Potentiating effect of reovirus on immune checkpoint inhibition in microsatellite stable colorectal cancer.

The majority of colorectal cancers (CRCs) are microsatellite stable (MSS) and resistant to immunotherapy. The current study explores the possibility of using oncolytic reovirus to sensitize MSS CRC to immune checkpoint inhibition. While reovirus reduced metabolic activity among KRAS Mut cells, microarray/computational analysis revealed microsatellite status-oriented activation of immune-response pathways. Reovirus plus anti-PD-1 treatment increased cell death among MSS cells ex vivo. Reduced tumorigenicity and proliferative index, and increased apoptosis were evident among CT26 [MSS, KRAS Mut], but not in MC38 [microsatellite unstable/MSI, KRAS Wt] syngeneic mouse models under combinatorial treatment. PD-L1-PD-1 signaling axis were differentially altered among CT26/MC38 models. Combinatorial treatment activated the innate immune system, pattern recognition receptors, and antigen presentation markers. Furthermore, we observed the reduction of immunosuppressive macrophages and expansion of effector T cell subsets, as well as reduction in T cell exhaustion. The current investigation sheds light on the immunological mechanisms of the reovirus-anti-PD-1 combination to reduce the growth of MSS CRC.

Oncolytic Reovirus (pelareorep) Induces Autophagy in KRAS-mutated Colorectal Cancer.

PURPOSE: To explore the effects of pelareorep on autophagy in multiple models of colorectal cancer, including patient-derived peripheral blood mononuclear cells (PBMCs). EXPERIMENTAL DESIGN: HCT116 [KRAS mutant (mut)] and Hke3 [KRAS wild-type (WT)] cells were treated with pelareorep (multiplicity of infection, 5) and harvested at 6 and 9 hours. LC3 A/B expression was determined by immunofluorescence and flow cytometry; five autophagic proteins were analyzed by Western blotting. The expression of 88 autophagy genes was determined by qRT-PCR. Syngeneic mouse models, CT26/Balb-C (KRAS mut) and MC38/C57B6 (KRAS WT), were developed and treated with pelareorep (10 × 106 plaque-forming unit/day) intraperitoneally. Protein and RNA were extracted from harvested tumor tissues. PBMCs from five experimental and three control patients were sampled at 0 (pre) and 48 hours, and on days 8 and 15. The gene expression normalized to "pre" was determined using 2-ΔΔC t method. RESULTS: Pelareorep induced significant upregulation of LC3 A/B in HCT116 as compared with Hke3 cells by immunofluorescence (3.24 × and 8.67 ×), flow cytometry (2.37 × and 2.58 ×), and autophagosome formation (2.02 × and 1.57 ×), at 6 and 9 hours, respectively; all P < 0.05. Western blot analysis showed an increase in LC3 A/B (2.38 × and 6.82 ×) and Beclin1 (1.17 × and 1.24 ×) at 6 and 9 hours, ATG5 (2.4 ×) and P-62 (1.52 ×) at 6 hours, and VPS-34 (1.39 ×) at 9 hours (all P < 0.05). Induction of 13 transcripts in cell lines (>4 ×; 6 and 9 hours; P < 0.05), 12 transcripts in CT26 (qRT-PCR), and 14 transcripts in human PBMCs (P < 0.05) was observed. LC3 A/B, RICTOR, and RASD1 expression was upregulated in all three model systems. CONCLUSIONS: Pelareorep hijacks host autophagic machinery in KRAS-mut conditions to augment its propagation and preferential oncolysis of the cancer cells.

Excision repair cross-complementing group-1 (ERCC1) induction kinetics and polymorphism are markers of inferior outcome in patients with colorectal cancer treated with oxaliplatin.

BACKGROUND: ERCC1, a component of nucleotide excision repair pathway, is known to repair DNA breaks induced by platinum drugs. We sought to ascertain if ERCC1 expression dynamics and a single nucleotide polymorphism (SNP) rs11615 are biomarkers of sensitivity to oxaliplatin therapy in patients with colorectal cancer (CRC). METHODS: Western blot and qPCR for ERCC1 expression was performed from PBMCs isolated from patients receiving oxaliplatin-based therapy at specified timepoints. DNA was also isolated from 59 biorepository specimens for SNP analysis. Clinical benefit was determined using progression free survival (PFS) for metastatic CRC. RESULTS: ERCC1 was induced in PBMC in response to oxaliplatin in 13/25 patients with mCRC (52%). Median PFS with ERCC1 induction was 190d compared to 237d in non-induced patients (HR 2.35, CI 1.005-5.479; p=0.0182). ERCC1 rs11615 SNP analysis revealed that 43.3% harbored C/C, 41.2%-T/C and 15.5%-T/T genotype. Median PFS was significantly lower with C/C or T/C (211 and 196d) compared to T/T (590d; p=0.0310). CONCLUSIONS: ERCC1 was induced in a sub-population of patients undergoing oxaliplatin treatment, which was associated with poorer outcome, suggesting this could serve as a marker of oxaliplatin response. C/C or C/T genotype in ERCC1 rs11615 locus decreased benefit from oxaliplatin.