic reovirus in combination with chemotherapy is underway in a phase 1 study of metastatic CRC. This study evaluates the nature of immune response by determining the cytokine expression pattern in peripheral circulation along with the distribution of antigen presenting cells (APCs) and activated T lymphocytes. Further the study evaluates the alterations in exosomal and cellular microRNA levels along with the effect of reovirus on leukocyte transcriptome.Methods Reovirus was administered as a 60-minute intravenous infusion for 5 consecutive days every 28 days, at a tissue culture infective dose (TCID50) of 3x1010. Peripheral blood mononuclear cells (PBMC) were isolated from whole blood prior to reovirus administration and post-reovirus on days 2, 8, and 15. The expression profile of 25 cytokines in plasma was assessed (post PBMC isolation) on an EMD Millipore multiplex Luminex platform. Exosome and cellular levels of miR-29a-3p was determined in pre and post reovirus treated samples. Peripheral blood mononuclear cells were stained with fluorophore labelled antibodies against CD4, CD8, CD56, CD70, and CD123, fixed and evaluated by flow cytometry. The expression of granzyme B was determined on core biopsy of one patient. Finally, Clariom D Assay, was used to determine the expression of 847 immune-related genes when compared to pre reovirus treatment by RNA sequencing analysis. A change was considered if the expression level either doubled or halved and the significance was determined at a p value of 0.001. Results Cytokine assay indicated upregulation at day 8 for IL-12p40 (2.95; p=0.05); day 15 for GM-CSF (3.56; p=0.009), IFN-Ƴ (1.86; p=0.0004) and IL-12p70 (2.42; p=0.02). An overall reduction in IL-8, VEGF and RANTES/CCL5 was observed over the 15-day period. Statistically significant reductions were observed at Day 15 for IL-8 (0.457-fold, 53.3% reduction; p=0.03) and RANTES/CC5 (0.524-fold, 47.6% reduction; p=0.003). An overall increase in IL-6 was observed, with statistical significance at day 8 (1.98-fold; 98% increase, p=0.00007). APCs were stimulated within 48 hours and activated (CD8+ CD70+) T cells within 168 hours as determine by flow cytometry. Sustained reductions in exosomal and cellular levels of miR-29a-3p (a microRNA upregulated in CRC and associated with decreased expression of the tumor suppressor WWOX gene) was documented. Reovirus administration further resulted in increases in KRAS (33x) , IFNAR1 (20x), STAT3(5x), and TAP1 (4x) genes after 2 days; FGCR2A (23x) and CD244 (3x) after 8 days; KLRD1 (14x), TAP1 (2x) and CD244(2x) after 15 days. Reductions (>0.5x) were observed in VEGFA (2x) after 2 days; CXCR2 (2x), ITGAM (3x) after 15 days.Conclusions Reovirus has profound immunomodulatory properties that span the genomic, protein and immune cell distribution levels. This is the first study with reovirus in cancer patients that demonstrates these multi-layered effects, demonstrating how reovirus can function as an immune stimulant (augmenting the efficacy of immuno-chemo-therapeutic drugs), and an oncolytic agent. Reovirus thus functions bimodally as an oncolytic agent causing lysis of tumor cells, and facilitator of immune-mediated recognition and destruction of tumor cells.